Transparent Electrostatic Chuck for Laser Wafer Processing
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Solution Overview
Problem
Existing laser processing methods for wafers with semiconductor or optical devices face limitations due to the inability of laser beams to transmit through metal layers, requiring specific handling and design modifications, which restrict processing capabilities.
Innovation Solution
An electrostatic chuck table with a plate-shaped base and an electrostatic attraction electrode capable of transmitting laser beams, allowing the beam to be applied through the chuck table to the back side of the wafer, eliminating the need for vacuum lines and special designs, and enabling efficient processing of wafers with MEMS devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a vacuum line is formed inside the chuck table to apply vacuum to the holding surface, then the workpiece can be held on the chuck table, but the laser beam cannot be transmitted through the chuck table in the area where the vacuum line is formed, limiting processing capability
Solution Approach 1:
The chuck table is divided into a transparent base portion that transmits laser beams and an electrode portion formed on its surface. The vacuum application system is segmented into vacuum pads distributed on the holding surface, allowing laser transmission through the base while maintaining vacuum holding capability without blocking the laser path.
Solution Approach 2:
The transparent base portion acts as an intermediary that allows laser beams to pass through from the laser processing apparatus to the workpiece while the vacuum pads on its surface provide holding force. This intermediary structure enables both laser transmission and vacuum holding without interference.
2Productivity
If the front side of the wafer is held on the holding surface to allow laser beam transmission to the back side, then the laser can process the workpiece, but additional measures are required such as avoiding TEG patterns on division lines or removing them beforehand
Solution Approach 1:
Instead of holding the front side of the wafer and applying laser to the back side (which requires avoiding TEG patterns), the invention inverts the approach by holding the back side of the wafer on the chuck table's holding surface and applying the laser beam to the front side where TEG patterns are located, allowing direct processing without pattern removal.
3Reliability
If a laser processing apparatus with a chuck table is used to hold and process wafers, then processing can be performed, but the refractive index difference between the vacuum line and other portions of the chuck table limits laser beam transmission
Solution Approach 1:
The base portion of the chuck table is made uniformly transparent with consistent optical properties, eliminating refractive index variations. The electrode portion and vacuum pads are configured to maintain this optical homogeneity, allowing laser beams to pass through without deviation or energy loss.
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 suppresses processing limitations by allowing direct laser application to the wafer interior, reducing mechanical shock and kerf width, and enabling precise division of wafers without damaging the front-side devices or requiring special designs, thus enhancing processing flexibility and accuracy.
Implementation Method 1
an electrostatic attraction electrode portion capable of transmitting the laser beam, the electrode portion being formed on the first surface of the base portion, the electrostatic chuck table using method including a workpiece holding step of applying a voltage to the electrode portion formed on the first surface to thereby electrostatically hold the workpiece on the second surface
Data Source
AI summary
An electrostatic chuck table includes a plate-shaped base portion capable of transmitting a laser beam to be applied to a workpiece and an electrostatic attraction electrode portion capable of transmitting the laser beam. The laser beam has a transmission wavelength to the workpiece. The base portion has a first surface and a second surface opposite to the first surface. The electrode portion is formed on the first surface of the base portion. A method for using the electrostatic chuck table includes a workpiece holding step of applying a voltage to the electrode portion formed on the first surface to thereby electrostatically hold the workpiece on the second surface, and a modified layer forming step of applying the laser beam through the first surface to a predetermined position inside the workpiece held on the second surface to thereby form a modified layer inside the workpiece.