SUBSTRATE INTER-TERMINAL VOLTAGE SENSING CIRCUIT
A substrate inter-terminal voltage sensing circuit which can promptly sense a plasma charge-up occurring on a semiconductor wafer across a wide range without connection of a voltage measuring instrument. The substrate inter-terminal voltage sensing circuit is adapted to sense a voltage occurring between a pair of electrodes arranged on a semiconductor substrate. The voltage sensing circuit includes a resistance path that is connected between the electrodes. The voltage sensing circuit also includes a circuit power supply that is connected at one end to a midpoint of the resistance path. The voltage sensing circuit also includes at least two fuse circuits that are connected between one end of the resistance path and the other end of the circuit power supply so as to be in parallel with each other. The fuse circuits have different rated fusing currents from each other. Each of the fuse circuits includes a switch that turns ON or OFF depending on a potential difference between the one end and midpoint of the resistance path. Each fuse circuit also has a current path that is connected across the circuit power supply. The current path possesses a resistive element and a fuse element serially connected to the switch.
1 . A voltage sensing circuit for sensing a voltage occurring between a pair of electrodes arranged on a semiconductor substrate, the voltage sensing circuit comprising:
a resistance path that is connected between the electrodes;
a circuit power supply that is connected at one end to a midpoint of the resistance path; and
at least two fuse circuits that are connected between one end of the resistance path and the other end of the circuit power supply so as to be in parallel with each other, said at least two fuse circuits having different rated fusing currents from each other, wherein each said fuse circuit includes a switch that turns on or off depending on a potential difference between said one end of the resistance path and the midpoint of the resistance path, and a current path that is connected across the circuit power supply, and said current path has a resistive element and a fuse element serially connected to the switch.
2 . The voltage sensing circuit according to claim 1 , wherein the resistive elements have different resistances from each other.
3 . The voltage sensing circuit according to claim 1 , wherein the fuse elements have different rated currents from each other.
4 . The voltage sensing circuit according to claim 2 , wherein the fuse elements have different rated currents from each other.
5 . The voltage sensing circuit according to claim 1 , wherein the switches are MOS transistors.
6 . The voltage sensing circuit according to claim 5 , wherein the MOS transistors have different characteristics from each other.
7 . The voltage sensing circuit according to claim 1 further comprising at least two fuse blowout state display units, each said display unit being associated with each said fuse circuit for emitting light in a first color when the fuse element concerned is in a blowout state and for emitting light in a second color when the fuse element concerned is in no blowout state.
8 . The voltage sensing circuit according to claim 7 , wherein each said display unit is connected across the fuse element concerned.
9 . The voltage sensing circuit according to claim 7 , wherein each said display unit includes two light emitting devices that in combination serve as a single combined light emitting element.
10 . The voltage sensing circuit according to claim 9 , wherein one of the two light emitting devices is adapted to emit a red light, the other light emitting device is adapted to emit a green light, the combined light emitting element is adapted to emit a yellow light, the first color is green and the second color is yellow.
11 . A fuse blowout state display circuitry comprising a plurality of display units, each said display unit including at least one light-emitting device that is connected across each of the fuse elements of the substrate inter-terminal voltage sensing circuit of claim 1 , wherein each said light-emitting device emits light in different colors depending on whether the fuse element concerned is in a blown or not blown state.