摘要:

A method previously employed for characterizing lithographic performance independent of resist processing has been applied to Markle–Dyson optics working at 0.7 NA and 193 nm to demonstrate diffraction limited imaging down to 0.15 μm resolution. Excellent agreement is shown between theory and experimentally measured modulation as a function of spatial frequency, defocus, and numerical aperture. We have also measured both tangential and sagittal field curvatures and found close correlation with simulation. No loss of contrast was observed inside the semicircular field of 2 mm diameter. Reflective 1× masks required for the experiment were patterned in silicon on fused silica down to 0.12 μm linewidths. To characterize the projection optics further, we have printed 0.16 μm features in resist using no resolution enhancement techniques.

ISSN:0734-211X    

DOI:10.1116/1.587447

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The performance of a new 10×‐reduction Schwarzschild system for projection imaging at 13.4 nm wavelength is reported. The optical design is optimized to achieve 0.1 μm resolution over a 0.4 mm image field of view, an increase in area of a factor of 100 over previous designs. An offset aperture, located on the convex primary, defines an unobscured 0.08 numerical aperture. The system is illuminated using extreme ultraviolet (EUV) radiation emitted from a laser plasma source and collected by an ellipsoidal condenser. A 45° turning mirror is used to relay the collected EUV radiation onto a near‐normal reflecting mask. Multiple sets of primary and secondary elements were fabricated, matched, and clocked to minimize the effects of small figure errors on imaging performance. Optical metrology indicates that the wave‐front error within the subaperture used is within a factor of 2 of the design value. Images recorded in poly(methyl methacrylate) and ZEP 520 (Nippon Zeon) resists reveal good imaging fidelity over much of the 0.4 mm field with equal line/space gratings being resolved to 0.1 μm.

ISSN:0734-211X    

DOI:10.1116/1.587448

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

We have developed a magnetron sputtering system for the deposition of Mo/Si multilayer (ML) coatings onto large‐area, figured optics, as required for the imaging system in a practical, extreme‐ultraviolet (EUV) lithography tool. Coating uniformity on figured optics is adjusted by implementing contoured, shaped baffles during ML deposition. We have also developed an EUV reflectometer that is capable of measuring the reflectance versus wavelength across the surface of these optics, so that the coating uniformity can be determined with the required precision. We discuss the ML coating uniformity requirements for a practical EUV lithography tool, describe the facilities and techniques we have developed, and present some recent results wherein these facilities and techniques have been used to deposit high‐reflectance coatings onto a variety of spherical and aspherical substrates.

ISSN:0734-211X    

DOI:10.1116/1.587449

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Extreme ultraviolet lithographic masks with programmed defects on the mask substrates have been imaged to study substrate defects printability. The imaging was performed with a 2‐aspherical‐mirror system operating at 14 nm wavelength. Results showed that 25 nm thick substrate defects caused observable distortions of resist patterns. Defects of sizes approximately half the minimum resolvable features resulted in 15%–20% variations in resist linewidths. However, since the imaging system was operating at a reduced resolution due to misalignments of the optics, the effect of the defects may have been partially concealed by the phase front distortions caused by mirror misalignments. The defects are difficult to observe under a scanning electron microscope.

ISSN:0734-211X    

DOI:10.1116/1.587450

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

We report experimental and theoretical studies of the resist sidewall angles produced using extreme ultraviolet lithography at exposure wavelengths of 37.5, 13.9, and 6.8 nm. We show that high resist absorption in this wavelength region leads to a significant degradation in pattern sidewall angle. Because steep resist profiles are needed in semiconductor manufacturing to ensure adequate linewidth control it seems unlikely that a single‐layer resist process can be used in extreme ultraviolet lithography except at the shortest wavelength.  

ISSN:0734-211X    

DOI:10.1116/1.587451

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

We have constructed four optical components for use in an extreme ultraviolet shearing interferometer which will operate at a wavelength of 13.4 nm. The components that have been constructed include transmission diffractive optical components such as a Fresnel zone plate, angled gratings, and two‐frequency gratings, as well as pinhole apertures. All the components are fabricated in 110 nm of Ge, which is supported by a 0.5–0.7‐μm‐thick membrane of Si. The patterns were fabricated by first evaporating Ge and then spinning 100 nm polymethylmethacrylate (PMMA) onto the Si membranes. The desired patterns were exposed in the PMMA resist using electron beam lithography. Custom interative computer programs generated the patterns used to control the exposure. After developing the PMMA resist the Ge layer was etched using a reactive ion etching technique. Electron microscopy of the finished components show that the smallest features in our components are cleanly constructed, and the linewidths and placement of the features meet the desired accuracy.

ISSN:0734-211X    

DOI:10.1116/1.587452

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Dissolution rate and resolution measurements are used to show that a novel acid‐hardened deep‐ultraviolet photoresist ML93, based on a benzylic crosslinker, has excellent dissolution and reasonable resolution characteristics. Experimentally, we have observed that ML93 resist is about 20 times more sensitive than Shipley SNR248. While the high sensitivity is a promising result, it has made experimental reproducibility more difficult. In addition, the effect of the crosslinker structure on dissolution is examined with three more resists, ML239, ML240, and ML241, all analogous to ML93 except for variations in the structure of the crosslinker. A kinetic model describing negative resist lithography is applied to ML93 and ML239, and some profile cross sections are simulated usingsample. The kinetic model has provided a reasonable fit to the dissolution characteristics of ML93 and ML239 separately, but comparison indicates that the basic role played by the active sites in the dissolution process needs further investigation.

ISSN:0734-211X    

DOI:10.1116/1.587453

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Deep ultraviolet (UV) chemically amplified (CA) resists are leading candidates for semiconductor lithography manufacturing in the sub‐half‐micron regime. In this article, we describeinsitu, high data rate, accurate measurements of the chemical kinetics that occur in CA resists during the post‐exposure bake. The thermal and acid‐catalyzed deprotection of two candidate deep‐UV resist materials, poly(p‐t‐butoxycarbonyloxystyrene) (PTBOCST) and poly(t‐butylmethacrylate) (PTBMA), was characterized. The thermal deprotection of PTBOCST and PTBMA showed auto‐accelerated behavior as the reaction proceeds, while the acid‐catalyzed deprotection displayed inhibition as extent of conversion increased. We propose models for the thermal and acid‐catalyzed deprotection and extracted rate coefficients using a stochastic kinetics simulator. Excellent agreement between the model and experimental data was obtained.

ISSN:0734-211X    

DOI:10.1116/1.587454

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A positive tone chemically amplified photoresist was evaluated for use on a 0.44 NA 248 nm excimer laser stepper. The effects of various formulation changes were examined with respect to exposure latitude, depth of focus, resolution, and bias between isolated and grouped features. Of particular interest was the relationship between the percent of photo acid generator (PAG) in the resist and the process latitude. It was found that several aspects of the process window increased as the PAG content of the resist decreased. An increase in dose was expected and observed with the decrease in PAG concentration. This would reduce excimer stepper throughput by approximately 25%.

ISSN:0734-211X    

DOI:10.1116/1.587455

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Currently, the major approach to improving the performance of chemically amplified resists is by means of statistical design methods. These methods do not make use of information about the underlying chemical processes, information which could be useful in expediting the optimization process. We have developed techniques and equipment to monitor changes in resist chemistry during the bake steps usinginsituusing real time Fourier transform infrared spectrometry (RT‐FTIR). Using the Shipley SAL 605 negative chemically amplified resist, we monitored exposed resist as it was being baked at 110 °C; we were thus able to see several peaks change, including the growth of a peak at 982 cm−1which we associate with the formation of an ether linkage during cross‐linking. When the height of this peak is plotted over time from the start of the bake, it shows several things, among them (a) the reaction being monitored takes much longer to reach its final level of completion (≳300 s) than the statistically derived optimum (∼60 s), (b) as expected, the reaction rate is a function of dose, and (c) the results are reproducible between identically treated wafers. We speculate that the reason we see peak growth long after the resist is cross‐linked enough for processing is due to the multiple available sites on the cross‐linker molecule which allow continued bond formation after enough have formed to make the resist sufficiently insoluble. With chemically amplified resists there has been concern over residual solvent which can interfere with the catalytic mechanism of the photogenerated acid. The same RT‐FTIR techniques were also shown to be effective in monitoring the loss of solvent from the resist during the preexposure bake, giving the time at which the solvent can be assumed to have been removed—in the case of Shipley SAL 605, approx 30 s. Finally, the RT‐FTIR technique can be used to follow the individual contributions of the components of the resist formulation as their concentrations are changed to affect different resist properties. The monitoring is directly on the resist‐coated wafer, and special handling techniques, to be described in the text, are necessary to make these measurements directly applicable to resist processing.

ISSN:0734-211X    

DOI:10.1116/1.587565

出版商:American Vacuum Society    

年代:1994

数据来源: AIP