Epitaxially Coated Silicon Wafer Flatness Control
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Solution Overview
Problem
Existing methods for producing epitaxially coated silicon wafers often result in poor local flatness values, particularly in the edge region, making them unsuitable for future generations of electronic components with narrower line widths due to the impact of susceptor etching treatments on the silicon wafers.
Innovation Solution
A method where silicon wafers are polished and then coated in an epitaxy reactor with a hydrogen atmosphere and HCl etching medium, followed by regular susceptor etching treatments and hydrophilization, using a hydrophilic wafer to saturate the susceptor with oxygen, preventing hydrogen penetration and native oxide removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If susceptor etching treatments are performed regularly to maintain susceptor cleanliness, then susceptor performance is maintained, but hydrogen penetrates into the silicon wafer and native oxide is removed, degrading local flatness
Solution Approach 1:
A silane-based coating is applied to the susceptor surface as an intermediary layer. This coating acts as a barrier that prevents hydrogen from penetrating into the silicon wafer during etching treatments, while still allowing the susceptor to be cleaned and maintained. The coating thus mediates between the need for susceptor maintenance and the need to preserve wafer quality.
Solution Approach 2:
The susceptor is pre-coated with a silane-based material before the etching process begins. This preliminary action creates a protective barrier that anticipates and prevents the harmful effect of hydrogen penetration during subsequent etching treatments, thereby preserving the native oxide layer on the silicon wafer.
2Reliability
If epitaxial coating is performed to improve electrical properties and reduce defects, then component reliability is improved, but local flatness deteriorates due to edge region issues
Solution Approach 1:
The silane-based coating on the susceptor serves as an intermediary that prevents direct contact between hydrogen and the silicon wafer during epitaxial coating and etching processes. This eliminates the edge region flatness degradation that normally occurs, allowing epitaxial coating to proceed while maintaining high local flatness values.
3Manufacturing precision
If silicon wafers are polished to achieve good local flatness, then manufacturing precision is improved, but yield is reduced due to edge exclusion requirements
Solution Approach 1:
The silane-based coating on the susceptor prevents hydrogen-induced flatness degradation during processing, which eliminates the need for large edge exclusion zones. This allows a greater percentage of the wafer area to be usable, thereby increasing yield while maintaining high local flatness standards.
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 significantly improves the local flatness of epitaxially coated silicon wafers, achieving maximum SFQRmax values of 0.01-0.025 μm, suitable for producing electronic components with line widths less than 0.022 μm, and increases the yield of wafers with defined maximum flatness values.
Implementation Method 1
pretreated under a hydrogen atmosphere in a first step
Implementation Method 2
with addition of an etching medium to the hydrogen atmosphere in a second step
Implementation Method 3
an etching treatment of the susceptor is effected in each case after a specific number of epitaxial coatings
Implementation Method 4
the susceptor is hydrophilized after said etching treatment
Implementation Method 5
coated epitaxially on its polished front side
Data Source
AI summary
Epitaxially coated silicon wafers, are coated individually in an epitaxy reactor by placing a wafer on a susceptor, pretreating under a hydrogen atmosphere, in and then with addition of an etching medium, and coating epitaxially on a polished front side, wherein an etching treatment of the susceptor is effected after a specific number of epitaxial coatings, and the susceptor is then hydrophilized. Silicon wafer produced thereby have a maximum local flatness value SFQRmax of 0.01 μm to 0.035 μm relative to at least 99% of the partial regions of an area grid of measurement windows having a size of 26×8 mm2 on the front side of the silicon wafer with an edge exclusion of 2 mm.