Self-Aligned Contact Formation via Sacrificial Fill in Replacement Gate Processes
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Solution Overview
Problem
In advanced semiconductor manufacturing, the integration of self-aligned contact elements with replacement gate approaches is challenging due to the sensitivity of high-k dielectric materials and work function metal species to high temperature processes and critical process atmospheres, leading to yield loss and process non-uniformities.
Innovation Solution
The implementation of a sacrificial fill material in contact openings, selected for specific etch characteristics, allows for the replacement gate approach without affecting pre-formed self-aligned contact elements, enabling the deposition of contact metals with reduced thermal stability, such as aluminum, and ensuring process robustness and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If self-aligned contact elements are formed before replacement gate approach, then contact alignment precision is improved, but high-k dielectric materials and work function metal species are damaged by high temperature processes
Solution Approach 1:
The contact elements are formed in advance using the gate structure as etch mask before the replacement gate process. This preliminary action ensures precise self-alignment of contacts to the gate, while the gate structure itself serves as the alignment reference. The contact openings are formed through selective etching using the gate as mask, establishing precise spatial relationships before the sensitive high-k materials are introduced.
Solution Approach 2:
The process sequence is inverted from conventional approaches by performing contact formation before replacement gate processing. This parameter change in process timing allows the use of lower temperature processes for contact metal deposition (such as aluminum) before the high-k dielectric materials are exposed to high temperature steps, thereby preserving material integrity while maintaining alignment precision.
2Stability of the object's composition
If contact elements are formed with conventional metals, then thermal stability is improved, but packing density and electrical performance are reduced
Solution Approach 1:
The invention changes the thermal stability parameter of contact metals by selecting aluminum or aluminum alloys instead of conventional tungsten. This parameter change enables reduced melting points and lower processing temperatures, which in turn allows for better integration with high-k dielectric materials that are sensitive to high temperature. The reduced thermal stability is compensated by optimized deposition and formation processes that ensure adequate mechanical and thermal support during subsequent processing steps.
Solution Approach 2:
The contact structure utilizes composite material systems where aluminum contact metals are combined with appropriate barrier and adhesion layers. This composite approach allows the aluminum to provide superior electrical conductivity and packing density while the composite structure as a whole maintains adequate thermal stability through the integrated layer system, resolving the contradiction between metal thermal stability and electrical performance.
3Reliability
If high-k dielectric materials are used in gate electrode structures, then gate control capability is improved, but sensitivity to process atmosphere and temperature increases
Solution Approach 1:
The contact formation process is performed as a preliminary action before the high-k dielectric materials are deposited and processed. This sequencing ensures that the sensitive high-k materials are not exposed to the etching and deposition processes used for contact formation, thereby protecting them from process atmosphere damage while still enabling precise alignment through the gate-as-mask approach.
Solution Approach 2:
The process utilizes controlled inert or reducing atmosphere conditions during the formation and processing of high-k dielectric materials. By maintaining an inert environment during critical processing steps, the high-k materials are protected from oxidation and degradation, preserving their dielectric properties and gate control capability while allowing for subsequent contact formation with reduced thermal stability metals.
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 enables reliable formation of self-aligned contact elements with reduced thermal stability metals, enhancing process robustness and yield while maintaining the integrity of high-k gate electrode structures, thus addressing the limitations of conventional strategies.
Implementation Method 1
The etch characteristics are specifically selected in accordance with the dedicated placeholder material of the gate electrode structures
Implementation Method 2
replacing the placeholder material with at least one electrode metal in the presence of the sacrificial fill material
Implementation Method 3
exposing a surface of the placeholder material by planarizing the sacrificial fill material
Data Source
AI summary
When forming self-aligned contact elements in sophisticated semiconductor devices in which high-k metal gate electrode structures are to be provided on the basis of a replacement gate approach, the self-aligned contact openings are filled with an appropriate fill material, such as polysilicon, while the gate electrode structures are provided on the basis of a placeholder material that can be removed with high selectivity with respect to the sacrificial fill material. In this manner, the high-k metal gate electrode structures may be completed prior to actually filling the contact openings with an appropriate contact material after the removal of the sacrificial fill material. In one illustrative embodiment, the placeholder material of the gate electrode structures is provided in the form of a silicon/germanium material.