JPH10270696A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To irradiate an amorphous semiconductor film with beams having optimum energy in response to the structure of a foundation, to crystallize the whole film uniformly and to prevent the possibility of the breakdown of the film when the semiconductor film is crystallized. SOLUTION: An SiO2 film 14 is removed by etching while being left only in a region corresponding to a gate electrode 11 on a glass substrate 10. The plasma or ions of N-type impurities are doped to an amorphous Si film while using a photo-resist film as a mask, and a source region 18a and a drain region 18b are formed. The resist film is peeled, the amorphous Si film is irradiated with laser beams 19 from the substrate surface side and the amorphous Si film is melted and cooled at a room temperature, a melted region is crystallized, and a polycrystalline Si film 20 with the source and drain regions 18a, 18b is formed. Since the SiO2 film 14 as a temperature adjusting film is formed in a region corresponding to the gate electrode at that time, the reaching temperature of a film surface is equalized approximately, and the whole film is crystallized uniformly.

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 device in which a semiconductor film such as an amorphous silicon film is formed by irradiating an energy beam to crystallize the semiconductor film. LCD; Liquid Crystal Display)
Thin film transistor (TFT; Thin Film T)
The present invention relates to a method for manufacturing a semiconductor device having a structure in which the underlayer of a semiconductor film to be crystallized is not uniform, such as a ransistor.

[0002]

2. Description of the Related Art A TFT liquid crystal display uses a thin film transistor (TFT) as an element having a switching function, and the TFT is formed on a glass substrate corresponding to each pixel of the liquid crystal display. There are TFTs made of amorphous silicon film and polycrystalline silicon film. Among them, the TFT made of polycrystalline silicon film irradiates an amorphous silicon film with an energy beam, especially an excimer laser. Thereby, a high-performance glass substrate can be manufactured at a low temperature. Using such a polycrystalline silicon film TFT, a peripheral circuit of a liquid crystal display and a pixel switching element can be manufactured on the same substrate. And recently, TF made of polycrystalline silicon film
Of the TFTs, particularly, a TFT having a bottom gate structure has attracted attention because stable characteristics can be obtained.

The bottom gate TFT has a structure as shown in FIG. 9, for example. That is, a gate electrode 101 made of molybdenum tantalum (MoTa) is formed on a glass substrate 100, and this gate electrode 101 is formed.
An oxide film (Ta ₂ O ₅ ) 102 is formed thereon. On the glass substrate 100 including the oxide film 102, a silicon nitride (SiN _x ) film 103 and a silicon dioxide film (S
A gate insulating film made of iO ₂ ) 104 is formed, and a thin polycrystalline silicon film 105 is formed on the silicon dioxide film 104. This polycrystalline silicon film 105
The source region 105 is formed therein by introducing, for example, an n-type impurity.
a and the drain region 105b are formed respectively. On the polysilicon film 105, a silicon dioxide film (SiO ₂ ) 106 is selectively formed corresponding to the channel region 105c of the polysilicon film 105.
Polycrystalline silicon film 105 and silicon dioxide film 106
On the n ⁺ -doped polycrystalline silicon film 107, a source electrode 108 is formed on the n ⁺ -doped polycrystalline silicon film 107 so as to face the source region 105a, and a drain electrode 109 is formed on the n ⁺ doped polycrystalline silicon film 107 so as to face the drain region 105b. Have been.

[0004] The TFT having the bottom gate structure can be manufactured by the following method. That is, molybdenum tantalum (MoTa) is formed on the entire surface of the glass substrate 100.
After forming the film, the molybdenum tantalum film is patterned into a predetermined shape by etching to form the gate electrode 101.
To form Thereafter, the gate electrode 101 is anodized to form an oxide film 102 on the surface thereof. Next, PECVD (Plasma Enhanced Chemical Vapor Depo
A silicon nitride film 103, a silicon dioxide film 104, and an amorphous silicon film are continuously formed on the entire surface of the oxide film 102 by the sition) method.

Next, by irradiating the amorphous silicon film with a laser beam by, for example, an excimer laser,
This amorphous silicon film is once melted and then cooled to room temperature to be crystallized. Thus, the amorphous silicon film becomes the polycrystalline silicon film 105. Subsequently, after selectively forming a silicon dioxide film 106 having a shape corresponding to the channel region on the portion of the polycrystalline silicon film 105 to be a channel region, an n-type impurity such as phosphorus (P) or arsenic (As) is formed.
Is formed, and the laser beam is again irradiated with an excimer laser to form the n ⁺ -doped polycrystalline silicon film 107 and the impurities are electrically activated.

Next, argon (A) is used as a sputtering gas.
r), an aluminum (Al) film is formed on the entire surface by a sputtering method, and the aluminum film and the n ⁺ -doped polycrystalline silicon film 107 are patterned into predetermined shapes by etching, respectively.
05a and the source electrode 10 on the drain region 105b.
8 and the drain electrode 109 are formed. Subsequently, the channel region 105c is hydrogenated by hydrogen radicals and atomic hydrogen that are exposed to hydrogen and pass through the silicon dioxide film 106 to inactivate dangling bonds and the like. Through the above process, the TFT having the bottom gate structure shown in FIG. 9 can be obtained.

[0007]

As described above, in the conventional method, in the step of crystallizing the amorphous silicon film,
The amorphous silicon film is irradiated with an energy beam. At this time, the underlying structure of the amorphous silicon film is not uniform. That is, there is a metal film (gate electrode 101) on the glass substrate 100, and the base of the amorphous silicon film has a structure in which two types of materials, metal and glass, are different from each other. The crystalline silicon film is simultaneously irradiated with an energy beam. In this case, the same energy beam is applied to the glass substrate 1 based on the optimum condition of the crystallization energy of the amorphous silicon film in the channel region on the metal film (gate electrode 101).
Irradiation was also performed on the amorphous silicon film on the substrate No. 00.

However, even for the same amorphous silicon film, the optimum value of the energy for crystallization is different between the region where the base is a metal and the region where the base is a glass because the thermal conductivity is different. Therefore, the metal film (the gate electrode 10)
1) In the conventional method that is adapted to the optimum condition of the amorphous silicon film, the amorphous silicon film on the glass substrate 100 is irradiated with more energy beams than the optimum condition. There has been a problem that film destruction may occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to be able to irradiate an amorphous semiconductor film with a beam having an optimum energy according to the structure of a base when crystallizing the same. Another object of the present invention is to provide a method for manufacturing a semiconductor device which can be uniformly crystallized over the entire film and has no fear of film destruction.

[0010]

According to the present invention, there is provided a method of manufacturing a semiconductor device, comprising the steps of selectively forming a metal film on a substrate; and forming an amorphous and uniform semiconductor film on the metal film and the substrate. Forming a film, forming a temperature adjustment film having a lower thermal conductivity than the metal film in a region corresponding to the metal film on the semiconductor film, and irradiating the semiconductor film with an energy beam to form the semiconductor film. And a step of polycrystallization.

More specifically, the method for manufacturing a semiconductor device according to the present invention comprises the steps of forming a metal film as a gate electrode of a thin film transistor on the surface of a substrate, and forming an insulating film on the metal film and the substrate. Forming an amorphous semiconductor film having a uniform thickness on the insulating film; and forming a temperature adjustment film having a lower thermal conductivity than the metal film in a region corresponding to the metal film on the semiconductor film. Forming a source region and a drain region by introducing impurities into a region other than the region corresponding to the temperature adjustment film, and irradiating an energy beam to the semiconductor film on which the source region and the drain region are formed to perform polycrystallization. And the step of performing.

In the method for manufacturing a semiconductor device according to the present invention,
When an energy beam is irradiated to crystallize the amorphous semiconductor film, the amorphous semiconductor film is melted. After that, the amorphous semiconductor film is cooled to room temperature to crystallize a melted region to become a polycrystalline semiconductor film. At this time, since the temperature adjustment film having a lower thermal conductivity than the metal film is formed in a region corresponding to the metal film (gate electrode) on the amorphous semiconductor film, the maximum temperature reached on the surface of the semiconductor film is almost zero. As a result, the semiconductor film can be uniformly crystallized over the entire surface of the semiconductor film by irradiation with the same energy beam.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

Prior to the description of specific embodiments, first, the basic principle of the present invention will be described. As described above, even if the same amorphous silicon film is used, the optimum value of the energy for crystallization is different depending on whether the base is made of metal or glass. In the present invention, an insulating film having a lower thermal conductivity than the metal film is formed as a temperature adjusting film in a region where the metal film is present in the underlayer structure, so that the entire surface of the semiconductor film is uniformly irradiated with the same energy beam. It allows crystallization. Hereinafter, the reason will be described.

FIGS. 3A and 3B show examples of substrates having different underlying structures of the silicon film. In the structure of FIG. 3A, a nickel (Ni) film 61 is formed on a glass substrate 60, and a silicon nitride (SiN) film 62, an insulating film (SiO ₂ ) 63, and an amorphous silicon film (a) are formed thereon. -Si) 64
Are formed in this order. On the other hand, the structure of FIG. 3B has a silicon nitride (SiN) film 6 on a glass substrate 60.
2. An insulating film (SiO ₂ ) 63 and an amorphous silicon film 64 are formed in this order, and have the same structure except that the metal film (nickel film 61) does not exist under the amorphous silicon film 64. ing.

FIG. 4 shows an excimer laser (energy: 360 mJ / cm ² , pulse width: 30 n) as an energy beam for the amorphous silicon film 64 having the structure shown in FIG.
(s, wavelength of 308 nm) when simulating the temperature change of the outermost surface of the amorphous silicon film 64 when irradiating the amorphous silicon film 64. On the other hand, FIG. 5 shows a simulation result of a temperature change on the outermost surface of the amorphous silicon film 64 when the same excimer laser is irradiated on the amorphous silicon film 64 having the structure of FIG. It is. FIG. 6 shows parameters of the material of the film.

As is apparent from the results shown in FIGS. 4 and 5, the temperature of the amorphous silicon film 64 rapidly rises to the melting point (a-Si melting point) during the irradiation with the excimer laser. , Where the slope of the rise once becomes gentle due to the latent heat of melting, and then rises rapidly again. Here, when excimer lasers of the same energy are irradiated, the maximum attainable temperature differs depending on the underlying structure of the amorphous silicon film 64. That is, when the metal film (the nickel film 61) exists under the amorphous silicon film 64 (the structure of FIG. 3A), the maximum temperature is about 2653.
(K), the metal film (nickel film 6)
When 1) does not exist (the structure shown in FIG. 3B), the maximum temperature is about 2970 (K), which greatly differs depending on the structure of the base. The difference between the highest temperatures increases as the thickness of the insulating film 63 decreases. After the excimer laser irradiation is completed after the temperature reaches the maximum temperature, FIG.
In any of the structures shown in FIG.
, And the temperature of the amorphous silicon film 64 gradually decreases. Then, the crystallization temperature of silicon (1410 °)
When the temperature reaches C), latent heat of crystallization is generated, and the temperature becomes constant for a certain time (crystallization time), and then gradually decreases again.

When irradiating an excimer laser to the amorphous silicon film 64 having the respective structures shown in FIGS. 3A and 3B, in order to optimize laser conditions, it is necessary to use the same energy for each amorphous silicon film. It is desirable that the maximum temperature reached on the surface of the silicon film 64 be the same. For this reason, as shown in FIG. 7, the present inventor formed a silicon dioxide (SiO ₂ ) film 65 as a temperature adjusting film on the amorphous silicon film 64 having the structure of FIG. FIG. 3
It is considered that the temperature conditions of the structures (a) and (b) are the same as each other, so that the temperature of the outermost surface of the silicon film can be made the same regardless of the underlying structure (the presence or absence of the metal film), as shown in FIG. The characteristic diagram was obtained by an experiment.

FIG. 8 shows the maximum temperature at the outermost surface of the amorphous silicon film 64 and the reflectivity of the laser at the time of laser irradiation when the thickness of the silicon dioxide film 65 is changed in the structure of FIG. Things. That is, FIG. 8 shows that the film thickness of the insulating film (SiO ₂ ) 63 is 100 n in the structure of FIG.
m, the thickness of the silicon nitride (SiN) film 62 is fixed at 50 nm, the thickness of the amorphous silicon film 64 is fixed at 30 nm, the thickness of the silicon dioxide film 65 is changed, and an excimer laser is applied at 360 mJ / cm ² . It shows the result of simulating the maximum temperature and the reflectance of the outermost surface of the amorphous silicon film 64 at the time of irradiation. For example, FIG.
In the structure of FIG. 3B, the highest temperature at the outermost surface of the amorphous silicon film 64 rises to 2970K, and in the structure of FIG. 3A, it rises only to 2653K. According to the results of FIG. 8, in order to optimize the laser conditions in the structure of FIG. 3B and the structure of FIG.
The thickness of the silicon dioxide film 65 having the structure of FIG.
It can be seen that the wavelength may be set to 5 nm or 160 nm. Therefore, in the structure of FIG.
It can be seen that the temperature of the outermost surface of the amorphous silicon film 64 on the region where the nickel film 61 is present can be freely adjusted by changing the film thickness of No. 5.

The present invention utilizes such a result to form a temperature adjusting film having a lower thermal conductivity than the metal film on a certain region of the metal film on the same substrate, thereby achieving the maximum temperature over the entire film. And crystallization is carried out uniformly. Hereinafter, an example in which the present invention is applied to a method for manufacturing a thin film transistor will be described.

FIGS. 1 (a) to 1 (c) and FIGS.
(B) shows a method for manufacturing a thin film transistor according to an embodiment of the present invention in the order of steps. First, FIG.
As shown in (a), a gate electrode 11 made of a nickel (Ni) film having a thickness of 100 nm is formed on the entire surface of a substrate, for example, a glass substrate 10 by a sputtering method using argon (Ar) as a sputtering gas, for example. Subsequently, for example, helium (He) is also used as a sputtering gas.
A 50 nm-thickness silicon nitride (SiN _x ) film 12a is formed on the entire surface by a sputtering method using
A silicon dioxide (SiO ₂ ) film 12b of 0 nm is formed to form an insulating film 12 having a laminated structure.
An amorphous silicon film 13 having a thickness of 30 nm is continuously formed on the insulating film 12 by the CVD method. Amorphous silicon film 1
After forming the silicon nitride film 3, a silicon dioxide film 14 having a thickness of, for example, 70 nm is formed on the amorphous silicon film 13 by, for example, a sputtering method.

Next, as shown in FIG. 1B, a photoresist is applied to the entire surface of the silicon dioxide film 14 and, for example, a g-line ( Exposure (backside exposure) 16 with a wavelength of 436 nm is performed. At this time, the photoresist film 15 having the same width as the gate electrode 11 is formed in a self-aligned manner using the gate electrode 11 as a mask. Next, the silicon dioxide film 1
The silicon dioxide film 14 is left only in the region where the gate electrode 11 is formed on the glass substrate 10 as shown in FIG. 1C by etching away while leaving only the gate electrode 11 on the gate electrode 11. Next, using the photoresist film 15 as a mask, an n-type impurity 17, for example, phosphorus (P) is introduced into the amorphous silicon film 13 by plasma doping using PH ₃ plasma at a low temperature of, for example, 90 ° C. or ion doping. As a result, a source region 18a and a drain region 18b are formed. Subsequently, after the photoresist film 15 is peeled off, a laser beam 19 is irradiated from the substrate surface as shown in FIG. The irradiation of the laser beam 19 causes the amorphous silicon film 13 to melt, and then cools to room temperature to crystallize the melted region, thereby forming a polycrystalline silicon film 20 having a source region 18a and a drain region 18b. . Here, in the present embodiment, silicon dioxide film 14 having a lower thermal conductivity than the metal film is formed in a region corresponding to the metal film (gate electrode 11) on polycrystalline silicon film 20. As described above, the maximum temperature reached on the film surface becomes almost the same regardless of the presence or absence of the metal film on the underlayer, and crystallization can be performed uniformly over the entire film.

As the laser beam 19, a laser beam having a wavelength that the amorphous silicon film 13 absorbs, particularly a pulse laser beam using an excimer laser, is preferably used. As the excimer laser, a pulse laser beam (wavelength: 308 nm) using a XeCl excimer laser, a pulse laser beam (wavelength: 350 nm) using a XeF excimer laser, or the like is used.

Next, as shown in FIG. 2B, the source region 1 in the polycrystalline silicon film 20 is formed by a sputtering method using argon (Ar) as a sputtering gas, for example.
Electrodes 21a and 21b made of aluminum (Al) are formed on 8a and drain region 18b, respectively. Subsequently, a silicon nitride film 22 as a protective layer is formed by a sputtering method. Next, the channel region 18c in the polycrystalline silicon film 20 is hydrogenated by performing plasma hydrogenation in hydrogen plasma to inactivate dangling bonds and the like.

As described above, according to the method of manufacturing a thin film transistor according to the present embodiment, when irradiating the laser beam 19 for crystallization, a region where the metal film (gate electrode 11) is present has heat conduction from the metal film in advance. Since the silicon dioxide film 14 having a low rate is formed, the amorphous silicon film 13 can be uniformly crystallized over the entire surface of the substrate.
Therefore, there is no fear of film destruction, and the process margin can be increased.

Although the present invention has been described with reference to the embodiment, the present invention is not limited to the above-described embodiment and can be variously modified. For example, in the above embodiment, the metal film underlying the silicon film was described as a nickel film, but other metal films (for example, alumina (Al
₂ O ₃ ) film and an aluminum film).
In the above embodiment, a silicon dioxide film is used as the temperature adjustment film, but another film, for example, a silicon nitride film may be used. In the above embodiment, a silicon film is described as an amorphous semiconductor film. However, other amorphous films can be applied as long as they can be crystallized by irradiation with an energy beam. Further, in the above embodiment, an example in which the present invention is applied to a method for manufacturing a thin film transistor has been described. However, the present invention can be applied to a process for manufacturing another semiconductor device.

[0027]

As described above, according to the method of manufacturing a semiconductor device according to the present invention, a region having a lower thermal conductivity than a metal film is formed in a region corresponding to an underlying metal film on an amorphous semiconductor film. Since the adjustment film is formed, when irradiating the energy beam to crystallize the amorphous semiconductor film, it is possible to uniformly crystallize the entire surface of the semiconductor film with the same energy beam irradiation. it can. Therefore, there is an effect that the possibility of film destruction is eliminated and a process margin can be increased.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a method of manufacturing a thin film transistor according to an embodiment of the present invention for each process.

FIG. 2 is a cross-sectional view illustrating a process following the process in FIG.

FIG. 3 is a diagram for explaining a basic principle of the present invention;
(A) is a structure in which a metal film is formed under a silicon film,
(B) is a cross-sectional view showing a structure in which a metal film is not formed on a base of a silicon film.

FIG. 4 is a characteristic diagram for explaining a state of a temperature change of a silicon film when a laser beam is applied to the structure of FIG. 3A.

FIG. 5 is a characteristic diagram for explaining a state of a temperature change of a silicon film when a laser beam is applied to the structure of FIG. 3B.

FIG. 6 is a diagram showing parameters of each material used in a simulation for explaining the principle of FIG. 3;

FIG. 7 is a diagram for explaining a basic principle of the present invention;
FIG. 4 is a cross-sectional view illustrating a structure in which a metal film is formed under a silicon film, and an insulating film having lower thermal conductivity than the metal film is formed on the silicon film.

8 is a characteristic diagram showing a maximum temperature and a reflectance of a silicon film with respect to a thickness of an insulating film having a lower thermal conductivity than a metal film in the structure of FIG. 7;

FIG. 9 is a cross-sectional view illustrating a structure and a manufacturing method of a conventional thin film transistor.

[Explanation of symbols]

10: glass substrate, 11: gate electrode (metal film), 12
... an insulating film, 13 ... an amorphous silicon film, 14 ... a silicon dioxide film (temperature control film), 15 ... a photoresist film, 17
... n-type impurity, 18a ... source region, 18b ... drain region, 18c ... channel region, 19 ... laser beam, 2
0 ... polycrystalline silicon film

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Setsuo Usui 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation

Claims (5)

[Claims] A step of selectively forming a metal film on the substrate; a step of forming an amorphous semiconductor film having a uniform thickness on the metal film and the substrate; Forming a temperature adjustment film having a lower thermal conductivity than the metal film in a region corresponding to the film; and irradiating the semiconductor film with an energy beam to uniformly polycrystallize the semiconductor film. A method for manufacturing a semiconductor device, comprising: 2. The method according to claim 1, wherein the amorphous semiconductor film is a silicon film. 3. The method according to claim 1, wherein the energy beam is a beam generated by an excimer laser. 4. The method according to claim 1, wherein the thickness of the temperature adjustment film is determined according to the thickness of the metal film. 5. A step of forming a metal film as a gate electrode of a thin film transistor on a surface of a substrate, and forming an insulating film on the metal film and the substrate; and forming an amorphous and uniform film on the insulating film. Forming a temperature-controlling film having a lower thermal conductivity than the metal film in a region on the semiconductor film corresponding to the metal film; and forming a region other than the region corresponding to the temperature-controlling film. Forming a source region and a drain region by introducing an impurity into the region, and irradiating an energy beam to the semiconductor film on which the source region and the drain region are formed to polycrystallize the semiconductor film. Manufacturing method of a semiconductor device.