Silicon Wafer Glossary

Technical terms, which we use on the website:

A

alloy – the alloys are formed by mixing metal with metal or metal with another chemical element, resulting in metallic bonding between the atoms. Alloys are made to obtain specific properties of the material, such as corrosion resistance or some mechanical properties. It also allows to reduce the total cost of fabrication. Examples of alloys can be steel, duralumin and bronze.

angstrom, Å – unit length is 10-10 m. Used to numerically express the values of very small lengths, comparable to the size of the atoms. Commonly used in chemistry and physics to describe objects and phenomena occurring on the atomic scale.

annealing (glass) – a technology that removes internal stress within glass structures. This method involves the slow cooling of the hot formed glass. This is an important process that helps prevent spontaneous cracking. Annealing temperature is in the range 454°C-482°C.

C

chemical resistance – it may refer, for example, to the surface of a material. This is the ability of the surface not to react with other chemical agents that could destroy the chemical structure of the material from which the object is built.

conductivity – is a measure of the ability of a material to conduct electricity. The reverse of conductivity is resistance.

crystal – a solid in which molecules (molecular crystals), atoms (covalent crystals), or ions (ionic crystals) are arranged in an orderly pattern that repeats in all three spatial dimensions. In the body volume,  molecules occupy strictly defined places, called lattice nodes, and can only vibrate around these positions.

crystal orientation – is determined by miller indices (hkl), which are a notation system in crystallography which determine how the plane crosses the main crystallographic axes of the solid-state. Miller indices are a set of numbers that quantify the intersection and can determine a plane or surface.

Czochralski method – technique of obtaining monocrystals developed in 1916 by the Polish chemist Jan Czochralski. It is based on slow, gradual pulling out of molten crystal seed material in a way that ensures controlled and stable crystallization on its surface. In addition, if required, the crucible can be put to rotation to improve the mass and heat transport conditions.

D

defect concentration – the concentration of imperfections in crystals, which originate in the point or layer break of the regularity of their lattice system. Defects occur practically in all real crystals, as they result from the nature of the crystallization process.

density – is the magnitude used to compare the weights of different materials. This is the ratio of the weight of a certain quantity of substance to the volume occupied by it.

dopant –  this is the chemical element added to the semiconductor that changes the conductivity of the electron doped material.

doping – the process of adding dopants causing changes in the conductivity and resistivity.

E

epitaxy – semiconductor technology for the growth of new monocrystalline layers on an existing crystalline substrate that duplicates the existing crystal lattice system.

F

face-centered cubic structure – the crystallographic system in which all three axes are of equal length and are perpendicular to each other. The FCC is one of the centering types in the crystalline system where the elemental atoms are in the corners and in the middle of each wall.

float glass – glass production process. Material produced by this method is almost perfectly flat, with no distortion and optical defects. The following are used for the production: glass sand, sodium carbonate, limestone, dolomite, alumina and other substances acting as dyes or changing the physical and chemical properties. The glass is then poured into a molten metal float bath, which is usually tin.

I

ingot – pure product in the form of which the material is delivered for further processing. In this case, ingot is a crystal formed, among other things, by the Czochralski method, and then is cut into wafers.

insulator – material in which the electric current is very low. This can be a result of low concentration of electric charges, low mobility, or both.

N

N-type – is a doped semiconductor. The insertion of a dopant is giving an excess of electrons and produces an n-type semiconductor, the dopant is called a donor dopant (“electron donor”). In such a semiconductor, an additional energy level (donor level) is established in the band gap area below the conductivity level or in the conductivity band. The excess of electrons is released into the conduction band in the form of free electrons capable of conducting current. This is an electron conductivity or n-type (negative) conductivity. For conventional silicon, donor dopes are elements from 15th atom groups of the periodic table, mainly phosphorus.

P

phonon – in quantum mechanics is a quasiparticle, quantum energy of vibration of crystal lattice with bosonic properties.
This is nothing more than the thermal vibration of the crystal lattice.

P-type – is a doped semiconductor. The insertion of an dopant is giving an electron deficiency and produces a p-type semiconductor, the dopant is called an acceptor dopant (“electron acceptor”). In such a semiconductor, an additional energy level (acceptor level) is formed in the band gap area, above the valence level or in the valence band. These levels bind electrons in the valence band and forming free spaces. Such free space is called an electron hole. It behaves like a free particle with a positive charge and is capable of conducting electricity. The resistivity of the p-type materials is generally higher than that of the n-type materials having the same doping level. Typical silicon acceptors are elements from 13th atom groups of the periodic table, usually boron.

prime grade – wafer type of the highest quality. They are used to produce the devices, they have good mechanical and electrical properties.

R

refractive index – (denoted n) is the magnitude of the refraction of light from one medium to another. Numerical refractive index is expressed by the ratio of light velocity in one medium to velocity in the second medium. Based on this factor can be determine in which medium the speed of light is higher.

resistivity – this is the ratio of the magnitude of the electric field to the magnitude of the current density. Resistivity unit is Ohm-cm. Materials are put into different categories according to their level or resistivity. It is possible to control the silicon´s resistivity by doping.

roughness – solid surface feature means recognizable optical or mechanically perceptible surface irregularities, not forming from its shape, but at least one order of magnitude finer. The surface roughness depends on the type of material and especially on treatment.

S

sapphire – mineral characterized by high hardness (9 in Moh´s scale) from the oxide group – blue type of corundum. It is a rare mineral.

semiconductor – substance, most often crystalline, which conductivity can be varied by doping, heating, lighting or other factors. The conductivity of a typical semiconductor is between the conductivity of metals and dielectrics.

SIMOX – Separation by Implantation of Oxygen, silicon layer forming process involving implantation of the oxygen beam and subsequent annealing.

T

test grade – wafers of inferior quality to the prime grade. They are used for research and testing.

thermal oxidation – production of thin layers of oxide ​​- most often silicon dioxide – on the wafers. This technique consists in the fact that the oxidant diffuses on the surface at a temperature between 900ºC and 1200ºC in a furnace and reacts with it.

thermal resistance – physical magnitude representing the resistance that puts the material while transferring heat between two points. Thermal resistance is important in electronic systems, where heat dissipation can cause overheating of the components.

thickness – this is the distance between the front and back surfaces of the wafer.

W

wafer – is a thin plate made of a semiconductor material. It is used mostly in electronic integrated circuits and solar cells. Wafers are subjected to, among other things, doping or implantation of ions to fulfill their roles by forming a substrate of microelectronic devices.

Z

zincblende structure – the space group of the Zincblende structure is called F43m after the mineral sphalerite (zincblende). It crystallizes in cubic crystal structure, which has tetrahedral coordination and atoms form regular tetrahedrons.