JPH1197350A - Method of heat treating semiconductor film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an electronic device such as transistors superior in characteristics, by forming a semiconductor film on a layer formed on a substrate, partly including voids, and irradiating a pulse energy beam on the semiconductor film. SOLUTION: A method comprises steps of forming a layer 20 composed of voids 22, support layer 24 and base support layer 26 partly including voids on a substrate 10, forming an amorphous semiconductor layer 30 on the layer 20, and irradiating a pulse energy 40 on the semiconductor layer 30 to heat the sample, where the heat generated in the semiconductor layer 30 hardly conducts at the voids 22 but rapidly conducts at the solid support layer 24 to the substrate, i.e., the heat generated in the semiconductor layer 30 conducts laterally therein and to the substrate 10 via the support layer 24. Thus, it is possible to always cause the crystallization on the support layer 24 and control the 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 heat treating a semiconductor thin film, and more particularly to a method for efficiently performing a heat treatment on a semiconductor thin film for manufacturing a semiconductor device having excellent characteristics.

[0002]

2. Description of the Related Art Bipolar and MOS transistors using single crystal silicon and thin film transistors using polycrystalline silicon are widely used as elements constituting an electronic device. Since these transistors are all formed on a crystalline semiconductor, formation of a crystalline semiconductor is extremely important. In particular, a crystallization technique is important for a thin film transistor formed over an insulator and an insulating layer.

As a conventional thin film crystallization technique, a method of heating at a high temperature of 600 to 1000 ° C. for 2 to 20 hours in an electric furnace, or a method of irradiating a pulse laser to the thin film to melt the thin film in a short time, There is a known method for converting the data.
By using these techniques, crystal grains having a size of 0.1 to 5 μm have been obtained.

[0004]

The above-mentioned crystallization technique is
Although a high-quality polycrystalline silicon film can be formed, it is difficult to control the crystal growth direction and the formation of crystal grain boundaries. Therefore, the defect density in the transistor formed on the polycrystalline silicon film thus obtained varies, and the transistor characteristics such as threshold voltage, mobility, and leak current vary.

An object of the present invention is to provide a heat treatment method for a semiconductor thin film which solves such a problem and enables fabrication of an electronic device such as a transistor having excellent characteristics.

[0006]

In order to solve the above-mentioned problems, the present invention (claim 1) comprises a step of forming a layer having a partial void on a substrate and a step of forming a layer having a partial void on the substrate. Forming a semiconductor film, and irradiating the semiconductor film with a pulsed energy beam to heat the semiconductor film.

According to the present invention (claim 2), in the above-described method for heat treating a semiconductor film (claim 1), the partially voided layer is a layer in which voids are periodically formed in a lateral direction. It is characterized by the following.

The present invention (Claim 3) is characterized in that in the above-described method for heat treating a semiconductor film (Claim 1), the irradiation with the pulsed energy beam is performed for an irradiation time of 1 ns to 100 ms.

The present invention (claim 4) is characterized in that, in the above-mentioned heat treatment method for a semiconductor film (claim 3), the pulsed energy ray is a laser beam light.

The present invention (Claim 5) is characterized in that in the above-mentioned method for heat treating a semiconductor film (Claim 3), the irradiation of the pulsed energy beam is performed using gas combustion.

According to the present invention (claim 6), a step of forming a layer partially having a gap on a substrate, a step of forming a semiconductor film on the layer partially having a gap, Heating the semiconductor film by irradiating a pulsed energy beam, and crystallizing to form a crystalline film;
Forming a MOS transistor using the crystalline film as a channel layer.

According to the present invention (claim 7), a step of forming a layer partially having a gap on a substrate, a step of forming a semiconductor film on the layer partially having a gap, Heating to form a crystalline film, selectively introducing impurities into the crystalline film, and heating the crystalline film by irradiating the crystalline film with a pulsed energy ray, Activating impurities to form a source region and a drain region in the crystalline film.

According to the present invention (claim 8), a step of forming a layer partially having a gap on a substrate, a step of forming a semiconductor film containing impurities on the layer partially having a gap,
Irradiating the semiconductor film with a pulsed energy beam to heat the semiconductor film to crystallize the semiconductor film and / or activate the impurities, thereby manufacturing a solar cell element. Provide a way.

In the method for heat-treating a semiconductor film and the method for manufacturing a thin-film semiconductor device or a solar cell element according to the present invention, the pulse-like energy is applied to the semiconductor film formed on the partially voided layer. The semiconductor film is heated by irradiating the line. As a result, the semiconductor film is crystallized, impurities contained in the semiconductor film are activated, or both are performed.

As a semiconductor device to which the method of the present invention is applied, for example, a thin film transistor, a MOS FET, a bipolar transistor, a circuit using them, a solar cell element, a circuit using the same, and the like can be exemplified.

The method for heat treating a semiconductor film according to the present invention comprises:
A layer having a partial void is formed on a substrate. The layer having partial voids, for example, after forming a layer made of chromium, molybdenum, tungsten, etc., selectively removes this layer by etching or the like to form voids,
The voids are filled with a substance soluble in a solvent such as a resist or polyimide, and then a protective layer made of silicon oxide, silicon nitride, or the like is formed on the entire surface, and finally, the substances embedded in the voids are removed with a solvent. By doing so, it can be formed.

Next, a semiconductor film is formed on the layer partially having voids, and the semiconductor film is irradiated with pulsed energy rays. As the semiconductor film, any of an amorphous semiconductor and a crystalline semiconductor can be used. When using an amorphous semiconductor as the semiconductor film, irradiation with pulsed energy rays is performed for crystallization of the amorphous semiconductor, and when using a crystalline semiconductor, irradiation with pulsed energy rays is performed. Is performed to activate the impurities introduced into the crystalline semiconductor.

The irradiation time of the pulse energy beam is 1n
s to 100 ms are preferred.

As the irradiation of the pulse energy, irradiation of a laser beam, gas combustion heating, or the like can be used.

In a partially voided layer, the thermal conductivity of the void is significantly lower than that of the portion formed of the solid material. Therefore, when the semiconductor film is heated by irradiation with pulsed energy, it is possible to control the diffusion of heat in the voids and generate a temperature gradient.
As a result, the crystallization direction can be controlled by the temperature gradient to form a crystalline thin film at a desired position.

A preferred embodiment of the method of the present invention is to use a layer in which voids are formed periodically in the lateral direction. By using such a layer, a crystalline semiconductor film having periodically uniform properties can be formed, and a semiconductor element with less variation in characteristics can be formed.

[0022]

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

First, the basic concept of the present invention will be described with reference to FIG.

First, a layer 20 having a partially void portion is formed on a substrate 10. The partially voided layer 20 comprises the void 22, the support layer 24 and the underlying support layer 26.
It consists of. Next, the amorphous semiconductor layer 30 is formed over the layer 20. Next, the amorphous semiconductor layer 30 is irradiated with pulsed energy 40 to heat the sample (FIG. 1).
(A)). In this case, the temperature rise of the amorphous semiconductor layer 20 due to the irradiation heating of the pulse energy 40 is determined by the intensity of the pulse energy, the irradiation time, and the heat conduction to the lower substrate.

In general, the voids have a significantly lower thermal conductivity than solids. For example, the thermal conductivity of air is 2.4 × 10
A ^-2 Wm ^-1 K ^-1, which the thermal conductivity of silicon for the 168Wm ^-1 K ^-1, heat conductivity of quartz glass is 1.4W
m ⁻¹ K ^−1, which is much larger than the heat conduction of air.

Therefore, the heat generated in the amorphous semiconductor layer 30 by the pulsed energy irradiation is less likely to be transmitted downward in the gap 22, but is quickly transmitted to the substrate in the solid support region 24. For this reason, the temperature of the amorphous semiconductor layer 30 is extremely high in a portion having a gap below, and the temperature is not so high in a portion of the solid support region below. Therefore, as shown in FIG. 1B, a temperature gradient occurs in the lateral direction.

The heat generated in the amorphous semiconductor layer 30 by the irradiation of the pulse energy is transmitted laterally in the amorphous semiconductor layer 30 as shown by an arrow 50 and is transmitted through the solid support layer 24 as shown by an arrow 52. Through the substrate 10. Irradiation of sufficient pulse energy allows the amorphous semiconductor layer 30
When the temperature reaches the temperature required for crystallization, crystallization occurs in the lateral direction opposite to the direction of heat conduction, as shown by arrow 60 in FIG.

In this case, a void is formed at an appropriate position, and crystallization can always be caused to occur from above the solid support region 24 by irradiating the semiconductor layer with energy, whereby crystallization can be controlled. In addition, when the semiconductor layer is melted by irradiation with sufficient pulse energy, solidification of the semiconductor layer always occurs from the gap 22, so that crystallization can be controlled. In FIG. 1C, reference numeral 32 indicates a crystallized region, and reference numeral 34 indicates an amorphous region that has not been crystallized yet.

The temperature gradient of the semiconductor layer 30 depends on the pulse energy irradiation time. If the irradiation time is too long, heat conduction is sufficiently performed, and the entire sample becomes an isothermal state. When the irradiation time is too short and only the very surface layer of the semiconductor layer is heated, the effect of controlling the heat conduction by the voids is reduced. 10nm thickness of semiconductor thin film used as electronic device
Considering ~ 200 µm, the preferred irradiation time is 1n
s to 100 ms are preferred.

A pulsed laser beam can be exemplified as the pulsed energy irradiation means. Crystallization of a semiconductor thin film using a pulsed laser beam is widely used as a short-time crystallization method (Reference 1). According to this method, heating of ns to μs is possible depending on the pulse width.

Even when a CW laser beam is used, pulsed energy irradiation can be performed by sweeping the laser beam.

As the pulse energy irradiation means, a beam gas combustion flame can be exemplified (Reference 2). For example, as shown in FIG. 2, when a gas is ignited by a discharge 90 or the like in a container 80 containing a mixed gas 70 of hydrogen and laughing gas (N ₂ O), combustion spreads throughout the container 80,
The sample 100 can be heated in a short time. With this method, heating for 1 to 100 ms is possible.

Reference 1: T.I. Sameshima, M .; H
ara and S.A. Usui: “XeCl Exci
mer Laser Annealing Used
to Fabric Poly-Si TFT
s ", Jpn. J. Appl. Phys., 28 (19
89) 1789-1793. Reference 2: T. Sameshima Y. Sunaga
N. Takashima and A. Tajim
a ,: "Rapid Thermal Anneali
ng Use the Combustion o
f H ₂ withN ₂ O "Appl.Phys.Let
t. 69 (1996) 1205-1207. Pulsed energy irradiation can also be performed by sweeping a stationary gas irradiation beam as pulsed energy irradiation means.

FIG. 3 shows a method of forming a layer structure having a partial void by using a lithography technique.
First, a film 120 having a void layer structure is formed on the base 110 (FIG. 3A). Examples of the film material include metals such as chromium. However, the method of the present invention is not limited to chromium, and various other materials can be selected. As a film forming method, for example, a sputtering method can be given. However, the film formation method is not limited to the sputtering method, and another optimum film formation method can be selected.

Next, the film 120 is patterned using lithography and etching techniques.
As shown in (b), the film 120 is partially removed.

Next, as shown in FIGS. 3C and 3D, a substance 130 that is highly soluble in a solvent such as a resist is applied, and a part of the substance 130 is removed by etching. Is flattened so as to be exposed to light.

Thereafter, EC is used as a protective layer for the flat surface.
The film 140 is formed as shown in FIG. 3E by using a method capable of forming a film at a low temperature, such as R plasma CVD and sputtering. As a material of the film 140, for example, silicon oxide can be exemplified. However, the method of the present invention
The material is not limited to this, and various other materials can be selected.

After the formation of the film 140, the substance 130 can be removed by a solvent to form a layer structure having a partial gap 135 as shown in FIG.

When a layer structure having voids is formed periodically and a crystalline film is formed periodically, an amorphous semiconductor film must be formed as shown in FIG. It is preferred that the direction of crystallization be specified as indicated by arrow 150 by removing a portion of layer 30.

However, the layer structure having voids and the shape of the semiconductor layer are not limited to the above examples, and can be changed as appropriate. For example, as shown in FIG. 5, a dot-like solid support layer 160 is formed on a substrate 10, and a circular semiconductor layer centered on the dot-like solid support layer 160 is formed thereon via a base support layer 26. Upon formation of 170, crystallization occurs in the central support layer 160.
From the direction of arrow 180, and can form a crystallized region expanding in a circle.

As shown in FIG. 6, a rectangular point-shaped solid support layer 200 is formed, and a portion corresponding to the rectangular point-shaped solid support layer 200 is formed on one end of the solid support layer 200 via an underlayer support layer 26. Thus, when the rectangular semiconductor layer 190 is formed and pulsed energy is applied, the heat flow in the semiconductor layer 190 can be controlled so as to concentrate in the direction of the support layer. Therefore, the crystallization can be started from the region corresponding to the rectangular solid support layer 200 in the direction of the arrow 210, and can be extended to the entire semiconductor layer 190. This method is effective for forming a single crystal without grain boundaries.

Next, as a specific application example of the present invention, the production of a transistor element and a circuit using the same will be described. FIG. 7 shows a metal oxide semiconductor (MO)
An example of manufacturing an S) type crystalline thin film transistor (TFT) will be described.

First, the semiconductor layer formed on the underlying layer 220 having the void structure is crystallized by the method of the present invention,
A crystalline semiconductor film 230 is formed (FIG. 7A). Next, a gate insulating film 240 is formed over the crystalline semiconductor film 230, and a source region 250 and a drain region 252 are formed by doping impurities into the crystalline semiconductor film 230. Next, the gate electrode 260, the source electrode 262,
And drain electrodes 264, and further, by forming interlayer insulating films 270 and 272, a passivation layer 274, and metal wirings 280 and 282 between the transistor and an external circuit, a TFT is obtained (FIG. 7B). .

The method of the present invention can be applied not only to crystallization of an amorphous semiconductor layer but also to activation of impurities. FIG. 8 shows an example of manufacturing a TFT in which the heat treatment method according to the present invention is applied to the activation of impurities.

First, a crystalline silicon film 230 is formed on the underlying layer 220 having a void structure (FIG. 8A). The method for forming the crystalline silicon film is not limited to the irradiation with pulsed energy rays as used in the method of the present invention, and a heating method using a normal electric furnace can also be employed.

Next, after forming the gate insulating film 240 on the crystalline silicon film 230, an impurity is introduced into the crystalline silicon film 230 by ion implantation or the like, and the impurity layer 29 is formed.
0,292. Then, by irradiating a pulsed energy beam and performing a heat treatment according to the present invention,
Activation of the impurities is performed to form a source region 250 and a drain region 252 (FIG. 8B). Thereafter, a gate electrode 260, a source electrode 262, and a drain electrode 264 are formed, and further, interlayer insulating films 270 and 272, a passivation layer 274, and metal wirings 280 and 282 between the transistor and an external circuit are formed to obtain a TFT. (FIG. 8
(C)).

As another application example of the present invention, production of a crystalline solar cell element can be mentioned. FIG. 9 shows an example in which the method of the present invention is applied to the manufacture of a crystalline solar cell element, and the heat treatment according to the present invention simultaneously performs crystallization of the amorphous layer and activation of impurities.

First, an electrode 300, a P-type high-concentration impurity layer 310, a P-type semiconductor layer 320, and an n-type impurity layer 330 are sequentially formed on a base layer 220 having a void structure. Activation and activation (Fig. 9
(A)).

Next, an electrode 340 is formed, and a passivation layer 350 and a metal wiring 360 for connecting to an external circuit are formed.
Is formed to obtain a crystalline solar cell element (FIG. 9B).

[0050]

As described above, according to the method of the present invention, a semiconductor film formed on a partially voided layer has good crystallinity by irradiating it with pulsed energy rays. A semiconductor film can be formed by a simple process. Similarly, by irradiating a pulsed energy ray to a semiconductor film containing an impurity which is formed over a layer partially having a void, the impurity can be efficiently activated.

As described above, according to the method of the present invention, a semiconductor device having good crystallinity and excellent characteristics can be efficiently obtained by a simple process.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a basic concept of the present invention.

FIG. 2 is a diagram showing a pulsed gas combustion heating device used in the present invention.

FIG. 3 is a cross-sectional view showing a method for forming a layer structure having a partial gap.

FIG. 4 is a cross-sectional view and a plan view showing a crystallization method in which a crystallization direction is specified.

5A and 5B are a cross-sectional view and a plan view illustrating a crystallization method using a point-like solid support layer.

6A and 6B are a cross-sectional view and a plan view illustrating a crystallization method in which a solid support region layer for controlling heat flow is formed at one end of a rectangular semiconductor layer.

FIG. 7 is a cross-sectional view showing a manufacturing process of a MOS type crystalline thin film transistor TFT according to the method of the present invention.

FIG. 8 is a cross-sectional view showing another example of the manufacturing process of the MOS-type crystalline thin-film transistor TFT according to the method of the present invention. Metal oxide semiconductor using heating method according to the present invention also for impurity activation

FIG. 9 is a cross-sectional view showing a step of manufacturing a crystalline solar cell element according to the method of the present invention.

[Explanation of symbols]

10, 110: base, 20: layer having partial voids, 22
... void region, 24 ... support layer, 26 ... underlayer, 30 ... semiconductor layer, 40 ... pulsed energy irradiation, 50 ... lateral heat conduction direction, 52 ... substrate direction heat conduction direction, 60 ... crystallization,
70: mixed gas of hydrogen and N ₂ O gas, 80: combustion vessel,
90: discharge, 100: sample, 120: film constituting the void layer structure, 130: resist, 140: protective layer, 150,
180, 210: direction of crystallization, 160, 200: solid support layer, 170, 190: semiconductor layer, 220: layer having a void structure, 230: crystalline semiconductor film, 240: gate insulating film, 250: source region, 252: drain region.
260 gate electrode, 262 source electrode, 264 drain electrode, 270, 272 interlayer insulating film, 272 passivation layer, 280, 282 metal wiring, 290
.., Impurity layers, 300, 340, electrodes, 310, P-type high-concentration impurity layers, 320, P-type semiconductor layers, 330, n-type impurity layers, 340, metal wirings, and 350, passivation layers.

Claims (8)

[Claims] 1. A step of forming a layer partially having a gap on a substrate, a step of forming a semiconductor film on the layer partially having a gap, and irradiating the semiconductor film with pulsed energy rays. And a step of heating the semiconductor film. 2. The heat treatment method for a semiconductor film according to claim 1, wherein the partially voided layer is a layer in which voids are periodically formed in a lateral direction. 3. The method according to claim 1, wherein the irradiation of the pulsed energy beam is performed by:
The method according to claim 1, wherein the irradiation is performed for an irradiation time of ns to 100 ms. 4. The method according to claim 3, wherein the pulsed energy beam is a laser beam. 5. The heat treatment method for a semiconductor film according to claim 3, wherein the irradiation of the pulse energy beam is performed using gas combustion. 6. A step of forming a partially voided layer on a substrate, a step of forming a semiconductor film on the partially voided layer, and irradiating the semiconductor film with pulsed energy rays. A step of forming a crystalline film by heating and crystallizing the semiconductor film, and a step of forming a MOS transistor using the crystalline film as a channel layer. Manufacturing method. 7. A step of forming a partially voided layer on a substrate, a step of forming a semiconductor film on the partially voided layer, and heating the semiconductor film to form a crystalline film. Forming, selectively introducing an impurity into the crystalline film, and irradiating the crystalline film with a pulsed energy beam to heat the crystalline film to activate the impurity, Forming a source region and a drain region in the conductive film. 8. A step of forming a partially voided layer on a substrate, a step of forming a semiconductor film containing impurities on the partially voided layer, and applying a pulsed energy beam to the semiconductor film. Heating the semiconductor film by irradiating the semiconductor film to crystallize the semiconductor film and / or activate the impurities.