Alkaline Etchant for TSV Silicon Selectivity
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Solution Overview
Problem
Current methods for manufacturing microelectronic devices with Through Silicon Vias (TSVs) are costly due to multiple process steps, including dry etch and wet cleans, which require high silicon etch rates, low passivation etch rates, and low surface roughness, which are not efficiently addressed by existing silicon etchant compositions.
Innovation Solution
A composition comprising inorganic alkali basic hydroxides such as potassium hydroxide, cesium hydroxide, and additional alkaline compounds like tetraethylammonium hydroxide, with specific weight percentages and ratios, that preferentially etches silicon over silicon dioxide, providing high silicon etch rates and low surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple process steps (dry etch and wet cleans) are used for TSV manufacturing, then silicon etching can be achieved, but processing cost increases and manufacturing complexity increases
Solution Approach 1:
The patent combines multiple separate etching process steps (dry etch and wet cleans) into a single wet etching step using a specifically formulated alkaline solution. This consolidation maintains the required silicon etching quality while reducing the total number of process steps, thereby lowering manufacturing complexity and processing cost.
Solution Approach 2:
The alkaline etchant solution is designed to perform multiple functions simultaneously: it etches silicon at high rates, provides low etching of passivation layers (SiO2, TaN, TiN, SiN), and produces low surface roughness. This multi-functionality allows a single solution to replace multiple specialized process steps.
2Productivity
If high silicon etch rates are achieved, then productivity improves, but passivation layer etching may increase causing harmful effects
Solution Approach 1:
The etchant solution exhibits different etching characteristics for different materials: it provides high etch rates for silicon while maintaining low etch rates for passivation layers (SiO2, TaN, TiN, SiN). This material-selective etching behavior allows aggressive silicon removal without excessive damage to protective passivation layers.
Solution Approach 2:
The patent employs specific compositional parameters (concentrations of KOH, CsOH, TEAH, and other additives) and processing parameters (temperature, time) to optimize the etching selectivity. By carefully controlling these parameters, the solution achieves high silicon etch rates while minimizing passivation layer etching.
3Productivity
If conventional etchants are used to achieve high silicon etch rates, then productivity improves, but surface roughness increases causing harmful effects
Solution Approach 1:
The etchant solution is a composite formulation containing multiple alkaline compounds (KOH, CsOH, TEAH) and additional additives. This composite composition works synergistically to provide both high etch rates and smooth surface finish, overcoming the limitations of conventional single-component etchants that typically produce rough surfaces at high etch rates.
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 composition enables efficient etching of silicon with high selectivity over silicon dioxide, reducing surface roughness and processing costs by replacing multiple etching steps with a single etchant solution, thereby improving the throughput and quality of TSV manufacturing.
Implementation Method 1
The composition preferentially etches silicon present on a substrate as compared to silicon dioxide (SiO2), present on said substrate
Data Source
Figure 1~4
AI summary
Etching compositions and method of using the etching compositions comprising potassium hydroxide; one or more than one additional alkaline compounds selected from the group consisting of TEAH, TMAF and NH4OH; and water; or etching compositions comprising one or more than one inorganic alkali basic hydroxides selected from the group consisting of potassium hydroxide, cesium hydroxide, sodium hydroxide, rubidium hydroxide, or lithium hydroxide; optionally one or more than one additional alkaline compounds; water; and optionally one or more corrosion inhibitors; wherein the composition preferentially etches silicon present on a substrate as compared to silicon dioxide present on said substrate.