JP3788077B2 - Semiconductor crystal manufacturing method and manufacturing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor crystal manufacturing method and a manufacturing apparatus, and more particularly, to a low dislocation semiconductor crystal manufacturing method and a manufacturing apparatus used therefor.
[0002]
[Prior art]
As a method of growing a compound semiconductor crystal, a growth method called a vertical Bridgman method is known.
FIG. 4 (a) shows this method. Reference numeral 1 denotes a cylindrical heating device composed of a plurality of heaters 2 arranged in a chamber 16 with a heat insulating material 15 interposed therebetween. In addition, the temperature is set so that the lower part is a low temperature.
(B) shows an example of this temperature gradient, and is set under a small gradient of about 1 to 10 deg / cm so that thermal distortion does not occur in the temperature distribution in the vertical direction.
[0003]
Reference numeral 3 denotes a lowering device positioned at the axial center of the heating device 1 and descends at a predetermined fine speed. Reference numeral 4 denotes a crystal growth vessel mounted on a container receiver 5 at the tip of the lowering device 3. Contains a seed crystal 6. Reference numeral 8 denotes a melt of a semiconductor raw material accommodated above the seed crystal 6, and is melted by heat from the heating device 1.
[0004]
In the above configuration, for example, when a GaAs semiconductor crystal is grown, first, the GaAs raw material is heated to 1245 ° C. to form the melt 8, while the seed crystal 6 side is heated to 1200 ° C. After seeding between the melt 8 and the seed crystal 6, the lowering device 3 is lowered at a slow speed, and the semiconductor crystal 10 is gradually grown from the melt 8.
[0005]
The vertical Bridgman method for growing the crystal 10 as described above can produce a semiconductor crystal having a large diameter as compared with the liquid sealing pulling method (LEC method) and the like, and the low dislocation property of the obtained crystal. Characterized by.
[0006]
In this method, in order to suppress dislocations that cause crystal defects, it is necessary to prevent thermal distortion that occurs after crystal solidification, and a dent is generated on the crystal 10 side at the solid-liquid interface 11. Need to prevent.
[0007]
Conventionally, as a method for preventing thermal distortion, there is known a method for preventing thermal distortion by setting the temperature difference in the vertical direction of the heating apparatus 1 as small as possible, thereby slowing the cooling rate of the crystal solidification part and the growth part. It has been.
The small temperature gradient of 1-10 deg / cm shown in FIG. 1 (b) embodies this method.
[0008]
[Problems to be solved by the invention]
However, according to the conventional method of dealing with temperature gradients, low-speed cooling acts to inhibit heat dissipation from the seed crystal, and conversely, this causes dents at the solid-liquid interface. .
[0009]
The temperature gradient with a smaller temperature difference and the temperature gradient with a larger temperature are in conflict, and in the former case, dents are likely to occur at the solid-liquid interface, so the degree of dislocation generation due to mechanical strain is strong. On the other hand, in the latter case, the solid-liquid interface can be flattened, but the degree of occurrence of dislocation due to thermal strain increases. Therefore, it is subtle and difficult to deal with these two types of dislocations by simply operating the temperature gradient.
[0010]
Therefore, an object of the present invention is to use a semiconductor crystal manufacturing method capable of simultaneously suppressing the occurrence of dislocation due to mechanical strain and dislocation due to thermal strain due to the occurrence of a dent at the solid-liquid interface. It is to provide a manufacturing apparatus.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a crystal growth vessel containing a semiconductor raw material and a seed crystal with the former positioned at the top and the latter positioned at the bottom. The raw material is placed in a heating device, and the raw material is melted by the heating device to seed the raw material into the seed crystal, and then the crystal growth vessel is lowered to drop the raw material on the seed crystal. In a semiconductor crystal manufacturing method for growing a semiconductor crystal from a melt, a cooling zone for cooling the seed crystal is formed below a solid-liquid interface between the melt and the crystal, and the solid-liquid interface is the cooling zone. A method of manufacturing a semiconductor crystal is provided, wherein the crystal growth vessel is lowered in accordance with the growth of the crystal so as to be positioned above.
[0012]
Further, in order to achieve the above object, the present invention provides a heating device having a temperature gradient up and down so that the upper part becomes a high temperature, and the semiconductor material and seed crystal disposed in the heating device. A crystal growth vessel that houses the latter at the bottom and the position of the solid-liquid interface formed by the melt of the raw material and the crystal of the semiconductor that grows from the predetermined position in the vertical direction of the heating cylinder The heating apparatus has a cooling means for cooling the seed crystal located below the position of the solid-liquid interface. An apparatus for manufacturing a semiconductor crystal is provided.
[0013]
The cooling zone and the cooling means are provided to promote heat release from the seed crystal. Therefore, it is desirable for the heat released from the seed crystal to escape to the outside without stagnation. From this point of view, a slit-like (window-like) shape is preferable.
[0014]
The slits are formed along the descending direction of the descending means, and the number thereof may be one or plural. When the heating device is configured in a cylindrical shape, the slit is formed in the circle of the heating device in order to equalize the heat release from the seed crystal in the circumferential direction and at the same time avoid a biased thermal effect on the crystal growth region. It is preferable to arrange a plurality at equal intervals in the circumferential direction.
[0015]
Instead of forming a slit, it is possible to use a non-heat generating part as a cooling means, or a pipe for a cooling fluid such as water, oil, gas or the like is attached at a position where the cooling means is to be formed, thereby cooling means It is also possible.
[0016]
It is conceivable to configure the cooling means by combining a slit or a non-heating part and a cooling fluid pipe. When the cooling fluid piping is used, the temperature can be adjusted by adjusting the flow rate of the fluid.
[0017]
When a heat insulating layer is formed around the heating device, a portion such as a slit should be excluded from the object of heat insulation so that heat release from the seed crystal is not hindered.
The cooling fluid piping is different from a slit or the like in that it does not require such consideration.
[0018]
Examples of the semiconductor targeted by the present invention for crystal growth include compound semiconductors such as GaAs, GaP, and InP. In the vertical Bridgman method, when a GaAs crystal is grown, the growth is controlled while controlling the As pressure in the growth vessel, and volatilization of As is prevented by covering the melt surface with boron oxide. However, the production method and the production apparatus according to the present invention can be applied to any method.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of a semiconductor crystal manufacturing method and manufacturing apparatus according to the present invention will be described.
In FIG. 1 (a), 1 is a cylindrical heating device in which a predetermined temperature gradient is set so that the upper side is higher than the lower side, 2 is a plurality of heaters constituting the heating device 1, and 3 is heating. 2 shows a lowering device that is located at the axis of the device 1 and descends at a predetermined fine speed.
[0020]
4 is a quartz crystal growth container mounted on the container receiver 5 at the tip of the lowering device 3, 6 is a seed crystal container formed at the tip of the tapered portion of the crystal growth container 4, and 7 is placed in the container 6. The seed crystal 8 is placed in the container 9 and accommodated in the crystal growth container 4, and shows a melt of the semiconductor raw material melted by the heat from the heating cylinder 1.
[0021]
Reference numeral 10 denotes a semiconductor crystal grown on the seed crystal 6 after the seed crystal 6 and the melt 8 are seeded. A solid-liquid interface 11 is formed between the crystal 8 and the melt 8.
The descending device 3 descends at a slow speed so that the solid-liquid interface 11 is always at a constant position in the vertical direction as the crystal 10 grows.
[0022]
The certain position here does not necessarily have a strict meaning, and there may be some position fluctuation. In this embodiment, the container 9 is used to form a multilayer structure with the crystal growth container 4, but the container 9 may be omitted.
[0023]
Reference numeral 12 denotes a quartz cap that seals the inside of the crystal growth vessel 4, and 13 denotes a slit provided along the axial direction of the heating device 1 at a position below the solid-liquid interface 11. Are arranged at equal intervals in the circumferential direction as shown in (c). B indicates a cooling zone for cooling the seed crystal 6 formed by the slit 13.
[0024]
In the case of this embodiment, four slits are provided. However, when the temperature difference between the portion a at the position of the slit 13 in (c) and the portion b at which the slit is not located is disliked, the slit width is set. It is possible to make the temperature distribution in the circumferential direction uniform by narrowing, increasing the number of slits, or combining them.
[0025]
FIG. 2 shows measured values of the temperature gradient in the vertical direction inside the heating apparatus 1 having the above-described configuration. (A) shows the overall temperature gradient, and (B) shows the temperature gradient in the lower part.
Further, the broken line in (b) indicates the temperature gradient of the present embodiment in which the cooling zone B is formed, while the solid line indicates a conventional type temperature gradient in which the cooling zone B is not formed.
[0026]
As shown in (b), compared with the case where the present embodiment shows a temperature gradient of 2 to 7 deg / cm, the conventional apparatus is as small as 1 to 5 deg / cm, and there is a clear difference between the two. Differences were noted.
[0027]
In the present embodiment having the cooling zone B, the temperature difference between the upper and lower portions in the lower part of the heating device 1 is steeper, and therefore heat dissipation from the seed crystal 6 becomes more active. The dislocation caused by the mechanical distortion due to is suppressed.
[0028]
Since the entire temperature gradient is set to a level of 1 to 10 deg / cm with a small temperature difference, dislocation based on thermal strain is also suppressed. As a result, dislocation due to mechanical strain and dislocation due to thermal strain are suppressed. It is possible to grow a high-quality semiconductor crystal in which both are suppressed.
[0029]
FIG. 3 shows another embodiment of the present invention, in which the surface of the melt 8 is covered with boron oxide 14, and a chamber is formed around the heating device 1 via a heat insulating layer 15. 16 is formed airtight, and an inert gas is sealed in the space 17. There is no heat insulating layer 15 in the slit 13.
[0030]
[Example 1]
In FIG. 1, a seed crystal 6 is placed in the accommodating portion 7 of the crystal growth container 4, and then a container 9 containing 4500 g of GaAs raw material is placed therein, and then the inside of the crystal growth container 4 is evacuated, The container 4 was evacuated by attaching the cap 12.
[0031]
Next, the crystal growth container 4 is mounted on the container receiver 5 of the lowering device 3, the lowering device 3 is moved up and down, the position is set so that the seed crystal 6 is surrounded by the slit 13, and the heater 2 is energized. Then, the seed crystal 6 portion was heated to 1200 ° C., the GaAs raw material portion was heated to 1245 ° C., and the GaAs raw material was melted to form the melt 8.
[0032]
Next, the temperature is adjusted so that the temperature gradient in the vicinity of the solid-liquid interface 11 formed by the produced crystal 10 and the melt 8 is 4 ° C./cm, and the seed crystal 6 and the melt 8 are seeded. After that, the lowering device 3 was lowered at a slow speed of 3 mm / hr to advance the growth of the crystal 10.
[0033]
After the entire crystal was solidified, the temperature of the heating device 1 was lowered at a rate of 30 ° C. per hour and cooled to room temperature.
In the GaAs single crystal obtained as described above, the solid-liquid interface 11 portion had a preferable convex shape, and had a diameter of about 80 mm and a length of the straight body portion of 150 mm.
When the dislocation density was measured, good results of 500 pieces / cm ² were obtained over the entire length.
[0034]
[Example 2]
In FIG. 3, GaAs raw material was used as the semiconductor raw material, and the temperature condition was set to be the same as in Example 1, and the growth of the single crystal was advanced. A convex single crystal of GaAs was obtained, and from this single crystal, the same dislocation density as in Example 1 was confirmed.
[0035]
【The invention's effect】
As described above, according to the method and apparatus for manufacturing a semiconductor crystal according to the present invention, a cooling zone for cooling the seed crystal is formed in a portion located below the solid-liquid interface, thereby removing the seed crystal from the seed crystal. Since the heat release is activated, it is possible to effectively suppress the generation of dents at the solid-liquid interface caused by insufficient heat release from the seed crystal and the occurrence of dislocation due to mechanical strain caused by this. it can.
[0036]
Therefore, if a temperature gradient with a small temperature difference is set in the heating device to prevent dislocation due to thermal strain, dislocation due to mechanical strain and thermal strain can be suppressed at the same time. Can grow.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory view showing an embodiment of a semiconductor crystal manufacturing method and a manufacturing apparatus according to the present invention. The AA sectional view of (i) is shown.
2 shows the temperature gradient of the manufacturing apparatus of FIG. 1, (A) is the temperature gradient of the entire apparatus, (B) is the temperature gradient of the cooling zone B of FIG. 1 (A) and the lower part of the conventional type heating apparatus. The temperature gradient is shown.
FIG. 3 is an explanatory view showing another embodiment of a semiconductor crystal manufacturing method and manufacturing apparatus according to the present invention.
4A and 4B are explanatory views showing a conventional method for manufacturing a semiconductor crystal, where FIG. 4A is a cross-sectional view of the manufacturing apparatus, and FIG.
[Explanation of symbols]
1 Heating device 2 Heater 3 Lowering device 4 Crystal growth vessel 6 Seed crystal 8 Melt (semiconductor raw material)
10 Crystal 11 Solid-liquid interface 13 Slit 14 Boron oxide B Cooling zone

Claims (1)

A crystal growth device that has a temperature gradient up and down so that the upper part becomes high temperature, and is placed in the heating device, and contains semiconductor raw materials and seed crystals with the former positioned at the top and the latter positioned at the bottom A lowering means for lowering the crystal growth container so that the position of the solid-liquid interface formed by the container and the melt of the semiconductor raw material and the semiconductor crystal grown therefrom is a predetermined position in the vertical direction of the heating device; is configured, the heating device, the overall temperature gradient as 1~10deg / cm, located lower than the position of the solid-liquid interface have a cooling means for cooling the seed crystal, the cooling means, A semiconductor crystal manufacturing apparatus comprising a slit provided in the heating device along a descending direction of the descending means .

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