JPH06204132A - Forming method and forming equipment of crystal film - Google Patents

Abstract

PURPOSE:To obtain a crystal film of large grain diameter in a short time, by changing energy necessary to crystallization, according to the degree of crystallization of a non-single crystal film on a substrate. CONSTITUTION:By measuring the optical constants of a non-single crystal film on a substrate 11, the degree of crystallization of the non-single crystal film on the substrate 11 is obtained, and the energy necessary to crystallization is changed, according to the degree of crystallization of the non-single crystal film on the substrate 11. Values of the real part (n) and the imaginary part (k) of a complex refractive index are desirably observed as the monitor of crystal growth of a non-single crystal film. By processing the change of values of (n) and (k), the change of each process of crystal growth is obtained, and supply of energy necessary to crystal growth is controlled so as to conform to crystal growth of a non-single crystal film. Thereby process temperature is changed, and the film is effectively processed at the optimum temperature in each growth process. Hence a polycrystalline film of large grain diameter can be obtained in a short time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a crystalline semiconductor film, particularly to a method for producing a polycrystalline semiconductor film by crystallizing a non-single-crystal semiconductor film formed on an insulating substrate such as glass. is there.

[0002]

2. Description of the Related Art A non-single-crystal film is formed on a substrate by a chemical vapor deposition method, a sputtering method, or the like, and then energy such as heat, light, or X-ray is supplied to the non-single-crystal film to melt it by increasing the temperature. There is known a method for producing a crystalline film by crystallizing by rearrangement of atoms in the liquid phase or in the solid phase even in the unmelted state. In general, it is very difficult to form a single crystal film by such a method for producing a crystal film, so that a polycrystalline film composed of a large number of crystal grains is obtained. Since the electrical characteristics of the polycrystalline film depend on the size of the crystal grain (hereinafter referred to as grain size), it is important to control the grain size when performing crystallization.

An example of producing a polycrystalline silicon film by crystallizing an amorphous silicon film by heat treatment will be described below.

FIG. 2 shows a sample obtained by subjecting an amorphous silicon film deposited by chemical vapor deposition to a thickness of 100 nm to a heat treatment at a constant temperature of 600 ° C. in an N ₂ gas atmosphere, and observing it under a microscope with respect to a change in the treatment time. It is the figure which showed the change of the crystallization rate calculated | required from the area of the crystallized part. From the amorphous silicon film, the process indicated by I in FIG. 2 before the start of crystal growth, the process indicated by III in FIG. 2 in which crystal grains grow, and the crystal grain growth is completed A polycrystalline silicon film is obtained through each process of the process shown in FIG. 2 in which complete bonds are bonded. Further, although it cannot be clearly distinguished in FIG. 2, crystal nuclei as seeds of crystal grains are formed by a microscope observation between the process indicated by I in FIG. 2 and the process indicated by III in FIG. There is a process indicated by II in FIG. By increasing the processing temperature, the progress speed of each process is increased, and a polycrystalline silicon film can be formed in a short time. However, in the process indicated by II in FIG. 2, the crystal nucleation density is increased by increasing the treatment temperature, and the grain size of the polycrystal is represented by the reciprocal of the nucleation density, so that the final grain size is decreased. . Therefore, it is possible to control the particle size by changing only the processing temperature in the process indicated by II in FIG. Actually, there is a method in which the relationship between the processing temperature and the progressing speed of each process is empirically investigated, and the processing time and the processing temperature of each process are set in advance to perform the processing. However, as can be seen from FIG. 2, the process indicated by I in FIG.
Since the boundary of the process shown in Medium II, that is, the beginning of the generation of crystal nuclei is unclear, it is difficult to process with good reproducibility.

[0005]

In order to produce a polycrystalline film having a desired crystal grain size in a short time, it suffices to process at a temperature according to each process, and in order to perform this with good reproducibility. It is essential to monitor the process of crystal growth of the non-single crystal film, and in particular, it is important to be able to observe the change between the process I in FIG. 2 and the process II in FIG. As a method of observing the crystal growth process, there is a method of directly observing with a microscope as described above, but it is difficult to observe it in situ during the crystallization treatment. Another method is to observe the properties peculiar to the crystal, for example, when the crystal has a specific wavelength or X
There is an observation method that utilizes the property of reflecting a line. Figure 3
As in FIG. 2, a sample obtained by heat-treating an amorphous silicon film having a film thickness of 100 nm deposited by the chemical vapor deposition method at a constant temperature of 600 ° C. in an N ₂ gas atmosphere was observed by X-ray, and the (111) axis of the silicon crystal was observed. It is the figure which showed the change of the reflection intensity of the X-ray which shows a direction. Although it shows almost the same change as in FIG. 2, the boundary between the process indicated by I in FIG. 2 and the process indicated by II in FIG. 2 cannot be clearly distinguished as in FIG. Occurrence cannot be detected.

[0006]

A method for producing a crystalline film according to the present invention is a method of crystallizing a non-single crystalline film formed on a substrate, which is an optical method of the non-single crystalline film on the substrate. By measuring the constant, the degree of crystallization of the non-single-crystal film on the substrate is obtained, and the energy required for crystallization is changed according to the degree of crystallization of the non-single-crystal film on the substrate. It is characterized by

Preferably, the values of the real part n and the imaginary part k of the birefringence are observed as a monitor for crystal growth of the non-single crystal film. By processing the changes in the values of n and k, the changes in each process of crystal growth are obtained, and the supply of energy necessary for crystal growth is controlled in accordance with the crystal growth of the non-single crystal film. By changing the treatment temperature, the treatment is efficiently performed at the optimum temperature for each growth process.

Preferably, the above optical constant is measured using a polarization analyzer capable of spectroscopic measurement.

Further, the apparatus for producing a crystalline film of the present invention measures the means for supplying a predetermined energy to the non-single crystalline film formed on the substrate and the optical constant of the non-single crystalline film on the substrate. It is characterized by comprising a polarization analyzer capable of spectroscopic measurement and a device that follows the output of the polarization analyzer and controls the energy supplied to the non-single crystal film on the substrate.

[0010]

In general, the refractive index of a substance is represented by a complex number and consists of a real part n and an imaginary part k. In the process of crystal growth of a non-single-crystal body, n and k can be adjusted depending on the state of the non-single-crystal body and the ratio of crystal parts. The value changes continuously. In particular n and k
The value of depends on the wavelength of light, and since the value greatly changes in the vicinity of the wavelength of light corresponding to the band width (energy band width) of a substance, the values of n and k By observing the wavelength dependence, it is possible to observe the change in the band level width accompanying the crystal growth.

The refractive index of a substance can be determined by measuring the transmission or reflection of light. However, when the object of measurement is a film, especially when the thickness thereof is thin, light interference occurs due to the relationship with the wavelength of light, and therefore it is necessary to take measures such as simultaneous measurement of transmission and reflection. Also, when measuring the transmission of a membrane, the substrate is naturally limited to a transparent material. As a method for solving these problems, there is a deflection analysis method (ellipsometry).

The polarization analysis method is the polarization state of the reflected light of the light obliquely incident on the surface of the sample, and more specifically, the polarized light component of the light component in the horizontal direction and the light component of the light component in the vertical direction with respect to the incident surface. This is a method of determining the values of n and k of the film existing on the sample surface by measuring the change in phase. Furthermore, the wavelength dependence of the values of n and k can also be measured by continuously changing the wavelength of the light to be measured. Therefore, the crystallization process of the non-single crystal film was investigated in detail by using a deflection analyzer capable of spectroscopic measurement (spectral ellipsometry).

[0013] Figure 4, an amorphous silicon film thickness 100nm is deposited similarly by chemical vapor deposition as in FIG. 2 and FIG. 3 N ₂
An example of the result of measurement using a deflection analyzer capable of spectroscopic measurement is shown for a sample heat-treated at a constant temperature of 600 ° C. in a gas atmosphere. In this figure, the crystallization rate is used on the vertical axis. This is because the amorphous silicon film before the treatment and the polycrystalline silicon film after the crystallization treatment are completed based on the measurement result of the deflection analyzer capable of spectroscopic measurement. Refractive indices n and k of
Is used as a reference to show the ratio of whether the n and k values of the sample at each heat treatment time are close to the values of the polycrystalline silicon film, and correspond perfectly to the ratio of the crystalline components in the actual film. I'm not doing it.

Similar to FIGS. 2 and 3, the process of crystal growth is shown. Further, FIG. 4 also shows changes in the process indicated by I in FIG. This is because the values of the refractive indices n and k simply reflect not only crystallization but also changes in substances such as hydrogen content in amorphous silicon and film deposition density. Is. Then, at the place where the process of generating crystal nuclei indicated by II in FIG. 2 starts, the opposite ratio is small. Like this
It was discovered that changes in the crystal growth process can be measured in more detail by using a deflection analyzer capable of spectroscopic measurement. The present invention applies this principle to a crystal growth method.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of a crystal growth apparatus showing an embodiment of a crystal growth method for a non-single crystal film according to the present invention.

A quartz furnace core tube 2 is installed inside the heater 1, and a substrate 11 having a non-single crystal film formed on the surface thereof by another method and a quartz tube in which the quartz core tube 2 is set in a direction perpendicular to the furnace core tube. The boat 10 is placed. N ₂ gas as a carrier gas is supplied to the core tube 2 through a pipe 5 through a valve 3 and a flow meter 4. Exhaust gas is discharged through an exhaust port 7 attached to the core tube cap 6. Core tube 2
An observation window 8 and a window 9 are attached to the surface of the substrate 11, and the incident light 21 is applied to the surface of the substrate 11 which is set on the foremost side of the boat 10 through the window 8 from a polarizer 12 having a halogen lamp and a monochromator. .

Reflected light 22 reflected from the surface of the substrate 11 with respect to the incident light 21 is detected by the analyzer 14 having a built-in photodetector through the window 9 and converted into an electric signal. The polarizer and the analyzer are electric signal lines 17 and signal lines 18, and the signal processed by the signal processing device 14 is sent as digital data to the computer 15 through the signal line 19 and the substrate 1
The optical constants n and k of the semiconductor film on one surface are calculated. In the computer 15, the optical constant of the semiconductor thin film is calculated at any time,
Memorize, monitor changes in optical constants, judge processing temperature,
An electric signal for controlling the processing temperature is sent to the heater controller 16 through the signal line 20, and the heater temperature is controlled by the heater controller 16.

A film thickness of 100 nm was formed by a chemical vapor deposition method using a quartz substrate as a substrate and monosilane as a source gas by the above apparatus.
An example of heat treatment of the deposited amorphous silicon film will be shown.

First, as a comparative example, the treatment was carried out at a constant temperature, which is a conventional method. FIG. 5 and FIG. 6 are diagrams showing the relationship between the temperature when the treatment is performed at a constant temperature, the treatment completion time, and the grain size of the polycrystalline silicon measured by observing the sample after the treatment with a microscope. It is shown in FIG. 5 that the nucleation density in the crystal nucleation process increases and the crystal grain size decreases as the processing temperature rises. On the other hand, FIG. 6 shows that as the processing temperature becomes higher, the progress speed of each process becomes faster and the processing completion time becomes shorter.

For example, when the treatment is carried out at a constant temperature of 650 ° C., the crystal grain size becomes about 0.4 μm. Meanwhile, 580
When the treatment was carried out at a constant temperature of ° C, the particle diameter was about 1.8 µm, but it took about 20 hours to complete the treatment. On the other hand, the processing temperature of the nucleation process is set to 58 in the computer 15.
Crystals obtained from the measurement result of the ellipsometer capable of spectroscopic measurement shown in FIG. 4 in order to determine the progress of each crystal growth process by inputting 0 ° C. and other processes as 650 ° C. The conversion rate data was stored and set to be processed correspondingly.

Specifically, the treatment was started at 650 ° C., and the treatment was started at the time when the crystallization rate obtained from the measurement result of the ellipsometer capable of spectroscopic measurement, which was increased initially as in FIG. 4, started to decrease. The temperature was changed to 580 ° C. When the crystallization rate started to increase again, the treatment temperature was returned to 650 ° C. and the rest of the treatment was performed. The time required for crystal growth was about 7 hours, and a polycrystalline silicon film having a grain size of 1.8 μm was obtained from the result of microscopic observation.

[0022]

According to the method for producing a crystalline film and the apparatus for producing a crystalline film of the present invention, a polycrystalline film having a large grain size can be obtained with good reproducibility in a short time.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a crystal growth apparatus shown in an example.

FIG. 2 is an explanatory diagram showing a crystal growth process.

FIG. 3 is a comparative example of a method for investigating a crystal growth process, X
It is explanatory drawing which shows the measurement result by a line diffraction method.

FIG. 4 is an explanatory diagram showing an example of a result of measurement of a crystal growth process by an ellipsometer capable of spectroscopic measurement.

FIG. 5 is an explanatory diagram showing the relationship between the processing temperature and the crystal grain size when crystal growth is performed by the conventional method using the crystal growth apparatus shown in the examples.

FIG. 6 is an explanatory diagram showing the relationship between the processing temperature and the processing completion time when crystal growth is performed by the conventional method using the crystal growth apparatus shown in the example.

[Explanation of symbols]

1 ... Heater, 2 ... Quartz core tube, 3 ... Gas valve, 4
… Gas flow meter, 5… gas pipe, 6… core tube cap,
7 ... Exhaust port, 8/9 ... Observation window, 10 ... Quartz boat, 11
... substrate, 12 ... polarizer, 13 ... analyzer, 14 ... signal processing device, 15 ... electronic calculator, 16 ... heater controller, 17 ...
18 ... Electrical signal line, 19/20 ... Digital signal line, 21
Incident light, 22 ... Reflected light

Claims (3)

[Claims] 1. A method for crystallizing a non-single-crystal film formed on a substrate, comprising measuring the optical constant of the non-single-crystal film on the substrate to obtain the non-single-crystal film on the substrate. A method for producing a crystalline film, wherein the degree of crystallization of the film is obtained, and the energy required for crystallization is changed according to the degree of crystallization of the non-single crystalline film on the substrate. 2. The method for producing a crystalline film according to claim 1, wherein the optical constant is measured by using a polarization analyzer capable of spectroscopic measurement. 3. A means for supplying a predetermined energy to a non-single crystal film formed on a substrate, and an ellipsometer capable of spectroscopic measurement for measuring an optical constant of the non-single crystal film on the substrate, An apparatus for producing a crystalline film, which comprises an apparatus that follows the output of the ellipsometer and controls the energy supplied to the non-single crystalline film on the substrate.