JP2014189425A5 - - Google Patents

Description

Under these circumstances, as a crucible material used for growing a sapphire single crystal by the Bridgman method or the VGF method, tungsten is a relatively low price among refractory metals and is smaller than the thermal expansion coefficient of the sapphire single crystal. Attention has been focused on (W) and molybdenum (Mo). For example, JP-in 2011- 0 42560 discloses, by focusing on differences from the linear expansion coefficient and the growth axis (c-axis) perpendicular to the direction of the linear expansion coefficient of the sapphire single crystal of the crucible, tungsten, molybdenum, or their A crucible made of the above alloy has been proposed. In this crucible, the inner peripheral surface is enlarged in diameter from the bottom surface toward the opening, and the taper angle of the inner peripheral surface is set to 1.2 ° to 2 °.

The taper angle of the inner peripheral surface of the crucible is preferably 1.0 ° to 3.0 ° , and the surface roughness of the mirror surface portion is 0.2 μm or less in terms of arithmetic average roughness Ra. Is preferred.

On the other hand, refractory metals such as tantalum (Ta, melting point: 3017 ° C.), iridium (Ir, melting point: 2466 ° C.), rhenium (Re, melting point: 3186 ° C.) have a larger thermal expansion coefficient than sapphire. Although it cannot be used as the main material of the crucible body, it is possible to add these refractory metals within the range where the thermal expansion coefficient of the crucible body does not exceed the predetermined value, depending on the application and size of the crucible. is there. Moreover, noble metals such as rhodium (Rh, melting point: 1964 ° C.), platinum (Pt, melting point: 1768 ° C.), palladium (Pd, melting point: 1555 ° C.), which have a lower melting point than sapphire, react with the sapphire raw material melt. Similarly, it is possible to add in a range where the thermal expansion coefficient of the crucible main body does not exceed the predetermined value. The allowable content of these metals varies depending on the type, but is usually 30% by mass or less, preferably 20% by mass or less, based on the total mass of the material of the entire crucible.

Claims (6)

  It is made of tungsten or an alloy of tungsten and molybdenum, and includes a bottom surface, an inner peripheral surface, and an opening, and the inner peripheral surface expands from the bottom surface side toward the opening side, 0.8 ° to 3 °. The surface roughness is 0.5 μm or less in terms of arithmetic average roughness Ra at a portion having a taper angle of 0 ° and in contact with at least the upper end portion of the sapphire raw material melt in the inner peripheral surface. A crucible for growing a sapphire single crystal provided with a mirror surface portion. The crucible for growing a sapphire single crystal according to claim 1 , wherein the tungsten content in the alloy of tungsten and molybdenum is 30% by mass or more. The crucible for growing a sapphire single crystal according to any one of claims 1 to 2 , wherein a taper angle of an inner peripheral surface of the crucible is 1.0 ° to 3.0 °. The crucible for growing a sapphire single crystal according to any one of claims 1 to 3 , wherein the surface roughness of the mirror surface portion is 0.2 µm or less in terms of arithmetic average roughness Ra. The crucible for growing a sapphire single crystal according to any one of claims 1 to 4 , wherein the mirror surface portion is mirror-finished by buffing and / or electrolytic polishing. The sapphire single crystal growing crucible according to any one of claims 1 to 5 , wherein the sapphire single crystal is solidified by melting a sapphire raw material by a vertical temperature gradient solidification method or a vertical temperature gradient solidification method. A method for producing a single crystal.