1、 Introduction

The semiconductor industry, as the core pillar of modern information technology, has extremely high requirements for equipment accuracy and stability in its manufacturing process. In critical processes such as wafer manufacturing and chip packaging, micrometer or even nanometer level positioning accuracy is the key to ensuring product quality and production efficiency. Traditional rotary motors achieve linear motion through mechanical transmission mechanisms such as screws and gears, which suffer from mechanical wear, elastic deformation, and clearance errors, making it difficult to meet high-precision positioning requirements. Linear motors drive loads directly through electromagnetic force, eliminating intermediate transmission links, and have the advantages of simple structure, fast dynamic response, and high positioning accuracy. They have become the preferred technology in the field of semiconductor precision positioning.

2、 The working principle and structural characteristics of linear motors

Linear motors are based on the principle of electromagnetic induction, which directly converts electrical energy into linear motion mechanical energy. Its basic structure is similar to that of a rotating motor, consisting of a stator and a rotor, but the stator and rotor are unfolded in a straight line form. When an alternating current is applied to the stator winding, a traveling wave magnetic field is generated, which interacts with the permanent magnet or induced current in the rotor, generating electromagnetic thrust and driving the rotor to move in a straight line direction. According to the different ways of generating magnetic fields, linear motors can be divided into permanent magnet synchronous linear motors (PMLSM), induction linear motors (ILM), and switched reluctance linear motors (SRM).

The structural characteristics of linear motors give them the following advantages:

No mechanical contact: There is no direct mechanical connection between the rotor and stator, eliminating mechanical wear and elastic deformation, and improving motion accuracy and lifespan.

High dynamic response: Due to the absence of an intermediate transmission mechanism, linear motors have faster acceleration and speed response, making them suitable for high-speed and high-precision positioning.

High positioning accuracy: Through high-precision encoders and closed-loop control, linear motors can achieve sub micron or even nanometer level positioning accuracy.

Modular design: Linear motors can be flexibly designed for length and stroke according to application requirements, making it easy to integrate and expand.

3、 The core requirement of semiconductor precision positioning for linear motors

In semiconductor manufacturing, linear motors are mainly used in wafer transfer, wafer inspection, photolithography alignment, packaging testing, and other processes. These applications pose the following core requirements for linear motors:

Nano level positioning accuracy: As the chip feature size shrinks, the positioning error needs to be controlled within the nanometer range to avoid wafer offset or alignment deviation.

High speed and high acceleration: In order to improve production efficiency, linear motors need to have fast start stop and high-speed motion capabilities, while maintaining smooth motion.

Low vibration and low noise: Semiconductor equipment is sensitive to vibration and noise, and linear motors need to reduce vibration and noise levels through optimized structure and control algorithms.

High reliability and long lifespan: Semiconductor production lines require continuous operation, and linear motors need to have high reliability and long lifespan to reduce maintenance and downtime.

4、 The key technology of linear motor in semiconductor precision positioning

（1） High precision drive control technology

The positioning accuracy of linear motors is directly affected by drive control technology. To achieve nanoscale positioning, high-resolution encoders (such as grating rulers, magnetic grating rulers) and closed-loop control algorithms are required. Key technologies include:

Current vector control: By using vector control algorithms to accurately control the amplitude and phase of stator current, precise adjustment of thrust can be achieved.

Feedforward compensation: Combining load models and motion trajectory planning, compensating for thrust fluctuations and friction forces in advance to improve dynamic response speed.

Model Predictive Control (MPC): Based on the system model, predict future states, optimize control inputs, and reduce positioning errors.

（2） Error compensation technology

The positioning error of linear motors mainly comes from mechanical error, thermal error, electromagnetic error, etc. To improve positioning accuracy, error compensation technology is required:

Mechanical error compensation: Calibrate mechanical errors through devices such as laser interferometers, establish error models, and perform real-time compensation in the control system.

Thermal error compensation: Monitor the temperature changes of the motor, establish a thermal deformation model, and compensate for positioning errors caused by thermal expansion.

Electromagnetic error compensation: Optimize magnetic field distribution to reduce thrust fluctuations caused by cogging and end effects.

（3） Vibration suppression technology

Linear motors are prone to vibration during high-speed motion, which affects positioning accuracy and equipment lifespan. Vibration suppression technology includes:

Structural optimization: Optimize the motor structure through finite element analysis to increase the natural frequency and avoid resonance.

Active vibration control: using acceleration sensors to monitor vibration in real time, applying reverse force through actuators such as piezoelectric ceramics to suppress vibration.

Friction compensation: Reduce the friction between the rotor and the guide rail, and lower the vibration source.

（4） Thermal management technology

Linear motors generate a large amount of heat during high-speed motion, leading to thermal deformation and performance degradation. Thermal management technology includes:

Heat dissipation design: Optimize the motor structure, add heat dissipation fins or water cooling channels to improve heat dissipation efficiency.

Thermal isolation: Use insulation materials to isolate heat sources and reduce the impact on loads.

Temperature compensation: Monitor motor temperature, adjust control parameters, and compensate for performance changes caused by thermal effects.

5、 Application case of linear motor in semiconductor precision positioning

（1） Wafer transfer system

In wafer manufacturing, the wafer transfer system driven by linear motors can achieve high-speed and high-precision transfer of wafers between multiple process equipment. Through closed-loop control and error compensation technology, the positioning accuracy can reach ± 1 μ m, meeting the requirements of wafer alignment.

（2） Photolithography alignment system

Photolithography machine is the core equipment in semiconductor manufacturing, and its alignment accuracy directly affects chip yield. The alignment platform driven by a linear motor can achieve nanometer level positioning, combined with visual inspection and closed-loop control, to ensure the alignment accuracy between the lithography pattern and the wafer.

（3） Encapsulation testing equipment

In chip packaging testing, the testing probe station driven by a linear motor can achieve high-precision contact between the probe and the chip pad, improving testing reliability and efficiency.

6、 Conclusion

Linear motors have shown great potential in the field of semiconductor precision positioning due to their advantages of high precision, high speed, high acceleration, and no mechanical contact. However, to achieve nanoscale positioning accuracy and stable operation, key technical issues such as drive control, error compensation, vibration suppression, and thermal management need to be addressed. In the future, with the development of new materials, processes, and algorithms, linear motors will further optimize their performance and provide more efficient and reliable positioning solutions for semiconductor manufacturing.

references

(Relevant technical literature, research reports, or patents can be listed here, but due to space limitations, they will not be expanded at this time)

This article provides comprehensive technical references for technical personnel in related fields by systematically analyzing the key technologies of linear motors in semiconductor precision positioning. With the continuous advancement of semiconductor technology, linear motors will play a more important role in future semiconductor manufacturing.