Pulse-Modulated Plasma Etching for Wafer Edge Rate Uniformity
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Solution Overview
Problem
Existing plasma etching technologies struggle to achieve uniform etching rates across the entire surface of a semiconductor wafer, particularly at the outer peripheral portion, leading to non-defective semiconductor device manufacturing challenges due to factors like plasma density differences and aspect ratio considerations.
Innovation Solution
A plasma processing apparatus utilizing pulse-modulated radio-frequency power with specific duration controls, including a first and second output duration for microwave and RF bias, allowing independent control of etching rate distributions through concave and convex distributions to achieve desired etching rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma etching is used, then etching can be performed on semiconductor devices, but the etching rate distribution becomes non-uniform across the wafer surface
Solution Approach 1:
The patent applies periodic action by dividing the plasma etching process into multiple stages with different microwave power levels. The process alternates between a first stage with higher microwave power to generate sufficient plasma density, and a second stage with reduced microwave power to achieve uniform etching rates. This periodic modulation of power levels resolves the contradiction by enabling both adequate plasma generation and uniform etching control.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting microwave power levels between different process stages. The microwave power is reduced from the first level (sufficient for plasma generation) to the second level (optimized for uniform etching). This parameter modulation allows the system to overcome the non-uniform etching rate distribution while maintaining ease of operation through automated control.
2Manufacturing precision
If microwave power is reduced to improve etching uniformity, then side etching is reduced, but plasma density becomes insufficient
Solution Approach 1:
The patent applies preliminary action by first establishing plasma with sufficient microwave power in the first stage, then transitioning to reduced power in the second stage. This sequential approach ensures that plasma density is adequate during the initial phase, and then maintained at appropriate levels during the uniform etching phase, resolving the contradiction between plasma density requirements and etching uniformity.
Solution Approach 2:
The periodic alternation between high power (for plasma generation) and reduced power (for uniform etching) allows the system to achieve both sufficient plasma density and improved etching rate distribution. The timing and duration of each stage are optimized to ensure plasma maintenance while achieving uniform etching.
3Productivity
If RF bias is turned on during plasma ignition, then etching can start immediately, but unstable plasma causes excessive side etching
Solution Approach 1:
The patent implements preliminary action by turning on the microwave power first to establish stable plasma before activating the RF bias. This sequence ensures that plasma is stable and controlled before the etching process begins, preventing excessive side etching while maintaining efficient productivity through the subsequent coordinated operation of both microwave and RF systems.
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
The apparatus effectively controls etching rate distributions on the wafer's outer peripheral portion, ensuring uniformity and desired etching rates, addressing the non-uniformity issues in existing technologies.
Implementation Method 1
plasma is generated by a microwave power supply
Implementation Method 2
ions and radicals generated by the microwave generated by a microwave power supply react with the sample
Implementation Method 3
a frequency of a microwave and a cyclotron frequency of an electron resonate
Data Source
AI summary
A plasma processing apparatus for controlling a length of a first output duration of a microwave power and a length of a second output duration to obtain a desired etching rate distribution of a wafer, in which one cycle of pulse modulation includes a first output duration of a microwave output and a second output duration having a finite value smaller than the first output, and an OFF duration. An etching rate distribution is a concave distribution for the first output and a convex distribution for the second output, and a control device controls a pulse generator such that when the etching rate distribution is the concave distribution, a length of the first output duration is longer than a length of the second output duration, and when the etching rate distribution is the convex distribution, the length of the first output duration is shorter than the length of the second output duration.