Silicon Wafer Thinning End Point Structure
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Solution Overview
Problem
Conventional methods for thinning semiconductor wafers risk damaging structures formed in the wafer due to inconsistent thickness, requiring sacrificial wafers to determine the grinding extent, which is not entirely satisfactory.
Innovation Solution
A method and system that involves creating an end point structure within the wafer, extending deeper towards the backside than the desired structure, allowing the grinding process to stop at this point without damaging the desired structures, using materials like tungsten or copper for the end structure to halt the grinding wheel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a wafer is thinned too much to achieve smaller size and lower cost, then productivity and cost efficiency are improved, but structures formed in the wafer may be damaged
Solution Approach 1:
An end structure is formed in advance during the integrated circuit fabrication process, extending deeper than the desired structures. This preliminary structure serves as a predetermined stop point that guides the grinding process, allowing aggressive thinning without risking damage to the actual device structures.
Solution Approach 2:
The end structure acts as an intermediary element between the grinding wheel and the desired structures. It absorbs the mechanical interaction, providing a controlled interface that stops the grinding process before the wheel contacts the sensitive device structures, thus protecting them while enabling efficient thinning.
2Manufacturing precision
If sacrificial wafers are used to determine the extent of grinding, then manufacturing precision is improved, but device complexity and process time increase
Solution Approach 1:
The function of determining grinding depth is extracted from a separate sacrificial wafer process and integrated directly into the production wafer through the end structure. This eliminates the need for separate test wafers and iterative adjustments, reducing process complexity while maintaining precise depth control.
Solution Approach 2:
The production wafer itself provides the grinding stop reference through its own end structure, rather than requiring external sacrificial wafers. The wafer is self-sufficient in defining its own processing parameters, eliminating the need for separate reference samples and simplifying the overall process.
3Ease of operation
If predetermined thickness is ground off to simplify the process, then ease of operation is improved, but manufacturing precision deteriorates due to wafer thickness variations
Solution Approach 1:
Instead of applying a uniform predetermined thickness removal across all wafers, the end structure provides a localized reference point at the specific depth where grinding should stop. This allows each wafer to be processed according to its own characteristics while maintaining consistent final thickness, combining simplicity with 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
Enables repeatable and precise wafer thinning without damaging internal structures, eliminating the need for sacrificial wafers and accommodating variations in wafer thickness and grinding tape, ensuring consistent results.
Implementation Method 1
grinding away said substrate by using a grinding wheel
Data Source
AI summary
Disclosed are a method of and system for fabricating a semiconductor wafer. The method comprises the steps of providing a silicon wafer having a front side an a back side, building an integrated circuit on the front side of the wafer, and thereafter removing substrate from the back side of the silicon wafer. The building step includes the steps of forming a desired structure in the wafer, and forming an end structure in the wafer, said end structure extending to a greater depth, toward the back side of the wafer, than the desired structure. Also, the removing step includes the step of removing said substrate only to the end structure, whereby no part of the desired structure is removed during the removing step.