Amorphous Crystalline Aluminum Oxide Etch Stop for 3D NAND
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Solution Overview
Problem
The challenge in fabricating 3D-NAND flash memory devices is selecting an etch stop material that meets stringent wet clean selectivity requirements while minimizing the formation of residual polysilicon in recesses, which affects the controllability and reliability of the device.
Innovation Solution
An etch stop material comprising amorphous aluminum oxide and crystalline aluminum oxide is used, where the amorphous aluminum oxide is selectively etchable at a faster rate than the crystalline aluminum oxide, allowing for controlled removal and minimizing residual polysilicon in recesses during the fabrication process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amorphous aluminum oxide is used as the etch stop material, then wet clean selectivity requirements are met, but residual polysilicon forms in the recesses during later processing
Solution Approach 1:
The etch stop material is segmented into two distinct layers: a first etch stop layer (amorphous aluminum oxide) and a second etch stop layer (crystalline aluminum oxide). This segmentation allows each layer to perform its specific function - the first layer provides wet clean selectivity while the second layer prevents residual polysilicon formation, thereby resolving the contradiction between meeting selectivity requirements and avoiding harmful residual material.
Solution Approach 2:
The crystalline aluminum oxide layer acts as an intermediary barrier between the amorphous aluminum oxide etch stop layer and the subsequent processing steps. This intermediary layer prevents polysilicon from penetrating into the recesses of the amorphous aluminum oxide, thus eliminating the harmful residual polysilicon while maintaining the wet clean selectivity benefits of the amorphous layer.
2Ease of manufacture
If a single etch stop material is used, then the fabrication process is simpler, but it cannot simultaneously meet wet clean selectivity and prevent residual polysilicon formation
Solution Approach 1:
The etch stop function is segmented into two specialized layers with distinct properties. The amorphous aluminum oxide layer handles wet clean selectivity while the crystalline aluminum oxide layer handles residual polysilicon prevention. This segmentation improves device reliability and controllability by ensuring both requirements are met, justifying the increased fabrication complexity.
Solution Approach 2:
The etch stop structure uses a composite of two different aluminum oxide materials - amorphous and crystalline forms. This composite structure combines the advantages of both materials: the amorphous form provides superior wet clean selectivity while the crystalline form provides resistance to polysilicon infiltration, thereby achieving both reliability requirements simultaneously.
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 ensures improved controllability and reliability of 3D-NAND flash memory devices by effectively preventing the formation of undesirable residual polysilicon, enhancing memory density and device performance.
Implementation Method 1
the amorphous aluminum oxide is selectively etchable at a faster rate than the crystalline aluminum oxide
Data Source
AI summary
Semiconductor structures including an etch stop material between a substrate and a stack of alternating insulating materials and first conductive materials, wherein the etch stop material comprises an amorphous aluminum oxide on the substrate and a crystalline aluminum oxide on the amorphous aluminum oxide; a channel material extending through the stack; and a second conductive material between the channel material and at least one of the first conductive materials in the stack of alternating insulating materials and first conductive materials, wherein the second conductive material is not between the channel material and the etch stop material. Also disclosed are methods of fabricating such semiconductor structures.