John M. Hutchinson

Thermal and acid‐catalyzed deprotection kinetics in candidate deep ultraviolet resist materials

Deep ultraviolet (UV) chemically amplified (CA) resists are leading candidates for semiconductor lithography manufacturing in the sub‐half‐micron regime. In this article, we describe in situ, 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.

Shot-noise impact on resist roughness in EUV lithography

Photospeed requirements for 193 nm and EUV lithography are approximately 10 mJ/cm2. As wavelengths are scaled, photon energy is increased, and the discrete photon events may become a fundamental contributor to resist edge roughness. A theoretical analysis of the shot noise impact on line edge roughness was performed. Based on the results, we estimate 1 nm of shot noise induced roughness at 10 mJ/cm2 resist sensitivity for 193 nm lithography. Therefore, discrete photon events are not expected to be a significant contributor to local CD control in 193 nm lithography. We conclude that edge roughness typically observed in 193 nm resists is therefore a process related effect.e However, at EUV, we are approaching a shot noise limit and edge roughness may be enhanced by photon counting effects. Without taking photo-acid diffusion into account, we estimate 8 nm of shot noise induced edge roughness at the EUVB wavelength and 10 mJ/cm2 sensitivity. Hence, local CD control may be compromised by the stringent 10 mJ/cm2 photospeed requirement. Edge roughness is improved by relaxing the resist sensitivity requirement. In addition, most resist technologies are likely to be chemically amplified, and thermally driven diffusion will improve local CD control but at the expense of image contrast and cross- wafer CD control.

Harmonically Mode-Locked Hybrid Silicon Laser With Intra-Cavity Filter to Suppress Supermode Noise

We present results from two hybrid silicon mode-locked lasers, each with a 2 GHz cavity and one with an intra-cavity ring resonator filter. We compare the performance of the two lasers with respect to the harmonic mode-locking behavior at 20 GHz, i.e., the tenth harmonic. The filter based laser design passively mode-locked at 20 GHz with an electrical spur mode suppression >45 dB. Furthermore, an optical supermode suppression of 55 dB and an RF linewidth of 52 kHz was also observed. Hybrid mode-locking the laser without the filter required 10 dBm input microwave power for 25 dB (electrical) spur mode suppression as opposed to the design with the filter showing >45 dB suppression at 0 dBm input power.

Top surface imaging resists for EUV lithography

The strong attenuation of extreme UV (EUV) radiation by organic materials necessities the use of a thin layer imaging (TLI) process for EUV lithography. Several TLI processes have been identified for potential use for EUVL, and the common theme in these approaches is the transfer of the aerial image to a thin layer of refractory-containing material, which is then used as a dry O2 etch mask during a subsequent pattern transfer to the device layer. One TLI process that has been extensively examined for EUVL is the silylated top-surface imaging (TSI) technology, which is discussed in this paper. Using a new disilane silylation reagent, dimethylaminodimethyldisilane (DMDS) and 13.4 nm exposure, the TSI process has been sued to print 100 nm lines and spaces at equal pitch and 70 nm lines and spaces at a higher 1:2 pitch. The line edge roughness for the printed lines has been determined using a custom image analysis program and, as expected, varies with the particular EUV exposure system and numerical aperture. Exposures done with 193 nm lithography and the TSI process using DMDS are also shown for comparison to the EUV results.

2.5-Gb/s error-free wavelength conversion using a monolithically integrated widely tunable SGDBR-SOA-MZ transmitter and integrated photodetector

Error-free operation at 2.5 Gb/s was demonstrated for the first monolithically integrated widely tunable photocurrent-driven Mach-Zehnder based wavelength converter. Power penalties of 1-2 dB were measured across the 37-nm wavelength range of the sampled grating distributed Bragg reflector.

High efficiency widely tunable SGDBR lasers for improved direct modulation performance

We report on two novel approaches to improve the differential quantum efficiency (DQE) of widely tunable 1.55-/spl mu/m lasers: the bipolar cascade sampled grating distributed Bragg reflector (BC-SGDBR) laser and the gain-levered SGDBR (GL-SGDBR) laser. Each is fabricated on a robust InGaAsP/InP photonic integrated circuit platform. The lasers demonstrate improved direct modulation performance over conventional SGDBR lasers. The BC-SGDBR laser was also monolithically integrated with a semiconductor optical amplifier and photodetector receiver in order to perform wavelength conversion. Error free wavelength conversion at 2.5 Gb/s and improvements in conversion efficiency are demonstrated.

Monolithically integrated InP-based tunable wavelength conversion

In this work, we describe tunable wavelength converters based on a photodiode receiver integrated with a tunable laser transmitter. Devices are fabricated on a robust InP ridge/InGaAsP waveguide platform. The photodiode receiver consists of an integrated SOA pre-amplifier and a PIN diode to improve sensitivity. The laser transmitter consists of a 1550 nm widely tunable SGDBR laser modulated either directly or via an integrated modulator outside the laser cavity. An SOA post-amplifier provides high output power. The integrated device allows signal monitoring, transmits at 2.5 GB/s, and removes the requirements for filtering the input wavelength at the output. Integrating the SGDBR yields a compact wavelength agile source that requires only two fiber connections, and no off-chip high speed electrical connections. Analog and digital performance of directly and externally modulated wavelength converters is also described.

Electrical critical dimension metrology for 100-nm linewidths and below

In this paper, we have demonstrated an electrical CD process capable of resolving linewidth swell below 100 nm compatible with a standard polysilicon patterning flow. Appropriate selection of dopant species combined with a reduction in anneal temperature were in the primary means for achieving a physical to electrical linewidth bias of 20 nm. These findings supported our hypothesis that dopant our-diffusion was the primary source of the bias. Also, ECD metrology is applied to quantifying poly CD variations in the presence of substrate topography.

Characterization and modeling of a chemically amplified resist for ArF lithography

There is increasing interest in chemically amplified (CA) single-layer photoresist for 193 nm excimer laser lithography as a route to sub-quarter micron imaging. A quantitative understanding of the factors that limit the ultimate resolution of CA resists requires a detailed knowledge of both the kinetics of the acid-catalyzed chemical reaction and the diffusion properties of the photogenerated acid. Information of this type is key to the accurate modeling of all CA resists regardless of exposure wavelength. We have investigated the exposure, thermal processing and dissolution behavior of a methacrylate terpolymer-based 193 nm resist. The chemical reactions occurring during post-exposure bake were monitored by FTIR microscopy over a range of PEB temperatures and exposure doses. Using the FTIR data and dissolution contrast curves, parameters for a model of the exposure, the post-exposure bake and the development were extracted. The model was implemented in the SAMPLE lithography simulation tool to predict resist profiles and process latitudes of methacrylate resists on a 193 nm step and scan tool. Excellent agreement between the simulated photoresist profiles and SEM cross-sections was obtained.

Top surface imaging process and materials development for 193 nm and extreme ultraviolet lithography

The maturity and acceptance of top surface imaging (TSI) technology have been hampered by several factors including inadequate resist sensitivity and line edge roughness. We have found that the use of a chemically amplified resist can improve the sensitivity in these systems by 1.5– 2× without compromising the line edge roughness. In addition, we have shown improved line edge roughness by increasing the molecular weight of the polymeric resin in the resist. Using these materials approaches, we have been able to show excellent resolution images with the TSI process for both 193 nm and extreme ultraviolet (13.4 nm) patterning.