Directional Trench Elongation Using Angled Reactive Ion Etching
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Solution Overview
Problem
The challenge in semiconductor manufacturing is the ability to pattern features at target sizes and shapes, particularly due to limitations in ion beam access beyond a critical aspect ratio, leading to difficulties in achieving precise placement and shape of patterned features.
Innovation Solution
A method involving a reactive ion etching process with ions delivered at a non-zero angle relative to the substrate surface is used to selectively elongate certain trenches by etching the end walls of specific trenches without affecting perpendicular trenches, leveraging ion beam shadowing based on aspect ratios to achieve selective etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ions are delivered perpendicular to the substrate surface, then etching can reach the bottom of trenches, but lateral etch drops sharply when the critical aspect ratio is exceeded
Solution Approach 1:
The patent changes the ion beam delivery angle from perpendicular (0 degrees) to a non-zero angle (e.g., 15-30 degrees relative to the substrate surface normal). This parameter change allows ions to etch trench sidewalls effectively while still reaching the bottom, overcoming the critical aspect ratio limitation that plagues perpendicular etching.
2Ease of manufacture
If conventional etching methods are used, then all trenches are etched uniformly, but selective elongation of specific trenches cannot be achieved
Solution Approach 1:
The patent applies local quality by making different trenches have different orientations relative to the ion beam direction. Trenches oriented parallel to the ion beam projection receive full etching, while perpendicular trenches are protected by shadowing effects. This allows selective elongation of specific trench sets without affecting others, achieving precise feature placement control.
Solution Approach 2:
The patent introduces asymmetry in the etching process by using an angled ion beam rather than a symmetric perpendicular beam. This asymmetric approach creates directional selectivity where trenches aligned with the beam direction are etched differently than those perpendicular to it, enabling selective trench modification.
3Manufacturing precision
If multiple masking and etch steps are used to achieve complex feature arrays, then precise feature placement can be obtained, but process complexity increases
Solution Approach 1:
The patent makes the angled ion beam etching process multi-functional by simultaneously achieving trench elongation, feature placement control, and pattern definition in a single step. This replaces multiple sequential masking and etching operations, reducing process complexity while maintaining manufacturing precision.
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 elongation of targeted trenches without altering perpendicular trenches, potentially eliminating masking and etch/EUV steps, and enabling more complex feature arrays with controlled aspect ratios.
Implementation Method 1
delivering ions into the substrate in a reactive ion etching process, wherein the ions are delivered at a non-zero angle relative to a perpendicular extending from the substrate
Implementation Method 2
leveraging ion beam shadowing based on aspect ratios to achieve selective etching
Implementation Method 3
reactive ion etching process
Data Source
AI summary
Disclosed herein are approaches for device modification, namely, trench elongation. In one approach, a method may include providing a substrate including a plurality of surface features defining a plurality of trenches, wherein a first trench has a first trench length extending in a first direction, wherein a second trench connected to the first trench has a second trench length extending in a second direction, and wherein the first direction and the second direction are non-parallel. The method may further include delivering ions into the substrate in a reactive ion etching process, wherein the ions are delivered at a non-zero angle relative to a perpendicular extending from the substrate, and wherein the reactive ion etching process increases the first trench length of the first trench without increasing the second trench length of the second trench.