Substrate Etching with Polymer-Filled Grain Boundaries for Smoother Surfaces
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Solution Overview
Problem
Existing substrate processing methods face challenges in reducing the roughness of the front surface due to differences in etching rates between crystal grains and crystal grain boundaries, leading to uneven etching and increased surface roughness.
Innovation Solution
A substrate processing method involving a first etching step, a polymer layer forming step where a polymer layer is embedded in the crystal grain boundary, and a second etching step, which suppresses the etching liquid from entering the crystal grain boundary, thereby reducing surface roughness by controlling the etching rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If etching liquid is supplied to etch the processing object layer, then etching progresses, but the etching rate differs between crystal grains and crystal grain boundaries causing surface roughness
Solution Approach 1:
The patent applies local quality by forming a polymer layer specifically at the crystal grain boundaries through selective supply of polymer-containing liquid. This creates a localized modification where only the grain boundary regions receive the polymer coating, while the crystal grain centers remain unaffected. The polymer layer locally changes the etching characteristics at grain boundaries, making them more resistant to etching compared to the grain centers, thereby achieving uniform etching rates across different regions and reducing surface roughness.
Solution Approach 2:
The patent employs preliminary action by forming the polymer layer at the crystal grain boundaries before the main etching process. This preparatory step modifies the grain boundary regions in advance, creating a protective polymer coating that will regulate the etching rate during subsequent etching steps. By performing this modification beforehand, the patent ensures that when etching liquid is supplied, the grain boundaries already have the polymer layer in place to control the etching rate and prevent excessive etching that would cause surface roughness.
2Manufacturing precision
If polymer layer is formed at crystal grain boundary, then etching rate uniformity improves, but process complexity increases
Solution Approach 1:
The patent applies universality by using the polymer-containing liquid to serve multiple functions: it acts as both the polymer source for forming the protective layer and as a vehicle for selective delivery to grain boundaries. The same liquid phase delivers the polymer material and enables the selective coating process, reducing the need for separate application steps and simplifying the overall process while achieving the desired etching rate uniformity.
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 method effectively reduces the surface roughness of the processing object layer by ensuring a higher etching rate at the crystal grain boundary, allowing for more uniform etching and improved substrate processing outcomes.
Implementation Method 1
The etching liquid more easily permeates the crystal grain boundary than the crystal grains. Therefore, etching rate with respect to the crystal grain boundary is higher than etching rate with respect to the crystal grains.
Implementation Method 2
at least portion of the polymer layer is embedded in a crystal grain boundary which is a boundary of the crystal grains
Data Source
AI summary
An etching liquid is supplied to a principal surface of a substrate that has the principal surface on which a processing object layer having a plurality of crystal grains is exposed (first etching step). A polymer-containing liquid containing a polymer is supplied to the principal surface of the substrate after the first etching step, and a polymer layer at least portion of which is embedded in a crystal grain boundary which is a boundary of the crystal grains is formed (polymer layer forming step). The processing object layer is etched by supplying an etching liquid to the principal surface of the substrate after the polymer layer forming step (second etching step).