JPS63144189A - Apparatus for liquid epitaxy - Google Patents

Abstract

PURPOSE:To enable temperature distribution control in the radial direction in the furnace core tube, by additionally providing an auxiliary heater under a crucible in an apparatus for liquid epitaxy. CONSTITUTION:An auxiliary heater 25 is provided under a crucible 11 containing a solution 19 containing a crystal substance in a furnace core tube 17.

Description

[Detailed Description of the Invention] [Summary] By attaching an auxiliary heater below the crucible, it is possible to control the temperature distribution in the radial direction within the furnace core tube.

[Industrial application field]

The present invention provides a liquid phase epitaxial growth (LPE) apparatus,
In particular, it relates to improvements in the heating device.

[Conventional technology]

Conventionally, in order to control the crystal growth temperature, a resistance heater disposed around the furnace core tube is divided into three parts, for example, to control the temperature distribution in the longitudinal direction of the furnace core tube as uniformly as possible.

According to this method, temperature control in the longitudinal direction can be performed relatively accurately, but the temperature distribution in the radial direction of the substrate (wafer) on which the crystal is to be grown cannot be controlled.

[Problem that the invention seeks to solve]

As mentioned above, in conventional LPE equipment, the growth temperature is controlled by a resistance heating coil installed around the furnace core tube, so a temperature gradient does not occur between the center of the furnace core and the peripheral wall of the furnace core. (The central part of the furnace core is at a low temperature), making it difficult to accurately control the crystal growth temperature.

An object of the present invention is to control the temperature in the radial direction of the furnace core to make the temperature distribution in the same direction uniform.

[Means for solving problems]

According to the present invention, in order to achieve the above object, an auxiliary heater is provided below the crucible.

[For production]

The above-mentioned auxiliary heater can control the temperature in the radial direction of the furnace core tube, in addition to the conventional temperature control in the vertical direction by the heater around the furnace core tube, and as a result, it is possible to make the temperature distribution in the radial direction uniform. can.

〔Example〕

FIG. 1 shows an embodiment of the LPE device of the present invention.
Inside the furnace core tube 17, a platinum crucible 11 containing a solution 19 containing a crystal material to be grown on a substrate or wafer 10 is placed on a crucible stand 15. The wafer 10 is held by a rotatable holder 12, and can be taken in and out of the crucible 11 by moving the holder 12 up and down.

The solution 19 is, for example, an arrangement of constituent elements of magnetic bulb garnet (SmzOz, Yz03.FegO1+G
ate3, etc.) and fluxes PbO and BtCh, and is maintained at a high temperature of 900° to 1000°C.

When this melt is supercooled and the substrate 10 is immersed, a magnetic bubble garnet film is epitaxially grown on the substrate.

The substrate is held horizontally by a substrate holder 12 and rotated in the melt. This makes it possible to suppress variations in film thickness and composition within the wafer.

The heating temperature control described above is performed by the coil heater 13 disposed around the furnace core tube 17. The heaters 13 are arranged as described above (for example, in groups G of three so that the temperature distribution in the longitudinal direction of the furnace core tube 17 is uniform).

Gz, G! It is divided into two parts, each of which can be controlled independently. In other words, heater groups at, Gx.

By appropriately controlling G, the vertical temperature distribution of the solution 19 inside the furnace tube 17, that is, inside the crucible 11, can be made uniform. The above configuration is publicly known.

According to the invention, another auxiliary heater 2 is provided below the crucible 19.
5 is attached. The auxiliary heater 25 may be a resistance heating coil heater similar to the heater 13 described above, a plane heater, or any other type of heater. Auxiliary heater 25
It may be brought into direct contact with the bottom surface of the crucible 19, or it may be attached via a heat conductive pedestal 27. Note that, like the heater 13, the auxiliary heater 25 may also be divided into several parts in the radial direction and independently controlled for each group.

The division method is, for example, 3 heaters arranged concentrically.
It is sufficient that the ring heater is shaped as a ring heater.

The auxiliary heater 25 is used to correct (heat) the temperature of the center of the solution 19, which tends to be lower than the temperature of the surrounding area.

Fig. 2 shows the effect of the present invention. Fig. 2 (a) shows the case where an auxiliary heater is provided at the bottom of the crucible according to the present invention, and Fig. 2 (b) shows the conventional technique (when no auxiliary heater is provided at the bottom).
The temperature distribution in the radial direction of the furnace core tube 11 is measured in each case. The diameter of the furnace core tube is 8c11, and the liquid level is approximately 6cm.
It is. Figure 2(a).

As is clear from (b), by providing the auxiliary heater 25, the temperature distribution in the radial direction becomes almost uniform, and much better temperature control can be achieved than in the prior art.

The graphs shown on the right side in FIGS. 2(a) and 2(b) are for reference to the temperature distribution in the longitudinal direction at the center of the furnace core tube, and the temperature variation ΔT is reduced by the divided heater 13 around the furnace core tube 11. This shows that it is possible to suppress the temperature within the range of ±1.0°C.

Figure 3 shows the temperature change of the solution during actual crystal growth. According to the present invention shown in figure (a), the temperature change is much smaller than that of the conventional solution shown in figure (b). I understand that. That is, in the present invention, ΔT≦0.5°C, whereas in the prior art, ΔTz was 2°C.

〔Effect of the invention〕

As described above, according to the present invention, the temperature distribution of the solution in the crucible is maintained substantially uniform both in the longitudinal direction and in the radial direction, so that changes in the solution temperature during crystal growth can be reduced and the growth can be improved. Can be done easily and accurately.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the liquid phase epitaxial growth apparatus according to the present invention, and FIG. 2 is a diagram showing the temperature distribution characteristics of the solution. Figure 3 is a diagram showing the change in solution temperature during growth.
Figure a) shows the present invention, and figure (b) shows the prior art. 11... Crucible, 13... Heater, 17
...Furnace core tube, 25...Auxiliary heater.

Claims (1)

[Claims] A liquid phase epitaxial growth apparatus characterized in that an auxiliary heater (25) is provided in a furnace core tube (17) below a crucible (11) for a solution containing a crystalline substance.