Semiconductor Chip Buffer Plate for Thermal Stress Relief
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Solution Overview
Problem
Conventional semiconductor devices experience internal fracture and peeling due to thermal stress, particularly in power cycling tests, where the main electrode with an aluminum layer undergoes significant thermal deformation.
Innovation Solution
The semiconductor device incorporates a buffer plate with a lower coefficient of linear thermal expansion than the main electrode, bonded via a specific bonding material, to mitigate thermal stress and prevent internal fracture. The buffer plate is typically made of a laminated material or an iron-nickel alloy, with a thickness between 0.05 mm and 0.25 mm, and is designed to effectively suppress thermal deformation and stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a main electrode with aluminum layer is used in conventional semiconductor devices, then electrical conductivity is improved, but thermal stress causes internal fracture and peeling during power cycling
Solution Approach 1:
A buffer plate is introduced as an intermediary component between the semiconductor chip and the external environment. This buffer plate has a coefficient of linear thermal expansion matching that of the semiconductor substrate, serving as a mediator that absorbs and distributes thermal stress, preventing direct transmission of harmful thermal forces to the aluminum-containing main electrode.
Solution Approach 2:
The invention changes the physical parameter of thermal expansion by selecting a buffer plate material whose coefficient of linear thermal expansion matches the semiconductor substrate. This parameter matching creates a buffer zone that compensates for the high thermal expansion of aluminum, reducing thermal stress during temperature cycling without requiring changes to the aluminum electrode itself.
2Reliability
If the buffer plate has a coefficient of linear thermal expansion less than the semiconductor substrate, then thermal stress on the main electrode is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The invention specifies a precise parameter range for the buffer plate's coefficient of linear thermal expansion (0.5×10^-6 to 5.0×10^-6 /°C.), which balances two needs: matching the semiconductor substrate sufficiently to provide thermal stress protection, while remaining distinguishable from aluminum's high expansion coefficient. This parameter specification enables manufacturers to select from multiple suitable materials within the defined range.
Solution Approach 2:
The buffer plate is constructed from composite materials or alloys (such as copper-beryllium, invar, or other metal alloys) that can be engineered to achieve the desired coefficient of linear thermal expansion within the specified range. These composite materials provide both the required thermal expansion properties and mechanical strength, facilitating manufacturing while achieving the thermal stress protection function.
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 configuration significantly reduces thermal stress on the main electrode, thereby preventing internal fracture and extending the lifespan of the semiconductor device, even under high-temperature conditions.
Implementation Method 1
each of a first coefficient of linear thermal expansion of the semiconductor substrate and a second coefficient of linear thermal expansion of the buffer plate is less than a third coefficient of linear thermal expansion of the main electrode, and the second coefficient of linear thermal expansion is less than the first coefficient of linear thermal expansion
Data Source
AI summary
A semiconductor device includes a semiconductor chip including a semiconductor substrate and a main electrode provided on the semiconductor substrate, a buffer plate, and a bonding material provided between the main electrode and the buffer plate. The main electrode includes an aluminum or aluminum alloy layer. Each of a first coefficient of linear thermal expansion of the semiconductor substrate and a second coefficient of linear thermal expansion of the buffer plate is less than a third coefficient of linear thermal expansion of the main electrode. The second coefficient of linear thermal expansion is less than the first coefficient of linear thermal expansion.