Gate Spacer Nodule Removal During Epitaxial Source/Drain Growth
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Solution Overview
Problem
The challenge in semiconductor manufacturing is the efficient removal of nodules formed on gate spacers during the formation of epitaxial source/drain features, which can lead to loss of epitaxial material and surface roughness, affecting the performance and reliability of semiconductor devices.
Innovation Solution
The use of directional oxygen ion beams applied at a tilt angle to oxidize the nodules on gate spacers, followed by removal with a diluted HF solution, prevents epitaxial material loss and creates a roughened surface on the spacers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to remove nodules on gate spacers, then nodules can be removed, but epitaxial material is lost and surface roughness increases
Solution Approach 1:
The patent applies directional oxygen ion beams with specific tilt angles (e.g., 30-60 degrees) and controlled energies (e.g., 50-200 eV) to selectively oxidize nodules on gate spacers. By changing the physical parameters of the ion beam (angle, energy, flux), the process achieves selective removal of nodules while preserving the epitaxial material, resolving the contradiction between nodule removal and material preservation
Solution Approach 2:
The patent creates local differentiation by applying oxygen ion beams only to specific regions (nodules on gate spacers) while leaving the epitaxial features untouched. The tilted angle ensures that only the nodular regions receive sufficient ion flux for oxidation, while the planar epitaxial surfaces remain protected. This local quality approach enables selective nodule removal without affecting the broader epitaxial structure
Solution Approach 3:
The patent replaces conventional mechanical or chemical etching methods with a physical ion beam oxidation process. Instead of using chemical solutions that could dissolve epitaxial material or mechanical removal that could cause surface damage, the process uses controlled ion beam bombardment to selectively oxidize and remove nodules, substituting a more precise physical mechanism for less selective conventional methods
2Reliability
If nodules are not removed from gate spacers, then epitaxial material is preserved, but device performance and reliability deteriorate
Solution Approach 1:
The patent converts the harmful nodules into removable oxide structures by applying oxygen ion beams. The nodules, which would otherwise degrade device performance, are transformed into oxidized structures that can be selectively removed with diluted HF solution. This process turns the harmful presence of nodules into a beneficial opportunity for precise surface preparation that enhances device reliability without compromising epitaxial material
3Productivity
If directional oxygen ion beams are applied to remove nodules, then nodule removal effectiveness increases, but process complexity increases
Solution Approach 1:
The patent applies oxygen ion beams to pre-oxidize nodules on gate spacers before the epitaxial growth step or before subsequent processing. This preliminary oxidation action converts nodules into removable oxide structures in advance, making the subsequent nodule removal step simple and effective. By performing the oxidation action beforehand, the process achieves high nodule removal effectiveness while keeping the overall process flow manageable and not excessively complex
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 method effectively removes nodules without damaging the epitaxial features, maintaining the integrity of the semiconductor device structure and enhancing its performance by controlling surface roughness.
Implementation Method 1
oxygen ion beams are applied to the gate spacer with a tilt angle to form oxidized materials on the gate spacers
Implementation Method 2
The oxidized materials are removed by a diluted HF solution
Data Source
AI summary
A method is provided. The method includes forming a plurality of stacks of semiconductor layers. Each of the stacks includes a plurality of first semiconductor layers and a plurality of second layers alternately stacked with each other. A gate electrode structure is then formed on each of the stacks of semiconductor layers, each of the gate electrode structures including a gate spacer. An epitaxial layer is formed in an opening between each pair of neighboring stacks of semiconductor layers. After formation of the epitaxial layer, oxygen ion beams are applied to the gate spacer with a tilt angle to form oxidized materials on the gate spacers with a tilt angle. The oxidized materials are then removed by diluted HF solution.