Improve Thickness Uniformity Research Articles

Design for the plating process utilizing 3D modeling

An effective method to improve thickness uniformity in nickel electroforming for the LIGA process to produce metallic microstructures is described. The deposited metal distribution is naturally a concave shape over the whole area of the plating base proved by experiments. The edge thickness of the plating area is usually twice or higher than the center of the plating area. A secondary cathode (guard ring) was applied to improve the electroform uniformity. The experimental result of a Joule–Thomson micro-cooler proved its feasibility. The thickness ratio of edge to center of a 500 μm sample decreased from 2.5 to 1.4. The thickness uniformity improvement is achieved without a loss in plating rate in the center of the features.

Improvement of thickness uniformity in nickel electroforming for the LIGA process

An effective method to improve thickness uniformity in nickel electroforming for the LIGA process to produce metallic microstructures is described. The deposited metal distribution is naturally a concave shape over the whole area of the plating base proved by experiments. The edge thickness of the plating area is usually twice or higher than the center of the plating area. A secondary cathode (guard ring) was applied to improve the electroform uniformity. The experimental result of a Joule–Thomson micro-cooler proved its feasibility. The thickness ratio of edge to center of a 500 μm sample decreased from 2.5 to 1.4. The thickness uniformity improvement is achieved without a loss in plating rate in the center of the features.

A novel pulsed magnetron sputter technique utilizing very high target power densities

Abstract Using a novel pulsed power supply in combination with a standard circular flat magnetron source, operated with a Cu target, a peak power density of 2800 W cm -2 was achieved. This results in a very intense plasma with peak ion current densities of up to 3.4 A cm −2 at the substrate situated 10 cm from the target. The ionized fraction of the deposited Cu flux was estimated to be approximately 70% from deposition rate measurements. The potential for high-aspect-ratio trench filling applications by high power pulsed magnetron sputtering is demonstrated by deposition in via-structures. The high power pulsed technique also results in a higher degree of target utilization and an improved thickness uniformity of the deposited films compared with conventional d.c. magnetron sputtering.

Improving thickness uniformity of freestanding diamond sheets synthesized by the combustion flame method

By use of the chamber combustion flame method which utilizes an oxyacetylene flame torch contained within the chamber, we have discovered the possibility of fabricating relatively thick diamond films or high-quality diamond disc sheets that may be utilized for various optical or electronic applications. The sheets have the disadvantage, however, of poor uniformity of thickness that has yet to be solved. In this paper, we propose an improvement of the chamber combustion flame apparatus comprising a swinging torch structure that can contribute to a significant improvement in the thickness distribution without sacrificing the fundamental advantages of the chamber combustion flame method, i.e. high quality in terms of Raman characteristics, optical transparency and the cathodoluminescence characteristic, as compared with the conventional open air combustion flame method.

Improved uniformity of multielement thin films prepared by off-axis pulsed laser deposition using a new heater design

A new compact substrate heater for the pulsed laser deposition (PLD) technique has been developed. The heater is built up of a radiation part, consisting of two quartz halogen lamps, and a rotating absorber, made of a SiC disk, to which the substrate is attached. The advantage of this system in comparison to conventional heaters is its suitability for substrate temperatures up to 800 °C in any ambient (vacuum as well as corrosive gases). The heater is applied for the deposition of thin, multielement films with improved thickness uniformity using off-axis PLD. This technique makes use of a rotating substrate which is off-centered from the depositing plasma plume. The thickness profile is modeled using predetermined stationary thickness distributions. For a variety of multielement materials good experimental uniformities in terms of thickness (in close agreement with the calculations) and of chemical composition are obtained. A relation is found between the value of experimental parameters and the achievable uniformity area within a large pressure range.

Growth, structuring and characterisation of all-oxide thin film devices prepared by pulsed laser depostion

The combination of a variety of oxidic thin films in two materials systems is described. The first one focuses on the growth of BaZrO3 on SrTiO3 (both perovskites) and the use of these stacks as a substrate for the growth of magnetic ferrite spinel films. The second system shows the combination of oxidic conductors, ferroelectrics and semiconductors in all-oxide field effect devices. The control of stoichiometry for the ferroelectric used in this device (consisting of highly volatile components) as well as the improvement of thickness uniformity using off-axis PLD are discussed.

Advanced Quality in Epitaxial Layer Transfer by Bond and Etch-back of Porous Si

We report recent qualitative advances in bonding and etch-back of silicon on insulator (SOI) using structure-sensitive selective etching of porous Si. The defect density in the epitaxial layer grown on the porous Si is lowered to 3.5×102/cm2 by raising the H2 prebake temperature in conjunction with the “preinjection technique” in which a small amount of Si is supplied during the high-temperature H2 prebake prior to epitaxial growth. H2 annealing also gives a smooth SOI surface comparable to the bulk polished wafer. Improved thickness uniformity of ±1.8% is achieved using the single wafer processing epi-reactor. The electrical characteristics are evaluated by fabricating pn-junction diode.

Electroplating of Nickel Using a Modified Barrel Design

SummaryNickel is a metal electroplated on a wide variety of articles both ferrous and nonferrous. Small articles which are difficult to jig are frequently plated by barrel plating technique.In conventional barrel plating the parts to be plated are contacted by either a rod, dangler or metallic wall as they rotate inside the barrel. A modified barrel design has been effected by changing the dangler contact with uniformly distributed contact tips at varying points on the periphery of the barrel. A modification in anode positioning is also made. Improvement in thickness uniformity brought about by use of this modified design are reported in this paper.

Flux masking and thickness uniformity in molecular beam epitaxy

We suggest that properly designed masks altering the rotation-integrated flux arriving at the substrate may be used to improve thickness uniformity in a variety of crystal growth techniques. As an illustration, we calculate the dimensions of the mask required to produce a perfectly uniform flux for a single group-III species in single- and multiple-wafer III–V molecular beam epitaxy. Estimates of the detrimental role of errors in mask machining and position are provided and schemes for correcting flux nonuniformities for multiple sources are suggested. Our results imply that flux masking can lead to significant uniformity improvements for growth on single or multiple wafers.

Improved thickness uniformity in molecular beam epitaxial growth of GaAs using a tilted conical insert crucible

Significant improvements in the uniformity of epitaxial layers of GaAs, deposited using a V80-H molecular beam epitaxy system, can be obtained by modifying the crucible so that the flux is directed towards the center of rotation of the substrate. This has been obtained with a dual crucible system, consisting of a tilted conical insert inside a large capacity straight sided crucible. With this combination the layer uniformity can be improved to better than ±1.5% over the useable area of a 76 mm diam substrate and to ±0.7% for 50 mm diam substrates. These results are in excellent agreement with the predictions of recent flux modeling calculations.

Silicon Gate Oxide Thickness Uniformity during HCl Oxidation

Systematic oxide thickness variations across individual wafer surfaces, as well as from wafer to wafer within quartz boats were observed during oxidation. These variations, namely, a radial oxide thinning toward the wafer center and a wafer spacing dependence of average oxide thickness, were associated with the use of during “dry” gate oxidation. The “bull's eye” thickness profile amounted to a 5% variation in a 25.0 nm gate oxide for densely packed (5 mm spacing) wafers. The radial variation disappeared when wafers were spaced far apart (50 mm). The oxide thickness variation was quantitatively correlated to the amount of chlorine incorporated in the oxide where the chlorine content was found to be linearly proportional to the oxide thickness. This oxidation nonuniformity could be modeled by the radial depletion of an active intermediate, chlorine‐containing species during oxidation. While oxides grown in or , did not exhibit a radial thickness variation, those grown in did exhibit thickness variations similar to oxidations. The absolute enhancement of the oxidation rate due to the additions of , , , or in an otherwise dry oxidation was also studied, with alone and alone producing a large enhancement in growth rate (35% thicker oxide for 2.25% or 4.5% additions). The enhancement due to addition was more modest (15% for 2.5% addition). Transients during the switchover in gases, e.g., from during loading to for oxidation, apparently did not play a major role in causing the observed nonuniformities. The use of thick‐oxide “dummy” wafers, grown in a hydrogen‐ or chlorine‐containing atmosphere, between bare silicon wafers had a profound effect on improving thickness uniformity. The oxide thickness variation was reduced when wafers with 0.4 μm dry oxides were interspersed between growing gate oxides; however, this improved oxide uniformity was attributed to a larger spacing between oxidizing wafers. Surprisingly however, variations completely disappeared when the dummy wafers were grown in steam, dry , or dry , suggesting that these dummy wafers play an active role in enhancing the supply of reactive intermediates to adjacent wafers.

Blown Film Bubble Collapsing Improvement

The forces exerted on the blown film bubble during the collapsing process are not uniformly distributed around the bubble. Standard collapsing geometry and the fric tional drag coefficient can be modified to improve this force distribution and reduce the force level. The net result to the film product is better flatness, even distribution of film mechanical properties, and improved thickness uniformity. Furthermore, it provides a film which greatly reduces the wrinkles and distortions which frequently occur when printing and laminating film.

Abstract: Resist coating technique for light or electron beam exposure to achieve improved thickness uniformity

Abstract: Resist coating technique for light or electron beam exposure to achieve improved thickness uniformity