Semiconductor Trench Oxidation for Smoother TSV Sidewalls
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Solution Overview
Problem
Existing TSV fabrication processes, such as DRIE, result in sidewall defects like scallops and silicon needles, leading to increased electrical roughness, leakage current, and reduced breakdown voltage, which are not effectively addressed by increasing isolation oxide thickness or using new materials and equipment.
Innovation Solution
A method involving an oxidation step to convert substrate material into oxide, forming a thin SiO2 layer on sidewalls, followed by passivation and metallization, to increase isolation thickness and reduce defect impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If DRIE process is used to etch deep trenches, then high etch rate and anisotropy are achieved, but sidewall defects like scallops and silicon needles are formed
Solution Approach 1:
A sacrificial oxide layer is introduced as an intermediary between the silicon substrate and the final trench structure. This oxide layer is formed by thermal oxidation before etching, serves as a buffer during the DRIE process to prevent direct contact between etching radicals and the silicon sidewalls, and is subsequently removed to leave a smooth sidewall profile without scallops or silicon needles
Solution Approach 2:
Thermal oxidation is performed as a preliminary action before the DRIE etching process. This pre-oxidation step creates a protective oxide layer on the silicon surface that prevents sidewall defect formation during etching. The oxide layer is formed in advance, then etched away along with the silicon to reveal a defect-free trench sidewall
2Reliability
If isolation oxide thickness is increased to compensate for sidewall defects, then breakdown voltage improves, but leakage current increases and device complexity increases
Solution Approach 1:
The sacrificial oxide layer, which initially appears as an additional material layer that could increase complexity, actually reduces leakage current by providing a clean, oxide-terminated sidewall surface. The thermal oxidation process creates a high-quality Si-SiO2 interface that passivates surface states and reduces interface trap density, thereby decreasing leakage current while maintaining appropriate breakdown voltage
3Manufacturing precision
If multiple passivation deposition cycles are performed to smooth sidewalls, then sidewall roughness decreases, but process time increases and deposition-removal rate balance becomes difficult to maintain
Solution Approach 1:
The mechanical deposition process (CVD or PECVD of passivation layers) is replaced with a thermal oxidation process. Thermal oxidation grows the oxide layer in-situ from the silicon substrate itself, eliminating the need for separate deposition and removal cycles. This substitution achieves smooth sidewalls through a single, well-controlled oxidation step rather than multiple iterative deposition-removal cycles
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 method enhances electrical performance by reducing leakage current and increasing breakdown voltage, enabling the production of 3D integrated devices with improved reliability and yield.
Implementation Method 1
An oxide layer is formed at least on a sidewall of the trench by means of oxidation of the substrate
Data Source
Figure 1~2Ad
Figure 2Ba~2Bb2
Figure 3
AI summary
A method is proposed of producing a semiconductor body with a trench. The semiconductor body (10) comprises a substrate (16). The method comprising the step of etching the trench (11) into the substrate (16) using an etching mask (38). An oxide layer (12) is formed at least on a sidewall (14) of the trench (11) by oxidation of the substrate (16). A passivation layer (13) is formed on the oxide layer (12) and the bottom (15) of the trench (11). The passivation layer (13) is removed from the bottom (15) of the trench (11). Finally, a metallization layer (18) is deposited into the trench (11).