SILICON WAFERS OPTIONS

Prime wafers are the highest grade of commercial silicon wafers. They are referred to as ‘device-quality’. Prime wafers have a high-quality polished. Prime wafers are typically more expensive than test wafers, and are used for applications that include photolithography and particle monitors. Prime wafers typically offer tighter resistivity specs and are used in “high tech” projects or semiconductor manufacturing.

Test or monitor wafers can be used for a variety of purposes, especially in equipment testing and other applications where a large quantity of wafers is necessary (marathon runs). Test and monitor wafers are used in testing and managing the control of semiconductor fabrication lines and processes. Although monitor wafers are substantially the same as prime polished wafers with respect to cleanliness, and in some cases flatness, other specifications are generally less rigorous. They are a more affordable option than prime wafers as they typically fall short on one or more specifications required to be classified as a prime wafer. In other words, test wafers are prime wafers with one or more non-compliant specification. 

Reclaimed wafers are essentially used test and prime wafers, which have gone through the process of being completely stripped of the thin film and re-polished to remove all of the previous patterns, films, or any surface defects. After the reclaiming process, the wafers will achieve the same level of standards as a normal test wafer. While reclaimed wafers are often thinner than virgin wafers, they usually offer the same performance as a virgin test wafer and are suitable for many of the same uses. 

Silicon wafers are available in several sizes (diameters)

Addison provides silicon wafers in these dopant types:

Resistivity identifies the level of resistance to current flow and the movement of electrons and holes in the silicon. Resistivity is related to the ratio of voltage across the silicon to the current flowing through the silicon per unit volume of silicon. The units for resistivity are Ohm-cm, and these are the units used to specify the resistivity of silicon wafers and crystals. Resistivity range targets are achieved by adding impurities such as As, Phosphorous, and Boron to the silicon. As the amount of impurity or dopant is increased, the resistivity is decreased. For example, heavily doped wafers have low resistivity. 

Thickness is defined as the distance through a wafer in a direction normal to the surface (front or back) at a given point. A wide variety of wafer thicknesses are available and others can be made to a specific requested thickness. Some typical thicknesses are listed below.

Usually both sides of silicon wafers are at least lapped and etched. Surface polishing is performed either on one (SSP = Single-Side Polished) or both sides (DSP = Double- Side Polished)

Wafers are typically available in quantities of 25 (or 24). They are factory sealed in wafer cassettes placed in wafer cassette boxes and double bagged and vacuum sealed at the time of manufacture. Smaller quantities (partials) or individually packed wafers may be available on request.