Recess Sidewall Etching Using Dissolved Oxygen Switching
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Solution Overview
Problem
Existing substrate processing methods fail to uniformly etch the side surfaces of recesses on substrates, such as semiconductor wafers, while efficiently reducing processing time, particularly when patterns or non-uniform etching is required.
Innovation Solution
A method involving two-step etching using alkaline etching liquids with different dissolved oxygen concentrations, where the first liquid has a low dissolved oxygen concentration and the second liquid has a higher concentration, allowing for non-uniform etching of the side surfaces of recesses by oxidizing the surface layer selectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single alkaline etching liquid is supplied to etch the side surface of the recess, then the etching process is simple and processing time is reduced, but the etching uniformity deteriorates and cannot achieve intentional non-uniform etching
Solution Approach 1:
The etching process is divided into two distinct steps: a first etching step using alkaline etching liquid with low dissolved oxygen concentration to achieve uniform etching, and a second etching step using alkaline etching liquid with high dissolved oxygen concentration to achieve non-uniform etching. This segmentation allows each step to optimize for its specific etching characteristic, resolving the contradiction between processing speed and etching uniformity control.
Solution Approach 2:
The dissolved oxygen concentration of the alkaline etching liquid is changed between etching steps. The first etching liquid has low dissolved oxygen concentration (0.5-5 ppm) for uniform etching, while the second etching liquid has high dissolved oxygen concentration (5-20 ppm) for non-uniform etching. This parameter change enables intentional control of etching uniformity while maintaining efficient processing.
2Speed
If alkaline etching liquid with high dissolved oxygen concentration is used, then etching speed increases, but etching uniformity deteriorates due to oxidation of the surface layer
Solution Approach 1:
The first etching step using low dissolved oxygen concentration alkaline etching liquid is performed preliminarily to remove the oxide film formed during recess formation and to create a uniform etching surface. This preliminary action prepares the surface for the second etching step, ensuring that the high dissolved oxygen concentration liquid can achieve its intended non-uniform etching effect without compromising overall uniformity.
Solution Approach 2:
The etching process uses periodic action by alternating between two different etching liquids with different dissolved oxygen concentrations. The first periodic action (low oxygen concentration) provides uniform etching baseline, while the second periodic action (high oxygen concentration) introduces controlled non-uniformity. This periodic alternation resolves the contradiction by applying each liquid's strengths at appropriate intervals.
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 enables high-speed, non-uniform etching of substrate side surfaces, reducing processing time and achieving precise control over the etching process, minimizing irregularities and uniformity issues.
Implementation Method 1
a first etching step of etching the etching target exposed on the side surface of the recess by supplying the substrate with alkaline first etching liquid in which inert gas is dissolved, and a second etching step of etching the etching target exposed on the side surface of the recess by supplying the substrate with alkaline second etching liquid in which dissolution gas is dissolved
Implementation Method 2
When liquid having high dissolved oxygen concentration is supplied to the etching target, the surface layer of the etching target changes to silicon oxide. Silicon oxide is not etched or hardly etched by alkaline etching liquid.
Data Source
AI summary
According to the present invention, a substrate W is provided with a recess 95. The width of the recess 95 is smaller than the depth of the recess 95. An etching target which is at least one of a single crystal of silicon, a polysilicon and an amorphous silicon is exposed in at least a part of the upper part of a lateral surface 95s and in at least a part of the lower part of the lateral surface 95s. The etching target is etched by supplying an alkaline first etching liquid, in which an inert gas is dissolved, to the substrate W. The etching target is etched by supplying an alkaline second etching liquid, in which a dissolution gas is dissolved, and which has a dissolved oxygen concentration higher than that of the first etching liquid, to the substrate W before or after the first etching liquid is supplied to the substrate W.