Semiconductor Wafer Processing for Plane-Parallel Low-Defect Discs
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Solution Overview
Problem
Existing methods for producing semiconductor wafers from cylindrical ingots result in wafers with uneven plane-parallelism and structural defects, making them unsuitable for demanding applications.
Innovation Solution
A method involving multi-wire slicing, followed by etching with an alkaline etchant at controlled temperatures and residence times, and then simultaneous double-disk grinding with annular abrasive covering to achieve high plane-parallelism and low defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multi-wire slicing is used to remove wafers from the ingot, then productivity is improved, but manufacturing precision deteriorates due to uneven plane-parallelism and structural defects
Solution Approach 1:
The patent divides the wafer production process into distinct sequential stages: multi-wire slicing for rapid wafer separation, followed by etching to remove damaged layers, and finally double-disk grinding for precision finishing. This segmentation allows each process to be optimized independently - slicing for speed, etching for defect removal, and grinding for precision - thereby resolving the contradiction between productivity and manufacturing precision.
Solution Approach 2:
The etching process is introduced as a preliminary action before the final grinding step. By etching away the damaged surface layers created during slicing, the substrate is prepared in advance for high-precision grinding, ensuring that the subsequent grinding operation works on clean, defect-free material and achieves superior plane-parallelism without compromising productivity.
2Ease of manufacture
If conventional slicing and grinding methods are used, then ease of manufacture is maintained, but manufacturing precision deteriorates due to crystalline and structural defects
Solution Approach 1:
The patent introduces etching as an intermediary process between slicing and grinding. This intermediary step chemically removes the crystalline and structural defects generated during slicing, preparing the wafer surface for high-precision grinding. The etching process acts as a mediator that eliminates defects without adding significant complexity to the overall manufacturing flow.
Solution Approach 2:
The patent replaces purely mechanical slicing and grinding operations with a hybrid approach that incorporates chemical etching. Instead of relying solely on mechanical removal of material, the chemical etching process selectively removes damaged crystalline structures, thereby improving manufacturing precision while maintaining ease of manufacture through a straightforward sequential process.
3Manufacturing precision
If extensive material removal is performed during grinding, then manufacturing precision improves, but loss of substance increases
Solution Approach 1:
By performing etching as a preliminary action before grinding, the damaged and defective material is removed chemically in advance. This preliminary removal of compromised material means that the subsequent grinding operation only needs to remove minimal amounts of material to achieve the required plane-parallelism, thereby significantly reducing overall material loss while maintaining high manufacturing precision.
Solution Approach 2:
The patent substitutes chemical etching for mechanical material removal in the preliminary preparation stage. Instead of using mechanical grinding to remove all defective material, the chemical etching process selectively eliminates damaged layers, reducing the burden on the mechanical grinding operation and minimizing the total amount of material that needs to be removed to achieve high precision.
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 method produces wafers with improved plane-parallelism and reduced structural and crystalline defects, meeting challenging requirements in shape and surface quality efficiently and economically.
Implementation Method 1
etching of the sliced wafers with an alkaline etchant in an etching bath at a temperature of 20° C. to 50° C. and for a residence time
Implementation Method 2
grinding of the etched wafers by simultaneous double-disk grinding using an annular abrasive covering
Data Source
AI summary
A method produces wafers from a cylindrical ingot of semiconductor material having an axis and an indexing notch in an outer surface of the cylindrical ingot and parallel to the axis. The method includes, in the order specified: (a) simultaneous removal of a multiplicity of sliced wafers from the cylindrical ingot by multi-wire slicing in the presence of a cutting agent; (b) etching of the sliced wafers with an alkaline etchant in an etching bath at a temperature of 20° C. to 50° C. and for a residence time, such that the material removed from each of the sliced wafers is less than 5/1000 of an initial wafer thickness; and (c) grinding of the etched wafers by simultaneous double-disk grinding using an annular abrasive covering.