The following is a study on the influencing factors of double - sided grinding and etching of indium phosphide wafers:
Low Hardness: Indium phosphide has relatively low hardness. Compared with materials such as silicon (Si) and gallium arsenide (GaAs), it is more prone to damage during processing. This requires milder process conditions during grinding. The grinding pressure must be appropriate. Otherwise, scratches or cracks may appear on the material surface.
High Brittleness: As a brittle material, indium phosphide is likely to crack or generate micro - cracks due to mechanical stress. Therefore, the settings of the grinding equipment need to be precisely controlled. The rotation speed of the grinding head, the flatness of the grinding disc, etc. must be strictly checked to avoid excessive force causing the material to break.
Grinding Pressure: Excessive pressure will generate large mechanical stress on the surface of the indium phosphide wafer, which may not only cause the wafer to break but also increase the surface roughness and lead to defects such as scratches. Insufficient pressure will result in low grinding efficiency and failure to achieve the desired grinding effect.
Rotation Speed of Grinding Disc: The rotation speed affects the grinding efficiency and the surface quality of the wafer. If the rotation speed is too fast, the friction between the wafer and the grinding disc will increase, generating a large amount of heat. This may cause local overheating of the wafer, change the material properties, and also make the grinding fluid splash, affecting the uniformity of grinding. If the rotation speed is too slow, it will extend the grinding time and reduce production efficiency.
Flow Rate of Grinding Fluid: An appropriate flow rate of the grinding fluid can timely remove the debris and heat generated during grinding, playing a role in cooling and lubrication. Insufficient flow rate will cause debris to accumulate on the wafer surface, resulting in uneven grinding and even scratching the wafer surface. Excessive flow rate may wash away the abrasive particles, reduce the grinding efficiency, and cause waste of the grinding fluid.
Type of Abrasive: Different abrasives have different hardness, shape, and particle size, which have a great impact on the grinding effect of indium phosphide wafers. For example, the commonly used alumina (Al₂O₃) abrasive has high hardness and relatively high grinding efficiency. However, if the particle size is too large or the shape is irregular, it may leave deep scratches on the wafer surface.
Particle Size of Abrasive: The particle size determines the grinding removal rate and surface roughness. Generally, the larger the particle size, the faster the grinding removal rate, but the surface roughness will also increase accordingly. Smaller particle sizes can obtain better surface quality, but the grinding efficiency is lower.
Suspending Agent: The function of the suspending agent is to evenly disperse the abrasive in the grinding fluid and prevent the abrasive from precipitating and agglomerating. If the performance of the suspending agent is poor, the abrasive is likely to gather together, resulting in uneven grinding and affecting the surface quality of the wafer.
Type and Concentration of Acid: Commonly used etching solutions contain hydrochloric acid, sulfuric acid, etc. If the concentration of hydrochloric acid is too high, the etching rate will be too fast to control, which may lead to excessive etching on the wafer surface, resulting in a rough surface. Changes in the concentration of sulfuric acid will also affect the etching effect. Different acid concentration ratios will change the redox potential and chemical reaction activity of the etching solution.
Additives: Adding some specific additives, such as hydrogen peroxide, to the etching solution can change the properties of the etching solution and affect the etching rate and selectivity. For example, hydrogen peroxide can play an oxidation role, promote the etching reaction of indium phosphide, and at the same time inhibit the dissolution of certain impurities, improving the surface quality after etching.
Etching Temperature: An increase in temperature will accelerate the etching reaction rate. However, too high a temperature may make the etching reaction too intense to control, and may also cause thermal stress on the wafer surface, affecting the performance and quality of the wafer. Too low a temperature will result in a slow etching rate and low production efficiency.
Etching Time: If the etching time is too short, the damaged layer and surface impurities of the wafer after grinding cannot be completely removed. If the etching time is too long, the wafer surface will be over - etched, the roughness will increase, and even the wafer thickness may become uneven.
Degree of Grinding Damage: If deep scratches, cracks, or large stresses are generated on the wafer surface during grinding, these parts will react preferentially during the etching process, resulting in uneven etching and affecting the flatness and surface quality of the wafer.
Surface Impurities: Residual abrasive, oil stains, dust, and other impurities on the wafer surface will prevent the etching solution from coming into contact with the wafer surface, making the etching reaction unable to proceed evenly. It may also form local etching pits or defects on the wafer surface.
