Single Crystal Sapphire Ingot

Single Crystal Sapphire Ingot

Sapphire ingot can be offered by PAM-XIAMEN, one of sapphire ingot manufacturers. The chemical composition is alumina and is composed of three oxygen atoms and two aluminum atoms covalently bonded together. Sapphire crystal structure is a hexagonal lattice structure, and the commonly used section has A orientation, C orientation and R orientation. It has the properties of high sound velocity, high temperature resistance, corrosion resistance, high hardness, high light transmittance, and high melting point (2050℃). Therefore, pure sapphire boule is used to produce sapphire substrate for semiconducting circuits, laser and endoprostheses. And it is often used as optical components, infrared devices, high-intensity radium radiation materials and mask materials.

sapphire ingot

1. Specifications of Sapphire Ingot


No. 1:

Material Sapphire Ingot
Diameter of Ingot 3 ± 0.05 inch
Ingot length 25±1 mm
Defect (pore, chip, twin etc) ≤ 10%
EPD ≤1000/cm2
Surface Orientation (0001)(on-axis:±0.25°)
Surface as cut
Primary and Secondary flats Required


No. 2:

Material Sapphire Ingot
Diameter of Ingot 4 ± 0.05 inch
Ingot length 25±1 mm
Defect (pore, chip, twin etc) ≤ 10%
EPD ≤1000/cm2
Surface Orientation (0001) (on-axis: ±0.25°)
Surface as cut
Primary and Secondary flats Required


2. About Sapphire Crystal Growth

The sapphire crystal growth process has five major steps: seed crystal-filling-melting-growth-forming ingots. In the process of seed crystal growth, temperature control has a significant impact on the quality of the crystal. At present, the main crystal growth methods of sapphire mainly include: Kyrgyzstan (KY), Czochralski (CZ), Heat Exchange Method (HEM), and Edge Defined Film-fed Growth (EFG). Among them, the Kyrgyzstan method and the heat exchange method are the mainstream technologies in the market because they can grow large-volume sapphire crystals. The Kyrgyzstan method has the largest market share of over 70%, followed by the heat exchange method.

Comparison of various sapphire ingot growth characteristics are show in the table:

Growth Method Advantages Disadvantages Characteristics
Ky Low impurity content and good uniformity Complex operation and low crystal utilization Crystal 31-200kg, cycle no more than two weeks
CZ The crystal growth process is easy to observe, the growth period is short, and the shape is regular Limited size and high cost Suitable for preparing crystals that the length is larger than the diameter
HEM Stable process and large size Long growth cycle, high cost, poor single crystal easy to crack, not suitable for LED substrate When applied to consumer electronic products, the material is taken and the shape can be customized
EFG Fast crystal growth (1-4cm/h), low cost Complex and sophisticated process preparation for equipment construction This method is suitable for display windows, watch windows and small semiconductor substrate


3. Industrial Standards for Monocrystalline Sapphire Rod

The sapphire crystal ingot is high-purity α -Al2O3, and its total impurity content should be less than 100 mg/kg.

For the crystal quality, the colorless sapphire crystal should be single crystal within the effective diameter range, the dislocation density should be less than 104 pcs/cm2, and the half-width value (FWHM) of the double crystal yaw curve should be less than 30arcsec.

The growth method used to prepare the ingot shall be in accordance with the contract between the two parties.

The surface orientation of the synthetic sapphire boule and the orientation of the reference plane should meet the requirements of Table 1.

Table 1 Surface Orientation and Reference Plane Orientation

Item Requirements
Surface Orientation c-plane (0001) ± 0.15 ° R-plane (1102) ±0.15 a-plane (1120) ± 0.15 ° m-plane(1010) ±0.15°
Reference Plane Orientation a-plane (1120) ±0.3° or m-plane (1010) ±0.3° The projection of the c-axis on the (1120) plane is rotated 45°±0.3° counterclockwise (as shown in the figure below) c-plane (0001) ±0.3° or R-plane (1102) ±0.3° c-plane (0001) ±0.3°


R-plane sapphire crystal orientation

Orientation of the main reference plane of the R-plane sapphire crystal

The size and allowable deviation of the sapphire single crystal ingot shall meet the requirements of Table 2. If the buyer has other requirements for dimensions and allowable deviations, they can be negotiated between the supplier and the buyer and indicated in the contract.

Table 2 Dimensions and Allowable Deviations (mm)

Item Requirement
Diameter 50.9+0.2/0 100.1+0.2/0 150.1+0.2/0
Ovality 0.05 0.05 0.05
Cylindricity 0.03/100 0.05/100 0.05/100
Reference surface size 16.0±1.0 31±1.0 47.5±1.0


The defects of the sapphire boule for sale shall meet the requirements of Table 3.

Table 3 Defects

Defects Requirement
Edge collapse, bubbles, wraps, scattering particles and others 15% of total length
Mosaic, twinning None
Localized light-scatterer None


In addition, the light transmittance of the sapphire single crystal in the 410 nm ~ 780 nm band should reach 85% or more. The special technical requirements of the sapphire ingot shall be negotiated by the supplier and the buyer, and shall be indicated in the contract.

Please note: usually, the requirement for producing single crystal sapphire ingot by PAM-XIAMEN-a sapphire processing company will be higher than the industry standards.

4. Stress Measurement of Sapphire Single Crystal by Using Stress Meter

Schematic Diagram of Stress Meter

Schematic Diagram of Stress Meter

Firstly, place the instrument in a semi-dark room with no direct light source to work;

Secondly, plug the light source into the 220V AC power supply;

Then, put the sample on the platform to be tested; and for the unpolished sample, drop refracting oil on the upper and lower surfaces;

Finally, move the sapphire crystal rod to the center of the light source, and confirm that the test probe scans different positions on the surface of the sapphire crystal to determine whether there are defects such as stress, mosaic, twins, etc.

The stress-free crystals are shown as:

stress-free sapphire crystal

The embedded crystals are shown in the figure:

embedded sapphire ingot

The slightly stressed and large-stressed crystals are shown in diagrams:

sapphire ingot with slight stresssapphire ingot with large stress

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