DRAM Bit Line Contact Structure Void Prevention
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Solution Overview
Problem
As DRAM devices shrink, the small size of bit line contact holes leads to voids in the bit line contact structure, affecting electrical properties and write recovery time, resulting in poor performance.
Innovation Solution
A contact structure manufacturing method involving a substrate with a shallow trench isolation structure, a medium layer, and a contact hole with a first penetrating hole through the medium layer and a second hole at the bottom, where the second hole's aperture increases along the direction towards the first hole, ensuring a larger opening size and reducing the aspect ratio, thereby improving step coverage and avoiding pores.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the BLC hole size is reduced to accommodate smaller DRAM devices, then device miniaturization is achieved, but voids form in the bit line contact structure affecting electrical properties
Solution Approach 1:
The contact hole is divided into two segments: a first contact hole through the medium layer and a second contact hole in the substrate. This segmentation allows each part to be optimized independently - the first hole provides a larger opening for better step coverage while the second hole provides adequate depth for proper electrical contact, resolving the contradiction between miniaturization and void formation.
Solution Approach 2:
Different regions of the contact structure are given different properties. The medium layer region (first contact hole) has a larger aperture for improved filling and step coverage, while the substrate region (second contact hole) has controlled dimensions for proper electrical contact. This local differentiation allows the overall structure to achieve both small device footprint and reliable electrical properties without voids.
2Volume of moving object
If the BLC hole size is reduced, then device scaling is achieved, but write recovery time performance deteriorates
Solution Approach 1:
By segmenting the contact hole into two parts with different aperture characteristics, the structure achieves effective electrical contact area sufficient for fast write recovery time while maintaining small overall device dimensions. The first contact hole's larger opening ensures proper material deposition without voids that would slow write recovery.
3Device complexity
If a single small contact hole is used, then manufacturing simplicity is maintained, but step coverage is insufficient leading to poor contact structure quality
Solution Approach 1:
The contact hole structure is segmented into a first contact hole through the medium layer and a second contact hole in the substrate. This segmentation provides a larger effective opening area that improves step coverage during deposition processes, ensuring uniform material distribution and preventing void formation while maintaining a relatively simple overall manufacturing process.
Solution Approach 2:
The contact structure transitions from a single vertical hole to a two-stage structure with different aperture dimensions at different depths. This dimensional variation along the vertical axis enables improved step coverage by providing a larger opening area for material deposition while still achieving the required contact depth in the substrate.
Data Source
AI summary
The present disclosure relates to a contact structure, a method of manufacturing a contact structure, and a semiconductor structure. The method of manufacturing a contact structure includes: providing a substrate, where the substrate is provided with a shallow trench isolation structure; forming a medium layer covering the substrate and the shallow trench isolation structure; forming a contact hole in an active region of the substrate and in the medium layer, where the contact hole includes a first contact hole penetrating through the medium layer, and a second contact hole located at the bottom of the first contact hole and formed in the substrate; and forming a contact structure extending along a first direction in the contact hole and on the medium layer.