Cryogenic Stack Etching for High-Aspect-Ratio Profile Control
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Solution Overview
Problem
Existing etching methods for semiconductor stacks face challenges in controlling profile in very high aspect ratio contact dielectric etch, particularly in 3D NAND pillar structures, leading to issues like bow CD enlargement, capping, and contact twisting due to increased by-product accumulation and reliance on high-energy ions.
Innovation Solution
The method involves cooling the substrate support to below 0°C, using a halogen and phosphorous containing etch gas, generating plasma, and applying a bias to accelerate ions for selective etching of silicon oxide and silicon nitride layers with a carbon-containing mask, reducing the activation energy and reliance on high-energy ions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-energy ions are used to increase etch rate, then productivity is improved, but manufacturing precision deteriorates due to bow CD enlargement, capping, and contact twisting
Solution Approach 1:
The patent changes the physical state parameters of the etch chamber by cooling it to cryogenic temperatures (below 0°C, preferably below -40°C). This temperature parameter change modifies the etching chemistry to reduce reliance on high-energy ions, thereby maintaining etch rate while improving profile control and reducing defects like bow CD enlargement and contact twisting
Solution Approach 2:
The patent substitutes the mechanical/physical mechanism of high-energy ion bombardment with a chemically-driven etching process enabled by cryogenic temperatures. The low-temperature environment facilitates chemical reactions that etch the dielectric material effectively without requiring the mechanical impact of high-energy ions, thus resolving the contradiction between productivity and precision
2Ease of manufacture
If conventional etching methods are used, then ease of manufacture is maintained, but object-generated harmful factors increase due to by-product accumulation
Solution Approach 1:
By changing the temperature parameter to cryogenic levels, the patent fundamentally alters the etching chemistry and by-product formation characteristics. The low-temperature environment changes the chemical reaction pathways, reducing the accumulation of harmful by-products while maintaining a relatively simple process implementation through the use of standard etch gases in a modified temperature environment
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 approach enables efficient etching of high aspect ratio features with reduced bowing and distortion, maintaining a high etch rate while using a carbon mask, which is cost-effective and reduces defects.
Implementation Method 1
A substrate support for supporting the stack in an etch chamber is cooled to a temperature below 0° C.
Implementation Method 2
A plasma is generated from the etch gas.
Implementation Method 3
A bias is provided to accelerate ions from the plasma to the stack.
Data Source
AI summary
A method for etching features in a stack comprising a silicon oxide layer below a mask is provided. A substrate support for supporting the stack in an etch chamber is cooled to a temperature below 0° C. An etch gas comprising a halogen containing component and a phosphorous containing component is provided. A plasma is generated from the etch gas. A bias is provided to accelerate ions from the plasma to the stack. Features are selectively etched in the stack with respect to the mask.