Process parameter optimization analysis of high-temperature SPM cleaning technology in chip manufacturing

Abstract  

With the advancement of integrated circuit technology, the requirements for surface cleanliness in chip cleaning processes are becoming increasingly stringent. High-temperature SPM (sulfuric acid-hydrogen peroxide mixture) cleaning technology, with its highly efficient organic removal capability, has become the core of advanced wet cleaning processes. This article systematically describes the process principles of high-temperature SPM technology and the impact mechanism of key process parameters (temperature, concentration, flow method) on cleaning performance. Through flow field modeling and optimization analysis, it provides theoretical support for equipment design and process improvement.

1. High-Temperature SPM Cleaning Technology

High-temperature SPM cleaning technology is based on a mixed solution of concentrated sulfuric acid (H₂SO₄) and hydrogen peroxide (H₂O₂), which removes organic contaminants (such as photoresist residue) from the wafer surface through oxidation reactions.

Its typical process parameters are:

- Solution ratio: The volume ratio of H₂SO₄ to H₂O₂ is 2:1 to 8:1;

- Temperature range: 90~280℃, infrared heating technology can instantaneously increase the solution temperature to above 130℃;

- Application scenarios: Photoresist stripping, post-etch cleaning, post-chemical mechanical polishing (CMP) cleaning, etc.

According to the equipment type, the process technology is divided into two categories:

1. Batch cleaning: Suitable for batch processing, uniform cleaning is achieved through immersion, but the cleaning capability is insufficient for technology nodes below 28 nm;

2. Single-wafer cleaning: Local cleaning efficiency is improved through spraying and wafer rotation, but high-temperature heating is required, resulting in increased chemical consumption.

In order to balance efficiency and environmental protection, advanced equipment adopts a two-step method of "batch + single wafer": First, preliminary cleaning is completed through the batch module, and then transferred to the single wafer module for fine processing to reduce sulfuric acid usage.

▲High-temperature SPM cleaning technology production line application

2. Analysis of Key Process Parameters

2.1 Cleaning solution temperature

Temperature is a core factor affecting the rate of oxidation reactions:

Batch equipment: The temperature stability is maintained through an online circulation system. Above 180℃, photoresist after ion implantation can be effectively removed;

Single-wafer equipment: Local rapid heating is achieved using infrared radiation. Precise temperature control is needed to avoid side reactions (such as H₂O₂ decomposition).

2.2 Cleaning solution concentration

The stability of the solution ratio directly affects the cleaning efficiency:

Challenges: High-temperature decomposition of H₂O₂ and reaction by-products (such as H₂O) can cause concentration fluctuations;

Solutions: Maintain constant chemical composition through real-time monitoring and an automatic replenishment system.

2.3 Cleaning solution flow method

Flow uniformity determines the cleaning effect on the wafer surface:

Batch equipment: It is necessary to optimize the tank design to avoid dead zones or short circuits in the flow field and ensure uniform liquid flow rate;

Single-wafer equipment: Comprehensive and consistent spray coverage is achieved through the synergistic effect of the swing arm and wafer rotation.

3. Directions for Cleaning Technology Optimization

Based on flow field simulation and experimental verification, the following optimization strategies can improve cleaning performance:

1. Uniform flow field design: Using computational fluid dynamics (CFD) to simulate the flow field distribution in the tank to reduce turbulence and dead corners;

2. Temperature-concentration coupled control: Develop a dynamic feedback system to simultaneously adjust the heating power and replenishment rate;

3. Environmental protection process improvement: Promote the two-step cleaning technology to reduce sulfuric acid usage and waste discharge.

Conclusion

High-temperature SPM cleaning technology, through precise control of temperature, concentration, and flow method, demonstrates high efficiency and environmental friendliness in chip manufacturing. Future research needs to further explore the synergistic optimization mechanism of process parameters and combine intelligent control technology to promote the development of cleaning equipment towards high precision and low energy consumption to meet the stringent requirements of advanced processes.

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