Metal Hardmask Etch for Vertical Vias and Trenches
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Solution Overview
Problem
Existing methods for forming vias and trenches in dielectric layers during semiconductor wafer processing face challenges in achieving vertical sidewalls and efficient filling with conductive materials, often resulting in tapered vias and trenches with corner overhangs that increase leakage and complicate deposition processes.
Innovation Solution
A method involving partial etching of vias through a via mask, followed by trench etching through a trench mask that completes and over-etches the vias to widen their bottoms, while rounding the tops above a planarization line, followed by filling with a conductive material and planarization, ensures vertical sidewalls and improved deposition without increasing leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional etching methods are used to form vias and trenches, then the formation process is simplified, but the sidewalls become tapered and corner overhangs increase leakage
Solution Approach 1:
The etching process is divided into two separate stages: first etching vias through a via mask, then etching trenches through a trench mask. This segmentation allows independent optimization of each etching step to achieve vertical sidewalls and prevent corner overhangs while maintaining process simplicity
Solution Approach 2:
The via mask is formed and etching parameters are optimized in advance before trench formation. This preliminary action establishes vertical via sidewalls and proper via dimensions before trench etching begins, preventing corner overhangs from the outset
2Manufacturing precision
If via and trench etching are performed in separate steps, then vertical sidewalls are achieved, but the process complexity increases
Solution Approach 1:
The trench mask serves multiple functions: it defines the trench pattern and simultaneously protects the via regions during trench etching. This multi-functionality allows separate via and trench etching to achieve vertical sidewalls without proportionally increasing process complexity
3Ease of manufacture
If corner overhangs are present in vias and trenches, then deposition may be simplified, but leakage increases and filling becomes problematic
Solution Approach 1:
The via mask is designed with intentionally rounded corners that are larger than the final desired via dimensions. During via etching, this rounded mask pattern prevents corner overhang formation and ensures sharp, clean via corners that eliminate leakage paths, while the extra mask material is simply removed in the planarization step
4Reliability
If over-etching is used to complete vias, then via connectivity is ensured, but via bottom widening occurs
Solution Approach 1:
The etching process is optimized with different parameters for via formation versus trench formation. During via etching, parameters are tuned to achieve precise via dimensions with minimal over-etching. The via mask dimensions are carefully controlled to account for any necessary over-etching while maintaining precise via bottom dimensions for proper connectivity
Data Source
AI summary
A method for forming conductive contacts in a dielectric layer is provided. Partial vias are etched into the dielectric layer through a via mask. Trenches are etched into the dielectric layer through a trench mask, wherein the etching the trenches completes and over etches the vias to widen bottoms of the vias. Tops of the trenches or vias are rounded.