EP0112492B1

EP0112492B1 - Alarm and control system for semiconductor manufacturing plants

Info

Publication number: EP0112492B1
Application number: EP19830111572
Authority: EP
Inventors: Shoichi C/O Nohmi Bosai Kogyo Co. Ltd. Kimura
Original assignee: Nohmi Bosai Kogyo Co Ltd
Current assignee: Nohmi Bosai Ltd
Priority date: 1982-11-27
Filing date: 1983-11-19
Publication date: 1990-01-10
Anticipated expiration: 2003-11-19
Also published as: JPS5998293A; ES8505125A1; EP0112492A2; DE3381099D1; EP0112492A3; ES527814A0

Description

An alarm and control system for semiconductor factories for protecting them against fire or gas leaks comprising a gas detector at locations where poisonous and inflammable treatment gases are used, an exhaust system and electrical devices, controlled by this detector, to raise the alarm, and a protection device.
From GB-A-1,364,408 is known an installation for protecting an enclosed space against gas leaks, comprising a gas detector inside the enclosed space, and electrical devices, controlled by this detector, to raise the alarm, shut off the gas supply and switch on a ventilation system, and a self-contained emergency power supply.
From US-A-4,267,889 is known a system for sensing and acting to suppress flame conditions as well as an explosion associated with a flame front in an enclosure which is susceptible to fire and explosion condition, such as trash shredders, grain elevators and enclosed areas where oxygen and combustible material may be present in the necessary proportions to feed a fire. In accordance with the special purpose of this system flame detectors of the available infrared sensor type and pressure rise detector devices are used to release a fire suppressing agent into the area to be protected.
The known systems used for protecting enclosed spaces against gas leaks and to protect dust laden atmospheres, as for instance grain elevators or grinding or shredder chambers of mills, are not suitable to be used in an alarm and control system for semiconductor factories.
In semiconductor factories for very large-scale integration (LSI) manufacturing processes which have recently been making rapid progress, at the time of applying an isolation film to a silicon wafer a silane gas is utilized, but such treatment gas is not only poisonous, but also dangerous since when the concentration of the gas becomes 2 to 5% or more it reacts to oxygen in the air to be ignited and burn. In fact, a fire has occurred in a certain LSI factory possibly caused by leakage of this gas and brought about enormous losses.
In view of such situation the present invention aims at providing an alarm and control system for semiconductor factories which can detect leaked treatment gas whether in the state of the gas itself or in the state of products of combustion as a result of combustion due to its reaction to oxygen in the air so that an appropriate control can be carried out either before the occurrence of or at the initial stages of fire.
The system of US-A-4,267,889 is not suitable for an alarm and control system for semiconductor factories since it uses infrared flame detectors and pressure rise detector devices which cannot detect the initial stages of fires of silane.
In accordance with the present invention an alarm and control system for protecting semiconductor factories against fire or gas leaks is provided which is characterized in that gas detectors to detect the leakage of treatment gases including silane gas and optical smoke detectors to detect products of combustion of said treatment gases are provided at locations where said treatment gases, including silane gas, are used and that an electrical device to raise the alarm comprises circuitry means which, upon a change in the output stage of either of said gas detectors or said optical smoke detectors, causes an alarm signal to issue, and means responsive to said alarm signal connected to control the protection device as well as said manufacturing process of semiconductors are provided.
The present invention will be explained below with reference to the attached drawings concerning its one embodiment as utilized in a chemical vapor deposition (CVD) apparatus as well as associated apparatuses used at the time of applying an insulation film to a semiconductor wafer.

Figure 1 is a schematical view of the embodiment of the present invention,
Figure 2 is a circuit diagram of the embodiment according to Figure 1, and
Figure 3 shows the characteristic curves of a photoelectric type smoke detector and an ionization type smoke detector.

In Figure 1, the reference numeral 1 is a silane gas cylinder, 2 is an ammonia gas cylinder, 3 is a housing to house these cylinders, 6 is a nitride film forming device (CVD) to form an insulating film on a semiconductor wafer by supplying silane and ammonia gases through pipes 4 and 5 respectively, 8 is a scavenging device which forcedly oxidizes, namely to treat by combustion the unreacted silane gas discharged from the device 6 through a pipe 7 with oxygen being supplied, 10 is a detection box provided between pipes 9 to monitor the state of the gas to be discharged to an exhaust duct 11 from the scavenging device 8, 12 is a vacuum pump to make the CVD 6 vacuous, and 13 is an exhaust vent for the room air. The housing 3 and the detection box 10 are provided with gas detectors G_i, G₂, respectively, to detect the leakage of the treatment gases such as silane gas, etc. and fire detector 0, and D₂, respectively, to detect the products of combustion from the burning of the gases. As the gas detectors G" G₂, although a photoelectric type gas detector in which the light scattered by the gas particles is detected can be used, a gas detector as disclosed in Japanese Laid Open Patent Publication No. 14380/1.980 is preferably utilized in the embodiment shown here which operates on the basis of such phenomena that when a metal oxide semiconductor which contains platinum black in the composition of stannic oxide known by the above patent as a detecting element for carbon monoxide, is aged in an atmosphere of silane gas it responds to low concentrations of silane gas of 0.2 to 0.5% and above. As the fire detector to detect the products of combustion even though a photoelectric or ionization type smoke detector can be utilized, judging from the characterizing curves shown in Figure 3 wherein the outputs of these detectors and the concentration of the combustion products of the silane gas are illustrated as the ordinate and the abscissa, respectively, the ionization smoke detector (b) has a more effective than the photoelectric type smoke detector (a) in detecting the products of combustion of the silane gas, the former detecting the generation of the products of combustion earlier than the latter. As shown in Figure 2, among the gas and fire detectors G_i, G₂ and D_i, D₂, the gas detector G₁ and the fire detector 0, provided in the housing 3 are connected to a first OR-circuit OR,, and the gas detector G₂ and the fire detector O2 provided in the detection box 10 are connected directly and through an inverter I respectively to a second OR circuit OR₂, the outputs of the OR,, and OR₂ being connected to a third OR-circuit, OR₃, and the output of OR₃ is connected to a relay means which appropriately controls the manufacturing process of the semiconductor or a device for prevention of disasters such as a fire alarm or a fire extinguishing device.
Operation of the apparatus described above is as follows.
The nitride film forming device 6 has semiconductor wafers contained therein, and after it is made vacuous by the vacuum pump 12, the silane and ammonium gas cylinders 1 and 2 are opened to supply the silane and ammonia gases to the device 6, whereby nitride films necessary for the semiconductor wafers, i.e. insulating films are made to be generated thereon. The gases which contain the unreacted gases after the treatment are forcibly oxidized in the scavenging device 8 and discharged from the exhaust duct 11 through the pipe 9 as a safe gas.
In this state, should silane gas leak from the silane gas cylinder 1 in an amount that is of a degree insufficient to react to oxygen in the air and to burn, the gas detector G, is operated to detect the gas itself. If a large amount of silane gas leaked from the silane gas cylinder 1, and the gas promptly reacts to the oxygen and burns, the fire detector D₁ is operated by the products of combustion through the OR-circuits, i.e. OR, and OR₃ so that a control means not shown is operated which controls a device for prevention of disasters such as a fire alarm, a fire extinguishing device or the manufacturing process. As to the detection box 10, during normal operation of the scavenging device 8, the burnt out products of combustion are discharged to the exhaust duct 11 through the pipe 9. Therefore, neither the gas detector G₂ nor the fire detector D₂ operate the OR-circuit OR₂, because of operation of the inverter. Should the silane gas be discharged without being treated due to trouble in the scavenging device 8, either the gas detector G₂ directly or the fire detector D₂ through the operation of the inverter I operate the OR-circuit, OR₂, so that a relay means not shown is operated which controls the manufacturing process or a device for prevention of disasters such as a fire alarm, a fire extinguishing device, or the like.
Although in the above embodiment the gas detector and the smoke detector are separately provided the two detectors may be integrally constituted and the circuit shown in Figure 2 may be incorporated with them.
As stated above, the present invention reveals such an effect as providing an alarm and control system for semiconductor factories or the like in which since at locations where poisonous and inflammable treatment gases are used such as in a semiconductor manufacturing process etc. gas detectors to detect leakage of the treatment gases themselves and fire detectors to detect the products of combustion resulting from combustion of the gases are provided so that either type of leakage of the gases can be dealt with, allowing an appropriate control before or at the early stages of fire breaking out.

Claims

1. An alarm and control system for semiconductor factories for protecting them against fire or gas leaks comprising a gas detector (G) at locations (3) where poisonous and inflammable treatment gases are used, an exhaust system (9, 10, 11) and electrical devices (I, OR1, OR2, OR3), controlled by this detector (G) to raise the alarm, and a protection device, characterized in that gas detectors (G1) to detect the leakage of said treatment gases, including silane gas, and fire detectors (D1) to detect products of combustion of said treatment gases, are provided at locations (3) where said treatment gases, including silane gas, are used, in that the electrical device (I, OR1, OR2, OR3) to raise the alarm comprises circuitry means which, upon a change in the output stage of either of said gas detectors (G1) or said fire detectors (D1), cause an alarm to issue, and in that there are means responsive to said alarm signal to control the protection device as well as said manufacturing process of semiconductors.

2. An alarm and control system according to claim 1, characterized in that gas detectors (G2) and fire detectors (D2) are provided in said exhaust system (9, 10, 11) and that said fire detectors (D2) have inverters (I) at their outputs.

3. An alarm and control system according to any of claims 1 and 2, characterized in that gas detectors (G1) and fire detectors (D1) are provided in a housing (3) in which cylinders (1, 2) of said treating gases are housed.

4. An alarm and control system according to any of claims 1 to 3, characterized in that said gas detectors (G1, G2) utilize a metal oxide semiconductor containing platinum black as a detecting element for detecting the leakage of said treatment gases, including silane gas, and any said metal oxide semiconductor used as said detecting element is aged in an atmosphere of silane gas.

5. An alarm and control system according to any of claims 1 to 3, characterized in that said fire detectors (D1) consist of ionization-type smoke detectors.