JP4348902B2 - Manufacturing method of semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor element, such as a transistor element, and a semiconductor element. Further, the present invention relates to an integrated circuit, an electro-optical device, and an electronic apparatus using the semiconductor element.
[0002]
[Prior art]
Light valves used in active liquid crystal display devices, image sensors, and video projectors that use thin-film semiconductor elements on a substrate having an insulating surface such as quartz to drive pixels. Etc. are known.
[0003]
Generally, a thin film semiconductor device used for a light valve is a polycrystalline thin film semiconductor device manufactured using a high temperature process. The high-temperature process is a process that adopts a thermal oxide gate insulating film following the LSI technology. Although there is a difficulty in using an expensive quartz substrate that can withstand a process temperature of 1000 ° C. or higher, reproducibility and stability It is a technology that has features such as mass productivity.
[0004]
Hereinafter, a method for manufacturing a polycrystalline thin film semiconductor device by a general high-temperature process will be briefly described. First, a silicon oxide film is formed as a base protective film on a quartz substrate by a chemical vapor deposition method (CVD method) or the like. Next, an amorphous silicon semiconductor film (a-Si film) is formed on the silicon oxide film by a low pressure chemical vapor deposition method (LPCVD method) or the like. Since the semiconductor film is later thermally oxidized to reduce the film thickness, it is necessary to form the semiconductor film thicker than the final semiconductor film thickness when forming the amorphous silicon semiconductor film. This amorphous silicon semiconductor film is crystallized by a solid phase growth method (SPC method) to become a polycrystalline silicon semiconductor film. The solid phase growth method is a method of crystallizing a semiconductor film in a solid phase without melting the semiconductor film, and annealing is performed at a temperature of about 550 ° C. to 650 ° C. for several hours to several tens of hours. After the semiconductor film is processed into an island shape in a predetermined pattern, a gate insulating film is formed. In the high temperature process, a thermal oxidation method is used, and a silicon oxide film is grown on the surface of the semiconductor film at a temperature of about 1000 ° C. in an oxygen-containing atmosphere. Here, instead of growing the silicon oxide film, the semiconductor film thickness is reduced. In addition, since the surface of the semiconductor film undergoes an oxidation reaction at a high temperature of about 1000 ° C. when the gate insulating film is formed, the crystallinity of the polycrystalline silicon semiconductor film is improved. Subsequently, a gate electrode is formed, and impurity ions are implanted into the semiconductor film to create a source / drain region and a channel formation region. Next, an interlayer insulating film is formed, contact holes are opened, and source / drain extraction electrodes and wirings are formed. A polycrystalline thin film semiconductor device is thus completed.
[0005]
However, the polycrystalline silicon film crystallized by the solid phase growth method contains many defects. This defect captures carriers and causes the electrical characteristics of the thin film semiconductor element to deteriorate. Therefore, as one of the techniques for reducing defects in the polycrystalline silicon film, there is a melt crystallization of the silicon film by excimer laser annealing. The excimer laser annealing method is generally used for manufacturing a polycrystalline thin film semiconductor device by a low-temperature process. A silicon film is irradiated with xenon / chlorine (XeCl) excimer laser light (wavelength 308 nm) or the like. In this method, the film is melted once and then crystallized through a cooling and solidification process. Since the polycrystalline silicon film obtained by the excimer laser annealing method has undergone a melting and solidifying process, it has few defects and good crystallinity. When this excimer laser annealing method is applied to a method for manufacturing a polycrystalline thin film semiconductor device by a high temperature process, the quality of the polycrystalline silicon film is improved and the electrical characteristics of the thin film semiconductor device are also improved.
[0006]
FIG. 2 is a process diagram showing a conventional method of manufacturing a thin film semiconductor device in which excimer laser annealing is applied to a high temperature process. Hereinafter, a conventional method for manufacturing a thin film semiconductor device will be described with reference to this drawing.
[0007]
In a method of manufacturing a thin film semiconductor device using a semiconductor film formed on a substrate as an active region (semiconductor device active region) of a semiconductor device, a quartz substrate 211 having a thickness of 1.2 mm is used as the substrate, and the quartz substrate 211 is used. A silicon oxide film 212 is deposited as a base protective film by a chemical vapor deposition method (CVD method) to a thickness of about 800 nm. An amorphous silicon film 213 is deposited to a thickness of about 85 nm on the silicon oxide film 212 as the base protective film by low pressure chemical vapor deposition (LPCVD). Next, the amorphous silicon film 213 is irradiated with xenon / chlorine (XeCl) excimer laser light 214 to form a polycrystalline silicon film 213. Here, the crystal grain boundary surface 215 of the polycrystalline silicon film 213 is raised. Next, the polycrystalline silicon film 213 is patterned by photolithography. The polycrystalline silicon film 213 is thermally oxidized to form a silicon oxide film 216 as a gate insulating film with a thickness of about 90 nm. At this time, the polycrystalline silicon film 213 is about 40 nm. Next, a gate electrode 217 is formed on the gate insulating film 216, and impurity ions are implanted into the polycrystalline silicon film 213 to form a source region 213a, a drain region 213c, and a channel formation region 213b. Next, an interlayer insulating film 218 is formed, contact holes are opened, and source / drain extraction electrodes 219 and 220 and wirings are formed. A polycrystalline thin film semiconductor device is thus completed.
[0008]
[Problems to be solved by the invention]
The thin film semiconductor device manufactured by such a conventional manufacturing method has a problem that it is difficult to perform melt crystallization of the semiconductor film. In the high temperature process, the gate insulating film is formed by a thermal oxidation method. Since the gate insulating film needs to be thickened to some extent due to problems such as reliability, the semiconductor film thickness is reduced accordingly. Therefore, the amorphous semiconductor film must first be formed thick. When excimer laser annealing is performed on such a thick semiconductor film, the semiconductor film must be irradiated with a laser beam having very high energy in order to melt the thick semiconductor film. If the semiconductor film is too thick, it is not possible to irradiate a laser beam having the optimum energy due to the limitations of the apparatus, and the crystallization of the semiconductor film becomes insufficient. As a result, the electrical characteristics of the thin film semiconductor element are not significantly improved.
[0009]
Moreover, in the thin film semiconductor element manufactured with the conventional manufacturing method, there existed a subject that productivity was bad. In the conventional manufacturing method, it is necessary to irradiate the semiconductor film with light having a high energy density, which places a heavy burden on the apparatus. As a result, equipment maintenance had to be performed frequently, and productivity was very poor.
[0010]
Further, the thin film semiconductor device manufactured by the conventional manufacturing method has a problem that the reliability of the gate insulating film is poor. The surface of the semiconductor film after laser annealing is greatly raised at the crystal grain boundary. In the low-temperature process, after the semiconductor film is crystallized, the gate insulating film is formed by CVD or the like. Therefore, even if the semiconductor film surface is raised, the gate insulating film surface is planarized to some extent. However, since the gate insulating film is formed by a thermal oxidation method in a high-temperature process, if the semiconductor surface is raised, the surface of the gate insulating film is also raised. This bulging causes a significant deterioration in the reliability of the gate insulating film. Further, since the height of this ridge is about the same as the thickness of the semiconductor film, the bulge becomes higher as the semiconductor film thickness is larger. That is, in the conventional method, it is necessary to form a thick semiconductor film before laser annealing, so that the height of the semiconductor film surface protrusion after laser annealing becomes very high.
[0011]
The invention disclosed in this specification provides means for solving the above-described problems. Specifically, in a method for manufacturing a thin film semiconductor element formed on a substrate, a thin film having good crystallinity of a semiconductor film, good electrical characteristics of the thin film semiconductor element, high reliability of a gate insulating film, and high productivity. It is an object of the present invention to provide a method for manufacturing a semiconductor element.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, a method of manufacturing a semiconductor device of the present invention includes a step of oxidizing a surface of a semiconductor film to form a first insulating film, and a step of depositing a second insulating film on the first insulating film. It is characterized by including these.
[0013]
The method further includes the step of polycrystallizing the semiconductor film, wherein the step of forming the first insulating film is performed after the step of polycrystallizing the semiconductor film.
[0014]
The semiconductor element of the present invention includes a semiconductor film, a first insulating film formed on the semiconductor film, and a second insulating film formed on the first insulating film. The etching rate in the same solution is different between the insulating film and the second insulating film, and the etching rate of the first insulating film is slower than the etching rate of the second insulating film. More specifically, the etching rate of the first insulating film when using a 0.5% HF solution is preferably 2 nm / min or more and less than 4 nm, and the etching rate of the second insulating film is preferably 4 nm / min or more. More preferably, the etching rate of the first insulating film is about 3 nm / min, and the etching rate of the second insulating film is preferably about 5 nm / min or more. The semiconductor film may have a thickness of 40 nm to 70 nm, and the first insulating film may have a thickness of 20 nm to 60 nm.
[0015]
The second insulating film is thicker than the first insulating film.
[0016]
The integrated circuit of the present invention is characterized in that any of the semiconductor elements described above is used as the semiconductor element in an integrated circuit including a semiconductor element.
[0017]
The electro-optical device according to the present invention includes a switching element and a pixel driven by the switching element, wherein the switching element includes any one of the semiconductor elements described above.
[0018]
According to another aspect of the present invention, there is provided an electronic apparatus including the display unit, wherein the electro-optical device is mounted as the display unit.
[Action]
According to the above method for manufacturing a semiconductor element, the second insulating film formed by deposition is formed on the first insulating film obtained by oxidation. That is, a first insulating film having good characteristics by oxidation is formed on the semiconductor film, and a necessary insulating film thickness is secured by the second insulating film by deposition. That is, even if the first insulating film is thinly formed by oxidation, a sufficiently thick insulating film can be obtained, so that a semiconductor element having good characteristics can be realized without making the semiconductor film so thick. A specific example of the method for forming the first insulating film is a thermal oxidation method, and a specific example of the second insulating film is a chemical vapor deposition method.
[0019]
Here, the first insulating film formed by oxidation has an etching rate of about 3 nm / min with a 0.5% HF solution, and the second insulating film manufactured by deposition is etched with a 0.5% HF solution. The rate is about 5 nm / min or more.
[0020]
Adopting melt crystallization as a means for crystallizing the semiconductor film improves the crystallinity of the polycrystalline semiconductor film and reduces defects in the semiconductor film, thereby improving the electrical characteristics of the semiconductor element. Have.
[0021]
In addition, there is an effect that the semiconductor film can be sufficiently melt-crystallized.
[0022]
In the conventional manufacturing method, only the gate insulating film is formed by oxidation. Therefore, in order to increase the thickness of the gate insulating film due to problems such as reliability, it is necessary to increase the thickness of the semiconductor film. There was a problem that it was not enough. For example, when the semiconductor film is a silicon film, the relationship between the thickness of the silicon film and the XeCl excimer laser energy density at which the silicon film is crystallized or microcrystallized is as shown in FIG. As can be seen from FIG. 3, when the silicon film is thick as in the conventional manufacturing method, a high laser energy density is required to melt and crystallize the silicon film satisfactorily. Since there is an upper limit to the laser energy density that can be output due to the limitations of the apparatus, if the silicon film is too thick, sufficient crystallization cannot be performed. However, according to the above manufacturing method, since the insulating film is composed of the first insulating film formed by oxidation and the second insulating film formed by deposition, if the first insulating film alone is not sufficient, the insufficient film thickness is increased. It can be supplemented with two insulating films. That is, it is not necessary to form the insulating film only by the first insulating film formed by oxidation, and the semiconductor film can be formed thin. Therefore, the semiconductor film can be sufficiently melted and crystallized even with light having a low energy density.
[0023]
In addition, since the semiconductor film is thick in the conventional manufacturing method, it is necessary to irradiate the semiconductor film with light having a high energy density. Therefore, an expensive light irradiation apparatus that can irradiate light with high energy density is required. In addition, a heavy burden is placed on the light irradiation apparatus, and the apparatus maintenance must be frequently performed, and the productivity is very poor. However, according to the manufacturing method described above, the semiconductor film can be thinned, so that the energy density of light applied to the semiconductor film can be lowered. Therefore, the burden on the light irradiation device is reduced, the frequency of device maintenance is reduced, and the productivity is improved.
[0024]
Furthermore, the reliability of the insulating film can be improved. When melt crystallization of a semiconductor film is performed, the surface of the semiconductor film is raised. When the insulating film is formed by oxidizing the semiconductor film having the raised surface, the surface of the insulating film is also raised, causing a serious deterioration in the reliability of the insulating film. However, according to the above manufacturing method, the insulating film is composed of the first insulating film formed by oxidation and the second insulating film formed by deposition. Therefore, even if the surface of the first insulating film formed by oxidation is raised, the second insulating film is deposited thereon. By forming the insulating film, the surface of the insulating film is planarized to some extent. In this way, the reliability of the insulating film can be improved.
[0025]
Further, the height of the protrusion on the surface of the semiconductor film after crystallization is approximately the same as the thickness of the semiconductor film. Therefore, since the semiconductor film thickness is large in the conventional manufacturing method, the surface bulge of the semiconductor film after crystallization becomes high. However, according to the above manufacturing method, since the semiconductor film can be thinned, the height of the ridge is also reduced. Therefore, the reliability of the insulating film can be improved.
[0026]
Here, even when the insulating film is only deposited, it is not necessary to form the semiconductor film thickly, so that the semiconductor film can be sufficiently crystallized, and the reliability of the insulating film due to the protrusion of the semiconductor film surface It is also possible to prevent deterioration. However, when only the gate insulating film is deposited, the interface state between the semiconductor film and the insulating film is deteriorated, and further, the effect of improving the quality of the semiconductor film during the oxidation process is lost. It is far inferior to a thin film semiconductor device manufactured by the method.
[0027]
As described above, according to the above-described manufacturing method, it is possible to manufacture a thin film semiconductor element having good crystallinity of the semiconductor film, good electrical characteristics of the thin film semiconductor element, high reliability of the insulating film, and high productivity. Have
As a specific example of the means for melt crystallization, pulsed laser light can be used. By using pulsed laser light, the semiconductor film can be easily melted, and a polycrystalline semiconductor film having a high purity and smooth surface can be obtained. On the other hand, in continuous wave laser light irradiation, the semiconductor film is in a molten state for a long time of several milliseconds or more. For this reason, impurities are likely to be mixed into the film from the gas phase, and surface roughness is likely to occur. On the other hand, in pulse oscillation in which the substrate can be moved by an appropriate distance for each laser irradiation, the melting time of the active semiconductor film is several hundred microseconds or less. Therefore, impurities are hardly mixed into the film and the surface is not easily roughened.
[0028]
As another specific example of the means for melt crystallization, the semiconductor film may be irradiated with light having a wavelength of about 240 nm or more and about 550 nm or less. Since light of this wavelength is efficiently absorbed by the semiconductor film, particularly the silicon semiconductor film, the semiconductor film can be easily melted. Examples of the irradiation light include krypton / fluorine (KrF) excimer laser light (wavelength 248 nm), xenon / chlorine (XeCl) excimer laser light (wavelength 308 nm), second harmonic of Nd: YAG laser light (wavelength 532 nm), and the like. It is preferable because it is high energy and stable.
[0029]
As a specific example of the semiconductor film, an amorphous silicon semiconductor film can be used. This is because the amorphous silicon semiconductor film is easy to manufacture and lowers the manufacturing cost. Furthermore, since it is easy to absorb light in a wide wavelength range, there is an advantage that it is easy to melt and crystallize.
[0030]
As another specific example of the semiconductor film, a polycrystalline silicon semiconductor film obtained by crystallizing an amorphous silicon semiconductor film by a solid phase growth method may be used. The amorphous silicon semiconductor film is crystallized by a solid phase growth method and becomes a polycrystalline silicon semiconductor film having a large grain size. Therefore, the polycrystalline semiconductor film after melt crystallization becomes a polycrystalline silicon semiconductor film having a large grain size and few defects, and the electrical characteristics of the semiconductor element are very excellent.
[0031]
The semiconductor film is preferably deposited to 40 nm to 70 nm. By forming the semiconductor film with this thickness, there is an effect that a polycrystalline semiconductor film having excellent film quality can be stably formed. At the time of melt crystallization, if the thickness of the semiconductor film is too large, the semiconductor film becomes difficult to melt, so that the semiconductor film cannot be sufficiently melted and crystallized. When the semiconductor film is a silicon film, the relationship between the thickness of the silicon film and the XeCl excimer laser energy density at which the silicon film is crystallized or microcrystallized is as shown in FIG. Here, when the silicon film thickness is 80 nm, in order to sufficiently melt and crystallize the silicon film, 600 mJ · cm ^-2 It must be irradiated with light of a very high laser energy density. In order to irradiate light with such a high laser energy density, a heavy burden is placed on the light irradiation device. Or since the light of such a high laser energy density cannot be irradiated depending on the light irradiation apparatus, the laser energy density must be lowered. In this case, of course, the semiconductor film is not sufficiently crystallized. On the other hand, if the thickness of the semiconductor film is too thin, the semiconductor film is likely to be completely melted, the crystal grain size of the semiconductor film after melt crystallization becomes very small, or ablation is likely to occur, and the semiconductor film is damaged. I do. In addition, since it is necessary to consider film reduction due to thermal oxidation, a semiconductor film that is somewhat thick is necessary. According to the experiments by the present inventors, when the film thickness of the semiconductor film is 40 nm or more and 70 nm or less, a polycrystalline semiconductor film having excellent film quality can be stably formed. From FIG. 3, when the film thickness of the silicon film is 40 nm or more and 70 nm or less, in order to obtain a polycrystalline silicon semiconductor film having excellent film quality by melt crystallization, the XeCl excimer laser energy density is 250 mJ · cm. ^-2 More than about 550mJ · cm ^-2 What is necessary is just to be below a grade. Light in this energy density range can be output stably without imposing a burden on the light irradiation device.
[0032]
A silicon oxide film is preferably used as the first insulating film. This is because the production of the first insulating film is easy and the production cost is reduced. In addition, there is an advantage that the interface state density with the silicon semiconductor film is lowered and the electrical characteristics of the thin film semiconductor element are improved.
[0033]
In addition, when the first insulating film is formed to have a thickness of 20 nm to 60 nm, a polycrystalline semiconductor film having excellent film quality can be stably formed. In addition, since the thickness of the first insulating film is sufficiently thin, the reduction of the semiconductor film due to the oxidation process is reduced. Therefore, the original semiconductor film can also be deposited thinly. For example, if the semiconductor film thickness after oxidation is 40 nm, the original semiconductor film thickness is about 50 nm in order to make the first gate insulating film 20 nm, and the original semiconductor film is used in order to make the first gate insulating film 60 nm. The film thickness is about 70 nm. That is, the original semiconductor film can be deposited to a thickness of 50 nm to 70 nm. If the semiconductor film can be deposited to such a thickness, it becomes easy to control the melt crystallization of the semiconductor film, and as a result, a polycrystalline semiconductor film having excellent film quality can be stably formed.
[0034]
As an example of the second insulating film, a silicon oxide film may be used. This is because the second insulating film can be easily manufactured and the manufacturing cost is reduced. In addition, there is an advantage that the interface state density with the first insulating film is lowered and the reliability of the insulating film is improved.
[0035]
A silicon hydronitride film may be used as another example of the second insulating film. This silicon hydronitride film can be formed by plasma enhanced chemical vapor deposition (PECVD). In this case, since the relative dielectric constant of the silicon nitride film is as large as 7.5, even if the second insulating film is made thick, the insulating film capacitance can be obtained, and the electrical characteristics of the semiconductor element are improved. In addition, since hydrogen atoms contained in the silicon nitride film hydrogenate defects present at the semiconductor film and the interface between the semiconductor film and the first insulating film, the electrical characteristics of the semiconductor element are improved.
[0036]
The thickness of the second insulating film is preferably 40 nm or more and 80 nm or less. With this thickness, a polycrystalline semiconductor film having excellent film quality can be stably formed, and the reliability of the insulating film can be increased. In order to increase the reliability of the insulating film, it is necessary to increase the thickness of the insulating film to some extent. When the insulating film thickness is 100 nm, the first gate insulating film thickness is 20 nm or more and 60 nm or less. Therefore, when the oxidized semiconductor film thickness is 40 nm, the original semiconductor film thickness can be deposited to 50 nm to 70 nm. If the semiconductor film can be deposited to such a thickness, it becomes easy to control the melt crystallization of the semiconductor film, and as a result, a polycrystalline semiconductor film having excellent film quality can be stably formed.
[0037]
The second insulating film is formed thicker than the first insulating film. More specifically, when the first insulating film thickness is T1 and the second insulating film thickness is T2, the film thickness ratio T2 / T1 is preferably 1 or more and 3 or less. Within this range, the insulating film has high reliability and a semiconductor element with good electrical characteristics. Of the first insulating film and the second insulating film, the first insulating film, which is an oxide film, has better film quality as the insulating film. However, if the first insulating film thickness T1 is increased because the film quality is good, the effect of the present invention obtained by forming the second insulating film described so far becomes dilute. Therefore, the ratio T2 / T1 between the first insulating film thickness T1 and the second insulating film thickness T2 is set to 1 or more, that is, the first insulating film thickness T1 is set to be equal to or less than the second insulating film thickness T2. When the first insulating film thickness T1 is reduced, the film quality of the entire insulating film is lowered, and the reliability of the insulating film is also deteriorated. Therefore, the film thickness ratio T2 / T1 is preferably 3 or less, that is, T1 is preferably 1/3 or more of T2.
[0038]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0039]
Example 1
FIG. 1 is a process diagram illustrating a method of manufacturing a thin film semiconductor device according to an embodiment of the present invention. Hereinafter, a method for manufacturing a thin film semiconductor device according to the first embodiment of the present invention will be described with reference to this figure in (a), (b), (c), (d), (e), and (f). .
[0040]
(A) Process of Fig.1 (a)
In a method of manufacturing a thin film semiconductor device using a semiconductor film formed on a substrate as an active region (semiconductor device active region) of a semiconductor device, a quartz substrate 111 having a thickness of 1.2 mm is used as the substrate, and the quartz substrate 111 is used. A silicon oxide film 112 is deposited as a base protective film by a chemical vapor deposition method (CVD method) to a thickness of about 800 nm. An amorphous silicon film 113 having a thickness of about 55 nm is deposited on the silicon oxide film 112 as the base protective film by a low pressure chemical vapor deposition method (LPCVD method) as a semiconductor film that will later become a semiconductor element active region. The source gas is monosilane (SiH ₄ The deposition temperature is about 550 ° C. and the pressure is about 30 Pa. By depositing under such conditions, an amorphous silicon film with good uniformity can be deposited.
[0041]
(B) Process of FIG.1 (b)
By irradiating a pulsed laser beam 114 as light to the semiconductor film 113 which later becomes a semiconductor element active region, the semiconductor film 113 is melted and crystallized to make the semiconductor film 113 a polycrystalline semiconductor film with few defects and good crystallinity. As the pulse laser beam 114, xenon / chlorine (XeCl) excimer laser beam (wavelength 308 nm) is used. The irradiation region of the XeCl excimer laser beam is a rectangle having a length of 200 mm and a width of 0.4 mm, and shows a substantially constant intensity distribution. The irradiation energy density of XeCl excimer laser light is 420 mJ · cm ^-2 Then, the amorphous silicon film 113 as a semiconductor film is completely melted and the semiconductor film is microcrystallized. In order to increase the crystal grain size of the polycrystalline silicon film, laser light may be irradiated at an irradiation energy density slightly lower than the irradiation energy density at which the semiconductor film is microcrystallized. Therefore, the irradiation energy density is 400 mJ · cm. ^-2 Or 410 mJ · cm ^-2 It is good to do. Further, an arbitrary point on the semiconductor film is subjected to pulse laser irradiation 20 to 30 times. Here, although the pulse laser beam is a xenon / chlorine (XeCl) excimer laser beam (wavelength 308 nm), the pulse laser beam is krypton / fluorine (KrF) excimer laser beam (wavelength 248 nm), and the second harmonic of the Nd: YAG laser beam. Even when a wave (wavelength of 532 nm) or the like is used, melt crystallization can be performed well. When the semiconductor film 113 is melted and crystallized by irradiating light 114, the surface of the crystal grain boundary portion of the polycrystalline silicon film rises like 115.
[0042]
(C) Process of FIG.1 (c)
Next, the semiconductor film 113 is patterned by photolithography.
[0043]
(D) Process of FIG.1 (d)
Next, the semiconductor film 113 is thermally oxidized. After the substrate is inserted into a heat treatment furnace having a temperature of 800 ° C., nitrogen and a slight amount of oxygen are allowed to flow in the heat treatment furnace so that the atmosphere in the heat treatment furnace is an atmosphere in which the oxygen in the nitrogen is about 10 ppm to 1%. The temperature is increased at a rate of about 4 ° C. to 20 ° C. per minute, and the temperature in the heat treatment furnace is set to 1000 ° C. If the temperature rising rate is as low as about 4 ° C., the temperature controllability is improved, but it takes a long time to raise the temperature, so the productivity is lowered. On the other hand, if the rate of temperature increase is as high as 20 ° C., the temperature controllability is deteriorated, but the temperature increase time is shortened, so the productivity is improved. When the above temperature increasing process is performed in a 100% nitrogen atmosphere, there is a problem that a hole is formed in the semiconductor film. As described above, when the oxygen in the nitrogen atmosphere is about 10 ppm, an ultrathin oxide film is formed on the semiconductor film, so that it is possible to prevent a hole from being formed in the semiconductor film. Here, if the oxygen concentration is too high, such as about 1% or more, the oxide film thickness becomes thick. Since this oxide film is formed at a low temperature, the film quality is poor, and when it becomes a gate insulating film, it causes deterioration in characteristics and reliability of the thin film semiconductor element. Therefore, in the above temperature rising process, the oxygen concentration is kept sufficiently low, such as 10 ppm to 1%, so that holes are not formed in the semiconductor film and a gate insulating film with poor film quality is not grown more than necessary. There is a need to. After the temperature rises, the atmosphere in the heat treatment furnace is set to 2% oxygen or 100% oxygen in the nitrogen, and the polysilicon film 113 as the semiconductor film is oxidized to oxidize the silicon oxide film as the first gate insulating film. 116 is formed to a thickness of about 30 nm. At this time, the thickness of the semiconductor film 113 is about 40 nm. Further, a silicon oxide film 117 as a second gate insulating film is deposited on the silicon oxide film 116 as the first gate insulating film by a chemical vapor deposition method (CVD method) to a thickness of about 50 nm. Low pressure chemical vapor deposition (LPCVD) is used to form the second gate insulating film, and the source gas is monosilane (SiH ₄ ) And dinitrogen monoxide (N ₂ O), the deposition temperature is about 800 ° C. to 850 ° C., and the pressure is about 80 Pa. The bump 115 on the surface of the semiconductor film 113 also remains on the surface of the first gate insulating film 116. This is because the first gate insulating film 116 is formed by thermally oxidizing the semiconductor film 113. However, since the second gate insulating film 117 is deposited by the CVD method, the surface of the second gate insulating film 117 is planarized to some extent. The film thickness ratio T2 / T1 between the first gate insulating film thickness T1 and the second gate insulating film thickness T2 is about 1.67.
[0044]
(E) Process of FIG. 1 (e)
A gate electrode 118 is formed on the second gate insulating film 117. The gate electrode is monosilane (SiH) as a source gas. ₄ ) And phosphine (PH ₃ ), A conductive polycrystalline silicon semiconductor film containing phosphorus (P) deposited by a low pressure chemical vapor deposition method (LPCVD method) at a temperature of 550 ° C. and a pressure of 120 Pa is used. After forming the gate electrode 118, impurity ions are implanted into the polycrystalline silicon film 113 to form a source region 113a, a drain region 113c, and a channel formation region 113b. Impurity ions include B ions or BF in the case of an N-type thin film semiconductor element. ₂ Ions are implanted, and in the case of a P-type thin film semiconductor element, P ions are implanted.
[0045]
(F) Process of FIG. 1 (f)
Next, an interlayer insulating film 119 is formed, contact holes are opened, and source / drain extraction electrodes 120 and 121 and wirings are formed. A polycrystalline thin film semiconductor device is thus completed.
[0046]
As described above, according to the first embodiment, the semiconductor film has good crystallinity, the electric characteristics of the thin film semiconductor element are good, the reliability of the gate insulating film is high, and the productivity is high. Can be manufactured.
[0047]
(Example 2)
In the step (a) of the first embodiment, the deposition pressure of the amorphous silicon film 113 is set to about 100 Pa. By increasing the deposition pressure in this manner, generation of crystal nuclei in the amorphous silicon film can be suppressed. After the amorphous silicon film 113 is deposited, the amorphous silicon film 113 is crystallized by a solid phase growth method. Since the amorphous silicon film 113 has few crystal nuclei, by performing solid phase growth, the amorphous silicon film 113 becomes a polycrystalline silicon film having a large grain size, and the electrical characteristics of the thin film semiconductor element become excellent. . In the solid phase growth, a substrate is inserted into a heat treatment furnace having a temperature of 600 ° C. to 640 ° C. in a nitrogen atmosphere, and heat treatment is performed for 6 hours to 24 hours. If the temperature is low, the crystal grain size of the polycrystalline silicon film becomes large, but the processing time becomes long, so the productivity becomes poor. On the other hand, when the temperature is high, the crystal grain size of the polycrystalline silicon film is smaller than that when the temperature is lowered, but the processing time is shortened, so that the productivity is improved. Thus, the semiconductor film 113 is changed from an amorphous silicon film to a polycrystalline silicon film having a large grain size.
[0048]
In the step (b) of Example 1, the irradiation energy density of the XeCl excimer laser light is 420 mJ · cm. ^-2 Or 430mJ · cm ^-2 And This is because the semiconductor film 113 has already become a polycrystalline silicon film by solid phase growth, and 440 mJ · cm ^-2 This is because the semiconductor film 113 is completely melted.
[0049]
Except for the above, the polycrystalline thin film semiconductor device is completed in the same manner as in Example 1.
[0050]
As described above, according to the second embodiment, the crystallinity of the semiconductor film is good, the crystal grain size of the semiconductor film is large, the electrical characteristics of the thin film semiconductor element are good, and the reliability of the gate insulating film is high. In addition, a thin film semiconductor element with high productivity can be manufactured.
[0051]
(Example 3)
In the step (a) of Example 1, disilane (Si ₂ H ₆ ) And the deposition temperature is lowered to about 425 ° C. Thus, by lowering the deposition temperature, the generation of crystal nuclei in the amorphous silicon film can be suppressed. Next, in the same manner as in Example 2, solid phase growth of the semiconductor film 113 is performed to make the semiconductor film 113 a polycrystalline silicon film having a large grain size. Further, XeCl excimer laser light is irradiated to the semiconductor film 113 in the same manner as in the second embodiment.
[0052]
Except for the above, the polycrystalline thin film semiconductor device is completed in the same manner as in Example 1.
[0053]
As described above, according to the third embodiment, the crystallinity of the semiconductor film is good, the crystal grain size of the semiconductor film is large, the electrical characteristics of the thin film semiconductor element are good, and the reliability of the gate insulating film is high. In addition, a thin film semiconductor element with high productivity can be manufactured.
[0054]
(Example 4)
In the step (d) of Example 1, a silicon hydronitride film (SiN) is formed as a second gate insulating film by a plasma chemical vapor deposition method (PECVD method). _X : H) 117 is deposited to a thickness of about 50 nm. The source gas is monosilane (SiH ₄ ) And ammonia (NH ₃ ). The substrate temperature during deposition of the second gate insulating film is set to about 200 ° C. to 350 ° C. so that hydrogen does not desorb from the silicon hydronitride film 117. When the silicon hydronitride film is deposited as the second gate insulating film by plasma enhanced chemical vapor deposition (PECVD), the gate insulating film capacity is large, and the semiconductor film and the interface between the semiconductor film and the first gate insulating film Since the defects present in the metal are hydrogenated, the electrical characteristics of the thin film semiconductor device are excellent.
[0055]
Except for the above, the polycrystalline thin film semiconductor device is completed in the same manner as in Example 1.
[0056]
As described above, according to the fourth embodiment, the crystallinity of the semiconductor film is good, the defects existing at the interface between the semiconductor film and the semiconductor film and the first gate insulating film are hydrogenated, and the thin film A thin film semiconductor element having good electrical characteristics, high reliability of the gate insulating film, large capacity of the gate insulating film, and high productivity can be manufactured.
[0057]
(Example 5)
FIG. 4 shows an electro-optic element according to the fifth embodiment of the present invention. An electro-optical element according to a fifth embodiment of the present invention includes an element substrate 401 on which the thin film semiconductor element described in the first to fourth embodiments is formed and a counter substrate. The element substrate 401 and the counter substrate are opposed to each other. A liquid crystal layer is sealed between the two. On the inner surface side of the element substrate 401, a large number of source lines 402 and a large number of gate lines 403 are provided in a lattice shape so as to intersect each other. A thin film semiconductor element 404 is formed in the vicinity of the intersection of each source line 402 and each gate line 403, and a pixel electrode made of a transparent electrode such as ITO is connected through each thin film semiconductor element 404. That is, one thin film semiconductor element 404 and one pixel electrode are provided for each pixel arranged in a matrix. On the other hand, on the entire inner surface side of the counter substrate, one common electrode made of a transparent electrode such as ITO is formed over the entire display region in which a large number of pixels are arranged in a matrix. In addition, a drive circuit 405 for driving the thin film semiconductor element 404 in the pixel region is formed around the pixel region, and the drive circuit 405 is also configured to include many thin film semiconductor elements.
[0058]
Since this electro-optic element is made of a thin film semiconductor element having excellent electrical characteristics, it exhibits beautiful display characteristics. In addition, the drive voltage can be lowered and the drive circuit can be operated at high speed. Therefore, high definition and low power consumption can be realized.
[0059]
(Example 6)
FIG. 5 shows an electronic apparatus according to a sixth embodiment of the present invention. An electronic apparatus according to a sixth embodiment of the present invention is a liquid crystal projector using the electro-optic element described in the fifth embodiment as a light valve. Three electro-optic elements 502 described in the fifth embodiment are arranged so as to surround a dichroic prism 501 having a characteristic of reflecting and transmitting light having a specific wavelength. Light of red 503, green 504, and blue 505 is incident on each electro-optic element 502, respectively. The amount of light transmitted through each electro-optic element 502 is adjusted by an image signal input to each electro-optic element 502. The adjusted light is combined by the dichroic prism 501. The synthesized light is projected onto a screen or the like through the projection lens 506 and displayed as an image.
[0060]
Since this electronic device is composed of an excellent electro-optic element, it exhibits beautiful display characteristics. In addition, high definition and low power consumption can be realized.
[0061]
【The invention's effect】
As described in detail above, according to the present invention, a thin film semiconductor device having good crystallinity of a semiconductor film, good electrical characteristics of a thin film semiconductor device, high reliability of a gate insulating film, and high productivity is manufactured. can do. According to the method for manufacturing a thin film semiconductor device of the present invention, a high performance thin film semiconductor device can be manufactured easily and stably. Therefore, when the method for manufacturing a thin film semiconductor element of the present invention is applied to an active matrix liquid crystal display device, a large-sized and high-quality liquid crystal display device can be manufactured easily and stably. Further, even when applied to the manufacture of other electronic circuits, a high-quality electronic circuit can be manufactured easily and stably.
[Brief description of the drawings]
FIG. 1 is a process diagram illustrating a method of manufacturing a thin film semiconductor device according to an embodiment of the present invention.
FIG. 2 is a process diagram showing a conventional method of manufacturing a thin film semiconductor device.
FIG. 3 is a diagram showing the relationship between the film thickness of a silicon film and the XeCl excimer laser energy density necessary for satisfactory crystallization or microcrystallization of the silicon film.
FIG. 4 is a diagram showing an electro-optical element according to a fifth embodiment of the invention.
FIG. 5 is a diagram showing an electronic apparatus according to a sixth embodiment of the present invention.
[Explanation of symbols]
111, 211 ... quartz substrate
112, 212 ... base protective film
113, 213 ... Semiconductor film
113a, 213a ... source region
113b, 213b ... channel formation region
113c, 213c ... drain region
114, 214 ... Light (xenon / chlorine excimer laser light)
115, 215 ... bumps on the surface of the silicon film
116: first gate insulating film
117 ... Second gate insulating film
118, 217 ... gate electrode
119, 218 ... Interlayer insulating film
120, 219 ... Source electrode
121, 220 ... Drain electrode
216 ... Gate insulating film
401 ... element substrate
402 ... Source line
403 ... Gate line
404 ... Thin film semiconductor element
405 ... Driving circuit
501 ... Dichroic prism
502 ... Electro-optical element
503 ... Red light
504 ... Green light
505 ... Blue light
506 ... Projection lens

Claims (4)

In a method for manufacturing a semiconductor element,
Forming an amorphous semiconductor film on a quartz substrate;
Polycrystallizing the amorphous semiconductor film by solid phase growth;
A step you melt crystallization by light irradiation the polycrystallized semiconductor film,
Forming a first insulating film is oxidized with oxygen atmosphere at a temperature higher than 800 ° C. The surface of the semiconductor film mentioned above melt crystallization,
Anda step you deposited by the second insulating film low-pressure chemical vapor deposition on the first insulating film,
In the step of forming the first insulating film, the quartz substrate is placed in a heat treatment furnace in which oxygen in nitrogen is 10 ppm to 1% and temperature is 800 ° C., and the temperature in the heat treatment furnace is increased to 1000 ° C. Then, the atmosphere in the heat treatment furnace is such that oxygen in nitrogen is 2% or more or oxygen is 100% . In the manufacturing method of the semiconductor device according to claim 1,
A method of manufacturing a semiconductor device, wherein the increase is performed at a rate of 4 to 20 ° C. per minute. In the manufacturing method of the semiconductor element of Claim 1 or 2,
The amorphous semiconductor film has a thickness of 40 nm to 70 nm,
Thickness of the first insulating film, 20 nm or more and 60nm or less,
The method of manufacturing a semiconductor element, wherein the second insulating film has a thickness of 40 nm or more and 80 nm or less. In the manufacturing method of the semiconductor element in any one of Claims 1 thru / or 3,
A method of manufacturing a semiconductor element, wherein the thickness of the second insulating film is set to be 1 to 3 times the thickness of the first insulating film.

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