ALD Tungsten Etching for Microelectronic Feature Filling
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Solution Overview
Problem
Existing deposition processes, such as PVD and ALD, often result in material buildup or overhang at the upper corners of features in substrates, leading to premature closure of feature openings and void formation during microelectronic device fabrication.
Innovation Solution
A method involving exposure to tungsten chloride (WClx) followed by hydrogen-containing gases in a controlled pressure and time sequence within a process chamber to etch and reduce overhang, ensuring uniform coverage and preventing void formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If typical deposition processes (PVD, CVD, or ALD) are used to deposit material onto the substrate, then material can be deposited along the surfaces of the feature and/or completely fill the feature, but material buildup or overhang occurs at the upper corners of features, leading to premature closure of feature openings and void formation
Solution Approach 1:
Instead of attempting to deposit material directly into the feature opening, the patent inverts the approach by first depositing material on the upper surface of the substrate, then selectively removing the overhanging material through etching. This inversion transforms the deposition problem into a controlled removal problem, achieving uniform sidewall coverage without overhang.
Solution Approach 2:
The patent changes the physical and chemical parameters of the deposition and etching processes. Specifically, it uses atomic layer deposition (ALD) with controlled precursor exposure times and temperatures, followed by selective etching with hydrogen-containing gases. By adjusting deposition temperature, pressure, and etching gas composition, the process achieves uniform material distribution without overhang formation.
2Reliability
If deposition processes are used to fill features, then conductive pathways can be formed between devices, but the opening of the feature closes off prematurely due to overhang, forming pockets or voids where no material is present
Solution Approach 1:
The patent performs preliminary etching of the deposited material to remove overhang before completing the feature filling process. By pre-etching the upper surface material and overhanging portions, the process ensures that subsequent deposition steps can uniformly fill the feature without creating voids or pockets, thereby ensuring complete and reliable conductive pathway formation.
Solution Approach 2:
The patent implements a continuous cyclic process alternating between deposition and etching steps. This continuous action ensures that material is deposited uniformly on sidewalls while overhang is continuously removed, maintaining an open feature opening throughout the filling process and preventing void formation, leading to complete and reliable feature filling.
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 reduces or eliminates overhang, ensuring uniform deposition and preventing voids, thereby enhancing the filling of features in microelectronic devices.
Implementation Method 1
exposing a first layer disposed atop the substrate to a first gas comprising tungsten chloride (WClx) for a first period of time... exposing the substrate to a hydrogen-containing gas for a third period of time to etch the first layer
Data Source
AI summary
Methods for etching a substrate are provided herein. In some embodiments, a method for etching a substrate disposed within a processing volume of a process chamber includes: (a) exposing a first layer disposed atop the substrate to a first gas comprising tungsten chloride (WClx) for a first period of time and at a first pressure, wherein x is 5 or 6; (b) purging the processing volume of the first gas using an inert gas for a second period of time; (c) exposing the substrate to a hydrogen-containing gas for a third period of time to etch the first layer after purging the processing volume of the first gas; and (d) purging the processing volume of the hydrogen-containing gas using the inert gas for a fourth period of time.