How Silicon Wafers Are Made?

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What is Silicon Wafer Made Of?

Semiconductors are most commonly fabricated with Silicon, which is the second most abundant material on earth at 30%. Pristine beach sand from certain beaches in Australia and Italy are used in the first process of growing a silicon ingots that will become wafers which then are turned into chips.

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How are Silicon Wafers Made?

Silicon is the second most abundant material on earth after carbon. Silicon makes up 27.8% of the earth's crust. Silicon abundancy makes it much less-expensive than other materials such as Germanium. Silicon is also very versatile. Silicon is mined from beach sand found on several pristine beaches. While growing the ingot, dopants can be added to control electricity in the finished product, usually a semiconductor.

Manufacturing of Silicon Wafer

Silicon wafers are grown using two methods. The most common method of growing single crystal silicon is the Czochralski (CZ) method. A more expensive and less common ingot growth method is the Float Zone (FZ) method. The silicon seed is grown in a long tube called a crucible..

Single Crystal Silicon Pulling

The Silicon Ingots are grown by placing Polycrystalline Silicon Chunks into a quartz crucible. Dopants such as Boron, Arsenic, Antimony and Phosphorous are added. This gives the ingot a N-type, P-type or undoped specification.

The crucible is heated to 2552 deg Fahrenheit in high purity Argon gas ambient. Once the chunk melts, a single crystal silicon seed is placed into the melting chunk and pulled out at a slow rate. Using the surface tension, and slow pull rate forms a circular monocrystalline ingot with the same silicon orientation with the seed.

Orientation

The finished monocrystalline ingot is machined to have either a flat or notch along the entire length of the ingot to give the respective orientation which can be but not limited to (100), (111), (110).

Silicon Ingot Slicing

Using a diamond saw, the silicon ingot is sliced into certain thicknesses.

Silicon Wafer Edge grinding

To increase a silicon ingot's yied, the edges of the sliced wafers are diced.

Silicon Wafer Lapping

After slicing, the silicon wafers surface are rough to the touch from the sawing. The silicon lapping process removes the suface defects.

Silicon Etching and cleaning

Below are some of the acids used to fix the microscopic cracks and surface damage.

  • sodium hydroxide
  • acetic
  • nitric acids

Then deionized water is used to rinse the etched silicon wafers.

Silicon Wafer Polishing

Polishing requires a number of steps.

Slurry is used in finer and finer grains to make polished sides as flat as possible. The tighter the specs, the more the substrates cost as the equipment used is more expensive and the process requires more time.

 

 

Steps to Make Silicon Wafers

When we talk about what is silicon wafer made of, we are talking about the thin membrane that is used to hold the wafer intact until the time it's used in electronics. The silicon, or glass, is very pure. When device production is first started, the silicon contains a normal impurity level of less than one percent. To improve upon the performance of the silicon, the industry uses what is called the substrate.

Silicon substrate is what gives the wafer its thin and smooth surface. In order to create the wafer top layer, the silicon must be placed onto a quartz or silica compound, mixed with dyes in order to give the wafer the color that is desired. After the coating of the silicon is dry, the silicon is passed on to the next stage of production, which is what causes the silicon to become a solid.

This is how the silicon wafer suppliers go about making the devices that we use every day. The silicon is mixed with sand, usually sodium silicate sand. When this mixture is heated it becomes molten, which causes the silica to solidify. This makes a solid layer of sand around the silicon, which is known as the substrate. This solid layer also traps some of the heat that comes from the device, which allows the device to function better.

There are many different ways that the substrate is applied to the wafer sort. It is typically applied with a spatula-like instrument. When this is done properly, the tool will make sure to distribute the pressure equally across the surface of the wafer sort. If there is any excess pressure, it is released from the tool as the heat of the procedure itself cools off. Once the pressure is evenly distributed, it is removed and the wafer sort is turned over so that it can be viewed.

Silicon wafer sheets that have gone through this process have a two layers of silica on them. The first layer is called the oxidation layer. This layer provides protection to the silicon dioxide. When the silicon dioxide comes into contact with any impurities, such as water or moisture, it bonds with those impurities and forms the oxide layer. This layer serves to prevent moisture from penetrating into the wafer, but it also limits the amount of the oxide that forms.

Silicon oxide is actually a silicate relative. This silicate relative has the same crystal growth behavior as pure silica, but without the ability to form oxide layers upon itself. If moisture is present on the wafer surface, then crystalline growth will occur. It is this crystalline growth that produces the desirable pattern on the wafer surface. On a smooth and flat silicon wafer surface, a monochrome pattern results.

On the other hand, when there is some humidity present on the silicon wafer, monochromatic doped wafer cutters can be used to produce the pattern in which the desired pattern occurs. The doped silicon wafers are produced with one side of the wafer having a single layer of pure silicon and the other side of the wafer having a layer of doped silicon. When moisture is present on the single sided wafer, the doped silicon lets the moisture pass through the solid silica while preventing the moisture to enter the single sided wafer. This is a great benefit in that the single sided wafer cuts more smoothly than the doped wafer.

Most silicon wafer suppliers sell both types of wafers; the single and the double sided wafers. Many times, it is necessary to find a supplier that offers both types of wafers so that you can get the most options available to you. Some suppliers offer the single sided wafer, but they also offer the double sided wafer. Because they know the demand for both types of wafers, they will often offer the two wafers to their customers. Whether you need single or double sided waffles, you should be able to find a supplier that offers them by searching on the Internet. The good news is that many of the suppliers that offer the silicon dioxide wafer are also able to provide the sand wafers as well.

How do they make Silicon Wafers and Computer Chips?