JPH0493730A - Temperature measuring apparatus - Google Patents

Abstract

PURPOSE:To make it possible to measure the temperature of a substrate such as a semiconductor simply and accurately by utilizing the temperature dependency of a light absorbing end inherent to a material to be measured, and measuring the temperature of the material from the point where the intensity of transmitted light is largely changed. CONSTITUTION:In this infrared-ray measuring system, the film forming temperature of a GaAs substrate 2 in a molecular beam epitaxial device 3 is set at, e.g. 600 deg.C. Therefore, infrared rays are made to pass through a filter 5 which absorbs the infrared rays having the wavelength of 1.09 mum or longer so that 1.09 mum at the absorbing end of the substrate 2 at 600 deg.C can be efficiently measured. Then the infrared rays enter into an infrared radiation thermometer 6. When the amount of the infrared-ray radiation from an infrared-ray source 1 is increased, the intensity of the infrared rays passing the substrate 2 is also increased. Meanwhile, the substrate 2 is heated, and the absorbing end is shifted to the side of the long wavelength. Thus, the increase in transmitting infrared rays is suppressed. When the temperature of the substrate 2 becomes 600 deg.C, the absorbing end becomes a wavelength region which does not pass through the filter 5. Therefore, the incident infrared rays into the thermometer 6 are rapidly decreased. Errors due to the light transmittance through a window 4 and the like do not occur in this change. Therefore, the temperature of the substrate 2 which is set with the filter 5 can be measured with good reproducibility.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention detects that the absorption edge wavelength of transmitted light of a material to be measured has reached a set value, and detects that the temperature of the material has reached the set value. The present invention relates to a /M meter measuring device for detecting.

<Background Art> Currently, with the development of the semiconductor industry, its manufacturing technology has become particularly sophisticated, and a wide variety of analysis devices and manufacturing devices are now being used. In particular, molecular beam ethitaxy (MBE)
Many of the devices that precisely epitaxially grow extremely thin films or superlattice films require accurate temperature control. Further, in order to prevent contamination and thermal distortion when the substrate is mounted on a heater and to maintain uniformity of heating, an increasing number of devices use heating by irradiation with radiant light.

As described above, it is generally difficult to measure temperature using a thermocouple when heating is performed by irradiation with synchrotron radiation. This is because when performing optical heating, the heat capacity of the substrate is small, and if the heat capacity is small, especially in a high vacuum, there are problems such as the temperature changing even when it comes in contact with a thermocouple. Alternatively, it is also possible to use an infrared radiation thermometer (pyrometer) that measures the temperature from the emitted light of the measurement target, which is widely used in crystal growth and the like. However, since this infrared radiation thermometer measures from outside the device through a glass window, the spectral transmittance may change due to dirt on the glass, or the semiconductor may transmit noise infrared rays from behind, making it difficult to accurately measure the temperature. Sometimes the temperature could not be measured.

Furthermore, the spectral transmittance of this infrared radiation thermometer changes depending on the device used, as the spectral transmittance changes in the infrared region measured depending on the device, such as the thickness and type of window glass, so the thermometer must be calibrated every time the device used for measurement changes. This made temperature measurement complicated.

The following methods have been proposed as temperature measurement methods to solve the above-mentioned problems in temperature measurement of semiconductor films.

One method is to use a monochromator to spectrally analyze infrared light irradiated to heat a semiconductor substrate to measure the absorption edge. (e.g. E, S-Hellmanet al
, Journal of Cr37sta1. Gr.
owth81 (1987) 38-42), this is G
Temperature measurement is performed by utilizing the fact that the absorption edge of a semiconductor such as aAs moves with temperature. Another method is to measure the temperature by measuring the refractive coefficient of the semiconductor surface using reflected light ellipsometry (for example, Takashi Tomita et al.
aL Japanese Journalof
Applied Ph37sics, 25 (1
986) L925-927).

<Problems to be Solved by the Invention> In temperature measurement using the method described above, the absorption edge of the semiconductor substrate is determined by performing spectroscopic analysis. However, there was a problem in that the measured absorption edge wavelength was converted into a temperature corresponding to the semiconductor, which lacked simplicity, and the measurement took a long time. Furthermore, since temperature measurement using the ellipsome I-IJ requires precise measurement, accurate adjustment of the measuring instrument, especially its optical system, and precise and quick operation are required.

As mentioned above, it is difficult to accurately measure the temperature of a semiconductor substrate over a wide range, but it is possible to accurately measure only the temperature of such semiconductor substrates during crystal growth or analysis. In general, rather than directly measuring the absolute value of temperature, it is more accurate to determine a fixed point where the temperature is a constant value, which is easy to measure, and then measure the relative temperature difference from that fixed point temperature.

The present invention solves the above-mentioned problems of the temperature measurement device for substrates such as semiconductors and insulators, satisfies the conditions necessary for temperature measurement, and easily measures the temperature of substrates such as semiconductors.
The purpose is to provide a temperature measuring device that can accurately detect temperature.

<Means for solving charges> Temperature measurement according to the present invention is performed at fixed points. That is, the temperature of a material is detected using an absorption edge that transmits light having a wavelength equal to or longer than a specific wavelength unique to the material.

The above is based on the fact that the optical absorption edge of materials such as semiconductors and insulators is determined by the size of the bandgap of that material, and that, historically, the size of the bandgap changes depending on the temperature of the material. It is measured by

For example, in GaAs, its optical absorption edge is in the infrared region, but its band gap kE (eV)...! :If the substrate temperature is T(K), then E(T)-1,519-45,405XIO-' XT
2/(204+T)] ...(Represented by 1.

Further, the following relational expression holds between the band gap E and the optical absorption edge wavelength λ (μm).

λ-1,24/E ... (2) From the above equations (1) and (2), for example, when the GaAs temperature T is 500°C, the optical absorption edge wavelength λ is 1.04 μm,
T=60 (When Mc, λ=1.09.am.

At this time, light with energy smaller than the energy of the band gap, and light with a wavelength longer than the optical absorption edge wavelength, are Ga
Light that passes through As and has an energy greater than the energy of the band gap, and light that has a wavelength shorter than the optical absorption edge wavelength, is absorbed.

Using the above relationship, the temperature of the GaAs substrate is measured from the following configuration. First, a heating device using infrared radiation is installed on the back side of the GaAs substrate whose temperature is to be measured, and after passing through a filter that only transmits light with a wavelength of 1.09 μm or less on the front side of the substrate, a measurement system is used in which the temperature is measured with an infrared intensity meter. will be established. With this, you can increase the power of the infrared heating device to its full potential and use GaA.
If you gradually raise the temperature of the s-substrate until it reaches 600℃, the GaAs substrate will transmit infrared rays with wavelengths shorter than 109 μm, so the infrared intensity meter will indicate the corresponding value.
When the temperature of the substrate reaches 600° C., light with a wavelength shorter than 109 μm no longer passes through the substrate, so that the value indicated by the infrared intensity meter rapidly decreases. In other words, the indicated value of this infrared intensity meter shows 600c at the point where it suddenly decreases to a and approaches zero.

Further, even if only the wavelength of i1.09 μm is measured, a similar fAll determination can be made.

<Function> The present invention measures the temperature of a sample by utilizing the fact that the absorption edge of the material whose temperature is measured changes depending on the sample.

In this measurement, the temperature of the sample is increased by either passing the light through a filter that only passes light with a wavelength below the absorption edge wavelength of the sample at a given temperature, or by measuring only the light at the absorption edge wavelength. When heated, the absorption edge wavelength correspondingly shifts to longer wavelengths due to the rise in temperature of the sample. Therefore, when the sample reaches a predetermined temperature, the transmitted light rapidly decreases to a value close to zero. From the above, it is possible to easily detect that the sample has reached a predetermined temperature.

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

FIG. 1 shows a schematic configuration of an embodiment of the temperature measuring device of the present invention. This shows a molecular beam epitaxy device (MBE device) 3, only a portion of which is shown, and a temperature measuring device installed therein for a GaAs substrate 2 on which an MBE thin film is to be formed. The G a A, s substrate 2 is a non-doped, semi-insulating GaAs substrate with a thickness of 450 μm, and after cleaning the surface of the substrate by performing pre-treatment such as degreasing and etching using the usual method, the substrate 2 is irradiated with an infrared ray source 1. It is attached to a board holder (not shown) that can be directly heated by light.
The substrate 2 and the infrared light source 1 are installed in the MBE device 3. In addition, the infrared source 1, the heater of the substrate 2, and the substrate 2
The infrared rays transmitted through the substrate 2 are arranged to enter the infrared measurement system for temperature measurement through a window 4 provided in the MBE device 3. .

In the above infrared measurement system, since the growth temperature of the substrate 2 in the MBE device 3 was set to 600°C,
In order to efficiently measure the absorption edge of 109 μm at 00° C., the infrared light is passed through a filter 5 that absorbs infrared light with a wavelength of 109 μm or more, and then enters an upper infrared radiation thermometer 6.

The second section shows the relationship between the input to the infrared 1 needle 6 and each part when the temperature of the substrate 2 is raised by increasing the power applied to the infrared source 1 at a constant rate under the above conditions. Figure 3.

FIG. 2 shows the spectral transmittance of the filter 5 and the GaAs substrate 2, with the vertical axis representing the transmittance and the corresponding wavelength of light representing the horizontal axis. When the id substrate 2 in FIG.
Figure 2(b) shows that the substrate 2 is at 500°C and its absorption edge is within the transmission wavelength of the filter 5, and the transmitted light of the substrate 2 is incident on the thermometer 6. It shows that there is.

FIG. 3 shows the infrared intensity incident on the infrared thermometer 6 when the power applied to the infrared light source 1 is increased, the radiated infrared intensity is increased, and the temperature of the substrate 2 is raised as described above. It shows the passage of time.

The vertical axis of FIG. 3 is the intensity of light incident on the thermometer 6, and the horizontal axis is the elapsed time.

FIG. 3 shows a state in which the infrared light source lK power is input to the temperature measuring device shown in FIG. 1, and the input power is being increased at a constant rate. At this time, the amount of infrared radiation from the infrared light source 1 increases, and the intensity of the infrared rays transmitted through the substrate 2 also increases, but on the other hand, the substrate 2 is heated by the irradiation of this infrared rays, and its absorption edge shifts to the longer wavelength side. When the temperature of the substrate 2 reaches 600° C., the absorption edge of the substrate 2 becomes a wavelength region that is not transmitted by the filter 5, so that the infrared light incident on the thermometer 6 rapidly decreases. This decrease in the incidence of infrared rays results in a sudden change in an extremely narrow range of the enemy's side (°C).

This change does not cause errors due to light transmittance due to the window 4 provided between the substrate 2 and the infrared radiation thermometer or the atmosphere, so the temperature of the substrate 2 set by the above filter 4 can be reproducibly Can be measured well.

Above, the temperature measuring device of the present invention has been explained using an example using a filter having a characteristic of transmitting light having a wavelength below a certain wavelength, but the present invention is not limited to the above example. Instead of the filler and infrared radiation thermometer of the example,
Temperature measurement can also be carried out in the same manner as in the embodiment using a monochromator that measures only the transmitted light at the absorption edge wavelength of the substrate at a set temperature in a narrow band.

When changing the measured temperature of the substrate with a temperature measuring device configured as described above, if it uses a filter, you can do so by replacing it with a filter with a different spectral transmission characteristic, but if you use a monochromator, you can change the measurement wavelength. It is possible to detect any temperature by just setting it.

In addition, the material of the substrate to be measured is not only GaAs, but also semiconductors or insulators whose band gap width changes depending on temperature, and whose absorption edge also changes.The wavelength range of the light source, filter, spectrometer, etc. The method of the present invention can be used for temperature measurement by changing.

<Effects of the Invention> The temperature measuring device of the present invention utilizes the temperature dependence of the light absorption edge unique to the material to be measured to measure the temperature of the material from the point where the intensity of transmitted light changes significantly. Since it is not affected by glass or noise light present in the measurement path, temperature can be measured extremely accurately, easily, and quickly.

Note that by connecting the temperature measuring device, the material substrate heating device, etc. to a computer, it is easy to automatically control the substrate temperature to a predetermined temperature with high accuracy.

[Brief explanation of the drawing]

FIG. 1 (1) is a configuration diagram showing an overview of an embodiment of the temperature measuring device of the present invention; FIG. 2 is a diagram showing the spectral transmittance of a GaAs substrate when changing the filter and temperature of the embodiment;
FIG. 3 is a diagram showing the intensity of transmitted infrared rays corresponding to the G' a As substrate temperature of the example. l...Infrared light source, 2...GaAs substrate. 3 ・MBE device it, 4...window, 5
...filter, 6...infrared radiation thermometer. 0.7 08 0q/, 0 , /, / /, 2
j Ui (Voice 1) Figure 2 Agent Patent Attorney Ume 1) Katsu (and 2 others) Houki! figure

Claims (1)

[Claims] 1. Light from a light source containing light with a wavelength below the optical absorption edge wavelength of the material whose temperature is to be measured is irradiated onto the material, and light at a set temperature of the material is separated from light transmitted through the material. A temperature measurement device characterized in that the temperature of the material is detected from the degree of change in light intensity of light having a wavelength below the absorption edge wavelength. 2. The temperature measurement device according to claim 1, wherein the separation of the light having a wavelength below the light absorption edge wavelength is an optical filter that transmits only light having a wavelength below the light absorption edge wavelength of the material at the set temperature. . 3. The temperature measuring device according to claim 1, wherein the detection of the light intensity of a wavelength equal to or less than the optical absorption edge wavelength is performed using a narrow band monochromator set to the optical absorption edge wavelength at a set temperature of the material. .