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A study was undertaken to correlate macroscopic profile variations in the photoresist during lift‐off procedures with changes in material properties. It was established that soaking in chlorobenzene, which gave rise to negative slopes, was accompanied by hardening of the top layer of the photoresist and caused the surface to become hydrophobic. FTIR measurements did not yield new information about variations in chemical bonding.

Line widths are rapidly shrinking and the complexities of boards place increased demands on the resolution capabilities of the photoresists. A new technology is emerging that offers the user unparalleled resolution, a completely aqueous system, and complete, uniform, three‐dimensional coverage of the panel. The unique properties of this system result from the extraordinary method of application of the photoresist. Electrophoresis, or electrocoating, allows the deposition of a very thin, uniform, highly chemically resistant photoresist layer. Any exposed conductive surface, including scratches or other panel imperfections, are coated. The combination of a very thin layer and no cover sheet allows the printing of sub‐mil geometries without the need for a collimated light source. This new application offers the user high yields, both from the chemistry and in circuit yields. Even more so, the resolution capabilities offer opportunities beyond the limitations of dry film and other liquid resists. The photoresist no longer needs to be the gating factor in process capability.

The importance of miniaturisation of hybrid microwave integrated circuits (HMICs) and the increasingly stringent demands on the line‐width control of conductor lines in satellite communications and digital radio systems are well established. The importance of photolithographic processes for achieving accuracy and control of the line width necessary to guarantee performance and repeatability of HMICs is acknowledged. The purpose of this paper is to discuss problems concerning the photoresist deposition process and how spin coating is necessary for obtaining the quality, precision and repeatability required for fine line HMICs for high frequency applications.

The development of chemical sensors based on nanostructures, such as nanotubes or nanowires, depends on the capability to reproducibly control the processing of the sensor. Alignment and consistent electrical contact of nanostructures on a microsensor platform is challenging. This can be accomplished using labor‐intensive approaches, specialized processing technology, or growth of nanostructures in situ. However, the use of standard microfabrication techniques for fabricating nanostructured microsensors is problematic. The purpose of this paper is to address this challenge using standard photoresist processing combined with dielectrophoresis.

Nanostructures are suspended in photoresist and aligned between opposing sawtooth electrode patterns using an alternating current (AC) electric field (dielectrophoresis). The use of photoresist processing techniques allow the burying of the nanostructures between layers of metal, thus improving the electrical contact of the nanostructures to the microsensor platform.

This approach is demonstrated for both multi‐walled carbon nanotubes and tin oxide nanowires. Preliminary data show the electrical continuity of the sensor structure as well as the response to various gases.

It is concluded that this approach demonstrates a foundation for a new tool for the fabrication of microsensors using nanostructures, and can be expanded towards enabling the combination of common microfabrication techniques with nanostructured sensor development.

This approach is intended to address the significant barriers of deposition control, contact robustness, and simplified processing to realizing the potential of nanotechnology as applied to sensors.

Photoresist imaging traditionally uses silver halide or diazo based phototools for contact exposure to an actinic UV light source. By contrast, laser direct imaging uses digital imaging data to control a laser beam scanner to write directly on to the photoresist, therefore eliminating the need for phototools. In the past, even though the benefit of a UV system was recognised, laser direct imaging was mainly limited to the use of a visible laser as early UV lasers were low in power, unreliable and expensive. So far, no visible systems have gained commercial recognition because of the inherent deficiencies of the visible system. Recent advantages in UV laser equipment and UV sensitive photoresist have now made UV laser direct imaging a viable alternative to traditional contact imaging. As new UV laser imaging systems start to emerge, interest and attention are also growing among printed circuit board manufacturers. This paper discusses various attributes of a UV laser direct imaging system and fundamental differences in photophysics between laser direct imaging and conventional UV imaging.

The processing techniques and materials utilized in the fabrication of a two-terminal electrostatically actuated micro-electro-mechanical cantilever-arrayed device used for radio frequency tuning applications are presented in this work. The paper aims to discuss these issues.

The process, which is based on silicon surface micromachining, uses spin-coated photoresist as the sacrificial layer underneath the electroplated gold structural material and an insulating layer of silicon dioxide, deposited using plasma enhanced chemical vapour deposition (PECVD), to avoid a short circuit between the cantilever and the bottom electrode in a total of six major fabrication steps. These included the PECVD of the silicon dioxide insulating layer, optical lithography to transfer photomask layer patterns, vacuum evaporation to deposit thin films of titanium (Ti) and gold (Au), electroplating of Au, the dry release of the cantilever beam arrays, and finally the wafer dicing to split the different micro devices. These process steps were each sub-detailed to give a total of 14 micro-fabrication processes.

Scanning electron microscope images taken on the final fabricated device that was dry released using oxygen plasma ashing to avoid stiction showed 12 freely suspended micro-cantilevered beams suspended with an average electrostatic gap of 2.29±0.17 μm above a 4,934±3 Å thick silicon dioxide layer. Preliminary dimensional measurements on the fabricated devices revealed that the cantilevers were at least 52.06±1.93 μm wide with lengths varying from 377.97±0.01 to 1,491.89±0.01 μm and were at least 2.21±0.05 μm thick.

The cantilever beams used in this work were manufactured using electroplated gold, and photoresist was used as a sacrificial layer underneath the beams. Plasma ashing was used to release the beams. The beams were anchored to a central electrode and each beam was designed with varying length.

Reviews the use and development of dry film photoresists and liquid resists. Provides an historical perspective and considers factors affecting investment in the future. Discusses both the advantages and limitations of dry film and liquid photoresists. Provides an outlook for future developments.

3D bulk image effects in high‐NA lens lithography are studied through 3D exposure and development simulations by applying a Mack model to the 3D exposure process.

Major trends in the PWB industry and the requirements from the manufacturers to reduce reject rates at the imaging and chemical process stages have demanded a new generation of dry film photoresists. Details are given of the requirements laid down by the industry, how the dry film resist manufacturers have responded, and how the improved resist technology meets these demands. These latest products are extensively available in Europe and resist improvements have been welcomed by the board manufacturers.

Photolithographic techniques are universally employed in multi‐layer printed circuit board manufacturing. The growing demand for miniaturization of electronics means that finer lines and smaller vias are increasingly required and these very fine lines on the substrate are increasingly difficult to produce by conventional means. One very promising means of meeting these fine line requirements is via the etching of sputtered thin films on a substrate and then growing copper on these lines using an additive method. In this work we tested the capability of an electrodeposited, positive‐acting photoresist for patterning thin film circuits on sputtered seed layers such as chromium. A fully additive electroless copper was then used to produce the copper lines. Epoxy reinforced fibreglass was used as a core material. The performance and quality properties of the process were examined, along with limitations of the process when compared with both a conventional dry film method and a spin coating method.