Wafer Division via Back-Side Plasma Etching and Laser Grooving
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Solution Overview
Problem
Existing wafer processing methods face challenges in dividing wafers into individual device chips without damaging the devices, particularly due to the difficulty in etching the device layer on streets and the risk of mask damage during plasma etching.
Innovation Solution
A wafer processing method involving a mask forming step on the back side of the wafer to create etched grooves, followed by plasma etching through the mask, and a device layer dividing step using a laser beam to form grooves in the device layer before plasma etching, ensuring the etched grooves are deep enough to divide the wafer without exposing the front side devices to plasma.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If plasma etching is performed from the front side through a mask, then the wafer can be divided into individual device chips, but the mask may be partially removed in thin areas causing damage to the devices
Solution Approach 1:
The patent applies inversion by performing plasma etching from the back side of the wafer instead of the front side. This reverses the conventional approach where a mask is placed on the front side, eliminating the risk of mask damage to devices. The back-side etching creates grooves that extend through the substrate thickness without requiring a mask that could compromise device integrity on the front side.
Solution Approach 2:
The patent segments the etching process into two distinct stages: first forming grooves in the device layer from the front side, then performing plasma etching from the back side to complete the division. This segmentation allows each step to be optimized independently, with the front-side groove formation protecting devices and the back-side plasma etching ensuring complete separation without mask interference.
2Productivity
If the street width is reduced to increase device density, then more devices can be obtained from a wafer, but the risk of device damage during processing increases
Solution Approach 1:
The patent applies preliminary action by forming protective grooves in the device layer before performing plasma etching. These pre-formed grooves create physical separation and protection for devices in narrow streets during the subsequent plasma etching process, allowing high device density to be achieved without increasing damage risk.
Solution Approach 2:
The patent addresses the narrow street problem by working from the back side of the wafer in the vertical dimension, rather than laterally from the front side. This dimensional approach allows etching to proceed through the substrate thickness without lateral interference between adjacent devices in narrow streets, maintaining device safety while enabling high density.
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 divides wafers into individual device chips while minimizing damage to the devices and improving die strength by controlling the width and depth of the etched grooves, reducing the risk of chipping and defective mounting.
Implementation Method 1
a device layer dividing step of applying a laser beam to the device layer along each street from a front side of the wafer before performing the plasma etching step and the mask forming step, thereby forming a device layer dividing groove corresponding to the etched groove along each street
Implementation Method 2
a plasma etching step of performing plasma etching from the back side of the wafer through the mask to the substrate after performing the mask forming step, thereby forming the etched groove in the substrate along each street
Data Source
AI summary
A wafer processing method for processing a wafer having a substrate and a device layer formed on a front side of the substrate includes forming a mask on a back side of the wafer, so as to form an etched groove along each street through a thickness of the substrate from the back side of the wafer, performing plasma etching from the back side of the wafer through the mask to the substrate after forming the mask, thereby forming the etched groove in the substrate along each street so that the etched groove has a depth equal to the thickness of the substrate, and applying a laser beam to the device layer along each street from the front side of the wafer before etching and mask forming, thereby forming a device layer dividing groove corresponding to the etched groove along each street.