JPS62241897A - Method for single crystal growth - Google Patents

Abstract

PURPOSE:When a single crystal of III-V compound semiconductor is allowed to grow by the liquid-sealed pulling-up method, the growing single crystal ingot is irradiated with X-ray on its surface and the Brag's reflection is monitored to effect early detection of crystal defects to increase the yield of single crystals. CONSTITUTION:When a single crystal of III-V compound such as GaAs is pulled up from the polycrystalline melt 16, the melt is sealed with a sealant such as diboron trioxide 17, the seed crystal 18 of GaAs is dipped and gradually pulled up to allow the single crystal of GaAs to grow on the end. At this time, X-ray beam is projected to the surface of the single crystal 19 in the sealant 17 to monitor the Brag's reflection with the detector 26. When the crystal defects such as poli, twin or the like are detected, the defect parts are melted again in the GaAs melt and pulled up again. Thus, single crystals of III-V compound semiconductor such as GaAs of good quality is always obtained with extremely reduced defects.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for growing an m-v group compound semiconductor single crystal by a liquid-sealed pulling method.

(Prior art and its problems) Conventionally, in order to grow an m-v group compound semiconductor single crystal by the pulling method, a raw material element is placed in a crucible made of PBN or quartz, heated and melted, and the A method is used in which a small piece of a single crystal called a seed crystal is immersed in the liquid and a single crystal with the same crystal orientation as the seed crystal is pulled out of the melt.In this case, group V elements are highly volatile at high temperatures. Therefore, in order to obtain a single crystal with an equimolar ratio with the group Ⅰ element, it is necessary to suppress the volatilization of the group Ⅰ element.
Evaporation of group V elements is prevented by covering the melt surface with a highly viscous liquid sealant such as O, and pressurizing the inside of the growth container. This is the liquid seal pulling method.

In this method, the single-crystal ingot is usually pulled up while rotating, and the pulling rate is usually about several lll11 to several 1 OIIIllZ hours, the rotational speed is about 10 rpm, and in the case of GaAs, it is 3 to 50 kg/cll! Apply some pressure.

By the way, when a single crystal ingot is pulled up using the liquid-sealed pulling method, defective portions such as polygons and twins may occur in the single crystal ingot. Detection of this defective part is usually done visually, but while the defective part is in the liquid sealant, it is virtually impossible to detect due to fluctuations in the liquid level and brightness, but it becomes possible to detect the defective part. This is done after the defective part is well above the level of the liquid sealant, or after the ingot is taken out.

However, when detected at that point, the defective portion often occupies a large portion of the single crystal ingot. Such an ingot will either become unusable, or it will have to be melted again from the beginning and pulled again as a single crystal, but even if the latter method is used, the pulling speed is slow, and it will take time and energy. The loss of material is extremely large, and the scattering of group V elements makes it difficult to obtain good products.

[Means for solving problems and their effects]

In view of the problems of the prior art as described above, the present invention provides a method for detecting defective parts such as poly and twin as early as possible and improving the single crystallization rate.

To achieve this objective, the present invention provides a method for growing an m-v group compound semiconductor single crystal by a liquid confinement pulling method, in which the surface of a single crystal ingot being pulled is irradiated with X-rays and its Bragg reflection is detected. The ingot is monitored for the occurrence of defective parts by doing so, and when a defective part is detected, the ingot is remelted to the point where there is no defective part, and then pulling of the single crystal is started again. be.

Figure 6 shows the principle of Brung's reflection.Like a single crystal,
When X-rays of wavelength λ are incident on a large area where lattice planes f are regularly arranged at intervals d, when the incident angle θ of the X-rays satisfies the following equation,
The rays will be diffracted and reflected together in a reinforced manner. This is the Bragg reflex.

2dsinθ−1−fiλ (n −1, 2)3==
-・) According to this condition, if the lattice spacing d of the single crystal and the wavelength λ of the X-ray are known, and the incident angle θ of the X-ray is set to satisfy the above equation, then in the case of the single crystal, Strong X-rays due to diffraction can always be detected, and when the crystal is not a single crystal (poly,
When a defective part such as twin occurs), it cannot be detected. Therefore, by using this, it is possible to determine whether it is a single crystal or not.

When a single crystal ingot has rotational symmetry, when the surface is irradiated with X-rays from a predetermined angle, under normal conditions, Bragg reflections can be detected every time the ingot rotates by a predetermined angle.

If this cannot be detected, it can be determined that a defective part has occurred.

Furthermore, if Bragg reflection can be detected at an angle where Bragg reflection should not occur, this can also be determined to be defective.

When a defective portion is detected in this manner, by remelting the ingot containing the defective portion to eliminate the defective portion and starting pulling again, a single crystal ingot free of defective portions can be grown.

By irradiating X-rays onto the single crystal ingot in the liquid encapsulant and detecting defects at that position, the amount of remelting is reduced when a defective part occurs, and the X-ray irradiation position is is preferably set on the surface of the single crystal ingot several to several tens of sl above the solid-liquid interface in the crucible.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. In Figures 1 and 2, 11 is a growth container;
2 is a susceptor supported therein so as to be rotatable and vertically movable; 13 is a drive device for the susceptor 12; 14 is the susceptor 1;
A crucible 2 is installed in the crucible, and 15 is a heater installed around the susceptor 12.

In the crucible 13, Ga and As as raw materials and a sealant (
BzOi) and are heated by the heater 15 to melt them. 16 is the raw material melt obtained thereby, and 17 is a liquid sealant. In addition, the container 11 is filled with argon gas at 50°C.
Nig/Cl1l! The 0-seed crystal 18 under the pressure of
6 and pulled up a single crystal ingot 9 with a diameter of 3 mm. 20 is a pulling drive device.

Further, 21 is a monochromatic X-ray source, 22 is a collimator, 23 is an entrance window, 24 is an exit window, 25 is a collimator, 26 is an X-ray detector (synnaration counter), and 27 is a discrimination circuit. The X-ray source 21 uses a white X-ray source with a tungsten target with a maximum output of 320 -.In order to avoid the influence of various noises, the white X-rays are made monochromatic to produce monochromatic X-rays of 240 KeV.The collimator 22) is made of beryllium. entrance window 2
3, the surface of the ingot 19 in the liquid sealant 17 was irradiated. Monochromating the X-rays was achieved by placing a single crystal in front of the collimator 22 and subjecting the X-rays to Blang reflection there.

Single crystal ingot 19 was pulled in the (100) direction by seed crystal 18. In order to avoid the influence of the solid-liquid interface, X-rays were irradiated onto the surface of the single crystal ingots 9 in the liquid sealant 17, approximately lo#m above the solid-liquid interface. Ingot 19 is 5
Rotated at rpm. Therefore, when the ingot 19 comes to a position that satisfies the conditions for Bragg reflection, the X-rays are diffracted there, pass through the exit window 24 and the collimator 25, and are detected by the detector 26. Since the GaAs single crystal ingot 19 pulled in the (100) direction has a four-fold symmetry, four peak values can be detected during one rotation. For example, in Figure 2, if the Bragg reflection is currently observed at point A, ingot 19 is 90
Even when the object rotates and X-rays are irradiated at point B, Bragg reflections can be observed.

In this embodiment, the discrimination circuit 27 integrates the counter value synchronized with the rotation of the ingot 19 to increase the S/N ratio. Furthermore, in order to avoid fluctuations in the X-ray source 21, the measured values were calibrated using a reference light. Furthermore, as the ingot 19 grows, the solid-liquid interface moves downward in the crucible 14, but the susceptor 12) pushes the crucible 14 upward in accordance with the speed of the movement, thereby keeping the solid-liquid interface at a constant height. It is now possible to irradiate X-rays to certain areas. This method is extremely effective in minimizing the amount of ingot to be remelted when a defective part such as poly or twin is discovered.

FIG. 3 schematically shows the single crystal ingot 19 in a cylindrical shape. In the figure, it is assumed that the single crystal ingots 9 are pulled up as indicated by the arrows. A, B, C, D
is a 4-fold symmetry plane, and when X-rays are incident there, Bragg reflection occurs.

If a twin 32 is generated at a point 31 of the ingot 19 during pulling, it grows as shown by diagonal lines as the ingot 19 is pulled up. When all the crystals are single crystals, the X-ray intensity detected by the detector 26 has peaks at 90'' intervals as shown in Figure 4, but as the twin 32 grows, the X-rays hit points 33 and 34. When scanning begins, the X-ray intensity detected by the detector 26 becomes as shown in FIG. 5, and peaks no longer appear where they should appear.

When a defective portion is detected in this way, the determination circuit 27 estimates the generation point 31 from the diameter of the ingot 19, etc., and the drive device 13.20 remelts the ingot 9 to the twin generation point 31. After that, pulling of the single crystal is started again.

In the GaAs single crystal made as described above, the defective part is detected in the liquid sealant and does not come out above it, so there is no scattering of A3 and the single crystal made in normal conditions. No differences were observed between the crystal and electrical properties and amount of dislocations.

In the above example, the occurrence of a defective part (change in lattice spacing) was detected from the observation of the X-ray counter value synchronized with the rotation of the single crystal ingot. For example, when a weak peak is detected between sharp peaks detected at 90° intervals due to rotation of the ingot. can be considered as a failure.

Furthermore, if the X-rays are irradiated with a width in the direction of pulling the single crystal, the scanning range of the X-rays will be expanded, so that the occurrence of defective parts can be detected earlier.

〔Effect of the invention〕

As described above, according to the present invention, by utilizing Bragg reflection of X-rays, defective portions occurring in a single crystal ingot being pulled can be detected at an early stage.

Furthermore, when a defective part is detected, the part is remelted and the single crystal is pulled again, so not only is a high quality single crystal ingot always obtained, but also Re-melting of the ingot is reduced,
This has the advantage of significantly reducing losses in terms of time and energy.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view showing a single crystal growth method according to an embodiment of the present invention, Fig. 2 is a cross-sectional view of the main part thereof, and Fig. 3 is a defective part generated in the single crystal ingot being pulled. FIGS. 4 and 5 are graphs showing the output of the X-ray detector when there is no defective part and FIG. 6 is an explanatory diagram showing the principle of Bragg reflection. 11-growth container, 12-susceptor, 14-crucible, 15
~Heater, 16~Raw material melt, 17~Liquid sealant, 18~
Seed crystal, 19-single crystal ingot, 21-X-ray source, 22
- collimator, 23 - entrance window, 24 - exit window, 25 - collimator, 26 - X & 1 detector.

Claims (4)

[Claims] (1) In the method of growing III-V compound semiconductor single crystals by liquid confinement pulling method, defective parts are detected by irradiating the surface of the single crystal ingot being pulled with X-rays and detecting the Bragg reflection. A method for growing a single crystal, which is characterized in that when a defective part is detected, the ingot is remelted to a point where the defective part disappears, and then pulling of the single crystal is started again. (2) The method according to claim 1, wherein the defective portion is detected by utilizing the rotational symmetry of the single crystal ingot, and the Bragg reflection is detected at a rotation angle at which the Bragg reflection should be detected. It depends on whether or not. (3) A method according to claim 1 or 2, characterized in that the surface of a single crystal ingot in a liquid sealant is irradiated with X-rays. (4) The method according to claim 1, 2, or 3, in which X-rays are transmitted from the solid-liquid interface regardless of a decrease in the solid-liquid interface in the crucible as the single-crystal ingot is pulled. The X-ray irradiation system is characterized by controlling the height of the crucible or the X-ray irradiation system so that the irradiation is performed at a constant height.