Wafer Backside Trenches for Stress Relief During Thinning
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Solution Overview
Problem
Existing methods to reduce wafer warpage, such as specialized grinding devices and etching processes, significantly increase manufacturing costs in the IC manufacturing process.
Innovation Solution
Forming a plurality of second trenches on the backside of a wafer using secondary grinding, with the trenches oriented parallel, perpendicular, or at a specified angle to the first trenches on the frontside, to balance internal stress and reduce warpage, utilizing existing grinding equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If specialized grinding devices or etching processes are used to reduce wafer warpage, then wafer warpage is reduced, but manufacturing cost significantly increases
Solution Approach 1:
The patent uses a simple, inexpensive grinding mask made of adhesive tape with patterned abrasive particles instead of expensive specialized grinding devices or etching processes. The mask is disposable and can be easily replaced, significantly reducing manufacturing cost while still achieving the goal of reducing wafer warpage through selective stress relief.
Solution Approach 2:
The patent changes the physical parameters of the wafer by creating controlled stress relief zones through the grinding mask. By varying the distribution, depth, and pattern of ground regions, the patent balances internal stresses without requiring complex equipment, thereby reducing warpage at low cost.
2Length of stationary object
If the grinding amount increases to thin the wafer, then wafer thickness decreases, but structural stress and mechanical stress accumulate causing warpage
Solution Approach 1:
The patent applies local quality by creating non-uniform grinding patterns on the wafer backside. The grinding mask has different abrasive distributions in different regions, creating localized stress relief zones that counterbalance the stress accumulated from overall thinning. This selective local grinding prevents warpage while maintaining the reduced thickness.
Solution Approach 2:
The patent converts the harmful effect of stress accumulation from wafer thinning into a benefit by strategically placing grinding patterns that create compressive stress zones to counterbalance the tensile stress from thinning. The harmful stress is transformed into a useful stress distribution that reduces warpage.
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
Reduces wafer warpage effectively while saving manufacturing costs by using existing equipment and techniques, improving yield and reducing the risk of breakage.
Implementation Method 1
a grinding device is used to grind a backside of the wafer to achieve a desired thickness. Subsequently, the grinding device is used to perform a local grinding on the backside of the wafer
Data Source
AI summary
A wafer stress relief structure and a method for manufacturing the same are provided. The method mainly involves performing a secondary grinding on a wafer after backside grinding to reduce a thickness of the wafer. The secondary grinding forms one or a plurality of trenches locally on a surface opposite to an epitaxial surface of the wafer, to balance and relieve stress accumulated in the wafer during a thinning process, thereby improving wafer warpage.