Self-Aligned Two-Time Forming Method for Sidewall Deformation Prevention
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Solution Overview
Problem
In semiconductor manufacturing, the self-aligned two-time forming process results in metal wire deformation due to mismatched stress in film combinations, leading to inclined sidewalls and inaccurate dimensioning of titanium nitride, affecting the shape of the final metal wire, especially after the core SiO2 layer is removed.
Innovation Solution
A self-aligned two-time forming method involving the sequential growth of composite film layers including silicon nitride, silicon oxide, titanium nitride, and polysilicon layers, with specific etching steps using these layers as hard masks to form and pattern structures, ensuring stress matching and preventing sidewall deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a one-step formation process is used at 530°C, then the formation process is simplified, but the stress mismatch between film layers causes sidewall deformation and metal wire shape inaccuracies
Solution Approach 1:
The patent divides the formation process into two separate steps: first forming the core layer SiO2 and NDC, then forming the sidewalls. This segmentation allows each layer to be formed under optimized stress conditions, preventing the cumulative stress deformation that occurs in one-step processes. The two-time formation method explicitly separates the core layer formation (step 1) from the sidewall formation (step 2), resolving the stress mismatch problem.
Solution Approach 2:
The patent changes the formation temperature parameter from the conventional 530°C to 400°C for the second formation step. This temperature adjustment modifies the stress characteristics of the deposited films, enabling better stress matching between layers and preventing sidewall deformation. The parameter change is applied specifically to the sidewall formation step while maintaining the core layer formation at its optimal temperature.
2Ease of operation
If the core layer SiO2 is removed by wet process, then the sidewall structure is exposed, but stress release causes obvious sidewall inclination and angle reduction from 87° to 82°
Solution Approach 1:
The patent applies preliminary stress compensation during the sidewall formation step, before the core layer removal. By adjusting the deposition parameters and film composition during sidewall formation, the structure is pre-conditioned to maintain its shape after subsequent core layer removal. This preliminary action prevents the stress release deformation that would otherwise occur when the core layer is removed by wet etching.
3Manufacturing precision
If sidewall etching is performed to define metal wire dimensions, then the metal wire shape is determined, but the NDC at the bottom of sidewalls is deformed and titanium nitride dimensioning becomes inaccurate
Solution Approach 1:
The patent segments the etching process into selective steps that protect different layers. The sidewall etching step is designed to etch only the NDC and SiO2 layers while leaving the titanium nitride layer intact as a protective mask. This segmentation prevents the deformation of NDC at the bottom of sidewalls that would occur in conventional single-step etching, thereby maintaining both the dimensional accuracy and structural integrity.
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 effectively prevents sidewall deformation by matching stress between film layers, ensuring accurate pattern definition and smooth two-time formation, overcoming the limitations of prior art and enhancing industrial utility.
Implementation Method 1
the first silicon oxide layer and the second silicon oxide layer are formed by adopting a chemical vapor deposition method
Implementation Method 2
the polysilicon layer is formed by adopting a diffusion furnace process
Implementation Method 3
the silicon nitride pattern structures in the sidewalls are removed by adopting a wet etching method
Data Source
AI summary
The present disclosure provides a self-aligned two-time forming method capable of preventing sidewalls from being deformed, comprises sequentially growing a first silicon nitride layer, a first silicon oxide layer, a titanium nitride layer, a second silicon oxide layer, a second silicon nitride layer and a polysilicon layer on a via layer from bottom to top; defining a pattern by using the polysilicon layer as a hard mask, and etching the second silicon nitride layer to an upper surface of the second silicon oxide layer to form a plurality of silicon nitride pattern structures from the second silicon nitride layer; forming sidewalls on sidewalls of the plurality of silicon nitride pattern structures; removing the silicon nitride pattern structures in the sidewalls; etching the silicon nitride layer and the titanium nitride layer by using the sidewalls as a hard mask to form a titanium nitride pattern structure.