Monocrystalline Silicon Wafers from Nanoshel

By AZoNano.com Staff Writers

Topics Covered

Introduction
Properties of Monocrystalline Silicon Wafers
     Conductivity
     Resistivity
     Dopant
     Sheet Resistance
Specifications of Silicon Wafers
     Diameter and Thickness
     Total Thickness Variation (TTV)
     Orientation
Other specifications of Silicon Wafers
Conclusion
About Nanoshel

Introduction

Nanoshel offers monocrystalline silicon wafers that are quality tested on well defined parameters by its team of quality analysts. This article discusses the properties and specifications of monocrystalline silicon wafers (Figure 1) in detail.

Figure 1. Silicon wafers

Properties of Monocrystalline Silicon Wafers

Conductivity

Conductivity defines the type of charged-carrier in the crystal that conducts electricity. There are two types of conductivity: n-type and p-type.

In the former type, Si material has electrons as the majority current carriers and these electrons have negative charge (n); n-type material is created by doping with Antimony, Arsenic and Phosphorous.

In the latter type, Si material has holes as the majority current carriers and these holes exhibit positive charge (p); p- type material is produced by doping with Boron.

Resistivity

Resistivity is related to the ratio of voltage across the silicon to the current passing via the silicon per unit volume of silicon. Ohm/cm are the units for resistivity; these units are utilized to indicate the resistivity of crystals and silicon wafers.

Resistivity is generally controlled by including Arsenic, Boron, Phosphorus, and other impurities to the silicon. By increasing the amount of dopant or impurity, the resistivity is reduced. Materials which are heavily doped have low resistivity.

Dopant

In order to change the resistivity, impurities such as Arsenic, Boron and Phosphorus are added to the silicon. The resistivity is reduced as the dopant increases in concentration per cubic cm. Standard dopant levels in silicon are 1-100 ppma.

Sheet Resistance

Sheet resistance is related to the ratio of voltage across the silicon to the current passing via the silicon per unit surface area of silicon. Ohm/Square are the units for sheet resistance; these units are normally utilized to indicate the sheet resistance of silicon wafers that have a diffusion or epitaxial layer on the surface.

Specifications of Silicon Wafers

Diameter and Thickness

Standard diameters of silicon wafer are 25.4, 50.4, 76.2, 100, 125, 150, 200 and 300mm. Thickness refers to the normal distance via a wafer or slice in a direction normal to the surface at a given point.

Total Thickness Variation (TTV)

Total Thickness Variation is the highest variation in the wafer thickness. It is usually determined by calculating the wafer in five locations of a cross pattern and measuring the highest measured difference in thickness.

Orientation

Orientations are illustrated by using Miller Indices like (100), (111), (110), (211), etc. Different orientations and growth planes exhibit different arrangements of the lattice or atoms as observed from a specific angle.

Other specifications of Silicon Wafers

Other specifications of silicon wafers include slice orientation, warp, bow, primary flat, secondary flat, haze free, prime grade, and test grade.

Slice orientation refers to the crystallographic orientation of a wafer’s surface. Common slice orientations are (100), (111) and (110). The primary flat has a particular crystallographic orientation relative to the surface of a wafer and has the longest length appearing in the wafer’s circumference, while secondary flat is the shortest length that appears in the wafer’s circumference.

Bow refers to the curvature, concavity, or deformation of the wafer centerline, regardless of the presence of any thickness variations. Warp refers to the deviation from a plane of a wafer centreline which includes convex as well as concave regions.

Haze free is referred to a silicon wafer that has optimum micro-roughness and surface finish of less than 10A. Prime grade is the highest grade of a silicon wafer, while test grade refers to a virgin silicon wafer of reduced quality and is utilized mainly for testing processes.

The specifications of monocrystalline silicon wafers are summarised below:

Length Of Wafer Edge 2inch, 4 inch, 6inch (125mm), 8inch (156mm)
Diagonal 2inch, 4 inch, 6inch (125mm), 8inch (156mm)
Conductive Type P-Type, N-Type
Dopant Boron, Arsenic, Phosporous
Thickness 200 ±20µm or as per requirement
Resistivity 1-3Ωcm, 3-6Ωcm
Oxygen Concentration <1 x 1018 atoms/cm³
Carbon Concentration <5 x 1016 atoms/cm³
Lifetime ≥ 10µs
Chamfer Discrepancy 0.5mm
Vertical angle deviate 90 ± 0.3º
Orientation <100>, <111> ±2
Dislocation Density ≤3000/cm²
TTV < uniwafer thickness 15% <30µm
Wrap <50 µm
Sawmarks <15 µm
Cracks and pin holes No visible cracks and silicon drops
Edge No edge defect and silicon drop
Surface As clean cut, No Stains and detergent vestigital
Surface No visual knife marks, concave pit

Conclusion

Figure 2. Quality testing process of silicon wafers

This article describes the properties and specifications of Nanoshel’s monocrystalline silicon wafers that are processed using high grade chemicals and other related ingredients at the company’s advanced production units. All the silicon wafers are tested by quality analysts, as shown in Figure 2.

About Nanoshel

NANOSHEL makes more than 50 types of products, among which the main products are nanotubes, SWCNT's, MWCNT's, and nanoparticles. These products are widely used in the fields such as textile industry, ceramics, chemical fiber, plastics, coatings, cosmetics, rubber, electrical and electronic equipments, electric power generation and boiler and so on.

Through providing the customers with nanomaterials and the application process solution, the company commits itself to assist clients to improve the functionality and technology content of the products so that the clients can promote their product added-values and market competitive competencies, keep their creative advantages for a long time in the concerned fields and make good economic benefits.

This information has been sourced, reviewed and adapted from materials provided by Nanoshel.

For more information on this source, please visit Nanoshel.

Date Added: Oct 23, 2013 | Updated: Oct 30, 2013
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