Semiconductor Isolation Structure Cleaning With Controlled Dielectric Etch
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Solution Overview
Problem
Existing semiconductor isolation technologies face challenges in effectively electrically isolating components within a semiconductor substrate while avoiding surface damage and contamination, particularly when using etchants like phosphoric acid, which can degrade the substrate and introduce impurities.
Innovation Solution
A method involving the formation of a first and second dielectric layer, with controlled etch rates using diluted hydrofluoric acid, followed by a cleaning process that selectively removes the second layer to form a recess, which is then filled with dielectric material, thereby creating an isolation structure that minimizes substrate damage and contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phosphoric acid is used for cleaning the recess, then the cleaning effectiveness is improved, but the semiconductor substrate surface is damaged and contaminated
Solution Approach 1:
The patent introduces an intermediary cleaning solution comprising ammonium fluoride, hydrofluoric acid, and water that mediates between the cleaning requirement and substrate protection. This intermediary solution effectively removes etch byproducts and residues while being less harmful to the substrate compared to phosphoric acid, thus resolving the contradiction between cleaning effectiveness and substrate integrity
Solution Approach 2:
The patent changes the chemical parameters of the cleaning solution by using a specific composition ratio of ammonium fluoride (0.01-10 wt%), hydrofluoric acid (0.01-10 wt%), and water (88.98-99.98 wt%). This parameter optimization allows the cleaning solution to be effective at removing contaminants while maintaining substrate integrity, resolving the contradiction between cleaning power and substrate damage
2Manufacturing precision
If additional etching steps are performed to clean the recess, then the cleaning thoroughness is improved, but the substrate integrity deteriorates
Solution Approach 1:
The patent uses a specially formulated cleaning solution as an intermediary that provides thorough cleaning without requiring additional aggressive etching steps. The solution contains ammonium fluoride and hydrofluoric acid in optimized concentrations that effectively remove etch byproducts while protecting the substrate, thus achieving cleaning thoroughness without compromising substrate integrity
Solution Approach 2:
The patent converts the potentially harmful effect of hydrofluoric acid into a beneficial cleaning mechanism by optimizing its concentration (0.01-10 wt%) and combining it with ammonium fluoride. This conversion allows the solution to effectively remove contaminants that would otherwise require additional etching steps, achieving thorough cleaning while maintaining substrate integrity
3Manufacturing precision
If the etch rate ratio of the first dielectric layer to the second dielectric layer is increased, then the selective removal of the second layer is improved, but the control precision over the isolation structure formation deteriorates
Solution Approach 1:
The patent optimizes the etch rate ratio parameter by selecting specific dielectric materials with appropriate etch rate differences. The first dielectric layer is chosen to have a higher etch rate than the second layer when exposed to the cleaning solution, enabling selective removal while maintaining control over the isolation structure formation process
Solution Approach 2:
The patent applies partial action by using a cleaning solution that selectively removes portions of the second dielectric layer while leaving the first layer intact. This partial selective removal achieves the necessary cleaning and isolation without requiring complete removal or overly complex control mechanisms
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 precise control of the isolation structure, reducing parasitic sub-threshold transistor effects and enhancing active area utilization while maintaining substrate integrity and increasing yield by avoiding additional etching steps that could harm the substrate.
Implementation Method 1
A recess is formed through the second dielectric layer and the first dielectric layer into the semiconductor substrate. The recess is cleaned. Cleaning the recess includes using an etchant. A ratio of an etch rate of the first dielectric layer by the etchant to an etch rate of the second dielectric layer by the etchant is in a range from 0.10 to 4.
Implementation Method 2
The trench is cleaned. Cleaning the trench includes using hydrofluoric acid.
Data Source
AI summary
The present disclosure generally relates to semiconductor processing for forming an isolation structure in a semiconductor substrate. In an example, a first dielectric layer is formed over a semiconductor substrate. A second dielectric layer is formed over the first dielectric layer. A recess is formed through the second dielectric layer and the first dielectric layer into the semiconductor substrate. The recess is cleaned. Cleaning the recess includes using an etchant. A ratio of an etch rate of the first dielectric layer by the etchant to an etch rate of the second dielectric layer by the etchant is in a range from 0.10 to 4. The recess in the semiconductor substrate is filled with a dielectric material.