Farid M. Tranjan

Integrated force array: interface to external systems

Integrated Force Arrays (IFAs) are thin film linear actuators which operate with substantial displacement and force. The methods of attachment of these devices to external systems are under development. Our current methods to incorporate IFAs in an scanning ultrasound imaging systems as well as a new material and method for attachment will be described.

Plasma resistant modified I-line, deep UV and E-beam resists

This paper presents chemically modified photoresists for use as plasma etch masks over various substrates during patterning in IC manufacturing with sub-0.5 micron resolution. The modification consists of directly adding the modifying compounds into the photoresist solutions. The added compounds increase the Oxygen, Fluorine and Chlorine plasma resistance of photoresists, thus promoting a high etch rate selectivity with respect to other substrates and films (e.g. polyimide, PMGI, oxide, etc.).<<ETX>>

Detecting small defects in conductive thin metallic layers using injected AC current and GMR magnetic sensor

In this paper, injected current technique and giant magneto-resistance (GMR) sensor were used to detect small defects in the order of few hundred micrometers in thin layers. This technique is based on injecting AC currents through the thin film using two connectors and detecting the perturbation of the magnetic field due to a defect using a GMR sensor. A sample of silicon wafer with copper metallization of few micrometers in thickness was used. On the conductive surface a 2.5 mm long scratch was created where the width of the scratch was 0.2 mm. Two measurements were conducted to detect this defect. The first measurement was performed when the sensitive axis of GMR sensor was perpendicular to scratch. The second measurement was performed when the sensitive axis of the sensor was parallel to scratch. By comparing the voltage output amplitude for both measurements, it was found that the scratch was successfully detected. It was verified that the signal-to-noise ratio (SNR) is much more than 3 (minimum for detection) in both measurements. Applications of injecting current technique include detecting defects in thin metallic layers (5-10 micrometers in thickness) and quality control of metallization layers on silicon wafers for IC manufacturing.

Integrated force array: positioning drive applications

Integrated Force Arrays (IFAs) are thin film membrane actuators that act as transfer devices for electrostatic force. They are capable of large amplitude motion and evidence significant energies per unit volume (eg. 8.2 erg/mm3). Devices which use IFAs as drivers to scan PZT acoustic imaging transducers are under development and will be discussed here.

Measured forces and displacements of integrated force arrays

IFAs are MEMS actuators which are powered by the electrostatic forces between the plates of many microscopic deformable capacitors arranged in monolithic arrays. IFAs are fabricated using standard techniques of VLSI electronics. The IFAs reported here resemble thin, flexible plastic membranes 10 mm long and either 1 or 3 mm wide, which contain from 75,000 to 200,000 cells. They are low-weight, high-efficiency actuators with low power consumption, silent operation, and absence of sliding friction. Testing methods applicable to these free- standing MEMS structures are discussed, along with experimental observations and measurements of forces and displacements. We have measured forces in excess of 6 dynes and displacements of over 700 micrometers . The force/cross-sectional area of this MEMS structure is 2800 dynes/mm2, and the work done by the IFA divided by its volume is in excess of 7 ergs/mm3. A rate over 20,000 contractions/second has been observed, as well as lifetimes of greater than 108 contractions. The metalization of the IFA strongly affects the performance. Experimental results are presented demonstrating the improvements in the performance with a Cr/Au metal system compared to the Cr/Pd metal system originally used.

GMR magnetic sensor for scratch detection on PCBs

The inspection of defects on printed circuit boards (PCBs) by GMR sensor and injecting current was proposed in this paper. This technique is based on injecting AC currents through the metallic layer using two probes and detecting the perturbation of the magnetic field. Two experiments were performed on a sample of rectangular piece of PCB to detect 3mm length of scratch which was located on the sample. Two measurements were conducted to detect this defect. The first measurement was performed when the sensitive axis of GMR sensor was perpendicular to scratch. The second measurement was performed when the sensitive axis of the sensor was parallel to scratch. The PCB sample was made of aluminum of dimensions 50 mm ×15 mm. The metal layer in this sample is about 100 Microns in thickness. Two wires were soldered at the two ends of the rectangular sample. An AC current was supplied through these wires to the metal layer of the sample. The optimal frequency for detecting the small scratch was 1 kHz. By comparing the voltage output amplitude for both measurements, it was found that the scratch was successfully detected. It was verified that the signal-to-noise ratio (SNR) is much more than 3 (minimum for detection) in both measurements. Applications of injecting current technique include detecting defects in thin metallic layers for IC manufacturing.

Eddy Current Testing for Detecting Small Defects in Thin Films

Presented here is a technique of using Eddy Current based Giant Magneto‐Resistance sensor (GMR) to detect surface and sub‐layered minute defects in thin films. For surface crack detection, a measurement was performed on a copper metallization of 5–10 microns thick. It was done by scanning the GMR sensor on the surface of the wafer that had two scratches of 0.2 mm, and 2.5 mm in length respectively. In another experiment, metal coatings were deposited over the layers containing five defects with known lengths such that the defects were invisible from the surface. The limit of detection (resolution), in terms of defect size, of the GMR high‐resolution Eddy Current probe was studied using this sample. Applications of Eddy Current testing include detecting defects in thin film metallic layers, and quality control of metallization layers on silicon wafers for integrated circuits manufacturing.

Integrated force arrays: scaling methods for extended range and force

Integrated Force Arrays (IFAs) are thin, flexible, metallized membranes which may be configured as actuators or sensors. The current prototype structures are approximately 1 cm long by 1 mm wide and designed for deformations of 2 mm. In this paper we will discuss how the devices may be scaled-up for extended range and force.

Membrane based actuator-integrated force arrays

Integrated Force Arrays (IFAs) are membrane based actuators that are made of polyimide material. They are metallized membranes that are flexible enough to undergo substantial deformation when a voltage is applied. IFAs can be patterned using the techniques of VLSI electronics. They can be integrated in arrays to form complex systems that have wide range of applications. The theory of operation and the methods of construction are presented.<<ETX>>

ON THE INTEGRATION OF DESIGN AND MANUFACTURING FOR IMPROVED TESTABILITY

We present a new Manufacturing-For-Test technology based on new physical methods of testing digital VLSIIULSI circuits for faults, which has the potential for much greater testing efjciency than possible by conventional electrical addressing through external pins alone. The method uses variants of the pulsed laser probing of microelectronic devices, and various holographic techniques of formation of virtual (transient) interconnects, together with electrical pulse testing, to greatly increase test coverage. Combined with a Design-for-Test scheme, the new technology can significantly improve fault coverage by allowing direct access to internal nodes. The new Manufacturing-For-Test method utilizes standard fabrication technologies and introduces only a small area overhead, and circuit loading; it has the promise of low cost in manufacture and test, and requires no significant increase in the number of physical chip connections.