Wafer Back Surface Scratch Detection via Optical Imaging
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Solution Overview
Problem
The existing wafer polishing processes often result in incomplete formation of minute scratches on the back surface, leading to inadequate gettering effects, which can cause metallic elements to migrate to the front surface, increasing the likelihood of operation failures due to the difficulty in visually inspecting the entire surface for scratches.
Innovation Solution
A processing apparatus equipped with a scratch determining unit that uses a camera to image the back surface of the wafer and analyze contrasting density to determine the presence of scratches, informing the operator of any regions without scratches, allowing for precise and efficient verification of scratch formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If visual inspection is used to check scratch formation on the wafer back surface, then the operator can identify regions without scratches, but the inspection process requires enormous labor and time and may overlook regions without scratches
Solution Approach 1:
The patent replaces the mechanical visual inspection method with an optical imaging system. A camera captures images of the wafer back surface, and image processing automatically detects regions without scratches. This substitution eliminates manual labor and time consumption while improving detection accuracy and consistency.
Solution Approach 2:
The patent creates an optical copy (image) of the wafer back surface using a camera. This copy allows for automated analysis of scratch patterns without requiring direct visual inspection. The image can be processed computationally to identify regions without scratches, enabling rapid and accurate assessment.
2Ease of operation
If the polishing pad and wafer are not properly aligned or have thickness variation, then the polishing process becomes simpler to operate, but scratches are not formed uniformly across the entire wafer back surface
Solution Approach 1:
The patent implements a feedback mechanism where the imaging system detects regions without scratches after polishing. This information is fed back to operators or control systems, allowing them to adjust polishing parameters or re-polish affected areas. The feedback loop ensures uniform scratch formation while maintaining operational simplicity.
Solution Approach 2:
The patent performs scratch formation verification as a preliminary check before subsequent processing steps. By identifying regions without scratches early in the process, operators can correct alignment or thickness issues before they affect device performance, preventing rework later.
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 easy and reliable verification of scratch formation on the entire wafer surface, reducing labor and time spent on visual inspections and ensuring consistent gettering effects across the entire wafer, thereby minimizing operation failures.
Implementation Method 1
a scratch determining unit that determines whether or not the scratches exist on the back surface side of the wafer polished by the polishing unit
Data Source
AI summary
There is provided a processing apparatus that polishes the back surface side of a wafer on which devices are formed on the front surface side. The processing apparatus includes a chuck table that holds the wafer and rotates and a polishing unit that forms scratches on the back surface side of the wafer while polishing the back surface side of the wafer. The processing apparatus includes also a scratch determining unit that determines whether or not the scratches exist on the back surface side of the wafer polished by the polishing unit and an informing unit that informs that a region in which the scratches do not exist is included in the wafer when a region for which it has been determined that the scratches do not exist by the scratch determining unit is included in the wafer.