Stress Buffer Region for Copper TSV in Semiconductor Devices
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Solution Overview
Problem
The thermal expansion mismatch between silicon semiconductor substrates and copper through-hole electrodes leads to stress propagation, affecting the electrical characteristics of devices like transistors and limiting high-speed operation in stacked semiconductor devices.
Innovation Solution
Incorporating a stress buffer region with a material having a higher thermal expansion coefficient than the substrate, sandwiched between the through-hole electrode and the active region, to compensate for the stress caused by the copper electrode, using insulating materials like silicon oxide or silicon nitride, and arranging stress buffer parts in specific patterns around the through-hole electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a copper through-hole electrode is formed in a silicon semiconductor substrate, then interconnection resistance is reduced and high-speed operation is enabled, but stress propagates through the substrate due to thermal expansion mismatch, increasing characteristic variation of devices
Solution Approach 1:
The patent introduces a stress buffer part made of insulating material with higher thermal expansion coefficient than silicon (e.g., silicon oxide, silicon nitride) as an intermediary between the copper through-hole electrode and the active region. This stress buffer part absorbs and compensates for the stress generated by thermal expansion mismatch, preventing stress propagation to the transistor while maintaining the electrical connection benefits of copper TSVs.
Solution Approach 2:
The patent changes the material parameter (thermal expansion coefficient) by selecting insulating materials with higher thermal expansion coefficients than silicon for the stress buffer part. This parameter change enables the stress buffer part to expand more than the silicon substrate during thermal cycles, thereby compensating for the compressive stress generated by the copper electrode's higher thermal expansion coefficient.
2Productivity
If through-hole electrodes are used to connect stacked semiconductor chips, then wire length is reduced and interconnection resistance decreases, but device size must be increased to accommodate the through-hole structure
Solution Approach 1:
The patent applies local quality by providing stress buffer parts only in specific locations where stress compensation is needed - namely, between the through-hole electrode and the active region. The stress buffer part is not uniformly distributed but is strategically placed to provide stress compensation exactly where required, minimizing the overall area impact while maintaining device performance.
3Volume of moving object
If the semiconductor substrate is thinned to reduce device size, then miniaturization is achieved, but the substrate becomes more susceptible to stress effects from through-hole electrodes
Solution Approach 1:
The patent implements beforehand cushioning by pre-positioning the stress buffer part between the through-hole electrode and the active region before the substrate is thinned. This stress buffer part acts as a protective cushion that absorbs stress effects, allowing the substrate to be thinned for miniaturization without increasing stress susceptibility. The stress buffer part is formed as part of the interlayer insulating film structure before substrate thinning operations.
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 solution effectively reduces the influence of stress from the through-hole electrode on semiconductor devices, stabilizing electrical characteristics and enabling high-speed operation while minimizing the size of the semiconductor device.
Implementation Method 1
the thermal expansion coefficient of the semiconductor substrate (i.e., 2.3 ppm/° C.) greatly differs from the thermal expansion coefficient of the copper TSV (i.e., 16.7 ppm/° C.)
Data Source
AI summary
A semiconductor device includes: an active region located in an upper portion of a semiconductor substrate; a through-hole electrode penetrating the substrate, and made of a conductor having a thermal expansion coefficient larger than that of a material for the substrate; and a stress buffer region located in the upper portion of the substrate and sandwiched between the through-hole electrode and the active region. The stress buffer region does not penetrate the substrate and includes a stress buffer part made of a material having a thermal expansion coefficient larger than that of the material for the substrate and an untreated region where the stress buffer part is not present. The stress buffer part is located in at least two locations sandwiching the untreated region in a cross section perpendicular to a surface of the substrate and passing through the through-hole electrode and the active region.