Wafer Thickness Measurement via Laser Modified Region Position
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Solution Overview
Problem
Existing inspection devices face challenges in accurately determining the thickness of wafers, especially when unknown wafers are used, leading to potential inaccuracies in processing conditions.
Innovation Solution
An inspection device that includes an irradiation unit to form modified regions inside the wafer with a laser beam, an imaging unit to detect light passing through the wafer, and a control part to derive the wafer thickness based on the position of the modified region and set processing conditions, using a database to associate processing conditions with modified region widths for precise calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the wafer thickness is manually input for inspection, then the inspection process can be performed, but the accuracy deteriorates when unknown wafers are used
Solution Approach 1:
The inspection device automatically measures wafer thickness using optical interference patterns without requiring manual input. The system self-calibrates by analyzing the interference fringes generated when light passes through the wafer, eliminating the need for operators to manually enter thickness values and ensuring accurate measurement even for unknown wafers.
Solution Approach 2:
The patent replaces manual thickness input with an optical measurement system. By using light interference patterns and automated image processing, the system substitutes the mechanical/manual thickness entry process with an optical-field solution that automatically determines thickness based on interference fringe analysis.
2Reliability
If the wafer thickness is accurately determined using manual input, then processing conditions can be precisely set, but this approach fails when unknown wafers are used
Solution Approach 1:
The system dynamically determines wafer thickness by analyzing optical interference parameters rather than relying on fixed manual inputs. By measuring the interference pattern characteristics (fringe spacing, intensity distribution) and calculating thickness from these parameters, the system adapts to different wafer types while maintaining reliable processing condition determination.
Solution Approach 2:
The inspection device incorporates a feedback mechanism where the measured interference patterns are continuously analyzed to determine wafer thickness. This measured thickness then feeds back into the processing condition setting, ensuring that accurate, real-time thickness data is used for unknown wafers, thereby improving both reliability and adaptability.
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 derivation of wafer thickness by determining the position of modified regions and applying set processing conditions, ensuring high precision in wafer processing.
Implementation Method 1
an imaging unit configured to output light having permeability to the wafer and to detect the light propagating through the wafer
Implementation Method 2
an irradiation unit configured to irradiate a wafer having a first surface and a second surface with a laser beam from a first surface side of the wafer
Implementation Method 3
a first process of controlling the irradiation unit so that a modified region is formed inside the wafer by irradiating the wafer with the laser beam
Data Source
AI summary
This inspection device includes: a laser irradiation unit that irradiates a wafer having a back surface and a front surface with a laser beam from the back surface side of the wafer; an imaging unit that outputs light having permeability to the wafer and detects the light propagating through the wafer; and a control part configured to perform a first process of controlling the laser irradiation unit so that a modified region is formed inside the wafer by irradiating the wafer with the laser beam and a second process of deriving a position of the modified region on the basis of a signal output from the imaging unit that detects the light and deriving a thickness of the wafer on the basis of the derived position of the modified region and a set recipe.