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Robust and reliable micro-scale integrated electro- chemical sensors need a reference electrode that can provide a stable electrochemical potential. This can be achieved using a silver/silver chloride (Ag/AgCl) electrode, produced by the chemical chlorination of a thin patterned silver layer. Well understood and controlled processes are required to produce the Ag/AgCl electrode. This paper shows how previously reported test structures have been used to characterise and inform the fabrica- tion procedure. Wafer mapping of these structures was carried out using a Python controlled measurement system, consisting of a semi-automatic prober connected to an HP4062UX based analyser. The measurements were analysed to determine whether the chlorination process was affected by the test structure geometry. This was found to have no clear effect on chlorination.

We present a compact, Ultra High Frequency Radio Frequency Identification (UHF RFID) Bio-sensing system, which operates in the 865 - 868 MHz band. The proposed system was designed, using custom and commercial off-the shelf (COTS) components. The main system blocks consist of: (1) A compact, low power UHF RFID reader, with an effective isotropic radiated power (EIRP) level of 10.82 mW (+10.34 dBm), (2) A 16×15×1 mm3 custom designed electrically small antenna (ESA), fabricated on an FR4 substrate, and (3) A battery free UHF RFID sensor tag, with an internal temperature sensor. Wireless connectivity and power transfer, between the UHF RFID reader ESA assembly and the battery free sensor tag, were achieved at a distance of 31 cm. The reader assembly successfully recorded sensor tag localised ambient temperature measurements. Sensor tag temperature measurements were performed using its internal temperature sensors and compared to a reference temperature sensor. Both sensor tag and reference sensor measurements were performed concurrently, in a temperature-controlled environment. The reader-ESA assembly has a mass of approximately 20 g, suitable for portable applications. Low EM emissions, from the proposed system, are at a safer level for operation in proximity to sensitivity electronic medical devices, such as pacemakers. Healthcare practitioners can use this system, to remotely monitor infants localised body temperature in neonatal or transitional care wards, when performing routine patient checks.

This paper describes the use of open-source electronic design automation tools, which have been developed and adapted for maskless lithography, to enable automation of the design, layout and measurement of parametric test structures. Two test structures are presented as case studies for characterisation of microelectronic and micro-electromechanical systems technologies using electrical and profilometry measurements respectively.

Robust and repeatable processes are required to fabricate reference electrodes for micro-scale integrated elec- trochemical sensors. One method for this is to produce a “silver/silver chloride” (Ag/AgCl) electrode through chemical chlorination of a thin film silver layer. This paper presents test structures, which can electrically characterise the process to aid process development and in-line control of the chlorination process.

Electrical impedance tomography (EIT) is an imaging technique that reconstructs the conductivity distribution of an inhomogeneous medium and is capable of monitoring physiological changes in biological materials. This paper focuses on comparison of state-of-the-art regularisation methods in solving the image reconstruction problem in micro-scale EIT for biomedical applications. Since the quality of image reproduction is weak for micro-scale phantoms, it is vital to study the image reconstruction algorithm. Hence, we present three regularisation methods in this paper — Tikhonov, Gaussian-Laplace and L1 — for the image reconstruction of 700 pm diameter test samples. We verified our method using 500 μm × 250 μm rectangular Pt electrodes and compared the performance of these regularisation methods. The results suggest that Gaussian-Laplace regularisation provides better image reconstruction than L1 and Tikhonov algorithms.

Test structures were produced for optimizing the design and fabrication of a patterned solid polymer electrolyte in an electrochemical oxygen sensor. Measurements showed that choice of photoresist developer and the underlying insulator material affected durability of the polymer structures. Test electrodes covered by the polymer were effective at supporting electrochemical oxygen detection.

This paper presents three test structures targeted at characterising sensor packaging materials for liquid environments. The test structures enable the evaluation of: 1) the successful removal of packaging material on sensing areas, 2) the permeability of the packaging material to its environment, 3) electrical continuity through the packaging process, and 4) the ingress of the liquid environment between the packaging material and the chip surface. The paper presents an example of the evaluation of a UV curable resin as packaging process for a biomedical sensor.

Electrical test structures for the characterisation of Optical Proximity Correction (OPC) have been fabricated in thin aluminium using i-line lithography and reactive ion etching. Initial electrical measurements are presented which show an increase in the resistance of a right angled section of Al track as the level of OPC on the inside corner is increased. Structures with OPC applied to the outer corner do not show the same change in resistance. SEM images of similar Al test structures clearly show the effects of applying OPC and suggest that inner corner serif OPC leads to a narrowing of the conducting track.

The effects of the GHOST proximity correction process on chrome-on-quartz photomasks can prove difficult to quantify and so they are not routinely characterised. This paper presents a methodology for addressing this issue using electrical test structures designed to measure dimensional mismatch. In the past these have been used successfully to characterise standard GHOSTed photomasks, which displayed systematic offsets that were not seen on an unGHOSTed mask using the same design. In order to investigate this further, a second mask was fabricated using a variation of the GHOST process which increased the resolution of the secondary exposure to be the same as the primary pattern. This enabled the source of the previously observed systematic offset to be determined as test structures on the new mask did not show the same overall dimensional bias. However, the range of mismatch in some of the structures was increased as a result of the new process.

Electrical test structures have been designed to enable the characterisation of corner serif forms of optical proximity correction. These structures measure the resistance of a conducting track with a right angled corner. Varying amounts of OPC have been applied to the outer and inner corners of the feature and the effect on the resistance of the track investigated. A prototype test mask has been fabricated which contains test structures suitable for on-mask electrical measurement. The same mask was used to print the structures using an i-line lithography tool for on-wafer characterisation. Results from the structures at wafer level have shown that OPC has an impact on the final printed features. In particular the level of corner rounding is dependent upon the dimensions of the OPC features employed and the measured resistance can be used to help quantify the level of aggressiveness of the inner corner serifs.

This paper presents results from the use of electrical measurements to investigate dimensional mismatch in an advanced photomask process. Test structures consisting of matched pairs of Kelvin resistors have been measured and the results analysed to obtain information about the capability of the mask making process. The mask plate used in this work has an array of over 350 sets of mismatch test structures, providing an unprecedented volume of data. A second mask, which was underexposed, has allowed the relationship between mismatch and the location of nearby mask writing pattern boundaries to be investigated for the first time.

This paper reports the measurement results from a set of electrical, on-mask test structures based on industry standard test feature layouts normally used to investigate process proximity effects and improve optical proximity correction (OPC) models. The electrical test structures were fabricated on a binary photomask using the GHOST proximity correction technique to compensate for typical e-beam induced proximity errors. This is one of the first times that electrical test structures have been used to evaluate GHOST exposure. The test structures were measured electrically and optically with a dedicated photomask metrology tool and the results from the two techniques are presented.

This paper compares electrical, optical and AFM measurements of critical dimension (CD) made on a chrome on quartz photomask. Test structures suitable for direct, on-mask electrical probing have been measured using the three techniques and the results show very good agreement between the electrical measurements and those made with a calibrated CD-AFM system.

This paper describes the design and measurement of electrically measured test structures for the characterisation of dimensional mismatch in an advanced photomask making process. Test structures consisting of pairs of Kelvin connected bridge resistors have been fabricated on a chrome-on-quartz photomask plate. These have been electrically measured on-mask and the results used to obtain information about dimensional mismatch in the mask making process.

The standard approach to generate the data required for automated proximity correction is to measure a set of patterned features using an optical tool or a critical dimension scanning electron microscope (CD-SEM). This paper describes the design of a set of on-mask electrical test structures to perform the same task which has a number of attractions. The electrical test structures are based on the Kelvin bridge resistor to measure the widths of isolated and densely packed lines and spaces. The results from these measurements can be used to extract information about proximity effects in the mask making process and to generate rules or models for the correction of mask designs. Electrical results from a test mask, fabricated without any correction for e-beam proximity effects, are presented and compared with optical measurements of the same structures made with an industry standard mask metrology tool.

This paper presents a comparison of optical and electrical techniques for critical dimension (CD) metrology on binary and alternating aperture phase shifting masks. For the first time, measurements obtained from on-mask electrical CD structures are compared with optical measurements made using a deep ultra-violet (DUV) mask metrology system. Initial results show that the presence of alternating phase shifting trenches between the chrome blocking features has a detrimental effect on the optical measurements. In addition the optical metrology system appears to have problems with the measurement of the narrowest isolated features due to calibration related issues. Electrical CD measurements are seen as a way of probing the limits of optical tool calibration, and for highlighting and managing the need to extend the complexity of the calibration schedule.