Wafer Edge Flat Pattern for Front/Back Surface Identification
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Solution Overview
Problem
Conventional semiconductor wafers with tiny flat surfaces formed for crystal orientation identification are difficult to distinguish, as these surfaces are too small to be effectively used as signs to identify the front and back surfaces.
Innovation Solution
A wafer design with at least three tiny flat surfaces along the circumferential direction of the outer chamfered portion, where the flat surfaces define circular arcs with different lengths, and a method using a sensor to detect these surfaces by irradiating the side surface with light and determining the surface orientation based on the intervals of the detected flat surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two orientation flats of different lengths are formed to indicate crystal orientations, then the front surface and back surface of the wafer can be identified, but the device region is reduced due to the notch or orientation flat
Solution Approach 1:
The patent transitions from using traditional orientation flats on the wafer surface to forming tiny flat surfaces on the outer circumferential chamfered portion. This dimensional change moves the identification feature to the edge region, preserving the device region while maintaining identification capability through asymmetric arrangement of flat surfaces
Solution Approach 2:
The patent uses multiple tiny flat surfaces (at least three) with different circular arc lengths between adjacent surfaces to create an asymmetric pattern that copies the identification function of traditional orientation flats. The asymmetric arrangement of these flat surfaces allows determination of front/back surfaces without requiring large notches
2Area of stationary object
If two tiny flat surfaces are formed instead of orientation flats, then the device region is preserved, but the flat surfaces are too tiny to be identified as front or back surface
Solution Approach 1:
The patent divides the identification function into multiple tiny flat surfaces (at least three) arranged asymmetrically on the chamfered portion. By segmenting the identification feature across multiple small surfaces with different spacing, the system achieves both space efficiency and identification capability
Solution Approach 2:
The patent employs asymmetric arrangement of tiny flat surfaces where the circular arc lengths between adjacent flat surfaces are different. This asymmetry creates a unique pattern that can be detected to determine front/back surface orientation, overcoming the limitation of tiny individual surfaces
3Loss of information
If traditional orientation flats are used, then crystal orientation can be identified, but the notch or orientation flat reduces the region where devices can be formed
Solution Approach 1:
The patent relocates the crystal orientation identification feature from the wafer surface to the outer circumferential chamfered portion. This dimensional relocation preserves the entire device region while maintaining orientation identification capability through asymmetric flat surfaces on the edge
Solution Approach 2:
The patent creates a copy of the orientation identification function using tiny flat surfaces on the chamfered portion. These flat surfaces replicate the information-carrying capability of traditional orientation flats without occupying device formation space
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 accurate determination of the front and back surfaces of the wafer despite the tiny flat surfaces, allowing for a larger device region on the wafer and improving the identification process.
Implementation Method 1
a sensor having a light transmitter unit that irradiates the side surface of the outer circumferential chamfered portion with the light and a light receiver unit that receives reflected light from the side surface
Data Source
AI summary
A wafer has an outer circumferential chamfered portion, and at least three tiny flat surfaces formed along a circumferential direction of the wafer in a region of the outer circumferential chamfered portion. The flat surfaces define circular arcs between adjacent ones thereof, respectively, and at least two of the circular arcs have lengths different from each other.