Negative photoresists are materials that become insoluble in developing solutions when exposed to optical radiation. They were the first systems used to pattern semiconductor devices, and still comprise the largest segment of the photoresist industry because they are widely used to define the circuitry in printed wiring boards. However, the current use of negative resists in the semiconductor industry has been limited by past difficulties in achieving high-resolution patterns. Recent advances in the chemistry of negative-resist systems, however, have provided materials with wide processing latitude and high resolution that are used to manufacture IBM's advanced CMOS devices and to achieve high-aspect-ratio patterns for micromachining applications. This paper provides an overview of the history and chemistry of negative-resist systems and their development in IBM.

Negative photoresists for optical lithography

The extended gate chemically sensitive field effect transistor as multi-species microprobe☆

Planar Amperometric Enzyme-Based Glucose Microelectrode

Fabrication and characterization of a planar electrochemical cell and its application as a glucose sensor

A multi-element superconducting nanowire single photon detector (MESNSPD) is presented that consists of multiple independently-biased superconducting nanowire single photon detector (SNSPD) elements that form a continuous active area. A two-element SNSPD has been fabricated and tested, showing no measurable crosstalk between the elements, sub-50-ps relative timing jitter, and four times the maximum counting rate of a single SNSPD with the same active area. The MESNSPD can have a larger active area and higher speed than a single-element SNSPD and the input optics can be designed so that the detector provides spatial, spectral or photon number resolution.

Multi-Element Superconducting Nanowire Single-Photon Detector

A process is described that allows the use of the lift-off metallization technique with ultraviolet exposure of a single layer of ®AZ-type photoresist. The process consists of soaking the resist layer for a predetermined time either in chlorobenzene or other aromatic solvents such as toluene and benzene before or after exposure. After development, resist profiles with overhangs suitable for lift-off metallization are obtained. It appears that removal of solvent and low-molecular-weight resin from the ®AZ resist may be responsible for the observed differential development rates. In addition, the soak time and temperature behavior indicate a diffusion-type process.

B. J. Canavello

Papers

Single-step optical lift-off process