Wafer Dicing with Dual-Side Femtosecond Scribing and Plasma Etching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional dicing methods for semiconductor wafers, such as scribing and sawing, result in chipping, cracking, and waste of wafer real estate due to jagged separation lines and the need for additional spacing between dice, while plasma dicing faces cost and implementation limitations, especially with metals like copper.
Innovation Solution
A method involving femtosecond-based laser scribing on both the backside and frontside of a monocrystalline silicon substrate, followed by plasma etching, to singulate integrated circuits, using a water-soluble mask and minimizing thermal damage for precise and efficient die separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional scribing or sawing is used to dice the wafer, then the wafer can be separated into individual dice, but chipping and cracking occur along the severed edges and additional spacing is required between dice
Solution Approach 1:
The patent replaces conventional mechanical scribing and sawing methods with a laser-based dicing system. The laser beam precisely ablates the wafer material along the street regions without mechanical contact, eliminating the chipping and cracking that occurs with diamond-tipped scribes and saw blades. This substitution enables cleaner separation lines and reduces the spacing required between dice.
Solution Approach 2:
The patent utilizes controlled laser parameters including pulse duration, power, and scanning speed to achieve precise material removal. By adjusting these parameters, the laser can selectively remove material from the street regions while preserving the dice edges, thereby improving separation quality and reducing the need for additional spacing between adjacent dice.
2Strength
If a diamond saw is used to dice the wafer, then thicker wafers can be processed, but the blade thickness requires three to five hundred microns separation between circuitry
Solution Approach 1:
The patent replaces the mechanical saw blade with a laser-based system that removes material through photothermal ablation. This eliminates the need for a physical blade with finite thickness, allowing for much narrower street regions and thereby maximizing the use of wafer real estate while still being capable of processing thicker wafers.
Solution Approach 2:
The laser beam can be focused to a very small spot size and precisely controlled in three-dimensional space, allowing material removal with sub-micron precision. This dimensional control enables the creation of extremely narrow streets between dice, dramatically reducing the spacing requirements compared to mechanical sawing where the blade thickness dictates minimum separation.
3Manufacturing precision
If conventional scribing is used, then only one side of a die can be scribed in the direction of the crystalline structure, but cleaving the other side results in a jagged separation line
Solution Approach 1:
The laser-based dicing system is not constrained by the crystalline structure of the wafer material in the same way mechanical scribing is. The laser can ablate material along any desired path with equal precision, allowing for clean separation lines on both sides of each die regardless of crystal orientation. This provides operational flexibility that mechanical methods cannot achieve.
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 enables clean and precise separation of integrated circuits with minimal thermal damage, allowing for denser packing and reduced waste, as well as effective handling of wafers with backside metallization, improving the efficiency and yield of the dicing process.
Implementation Method 1
patterning the metallization on the backside of the monocrystalline silicon substrate with a first femtosecond-based laser scribing process to provide a first plurality of laser scribe lines on the backside
Implementation Method 2
patterning, from the front side, the water soluble mask with a second femtosecond-based laser scribing process to provide a patterned water soluble mask and to provide a second plurality of scribe lines
Implementation Method 3
plasma etching the monocrystalline silicon substrate through the second plurality of scribe lines to singulate the integrated circuits
Data Source
Figure 1
Figure 2A~2B
Figure 2C~2E
AI summary
A method of dicing a monocrystalline silicon substrate including a plurality of integrated circuits on a front side thereof and metallization on a backside thereof is described. The method includes: patterning the metallization on the backside of the monocrystalline silicon substrate with a first femtosecond-based laser scribing process to provide a first plurality of laser scribe lines on the backside, the patterning performed without using a mask; forming a water soluble mask on the front side of the monocrystalline silicon substrate; patterning, from the front side, the water soluble mask with a second femtosecond-based laser scribing process to provide a patterned water soluble mask and to provide a second plurality of scribe lines exposing regions of the monocrystalline silicon substrate between the integrated circuits, wherein the second plurality of scribe lines is aligned with the first plurality of scribe lines; plasma etching the monocrystalline silicon substrate through the second plurality of scribe lines to singulate the integrated circuits; and removing the patterned water soluble mask with an aqueous solution.