3D Memory Alignment Marks Using Alternating Sacrificial Tiers
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Solution Overview
Problem
The existing methods for forming integrated circuitry, such as memory arrays, face challenges in precise alignment and patterning during the manufacturing process, particularly in the formation of registration and alignment marks, which can lead to inaccuracies and increased complexity due to the need for radiation-opaque materials to ensure vertical feature perfection.
Innovation Solution
The method involves forming a stack with vertically-alternating tiers of sacrificial and non-sacrificial materials, where horizontally-spaced features are created in both tiers, and sacrificial material is replaced with metal, allowing for the formation of registration or alignment marks that extend through both insulative and metal tiers, thereby simplifying the alignment process and reducing the need for additional opaque layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If radiation-opaque materials are used to form registration and alignment marks, then vertical feature perfection is ensured, but fabrication complexity and process difficulty increase
Solution Approach 1:
The patent extracts the radiation-opaque material requirement from the alignment mark formation process. Instead of using opaque materials, the invention uses vertically-aligned sacrificial and non-sacrificial material tiers that are transparent to radiation, eliminating the need for opaque materials while maintaining vertical alignment precision through the alternating tier structure
Solution Approach 2:
The patent inverts the conventional approach by not trying to create opaque vertical features, but rather creating vertically-aligned transparent features through alternating sacrificial and non-sacrificial material tiers. The alignment is achieved through the vertical stacking geometry rather than through radiation opacity
2Use of energy by moving object
If additional opaque layers are added to ensure alignment mark visibility, then radiation penetration is improved, but process steps and fabrication complexity increase
Solution Approach 1:
The patent removes the additional opaque layers from the fabrication process. The alternating sacrificial and non-sacrificial material tiers provide sufficient radiation penetration characteristics without requiring extra opaque layers, as the vertical alignment is achieved through the tier structure itself rather than through radiation absorption contrast
Solution Approach 2:
The sacrificial and non-sacrificial material tiers serve multiple functions: they provide structural support during fabrication, enable vertical alignment through their alternating geometry, and allow radiation penetration for imaging without requiring separate opaque layers. This multi-functionality eliminates the need for additional process steps
3Volume of moving object
If vertically-stacked memory cells are formed with complex stair-step structures, then three-dimensional integration is achieved, but alignment precision and manufacturing difficulty increase
Solution Approach 1:
The patent segments the vertically-stacked structure into alternating sacrificial and non-sacrificial material tiers. This segmentation simplifies the stair-step structure by creating distinct, repeatable units that are easier to align and manufacture while maintaining the three-dimensional integrated architecture
Solution Approach 2:
The sacrificial material tiers are formed first to establish the vertical framework and alignment references. The non-sacrificial material tiers are then deposited in alignment with these pre-formed sacrificial tiers, ensuring precise alignment before the sacrificial materials are removed and replaced with conductive materials
Data Source
AI summary
A method used in forming integrated circuitry comprises forming a stack comprising vertically-alternating first tiers and second tiers. The first tiers comprise sacrificial material and the second tiers comprise non-sacrificial material that is of different composition from that of the sacrificial material. The stack extends from individual die areas to and across scribe-line area that is between immediately-adjacent of the individual die areas. The scribe-line area comprises a horizontal area in which a registration mark or an alignment mark is being fabricated. Horizontally-spaced features of the registration mark or of the alignment mark are simultaneously formed in the first tiers and the second tiers in the horizontal area and in the individual die areas. The horizontally-spaced features in the horizontal area are grouped in sections that are horizontally-separated by gaps in at least one vertical cross-section where there are less, if any, such horizontally-spaced features than are in the sections. Horizontally-spaced vertical slots are formed through uppermost of the first and second tiers of the stack in the horizontal area of the registration mark or of the alignment mark. Through the horizontally-spaced vertical slots, the sacrificial material is replaced with metal material. After the replacing, the first and second tiers in the scribe-line areas are cut through to form individual die that individually comprise one of the individual die areas. Other embodiments, including structure, are disclosed.