JP4296371B2 - Polycrystalline silicon film forming method and film forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a polycrystalline silicon film and a film forming apparatus therefor, and more particularly to a method for forming a polycrystalline silicon film directly on a large area substrate and a film forming apparatus therefor.
[0002]
[Prior art]
In recent years, a liquid crystal display device in which a driving circuit is formed on a glass substrate has been realized by forming a polycrystalline silicon (poly-Si) thin film on an inexpensive glass substrate and using this to form a thin film transistor (TFT). It is becoming. In general, a poly-Si thin film is formed by indirectly depositing an amorphous silicon (a-Si) thin film and then crystallizing the a-Si thin film by thermal annealing or excimer laser annealing to obtain a poly-Si thin film. A typical forming method is used. In the case of a poly-Si thin film formed by the indirect formation method, the field effect mobility of the TFT is 100 cm ² / V · s or more, and particularly when the laser annealing method is used, the value is 300 cm ² / V · s or more There is also. However, in the case of this indirect formation method, an extra crystallization step is required as compared with a method of directly forming a poly-Si thin film, which causes a problem that costs increase and throughput decreases.
[0003]
On the other hand, when a poly-Si thin film is directly formed by plasma CVD (PECVD) or low pressure CVD (LPCVD), there is a problem that the Si crystal grain size is small and the field effect mobility of the film is low. Therefore, the poly-Si thin film obtained by the direct method is difficult to use as an active layer even though it is used as a gate wiring in an actual TFT.
[0004]
For example, as disclosed by Kono et al. In Materials Research Society Symposium Proceedings 283: 629-634 (Mat. Res. Soc. Symp. Proc., Vol. 283, pp. 629-634) It is possible to directly form a poly-Si thin film by PECVD using SiH ₄ / SiF ₄ gas, but the field effect mobility of a TFT using the poly-Si thin film as an active layer is 44 cm ² / V at the maximum.・ Stays at s. Here, the reason why SiF ₄ gas containing fluorine (F) which is a halogen element is used is that halogen promotes crystallization.
[0005]
In general, in film formation by PECVD, deposition in which atoms in the gas phase are adsorbed on the substrate or the film surface that has already been formed coexists with etching in which atoms on the film surface that have already been formed are separated in the gas phase. To do. As a role of the halogen element, it is considered that crystallization is promoted by an etching effect of an already deposited film and an atomic rearrangement effect. However, it is difficult to obtain a film with high mobility because the defect density of the crystal structure is large and the crystal grain size is small.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to solve the problems of the above-described conventional example, and the object thereof is to enable a large particle size on a large-area substrate by making it possible to independently control the reactions of deposition and etching. It is to be able to directly form a high mobility polycrystalline silicon thin film.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, a polycrystalline silicon film is formed by applying a high frequency to form a plasma by introducing a silicide gas containing halogen and a silicide gas not containing halogen into the chamber. In this method, a silicide gas containing no halogen is introduced into the chamber when the applied high frequency is low, and the silicide gas containing halogen is introduced into the chamber when the applied high frequency is high. A method for forming a polycrystalline silicon film is provided.
[0008]
In order to achieve the above object, according to the present invention, a polycrystalline silicon film is formed by introducing a silicide gas containing halogen and a silicide gas not containing halogen into the chamber to form plasma. In the method, a halogen-containing silicide gas and a halogen-free silicide gas are introduced into different reaction chambers, and are applied to form plasma in the reaction chamber into which the halogen-containing silicide gas is introduced. Provided is a method for forming a polycrystalline silicon film, characterized in that a high-frequency frequency is high and a high-frequency frequency applied to form plasma is low in a reaction chamber into which a silicide gas containing no halogen is introduced. Is done.
[0009]
In order to achieve the above object, according to the present invention, a polycrystalline silicon film is formed by introducing a silicide gas containing halogen and a silicide gas not containing halogen into the chamber to form plasma. In the method, a plasma generation chamber and a substrate processing chamber are formed in the chamber with a first mesh electrode interposed therebetween, and a silicide gas containing halogen is introduced into the plasma generation chamber. Provides a method for forming a polycrystalline silicon film, wherein a silicide gas containing no halogen is introduced.
[0010]
In order to achieve the above object, according to the present invention, an apparatus for forming a polycrystalline silicon film by introducing a silicide gas containing halogen and a silicide gas not containing halogen to form plasma, A polycrystalline silicon film characterized in that two high-frequency oscillators for low / high-frequency and high / high-frequency are applied to form plasma, and the two high-frequency oscillators are switched and applied alternately A film forming apparatus is provided.
[0011]
In order to achieve the above object, according to the present invention, a first reaction chamber into which a halogen-containing silicide gas is introduced and a second reaction chamber into which a halogen-free silicide gas is introduced are provided. provided, a respective reaction chamber apparatus for forming the formed polycrystalline silicon film a plasma at, one wall surface of each of the reaction chambers Ri frequency application electrode der with a gas ejection port, and The high-frequency application electrodes constituting the wall surfaces of the reaction chambers are provided so as to be intertwined with each other, and are provided in parallel with the substrate stage on which the substrate is placed. A membrane device is provided.
[0012]
In order to achieve the above object, according to the present invention, a plasma generation chamber having a high frequency application electrode into which a halogen-containing silicide gas is introduced, and a silicide gas not containing a halogen are introduced. A substrate processing chamber having a substrate stage to which a constant voltage is applied, and a first mesh electrode to which a constant voltage is applied is provided between the plasma generation chamber and the substrate processing chamber, and the substrate In the processing chamber, a second mesh electrode to which a high frequency is applied is provided in parallel with the first mesh electrode, and plasma is also formed between the second mesh electrode and the substrate stage. A polycrystalline silicon film forming apparatus is provided.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to examples.
[First embodiment]
FIG. 1 is a cross-sectional view of a parallel plate type PECVD apparatus used in the first embodiment of the present invention. In the chamber 110, a substrate stage 105 serving also as a lower electrode on which the substrate 106 is mounted, and an upper electrode 101 having a gas outlet 108 opened downward are disposed. The substrate stage 105 is grounded, and a heater 109 for heating the substrate 106 is disposed therein. The upper electrode 101 is connected to either the VHF oscillation source 102 that outputs a high frequency of 100 MHz or the rf oscillation source 103 that outputs a high frequency of 13.56 MHz via a changeover switch 104. A gas inlet 111 for introducing a reaction gas is provided on the upper electrode 101. The chamber 110 is provided with an exhaust port 107 for exhausting the gas in the chamber.
[0014]
The film forming conditions in this example are a substrate temperature of 450 ° C., a pressure of 100 Pa, and a SiH ₄ / H ₂ / SiF ₄ gas flow rate of 5/20/60 sccm. The upper electrode 101 is switched by the changeover switch 104 so that the upper electrode 101 is connected to the rf oscillation source 103 side at an interval of 20 seconds and to the VHF oscillation source 102 side at an interval of 10 seconds, and the high frequencies of 13.56 MHz and 100 MHz are 20 seconds and 10 seconds. Application was repeated at intervals of seconds. All oscillation outputs were 300 W. A poly-Si film having a total oscillation time of 180 seconds and a film thickness of 60 nm and a particle size in the film plane direction of about 85 nm was formed on the substrate 106. The particle size in the film plane direction was determined by observing the film cross section with a transmission electron microscope.
[0015]
Using this poly-Si film, the n-ch. When a TFT was produced, a mobility of 80 cm ² / V · s was obtained. In addition, when a substrate bias of −50 V was applied at the time of 100 MHz oscillation, the mobility was improved by about 5%. At this time, no significant increase in particle size was observed. Therefore, it is judged that the bias application was effective in reducing the defect density in the crystal grains.
FIG. 5 collectively shows the film forming conditions and results of each example.
[0016]
[Comparative example]
When the apparatus shown in FIG. 1 is used and the other conditions are the same, and the high frequency applied to the upper electrode is only 13.56 MHz or only 100 MHz, the particle size and mobility are 5 nm and 10 cm ² / V · s or 50 nm and 40 cm ² / V · s.
[0017]
[Second Embodiment]
Also in the second embodiment, the PECVD apparatus shown in FIG. 1 was used. In this example, the substrate temperature, pressure, oscillation output, two types of frequencies, and the application time thereof were the same as those in the first example. Here, the deposition gas is varied with the frequency, introduced from the SiH ₄ / H ₂ gas 5/20 sccm, a H ₂ / SiF ₄ gas during 100MHz applied 5/60 sccm gas inlet at 13.56MHz applied. The application time of both frequencies was 180 seconds in total, and a poly-Si film having a film thickness of 60 nm and a particle size of about 110 nm was formed on the substrate 106. Using this poly-Si film, n-ch. When a TFT was produced, a mobility of 100 cm ² / V · s was realized. Similarly to the first example, when a substrate bias of −50 V was applied in accordance with the application of 100 MHz, the mobility was improved by about 5%. At this time, no significant increase in particle size was observed. Therefore, as in the first embodiment, it is judged that the bias application was effective in reducing the defect density in the crystal grains.
[0018]
[Third embodiment]
FIG. 2A is a cross-sectional view of parallel plate type PECVD used in the third embodiment of the present invention, and FIG. 2B is a plan view of the upper electrode portion thereof. FIG. 2A corresponds to a cross-sectional view of FIG. 2B viewed along line AA. As shown in FIG. 2B, the first and second upper electrodes 201 and 202 are separated from each other by the partition 211 and formed in a mutually spiral manner. These upper electrodes are provided with a large number of gas outlets 208 for discharging gas over the entire surface. In addition, a first gas supply path 216 partitioned by a partition 211 is formed in the upper part of the first upper electrode 201, and one end of the first gas supply path is connected to the first gas introduction port 214. . Similarly, a second gas supply path 217 having one end connected to the second gas introduction port 215 is also formed on the second upper electrode 202. First and second reaction chambers 203 and 204 defined by first and second upper electrodes 201 and 202 and a partition 211 are formed below the first and second upper electrodes. Each gas supply path and each reaction chamber are connected to each other by a gas outlet 208 formed in each upper electrode. The first and second upper electrodes 201 and 202 are connected to the rf oscillation source 213 and the VHF oscillation source 212, respectively. In addition, a grounded substrate stage 205 serving also as a lower electrode is installed on the counter electrode surface of the first and second upper electrodes 201 and 202, and a substrate 206 is mounted thereon. A heater 209 for heating the substrate 206 is provided in the substrate stage 205. The gas in the chamber 210 is exhausted to the outside through the exhaust port 207.
[0019]
The substrate temperature, pressure, and oscillation output were the same as in the first example. Here, 5/20 sccm of SiH ₄ / H ₂ gas is introduced into the first reaction chamber 204 via the first gas inlet 214 and the first gas supply path 216, and the rf oscillation source is supplied to the first upper electrode 201. A high frequency of 13.56 MHz is applied by 213. 20 seconds after high-frequency application to the first upper electrode 201 was started, 5/60 sccm of H ₂ / SiF ₄ gas was introduced into the second reaction chamber 204 via the second gas inlet 215 and the second gas supply path 217. A high frequency of 100 MHz is applied to the second upper electrode 202 by the VHF oscillation source 212. When the oscillation of both oscillation sources was stopped after 140 seconds, a poly-Si film having a film thickness of 60 nm and a particle size of about 110 nm was formed on the glass substrate. Using this poly-Si film, n-ch. When a TFT was produced, a mobility of 100 cm ² / V · s was realized. Similarly to the first and second embodiments, a high mobility poly-Si film can be formed by alternately oscillating the reaction chamber 203 and the reaction chamber 204.
[0020]
[Fourth embodiment]
FIG. 3 is a cross-sectional view of a remote plasma CVD apparatus used in the fourth embodiment of the present invention. An upper electrode 301 having a first gas inlet 310 opened at the upper portion and a gas outlet 303 formed at the lower portion is connected to a high-frequency oscillation source 309. A substrate stage 304 also serving as a grounded lower electrode is installed on the counter electrode surface of the upper electrode 301, and a substrate 305 is mounted thereon. A heater 307 for heating the substrate 305 is provided in the substrate stage 304. A mesh electrode 302 that is grounded is provided near the upper electrode between the upper electrode 301 and the substrate stage 304, and a second gas introduction port 311 is provided on the chamber wall surface between the mesh electrode 302 and the substrate stage 304. ing. The gas in the chamber 308 is exhausted to the outside through the exhaust port 306.
[0021]
SiH ₄ / H ₂ gas is introduced at 10/40 sccm from the second gas inlet 311. Fifteen seconds after the start of SiH ₄ / H ₂ gas introduction, 10/80 sccm of H ₂ / SiF ₄ gas is introduced from the first gas inlet 310, and high frequency power is supplied from the high frequency oscillation source 309 to the upper electrode 301. And a mesh electrode 302 generate plasma. At this time, the oscillation frequency of the high-frequency oscillation source 309 was 13.56 MHz, the oscillation output was 200 W, the substrate temperature was 450 ° C., and the pressure was 120 Pa. When the oscillation and gas introduction were stopped after 200 seconds, a poly-Si film having a film thickness of 50 nm and a particle size of about 130 nm was formed on the glass substrate. Using this poly-Si film, n-ch. When a TFT was produced, a mobility of 100 cm ² / V · s was obtained.
[0022]
[Fifth embodiment]
FIG. 4 is a cross-sectional view of a remote plasma CVD apparatus used in the fifth embodiment of the present invention. An upper electrode 401 having a first gas inlet 412 opened at the top and a gas outlet 404 formed at the bottom is connected to the first high-frequency oscillation source 410. A substrate stage 405 also serving as a grounded lower electrode is installed on the counter electrode surface of the upper electrode 401, and a substrate 406 is mounted thereon. A heater 409 for heating the substrate 406 is provided in the substrate stage 405. An upper mesh electrode 402 that is grounded is provided near the upper electrode between the upper electrode 401 and the substrate stage 405, and is connected to the second high-frequency oscillation source 411 between the upper mesh electrode 402 and the substrate stage 405. A lower mesh electrode 403 is provided. A second gas inlet 413 is provided on the chamber wall surface between the lower mesh electrode 403 and the substrate stage 405. The gas in the chamber 408 is exhausted to the outside through the exhaust port 407.
[0023]
SiH ₄ / H ₂ gas is introduced at 5/20 sccm from the second gas inlet 413, and high frequency power is supplied from the second high frequency oscillation source 411 to generate plasma between the lower mesh electrode 403 and the substrate 406. The oscillation frequency at this time was 13.56 MHz, and the oscillation output was 150 W.
On the other hand, 10/80 sccm of H ₂ / SiF ₄ gas is simultaneously introduced from the first gas inlet 412, high frequency power is supplied from the first high frequency oscillation source 410, and plasma is generated between the upper electrode 401 and the upper mesh electrode 402. generate. The oscillation frequency at this time was 13.56 MHz, and the oscillation output was 200 W. The substrate temperature was 450 ° C. and the pressure was 120 Pa. When the oscillation and gas introduction were stopped after 200 seconds, a poly-Si film having a film thickness of 50 nm and a particle size of about 130 nm was formed on the glass substrate. Using this poly-Si film, n-ch. When a TFT was produced, a mobility of 100 cm ² / V · s was realized.
[0024]
As apparent from FIG. 5, according to the first to fifth embodiments of the present invention, the poly-Si thin film having a large particle size and high mobility can be obtained by independently controlling the reaction of deposition and etching. It became possible to form.
[0025]
The preferred embodiments of the present invention have been described above. However, the present invention is not limited to these embodiments, and appropriate modifications can be made without departing from the scope of the present invention. . For example, conditions such as the gas flow rate, film forming pressure, and oscillation output shown in the first to fifth embodiments vary depending on the substrate size, chamber volume, gas inlet position, and the like. In the first and second embodiments, two oscillation sources are prepared and switched. However, it is also possible to obtain one output from two oscillation sources by using one oscillation source. The shape of the first and second upper electrodes in the third embodiment shown in FIG. 2 may be other than a spiral shape such as an interdigit shape. In the fourth embodiment shown in FIG. 3, a high frequency of 100 MHz may be supplied from a high frequency oscillation source. Furthermore, in the fifth embodiment shown in FIG. 4, only the first high-frequency oscillation source may oscillate at 100 MHz, or both the first and second high-frequency oscillation sources may oscillate at 100 MHz. Good.
[0026]
【The invention's effect】
As described above, the method for producing a polycrystalline semiconductor thin film according to the present invention controls the reaction of deposition and etching independently, so that polycrystalline silicon having a large grain size and high mobility on a large area substrate. A thin film can be formed directly.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a parallel plate type PECVD apparatus used in first and second embodiments of the present invention.
FIG. 2 is a cross-sectional view and a plan view of a parallel plate type PECVD apparatus used in a third embodiment of the present invention.
FIG. 3 is a cross-sectional view of a remote plasma CVD apparatus used in a fourth embodiment of the present invention.
FIG. 4 is a sectional view of a remote plasma CVD apparatus used in a fifth embodiment of the present invention.
FIG. 5 is a table summarizing film forming conditions and results of the first to fifth examples of the present invention.
[Explanation of symbols]
101, 301, 401 Upper electrode 102, 212 VHF oscillation source 103, 213 rf oscillation source 104 changeover switch 105, 205, 304, 405 Substrate stage (lower electrode)
106, 206, 305, 406 Substrate 107, 207, 306, 407 Exhaust port 108, 208, 303, 404 Gas outlet 109, 209, 307, 409 Heater 110 210, 308, 408 Chamber 111 Gas inlet 201 First upper part Electrode 202 Second upper electrode 203 First reaction chamber 204 Second reaction chamber 211 Partitions 214, 310, 412 First gas inlet 215, 311, 413 Second gas inlet 216 First gas supply path 217 Second gas supply path 302 mesh electrode 309 high frequency oscillation source 402 upper mesh electrode 403 lower mesh electrode 410 first high frequency oscillation source 411 second high frequency oscillation source

Claims (13)

In a method for forming a polycrystalline silicon film by introducing a high-frequency gas to form a plasma by introducing a halogen-containing silicide gas and a halogen-free silicide gas into the chamber , the frequency of the applied high-frequency is A silicide gas containing no halogen is introduced into the chamber when the frequency is low, and a silicide gas containing halogen is introduced into the chamber when the frequency of the applied high frequency is high. Membrane method.   The method for forming a polycrystalline silicon film according to claim 1, wherein a negative substrate bias is applied to the substrate on which the film is formed when the changing frequency is on the high side.   In a method of forming a polycrystalline silicon film by introducing a halogen-containing silicide gas and a halogen-free silicide gas into a chamber to form a plasma, a halogen-containing silicide gas and a halogen-free silicide are formed. In a reaction chamber in which a gas is introduced into different reaction chambers and a silicide gas containing halogen is introduced, a high-frequency frequency applied to form plasma is introduced and a silicide gas containing no halogen is introduced. A method for forming a polycrystalline silicon film, wherein a high frequency applied to form plasma in a reaction chamber is low. The frequency of the high frequency to be applied is set so that decomposition of a silicide gas containing a halogen hardly occurs on a lower side thereof, and decomposition of a silicide gas containing a halogen easily occurs on a higher side thereof. The method for forming a polycrystalline silicon film according to any one of 1 to 3.   In a method for forming a polycrystalline silicon film by introducing a halogen-containing silicide gas and a halogen-free silicide gas into a chamber to form a plasma, the halogen-containing silicide gas is plasma-decomposed to form the plasma. A method for forming a polycrystalline silicon film, comprising thermally decomposing a silicide gas containing no hydrogen.   In a method of forming a polycrystalline silicon film by introducing a halogen-containing silicide gas and a halogen-free silicide gas into a chamber to form a plasma, a first mesh electrode is sandwiched in the chamber. A polycrystal having a plasma generation chamber and a substrate processing chamber, wherein a silicide gas containing halogen is introduced into the plasma generation chamber and a silicide gas not containing halogen is introduced into the substrate processing chamber A method for forming a silicon film. 7. The method of forming a polycrystalline silicon film according to claim 6, wherein a constant voltage is applied to the first mesh electrode. Wherein the substrate processing chamber are installed a second mesh electrode high frequency for generating plasma is applied, according to claim 6 or 7 characterized in that it also plasma is formed in the substrate processing chamber A method for forming a polycrystalline silicon film.   In an apparatus for forming a polycrystalline silicon film by introducing a halogen-containing silicide gas and a halogen-free silicide gas to form a plasma, a high-frequency oscillator applied to form the plasma has a low and high frequency. The polycrystalline silicon film forming apparatus is characterized in that two high frequency and high frequency are prepared, and two high frequencies are switched and applied alternately. There are provided a first reaction chamber into which a halogen-containing silicide gas is introduced and a second reaction chamber into which a halogen-free silicide gas is introduced. an apparatus for forming a silicon film, one wall surface of each of the reaction chambers Ri frequency application electrode der with a gas ejection port, and the high frequency application electrode which constitutes the wall of the reaction chamber, An apparatus for forming a polycrystalline silicon film, wherein the apparatus is provided so as to be intricately provided and parallel to a substrate stage on which a substrate is placed . 2. The high frequency applied to the high frequency application electrode of the first reaction chamber is higher than the high frequency applied to the high frequency application electrode of the second reaction chamber. The polycrystalline silicon film deposition apparatus according to 0. A plasma generation chamber having a high-frequency applying electrode into which a halogen-containing silicide gas is introduced; a substrate processing chamber having a substrate stage to which a constant voltage is applied, into which a halogen-free silicide gas is introduced; A first mesh electrode to which a constant voltage is applied is provided between the plasma generation chamber and the substrate processing chamber, and a second mesh electrode to which a high frequency is applied is provided in the substrate processing chamber. An apparatus for forming a polycrystalline silicon film , wherein the apparatus is provided in parallel with the first mesh electrode, and plasma is also formed between the second mesh electrode and the substrate stage . Wherein the high frequency application electrode, a polycrystalline silicon film forming apparatus according to claim 1 2, wherein a gas jet port for introducing a silicide gas into the plasma generating chamber is provided.

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