Silicon Substrate Etching with Alternating Alkaline Liquids
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Solution Overview
Problem
Current substrate processing methods using TMAH with propylene glycol reduce etching speed and anisotropy, leading to increased processing time, and alkaline etching liquids struggle to achieve high selectivity for silicon single crystal or polysilicon while inhibiting silicon oxide or silicon nitride etching.
Innovation Solution
A substrate processing method involving alternating steps of alkaline first and second etching liquids, where the second etching liquid contains a chemical compound that inhibits hydroxide ion contact with the etching target, reducing etching speed differences between silicon crystal planes and enhancing etching uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If alkaline etching liquid containing propylene glycol is supplied to the substrate, then anisotropy of etching is lowered, but the etching speed is lowered and processing time increases
Solution Approach 1:
The etching process is divided into multiple sequential steps, each using different alkaline etching liquids with varying propylene glycol concentrations. The first etching step uses a liquid with lower propylene glycol concentration for faster etching, while subsequent steps use liquids with higher propylene glycol concentrations to reduce anisotropy and achieve uniform etching.
Solution Approach 2:
The concentration of propylene glycol in the alkaline etching liquid is changed between different etching steps. By adjusting this parameter, the etching characteristics are optimized for each step - initially prioritizing speed, then transitioning to uniformity and anisotropy control.
2Productivity
If acid etching liquid is used, then the etching target is uniformly etched in a short time, but high selectivity for silicon single crystal or polysilicon while inhibiting silicon oxide or silicon nitride etching cannot be obtained
Solution Approach 1:
The invention changes the chemical composition parameters of the etching liquid by using alkaline solutions with controlled propylene glycol concentrations. This allows achieving both high etching speed and uniformity while maintaining high selectivity for silicon single crystal or polysilicon over silicon oxide or silicon nitride, which acid etching liquids cannot achieve.
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 allows for uniform etching of silicon single crystal and polysilicon while shortening processing time by alternating between high-speed, anisotropic etching with alkaline first liquid and low-anisotropy, slower etching with the second liquid, maintaining high selectivity and reducing oxidation.
Implementation Method 1
the second etching liquid containing a chemical compound that inhibits contact of a hydroxide ion and the etching target
Implementation Method 2
a first etching step of etching the etching target by supplying the substrate with alkaline first etching liquid
Data Source
AI summary
In the present invention, an alkaline first etching liquid is fed to a substrate, whereby an etching target representing a silicon monocrystal and/or polysilicon is etched. An alkaline second etching liquid is fed to the substrate after or before the first etching liquid is fed to the substrate, whereby the etching target is etched, the second etching liquid containing a compound that inhibits contact between hydroxide ions and the etching target, the difference between the maximum value and the minimum value of the etching speed with respect to the (110) face, the (100) face, and the (111) face of silicon being smaller in the second etching liquid than in the first etching liquid, and the maximum value of the etching speed being smaller in the second etching liquid than in the first etching liquid.