Wafer Thickness Profiling for Uniform Plasma Dicing
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Solution Overview
Problem
Plasma etching rate variations during wafer division lead to imperfect or excessive processing, resulting in reduced quality of device chips due to uneven etching across the wafer.
Innovation Solution
A method involving a measurement wafer to determine etching rate variations, adjusting the thickness of a product wafer accordingly, and using plasma etching to synchronize the completion of division across the wafer, with protective members to control the etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If etching conditions are adjusted to ensure grooves reach the lower surface in the hardest to etch areas, then division reliability is improved, but excessive etching occurs in easier to etch areas causing quality degradation
Solution Approach 1:
The patent applies local quality by making the wafer thickness non-uniform, specifically thinner at the center and thicker at the periphery. This compensates for the etching rate variations where the center etches faster than the periphery, allowing all areas to reach the lower surface simultaneously and achieving both reliable division and uniform etching quality.
Solution Approach 2:
The patent implements preliminary action by adjusting the wafer thickness before the plasma etching process begins. By pre-thinning the center area and keeping the periphery thicker, the etching process can proceed uniformly across all areas without requiring real-time adjustment, ensuring both reliability and precision from the start.
2Ease of manufacture
If standard plasma etching is used with uniform wafer thickness, then process simplicity is maintained, but etching rate variations cause imperfect or excessive processing
Solution Approach 1:
The patent maintains process simplicity by using standard plasma etching equipment and procedures, but introduces local quality through non-uniform wafer thickness. This allows the simple etching process to achieve uniform results by compensating for inherent etching rate variations through the thickness distribution.
3Productivity
If cutting blade or laser process is used for wafer division, then division speed is improved, but processing defects such as chippings or crystal strain layers are generated
Solution Approach 1:
The patent replaces the mechanical cutting blade process with plasma etching, which uses chemical reactions rather than mechanical force. This substitution eliminates chippings and mechanical stress while maintaining division capability. The plasma process removes material through chemical vapor deposition reactions, preserving surface quality and crystallinity.
Solution Approach 2:
The patent changes the physical and chemical parameters of the etching process by controlling plasma conditions, gas composition, and wafer thickness distribution. These parameter changes enable the plasma etching to achieve both high productivity and excellent surface quality, avoiding the defects associated with mechanical or laser-based methods.
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
Ensures proper division of the wafer by reflecting etching rate variations in the thickness distribution, preventing imperfect or excessive etching, and maintaining the quality of device chips.
Implementation Method 1
supplying a gas in a plasma state to areas of the product wafer that are exposed through the second mask and correspond to the streets to etch the second areas
Data Source
AI summary
A method of processing a wafer includes a wafer preparing step of preparing a measurement wafer and a product wafer, a measurement etching step of supplying a gas in a plasma state to first areas of the measurement wafer that correspond to streets thereon to form grooves in the measurement wafer, a measuring step of demarcating a plurality of concentric areas in an array from a center to an outer circumference of the measurement wafer, and measuring depths of the grooves in the respective concentric areas, a thickness adjusting step of adjusting a thickness of the product wafer such that the product wafer is progressively thinner in areas thereof that correspond to the areas of the measurement wafer where the grooves are shallower, and an etching step of supplying a gas in a plasma state to second areas of the product wafer that correspond to streets thereon.