SiC Back Surface Electrode Adhesion
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Solution Overview
Problem
The peeling of the back surface three-layer metal occurs after wafer dicing and subsequent picking up from a dicing tape in silicon carbide semiconductor elements, due to inadequate adhesion between the TiC and Ni2Si layers and the multilayer film, leading to poor bonding and increased ohmic contact resistance.
Innovation Solution
A silicon carbide semiconductor element with a back surface electrode structure featuring a thin film of Ni2Si and TiC formed by sintering Ni and Ti layers, followed by a multilayer thin film with a Ti layer as the first film and an Ni layer as the second film, where the TiC-derived C composition ratio is set to 15% or more at the interface between the TiC and Ti layers, and a Ti/Ni film thickness ratio of 0.25 to 0.67, ensuring strong adhesion and preventing peeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thin film of Ni2Si and TiC is formed by sintering Ni and Ti layers on SiC substrate, then ohmic contact resistance is reduced, but the multilayer film peels off after wafer dicing and picking up
Solution Approach 1:
The patent changes the chemical composition parameters at the interface between TiC layer and multilayer thin film by controlling the Ti/Ni film thickness ratio (0.25 to 0.67) during sintering. This parameter change creates a specific carbon composition ratio (15% or more) at the interface, which improves adhesive strength and prevents peeling while maintaining low ohmic contact resistance
Solution Approach 2:
The patent creates a composite structure at the interface between TiC layer and multilayer thin film by forming a region with specific carbon composition. This composite interface structure combines the low resistance properties of Ni2Si with the adhesive properties of TiC and carbon, resolving the contradiction between electrical conductivity and mechanical bonding
2Strength
If Ti and Ni layers are deposited in a thin film structure, then adhesion is improved, but the fabrication process complexity increases
Solution Approach 1:
The patent merges the functions of multiple layers into a single sintering process. By depositing Ti and Ni layers sequentially and then sintering them together to form Ni2Si and TiC phases with a specific interface composition, the patent achieves both adhesion and low resistance in one thermal processing step, reducing overall fabrication complexity
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
The proposed solution effectively prevents the peeling of the back surface electrode, enhancing the adhesive strength and maintaining the integrity of the semiconductor element during processing and use, as demonstrated by the increased TiC-derived carbon composition at the interface and the optimized film thickness ratios.
Implementation Method 1
a thin film of Ni2Si and TiC formed by sintering after deposition of a thin layer including Ni and a thin layer of Ti
Implementation Method 2
carbon with a graphite structure is formed on the top surface. A portion of this graphite is precipitated on the Ni2Si layer surface and stable in terms of energy
Implementation Method 3
a multilayer thin film including a Ti layer as a first thin film and an Ni layer as a second thin film sequentially deposited on the TiC layer surface
Data Source
AI summary
An Ni2Si layer and a TiC layer formed by sintering after deposition of a thin layer including Ni and a thin layer including Ti on a silicon carbide substrate have a structure in which the TiC layer is precipitated on a surface of the Ni2Si layer. A multilayer thin film including a Ti layer as a first thin film and an Ni layer as a second thin film is formed on the TiC layer surface in the structure. A TiC-derived C composition ratio is set to 15% or more at an interface between the TiC layer and the Ti layer of the multilayer thin film. As a result, a silicon carbide semiconductor element can be provided without occurrence of peeling after wafer dicing and subsequent picking up by a dicing tape.