JPS61251126A - Vapor growth method - Google Patents

Abstract

PURPOSE:To facilitate the maintenance of a device and to prevent the occurrence of slippage by using infrared rays from an auxiliary heat increase source only for the heating process of a substrate. CONSTITUTION:The heat is mainly obtained from a high-frequency induction heater in which a susceptor 5 is used. The heating from the surface side of a substrate 6 by means of infrared rays is auxiliary used for the heating in the heat increase process which is most problematic in the occurrence of a slippage. Thus, it is made possible to transfer the substrate 6 from a elastic state to a plastic state while making the temperature distribution within the susceptor 5 and the surface of the substrate 6 supported by it uniform, thereby preventing the occurrence of slippage. Moreover, it is possible to increase the lifetime of an auxiliary heat source such as a lamp 2 since no auxiliary heater during the vapor growth where reaction gas is flown.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a vapor phase growth method for forming a thin film on a substrate such as a semiconductor or an insulator.

[Technical background and problems]

To heat a substrate during vapor phase growth for manufacturing semiconductor devices, a carbon susceptor is usually used, the substrate is supported by this susceptor, and the susceptor is heated by resistance heating, high frequency induction heating, or even infrared rays using a lamp or the like. A method is adopted in which heat is generated by heating and the substrate supported by the heat is heated. In particular, recently, high-frequency induction heating and infrared heating using lamps are the most common methods.

When heating a substrate in vapor phase growth, particularly in epitaxial vapor growth, it is necessary to maintain a uniform temperature distribution within the substrate in order to suppress the occurrence of slip, which is a crystal defect. Uniform temperature distribution within the substrate includes not only temperature distribution in the plane but also uniformity of temperature in the thickness direction, that is, on the front and back surfaces, and it is necessary to maintain the entire substrate at a uniform temperature to perform vapor phase growth. It was said that there was.

Conventionally, it has been thought that infrared heating using the above-mentioned lamp is the most preferable method for performing vapor phase growth, which can heat the entire substrate more uniformly and cause fewer slips. However, infrared heating by lamps.

The lamp life is relatively short and maintenance is difficult.

In addition, 1. For example, when a semiconductor material gas with a low decomposition temperature, such as monosilane (SiH4), is used as a reaction gas, 1.
This has the disadvantage that vapor phase growth can only be carried out using a limited amount of semiconductor material gas because the substrate is unable to be heated because it blocks the infrared rays that are the heating source.

On the other hand, high-frequency induction heating has the advantage that the equipment has a long life and is easy to maintain, and the heating efficiency does not decrease due to the adhesion of Sl that occurs in one reaction chamber. It is very difficult to uniformly heat the entire substrate, and as a result, when the diameter of the substrate increases, the uniformity of temperature distribution within the substrate deteriorates, resulting in slippage. In other words, the vertical vapor phase growth loading shown in Fig. 3 is known to provide the most uniform temperature distribution among high-frequency induction heating devices, but this device also has the following problems. There's a problem. In Figure 3, %3 is the reaction chamber and 4 is the nozzle.

5 is a susceptor, 6 is a substrate, and 7 is a high frequency induction coil.

(hereinafter referred to as an RF coil), a high frequency, high voltage and high current (hereinafter referred to as high frequency power) is applied to the RF coil 7, the susceptor 5 is heated to a predetermined temperature by induction heating, and the substrate 6 is heated to a predetermined temperature by induction heating.
is heated to the vapor phase growth temperature by the susceptor 5, but it is difficult to make the magnetic flux density uniform between the outer circumference and the inner circumference of the susceptor 5.
Various measures have been taken, such as adjusting the distance between the susceptor 5 and the outer periphery, but the magnetic flux density is higher on the outer periphery than on the inner periphery, and furthermore, the outer periphery has poorer heat conduction than the carbon susceptor 5. Because it is surrounded by gas, the outward heat transfer is smaller than the inward heat transfer.

Heat tends to concentrate on the outer circumference, and the inner circumference of the susceptor 5 cannot be heated by induction by the RF coil 7 due to its mechanical structure. The outer periphery becomes hotter than the periphery.

The temperature difference between the inner and outer circumferential parts of the susceptor 5 is such that when the temperature of the susceptor 5 reaches a predetermined vapor phase growth temperature and becomes stable, the flow of heat within the susceptor 5 becomes small, and the carbon forming the susceptor 5 is Because of the good heat conduction, the temperature distribution is made uniform to the extent that it is practically not a problem. In addition.

In the temperature-lowering process, the tendency is opposite to the temperature-raising process, that is, the outer peripheral part is more easily cooled than the inner peripheral part, so the temperature is lower in the outer peripheral part, although the value is relatively small. Therefore, the substrate 6 supported by the soot porcelain 5 is forced to be heated unevenly, especially during the temperature rising process, and is subjected to thermal stress, resulting in slippage, which is a crystal defect. This tendency is reflected in the substrate 6
becomes larger as the diameter becomes larger, for example, 5 inches (127 mm) or more. The inventors of the present application have conducted various studies on the occurrence of slips, and have found the following.

In other words, if the temperature distribution on the surface of the substrate 5 is uniform when the substrate 6 is grown from room temperature to a vapor phase growth source in a mechanically unstable elastoplastic region, no slip occurs and the difference in temperature distribution within this plane is When the temperature exceeds several tens of degrees Celsius, slipping occurs. Similarly, when the temperature is lowered from a high temperature in a plastic state to room temperature, slip occurs if the temperature distribution is poor in the elastoplastic region midway. The occurrence of this slip is remarkable when the vapor-phase grown film is thick.

[Purpose of the invention]

The present invention was made in view of the above-mentioned points, and its purpose is to reduce the limitation of usable semiconductor material gases by 8%.
It is an object of the present invention to provide a vapor phase growth method in which iHa can also be used, the equipment is easy to maintain, and slip does not occur.

[Summary of the invention]

In order to achieve this object, the present invention uses high-frequency induction heating using a susceptor as the main heating method, and uses infrared rays from the surface side of the substrate for heating during the temperature rising process, where the amount of slip generation is a problem in this heating method. By performing supplementary heating, the temperature distribution within the surface of the susceptor and the substrate supported by it is made uniform, and the substrate transitions from an elastic state to a plastic state. The heating is substantially performed by high-frequency induction heating.

〔Example〕

1 and 2 showing one embodiment of the present invention will be explained below. In FIG. 1, the same parts as in FIG. 3 are denoted by the same reference numerals, and a description of the structure will be omitted. A plurality of lamps are installed above the bell jar 3a forming one reaction chamber 3, and a plurality of lamps are used as auxiliary heating sources that emit infrared rays.
It is configured to irradiate infrared rays more uniformly over the entire surface area of the substrate 6 and the susceptor 50. In addition.

8 is an exhaust port, and 9 is a hollow rotating shaft that supports the susceptor 5.

FIG. 2 shows the entire heating state of the substrate 6 in the vapor phase growth method of the present invention using the apparatus shown in FIG.

A-F on the horizontal axis indicates each step of vapor phase growth, and the vertical axis indicates the substrate 6.
The temperature T, the output W+ of the RF coil 7, and the output W2 of the lamp 2, which is an auxiliary heating source, are shown.

The process shown in FIG. 2 is a pre-gas purge process, in which the pre-gas purge process involves setting the substrate 6 on the susceptor 5, closing the bell jar 3a, and first spouting nitrogen gas (N2) from the nozzle 4 for a predetermined period of time. Reaction chamber 3 from exhaust port g
In this step, the air inside the reaction chamber 3 is exhausted, the inside of the reaction chamber 3 is replaced with N2 gas, and then the N2 gas necessary as a vapor phase growth atmosphere is jetted out from the nozzle 4 to replace the inside of the reaction chamber 3 with N2 gas. During the pre-gas purge process, neither main heating by the RF coil 7 nor auxiliary heating by the lamp 2 is performed as shown in FIG.

After a predetermined period of time has passed and the inside of the reaction chamber 3 has been completely replaced with N2 gas, the first temperature raising step B1 begins, in which high-frequency power is applied to the RF coil 7 while rotating the susceptor 5 at a low speed by the hollow rotating shaft 9. is supplied to start heating the susceptor 5. At this time, N2 gas continues to be ejected from the nozzle 4. Said R
As shown in FIG. 2, the power supplied to the F coil 7, that is, the output W, is preferably output-controlled to a value P to have an appropriate slope. The increase in output is stopped at this value p□. By supplying high frequency power to the RF coil 7, the susceptor 6 is heated by induction, and the substrate 6 is heated from the back side. At this time, the temperature of the susceptor 5 increases.

As described above, the outer circumferential portion is higher in temperature than the inner circumferential portion, creating a temperature gradient in the radial direction. Initially, the temperature of the substrate 6 rises relatively rapidly as shown by the curve T (the surface of the susceptor 5 also increases the temperature of the substrate 6).
), but the output W of the RF coil 7 is
is limited to the value Po as described above, the substrate 6
The temperature becomes stable at point t1.

This temperature t is as high as possible within the range where the substrate 6 is in a completely elastic state. For example, if the substrate 6 is 8□,
The value P of the output W is set in advance so that the temperature is 50 to 500°C.
. It is set by determining ==+4=1e or by detecting the temperature T and controlling the output W1 of the RP coil 7.

When the temperature of the substrate 6, that is, the susceptor 5 is stabilized at point t1, since the susceptor 5 is made of carbon and has good heat conduction, the temperature distribution becomes almost uniform throughout.

When this state is reached, or slightly before reaching this state, power is supplied to the lamp 2 and the second temperature raising step B2 is started.
to go into. The start of power supply to the lamp 2 is preferably carried out by controlling the output so that an appropriate slope is achieved, as shown in FIG. When the lamp 20 is turned on, infrared rays emitted from it pass through the quartz belljar 3a and heat the surface of the substrate 6 and the exposed surface of the susceptor 5. The heating by the lamp 2 is performed almost uniformly over the entire surface of the susceptor 5 due to its arrangement and the action of the reflector 1, and the temperature of the substrate 6 is reduced by the N2 gas and heat radiation from the nozzle 4. Since the substrate 6 is heated directly from the generated surface side, the substrate 6 is heated to have a more uniform temperature distribution both in the plane and in the thickness direction, and is heated to a temperature t2 at which it becomes completely plastic. . This temperature t2
When the substrate 6 is 81, the temperature is preferably 950° C. or higher.

During the period from t to t2 when the temperature of the substrate 6 reaches t2, high-frequency induction heating of the substrate 6 and susceptor 5 by the RF coil 7 and infrared heating by the lamp 2 are performed. Also, the value of the output W2 of the lamp 2 at this time is % the output P of the RF coil 7. It is about 50 inches.

In this way, the entire substrate 6 is heated uniformly through the auxiliary heating by the lamp 2 to pass through the elastoplastic region where slips are likely to occur in the substrate 6, thereby suppressing the occurrence of slips.

Next, a third temperature raising step B is entered. In this step B3, as shown in FIG. 2, the output W of the RF coil 7 is preferably increased to P with an appropriate gradient, and
The output W2 to the lamp 2 is preferably reduced to zero with a suitable gradient, and the susceptor 5 is reduced by only the RF coil 7.
is heated, and the substrate 6 is brought to a vapor phase growth temperature tg (for example, 116
Heat to 0℃).

When the temperature rises from temperature t2 to t5-1, a phenomenon occurs again where the temperature is higher at the inner circumference than at the outer circumference of the susceptor 5, but since the substrate 6 is in a completely plastic state, the temperature distribution Even if the surface is uneven, slip will not occur.

When the temperature of the substrate 6, that is, the temperature of the surface of the susceptor 5 stabilizes at the vapor growth temperature t5, the temperature distribution in the radial direction of the susceptor 5 becomes uniform. Note that the output W to the RF coil 7 at this time is completely constant as shown in FIG. 2 because the surface temperatures of the substrate 6 and susceptor 5 are controlled to be maintained at the vapor growth temperature t. It does not necessarily take a certain value P1, but changes slightly up and down.

After the substrate 6 reaches the vapor growth temperature t3 in this way, the etching process C begins, in which hydrogen chloride (HCt) gas is ejected from the nozzle 4 together with H2 gas as a carrier gas, and the surface of the substrate 6 is etched extremely thinly. Then, the semiconductor material gas (reactive gas) is ejected from the nozzle 4 instead of HCt gas, and the vapor phase growth process begins. This is because the susceptor 5 is uniformly heated in this vapor phase growth step.

The entire surface of the substrate 6 is also heated uniformly, and a vapor-phase grown layer having uniform quality and thickness can be obtained over the entire surface. In addition.

Since the front surface of the substrate 6 has a lower temperature than the back surface and tends to warp, in order to prevent deterioration of the temperature distribution in the plane due to this warping, a well-known counterbore with a recess is provided in the substrate support portion of the susceptor 50. It is preferable to provide one.

Once a predetermined time has elapsed after entering the vapor phase growth step D1,
The reaction gas is stopped, a post-gas purge step is started, and only the residual gas is ejected from the nozzle 4, so that the inside of the reaction chamber 3 is again made into an atmosphere of only H2 gas.

Next, the power supply to the RF coil 7 is cut off, its output W is set to zero, and the temperature lowering step E is started. However, slightly before or at the same time, the lamp 2 is turned on again. This temperature lowering step E is the temperature raising step B7. Since there is no phenomenon in which the outer circumference of the susceptor 5 becomes hotter than the inner circumference as in B5, auxiliary heating by the lamp 2 is not particularly necessary, but as shown in FIG. 2, the output of the RF coil 7 By reducing W to zero and performing auxiliary heating using the lamp 2 that can heat the entire surface of the susceptor 2 more uniformly, rapid temperature changes in the substrate 6 can be suppressed and the temperature distribution of the substrate 6 can be kept more uniform to maintain the elastic-plastic region. It is designed to allow the .

The lighting of the lamp 20 during this temperature drop can be turned off once the temperature T of the substrate 6 has fallen to a point where it becomes completely elastic, in order to shorten the cycle time.

Thereafter, it is preferable to lower the temperature as quickly as possible.

The reaction chamber 3 is made into an N2 gas atmosphere by blowing out gas (step E), and one reaction chamber 3 is opened and the substrate 6 is taken out.

In the above-mentioned embodiment, in order to make it easier to understand the present invention, the substrate '6, that is, the susceptor 5 is
The temperature of 1. Although we have shown an example in which auxiliary heating is performed using the lamp 2 once the temperature is stabilized at (the temperature at which the substrate 6 is in an elastic state), direct heating of the substrate 6 using infrared rays is added to the high-frequency induction heating using the RF coil 7. By doing so, it is possible to suppress the temperature gradient inside the susceptor 5, which occurs when the temperature is raised only by high-frequency induction heating, and thereby suppress the occurrence of slip. You can also do it with your body.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to reliably prevent the occurrence of slips, and the auxiliary heating by lamps etc.
Since the temperature is raised or lowered during the temperature rising and cooling process in which no reactant gas flows, there is no deposition of vapor-grown substances on the walls of the reaction chamber. The service life of auxiliary heating sources such as is obtained.

[Brief explanation of drawings]

Fig. 1 is a schematic sectional view showing an example of a vapor phase growth apparatus for carrying out the present invention. Fig. 2 shows an embodiment of the vapor phase growth method according to the present invention. Output W1% A curve diagram showing the relationship between the output W of the auxiliary heating source and the temperature T of the substrate heated by these, and Fig. 3 is a schematic cross section showing an example of a conventional high-frequency induction heating type vapor phase growth apparatus. It is a diagram. 1...Reflector, 2...Lamp (auxiliary heating source). 3... Reaction chamber % 4... Nozzle, 5... Susceptor, 6... Substrate, 7... High frequency induction coil (RF coil).

Claims (1)

[Claims] 1. In a method for performing vapor phase growth by supporting a substrate on a susceptor and heating the substrate by causing the susceptor to generate heat by high-frequency induction heating, the temperature of the substrate is raised by the susceptor. A vapor phase method characterized in that in the process, infrared rays from an auxiliary heating source are directly irradiated onto the surface of the substrate to perform auxiliary heating, and during vapor phase growth, the substrate is heated by a susceptor that is substantially heated by high-frequency induction heating. How to grow. 2. The vapor phase growth method according to claim 1, wherein the surface of the substrate is directly irradiated with infrared rays from an auxiliary heating source even during the temperature cooling process after vapor phase growth. 3. The vapor phase growth method according to claim 1 or 2, wherein the heating of the substrate by the auxiliary heating source is performed mainly when the substrate transitions from an elastic state to a plastic state.