3D Contact Formation via Spacer-Assisted Stepped Etching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for forming 3D contact structures in semiconductor devices require repeated and precise patterning and etching operations, leading to increased process complexity, reduced error margins, and higher costs due to the need for thicker mask layers and more extensive patterning and etching steps.
Innovation Solution
The method involves exposing multiple layers in a single pattern and etch process, using spacer processes to separate layers, reducing the number of masks, patterning steps, and etch steps, and employing a mask layer and spacers to form stepped structures, thereby minimizing errors and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If repeated patterning and etching operations are performed to form contacts to each word line in 3D memory, then each conductive layer can be exposed and contacted, but the number of process steps increases and process time is extended
Solution Approach 1:
The patent combines multiple patterning and etching operations into a single integrated process. Specifically, a mask layer is formed once and used to simultaneously expose multiple conductive layers through a single etching operation, eliminating the need for repeated separate operations for each word line contact formation.
Solution Approach 2:
The patent transitions from a planar contact approach to a three-dimensional contact structure. By forming contacts that extend through multiple layers in the vertical dimension and using spacer-based separation, the process achieves multi-layer exposure without requiring repeated lateral patterning operations.
2Quantity of substance
If the number of layers is increased to increase storage capacity, then storage capacity is improved, but the process margin becomes smaller and error accumulation increases
Solution Approach 1:
The patent segments the contact formation process into distinct phases: initial mask formation, single etching operation to create stepped structure, spacer formation for separation, and final contact completion. This segmentation allows each high-layer-count device to be processed through the same standardized steps without compounding errors.
Solution Approach 2:
The patent uses spacer structures as templates to replicate the separation pattern across multiple layers simultaneously. The spacer material is deposited and etched to create identical separation features for all exposed layers in a single operation, ensuring consistency across the entire stack.
3Ease of manufacture
If a thicker starting mask layer is used to accommodate repeated patterning, then the mask layer can withstand multiple operations, but dimensional control precision is reduced and accumulated errors increase
Solution Approach 1:
The patent performs the mask formation and initial etching operation before any spacer-based separation is implemented. This preliminary action establishes the basic contact footprint early in the process, and subsequent spacer operations merely refine and separate the structure without requiring additional mask re-patterning.
Solution Approach 2:
The patent introduces spacer material as an intermediary element that performs the separation function previously requiring repeated mask operations. The spacer acts as a self-aligned mask that defines the final contact dimensions without requiring the original photoresist mask to be re-patterned.
Data Source
AI summary
A method for forming a semiconductor device includes providing a semiconductor structure which has a substrate and N sub-stack structures numbered from 1 to N, where N is an integer. Each sub-stack structure includes two sub-stacks, and a mask layer overlying the N sub-stack structures. The method also includes repeatedly removing a portion of the mask layer and removing exposed portions of the sub-stack structures to form a first stepped structure, and forming first spacers on sidewalls of the mask layer and the sub-stack structures in the stepped structure, each spacer covering a portion of the exposure portions of the sub-stack structures. The method further includes using the mask layer and the first spacers as masks to remove exposed portions of an upper sub-stack in the first stepped structure, and removing the mask layer and the spacers to form a second stepped structure.