Semiconductor Dry Etching Processes

High-Precision Modular Temperature Controller - Achieving Precise Temperature Control in the Dry Etching Process

The purpose of the etching process is to create specific patterns by removing certain areas on the surface of a wafer. This is typically achieved using either "wet" etching or "dry" etching methods. Wet etching uses a chemical solution to remove the thin film material from the wafer surface, producing the desired pattern. Dry etching (Reactive-Ion Etching, RIE), on the other hand, usually employs plasma technology to form patterns. It uses gas molecules or ions and free radicals generated by the plasma to physically sputter and chemically react with the wafer material, thereby removing the etched portions.

As semiconductor advanced processes continue to evolve, the process linewidths are shrinking, and the requirements for critical dimension (CD) accuracy and consistency are becoming increasingly strict. In the dry etching process, to achieve a stable and uniform etching rate, not only is precise control of gases and plasma required, but temperature control also plays a critical role. In addition to adjusting the temperature control PID for different process recipes, it is necessary to address temperature disturbances caused by introducing gases and plasma, and implement corresponding temperature control measures.

Solution Introduction

Temperature Control Challenges in Dry Etching Equipment

Complex Process Recipes

Temperature Disturbances

Heating Delay

In the dry etching process, temperature control is a crucial factor. The wafer is heated to a specific temperature using an electrostatic chuck (E-Chuck, ESC) heater, enabling efficient and uniform etching reactions.

The dry etching process involves introducing different gases in stages, where the plasma interacts with the wafer's thin film to carry out the etching reaction. However, the complexity of the process recipe and gas introduction can disrupt the stability of wafer temperature control, ultimately impacting the yield and quality of semiconductor devices.

The shape and linewidth of dry etching are governed by the sidewall deposition of etching byproducts, and the adhesion of these byproducts is strongly influenced by temperature. As gases are introduced and the plasma etching progresses, the wafer temperature is simultaneously cooled by gases and heated by plasma. To enhance the precision of etching and sidewall deposition, it is essential not only to precisely control the wafer’s heating by the electrostatic chuck, but also to account for the additional cooling and heating effects caused by the gases and plasma.

In addition, during the heating process, due to the wafer's thickness and the delay in temperature rise, the heater will continue to output heat toward the target temperature (SV). This overshoot can lead to excessive heating of the wafer, potentially affecting the quality of the components.
 
High-Precision Modular Temperature Controller DTDM Series
 
Challenge: Complex Process Recipes and Temperature Control
SV Target Temperature

Switching, PID Group

The temperature controller DTDM supports SV target temperature switching and PID group functions. When introducing different process recipes, system will switch to one of the four PID groups with suitable PID parameters based on different SV threshold ranges. By pre-setting up to four corresponding PID parameter groups, the electrostatic chuck can provide more precise heating for the wafer in each heating zone, ensuring the quality of wafer etching.








 
Challenge: Temperature Disturbances Caused by the Introduction of Gases and Plasma
Feed-Forward Control

To reduce the temperature disturbances caused by the introduction of gases and plasma, the temperature controller DTDM features a feed-forward control function. This function can simulate, predict, and pre-set temperature compensation for the temperature disturbances caused by known process behaviors. Upon detecting specific process behaviors, the system immediately performs proactive temperature compensation to maintain temperature stability.




 
Challenge: Delay in Wafer Heating
PID Cascade Control

The temperature controller DTDM supports cascade control, utilizing multiple temperature sensors to monitor the temperatures of both the wafer and the heater. It employs outer and inner loops to rapidly calculate the setpoint temperature (SV) and the current temperature (PV), and then outputs control commands in real-time. By leveraging the fast response and low-latency characteristics of the inner loop, the system quickly eliminates disturbances, achieving stable temperature control.





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