JPH0316996A - Production of compound semiconductor single crystal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a single crystal production technique and a compound semiconductor single crystal growth technique using the liquid-encapsulated Czochralski method (hereinafter referred to as LEC method), for example. The present invention relates to a technique that can be effectively used to reduce the ψ○ defect density in InP single crystals.

[Conventional Techniques Compound semiconductor single crystals such as InP have a wider range of uses than silicon, including light-emitting diodes, semiconductor lasers, light-receiving elements, solar cells, FETs, and optical ICs, and are promising as high-speed devices and high-frequency devices. It is. However, compound semiconductor single crystals are prone to crystal defects, and if there are many crystal defects, the surface condition will deteriorate when an epitaxial layer is formed, device characteristics will deteriorate, and yield will decrease. Conventionally, crystal defects in compound semiconductor single crystals have been thought to be caused by dislocations, and many proposals have been made for crystal growth techniques that reduce dislocations.

[Problems to be Solved by the Invention] However, when a compound semiconductor single crystal is etched with a Huber etching solution, in addition to defects observed along with dislocation corrosion holes, there are also plate-shaped corrosion holes, egg-shaped corrosion holes, and shallow corrosion holes. It has become clear that defects called holes exist. Conventionally, in the photomicrograph in Figure 4, the round hole in the center, and in the photo in Figure 5, the square hole in the lower right corner are called dish-shaped, egg-shaped, or shallow corrosion holes, and the others are dislocations. This is accompanied by corrosion holes. Although many techniques have been proposed to reduce dislocation density, the reality is that the mechanisms by which defects not related to dislocations occur have not been analyzed, and no technology has been established to reduce them.

The present invention was made against the above-mentioned background, and its purpose is to provide a technology for growing compound semiconductor single crystals with fewer crystal defects called dish-shaped corrosion holes, egg-shaped corrosion holes, or shallow corrosion holes. Our goal is to provide the following.

[Means for Solving the Problems] The present inventors believe that crystal defects that are not caused by dislocations, such as dish-shaped corrosion holes, egg-shaped corrosion holes, or shallow corrosion holes, are caused by some impurity contained in the raw material or furnace material. I thought that this might be the case, and conducted extensive research. the result,
In growing compound semiconductor single crystals using the LEC method,
The period between the time from when the raw material in the crucible is completely melted to when the crystal starts to be pulled out (in this specification, this is referred to as the melt standing time) and the crystal defects described in "2" is as shown in Figure 1. We found that there is a correlation as shown in In addition, the first engineering drawing is I
Approximately 1 nP synthesis raw material mass 1. Crystal defect density in the upper part of the crystal and melt leaving time when InP single crystals were grown in an O O g crucible, using B,03 (300 g) as a sealant, and changing the melt standing time from 100 to 500 minutes. It is a correlation with time. From the same figure, it can be seen that in this case, by setting the melt leaving time to 5 hours or more, the number of defects to be noted can be reduced to about 10 or less per inspection. Furthermore, it has been found that the longer the melt is allowed to stand, the more raw materials there are.

This invention was made based on the above knowledge, and a raw material and a sealant are placed in a crucible, heated and melted by a heater, and seed crystals are placed on the surface of the raw material melt in the crucible covered with the liquid sealant. In order to grow a compound semiconductor single crystal by gradually pulling it up while rotating, the furnace is filled with an inert gas and the temperature is kept almost constant. It is proposed that the crystal be left for a predetermined period of time or more, and then the crystal pulling should be started.

Further, the melt leaving time is determined depending on the weight of the raw material in the crucible.

Note that the longer the time the melt is allowed to stand, the fewer defects there will be, but the longer the time the melt is allowed to stand, the lower the productivity.
It is reasonable to set it within hours.

[Operation] According to the above method, it is possible to grow a compound semiconductor single crystal with few crystal defects called dish-shaped corrosion holes, egg-shaped corrosion holes, shallow corrosion holes, etc., which are not caused by dislocations.

The above method reduces crystal defects that are not caused by dislocations because impurities that form the core of crystal defects contained in raw materials, furnace materials, etc. are incorporated into the sealant while the melt is left to stand. Alternatively, this may be due to reaction with other impurities and diffusion into the sealant or atmospheric gas.

[Example] 4 As an example, a nP single crystal was grown by applying the LEC method according to the present invention.

Engineering nP synthesis raw material mass 11. OOg in a quartz crucible (pB
After filling the crucible with 300g of B2O3 as a sealant and placing it in the furnace, the inside of the furnace is filled with N2 gas at about 40 atmospheres, and power is supplied to the heater placed around the crucible to start the furnace. Increased internal temperature. When the InP composite raw material in the crucible melted, the temperature increase was stopped and the temperature was kept at 300 ℃.
After leaving the melt for more than a minute, a seed crystal was brought into contact with the surface of the melt and pulling was started.

Three InP single crystals were grown using the above method, and wafers with different distances from the seed crystal were cut out from the grown InP single crystal ingot in a direction perpendicular to the pulling axis, and the surfaces were etched with Huber etching solution. observe,
The density of crystal defects called dish-shaped corrosion holes, egg-shaped corrosion holes, shallow corrosion holes, etc. was measured.

Figure 2 shows the measurement results.

The figure shows that when the present invention is applied, crystal defects called dish-shaped corrosion holes, egg-shaped corrosion holes, shallow corrosion holes, etc. are reduced to less than 10/1 throughout the entire single crystal.

For comparison, I,nP was grown under the same conditions as in the above example except that the melt was allowed to stand for 250 minutes or less.
For each single crystal ingot, wafers were cut out at different distances from the seed crystal of each ingot, and the density of crystal defects called dish-shaped corrosion holes, egg-shaped corrosion holes, shallow corrosion holes, etc. was measured.

The measurement results are shown in FIG.

According to the same figure, if the melt leaving time is short, several tens to
It can be seen that hundreds of corrosion holes are generated and the variation in crystal defect density is large.

In addition, when growing a single crystal using, for example, 3000 g of InP raw material lump, if the melt is allowed to stand for 600 minutes, dish-shaped corrosion holes, egg-shaped corrosion holes, or It has been confirmed that it is possible to grow InP single crystals with few crystal defects called shallow corrosion holes.

Therefore, the melt leaving time is appropriately determined depending on the weight of the melt.

Further, in the above embodiment, the growth of an InP single crystal was explained as an example, but the present invention can also be used for growing a GaAs or other compound semiconductor single crystal.

As explained above, in the present invention, a raw material and a sealant are placed in a crucible, heated and melted by a heater, and a seed crystal is brought into contact with the surface of the raw material melt covered with the liquid sealant in the crucible. To grow compound semiconductor single crystals by gradually pulling them up while rotating, after the raw materials are melted, the melt is left for a predetermined period of time or more while keeping the temperature almost constant in a furnace filled with inert gas. Since the pulling of the crystal is then started, crystal defects called dish-shaped corrosion holes, egg-shaped corrosion holes, shallow corrosion holes, etc. can be reduced.

[Brief explanation of drawings]

The first diagram is a correlation diagram showing the relationship between the melt leaving time and the density of crystal defects called dish-shaped corrosion holes, egg-shaped corrosion holes, shallow corrosion holes, etc. in the upper InP single crystal wafer. Figure 2 is the melt leaving time. Relationship between crystal defect density and crystal position (distance from seed crystal) called dish-shaped corrosion holes, egg-shaped corrosion holes, shallow corrosion holes, etc. when InP single crystal is grown by the LEC method with Figure 3 shows the density of crystal defects called dish-shaped corrosion holes, egg-shaped corrosion holes, shallow corrosion holes, etc. when InP single crystals are grown by the LEC method with the melt leaving time within 250 minutes. Figures 4 and 5 are microscopic photographs showing the crystal structure of the wafer surface after etching with the Huber etching solution. -8- Fig. 1 (Electrical Compensation) Fig. 2 Unexamined Japanese Patent Application Publication No. 1999-3 16996 (4) Fig. 3

Claims (2)

[Claims] (1) Put raw materials and sealant into a crucible, heat and melt them with a heater, bring a seed crystal into contact with the surface of the raw material melt in the crucible covered with liquid sealant, and gradually rotate it. To grow compound semiconductor single crystals by pulling, after the raw materials are melted, the furnace is filled with inert gas and the raw material melt is left for a predetermined period of time or longer while keeping the temperature almost constant, and then the crystal is pulled. A method for manufacturing a compound semiconductor single crystal, characterized in that the method starts with: (2) The method for producing a compound semiconductor single crystal according to claim 1, wherein the melt leaving time is determined depending on the weight of the raw material in the crucible.