Method of manufacturing semiconductor device

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a method for manufacturing a semiconductor device, which includes a step of removing unnecessary ruthenium-based metal adhering to a semiconductor substrate.

【0002】

[Conventional technology]

In recent years, as a capacitive insulating film for DRAM and FeRAM, Ta has replaced the conventional silicon oxide film and silicon nitride film.₂O₅High dielectric constant films such as the above have come to be used. By using such a high dielectric constant film, it is possible to secure the required storage capacity in a small occupied area, and it is possible to improve the degree of memory cell integration.

【0003】

When these high dielectric constant films are used and polysilicon or the like is used as the electrode material sandwiching the capacitive film, oxygen is released from the high dielectric constant film in the heat treatment step of the semiconductor device to oxidize the electrode material. Therefore, a dielectric film (silicon oxide film) having a lower dielectric constant than the high dielectric constant film exists between the electrode materials, which reduces the capacitance. As described above, when a high dielectric constant film is used, it is important to select a material that does not form an insulating film by oxidation as an electrode material that sandwiches the capacitive film. This is because when a part of the electrode becomes an insulating film due to oxidation, this forms a part of the capacitive film, and as a result, the capacitance is not small. As an electrode material that meets such demands, ruthenium has recently been attracting attention. Since ruthenium has conductivity even when oxidized, it does not cause a decrease in capacity and is inexpensive, and is suitable as an electrode material. ..

【0004】

However, when the electrode is formed using ruthenium, the ruthenium-based metal (ruthenium, ruthenium oxide, etc.) adhering to the end face and the back surface of the silicon substrate is peeled off, and this adheres to the element forming portion or the device via the transport system. It could cause cross-contamination between inter- and inter-wafer. Further, in recent years, in order to reduce the occupied area of the capacitor, a method such as forming an electrode film in a narrow hole is often adopted, and a thin ruthenium film needs to be uniformly formed. In many cases, it is essential to use a CVD method with good coverage as a method. In this case, the adhesion of the ruthenium-based metal to the end face and the back surface of the silicon substrate becomes more intense.

【0005】

Ruthenium-based metals are known as so-called lifetime killer of semiconductor devices, and have various effects such as lowering carrier mobility and adversely affecting the operation of the devices and changing the threshold voltage of transistors over time. It may cause harmful effects. Ruthenium also diffuses faster in a silicon substrate than platinum, which is also known as a life killer. Therefore, even if a small amount of ruthenium-based metal remains on the surface of the silicon substrate, the device characteristics may be significantly adversely affected. As described above, if unnecessary ruthenium-based metal remains on the surface of the silicon substrate, it causes a decrease in the reliability of the device.

【0006】

Therefore, when ruthenium is used as an electrode material, it is important to remove unnecessary ruthenium-based metal by treatment with a chemical solution. However, a chemical solution capable of dissolving and removing ruthenium-based metals has not been found so far. For example, aqua regia or the like used for forming a platinum electrode is difficult to use as a ruthenium-based metal removing solution because its dissolving ability is not sufficient.

【0007】

Further, in order to efficiently remove the ruthenium-based metal adhering to the silicon substrate, not only the ruthenium-based metal is melted, but also the reattachment of the melted ruthenium-based metal to the silicon substrate is effectively prevented. There must be.

【0008】

[Problems to be Solved by the Invention]

The present invention has been made in view of the above circumstances, and in a method for manufacturing a semiconductor device including a step of forming a ruthenium film, unnecessary ruthenium-based metal is sufficiently dissolved and removed, and further, the dissolved ruthenium-based metal is regenerated. The purpose is to effectively prevent adhesion.

【0009】

[Means for solving problems]

According to the present invention that solves the above problems, the following methods for manufacturing a semiconductor device are provided.

【0010】

[1] A step of forming an insulating film on an element forming region on a semiconductor substrate, a step of forming a barrier metal film on the insulating film, and a step of forming a first ruthenium film on the barrier metal film. The step and the ruthenium-based metal adhering to the region other than the element forming region are (a) chloric acid, perchloric acid, iodiic acid, perioic acid, salt containing bromion oxide, salt containing manganese oxide ion and 4 A first containing one or more compounds selected from the group consisting of salts containing valent cerium ions and (b) one or more acids selected from the group consisting of nitric acid, acetic acid, iodic acid, chloric acid. The step of removing with the removing liquid of the above, the step of removing the residue of the first removing liquid with the first cleaning liquid, and after patterning the first ruthenium film, the capacitive insulating film and the second ruthenium The step of forming the film in this order and the ruthenium-based metal adhering to the region other than the element forming region are (a) a salt containing chloric acid, perchloric acid, ioditic acid, periodic acid, and bromion oxide. One or more compounds selected from the group consisting of salts containing manganese oxide ions and salts containing tetravalent cerium ions, and one or more selected from the group consisting of (b) nitric acid, acetic acid, iodic acid, chloric acid. Manufacture of a semiconductor device comprising a step of removing using a second removing liquid containing the acid of the above, and a step of removing a residue of the second removing liquid using a second cleaning liquid. Method.

【0011】

[2] A step of forming an insulating film on an element forming region on a semiconductor substrate, a step of forming a barrier metal film on the insulating film, and a step of forming a first ruthenium film on the barrier metal film. The step and the ruthenium-based metal adhering to the region other than the element forming region are (a) chloric acid, perchloric acid, iodiic acid, perioic acid, salt containing bromion oxide, salt containing manganese oxide ion and 4 A first containing one or more compounds selected from the group consisting of salts containing valent cerium ions and (b) one or more acids selected from the group consisting of nitric acid, acetic acid, iodic acid, chloric acid. A step of removing the first ruthenium film using the removal liquid of the above, a step of forming a capacitive insulating film and a second ruthenium film in this order after patterning the first ruthenium film, and a step of adhering to a region other than the element forming region. A ruthenium-based metal selected from the group consisting of (a) chloric acid, perchloric acid, iodiic acid, perioic acid, salt containing bromion oxide, salt containing manganese oxide ion and salt containing tetravalent cerium ion. Alternatively, a step of removing using a second removing solution containing two or more compounds and (b) one or more acids selected from the group consisting of nitric acid, acetic acid, iodic acid, and chloric acid, and a second A method for manufacturing a semiconductor device, which comprises a step of removing a residue of a second removing liquid using the cleaning liquid of the above.

【0012】

[3] A step of forming an insulating film on an element forming region on a semiconductor substrate, a step of forming a barrier metal film on the insulating film, and a step of forming a first ruthenium film on the barrier metal film. A step, a step of forming a capacitive insulating film and a second ruthenium film in this order after patterning the first ruthenium film, and a ruthenium-based metal adhering to a region other than the element forming region (a). One or more compounds selected from the group consisting of chloric acid, perchloric acid, iodic acid, iodioic acid, salt containing bromion oxide, salt containing manganese oxide ion and salt containing tetravalent cerium ion, and ( b) A step of removing with a second removing solution containing one or more acids selected from the group consisting of nitric acid, acetic acid, iodic acid and chloric acid, and a second using a second cleaning solution. A method for manufacturing a semiconductor device, which comprises a step of removing a residue of a removing liquid.

【0013】

[4] A method for manufacturing a semiconductor device, comprising a step of forming a lower electrode film, a capacitive insulating film, and an upper electrode film in this order in an element forming region on a semiconductor substrate, wherein the lower electrode film and / or the upper portion thereof are formed. The electrode film is a ruthenium film, and after the film formation of the ruthenium film, the ruthenium-based metal adhering to the region other than the element forming region on the semiconductor substrate is (a) chloric acid, perchloric acid, iodiic acid, and perioic acid. Consists of one or more compounds selected from the group consisting of salts containing bromide oxide, salts containing manganese oxide ion and salts containing tetravalent cerium ion, and (b) nitrate, acetic acid, iodic acid, chloric acid. A method for manufacturing a semiconductor device, which comprises removing with a removing liquid containing one or more acids selected from the group, and then removing the residue of the removing liquid with a cleaning liquid.

【0014】

[5] The step of forming a ruthenium film on the element forming region on the semiconductor substrate, and the semiconductor substrate is held substantially horizontally and rotated, and (a) chloric acid and perchlorine are applied to a predetermined portion of the semiconductor substrate. One or more compounds selected from the group consisting of acids, iodiic acids, perioic acids, salts containing bromion oxide, salts containing manganese oxide and salts containing tetravalent cerium ion, and (b) nitric acid, acetic acid. It is characterized by having a step of spraying a removing liquid containing one or more acids selected from the group consisting of iodiic acid and chloric acid to remove the ruthenium-based metal adhering to a region other than the element forming region. A method for manufacturing a semiconductor device.

【0015】

According to the method for manufacturing a semiconductor device of the present invention, since the removing liquid containing the above components (a) and (b) is used, the ruthenium-based metal can be sufficiently dissolved and removed, and the ruthenium-based metal is removed. Reattachment of metal can be effectively prevented.

【0016】

Further, in the method for manufacturing a semiconductor device of the present invention, the removing liquid is used for cleaning a semiconductor substrate. Therefore, unlike the case where such a liquid is used for wet etching, a particularly high level of ability is required for preventing the reattachment of the ruthenium-based metal that has been dissolved and removed. On the other hand, according to the present invention, an excellent ruthenium-based metal removing ability and a high level of anti-reattachment ability can be realized by the synergistic action of the combination of the components (a) and (b) contained in the removing liquid. Cleaning can be preferably performed. The region other than the element forming region refers to the end surface and the back surface of the semiconductor substrate as well as the peripheral portion of the element forming surface (Fig. 1).

【0017】

In addition, the removal liquid used in the present invention is inexpensive as a raw material and does not require a processing cost. Further, by adopting a method such as spin cleaning, sufficient removal performance is exhibited even at a low temperature, so that the life of the chemical solution can be extended.

【0018】

The manufacturing method of the semiconductor device of the above [1] to [4] has a step of removing the residue of the removing liquid by using the cleaning liquid after performing the treatment with the removing liquid, and this point is one of the features. It has become. When the removal solution having the specific composition is used, the second cerium nitrate salt may be precipitated after the removal treatment. Therefore, in the method for manufacturing the semiconductor device, a cleaning liquid is used to remove the residue of the removing liquid. As a result, cross contamination between devices and between wafers due to residual cerium nitrate can be effectively prevented, and the reliability of the device can be further improved. As the cleaning liquid in this case, it is preferable to use a hydrofluoric acid-containing liquid. This is because the precipitated second cerium nitrate salt can be efficiently dissolved and removed, and the reattachment of the removed second cerium nitrate salt can be prevented. Specific examples of the hydrofluoric acid-containing liquid include an aqueous solution of hydrofluoric acid, an aqueous solution containing nitric acid and hydrofluoric acid, and the like. Here, the concentration of hydrofluoric acid can be, for example, 0.1% by mass or more and 60% by mass or less.

【0019】

Further, the above-mentioned methods for manufacturing a semiconductor device [1] to [4] form a capacitor on a semiconductor substrate, and can be suitably applied to the manufacture of DRAM or FeRAM. In general, a higher level of pollution prevention is required in the DRAM or FeRAM manufacturing process than in the manufacturing process of other semiconductor devices. If even a small amount of ruthenium-based metal remains, it diffuses in the silicon substrate and causes various harmful effects such as impairing the reliability of transistor operation. According to the present invention, an extremely high level of pollution prevention (remaining ruthenium is 10).⁹atoms / cm²Since (order) can be realized, it can be particularly preferably applied to the production of DRAM and FeRAM including a capacitor forming step.

【0020】

In the method for manufacturing the semiconductor device in [5] above, a so-called spin cleaning method is adopted in which the semiconductor substrate is held substantially horizontally and the removing liquid is sprayed while rotating the semiconductor substrate. When the ruthenium-based metal removal treatment by removal is performed by the spin cleaning method, the ruthenium-based metal removal performance is significantly improved (described later in the examples). In addition, the temperature dependence of the removal performance becomes small, and the ruthenium-based metal can be sufficiently removed even at room temperature. Therefore, it is not necessary to heat the chemical solution, the auxiliary equipment for cleaning can be simplified, and the life of the chemical solution can be extended.

【0021】

In the method for manufacturing a semiconductor device according to [5] above, after the lower electrode film is formed and before the capacitive insulating film is formed, the ruthenium-based metal adhering to the region other than the element forming region on the semiconductor substrate is (a) chlorine. One or more compounds selected from the group consisting of acids, perchloric acid, iodic acid, iodioic acid, salts containing bromion oxide, salts containing manganese oxide and salts containing tetravalent cerium ion, and (b). ) It may be removed by using a second removing solution containing one or more acids selected from the group consisting of nitric acid, acetic acid, iodic acid and chloric acid. In this way, contamination by ruthenium-based metals can be prevented more effectively.

【0022】

In the method for manufacturing a semiconductor device of the present invention, when the ruthenium-based metal is removed by the second removing liquid and then the residue of the second removing liquid is removed by using the second cleaning liquid, nitric acid is used. Not only can the residue of the second cerium salt be removed, but also the effect of simultaneously removing the unnecessary capacitive insulating film adhering to the back surface and the end surface of the semiconductor substrate can be obtained by appropriately selecting the type of the second cleaning liquid. .. As a result, the number of steps for removing an unnecessary capacitive insulating film can be reduced, and productivity can be improved. For example, Ta as a material for capacitive insulating film₂O₅If a hydrofluoric acid aqueous solution is used as the second cleaning solution, the residue of dicerium nitrate and Ta₂O₅Can be removed at the same time. Figure 7 shows Ta₂O₅Ta when a silicon substrate on which a film is formed is immersed in an aqueous hydrofluoric acid solution₂O₅Shows the film etching rate. Ta by increasing the concentration₂O₅It can be seen that can be dissolved suitably.

【0023】

Examples of the cleaning liquid for removing the residue of the removal liquid include a hydrofluoric acid-containing liquid, and specific examples thereof include an aqueous solution of hydrofluoric acid and an aqueous solution containing nitric acid and hydrofluoric acid. The concentration of hydrofluoric acid can be, for example, 0.1% by mass or more and 60% by mass or less. However, as mentioned above, Ta₂O₅When the purpose is to remove the capacitance insulating film such as, etc. at the same time, the content concentration of hydrofluoric acid is preferably 20% by mass or more, more preferably 30% by mass or more, and most preferably 40% by mass or more. ..

【0024】

As described above, one of the features of the method for manufacturing a semiconductor device of the present invention is that a removing liquid containing a second cerium nitrate salt and an acid is used.

【0025】

Regarding the composition in which the second cerium nitrate salt and the acid were combined, there was an example in which the composition was used as an etching solution for producing a chromium mask used in the lithography process (Japanese Patent Laid-Open No. 7-7757, JP-A). 11-131263). In producing this chrome mask, it is required to etch the chrome film so as to have a tapered cross section. After providing the resist mask on the chrome film, wet etching is performed using the composition having the above constitution. Then, it is known that the tapered shape is preferably formed. This is because the dissolution of chromium by the second cerium nitrate salt proceeds while nitric acid peels off the resist mask and the chromium film.

【0026】

However, the etching target in these publications is chromium, and the action on ruthenium-based metals is not described.

【0027】

Further, Japanese Patent Application Laid-Open No. 11-84627 discloses a technique relating to patterning of a chromium film, and describes that ruthenium can be used as an alternative to the chromium film. However, as for the etching when ruthenium is used, only the method by dry etching is shown, and there is no description about the technique of wet etching ruthenium using a chemical solution.

【0028】

As described above, it has not been conventionally obtained that the combination of the dicerium nitrate salt and a specific acid is excellent in the removal performance of the ruthenium-based metal and can effectively prevent the reattachment of the ruthenium-based metal after the removal. The present invention has been made based on such findings.

【0029】

BEST MODE FOR CARRYING OUT THE INVENTION

The component (a) in the present invention is selected from the group consisting of chloric acid, perchloric acid, iodiic acid, perioic acid, salt containing brom ion oxide, salt containing manganese oxide ion and salt containing tetravalent cerium ion. One or more compounds. Chlorate ion (ClO₃^-), Examples of the acid include chloric acid and perchloric acid. Iodine acid ion (IO₄^-), Examples of the acid include iodic acid and periodic acid. Examples of the salt containing brom oxide ion include brom oxide and bromoacetic acid. Examples of the salt containing manganese oxide ion include manganese oxide and manganese dioxide. Examples of the salt containing tetravalent cerium ion include a second cerium nitrate salt.

【0030】

Of the above, as the component (a) in the present invention, a salt containing tetravalent cerium ion is preferable, and a second cerium nitrate salt is particularly preferably used. In this case, not only ruthenium but also ruthenium oxide can be efficiently dissolved, and the ruthenium-based metal adhering to the substrate after the ruthenium film formation can be effectively removed. In addition, since it sufficiently removes ruthenium-based metals even at a low temperature of about 30 ° C, it is not necessary to heat the chemical solution, which simplifies the incidental equipment for the removal process and prolongs the life of the chemical solution. Benefits are obtained. Further, since the precipitation of cerium after the removal treatment can be suppressed to a relatively small amount, the surface of the substrate can be made sufficiently clean by subsequent cleaning.

【0031】

On the other hand, when, for example, a periodic acid is used as the component (a), it may be difficult to effectively remove the ruthenium-based metal adhering to the substrate because the dissolving ability for ruthenium oxide is not sufficient. In addition, the chemical solution cost is higher than that of the dicerium nitrate salt, and the processing cost is high.

【0032】

Specific examples of the di-cerium nitrate salt include di-cerium nitric acid ammonia, di-cerium nitric acid potassium, etc. Of these, ammonium di-cerium nitrate is preferably used because it has little adverse effect on device performance. ..

【0033】

The component (b) in the present invention is one or more acids selected from the group consisting of nitric acid, acetic acid, iodic acid and chloric acid. Nitric acid or acetic acid is preferable, and nitric acid is most preferable. By selecting such an acid, a synergistic effect due to the combination with (a) is exhibited, and a remarkable ruthenium-based metal removing effect can be obtained.

【0034】

In the present invention, the content of the component (a) is preferably 5% by mass or more, more preferably 10% by mass or more. In this way, the ruthenium-based metal can be sufficiently dissolved and removed, and the reattachment of the removed ruthenium-based metal can be prevented. The upper limit of the content is preferably 30% by mass or less, more preferably 25% by mass or less. By doing so, the precipitation of the component (a) can be effectively prevented.

【0035】

In the present invention, the content of the component (b) is preferably 1% by mass or more, more preferably 5% by mass or more. In this way, the ruthenium-based metal can be sufficiently dissolved and removed, and the reattachment of the removed ruthenium-based metal can be prevented. The upper limit of the content is not particularly limited, but is, for example, 30% by mass or less.

【0036】

The removing liquid in the present invention realizes high ruthenium-based metal removing performance and reattachment prevention performance by the synergistic action obtained by using the above components (a) and (b) in combination. It is difficult to sufficiently remove the ruthenium-based metal with only the component (a) or the component (b) alone.

【0037】

The removing liquid in the present invention preferably contains water as a component (c) in addition to the above components (a) and (b). With such a configuration, the ruthenium-based metal removal performance of the above components (a) and (b) is more effectively exhibited.

【0038】

Further, a water-soluble organic solvent may be contained in place of the component (c) or together with the component (c). As the water-soluble organic solvent, a solvent miscible with water and other components of the present invention can be used.

【0039】

Further, the removing liquid in the present invention may contain other components such as a surfactant in addition to the above-mentioned components.

【0040】

Preferred embodiments of the removing liquid in the present invention include a configuration consisting of only the above (a) to (c), or a configuration in which a small amount of an additive or the like is added thereto.

【0041】

Since the removing solution in the present invention is less likely to cause chemical fatigue, it can be used repeatedly. For example, when this removing liquid is applied to spin cleaning, the removing liquid sprayed on the substrate may be recovered and used again for processing another substrate. When a ruthenium film is formed on the surface of a substrate, an unnecessary ruthenium-based metal adheres to a band-shaped region (peripheral portion) of 0.8 mm from the peripheral edge of the substrate surface and the back surface of the substrate. When removing these, as described above, when the method of reusing the collected removal liquid was adopted and the circulation system of the removal liquid was kept at 60 ° C, it was possible to process 3000 silicon wafers. .. The area 0.8 mm from the peripheral edge of the substrate surface corresponds to the area where the handler and the carrier come into contact with the wafer. By preventing ruthenium contamination in this region and the back surface of the substrate, cross contamination can be effectively prevented.

【0042】

In the present invention, the semiconductor substrate includes a silicon substrate, a III-V compound semiconductor substrate such as GaAs, InP, and GaN, and a II-VI compound semiconductor substrate such as ZnSe. The present invention is particularly suitable for use in processing a silicon substrate. This is because the present invention is excellent in the removal performance of ruthenium-based metals, and therefore, when applied to a silicon substrate in which deterioration of element performance due to diffusion of ruthenium in the substrate is a problem, a more remarkable effect can be obtained.

【0043】

In the present invention, as a method for removing a ruthenium-based metal using a removing liquid, it is possible to adopt a method in which a semiconductor substrate is held substantially horizontally and rotated, and a first removing liquid is sprayed on a predetermined portion of the semiconductor substrate. preferable. By doing so, the removal performance of the ruthenium-based metal is remarkably improved, the temperature dependence of the removal performance is reduced, and the ruthenium-based metal can be sufficiently removed even at room temperature. Therefore, it is not necessary to heat the chemical solution, and it is possible to simplify ancillary equipment for cleaning and to obtain an advantage that the life of the chemical solution is extended.

【0044】

Further, in the present invention, when the ruthenium-based metal is removed by the removing liquid, if a gas or liquid is sprayed on the surface of the semiconductor substrate having the element forming region, it is possible to prevent the removing liquid from sneaking into the element forming region, and the device can be prevented. It is possible to prevent damage to the ruthenium film formed on the portion.

【0045】

Next, an example of the treatment procedure after the ruthenium film is formed in the present invention will be described with reference to FIG. First, the ruthenium film forming step 30 is performed by the CVD method or the like. Next, the brush scrub cleaning step 31 is performed. As a result, when the ruthenium film forming process is completed, particle-like contaminants 52 such as ruthenium adhere to the back surface of the semiconductor substrate 50 and the peripheral portion of the front surface (element forming surface) (FIG. 12). By performing brush scrub cleaning, this contaminant 52 can be efficiently removed. In particular, since it is difficult to remove the contaminant 52 adhering to the edge portion of the ruthenium film 51 in the peripheral portion on the element forming surface side, brush scrub cleaning is effective.

【0046】

For example, as shown in FIG. 11, the brush scrub cleaning is performed by dropping the cleaning liquid on the front surface and the back surface of the semiconductor substrate 42 while rotating the semiconductor substrate 42 in a state where the semiconductor substrate 42 is sandwiched between the pair of brushes 41. In addition to the roll-type brush shown in the figure, a disc-type brush may be used. As a method of supplying the cleaning liquid, a method of dropping onto a brush or a method of dropping onto a wafer in the vicinity of the brush can be used. Alternatively, the method of supplying the inside of the brush may be used.

【0047】

As the cleaning liquid used in the brush scrub cleaning step 31, pure water, aqueous ammonia, electrolytic cathode water, dissolved hydrogen water, or the like can be used, and additives such as a surfactant may be added as appropriate. Here, the electrolytic cathode water refers to a liquid generated on the cathode side when pure water or water containing a small amount (0.5% by weight or less) of ammonium ions is electrolyzed. A two-tank electrolysis device is generally used as a generator for obtaining electrolytic cathode water (P.277, etc., 4th edition of the Electrochemical Handbook published in 1985). The hydrogen dissolved liquid is an aqueous solution in which hydrogen is dissolved in pure water or water containing a small amount (0.5% by weight or less) of ammonium ions. Bubbling or the like is used as a method for dissolving hydrogen.

【0048】

After the brush scrub cleaning step 31, the removal treatment step 32 with the removing liquid is performed. As the removing liquid, the above-mentioned one can be used. For example, a solution obtained by mixing a dicerium nitrate salt and an acid such as nitric acid is used. As a result, the ruthenium-based metal adhering to the back surface of the semiconductor substrate and the peripheral portion of the front surface (element forming surface) is removed. At the stage of performing this removal treatment, the particulate ruthenium has already been removed by the brush scrub cleaning step 31 prior to the removal process. Therefore, in this removal treatment step, the ruthenium-based metal adhering to the film is mainly removed. As described above, by using the brush scrub cleaning step 31 and the removal treatment step 32 with the removing liquid in combination, the particle-like and film-like ruthenium-based metals are efficiently removed.

【0049】

Next, the pure water rinsing step 33 is performed. That is, water is sprayed on the surface of the semiconductor substrate having the element forming region to wash it with water. As a result, the precipitate of the second cerium nitrate salt can be removed. It is preferable that this step is performed by a spin cleaning method from the viewpoint of removal efficiency.

【0050】

Next, the treatment step 34 of the removal liquid residue with the cleaning liquid is performed. As the cleaning liquid used here, it is preferable to use a hydrofluoric acid-containing liquid as described above. By this treatment, the residue of the removal liquid such as the dicerium nitrate salt is removed.

【0051】

Subsequently, the pure water rinsing step 35 is performed. When the treatment with the cleaning solution in the previous step is performed, the dicerium nitrate dissolves in the cleaning solution. However, if the cleaning liquid in which the second cerium nitrate is dissolved remains, the second cerium nitrate may be precipitated after drying. Therefore, it is desirable to rinse with pure water. By performing this step, the cleanliness of the semiconductor substrate can be further improved.

【0052】

After that, the semiconductor substrate is dried by nitrogen blow or the like, and the cleaning process is completed.

【0053】

The process described above is an example of a preferable cleaning process, but the brush scrub cleaning step 31 and the pure water rinsing steps 33 and 35 may be omitted as appropriate.

【0054】

Next, a preferred embodiment of the present invention will be described with reference to FIGS. 1 to 4 by taking a DRAM capacitor manufacturing process as an example. In the present embodiment, a capacitor having a structure in which a lower electrode film, a capacitive insulating film, and an upper electrode film are laminated is formed in a recess provided in the insulating film on the semiconductor substrate.

【0055】

First, as shown in FIG. 3A, after forming a MOS transistor including a source / drain diffusion region on the silicon substrate 1 (not shown), an interlayer insulating film 2 is formed on the entire surface of the silicon substrate 1. Next, a contact plug 4 is formed on a diffusion region (not shown). Polysilicon, tungsten, or the like can be used as the embedding material for the contact plug 4. After forming the plug, the entire surface of the substrate is flattened, and the interlayer insulating film 3 is formed on the flat surface.

【0056】

Next, dry etching is performed to form holes reaching the contact plug 4 in the interlayer insulating film 3 (FIG. 3 (b)). The cross section of the hole is preferably elliptical or the like. In this case, for example, the dimensions are set to about 0.2 μm on the minor axis and about 0.4 μm on the major axis.

【0057】

Subsequently, the adhesive film 5 is formed on the entire surface of the substrate (Fig. 3 (c)). The adhesive film 5 is, for example, a film in which Ti and TiN are laminated in this order, and is formed by a sputtering method, a CVD method, or the like.

【0058】

Next, a lower electrode film 6 made of ruthenium is formed on the entire surface of the substrate (Fig. 4 (a)). By using ruthenium as the electrode material, it is possible to effectively prevent a decrease in capacity due to oxidation of the electrode material, and it is possible to reduce the manufacturing cost. As a ruthenium film forming method, a sputtering method, a CVD method, or the like can be used, of which the CVD method is preferable. This is because the CVD method is most suitable for uniformly forming the ruthenium thin film with good coverage in the narrow pores shown in FIG. 4 (a). When the CVD method is used, for example, bis- (ethylcyclopentadienyl) ruthenium can be used as the raw material gas.

【0059】

Next, in order to remove the ruthenium-based metal adhering to the region other than the element forming region of the silicon substrate, a treatment using a removing liquid is performed. When the lower electrode film 6 made of ruthenium is formed by the CVD method, ruthenium 6'attaches to the end face and the back surface of the semiconductor substrate 10 as shown in FIG. Here, the silicon substrate 10 of FIG. 1 corresponds to the state after the end of the process of FIG. 4 (b), and represents the one in which each film is formed on the silicon substrate 1 of FIG.

【0060】

Ruthenium 6'is then partially oxidized to ruthenium oxide. If the semiconductor substrate 10 is sent to the transport system in a state where the ruthenium-based metal made of ruthenium oxide, ruthenium-based metal 6'or the like is attached, cross contamination of the film forming apparatus occurs. In addition, ruthenium-based metals tend to adversely affect device characteristics. In order to prevent such a situation, in the present embodiment, a treatment using a removing liquid is performed.

【0061】

The removal liquid is selected from the group consisting of (a) chloric acid, perchloric acid, iodiic acid, perioic acid, salt containing bromion oxide, salt containing manganese oxide ion and salt containing tetravalent cerium ion. Alternatively, one containing two or more compounds and one or two or more acids selected from the group consisting of (b) nitrate, acetic acid, iodic acid and chloric acid is used. As the acid, it is preferable to use one or more acids selected from the group consisting of nitric acid, perchloric acid and acetic acid. By using such a removing liquid, as described above, the ruthenium-based metal can be effectively removed, and the reattachment of the removed ruthenium-based metal can be effectively prevented.

【0062】

The purpose of this removing liquid is to remove ruthenium-based metals adhering to regions other than the device forming region. Therefore, when performing the removal treatment, it is desirable to prevent the removal liquid from adhering to the device forming region. A method of performing such processing will be described below with reference to FIGS. 5 and 6.

【0063】

FIG. 5 shows an example of the spin cleaning method, in which gas is blown onto the surface of the semiconductor substrate (device forming surface) to prevent the removing liquid from adhering to the device forming region. While rotating the silicon substrate 10, the removing liquid is dropped on the back surface of the substrate while spraying a gas such as nitrogen on the surface of the substrate. By spraying gas, the removal liquid that wraps around the end face is controlled to protect the element forming surface. As the gas, an inert gas such as nitrogen can be used.

【0064】

FIG. 6 shows an example of the spin cleaning method, in which a liquid is sprayed on the surface (element forming surface) of the silicon substrate 10 to prevent the removing liquid from adhering to the element forming region. While rotating the silicon substrate 10, the removing liquid is sprayed from the front surface nozzle 21 and the end surface nozzle 23, and the liquid is sprayed from the back surface nozzle 22 on the back surface. This prevents the removing liquid from wrapping around to the device forming region. As the liquid to be sprayed from the back surface nozzle 22, a liquid that does not damage the element forming region is used, and for example, pure water or the like is used.

【0065】

Using the above method, the ruthenium-based metal removal treatment with the removal liquid is performed.

【0066】

After the treatment with the removing liquid, the step of removing the residue of the removing liquid with the cleaning liquid may be carried out. When the removal treatment as described above is performed, the second cerium nitrate salt may be precipitated and remain on the semiconductor substrate 10. By cleaning and removing this, cross contamination between devices and between wafers can be more effectively prevented, the yield can be improved, and the reliability of the device can be further improved. In this case, it is preferable to use a hydrofluoric acid-containing liquid as the cleaning liquid. This is because the second cerium nitrate salt can be efficiently dissolved and removed, and the reattachment of the removed second cerium nitrate salt can be prevented.

【0067】

Subsequently, unnecessary parts of the adhesion film 5 and the lower electrode film 6 are removed by etchback or chemical mechanical polishing (CMP). The removed state is shown in Fig. 4 (b). By aligning the adhesion film 5 and the lower electrode film 6 at the same height as the interlayer insulating film 3 in this way, it is possible to prevent the electrodes of other adjacent capacitors from coming into contact with the lower electrode film 6 in the drawing.

【0068】

Next, Ta on the entire surface of the board₂O₅A capacitive insulating film 7 made of ruthenium and an upper electrode film 8 made of ruthenium are formed in this order (Fig. 4 (c)).

【0069】

The capacitive insulating film 7 can be formed by, for example, a CVD method using pentaethoxytantalum and oxygen as main raw materials. The dielectric material constituting the capacitive insulating film 7 is Ta.₂O₅Besides, BST (Ba_xSr_1-xTiO₃), PZT (PbZr)_xTi_1-xO₃), PLZT (Pb)_1-yLa_yZr_xTi_1-xO₃), SrBi₂Ta₂O₉Perovskite-based materials such as the above can be used. The method for forming these capacitive insulating films is not particularly limited, but a CVD method, a sol-gel method, a sputtering method, or the like can be used.

【0070】

After forming the upper electrode film, the ruthenium-based metal is removed again. The state of the substrate immediately before performing this removal process is as shown in FIG. 2 (a) or FIG. 2 (b). The capacitive insulating film 7 and the upper electrode film 8 are placed on the silicon substrate 10 on the end face and the back surface of the substrate. Is also in a laminated state. As the removal liquid, as described above, from (a) chloric acid, perchloric acid, iodiic acid, perioic acid, salt containing bromion oxide, salt containing manganese oxide ion and salt containing tetravalent cerium ion. Those containing one or more compounds selected from the group consisting of (b) nitric acid, acetic acid, iodic acid, and chloric acid and one or more acids selected from the group consisting of nitric acid, acetic acid, iodic acid, and chloric acid are used. Preferably, nitric acid or acetic acid is used as the component (b). By using such a removing liquid, as described above, the ruthenium-based metal can be effectively removed, and the reattachment of the removed ruthenium-based metal can be effectively prevented.

【0071】

After the treatment with the removing liquid, a step of removing the residue of the removing liquid with a cleaning liquid may be carried out. As the cleaning liquid, it is preferable to use a hydrofluoric acid-containing liquid. Here, if a hydrofluoric acid aqueous solution of preferably 20% by mass or more is used as the cleaning liquid, Ta adhering to the end face and the back surface of the silicon substrate₂O₅And ruthenium-based metals can be removed at the same time.

【0072】

After that, dry etching is performed to separate the capacitive insulating film 7 and the upper electrode film 8 into chip units. As described above, a capacitor composed of the adhesion film 5, the lower electrode film 6, the capacitive insulating film 7, and the upper electrode film 8 is formed.

【0073】

In the present embodiment, the treatment with the ruthenium-based metal removing liquid is performed twice, after the formation of the lower electrode and after the formation of the upper electrode. This is most preferable, but the ruthenium-based metal may be removed only after the upper electrode is formed.

【0074】

Further, in the present embodiment, the cleaning treatment of the removal liquid residue is performed twice, after the ruthenium-based metal removal treatment after the formation of the lower electrode and after the ruthenium-based metal removal treatment after the formation of the upper electrode. This is most preferable, but the cleaning may be performed only after the formation of the upper electrode or only after the formation of the lower electrode.

【0075】

In the present embodiment, both the lower electrode film 6 and the upper electrode film 8 are ruthenium films, but only one of them may be a ruthenium film. Examples of the electrode other than ruthenium in this case include a platinum film, a laminated film of an iridium film and an iridium oxide film, and the like. Further, the thickness of each film constituting the capacitor is appropriately set according to the diameter of the recesses in FIGS. 3 to 4. For example, when the diameter of the recess is about 0.2 μm, the adhesive film 5 can be about 5 to 30 nm, the lower electrode film 6 and the upper electrode film 8 can be about 20 to 50 nm, and the capacitive insulating film 7 can be about 5 to 20 nm. ..

【0076】

Further, there is no particular limitation on the form of the capacitor to which the present invention can be applied. In the present embodiment, the capacitor is formed in the concave portion provided in the insulating film on the semiconductor substrate, but a convex portion may be provided in the insulating film and the capacitor may be formed in this portion. In this case, the shape of the capacitor is a so-called cylinder type. In addition to these forms, it can be applied to various types of capacitors such as a planar type, a stack type, and a fin type.

【0077】

Needless to say, the present invention can be suitably applied not only to DRAM and FeRAM but also to SOCs and the like in which these and logic devices are mixedly mounted.

【0078】

[Example]

Example 1 A sample was prepared by cutting a ruthenium film formed on a silicon substrate (thickness 50 nm) into a chip of about 2 cm square. This sample was immersed in a removal solution consisting of 30% by mass of dicerium ammonium nitrate, 10% by mass of nitric acid, and water residue, and left to stand until the membrane almost disappeared. The temperature of the removal liquid was set in 4 steps of 30 ° C, 40 ° C, 50 ° C and 60 ° C, and the ruthenium dissolution rate at each temperature was measured. The results are shown in Table 1. The unit of dissolution rate in the table is nm / min.

【0079】

[table 1]

<img file="JP2001237389A_D0001.tif" />【0080】

Comparative example 1 An attempt was made to perform the same evaluation as in Example 1 assuming that the removal liquid consisted of 10% by mass of cerium ammonium nitrate and water residue, but it could not be used for evaluation because it became cloudy when the removal liquid was prepared.

【0081】

Comparative example 2 An attempt was made to perform the same evaluation as in Example 1 assuming that the removal liquid consisted of 30% by mass of ammonium dicerium nitrate, 5% by mass of hydrochloric acid, and water residue, but it foamed during the preparation of the removal liquid, so it could be used for evaluation. There wasn't.

【0082】

Comparative example 3 An attempt was made to perform the same evaluation as in Example 1 assuming that the removal liquid consisted of 30% by mass of dicerium ammonium nitrate, 5% by mass of sulfuric acid, and water residue, but a precipitate was generated during the preparation of the removal liquid, so it was used for evaluation. I couldn't.

【0083】

Example 2 A sample was prepared by depositing ruthenium on a silicon substrate using the CVD method (film thickness 50 nm). This sample was spin-washed with a removal solution consisting of 30% by mass of dicerium ammonium nitrate, 5% by mass of nitric acid, and water residue, and the dissolution rate of the ruthenium film was evaluated. The temperature of the removal liquid during cleaning was set in three stages of 30 ° C, 45 ° C and 60 ° C. The time until the ruthenium film completely disappeared was measured, and the dissolution rate was calculated from this time. The results are shown in Fig. 8. Comparing the results in Fig. 8 with the results in Table 1, it can be seen that the dissolution capacity of the removal liquid is significantly increased by using the spin cleaning method. Further, since a sufficient removing ability can be obtained even at room temperature, a device for heating the removing liquid becomes unnecessary, and the manufacturing cost can be reduced.

【0084】

In the DRAM manufacturing process, the film thickness of the ruthenium film is usually set to 50 nm or less. At this time, the ruthenium film on the back surface of the substrate is also 50 nm or less. On the other hand, the cleaning time for spin cleaning is preferably 60 seconds or less due to the demand for process efficiency. From the above, the removal liquid is required to have the ability to remove ruthenium having a film thickness of about 50 nm by spin cleaning within 60 seconds (dissolution rate 50 nm / min). From the results shown in the figure, it can be seen that the removal liquid used in this example shows a dissolution rate of 150 nm / min or more at any temperature, and has sufficient removal performance in practical use.

【0085】

Example 3 A sample was prepared by depositing ruthenium on the surface of a silicon substrate using the CVD method (film thickness 50 nm). Along with this film formation, a large amount of ruthenium-based metals (ruthenium and ruthenium oxide) adhere to the back surface of the substrate, and ruthenium contamination occurs.

【0086】

The effect of applying the removal solution on this ruthenium contamination was evaluated. As the removing liquid, 30% by mass of dicerium ammonium nitrate, 5% by mass of nitric acid, and water residue were used, and spin cleaning was used. The conditions for spin cleaning are as follows. Rotation speed: 300 rpm Cleaning time: 40 seconds Removal liquid temperature: 45 ° C The washed substrate was rinsed with pure water and dried by nitrogen blowing.

【0087】

The amount of ruthenium-based metal adhering to the back surface of the substrate before and after cleaning was measured as follows. The amount of ruthenium-based metal was measured by analysis by HF vapor decomposition-ICP-MS method (inductively coupled plasma-mass spectrum). The results are shown in Fig. 9. As can be seen from the figure, a remarkable ruthenium-based metal removal effect can be obtained by performing the removal treatment by a spin cleaning method using a removal liquid having a specific composition.

【0088】

Example 4 After forming ruthenium on a silicon substrate by the CVD method (film thickness 50 nm), spin cleaning was performed using a removing solution consisting of 30% by mass of dicerium ammonium nitrate, 5% by mass of nitric acid, and water residue. The substrate temperature was 60 ° C. and the cleaning time was 20 seconds. This substrate was rinsed with pure water, spin-dried, and then the amount of cerium adhered was measured. As a result, 460 x 10¹⁰atoms / cm²Met.

【0089】

The substrate was spin-cleaned using the cleaning solutions shown in Table 2. The content of each component was expressed as a value of mass% with respect to the entire cleaning solution. The washing time was 20 seconds. Then, it was rinsed with pure water, dried, and the amount of cerium adhered was measured. The results are shown in Table 2. The amount of cerium adhered was measured by using ICP-MS as in Example 3.

【0090】

[Table 2]

<img file="JP2001237389A_D0002.tif" />【0091】

Example 5 An example in which the present invention is applied to the capacitor forming process will be described.

【0092】

First, as shown in FIG. 3A, after forming a MOS transistor including a source / drain diffusion region on the silicon substrate 1 (not shown), an interlayer insulating film 2 made of silicon oxide is formed on the entire surface of the silicon substrate 1. Then, a contact plug 4 was formed on a diffusion region (not shown). Next, dry etching was performed to form a hole having an elliptical cross section with an inner diameter of 0.2 μm × 0.4 μm reaching the contact plug 4 (Fig. 3 (b)). Subsequently, an adhesive film 5 (total film thickness 10 nm) in which Ti and TiN were laminated in this order was formed on the entire surface of the substrate (Fig. 3 (c)).

【0093】

Next, a lower electrode film 6 (thickness 30 nm) made of ruthenium was formed on the entire surface of the substrate (Fig. 4 (a)). The film formation method was the CVD method, and bis- (ethylcyclopentadienyl) ruthenium was used as the raw material gas.

【0094】

Next, in order to remove the ruthenium-based metal adhering to the region other than the element forming region of the silicon substrate, a treatment using a removing liquid was performed. The composition of the removal solution is shown below. Second cerium ammonium nitrate 30% by mass Nitric acid 5% by mass Water balance The ruthenium-based metal was removed by spin cleaning, and the removal liquid was dropped on the back surface by spraying nitrogen gas on the front surface (element forming surface) while rotating the substrate. At this time, the temperature of the removing liquid was set to 30 ° C, and the washing time was set to 40 seconds.

【0095】

After the removal treatment, a pure water rinse was performed, and the residue of the removal liquid was removed by spin washing with a 40% aqueous solution of hydrofluoric acid. The cleaning time was 20 seconds, and the cleaning temperature was room temperature (about 25 ° C).

【0096】

Next, on the whole surface, Ta₂O₅A capacitive insulating film 7 (film thickness 10 nm) made of ruthenium and an upper electrode film 8 (film thickness 30 nm) made of ruthenium were formed in this order (Fig. 4 (c)). The capacitive insulating film 7 was formed by a CVD method using pentaethoxytantalum and oxygen as main raw materials. Next, dry etching was performed to separate the capacitive insulating film 7 and the upper electrode film 8 into chip units.

【0097】

Subsequently, in order to remove the ruthenium-based metal adhering to the region other than the element forming region of the silicon substrate, the treatment using the removing liquid was performed again. The removal liquid used was the same as that described above. Then, spin washing was performed using a 40% aqueous solution of hydrofluoric acid in the same manner as described above to remove the residue of the removal liquid. The cleaning time was 20 seconds, and the cleaning temperature was room temperature (about 25 ° C). Ta adhering to the end face and back surface of the silicon substrate by this treatment₂O₅And ruthenium-based metals can be removed at the same time.

【0098】

As described above, a capacitor composed of the adhesion film 5, the lower electrode film 6, the capacitive insulating film 7, and the upper electrode film 8 was formed (FIG. 4 (c)).

【0099】

The above-mentioned method for manufacturing a semiconductor device has a good yield, and the quality of the obtained semiconductor device is also excellent.

【0100】

Example 6 A semiconductor device was manufactured in the same manner as in Example 5 except that the residue of the removal liquid was washed only once after the ruthenium-based metal removal treatment after the formation of the upper electrode.

【0101】

The method for manufacturing the semiconductor device of this embodiment had a good yield, and the quality of the obtained semiconductor device was also excellent.

【0102】

[Effect of the invention]

As described above, according to the method for manufacturing a semiconductor device of the present invention, the ruthenium-based metal can be sufficiently dissolved and removed because the treatment is performed using a removing solution containing a dicerium nitrate salt and an acid. Moreover, it is possible to effectively prevent the reattachment of the removed ruthenium-based metal. Therefore, it can be suitably applied to processes such as DRAM, which have strict requirements for pollution prevention.

【0103】

Further, in the present invention, if the cleaning treatment is performed with a hydrofluoric acid-containing liquid or the like after the treatment with the removing liquid, the residual of the removing liquid can be effectively prevented, and a higher level of pollution prevention can be realized. ..

[Simple explanation of drawings]

[Figure 1]

It is a figure which shows the appearance of the silicon substrate after the film formation of the upper electrode.

[Figure 2]

It is a figure which shows the appearance of the silicon substrate after the lower electrode film formation.

[Fig. 3]

It is a process sectional view which shows the example which applied this invention to a capacitor manufacturing process.

[Fig. 4]

It is a process sectional view which shows the example which applied this invention to a capacitor manufacturing process.

[Fig. 5]

It is a figure for demonstrating the method of removing a ruthenium-based metal using a removal liquid.

[Fig. 6]

It is a figure for demonstrating the method of removing a ruthenium-based metal using a removal liquid.

[Fig. 7]

It is a graph which shows the etching rate of the tantalum oxide film.

[Fig. 8]

It is a figure which shows the ruthenium dissolution rate at the time of spin washing using the removal liquid containing 2 cerium ammonium nitrate and nitric acid.

[Fig. 9]

It is a figure which shows the removal effect of the ruthenium-based metal by this invention.

[Fig. 10]

It is a figure which shows an example of the processing procedure after the ruthenium film film formation in this invention.

[Fig. 11]

It is a figure for demonstrating brush scrub cleaning.

[Fig. 12]

It is a figure which shows the state of the peripheral part of the semiconductor substrate after the ruthenium film film formation.

[Explanation of symbols]

1 Silicon substrate 2 interlayer insulating film 3 interlayer insulating film 4 contact plug 5 Adhesive membrane 6 Lower electrode membrane 6'Ruthenium 7 Capacitive insulating film 8 Upper electrode membrane 10 Silicon substrate 11 Board mount 21 Surface nozzle 22 Back nozzle 23 End face nozzle 30 Ruthenium film film formation process 31 Brush scrub cleaning process 32 Removal process with removal liquid 33 Pure water rinse process 34 Treatment process of removal liquid residue with cleaning liquid 35 Pure water rinse process 41 brush 42 Semiconductor substrate 50 semiconductor substrate 51 Ruthenium film 52 Particle-like contaminants