Backside Metal Formation on Thin Semiconductor Wafers
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Solution Overview
Problem
Semiconductor wafers with average thicknesses less than 39 microns face challenges in die handling, die strength, and processing due to traditional singulation methods that cause chipping and cracking, and forming a metal layer on the second side can damage the wafer, while sputtering processes overheat thin substrates.
Innovation Solution
The method involves placing a semiconductor wafer in an evaporator dome with a crucible containing metals like titanium, gold, or copper, using resistive or electron beam heating to vaporize the material and deposit it on the second side of the wafer, which is not coupled to a carrier, and includes etching to form a metal layer without using a carrier, thereby avoiding overheating and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional singulation methods are used on thin wafers, then die can be separated, but die strength decreases and chipping and cracking occur
Solution Approach 1:
The patent applies preliminary action by forming the metal layer on the backside of the wafer before the singulation process. This metal layer acts as a strengthening element that prevents chipping and cracking during subsequent die separation, allowing traditional singulation methods to be used without compromising die strength
Solution Approach 2:
The patent uses composite materials by combining the semiconductor material with a metal layer (such as copper, aluminum, or tungsten) deposited on the backside of the wafer. This composite structure provides mechanical strength to thin wafers during handling and processing, preventing die damage while maintaining productivity
2Manufacturing precision
If sputtering process is used to form metal layer, then metal layer can be deposited, but thin substrates overheat
Solution Approach 1:
The patent changes the process parameters by switching from sputtering to evaporation deposition. This parameter change allows metal layer formation without the excessive heating associated with sputtering, as evaporation operates at lower substrate temperatures that are compatible with thin substrate processing
Solution Approach 2:
The patent substitutes the sputtering process (which uses plasma and ion bombardment causing heating) with an evaporation process (which uses thermal or electron beam heating of the source material). This replacement eliminates the overheating issue while still achieving precise metal layer deposition on thin substrates
3Ease of operation
If carrier is used during processing, then wafer can be handled, but wafer damage occurs during removal
Solution Approach 1:
The patent uses the metal layer deposited on the backside of the wafer as a composite strengthening element. This metal layer provides sufficient mechanical support during carrier removal and handling, eliminating the need for carrier attachment while maintaining wafer integrity and preventing damage
4Length of moving object
If wafer thickness is reduced, then device performance improves, but die handling and processing become difficult
Solution Approach 1:
The patent applies composite materials by depositing a metal layer on the backside of thin wafers. This metal layer compensates for the reduced mechanical strength of thin substrates, making handling and processing of ultra-thin wafers (less than 39 microns) as easy as processing thicker wafers, thus enabling device performance improvement without sacrificing ease of operation
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 allows for effective metal layer formation on thin semiconductor wafers without overheating or damage, enhancing die strength and yield by eliminating the need for carriers and reducing the risk of cracking during processing.
Implementation Method 1
heating the material in the crucible to a vapor and depositing the material on a second side of the semiconductor wafer
Implementation Method 2
heating the material in the crucible to a vapor and depositing the material on a second side of the semiconductor wafer
Implementation Method 3
Heating may include one of resistive heating or electron beam heating
Implementation Method 4
Heating may include one of resistive heating or electron beam heating
Data Source
AI summary
Implementations of methods of forming a metal layer on a semiconductor wafer may include: placing a semiconductor wafer into an evaporator dome and adding a material to a crucible located a predetermined distance from the semiconductor wafer. The semiconductor wafer may include an average thickness of less than 39 microns. The method may also include heating the material in the crucible to a vapor and depositing the material on a second side of the semiconductor wafer.