Dual damascene technique has been widely applied to IC device fabrication in copper interconnect
process. For traditional via-first dual damascene application, a fill material is first employed to fill via to protect
over-etching and punch-through of the bottom barrier layer during the trench-etch process. Etch-back process is then
applied to remove excess overfill thickness and maintain a greater planar topography. To get better CD control, a thin
organic BARC is finally coated to reduce reflectivity for trench patterning but not in this study. It is a multi-step and
costly dual damascene process. In this study, a new gap-filling BARC material with good via fill and light
absorption features was adopted to explore the via-first dual damascene process by skipping etch-back and BARC
coating steps. The results show not only the reduction of process cycle time and cost saving but also the CP yield
improvement based on data from pilot production of 0.11/0.13 μm logic device.
The IC industry is moving toward 90nm node and below. The CD size of implant layers has shrunk to 220nm. To achieve better CD uniformity, dyed KrF resist and top anti-reflective coating (TARC) are commonly used in advanced photo process of implant layers. It’s well known that bottom anti-reflective coating (BARC) has better reflection control over TARC. However, dry etching process is required if typical organic BARC is applied to photo process of implant layers. It is undesirable for two reasons. The first reason is the substrate damage caused by plasma etching could affect the device performance. The second reason is higher cost due to additional processing steps. In order to overcome those two shortcomings, developable BARC (DBARC) is introduced. It is a new type of BARC, which is soluble to developer, TMAH solution, in the resist development step. There are some reports on the developer-soluble KrF BARC. Most of them are polyamic acid and their solubility to alkline could be adjusted by changing bake condition. However, its development is isotropic, which make it difficult to get a vertical profile. Therefore, we have developed a photosensitive developer-soluble BARC (DBARC) which is anisotropic after exposure and thus results in a nice vertical profile. The photosensitive DBARC utilizes the same concept as chemically amplified resist. It has acid-cleavable groups in the resin and PAGs in the formulation. The photosensitive DBARC turns soluble to TMAH developer after exposure and resist PEB. The solubility difference caused by exposure makes developing process anisotropic and thus improves profile control. In this article, we will report the evaluation results of various combinations of KrF resists and DBARC for implant layers. Since both the resist and DBARC are photosensitive, matching of the photo speeds of them is essential. The amount and type of PAG in both the resist and the DBARC play a very import role. Finally, the optimized combination showed acceptable lithography process window and good CD uniformity over topography.
Harmonic and rational-harmonic mode-locking of erbium-doped fiber lasers (EDFLs) with wavelength tunability is achieved by seeding optical pulses from a gain-switched Fabry-Perot laser diode that is feedback-injection controlled with the slave EDFLs via optical circulator.
A DC-voltage controlled optoelectronic phase shifter (OEPS) integrated with a PZT-controlled active stabilizer is proposed for both the reduction in timing jitter and the tuning in delay-time of optical pulses generated from argon- ion-laser-pumped, passively mode-locked femtosecond Ti:sapphire laser with intracavity saturable Bragg reflector (SBR). The rms timing jitter (100 - 500 Hz) of the Ti:sapphire/SBR laser is significantly suppressed down to 290 fs with uncorrelated single-sided-band phase noise of less than -120 dBc/Hz at offset frequency of 5 KHz. The pulsewidth, the repetition rate, and the single-sided-band phase noise of the laser are found to keep invariant during the delay-time tuning process. The maximum phase-tuning range and tuning gain of the OEPS is approximately equals 11.3 ns and 2.3 ns/volt.
Waveform sampling of the positive ECL signals generated from microwave frequency divider by using a delay-line-free electro-optic sampling system with a voltage-controlled phase-tuning circuit is primarily reported. The distorted waveform of the ECL signal frequency-prescaled from microwave oscillator operated at high output level is sampled and compared by using the proposed technique and the conventional sampling oscilloscope. The divisor of the frequency prescalar is found to vary from 2 to 5 at input power of less than 114dBm.
A delay-time tunable, actively mode-locked erbium-doped fiber ring laser is demonstrated. The phase and the delay- time of optical pulse-train with repetition rate of about 500 MHz can be adjusted with maximum tuning range of up to 340 degree(s) (~1.9(pi) ) and nearly 1 period.
We propose for the first time the in-situ frequency discriminating and continuous phase-tuning of the microwave signal or pulse-train generated from directly modulated laser diode with respect to a free-running microwave clock by integrating a DC-voltage controlled optoelectronic phase shifter (OEPS) with the laser source. This technology facilitates the combination of the frequency synchronization and the phase shifting functions in one circuit. The transferred function of the phase shift versus the controlling voltage is linear with a maximum phase-tuning range and a tuning slope of up to 3.6(pi) (640 degrees) and 90 degrees/volt, respectively. The fluctuation and drift in phase of the controlled signal is about 0.05 degrees and 0.003 degrees/min. The tuning resolution of 0.2 degrees at a 3-mV increment of the controlling voltage is achieved by using a high-precision voltage regulator. Relative timing jitter of the controlled optical microwave clock is less than 5 ps. By using the delay-time tunable pulsed laser, we demonstrate for the first time the delay-line-free electro-optic sampling of the waveforms, which are RF sinusoidal and pulse signals with repetition rate of 500 MHz. The maximum sampling range and highest sampling resolution are about 1.9 periods and 0.2 ps/mV, respectively.
By employing an optoelectronic phase shifter as a delay-time controller to replace the conventional opto-mechanic delay line, a delay-line-free high-speed electro-optic sampling (EOS) System is proposed as a novel and unique module which overcomes the drawbacks of conventional electro-optic sampling system, such as the measuring distortion caused by misalignment of probe beam and difficulty in sampling of free-running high-speed transients. Versatile configurations of PLL circuits suitable for modifying as an ODTC in the EOS system are interpreted and the performance of the ODTC such as maximum tuning range, linearity, speed, and resolution are determined. The waveform sampling of the free-running sinusoidal microwave signal, the digital signal output from a frequency divider (or prescaler), and the electrical pulse generated by the comb generator are demonstrated.
By using a phase-tunable optoelectronic phase-locked loop, we are able to continuously change the phase as well as the delay-time of optically distributed microwave clock signals or optical pulse train. The advantages of the proposed technique include such as wide-band operation up to 20GHz, wide-range tuning up to 640 degrees, high tuning resolution of <6x10-2 degree/mV, ultra-low short-term phase fluctuation and drive of 4.7x10-2 degree and 3.4x10- 3 degree/min, good linearity with acceptable deviations, and frequency-independent transferred function with slope of nearly 90 degrees/volt, etc. The novel optoelectronic phase shifter is performed by using a DC-voltage controlled, optoelectronic-mixer-based, frequency-down-converted digital phase-locked-loop. The maximum delay-time is continuously tunable up to 3.9 ns for optical pulses repeated at 500 MHz from a gain-switched laser diode. This corresponds to a delay responsivity of about 0.54 ps/mV. The using of the OEPS as being an optoelectronic delay-time controller for optical pulses is demonstrated with temporal resolution of <0.2 ps. Electro-optic sampling of high-frequency microwave signals by using the in-situ delay-time-tunable pulsed laser as a novel optical probe is primarily reported.