Reactive Ion Beam Etching Research Articles

Etching Behavior and Damage Rejuvenation of Top Electrode and Bi3.15Nd0.85Ti3O12 Films Applied in Ferroelectric Random Access Memory Devices

Reactive ion etching (RIE) and ion beam etching (IBE) were used to etch the Bi3.15Nd0.85Ti3O12 (BNdT) ferroelectric layer and top electrode (TE), respectively, for ferroelectric random access memory (FeRAM) applications. The effect of dry etching on the ferroelectric properties of Pt/BNdT/Pt capacitors and the film etching mechanism were investigated. After TE etching, the remanent polarization (2Pr) of capacitors decreased through the charging effect, but was recovered by rapid thermal annealing (RTA). A distinct polarization suppression of the capacitors was observed after BNdT layer dry etching owing to the large amount of ions accumulated in the electrode/film interface and within the films. The property damage could be recovered after long-time furnace annealing. The capacitor property rejuvenation was complete even after 1010 switching cycles of fatigue test. The capacitor size effect and recovery of the ferroelectric properties after film etching process were also studied.

Bumpless Interconnect of 6-$\mu$m-Pitch Cu Electrodes at Room Temperature

Bumpless interconnect of 6-mum-pitch Cu electrodes was realized at room temperature with the surface activated bonding (SAB) method. In this study, we propose a novel bumpless structure, where the electrodes and a surrounding Cu frame are fabricated with the same height to increase bond strength and demonstrate the feasibility of a sealing interconnection between Cu surfaces. The damascene process, assisted by the reactive ion beam etching (RIE), was used to fabricate the Cu structures. 923 521 electrodes placed inside the frame were arranged into a spiral chain to enable the detection of the positions with insufficient interconnection by electrical resistance measurements. Using the SAB conditions optimized with simple chemo-mechanical polishing (CMP)-Cu film samples, we found that 744 769 electrodes were successfully interconnected, except some specific lines near the frame, which might be due to sample preparation error rather than a bond defect. The mean contact resistance was below 0.08 Omega a sealing effect was achieved at the frame structure because there was little increase in the contact resistance in high temperature storage testing performed at 150degC for 1000 h, in ambient air.

In situ endpoint detection of reactive ion-beam etching of dielectric gratings with an etch-stop layer using downstream mass spectrometry

Downstream mass spectrometry is successfully used in the reactive ion-beam etching of dielectric diffraction gratings of deep grooves with vertical sidewalls to achieve in situ endpoint detection. Silica (SiO 2) gratings with a Sc 2O 3 etch-stop layer are fabricated by reactive ion-beam etching with CHF 3 as etchant, and the mass spectrometric signal of SiF 3 + produced by the reactive etching of the SiO 2 grating material is monitored. When the etch-stop layer is reached, a drop of this signal occurs. By comparing the monitoring curves and resulting gratings of different etching methods, we find that the decrease of the monitored signal is strongly influenced by the sidewall steepness of the etched grating grooves. All conditions being equal, the greater sidewall steepness renders the faster decrease of the signal. Consequently, the proposed approach of endpoint detection applies well to the gratings with steep sidewalls. With the help of two previously developed methods, the sidewall steepness of grating grooves is increased, and the optimal endpoint is detected. Employing the proposed technique, we have reproducibly fabricated dielectric gratings with proper groove depth and even groove bottom.

Effect of reactive ion beam etching on the photoluminescence of CdTe epitaxial layers

We demonstrated the effect of reactive ion beam etching (RIBE) process on the PL properties of CdTe/sapphire metal organic vapor phase epitaxy layers. At optimum conditions, the RIBE attack does not make significant morphological changes but it results in an increase of the concentration of acceptor impurities. This was revealed by an increase of the overall photoluminescence (PL) intensity and, simultaneously, a decrease of the PL decay time, more important on the low energy side of PL spectrum due to the recombination of carriers in acceptor pairs.

Growth of Si nanorods in honeycomb and hexagonal-closed-packed arrays using glancing angle deposition

Regular arrays of Si nanorods with a circular cross section in hexagonal-closed-packed and triangular cross section in honeycomblike arrangements were grown using glancing angle deposition on Si(100) and fused silica substrates that were patterned with Au dots using self-assembled mono- and double layers of polystyrene nanospheres as an evaporation mask. The Au dots were used as an etching mask for the underlying silica substrates in a reactive ion beam etching process, which greatly enhanced the height of the seeding spaces for the subsequent glancing angle deposition. An elongated shadowing length l of the prepatterned nucleation sites and less growth of Si structures between the surface mounds could be achieved this way. Differences in form, height, and diameter of the Si nanorods grown on either hcp or honeycomb arrays are explained by purely geometrical arguments. Different seed heights and interseed distances are found to be the main reasons for the strong distinctions between the grown nanorod arrays.

Fabrication of Phase Mask for Optical Fiber Grating

A fused silica phase mask with the period of 1069nm, and ruled area 50×50mm2 has been fabricated by a new technique, which combines holographic-ion beam etching and reactive ion beam etching. This involves several steps: coating of substrates with controlled thickness of photoresist, formation of a grating mask by holograph interference exposure and development, and finally transferring etching of this mask into the fused silica substrate to form a permanent phase mask. Experimental measurements have shown that the zero order diffraction efficiency is less than 4% and the plus and minus first-order diffraction efficiency is more than 35%. Theoretical analysis has shown that these phase masks can be used for fabricating UV written Fiber Bragg Gratings.

Cause of Damage of Reactive Ion Beam Etching for Ni-Fe films with CO/NH3 and CH3OH Chemicals

The damage caused by reactive ion beam etching (RIBE) using CO/NH3 and CH3OH chemicals was investigated for Ni-Fe films thinner than 20 nm. Measurement of the changes in magnetization of films etched at a stage temperature from 40 to 100ºC and a bias power from 100 to 500 W revealed that the dominant damage with CO/NH3 was chemical, while that with CH3OH was physical. The amount of damage in the latter case was 1/3 to 1/2 that in the former case. The effect of RIBE on the soft magnetic properties was also investigated. A sample etched under conditions that cause a thicker damaged layer had a lower anisotropy field (Hk) and a lower easy axis coercive force (Hc). This indicates that RIBE degrades magnetic anisotropy in the Ni-Fe films.

Brief rapid thermal treatment effect on patterned CoFeB-based magnetic tunneling junctions

The brief thermal treatment effects on the magnetoresistance of microstructured Co60Fe20B20-based magnetic tunneling junctions have been studied. The elliptical shape of devices with long/short axis of 4∕2μm was patterned out of film stack of seed layer (20)∕PtMn(15)∕Co60Fe20B20(3)∕Al(0.7)oxide∕C60Fe20B20(20)∕capping layer (48) (thickness unit in nanometers) combining conventional lithography and inductively coupled plasma reactive ion beam etching technologies. The thermal annealing was carried out with device loading into a furnace with preset temperatures ranging from 100to400°C for only 5min in the absence of any external magnetic field. The magnetoresistance was found to increase with increasing annealing temperatures up to 250°C and then decrease at higher annealing temperatures. In addition, the magnetoresistance ratio of around 35%, similar to that of as-fabricated devices, sustains up to annealing temperature of 350°C. This survival of magnetoresistance at higher annealing temperature is due to boron conservation in the amorphous CoFeB ferromagnetic layer at higher annealing temperature for only a short time, which is manifested using x-ray diffractometer technique.

Precise control of dry etching for nanometer scale air-hole arrays in two-dimensional GaAs/AlGaAs photonic crystal slabs

Precise control of highly anisotropic reactive-ion-beam-etching (RIBE) for GaAs/AlGaAs-based two-dimensional photonic crystals (2DPCs) is investigated in terms of the substrate temperature, T s, ion accelerating voltage, V i, and Cl 2 gas pressure, p. T s is shown to influence the shape of the sidewall, while the balance of the physical etching dominated by the value of V i and the chemical etching dominated by the value of p is essential for keeping smooth and vertical sidewalls of 100-nm-scale air-holes. 2DPC air-hole patterns are defined by an electron beam (EB) lithography machine and air-holes are dry-etched with the EB resist as an etching mask. The optimized balance between the V i and p for 0.5–1.0-μm-deep air-holes results in the high-rate-etching regime given at V i = 500 V and p = 8 × 10 −4 Torr using a 650-nm-thick resist mask, while the optimized balance for 50-nm-scale fine air-holes results in the low-rate-etching regime given at V i = 330 V and p = 5 × 10 −4 Torr using a 350-nm-thick resist mask. In particular, the latter condition is essential for fabricating topology-optimized 2DPC air-hole arrays with the minimum air-hole-size of 50 nm or less. These process conditions definitely contribute to excellent measured transmission spectra in good agreement with the calculated one in a near-infrared range.

Bumpless interconnect of ultrafine Cu electrodes by surface activated bonding (SAB) method

AbstractIn this study, an ultrafine bumpless interconnect was realized by applying the surface activated bonding (SAB) method to the room‐temperature direct bonding of Cu electrode, and its electrical performance was verified. Also, a thin flash memory chip and a Si interposer were interconnected with the bumpless structure to demonstrate its applicability to practical devices. We used the combination of the damascene process and RIE (reactive ion beam etching) process to fabricate bumpless electrodes with a diameter of 3 µm, pitch of 10 µm, and height of 60 nm, and bonded them with a highly accurate SAB flip chip bonder. One hundred thousand fabricated bumpless electrodes were successfully interconnected, and we showed that the contact resistance could be less than 1 mΩ with high thermal reliability at the interface. Also, we developed a fabrication process of bumpless electrodes that has a polyimide insulation layer by the combination of oxygen plasma ashing and CMP (chemical mechanical polishing), and applied it to the interconnection between a 0.1‐mm‐thick flash memory chip and an interposer with the same thickness. The bonded memory chip was assembled into a compact flash (CF) memory card module, and the entire memory region was successfully verified. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 89(12): 34–42, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20247

Micron and submicron patterning of polydimethylsiloxane resists on electronic materials by decal transfer lithography and reactive ion-beam etching: Application to the fabrication of high-mobility, thin-film transistors

We describe a technique for fabricating micron and submicron-sized polydimethylsiloxane (PDMS) patterns on electronic material substrates using decal transfer lithography (DTL) in conjunction with reactive ion-beam etching (RIE). We validate the use of this unconventional polymeric system as a suitable resist material for fabricating Si-based microelectronic devices. In this process, an O2∕CF4 gas mixture was used to etch a supporting PDMS thin film that resides atop a closed-form decal polymer to reveal conventional resist structures. These structures provide an effective latent image that, in turn, provides for an extension of soft lithography as a form of multilayer lithography—one yielding submicron structures similar to those obtained from the conventional photochemical methods used to prepare such resists. This combined DTL/RIE patterning procedure was found to be compatible with commercially available planarization layers and provides a direct means for preparing high aspect ratio resist features. We illustrate the applicability of soft lithography as a means for fabricating electronic devices by using it to prepare model silicon-based thin-film transistors exploiting silicon-on-insulator wafer technology.

Optical waveguides in laser crystals

This article reviews the recent research on different types of planar and channel crystalline optical waveguides, fabrication methods such as liquid phase epitaxy, pulsed laser deposition, thermal bonding, reactive ion or ion beam etching, wet chemical etching, ion in-diffusion, proton exchange, ion beam implantation, and femtosecond laser writing, as well as waveguide laser operation of rare-earth and transition-metal ions in oxide crystalline materials such as Al 2O 3, Y 3Al 5O 12, YAlO 3, KY(WO 4) 2, and LiNbO 3. To cite this article: M. Pollnau, Y.E. Romanyuk, C. R. Physique 8 (2007).

Hole-type two-dimensional photonic crystal fabricated in silicon on insulator wafers

We report the realization of two-dimensional (2D) photonic crystal (PhC) holes array using synthesized processing techniques of deep UV lithography, time-multiplexed reactive ion etching (TMRIE) and focus ion beam (FIB) etching. In this study, mixed density of holes and waveguide patterns of 2D PhC structures was first formed in silicon on insulator wafers through use of a scanner. Ultra wide grooves were then defined, aligned to the deep submicron size devices. Following deep etching of more than 50 μm by TMRIE, PhC structures were then revealed for device etching. Such design of fabrication process allows realization of disparate pattern dimensions and also etching depths. Through avoidance of etch lag effect, notching of devices at interface of device silicon and buried oxide layer was avoided. At the same time, through a singular FIB etch in the final step of the process following buried oxide release for PhC structures on critical dimension structures, severe loading effects of such structures were avoided to enable a wide process window of lithography and etch.

Cause of Damage of Reactive Ion Beam Etching for Ni-Fe films with CO/NH3 and CH3OH Chemicals

not Available.

Reactive ion beam etching of HfO2 film and removal of sidewall redeposition

Comparative studies on ion beam etching (IBE) and reactive ion beam etching (RIBE) of HfO2 film have been carried out using photoresist as the masking layer. The etching rates of HfO2 film and photoresist mask in pure Ar and Ar∕CHF3 mixture plasmas were measured as a function of ion energy, plasma composition, and ion beam incident angle. It has been found that the RIBE with Ar∕CHF3 plasma is capable of lowering the threshold energy of ion beam and increasing sputtering yield, compared to the IBE with pure Ar. The redeposition of photoresist sidewall is a major issue, due to the formation of nonvolatile etching products during sputtering of HfO2 film in both IBE and RIBE. However, the sidewall redeposition can be easily removed in HCl solutions with assistance of ultrasonic wave for RIBE with Ar∕CHF3 plasma. Alternatively, the sidewall redeposition can be eliminated by controlling the slope of photoresist sidewall or combined with ion incident angle.

Bumpless Interconnect Through Ultrafine Cu Electrodes by Means of Surface-Activated Bonding (SAB) Method

In this paper, we demonstrate the feasibility of ultrahigh-density bumpless interconnect by realizing the ultrafine pitch bonding of Cu electrodes at room temperature. The bumpless interconnect is a novel concept of bonding technology that enables a narrow bonding pitch of less than 10 /spl mu/m by overcoming the thermal strain problem. In the bumpless structure, two thin layers including an insulator and metallic interconnections on the same surface are bonded at room temperature by the surface-activated bonding (SAB) method. In order to realize the bumpless interconnect, we invented a SAB flip-chip bonder that enabled the alignment accuracy of /spl plusmn/1 /spl mu/m in the high vacuum condition. Moreover, the fabrication process of ultrafine Cu electrodes was developed by using the damascene process and reactive ion beam etching (RIE) process, and the bumpless electrodes of 3 /spl mu/m in diameter, 10 /spl mu/m in pitch, and 60 nm in height were formed. As a result, we succeeded in the interconnection of 100 000 bumpless electrodes with the interfacial resistance of less than 1 m/spl Omega/. An increase of the resistance was considerably small after thermal aging at 150/spl deg/C for 1000 h.

Microfabrication of PZT force sensors for minimally invasive surgical tools

Minimally invasive surgery (MIS) is the most exciting and rapidly developing area where force sensing is actually of central importance. Micromachined piezoelectric sensors can be integrated onto MIS tools for improved diagnosis and treatment monitoring. A micro-machined freestanding lead zirconate titanate (PZT) force sensor is fabricated using five masks process incorporating deep reactive ion, ion beam and wet-chemical etching techniques. The PZT sensor is designed as a parallel plate capacitor structure in which the sol-gel prepared 1-µm thick PZT film is sandwiched between top (Au/Cr) and bottom (Pt/Ti) metal electrodes mounted on a thin Si membrane. This paper also describes a new wet chemical approach for patterning PbZr0.52Ti0.48O3 films. The etch recipe provided excellent etch control, minimized undercut, preserved the photoresist mask, and effectively removed the residues on the etched surfaces. A high etch rate (200 nm/min), high selectivity with respect to photoresist, and limited under-cutting (1.5:1, lateral : thickness) were obtained. The fabricated force sensor exhibited good ferroelectric properties. The current fabrication procedure and electrical analysis can be considered as a breakthrough for fabricating freestanding PZT force sensor in any desired shape and dimensions, as well as a good example of ferroelectric microdevices.

Nanoimprint lithography using IR laser irradiation

A new technique called “infrared laser-assisted nanoimprint lithography” was utilised to soften the thermoplastic polymer material mR-I 8020 during nanoimprint lithography. A laser setup and a sample holder with pressure and temperature control were designed for the imprint experiments. The polymer was spin coated onto crystalline Si <111> substrates. A prepatterned Si <111> substrate, which is transparent for the CO2 laser irradiation, was used as an imprint stamp as well. It was shown, that the thermoplastic resist mR-I 8020 could be successfully imprinted using the infrared CW CO2 laser irradiation (λ=10.6μm). The etching rate of the CO2 laser beam irradiated mR-I 8020 resist film under O2 RF (13.56MHz) plasma treatment and during O2 reactive ion beam etching was investigated as well.

Ion-beam processing of single crystal diamond using SOG mask

Various ion-beam etching characteristics of diamond and selectivity between diamond and spin-on-glass (SOG) were examined. The maximum selectivity of diamond and SOG was 12.7 in oxygen reactive ion-beam etching process at 100 V acceleration voltage. Using this etching condition and dot-shaped SOG mask, conical diamond field electron emitter arrays with 30 nm curvature radius, 2.58 μm base radius and 5.86 μm height were fabricated.

Additive Soft-Lithographic Patterning of Submicrometer- and Nanometer-Scale Large-Area Resists on Electronic Materials

We describe a novel soft-lithographic technique possessing broad utility for the fabrication of large area, nanoscale ( approximately 100 nm) multilayer resist structures on electronic material substrates. This additive patterning method transfers ultrathin poly(dimethylsiloxane) (PDMS) decals to an underlying SiO(2)-capped organic planarazation layer. The PDMS patterns serve as a latent image through which high-quality multilayer resist structures can be developed using reactive ion-beam etching.