JPH11354446A - Production method of semiconductor film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method which can prevent crystallization from deteriorating after completing growing process of a solid phase or after laser irradiation. SOLUTION: With the use of LPCVD(Low Pressure CVD) method based on disilane as a raw material, a-Si film 2 is piled on a glass substrate 1, and it is heat-treated at 600 deg.C in the nitrogen or in the air, and then a solid-phase growth polycrystalline silicon film 3 is produced by the solid phase growth. Successively, following the LPCVD method, an impurities are inducted by using mixed gas of disilane and diborane, and impurities-inducted silicone film 41 is piled. After the pile-up of the impurities-inducted film 41, it is irradiated with laser 5 for crystallization.

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 film, and more particularly, to a method for forming a semiconductor film on a glass substrate at a low temperature used for input / output devices such as an active matrix liquid crystal display panel and a contact type image sensor and portable equipment. To a method for manufacturing a silicon thin film of a thin film transistor to be manufactured.

[0002]

2. Description of the Related Art A thin film transistor (TF) is formed on a glass substrate.
Representative techniques for forming a thin film transistor (T: Thin Film Transistor) include a hydrogenated amorphous semiconductor TFT technique and a polycrystalline silicon TFT technique.

The former has a maximum fabrication process temperature of about 300 ° C. and realizes a carrier mobility of about 1 cm ² / Vsec. The latter uses, for example, a quartz substrate and
By using a high-temperature process similar to an LSI (large-scale integrated circuit) of about 00 ° C., the carrier mobility is 100 cm ^2.
/ Vsec.

[0004] The realization of such high carrier mobility is as follows.
For example, when the above-described TFT is applied to a liquid crystal display, a pixel driver for driving each pixel and a peripheral driving circuit portion can be formed simultaneously on the same glass substrate.

However, in the polycrystalline silicon TFT technology, when the above-described high-temperature process is used, an inexpensive low softening point glass that can be used in the former process cannot be used. Therefore, research and development of low-temperature polycrystalline silicon thin film transistors having high mobility at low temperatures are being actively conducted.

An excimer laser crystallization technique is most effective for obtaining high-performance polycrystalline silicon at a low temperature. There is also a report that a high mobility of 300 cm ² / Vsec was realized by using this method. However, since a melt crystallization technique using a pulse laser is used, there remains a problem in uniformity and reproducibility.

As a means for solving such a problem, there has been proposed a method of recrystallizing a film previously crystallized by a solid phase growth method by excimer laser irradiation. That is, a polycrystallized film having a large grain size is produced by a solid phase growth method, and the polycrystalline film is subjected to grain boundary treatment by excimer laser irradiation to uniformly obtain a film having a high mobility.

On the other hand, to form a driving circuit, CMOS
(Complementary Metal Oxid
e Semiconductor) TFT is required. It is generally known that when a TFT is manufactured using an intrinsic polycrystalline silicon thin film, the threshold value of the transistor shifts to the negative side in both the n-channel and the p-channel.

This is because the energy of trap levels existing in polycrystalline silicon is not uniformly distributed in a band. Therefore, in order to maintain the balance between the characteristics of the n-type TFT and the p-type TFT, a slight amount of doping is performed on the channel to control the threshold.

As described above, as a method of introducing impurities to control the threshold value, there are an ion implantation technique into a thin film and an ion doping technique, and the technique disclosed in Japanese Patent Application Laid-Open No. 6-181222 is representative. A technique has been proposed in which an impurity gas is decomposed in a gas phase to introduce an impurity into a thin film, and then crystallized by solid phase growth and laser irradiation. Since the method of mixing trace impurities in this gas phase does not require a process such as injection compared to other methods,
It is expected as a simple method.

[0011]

In the above-described conventional method of manufacturing a silicon thin film, impurities are mixed in the film. However, the state of crystal growth by the solid phase growth method is different from the method in which impurities are not mixed. There is a problem.

In the case of a film containing impurities, the nucleation rate from the impurities becomes dominant, and a large grain size cannot be obtained. Therefore, there is a problem that the above-mentioned means of laser annealing of a solid-phase-grown crystallized film, which is a means of achieving high mobility and high uniformity, cannot be taken. Therefore, conventionally, after the solid phase growth is performed, the threshold value is controlled by a small amount of doping using ion implantation, ion doping, or the like.

An object of the present invention is to provide a method of manufacturing a semiconductor film which can solve the above-mentioned problems and can prevent the deterioration of crystallinity after a solid phase growth process or after laser irradiation.

[0014]

According to a first method of manufacturing a semiconductor film according to the present invention, after a first semiconductor film is formed on an insulating substrate, solid phase growth of the first semiconductor film is performed. Impurities are added to the solid-phase grown film in an amount of 0.1 ppm to 100 p.
pm, a second semiconductor film containing the second semiconductor film is formed.
The semiconductor film is irradiated with a laser.

In a second method for manufacturing a semiconductor film according to the present invention, after a first semiconductor film is formed on an insulating substrate, crystallization is performed by laser irradiation, and impurities are removed on the crystallized film. A second semiconductor film containing in the range of 0.1 ppm to 100 ppm is formed, and laser irradiation is performed on the second semiconductor film.

According to a third method of manufacturing a semiconductor film of the present invention, a semiconductor film having a concentration gradient is deposited on an insulating substrate so that impurities in the film are continuously reduced from the film surface to the substrate interface. Laser irradiation is performed on the surface of the semiconductor film having a concentration gradient.

In a fourth method of manufacturing a semiconductor film according to the present invention, a semiconductor film having a concentration gradient is deposited on an insulating substrate so that impurities in the film are continuously reduced from the film surface to the substrate interface. After solid-phase growth of a semiconductor film having a concentration gradient, laser irradiation is performed on the surface of the solid-phase-grown film.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a semiconductor film, comprising the steps of: forming a first semiconductor film on an insulating substrate; performing a solid phase growth of the first semiconductor film; 0.1 ppm to 100 ppm of impurities on the grown film
And a step of irradiating a laser on the second semiconductor film.

According to a sixth method of manufacturing a semiconductor film according to the present invention, there are provided a step of forming a first semiconductor film on an insulating substrate, a step of performing crystallization by laser irradiation, and a step of performing crystallization on the crystallized film. The method includes a step of forming a second semiconductor film containing an impurity in a range of 0.1 ppm to 100 ppm, and a step of irradiating the second semiconductor film with laser.

A seventh method of manufacturing a semiconductor film according to the present invention comprises the steps of: depositing a semiconductor film having a concentration gradient on an insulating substrate such that impurities in the film are continuously reduced from the film surface to the substrate interface. Irradiating the surface of the semiconductor film having the concentration gradient with laser.

An eighth method of manufacturing a semiconductor film according to the present invention comprises the steps of: depositing a semiconductor film having a concentration gradient on an insulating substrate such that impurities in the film are continuously reduced from the film surface to the substrate interface. A step of solid-phase growing a semiconductor film having the concentration gradient, and a step of irradiating a laser to the surface of the solid-phase-grown film.

That is, according to the method of manufacturing a semiconductor film of the present invention, a film containing impurities and a film containing no impurities are used without diffusing and introducing impurities used for controlling a threshold value of a silicon thin film used as an active layer throughout the film. The impurity gas is introduced during the separation formation or the deposition to form a gradient in the impurity concentration, leaving a film in which the impurities are not mixed. This makes it possible to prevent crystallinity from deteriorating after the solid phase growth process or after laser irradiation.

[0023]

Next, an embodiment of the present invention will be described with reference to the drawings. 1A to 1C are cross-sectional views illustrating a process of manufacturing a semiconductor film according to an embodiment of the present invention. The manufacturing process of the semiconductor film according to one embodiment of the present invention will be described with reference to FIG.

First, LPCVD (Low Pressure Chem) using disilane as a raw material is placed on a glass substrate 1.
Iical Vapor Deposition: Decompression C
The a-Si film 2 is grown at a growth temperature of 450 ° C. by using the VD) method.
Deposit from 00 ° to 900 ° [see FIG. 1 (a)].

After that, a heat treatment is performed in nitrogen or air at 600 ° C., and then a solid phase growth is performed to form a solid phase grown polycrystalline silicon film 3 (see FIG. 1B).
Mixed gas of disilane and diborane (mixing ratio is 0.1 ppm to 100 ppm of diborane to disilane by the method)
), And an impurity-doped silicon film 41 is deposited at 500 to 100 degrees. After this deposition, crystallization is performed by irradiating the laser 5 onto the impurity-doped silicon film 41 (see FIG. 1C).

At this time, the irradiation intensity of the laser 5 is adjusted to such an extent that only the upper portion of the solid-phase grown polycrystalline silicon film 3 as the lower layer is melted. As a result, since the lower solid-phase growth film does not contain impurities, the grain size can be increased. Therefore, after the second silicon layer is laminated and irradiated with laser, crystal growth is performed from the lower solid-phase growth film. Occurs, and a polycrystalline silicon film having a large grain size and a high mobility is obtained with uniformity by reflecting the grain size of the solid phase growth film.

In this case, since the upper layer film contains impurities in advance, polycrystalline silicon containing a small amount of impurities can be uniformly produced. As described above, a polycrystalline silicon film having high mobility can be uniformly formed without using a process such as ion implantation or ion doping.

Normally, when the a-Si film 2 is solid-phase grown,
The columnar crystal grows in a rod shape and randomly, and crystallizes after laser irradiation while leaving the shape of the columnar crystal. The particle size of the silicon film containing impurities beforehand after the solid phase growth film is 1 when the diborane / disilane gas ratio is 100 ppm.
When the gas concentration ratio is 10 ppm or less, the particle size is 500 nm, and when the gas concentration ratio is 1 ppm or less, a particle size of 1000 nm is obtained (see FIG. 4). From this, it can be seen that it is disadvantageous in terms of crystal growth to carry out solid phase growth by mixing impurities in the gas phase.

FIGS. 2A to 2D are cross-sectional views showing the steps of manufacturing a thin film transistor according to one embodiment of the present invention. Each manufacturing process of the thin film transistor according to one embodiment of the present invention will be described with reference to FIG.

Using a LPCVD method on a glass substrate 1,
The temperature inside the reaction tube was kept uniform at 450 ° C., disilane gas (Si ₂ H ₆ ) was introduced, and the a-Si film 2 was formed at 500 ° C.
Deposit. 50 in N ₂ at 600 ° C. in the same reaction tube
The solid phase growth film 3 is obtained for a time [see FIG. 2 (a)].

Thereafter, a mixed gas of diborane gas (B ₂ H ₆ ) and disilane gas (Si ₂ H ₆ ) is introduced, and the impurity-introduced film 4 is deposited at 300 °. Thereafter, the impurity-doped film 4 is irradiated with a laser 5 to be crystallized, and the impurities are redistributed in the solid-phase growth film 3 [FIG.
(B)]. In this case, an excimer laser capable of uniformly irradiating a large area is used as the laser 5.

After crystallization after irradiation with the laser 5, the solid-phase growth film 3 is processed into an island shape, and a gate insulating film 6 is formed by LPCVD. Subsequently, a silicide gate electrode 7 is formed using a high melting point silicide metal, a source / drain electrode 9 is formed by ion doping 8, and an interlayer insulating film (SiN _x ) 10 is deposited to a thickness of 300 nm [FIG.
(C)].

After that, a contact hole is formed in the gate insulating film 6 and the interlayer insulating film 10, and an aluminum electrode 11 is formed in the contact hole to manufacture a transistor (see FIG. 2D).

The transistor manufactured in the above manufacturing process has a uniform mobility of 100 c for both the n-channel and the p-channel.
A high-performance thin film transistor having a value of m ² / Vsec or more can be manufactured uniformly. Further, it has been obtained from experiments and the like that the n-channel and p-channel transistor characteristics exhibit symmetric characteristics with respect to the gate voltage of 0 V as a center, and the threshold value is well controlled.

FIGS. 3A to 3C are cross-sectional views showing the steps of manufacturing a semiconductor film according to another embodiment of the present invention. A manufacturing process of a semiconductor film according to another embodiment of the present invention will be described with reference to FIG.

First, a-Si was grown on a glass substrate 1 at a growth temperature of 450 ° C. by LPCVD using disilane as a raw material.
A mixed gas of disilane and diborane is introduced as an impurity gas during the growth for depositing the film 2, and the impurity introduction film 42 is formed.
Is formed [see FIGS. 3A and 3B]. Then,
The laser 5 is irradiated onto the impurity introduction film 42 [FIG.
(C)]. In this case, 600 ° C. before the irradiation with the laser 5
May be performed.

FIG. 4 is a diagram showing the particle size depending on the diborane / disilane gas concentration of the prior art, and FIG. 5 is a diagram showing the particle size depending on the diborane / disilane gas concentration of the present invention. The particle diameter depending on the concentration of diborane / disilane gas will be described with reference to FIGS.

When the a-Si film 2 is solid-phase grown, columnar crystals grow randomly in a rod shape and crystallize after laser irradiation while maintaining the shape of the columnar crystals. When the impurities are introduced into the entire film, the particle size after the solid phase growth film is 100 when the diborane / disilane gas ratio is 100 ppm.
When the gas concentration ratio is 10 ppm or less, a particle size of 500 nm or 1 ppm or less is obtained, whereas the particle size is 1000 nm or less (see FIG. 4).

When the impurities are redistributed with a laser to achieve the target impurity concentration in the film, the gas concentration ratio at the time of forming the impurities differs depending on the ratio with the film thickness to which the impurities are not introduced. In this case, a gas concentration ratio of about 1.1 to 5 times the gas concentration is required. As a result, the gas concentration of the impurity introduced in order to obtain the same impurity concentration in the film is preferably about twice, and when the particle size in this case is compared, the particle size is 500 nm at a gas concentration of 10 ppm, 800 nm at 20 ppm
(See FIG. 5). The crystallinity and the particle size are evaluated by observation with a scanning electron microscope and a transmission electron microscope.

As described above, the impurity introduction films 41 and 42
The solid-phase growth film 3 into which impurities are not introduced is formed separately from the solid-phase growth film 3 into which impurities are not introduced after the laser irradiation. By causing nucleation to occur dominantly, a good crystalline thin film can be obtained.

That is, the impurity used for controlling the threshold value of the silicon thin film used as the active layer is not diffused and introduced into the entire film. Is introduced to form a gradient in the impurity concentration and leave a film in which the impurity is not mixed, whereby the deterioration of the crystallinity after the solid phase growth process or after the laser irradiation can be prevented.

The solid-phase growth of the solid-phase growth film 3 into which impurities are not introduced is performed first to provide a polycrystalline silicon thin film which is not microcrystallized by impurities and has a large grain size after irradiation with the laser 5. Accordingly, a thin film transistor having high mobility can be manufactured.

[0043]

As described above, according to the present invention, after a first semiconductor film is formed on an insulating substrate, the first semiconductor film is subjected to solid phase growth, and the solid phase growth is performed. Second containing impurities in the range of 0.1 ppm to 100 ppm on the film
By forming a semiconductor film and irradiating the second semiconductor film with laser, there is an effect that deterioration of crystallinity after a solid phase growth process or after laser irradiation can be prevented.

[Brief description of the drawings]

1A to 1C are cross-sectional views illustrating a process of manufacturing a semiconductor film according to an embodiment of the present invention.

FIGS. 2A to 2D are cross-sectional views illustrating respective manufacturing steps of a thin film transistor according to an embodiment of the present invention.

FIGS. 3A to 3C are cross-sectional views illustrating the steps of manufacturing a semiconductor film according to another embodiment of the present invention.

FIG. 4 is a view showing a particle diameter depending on a diborane / disilane gas concentration in a conventional technique.

FIG. 5 is a diagram showing a particle size depending on a diborane / disilane gas concentration of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate 2 a-Si film 3 Solid phase growth film 5 Laser 6 Gate insulating film 7 Silicide gate electrode 8 Ion doping 9 Source drain electrode 10 Interlayer insulating film 11 Aluminum electrode 41,42 Impurity introduction film

Claims (16)

[Claims] After a first semiconductor film is formed on an insulating substrate, solid phase growth of the first semiconductor film is performed, and impurities on the film on which the solid phase growth is performed are 0.1 ppm to 100 ppm.
A method for producing a semiconductor film, comprising: forming a second semiconductor film containing the second semiconductor film in the range described above; and irradiating the second semiconductor film with a laser. 2. The semiconductor device according to claim 1, wherein a concentration of a conductive impurity contained in said second semiconductor film is higher than a concentration of a conductive impurity contained in said first semiconductor film. Of manufacturing a semiconductor film. 3. The method according to claim 1, wherein the first semiconductor film does not contain a conductive impurity. 4. After the first semiconductor film is formed on the insulating substrate, crystallization is performed by laser irradiation, and the second film containing impurities in the range of 0.1 ppm to 100 ppm on the crystallized film. A method of manufacturing a semiconductor film, comprising: forming a semiconductor film according to (1), and irradiating the second semiconductor film with a laser. 5. The semiconductor device according to claim 4, wherein a concentration of a conductive impurity contained in said second semiconductor film is higher than a concentration of a conductive impurity contained in said first semiconductor film. Of manufacturing a semiconductor film. 6. The method according to claim 4, wherein the first semiconductor film does not contain a conductive impurity. 7. A semiconductor film having a concentration gradient is deposited on an insulating substrate such that impurities in the film continuously decrease from the film surface to the substrate interface, and laser irradiation is performed on the surface of the semiconductor film having the concentration gradient. A method of manufacturing a semiconductor film. 8. A semiconductor film having a concentration gradient is deposited on an insulating substrate so that impurities in the film are continuously reduced from the film surface to the substrate interface, and the semiconductor film having the concentration gradient is solid-phase grown. A method of manufacturing a semiconductor film, characterized in that the surface of the film that has been solid-phase grown is irradiated with laser light. 9. A step of forming a first semiconductor film on an insulating substrate; and a step of performing solid phase growth of the first semiconductor film.
Impurities are added to the solid-phase grown film at 0.1 ppm to 1 ppm.
A method for manufacturing a semiconductor film, comprising: a step of forming a second semiconductor film having a content of 00 ppm, and a step of irradiating a laser beam on the second semiconductor film. 10. The semiconductor device according to claim 9, wherein the concentration of the conductive impurity contained in the second semiconductor film is higher than the concentration of the conductive impurity contained in the first semiconductor film. Of manufacturing a semiconductor film. 11. The method according to claim 9, wherein the first semiconductor film does not contain a conductive impurity. 12. A step of forming a first semiconductor film on an insulating substrate, a step of crystallization by laser irradiation, and a step of depositing an impurity of 0.1 ppm to 100 ppm on the crystallized film.
A method for manufacturing a semiconductor film, comprising: a step of forming a second semiconductor film containing pm, and a step of irradiating a laser on the second semiconductor film. 13. The semiconductor device according to claim 12, wherein a concentration of a conductive impurity contained in said second semiconductor film is higher than a concentration of a conductive impurity contained in said first semiconductor film. Of manufacturing a semiconductor film. 14. The semiconductor device according to claim 12, wherein the first semiconductor film does not contain a conductive impurity.
The method for manufacturing a semiconductor film according to the above. 15. A step of depositing a semiconductor film having a concentration gradient on an insulating substrate so that impurities in the film continuously decrease from the film surface to the substrate interface, and forming a semiconductor film having a concentration gradient on the surface of the semiconductor film having the concentration gradient. Irradiating a laser beam. 16. A step of depositing a semiconductor film having a concentration gradient on an insulating substrate so that impurities in the film are continuously reduced from the film surface to the substrate interface; A method of manufacturing a semiconductor film, comprising: a step of growing; and a step of irradiating a laser to the surface of the film that has been solid-phase grown.