JPS6317518A - Heating method for susceptor - Google Patents

Abstract

PURPOSE:To prevent the generation of a slip by gradually increasing an output from an oscillator by stages from a low value, PID-controlling the output from the oscillator, using a temperature as a parameter after the temperature reaches a fixed value and heating a substrate. CONSTITUTION:An output from an oscillator 8 is applied to a high frequency induction coil 6 by stages, thus heating a substrate 4 through the heating of a susceptor 3. The output from the oscillator 8 is adjusted, observing the state of the heating of the inner and outer circumferences of the susceptor 3 at that time. Since the substrate is heated up to an elastoplastic region of 600-850 deg.C, in which a slip is easy to be generated, and the output from the oscillator is changed over to a heating system by PID control at a time when the susceptor reaches 850 deg.C, the output suddenly increases, but the output lowers with approach to an objective susceptor temperature, and a fixed value is taken when the susceptor reaches the objective susceptor temperature. Accordingly, the generation of the slip can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a susceptor heating method in a vapor phase growth method for forming a thin film on a substrate such as a semiconductor or an insulator.

(Prior Art) To heat a substrate during vapor phase growth for manufacturing semiconductor devices, a susceptor made of carbon is usually used, the substrate is supported by the susceptor, and the susceptor is heated by high-frequency induction heating. A method of heating the supported substrate has been adopted.

This will be explained with reference to FIG.

In FIG. 2, 1 is a reaction chamber, 2 is a nozzle, 3 is a susceptor, 4 is a substrate, and 6 is a high frequency induction coil (hereinafter referred to as RF coil). 3 is heated to a predetermined temperature by induction heating, the temperature of the susceptor 3 is detected by a temperature sensor 7, the value is fed back to the oscillator 8, and the substrate 4 is heated to a predetermined temperature by induction heating.
It is heated to the vapor phase growth temperature. In addition,
9 is an exhaust pipe, and 10 is a sussegator support.

(Problems to be Solved by the Invention) However, in such a conventional device, it is difficult to make the magnetic flux density uniform between the outer circumferential portion and the inner circumferential portion of the susceptor 3. Various measures have been taken, such as adjusting the distance between the susceptor 3 and the susceptor 3, but the outer periphery has a higher density than the inner periphery, and the outer periphery has poorer heat conduction than the Carmen susceptor 3. Surrounded by gas, the outward heat transfer is smaller than the inward heat transfer, so heat tends to concentrate on the outer periphery, and furthermore, the inner periphery of the susceptor 3 is Since the induction heating by the RF coil 6 does not reach the load, there is a large heat flow n in the susceptor 3. During the temperature increase process, the inner circumference becomes hotter than the outer part. The temperature difference between the inner and outer circumferential parts of this soot pig 3 is
When the temperature of the susceptor 3 reaches a predetermined vapor phase growth temperature and stabilizes, the heat flow n inside the susceptor 3 is small and the carbon forming the susceptor 3 has good thermal conductivity, so the temperature distribution becomes substantially uniformity to such an extent that it does not cause any problems.

As shown in Fig. 4, the output of the oscillator 8 is kept constant until the 0 point, and when the temperature of the susceptor 3 reaches H1°C, gradient heating, so-called ramping, is performed.
The susceptor 3 is heated to a predetermined temperature under control.
Ru. Generally, the specific range for performing PID control is 750 to 1250° C., which can be measured by a temperature sensor. As mentioned above, the substrate 4Fi supported by the susceptor 3 is heated unevenly during the heating process, for example, the temperature difference between the outer circumference and the inner circumference of the susceptor is 1000°C.
Until then, the temperature was forced to be about 80°C, and the n1 thermal stress caused scratches and scratches, which are crystal defects. This tendency is reflected in the substrate 4
becomes larger as the diameter becomes larger, for example, 5 in% 125+a+) or more.

The inventors of the present application have made the following findings as a result of various studies on the occurrence of slips and slips. That is, while heating the substrate 4 from room temperature to a vapor growth temperature (for example, 1160° C.), the substrate 4 changes from an elastic state to a plastic state, but in the middle of this change, it is in an elastoplastic region that is unstable due to thermal stress. If the temperature distribution on the surface of the substrate 4 is uniform, no slipping will occur, but if the difference in temperature distribution within this plane is 20° C. or higher in the temperature range of 600° C. to 850° C., slipping will occur.

Furthermore, once a temperature difference occurs between the inner and outer circumferences of the susceptor 3,
It takes time to remove depending on PID control.

The present invention was developed in view of the above-mentioned points, and its purpose is to suppress the increase in heating time as much as possible while minimizing the temperature difference between the inner and outer circumferences of the susceptor, and to more reliably prevent the occurrence of slippage. The present invention provides a method for heating a susceptor.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention supports a substrate on a susceptor and heats the substrate by causing the susceptor to generate heat by high-frequency induction heating to perform vapor phase growth. In this method, the oscillator output is gradually increased from a low value at time intervals of a predetermined value or more until the susceptor passes a temperature at which slips and drops are likely to occur during the process of raising the temperature of the substrate. After reaching the temperature, the temperature is set to /4 rammeter and the oscillator output is PID-controlled to heat the substrate.

(Function) That is, in the present invention, when heating a substrate in the vapor phase growth process, the oscillator output is initially kept low, and the heating temperature is passed through a temperature at which sagging or sagging is likely to occur, such as in the elastoplastic region of the substrate. suppressing the generation of temperature difference between the inner and outer circumferences of the susceptor by increasing the output of the oscillator stepwise over time until
It is possible to prevent slip from occurring.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 to 3.

As shown in FIG. 2, after the substrate 4 is placed on the susceptor 3, the air in the reaction chamber 1 is replaced with nitrogen gas N2.Then, this nitrogen gas N2 is replaced with hydrogen gas H2. Next, the susceptor 3 is heated by induction using the RF coil 6, which will be explained in detail below.

The output of the oscillator 8 is determined in advance so as not to generate a temperature difference between the inner and outer circumferences of the susceptor, and then the susceptor 3 is heated using a heating method that can output a predetermined set value for a predetermined set time. This is the feature of this application. For example, the output of the oscillator 8 for time t1 is Pl+tl.
2, the output of the oscillator 8 is sent to the RF coil 6 in stages.
The substrate 4 is heated through the heating of the susceptor 3 by applying .

In this case, while checking the heating status of the inner and outer circumferences of the susceptor 3,
By adjusting the output of the oscillator 8, for example, the output P of the oscillator 8 can be
In the case of 3, p, by taking a longer time t3,
Both the inner and outer circumferences can be heated within a range of approximately 10 to 20°C.

As mentioned above, the elastoplastic range 600 to 8 where scratches and flops are likely to occur.
The oscillator output is heated to 50℃, and at the 0 point when it reaches 850℃, the oscillator output increases rapidly to the PID control heating method, but as it approaches the target susceptor temperature, it decreases, and once it reaches it, it reaches a certain level. It will take on a value. The temperature measurement results obtained by the above heating method are shown in FIG. In addition, the third
The figure shows only the range in which the susceptor temperature is 800°C or higher.

〔Effect of the invention〕

In the conventional susceptor heating method in vapor phase growth, for example, in the case of silicon substrates, slips are likely to occur unless uniform heating is carried out in the temperature range of 600 to 850 °C.
Since the temperature detection range of the susceptor is never less than 750°C, unreasonable heating methods have been used. For example, even if PID control is performed at a minimum temperature detection value of 750°C, Since there is a temperature difference between the parts, it is difficult to uniformly heat the parts.However, by implementing the method of heating slag as described in the present invention, it is possible to eliminate the occurrence of slippage on substrates of 5 inches or more.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the susceptor heating method of the present invention, FIG. 2 is a cross-sectional view of a vapor phase growth apparatus, FIG. 3 is a diagram showing temperature measurement curves of the inner and outer peripheral parts of the susceptor according to the present invention, FIG. 4 is a diagram showing a conventional susceptor heating method. 1... Reaction chamber, 2... Nozzle, 3... Susceptor,
4... Board, 6... High frequency induction coil, 7...
Temperature sensor, 8... oscillator. Applicant's agent Patent attorney Takeshi Suzue 2 Figure 1 Figure 2rSIJ

Claims (1)

[Claims] (1) In a method of supporting a substrate on a susceptor and heating the substrate by causing the susceptor to generate heat by high-frequency induction heating to perform vapor phase growth, slipping may occur during the process of heating the substrate with the susceptor. The oscillator output is gradually increased from a low value at time intervals of a predetermined value or more until the temperature reaches a certain temperature, and after reaching the temperature, the oscillator output is PID-controlled using the temperature as a parameter to control the oscillator output. A susceptor heating method characterized by heating.