Silicon Nitride Gap-Filling Layer Fabrication
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Solution Overview
Problem
The existing silicon nitride contact etching stop layers face challenges in achieving sufficient thickness and tensile stress for improved transistor efficiency due to limitations in thermal budget and gap-filling capabilities, leading to issues like void generation and cracking.
Innovation Solution
A method involving a pre-multi-step formation process with stacked film layers and a post single-step deposition process to form a cap layer, using techniques like ALD, PECVD, and LPCVD, with specific gas flow rates and curing processes to achieve a dense and sparse film structure, enhancing both thickness and stress while preventing cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the silicon nitride contact etching stop layer is increased to improve tensile stress and device efficiency, then the device efficiency and ion gain are improved, but seam and void are easily generated due to insufficient gap-filling capability
Solution Approach 1:
The silicon nitride layer is divided into multiple sub-layers (first, second, and third silicon nitride layers) with different thicknesses and deposition conditions. The first layer provides initial stress, the second layer (with greater thickness) provides additional stress and gap-filling, and the third layer provides final stress enhancement. This segmentation allows each layer to be optimized for specific functions, achieving cumulative stress improvement while maintaining gap-filling capability through controlled deposition of each individual layer.
2Reliability
If the silicon nitride layer is deposited below 550°C to protect the silicide layer, then the silicide layer is protected from thermal damage, but the tensile stress of the silicon nitride is inadequate
Solution Approach 1:
The deposition process is segmented into multiple steps, each depositing a portion of the total silicon nitride thickness at temperatures below 550°C to protect the silicide layer. By accumulating stress through multiple thin layers rather than one thick layer deposited at high temperature, the patent achieves adequate total tensile stress while maintaining silicide layer protection.
Solution Approach 2:
The deposition parameters are changed and optimized for each individual layer deposition step, including controlling gas flow rates, pressure, and temperature to maximize stress generation within the low-temperature constraint. Multiple deposition cycles with optimized parameters accumulate the required total stress without exceeding the thermal budget that would damage the silicide layer.
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 solution provides a silicon nitride gap-filling layer with sufficient thickness and stress to enhance ion gain and device efficiency, while improving gap-filling capability and preventing seam and void formation, thus addressing the limitations of existing technologies.
Implementation Method 1
performing a pre-multi-step formation process, wherein a stacked film layer is formed on a substrate
Implementation Method 2
the tensile stress of a contact etching stop layer is typically improved by performing a curing process after deposition
Data Source
AI summary
A method for fabricating a silicon nitride gap-filling layer is provided. A pre-multi-step formation process is performed to form a stacked layer constituting as a dense film on a substrate. Then, a post-single step deposition process is conducted to form a cap layer constituting as a sparse film on the stacked layer, wherein the cap layer has a thickness of at least 10% of the total film thickness.