DRAM Capacitor Carbon Mold for Isotropic Core Removal
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Solution Overview
Problem
The challenge in DRAM manufacturing is to reduce the size of DRAM cells while maintaining sufficient cell capacitance and avoiding cell-to-cell leakage, which is hindered by the limitations of current etch mask materials and the need for isotropic oxide mold removal, leading to increased complexity and thickness requirements.
Innovation Solution
The use of carbon as a removable mold material in DRAM capacitors, with a dense plasma-enhanced chemical vapor deposition (PECVD) carbon material forming a mold stack that includes core carbon layers and support layers, allowing for isotropic etching and reducing the need for hydrofluoric acid, thereby simplifying the etching process and maintaining selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If oxide mold material is used with hydrofluoric acid removal, then isotropic etching is achieved, but support layer removal increases and process complexity increases
Solution Approach 1:
The patent changes the material parameter from oxide to carbon, which fundamentally alters the etching chemistry required. Carbon enables isotropic etching without requiring hydrofluoric acid, eliminating the need to remove support layers and simplifying the overall etching process while maintaining manufacturing precision.
Solution Approach 2:
The carbon mold material serves as a disposable element that is easily removed after serving its purpose as an etch mask. The carbon is designed to be consumed during the isotropic etching process, eliminating the need for complex removal steps and support layer protection.
2Manufacturing precision
If oxide mold is used, then mold removal is achieved, but deposited thickness must be increased to compensate for support layer removal
Solution Approach 1:
By changing from oxide to carbon as the mold material, the patent eliminates the support layer removal issue entirely. This allows for optimized deposited thickness without needing to compensate for unnecessary material removal, improving capacitor formation precision while reducing overall structure thickness.
3Shape
If high aspect ratio etching is performed with oxide mold, then vertical etch profile is achieved, but critical dimension increases after clean
Solution Approach 1:
The patent changes the mold material from oxide to carbon, which eliminates the need for wet clean steps that cause critical dimension growth. Carbon's chemical properties allow for dry etching processes that maintain vertical profiles without the subsequent CD increase that occurs with oxide-based approaches.
4Productivity
If DRAM cell size is reduced, then memory density increases, but cell capacitance maintenance becomes difficult
Solution Approach 1:
The patent changes the etching approach from oxide-based to carbon-based, enabling better control over capacitor geometry and dimensions. This improved dimensional control allows for optimized capacitor structures that maintain sufficient capacitance even as overall cell size is reduced for higher density.
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 the formation of DRAM capacitors with improved aspect ratio etching and reduced support layer removal, allowing for smaller cell sizes and increased memory density without the complications of oxide mold removal, thus addressing the limitations of current technologies.
Implementation Method 1
a dense plasma-enhanced chemical vapor deposition (PECVD) carbon material forming a mold stack that includes core carbon layers
Implementation Method 2
exposing the mold stack to isotropic etching to remove the first core carbon layer and the second core carbon layer
Data Source
AI summary
Memory devices and methods of forming memory devices are described. Methods of forming electronic devices are described where carbon is used as the removable mold material for the formation of a DRAM capacitor. A dense, high-temperature (500° C. or greater) PECVD carbon material is used as the removable mold material, e.g., the core material, instead of oxide. The carbon material can be removed by isotropic etching with exposure to radicals of oxygen (O2), nitrogen (N2), hydrogen (H2), ammonia (NH3), and combinations thereof.