Application Cases

Solid-state lighting, recognized globally as an efficient and energy-saving approach, has undergone a significant transformation from indicator lights to the lighting domain with the advent of high-brightness light-emitting diodes (LEDs). The initiation of China's semiconductor lighting project has further propelled the LED industry into a phase of rapid development. In the semiconductor lighting industry, the substrate is the cornerstone and core material for technological advancement. Sapphire (α-Al₂O₃), with its superior physical, chemical, and optical properties, has become a commonly used substrate and window material, widely applied in LED substrates and infrared windows. To enhance the processing quality of sapphire, researchers have introduced ultrasonic vibration into CMP, developing the ultrasonic vibration-assisted chemical mechanical polishing (UV-CMP) process for sapphire. This process applies ultrasonic vibration to the rotating polishing head, adding an ultrasonic-assisted function to traditional CMP.

At this juncture, the power amplifier plays a crucial role. It amplifies the received ultrasonic electrical signal, enabling the signal to reach the working voltage and power required by the ultrasonic transducer. The amplified electrical signal is then transmitted to the ultrasonic transducer, which converts it into mechanical vibrations of the same frequency. With this, the CMP polisher is upgraded to UV-CMP, and traditional chemical mechanical polishing is enhanced to ultrasonic vibration-assisted chemical mechanical polishing. By switching off the ultrasonic signal generator, the equipment can revert to the traditional chemical mechanical polishing mode. Clearly, the power amplifier acts as a bridge connecting the ultrasonic signal generator and the ultrasonic transducer in the entire UV-CMP process, playing a vital role in realizing the ultrasonic vibration-assisted function and improving the efficiency and quality of sapphire processing.

The driving signal output by the signal generator is insufficient for the normal operation of the ultrasonic transducer. Therefore, a power amplifier is also required to amplify the electrical drive signal. The amplified electrical signal enables the normal operation of the ultrasonic transducer. The power amplifier selected is the Aigtek-ATA-68020, with a voltage of 850 Vp-p and a maximum output current of 2.12 Ap.

Experiment Name: Ultrasonic Chemical Mechanical Polishing Equipment

Experiment Principle: The ultrasonic signal generator in the experimental equipment produces electrical signals of specific frequency and waveform. These signals are amplified by the power amplifier and then transmitted to the ultrasonic transducer. The piezoelectric ceramic disc within the transducer converts the electrical signal into mechanical vibrations of the same frequency, which are then amplified by the horn-shaped cover plate and transmitted to the sample holder, causing the polishing head to vibrate ultrasonically during rotation. This vibration gives the abrasive particles in the slurry additional energy, accelerating their impact on the wafer surface. Meanwhile, the heat released by the ultrasound can accelerate the chemical reaction between the slurry and the wafer surface.

Experiment Block Diagram:

Experiment Photographs:

Experiment Process: First, prepare 2-inch C(0001)-oriented single-sided sapphire wafers, polyurethane pads, silicon sol with specific particle size and concentration, and various chemical additives. Next, formulate the polishing slurry by dissolving different doses of chemical additives in deionized water, adding silicon sol, and diluting to a silica abrasive concentration of 15%, stirring for 30 minutes. Begin the experiment by adhering the polishing pad to the polishing platen and setting the process parameters such as downforce, polishing head/platen rotation speed, flow rate, time, and ultrasonic vibration amplitude. Place the formulated slurry containing different chemicals into the supply pump. Then, clean the initial sapphire wafer and weigh it, attaching it to the sample holder of the polishing head. Condition the polishing pad, which has been moistened with deionized water, using a conditioning disk. At this point, the ultrasonic signal generator produces an ultrasonic electrical signal, which is transmitted to the power amplifier for amplification. The amplified signal is then sent to the ultrasonic transducer, converting the electrical signal into mechanical vibrations that drive the polishing head to vibrate, achieving ultrasonic chemical mechanical polishing. After the experiment, remove the workpiece, clean and weigh it, calculate the material removal rate, observe the surface morphology using an atomic force microscope, and conduct XPS, SEM, and other inspections.

Application Directions: Chip packaging polishing, aerospace component polishing, medical device manufacturing, mirror polishing, etc.

Application Scenarios: Ultrasonic chemical mechanical polishing, sapphire wafers, ultrasonic chemical mechanical polishing experiments, ultrasonic polishing of hard and brittle materials

Product Recommendations: ATA-4000, ATA-L series, ATA-M series power amplifiers

Figure: Specifications of the ATA-4000 Series High-Voltage Power Amplifiers

Figure: Specifications of the ATA-L Series Acoustic Power Amplifiers