Silicon Wafer Flats to Determine Type/Doping and Orientation

Why Do You Need Silicon Wafer Flats?

A silicon wafer's flat helps to determine the type and orientation of a silicon wafer, which is important for research purposes.

Without knowing what type and orientation a silicon wafer is, researchers can't accurately study its properties and how it will react in different situations.

Silicon Wafer Flats take the guesswork out of determining a silicon wafers type and orientation. These helpful flats let you see exactly what you're working with, so you can conduct accurate research without any mistakes.

Silicon Wafer Flat or Notches

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What does a Silicon Wafer (Si) Flat Look Like?

Below is an example of a 100mm silicon wafer flat orientation with a primary and secondary flat. But they don't have to have two flats. Wafers can be customized to h ave only one flat, of any length. Request for silicon wafers without any flats is common. Request for more than two flats is rare.

Silicon Wafer Notch

Silicon wafers with diameters smaller than 200 mm have flats cut into one or more sides for crystallographic orientation. 200mm diameter wafers and larger wafers use a single small notch to show orientation. Unlike flats, a V notch does not help user to determine the wafer's doping type.

Wafer Flats or Notches?

A wafer with a diameter of 200 mm has a flat cut on one or more sides, which is indicated by the flat surface. Large and small values are typically set by wafer manufacturers for the size and shape of the surface of each silicon surface, as well as for width and height. [Sources: 3, 8, 9]

What are Silicon Wafer Flats?

Since Silicon Wafers look basically the same! Flats are cut into the edge of the wafers so users could determine the wafer's dopant-type and orientation.

It's a straight edge on a wafer that is used to position it in production systems. In single-crystal oriented semiconductors, a wafer flat is well on the crystal orientation. For a standard 100-mm-diameter wafer, the flat is attached to orientation 110. To identify the flat, X-ray diffraction is used to determine the crystal orientation. CNC-controlled grinding machines are used to grind flats into ingots.

Traditionally, the flats are made of polysilicon and can be used for wafers up to 150 millimeters in diameter. Larger wafers are marked with notches or barcodes and can also have a secondary flat that is 90 degrees ccw to the primary flat. The secondary or third flat is used to identify the type of wafer. These two flats are used to produce high-quality semiconductors.

Typically, a wafer is made of two flats: a primary and secondary. The primary flat is the longest flat on the wafer, and it indicates the crystal orientation. The secondary is the second flat. The notch is used to indicate the orientation of the crystal. Once the two flats are aligned, the cleaved pieces form a rectangular shape. The flats are placed at the corners of the rectangles, and then trimmed.

Silicon Wafer Flat Length

Below is an example of silicon wafer flat dimensions. The flat position also helps determine the substrate's dopant.

Spec.	50.8mm (2”)		76.2mm (3”)	100mm	125mm (5")	150mm (6")	200mm (8")	300mm (12")
Diameter	2.000+/-.015” 50.8+/-.38mm		3.000+/-.025” 76.2+/-.63mm	100+/-.5mm	125+/-.5mm	150+/-.2mm	200+/-.2mm	300+/-.2mm
Thickness	0.011+/-.001” 279+/-25um		0.015+/-.001” 381+/-25um	525+/-20 um or 625+/-20um	625+/-20um	675+/-20um or 625+/-15um	725+/-20um	775+/-20um
Primary Flat Length	0.625+/-.065” 15.88+/-1.65mm		0.875+/-.125” 22.22+/-3.17mm	32.5+/-2.5mm	42.5+/-2.5	57.5+/-2.5mm	Notch	Notch
Secondar y Flat Length	0.315+/-.065” 8+/-1.65mm		0.44+/-.06” 11.18+/-1.52mm	18.0+/-2.0mm	27.5+/-2.5	37.5+/-2.5mm
Primary Flat Location	{110}+/-1 deg.		{110}+/-1 deg.	{110}+/-1 deg.	{110}+/-1 deg.	{110}+/-1 deg.	{110}+/-1 deg.	{110}+/-1 deg.

But flats are not a universal standard. You can order any silicon ingot and have the plant cut any type of flat out of the wafer. So P/Boron (100) Silicon Wafers may have just one flat such as Silicon item #452.

What Are Silicon Wafer Flats?

Silicon wafers are thin slices of semiconducting material widely used in the production of electronics and micromechanical devices. In electronics, wafer (also called slice substrate) is the crystalline silicon (C - Si) used to manufacture integrated circuits and solar cells. [Sources: 5, 8]

A wafer with a diameter of 200 mm has a flat cut on one or more sides, which is indicated by the flat surface. Large and small values are typically set by wafer manufacturers for the size and shape of the surface of each silicon surface, as well as for width and height. [Sources: 3, 8, 9]

The conversion to a larger 450 mm wafer would reduce the price of the die, as in some cases the costs are not related to the area but the number of wafers. Only one wafer is processed at a time, and as the diameter increases, tools developed specifically for single-weight processing become more and more common. [Sources: 1, 8]

Semiconductor manufacturing factories, colloquially known as Fabs, are defined because they are designed to produce wafers for use in semiconductor devices such as mobile phones, televisions and other electronic devices. Silicon sellers buy the wafer in rolls, with hundreds of them stacked on top of each other, like a coin roll. Waves that do not meet the specification are collected and sold as "coin rolls" or "wafer rolls." Silicon wafers are available in a wide range of sizes, from small to large, as well as in various shapes and sizes. [Sources: 4, 8]

Normally we speak of about one inch, and the typical size is about 1.5 mm (0.3 inches) in diameter. Circular wafers are used in the semiconductor industry, which we hereinafter call "wafers," and they are most commonly used in industry and academia. P-type wafers are doped with boron to act as an acceptor for silicon, while gallium can also be used. Although only the "P" dopant is used in the manufacture of silicon devices, it is also often applied to the surface of a silicon chip, such as a mobile phone or TV. [Sources: 1, 4, 5, 10]

The applicant finds certain advantages which arise when a technique known as electrostatic bonding is used to produce optically flat silicon wafers. The use of contact bonding technology, such as the electrochemical bonding method, allows contact-bonded silicon and boron-gallium-silicon bonds to form on the surface of the wafer in the flat state. [Sources: 7]

Therefore, primary flat silicon wafers are often used as a reference for all types of wafer orientations. Flat was originally used to identify the type or better ORIENTATION, but there are fewer conventions today about what flat means. Notches are quite common at 8,200 mm waves, and a second layer is used for the detection of doped and not always used silicon chips. [Sources: 0, 3, 5]

The exact crystallographic direction of a silicon wafer can be detected by mounting an X-ray diffraction unit on a mask aligner. When the wafers stop rotating, a sensor (for example, a photocell) determines whether the flat 12A wafers are aligned. The location and number of waves per apartment contain information about the surface of each apartment as well as the number and orientation of the layers. [Sources: 1, 3, 6]

This orientation influences how the silicon wafer is etched and how it interacts with the surface. The unit of plate resistance is ohm square and is the unit typically used to determine the epitaxial diffusion layer that a silicone wafer has on the surfaces. It is an ohmcm and it is a unit used to indicate the resistance of a silicon wafer crystal. [Sources: 5, 9]

SEMI specifies the bulk of the physical properties of the surface, which are known as true prime wafers for silicon wafers. Prime Wafer or Prime is the highest possible silicone quality, but there are a variety of Prime Wafers available. A true Prime Wafer is a device - a high-quality wathor that could be used by major labels for the latest technology in semiconductor devices. However, shafts that meet these specifications are rare and quite expensive and not available on the market. [Sources: 4]

Wafers grown with materials other than silicon are not usually available in 100 mm sizes. They will have the same physical properties as a real Prime wafer, but a smaller surface area and a larger diameter than the real Prime wafer. These will have similar physical properties to a true prime wafer, such as the thickness of the surface. [Sources: 2, 8]

It may also be desirable to produce a device with curved contours, such as a semiconductor component with a high surface area and small diameter. [Sources: 7]

The problem is that Si wafers are made up of simple atoms, the surface of which is confused with the inversion in this work and they exhibit anisotropy. When the optical plane is pressed into the wafer, it deforms through the bond to the base plate. Other methods of processing the wafer, such as gate oxidation, cause uneven surfaces on the wafer during such processing. Such a method would also be more expensive than other processing methods, where the semiconductor wafers must be optically flat and must also be removed without damaging them, but this causes an uneven surface on them. [Sources: 7, 10]

Sources:

[0]: https://www.halbleiter.org/en/waferfabrication/wafer/

[2]: https://www.wikidoc.org/index.php/Wafer_(electronics)

[3]: https://link.springer.com/article/10.1186/s40486-018-0066-1

[4]: https://cleanroom.byu.edu/ew_wafer_specs

[5]: https://www.inseto.co.uk/wafer-selection-guide/

[6]: https://patents.justia.com/patent/5383759

[7]: https://www.freepatentsonline.com/5160560.html

[8]: https://en.wikipedia.org/wiki/Wafer_(electronics)

[10]: https://patents.google.com/patent/EP1437762A1/en