Indium Phosphide Substrate Backside Flatness for Uniform Epitaxy
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Solution Overview
Problem
The indium phosphide substrate exhibits significant warpage during epitaxial growth, leading to non-uniform heat conduction and substrate temperature, which deteriorates the quality of the epitaxial crystal layer and semiconductor epitaxial wafer performance.
Innovation Solution
The substrate's back surface warpage is controlled within specific BOW, SORI, and WARP values, ensuring uniform contact with the susceptor, achieved through precise cutting and etching processes using a wire saw with controlled wire delivery and etching solutions, resulting in a substrate with reduced warpage and improved heat conduction uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the indium phosphide substrate is supported by a susceptor from the back surface side during epitaxial growth, then the substrate can be held in position for processing, but larger warpage of the back surface results in non-uniform contact with the susceptor
Solution Approach 1:
The patent applies preliminary anti-action by controlling the warpage of the back surface to be within specific BOW, SORI, and WARP value ranges before the epitaxial growth process begins. This pre-control prevents the warpage from causing non-uniform contact with the susceptor during processing, thereby eliminating the harmful effect before it can occur.
2Ease of manufacture
If the back surface of the substrate has large warpage, then the substrate can be manufactured with simpler processes, but this results in non-uniform in-plane distribution of heat conduction
Solution Approach 1:
The patent employs a combination of etching solutions and controlled processing conditions that create uniform material removal across the substrate surface. The etching process, conducted under controlled conditions with specific solutions, acts similarly to a uniform hydraulic action that removes material evenly, achieving flat back surfaces with BOW values within the specified ranges.
3Ease of manufacture
If the substrate has large warpage, then manufacturing costs are reduced, but this causes non-uniform substrate temperature during epitaxial growth
Solution Approach 1:
The patent applies parameter changes by establishing specific numerical ranges for BOW, SORI, and WARP values that optimize the balance between manufacturing feasibility and temperature uniformity. By controlling warpage parameters within these defined ranges, the substrate achieves sufficient flatness for uniform heat distribution while maintaining practical manufacturability.
4Productivity
If the back surface warpage is not controlled, then the substrate manufacturing process is simpler and faster, but this deteriorates the quality of the epitaxial crystal layer
Solution Approach 1:
The patent implements preliminary action by controlling the warpage of the back surface through optimized cutting and etching processes before the epitaxial growth stage. This pre-control ensures that the substrate is properly prepared with acceptable flatness parameters, preventing quality deterioration during subsequent high-precision epitaxial processing.
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
The controlled warpage of the indium phosphide substrate ensures uniform heat distribution during epitaxial growth, enhancing the quality of the epitaxial crystal layer and reducing performance issues such as emission wavelength shifts.
Implementation Method 1
cutting a wafer from an indium phosphide ingot with a wire saw
Implementation Method 2
etching the cut wafer; etching the polished wafer
Implementation Method 3
polishing at least one surface of the chamfered wafer
Implementation Method 4
non-uniform in-plane distribution of heat conduction to the substrate
Data Source
AI summary
Provided is an indium phosphide substrate, a semiconductor epitaxial wafer, and a method for producing an indium phosphide substrate, which can satisfactorily suppress warpage of the back surface of the substrate. The indium phosphide substrate includes a main surface for forming an epitaxial crystal layer and a back surface opposite to the main surface, wherein the back surface has a BOW value of −2.0 to 2.0 μm, as measured with the back surface of the indium phosphide substrate facing upward.