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Area-selective Deposition-enabled ultiMAte extensIon of lithogRaphy

Periodic Reporting for period 1 - ADMAIR (Area-selective Deposition-enabled ultiMAte extensIon of lithogRaphy)

Reporting period: 2020-06-01 to 2022-05-31

Nanopatterning is the core of semiconductor technology as it drives the downscaling below the 7 nm node, enabling higher speed, density of transistors and computing performance. In addition, nanofabricated three-dimensional patterned structures are used in devices for photonics, biotechnology and other forms of nanotechnology.[1] In the early 2000s, the 193nm immersion lithography enabled 45nm node patterning. From then, for scaling, either light source (from 193nm to Ar-F) or integration routes (multiple patterning) have been developed. For beyond the 10nm node, extreme ultraviolet lithography (EUVL) with a light source of 13.5 nm, can be applied. , Associated with nano-patterning, there is a long list of challenges: (i) EUVL photoresists (PR) and mask infrastructure and control of the created nanoscale patterns; (ii) low throughput and process cost; (iii) environmental footprint as it is based on litho-etch subtractive processes; (iv) high complexity thus decreasing fabrication reliability; (v) overlay errors and defectivity. Therefore, innovative solutions are required. Area selective deposition (ASD) offers the potential to relax downstream processing steps by enabling self-aligned processes and bottom-up lithography. The main goal of this MSCA proposal Area-selective Deposition-enabled ultiMAte extensIon of lithogRaphy (ADMAIR) is to overcome the potentially show-stopping challenges associated with EUV lithography and EUV materials at the sub-10nm scale by depositing additive bottom-up materials.

As planned, the project duration was 24 months but within this period, ADMAIR has not been able to address fully all the scientific objectives. In resolution, alternative approaches have been investigated, opening promising perspectives for future application domains. The project did benefit from interdisciplinary joint development projects involving material suppliers and lithography stakeholders, which is a unique advantage of IMEC and offered valuable professional development and training opportunities for the MSCA candidate.

The details of those approaches will be descripted in the part B of the report. The initial WP are presented below.

Work Package 1 (WP1): Surface treatments and ASD on blankets and patterned

Work Package 2 (WP2): Surface characterization methodologies

Work Package 3 (WP3): Development of defect removal strategies

Work Package 4 (WP4): Application oriented demonstrators

A new project plan focusing on the three applications described above was worked out and executed and is presented in the table 1. The different applications identified have been defined as individual work packages.

• Approach 1: Hard Mask ASD lithography
• Approach 2: Add a passivation step to get a nucleation delay
• Approach 3: Tone inversion using hydrophobic sensitive materials
• Approach 4: Resist Hardening
The main results for each approach are presented here. More details can be found in the Part B of this report.

Approach 1: no relevant results but very elegant and innovative approach. Need to work in close collaboration with material suppliers

Approach 2: interesting results are demonstrated

- NF3 plasma allows to graft F bonds at the PR surface
- F-bonds block the HM growth around 100 cycles
- Material is still sensitive at EUV exposure even if sensitivity is degraded

- Necessary to find the best compromise between passivation efficiency and PR sensitivity

Approach 3: few interesting observations have been done but necessary to work in close collaboration with material suppliers to achieve the ASD process

- Nucleation delay is found on exposed area as expected
- However, Ti diffusion is detected which is bad for etch contrast
- Higher exposure dose allows to reduce Ti diffusion mechanisms, but nucleation delay is reduced

- Need to develop new material with higher density to avoid the Ti diffusion


Approach 4: good preliminary results

- DMA-TMS treatment block HM growth on Si based surfaces. No impact for growth on PR.
- Selectivity is degraded for blanket unexposed samples.
- Need to tune exposure dose and PEB T to get an efficiency rinse. Mandate to reach the Si surface and have TMS grafting good enough.

- More promising results / need to progress
Although the project did not result in the expected outcome, focus can be done on few important points which should allow success in the future:

- To be able to block HM material nucleation on non-growth area, WCA value needs to be above 100° and the polar part as low as possible
- The density of the PR/UL needs to be high enough in order to avoid precursor diffusion (in case of ALD precursor has a small size) and etch contrast degradation
- Add a passivation step can help to block HM nucleation but the PR/UL sensitivity is reduced and so selectivity window can be too short