Metal Block Masks for Precise Source/Drain Epitaxy
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Solution Overview
Problem
As semiconductor devices continue to shrink in size, challenges arise in forming source/drain regions with high precision and minimizing defects during epitaxy processes, particularly due to precursor absorption and residue issues with existing masks.
Innovation Solution
The use of a metal-comprising mask, such as aluminum oxide or hafnium oxide, during source/drain epitaxy processes to protect device structures and enhance epitaxial growth, reducing precursor absorption and facilitating residue removal, thereby improving processing windows and reducing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional masks are used during source/drain epitaxy processes, then device structures can be protected, but precursor absorption and residue issues arise that increase defects
Solution Approach 1:
The patent changes the material parameter of the mask from conventional materials (such as silicon oxide or silicon nitride) to metal-containing materials (such as tungsten, molybdenum, or their oxides). This material parameter change fundamentally alters the interaction between the mask and precursors, preventing absorption and eliminating residue formation, thereby resolving the contradiction between protecting device structures and avoiding harmful precursor absorption.
Solution Approach 2:
The patent employs composite material structures where metal layers (tungsten, molybdenum) or metal oxides are combined with other materials to form multi-layer masks. These composite structures provide both the protective function for device structures and the chemical inertness toward precursors, simultaneously achieving structure protection and eliminating precursor absorption issues.
2Productivity
If minimum feature sizes are reduced to improve integration density, then more components can be integrated, but additional problems arise in forming source/drain regions with high precision
Solution Approach 1:
By changing the mask material parameters to metal-containing materials with specific physical and chemical properties (high melting point, chemical inertness, controlled reactivity), the patent enables precise control of epitaxial growth at smaller feature sizes. The metal masks provide stable thermal and chemical properties that maintain manufacturing precision even as feature sizes are reduced to increase integration density.
Solution Approach 2:
The patent replaces conventional mechanical/physical masking approaches with chemically-active metal masks that interact with precursors through controlled chemical reactions. This substitution allows for more precise control of epitaxial growth fronts at small dimensions, maintaining manufacturing precision while enabling higher integration density through smaller minimum feature sizes.
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 metal-comprising mask provides high-energy bonds with precursors, minimizing absorption and facilitating residue removal, leading to improved source/drain regions with reduced defects and enhanced epitaxial growth control.
Implementation Method 1
the precursors may remain on a surface of the metal-comprising mask rather than be absorbed into the metal oxide mask
Implementation Method 2
The metal-comprising mask protects structures in the n-type or p-type device regions of the die while source/drain regions for the other type device are grown
Implementation Method 3
epitaxially growing a second epitaxy region in the first recess over the first epitaxy region
Data Source
AI summary
A method includes etching a first recess adjacent a first dummy gate stack and a first fin; etching a second recess adjacent a second dummy gate stack and a second fin; and epitaxially growing a first epitaxy region in the first recess. The method further includes depositing a first metal-comprising mask over the first dummy gate stack, over the second dummy gate stack, over the first epitaxy region in the first recess, and in the second recess; patterning the first metal-comprising mask to expose the first dummy gate stack and the first epitaxy region; epitaxially growing a second epitaxy region in the first recess over the first epitaxy region; and after epitaxially growing the second epitaxy region, removing remaining portions of the first metal-comprising mask.