Integrated Circuit Trenches With Zone-Specific Depth Control
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Solution Overview
Problem
Conventional techniques for forming trenches in semiconductor substrates for integrated circuits face challenges in achieving trenches of different depths without introducing parasitic effects, such as 'hump' deformations, which are costly and difficult to modify, especially in high-voltage non-volatile memory portions and logic portions with high dopant concentrations.
Innovation Solution
A process involving the formation of a first and second stop layer on a semiconductor substrate, where a dry etch is used to create trenches of varying depths by controlling etching time, and a wet etch is employed to completely remove the second stop layer, allowing for the formation of shallower and deeper trenches in different zones without parasitic effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the volume of dielectric in shallow trench isolations is decreased to reduce mechanical stresses in logic portions, then stress relaxation is improved, but lateral isolation in non-volatile memory portions deteriorates
Solution Approach 1:
The patent applies local quality by creating different trench depths in different zones of the semiconductor substrate. Logic portions receive shallower trenches that reduce mechanical stress, while non-volatile memory portions receive deeper trenches that provide improved lateral isolation. This zone-specific approach allows each region to have the optimal trench depth for its specific functional requirements.
Solution Approach 2:
The patent segments the substrate into different zones (logic portions and non-volatile memory portions) with different trench depth requirements. By using a multi-layer stop layer structure, the patent enables independent control of trench depth in each zone, allowing shallower trenches in logic areas and deeper trenches in memory areas without affecting other regions.
2Reliability
If trenches of different depths are fabricated to meet different zone requirements, then performance in each zone is improved, but fabrication complexity and cost increase
Solution Approach 1:
The patent merges multiple trench formation operations into a single etching process. By using a multi-layer stop layer structure (first stop layer and second stop layer), the patent enables simultaneous formation of trenches with different depths in different zones during one etching operation, eliminating the need for separate etching processes for each zone and reducing fabrication complexity.
Solution Approach 2:
The patent introduces stop layers as intermediary structures that control the etching process. The first stop layer and second stop layer act as mediators that define different etching depths for different zones. These intermediary layers enable precise depth control without requiring complex process sequencing or multiple etching steps.
3Stress or pressure
If conventional techniques remove portions of dielectric to decrease volume and relax stresses, then mechanical stress is reduced, but parasitic effects such as hump deformations are introduced
Solution Approach 1:
The patent applies preliminary action by forming the appropriate trench depth during the initial etching process using stop layers, rather than removing dielectric material after trench formation. The stop layers are deposited beforehand to define the desired trench depth, preventing the need for subsequent dielectric removal that would cause hump deformations and parasitic effects.
Solution Approach 2:
The patent converts the potential harm of over-etching or excessive dielectric removal into a benefit by using stop layers as protective barriers. The stop layers prevent the etching process from going too deep, thereby eliminating the need for harmful dielectric removal steps while still achieving the desired stress relaxation through controlled trench depth.
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 process enables the cost-effective fabrication of trenches of different depths in integrated circuits, reducing mechanical stresses in logic portions and improving lateral isolation in non-volatile memory portions, while increasing capacitive value per unit area without introducing parasitic effects.
Implementation Method 1
performing a dry etch delimited by an etch mask in the first zone and in the second zone which is configured to etch, in a given time, in the first zone, the first stop layer, then at least one first trench into the substrate down to a first depth
Implementation Method 2
a wet etch is employed to completely remove the second stop layer
Data Source
AI summary
Trenches of different depths in an integrated circuit are formed by a process utilizes a dry etch. A first stop layer is formed over first and second zones of the substrate. A second stop layer is formed over the first stop layer in only the second zone. A patterned mask defines the locations where the trenches are to be formed. The dry etch uses the mask to etch in the first zone, in a given time, through the first stop layer and then into the substrate down to a first depth to form a first trench. This etch also, at the same time, etch in the second zone through the second stop layer, and further through the first stop layer, and then into the substrate down to a second depth to form a second trench. The second depth is shallower than the first depth.