Self-Aligned Source/Drain Contacts Using Etch Stop Spacers
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Solution Overview
Problem
The challenge in semiconductor manufacturing is forming smaller MOL contacts that avoid contact-to-gate shorts while minimizing processing complexity and maintaining wafer throughput.
Innovation Solution
The use of etch stop spacers in the MOL process allows for self-aligned formation of source/drain contacts, ensuring precise alignment and size without the need for complex mask alignment, thereby reducing the risk of contact-to-gate shorts and parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If precise overlay and high dosage of exposure are used to form smaller contacts, then contact alignment precision is improved, but processing complexity and wafer reworks increase
Solution Approach 1:
The patent applies preliminary action by forming etch stop spacers before the contact opening process. These spacers are deposited and patterned in advance to define the contact footprint, enabling self-aligned contact formation without requiring precise overlay of subsequent lithography steps. This preliminary structuring eliminates the need for high-dosage EUV lithography and complex alignment procedures.
Solution Approach 2:
The etch stop spacers serve a dual function: they act as etch stops during contact hole etching and simultaneously define the contact alignment. This self-service mechanism eliminates the need for separate alignment processes and reduces processing complexity while maintaining precise contact registration.
2Manufacturing precision
If precise overlay and high dosage of exposure are used to form smaller contacts, then contact alignment precision is improved, but wafer throughput decreases
Solution Approach 1:
By forming etch stop spacers in advance, the patent enables contact holes to be opened using simple isotropic or slightly anisotropic etching processes rather than requiring complex, time-consuming high-dosage lithography and precise overlay steps. This dramatically reduces cycle time per wafer and increases throughput.
Solution Approach 2:
The self-aligned nature of the etch stop spacer approach means that contact alignment is determined by the spacer geometry rather than by lithographic overlay precision. This eliminates iterative alignment adjustments and wafer reworks, thereby improving wafer throughput.
3Object-generated harmful factors
If contact size is reduced to decrease parasitic effects, then contact-to-gate capacitance is reduced, but contact formation complexity increases
Solution Approach 1:
The etch stop spacers automatically define the contact dimensions and position through their own geometry, eliminating the need for complex lithographic patterning to achieve small contact sizes. This self-service approach reduces contact-to-gate capacitance while avoiding increased process complexity.
4Length of moving object
If traditional lithography alignment methods are used for small contacts, then contact size is reduced, but the number of masks and processing steps increases
Solution Approach 1:
The patent extracts the alignment function from the lithography process and transfers it to the etch stop spacer structure. By removing the dependency on lithographic masks for contact alignment, the process complexity and number of required masks are significantly reduced while maintaining small contact dimensions.
Data Source
AI summary
Disclosed are techniques for a semiconductor structure. In an aspect, a semiconductor structure includes a gate structure disposed on a substrate, a gate spacer adjacent to the gate structure, a source/drain structure adjacent to the gate spacer, a first dielectric layer disposed on the substrate and the source/drain structure, an etch stop spacer over the first dielectric layer and adjacent to the gate spacer, and an etch stop layer over the gate structure, the gate spacer, and the etch stop spacer. The semiconductor structure further includes a source/drain contact extending through the etch stop layer and the first dielectric layer and in contact with the source/drain structure, a sidewall of the source/drain contact adjoining a sidewall of the etch stop layer and a sidewall of the etch stop spacer.