Method of manufacturing capacitor of 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 capacitor of a semiconductor device, and more specifically, to a method for manufacturing a capacitor of a semiconductor device capable of sufficiently securing a charging capacity required for the semiconductor device.

【0002】

[Conventional technology]

Currently, in order to achieve high integration of semiconductor devices, research and development on reduction of cell area and reduction of operating voltage are being actively carried out.

【0003】

The area of capacitors decreases rapidly with the progress of high integration. However, the charge capacity required for the operation of the storage element must be 25 fF / cell or more in order to prevent the occurrence of soft errors and the shortening of the refresh time, despite the decrease in cell area. is there.

【0004】

Therefore, various methods have been proposed so far in order to secure a sufficient capacity of a DRAM capacitor. For example, a method has been proposed in which a sufficient capacitor capacity is secured by increasing the area of the capacitor or reducing the thickness of the dielectric film by changing the normal cylinder structure.

【0005】

Recently, instead of the conventionally used silicon oxide, a dielectric film having a NO (Nitride-Oxide) or ONO (Oxide-Nitride-Oxide) structure is formed, or a high capacitance (dielectric constant; Ta that can secure ε: 20 ~ 25)₂O₅Or BST (BaSrTiO₃) Etc., research is underway to replace the dielectric film made of silicon oxide.

【0006】

However, a capacitor having a NO dielectric film has a limit in securing the capacity required for a next-generation memory of 256 M or more, so a next-generation dielectric material such as Ta₂O₅Research and development of dielectrics is underway.

【0007】

However, the Ta₂O₅Since the thin film has an unstable stoichiometry ratio, substituted Ta atoms due to the difference in composition ratio between Ta and O are inevitably present in the thin film.

【0008】

Also, Ta₂O₅When forming the dielectric film, Ta₂O₅Organic compound Ta (OC) which is a precursor of₂H₅)₅And O₂(Or N₂O) By reacting with gas, carbon atoms, which are impurities, and carbon compounds (C, CH)₄, C₂H₄Etc.) and water is formed.

【0009】

As a result, Ta₂O₅Oxygen vacancies existing in the thin film and carbon atoms, ions and radicals existing as impurities increase the leakage current of the capacitor and deteriorate the dielectric properties.

【0010】

Ta like this₂O₅Impurities in the thin film are low temperature heat treated (eg Plasma N)₂O or UV-O₃Although it can be removed by performing the treatment) two or three times, this heat treatment step is complicated. In addition, Ta₂O₅Due to the low oxidation resistance of the thin film, this step has the disadvantage that oxidation of the lower electrode occurs.

【0011】

[Problems to be Solved by the Invention]

Therefore, it is a main object of the present invention to provide a method for manufacturing a capacitor of a semiconductor device which has excellent electrical characteristics and can secure a high capacity by solving various problems of the prior art. To do.

【0012】

Further, the present invention omits the manufacturing process for increasing the cross-sectional area of the lower electrode required to secure a high capacity of the capacitor, and reduces the number of unit processes and shortens the process time. It is also an object of the present invention to provide a method for manufacturing a capacitor of a semiconductor device, which can reduce the production cost.

【0013】

[Means for solving problems]

The first method for manufacturing a capacitor of a semiconductor device according to the present invention is a step of forming a lower electrode on a lower structure of a semiconductor substrate, and after forming an amorphous TaON thin film on the lower electrode, NH₃Perform the heat treatment process in the atmosphere and Ta₃N₅The stage of forming the dielectric film and the Ta₃N₅It is characterized by including a step of forming an upper electrode on a dielectric film.

【0014】

Further, the second method for manufacturing a capacitor of a semiconductor device according to the present invention is a step of forming a lower electrode on a lower structure of a semiconductor substrate, and after forming an amorphous TaON thin film on the lower electrode, 600 to 950. ° C temperature and NH₃Perform the heat treatment process in the atmosphere and Ta₃N₅The stage of forming the dielectric film and the Ta₃N₅The stage of annealing the dielectric film and the Ta₃N₅It is characterized by including a step of forming an upper electrode on a dielectric film.

【0015】

Further, the third method for manufacturing a capacitor of a semiconductor device according to the present invention includes a stage of forming a lower electrode on a lower structure of a semiconductor substrate and NH.₃After nitriding in the atmosphere and forming an amorphous TaON thin film on the lower electrode, the temperature and NH are 600 to 950 ° C.₃Perform the heat treatment process in the atmosphere and Ta₃N₅The stage of forming the dielectric film and the Ta₃N₅The stage of annealing the dielectric film and the Ta₃N₅It is characterized by including a step of forming an upper electrode on a dielectric film.

【0016】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a method for manufacturing a capacitor of a semiconductor device according to the present invention will be described in detail with reference to the accompanying drawings.

【0017】

1 to 4 show Ta with a high dielectric constant according to the present invention.₃N₅It is sectional drawing which shows a series of steps for manufacturing the capacitor of the semiconductor device provided with the dielectric thin film. In the method for manufacturing a capacitor of a semiconductor device according to the present invention, although not shown, a predetermined circuit element or circuit element such as a gate electrode, a source / drain, etc. is first formed on the upper surface of an active region of a silicon substrate 10 as a semiconductor substrate according to a conventional method. (Not shown) is formed.

【0018】

Thereafter, as shown in FIG. 1, silicon entire surface USG (Undoped Silicate Glass) of emission substrate 10, BPSG (Boro Phospho Silicate Glass ) and was deposited on selected materials from SiON, chemical mechanical polishing the surface (Chemical Mechanical The interlayer insulating film 20 is formed by polishing in the polishing) step.

【0019】

Then, in order to secure a desired cross-sectional area of the capacitor in contact with the relevant active region of the silicon substrate 10, a part of the interlayer insulating film 20 is selectively removed by an exposure and development step using photolithography. Form a contact hole (not shown).

【0020】

Then, a conductive substance such as doped polysilicon or amorphous doped polysilicon is deposited in the contact hole, and then the vapor-deposited conductive substance is selectively removed by an exposure and development process using photolithography. The lower electrode 30 is formed on the corresponding portion of the interlayer insulating film 20 in which the contact hole is formed. At this time, each of the lower electrodes 30 formed by the method of the present invention has a stack structure.

【0021】

The structure of the lower electrode 30 can be formed by selecting any one of a stack shape, a cylinder shape, a fin shape, and a stack cylinder shape.

【0022】

Then, as shown in FIG. 2, after depositing an amorphous TaON thin film on the upper surface of the lower electrode 30, NH₃By subjecting to the heat treatment process in the atmosphere, Ta₃N₅The dielectric film 32 is formed.

【0023】

At this time, in the vapor deposition step of the amorphous TaON thin film, the low-pressure chemical vapor phase maintained at a temperature of about 300 to 600 ° C (preferably about 350 to 550 ° C, more preferably about 370 to 540 ° C). Ta (OC) as a precursor of an organometallic compound in a vapor deposition chamber₂H₅)₅Or Ta (N (CH)₃)₂)₅After vaporizing by the chemical vapor deposition method, NH₃It is preferable to react with gas.

【0024】

Further, the chemical vapor of the Ta component (vapor of the Ta compound) used in the vapor deposition process of the amorphous TaON thin film is obtained by the following process.

【0025】

First, liquid Ta (OC) with a purity of 99.999% or higher₂H₅)₅Or Ta (N (CH)₃)₂)₅Is maintained at a temperature of about 150 ° C to 300 ° C (preferably about 160 to 250 ° C, more preferably about 170 to 200 ° C) through a mass flow controller or an evaporator. A fixed amount of about 300 to 1000 mg / min (preferably about 320 to 800 mg / min, more preferably about 330 to 700 mg / min) is supplied to the evaporation tube.

【0026】

At this time, the Ta (OC)₂H₅)₅Or Ta (N (CH)₃)₂)₅The evaporator containing the orifice or nozzle used to completely evaporate and the supply pipe that serves as the flow path for Ta steam are always maintained in the temperature range of 150 to 200 ° C to prevent condensation of Ta steam. To do. A predetermined amount of Ta vapor supplied into the low-pressure chemical vapor deposition chamber is a predetermined amount of NH.₃The surface reacts with the reaction gas (5 to 500 sccm) at a pressure of 100 torr or less to form an amorphous TaON thin film.

【0027】

Also, NH₃The heat treatment step performed in the atmosphere is carried out in the temperature range of 600 to 950 ° C for crystallization of the amorphous TaON thin film. This heat treatment step is performed using a rapid thermal process or a constant pressure / normal pressure electric furnace.

【0028】

Then, as shown in FIG. 3, the NH₃Ta heat treated in the atmosphere₃N₅A subsequent heat treatment (annealing) step is performed on the dielectric film 32, and the Ta₃N₅A homogeneous oxide film 34 is further formed on the surface of the dielectric film 32.

【0029】

The subsequent annealing step is O₂Or N₂Performed in an O atmosphere using a plasma or rapid heat treatment step, or UV-O₃Or O₃Conduct in an atmosphere. By such an annealing process, Ta₃N₅Since the N content in the dielectric film 32 can be adjusted, various characteristics of the capacitor related to the leakage current or the breakdown voltage can be improved.

【0030】

Then, as shown in FIG. 4, the Ta₃N₅By depositing a conductive substance such as doped polysilicon on the upper surface of the dielectric film 32 and patterning it to form the upper electrode 36, Ta according to the illustrated embodiment₃N₅Complete the manufacturing process of a high capacity capacitor with a dielectric film.

【0031】

In the manufacturing process of a capacitor of a semiconductor device according to an embodiment of the present invention, Ta₃N₅Prior to the formation of the dielectric film 32, a dry cleaning step using HF vapor or a wet cleaning step using an HF solution was carried out in-situ or ex-situ on the surface of the lower electrode 30. Natural oxide films and particles that may be present can be removed.

【0032】

In addition, the Ta₃N₅When forming the dielectric film 32, the lower electrode and Ta₃N₅The surface of the lower electrode 30 is nitrided in order to prevent the formation of a natural oxide film with the dielectric film.

【0033】

The nitriding process includes NH.₃It is preferable to perform plasma treatment in an atmosphere for 1 to 5 minutes. By this nitriding treatment, it is possible to prevent the interface between the lower electrode and the high dielectric film from being oxidized, so that a good quality dielectric film can be obtained.

【0034】

5 and 6 show the case where the amorphous TaON dielectric film is formed in the capacitor of the present invention (Fig. 5), and the case where the amorphous TaON dielectric film is NH.₃Ta after annealing in the atmosphere₃O₅It is a graph comparing the concentrations of various elements existing in two dielectric films when a dielectric film is formed (Fig. 6).

【0035】

As is clear from the comparison between Fig. 5 and Fig. 6, after depositing the amorphous TaON thin film, NH₃By performing annealing in an atmosphere, the O component in the amorphous TaON thin film can be reduced and the activated N component can be increased. Thus, Ta is a ferroelectric substance having a dielectric constant of about 100 (ε) or more.₃N₅Since a film can be obtained, a capacitor having a significantly increased capacitance can be obtained.

【0036】

FIG. 7 shows Ta according to another embodiment of the present invention.₃N₅It is sectional drawing which shows the capacitor structure of the semiconductor device which has a dielectric film.

【0037】

Ta according to another embodiment of the present invention₃N₅In the method for manufacturing a capacitor of a semiconductor device having a dielectric film, as shown in FIG. 7, the interlayer insulating film 50 and the lower electrode are first placed on a silicon substrate 40 by the same method as in the manufacturing steps of FIGS. 1 and 2. 60 and Ta₃N₅The dielectric film 62 is sequentially formed.

【0038】

After that, the Ta₃N₅A metal layer 65 acting as a conduction barrier and a doped polysilicon layer 66 acting as a buffer are sequentially laminated on the upper surface of the dielectric film 62 to have a MIS (Metal-Insulator-Silicon) structure. It constitutes the upper electrode.

【0039】

In another embodiment of the present invention, each of the upper electrode and the lower electrode is TiN, Ti, TaN, W, WN, Wsi, Ru, RuO instead of doped polysilicon.₂, Ir, Pt, and any other metal-based material.

【0040】

Therefore, when such a metal-based material is used as the upper electrode and the lower electrode, Ta of the entire structure of MIM (Metal-Insulator-Metal)₃N₅Capacitors can be formed.

【0041】

FIG. 8 shows Ta according to still another embodiment of the present invention.₃N₅It is sectional drawing which shows the capacitor structure of the semiconductor device which has a dielectric film.

【0042】

In the method for manufacturing a capacitor according to still another embodiment of the present invention, first, an interlayer insulating film 80 and a lower electrode 90 are formed on a silicon substrate 70 by the same method as in the manufacturing steps of FIGS. 1 and 2.

【0043】

In this embodiment, the upper surface of the lower electrode 90 has an HSG (Hemi Spherical Grain) morphology in which polysilicon is grown in a convex hemispherical shape. Next, Ta is applied to the upper surface of the lower electrode 90 by the same method as in the manufacturing process of FIG.₃N₅The dielectric film 92 is formed.

【0044】

Then, the Ta₃N₅By forming the upper electrode 96 on the dielectric film 92, the production of the capacitor is completed.

【0045】

[Effect of the invention]

According to the method for manufacturing a capacitor of a semiconductor device according to the present invention, the following effects are achieved.

【0046】

In the manufacturing process of the capacitor dielectric film, after depositing amorphous TaON, this is NH.₃By annealing in the atmosphere, the oxygen component in the initially deposited amorphous TaON is completely replaced by the activated nitrogen component, so that a high dielectric having a dielectric constant of about 100 (ε) or more. Ta₃N₅A membrane can be obtained.

【0047】

Therefore, Ta in the present invention₃N₅The dielectric is the conventional Ta₂O₅Since it has a dielectric constant four times or more higher than that of a capacitor, it can replace the dielectric of a capacitor of a next-generation semiconductor memory device of 256M class or higher.

【0048】

In addition, Ta in the present invention₃N₅Since the dielectric has a high dielectric constant, Ta of the capacitor of the existing MIS structure₂O₅Compared to the dielectric film, it has the effect of reducing the thickness of the oxide film (Tox) of the dielectric film to about 25 Å or less.

【0049】

Further, in the present invention, even when a lower electrode having a simple stack structure is used without increasing the area of the lower electrode, Ta with a high dielectric constant is used.₃N₅Since the desired high capacity can be obtained from the film, it is possible to manufacture a capacitor for a highly integrated semiconductor device.

【0050】

Further, Ta in the present invention₃N₅Since the dielectric film has a high dielectric constant, the manufacturing process for increasing the cross-sectional area of the lower electrode can be omitted. Therefore, the effect of reducing the number of unit processes and shortening the manufacturing process time is achieved.

[Simple explanation of drawings]

[Figure 1]

High Dielectric Ta according to an embodiment of the present invention₃N₅It is a part of the process drawing for explaining the manufacturing method of the capacitor of the semiconductor device which has.

[Figure 2]

High Dielectric Ta according to an embodiment of the present invention₃N₅It is a part of the process drawing for demonstrating the manufacturing method of the capacitor of the semiconductor device which has, and is the drawing which shows the stage following FIG.

[Fig. 3]

High Dielectric Ta according to an embodiment of the present invention₃N₅It is a part of the process drawing for demonstrating the manufacturing method of the capacitor of the semiconductor device which has, and is the drawing which shows the stage following FIG.

[Fig. 4]

High Dielectric Ta according to an embodiment of the present invention₃N₅It is a part of the process drawing for demonstrating the manufacturing method of the capacitor of the semiconductor device which has, and is the drawing which shows the final stage following FIG.

[Fig. 5]

It is a graph which shows the concentration of various elements existing in the formed amorphous TaON dielectric film in a capacitor.

[Fig. 6]

In the capacitor according to the manufacturing method of the present invention, the amorphous TaON dielectric film is NH.₃Ta by annealing in the atmosphere₃N₅It is a graph which shows the concentration of various elements existing in a dielectric film when it is changed to a dielectric film.

[Fig. 7]

It is sectional drawing of the semiconductor element for demonstrating the manufacturing method of the capacitor of the semiconductor apparatus by another Example of this invention.

[Fig. 8]

It is sectional drawing of the semiconductor element for demonstrating the manufacturing method of the capacitor of the semiconductor apparatus by still another Example of this invention.

[Explanation of symbols]

10 Silicon substrate 20 interlayer insulating film 30 Lower electrode 32 Ta₃N₅Dielectric film 34 Oxidation film 36 Upper electrode 40 Silicon substrate 50 interlayer insulating film 60 Lower electrode 62 Ta₃N₅Dielectric film 65 metal layer 66 polysilicon layer 70 Silicon substrate 80 interlayer insulating film 90 Lower electrode 92 Ta₃N₅Dielectric film 96 Upper electrode