Trench Isolation Structure Bottom-Up Selective Oxide Growth
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Solution Overview
Problem
Existing methods for filling high aspect ratio trench isolation structures in semiconductor technology face challenges such as cavity formation, seam issues, and difficulties in controlling the growth of silicon oxide, particularly in sub-100 nm technology, which affect the quality and yield of integrated circuits.
Innovation Solution
A method that involves forming an oxide layer in the trench after etching, uncovering the silicon substrate at the bottom of the trench, and selectively growing silicon oxide from the bottom towards the upper edge, using thermal oxidation and potentially an intermediate layer to enhance selectivity, along with surface implantation and annealing steps to prevent cavity formation and ensure proper filling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If HDP-CVD process is used to fill isolation trenches, then dense insulation layers can be obtained, but cavity and seam formation occurs in sub-100 nm technology
Solution Approach 1:
The patent applies preliminary action by performing an initial oxidation step to form an oxide layer on the trench walls before the main SelOx filling process. This preparatory oxidation modifies the surface conditions to enable subsequent selective oxide growth from the bottom upward, preventing cavity and seam formation that occur with direct HDP-CVD filling in sub-100 nm trenches
Solution Approach 2:
The patent inverts the conventional filling approach by using selective oxide growth that proceeds from the bottom of the trench upward, rather than depositing material from the top down or attempting to fill the entire trench at once. This inverted growth direction ensures complete filling without cavities or seams, resolving the reliability issue while maintaining manufacturing precision
2Reliability
If thermal oxidation is performed after trench etching, then damage is annealed, but uncovered silicon is required for SelOx which conflicts with the oxidation step
Solution Approach 1:
The patent segments the oxidation process into two distinct stages: first, an initial thermal oxidation step to anneal damage and form a preparatory oxide layer on trench walls; second, a selective oxide growth step that proceeds from the bottom upward. This segmentation allows both damage annealing and selective growth requirements to be satisfied at different times, resolving the contradiction between needing covered silicon for annealing and uncovered silicon for SelOx
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 allows for seamless and controlled filling of high aspect ratio trenches, preventing cavity and seam formation, and improving the quality of isolation structures, particularly for DRAM memory cells, by optimizing the process sequence and using selective growth techniques.
Implementation Method 1
selectively growing silicon oxide from the bottom towards the upper edge, using thermal oxidation
Implementation Method 2
The deposition of silicon oxide with the aid of an HDP-CVD process (high density plasma chemical vapor deposition) is known as a method for filling isolation trenches
Implementation Method 3
As a result of the high plasma density, this process also has a sputtering component in addition to the deposition
Implementation Method 4
since the isolation trench is severely damaged at the surface directly after the standard RIE etching (reactive ion etching)
Data Source
AI summary
A method for fabricating a trench isolation structure wherein a trench is formed in a silicon body and an oxide layer is formed in the trench. The silicon body is exposed at the bottom of the trench by means of an etching step, and silicon oxide is selectively grown on the silicon exposed at the bottom of the trench, the silicon oxide being grown from the bottom of the trench toward an upper edge of the trench.