Pulsed Bias Plasma Etching for Microloading Control
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Solution Overview
Problem
During semiconductor wafer processing, high aspect ratio features lead to microloading issues where open features etch faster than dense features, potentially causing damage when attempting to complete etching of dense features, as the etching process can extend into underlying layers.
Innovation Solution
A method involving a steady state etch gas flow with a pulsed bias voltage between 1 to 10,000 Hz is used to form a plasma for etching, balancing the etch rate between wide and narrow features, reducing microloading by controlling the etch and deposition processes through duty cycle and recipe adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If continuous etching is performed to complete etching of dense features, then dense features are fully etched, but open features are over-etched into underlying layers causing damage
Solution Approach 1:
The patent applies periodic pulsed bias voltage during the etching process to control the etch rate dynamically. By pulsing the bias voltage at specific frequencies, the process alternates between etching phases and deposition phases, enabling precise control over etch depth uniformity across features with different aspect ratios while preventing over-etching damage to open features
2Object-affected harmful factors
If etching process is stopped early to prevent over-etching, then open features are protected, but dense features remain partially etched
Solution Approach 1:
The pulsed bias voltage creates periodic cycles of etching and deposition that allow the process to continue beyond what would traditionally be considered the endpoint. The deposition phases refill material in open features while the etching phases progress dense features, achieving uniform etch depth without stopping early and leaving dense features partially etched
3Productivity
If higher etch power is used to etch dense features, then etch rate increases, but microloading effect worsens and open features etch even faster
Solution Approach 1:
By using pulsed bias voltage with controlled duty cycles, the patent modulates the etch rate to be consistent across features of different aspect ratios. The periodic deposition phases compensate for the microloading effect by refilling material in open features during deposition, allowing higher overall etch power to be used while maintaining microloading control and achieving uniform etch depth
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 effectively reduces microloading, ensuring that both wide and narrow features are etched to the same depth without damaging underlying layers, maintaining the integrity of semiconductor devices by balancing etch and deposition rates.
Implementation Method 1
A steady state RF power is provided to form a plasma from the etch gas in the plasma chamber
Data Source
AI summary
A method for etching a conductive layer through a mask with wider and narrower features is provided. A steady state etch gas is flowed. A steady state RF power is provided to form a plasma from the etch gas. A pulsed bias voltage is provided during the steady state etch gas flow, wherein the pulsed bias voltage has a frequency between 1 to 10,000 Hz. Wider and narrower features are etched into the conductive layer using the plasma formed from the etch gas.