Semiconductor Recess Etching With Masked Catalyst Access Control
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Solution Overview
Problem
Current metal-assisted chemical etching methods for semiconductor surfaces face challenges in forming high aspect ratio recesses with precise control, leading to process defects and reduced electric capacitance due to uneven catalyst distribution and etching agent access.
Innovation Solution
The method involves forming a first layer with openings on a semiconductor substrate, followed by a noble metal catalyst layer and a second mask layer to control etching agent access, using an etching agent containing an oxidizer and hydrogen fluoride to create recesses with controlled dimensions, and subsequently forming electrodes and dielectric layers to achieve high electric capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If metal-assisted chemical etching is used to form high aspect ratio recesses, then the aspect ratio of recesses is improved, but uniformity of etching and catalyst distribution deteriorates
Solution Approach 1:
The etching process is segmented into multiple stages with different etching agents. First, a high concentration etching agent is used to rapidly form the recess to the target depth. Then, a low concentration etching agent is used to uniformly etch the sidewalls and remove catalyst particles. This segmentation allows achieving high aspect ratio while maintaining uniformity.
Solution Approach 2:
The catalyst layer is pre-formed on the semiconductor surface before etching begins. This preliminary action ensures uniform catalyst distribution that guides the etching process, enabling controlled formation of high aspect ratio recesses with uniform sidewalls.
2Productivity
If high concentration etching agent is used to increase etching speed, then productivity is improved, but etching uniformity and catalyst removal deteriorate
Solution Approach 1:
The etching process is divided into two sequential stages with different concentrations. The first stage uses high concentration etching agent for rapid depth formation, while the second stage uses low concentration agent for uniform sidewall etching and catalyst removal. This resolves the contradiction between speed and uniformity.
Solution Approach 2:
The concentration parameter of the etching agent is changed between stages. High concentration is used initially for speed, then switched to low concentration for uniformity and catalyst removal. This dynamic parameter adjustment resolves the contradiction.
3Reliability
If catalyst layer is formed to enable MacEtch, then etching capability is improved, but non-uniform catalyst distribution causes process defects
Solution Approach 1:
The catalyst layer is formed as a preliminary step before etching, ensuring uniform distribution across the surface. This pre-formed uniform catalyst layer guides the etching process uniformly, preventing process defects while maintaining etching capability.
Solution Approach 2:
The catalyst layer provides localized catalytic activity at the semiconductor surface, enabling controlled etching. The uniform local distribution of catalyst particles ensures consistent etching behavior across different regions, preventing defects.
4Quantity of substance
If recess depth is increased to form high aspect ratio structures, then capacitance is improved, but etching control and catalyst removal become difficult
Solution Approach 1:
The etching process is segmented into depth-forming stage and sidewall-forming stage. The first stage rapidly creates the required depth for high capacitance, while the second stage uniformly etches sidewalls and removes catalyst. This segmentation maintains control even at high aspect ratios.
Solution Approach 2:
The etching agent concentration is changed from high to low as the process progresses. This parameter change enables achieving greater depths while maintaining uniformity and catalyst removal, supporting higher capacitance formation.
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 the formation of capacitors with large electric capacitance while minimizing process defects by ensuring uniform catalyst distribution and precise etching, allowing for the creation of recesses with optimal dimensions for electrode and dielectric layer formation.
Implementation Method 1
Metal-assisted chemical etching (MacEtch) is a method of etching a semiconductor surface using a noble metal as a catalyst
Implementation Method 2
etching the substrate with an etching agent containing an oxidizer and hydrogen fluoride
Implementation Method 3
forming a catalyst layer containing a noble metal on a portion(s) of the main surfaces exposed in the plurality of openings or the one or more openings by a plating method
Data Source
AI summary
According to an embodiment, an etching method includes forming a first layer on a substrate having a main surface including first and second regions adjacent to each other, the first layer including a portion covering the first region and having a plurality of openings or one or more openings defining a plurality of island-shaped portions, and the first layer further including a portion as a continuous layer covering the second region, forming a catalyst layer an a portion(s) of the main surface exposed in the openings by plating, forming a second layer to cover a portion of the catalyst layer adjacent to a boundary between the first and second regions and expose a portion of the catalyst layer spaced apart from the boundary, and etching the substrate in a presence of the catalyst layer and the second layer.