Wire bonding annealing

NTD wafers were produced by irradiating natural ultra pure Ge crystals by means of a flux of thermal neutrons (see Section 15.2.2). To realize the electrical contacts, both sides of the wafers (disks, 3 cm in diameter, 3 mm thick) were doped by implantation with B ions to a depth of 200nm. The implanted layers are doped to such a high concentration that the semiconductor becomes metallic. Then a layer of Pd (about 20 nm) and Au (about 400 nm) was sputtered onto the both sides of the wafers. Finally, the wafers were annealed at 200°C for 1 h. The wafers are cut to produce thermistors of length 3 mm between the metallized ends (3x3x1 mm3 typical size) the electrical contacts are made by ball bonding with Au wires. 

A substrate 10 of HgCdTe is provided with an upper surface region 11 formed by an annealing procedure, or as an epitaxial layer or evaporated film. A layer of insulating material 12 is formed in which windows are provided. The windows are partially filled with a thin layer of metal 13 which is deposited therein to form a metal-semiconductor diode with the upper surface region. The metal layer is deposited to a thickness on the order of 10-50 nm thick and is sufficiently thin to be semi-transparent to infrared radiation. A thick layer of metal 14 is deposited to form an expanded contact and an anti-reflection coating 15 is provided. External conductors in the form of jumper wires 16 are ball bonded to the contact 14. 

Cladding of steel sheets with aluminum has been a commercial process for more than three decades and is of particular use in several corrosive environments. Work by Cooke and Levy [124] has demonstrated the importance of surface pretreatment, pressure, and heat treatment. For example, the required bonding temperature was found to be an inverse function of pressure (e.g., the same bonding strength could be attained at either 13.8 MPa/400°C or 20.7 MPa/345°C) subsequent annealing could double the bond strength. The sheets are preroughened by rotary wire brushes, rolled at... 

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