Wafer Backside Laser Marking Before Dicing
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Solution Overview
Problem
Marking product information on the back side of individual devices after dicing reduces productivity due to inefficiencies in the process.
Innovation Solution
A method involving back side grinding of the wafer to a desired thickness, followed by laser marking of product information before separation, with an optional mirror finishing step to enhance surface quality and visibility of markings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If product information is marked on individual devices after dicing, then each device can be individually identified, but productivity is reduced due to the troublesome marking process on each separate device
Solution Approach 1:
The patent applies preliminary action by marking product information on the back side of devices while they are still in wafer form, before the dicing process separates them into individual devices. This allows all devices on a single wafer to be marked simultaneously in one operation rather than requiring separate marking operations for each device after dicing, thereby dramatically improving marking efficiency and productivity
2Manufacturing precision
If the back side of the wafer is ground to obtain desired thickness, then the wafer achieves proper dimensions for subsequent processing, but the surface quality may be compromised requiring additional finishing steps
Solution Approach 1:
The patent performs the back side grinding operation to achieve desired wafer thickness before the laser marking step. By establishing the correct thickness early in the process sequence, the wafer is properly prepared for subsequent marking and separation operations, ensuring dimensional precision is achieved before surface quality becomes the primary concern
Solution Approach 2:
The patent changes the surface condition parameter by applying a mirror finishing step that transforms the ground back side surface into a high-quality mirror surface. This parameter change from a ground surface to a mirror-finished surface improves both the aesthetic quality and the visibility of laser markings while maintaining the thickness precision already achieved
3Strength
If a mirror finishing step is performed before marking, then die strength increases and markings are more visible, but the gettering effect of copper ions is reduced
Solution Approach 1:
The patent applies parameter changes by controlling the timing and conditions of the mirror finishing step. By performing mirror finishing at a specific stage before laser marking, the process optimizes both die strength and marking visibility while managing the trade-off with the gettering effect. The parameter of surface finish quality is enhanced to improve marking visibility and structural strength
4Productivity
If product information is marked before separation, then marking efficiency is improved, but the markings must be applied to all devices including defective ones
Solution Approach 1:
The patent performs the marking operation on all devices in wafer form before separation and defect sorting. Although this means defective devices are also marked, the overall productivity gain from performing one simultaneous marking operation on the entire wafer far outweighs the minor waste of marking defective devices. The alternative of marking only after individual device identification would require multiple separate operations, significantly reducing efficiency
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
Improves marking efficiency and productivity by allowing product information to be marked on the wafer before separation, increasing die strength and reducing the gettering effect, thus enhancing the quality and visibility of markings.
Implementation Method 1
a marking step for marking product information on the back side of each device by applying a laser beam to the back side of the wafer
Implementation Method 2
a back side grinding step for grinding the back side of a wafer having a plurality of devices formed on the front side so as to be partitioned by a plurality of separation lines, thereby obtaining a desired thickness of the wafer
Implementation Method 3
a mirror finishing step to be performed before the marking step, wherein a strain layer is removed from the back side of the wafer by chemical mechanical polishing or dry polishing to thereby obtain a mirror surface on the back side of the wafer
Data Source
AI summary
A product information marking method including a back side grinding step for grinding the back side of a wafer having a plurality of devices formed on the front side so as to be partitioned by a plurality of separation lines, thereby obtaining a desired thickness of the wafer. After performing the back side grinding step, a marking step for marking product information on the back side of each device by applying a laser beam to the back side of the wafer is performed before separating the devices from each other. Thus, the product information is marked on each device in the stage of the wafer.