Nobukazu Ito

New thermally isolated pixel structure for high-resolution (640×480) uncooled infrared focal plane arrays

A new pixel structure with twice-bent beams and eaves structure, suitable for high-resolution uncooled infrared (IR) focal plane arrays (FPAs), is proposed. In comparison with previous results (FPA of 37-µm pixel pitch), the thermal conductance of the test device with the proposed pixel structure of 23.5-µm pitch is reduced about 2.5 times. The eaves structure, which is adopted to increase the fill factor of pixels, improves the responsivity by a factor of 1.3. A 640×480 bolometer-type uncooled IRFPA is demonstrated by utilizing the new pixel structure, with supplementary modification to improve thermal conductance and thermal time constant. It shows a noise equivalent temperature difference (NETD) of 50 mK for F/1.0 optics at 30 frames/sec, a thermal conductance of 0.03 µW/K, and a thermal time constant of 16 msec.

New thermally isolated pixel structure for high-resolution uncooled infrared FPAs

This paper proposes a new thermally isolated pixel structure, having a twice-bent beam structure and eaves structure, suitable for high-resolution uncooled infrared (IR) focal-plane arrays (FPAs). It also describes the properties of test devices, fabricated to verify the effect of the new pixel structure. Although the pixel size of the test devices is 23.5 μm × 23.5 μm, which represents a smaller area by a factor of about 2.5 than the 37 μm × 37 μm pixel size for the 320 × 240 bolometer-type uncooled IRFPA, previously developed by the authors, the test devices have beams with almost the same length as in the previous IRFPA by utilizing the new beam structure. In addition, the cross-sectional area of the beam is reduced. Accordingly, the thermal conductance of the test devices can be reduced by a factor of about 2.5. The eaves structure, which is adopted to increase the fill factor of pixels, improves the responsivity by a factor of 1.3, which is consistent with our calculations. By utilizing the new thermally isolated pixel structure, the test devices with 23.5 μm pixels enable us to achieve thermal sensitivity equivalent to the previous 37 μm pixels.

Development of a two-step electroplating process with a long-term stability for applying to Cu metallization of 0.1-/spl mu/m generation logic ULSIs

Developed a two-step copper (Cu) electroplating (EP) process using a seed-enhancement step with an alkali-metal-free Cu-pyrophosphate solution. The solution for the seed-enhancement step has low solubility of Cu compared with conventional Cu-sulfate solution and high macrothrowing power. As a result, the two-step EP solution provided a superior seed-enhancement effect and filling properties compared to conventional Cu sulfate EP. The seed-enhancement solution has excellent long-term stability of each components concentration, and there is no change of process performance over a two-month period. The authors can easily control sheet resistance (Rs) of electroplated films which correlates with thickness and nonuniformity of seed-enhancement films with no maintenance other than the addition of de-ionized (DI) water to compensate for evaporated water. The two-step EP process achieved an excellent via-chain yield and a tight distribution of electromigration (EM) lifetime compared with the conventional EP process. Thus, the two-step EP process is a promising process for manufacturing technique of 0.1-/spl mu/m generation and beyond logic LSIs.