Memory Array Trench Isolation Void Trapping
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Solution Overview
Problem
As semiconductor feature sizes shrink, it becomes increasingly difficult to uniformly fill trenched isolation regions with insulative material, leading to void formation and issues with device functionality and integration, particularly due to the high aspect ratios and redeposition of sputtered atoms during high-density plasma oxide deposition.
Innovation Solution
The design of trenches with narrow lower portions and wider upper portions forces voids to occur at lower positions, using a sacrificial material and liner structure to create a step transition, allowing the insulative material to fill the upper regions while leaving voids in the narrow lower portions, which are then contained within the isolation regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-density plasma oxide deposition is used to fill trenched isolation regions, then the insulative material can be deposited, but voids become trapped in the trenches due to redeposition of sputtered atoms
Solution Approach 1:
The trench is divided into two distinct regions: a lower region with a first width and an upper region with a second width greater than the first width. This segmentation allows the lower region to accommodate voids while the upper region ensures complete filling with insulative material, thereby resolving the contradiction between material filling and void formation.
Solution Approach 2:
Different regions of the trench are given different widths to serve different functions. The lower region is designed with a narrower width to trap voids, while the upper region has a wider width to ensure complete filling. This local differentiation resolves the contradiction by assigning specific quality characteristics to different parts of the same structure.
2Productivity
If trenched isolation regions are made narrower and deeper with increasing integration levels, then device density increases, but uniform filling with insulative material becomes increasingly difficult
Solution Approach 1:
The trench cross-section is segmented into a lower portion and an upper portion with different widths. This segmentation enables the lower portion to be filled first (accommodating voids) while the upper portion is filled last (ensuring uniform filling), thereby resolving the contradiction between high integration density and uniform filling precision.
Solution Approach 2:
The trench geometry transitions from a uniform cross-section to a non-uniform cross-section with varying width along the depth dimension. This dimensional change allows the trench to accommodate both voids and ensure uniform filling, resolving the contradiction between increased integration density and manufacturing precision.
3Area of stationary object
If the trench width is reduced to increase integration density, then more devices can be packed, but void formation increases due to redeposition effects
Solution Approach 1:
The trench is segmented into a lower region with reduced width and an upper region with greater width. This segmentation allows the lower region to trap voids that form during deposition, while the upper region maintains sufficient width to ensure complete filling and proper isolation, thereby resolving the contradiction between area reduction and reliability maintenance.
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 effectively traps voids within the narrow portions of the trenches, maintaining the insulative properties of the isolation regions and preventing voids from causing integration and functionality issues, while allowing uniform filling of the wider portions with high-density plasma-deposited oxide.
Implementation Method 1
high-density plasma (HDP) oxide has been widely used in trenched isolation regions... redeposition of sputtered atoms during high-density plasma oxide deposition
Data Source
AI summary
The invention includes semiconductor constructions having trenched isolation regions. The trenches of the trenched isolation regions can include narrow bottom portions and upper wide portions over the bottom portions. Electrically insulative material can fill the upper wide portions while leaving voids within the narrow bottom portions. The trenched isolation regions can be incorporated into a memory array, and/or can be incorporated into an electronic system. The invention also includes methods of forming semiconductor constructions.