JPH02192490A - Production of single crystal and temperature measuring jig therefor - Google Patents

Abstract

PURPOSE:To presume operating conditions readily growing a single crystal relatively to an optionally heater temperature profile by controlling an interfacial position of a raw material melt and a liquid encapsulating agent to a specific relationship. CONSTITUTION:A heat incident hole 13 is provided at a position in the perpendicular direction to a supporting rod 12 on the surface of a hollow sphere 11 of a bisectional structure, having 2-5mm wall thickness and 30-50mm diameter, fixed to a supporting rod 12 for fixing and made of stainless steel subjected to specular finish and a thermocouple 15 fixed along the supporting rod 12 with fixing jigs 17 is inserted through an insertion hole 16 into the hollow sphere 11. The tip thereof is then set in the center (O) of the hollow sphere 11 to construct a temperature measuring jig 5. A heater 7 is assembled into a hot zone 6 and heated in a vacuum heating vessel 2. The temperature measuring jig 5 is then set and vertically moved along the center line of the heater 7. Thereby, a single crystal is pulled up while controlling an interfacial position of a raw material melt 1 and a liquid encapsulating agent 2 so as to keep relationships of H>=20 and D/H<=1.0 taking D/H as a parameter on the assumption that the heater length within the temperature region within 1.6 deg.C from the maximum temperature of the heater is Hmm and the distance of the position at the maximum temperature of the heater and the interfacial position between the raw material melt 1 and the liquid encapsulating agent 2 is Dmm.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a compound semiconductor single crystal manufacturing method using the LEC method (liquid pair 111 pulling method).

[Conventional technology]

Compound semiconductor single crystals are electronic devices 2! It is important for temporary use, and the demand for it is increasing, and the method of manufacturing large compound semiconductor single crystals has become an issue.

In other words, it is required to obtain large-diameter single crystals at a high yield, and the most important consideration is the thermal balance of the pulling device. When the number of times of pulling increases, there is a problem that the heat balance collapses and it becomes impossible to grow a single crystal. The reason for this is considered to be that the thermal environment inside the furnace during crystal growth changes under the same operating conditions due to changes in the heater temperature profile characteristics. Here, the operating conditions are the distance from the upper end of the heater to the interface between the raw material melt and the liquid to the arsenic agent at the start of crystal pulling, and the crucible push-up speed during crystal pulling. Further, the in-furnace thermal environment refers to the temperature gradient in the pulling direction and in the direction perpendicular thereto near the interface between the raw material melt and the liquid sealant.

Currently, in order to maintain a constant thermal environment, heaters are replaced when the number of pumps used exceeds a certain limit.
Even when using a new heater, keeping the thermal conditions constant requires delicate adjustments.

This invention measures the temperature profile of a heater with a simple device, clarifies the influence of the profile characteristics on single crystal growth, and
The purpose of this study is to predict operating conditions that facilitate the growth of single crystals, and to use this information to improve the yield rate of single crystals.

As shown in Figure 3, compound semiconductor single crystals such as GaAs are manufactured by placing a quartz crucible or PBN (PBN) inside a graphite crucible.
Using a device equipped with a pyrolytic boron nitride (pyrolytic boron nitride) crucible, a semiconductor raw material is placed inside the crucible, the raw material is melted by a resistance graphite heater set outside the crucible, and a seed crystal is immersed in the melt. , by pulling it up. The heater is the most likely to deteriorate during crystal pulling, and the heater is usually replaced after 20 to 30 pulls.

[Problem to be solved by the invention]

Conventionally, the temperature profile of a heater has been measured by installing a heater and crucible in a lifting device, heating it, and then inserting a thermocouple sealed in a ceramic protection tube into the crucible to measure the temperature. Ta. In this case, in order to accurately measure the temperature profile, the thermocouple is moved over a wide range within the crucible, or multiple thermocouples are inserted to measure the temperature at the same time. When such a method is used, measurement is very complicated and there is a problem of lack of accuracy. Possible reasons for the lack of accuracy are the large influence of gas convection within the crucible and the exposure to heat radiation from the solution and hot zone.

With such conventional methods, it is difficult to eliminate error factors and measure the temperature distribution due to the true heat generation of the heater. Based on measurements with low precision, even if the heater is updated, an appropriate temperature profile cannot be obtained, and single crystals cannot be pulled with a high yield.

[Means to solve the problem]

It was assumed that the change in the thermal environment inside the furnace that occurs when replacing the heater, as described above, occurs because the temperature profile characteristics of the heater are different. Then, using a pulling device using the heater, we can accurately and quickly measure the temperature distribution inside the furnace in the presence of the melting point and liquid sealant, and determine the thermal environment inside the furnace based on the characteristics of the heater temperature profile. We experimentally studied the effect on

First, a measuring jig for thermocouples according to the present invention will be explained.

Details of the measurement jig are shown in Figure 1. FIG. 1 is a sectional view showing the structure of the jig. The tip of the jig consists of a mirror-finished hollow sphere 11 made of stainless steel, and a fixing support rod 12 is fixed to one end 13a of the hollow sphere 11 by welding.

A heat incidence hole 13 is provided on the surface of the hollow sphere 11 at a position perpendicular to the support Hi 12. The thermocouple 15 is fixed by a fixing jig 17 along the support rod 12, and the welded part 1
It is inserted into the hollow sphere 11 through the thermocouple insertion hole 18 provided near 1a, and set so that the thermal contact 14 at the tip is located at the center O of the hollow sphere 11.

Hollow sphere II is made of stainless steel with a wall thickness of 2 to 5 mm,
It will have a split structure. The diameter of the sphere should be 30 to 50 mm.

The surface of the hollow sphere is finished to a mirror surface with four or more triangular marks by puff polishing. This increases the reflectance to 0.97,
Heat radiation in directions other than the intended direction has almost no effect.

The heat incidence hole 13 is a pore having a diameter of 3 to 5 mm, and is provided in a direction perpendicular to the support rod 12 and toward the center of the hollow sphere.

This makes it possible to measure only the amount of heat due to the heat rays in a certain direction among the heat rays emitted from the heater, and eliminate the influence of reflected heat rays. The heat rays exiting from the entrance hole can be ignored.

The inside of the hollow sphere is also mirror-finished and arranged so that the incident heat rays are totally reflected and concentrated at the center O of the sphere, heating the thermal junction 14 of the thermocouple.

A suitable gripping portion 12a is provided at the other end of the support rod 12 to enable vertical and rotational movement during measurement. Furthermore, a thermocouple terminal (not shown) may be attached.

Next, a method of measuring the temperature profile of a heater using the jig of the present invention will be explained.

〔Example〕

First, a heater 7 to be measured is installed in a carbon hot zone 6 as shown in FIG. 2, and heated in a vacuum heating container 2. The heating method is power control, applying approximately 5kW of power. The heater temperature profile is measured by setting the CA thermocouple 4 in a measuring jig 5 as shown in FIG. The heat incidence hole 13 is oriented in a certain direction, the Dj fixed fixture is moved up and down along the central axis of the cylindrical heater, and the thermoelectromotive force is measured. The measurement is performed by changing the direction of the heat incidence hole 13. Such measurements are repeated several times to measure the heat generation temperature distribution of the heater.

When measured using the method described above, the temperature profile of the heater results as shown in FIG. 4. As a result of detailed study, it was found that the reproducibility of the measurement was within 1.6°C and the accuracy was good. From the above data, parameters are determined to quantitatively examine the effect of heater temperature profile on single crystal growth.

It is a fact experimentally determined from measurements of the temperature distribution in the furnace that it is easier to grow a single crystal if the temperature gradient in the growth direction near the interface between the raw material melt and the liquid sealant is uniform.

In terms of heat transfer, if the heating near the interface between the raw material melt and the liquid sealant is uniform, the temperature gradient in the growth direction in that area will be uniform within the interface. Therefore, as shown in FIG. 4, D/H is set as a parameter indicating the uniformity of heating near the interface between the raw material melt and the liquid sealant. That is, in the heater temperature profile, considering the reproducibility of measurement, the length of the heater in the temperature range within 1.8° C. from the maximum temperature is defined as H. Further, in the profile, the distance between the interface between the raw material melt, the liquid pair +L, and the agent with respect to the highest temperature position is defined as D. Then, D/H is set as a parameter.

As a result of measurement, when D/H becomes small, it is easy to grow a single crystal, and conversely, when D/H becomes large, it becomes difficult to grow a single crystal.

The measurement results of the heater temperature profile by the measurement method of the present invention are shown in FIGS. 5(a), (b), and (e). Figures 5 (a) and (b) are before the start of lifting;
Figure (c) shows the result after being pulled up 20 times. (C
), there is a part where the curve lacks smoothness near the highest temperature zone, indicating that it is beginning to deteriorate. Next, the crystal was pulled up using heater A, and from the data during pulling, the distance from the upper end of the heater to the interface between the raw material melt and the liquid sealant and the temperature profile when the single crystal became polycrystallized. The parameter D/H was calculated. The ratio of the single crystal length (Lscρ) to the grown crystal length (L12,
Parameter D/H8 for which L /L was calculated previously
Figure 6 shows the arrangement of er er. From Figure W46, it can be seen that when the parameter D/H increases during crystal growth, it becomes difficult to grow the 111 crystal. It can be seen that it is better to set D/)1 to 1 or less.

That is, by measuring the temperature profile of an arbitrary heater and setting operating conditions such that the parameter D/H is small in the profile characteristics, single crystal growth becomes easy.

A specific method to maintain it below 1 is to first reduce D. In other words, the interface between the melt and the sealant should be brought as close to the highest temperature position of the heater as possible.

Next, increase H.

In other words, the heater should be designed so that the heater's constant calorific value band is wide. From FIG. 5, it is necessary to take H of the heater at least 20 mm or more.

If such a heater is used and D/H is maintained at 1 or less by adjusting the interface position between the melt and the sealant, the single crystal yield can be dramatically improved.

[For production]

When using the temperature measuring jig according to the present invention, only the heat rays incident on the thermocouple through the fine heat incidence holes are captured and measured, eliminating the effects of reflection and convection, and close to the energy generated by the true heater heat generation. This allows you to measure things and improves accuracy.

Furthermore, when using the method of the present invention, the maximum temperature range can be accurately determined, making it easier to maintain optimal pulling conditions.

〔effect〕

Measure the temperature profile of the heater and set parameter D
By using /H, it is possible to estimate operating conditions that facilitate the growth of single crystals for any heater temperature profile.

That is, the present invention is a method of measuring the temperature profile of a heater without complicating the apparatus and estimating operational conditions that facilitate the growth of single crystals based on the measured profile characteristics.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the structure of the temperature measuring jig of the present invention, and FIG. 2 is a diagram showing the temperature distribution of a pulling device using the temperature measuring jig of the present invention. FIG. 3 is a diagram for explaining a crystal pulling method using the LEC method. FIG. 4 is a diagram showing an example of the temperature profile of a heater made using the temperature measuring jig of the present invention, and FIG. 5 is a diagram showing an example of the temperature profile of the heater as well. FIG. 6 is a diagram showing the relationship between the parameter D/H and the 111 crystal acquisition rate. 1... Melt 2... Liquid sealant 4.
... Crucible 5 ... Temperature measurement jig 6 ... Hot zone 7 ... Heater 11 ... Hollow sphere 12 ... Support rod 13 ... Heat incidence hole
14... Thermal junction of thermocouple 15... Thermal lightning couple

Claims (2)

[Claims] (1) When pulling a single crystal using the liquid encapsulation pulling method (LEC method), the length of the heater in the temperature range within 1.6°C from the maximum temperature of the heater is defined as H (mm), and the maximum temperature position of the heater is When the distance between the material melt and the interface position between the raw material melt and the liquid sealant is D (mm), the raw material is A method for producing a single crystal, characterized by pulling the melt and a liquid sealant while controlling the interface position. (2) A heat incidence hole is provided on the surface of a stainless steel hollow sphere with a mirror-finished surface, a hot junction of a thermocouple is placed in the center of the hollow sphere, and a support rod can be attached at right angles to the heat incidence hole for suspension. A temperature measurement jig characterized by having a structure.