Hole Profile Research Articles

Contact CD Uniformity and Hole Circularity Improvement in 32/28 nm Node: Effect of Substrate Properties and Chemical Material Baking Temperature

Contact patterning is one of the critical steps in a state-of-the-art lithography process. One of the main challenges for developing contact patterning process in 32/28 nm technology node is to achieve better critical dimension uniformity (CDU) and smaller circularity of the contact holes. In this paper we study the CDU and pattern shape variation affected by material chemical properties and baking temperature. By employing DOE (Design of Experiment) methods, we have found that the contact holes CDU can be determined by the photoresist types and BARC (Bottom Anti-Reflective Coater) baking temperature. For one type photoresist, we have found that the circularity of contact holes falls into nearly linear relationship with the CD value, which can not be affected either by the baking temperatures of the photoresist and BARC materials or by the developing process. In addition, we have also found that contact layer defect scan results and final hole profile after etch can be altered by the sidewall angle and/or the profile of the photoresist, which is near vertical. To satisfy photoresist cross section profile sidewall angle requirement, the negative impact from the substrate films to the photoresist profile has to be studied and reduced. Finally, we will present the defect scan result for our experiments in CDU and pattern profile.

Ambient-controlled scanning spreading resistance microscopy measurement and modeling

An ambient-controlled scanning spreading resistance microscopy (AC-SSRM) apparatus is utilized for one-dimensional (1D) and two-dimensional doping profiling measurement. 1D SSRM profiling on a blanket (vertical) B-doped Si wafer is conducted to obtain a spreading resistance profile SR(x). Modeling is used to convert SR(x) to carrier profile n(x). Replacing the average mobility (μ) with a calibration using μ(x), the carrier (hole) profile n(x) is more accurate. This is especially pronounced near the surface and junction depth (xj) and is consistent with the continuous anodic oxidation technique/differential Hall effect (CAOT/DHE) measured carrier profiles. The model based on AC-SSRM data obtained xj = 103.4 nm, which was consistent to secondary ion mass spectrometry results of xj = 104.0 nm. Calibrated hole dose using μ(x) is 9.6 × 1014/cm2 and is relatively closer to DHE hole dose 1.4 × 1015/cm2. In addition, a fairly good consistency of sheet resistance (RS) values among 4 point probe (4PP), CAOT/DHE, and AC-SSRM methods has been demonstrated.

A Comparative Study of Carbide Tools in Drilling of CFRP and CFRP-Ti Stacks

A comparative study was conducted to investigate the resulting tool wear and hole quality when drilling the stacks made of titanium (Ti) and carbon-fiber reinforced plastic (CFRP) versus CFRP only plate using micrograin tungsten carbide (WC) twist drills. The experiments were designed to first drill CFRP alone to create 20 holes. Then, CFRP mechanically stacked with Ti was drilled for the next 20 holes with the same drill bit. This process was repeated until drill bit failure. The drilling experiment was performed at two distinct speeds. Scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM) were used for tool wear analysis. Hole size, hole profile, surface roughness, and Ti burrs were analyzed using coordinate measuring system, surface profilometer and optical microscope. The experimental results indicate that the Ti drilling accelerated flank wear while CFRP drilling deteriorated the cutting edge. Entry delamination, hole diameter errors, and surface roughness of the CFRP plate became more pronounced during the drilling of CFRP-Ti stacks when compared with the results from the drilling of CFRP only. Damage to CFRP holes during CFRP-Ti stack drilling may be caused by Ti chips, Ti adhesion on the tool drill margin or the increased instability as the drill bits wear.

Influence of laminate lay-up, hole size and coupling agent on the open hole tensile properties of flax yarn reinforced polypropylene laminates

The effect of laminate lay-up, open hole size and coupling agent on the open hole tensile properties of flax yarn reinforced polypropylene (PP) laminates were studied in this work. Unidirectional flax/PP laminates were prepared using a stacking technique, where newly developed interwoven fabric (flax/PP) and maleic anhydride grafted polypropylene (MAPP) copolymer film were used as a raw material and coupling agent respectively. The cross ply laminates (0/90/0)S showed high strength retention (98%) which ensured less notch sensitivity to the open hole profile. MAPP treated open hole samples achieved a reasonable improvement in tensile strength for all kind of laminate lay-up. Undrilled laminates tensile strength was improved by 14–17% due to MAPP treatment. Highest strength retention in MAPP treated sample was observed for cross ply laminates with 4mm hole size, which was noted as 92%. Fractography studies confirmed the tensile fracture of fiber across the hole and good interfacial adhesion between fiber and matrix for MAPP treated laminates.

MODELLING OF HOLE TAPER AND HEAT AFFECTED ZONE DUE TO LASER BEAM PERCUSSION DRILLING

Determination of hole taper and extent of heat affected zone is a challenging task for manufacturing engineers from the quality and accuracy point of view of the laser-drilled hole especially in reflecting materials like aluminum. In this article, an axisymmetric finite element method-based thermal model has been developed for the determination of the transient temperature distribution in the aluminum sheet, which is further used for determination of hole profile, hole taper and extent of heat-affected zone during laser beam percussion drilling. Simulation results showing the effect of pulse width, pulse frequency, and peak power on hole taper and extent of heat affected zone incorporating the temperature dependent thermal properties and phase change have been presented. The developed model is also capable of predicting the hole profile through the isotherm generated along the depth of hole due to repeated laser pulses. The predicted values of hole taper are compared with the experimental results. It is found that the effect of pulse width on hole taper is more prominent than the peak power and extent of heat affected zone increases with the increase of pulse width, pulse frequency but it decreases with the increase of peak power.

Prediction of hole characteristics and hole productivity during pulsed Nd:YAG laser beam percussion drilling

A thermal finite element model is proposed to simulate and predict hole taper ( Ta), heat-affected zone and material removal rate during laser beam percussion drilling in two difficult-to-laser-drill materials having wide difference in their thermophysical and optical properties. The developed model incorporates temperature-dependent thermal properties, optical properties and phase change phenomena of the sheet materials to predict the hole profile through the isotherm generated along the depth of the hole due to repeated laser pulses. Hole characteristics and hole productivity parameters are compared for both the sheet materials. The predicted values of hole taper with respect to pulse width have been compared with the experimentally obtained values. It is observed that hole characteristics are mainly affected by pulse width in the Aluminium alloy sheet and pulse frequency in the Inconel sheet, whereas peak power has prominent effect on material removal rate for both the sheet materials.

Dry Etching Solutions to Contact Etch for Advanced Logic Technologies

Dry Etching Solutions to Contact Etch for Advanced Logic Technologies Heavy polymer and byproducts from CD shrinkage will easily cause contact hole open, especially for the tapered hole profile. The sufficient over-etch without any silicon loss and too much silicide loss is also required to maintain enough process window for less junction leakage. Meanwhile, the circularity of contact hole needs to be well controlled to avoid the potential contact to poly gate bridge issue. In this work, we investigated the impact of dry etching process on contact hole profile and circularity, balanced contact hole CD shrink and contact open issue. Results demonstrate the overall contact hole profile needs to be rigorously controlled by optimizing the etch selectivity of silicon oxide over silicon nitride, the etch treatment is imperative to reduce the contact open issue. The circularity of contact hole can be well improved by tuning the etching chemistry at bottom anti-reflective coating open step and optimizing patterning film stack.

Observations on initiation of pier scour and equilibrium scour hole profiles in cohesive sediments

The present study investigates the initiation of scouring process around circular and square bridge pier models embedded within clay–sand mixed cohesive sediment beds based on laboratory flume experiments. Observations on the initiation and the temporal progress of scouring process around circular and square piers were made from 20 experimental runs. A camera placed within the pier model was used to visualise and record the initiation of the scouring process and its progress in detail. Profile of equilibrium scour hole and spatial variation of the point of maximum equilibrium scour depth was also studied to determine its relation with the characteristics of clay–sand mixed cohesive sediment beds, flow parameters and geometrical shape of the pier.

Broadband antireflective structures with hole for highly transparent glasses

Optimal sub-wavelength structures (SWS) with parabolic hole on glass substrate are designed using effective medium theory (EMT), which will reduce the reflectance over wavelength range from 300 to 1200nm and 0° to 80° angle of incidence. The performance of SWS integrated glass is verified by genetic algorithm. The optimized SWS with the cross-sectional profile of parabolic hole have parameters with ∼120nm diameter and 300nm height. The average reflectance over wavelength range from 300 to 1200nm and 0° to 80° angle of incidence could be reduced to only 0.5% by applying the optimized SWS onto glass.

Study on the etching characteristics of amorphous carbon layer in oxygen plasma with carbonyl sulfide

Carbonyl sulfide (COS) was added to oxygen as the additive etch gas for etching of amorphous carbon layers (ACL), and its effect on the etching characteristics of ACLs as the etch mask for high aspect ratio contact SiO2 etching was investigated. When a 50 nm amorphous carbon hole was etched in a gas mixture of O2 + 5% COS, not only did the etch profile of the ACL change more anisotropically but also the top/bottom opening ratio of the etch profile was improved by about 37% compared to those etched without COS. The improved ACL etch characteristics were related to the sidewall passivation of the amorphous carbon hole by the carbon sulfide related layer during the etching of the ACL. The distortion of the amorphous carbon hole was also reduced by about 6% due to the uniform deposition of the carbon sulfide related layer on the sidewall of the amorphous carbon hole. This uniform deposition improved the etch profile and opening ratio of the amorphous carbon hole, ultimately resulting in the enhanced contact oxide etching characteristics as evidenced by 5% improvement in the contact oxide opening and 20% improvement in the mask etch selectivity during the etching of an oxide having 20:1 high aspect ratio.

Analysis on profile accuracy for ultrasonic machining of alumina ceramics

Ultrasonic machining (USM) is a mechanical material removal process which has great potential for machining hard and brittle materials such as ceramics, semiconductors, glasses, etc. The accuracy of the job profile generated by USM can be improved by optimal control of the process parameters. This paper presents the study on the influences of ultrasonic machining process parameters such as abrasive grit size, slurry concentration, power rating, tool feed rate and slurry flow rate on generated hexagonal hole profile. The angular deviations at corner angles, dimensional deviations across flat surfaces and dimensional deviation across corners of the hexagonal hole profile have been studied. Based on experimental results, the influences of abrasive grit size, slurry concentration, power rating and tool feed rate were analysed. From the analysis of parametric influences based on various test results, the best parametric combination was found as grit number of 600, slurry concentration of 30 %, power rating of 50 % and feed rate of 1.08 mm/min for achieving better profile accuracy during machining of Al2O3 ceramics. The experimental investigations carried out for determining the influence of USM process parameters will provide effective guideline to select parametric settings for achieving desired job profile accuracy on non-circular holes during ultrasonic drilling of alumina.

The Machining Characteristics of Insulating AlN Ceramics by EDM

AlN ceramic materials have high thermal conductivity and electrical insulation, prompting consideration of their use as a semiconducting material. Although AlN should be machined with a high accuracy of form and dimension to achieve products and components with requisite precision, mechanical and other machining methods such as the micro blasting technology or laser method cannot be used because of the brittleness and high thermal conductivity of AIN. Recently, we have succeeded in machining many insulating ceramics by EDM with the assisting electrode method. We have already machined many insulating ceramic materials such as Si3N4, ZrO2 and Al2O3. However, inferior machining characteristics were obtained with AlN than with other materials. In this study, the effects of several electrical discharge conditions were examined to obtain better machining properties, such as high material removal rate and a low electrode wear ratio. It was found that machining time decreased with an increase in capacitance, while the electrode wear ratio increased. In addition, the machining hole profiles were straight along the depth direction, and the shape of holes was non-tapered

Penetration research of jacketed jet into concrete

The current study designs a shaped charge structure that could form a jacketed jet to enhance the cavity diameter created by a shaped charge jet into concrete. Moreover, three types of penetration modes during the process of jacketed jet penetration into concrete, including homogeneous jet penetration, “bi-erosion”, and “co-erosion” are discussed. A two-step mechanism of cavity growth that contains the trajectory of flowing jet erosion products and the radial momentum of the target is used to describe the penetration modes. Thus, an analytical model for predicting the crater size generated by jet is presented. Moreover, the jacketed and single material jets parameters which are needed in the analytical model are obtained using AUTODYN-2D finite-difference Eulerian code. Experimental results show that the jacketed jet creates a larger exit crater than the single material jet. Moreover, the entrance cavity diameter did not change. The calculated hole profile using the analytical method was in good agreement with experimental data.

Effects of submerged flexible vegetation and solid structure bars on channel bed scour

The effects of different submerged obstacle longitudinal bars with different arrangement densities on the flow profile and morphology of a scour hole were investigated under clear water conditions. Acoustic Doppler velocimetry (ADV) data were applied to plot the vertical distributions of three-dimensional velocities and turbulent contours. The experimental results indicate that arrangement density (also can represent porosity), structural material (flexible or solid), and the sidewall effect are the main factors impacting turbulent kinetic energy and the morphology of scour holes. For flexible vegetation, the maximum turbulent kinetic energy near the bed surface increased with the arrangement density. For the same structure, the depth and the magnitude of the lateral expansion of the scour hole also increased with the arrangement density. The flexible vegetation reduced the depth of the scour hole because of deflection and arrangement density. The larger volumes of scour found in the upstream and middle sections of solid structures compare well to those in flexible vegetation. The deflection of porous flexible vegetation transported the turbulent kinetic energy downstream, reduced the turbulent kinetic energy near the sediment bed, and increased the stability of the bars. Flexible vegetation bars are able to protect the bank and the bed of a river under normal conditions, making them a good alternative design in the management and restoration of rivers.

Stilling basin erosion due to vertical crossing jets

The scour process due to plunging jets has received considerable attention in the past few decades. This work analyses the effect of vertical jets crossing at various angles. Different scour morphologies created under various hydraulic and geometrical conditions are distinguished. The splash shapes are also analysed and a qualitative description is furnished. The scour phenomenon is analysed, resulting in relationships that can be used to predict the main geometrical scour parameters, including the maximum scour hole depth, the scour hole length, and the scour hole width. The scour hole and dune profiles are compared with those due to a single jet under identical hydraulic conditions, whose vertical inclination with respect to the horizontal plane equals the average vertical angle between the two crossing jets. It was found that for high tailwater condition, the scour hole depth due to crossing jets is less than that for the single jet.

Panel of resonators with variable resonance frequency for noise control

The article focuses on acoustic resonators made of perforated sheets bonded onto honeycomb cavities. This kind of resonators can be used in adverse conditions such as high temperature, dirt and mechanical constraints. For all these reasons, they are, for example, widely used in aeronautic applications. The acoustic properties are directly linked to the size, shape and porosity of holes and to the thickness of air gaps. Unfortunately, the acoustic absorption of these resonators is selective in frequency and conventional acoustic resonators are only well adapted to tonal noises. In case of variable tonal noise, the efficiency is limited if the resonators are not tunable. One common solution is to control the depth of cavities based on the noise to be attenuated. This article proposes another technology of tunable resonators with only a very small mass and size increase. It consists of two superposed and identically perforated plates associated with cavities. One plate is fixed and bonded to the cavities and the other plate is mobile. The present concept enables to change the internal shapes of the holes of the perforated layers. The article describes this system and gives a theoretical model of the normal incidence acoustic impedance that allows to predict the acoustic behavior, in particular the resonance frequency. The model shows that the resonance frequency varies with hole profiles and that the absorption peak moves towards the lower frequencies. The proposed model is validated by measurements on various configurations of resonators tested in an impedance tube. The perspectives of this work are to adapt the hole profiles using an actuator in order to perform active control of impedance.

The Effect of Nitrogen on the Energy Distribution of Hole Traps Generated under Negative Bias Temperature Stress

- We use low temperature measure technique to identify the energy distribution profile of recoverable hole traps, created under Negative Bias Temperature stress in PNO pMOSFETs. It is found that the energy distribution profile is quite similar as that in SiO2 devices after long time NBT stress. The results could be explained that the nitrogen in SiO2 gate oxide doesn't generate new type recoverable hole traps distribution within the Si bandgap under NBT stress.

Dry Etching Solutions to Contact Hole Profile Optimization for Advanced Logic Technologies

As CMOS technology has been continuously scaling down and the dual-stress liner scheme is introduced for simultaneous stress enhancement of both n-MOS and p-MOS, contact etch has started to act as a critical role for the robust performance of integrated circuit. In this work, we investigated the impact of dry etching process on contact hole profile. Results demonstrate the overall contact hole profile can be rigorously controlled if the radio frequency (rf) powers and etching chemistries in inter layer dielectric (ILD) etch step are well balanced. Free local pull-back at contact hole sidewall has to leverage the optimization of etch selectivity of silicon nitride over silicon oxide in liner removal step. Besides, the post etch treatment (PET) is also proven to be imperative for the process window enhancement for such pull-back reduction.

Numerical analysis and design of patterned electrode liquid crystal microlens array with dielectric slab

The phase profile of hole patterned electrode liquid crystal (LC) microlens array (MLA) was studied by a numerical method. It indicated that the formation of inverse domain and tilt wall in the liquid crystal cell limits the optical performance of the microlens array. The physical mechanism that determines the formation of inverse domain and tilt wall was elucidated by analyzing the phase profile and the liquid crystal director distribution. According to our numerical results, a new configuration for hole patterned electrode liquid crystal microlens array was proposed by introducing a dielectric slab between the patterned electrode and the liquid crystal. The physical parameters that influence the optical performance of this new configuration LC MLA were studied, which provide fundamental information for the design. The results indicate that the phase profile and focusing power of the new configuration is greatly improved.

Cold-formed steel flexural member with edge stiffened holes: Behavior, optimization, and design

Circular holes are commonly found on the web of cold-formed steel (CFS) flexural members for piping, electric-wiring, plumbing, or installing lateral bracing, etc. Traditional holes on CFS members are flat bunched without edge lips. A new generation of CFS C-section flexural members with edge stiffened holes was recently developed by the industry. However, research on the new generation C-section members is underdeveloped and available test results are limited. This paper presents finite element analyses to study on the stability of cold-formed steel thin plates and typical C-section members when edge stiffened circular holes are placed on those plates or members. Based on the elastic buckling analyses, the optimized profiles of the holes are obtained and then applied to standard C-section flexural members. The post-buckling finite element analysis is utilized to determine the flexural strength of those members. The results indicate that the stiffened holes can significantly improve the flexural strength of CFS C-sections. New design provisions are proposed to accurately predict the flexural strength of the new generation C-section flexural members with the optimized hole profiles.