Fabrication Method for Growing Single Crystal of Multi-Type Compound

Abstract

A fabricating method for growing a single crystal of a multi-type compound comprises steps of: (a) providing a seed crystal at a deposition region; (b) providing a powder material at a high purity source region; and (c) undertaking a vacuum process, a heating process, a growing process, a cooling process to prepare the singe crystal, wherein a heating source is used to move to control a temperature gradient within a gas temperature control region to form a temperature gradient motion so that the temperature gradient presents a variation. By reducing the possibility of other deficiencies being continuously induced in the following crystal growth process owing to the local slime occurring at the rear side of the seed crystal from the void deficiencies at the rear side of the original seed crystal may be excluded, but also the possibility of other multi-type bodies being induced by the above vacancies.

Claims

1. A fabricating method for growing a single crystal of a multi-type compound, comprising steps of: (a) providing a seed crystal at a deposition region; (b) providing a powder material at a high purity source region; and (c) undertaking a vacuum process, a heating process, a growing process, a cooling process to prepare the singe crystal, (d) wherein a heating source is used to move to control a temperature gradient within a gas temperature control region to form a temperature gradient motion so that the temperature gradient presents a variation.

2. The method as claimed in claim 1, wherein the powder material is a silicon carbon powder material or a nitride power material.

3. The method as claimed in claim 1, wherein the heating source is a heating coil.

4. The method as claimed in claim 1, wherein the heating coil has a moving direction of a vertical direction.

5. The method as claimed in claim 1, wherein the heating coil has a motion speed range of 30 mm/min to 5E-4 mm/min.

6. The method as claimed in claim 1, wherein the gas temperature gradient control region has a temperature gradient range of 3-12 C./cm.

7. The method as claimed in claim 1, wherein the deposition region and the high purity source region has a temperature difference ranging from 90-350 C./cm.

8. The method as claimed in claim 1, wherein the seed crystal is a single crystal wafer having a thickness of at least 350 m and a diameter of 2 inches to 6 inches and above, and used to grow the single crystal having a corresponding or larger size.

9. The method as claimed in claim 1, wherein the seed crystal is selected from a group consisting of 3C, 4H, 6H, 2H, a 15R, and a combination thereof, and used for growing the single crystal having a corresponding crystalline state.

Description

BRIEF DESCRIPTIONS OF THE DRAWINGS

[0013] The present invention will be better understood from the following detailed descriptions of the preferred embodiments according to the present invention, taken in conjunction with the accompanying drawings, in which:

[0014] FIG. 1 is a schematic diagram of defects of a crystal growth by using the prior art technology;

[0015] FIG. 2 is a schematic diagram of a high system furnace system for preparing and manufacturing a single crystal according to the present invention;

[0016] FIG. 3 is a flowchart for illustrating a fabricating method for a single crystal of a multi-type compound according to the present invention;

[0017] FIG. 4 is a schematic diagram of a temperature-pressure control when a physical vapor deposition method according to an embodiment of the present invention;

[0018] FIG. 5(a) is a single crystal SiC's slice as a comparative example according to the present invention; and

[0019] FIG. 5(b) is a single crystal SiC's slice as an embodiment according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements.

[0021] It is a main object to provide a fabricating method for a single crystal, such as SiC crystal and nitride crystal, having a high growth speed, where a heating coil (heating source) is controlled in its placement to promote a system temperature gradient and a supersaturation of a high temperature furnace and a SiC material's use speed, to promote a deposition speed of the SiC at a crystal growth surface of a seed crystal, so as to improve the quality of a seed crystal and promote the growth speed of the crystal. By using this technology, a large sized single crystal may be manufactured in an easier manufacturing fashion. In essence, when an atom is bonded at an interface, a bonding energy intension is in an inversely proportional relationship with neighboring atoms with a consideration of an interaction between the atom and the neighboring atoms. The larger the energy released from the crystal growth, the more benefitted the atom is bonded at this site. Hence, when only the interface is smooth, a stage may not be formed with an aid of an activation energy, and 2 dimensional nucleation is required to be continuously formed to form the stage. The stage is relied upon to maintain the growth. Therefore, the preparation of a single crystal surface having a high density stage is critical to the promotion of the single crystal' growth speed.

[0022] Referring to FIG. 2, a schematic diagram of the high system furnace system for preparing and manufacturing the single crystal according to the present invention is shown therein. As shown, the high temperature furnace includes a movable heating source (21), a high temperature cavity (22), a deposition region (23), a high purity source region (24), a gaseous temperature gradient control region (25). The movable heating source (21) may be a heating coil, and particularly an induced heating coil. Inside the deposition region (23), a holder may be arranged to fix the seed crystal. The whole deposition region (23) is located at a position above the high temperature furnace cavity (22), and the position is a cool end having a relatively lower temperature within the high temperature furnace cavity (22) during the crystal growth process. On the other hand, the high purity source region (24) is located at another position below the deposition region (23) to receive some material source (such as a high purity SiC or a nitride powder material), and the position is a hot end having a relatively higher temperature within the high temperature furnace cavity (22) during the crystal growth process. Based on this arrangement the raw material (powder material) may be sublimed to gaseous molecules from its original solid form, to control the temperature, heat field, atmosphere, and pressure within the heating device, so that the molecules such as the SiC's transported to on the seed crystal at the deposition region (23). By controlling the respective temperature of the cool end and the hot end, a temperature difference along the high temperature furnace system and a varied temperature gradient within the gaseous temperature gradient control region (25) and the pressure within the pressure within the system are controlled, so that the gaseous molecules of the SiC or the nitride deposit rapidly on the seed crystal to form a deposited single crystal. In this manner, the crystal growth occurring on the seed crystal's surface is larger in growth speed than a decomposition speed of the locally sublimed SiC occurring at a rear side of the seed crystal.

[0023] Referring to FIG. 3, a fabricating method for growing a single crystal of a multi-type compound according to the present invention is shown therein, in which the multi-type compound may be SiC or nitride. As shown, the method comprises following steps. (a) A seed crystal at a deposition region is provided (S31). (b) A powder material at a high purity source region (S32). (c) Undertaking a vacuum process, a heating process, a growing process, a cooling process to prepare the singe crystal (S33). In the method, a heating source is used to move to control a temperature gradient within a gas temperature control region to form a temperature gradient motion so that the temperature gradient presents a variation.

[0024] Referring to FIG. 4, a schematic diagram of a temperature-pressure control when a physical vapor deposition (PVT) method according to an embodiment of the present invention. As shown, the PVT method is relied upon to prepare and manufacture a 4H-Single crystal SiC in the embodiment. The growth process takes place on the high temperature furnace. The SiC powder material having a high purity of above 99% an average particle degree of 1 to 30 mm is used as a commence material. A crystal growth temperature is designated as about 2,100 to 2,250 C. Ar is selected as a carrier gas in the system. A pressure of about 0.7 to 5 torr is designated for the system crystal growth. A growth time is 30 hr. is designated. The seed crystal is a Single crystal SiC wafer having a thickness of about 350 m. In the vacuum process, the 4H-SiC seed crystal is fixed by a holder and then vacuumed, to remove air and other impurities within the high temperature furnace system. In the heating process, an inert gas Ar (or N.sub.2) and some auxiliary gases hydrogen, methane, ammonia are introduced. The heating coil is heated to about 2,100 to 2,250 C. within the whole system. In the crystal growth process, the crystal growth's pressure is 0.7 to 5 torr. The heating coil is lowered for its position by a speed about 1 mm/min with a lowered distance of 6 cm. The coil is displaced by using a time of 1 hr. Since the heating coil takes six times of motion, the temperature gradient within the gas temperature gradient control region presents a variation of the temperature gradient continuously, and the temperature gradient is enabled to become larger. In the crystal growth process, an upper portion (the deposition region) of the high temperature furnace and a lower portion (high purity source region) of the high temperature furnace, having a temperature up to 3-12 C./cm. In the cooling process, the finished single crystal may be subject to an annealing process. In a comparative example, the above same conditions are adopted except that the shift and position of the heating coil are not adjusted and controlled, the upper portion (deposition region) and the lower region (high purity source region) have a temperature difference of 40 to 80 C. and a temperature gradient of 1.3-2.7 C./cm.

[0025] Referring to FIG. 5(a) and FIG. 5(b), a single crystal SiC's slice as a comparative example according to the present invention and a single crystal SiC slice as an embodiment according to the present invention are shown therein, respectively. As shown, the quality within the single crystal may be ascertained for the embodiment's and comparative example's single crystal. It is found that only one slice from five of the comparative's grown single crystal SiC may be used to be undertaken with following processes (such as the slice framed with red). On the other hand, the SiC crystal manufactured in the embodiment have all six slices are qualified into the following process. Therefore, the quality and the qualified number are significantly promoted, and may effectively reduce a ratio of the seed crystal's deficiencies extending continuously into the crystal among all, showing an evidence that the present invention may effectively promote the quality and a yield of the single crystal SiC.

[0026] The present invention is a fabricating method for a single crystal of a multi-type compound. The effectiveness dwells in that the growth speed is high up to 300 600 m/hr. At the same time, the surface of the single crystal has a growth stage and the finished crystal may have a diameter of up to 2 to 6 inches. In the embodiment, the 350 m single crystal SiC wafer may cultivate a crystal after two to three hours by using the PVT method with a thickness of 0.8 to 1.5 mm and a high density growth stage larger than 100/cm at its surface. The seed crystal is then taken as a thick seed crystal for the following SiC seed crystal's growth. Not only the extended hexagonal vacancies, carbon group, silicon drip deposition caused from the void deficiencies at the rear side of the original seed crystal may be excluded, but also the possibility of other multi-type bodies being induced by the above vacancies. This may promote the single crystal SiC's growth quality and the powder material may be significantly used, well lending to its mass production.

[0027] From all these views, the present invention may be deemed as being more effective, practical, useful for the consumer's demand, and thus may meet with the requirements for a patent.

[0028] The above described is merely examples and preferred embodiments of the present invention, and not exemplified to intend to limit the present invention. Any modifications and changes without departing from the scope of the spirit of the present invention are deemed as within the scope of the present invention. The scope of the present invention is to be interpreted with the scope as defined in the claims.