Columnar Crystal Silicon

Columnar crystal silicon is a novel silicon material manufactured through the unidirectional solidification process of high purity silicon. Mitsubishi Materials Corp. successfully developed columnar crystal silicon through the integration of our own technologies: poly-crystalline silicon production, single crystal silicon production, and quartz crucible production. It has received high praise in various industrial fields.

Characteristics

  • ・Large size; Rectangular:1200×1200 × 230H, Cylinder:Φ1200×230H available.
  • ・High purity
  • ・High mechanical strength
  • ・Substantially the same thermal properties as single crystal silicon.
  • ・Substantially the same machinability as single crystal silicon.
  • ・Stable supply: less influenced by the single crystal silicon market.

Columnar Crystal Silicon Production Method and Characteristics

(1)Unidirectional Solidification Process

Columnar crystal silicon is manufactured through the unidirectional solidification process. This process enables silicon crystal growth from the bottom to the upper side in the crucible, releasing the inner stress originating from the volume expansion due to silicon solidification. This process manages to both squeeze out impurities and release the inner strain of silicon simultaneously. Thus, we can supply excellent columnar crystal silicon with ultra-low impurity and inner strain.


MMEC has the largest semiconductor-grade silicon casting furnace in the world. The furnace can cast silicon ingots of 1.2m×1.2m×0.5mH in size.

(2) Impurity

Columnar crystal silicon is manufactured through the unidirectional solidification process, squeezing out inner impurities during crystal growth. This allows us to supply high-purity silicon.

Analysis of Impurity in Columnar Crystal Silicon (Example)

Grade Purity Impurity(ppb)
Na K Al Fe Cr Ni Cu
H 7Nup <1 <1 3 4 1 <1 1
A 6N 2 <1 20 10 2 <1 4
B 5N 9 8 25 12 1 1 7

*1: Unit : ppb.
*2: Described purity is not guaranteed one.

(3) Advantages

  • ・Large size products; Rectangular:1200×1200×230H, Cylinder:Φ1200×230H, available.
  •  We can supply large size products which cannot be obtained with single crystal silicon.
  • ・Products of various shapes
  •  (We can supply products of various shapes through machining.)
  • ・High purity (We have a line up several grades according to their purity.)
  • ・High mechanical strength
  • ・Substantially the same thermal properties as single crystal silicon.
  •  (Columnar crystal silicon’s thermal properties are the most suitable for silicon wafer
  •   susceptors.)
  • ・Substantially the same machinability as single crystal silicon.
  •  (We can use various machine and machining techniques which are used for
  •  single crystal silicon processing)
  • ・A Stable supply which is less influenced by the single crystal silicon market.