Wafer TEG Cutting via Disposable Polymer Sheet
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Solution Overview
Problem
The contamination of focusing lenses due to debris scattering during the laser-based cutting of test element groups (TEGs) on wafers, and the potential degradation of device quality from adhesive residue after using protective tapes, particularly when using laser beams with transmission wavelengths for forming modified layers.
Innovation Solution
A wafer processing method involving thermoplastic polymer sheets for covering and protecting the wafer surface, where a first laser beam is applied through the sheet to cut the TEG and a second laser beam is applied to the backside to form modified layers, preventing debris scattering and adhesive residue by thermocompression bonding and peeling the sheet without leaving any residue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a protective tape is attached to the front side of the wafer to suppress debris scattering, then lens contamination is prevented, but adhesive residue is left on the wafer surface causing device quality degradation
Solution Approach 1:
The patent uses a disposable protective sheet that is discarded after use, eliminating the need for adhesive-based protective tapes. The sheet is designed to be used once and then removed without leaving residue, solving the contradiction between protecting the lens and maintaining device quality.
Solution Approach 2:
The protective sheet acts as an intermediary between the laser beam and the wafer surface. It allows the laser to pass through while blocking debris from reaching the lens, and can be removed without leaving adhesive residue on the wafer.
2Manufacturing precision
If the focal point of the laser beam is set on the TEG to perform ablation cutting, then precise cutting is achieved, but debris scatters causing focusing lens contamination
Solution Approach 1:
The protective sheet serves as an intermediary that allows the laser beam to focus precisely on the TEG for accurate cutting while simultaneously preventing debris from reaching and contaminating the focusing lens.
3Productivity
If a laser beam with transmission wavelength to the wafer is used to cut the TEG, then cutting efficiency is improved, but debris scattering and lens contamination are more prone to occur
Solution Approach 1:
The protective sheet is positioned between the laser beam and the wafer surface, allowing the high-efficiency laser beam to cut the TEG effectively while the sheet blocks the resulting debris from contaminating the lens, thus maintaining both cutting efficiency and preventing contamination.
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
This method effectively prevents lens contamination and ensures device quality by suppressing debris scattering and eliminating adhesive residue, allowing precise cutting and division of wafers into individual device chips.
Implementation Method 1
performing thermocompression bonding to bond the polymer sheet to the front side of the wafer
Implementation Method 2
applying a first laser beam through the polymer sheet to the wafer along each division line in a condition where a focal point of the first laser beam is set on each division line, thereby cutting the TEG formed on each division line
Implementation Method 3
there arises a problem such that debris scatters from the position where the laser beam is applied, causing contamination of a focusing lens
Implementation Method 4
applying a second laser beam to a back side of the wafer along each division line in a condition where a focal point of the second laser beam is set inside the wafer in an area corresponding to each division line, the second laser beam having a transmission wavelength to the wafer, thereby forming a modified layer inside the wafer along each division line
Data Source
AI summary
A wafer processing method includes a sheet bonding step of placing a polyolefin or polyester sheet on a front side of a wafer having a device area where devices are formed so as to be separated by division lines, the sheet having a size capable of covering the device area, and next performing thermocompression bonding to bond the sheet to the front side of the wafer, thereby protecting the front side of the wafer with the sheet. The method further includes a test element group (TEG) cutting step of applying a first laser beam through the sheet to the wafer along each division line thereby cutting a TEG formed on each division line, and a modified layer forming step of applying a second laser beam to a back side of the wafer along each division line, the second laser beam having a transmission wavelength to the wafer, thereby forming a modified layer inside the wafer along each division line.