With the continuous demand for higher performance of computer chips and memories, device patterns and structures are becoming smaller and more complicated. Hard mask processes have been implemented in various steps in the devise manufacturing, and requirements for those materials are versatile. In this paper, novel organometal materials are presented as a new class of spin on solution in order to support the hard mask process. Type of metals, formulation scheme and processing conditions were carefully designed to meet the fundamental requirements as a spin on solution, and their characteristic properties were investigated in comparison to other conventional films such as spin on carbons (SOC), organic bottom anti-reflective coatings (oBARC) and inorganic films formed by chemical vapor deposition (CVD). Several advantages were identified with these SOMHM materials over other films which include 1) better thermal stability than SOC once fully cured, 2) reworkable with industry standard wet chemistry such as SC-1 where conventional Si-BARC is difficult to remove, 3) a wide range of optical constants to suppress reflection for photoresist imaging, 4) high etch resistance and 5) better gap filling property. Curing conditions showed a significant impact on the performance of SOMHM films, and X-ray photoelectron spectroscopy (XPS) was utilized to elucidate the trends. With SOMHM film as a BARC, photolithographic imaging was demonstrated under ArF immersion conditions with 40nm linewidth patterning.
In the previous paper we discussed the relationship between blob defect count and the receding angle of a resist surface after development with an alkaline developer solution. This paper summarizes additional test results from our continued efforts in developing next generation embedded barrier layer (EBL) materials that render a resist film with even higher receding angle to further facilitate high speed and high acceleration scanning. How to reach a higher receding angle without sacrificing a low post development receding angle is also discussed in this paper. The ability for an EBL material to switch from a high receding angle to a receding angle of lower than 20° upon development is considered a very important attribute of an EBL, which is the key to reduce blob defect count by ensuring good dynamic wetting of a resist surface to DI water during a post development rinsing step. Resist formulations with different receding angles were studied for lithography performance and defectivity under different process conditions with varying wet processes. Both good lithography performance and low defectivity were obtained for contact hole resists including those with a surface receding angle of 78°.
In 193nm immersion lithography, immersion top coat was the first proposed technique for preventing the leaching of
photoresist (resist) components, such as photoacid generator (PAG) and quencher base, into the immersion fluid (DI
water). In this approach, the top coat is coated onto a resist film in a separate step including coating the top coat film and
baking the film. This approach certainly adds extra cost to the device manufacturing and incurs reduced throughput as
compared to the dry lithography process.
The embedded barrier layer (EBL) technology1-5 developed at Dow Electronic Materials has been demonstrated to be a
revolutionary approach, in which a suitable EBL material is formulated into an existing resist, and in a spin coating
process the EBL material comes to the resist surface to forms a leaching barrier in situ. This approach has now been
widely accepted and implemented in the integrated circuit manufacturing industry for replacing the conventional
immersion top coat process.
In addition to being an excellent leaching barrier, EBL materials, in general, result in a resist surface with a high receding
angle for water. This property makes the EBL approach more desirable in topcoat free immersion lithography, since it
allow for the latest scanners to perform at their maximum scan speed without generating watermark defects.
For immersion lithography, the most important issue for mass production is defectivity control. This is true for both top
coat and topcoat free approaches. In the top coat approach, the formulation optimization for both top coat and resists
was extensively involved for this technique finally to reach an acceptable defectivity level for mass production of
As a later developed technology, the EBL approach has gone through a series of research and development stages
particularly in material innovation to reach the same low defectivity level as that of an immersion top coat process. After
achieving the target of low defectivity in lithography, the challenges left to the EBL approach were to solve high
defectivity in bulk exposed and bulk unexposed regions, which became prominent in both bright field and dark field
lithographic applications. To solve the high defectivity issues, a thorough understanding of the blob defect formation
mechanism was imperative. In this paper, the defect formation mechanism in both bulk exposed and unexposed regions
is proposed, and this proposed mechanism is applicable not only to the EBL approach but also to the immersion top coat
approach in general.
With the decrease in pitch in the line/space patterning, micro-bridge defects have become the
major defect in the immersion applications. As a result, reducing micro-bridge defect count is one of
the key tasks for mass production of semiconductor devices using immersion lithography for both
topcoat and non-topcoat processes. In this paper, we focus on the non-topcoat approach particularly
the embedded barrier layer (EBL) technology. The advanced EBL materials discussed in this
paper have demonstrated to be able to reduce total defect including micro-bridge defect count to the
same level as that of a topcoat process. It was found that the developer solubility of the EBL
materials in both bright and dark fields and the contrast of the EBL materials play important roles for
reducing overall defectivity.
At the 32nm node, the most important issue for mass production in immersion lithography is defectivity control. Many methods have been studied to reduce post-exposure immersion defects. Although a topcoat process demonstrates good immersion defect prevention, a topcoat-less resist process is an attractive candidate for immersion lithography due to cost reduction from a simplified process. In this paper we took the innovative approach of chemically designing an internal self-assembling barrier material that creates a thin embedded layer which functions as a topcoat. Data will be presented on this novel self assembly concept, illustrating the control of leaching, contact angle and immersion defects. Several optimized process flows with non-topcoat resists were also studied to decrease the amount of immersion defects. This study was used to verify the capability of a topcoat-less immersion process to achieve the low-defectivity levels required for 32nm node production.