Wafer Backside Imaging Through Liquid Layer and Adhesive Sheet
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Solution Overview
Problem
The existing wafer processing methods struggle to accurately detect and divide wafers along crossing division lines when the back side is covered with a metal film, as infrared rays cannot pass through the metal film, hindering detection of division lines.
Innovation Solution
A wafer processing method and apparatus that uses an adhesive sheet to unite the wafer with a frame, forms a liquid layer on a transparent wafer table, and employs an imaging unit to detect division lines through the adhesive sheet and liquid layer, allowing for accurate processing and division of wafers even with a metal film on the back side.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the back side of the wafer is covered with a metal film, then the wafer can be protected or have improved electrical properties, but infrared rays cannot pass through the metal film, causing the division lines to be undetectable
Solution Approach 1:
The patent introduces a liquid layer as an intermediary medium between the imaging unit and the wafer. This liquid layer has optical properties that allow it to transmit imaging signals while the system maintains the metal film coverage on the wafer back side for protection. The liquid acts as a mediator that enables detection without requiring removal of the protective metal film.
Solution Approach 2:
The patent changes the optical parameters of the detection path by introducing a liquid medium with specific refractive index and transparency properties. This parameter change allows imaging signals to pass through the liquid layer and reach the division lines on the wafer front side, enabling detection while the metal film remains on the back side.
2Object-affected harmful factors
If the wafer is processed from the back side, then the front side devices are protected from processing dust, but the metal film on the back side blocks infrared detection of division lines
Solution Approach 1:
The liquid layer serves as an intermediary that enables optical detection through a medium that does not interfere with the protective function of the metal film. This allows back-side processing to continue while enabling division line detection through the liquid medium.
Solution Approach 2:
The liquid layer performs multiple functions: it allows optical transmission for detection, maintains the protective benefit of back-side processing, and works compatibility with the metal film coverage. This multi-functional approach resolves the contradiction between protection and detection.
3Strength
If an adhesive sheet is used to unite the wafer with the frame, then the wafer can be securely held for processing, but the adhesive sheet may interfere with optical detection
Solution Approach 1:
The liquid layer acts as an optical intermediary that compensates for the potential interference caused by the adhesive sheet. By optimizing the optical properties of the liquid, the system maintains detection capability while the adhesive sheet provides necessary mechanical fixation.
Solution Approach 2:
The system adjusts optical parameters by introducing the liquid medium with specific transparency and refractive index characteristics, which compensates for the light interference introduced by the adhesive sheet, thereby maintaining detection capability while ensuring secure wafer fixation.
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 processing and division of wafers along the division lines from the back side, even when the back side is covered with a metal film, and maintains clarity for detecting lines through the adhesive sheet, ensuring precise separation of individual device chips.
Implementation Method 1
an imaging unit which is positioned opposite to the supporting face of the wafer table to thereby detect the division lines formed on the front side of the wafer
Implementation Method 2
forming a layer of a liquid on a supporting face of a wafer table included in a supporting unit
Data Source
AI summary
A wafer processing apparatus including a supporting unit having a frame fixing section fixing the frame, and a wafer table having a front side and a rear side, the front side including a supporting face supporting the wafer and a transparent plate, a liquid layer forming unit including a nozzle section and forming a layer of a liquid on the supporting face of the wafer table, an imaging unit including an imaging camera positioned adjacent to the rear side of the wafer table and opposite to the supporting face on the front side of the wafer table and an air blowing nozzle blowing air to a region between the wafer table and the adhesive sheet.