The application of sensors in the semiconductor industry
Flow Sensor
(1) Suitable for core types in the semiconductor industry
In semiconductor production, the fluids mainly include process gases (such as silane, ammonia) and corrosive liquids (etching solution, cleaning solution). Flow control needs to take into account the accuracy of small flow rates, anti-contamination ability and corrosion resistance. The mainstream types include thermal gas mass flowmeters, laminar pressure difference flowmeters, Coriolis Flowmeters, and ultrasonic flowmeters. The selection can be made flexibly based on the medium type and flow range.
(2) Core Application Scenarios
1. Lithography Process: Ensuring Exposure and Coating Precision
Lithography is a core step in semiconductor manufacturing, with extremely high requirements for the stability of gas concentration and liquid ratio. Flow Sensors are mainly used for two aspects: Firstly, during the exposure process, they precisely control the flow rates of protective gases such as nitrogen and hydrogen fluoride to maintain the stability of the gas atmosphere in the exposure chamber, preventing dust adhesion and oxidation of the photoresist, and ensuring uniform exposure, suitable for small flow control (1 sccm = 1 cubic centimeter per minute); Secondly, in the coating process of photoresist, they monitor the flow rate of the diluent, precisely adjust the concentration and coating thickness of the photoresist, avoiding line width deviations, supporting the process requirements of advanced manufacturing technologies such as 7nm and below.
2. Etching Process: Regulating Reaction Rate and Uniformity
Etching processes include dry etching and wet etching, both of which require flow sensors for precise control. In dry etching, dynamic adjustment of the flow ratios of reaction gases such as oxygen, argon, and chlorine is achieved through thermal or Coriolis Flow Meters to control the plasma etching rate, keeping the rate fluctuations within ±0.5%, reducing edge damage and etching deviations of the wafer; In wet etching, the circulation flow rate of the etching solution is monitored to ensure sufficient contact and uniform reaction of the wafer surface with the etching solution, avoiding local over-etching or under-etching problems, especially suitable for the flow monitoring of corrosive liquids such as high-concentration hydrogen fluoride and sulfuric acid.
3. Film Deposition Process (CVD/PVD): Ensuring Film Quality
Chemical Vapor Deposition (CVD) and Physical Vapor Deposition (PVD) are key processes for fabricating semiconductor device films. Flow control directly determines the thickness, composition, and adhesion of the films. In CVD processes, precise control of the flow rates of reaction gases such as silane, ammonia, and methane is achieved through laminar pressure difference flow meters to achieve nanometer-level thickness control of films such as silicon nitride and silicon oxide, ensuring a uniformity of ±1% and reducing device leakage current; In PVD processes, the flow rate of inert gases such as argon is monitored to maintain the stability of the gas pressure in the vacuum chamber, preventing impurities from entering and ensuring the purity and adhesion of metal films (copper, aluminum).
4. Auxiliary Processes: Cleaning, Drying, and Tail Gas Treatment
In the wafer cleaning process, the flow rates of nitrogen and hydrogen are controlled by thermal gas mass flow meters to achieve precise spraying of cleaning solution and rapid drying of the wafer, avoiding residual impurities after cleaning; At the same time, the circulation flow rate of the cleaning solution is monitored to ensure consistent cleaning effects for batches of wafers. In the tail gas treatment process, the emission flow rate of production tail gas (containing chlorine gas, hydrogen fluoride, etc., toxic gases) is monitored by ultrasonic flow meters to ensure that the tail gas is purified and discharged in compliance with standards, avoiding environmental pollution and safety risks.
Pressure Sensors
(1) Core Types Suitable for the Semiconductor Industry
In semiconductor manufacturing, most core processes need to be carried out in high vacuum or specific pressure environments. The core requirements for pressure sensors are high precision, corrosion resistance, and miniaturization. The mainstream type is the semiconductor piezoresistive pressure sensor (suitable for MEMS technology, with high accuracy), supplemented by capacitive (low pressure, micro-pressure measurement) and piezoelectric (dynamic pressure monitoring) sensors, which can cover a wide pressure measurement range of 10⁻⁹ Pa to 1 MPa.
(2) Core Application Scenarios
1. Pressure Control of Vacuum Chambers: Supporting Core Processes
For processes such as lithography, etching, and thin film deposition, which all need to be carried out in a high vacuum environment (with a vacuum degree reaching 10⁻³ to 10⁻⁹ Pa), pressure sensors monitor the pressure changes in the chamber in real time and feed the signals back to the vacuum unit to dynamically adjust the speed and working state of the vacuum pump, maintaining a stable vacuum degree. If the vacuum degree is insufficient, it will cause problems such as film pinholes, uneven etching, and contamination of photomask, directly reducing wafer yield. Therefore, the pressure measurement accuracy needs to reach ±0.1% FS (full scale) for the entire range.
2. Pressure Regulation of Process Gases: Linking Flow Control Precisely
During the process gas transportation, pressure fluctuations directly lead to flow deviations, affecting process stability. Pressure sensors are linked with flow sensors to achieve "pressure-flow" dual closed-loop control, monitoring the gas pressure in the pipeline in real time, and dynamically adjusting the relief valve to avoid pressure fluctuations (within ±1%), especially suitable for the pressure monitoring of corrosive gases such as chlorine and hydrogen chloride, requiring special corrosion-resistant coatings to prevent sensor damage.
3. Packaging and Bonding Processes: Ensuring Adhesion Accuracy
In the processes of wafer bonding and chip packaging, pressure control directly determines product reliability. During wafer bonding, the piezoresistive pressure sensor precisely controls the bonding pressure (usually several millipascals to several tens of pascals), ensuring that the two wafers are tightly adhered without bubbles or misalignment, supporting advanced packaging processes such as stacked chips and chip packaging; in the plastic sealing process, the pressure of the plastic sealing material is monitored, and the pressure in the mold is dynamically adjusted to avoid chip deformation and insufficient filling of the plastic sealing material, improving the packaging qualification rate.
4. Equipment Safety Monitoring: Avoiding Leakage and Fault Risks
If there is a pressure leakage in the pipelines and chambers of semiconductor equipment, it will cause safety accidents and process failures. Pressure sensors monitor the pressure changes in vacuum chambers and process pipelines in real time. When the pressure exceeds the set threshold, an alarm is triggered and the process is cut off to prevent the leakage of corrosive gases and damage to the chamber; at the same time, the working pressure of vacuum pumps, compressors, etc. is monitored to promptly detect equipment overload, leakage, etc., extending the service life of the equipment.
Temperature Sensors
(1) Core Types Suitable for the Semiconductor Industry
The semiconductor process requires extremely high precision in temperature control. In some scenarios, the temperature must be within ±0.1℃. Common temperature sensors include thermal resistance sensors (PT100/PT1000, with high accuracy and good stability), thermocouple sensors (able to withstand high temperatures, suitable for scenarios ranging from 300 to 1800℃), and semiconductor thermistors (NTC/PTC, with small size and suitable for integration). The selection can be made based on the temperature control range and accuracy requirements.
(2) Core Application Scenarios
1. Lithography Process: Stabilizing the Temperature of Photoresist and Equipment
The viscosity and sensitivity of photoresist to temperature are extremely sensitive. Temperature deviations can lead to uneven coating and incomplete development. Temperature sensors monitor the temperature of the photoresist storage tank and coating platform in real time to maintain stable temperature (typically 23±0.5℃); at the same time, they monitor the temperature of the exposure machine lens to prevent the lens from deforming due to long-term operation and affecting the lithography accuracy, ensuring the consistency of line width.
2. Film Deposition and Annealing Process: Precise Temperature Control Ensures Crystal Quality
In CVD processes, the temperature of the reaction chamber is monitored by thermocouple sensors (300-1000℃), allowing for precise control of the reaction temperature to ensure complete and uniform reactions and pure film composition; in PVD processes, the temperatures of the target and substrate are monitored to prevent overheating of the target and control the temperature increase and decrease of the substrate to enhance the adhesion of the film. In the wafer annealing process, temperature sensors linked by thermal resistance and thermocouple sensors precisely control the temperature gradient, heating rate, and cooling rate of the annealing furnace to eliminate internal stress in the wafer and improve the crystal structure, thereby enhancing the electrical performance of the wafer.
3. Etching and Cleaning Processes: Regulating Reaction Efficiency
In wet etching, the etching rate is positively correlated with temperature. Temperature sensors monitor the temperature of the etching solution in real time and keep it within the set range (typically 25-40℃) to avoid excessive etching at high temperatures and incomplete etching at low temperatures; in dry etching, the plasma temperature is monitored to prevent damage to the circuit structure on the wafer due to high temperatures. In the cleaning process, the temperature of the cleaning solution is monitored to improve cleaning efficiency while avoiding damage to the oxide layer on the wafer surface due to high temperatures.
4. Equipment Maintenance: Preventing Overheating Failures
Semiconductor production equipment (vacuum pumps, compressors, cooling systems, transmission mechanisms) prone to overheating failures due to long-term high-speed operation. Temperature sensors monitor the temperatures of key parts of the equipment in real time. When the temperature exceeds the threshold, over-temperature protection and alarms are triggered to prevent equipment damage; at the same time, the temperature of the wafer transmission mechanism is monitored to prevent high temperatures from contaminating the wafer or affecting transmission accuracy, ensuring production continuity.
Level Sensors
(1) Core Types Suitable for the Semiconductor Industry
In semiconductor production, the liquids that need to be controlled include etching solution, cleaning solution, photoresist, deionized water, and waste liquid. These liquids are mostly corrosive and prone to contamination. The level sensors must meet the requirements of non-contact, corrosion resistance, and high precision. The mainstream types are capacitive level sensors (suitable for corrosive liquids), photoelectric level sensors (suitable for leak detection), and immersion level sensors (suitable for large storage tanks).
(2) Core Application Scenarios
1. Process Liquid Storage: Prevent Overflow and Supply Interruption
The process liquids such as etching solution, cleaning solution, and photoresist are stored in dedicated tanks. The level sensors monitor the liquid level height in real time and implement two-way warnings: when the liquid level is below the set threshold, a replenishment warning is triggered to prevent the process from being interrupted due to supply failure; when the liquid level is above the threshold, an overflow warning is triggered to prevent corrosive liquids from overflowing and polluting the production environment, damaging equipment and wafers. For corrosive liquids such as photoresist, an non-contact capacitive sensor is used to avoid contamination caused by the sensor contacting the liquid.
2. Pipeline Leak Detection: Avoid Safety Hazards
The joints and valves of the process liquid transportation pipelines (especially etching solution and hydrogen fluoride pipelines) are prone to leakage. The photoelectric level sensor is installed at the low point of the pipeline or at the joint, which can detect trace leaks. Once a leak is detected, an alarm is triggered immediately to prevent the spread of corrosive liquids and reduce equipment damage and wafer contamination, as well as minimize downtime losses.
3. Fluid Mixing and Water Supply: Ensure Precise Ratio
Semiconductor production requires a large amount of high-purity deionized water. The immersion level sensor monitors the liquid level in the deionized water storage tank to ensure stable water supply and avoid affecting processes such as cleaning and cooling due to insufficient water supply. In the chemical reagent mixing process, the liquid level in the mixing tank is monitored, combined with the stirring system and flow sensor, to ensure precise reagent mixing and avoid liquid overflow during the mixing process, ensuring process stability.
4. Waste Liquid Treatment: Compliance Control and Stable Process
The etching waste liquid and cleaning waste liquid produced during the production process need to be collected and treated uniformly. The level sensor monitors the liquid level in the waste liquid storage tank. When the liquid level reaches the set value, an emission warning is triggered to notify the staff to handle it in time to prevent waste liquid overflow from causing environmental pollution; at the same time, the liquid level of the waste liquid treatment equipment is monitored to ensure the stability of the treatment process and ensure that the waste liquid is discharged in compliance with standards.