Sidewall Masking for Back Metallized Die Dicing
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Solution Overview
Problem
Current dicing processes for semiconductor wafers often result in chipping, cracking, and metal deposition on die sidewalls, leading to reduced die yield and potential short circuits, especially when wafers have back surface metallization, which can cause metal to peel from adjacent dies.
Innovation Solution
The method involves applying a sidewall masking mechanism to the wafer's front surface to prevent metal deposition on die sidewalls, thinning the back surface to expose the masking mechanism, and depositing material on the back surface, thereby preventing metal peeling and allowing for clean separation of individual dies without causing short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional dicing processes (scribing, sawing, or dicing) are used to separate individual dies, then the wafer can be divided into individual dies, but chips and gouges are formed along the edges of dies and cracks propagate from the edges into the substrate, reducing die yield
Solution Approach 1:
The method applies a sidewall masking mechanism to the front surface of the wafer before the dicing process. This masking layer is deposited in advance to protect the sidewalls of the dies during subsequent grinding and dicing operations, preventing chips and gouges from forming on the die edges while allowing clean separation of individual dies
Solution Approach 2:
The sidewall masking mechanism serves as an intermediary protective layer between the dicing process and the die sidewalls. This masking material (such as photoresist or adhesive) is applied to the front surface and extends over the sidewalls, acting as a buffer that prevents direct mechanical contact between the dicing blade/grind and the die edges, thereby eliminating chipping and cracking
2Reliability
If additional spacing is required between dies to prevent damage spread, then cracking and chipping are prevented from spreading to adjacent ICs, but wasted wafer space increases and the number of dies produced from each wafer decreases
Solution Approach 1:
The method extracts the protective function from the traditional approach of increasing die spacing and relocates it to a sidewall masking mechanism applied directly to each die. By removing the need for additional spacing and replacing it with a targeted protective layer on each die's sidewall, the invention maintains reliability while maximizing wafer utilization and die count per wafer
3Ease of manufacture
If the wafer is diced before metal deposition, then the dicing process can be completed, but metal is deposited on the exposed sidewalls of the individual dies causing short circuits
Solution Approach 1:
The sidewall masking mechanism is applied to the front surface of the wafer before the dicing and metal deposition processes. This preliminary masking layer remains in place during metal deposition, preventing metal from contacting the die sidewalls and causing short circuits, while still allowing the dicing process to be completed
Solution Approach 2:
The sidewall masking material acts as an intermediary barrier between the metal deposition process and the die sidewalls. This masking layer is applied in advance and remains during metal deposition, blocking metal particles from adhering to the sidewalls and causing electrical shorts, thereby ensuring proper electrical isolation of individual dies
4Ease of operation
If an individual die is removed from a diced wafer with back surface metallization, then the die can be separated, but the metal on the back surface of adjacent dies is peeled away from the adjacent dies
Solution Approach 1:
The sidewall masking mechanism is applied to the front surface before the dicing and metal deposition processes. This masking layer is already in place when metal is deposited on the back surface, creating a protective framework that prevents metal peeling during subsequent die separation operations
Solution Approach 2:
The sidewall masking material serves as an intermediary structural support that prevents the back surface metal from peeling during die separation. By having this masking layer already applied before metal deposition, it provides a stabilizing framework that holds the metal in place during mechanical separation operations
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 approach reduces chipping and cracking, prevents metal deposition on sidewalls, and allows for the separation of individual dies without metal peeling, resulting in improved die yields and reduced waste, enabling efficient dicing before shipping and minimizing assembly site cycle time.
Implementation Method 1
a back surface of the wafer is removed (e.g., by grinding)
Data Source
AI summary
Semiconductor device processing and methods for dicing a semiconductor wafer into a plurality of individual dies that can have back surface metallization are described. The methods comprise providing a wafer with pre-diced streets in the wafer's front surface, applying a sidewall masking mechanism to the front surface of the wafer so as to substantially fill the pre-diced streets, thinning the back surface of the wafer so as to dice the wafer (e.g., by grinding, etching, or both) and expose a portion of the sidewall masking mechanism from the back surface of the wafer, and applying a material, such as metal, to the back surface of the diced wafer. These methods can prevent the metal from being deposited on die sidewalls and may allow the separation of individual dies without causing the metal to peel from the back surface of one or more adjacent dies. Other embodiments are also described.