JPH073454A - Substrate heater - Google Patents

Abstract

PURPOSE:To provide the substrate heater which unifies the temp. distribution of a substrate surface at the time of heating and decreases the strains acting on a substrate in direct heating of the substrate by energizing, etc. CONSTITUTION:The escape of heat from a substrate 6 through electrodes to a substrate holder 1 is minimized and the strains acting on the substrate 6 are decreased by using a corrugated metallic sheet having plural peak parts in a desired positional relation as the electrodes 3, by which the temp. from the central part to the ends of the substrate is unified and the low-stress and high-quality thin films are formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device for a substrate which is required when forming various thin films such as metal and semiconductor.

[0002]

2. Description of the Related Art There are various methods for forming thin films of metals and semiconductors, such as sputtering method and plasma CVD.
Method, MOCVD method, molecular beam epitaxy (MBE) method,
In addition, various methods such as application and combination of these are in practical use. Both are film forming methods using vacuum, and are suitable for forming a high-quality film with high purity. It is indispensable to heat the substrate during formation in order to speed up film formation and improve the crystallinity and characteristics of the film. Substrate heating methods are roughly classified into a method of indirectly heating by radiation using a heater and a direct heating method of utilizing heat generated by passing an electric current through the substrate. In many cases, such as when using a large substrate or when using substrates of different sizes frequently, indirect heating is often used because it is more convenient. On the other hand, in the method of supplying the raw material in a gas state to the film forming chamber, there are cases where the direct heating method must be used. When the heater for radiant heating is installed near the substrate, decomposition of the raw material gas occurs not only on or near the surface of the substrate but also near the heater, which adversely affects the required film formation control. On the other hand, the direct heating is an effective heating method in the CVD method, the gas source MBE method, etc., because the source gas is not decomposed except in the vicinity of the substrate.

There are various possible electrode structures for energizing the substrate, and the ones that are mainly used are those that are flatly fixed to the substrate holder or sandwiched by a clip-shaped metal piece. And so on. Basically, (1) it is necessary to allow an electric current to flow so that the entire substrate is heated uniformly, and (2) it is necessary not to give unnecessary strain to the substrate.

Conventionally, semiconductors such as silicon (Si) are most commonly used for substrates. As shown in the schematic view of FIG. 4A, a semiconductor substrate 41 and a substrate holder 4 which also serves as an electrode
2 is in surface contact.

[0005]

However, the above-mentioned FIG.
In this case, the current can flow relatively easily, but the heat of the substrate escapes from the electrode contact portion. FIG. 4B is a diagram in the case of heating at 600 ° C. as a target, but as shown here, there is a problem that the temperature distribution of the substrate becomes non-uniform. Further, even if it is called a surface contact, the contacting portion is a part of it from a microscopic point of view, and the size and position of the contacting portion are irregular and uncontrollable. Therefore, in reality, the temperature distribution cannot be reproduced every time the substrate is mounted. In addition, it is necessary to fix the board stably, but if it is completely fixed, the board may be distorted due to a difference in coefficient of thermal expansion between the board and the board holder and a slight twist of the board when fixing. The physical properties of the thin film formed on the surface are adversely affected. On the other hand, when the electrode is configured to make a point contact like a pin, the reproducibility of electrical contact is sure, but the current path flowing through the substrate is not uniform over the entire substrate, and as shown in FIG. As described above, a high temperature portion 52 and a low temperature portion 53 are generated in the electrode contact portion 51. As a countermeasure against this, measures such as forming a conductive thin film on the back surface of the substrate to make it easier for current to flow evenly over the entire substrate have been taken. There are many problems such as mixing of impurities during formation. In any case, the uneven temperature distribution of the substrate causes various in-plane variations in physical properties such as film thickness unevenness, resistance, and uneven crystallinity.

In order to solve the above-mentioned conventional problems, the present invention is directed to heating a substrate in order to make the temperature distribution on the substrate surface uniform during heating and reduce strain applied to the substrate in direct heating by energizing the substrate. The purpose is to provide a device.

[0007]

In order to achieve the above object, a substrate heating device of the present invention is a device for heating a substrate by passing a current from one end of the substrate to the other end thereof. The electrode contacting the substrate for energizing is made of a corrugated metal plate fixed to a part of a metallic substrate holder, and the corrugated metal plate has a plurality of top portions.

In the above structure, it is preferable that the substrate is fixed by a non-conductive substance. Further, in the above structure, it is preferable that the metal plate serving as an electrode is attached via a thin plate made of a non-conductive material.

[0009]

According to the above-mentioned structure of the present invention, the electrode contacting the substrate for energization is composed of the corrugated metal plate fixed to a part of the metallic substrate holder, and the corrugated metal plate has a plurality of top portions. As a result, the temperature distribution on the substrate surface during heating can be made uniform, and the strain applied to the substrate can be reduced. That is, in the substrate heating device having the above-mentioned configuration, the contact area between the substrate and the electrode is limited, so that the heat escape from the substrate to the electrode or the substrate holder is minimal, and the contact position is plural. Therefore, since the positional relationship such as the number and intervals of the protrusions can be controlled according to the size of the substrate, it is possible to obtain a uniform current path in the substrate, that is, a uniform temperature distribution.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings. FIG. 1A is a conceptual diagram showing the configuration of a substrate holder and electrodes according to an embodiment of the present invention, and FIG. 1B is a diagram showing a state in which a substrate is mounted. Here, a rectangular substrate (1
cm x 2 cm) is used. The substrate holder 1 is made of a refractory metal such as molybdenum (Mo), tantalum (Ta), or tungsten (W).
A groove 2 on which a substrate can be mounted is provided in this block. The surface of the board faces upward in the figure, and the corrugated metal part 3 serving as an electrode is placed at the bottom of this groove via a non-conductive plate 4 and a screw 5 made of the same material as the board holder 1 is used. Mounting. As shown in FIG. 1B, a silicon substrate 6 having a thickness of, for example, 0.3 to 0.5 mm is mounted on this electrode by using screws 8 made of the same material as the substrate fixing plate 7 and the substrate holder 1. . The corrugated metal part 3 is M
It is created with o, Ta, W, etc., but in the case of Ta, for example, 5
With a thickness of 0 to 100 μm, the wave top and the top 1 pitch length is, for example, 2 mm, the number of tops is 5, the length is 10 mm, and the height is 5.
mm can be used.

This is introduced into a vacuum film forming apparatus, and the substrate is heated by energizing it. A semiconductor material such as silicon (Si) has a high electric resistance at room temperature, and the resistance decreases as the temperature rises, and the current easily flows rapidly. Therefore, at the beginning of heating, a high voltage is applied to start the current flow. The high voltage is not necessary once the current starts flowing, and it is necessary to control so that a constant current flows. The Si substrate having the size of this embodiment requires an initial voltage of several V to several tens of V. If the size of the substrate is constant, the temperature and the current have a good reproducible correlation, and the calibration curve may be obtained in advance using the test substrate.

FIG. 2 shows the temperature distribution when the substrate heating apparatus of this embodiment is used. Conventionally, there is a temperature difference of 100 ° C. or more between the central portion and the end portion of the substrate as shown in FIG. FIG. 3 shows the film thickness distribution when the SiO ₂ thin film is formed under the condition that the temperature distribution is made uniform. A nearly uniform film thickness is obtained from the center of the substrate to near the edge of the fixing plate. In addition, the stress strain and the irregular film thickness irregularity caused by the conventional type of holder that completely fixes the substrate were eliminated.

[0013]

By using the substrate heating apparatus of the present invention, it is possible to eliminate the temperature non-uniformity which causes a large temperature difference between the central portion and the end portion of the substrate, and therefore a metal thin film is formed on the back surface of the substrate. The process becomes unnecessary. Further, since the electrode is a corrugated metal plate, its elasticity can be used to ensure electrical contact with the back surface of the substrate, and the electrode can be fixed without giving strain to the substrate. As a result, the thin film formed on the surface of the substrate has uniform film thickness, resistance, refractive index, crystallinity, and other important physical property values over the entire surface of the substrate, so that a desired thin film of good quality can be formed.

[Brief description of drawings]

FIG. 1 is a diagram showing a substrate holder and an electrode structure used in an embodiment of the present invention.

FIG. 2 is a diagram showing a temperature distribution when heating a substrate according to an embodiment of the present invention.

FIG. 3 is a diagram showing a film thickness distribution of an example of the present invention.

FIG. 4 is a diagram showing a state where a substrate and an electrode are in surface contact with each other in a conventional example (a) and a diagram showing a non-uniform temperature distribution at that time (b).

FIG. 5 is a diagram showing a non-uniform temperature distribution that occurs when an electrode having a sharp tip of a conventional example is used.

[Explanation of symbols]

 1 substrate holder 2 groove for installing substrate 3 corrugated plate-shaped metal component (electrode) 4 non-conductive thin plate 5 electrode fixing screw 6 substrate 7 substrate fixing plate 8 screw 41 semiconductor substrate 42 substrate holder 51 point electrode contact portion 52 high temperature Part 53 Low temperature part

Claims (3)

[Claims] 1. A device for heating a substrate by passing an electric current from one end of the substrate to the other end, wherein an electrode contacting the substrate for energization is fixed to a part of a metal substrate holder. And a corrugated metal plate, the corrugated metal plate having a plurality of top portions. 2. The substrate heating apparatus according to claim 1, wherein the substrate is fixed by a non-conductive substance. 3. The substrate heating apparatus according to claim 1, wherein the metal plate serving as an electrode is attached via a thin plate made of a non-conductive material.