Wafer Inspection Mark Formation for Back-Surface Defect Positioning
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Solution Overview
Problem
In wafer processing, when inspecting from the back surface, it is challenging to store the position of defective portions without imaging the front surface, as the alignment marks necessary for identification are not visible from the back side, leading to potential errors due to conveyance deviations.
Innovation Solution
A method involving holding the wafer by a processing unit that detects the planned dividing lines from either side, forming inspection marks on the back surface based on alignment marks on the front surface, and using characteristic points like notches or orientation flats to identify defective areas without direct imaging of the front surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If inspection is executed from the back surface side of the wafer, then the inspection can be performed without imaging through the inspection table, but it becomes impossible to store the defective portion in association with the mark formed on the front surface
Solution Approach 1:
The invention creates a copy of the alignment mark information by forming an inspection mark on the back surface of the wafer that corresponds to the alignment mark on the front surface. This inspection mark serves as a surrogate reference that can be detected from the back surface, allowing defective portions to be stored and identified without needing to image the front surface alignment marks directly.
Solution Approach 2:
The invention transitions the reference mark from two-dimensional imaging on the front surface to a three-dimensional structure that includes a back surface component. By forming the inspection mark that extends to or through the back surface, the reference information becomes accessible from the opposite dimension, enabling back-surface inspection while maintaining positional association.
2Productivity
If the wafer is conveyed to another step after inspection, then the processing can continue, but the defective portion becomes unknown due to conveyance deviation
Solution Approach 1:
The inspection mark on the back surface provides a feedback reference that can be detected during conveyance to another step. By detecting the position of the inspection mark relative to the wafer's characteristic points, the system can compensate for conveyance deviations and accurately identify defective portions in subsequent processing steps.
Solution Approach 2:
The inspection mark is formed on the back surface in advance before conveyance to another step. This preliminary creation of the reference mark ensures that the positional information is already established and can be used for accurate defective portion identification during subsequent processing, even when the wafer is moved.
3Measurement precision
If an infrared camera is used to image from the back surface, then the alignment mark can be detected, but specialized equipment is required
Solution Approach 1:
Instead of using specialized infrared equipment to detect the original alignment mark, the invention creates a copy (inspection mark) on the back surface that can be detected by conventional imaging equipment. This eliminates the need for infrared cameras or other specialized detection devices while maintaining the ability to accurately locate alignment marks from the back surface.
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 identification and storage of defective portions on the wafer even when inspecting from the back surface, ensuring correct recognition during subsequent processing steps despite potential conveyance deviations.
Implementation Method 1
detecting the planned dividing lines on the front surface from a side of the front surface through the holding table or from a side of a back surface by using an infrared camera
Data Source
AI summary
A wafer processing method for processing a wafer having a front surface on which a pattern and a plurality of crossing planned dividing lines are formed, along the planned dividing lines. The method includes holding the front surface of the wafer by a holding table, detecting the planned dividing lines on the front surface from a side of the front surface through the holding table or from a side of a back surface by using an infrared camera and processing the wafer by using a processing unit from the side of the back surface along the planned dividing lines, and an inspection step of placing the wafer on an inspection table and inspecting processing quality from the back surface after the processing step. In the inspection step, a defective portion is stored on a basis of a characteristic point such as a notch.