Plasma Trench Etching with AR-Dependent Passivation
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Solution Overview
Problem
Conventional anisotropic plasma etching struggles to simultaneously achieve ideal side profiles and uniform depth for both low and high aspect ratio trenches in semiconductor devices, leading to issues like notch and foot defects due to aspect ratio dependent etching effects, which complicates the fabrication of semiconductor devices with a wide range of trench aspect ratios.
Innovation Solution
A multi-step plasma etch process is employed, incorporating aspect-ratio dependent passivation (ARDP) during anisotropic etching, where the etch rate is adjusted by altering plasma etch process parameters such as gas flow rates and pressure to preferentially passivate low-AR trenches, allowing for concurrent etching and passivation, thereby counteracting the effects of aspect ratio dependent etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional anisotropic plasma etching is used to etch trenches with a wide range of aspect ratios, then the etching process can handle diverse geometries, but the side profiles become non-vertical and defects like notch and foot appear due to aspect ratio dependent etching effects
Solution Approach 1:
The patent applies dynamic adjustment of etch process parameters during the etching sequence. The etch rate is modulated by changing plasma conditions (such as power, pressure, or gas flow) at different stages of the etch process. This dynamic control allows the system to compensate for aspect ratio dependent etching effects in real-time, maintaining vertical side profiles across trenches with diverse aspect ratios without requiring separate etch processes for each AR range.
2Manufacturing precision
If the etching duration is extended to ensure uniform depth across all trenches, then depth uniformity improves, but the low-AR trenches develop notch and foot defects due to prolonged exposure to etching conditions
Solution Approach 1:
The patent implements periodic modulation of etch process parameters during the etching sequence. The etch rate is varied periodically or in distinct stages, with higher etch rates applied early when trenches are shallow, and reduced etch rates applied later as trenches deepen. This periodic action allows uniform depth to be achieved across all aspect ratios while preventing the formation of notch and foot defects by reducing the etch rate during the critical later stages when defects would form.
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 enables the fabrication of semiconductor devices with trenches having a wide range of aspect ratios, achieving vertical side profiles and uniform depth without notch and foot defects, thereby improving the manufacturing process window and reducing defects.
Implementation Method 1
exposing the substrate, for a first duration, to plasma generated using chlorine, hydrogen bromide, oxygen, and an inert gas
Implementation Method 2
plasma generated using chlorine, hydrogen bromide, oxygen, and an inert gas
Implementation Method 3
oxygen-containing etch byproducts are deposited to passivate exposed portions of the sides of the trenches
Data Source
AI summary
A method for fabricating a semiconductor device includes forming a pattern of trenches by etching a first layer formed over an underlying layer of a substrate, each of the trenches having an aspect ratio (AR) in a range with a lower limit of a first AR and an upper limit of a second AR, the pattern including a low-AR trench having the first AR and a high-AR trench having the second AR, the AR of a trench being a ratio of its depth to its opening width, the etching including: executing a first recipe in a plasma chamber to anisotropically etch the first layer for a first duration by flowing etchants through the chamber, an etch rate of the first layer being higher on the low-AR trench relative to that on the high-AR trench; and after executing the first recipe, executing a second recipe in the plasma chamber to etch the first layer anisotropically and concurrently deposit oxygen-containing etch byproducts to passivate exposed portions of sides of the trenches, the etch rate of the first layer being lower on the low-AR trench relative to that on the high-AR trench, wherein executing the second recipe increases a relative oxygen content in the plasma chamber from a first value during the executing of the first recipe to a second value.