Selective Metal Etching Using Basic Etchant and Hard Mask
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Solution Overview
Problem
Existing methods for selectively etching metal components in the presence of semiconductor materials like InSb suffer from inadequate resolution and excessive damage to the semiconductor, making it challenging to fabricate high-resolution devices such as quantum bits (qubits).
Innovation Solution
The use of a hard mask in combination with a basic etchant solution, such as an aqueous solution of tetramethyl ammonium hydroxide, allows for controlled etching of metal components like aluminium while minimizing damage to InSb and similar semiconductor materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing etching methods are used to remove metal selectively, then metal removal is achieved, but the etching resolution is inadequate and excessive damage occurs to the semiconductor
Solution Approach 1:
The patent changes the chemical parameter of the etchant from acidic to basic (using TMAH instead of acidic etchants), which fundamentally alters the etching mechanism. This parameter change enables high-resolution etching with minimal semiconductor damage, as the basic etchant selectively removes metal while being gentler on the InSb semiconductor material.
Solution Approach 2:
The patent introduces a hard mask layer as an intermediary between the etchant and the metal-semiconductor structure. This hard mask serves as a protective mediator that controls the etching process, allowing precise pattern transfer while preventing direct contact between the etchant and the semiconductor, thereby reducing damage.
2Manufacturing precision
If existing etching methods are used, then metal removal is achieved, but creep under the mask is excessive leading to poor edge definition
Solution Approach 1:
Changing the etchant chemistry from acidic to basic (TMAH) fundamentally reduces the creep effect. The basic etchant has different interaction properties with the metal and mask materials, resulting in minimal lateral etching under the mask and well-defined edges, directly addressing the edge definition problem.
3Manufacturing precision
If a basic etchant is used with a hard mask, then high-resolution etching is achieved with minimal semiconductor damage, but the process complexity increases
Solution Approach 1:
The hard mask is applied as a preliminary protective layer before etching. This preliminary action simplifies the overall process by providing built-in protection and control, eliminating the need for additional protective measures or complex process steps during etching.
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 achieves high-resolution etching with minimal creep under the mask, ensuring well-defined edges of the metal component and acceptable damage to the semiconductor, thereby facilitating the fabrication of complex semiconductor-superconductor heterostructures.
Implementation Method 1
etching the metal component using an etchant solution, whereby the hard mask controls the etching; wherein the etchant solution is a basic etchant solution
Data Source
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AI summary
A method for selectively etching a metal component of a workpiece comprises: forming a hard mask over the metal component; and etching the metal component using an etchant solution, whereby the hard mask controls the etching; wherein the etchant solution is a basic etchant solution; and wherein the workpiece includes a semiconductor component comprising a material of Formula (1): InAsxSb1-x where x is in the range 0 to 1. It has surprisingly been found that basic etchants do not damage the semiconductor material. Another aspect provides the use of a basic etchant to etch aluminium selectively in the presence of a semiconductor comprising a material of Formula 1, where x is in the range 0 to 0.25.