Deep Understanding of the SPC System in Wafer Manufacturing

1. Overview of the SPC System

SPC is a method that uses statistical techniques to monitor and control manufacturing processes. Its core function is to detect anomalies in the production process by collecting and analyzing real-time data, helping engineers make timely adjustments and decisions. The goal of SPC is to reduce variation in the production process, ensuring product quality remains stable and meets specifications.

SPC is used in the etching process to:

Monitor critical equipment parameters (e.g., etch rate, RF power, chamber pressure, temperature, etc.)

Analyze key product quality indicators (e.g., linewidth, etch depth, edge roughness, etc.)

By monitoring these parameters, engineers can detect trends indicating equipment performance degradation or deviations in the production process, thus reducing scrap rates.

2. Basic Components of the SPC System

The SPC system is composed of several key modules:

Data Collection Module: Collects real-time data from equipment and process flows (e.g., through FDC, EES systems) and records important parameters and production outcomes.

Control Chart Module: Uses statistical control charts (e.g., X-Bar chart, R chart, Cp/Cpk chart) to visualize process stability and help determine if the process is in control.

Alarm System: Triggers alarms when critical parameters exceed control limits or show trend changes, prompting engineers to take action.

Analysis and Reporting Module: Analyzes the root cause of anomalies based on SPC charts and regularly generates performance reports for the process and equipment.

3. Detailed Explanation of Control Charts in SPC

Control charts are one of the most commonly used tools in SPC, helping to distinguish between "normal variation" (caused by natural process variations) and "abnormal variation" (caused by equipment failures or process deviations). Common control charts include:

X-Bar and R Charts: Used to monitor the mean and range within production batches to observe if the process is stable.

Cp and Cpk Indices: Used to measure process capability, i.e., whether the process output can consistently meet specification requirements. Cp measures the potential capability, while Cpk considers the deviation of the process center from the specification limits.

For example, in the etching process, you might monitor parameters like etch rate and surface roughness. If the etch rate of a certain piece of equipment exceeds the control limit, you can use control charts to determine whether this is a natural variation or an indication of equipment malfunction.

4. Application of SPC in Etching Equipment

In the etching process, controlling equipment parameters is critical, and SPC helps improve process stability in the following ways:

Equipment Condition Monitoring: Systems like FDC collect real-time data on key parameters of etching equipment (e.g., RF power, gas flow) and combine this data with SPC control charts to detect potential equipment issues. For instance, if you see that the RF power on a control chart is gradually deviating from the set value, you can take early action for adjustment or maintenance to avoid impacting product quality.

Product Quality Monitoring: You can also input key product quality parameters (e.g., etch depth, linewidth) into the SPC system to monitor their stability. If some critical product indicators gradually deviate from the target values, the SPC system will issue an alarm, indicating that process adjustments are needed.

Preventive Maintenance (PM): SPC can help optimize the preventive maintenance cycle for equipment. By analyzing long-term data on equipment performance and process results, you can determine the optimal time for equipment maintenance. For example, by monitoring RF power and ESC lifespan, you can determine when cleaning or component replacement is needed, reducing equipment failure rates and production downtime.

5. Daily Usage Tips for the SPC System

When using the SPC system in daily operations, the following steps can be followed:

Define Key Control Parameters (KPI): Identify the most important parameters in the production process and include them in SPC monitoring. These parameters should be closely related to product quality and equipment performance.

Set Control Limits and Alarm Limits: Based on historical data and process requirements, set reasonable control limits and alarm limits for each parameter. Control limits are usually set at ±3σ (standard deviations), while alarm limits are based on the specific conditions of the process and equipment.

Continuous Monitoring and Analysis: Regularly review SPC control charts to analyze data trends and variations. If some parameters exceed control limits, immediate action is needed, such as adjusting equipment parameters or performing equipment maintenance.

Abnormality Handling and Root Cause Analysis: When an abnormality occurs, the SPC system records detailed information about the incident. You need to troubleshoot and analyze the root cause of the abnormality based on this information. It is often possible to combine data from FDC systems, EES systems, etc., to analyze whether the issue is due to equipment failure, process deviation, or external environmental factors.

Continuous Improvement: Using the historical data recorded by the SPC system, identify weak points in the process and propose improvement plans. For example, in the etching process, analyze the impact of ESC lifespan and cleaning methods on equipment maintenance cycles and continuously optimize equipment operating parameters.

6. Practical Application Case

As a practical example, suppose you are responsible for the etching equipment E-MAX, and the chamber cathode is experiencing premature wear, leading to an increase in D0 (BARC defect) values. By monitoring the RF power and etch rate through the SPC system, you notice a trend where these parameters gradually deviate from their set values. After an SPC alarm is triggered, you combine data from the FDC system and determine that the issue is caused by unstable temperature control inside the chamber. You then implement new cleaning methods and maintenance strategies, eventually reducing the D0 value from 4.3 to 2.4, thereby improving product quality.

7.In XINKEHUI you can get.

At XINKEHUI, you can achieve the perfect wafer, whether it's a silicon wafer or a SiC wafer. We specialize in delivering top-quality wafers for various industries, focusing on precision and performance.