Top coat less resist process development for contact layer of 40nm node logic devices
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ArF immersion lithography has been introduced in mass production of 55nm node devices and beyond as the post ArF dry lithography. Due to the existence of water between the resist film and lens, we have many concerns such as leaching of PAG and quencher from resist film into immersion water, resist film swelling by water, keeping water in the immersion hood to avoid water droplets coming in contact with the wafer, and so on. We have applied to the ArF dry resist process an immersion topcoat (TC) process in order to ensure the hydrophobic property as well as one for protecting the surface. We investigate the TC-less resist process with an aim to improve CoO, the yield and productivity in mass production of immersion lithography. In this paper, we will report TC-less resist process development for the contact layer of 40nm node logic devices. It is important to control the resist surface condition to reduce pattern defects, in particular in the case of the contact layer. We evaluated defectivity and lithography performance of TC-less resist with changing hydrophobicity before and after development. Hydrophobicity of TC-less resist was controlled by changing additives with TC functions introduced into conventional ArF dry resist. However, the hydrophobicity control was not sufficient to reduce the number of Blob defects compared with the TC process. Therefore, we introduced Advanced Defect Reduction (ADR) rinse, which was a new developer rinse technique that is effective against hydrophobic surfaces. We have realized Blob defect reduction by hydrophobicity control and ADR rinse. Furthermore, we will report device performance, yield, and immersion defect data at 40nm node logic devices with TC-less resist process.Keywords:
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A new method of making attenuated phase-shifting mask with photoresist shifter is proposed.The principle and manufacturing process of the method are described.The fabricated masks with this method are used for exposure experiments with the system of KrF excimer laser projection photolithography.The exprimental results have proved that the attenuated phase-shifting masks with photoresist shifter are able to improve the resolution of the photolithography evidently.
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We have developed new type of photolithography based on a nonadiabatic photochemical process that exposes an ultraviolet-photoresist using a visible optical near field. Investigating the exposure dependence of the developed depth using nonadiabatic photolithography, we found that the depth increased with the exposure threshold. To explain this result, the optical field intensity was simulated by using the finite-difference time-domain method. The evolution of the developed depth was proportional to the optical field intensity and its spatial gradient, agreeing closely with the simulated result that took into account the nonadiabatic processes. Another experimental result is to support our explanation, that in nonadiabatic photolithography, a component of the exposure progresses inside the photoresist.
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Application of Sub-resolution Assist Features in Photo Process. The pattern on the mask is projected on the photoresist through the exposure system. Due to the imperfection of the optical system and the diffraction effect, the pattern on the photoresist is not completely consistent with the pattern on the mask. Using optical proximity correction (OPC) can correct the pattern on the mask so that the pattern projected on the photoresist meets the design requirements as much as possible. At the 90nm node, the sub-resolution assist feature in the OPC method is introduced, which can solve the problem that the process window for some prohibiting periodic patterns is too small. But in other respects, there is little literature discussing the application of sub-resolution assist features. This paper reveals that in the photolithography process, adding sub-resolution assist features have other beneficial effects and functions for the photolithography process.
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Feature (linguistics)
Optical proximity correction
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The ultraviolet photolithography process of thick photoresists, AZ4620 and SU 8, was studied and optimized. The microstructures with high aspect ratio and vertical sidewalls can be patterned by SU 8 photoresist. The applications of thick resist photolithography in MEMS fabrication process are also presented in this paper.
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Computational lithography
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Extreme Ultraviolet Lithography
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Contact photolithography for photoresist layers thicker than 1 micron is widely used in creating microreliefs in production technologies of microelectromechanical systems, micropackaging, optical printed circuit boards and other microdevices. Microrelief walls slope in photoresist inflicts significant influence on the microdevice output parameters. Based on analysis of the contact photolithography features, it is proposed a mathematical model based on the Fresnel diffraction of image generation in the thick photoresist layers. The model and statistical processing of results obtained on its basis adequately describe relationship between the photolithography output parameters, i.e. the microrelief sidewalls slope, and the photoresist absorption coefficient and thickness.
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Computational lithography
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Along with the increase in the integrations of IC's, the process dimensions of photolithography is proceeding to more and more fine patterns. In the fabrication of 16 Mega bit DRAM which is the next generation device, the photolithography will be required to have a technology close to half micron geometry work. The role to be played by photoresists in such geometry work is extremely large and important. Under such circumstance, we have developed ultrahigh resolution positive working photoresist, TSMR-V3 which can cope with a half micron photolithography.
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A novel simple method is proposed to fabricate multilevel or three dimensional structures for integrated optoelectronic devices using modified two-step photolithography. First photolithographic step uses an epoxy type photoresist such as SU-8 and the second step uses a novolak type photoresist such as AZ1518. Because solubility of one photoresist to the other’s developer is different, the conventional exposure and develop process can be done consecutively without affecting the pre-existing patterns. However, flat deposition of the second novolaktype photoresist on patterned uneven surface by spin coating is difficult and in this work we suggest a method to get flat surface before the second exposure. This method has been applied successfully to prepare 3-D structures on optical printed circuit board.
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Deposition
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We describe a process that produces an index-of-refraction modulation requiring no wet development. A negative photoresist, which is currently employed as a surface-modulating material in high-resolution photolithography, was used. This process may be useful in real-time optical recording. It could eventually be shown to be responsible for defects in high-resolution photolithography.
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The cross-sectional dimensions of the photoresist in the photolithography process are estimated from top-down scanning electron micrographs for improved control of photolithography conditions. As semiconductor design rules shrink, strict process control is becoming increasingly important. Two primary process parameters in the photolithography process, exposure dose and focus position, require strict control in order to achieve the desired photoresist profile. The relationship between the photoresist profile and changes in these two parameters of photolithography is determined by simulation, and features suitable for estimation of the photoresist profile are identified in conventional images obtained for critical dimension monitoring. Experimental results demonstrate that process parameters can be estimated to within error of 1.0 mJ/cm2 for exposure dose and 80 nm for focus position, making the proposed method suitable for photolithography process control.
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Abstract The cross‐sectional dimensions of the photoresist in the photolithography process are estimated from top‐down scanning electron micrographs for improved control of photolithography conditions. As semiconductor design rules shrink, strict process control is becoming increasingly important. Two primary process parameters in the photolithography process, exposure dose and focus position, require strict control in order to achieve the desired photoresist profile. The relationship between the photoresist profile and changes in these two parameters of photolithography is determined by simulation, and features suitable for estimation of the photoresist profile are identified in conventional images obtained for critical dimension monitoring. Experimental results demonstrate that process parameters can be estimated to within error of 1.0 mJ/cm 2 for exposure dose and 80 nm for focus position, making the proposed method suitable for photolithography process control. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(8): 11–17, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/ecj.10153
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