Semiconductor Bit Line Spacer for Air Gap Formation
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Solution Overview
Problem
Conventional semiconductor devices face challenges in manufacturing due to spacer damage during subsequent processes, leading to corrosion and defects in wiring structures, particularly in the formation of air gaps.
Innovation Solution
A semiconductor device is manufactured with a first spacer made of silicon nitride, having a constant thickness, surrounding the bit line structure and contacting its sidewalls, and an air gap is defined between the capacitor contact structure and the spacer, preventing corrosion and etching during wet etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional spacer material is used during air gap formation, then the air gap can be created, but the spacer gets damaged during wet etching processes causing corrosion and defects in the bit line structure
Solution Approach 1:
A silicon nitride layer is introduced as an intermediary protective layer between the bit line structure and the wet etchant. This sacrificial spacer layer absorbs the harmful etching effects, preventing damage to the underlying bit line structure while enabling air gap formation. The silicon nitride layer is selectively removed after serving its protective function.
Solution Approach 2:
The silicon nitride spacer layer is applied beforehand to cushion and protect the bit line structure from subsequent wet etching damage. This pre-applied protective layer acts as a buffer that withstands the etching process, ensuring the structural integrity of the bit line before the air gap is formed.
2Manufacturing precision
If the spacer thickness is not constant, then manufacturing may be simpler, but the electrical characteristics and performance of the semiconductor device deteriorate
Solution Approach 1:
The mechanical deposition process is replaced with plasma-enhanced chemical vapor deposition (PECVD) to form the silicon nitride layer. This chemical deposition method provides superior thickness uniformity and control compared to mechanical approaches, achieving constant spacer thickness with better manufacturing precision while maintaining reasonable process complexity.
Solution Approach 2:
The deposition parameters (temperature, pressure, gas flow rates) are optimized and controlled during PECVD processing to achieve uniform silicon nitride layer thickness. By adjusting these parameters, constant spacer thickness is achieved with high precision, resolving the contradiction between manufacturing precision and process complexity.
3Ease of manufacture
If no protective layer is used, then the manufacturing process is simpler, but the bit line contact and structure are corroded and etched during wet etching
Solution Approach 1:
The harmful wet etching step is extracted and separated from the main manufacturing process by introducing a sacrificial silicon nitride layer. This allows the wet etching to proceed without damaging the bit line structure, as the silicon nitride layer absorbs the damage. The sacrificial layer is then removed, leaving the protected bit line structure with good electrical characteristics.
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 use of a silicon nitride spacer with constant thickness ensures the bit line contact and structure are not corroded or etched, maintaining good electrical characteristics and preventing defects in the semiconductor device.
Implementation Method 1
A first spacer having a constant thickness may surround and contact a sidewall of the bit line structure... preventing corrosion and etching during wet etching processes
Implementation Method 2
The capacitor contact structure on the substrate together with the first spacer may define an air gap therebetween
Data Source
AI summary
A semiconductor device includes a bit line structure on a substrate, the bit line structure having a polysilicon layer pattern doped with impurities, and a metal layer pattern on the polysilicon layer pattern, a first spacer surrounding and contacting a sidewall of the bit line structure, the first spacer having a constant thickness, and a capacitor contact structure on the substrate, an air gap being defined between the capacitor contact structure and the first spacer.