JP2758038B2 - Single crystal manufacturing equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a single crystal growing apparatus, and particularly to a crystal growing method for solidifying a melt as it is in a crucible to obtain a single crystal, for example,
The present invention relates to a single crystal growth apparatus capable of accurately forming a temperature environment for obtaining a high quality single crystal in a vertical Bridgman method.

[Conventional technology]

As a method for producing a semiconductor single crystal used as a substrate for various semiconductor elements such as a field effect transistor, a Schottky barrier diode, and an integrated circuit (IC), a crystal growth method from a melt is a mainstay. In the crystal growth method from the melt, it is required to precisely control the shape of the crystal growth surface (solid-liquid interface) from the start to the end of the crystal growth.

In the pulling method, which is one of the methods for growing crystals from the melt, the crystal growth surface is controlled by controlling the rotation speed of the crucible, the rotation speed of the crystal, and the pulling speed.

As another crystal growth method, a vertical boat growth method in which a melt is solidified in a crucible as it is to obtain a single crystal is effective. Vertical bridgeman method (VB method) for vertical boat growth method
And a temperature gradient solidification method (VGF method). The former VB method is a method of growing a single crystal by mechanically changing the relative position of the main heater and the crucible, while the latter VGF method is a method of heating the heater without changing the positional relationship between the heater and the crucible. This is a method of growing a single crystal by changing the temperature distribution. This vertical Bridgman method or VGF method is suitable for producing large-diameter circular wafers. However, this boat method
Compared to the pulling method of pulling the growing crystal out of the melt while rotating it and solidifying it, it is characterized by a static state change, so it is impossible to control the crystal growth surface by controlling the rotation speed or the like. In addition, the crystal growth surface is controlled by devising a hot zone structure.

Fig. 4 shows an example (WAGault et.al. JCG 74
(1986) 491-506). In FIG. 4, a melt 10 is prepared in a crucible 3a, and an inorganic compound semiconductor (hereinafter, referred to as a “III-V compound”) composed of a group IIIb and group Vb element of the periodic table upward from the seed crystal 9 accommodated in the bottom of the crucible. In a crystal growth method (for example, a vertical Bridgman method) for solidifying a single crystal (referred to as a “semiconductor”) (eg, a vertical Bridgman method), a groove 12 is formed in a susceptor 4a holding a crucible 3a, and the thermal environment and heat flow near the susceptor 4a are controlled. This is an example of trying. The arrows in FIGS. 5 (a) and 5 (b) indicate the heat flow at the beginning and the end of the crystal growth, respectively. By using the susceptor 4a provided with the groove 12, the dissipation of heat from the crystal can be controlled in the early stage of crystal growth. That is,
By providing the susceptor with a groove serving as a heat insulating portion, the heat flow in the horizontal direction among the heat flows passing through the susceptor can be suppressed, and the heat flow in the horizontal direction of the crystal can be controlled. However, in the method of controlling the heat flow with such a susceptor provided with a groove, the effect is naturally limited only in the vicinity of the susceptor, and becomes extremely small in a place away from the susceptor. As shown in FIG. 5 (b), in the latter stage of the crystal growth away from the susceptor, the effect of the grooved susceptor has almost no effect compared to FIG. 5 (a), and a large heat flow exists in the lateral direction. However, there is a large difference in the heat flow through the crystal growth surface between the initial stage and the late stage of the crystal growth.

By the way, in crystal growth from the melt, the shape of the crystal growth surface greatly depends on the heat flow near the crystal growth surface,
In order to control the shape of the crystal growth surface, it is necessary to control the heat flow throughout the entire crystal growth.

In the crystal growth by the above method, it is difficult to control the heat flow in the latter stage of the crystal growth, and a method of controlling the heat flow over the entire crystal growth is strongly desired for improving the quality of the crystal.

[Problems to be solved by the invention]

In crystal growth from the melt, precise control of the crystal growth surface over the entire crystal growth is essential for obtaining uniform and high-quality crystals, and for this purpose, heat flow through the crystal, especially crystal growth It is necessary to precisely control the heat flow passing near the surface (solid-liquid interface).

However, it has been difficult to solve the above problem by the conventional method.

An object of the present invention is to provide a single crystal manufacturing apparatus for manufacturing a uniform and high quality single crystal.

[Means for solving the problem]

The object of the present invention is to provide a vertically arranged crucible according to the present invention in which a seed crystal is accommodated at the bottom of the crucible, a raw material is filled above the raw material, the raw material is heated and melted, and the melt is solidified to obtain a single crystal. In a single crystal manufacturing apparatus for carrying out the Bridgman method or the VGF method, an auxiliary heat source capable of controlling the amount of heat generated independently of the main heating element inside the main heating element for heating and melting the raw material. The crystal is arranged from the start to the end of crystal growth by arranging the body slightly below the interface between the raw material melt and the crystal and controlling the relative positional relationship between the heat generating portion of the auxiliary heating element and the crystal plane. This is a single crystal manufacturing apparatus for controlling the shape of a growth surface (solid-liquid interface).

[Action]

According to the present invention, by providing an auxiliary heating element in addition to the main heating element around the crucible, the heat flow in the crystal can be controlled, so that a single crystal with less distortion can be obtained.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic vertical cross-sectional view of a vertical Bridgman method single crystal manufacturing apparatus showing one embodiment of the present invention, and FIG. 2 is a schematic view for explaining a heat flow during crystal growth according to the present invention. is there.

As shown in FIG. 1, the single crystal manufacturing apparatus of the present invention is almost similar to a known vertical Bridgman method, but an auxiliary heating element closer to the crucible is provided inside the heating element for melting the raw material in the crucible. The point of provision is different.

The single crystal apparatus of the present invention mounts and supports a quartz crucible 3 having an outer diameter of 800 mm and a height of 150 mm in an isotropic graphite susceptor 4 in an airtight container 1 having a heat insulating material 2 such as graphite felt. The crucible 3 is moved up and down together with the susceptor 4 by the shaft 7. An auxiliary heating element 6 was provided on the side of the crucible in addition to the conventional main heating element 5.

The heating element is made of isotropic graphite, and the height of the main heating element 5 is
The auxiliary heating element 6 having a height of 20 cm and a height of 4 cm was used.

Crystal growth was performed using a quartz crucible having an outer diameter of 80 mm and a height of 150 mm in the hot zone. The raw material is high-purity Ga
1.5 kg of As polycrystal and 300 g of B ₂ O ₃ were used.

Growth rate 3mm / h in argon atmosphere at 7 atm after raw material melting
With this, a crystal having a diameter of 3 inches could be grown.

FIG. 1 is a view of a crystal being grown, showing a seed crystal (GaAs) 8, a crystal 9, and a raw material melt 10 from below in the crucible, and a sealing material 11 is disposed thereon.

The position of the auxiliary heating element 6 was controlled throughout the crystal growth so as to be slightly below the interface (solid-liquid interface) A between the raw material melt 10 and the crystal 9 as shown in an enlarged manner in FIG.

FIG. 3 is a diagram showing a change in the calorific value of the heating element during the crystal growth according to the present invention. As the crystal growth progresses, the heat radiation from the solidified crystal becomes large. The amount of heat generated by the auxiliary heating element was increased, the amount of heat in the vicinity of the crystal growth surface was controlled, and crystal growth could be performed stably.

〔The invention's effect〕

As an evaluation of crystallinity, the dislocation density in the (100) plane was measured.

As described above, according to the present invention, in the obtained GaAs crystal, the region where the etch pit density (EPD) in the (100) plane exceeds 2 × 10 ⁴ cm ⁻² over the entire crystal is reduced. Moreover, the average value of the in-plane EPD is about 1 × 10 ⁴ cm ^-2, which is 1/5 or less of the GaAs single crystal by the conventional pulling method, and has excellent characteristics and a high yield of semiconductor devices. Can be greatly contributed to.

[Brief description of the drawings]

FIG. 1 is a schematic vertical cross-sectional view of a vertical Bridgman method single crystal manufacturing apparatus showing one embodiment of the present invention, and FIG. 2 is a schematic view for explaining a heat flow during crystal growth according to the present invention. FIG. 3 is a diagram showing a change in the calorific value of the heating element during the crystal growth according to the present invention. FIG. 4 is a schematic vertical sectional view for explaining a conventional example. (B) is a schematic diagram showing the heat flow in the initial stage and the late stage of the conventional crystal growth, respectively. DESCRIPTION OF SYMBOLS 1 ... Airtight container, 2 ... Heat insulation material, 3 ... Crucible, 4 ... Susceptor, 5 ... Heating element, 6 ... Auxiliary heating element, 7 ... Supporting shaft, 8 ... Seed crystal, 9 ... Crystal, 10 ... Raw material melt, 11 ... sealing material, 12 ... groove.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinichiro Kawabata 1000, Higashikianacho, Ushiku City, Ibaraki Prefecture Inside the Tsukuba Plant, Mitsubishi Monsanto Kasei Co., Ltd. (56) References JP-A-63-270379 (JP, A) JP-A-59-30795 (JP, A) Jpn.

Claims (1)

(57) [Claims] 1. A vertical boat growth method for accommodating a seed crystal at the bottom of a vertically arranged crucible, filling a raw material thereabove, heating and melting the raw material, and solidifying the melt to obtain a single crystal. In the single crystal production apparatus for performing the above, an auxiliary heating element capable of controlling the amount of heat generated independently of the main heating element is provided inside the main heating element for heating and melting the raw material. And a crystal growth surface (solid-liquid interface) from the start to the end of crystal growth by controlling the relative positional relationship between the heating part of the auxiliary heating element and the crystal surface. A) controlling the shape of the single crystal.