Plasma CVD apparatus

The present invention relates to a plasma CVD apparatus for forming a thin film such as a semiconductor, a liquid crystal, or an optical disk, and particularly, a plasma using a reaction chamber composed of a conductor chamber such as a metal. It relates to a CVD device.

[0002] As a method for forming a thin film on a substrate, a sputtering method using a sputtering phenomenon, a vacuum vapor deposition method using a vapor deposition phenomenon, and a plasma using low temperature gas decomposition by plasma as a method for forming a thin film on a substrate. Known methods include a CVD method, a thermal CVD method using thermal decomposition of gas, and a CVD (Chemical Vaper Deposition) method such as an optical CVD method in which gas is decomposed by the energy of short-wavelength light or ultraviolet rays. In addition, many of these combined technologies and applied technologies have been researched and developed, and have been used in actual manufacturing methods.

[0003] Among the thin film forming techniques as described above, in the plasma CVD method, a direct current or a high frequency voltage is applied to the reaction gas in a reduced pressure state, the reaction gas is decomposed and generated by glow discharge, and a film is deposited on the substrate. The method. Thin film formation by this method can decompose gas at a relatively low temperature (500 ° C or less) by plasma energy such as high electron temperature eV of plasma, and films with various compositions by changing the type of gas. Since it can be formed with high purity by using vacuum, it is carried out in various places such as a semiconductor field, a liquid crystal field, an optical disk field, and a magnetic disk field.

[0004] Until a while ago, when forming a thin film on a substrate, it was well known to use a batch-type plasma CVD apparatus that processes a large number of substrates at one time. However, in the case of batch processing, since the characteristics of the thin film change slightly for each substrate even when the processing is performed at the same time, it is difficult to meet the demand for a highly accurate thin film due to the large repetitive accuracy and variations between the substrates. Further, in order to process a plurality of boards (about 4 to 8 boards) at the same time, a board holder for mounting the boards and moving the boards together is required. When the film formation of the substrate is completed, the substrate holder goes out of the plasma CVD apparatus, mounts the next substrate, and is processed in the apparatus again. Therefore, a so-called peeling phenomenon has occurred in which the film adhering to the substrate holder is peeled off due to repeated vacuum heating and atmospheric pressure and room temperature.

[0005] For the above reasons, batch processing has recently been almost generally discontinued not only in plasma CVD equipment but also in thin film deposition etching, and single-wafer type equipment has come to be used instead.

[0006] In the case of the single-wafer type, the substrate is processed one by one in order without using a substrate holder that moves together with the substrate, and only the substrate is moved. A conventional plasma CVD apparatus using this method will be described with reference to FIGS. 2 and 3.

[0007] Although FIG. 2 shows a top view of the single-wafer plasma CVD apparatus, the chamber shown in 201 is a load chamber for loading and unloading the substrate. Chambers 202-206 become reaction chambers.

[0008] A plurality of substrates to be processed are set in the load chamber 201 by a cassette or the like. After setting the substrate in the load chamber 201, the pressure is reduced. When the pressure is reduced to a sufficient pressure, the gate valve 210 between the load chamber 201 and the common chamber 207 opens. The board transporting means 208 installed in the common chamber 207 moves one of the plurality of boards set in the cassette in the load chamber 201 from the load chamber 201 to the common chamber 207. The moved state is shown in FIG. 2, and the substrate 209 moves to the reaction chamber forming the thin film. The substrate 209 is moved to the reaction chamber by the substrate transport means 208.

[0009] The common chamber 207, the reaction chambers 202 to 206, and the load chamber 201 are connected by a gate valve 210, and the gate valve of the chamber is opened when the substrate 209 is taken in and out of each chamber. Further, the load chamber 201, the reaction chambers 202 to 206, and the common chamber 207 are each evacuated by the vacuum exhaust means. There are various types of thin film formation, such as a laminated type (P layer, I layer, N layer, etc.) such as an amorphous solar cell, and a single layer type such as a semiconductor protective film. Therefore, the treatment in each chamber differs depending on the type of film to be formed, the laminated type, and the like.

[0010] FIG. 3 shows a cross-sectional view of the common chamber 207 and the reaction chamber 204 cut by AA in FIG.

[0011] An electrode 211 and a substrate holder 212 are installed in the reaction chamber 204. The electrode 211 is connected to the power supply 213, and the substrate holder 212 and the reaction chamber 202 are grounded. Further, the substrate holder 212 is provided with a heater for heating the substrate (not shown). The substrate holder 212 exists in the reaction chamber 204 and is not transported together with the substrate 210, unlike the batch type described above.

[0012] Then, the substrate 209 is installed on the substrate holder 212 from the common chamber 207, and the reaction gas is introduced from the introduction pipe 214. Then, a voltage is applied to the electrode 211 to generate plasma in the space indicated by 215, and a thin film is formed on the substrate. The substrate 210 on which the thin film is formed is moved from the reaction chamber 204 to the common chamber 207 again by the transport means 208 in the common chamber 207, and is moved to the next processing. Then, another substrate is carried into the reaction chamber 204, and the thin film forming process is performed in the same manner. In these series of processes, only the substrate is moved.

[0013] Reference numerals 217 and 218 are vacuum exhaust means, and keep the common chamber and the reaction chamber under reduced pressure, respectively. Exhaust means are usually provided independently in each room.

[0014] The reaction chambers 203 to 206 also have the same structure as the reaction chamber 202, and each reaction chamber is used properly depending on the type and thickness of the film to be formed. For example, a silicon film is formed in the reaction chamber 202, a silicon oxide film is formed in the reaction chamber 203, and a silicon nitride film is formed in the reaction chamber 204. Alternatively, the same process of laminating the silicon nitride film, the silicon film, and the silicon nitride film is performed in each reaction chamber to improve the overall throughput, that is, productivity.

[0015] Of course, by determining the film type to be formed for each chamber in order to suppress impurities extremely, each film can be sequentially formed without mixing impurities, and the production efficiency can be improved. Is also possible.

[0016] Among the configurations of the plasma CVD apparatus described above, the constituent material of each chamber is mainly composed of a conductor such as metal, for example, aluminum or stainless steel. In addition to metal, it is known to use insulators such as quartz and alumina as the material of the chamber of the plasma CVD apparatus, but it is not used in the single-wafer type apparatus. This is due to the following reasons.

[0017] In the case of a single-wafer plasma CVD apparatus, it is necessary to provide a plurality of reaction chambers in order to process the substrates one by one to improve productivity. Providing a plurality of reaction chambers inevitably increases the size of the plasma CVD apparatus. Therefore, a strong material is required. In the case of materials such as quartz and alumina, they are hard but easily damaged. The material of the vacuum chamber is so delicate that even if there is a scratch on the hair, it cannot be kept in a vacuum. Further, in order to increase the size and complexity, a material that is easy to process and has high processing accuracy is required. Moreover, the one that is as cheap as possible is better. At present, when looking for a material that satisfies the above conditions, a reaction chamber or the like is often created using a metal material such as aluminum, an aluminum alloy, or stainless steel.

[0018] [Problem to be Solved by the Invention] When a thin film is formed by the single-wafer plasma CVD apparatus as described above, the reaction gas to be decomposed spreads not only on the substrate but also in the entire reaction chamber. In thermal CVD or the like, a film is formed not only on the substrate but also in the entire reaction chamber in order to heat the entire reaction chamber. In the case of the plasma CVD method, it is ideal that the film is formed only on the substrate on which plasma is generated, but the film is also formed on a place other than the substrate. That is, since the plasma 215 extends beyond the vicinity of the substrate 209, a film is also formed on the exposed portion such as the surface of the electrode 211 and the inner wall of the reaction chamber.

[0019] This is because not only the plasma is generated between the electrode and the substrate holder, but also the plasma is generated only between the electrode and the substrate holder because the reaction chamber is made of a metal material, that is, a conductor. The cause is that it spreads further than that. Unlike the substrate holder of a batch-type plasma CVD device, the film formed on other than the substrate does not come off immediately because it does not come into contact with the atmosphere or repeat the room temperature-high temperature cycle.

[0020] However, as the film formation is continued, it still begins to peel off. Then, this film becomes particles or flakes and falls on the substrate or the bottom of the reaction chamber. Therefore, it is necessary to periodically remove the film formed and deposited on a place other than the substrate after the film is formed several times before the film starts to peel off. The removal is performed by introducing an etching gas into the reaction chamber and generating plasma to etch the film.

[0021] In the worst case, unnecessary discharge such as arc discharge occurs between the inner wall of the reaction chamber near the electrode 211, for example, in the space shown by 216 in FIG. 3, and the film is formed on the inner wall. The film thickness may become thicker, and as a result, it may be easily peeled off.

The inner wall of the reaction chamber makes its surface relatively smooth. This is smoothed to suppress degassing from the wall to reduce impurities and to prevent arc discharge. Actually, it is made into a state close to a mirror surface by buffing # 400 or higher, electrolytic polishing, composite electrolytic polishing, etc. The film adhered to this smooth surface has poor adhesion and is easily peeled off. The peeled membrane becomes particles or flakes and falls into the reaction chamber and deposits. These deposits, which are once peeled off and become particles, flakes, etc., are more difficult to remove by plasma etching than the film-like deposits adhering to the inner wall during film formation. In reality, it cannot be completely removed. It is not theoretically known why it cannot be completely removed, but as a rule of thumb, film-like objects can be etched, but solid bodies such as particles and flakes cannot be completely etched.

[0023] Therefore, it is necessary to clean the reaction chamber long before the film adhering to the substrate other than the substrate is peeled off. Therefore, the ratio of production contribution decreases due to the balance between the film formation time that contributes to production and the etching time that does not contribute to production in the operating time of the apparatus. If the surface of the reaction chamber is made uneven, the ease of peeling of the film can be reduced, but the surface area becomes large and it takes time to evacuate, and the amount of degassing from the uneven surface with increased surface area increases. It deviates from the original purpose of forming a tall thin film.

[0024] The present invention solves the above problems. That is, while maintaining the size of the device and ease of processing, it prevents unnecessary discharge such as arc discharge, reduces the amount of particles due to the peeling of the film adhering to the reaction chamber, and contributes to the production of the operating time of the device. The purpose is to increase the proportion of.

[Means for Solving the Problems] The invention disclosed in the present specification faces a conductive reaction chamber maintained in a reduced pressure state, an electrode to which electrical energy is supplied to the reaction chamber, and the electrode. A plasma CVD apparatus having at least a substrate holder capable of holding a substrate, a gas system for supplying gas to the reaction chamber, and an exhaust system for exhausting the reaction chamber, wherein the electrode, the substrate holder, and an insulator are provided. It is characterized by generating plasma in a space surrounded by. Further, in the above configuration, the insulator is made of alumina.

[0026] Other inventions include a carry-in chamber, a common chamber and a reaction chamber made of a conductor held in a reduced pressure state, a transport means installed in the common chamber for moving a substrate into and out of the reaction chamber, and the above-mentioned. An electrode to which electrical energy is supplied, a substrate holder for holding the substrate facing the electrode, a gas system for supplying gas to the reaction chamber, and an exhaust system for exhausting the reaction chamber are provided in the reaction chamber. A plasma CVD apparatus having at least a space surrounded by the electrode, the substrate holder, and an insulator, wherein the insulator serves as a stopper when the substrate holder stops operating. To do. Further, in the above configuration, the insulator is made of alumina.

[Embodiments of the Invention] FIG. 1 shows the plasma CVD apparatus of the present invention. FIG. 1 shows a cross-sectional view of a common chamber 107 and one of the reaction chambers 104. The entire CVD apparatus includes a carry-in chamber, a common chamber, and a plurality of reaction chambers, as in the single-wafer type of FIG. 2, for example. It consists of.

[0028] The common chamber 107 and the reaction chamber 104 are made of a metallic material for the reasons described above. And it is connected by the gate valve 110. In the reaction chamber 104, the electrode 111 and the substrate holder 112 are installed. The electrode 111 is connected to the power supply 113, and the substrate holder 112 and the reaction chamber 104 are grounded. Further, although not shown, the substrate holder 112 is provided with a heater for heating the substrate.

[0029] Reference numerals 117 and 118 are vacuum exhaust means, and keep the common chamber and the reaction chamber in a reduced pressure state, respectively. Reference numeral 114 is a tube for introducing the reaction gas into the reaction chamber 104. In the case of FIG. 1, the electrode 111 has a network shape, and the reaction gas is introduced into the reaction chamber 104 from the electrode 111 through the introduction pipe 114.

[0030] Then, as shown in FIG. 1, an insulator 120, for example, alumina, is attached. When a voltage is applied to the electrode 111 in this state, the generated plasma 115 is surrounded by the electrode 111, the substrate holder 112, and the insulator 120. Therefore, the insulator 120 can prevent unnecessary discharge such as an arc discharge from occurring between the electrode 111 and the reaction chamber 104 without spreading the plasma from between the electrode and the substrate holder.

Further, the transfer means 108 is used to move the substrate 109 in and out of the reaction chamber 104 from the common chamber 107. At this time, the substrate holder 112 is located below as shown by the dotted line 112'in FIG. By doing so, the substrate 109 can be placed by the transport means 108 so that the insulator 120 does not become an obstacle.

Further, when forming a film on the substrate 109, the substrate holder 112 is raised so that the plasma is surrounded by the electrodes 111, the substrate holder 112, and the insulator 120. At this time, the insulator 120 serves as a stopper so that the substrate holder 112 stops. In this way, the substrate holder 112 does not rise too much and the substrate 109 does not come into contact with the electrode 111, which increases safety in the automation of the device.

[0033] As described above, since the plasma 115 does not spread, the plasma density increases, and unnecessary discharge such as arc discharge does not occur, so that the film forming speed of the film formed on the substrate 109 increases. Further, at the time of film formation, a film is mainly formed on the surface of the electrode 111 and the surface of the insulator 120. However, since the surface of the insulator 120 is uneven, the formed film has better adhesion than metal, and becomes particles or flakes that are difficult to remove. Therefore, the amount of particles and flakes can be reduced, and the reaction chamber can be easily cleaned by plasma etching. Further, since the coating film is mainly formed on the surface of the electrode 111 and the surface of the insulator 120 and hardly formed on the reaction chamber itself, the area to be cleaned is narrowed. Further, as described above, the plasma density does not spread because the plasma does not spread.

[0034] For the above reasons, the cleaning time can be shortened and the ratio of the production contribution of the operating time of the apparatus can be increased.

[Example] (Example 1) In this embodiment, the single-wafer plasma CVD apparatus of this embodiment will be described with an example of forming a silicon nitride film on a substrate. FIG. 4 shows a cross-sectional view of the reaction chamber of the plasma CVD apparatus of this example.

[0036] In FIG. 4, an electrode 402 and a substrate holder 403 are installed in the reaction chamber 401. The electrode 402 has a network shape, and the reaction gas passes through the introduction tube 409 and is introduced into the reaction chamber from the network electrode 402. Further, insulators such as alumina 406 and 407 are arranged between the space 405 between the electrode 402 and the substrate holder 404 and the reaction chamber 401.

[0037] The portion shown in 410 is made of quartz. Quartz 410 is installed for the following reasons. The reaction gas passes between the insulators 406 and 407 and comes into contact with the walls of the reaction chamber. Therefore, a film is also formed on the surface of the wall of the aluminum reaction chamber that comes into contact with the surface. Since this film is formed on aluminum, it becomes particles. Quartz 410 is installed to prevent this. Further, 411 is connected to a turbo molecular pump and a rotary pump in this order by an exhaust pipe to keep the reaction chamber in a depressurized state. In this example, the reaction chamber is first set to 0.3 torr.

Next, with the distance between the substrate holder 403 and the electrode 402 set to 65 mm, the glass substrate 404 is installed on the substrate holder 403 by a transport means (not shown). In this state, the insulators 406 and 407 do not interfere with the installation of the substrate 404. Then, the substrate holder is raised so that the distance between the substrate holder 403 and the electrode 402 is 15 to 25 mm, and the state shown in the figure is obtained. In this embodiment, it is set to 20 mm.

[0039] As described above, the board holder 403 is designed to move up and down, and when the board 404 is placed, the board holder 403 and the insulator 407 are lowered so as to be sufficiently separated from each other so that the board can be placed smoothly. , When a film is formed on this substrate, it rises as shown in FIG. The position of the substrate (distance between the substrate and the electrodes) can be adjusted. The insulator 407 also acts as a stopper when the board holder 403 is raised, increasing the safety when the board holder 403 is raised.

[0040] Further, although not shown, a heater for heating the substrate 404 is provided in the substrate holder 403.

[0041] Then, the silane, ammonia, a mixed gas of nitrogen and hydrogen, with a silane / ammonia / nitrogen / hydrogen = 30 / 0.99 / 250/100 SCCM, net of electrostatic introduced into the reaction chamber from the electrode 402. Then, under the condition of a total pressure of 0.2 to 1 torr, an RF of 100 to 300 W is applied to the electrode 402 from a power source (not shown) to generate plasma in the space 405. The substrate temperature at this time is 250 to 400 ° C. In this example, the total pressure is 0.5 torr, the RF is 200 W, and the substrate temperature is 325 ° C. Also, since the size of the electrode is 200 mmφ, the voltage applied to the electrode is about 0.3 to 1 W / cm.²Is. The plasma generated at this time does not spread due to the insulators 406 and 407, and no arc discharge or the like occurs between the wall of the reaction chamber and the electrode.

[0042] The silicon nitride film is formed as described above. The film formation rate of the silicon nitride film under the conditions of this example is about 1400 Å / min. Since the film formation rate in the case of film formation with a conventional plasma CVD apparatus is about 300 Å / min, it can be seen that the film formation rate is significantly increased.

[0043] It is better to make the insulators 406 and 407 parallel to each other as much as possible to obtain a film having good film quality. Especially when you want to obtain a good film quality, it is advisable to make this interval a little wider. In this embodiment, it is 3 to 5 mm.

[0044] The silicon nitride film is also formed on the surfaces of the insulators 406 and 407 on the space 405 side. However, the surface of the reaction chamber is hardly coated. Since these films are formed on the surface of alumina, they are hard to fall off as particles and the like, and the amount of particles and the like in the reaction chamber is reduced.

[0045] Then, a film is formed to some extent, and after a film is formed to some extent on the surfaces of the insulators 406 and 407, cleaning is performed. In this embodiment, cleaning is performed when the film adheres to the insulator by about 10 to 20 μm.

[0046] As the etching gas, a mixed gas of nitrogen vaporized nitrogen and nitrogen is used. In the reaction chamber, a mixed gas is flowed with nitrogen vaporized / nitrogen = 80/300 SCCM to bring the total pressure to about 0.2 to 1 torr. In this example, 0.5 torr is used. The distance between the substrate holder 403 and the electrodes is approximately 50 mm. This is because the silicon nitride film is also attached to the respective surfaces between the insulators 408 and 407. To etch these, lower the substrate holder and leave a gap between the insulators 407 and 408.

Then, a high frequency of about 100 to 200 W is applied to the electrode to perform cleaning. In this embodiment, 200 W is used. In this case, the etching is completed in about 40 minutes. In the past, it took 5 to 6 hours, but the etching time is reduced to about 1/8 to 1/9.

[0048] As described above, the surface of an insulator such as alumina is more uneven than the surface of the inner wall of the reaction chamber, that is, the metal surface. Therefore, the formed coating film is hard to peel off, the amount of particles and the like falling on the substrate and the bottom of the reaction chamber can be reduced, and cleaning becomes easy. Further, since the insulators 406 and 407 are arranged, it is possible to prevent the plasma from spreading. Therefore, unnecessary discharge such as arc discharge does not occur between the electrode and the inner wall of the reaction chamber, and the plasma density is high. Further, since the coating film is hardly formed on the wall of the reaction chamber and is mainly coated on the insulator, electrodes, etc., the area that must be cleaned is small.

[0049] From the above, cleaning can be simplified, the time can be shortened, and the ratio of the production contribution of the operating time of the apparatus can be increased.

(Example 2) A case where a silicon oxide film is formed on a substrate by using the apparatus shown in FIG. 4 will be described.

In the apparatus shown in FIG. 4, the reaction gas is introduced into the reaction chamber at TEOS / oxygen = 10/300 SCCM to bring the total pressure to approximately 0.5-1 torr. In this example, 0.75 torr is used.

[0052] Further, the substrate temperature is 300 to 400 ° C, the RF is 150 to 300 W, the distance between the substrate and the electrode is 10 to 15 mm, and a silicon oxide film is formed on the substrate. In this embodiment, the substrate temperature is 350 ° C, the RF is 200 W, and the distance is 13.5 mm.

[0053] The film forming speed at this time is about 2000 to 2300 Å / min, which is about three times the conventional film forming speed.

[0054] Further, cleaning is performed in the same manner as in Example 1. However, the total pressure in the reaction chamber shall be approximately 1 torr, and the distance between the substrate holder 403 and the electrode shall be 50 to 60 mm.

[0055] Also in this embodiment, the etching time is significantly shortened to 20 to 40 minutes.

[Effect of the Invention] As described above, in the plasma CVD apparatus, it is possible to obtain an apparatus in which an extra discharge such as an arc discharge does not occur while using a conductive material which is advantageous for upsizing and ease of processing. it can. Further, since the film does not adhere to the inner wall of the reaction chamber but adheres to the surface of the insulator, the amount of particles and the like in the reaction chamber can be reduced. Further, the cleaning time can be shortened, and the ratio of the production contribution of the operating time of the device can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS [Fig. 1] Cross-sectional view of a common chamber and a reaction chamber of the plasma CVD apparatus of the present invention [Fig. 2] Top view of a single-wafer plasma CVD apparatus [Fig. 3] Cross-sectional view of common chamber and reaction chamber [Fig. 4] Cross-sectional view of reaction chamber of the embodiment of the plasma CVD apparatus of the present invention [Explanation of reference numerals] 104 Reaction chamber 107 Common chamber 108 Substrate transfer means 109 Substrate 110 Gate valve 111 Electrode 112 , 112'Substrate holder 113 Power supply 114 Reaction gas introduction tube 115 Plasma space 117, 118 Vacuum exhaust means 120 Insulation 401 Reaction chamber 402 Electrode 403 Board holder 404 Board 405 Plasma space 406, 407, 408 Insulator 409 Introductory pipe 410 Quartz 411 Exhaust pipe