Glossary

BLOCK: A section of a crystalline ingot from which the wafers will be cut. The footprint of the block becomes the size of the wafer.

CRUCIBLE: A quartz vessel used for melting and crystallization of polysilicon when producing multi- and monocrystalline silicon ingots.

CRYSTAL: Solid material with a regular, periodic arrangement of atoms or molecules throughout the material.

CRYSTALLIZATION OF MONOCRYSTALLINE INGOTS: Usually made by the Czochralski process explained below, but may also sometimes refer to the Float Zone process. In order to produce monocrystalline ingots by the Czochralski process, high-purity silicon is first loaded into a round quartz crucible and melted. Thereafter, a seed crystal shaped as a thin rod is dipped into the molten silicon. The seed crystal’s rod is pulled upwards and rotated at the same time. By precisely controlling the temperature gradients, rate of pulling and speed of rotation, it is possible to extract a large, single-crystal, cylindrical ingot from the melt. This process is normally performed in an inert atmosphere.

CRYSTALLIZATION OF MULTICRYSTALLINE INGOTS: In order to produce multicrystalline ingots, high-purity silicon is first loaded into a square quartz crucible and melted. Thereafter, the crystallization starts from the bottom of the crucible and proceeds toward the top as it is gradually cooled (directional solidification) under strict temperature and atmosphere control.

CRYSTALLIZATION OF FLOAT-ZONE INGOTS: A high-purity alternative to the Czochralski process. A radio frequency (RF) field is used to produce a local melted zone on the polycrystalline rod, without the liquid being in contact with anything except silicon. The rod is moved relative to the RF field so that the molten (float) zone is moved across the rod. A seed crystal is used at one end in order to start the growth. This molten zone carries the impurities away with it, reducing impurity concentration.

ELECTRONIC GRADE SILICON: Silicon with a purity of between 99.9999999 percent to 99.999999999 percent (9N to 11N purity).

FLOAT ZONE SILICON: High quality polysilicon prepared to provide the highest quality float zone ingots.

FLUIDIZED BED REACTOR (FBR): A technology for deposition of polysilicon from gas phase using a reactor where solid particles (silicon) are “floating” and growing in an upward gas flow (typically silane or trichloro-silane) inside a chamber.

INGOT: The silicon piece created when polysilicon is melted and crystallized in a furnace. Typical size for multicrystalline ingots are 680 x 680 mm with a weight of 250–300 kg. Monocrystalline ingots are cylindrical with typical diameters between 150 mm and 200 mm and a weight of 40–60 kg.

MONOCRYSTALLINE SILICON: Processed silicon where all the material consists of only one crystal.

MULTICRYSTALLINE SILICON: Processed silicon where the material consists of several small (typically 1–20 mm diameter) crystal grains.

POLYSILICON: Highly purified silicon used in the electronic and solar industry.

SIEMENS REACTOR: Conventional reactor used for deposition of silane or trichlorosilane on long silicon rods. Used by most manufacturers of polysilicon.

SILANE: A compound gas consisting of hydrogen and silicon. An intermediate stage in the production of polysilicon.

SILICON: The second most abundant element (after oxygen) in the earth’s crust. The raw material for production of solar grade silicon as well as electronic grade silicon.

SILICON WAFER: A thin slice of crystalline silicon used as the key component in a solar cell.

SOLAR GRADE SILICON: Silicon with 99.9999 percent to 99.999999 percent purity. (6N to 8N -purity).

SOLAR ENERGY: Refers to electricity or heat energy made from solar radiation.

SOLAR PANEL: Interconnected solar cells encapsulated and protected behind transparent materials that protect against humidity, air and mechanical damage. Normally, solar panels are made with a glass front, a polymer backsheet and aluminum frame.

THIN-FILM: Photovoltaic technology where the generation of solar energy takes place in a thin film of semiconductor material, normally deposited as several layers on glass. Conventional solar panels are made with wafers as the semiconductor material.