JP2000174281A - Manufacture of semiconductor substrate, thin-film transistor, liquid crystal display device and contact type image sensor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor substrate by which transistors exhibiting different properties can be formed, a thin film transistor, a liquid crystal display device and a contact type image sensor device. SOLUTION: A semiconductor film 3, for example amorphous silicon, is deposited within a range of thickness between 200 and 500 Å on a substrate 2 of glass by LPCVD method or the like, constantly keeping the temperature in a reaction tube at 450 deg.C and introducing 200 sccm of disilane gas (Si2H6) (a). In a desired region of the semiconductor film 3, an uneven region 3b whose roughness on the surface is increased and a flat region 3a whose roughness of the surface is not increased are separately formed by irradiating the region with XeCl excimer laser at an intensity within a range between 500 and 650 mJ/cm2 (b). An amorphous semiconductor film 4, such as amorphous silicon film, is deposited on the uneven region 3b and the flat region 3a (c). The amorphous semiconductor film 4 is transformed to a polycrystalline silicon 5 by performing solid phase growth treatment at atmospheric pressure, at 600 deg.C, for 20-50 hours in an atmosphere of nitrogen, for example (d).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor substrate, a thin film transistor, a liquid crystal display device and a contact image sensor device, and more particularly to an input / output device such as an active matrix liquid crystal display panel and a contact image sensor. The present invention relates to a technology for forming an active layer silicon thin film of a thin film transistor. Method for manufacturing semiconductor substrate, thin film transistor, liquid crystal display device, and contact image sensor device

[0002]

2. Description of the Related Art Conventionally, as typical techniques for forming a thin film transistor (TFT) on a glass substrate, a hydrogenated amorphous semiconductor TFT technique and a polycrystalline silicon TFT are used.
Technology.

In the hydrogen amorphous semiconductor TFT technology, the highest temperature of the manufacturing process is about 300 ° C., and a TFT having a field effect mobility of about 1 cm ² / Vsec on inexpensive low softening point glass can be manufactured. it can.

The polycrystalline silicon TFT technology uses, for example, a quartz substrate and has a temperature of 1000 ° C., similar to an LSI.
By using a high-temperature process of the order, performance with a field-effect mobility of the order of 100 cm ² / Vsec can be obtained. The realization of such high field-effect mobility is, for example,
TFT fabricated by the above polycrystalline silicon TFT technology
Is applied to a liquid crystal display, it is possible to simultaneously form a pixel TFT for driving each pixel and a peripheral drive circuit portion on the same glass substrate.

However, when the above-described high-temperature process is used in the polycrystalline silicon TFT technology, an inexpensive low softening point glass that can be used in the hydrogen amorphous semiconductor TFT technology cannot be used. Therefore, research and development of a technique for manufacturing a polycrystalline silicon thin film transistor having high mobility by a low-temperature process at a temperature of about 300 ° C. have been actively conducted. Excimer laser crystallization technology is most effective for obtaining high-performance polycrystalline silicon by this low-temperature process. It has been reported that a high mobility of 640 cm ² / Vsec was realized by using this method.

Further, since the melting crystallization technique using the pulse laser is used, there is a problem in uniformity and reproducibility. As means for solving such a problem, a method has been disclosed in which a film crystallized by a solid phase growth method is recrystallized by irradiating an excimer laser to the film in advance. In this method, specifically, a polycrystalline film having a large grain size is uniformly produced by a solid-phase growth method, and then a crystal grain boundary is treated by excimer laser irradiation. This is to obtain a polycrystalline silicon film. In many cases, the solid phase growth method is mainly performed in a vacuum or nitrogen at a processing temperature of about 600 ° C. In order to increase the particle size of silicon,
It requires a long process of 40 hours. In addition, there is a problem that the particle size greatly depends on conditions for forming a silicon film before solid phase growth.

In order to solve such a problem, Japanese Patent Laid-Open No.
Japanese Patent No. 25572 proposes various methods for uniformly increasing the particle diameter in a short time. A method of forming irregularities on a substrate, forming a thin film, and then performing solid phase growth is disclosed.

Japanese Patent Application Laid-Open No. 8-1955491 discloses a technique for performing solid phase growth using an oriented polycrystalline film as a nucleus.

Further, Japanese Patent Application Laid-Open No. 2-72614 discloses that
A method of laminating a film having a low nucleation density and a film having a high nucleation density and performing solid phase growth is disclosed.

In each case, a layer or surface shape that can be a nucleus is formed on the underlayer, and nucleation from the underlayer is dominant.
This is to increase the grain size of silicon by solid phase growth of a semiconductor film provided as an upper layer.

However, these methods have a problem in producing a liquid crystal display element integrated with a peripheral driving circuit. This is because the required performance is different between the peripheral driver circuit and the transistor for switching the pixel, and it is difficult to form transistors that satisfy both at the same time on the same substrate. This is because a transistor applied to a circuit for driving a pixel requires a field-effect mobility of about 50 to 100 cm ² / Vsec or more, while a transistor for switching a pixel has a leakage current of about 10 ⁻¹² pA or less. This is related to the requirement for low leakage current.

In order to achieve high mobility, it is necessary to increase the grain size of the polycrystalline silicon film in the active layer. However, when the grain size is increased, there is a problem that variation in leak current increases.

Therefore, the active layer polycrystalline silicon film needs to have a structure in which the transistor in the drive circuit portion has a large grain size and the transistor for pixel switching has a medium grain size. A technique for forming transistors having different required performances on the same substrate is disclosed in Japanese Patent Application Laid-Open No. 8-203825.

Next, a method of manufacturing a transistor will be described. 15A to 15D are cross-sectional views illustrating a conventional transistor manufacturing method in the order of steps.

First, as shown in FIG. 15A, for example, irregularities 101a are formed on the surface of a substrate 101 made of glass to form a roughness shape.

Next, as shown in FIG.
For example, an amorphous silicon film is formed as the amorphous semiconductor film 102 on the semiconductor device 01.

Next, as shown in FIG. 15C, the amorphous silicon film is solid-phase grown in a short time to form a polycrystalline film 103 having crystal grains having a relatively large grain size.

Next, as shown in FIG. 15D, crystal grains having a relatively large grain size are partially formed on the substrate 101. The transistor 100 manufactured in that region is applied to the peripheral driver circuit, and the transistor 100 is switched in other regions to switch the pixels. A source / drain region 104 is formed, and a gate insulating film 105 is formed thereon. A gate electrode 106 is formed between the source / drain regions 104. Further, an interlayer insulating film 107 is formed,
A contact hole (not shown) is formed in this interlayer insulating film 107.
And a source / drain electrode 108 is formed. As a result, transistors 10 having different performances on the same substrate
0 can be produced.

[0019]

SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open No. Hei 8-2
No. 03825 and JP-A-4-225572 have disclosed a method of forming irregularities or roughness on the surface of a substrate, in which a method of forming a glass substrate by chemical etching has been proposed. There is a problem that it is necessary.

Japanese Unexamined Patent Application Publication No. 8-203825 proposes a method of forming irregularities by desorption of oxygen by subjecting a substrate to high-temperature heat treatment. The problem is that it triggers outbreaks. In each case, the processing time increases and the number of manufacturing steps also increases. In addition, there is a problem that damage to the substrate such as distortion of the substrate and generation of contamination is large.

The present invention has been made in view of such a problem. After forming a semiconductor film on a substrate, irregularities are formed on the surface by laser irradiation, and an amorphous semiconductor film is formed on the irregular surface. Provided are a method for manufacturing a semiconductor substrate, a thin film transistor, a liquid crystal display device, and a contact image sensor device, in which transistors having different properties can be formed in the same substrate by laser irradiation and crystallization after formation. The purpose is to:

[0022]

According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor substrate, comprising the steps of: depositing a semiconductor film on a substrate; and increasing the surface roughness of the semiconductor film by laser irradiation. Forming irregularities on the semiconductor film, depositing an amorphous semiconductor film on the irregularities of the semiconductor film, and crystallizing the amorphous semiconductor film by laser irradiation. .

According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor substrate, comprising the steps of: depositing a semiconductor film on the substrate; and forming irregularities on the surface by increasing the surface roughness of the semiconductor film by laser irradiation. And depositing an amorphous semiconductor film on the irregularities of the semiconductor film; and crystallizing the amorphous semiconductor film by solid-phase growth.

Further, the present invention further comprises, after the step of crystallizing the amorphous semiconductor film by solid phase growth, a step of recrystallizing the crystallized amorphous semiconductor film by laser irradiation. Is preferred.

Further, in the present invention, it is preferable that the semiconductor film is amorphous, polycrystalline or microcrystalline.
Further, it is preferable that the amorphous semiconductor film has a higher impurity concentration than the semiconductor film.

Further, in the present invention, it is preferable to form the unevenness by increasing the surface roughness roughness only in a part of the surface of the semiconductor film.

A thin film transistor according to the present invention is characterized in that a semiconductor substrate manufactured by the method for manufacturing a semiconductor substrate according to any one of claims 1 to 6 is used for an active layer.

In the liquid crystal display device according to the present invention, a thin film transistor in a region where no unevenness is formed on the surface of the semiconductor substrate of the thin film transistor according to claim 7 is used as a pixel switching element, and the unevenness of the semiconductor substrate is formed. The thin film transistor in the region defined above is used for a drive circuit.

The contact image sensor device according to the present invention comprises:
A thin film transistor in a region where no irregularities are formed on the surface of the semiconductor substrate of the thin film transistor according to claim 7 is used as a pixel switching element, and the thin film transistor in a region where the irregularities are formed on the semiconductor substrate is used as a shift register and an output circuit. Characterized in that it is used for a driving circuit composed of

In the present invention, when a polycrystalline semiconductor film having a large grain size is to be obtained by solid phase growth or laser irradiation, the semiconductor film is irradiated with a laser to generate surface roughness, thereby forming irregularities. Thereafter, an amorphous semiconductor film is deposited and crystallized by laser annealing or a combination of solid phase growth and laser annealing. In the region where the surface roughness is increased, the irregularities formed dominate the nucleation when the amorphous semiconductor film is crystallized, and the desired roughness can be obtained without depending on the film quality of the amorphous semiconductor film before crystallization. It is possible to obtain a polycrystalline film having the following crystal grain size.

Further, in the present invention, since the surface roughness due to laser irradiation can be realized only by changing the irradiation energy, the number of steps does not increase. In addition, areas with increased surface roughness roughness and areas where surface roughness does not occur can be easily created separately only by controlling the laser irradiation position and irradiation energy, and transistors having different active layer silicon film grain sizes can be formed on the same substrate. It can be realized with a simple process.

[0032]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 (a) to 1 (e)
3A to 3C are cross-sectional views illustrating a method for manufacturing a semiconductor substrate according to a first embodiment of the present invention in the order of steps.

In this embodiment, first, as shown in FIG. 1A, a temperature inside a reaction tube is set at 45 ° C. by using, for example, an LPCVD method on a substrate 2 made of, for example, glass.
The temperature was kept uniform at 0 ° C., and disilane gas (Si ₂ H ₆ ) was
sccm is introduced, and the semiconductor film 3 has a thickness of, for example, 2
Amorphous silicon is deposited in the range of 00 ° to 500 °.

Next, as shown in FIG. 1B, a desired area of the semiconductor film 3 is irradiated with, for example, an XeCl excimer laser at a laser irradiation intensity of 500 mJ / cm ^{2 to} 650 mJ / c.
Irradiation is performed in the range of m ² , and an uneven region 3 b having increased surface roughness and a flat region 3 a having no increased surface roughness are separately formed.

Next, as shown in FIG. 1C, an amorphous semiconductor film 4 made of, for example, an amorphous silicon film is deposited on the uneven region 3b and the flat region 3a.

Next, as shown in FIG. 1D, for example, assuming that the pressure is the atmospheric pressure and the temperature is 600 ° C.,
The solid phase growth process for a long time is performed in a nitrogen atmosphere to convert the amorphous semiconductor film 4 into a polycrystalline film 5 made of a polycrystalline silicon film.

As a result, as shown in FIG. 1E, the polycrystalline film 5 is formed on the uneven region 3b of the semiconductor film 3 formed on the substrate 2 as compared with the flat region 3a of the semiconductor film 3. As a result, a large grain size region 5b having a large crystal grain size is formed, and a small grain size region 5a is formed on a region of the semiconductor film 3 where no irregularities are formed.

As described above, in the present embodiment, by irradiating a desired region of the substrate 2 with a laser to form irregularities, crystal grains formed when the amorphous semiconductor film 4 is grown in solid phase. Since the diameter can be changed, the semiconductor substrates 1 having different particle diameters can be formed in the same substrate 2.

In the present embodiment, as a method of depositing the semiconductor film 3, silane gas is used as a raw material at a growth temperature of about 400 ° C. to 600 ° C. using the LPCVD method. The present invention is not particularly limited to this, and a plasma CVD method using a silane gas or a sputtering method using a silicon target may be used. In this embodiment, a XeCl excimer laser is used as a laser. However, the present invention is not particularly limited to this, and an Ar laser or a KrF laser may be used.

FIG. 2 is a graph showing the silicon film thickness dependency of the unevenness generation intensity on the surface, with the silicon film thickness on the vertical axis and the laser irradiation intensity on the horizontal axis. In the present embodiment, when the film thickness of the semiconductor film 3 is set to 500 °, the irradiation intensity at which the surface roughness roughness occurs varies depending on the film thickness of the semiconductor film 3, and the dependency of the surface roughness roughness generation intensity on the silicon film thickness is shown in FIG. The tendency shown in FIG. 500mm thick
In this case, the laser irradiation intensity is 580 mJ / cm ² .

FIG. 3 shows the maximum unevenness difference on the vertical axis.
FIG. 9 is a graph showing the relationship between the maximum unevenness difference and the conditions for increasing surface roughness roughness, with the horizontal axis representing the conditions for increasing surface roughness roughness. In this embodiment, the surface roughness roughness can be generated by changing the number of laser irradiations or the scanning movement pitch. That is, by changing these conditions, the surface state after the surface roughness can be controlled to a desired shape. As shown in FIG. 3, for example, the thickness of the semiconductor film 3 is 500 °, the laser irradiation intensity is 500 mJ / cm ² , and the scanning pitch is 1.2.
Under condition 1 of 5 μm, the depth of the unevenness of the surface (peak-
Valley) is at most 640 °. Further, the same film thickness as in condition 1, the laser intensity is 500 mJ / cm ² , and the scanning pitch is 5
Under the condition 2 of μm, the depth of the unevenness is 250 ° at the maximum.
It is. The depth of the unevenness of the unirradiated region is 60 at the maximum.
Å.

Furthermore, laser irradiation with a laser irradiation intensity of about 300 mJ / cm ² can be performed even in a region where the surface is not roughened. As described above, by changing the laser irradiation energy between the region where the surface roughness roughness is increased and the region where the surface roughness is not increased, several levels can be combined on the same substrate 2 surface and formed in the substrate 2 surface. For example, the laser irradiation intensity is set to 500 mJ / cm ² in a region where the surface roughness is increased in the same two substrates.
Irradiation can be performed at an arbitrary level in the range of 650 mJ / cm ^{2 to} 650 mJ / cm ² to form irregularities. When the laser irradiation intensity is 650 mJ / cm ² or more, the thickness of the amorphous silicon film as the first layer varies, but the thin film disappears. . Furthermore, by a region without the surface roughness treatment to laser irradiation intensity is formed a semiconductor film 3 by laser irradiation at any level in the range of about 300 mJ / cm ² to 480 mJ / cm ^2, prevents the formation of irregularities on the surface can do. In the present embodiment, the semiconductor film 3 is an amorphous silicon film, but the present invention is not particularly limited to this, and may be a polycrystalline silicon film or a microcrystalline silicon film.

Further, FIG. 4 is a graph showing the dependence of the crystallization ratio on the solid phase growth time, with the ordinate representing the crystallization ratio and the abscissa representing the solid phase growth time. In the present embodiment, there is a difference in the crystallization ratio due to solid phase growth between a region where the surface roughness roughness is increased and a region where the surface roughness is not increased. As shown in FIG. 4, in the region where the surface roughness roughness is increased, about 1
It took about 30 hours to completely crystallize in the range of 5 hours to 20 hours and to prevent the surface from being roughened. The crystal grain size at that time is 2 to 4 μm in a region where the surface roughness is increased, and 0.05 to 0.2 μm in a region where the surface is not roughened.

FIGS. 5A to 5D are cross-sectional views showing a method of manufacturing a semiconductor substrate in which irregularities are formed on the surface of the substrate in the order of steps. 6A to 6D are cross-sectional views illustrating a method for manufacturing a semiconductor substrate in which unevenness is not formed on the surface of the substrate.

In the semiconductor substrate 1 in which irregularities are formed on the surface of the substrate 2, first, as shown in FIG. 5A, a semiconductor film 3 is formed on the substrate 2.

Next, as shown in FIG. 5 (b), in the range laser irradiation intensity of 500 mJ / cm ² to 650 mJ / cm ^2, by irradiating a laser on the surface of the semiconductor film 3, irregularities in the surface region 3b To form

Next, as shown in FIG. 5C, an amorphous semiconductor film 4 is formed, solid-phase grown, and further subjected to laser annealing irradiation to grow nuclei. As a result, FIG.
As shown in FIG. 7, a large grain size region 5b having a relatively large crystal grain size is formed. Therefore, in a region where the surface roughness roughness is increased, it can be determined that crystallization is performed with the unevenness of the base as a nucleus.

In the semiconductor substrate 1 having no irregularities formed on the surface of the substrate 2, first, as shown in FIG. 6A, a semiconductor film 3 is formed on the substrate 2.

Next, as shown in FIG. 6B, the surface of the semiconductor film 3 is irradiated with a laser having a laser irradiation intensity of less than 500 mJ / cm ² .

Next, as shown in FIG. 6C, an amorphous semiconductor film 4 is formed and solid phase growth is performed. As a result, FIG.
As shown in (d), a small grain size region 5a is formed in which grains are grown smaller than when the unevenness is formed on the surface of the substrate 2. Therefore, it can be determined that in a region where the surface is not roughened, oxygen or other impurities contained in the film are crystallized as nuclei. That is, it can be determined that the film quality of the amorphous semiconductor film 4 is dominant.

Further, the impurity concentration of the amorphous semiconductor film 4 is made higher than that of the semiconductor film 3 and is selectively deposited, so that the surface of the flat region 3 a where the surface of the semiconductor film 3 is not roughened is reduced. Uneven area 3 which is a roughened area
The crystal grain size of the polycrystalline film 5 is smaller than b. This is because, for example, the oxygen concentration of the amorphous semiconductor film 4 is 5 × 10
²⁰ cm ⁻³ , and the oxygen concentration of the semiconductor film 3 is 1 × 10 ¹⁸ cm ^−3.
In this case, since the nucleation density of the amorphous semiconductor film 4 is high, the crystal grain size of the polycrystalline film 5 obtained in a region where the surface is not roughened in the subsequent solid phase growth is small. .

As a method of controlling the concentration of oxygen contained in the amorphous semiconductor film 4, there is a method of changing the deposition rate. For example, when 200 sccm of disilane gas is introduced by using the LPCVD method, the pressure is controlled, for example, 5 to 1 at a film forming pressure of 10 Pa.
A deposition rate of 0 ° / min or a deposition pressure of 30 to 5
At 0 Pa and a deposition rate of 25 to 30 ° / min,
The oxygen concentration can be increased by reducing the deposition rate.

Next, after the amorphous semiconductor film 4 is solid-phase grown,
For example, excimer laser irradiation intensity of 300 mJ
/ cm ² to irradiate the range of 500 mJ / cm ^2. The crystal grain size after excimer laser annealing is 5 μm at the maximum in a region where the surface roughness is increased, and 0.1 to 0.5 μm in a region where the surface is not roughened. Also, the solid-phase growth was not carried out, and the grain size of the region directly irradiated with excimer laser after the deposition of the amorphous semiconductor film 4 was observed. It was 3 μm. As a result, a large grain size can be obtained in a region where the surface roughness and roughness are increased only by melting and recrystallization by laser. The irregularities obtained thereby govern nucleation.

Next, a second embodiment of the present invention will be described with reference to FIG. The same components as those in the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted. 7A to 7D are cross-sectional views illustrating a method of manufacturing a thin film transistor according to a second embodiment of the present invention in the order of steps.
FIG. 7A shows the next step of FIG.

First, the small grain size region 5a and the large grain size region 5b of the semiconductor substrate 1 shown in FIG. 1E of the first embodiment of the present invention.
Are processed into an island pattern, and then, as shown in FIG. 7A, the gate insulating film 7 is formed by using the LPCVD method.
Is deposited to a thickness of, for example, 400 °.

Next, as shown in FIG. 7B, tungsten silicide, which is a refractory metal film having a thickness of 1000 °, is deposited as a gate electrode 8 on the gate insulating film 7 by a sputtering method. After patterning the gate electrode 8, source / drain regions 6 are formed in the respective regions corresponding to the p-channel and the n-channel by using impurity implantation by ion doping. Next, heat treatment for activating impurities in the source / drain regions 6 is performed.

Next, as shown in FIG. 7C, a 5000 nm thick silicon nitride film is deposited as the first interlayer insulating film 9 by using plasma CVD.

Next, as shown in FIG. 7D, a contact hole 10 for the source / drain region 6 and a contact hole 11 for the gate electrode 8 are formed thereafter. Next, contact holes 10 for source / drain regions 6 are formed.
For example, an aluminum electrode is formed as the source / drain electrode 12, and an aluminum electrode is formed as the contact electrode 13 in the contact hole 11 for the gate electrode 8. Thus, a thin film transistor 14 is formed.

As described above, in this embodiment, since the regions having different crystal grain sizes can be formed in the same substrate 2 in the same step, the characteristics can be improved without increasing the number of steps by dividing the steps. A thin film transistor having a different element can be formed.

In this embodiment, tungsten silicide is used as the material of the gate electrode 8. However, the present invention is not particularly limited to this.
May be titanium, tantalum, molybdenum, or the like as long as the material is a silicide of a high melting point metal.

Next, a third embodiment of the present invention will be described with reference to FIGS. The same components as those in the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted. FIG. 8 is a schematic view showing a first step of forming irregularities on a semiconductor film of a liquid crystal display according to a third embodiment of the present invention. FIG. 9 is a schematic view showing a second stage of forming irregularities on a semiconductor film of a liquid crystal display according to a third embodiment of the present invention. FIG. 10 is a sectional view showing a liquid crystal display according to a third embodiment of the present invention.

In this embodiment, as shown in FIG. 8, the surface of the semiconductor film 3 is irradiated with a laser having a laser irradiation line beam shape having a mask 15a for preventing irradiation on a region where surface roughness is not formed. The first irradiator 15 is used to irradiate the gate signal drive circuit region 16 as a first stage to form irregularities.

Next, as a second step, as shown in FIG. 9, the surface of the semiconductor film 3 is irradiated with a laser beam having a laser beam line shape having a mask 19a for preventing a region where the surface roughness is not formed. The data signal drive circuit area 17 is irradiated with a laser using a second irradiator 19 that can perform the unevenness. The first and second irradiators 15 and 19 employ a masking method for irradiating the laser by providing a slit of a desired shape at the end side of the condenser lens provided in the laser waveguide path. The irradiation position in the scanning direction is controlled by controlling the movement of the substrate 2 and the timing of the laser pulse.

In this embodiment, a liquid crystal display device is manufactured using the thin film transistor 14 shown in the second embodiment. Therefore, the steps up to the step of forming the thin film transistor 14 are the same as those of the first and second embodiments.

Next, a method of manufacturing the liquid crystal display device of this embodiment will be described. First, the thin film transistor 14 is formed. Next, as shown in FIG.
For example, a silicon nitride film having a thickness in the range of 5000 to 1 μm is deposited by using a plasma CVD method or a silicon oxide film by using a TEOSCVD method.

Next, a contact hole 21 is opened on the drain of the thin film transistor formed in a region where the surface roughness is not reduced. Then, for example, a transparent electrode 22 made of ITO is deposited using a sputtering method.
Further, a liquid crystal display device is completed by processing such as patterning and etching. In this liquid crystal display device, a thin film transistor formed in a region where the surface roughness is increased is used for a pixel driving circuit, and a thin film transistor manufactured in a region where the surface is not roughened is used for pixel switching.

As described above, in this embodiment, since silicon films having different crystal grain sizes can be simultaneously formed in the same substrate 2, the number of steps can be increased without increasing the number of steps.
The thin film transistor 14 formed in a region where the surface roughness is increased can be used for a pixel driving circuit, and the thin film transistor 14 formed in a region where the surface does not have a rough surface can be used for pixel switching.

Further, in this embodiment, a laser beam having a line shape was used when forming the irregularities on the semiconductor film 3. However, the present invention is not particularly limited to this. 2 may be rotated 90 degrees to change the position of the region to be irradiated. In addition, the area of the pixel switching element 18 of the liquid crystal display device is 500 m in which the non-irradiation or the surface roughness roughness does not increase as described above.
Irradiation may be performed by providing a slit having a desired shape capable of irradiating the pixel switching element region 18 with an irradiation intensity of less than J / cm ² .

Further, in the present embodiment, a method of forming a silicon nitride film by a plasma CVD method as the second interlayer insulating film 20 was used, but the present invention is not particularly limited to this. As the second interlayer insulating film 20, an organic interlayer film of a spin coating type may be used. After spin coating the organic interlayer film, 200 ° C. to 3 in N ₂
It is desirable to perform firing in a temperature range of 00 ° C.

Next, a fourth embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIGS. The same components as those in the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted. FIG. 11 is a schematic view showing a method of forming concavities and convexities on a semiconductor film of a contact type image sensor device according to a fourth embodiment of the present invention. 12 (a) to 12 (e), FIG. 13 (a)
FIGS. 14A to 14C and FIGS. 14A and 14B are cross-sectional views illustrating a method of manufacturing a contact image sensor device according to a fourth embodiment of the present invention in the order of steps.

In this embodiment, first, a semiconductor film 3 is formed on a substrate 2. A mask 2 for preventing the semiconductor film 3 from irradiating a region where surface roughness is not formed.
A driving circuit area 24 composed of a shift register and an output circuit is provided by using a third irradiation machine 23 capable of irradiating a laser beam having a laser irradiation line beam shape having 3a
Then, a laser beam is irradiated to form unevenness, and the switching pixel area 25 and the area are separated.

In this embodiment, a contact type image sensor device is manufactured using the semiconductor substrate 1 shown in the first embodiment. Therefore, the steps up to the step of forming the semiconductor substrate 1 are the same as those of the first embodiment. First, FIG.
As shown in FIG.
a and semiconductor substrate 1 on which large grain size region 5b is formed.
To form

Next, as shown in FIG. 12B, the small-grain size region 5a and the large-grain size region 5b of the semiconductor substrate 1 are processed into island-like patterns, respectively, and are then formed by LPCVD. ,
The gate insulating film 7 is deposited to a thickness of, for example, 400 °.

Next, as shown in FIG. 12C, a gate electrode 8 having a thickness of, for example, 1
Tungsten silicide, which is a high-melting metal film of 2,000 °, is deposited by a sputtering method. After patterning the gate electrode 8, source / drain regions 6 are formed in the respective regions corresponding to the p-channel and the n-channel by using impurity implantation by ion doping. Next, heat treatment for activating impurities in the source / drain regions 6 is performed. Thus, the respective thin film transistors 14 having different required performances are formed.

Next, as shown in FIG. 12D, as the first interlayer insulating film 9, for example, a
A silicon oxide film is deposited using a silicon nitride film or a TEOSCVD method in the range of 00 °.

Next, as shown in FIG. 12E, a lower electrode chrome for connecting the thin film transistor and the reading pixel portion is formed by sputtering, for example, with a film thickness of 1000 to 1500 °. accumulate. Then, the lower electrode 26 is formed by patterning.

Next, as shown in FIG. 13A, an amorphous silicon film, for example, is formed as the light receiving element 27 on the first insulating film 9 and the lower electrode 26. in addition,
A p-type amorphous silicon carbide film 28 having p-type conductivity is continuously deposited. Then, patterning of the light receiving element portion is performed. The amorphous silicon film is deposited in a thickness range of 5000 to 2 μm, and the p-type amorphous silicon carbide film 28 is deposited in a thickness range of 200 to 500 °.

Next, as shown in FIG. 13B, for example, ITO is deposited as the upper transparent electrode 29 by using a sputtering method. Then, patterning is performed. For example, tungsten silicide is deposited as a barrier metal 30 for connecting the upper transparent electrode 29 and the aluminum material serving as the extraction upper extraction electrode by a sputtering method, and is patterned.

Next, as shown in FIG. 13C, for example, a silicon nitride film is deposited as the third interlayer insulating film 31 by using a plasma CVD method in a thickness range of about 4000 to 1 μm.

Next, as shown in FIG. 14A, a contact hole 32 is etched on the lower electrode 26, the upper transparent electrode 29, and the source / drain region 6 of the thin film transistor by using a dry etching method. To form.

Next, as shown in FIG. 14B, as the contact electrode 33, for example, an aluminum electrode is deposited by a sputtering method and formed by patterning. Thereby, a contact image sensor device is formed.

In this embodiment, after forming a region for increasing the surface roughness roughness and a region for preventing the surface roughness, the amorphous semiconductor film (not shown) 4 is reacted by the same LPCVD method as the semiconductor film 3. The temperature inside the tube can be kept uniform at 450 ° C., and disilane gas (Si ₂ H ₆ ) can be introduced at 200 sccm to deposit the film in the range of 400 ° to 1000 °. At this time, diborane gas (B ₂ H ₆ ) may be introduced and deposited so that the gas concentration ratio with disilane (Si ₂ H ₆ ) becomes 0.1 ppm to 100 ppm. By controlling the boron concentration in the active layer silicon film by changing the B ₂ H ₆ concentration, the threshold values of the n-channel TFT and the p-channel TFT can be made to have zero-bias symmetric characteristics, which is effective in a CMOS circuit. .

[0083]

As described above in detail, according to the present invention, in the region where the roughness of the surface of the semiconductor film provided on the first layer is increased to increase the roughness, the second layer provided on the upper layer is provided.
Irregularities govern nucleation in the crystallization step of the layer, and a large grain polycrystalline film can be obtained by a simple method. In a region where the surface of the semiconductor film provided as the first layer is not roughened by laser irradiation, when a crystalline thin film is formed in the same process, a polycrystalline film having a smaller grain size can be obtained as compared with a region having unevenness. Can be As a result, two types of elements having different required performances of a thin film transistor requiring a large grain size and a thin film transistor not requiring a large grain size can be simultaneously manufactured without using different processes on the same substrate. Further, the crystallinity of the thin film formed in the surface roughness roughness region, even if the impurity concentration of the amorphous semiconductor film is high, nucleation from irregularities having increased surface roughness roughness formed in the semiconductor film becomes dominant, Since the film quality of the amorphous semiconductor film is not affected, the film quality provided in the second layer is a film having a high impurity concentration capable of obtaining a crystal grain size that meets the required performance of a transistor manufactured in a region where the surface is not roughened. You can choose. Therefore, controllability of the crystal grain size in the polycrystalline film can be improved.

The elements formed in the respective regions use a transistor having a high mobility and a large crystal grain size for a driving circuit of a liquid crystal display element or a driving circuit of a contact image sensor, and a crystal having a low leakage current is used. By using a transistor having a small particle size as a switching element of a pixel portion for a liquid crystal display element or a reading pixel switching element of a contact image sensor, a high performance peripheral drive circuit integrated liquid crystal display element and a contact image sensor device are provided. be able to.

[Brief description of the drawings]

FIGS. 1A to 1E are sectional views showing a method for manufacturing a semiconductor substrate according to a first embodiment of the present invention in the order of steps.

FIG. 2 is a graph showing the silicon film thickness dependence of the unevenness generation intensity.

FIG. 3 is a graph showing a relationship between a maximum unevenness difference and a condition under which surface roughness roughness increases.

FIG. 4 is a graph showing the dependence of the crystallization ratio on the solid phase growth time.

FIGS. 5A to 5D are cross-sectional views illustrating a method for manufacturing a semiconductor substrate in which irregularities are formed on the surface of the substrate in the order of steps.

FIGS. 6A to 6D are cross-sectional views illustrating a method for manufacturing a semiconductor substrate in which unevenness is not formed on the surface of the substrate.

FIGS. 7A to 7D are cross-sectional views illustrating a method of manufacturing a thin film transistor according to a second embodiment of the present invention in the order of steps.

FIG. 8 is a schematic view showing a first step of forming irregularities on a semiconductor film of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 9 is a schematic view showing a second step of forming irregularities on a semiconductor film of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 10 is a sectional view showing a liquid crystal display according to a third embodiment of the present invention.

FIG. 11 is a schematic view showing a method for forming unevenness on a semiconductor film of a contact image sensor device according to a fourth embodiment of the present invention.

12A to 12E are cross-sectional views illustrating a method for manufacturing a contact image sensor device according to a fourth embodiment of the present invention in the order of steps.

13 (a) to 13 (c) are cross-sectional views showing steps subsequent to FIG. 12 in the order of steps.

14 (a) and (b) are cross-sectional views showing steps subsequent to FIG. 13 in the order of steps.

FIGS. 15A to 15D are cross-sectional views illustrating a conventional transistor manufacturing method in the order of steps.

[Brief description of reference numerals]

 Reference Signs List 1: semiconductor substrate 2, 101; substrate 3: semiconductor film 3a; flat region 3b; uneven region 4, 102; amorphous semiconductor film 5, 103; polycrystalline film 5a; small grain region 5b; 6, 104; Source / drain regions 7, 105; Gate insulating films 8, 106; Gate electrodes 9; First interlayer insulating films 10, 11, 21, 32; Contact holes 12, 108; Source / drain electrodes 13, 33; Contact electrode 14; thin-film transistor 15; first irradiator 15a, 19a, 23a; mask 16; gate signal drive circuit region 17; data signal drive circuit region 18; pixel switching element region 19; second irradiator 20; Interlayer insulating film 22; Transparent electrode 23; Third irradiator 24; Drive circuit area 25; Switching pixel area 26; Lower electrode 27; Light receiving element 28 p-type amorphous silicon carbide film 29, the upper transparent electrode 30; barrier metal 31; the third interlayer insulating film 100; the transistor 101a; irregularities 107; interlayer insulating film

Continued on the front page F-term (reference) 2H092 JA24 JA46 KA02 KA04 KA05 LA08 MA07 MA12 MA17 MA29 MA30 MA37 NA25 PA01 PA07 RA10 5F052 AA02 BB01 BB07 DA01 DB02 FA14 JA04 5F110 AA06 AA07 BB01 BB02 CC02 DD02 EE04 GG23 GG43 GG04 EE04 GG23 GG04 EE23 GG45 GG47 HJ13 HL03 NN02 NN14 NN24 NN27 NN55 PP03 PP38

Claims (9)

[Claims] A step of depositing a semiconductor film on a substrate;
Forming irregularities on the surface by increasing the surface roughness of the semiconductor film by laser irradiation; depositing an amorphous semiconductor film on the irregularities of the semiconductor film; Crystallizing by irradiation;
A method for manufacturing a semiconductor substrate, comprising: 2. A step of depositing a semiconductor film on a substrate;
Increasing the surface roughness of the semiconductor film by laser irradiation to form irregularities on the surface, depositing an amorphous semiconductor film on the irregularities of the semiconductor film, and solidifying the amorphous semiconductor film. A step of crystallizing by phase growth. 3. A step of recrystallizing the crystallized amorphous semiconductor film by laser irradiation after the step of crystallizing the amorphous semiconductor film by solid phase growth. A method for manufacturing a semiconductor substrate according to claim 2. 4. The method according to claim 1, wherein the semiconductor film is amorphous, polycrystalline, or microcrystalline. 5. The semiconductor according to claim 1, wherein the amorphous semiconductor film has a higher impurity concentration than the semiconductor film. Method of manufacturing substrates. 6. The method for manufacturing a semiconductor substrate according to claim 1, wherein the unevenness is formed by increasing the surface roughness roughness of only a part of the surface of the semiconductor film. 7. A thin film transistor using a semiconductor substrate manufactured by the method for manufacturing a semiconductor substrate according to claim 1 as an active layer. 8. The thin-film transistor according to claim 7, wherein the thin-film transistor in the region where the unevenness is not formed on the surface of the semiconductor substrate is used as a pixel switching element, and the thin-film transistor in the uneven-formed region of the semiconductor substrate is driven by a driving circuit. A liquid crystal display device characterized by being used for: 9. The thin film transistor according to claim 7, wherein the thin film transistor in an area where no unevenness is formed on the surface of the semiconductor substrate is read and used as a pixel switching element, and the thin film transistor in the area where the unevenness is formed in the semiconductor substrate is shifted. A contact-type image sensor device used in a drive circuit including a register and an output circuit.