Heated Wafer Support to Mitigate First Wafer Effect
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Solution Overview
Problem
Current plasma etching and cleaning processes in semiconductor manufacturing suffer from the 'first wafer effect,' where the first wafer processed after chamber cleaning is under-processed, leading to defects and instability, and existing solutions either increase processing time or require frequent chamber cleaning.
Innovation Solution
A method involving exposing wafers to a plasma etching environment at a controlled temperature without immediate chamber cleaning, using a cleaning plasma with Ar and O2, and maintaining the wafer support at a higher temperature to absorb etchants on the chamber walls rather than the wafers, reducing the first wafer effect and extending burn-in time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chamber cleaning is performed frequently to maintain process stability, then process stability is improved, but productivity decreases due to increased downtime
Solution Approach 1:
The patent applies preliminary action by performing a burn-in process that deposits a protective layer on chamber walls before production wafers are processed. This preventive measure eliminates the need for frequent chamber cleaning, as the deposited layer prevents etch residue accumulation that would otherwise require periodic cleaning interruptions.
2Reliability
If chamber cleaning is performed after processing wafers to remove etch residues, then process stability is improved, but the first wafer effect occurs causing manufacturing precision degradation
Solution Approach 1:
The burn-in process performs preliminary deposition of a protective layer on chamber walls before production processing begins. This pre-conditioning prevents the first wafer effect by ensuring consistent surface properties from the first production wafer, eliminating the need to skip or reprocess wafers.
Solution Approach 2:
The patent changes the physical-chemical parameters of the chamber surface by depositing a controlled layer during burn-in. This modification alters the surface energy and composition of chamber walls, preventing unwanted etch residue adhesion and ensuring uniform etching on the first production wafer.
3Manufacturing precision
If seasoning or burn-in process is extended to fully eliminate the first wafer effect, then manufacturing precision is improved, but loss of time increases
Solution Approach 1:
The patent optimizes burn-in parameters including gas composition (CHF3, CF4, or SF6), pressure (10-100 mTorr), power (50-500W), and duration (1-24 hours) to achieve effective chamber conditioning in a time-efficient manner. These parameter optimizations enable sufficient protective layer deposition without excessive burn-in time.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces the decrease in etching efficiency for the first wafer post-chamber cleaning, eliminates the first wafer effect, and decreases burn-in time by ensuring etchants primarily absorb on chamber walls, thereby improving processing stability and throughput.
Implementation Method 1
capacitive or inductively coupled plasmas of etchant gases
Implementation Method 2
the energetic plasma species rapidly erode the chamber walls and chamber components
Implementation Method 3
cleaning plasma with Ar and O2
Implementation Method 4
maintaining the wafer support within the chamber at a second temperature greater than the first temperature
Data Source
AI summary
Embodiments of the disclosure relate to methods for reducing or eliminating the first wafer effect after chamber cleans for plasma etch processes. In some embodiments, the wafer support is maintained at an elevated temperature relative to the etch process. In some embodiments, the etch process is a NF3+NH3 plasma etch to remove native oxides from a silicon substrate.