JP2008053562A - Method for forming gate insulating film, method for manufacturing semiconductor element, and apparatus thereof - Google Patents

Abstract

An object of the present invention is to reduce the manufacturing temperature of a semiconductor device.
After a buffer oxide film is formed on the substrate by irradiating the substrate with ozone gas under irradiation of ultraviolet light, polysilicon is formed on the buffer oxide film. Next, an ozone gas is applied to the polysilicon of the substrate under irradiation of ultraviolet light from the light source 14 in the oxidation treatment furnace 10 to form a gate insulating film on the polysilicon. The substrate may be irradiated with ultraviolet light to crystallize the polysilicon of the substrate and increase the grain boundary size. In a CVD processing furnace (not shown), a gate insulating film is additionally formed on the substrate by applying ozone gas to the substrate on which the gate insulating film is formed while irradiating light in the ultraviolet region. The substrate on which the gate insulating film is formed is annealed by being irradiated with light in the ultraviolet region in the oxidation treatment furnace 10 as appropriate after the electrodes are deposited.
[Selection] Figure 1

Description

  The present invention relates to a technique for manufacturing a semiconductor element exemplified by a low-temperature polysilicon TFT used in a liquid crystal display panel of a semiconductor device, and a technique for forming a gate insulating film of the semiconductor element.

  In recent years, TFT (thin film transistor) type LCD devices have been widely used as display devices. In the LCD device, TFTs are formed in a matrix on a glass substrate, and the TFTs drive liquid crystals arranged above and below the TFTs.

  The TFT is formed by laminating an insulating film or a polysilicon film on a glass substrate. In recent years, soda glass, which is cheaper than quartz glass, has been used as the glass substrate. Soda glass has a softening point as low as about 500 ° C. compared to quartz, and Na contained in the soda glass diffuses in a high temperature environment, so that a film forming technique of 400 ° C. or less is required. In addition, the quality of the produced film is required to be high quality close to that of a film formed at a high temperature.

  In recent years, as represented by a flexible information terminal (flexible PC, mobile phone), silicon device fabrication technology on an organic (flexible) substrate such as plastic (polyimide) has become important. In this case, the process temperature is 250 ° C. or lower from the heat resistant temperature of polyimide or the like. Therefore, in the future, it will be required to produce a higher quality oxide film at a lower temperature. In recent years, a method of oxidizing by placing a glass substrate in an ozone gas atmosphere at 400 ° C. (a method of manufacturing a thin film transistor device disclosed in Patent Document 1) has become the lowest temperature process. As described above, a process under a temperature condition of 250 ° C. or less has not yet been realized.

  In the process of manufacturing a TFT at a low temperature, there is a post-annealing process as a process that is difficult to be performed at a low temperature in addition to the gate insulating film process. This is a process of annealing after depositing a metal electrode after forming a gate insulating film. The annealing temperature is usually 400 ° C. to 450 ° C. in nitrogen + hydrogen gas. Lowering the annealing temperature is also an important issue.

A TFT requires many steps to complete. If a separate chamber is prepared for each process, the equipment becomes enormous, and the site area and equipment costs are burdened. Therefore, it is desirable to reduce the number of chambers by using the same chambers between processes as much as possible. Further, in the method using the mainstream plasma at present in the production of the low temperature film, there is a problem that the volume of the antenna for generating the plasma becomes very large with respect to the increase in the substrate area to be processed.
JP2003-289079

  FIG. 11 is a cross-sectional view of the TFT after the initial stage of the manufacturing process of the low-temperature polysilicon TFT. Specifically, it is a view showing a cross section of a low-temperature polysilicon TFT in a state where the process up to electrode deposition is completed. The actual TFT is subjected to fine shape processing after the vapor deposition process, but the technology according to the invention is demonstrated up to the process, and will be described with reference to FIG.

  The illustrated low-temperature polysilicon TFT comprises a substrate 111, a buffer silicon oxide film 112 formed thereon, polysilicon 113, a gate insulating film 114, and a metal electrode 115. In manufacturing this low-temperature polysilicon TFT, it is necessary to lower the manufacturing process temperature from the viewpoint of the material of the substrate and the manufacturing cost.

  That is, as a first problem, it is necessary to form the gate insulating film 114 at a low temperature.

  For forming the gate insulating film 114 under a low temperature condition, a technique using plasma or ozone is the most powerful. At present, there is an example made using ozone (low concentration), but the temperature that can be produced is 450 ° C. or more, and a sufficient film thickness is not secured. The film is hardly formed by plasma oxidation. At present, there is no technique for producing a high-quality gate insulating film 114 on the polysilicon 113 at a production temperature of 400 ° C. or lower.

  Further, it is necessary to realize a film forming speed that does not depend on the plane direction of the polysilicon 113 on which the gate insulating film 114 is formed. This is because Si crystal planes of various plane orientations are deposited on the surface of the polysilicon 113. When an oxide film is grown by using a mechanism capable of growing a film different from the plane orientation of the Si crystal, it becomes a film having a large roughness and various characteristics are deteriorated. For this reason, the conventional thermal oxidation method using oxygen is not suitable because the oxidation rate greatly depends on the crystal orientation of the substrate. Therefore, it is required to create the gate insulating film 114 that does not depend on the surface orientation of the processing substrate at a low temperature.

  Furthermore, when forming the gate insulating film 114, it is necessary to prevent damage to the underlying polysilicon 113. When stimulating from the outside in order to promote the reaction at low temperature, the underlying layer should not be damaged. This is because if the underlying polysilicon 113 is damaged, its semiconductor characteristics deteriorate.

  As a second problem, it is necessary to lower the post-annealing temperature.

  In reducing the TFT process temperature, it is necessary to lower the temperature of the post-annealing temperature as well as the manufacturing temperature of the gate insulating film 114. For example, in the process that can be performed at the lowest temperature with the current technology, the manufacturing temperature of the gate insulating film 114 is 450 ° C., and the post-annealing temperature is 450 ° C. This post-annealing temperature of 450 ° C. is this temperature even when fabricated on a silicon substrate.

  As a third problem, it is necessary to simplify and downsize the manufacturing apparatus.

  The production of TFT requires many complicated processes. Considering the production of TFTs for liquid crystals, the substrate size becomes a metric size. For this reason, if a chamber (oxidation treatment furnace) is provided for each process, a huge site area and facilities are required. Therefore, it is necessary to share the chamber for each process as much as possible. For example, in the case of the post-annealing described above, in the present technology, annealing is performed while irradiating a laser. On the other hand, if light is used in the oxidation process, if this light can be applied as it is to post-annealing, the chamber can be shared. The simplicity of the equipment can be expected. The plasma generators that are mainstream in the current low-temperature oxidation treatment technology are extremely large with respect to the processing area. The optical process for activating the polysilicon 113 is to irradiate the polysilicon 113 with light. On the other hand, the light using the light in the oxidation process is directly used for crystallization of the polysilicon 113 and the grain boundary size. If it can be applied to enlargement, it can be expected to share the chamber and simplify the equipment. Note that the plasma generators that are mainstream in the current low-temperature oxidation treatment technology are extremely large with respect to the processing area.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a method of forming a gate insulating film, a method of manufacturing a low-temperature polysilicon TFT, and an apparatus thereof that can lower the manufacturing temperature of a low-temperature polysilicon thin film transistor. .

  Accordingly, in the method of forming a gate insulating film according to the first aspect, the substrate on which the polysilicon is formed is irradiated with ultraviolet light and ozone gas is used to form the gate insulating film on the polysilicon.

  The method for forming a gate insulating film according to claim 2 is the method for forming a gate insulating film according to claim 1, wherein the polysilicon of the substrate is irradiated with light in an ultraviolet region to crystallize the polysilicon and increase a grain boundary size. It has the process to change.

  According to another aspect of the present invention, an oxidation processing apparatus stores a substrate on which polysilicon is formed. The substrate is irradiated with light in the ultraviolet region and ozone gas is provided to form a gate insulating film on the polysilicon.

  According to a fourth aspect of the present invention, there is provided an oxidation processing apparatus according to the third aspect, further comprising a light source that irradiates the light in the ultraviolet region or the light in the ultraviolet region and the visible region.

  The method of manufacturing a semiconductor device according to claim 5 includes: forming a buffer oxide film on the substrate by irradiating the substrate with ozone gas under irradiation of ultraviolet light; and forming polysilicon on the buffer oxide film; And a step of forming a gate insulating film on the polysilicon by applying ozone gas to the polysilicon of the substrate under irradiation with light in the ultraviolet region.

  The method of manufacturing a semiconductor device according to claim 6 is the method of manufacturing a semiconductor device according to claim 5, wherein the substrate is irradiated with light in an ultraviolet region to crystallize polysilicon of the substrate and increase a grain boundary size. Have

  A method for manufacturing a semiconductor device according to claim 7 is the method for manufacturing a semiconductor device according to claim 5, wherein ozone gas is applied to the substrate on which the gate insulating film is formed while irradiating ultraviolet light to the substrate. A step of additionally forming.

  A method for manufacturing a semiconductor device according to claim 8 is the method for manufacturing a semiconductor device according to any one of claims 5 to 7, wherein after the electrode is deposited on the substrate on which the gate insulating film is formed, the substrate is irradiated with light in the ultraviolet region. A step of annealing treatment under irradiation.

  According to a ninth aspect of the present invention, there is provided a method of manufacturing a semiconductor device according to any one of the fifth to eighth aspects, further comprising the step of irradiating a substrate with visible region light together with the ultraviolet region light.

  A semiconductor device manufacturing apparatus according to claim 10 includes a CVD processing furnace for forming an oxide film on a substrate by introducing ozone gas under irradiation of light in an ultraviolet region and then forming polysilicon on the oxide film of the substrate, A substrate on which polysilicon is formed is provided from a CVD processing furnace, and an oxidation processing furnace is provided that introduces ozone gas under irradiation of ultraviolet light to form a gate insulating film on the polysilicon.

  The semiconductor element manufacturing apparatus according to claim 11 is the semiconductor element manufacturing apparatus according to claim 10, wherein the oxidation furnace irradiates the substrate with light in an ultraviolet region to cause crystallization and a large grain boundary size on the substrate. Turn into.

  The semiconductor device manufacturing apparatus according to claim 12 is the semiconductor device manufacturing apparatus according to claim 10 or 11, wherein the CVD processing furnace introduces a substrate from the oxidation processing furnace, and irradiates the substrate with light in an ultraviolet region. An ozone gas is provided to additionally form a gate insulating film on the substrate.

  A semiconductor device manufacturing apparatus according to claim 13, wherein the semiconductor device manufacturing apparatus according to any one of claims 10 to 12, further comprising: a deposition processing furnace configured to deposit an electrode on the substrate on which the gate insulating film is formed, and the oxidation process. A furnace introduce | transduces a board | substrate from the said vapor deposition processing furnace, and anneal-treats this board | substrate under irradiation of the light of an ultraviolet region.

  A semiconductor element manufacturing apparatus according to claim 14 is the semiconductor element manufacturing apparatus according to any one of claims 10 to 13, wherein a first beam splitter that supplies light in the ultraviolet region to the CVD processing furnace, and the ultraviolet region And a second beam splitter for supplying the light to the first beam splitter and the oxidation treatment furnace.

  According to a fifteenth aspect of the present invention, there is provided the semiconductor element manufacturing apparatus according to any one of the tenth to fourteenth aspects, further comprising a light source that emits the light in the ultraviolet region or the light in the ultraviolet region and the visible region.

  According to the inventions of the first to fifteenth aspects, the polysilicon TFT is formed at 200 ° C. or lower by utilizing the strong oxidizing power of ozone excited by light in the ultraviolet region and the surface heating by absorption of ultraviolet light of polysilicon. Can be made. In particular, a gate insulating film can be produced at room temperature by utilizing the strong oxidizing power of the excited ozone and surface heating by absorption of ultraviolet light of polysilicon. In addition, by using light in the wavelength band used for the production of the gate insulation film, post-annealing can be performed at a later stage of the formation of the gate insulation film in the same system as the production of the gate insulation film. Can be simplified. Ozone excitation requires light having a wavelength in the 210 to 300 nm band. Light in the region of 300 nm or more does not affect ozone. Therefore, the light source that emits light in the ultraviolet region may be any light source that can emit light in the 210 to 300 nm region, and may include light of 300 nm or more. From the viewpoint of heating the surface of the processed substrate, it is desirable that it be included because the absorption coefficient of polysilicon is large even in the 300 to 600 nm wavelength band.

  Utilizing the fact that polysilicon has a high absorption coefficient in a wide frequency band, and using a local surface heating light source separately from ultraviolet light, a light source including a wavelength range of 200 to 300 nm may not directly irradiate the substrate surface. For example, the ultraviolet light may be irradiated from the horizontal direction with respect to the substrate.

  Further, the ozone concentration of the ozone gas used in the inventions of claims 1 to 15 is higher in oxidation efficiency as the ozone concentration is higher. This is because the ozone life is increased as the high-concentration ozone gas is used. This is because ozonolysis does not occur in the collision between ozone molecules. This is because the decompression process becomes possible as the higher concentration ozone gas is used. This is because the gas flow rate increases as the pressure is reduced. This is because the lifetime of the excited ozone becomes longer as the higher concentration ozone gas is used. This is because gases other than ozone gas, such as oxygen gas, deactivate the excited ozone.

Further, since the layer of buffer made of SiO ₂ using the poor thermal conductivity of SiO ₂ is local heating effect is controlled so interposed between the substrate and the polysilicon layer in the production process of the present invention, The thermal destruction of the substrate is prevented and the film forming speed is increased.

  In the annealing process according to the eighth and thirteenth inventions, the annealing temperature can be lowered by 300 ° C. or more by using light in the ultraviolet region. This is because local heating of the surface occurs due to the light irradiation. This is performed while irradiating light during annealing. In addition, the annealing gas exemplified by nitrogen, hydrogen, and the like does not absorb in this frequency band, so that intensity attenuation is unlikely to occur in the gas phase.

  As described above, according to the method for forming a gate insulating film, the method for manufacturing a semiconductor element, and these apparatuses according to the present invention, the manufacturing temperature of the semiconductor element can be lowered. In addition, the semiconductor device manufacturing apparatus can be simplified and downsized.

(Embodiment 1)
The manufacturing process of the polysilicon TFT according to this embodiment up to the electrode deposition process will be described with reference to FIG.

Process 1 (Formation of SiO ₂ film 112 for buffer)
A buffer SiO2 film 112 is deposited on the glass or plastic substrate 11 shown in FIG. Since the substrate 111 does not contain Si, it is necessary to use a CVD deposition process. Further, since the substrate 111 has a low melting point, it is necessary to perform low temperature CVD.

  A photo-excited ozone CVD process is applied to this process. That is, while irradiating UV light, a source gas made of organic silicon exemplified by HMDS (hexamethyldisilazane) and 100% ozone gas are introduced to form a CVD film. If this method is used, the film can be formed even at 200 ° C. or lower without reducing the film forming speed. In addition, a dense CVD film can be formed as compared with lightless CVD. The ozone gas includes an ozone gas generated by an ozone generator (MPOG-31002) manufactured by Meidensha.

The film thickness is controlled by the CVD film forming time. Conventionally, the buffer SiO ₂ film formed on a plastic substrate should have a certain level or more from the viewpoint of consistency with polysilicon formed thereon. In the process according to the present invention, the film thickness of the buffer SiO ₂ film 112 also plays a role of controlling the temperature rise of the surface heating due to the light irradiation in relation to performing light irradiation for oxidation on the gate insulating film.

Process 2 (deposition of polysilicon 113)
The polysilicon 3 is deposited on the buffer SiO ₂ film 112 by CVD using a source gas containing Si (for example, monosilane (SiH ₄ )). The film thickness of the polysilicon 3 is controlled by the film forming time. This CVD process may use a chamber using Process 1 CVD. This is because there are no products other than Si and H in the chamber.

Process 3 (crystallization of polysilicon 113 and increase in grain boundary size)
Since the polysilicon 3 formed in the process 2 is manufactured by low-temperature CVD at 200 ° C. or lower, the crystallinity is low and the grain boundary is small. Therefore, it is not expected to manufacture a TFT having good characteristics as it is. Since the surface of the polysilicon 113 after the process 2 contains many amorphous (amorphous) states, crystallization is necessary. It has been reported that the crystallization of the polysilicon 113 occurs when the surface is exposed to about 1200 ° C. for about 0.6 ms (S. Higashi et.al, JJAP 40 480 (2001)). . Conventionally, the surface of the polysilicon 113 is irradiated with 532 nm CW laser light as in the TFT manufacturing process disclosed in Japanese Patent Application Laid-Open No. 2003-289079 (Patent Document 1) to increase the size of crystallization and grain boundaries. Has been done. However, the irradiation area is limited to 100 um square or less. The light is condensed to obtain a strong light intensity.

  In the prior art (for example, Patent Document 1) to which the plasma oxidation method is applied, chambers with irradiation windows are separately prepared for polysilicon crystallization and grain boundary size enlargement processes and gate insulating film formation processes. Therefore, the configuration of the TFT manufacturing apparatus cannot be simplified.

  On the other hand, in the process 3, light having a wavelength in the ultraviolet region is used for crystallization of the polysilicon 113 and enlargement of the grain boundary size. This is because light of 210 to 300 nm is used in the next process 4 (excited oxidation process of ozone).

FIG. 12 is a characteristic diagram showing light absorption characteristics regarding polysilicon, amorphous silicon, and single crystal silicon. “C-Si” means single crystal silicon. “P-Si: As” means heavy doped polysilicon (polysilicon with a large grain size). “P-Si: ud” means undoped polysilicon (polysilicon with a small grain size). “A-Si” means amorphous silicon. As is apparent from this characteristic diagram, in the wavelength region of 300 nm or more, the light absorption coefficient α (cm ⁻¹ ) of amorphous silicon is one to two orders of magnitude higher than the light absorption coefficient α of single crystal silicon. In the range of 300 nm, the light absorption coefficient α of amorphous silicon and single crystal silicon is equivalent.

  Therefore, by using light having a wavelength band of 210 to 300 nm, two different processes, that is, process 3 and process 4 can be executed with the same light source and processing system. Thereby, the configuration of the TFT manufacturing apparatus can be simplified.

  As described in the next process 4, the contribution of surface heating by light absorption is important for the growth of the gate insulating film according to the present invention. For 210-300 nm light, the absorption coefficient does not change before and after activation, so when using a 210-300 nm light source, it does not matter which process order of process 3 and process 4 is performed first. On the other hand, when light having a wavelength greater than 300 nm is included, a thicker oxide film can be formed by performing process 3 after performing process 4 first.

  A light source that emits light in the 210 to 300 nm region may be of either a pulse type or a continuous oscillation type. This is because the crystallization of the polysilicon 113 and the enlargement of the grain boundary size are completed in a time of milliseconds when the necessary temperature is reached. Since the band gap is smaller than 6 eV in the polysilicon 113, it is considered that the semiconductor characteristics are not destroyed even if light of 210 to 300 nm is irradiated.

Process 4 (Formation of gate insulating film 114)
FIG. 1 is a schematic configuration diagram of an oxidation processing apparatus that oxidizes polysilicon using ozone excited by UV. The oxidation treatment apparatus 1 includes an ozone generator 11, cylinders 12 and 13, an oxidation treatment furnace 10, and light sources 14 and 15.

  The oxidation furnace 10 includes a substrate loading / unloading port, an ozone gas supply port, a vacuum exhaust port, a leakage inert gas (for example, nitrogen) supply port, and a post-annealing gas supply port. Further, the oxidation furnace 10 includes an ozone excitation light irradiation window 101 (a window material that transmits 200 to 300 nm, for example, synthetic quartz) and an infrared light irradiation window 102 for substrate heating (in the infrared range in the case of infrared lamp heating). A transparent material (eg made of synthetic quartz) is provided. An O-ring may be interposed between the ozone excitation light irradiation window 101 and the substrate heating infrared light irradiation window 102. When the O-ring is installed in a place where it is heated to 200 ° C. or higher, it is necessary to introduce cooling by water cooling.

Since the present embodiment has a heating process, the oxidation treatment furnace 10 is preferably made of a material that can cope with a medium vacuum ( ^{-10 −4} Pa) and can cope with a high temperature up to 400 ° C. Further, quartz is desirable from the viewpoint of impurity diffusion and cleaning. However, since it is difficult in terms of work, it may be made of an inner surface processing that does not fly impurities and a metal that does not oxidize to ozone (for example, aluminum, SUS304). However, when a metal furnace body is used, it must be designed so that it can be evacuated using an O-ring at the boundary with the quartz window for the irradiation window. Here, since the O-ring is vulnerable to heat, cooling (for example, water cooling processing or air cooling in the furnace body) must be made so that the O-ring does not warm. In the present embodiment, aluminum is adopted as the material constituting the oxidation treatment furnace 10, and a mechanism for cooling the O-ring by providing a cooling water channel near the O-ring that seals the irradiation window is adopted.

  The ozone generator 11 generates 100% ozone gas. This ozone gas is used only for the polysilicon oxidation process of process 4. The flow rate of ozone gas is controlled by the pressure difference between the ozone generator 11 and the furnace body. As the ozone generator 11, an ozone generator (MPOG-31002) manufactured by Meidensha is exemplified. A valve V <b> 1 for supplying and stopping ozone gas is installed in a pipe connecting the ozone gas supply port of the oxidation treatment furnace 10 and the ozone generator 11.

  The cylinder 12 is filled with leak gas. Examples of the leak gas include nitrogen and argon gas. A valve V2 for supplying and stopping leakage gas is installed in a pipe connecting the inert gas supply port for leakage of the oxidation treatment furnace 10 and the cylinder 12.

  The cylinder 13 is filled with a gas used for post-annealing in the process 7. Examples of the gas include nitrogen gas containing 3% hydrogen which is generally used as a gas for post-annealing. A valve V3 for supplying and stopping leakage gas is installed in a pipe connecting the post-annealing gas supply port of the oxidation treatment furnace 10 and the cylinder 13.

  The ozone gas, leak gas, and post-annealing gas are selectively used for each process and are not supplied simultaneously. That is, in the oxidation processing apparatus 1, the valves V1, V2, and V3 are selectively operated for each process. In the gate insulating film manufacturing process of this process, only the valve V1 is set to open. The valves V2 and V3 are appropriately operated when using the oxidation treatment furnace 10 in other processes.

The light source 14 is a light source that irradiates light having a wavelength band of 210 to 300 nm that excites ozone. Light having a wavelength longer than 300 nm may intersect. The light source 14 is installed outside the oxidation treatment furnace 10 and is irradiated to the substrate (the substrate on which the polysilicon 113 is formed) through an ozone excitation light irradiation window made of a light transmitting material exemplified by synthetic quartz. In addition to the effect of exciting ozone, the light source 14 also has the effect of heating the extreme surface of the substrate by light absorption. Accordingly, it is desirable to set the length of the photo furnace in the oxidation processing furnace 10 to be short so that the light in the wavelength band reaches the surface of the substrate as much as possible. As shown in FIG. 1, the oxidation furnace 10 is designed to introduce light from above, and the height (gap length) of the oxidation furnace 10 is designed to be as small as possible. For example, when the volume of the oxidation treatment furnace 10 is 6000 cm ³ , the gap length is set to 5 cm. Further, since the amount of light absorption varies depending on the pressure and flow rate of ozone gas in the oxidation treatment furnace 10, optimization is necessary. If the ozone gas is small, a large amount of light can be delivered to the surface of the substrate, but the number of excited ozone is insufficient. Conditions that can produce a minimum amount of excited ozone are optimum conditions. Process 4 is performed at an ozone gas pressure of 330 Pa and an ozone gas flow rate of 150 ccm for a gap length of 5 cm. This has been confirmed to be near optimal conditions.

  The light source 15 is a light source for irradiating infrared rays to heat the substrate in the oxidation treatment furnace 10. Rather than directly irradiating the substrate, the substrate can be efficiently heated by placing the substrate on a susceptor 16 made of a material that absorbs infrared light. The light source 15 is disposed below the oxidation treatment furnace 10, and the light provided from the light source 15 is an infrared light irradiation window for heating a substrate made of a light transmissive material exemplified by synthetic quartz provided in the oxidation treatment furnace 10. The substrate is irradiated via The susceptor should not be a substance that contaminates the inside of the oxidation furnace 10, and is preferably made of a material that has a high infrared light absorption rate and does not scatter impurities even when heated. Examples of the susceptor include those made of opaque processed quartz glass, SiC, SiC coating C, and the like. When the oxidation treatment furnace 10 is a hot plate system, a susceptor made of aluminum that is inferior in infrared absorption may be employed.

  The exhaust pump 18 controls the pressure of the oxidation treatment furnace 19 based on the pressure measurement signal supplied from the pressure gauge 17 provided in the oxidation treatment furnace 10. The exhaust pump is also used for exhausting leak gas and annealing gas individually supplied from the cylinders 12 and 13. However, ozone gas must be decomposed into oxygen before being released into the atmosphere. Therefore, an ozone killer 19 is preferably installed. Further, a variable valve is appropriately installed in addition to the valve V4 in order to adjust the gas exhaust amount.

  The pressure gauge 17 is of a specification that can be measured in a reduced pressure state. This is because the process 4 is executed in a reduced pressure state. The measurement pressure range of the pressure gauge 17 is set to include 0.1 Pa to 1000 Pa. This is because the process pressure suitable for 100% ozone gas belongs to this range with respect to the gap length (> 3 mm) of the oxidation treatment furnace 10 that can be actually realized. However, when ozone gas having an ozone concentration lower than 100% is used, it means that the ozone partial pressure is within this pressure range. This ozone partial pressure is in a safe pressure range that is much lower than the explosion limit. Furthermore, it is a safe pressure range even when a decomposition reaction occurs due to ozone excitation generated by light irradiation of the light source 14 and the pressure rapidly increases.

  Further, when a moving means for moving the susceptor 16 holding the substrate in the oxidation treatment furnace 10 is provided, an insulating film can be formed on a large substrate. The oxidation treatment apparatus 1 shown in FIG. 2 performs oxidation treatment while moving a large substrate in the oxidation treatment furnace 10 by the moving means 20. The moving means 20 changes the portion to be oxidized while moving the susceptor 16 holding the substrate 110 during the oxidation process. The moving means 20 may be a known moving means used in a normal CVD method. Excited ozone has a short lifetime, and therefore can exist only in the vicinity where the light from the light source 14 hits the substrate 110. Therefore, the substrate 110 is oxidized only in the vicinity of the portion irradiated with the light from the light source 14. Since the light from the light source 14 is absorbed by the surface of the substrate 100, the extreme surface of the substrate 110 irradiated with the light is locally heated. This effect further promotes oxidation. On the other hand, the location where the substrate 110 is heated by infrared rays from the light source 16 and the location where strong light absorption and heating of the susceptor 16 are required are just below the portion where the light from the light source 14 strikes.

  When a laser is used as the light source 14, it is desirable to adopt a moving method by the moving means 20 because the irradiation area cannot be enlarged. Further, even for a light source that can ensure a wide irradiation area such as a deep UV lamp, in order to increase the local heating temperature of the substrate 110 as much as possible, the irradiation area is limited and only a part of the surface of the substrate 110 is concentratedly irradiated. Therefore, it is preferable that light is condensed on the substrate 110 by the moving means 20.

Process 5 (additional formation of gate insulating film 114)
When a film formed by oxidation by ozone excitation does not reach a desired film thickness, it is necessary to additionally form the film by a CVD method. In this embodiment, since oxidation using 100% ozone is used, a CVD method using 100% ozone that is compatible with this oxidation method may be employed.

  The CVD method in which light irradiation in the 210 to 300 nm region and 100% ozone are used in combination can be made even at a low temperature of 200 ° C. or less with 100% ozone and HMDS, as is apparent from the characteristic diagram of FIG. Has been confirmed. Furthermore, as will be apparent from the characteristic diagram of FIG. 5 described later, a film having a high film forming speed and excellent insulating characteristics at 200 ° C. or less by irradiating light in the 210 to 300 nm region compared to when not irradiating the light. It has been confirmed that can be formed.

  The CVD method using ozone has been applied to a technique for forming an oxide film on a silicon wafer. Although there is no example applied to the technology for forming an oxide film on polysilicon, there is no problem even if it is applied to a polysilicon substrate because the CVD method is a film forming technique that is not affected by the substrate.

  In the process 5, the oxidation treatment apparatus 1 separate from the process 4 is used. Since the CVD method contaminates the inside of the oxidation treatment furnace 10, it is desirable not to share the oxidation treatment furnace in which the process 5 is performed with the oxidation treatment furnace 10 used in the process 4. That is, since the structure and function of the CVD furnace and the oxidation treatment furnace are substantially the same, it is desired to use the oxidation treatment apparatus 1 as a shared apparatus for the process 5 and the process 4. However, CVD generates impurities in the reaction furnace. It is not desirable to share it with other oxidation furnaces. It is common knowledge of those skilled in the art that the oxidation furnace for the CVD process must be provided separately from the oxidation furnace for other processes.

Process 6 (deposition of electrode 115)
Until the deposition of the electrode 115, when the substrate 110 provided from the process 5 is exposed to the atmosphere, impurities are attached to the surface of the gate insulating film 2 of the substrate 110, so that the performance deteriorates. Therefore, a structure that can be vacuum-transferred to the oxidation treatment furnace for vapor deposition in process 6 is desirable. After vapor deposition, it is transported to an oxidation furnace for post-annealing in process 7.

Process 7 (post-annealing)
The post-annealing process is executed by the oxidation processing apparatus 1 used in the process 4 of FIG. The reason why the oxidation treatment apparatus 1 is used is as follows. Conventional post-annealing is performed for about 30 minutes with the substrate 20 at 400 ° C. to 450 ° C. (Patent Document 1). This annealing temperature is high and needs to be lowered. This is because light absorption by the light source 14 is used in order to perform annealing without increasing the temperature of the substrate 110. Specifically, the substrate is made to have a temperature lower than 400 ° C. by the light source 15, and the portion that is less than 400 ° C. is compensated by local surface heating by the light source 14. Since the ultraviolet light is not absorbed by the annealing gas supplied from the cylinder 13 such as hydrogen or nitrogen, the post annealing treatment is not hindered. Since the polysilicon 113 absorbs light better than the silicon substrate, this annealing method is easy to apply. Further, the film thickness of the polysilicon 113 and the film thickness of the buffer silicon oxide film 112 are important factors that determine the size of the surface heating temperature that can be reached. A necessary amount of the annealing gas filled in the cylinder 13 is supplied into the oxidation treatment furnace 10. The annealing gas is exhausted by the vacuum pump 18. The post-annealed substrate 110 is subjected to a known process that does not require a high temperature until the TFT is completed.

  As a TFT manufacturing apparatus that executes the process described above, there is a TFT manufacturing apparatus 31 of the form illustrated in FIG. FIG. 3A is a schematic configuration diagram of the TFT manufacturing apparatus 31. On the other hand, FIG.3 (b) is a schematic block diagram of the TFT manufacturing apparatus based on a prior art.

  The TFT manufacturing apparatus 31 includes a chamber and an external device necessary for a TFT manufacturing process (process 1 to process 7). As shown in FIG. 3A, the TFT manufacturing apparatus 31 includes a CVD processing furnace A1, an oxidation processing furnace B1, a vapor deposition furnace C1, and an ozone generator A11. The light source D1 is a light source that emits light in the ultraviolet region. The light source E1 supplies light in the infrared region to the substrate in the CVD processing furnace A1. The light source E2 supplies light in the infrared region to the substrate in the oxidation processing furnace B1. The beam splitter F1 supplies the light emitted from the light source D1 to the substrate in the CVD processing furnace A1. The beam splitter F2 supplies the light emitted from the light source D1 to the beam splitter F1 and also supplies it to the substrate in the oxidation processing furnace B1.

Process 1 (buffer SiO ₂ film manufacturing process) and process 2 (polysilicon manufacturing process) are performed in the CVD processing furnace A1. Process 3 (amorphous silicon activation process) and process 4 (gate insulating film production process: oxidation process) are performed in the oxidation treatment furnace B1. Process 5 (gate insulating film manufacturing process: CVD film manufacturing process) is performed in the CVD processing furnace A1. Process 6 (electrodeposition process) is performed in the vapor deposition furnace C1. Process 7 (post-annealing treatment) is performed in the oxidation treatment furnace B1.

  On the other hand, the TFT manufacturing apparatus 32 has a configuration in the case where plasma oxidation and plasma CVD are applied to the gate insulating film manufacturing process exemplified in the TFT manufacturing apparatus of Patent Document 1 as the prior art. As shown in FIG. 3B, the TFT manufacturing apparatus 32 includes a plasma CVD furnace A2, a processing furnace B21 for crystallization of polysilicon and an increase in grain boundary size, a plasma oxidation furnace B22, and a vapor deposition furnace C2. Plasma generators A21 and 22 are provided.

  Comparing both configurations with reference to FIGS. 3 (a) and 3 (b), the number of essential chambers of the TFT manufacturing apparatus 32 according to the prior art is one more than the number of essential chambers of the TFT manufacturing apparatus 31 according to the present invention. There are many. This is because the TFT manufacturing apparatus 32 requires an additional chamber (processing furnace) with an irradiation window for polysilicon crystallization and grain boundary size enlargement process (process 3).

  Further, the TFT manufacturing apparatus 31 can be supplied from a single ozone generator A11 to a plurality of chambers (CVD processing furnace A1 and oxidation processing furnace B1). Furthermore, the TFT manufacturing apparatus 31 can apply ozone excitation light to a plurality of chambers by using the beam splitter F1.

  On the other hand, the plasma generator of the TFT manufacturing apparatus 32 requires the CVD processing furnace A1 for the plasma CVD processing furnace A2 and the oxidation processing furnace B1 for the plasma oxidation furnace B22. Since it is necessary for each furnace, sharing is difficult.

  As is clear from the above description, the TFT manufacturing apparatus 31 based on the TFT manufacturing process according to the present invention can be simplified and miniaturized as compared with the conventional TFT manufacturing apparatus based on plasma oxidation and plasma CVD. Therefore, it is possible to reduce both the installation space and cost of the apparatus system when making capital investment for mass production of low-temperature polysilicon TFTs. It is clear that this difference in effect increases as the number of low-temperature polysilicon TFT production lines increases.

  Examples of the embodiment described above are shown below. With respect to the oxidation processing apparatus based on the configuration shown in FIG. 1, the characteristics of the oxide film formed on the polysilicon were evaluated under the following conditions.

  Excited ozone light source: KrF excimer laser (˜248 nm).

Laser intensity: 240mJ
Laser frequency: 100Hz
Laser irradiation area: 1 cm x 3 cm to 1 cm x 6 cm
Oxidation furnace: capacity 6000cm ³ , gap length 5cm
Ozone gas: 100% ozone gas generated by an ozone generator (MPOG-31002) manufactured by Meidensha Gas pressure: 330 Pa
Gas flow rate: 150sccm
Substrate temperature: room temperature to 400 ° C
Process time: 60 minutes (1) Verification of Si substrate orientation dependence of oxidation rate.

  Various Si crystal orientations exist on the surface of the polysilicon. For this reason, in order to form a flat film on polysilicon, it is necessary that the base does not depend on the crystal orientation of Si. In conventional high-temperature thermal oxidation with oxygen (up to 1000 ° C.), it has been found that the oxidation rate differs by 1.5 to 1.7 times between Si <100> and Si <111> substrates (Masud's). paper). That is, if thermal oxidation is performed on polysilicon, a roughness of about 50% with respect to the oxide film thickness is generated.

  On the other hand, the film thickness distribution of the oxide film formed by excited ozone oxidation is shown below.

  FIG. 4A is a thickness distribution diagram of an oxide film when Si <111> and Si <100> are arranged side by side and excited ozone oxidation is performed simultaneously, and FIG. 4B is a schematic diagram of light irradiation. . The temperature of the Si substrate was set to room temperature. Si <111> and Si <100> are arranged in a semicircular shape and arranged. Irradiate with KrF laser across both substrates (see schematic diagram in FIG. 4B). The flow direction of the ozone gas was parallel to the boundary between Si <111> and Si <100>.

  In the film thickness distribution chart shown in FIG. 4A, the left half is a film thickness distribution chart of Si <111>, the right half is a film thickness distribution chart of Si <100>, and is surrounded by a rectangle. The part is the part irradiated with laser. The film is thickest at the laser irradiated portion, and the film thickness decreases as the distance from the irradiated portion increases. This is an expected result. According to the film thickness distribution chart of FIG. 4A, there is no significant difference in the oxidation rate between Si <111> and Si <100>. The difference in oxidation rate is 5% or less with respect to the film thickness. Therefore, it can be seen that the excited ozone oxidation method according to the present invention is a method suitable for the oxidation of polysilicon.

(2) Insulation characteristics of insulating film formed on polysilicon using excited ozone A sample 50 having the form described in the schematic diagram shown in the characteristic diagram of FIG. 5 was prepared. Sample 50 is obtained by depositing polysilicon 52 on Si substrate 51. Using this sample, it is possible to compare the film quality evaluation with the silicon oxide film that has been formed on the Si substrate so far. In the case of the Si substrate, the insulation characteristic was measured by the electrode arrangement of the MIS capacitor, but the sample 50 was also subjected to the same measurement. That is, after forming the silicon oxide film 53 on the polysilicon 52 of the sample 50 by excited ozone, an MIS capacitor was formed and the insulation characteristics were evaluated.

FIG. 5 is an IV characteristic diagram. The horizontal axis is the applied voltage. The vertical axis represents the leakage current density. In the evaluation of the insulating characteristics, a voltage was applied to the 8.5 nm silicon oxide film 53 that had been standardized by the optical film thickness by the ellipso method for 60 minutes at room temperature. As is apparent from this characteristic diagram, the leakage current monotonously increased with an increase in electric field from 0 to 7 MV / cm, but it was 10 ⁻⁷ A / cm ² or less. From 7 MV / cm, the leakage current increased at a stretch. However, this behavior is due to the tunnel current, not because of poor film quality. Breakdown occurs at 13-14 MV / cm. The magnitude of this breakdown electric field is the same as when the film is formed on the Si substrate 50. In this way, it was confirmed that the insulating properties were comparable to those formed on the Si substrate 50 even though the film was formed on the polysilicon 51.

  Regarding the film forming speed, the polysilicon 51 is higher than the Si substrate 50. This is presumably because the surface of the polysilicon 51 is more light-absorbed than the surface of the Si substrate 50 and the temperature is increased by local heating.

(3) Comparison with thermal oxide film We tried to oxidize polysilicon by a conventional thermal oxidation method. Usually, since polysilicon is stacked on glass or plastic, it cannot be in a temperature range (˜900 ° C.) in which thermal oxidation is performed. However, the sample subjected to this comparative test can be thermally oxidized because polysilicon is stacked on the Si substrate. Differences between the conventional thermal oxidation method (comparative example) and the excited ozone oxidation method (example) of the present invention are disclosed below.

  FIG. 6 discloses a comparison table of optical film thickness and electric film thickness when oxide films according to Example 1, Example 2 and Comparative Example are formed.

  In Example 1, Si <100>, Si <111>, at a film formation temperature of room temperature and a film formation time of 1 hour under irradiation with ultraviolet light from a KrF excimer laser (248 nm) in an excited ozone oxidation 100% ozone atmosphere, A silicon oxide film was formed on each substrate to be processed of Poly-Si (polysilicon).

  In Example 2, Si <100> and Si <111> were formed at a film formation temperature of 400 ° C. and a film formation time of 1 hour under irradiation with ultraviolet light from a KrF excimer laser (248 nm) in an atmosphere of excited ozone oxidation 100% ozone. A silicon oxide film was formed on each substrate to be processed of Poly-Si (polysilicon).

  In the comparative example, a silicon oxide film is formed on each substrate to be processed of Si <100>, Si <111>, and polysilicon (Poly-Si) by thermal oxidation with oxygen at a film forming temperature of 820 ° C. and a film forming time of 2 hours. Formed.

  The number outside the parentheses in the table shown in FIG. 6 is the optical film thickness [nm], and the number inside the parenthesis is the electric film thickness [nm]. According to the comparison of the film thickness between Si <100> and Si <111>, the film thickness of the silicon oxide film formed on Si <100> by the excited ozone oxidation method of Example 1 and Example 2 and Si <111>. There is little difference in the film thickness of the silicon oxide film formed in this. On the other hand, the difference in film thickness between the silicon oxide films of Si <100> and Si <111> formed by the thermal oxidation method of the comparative example is large. The result for the thermal oxide film of the comparative example is consistent with the document “Eugene A. Irene et al. J. of Electrochem. Soc. 133, 1253 (1986)”.

  Further, in the excited ozone oxidation method for the polysilicon (Poly-Si) sample, the difference between the optical film thickness and the electric film thickness is small. On the other hand, in the thermal oxide film, “optical film thickness> electrical film thickness” is satisfied in the polysilicon (Poly-Si) sample.

  This behavior can be easily explained with reference to FIG. FIG. 7 is a schematic diagram of the surface roughness when the silicon oxide film 72 is formed on the polysilicon 71. In particular, FIG. 7A is a schematic diagram of the silicon oxide film formed by the thermal oxidation method according to the prior art. (B) is a schematic diagram of the silicon oxide film formed by the excitation ozone oxidation method based on this invention. The silicon oxide film 72 deposited on the polysilicon 71 shown in FIG. 7A has a large roughness because the film thickness difference between Si <100> and Si <111> is large. On the other hand, the silicon oxide film 72 deposited on the polysilicon 71 shown in FIG. 7B has almost no roughness on the surface because there is almost no difference in film thickness between Si <100> and Si <111>. For such a sample having a large roughness, the optical film thickness corresponds to the average film thickness, while the electric film thickness corresponds to the minimum portion. For this reason, it can be explained that “optical film thickness> electrical film thickness” in the thermal oxide film. The electrical film thickness of 11.5 nm of the thermal oxide film of the polysilicon sample (Poly-Si) is about the same as the film thickness of 12.8 nm of Si <100> formed under the same conditions. The portion with the smallest film thickness on the polysilicon is considered to be a place where the surface has a Si <100> orientation (see FIG. 7).

(4) Film-forming speed The experimental results for the polysilicon samples so far are of the chip size (15 mm square). On the other hand, the laser irradiation area is also 1 cm × 3 cm, and the light intensity is sufficiently strong to the sample. Actually, since it is necessary to oxidize a 12-inch substrate or recently a metric size substrate, it is considered that the light irradiation intensity must be reduced more than in this experimental situation in most cases. At this time, the thickness of the thermal oxide film is reduced.

  FIG. 8 is a characteristic diagram showing the relationship between the film forming time and the film thickness when the substrate temperature is room temperature (20 ° C.) and 400 ° C. The process conditions are the same except for the substrate temperature. That is, the amount of excited ozone to the sample is the same, and the temperature determines the film forming speed. The importance of temperature is understood from the fact that the film is thicker at 400 ° C. than at room temperature.

  Even at room temperature film formation, if the film formation time is secured, the film becomes thick, but the efficiency is low. This is because, from the relationship between the film formation time and the film thickness shown in FIG. 8, the oxide film grows rapidly in the first short time, and then the film is formed very slowly. The cause of this behavior is explained in a paper by Tosaka et al. (Aki Tosaka et al. Jpn. J. Appl. Phys. 44 (36B), L1144-L1146 (2005)).

  Eventually, the insufficient film thickness is compensated by the CVD film. However, since the CVD film is much inferior to the oxide film, it is desirable to compensate with the oxide film as much as possible.

  Therefore, to make a thick oxide film by the excited ozone oxidation method, it is more important to increase the surface heating effect of the processing substrate by light absorption than to increase the film forming time. Increasing the intensity of the light source is one way to increase the heating effect on the surface of the treated substrate, but the other is to increase the heating effect by creating a structure that does not allow the heat received on the surface to escape to the ground. An increasing trend has been confirmed.

(5) About the magnitude of the surface heating effect According to the table of FIG. 6, in the oxidation method using excited ozone, the film is formed on polysilicon (room temperature at room temperature) than when it is formed on a Si substrate (at room temperature, 5.8 nm). (8.6 nm) is thicker. This is due to the fact that the polysilicon surface absorbs more light than the Si substrate surface.

FIG. 9 is a characteristic diagram showing the relationship between the film forming temperature and the film thickness. The straight line L1 is a characteristic straight line showing the relationship between the film forming temperature and the film thickness of the oxide film formed on the Si wafer (sample 1). The straight line L2 is a characteristic straight line showing the relationship between the film forming temperature and the film thickness of the oxide film formed on the Si wafer (sample 2) on which polysilicon is deposited. The straight line L3 is a characteristic straight line showing the relationship between the film forming temperature and the film thickness of the oxide film formed on the Si wafer (sample 3) on which polysilicon is deposited through the SiO ₂ layer as the buffer layer.

In the characteristic diagram of FIG. 9, the straight line L1 is located below the straight line L2. This means that the surface heating of Sample 2 is more active than Sample 1. Sample 3 clearly has a larger surface heating effect than sample 2. This is because the heat received on the surface is suppressed from flowing to the base by the buffer layer (SiO ₂ layer). This indicates that the magnitude of the surface heating effect can be adjusted by the presence or absence of the buffer layer (SiO ₂ layer) and the film thickness of this layer.

  In addition, since an actual polysilicon TFT is formed on glass or plastic, a sample 4 formed by depositing polysilicon on quartz glass was also formed as a comparative example. As is clear from the position of the plot P1 shown in FIG. 9, a much thicker oxide film than the conventional samples 1 to 3 is formed. Since the sample 4 is a substrate made of glass having extremely poor heat conduction, it is considered that the temperature of the sample 4 became high because the heat obtained on the surface was completely confined.

(6) Lowering the post-annealing temperature Regarding the lowering of the process temperature of the polysilicon TFT, lowering the gate insulating film preparation temperature and the port annealing temperature described so far has been an issue. Although it was 400-450 degreeC until now, in this embodiment, since the surface of a process substrate is heated by the excitation of ozone by the light of an ultraviolet region, post-annealing temperature can be made low. In general, it is not easy to know the surface temperature of the substrate. However, according to the characteristic diagram of FIG. 9, the surface temperature can be estimated based on the film forming speed. It has already been described that Sample 2 has a higher film forming speed than Sample 1. When the surface temperature of the sample 2 is estimated, for example, a film thickness of 8.5 nm at room temperature film formation corresponds to a film formation temperature of about 380 ° C. in the film formation of a Si wafer, so that it is heated to about 380 ° C. means. From this, it can be seen that in order to bring the surface of the sample 2 to 400 to 450 ° C., the substrate temperature should be about 100 ° C. and light irradiation should be performed. That is, TFT 2 can be manufactured at 100 ° C. for sample 2. This 100 ° C. is only an example of a temperature condition. Actually, the lower limit temperature of the post-annealing temperature changes because the surface heating effect is changed by introducing the buffer SiO ₂ or making the substrate quartz as described above.

(Embodiment 2)
FIG. 10 is a schematic configuration diagram of an oxidation processing apparatus according to the second embodiment.

  It has been found that the light from the light source 14 for excitation ozone of the oxidation treatment apparatus 1 not only excites ozone but also causes local heating of the surface of the substrate 110, and this local heating amount determines the film forming speed. From another viewpoint, the light intensity of the light source 14 of the first embodiment sufficiently supplements the capacity for exciting ozone, and the surface of the substrate 110 is heated by a surplus.

  If another light source is used for heating the surface of the substrate 110 in addition to the light source 14 that emits light in the ultraviolet region, the output of the ultraviolet light is much smaller than the conventional intensity. Although cost and equipment are required to increase the oscillation intensity in the wavelength range of 210 to 300 nm, the output in the wavelength range of 300 to 500 nm can be easily increased economically.

  The oxidation processing apparatus 2 of the present embodiment takes this advantage into consideration. In addition to the light in the ultraviolet region of the light source 14, the substrate 110 is irradiated with strong light in the visible region of the light source 21. The upper limit of the wavelength range of the light emitted from the light source 21 is defined as 550 nm. Light of 308 to 532 nm is used for the activity of the polysilicon formed on the substrate 110. If it is the light of this wavelength range, the Si bond of polysilicon is not destroyed. If the light from the light source 21 is introduced, the light from the light source 14 does not need to be applied to the substrate 110. The light from the light sources 14, 15, and 21 may be applied horizontally to the substrate 110. In this embodiment, the light source 14 for irradiating light in the ultraviolet region and the light source 21 for irradiating light in the visible region are provided. However, a known light source (for example, SX) -UID2000MUV2V / SUN, USHIO corp.).

  As described above, according to the manufacturing method of the low-temperature polysilicon TFT of the first and second embodiments, an excellent oxide insulating film can be formed on polysilicon at room temperature. Further, it is possible to secure a film forming speed independent of the crystal plane orientation of the substrate and reduce the roughness of the film surface of the substrate. Further, in this manufacturing method, the frequency band of light irradiated on the substrate does not adversely affect the polysilicon surface roughness and does not damage the substrate. Further, the process can be performed in the same chamber as the process of crystallization of polysilicon and the enlargement of the grain boundary size. Furthermore, the post-annealing temperature can be reduced by the local heating effect of the substrate. Also, the light source having the same wavelength can be used for the active annealing of polysilicon. Furthermore, by making the irradiation direction of the laser beam and the substrate movable in the processing furnace (scanning method), a large substrate can be applied. In addition, it is possible to expand to a flexible TFT manufacturing and roll-to-roll processing mode. Further, the magnitude of the light absorption heating can be adjusted by the thickness of the polysilicon layer or the light irradiation intensity. Further, high-speed oxidation and uniform film formation by the oxide film growth mechanism are facilitated. Further, the film thickness can be easily adjusted by adjusting the local heating amount.

  In particular, according to the manufacturing method of the low-temperature polysilicon TFT of the second embodiment, different light sources can be irradiated simultaneously for different purposes. For example, by providing a light source for ozone excitation and a light source for heating, a large heating effect can be expected by irradiating a frequency band (300 to 500 nm) where the light intensity can be obtained relatively easily than the UV frequency band.

  The manufacturing method according to the first and second embodiments relates to a method for manufacturing a low-temperature polysilicon TFT, but it can be applied to a method for manufacturing a semiconductor element other than a low-temperature polysilicon TFT having a gate oxide film. It is clear from the explanation.

1 is a schematic configuration diagram of an oxidation treatment apparatus according to Embodiment 1. FIG. The schematic block diagram of the oxidation processing apparatus which oxidizes while moving a board | substrate within an oxidation treatment furnace. (A) The schematic block diagram of the TFT manufacturing apparatus which concerns on embodiment of invention, (b) The schematic block diagram of the conventional TFT manufacturing apparatus. The film thickness distribution diagram and schematic diagram of light irradiation when the excited ozone oxidation is performed simultaneously with the Si <111> substrate and the Si <100> substrate being arranged. The IV characteristic view which showed the insulation characteristic of the insulating film formed using the excitation ozone in the polysilicon deposited on Si substrate. Excitation ozone oxidation (100% ozone atmosphere and KrF excimer laser (248 nm) irradiated with ultraviolet light at room temperature and 400 ° C. film formation temperature (film formation time 1 hour) ), A comparison table of optical film thickness and electrical film thickness when an oxide film is formed (film formation time 2 hours) by thermal oxidation (820 ° C.) with oxygen according to a comparative example (prior art). (A) Schematic diagram of surface roughness when a thermal oxide film is formed on polysilicon, (b) Schematic diagram of surface roughness when an excited ozone oxide film is formed on polysilicon. The characteristic view which showed the relationship between the film-forming time and film thickness when a substrate temperature is room temperature and 400 degreeC. The characteristic view which showed the relationship between film forming temperature and film thickness. FIG. 3 is a schematic configuration diagram of an oxidation processing apparatus according to a second embodiment. The sectional view of TFT after going through the initial process (electrode deposition) of the manufacturing process of low-temperature polysilicon TFT. The characteristic view which showed the light absorption characteristic regarding polysilicon and amorphous silicon.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Oxidation processing apparatus 10 ... Oxidation processing furnace, 101 ... Ozone excitation light irradiation window, 102 ... Infrared light irradiation window for substrate heating, 11 ... Ozone generator, 12, 13 ... Cylinder, 14, 15, 21 ... Light source, DESCRIPTION OF SYMBOLS 16 ... Susceptor, 17 ... Pressure gauge, 18 ... Vacuum pump, 19 ... Ozone killer 31 ... TFT manufacturing apparatus, A1 ... CVD processing furnace, B1 ... Oxidation processing furnace, C1 ... Deposition furnace, A11 ... Ozone generator, D1, E1 ... light source, F1 ... beam splitter

Claims (15)

  A method for forming a gate insulating film, comprising: irradiating a substrate on which polysilicon is formed with ultraviolet light; and applying ozone gas to form a gate insulating film on the polysilicon.   2. The method of forming a gate insulating film according to claim 1, further comprising the step of irradiating the polysilicon of the substrate with light in an ultraviolet region to crystallize the polysilicon and enlarge a grain boundary size.   An oxidation processing apparatus characterized in that a substrate on which polysilicon is formed is stored, and an ultraviolet gas is irradiated to the substrate and ozone gas is provided to form a gate insulating film on the polysilicon. The oxidation processing apparatus according to claim 3, further comprising a light source that irradiates the light in the ultraviolet region or the light in the ultraviolet region and the visible region. Forming a buffer oxide film on the substrate by applying ozone gas to the substrate under irradiation of light in the ultraviolet region, and then forming polysilicon on the buffer oxide film;
And a step of forming a gate insulating film on the polysilicon by applying ozone gas to the polysilicon of the substrate under irradiation with light in an ultraviolet region. 6. The method of manufacturing a semiconductor device according to claim 5, further comprising a step of irradiating the substrate with light in an ultraviolet region to crystallize polysilicon of the substrate and increase a grain boundary size. 6. The method of manufacturing a semiconductor device according to claim 5, further comprising: forming an additional gate insulating film on the substrate by applying ozone gas to the substrate on which the gate insulating film is formed while irradiating light in an ultraviolet region. Method.   8. The method according to claim 5, further comprising a step of annealing the substrate under irradiation with light in an ultraviolet region after depositing an electrode on the substrate on which the gate insulating film is formed. The manufacturing method of the semiconductor element of description. In the manufacturing method of the semiconductor device according to any one of claims 5 to 8,
A method for manufacturing a semiconductor device, comprising: irradiating a substrate with a light in a visible region together with the light in the ultraviolet region. A CVD furnace that forms an oxide film on the substrate after introducing ozone gas under irradiation of light in the ultraviolet region and then forming polysilicon on the oxide film on the substrate;
A substrate on which polysilicon is formed is provided from this CVD processing furnace, and an oxidation processing furnace is provided that introduces ozone gas under irradiation of ultraviolet light to form a gate insulating film on the polysilicon. A semiconductor device manufacturing apparatus. The apparatus for manufacturing a semiconductor device according to claim 10, wherein the oxidation processing furnace irradiates the substrate with light in an ultraviolet region to increase crystallization and grain boundary size on the substrate. 12. The CVD processing furnace introduces a substrate from the oxidation processing furnace and supplies an ozone gas to the substrate while irradiating light in an ultraviolet region to additionally form a gate insulating film on the substrate. The manufacturing apparatus of the semiconductor element of description. A deposition furnace for depositing electrodes on the substrate on which the gate insulating film is formed;
13. The semiconductor according to claim 10, wherein the oxidation treatment furnace introduces a substrate from the vapor deposition treatment furnace, and anneals the substrate under irradiation with light in an ultraviolet region. Device manufacturing equipment. A first beam splitter for supplying light in the ultraviolet region to the CVD processing furnace;
14. The semiconductor device according to claim 10, further comprising a second beam splitter that supplies the light in the ultraviolet region to the first beam splitter and the oxidation treatment furnace. Manufacturing equipment. The semiconductor device manufacturing apparatus according to claim 10, further comprising a light source that irradiates light in the ultraviolet region or light in the ultraviolet region and visible region.

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