JPH06283589A - Temperature measuring method of substrate surface, semiconductor film forming method using the same and its equipment - Google Patents

Abstract

PURPOSE:To form a high quality silicon semiconductor thin film of uniform thickness, with superior reproducibility in a substrate surface, by precisely measuring the silicon substrate temperature and the temperature distribution in the substrate surface. CONSTITUTION:The following are installed; an irradiation part la casting a parallel polarized light having a wavelength capable of being absorbed in a light absorber, on the light absorber caused by dangling bonds on a silicon substrate 20 surface, a light receiving part 2a supplying reaction gas containing atoms to be chemically adsorbed by the silicon substrate 20, stopping the gas supply, and measuring the intensity of light reflected from the substrate surface, and a temperature reducing part 3a obtaining the change of the reflected light intensity with time, operating the attenuation time constant of the reflected light intensity, comparing the time constant with the known data of temperature dependency of the desertion speed of atoms, and calculating the substrate surface temperature. While the temperature of the silicon substrate 20 is measured and controlled, a film is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate surface measuring method for measuring a substrate surface temperature applied when a thin film is formed by crystal growth on a semiconductor substrate, particularly a silicon substrate, and a semiconductor film formation using the same. A method and its apparatus.

[0002]

2. Description of the Related Art Generally, in order to form a semiconductor thin film on a silicon substrate, which is a semiconductor substrate, a silane-based gas is supplied onto a heated silicon substrate, and the silane-based gas undergoes thermal decomposition and chemical reaction on the surface. It was done using it. Further, when forming a film on this substrate, since the progress rate of the chemical reaction is determined by the substrate temperature, accurate temperature control is indispensable in order to obtain a good quality film having a uniform film thickness within the plane. It was a condition. In particular, with the recent miniaturization of LSIs, the deposition film has become thinner and the diameter of the substrate has been increased in order to reduce the cost.

Conventionally, in this type of semiconductor film forming apparatus, a silicon substrate placed in a depressurized reaction tube is heated by an infrared lamp from outside the reaction tube, and Si, which is a reaction gas in the reaction tube, is heated.
H ₂ Cl ₂ (hereinafter referred to as dichlorosilane) and hydrogen were introduced and reacted to form a silicon semiconductor thin film on a silicon substrate. In addition, a thermocouple measurement method has been used for measuring the temperature of the silicon substrate heated during film formation.

FIG. 6 is a side view showing a substrate mounting portion of a film forming apparatus for explaining an example of a conventional method for measuring the temperature of a silicon substrate surface. As shown in FIG. 6, for example, as shown in FIG. 6, the temperature of the surface of the silicon substrate is measured by inserting a thermoelectric material into a small hole 25 of a graphite susceptor 10 whose surface is coated with silicon carbide. The temperature of the silicon substrate 20 is detected by the pair 24, and the temperature detected by the thermocouple 24 is output as a voltage, input to a voltmeter outside the reaction tube, and read as the temperature.

[0005]

In the above-mentioned conventional method for measuring the temperature of the substrate surface in the film formation, although the thermocouple is not directly contacted with the substrate so as not to damage the substrate,
What the thermocouple is measuring is not the temperature of the substrate itself, but the temperature inside the susceptor. For this reason, even if the substrate surface temperature is lowered due to the flow of carrier gas during the deposition of the film, the thermocouple placed inside the susceptor may remain at a high temperature or the substrate surface temperature may be accurately measured. Can not. Furthermore, it is almost impossible to measure the temperature distribution of the substrate. Further, since the temperature thus detected is inaccurate, it is difficult to control the substrate temperature, and it is impossible to control it accurately. This means that it is difficult to control the film thickness that changes exponentially with respect to the change in the substrate temperature, the reproducibility in thin film formation deteriorates, and a uniform semiconductor thin film with good quality can be obtained. There is a problem that there is no.

Therefore, an object of the present invention is to enable the substrate temperature and the in-plane temperature distribution to be measured with high accuracy, whereby a high-quality silicon semiconductor thin film with a uniform film thickness can be formed in the substrate plane with good reproducibility. A semiconductor film forming method and an apparatus thereof are provided.

[0007]

The first feature of the present invention is to:
Supplying a reaction gas containing atoms that are chemically adsorbed to the silicon substrate by irradiating a light absorber caused by dangling bonds on the surface of the silicon substrate with parallel-polarized light having a wavelength that can be absorbed by the light absorber. And stop to measure the reflected light intensity from the surface of the silicon substrate to obtain a change with time of the reflected light intensity, the time constant of the attenuation of the obtained reflected light intensity and the temperature dependence of the detachment rate of the atoms. This is a method for measuring the temperature of the surface of the substrate by comparing the temperature of the surface of the silicon substrate with the known data.

The second feature of the present invention is a semiconductor film forming method for forming a thin film by growing a crystal of silicon while measuring the temperature of the surface of the silicon substrate by using the method for measuring the temperature of the surface of the silicon substrate described above. is there.

A third feature of the present invention is that a mechanism for mounting a silicon substrate is housed, heating means for heating the silicon substrate, and supply / stop of a reaction gas containing atoms chemically adsorbed to the silicon substrate are provided. A reaction chamber having a means for performing and a decompression pump for maintaining the pressure of the reaction gas at a predetermined pressure, and a wavelength that can be absorbed by the light absorber with respect to the light absorber due to dangling bonds on the surface of the silicon substrate. The irradiation means for irradiating the surface of the silicon substrate with the parallel-polarized light, the light receiving means for receiving the reflected light from the surface of the silicon substrate, and the reflected light intensity data of the reflected light intensity obtained by the light receiving means. A semiconductor device provided with a calculating means for obtaining a time constant of decay and collating the time constant with known data of temperature dependence of the detachment rate of the atoms to calculate the temperature of the surface of the silicon substrate. It is a device.

[0010]

When the parallel-polarized light is applied to the surface of the silicon substrate, the intensity of the reflected light changes extremely sensitively to the surface condition. For example, on a clean surface where foreign atoms are not adsorbed on the silicon substrate, there is a light absorption band due to dangling bonds. When light having a wavelength that is absorbed in this absorption band is irradiated, the light is absorbed, and as a result, the reflected light intensity decreases. On the other hand, when a gas containing hydrogen chloride, dichlorosilane, silane, or the like is supplied to the silicon substrate, chlorine atoms or hydrogen atoms that are likely to bond with dangling bonds are chemically bonded and adsorbed to the silicon substrate surface, and the number of dangling bonds on the surface is reduced. Decrease. As a result, the amount of light absorbed in the absorption band decreases and conversely the intensity of reflected light increases. Further, when the supply of gas is stopped, chlorine or hydrogen atoms adsorbed on the surface of the silicon substrate are removed by the action of heat, and a clean surface appears again and the reflected light intensity decreases.

FIG. 5 is a graph showing the degree of decrease in reflected light intensity with the passage of time after the gas supply is stopped. As described above, the number of dangling bonds increases due to the detachment of the adsorbed atoms, so that the amount of light absorbed in the absorption band increases and the reflected light intensity decreases. For example, if the gas used is dichlorosilane, as shown in FIG.
After the supply of dichlorosilane to the surface of the silicon substrate, which is the (00) plane, is stopped, the reflected light intensity indicated by the reflectance decreases exponentially. Here, the change in reflectance with respect to the elapsed time after the stop is shown by an equation as follows.

R (t) = C ₁ exp (−t / τ) where R (t) is the reflectance at time t after the gas supply is stopped, C ₁ is a constant, and τ is a time constant of desorption. Is.
The relationship between the detachment time constant τ and the substrate temperature is given by the following equation.

Τ (T) = C ₂ exp (E / kT) where T is the absolute temperature of the substrate, τ (T) is the detachment time constant at the substrate temperature T, and k is the Boltzmann constant. E is the activation energy for withdrawal, and in the case of the above system, 21 k
Cal / mol.

Therefore, in an attempt, the silicon substrate was irradiated with a parallel-polarized argon laser, the change in the reflected light intensity over time was measured, and the time constant .tau. Then, the measured temperature was obtained from the previously known relationship between the time constant and the temperature. As a result, when compared with the case where the thermocouple was actually contacted with the silicon substrate surface and measured,
The agreement was within the error range of 5%.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view showing a semiconductor film forming apparatus for explaining a first embodiment of the present invention. As shown in FIG. 1, this semiconductor film forming apparatus includes a reaction tube 4 for accommodating a susceptor 10 on which a silicon substrate 20 is placed, and a reaction tube 4 for this reaction tube 4.
An infrared lamp 5 arranged outside the chamber for heating the silicon substrate 20, a mass flow meter and a valve (not shown) for controlling the supply / stop of the reaction gas from the gas inlet 7 of the reaction tube 4, and the introduced reaction. This is a kind of decompression type CVD apparatus provided with a vacuum pump 6 for keeping the gas pressure constant.

Further, in this apparatus, an irradiation section 1a for projecting parallel-polarized light onto the silicon substrate 20 through the window 8 of the reaction tube 4 and reflected light from the silicon substrate 20 through the window 9 are received. The light receiving portion 2a is collated with the time constant of the attenuation of the reflected light obtained from the light receiving portion 2a and the previously stored data of the temperature dependence of the desorption rate of the atoms adsorbed on the silicon substrate 20, and the substrate surface is checked. The temperature conversion unit 3 for calculating the temperature is provided.

The irradiation unit 1a includes a laser oscillator 15 of argon gas for generating laser light, a deflector 14 for deflecting the laser light in parallel with the substrate surface, a chopper 13 for converting the laser light into pulsed light, and a pulsed light. And a mirror 11 for reflecting the laser light of the above and entering the reaction tube 4 through the window 8. Further, the light receiving section 2a has a mirror 12 that receives reflected light from the silicon substrate 20 through the window 9 and reflects it in one direction, and a photodetector 16 that receives the reflected light from the mirror 12. Further, the temperature conversion unit 3 calculates the time constant of the attenuation of the reflected light by the lock-in amplifier 17 that amplifies the reflected light intensity signal from the photodetector 16 and the amplified reflected light intensity signal value, and A computer 19 for calculating the temperature of the substrate surface by collating with previously stored data of the temperature dependence of the desorption rate of atoms adsorbed on the silicon substrate 20, and a display unit 19 for displaying the calculated temperature are provided. ing.

Next, a method of measuring the substrate surface temperature by this apparatus and a film forming method using the same will be described together with an explanation of the operation of the apparatus. First, prepare a silicon substrate from which a natural oxide film has been removed by washing with diluted hydrofluoric acid or heat treatment in a reaction tube at 900 ° C. or higher.
Place at 0. Next, depressurize the reaction tube 4 with a vacuum pump,
Laser light is generated from the laser oscillator 15, the generated laser light is parallel-deflected by the deflector 14, and the chopper 13 turns the laser light into pulsed light in order to improve the S / N ratio. Then, the laser light is reflected by the mirror 11 and projected onto the surface of the silicon substrate 20 through the window 8. The angle of incidence on the silicon substrate 20 should be set so that the intensity of reflected light is maximized.

FIG. 2 is a graph showing the reflected light intensity when dichlorosilane is supplied to the surface (100) of the silicon substrate and stopped. Next, for example, dichlorosilane is introduced through the gas introduction port 7 of the reaction tube 4 to clean the silicon substrate 20.
On the surface (100) of the
Maintain pressure at Torr. As a result, the surface is covered with chlorine, and as shown in FIG. 2, the reflected light intensity of the parallel-polarized laser light increases and becomes saturated after a lapse of a predetermined time. Next, when the supply of dichlorosilane is stopped, the intensity of reflected light decreases. The reflected light intensity is output by the photodetector 16 in the magnitude of the signal value, and is input to the lock-in amplifier 17 to be amplified. Then, the signal values in which the reflected light intensity decreases depending on the temperature are sequentially input to the computer 18, and arithmetic processing is performed to obtain the attenuation time constant. Then, the surface temperature of the silicon substrate 20 is obtained by collating with the known data of the temperature dependence of the stored time constant of the attenuation.

Further, during the epitaxial growth with dichlorosilane and hydrogen gas, the supply of the raw material gas is stopped at certain time intervals, the temperature is measured from the phenomenon of reflected light, and then the raw material gas is supplied again. These operations are repeated during film formation to measure the substrate temperature precisely,
The output of the infrared lamp 5 is controlled to control the temperature.

As described above, in this embodiment, dichlorosilane was supplied to the silicon substrate to terminate the surface of the substrate with chlorine.
iH ₂ Cl ₂ or another molecule consisting of a halogen atom and a silicon atom, or HCl, Cl ₂ or another halogen and hydrogen,
Even with a molecule composed of only halogen, the surface of the silicon substrate is similarly terminated by a halogen atom, and the same effect is obtained. Further, even if a molecule such as SiH ₄ containing silicon and hydrogen is supplied, dangling bonds existing on the surface are terminated by hydrogen and the reflectance increases. That is, the temperature of the substrate surface can be measured by measuring the attenuation of the reflectance corresponding to the release of hydrogen.

FIG. 3 is a schematic view showing a semiconductor film forming apparatus for explaining the second embodiment of the present invention. This semiconductor film forming apparatus, in the light irradiation unit for measuring the temperature of the substrate surface,
That is, the surface of the silicon substrate is irradiated with light including parallel waves and vertical waves. That is, as shown in FIG. 3, the laser light generated from the laser oscillator 15 is pulsed by the chopper 13, deflected by the deflector 14a at 45 degrees with respect to the substrate surface, reflected by the mirror 11 and projected onto the silicon substrate 20. It The reflected light from the silicon substrate 20 is reflected by the mirror 12 and separated by the polarized splitter 21 into a vertical wave and a parallel wave. The reflected light thus separated enters the respective photodetectors 16a and 16b. The reflected light that has entered is converted into current signals by the photodetectors 16a and 16b, amplified by the respective lock-in amplifiers 17a and 17b, input to the computer 18, and calculated in the same manner as in the above-mentioned embodiment to determine the temperature of the substrate surface. It is calculated.

The inclusion of the vertical wave in the projected light is to standardize the signal strength of the parallel wave having information by the signal strength of the vertical wave having no information. That is, by irradiating the reflected light of the parallel wave and the vertical wave and measuring each reflected light, the signal component of the reflected light of the vertical wave is removed, and the noise component such as the fluctuation of the laser light intensity is removed. is there. Therefore, the light irradiation system according to this embodiment has an advantage that a signal intensity having a high S / N ratio can be obtained and the substrate surface temperature can be measured with higher accuracy as compared with the above-described embodiments.

By the way, an attempt was made to measure the temperature by supplying and stopping dichlorosilane to the silicon substrate 20. As a result, when the temperature determined from the time constant of the attenuation of the reflectance was compared with the temperature measured by bringing the thermocouple into contact with the substrate surface as in the above-mentioned Examples, it was 500 ° C to 1
The maximum difference between the two was 5 ° C in the temperature range of 000 ° C.

Although the laser light of the argon gas laser oscillator is used as the light source in this embodiment, the light source is not limited to this laser light. The point is that the light has a wavelength that is absorbed in the light absorption band due to the dangling bond existing on the surface of the silicon substrate. For example, a lamp having this wavelength may be used, or white light may be extracted using a bandpass filter to obtain light having this wavelength.

FIG. 4 is a diagram showing a light source optical path for temperature measurement for explaining a third embodiment of the present invention. In this semiconductor film forming apparatus, a rotating mirror 22a is arranged on the irradiation side in the light source optical path for temperature measurement, and light can be irradiated to an arbitrary position on the silicon substrate 20 by changing the rotation angle of the rotating mirror 22a. Further, a rotating mirror 22b for changing the direction of reflected light and a reversing mirror 23 for rotating and aligning the direction of reflected light are provided on the light receiving portion side. As a result, reflected light from all positions of the silicon substrate 20 enters the same photodetector 16c.

As described above, it is possible to measure the temperature at any place on the surface of the substrate, and the temperature distribution on the surface of the substrate can be measured with a resolution about the diameter of the light spot projected on the surface of the silicon substrate.

[0029]

INDUSTRIAL APPLICABILITY As described above, the present invention irradiates a light absorber due to dangling bonds on the surface of a silicon substrate with parallel-polarized light having a wavelength that can be absorbed by the light absorber. Section, a light receiving section for measuring the intensity of reflected light from the surface of the silicon substrate by supplying and stopping a reaction gas containing atoms that are chemically adsorbed on the silicon substrate, and obtaining a change with time of the reflected light intensity By calculating a time constant for the attenuation of the reflected light intensity and comparing the time constant with the known data of the temperature dependence of the detachment rate of the atoms to calculate the temperature of the silicon substrate surface, the silicon is provided. The substrate temperature can be measured accurately without damaging the substrate, which allows the silicon substrate temperature to be accurately controlled, and provides a uniform high quality There is an effect that the emissions thin film with good reproducibility can grow.

[Brief description of drawings]

FIG. 1 is a schematic view showing a semiconductor film forming apparatus for explaining a first embodiment of the present invention.

FIG. 2 is a graph showing the intensity of reflected light when dichlorosilane is supplied / stopped on the surface (100) of a silicon substrate.

FIG. 3 is a schematic view showing a semiconductor film forming apparatus for explaining a second embodiment of the present invention.

FIG. 4 is a diagram showing a light source optical path for temperature measurement for explaining a third embodiment of the present invention.

FIG. 5 is a graph showing the degree of decrease in reflected light intensity over time after the gas supply is stopped.

FIG. 6 is a side view showing a substrate mounting portion of a film forming apparatus for explaining an example of a conventional method of measuring a temperature of a surface of a silicon substrate.

[Explanation of symbols]

 1a, 1b Irradiation part 2a, 2b Light receiving part 3a, 3b Temperature conversion part 4 Reaction tube 5 Infrared lamp 6 Vacuum pump 7 Gas introduction port 8, 9 Window 10 Susceptor 11, 12 Mirror 13 Chopper 14, 14a Polarizer 15 Laser oscillator 16 , 16a, 16b Photodetector 17, 17a, 17b Lock-in amplifier 18 Computer 19 Display 20 Silicon substrate 21 Polarized splitter 22a, 22b Rotating mirror 23 Inversion mirror 24 Thermocouple 25 Small hole

Claims (4)

[Claims] 1. A light absorber caused by dangling bonds on the surface of a silicon substrate is irradiated with parallel-polarized light having a wavelength that can be absorbed by the light absorber, and atoms chemically adsorbed to the silicon substrate are detected. The reaction gas containing the gas is stopped and supplied, and the intensity of reflected light from the surface of the silicon substrate is measured to determine the change in the intensity of the reflected light with respect to time. The method for measuring the temperature of the surface of the substrate is characterized by comparing the temperature of the surface of the silicon substrate with the known data of the temperature dependency. 2. A method for forming a semiconductor film, comprising forming a thin film by growing a crystal of silicon while measuring the temperature of the surface of a silicon substrate according to the method of measuring the temperature of the surface of a silicon substrate according to claim 1. . 3. A heating means for accommodating a mechanism for mounting a silicon substrate and heating the silicon substrate, a means for supplying / stopping a reaction gas containing atoms chemically adsorbed by the silicon substrate, and a reaction gas for the reaction gas. A reaction chamber equipped with a decompression pump for maintaining the pressure at a predetermined pressure, and a parallel-polarized light having a wavelength that can be absorbed by the light absorber due to a dangling bond on the surface of the silicon substrate. An irradiation unit that irradiates the surface of the silicon substrate, a light receiving unit that receives the reflected light from the surface of the silicon substrate, and a reflected light intensity data obtained by the light receiving unit to obtain a time constant of attenuation of the reflected light intensity. A semiconductor film forming apparatus comprising a calculation means for calculating a temperature of the surface of the silicon substrate by collating a time constant with known data of temperature dependence of the detachment rate of the atoms. . 4. A means for scanning the silicon substrate with the light from the irradiation means.
The semiconductor film forming apparatus described.