Angled Ion Beam Etching for Unidirectional Cavity Elongation
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Solution Overview
Problem
As semiconductor devices shrink, patterning small features such as cavities with nanometer-scale separation becomes challenging due to overlay issues and loss of layer thickness during etching, making it difficult to reliably print small cavities at a small pitch without multiple masks and resulting in either overlap or excessive separation.
Innovation Solution
A method involving the deposition of a sacrificial polymer layer followed by angled ion beam etching, which selectively elongates cavities along a desired direction while preserving layer thickness and preventing unwanted enlargement in orthogonal directions, using a combination of deposition and etching operations in a plasma-based tool to achieve precise feature patterning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple masks are used to pattern small cavities at small pitch, then the separation between cavities can be controlled, but overlay errors cause cavity overlap or excessive separation
Solution Approach 1:
The patent extracts the cavity enlargement process from conventional isotropic etching and applies selective directional etching that removes material only in the lateral direction while preserving vertical layer thickness. This eliminates the need for multiple masks by enabling precise cavity shaping in a single etching step, resolving the overlay error problem inherent in multi-mask approaches.
Solution Approach 2:
The patent changes the etching parameters by using directional ion beam etching with controlled angles and selective chemistry. By adjusting the ion beam angle and etching selectivity, the process achieves precise lateral cavity enlargement while maintaining vertical dimensional control, thereby achieving small pitch patterning without multiple masks.
2Area of moving object
If cavities are etched to enlarge them, then the cavity size increases, but layer thickness is lost during etching
Solution Approach 1:
The patent applies local quality by creating anisotropic etching conditions where the etching rate differs dramatically between lateral and vertical directions. The directional ion beam etching selectively removes material from cavity sidewalls while protecting the top layer surface, enabling cavity enlargement without proportional layer thickness loss.
Solution Approach 2:
The patent introduces asymmetry in the etching process by using angled ion beam incidence that preferentially attacks lateral cavity walls while minimizing vertical material removal. This asymmetric etching geometry enables selective cavity widening while preserving the integrity and thickness of the overlying layer structure.
3Ease of manufacture
If conventional lithography is used to print small cavities, then the process is simple, but overlay issues make it unreliable for nanometer-scale separation
Solution Approach 1:
The patent applies preliminary action by first forming cavities with conventional lithography and then using directional etching to selectively enlarge them. This preliminary cavity formation followed by controlled enlargement allows the use of simple single-mask lithography while achieving the precise small pitch patterning that would otherwise require complex multi-mask processes.
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 the selective elongation of cavities along one direction without increasing width or thickness loss, reducing the need for multiple masks and minimizing overlay errors, enabling the creation of features with reduced tip-to-tip separation and preserving layer thickness, thus improving the reliability of small-scale patterning.
Implementation Method 1
directing angled ions to the cavity in a first exposure, wherein the cavity is etched
Implementation Method 2
a first exposure, wherein the cavity is etched
Implementation Method 3
depositing a sacrificial layer over the cavity in a first deposition procedure
Data Source
AI summary
A method of patterning a substrate. The method may include providing a cavity in a layer, disposed on the substrate, the cavity having a first length along a first direction and a first width along a second direction, perpendicular to the first direction, and wherein the layer has a first height along a third direction, perpendicular to the first direction and the second direction. The method may include depositing a sacrificial layer over the cavity in a first deposition procedure; and directing angled ions to the cavity in a first exposure, wherein the cavity is etched, and wherein after the first exposure, the cavity has a second length along the first direction, greater than the first length, and wherein the cavity has a second width along the second direction, no greater than the first width.