1. Field of the Invention
The present invention relates to fuse structures in integrated circuits, and specifically, to a novel thermal fuse device and circuit architecture for providing thermal protection of semi-conductor chips and circuit structures.
2. Discussion of the Prior Art
Thermal runaway may occur in integrated circuit chips/devices due to the following reasons: 1) during a chip/device "burn-in " performed at high temperature (e.g., 140.degree. C.-150.degree. C.); 2) voltages above 1.5.times. operating voltages; or 3) if the chips go into latchup. Also, chips can experience current runaway, with accompanying heating and destruction when operating in systems.
While current fuse devices are manufactured as elements in semiconductor devices, i.e., IC chips, they are predominantly large and cumbersome requiring application of a laser stimuli for their fuse blowing. Typically, these fuses are applied in circuit trimming applications and/or removing unwanted or defective circuits prior to chip packaging. Currently, there is no thermal fuse protection device that is designed to protect integrated circuit devices from thermal run-away, latch-up, and over-current conditions during normal operation, and, that is capable of being blown at a pre-determined operating condition, e.g., a specified current and/or voltage level, for instance.
U.S. Pat. No. 4,272,753 discusses a method for fabricating a discrete metallic fuse device using fusible material which is necked to a narrow region. The fusible material is separated from an insulative layer by an air gap which provides lower thermal conductivity environment.
U.S. Pat. No. 4,089,734 discusses a metallic fuse device for read only memory and memory reconfiguration applications which involves a complicated technique including a four layer deposition of metallizations, requires the etching at two sides of a fusible link layer to form the resultant fusible link, and etching of the silicon substrate material to form a mesa structure.
U.S. Pat. No. 4,879,587 discusses manufacture of a metallic fuse device that is provided on top of a supporting insulating bridge structure for connecting two conductive regions.
The manufacture of each of the fuse devices described in the above-mentioned prior art is generally complicated requiring many processing steps. Additionally, they are treated as discrete elements, and are not integral with the conducting line itself. Further, these prior art fuse devices are not configured to destruct according to a designed voltage and current operating condition, and, do not readily detect thermal runaway phenomena that may occur in integrated circuits.
Accordingly, it would be highly desirable to provide a novel electrical fuse structure for integrated circuits that comprises actual conductive chip wiring and that may be easily blown at a specified voltage and current level, and, that may be used to provide thermal runaway and over-current protection for integrated circuit devices and structures.
It would additionally be highly desirable to provide a novel electrical fuse structure for integrated circuits that are defined by the designer and tailored to the capacity of currents they must carry.