Shallow Trench Etch-Cleaning Process for STI Leakage
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Solution Overview
Problem
The increasing aspect ratio of shallow trenches in semiconductor substrates during fabrication makes it difficult to effectively clean by-products, leading to defective electrical isolation in shallow trench isolation (STI) structures due to the accumulation of charged particles, which affects the insulation properties and can result in electrical leakage.
Innovation Solution
An etch-cleaning process involving multiple etching steps with a plasma cleaning process after each step using an electronegative plasma to capture and remove positive ions and by-products, disrupting their accumulation and improving the removal efficiency, thereby enhancing the structure and insulation of the shallow trench.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the aspect ratio of the shallow trench is increased to achieve better electrical isolation, then the insulation performance is improved, but it becomes increasingly difficult to clean by-products from the inner walls, leading to defective electrical isolation
Solution Approach 1:
The patent segments the trench cleaning process into multiple discrete plasma treatment steps performed at different stages (during etching, after etching, before filling). This segmentation allows each plasma step to target specific by-product accumulation zones, making the cleaning of high aspect ratio trenches effective by breaking down the complex cleaning task into manageable phases rather than attempting single-step removal
Solution Approach 2:
The patent applies preliminary plasma cleaning actions during the etching process itself (in-situ cleaning) before by-products can firmly adhere to the trench inner walls. This preliminary action prevents by-product accumulation that would otherwise be difficult to remove later, addressing the cleaning difficulty of high aspect ratio trenches by acting early when removal is still feasible
2Manufacturing precision
If a dry etching process is used to achieve anisotropic etch profile and desired sidewall control, then the trench structure is improved, but by-products are generated and accumulate on the trench inner walls, affecting insulation properties
Solution Approach 1:
The patent converts the harmful by-products generated during dry etching into removable species by introducing plasma cleaning steps. The plasma process transforms adhered by-products into volatile compounds that can be evacuated, turning the persistent contamination problem into a removable state. This resolves the contradiction by maintaining the beneficial anisotropic etching while eliminating the harmful by-product accumulation through chemical transformation
Solution Approach 2:
The patent introduces plasma as an intermediary substance between the dry etching process and the final trench structure. The plasma acts as a mediator that reacts with by-products on the trench inner walls, transforming them into removable species. This intermediary plasma step allows the process to maintain both the precision of dry etching and the cleanliness required for good insulation
3Object-generated harmful factors
If inert gases are supplied and circulated during dry etching to remove by-products, then some cleaning effect is achieved, but existing cleaning processes cannot effectively clean by-products inside high aspect ratio shallow trenches
Solution Approach 1:
The patent replaces the mechanical gas circulation cleaning system with a plasma-based chemical cleaning system. Instead of relying on inert gas flow to physically remove by-products from high aspect ratio trenches, the plasma chemically transforms by-products into volatile species that diffuse and evacuate more effectively. This substitution overcomes the limitations of mechanical cleaning in deep, narrow geometries where gas flow is insufficient
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
The method effectively cleans the shallow trench, improving the structure and reducing electrical leakage risks in the subsequently formed STI structures by efficiently removing charged particles and by-products, ensuring better insulation properties.
Implementation Method 1
performing a plasma cleaning process after each of the one or more etching steps. The plasma cleaning process can use a plasma that is electronegative
Implementation Method 2
The plasma cleaning process can use a plasma that is electronegative
Implementation Method 3
an etching gas is excited into a plasma by a high-frequency electric field. Next, for chemical actions, the plasma generates reactive elements including free radicals and reactive atoms
Implementation Method 4
The reactive elements can react with the semiconductor substrate, and etch the semiconductor substrate
Implementation Method 5
The energetic ions can be accelerated by an electric field vertical to a surface of the semiconductor substrate to bombard the semiconductor substrate, and remove a surface material of the semiconductor substrate using sputtering etch
Implementation Method 6
The energetic ions can be accelerated by an electric field vertical to a surface of the semiconductor substrate
Data Source
AI summary
Various embodiments provide shallow trenches and fabrication methods. In an exemplary method, a semiconductor substrate can be provided. A mask layer can be provided on the semiconductor substrate. An etch-cleaning process can be performed. The etch-cleaning process can include etching the semiconductor substrate to form a shallow trench by one or more etching steps using the mask layer as an etch mask. The etch-cleaning process can further include performing a plasma cleaning process after each of the one or more etching steps. The plasma cleaning process can use a plasma that is electronegative.