Wafer Thinning via Direct Suction and Flush Cutting
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Solution Overview
Problem
Existing methods for machining semiconductor wafers with protruding metals and resin parts result in nonuniform thickness and height of protruding electrodes, leading to warping or breakage during the thinning process, due to the use of protective tapes that unevenly distribute machining loads during back-side surface grinding.
Innovation Solution
A method involving direct suction of the substrate's back-side surface onto a suction table without protective tapes, followed by cutting and grinding steps to ensure the protruding metals and resin parts are flush, allowing for uniform thickness and height adjustment, and subsequent removal of the resin part to achieve uniform substrate thickness and enhanced dimensional accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective tape is adhered to the face side of the wafer during back-side surface grinding, then the protruding electrodes are protected from damage, but the machining load is unevenly distributed causing nonuniform wafer thickness
Solution Approach 1:
The resin part is formed to protrude beyond the top surface of the electrodes before grinding begins. This preliminary configuration allows the resin to absorb machining loads during grinding, protecting the electrodes from direct contact with the grindstone and chuck table, while the soft resin material ensures uniform load distribution that prevents wafer warping and maintains thickness uniformity.
Solution Approach 2:
The resin part acts as an intermediary between the grindstone and the electrodes. Instead of the hard electrodes directly contacting the grinding tools, the soft resin material absorbs and distributes the machining loads uniformly, preventing both electrode damage and wafer warping while maintaining dimensional accuracy.
2Manufacturing precision
If the wafer is thinned by grinding before forming protruding electrodes, then the desired thickness is achieved, but warping or breakage occurs during subsequent electrode formation or tip cutting
Solution Approach 1:
The method performs tip cutting of the electrodes before the final thinning grind. By cutting the electrode tips while the wafer is still at its original thickness, the wafer maintains sufficient structural strength to prevent warping and breakage. The soft resin material absorbs machining loads during this sequence, protecting the electrodes and maintaining wafer integrity throughout the process.
3Productivity
If the circumferential velocity of the revolving wafer is higher on the outer peripheral side during grinding, then the wafer rotates faster for higher productivity, but the protective tape compresses more causing greater thickness nonuniformity
Solution Approach 1:
The invention changes the material parameter of the protective layer from a thick elastic protective tape to a soft resin material with appropriate mechanical properties. This parameter change allows the material to absorb higher machining loads at higher circumferential velocities without excessive compression, enabling faster wafer rotation for improved productivity while maintaining thickness uniformity.
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 ensures uniform height and thickness of protruding metals on semiconductor wafers, preventing warping and breakage, and achieving enhanced dimensional accuracy by eliminating the influence of protective tapes on machining loads during grinding.
Implementation Method 1
holding the substrate by suction in the condition where the back side of the substrate is matched to a suction surface of a suction table
Data Source
AI summary
A method of machining a wafer is disclosed, in which the wafer is held by sucking its back-side surface directly onto a suction surface of a chuck table, and the tips of protruding electrodes and a resist layer are cut to make them flush with each other (appendant part cutting step). Next, the wafer is held by sucking the surface of the cut appendant part directly onto the suction surface of the chuck table, and the back-side surface of the wafer is ground (back-side surface grinding step), followed by removing the resist layer. The wafer is held onto the chuck table without using any protective tape but by directly holding the wafer, whereby the wafer can be ground to have a uniform thickness.