Sapphire is a type of gemstone that is obtained from the minerals – corundum and aluminum oxide. It is considered to be one of the hardest minerals after diamond and moissanite. The hardness of sapphire is rated as 9 on the Mohs scale.
Sapphire is used for a hi-tech range of applications for its excellent physical and chemical properties. Sapphire substrates are mainly used in the LED industry due to their reliability, abundance, and cost-efficiency.
What is Sapphire Substrate Wafer?
Sapphire substrate wafer is produced by cutting, grinding, and polishing a sapphire crystal bar. This substrate is particularly used by those working within the laser industry. That’s mainly because it has a uniform dielectric constant and high-quality crystalline structure.
Today, sapphire has gained immense popularity in the Radio Frequency (RF) switch applications. Also, there is a remarkable increase in the use of sapphire substrates for blue laser diodes.
How is the Sapphire Wafer Manufactured?
The manufacturing process of this sapphire substrate involves various steps that are as follows:
- Orientation – Firstly, the position of the sapphire crystal rod is accurately located on the slicing machine to simplify the slicing process.
- Slicing – The sapphire crystal rod is then cut down into thin wafers.
- Grinding – Slicing causes chip cutting damage layer. This layer is removed to improve the flatness of the wafer.
- Chamfering – The wafer edges are trimmed into a circular arc. This increases the mechanical strength of the edges to avoid the damages that can be caused by stress concentration.
- Polishing – The wafers are then polished to reach their epitaxial precision.
- Cleaning – This step involves the removal of contaminants such as metals, dust particles, or organic contaminants from the wafer’s surface.
- Quality inspection – The quality of the wafer including its flatness, surface dust particles, etc., is thoroughly inspected with the help of high-precision testing instruments. This is done to meet the customers’ requirements.
What are the Methods of Polishing Sapphire Wafer?
The main objective of polishing the sapphire substrate wafer is to minimize the overall thickness of the wafer to the required target value. The roughness of the wafer’s surface should be finally less than 2nm with a TTV of more than +/-2 microns.
The primary methods of polishing sapphire substrate wafers are chemical polishing, mechanical polishing, laser beam polishing, ion beam polishing, and many more. However, every polishing method has a specific purpose.
While mechanical polishing can be done to achieve global planarization, the chemical polishing method can be used to achieve nano-level polishing.
What are the Methods of Cleaving Sapphire Substrate Wafer?
Cleaving is considered to be a simple and fast technique used for preparing samples of silicon as well as other semiconductor materials. Sapphire wafer is a single crystal material, and that’s why it does not cleave well.
However, since cleaving is an inexpensive and fast technique that reduces material loss, several sapphire substrate wafers are attained by the LatticeGear cleaving and scribing tool. The two main steps required for cleaving a sample are as follows:
- Step #1: Creating a Weak Point
The weak point is typically referred to as a defect that has developed on the sample. It is the point at which cleaving is initiated. This weak point developed on the edge of the sample plays a vital role as it determines the quality and accuracy of the cleave
- Step #2: Cleaving
The second step in producing a cleaved sample is cleaving. This is done by creating stress on the weak point. The cleave is initiated based on the type of sample. While the best weak point for a crystalline sample is a short scribe, the direction of the weak point for an amorphous sample is a long scribe.
You will find a sapphire wafer at different prices across different sellers in the market. Today, a number of online sites also sell this sapphire substrate. But always make sure to consider the quality of the wafer while purchasing it.