GaN MIM Capacitor Via Structure With Halogen Barrier Layer
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Solution Overview
Problem
In semiconductor elements, the formation of via holes for interconnection can lead to capacitance degradation and corrosion due to the dispersion of Au into AuSn solder, and the intrusion of gaseous halogens like Br into MIM capacitors, affecting reliability and leakage current.
Innovation Solution
A semiconductor element structure is designed with a SiC substrate, a GaN layer, a MIM capacitor, and a source electrode that includes a barrier metal layer resistant to halogen elements, such as Cr or V, positioned between the source electrode and the via hole to prevent halogen intrusion into the insulating film of the MIM capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a via hole is formed under the MIM capacitor to establish conduction, then the capacitance and leakage current are improved, but the reliability deteriorates due to halogen intrusion into the insulating film
Solution Approach 1:
A barrier metal layer (Cr or V) is introduced as an intermediary between the AuSn solder and the MIM capacitor insulating film. This barrier layer prevents halogen elements from the solder from intruding into the insulating film, thereby maintaining reliability while allowing the via hole to function for conduction establishment.
Solution Approach 2:
The source electrode is constructed as a composite structure with multiple layers including Au, Cr/V barrier metal, and Cu. This composite structure combines the advantages of each material: Au for conductivity, Cr/V for halogen barrier properties, and Cu for cost-effectiveness and electrical performance, resolving the contradiction between via hole functionality and halogen prevention.
2Reliability
If a barrier metal layer is added to prevent Au dispersion into AuSn solder, then corrosion is prevented, but the device complexity increases
Solution Approach 1:
The barrier metal layer (Cr or V) serves multiple functions simultaneously: it prevents Au dispersion into the AuSn solder, acts as a halogen barrier for the MIM capacitor, and provides adhesion between layers. This multi-functionality prevents corrosion while minimizing the increase in device complexity.
Solution Approach 2:
The patent combines the barrier metal function with the existing source electrode structure by integrating Cr or V layers into the electrode stack. This merging approach allows the barrier function to be incorporated without adding separate discrete components, thereby limiting the increase in device complexity.
3Reliability
If AuSn solder is used to establish conduction in the via hole, then conductivity is improved, but Au dispersion causes corrosion
Solution Approach 1:
The barrier metal layer (Cr or V) acts as an intermediary between the AuSn solder and the Au source electrode. This intermediary layer prevents direct contact and diffusion between Au and the solder, eliminating Au dispersion and corrosion while maintaining the electrical conduction function of the AuSn solder in the via hole.
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 effectively suppresses halogen intrusion and corrosion, ensuring long-term reliability and reducing leakage current by using a barrier metal layer that resists halogen elements, thereby enhancing the stability of the insulating film and overall element performance.
Implementation Method 1
a barrier metal layer is included in the source electrode; wherein a bottom of the via hole is placed between a rear surface of the source electrode and a rear surface of the barrier metal layer
Data Source
AI summary
Provided herein is: a SiC substrate having a front surface on which a GaN layer is stacked; a source electrode formed on a front surface of the GaN layer; a MIM capacitor formed on a front surface of the source electrode; and a via hole extending from a rear surface of the SiC substrate to reach the source electrode; wherein a barrier metal layer is included in the source electrode, and wherein the depth end of the via hole is placed between a rear surface of the source electrode and a rear surface of the barrier metal layer. Accordingly, intrusion of a halogen element, in particular, Br, into an insulating film that is placed in the MIM capacitor, is suppressed over a long term.