Memory Stack Slot Recesses for Staircase Adhesion
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Solution Overview
Problem
In semiconductor fabrication, particularly in the formation of staircase structures for vertical memory arrays, there is a challenge with poor adhesion between photoresist or spin-on dielectric materials and adjacent conductive and insulating structures, leading to delamination and defects in the staircase structure.
Innovation Solution
The method involves forming a slot in the alternating conductive and insulating structures and creating recesses in these structures to increase the surface area for adhesion. A photoresist or spin-on dielectric material is then formed over the structures and within the slot and recesses, enhancing the adhesion and reducing delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photoresist or spin-on dielectric material is formed over conventional vertical memory array structures, then the memory device can be manufactured, but poor adhesion occurs between the photoresist/dielectric material and the conductive/insulating structures leading to delamination
Solution Approach 1:
The patent introduces recesses that extend vertically into the conductive and insulating structures, transforming the adhesion interface from a two-dimensional surface contact to a three-dimensional interlocking structure. This dimensional change allows the photoresist material to physically engage with the recesses, creating mechanical interlocking that significantly enhances adhesion strength and prevents delamination during subsequent fabrication processes.
Solution Approach 2:
The recesses create a porous or cavity-containing structure within the conductive and insulating layers. These cavities increase the effective surface area and provide anchoring points for the photoresist material, similar to how porous materials enhance adhesion through increased surface area and mechanical interlocking. The photoresist fills these recesses, creating a more robust bonded interface.
2Ease of manufacture
If staircase structures are formed by etching exposed regions of conductive structures, then electrical connections can be established, but defects occur in the staircase structure due to poor adhesion
Solution Approach 1:
By creating vertical recesses in the conductive and insulating structures before forming the staircase, the patent adds a third dimension to the interface geometry. This enables the photoresist to anchor deeply within the structure, maintaining adhesion strength throughout the multi-step etching process required to form the staircase, thereby preventing defects and ensuring manufacturing precision.
Solution Approach 2:
The recesses are formed in advance, before the photoresist is applied and before the staircase etching begins. This preliminary action prepares the substrate with enhanced adhesion features that will persist through all subsequent processing steps, ensuring that the photoresist remains firmly attached during the staircase formation process and preventing delamination-related defects.
3Productivity
If vertical memory array architectures are implemented to increase memory density, then more memory cells per die area are achieved, but complex fabrication processes are required including staircase structure formation
Solution Approach 1:
The introduction of vertical recesses adds a dimensional feature that simplifies the overall fabrication process by providing inherent adhesion enhancement. This structural modification allows for more robust processing during staircase formation, reducing the need for additional adhesion-promoting steps and simplifying the complex fabrication sequence required for vertical memory arrays.
Solution Approach 2:
The recesses act as a pre-prepared cushion or buffer that absorbs the stress and potential delamination issues that arise during the complex staircase formation process. By having this adhesion-enhancing feature in place beforehand, the process becomes more forgiving and reliable, reducing the complexity of process control and defect management.
Data Source
AI summary
Methods of improving adhesion between a photoresist and conductive or insulating structures. The method comprises forming a slot through at least a portion of alternating conductive structures and insulating structures on a substrate. Portions of the conductive structures or of the insulating structures are removed to form recesses in the conductive structures or in the insulating structures. A photoresist is formed over the alternating conductive structures and insulating structures and within the slot. Methods of improving adhesion between a photoresist and a spin-on dielectric material are also disclosed, as well as methods of forming a staircase structure.