Damascene Conductor Trench Etching for 3D Memory
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Solution Overview
Problem
Manufacturing high aspect ratio conductors for 3D memory devices is challenging due to defects such as stringers and critical dimension thinning, which affect the formation of straight corners and vertical walls in trench structures.
Innovation Solution
A method involving a two-step etching process where a lining material with a higher etch rate than the insulating fill material is used to form trenches with straight corners and vertical walls, followed by radiation weakening and selective removal of the lining to create a damascene conductor structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching processes are used to form high aspect ratio trenches, then the trenches can be formed, but the corners become rounded and walls become non-vertical due to stringers and critical dimension thinning
Solution Approach 1:
A lining material is deposited on the trench walls before the main etching process to protect the corners and walls during etching, ensuring straight corners and vertical walls are maintained throughout the high aspect ratio trench formation
Solution Approach 2:
The patent uses a two-step etching process with different parameters: a first etch process with controlled depth to avoid over-etching, and a second etch process that selectively removes the lining material. This parameter control prevents corner rounding and wall non-verticality while maintaining structural integrity
2Manufacturing precision
If the lining material is completely removed during etching, then the trenches are clean, but the corners become rounded and walls lose verticality
Solution Approach 1:
The first etch process is controlled to be partial, etching only to a specific depth without completely removing the lining material. This partial action maintains the protective lining on corners and walls, preventing rounding and non-verticality while still forming the trench structure
Solution Approach 2:
The lining material serves different functions in different locations: it is selectively removed in areas where conductor deposition is needed, while being retained in corners and along walls to maintain straight profiles and verticality during the etching process
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
This method enables the formation of high aspect ratio conductor structures with desirable straight corners and vertical walls, maintaining the profile of the stack and improving the integrity of 3D memory device structures.
Implementation Method 1
The lining, including those in the corners at the bottom of the trenches, has an etch rate greater than the insulating fill material in a selected second etch process
Implementation Method 2
The remaining lining material can be further weakened by exposure to radiation, such as energized particles
Data Source
AI summary
A method of forming a conductor structure can result in vertical sidewalls. The method deposits a lining over a plurality of spaced-apart stacks of active layers. An isolation material is formed over the lining, over and in between the spaced-apart stacks. A plurality of trenches in the isolation material is arranged to cross over the plurality of spaced-apart stacks of active strips, leaving at least a residue of the lining on a bottom of the trenches between the stacks of active strips and over a sidewall of the spaced-apart stacks of active strips. The residue of the lining on the bottom of the trenches and the sidewalls of the spaced-apart stacks of active layers is selectively removed. Then the plurality of trenches is filled with conductive or semiconductor material to form the damascene structure.