Patent Publication Number: US-6986111-B2

Title: Self-diagnostic circuit of I/O circuit system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a Continuation Application of PCT Application No. PCT/JP01/07651, filed Sep. 4, 2001, which was not published under PCT Article 21(2) in English. 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-272644, filed Sep. 8, 2000, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a self-diagnostic circuit for an I/O circuit system incorporated in the controller of a semiconductor manufacturing apparatus or the like. 
     2. Description of the Related Art 
     In general, many driving systems and various sensors (to be referred to as driving portions) are attached to a semiconductor manufacturing apparatus or the like in order to drive each building portion. For example, to operate the driving systems, a main controller having a microcomputer properly acquires analog or digital sensor outputs from the sensors of the driving systems. The main controller analyzes these sensor outputs, and sends a control instruction to each driving system in accordance with a control sequence or control program in order to cause the driving system to perform a predetermined operation. For example, to introduce process gas into a processing chamber, the main controller instructs a flow controller of the gas species or gas flow rate corresponding to processing to be performed for a semiconductor wafer (to be referred to as a wafer hereinafter). The flow controller sends a return signal concerning the gas flow rate or the like to the main controller, and feedback control is executed. Similarly, the main controller instructs a high-frequency power supply for generating a plasma of a high-frequency power output value to be applied. A stable plasma is generated by control based on a return signal from the high-frequency power supply or a sensor signal from a sensor arranged in the processing chamber. The main controller drives an exhaust system on the basis of a measurement value from a pressure gauge which detects the internal pressure of the processing chamber. The main controller controls the pressure so as to set a desired pressure in the processing chamber. 
     Control signals and sensor signals exchanged between the main controller and each driving system or sensor system are used after conversion into analog and digital signals. 
     Each building portion which constitutes an apparatus generally undergoes part replacement, adjustment, and the like by general maintenance. Depending on the degree of maintenance, a signal cable which connects building portions may be disconnected. When the signal cable is disconnected, whether the cable is correctly connected must be checked at the start of operation. 
     Even with periodic maintenance, part replacement, adjustment, and the like, damage to a part, an adjustment error, short-circuiting in a circuit, or the like may occur for some reason. Quick corrective maintenance is required for such a fault. It is therefore important to quickly detect which of many circuit networks or which of parts suffers a fault. 
     In a conventional apparatus arrangement, a fault can be detected at each building portion within a relatively short time. However, when building portions are assembled into an apparatus and connected to each other by cables or the like, it is very difficult to detect which part suffers an electrical defect or which portion was the cause. For this reason, building portions must be checked by disconnecting cables, or a faulty portion is detected on the basis of empirical knowledge of the operator or by checking the previous fault log. A long time is taken for detecting a faulty portion. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a self-diagnostic circuit for an I/O circuit system that can quickly, easily detect an electrically defective portion. 
     To achieve the above object, the present invention provides a self-diagnostic circuit for an I/O circuit system that is mounted in the I/O circuit system incorporated in the controller of a semiconductor manufacturing apparatus or the like, comprises tie switches interposed between output channels which output control signals in order to drive and control apparatus-side driving portions constructed on an I/O board, and input channels which input return signals in response to the control signals, and self-diagnostic switches arranged on power supply lines for supplying power to the driving portions of the apparatus and stop power supply to the driving portions. 
     To achieve the above object, the present invention provides a self-diagnostic circuit for an I/O circuit system that is mounted in the I/O circuit system which is incorporated in a main controller for controlling and driving an apparatus having a plurality of driving portions and has a plurality of output and input channels, and that comprises tie switches which connect the corresponding output channels and input channels in the I/O circuit, and self-diagnostic switches which are arranged on lines of the output and input channels in the I/O circuit and electrically disconnect the apparatus-side driving portions, wherein in normal operation, the apparatus is driven and controlled by the main controller via the tie switches in a nonconductive state and the self-diagnostic switches in a conductive state, and in self-diagnosis, self-diagnostic signals output from the main controller to the output channels are returned to the main controller via the input channels by using the tie switches in the conductive state and the self-diagnostic switches in the nonconductive state, determining that the I/O circuit system is normal. 
     According to the present invention, in normal operation, the tie switches are in a nonconductive state, and the self-diagnostic switches are in a conductive state, outputting signals to apparatus-side building portions via the output digital channels. Return signals from the building portions or sensor signals from sensors attached to the building portions are input to the main controller via the input channels, controlling the building portions. In self-diagnosis, the self-diagnostic switches are in a nonconductive state, and all the tie switches are in a conductive state to electrically disconnect the apparatus. The loopbacks of the output and input channels are constructed. If a return signal corresponding to a self-diagnostic signal output from the main controller is returned, no electrical fault is determined to occur. If no return signal is returned, an electrical fault is determined to have occurred. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  is a diagram showing an arrangement of a semiconductor manufacturing apparatus which incorporates the self-diagnostic circuit of an I/O circuit system according to the present invention; 
         FIG. 2  is a diagram showing the arrangement of the self-diagnostic circuit of an I/O circuit system according to the first embodiment of the present invention; 
         FIG. 3  is a waveform chart showing an example of a digital self-diagnostic signal in the self-diagnostic circuit according to the first embodiment; 
         FIG. 4  is a diagram showing the arrangement of the self-diagnostic circuit of an I/O circuit system according to the second embodiment of the present invention; 
         FIG. 5  is a waveform chart showing an example of a analog self-diagnostic signal in the self-diagnostic circuit according to the second embodiment; 
         FIGS. 6A ,  6 B, and  6 C are waveform charts showing modifications to an analog self-diagnostic signal; 
         FIG. 7  is a diagram showing the arrangement of the self-diagnostic circuit of an I/O circuit system according to the third embodiment of the present invention; and 
         FIGS. 8A ,  8 B, and  8 C are waveform charts showing examples of a digital self-diagnostic signal in the self-diagnostic circuit according to the third embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments according to the present invention will be described in detail below. 
       FIG. 1  is a diagram showing the schematic arrangement of a semiconductor manufacturing apparatus which incorporates the self-diagnostic circuit of an I/O circuit system according to the present invention. An object to be controlled is the driving portion of the semiconductor manufacturing apparatus, and the apparatus is, e.g., a plasma etching apparatus. 
     A semiconductor manufacturing apparatus  2  having, e.g., a cylindrical processing chamber  4 . The processing chamber  4  incorporates a lower electrode  6  serving as a susceptor, and an upper electrode  8  which is arranged above and parallel to the lower electrode  6 . A semiconductor wafer W serving as an object to be processed is set on the lower electrode  6 . 
     The upper electrode  8  is connected via a matching box  10  to a high-frequency generator  12  capable of changing the output. A high-frequency output is applied to the upper electrode  8  to generate a plasma between the upper and lower electrodes  8  and  6 . The matching coefficient of the matching box  10  and the high-frequency output of the high-frequency generator  12  are controlled by a main controller  14  having a microcomputer or the like. 
     An evacuation system  22  is connected to an exhaust port  16  formed in the bottom of the processing chamber  4 . The evacuation system  22  is constituted by connecting, via an exhaust pipe, a pressure control valve  18  whose opening is adjustable, and a vacuum pump  20 . The valve opening of the pressure control valve  18  and the exhaust ability of the vacuum pump  20  are also controlled by the main controller  14 . 
     The semiconductor manufacturing apparatus  2  also comprises a gas supply system  28  for supplying the necessary process gas into the processing chamber  4  in accordance with an instruction from the main controller  14  while controlling the flow rate. The gas supply system  28  is constituted by connecting, via a gas pipe, a gas nozzle  24  which is arranged in the side wall of the processing chamber  4 , a flow controller  26  such as a mass-flow controller, and a process gas source (not shown). In general, a gas supply system which treats a plurality of types of gases is made up of a plurality of gas lines. In this embodiment, only one gas line is illustrated, for simplicity, in FIG.  1 . 
     An evacuation line  32  which is branched from a portion between the gas nozzle  24  and the flow controller  26  and connected to the evacuation system  22  via an evacuation on-off valve  30  is arranged in the gas supply system  28 . The evacuation on-off valve  30  is in a nonconductive state/in a conductive state under the control of the main controller  14 . This allows exhausting unwanted gas to the evacuation system  22  via the evacuation line  32  without supplying gas into the processing chamber  4  until the flow controller  26  can stably supply process gas. 
     A pressure sensor  34  having, e.g., a capacitance manometer is installed in the processing chamber  4 . Detection data obtained from the pressure sensor is output to the main controller  14 . 
     A load/unload port for the wafer W is formed in the side wall of the processing chamber  4 . An externally openable/closable gate valve  36  is so arranged as to close the load/unload port. A shutter member  38  which can be elevated is so arranged as to cover the load/unload port from inside the processing chamber  4 . The shutter member  38  can easily achieve thermal equilibrium in the processing chamber  4 . Opening/closing driving of the gate valve  36  and elevating driving of the shutter member  38  are controlled by the main controller  14 . The gate valve  36 , shutter member  38 , evacuation on-off valve  30 , and the like are in a nonconductive state/in a conductive state by air cylinders (not shown) having solenoids. For example, photosensors (not shown) for detecting the nonconductive/conductive state are arranged near the movable portions of the air cylinders. A cooling jacket  42  which can change the cooling temperature is arranged in a support  40  which supports the lower electrode  6 . The cooling temperature is controlled by the main controller  14 . 
     The first embodiment according to the present invention will be explained with reference to  FIG. 2  showing an example in which the self-diagnostic circuit of the I/O circuit system driven by a digital signal is applied to the semiconductor manufacturing apparatus  2 .  FIG. 3  is a waveform chart showing a digital self-diagnostic signal used for self-diagnosis in this embodiment. 
     Output digital channels  44 A,  44 B, and  44 C, and input digital channels  46 A,  46 B, and  46 C are illustrated as an example of three signal paths for the main controller  14 . In practice, many channels are arranged in accordance with the control. 
     The output digital channels  44 A to  44 C are respectively connected to photocouplers  48 A to  48 C, output port circuits  50 A to  50 C which incorporate various circuit elements, and diodes  52 A to  52 C. The input digital channels  46 A to  46 C are respectively connected to photocouplers  54 A to  54 C, input port circuits  56 A to  56 C which incorporate various circuit elements, and diodes  58 A to  58 C. 
     The output digital channels  44 A to  44 C, and input digital channels  46 A to  46 C are terminated at many terminals  60 . The arrangement up to the terminals  60  constitutes a digital I/O circuit system. In practice, the I/O circuit system is constituted by mounting the above-mentioned building portions (output port circuits, input port circuits, and the like) on an I/O board. 
     This I/O circuit system is connected to various driving systems and sensors of the above-described semiconductor manufacturing apparatus  2 . For example, the output digital channels  44 A to  44 C are respectively connected to the solenoids of the gate valve  36 , shutter member  38 , and evacuation on-off valve  30  serving as loads. The other terminal of each solenoid is commonly connected, returns to the I/O board, and is connected to a positive power supply  62 . 
     The input digital channels  46 A to  46 C are respectively connected to one terminal of a sensor  36 A which detects the nonconductive/conductive state of the gate valve  36 , one terminal of a sensor  38 A which detects the elevating state of the shutter member  38 , and one terminal of a sensor  30 A which detects the nonconductive/conductive state of the evacuation on-off valve  30 . The other terminal of each sensor is commonly connected, returns to the I/O board, and is grounded to a ground potential. Note that the sensors  36 A,  38 A, and  30 A are so constituted as to be turned on upon detection. 
     The self-diagnostic circuit as the gist of the present invention is arranged in the I/O circuit system. 
     As shown in  FIG. 2 , tie switches (bypass switch)  64 A,  64 B, and  64 C are respectively interposed between the lines of the output digital channels  44 A to  44 C and the lines of the input digital channels  46 A to  46 C. The tie switches  64 A to  64 C are interposed between the port circuits  50 A to  50 C and  56 A to  56 C, and the diodes  52 A to  52 C and  58 A to  58 C. 
     On the I/O board, self-diagnostic switches  66 A and  66 B are respectively interposed between the positive power supply  62  and a signal line extending from loads, i.e., the gate valve  36 , shutter member  38 , and evacuation on-off valve  30 , and between ground and a signal line extending from the sensors  36 A,  38 A, and  30 A. 
     The tie switches  64 A to  64 C integrally operate to be opened (nonconductive state) in normal operation and closed (conductive state) in self-diagnosis. The self-diagnostic switches  66 A and  66 B integrally operate to be in a conductive state in normal operation and in a nonconductive state in self-diagnosis. Note that the tie switches  64 A to  64 C are allowed to have a small resistance load even in the conductive state, and semiconductor switches such as FETs may be used. However, it is not preferable that the self-diagnostic switches  66 A and  66 B have a resistance load in the closed state (conductive state), and relay switches having metal contact pieces are preferably used. 
     A self-diagnostic operation in the I/O circuit system having this arrangement will be explained. To normally operate the semiconductor manufacturing apparatus  2 , the tie switches  64 A to  64 C are in a nonconductive state, and the self-diagnostic switches  66 A and  66 B are in a conductive state.  FIG. 2  shows a normal operation state. 
     In this state, the main controller  14  individually sends control signals, complying with the semiconductor device manufacturing process, to the output digital channels  44 A to  44 C. The gate valve  36 , shutter member  38 , and evacuation on-off valve  30  are respectively driven and controlled. In response to this, sensor signals from the sensors  36 A,  38 A, and  30 A are input to the main controller  14  via the input digital channels  46 A to  46 C. 
     Self-diagnosis is performed when whether the I/O circuit is properly connected is to be checked at the start of operation after a wiring cable is temporarily disconnected for maintenance or repair of the semiconductor manufacturing apparatus and then connected, or when any electrical fault occurs in the I/O circuit and the I/O circuit must be checked to detect the faulty portion. 
     In self-diagnosis, the respective switches are switched to be in an opposite state to those in normal operation. More specifically, the self-diagnostic switches  66 A and  66 B are in a nonconductive state to disconnect the power supply  62  and ground potential. All the tie switches  64 A to  64 C are in a conductive state to construct loopback. As a result, the output digital channels  44 A to  44 C and input digital channels  46 A to  46 C are electrically connected (short-circuited). As an example of the loopback, a loop of the photocoupler  48 A, output port circuit  50 A, tie switch  64 A, input port circuit  56 A, and photocoupler  54 A is formed. 
     The main controller  14  outputs digital self-diagnostic signals of pulse signals “1” as shown in  FIG. 3  to the output digital channels  44 A to  44 C. The main controller  14  reads return signals which appear in the input digital channels  46 A to  46 C every time the main controller  14  receives signals. 
     The channel  44 A shown in  FIG. 3  exhibits an example of a digital self-diagnostic signal output to the output digital channel  44 A. The channel  44 B exhibits an example of a digital self-diagnostic signal output to the output digital channel  44 B. The channel  44 C exhibits an example of a digital self-diagnostic signal output to the output digital channel  44 C. A “1” signal is output to the channels  44 A to  44 C with a small timing shift. If the same “1” signal is input from the input digital channels  46 A to  46 C at the same timing, the channels are determined to be normal. 
     To the contrary, if the “1” signal is input from the input digital channels  46 A to  46 C at different timings or a plurality of “1” signals are input, the channels are determined to be short-circuited. If no “1” signal is input, it is determined that a corresponding channel is disconnected or any one of the output port circuits  50 A to  50 C or an element in any one of the corresponding input port circuits  56 A to  56 C is damaged. 
     The “1” signal is output as a digital self-diagnostic signal to the channels at different timings because if the pulse is output to the channels at the same timing and the channels are short-circuited, the short-circuited portion cannot be detected. 
     In the above-described way, the self-diagnostic circuit having a relatively simple arrangement can quickly, easily specify and detect a channel in which a fault or the like occurs. In this embodiment, the digital self-diagnostic signal is supplied only once. Diagnostic operation may be repeated a plurality of number of times to increase the diagnostic reliability. Three channels are arranged for each of the output and input of one I/O board in this embodiment, but the number of channels is not particularly limited. For example, eight channels are arranged for each of the output and input of an actual I/O board, and many I/O boards are arranged in the I/O circuit. A diagnostic circuit identical to the above-described one is arranged for each board. 
     In the above-described embodiment, a “1” signal is output as a digital diagnostic signal with a timing shift. It is also possible to set the level of each channel to “1” in self-diagnosis and generate a “0” signal with a timing shift. 
     The first embodiment concerns a digital I/O circuit system, but this arrangement can also be applied to an analog I/O circuit system. 
     The second embodiment according to the present invention will be explained with reference to  FIG. 4  showing an example in which the self-diagnostic circuit of an I/O circuit system driven by an analog signal is applied to a semiconductor manufacturing apparatus  2 . In the second embodiment, the same reference numerals as in  FIG. 2  denote the same parts, and a description thereof will be omitted.  FIG. 5  is a waveform chart showing an analog self-diagnostic signal used for self-diagnosis in this embodiment. 
     Output analog channels  70 A,  70 B, and  70 C, and input analog channels  72 A,  72 B, and  72 C are arranged for one I/O board as a plurality of, e.g., three paths for a main controller  14 . The output analog channels  70 A to  70 C are connected to photocouplers  74 A to  74 C, D/A converters  75 A to  75 C, and output port circuits  76 A to  76 C in which various circuit elements are integrated. The input analog channels  72 A to  72 C are connected to photocouplers  78 A to  78 C, A/D converters  80 A to  80 C, and input port circuits  82 A to  82 C in which various circuit elements are integrated. 
     The output analog channels  70 A to  70 C, and input analog channels  72 A to  72 C are terminated at many terminals  94 . The arrangement up to the terminals  94  constitutes an analog I/O circuit system. More specifically, these building portions are mounted on an I/O board. 
     Various driving systems and sensors of the semiconductor manufacturing apparatus  2  are connected to this I/O circuit system. The output analog channels  70 A to  70 C are respectively connected via A/D converters  83 A to  83 C to, e.g., a flow controller  26 , high-frequency generator  12 , pressure control valve  18 , and high-voltage generator (not shown) serving as loads. The input analog channels  72 A to  72 C are respectively connected via D/A converters  85 A to  85 C to, e.g., the return signal line of the flow controller  26 , the return signal line of the high-frequency generator  12 , and a pressure sensor  34 . 
     In the arrangement shown in  FIG. 4 , the analog channels  70 A to  70 C and  72 A to  72 C are connected to various driving systems and sensors via the independently arranged A/D converters  83 A to  83 C or D/A converters  85 A to  85 C. However, the analog channels  70 A to  70 C and  72 A to  72 C may be connected to A/D converters or D/A converters arranged in respective driving systems and sensors. 
     The self-diagnostic circuit as the feature of the present invention is arranged in the I/O circuit system having the above arrangement. 
     As shown in  FIG. 4 , tie switches  86 A,  86 B, and  86 C are respectively interposed between the output analog channels  70 A to  70 C and the input analog channels  72 A to  72 C. The tie switches  86 A to  86 C are connected between output port circuits  76 A to  76 C and input port circuits  82 A to  82 C, and the respective terminals  94 . 
     Self-diagnostic switches  88 A,  88 B, and  88 C are respectively located on the input sides of the terminals  94  of the output analog channels  70 A to  70 C. Self-diagnostic switches  90 A,  90 B, and  90 C are respectively located on the input sides of the terminals  94  of the input analog channels  72 A to  72 C. 
     In normal operation, the tie switches  86 A to  86 C are open, and the self-diagnostic switches  88 A to  88 C and  90 A to  90 C are in a conductive state. In self-diagnosis, the tie switches  86 A to  86 C are in a conductive state, and the self-diagnostic switches  88 A to  88 C and  90 A to  90 C are open. The tie switches  86 A to  86 C, and self-diagnostic switches  88 A to  88 C and  90 A to  90 C can adopt semiconductor switches such as FETs or relay switches, and are integrally in a nonconductive state/in a conductive state under the control of the main controller  14 . 
     Self-diagnostic operation in the I/O circuit system having this arrangement will be explained. 
     To normally operate the semiconductor manufacturing apparatus  2 , the tie switches  86 A to  86 C are in a nonconductive state, and the self-diagnostic switches  88 A to  88 C and  90 A to  90 C are in a conductive state.  FIG. 4  shows a normal operation state. 
     In this state, the main controller  14  individually sends control signals complying with the semiconductor device manufacturing process to the output analog channels  70 A to  70 C. The flow controller  26 , high-frequency generator  12 , pressure control valve  18 , high-voltage generator (not shown), and the like are respectively controlled. At the same time, return signals from these building portions and a sensor signal from the pressure sensor  34  are input to the main controller  14  via the input analog channels  72 A to  72 C. 
     Self-diagnosis is performed when whether the I/O circuit is properly connected is to be checked at the start of operation after a wiring cable is temporarily disconnected for maintenance or repair of the semiconductor manufacturing apparatus and then connected, or when any electrical fault occurs in the I/O circuit and the I/O circuit must be checked to detect the faulty portion. 
     In self-diagnosis, the respective switches are switched to directions opposite to those in normal operation. More specifically, the self-diagnostic switches  88 A to  88 C and  90 A to  90 C are in a nonconductive state to disconnect the semiconductor manufacturing apparatus  2 . All the tie switches  86 A to  86 C are in a conductive state to construct loopback. As a result, the output analog channels  70 A to  70 C and input analog channels  72 A to  72 C are in a conductive state (short-circuited). 
     The main controller  14  outputs analog self-diagnostic signals as shown in  FIG. 5  to the output analog channels  70 A to  70 C. The main controller  14  reads return signals which appear in the input analog channels  72 A to  72 C. 
     In this example, the analog self-diagnostic signal has different application voltage values for the respective output analog channels  70 A to  70 C. For example, 1 V is applied to the first output analog channel  70 A; 2 V, to the second output analog channel  70 B; and 3 V, to the third output analog channel  70 C. In this case, if the wiring is disconnected or a defective element exists in a loop (channel), a return signal from this loop cannot be detected. If the channels are short-circuited, voltage values different from input voltages are obtained as return signals in the channels. Hence, short-circuiting between wiring lines or generation of a defective element can be quickly, easily recognized and detected. 
     In this example, the voltage of the self-diagnostic signal is changed by 1 V for each channel, but the difference voltage is not particularly limited. However, different voltage values are desirable because a defective portion cannot be determined with a plurality of self-diagnostic signals having the same voltage values. That is, short-circuiting between channels cannot be recognized. 
     In the second embodiment, the voltage value applied to each output analog channel is constant, as shown in FIG.  5 . However, the voltage value is not limited to this, and may be changed stepwise at different timings, like analog self-diagnostic signals shown in  FIGS. 6A  to  6 C. 
       FIG. 6A  shows the waveform of a self-diagnostic signal applied to the first output analog channel  70 A.  FIG. 6B  shows the waveform of a self-diagnostic signal applied to the second output analog channel  70 B.  FIG. 6C  shows the waveform of a self-diagnostic signal applied to the third output analog channel  70 C. 
     As shown in  FIGS. 6A  to  6 C, the voltage value is changed stepwise by 1 V from 1 to 3 V, and applied to the channels  70 A,  70 B, and  70 C. Further, the application timing is different between the channels. By sequentially changing and applying the voltage value of the self-diagnostic signal, whether adjustment of the gain or the like in the output and input port circuits  76 A to  76 C and  82 A to  82 C is appropriate can be confirmed. 
     Three channels are arranged for each of the output and input of one I/O board in this embodiment, but the number of channels is not particularly limited. For example, eight channels are arranged for each of the output and input of an actual I/O board, and many I/O boards are arranged in the I/O circuit. A diagnostic circuit identical to the above-described one is arranged for each board. In this case, self-diagnosis is executed using a self-diagnostic signal voltage having eight voltage values different by 1 V from 1 to 8 V. 
     The third embodiment according to the present invention will be explained with reference to  FIG. 7  showing an example in which the self-diagnostic circuit of an I/O circuit system having a communication function is applied to a semiconductor manufacturing apparatus  2 .  FIG. 8  shows waveform charts of a digital self-diagnostic signal used for self-diagnosis in this embodiment. Serial communication is assumed as the communication method, and a plurality of, e.g., three signal channels are adopted for a main controller  14 . 
     In this arrangement, the main controller  14  having a host computer which controls the whole operation of the semiconductor manufacturing apparatus  2  is connected to a host-side communication I/O board  200 . The semiconductor manufacturing apparatus  2  is connected to a slave-side I/O board  201  having the same arrangement as that of the host side. Data is exchanged between the host and slave sides by serial communication. 
     The I/O board  200  comprises a board controller  100  having a microcomputer or the like, and a transmitter/receiver  102  having, e.g., an integrated circuit (RS232C) having a transmission/reception communication function. The transmitter/receiver  102  is connected to, e.g., three transmission digital channels  104 A to  104 C and three reception digital channels  106 A to  106 C. 
     The channels  104 A to  104 C and  106 A to  106 C are terminated at terminals  108 . Each terminals  108  is connected to an interface  110  to actually perform transmission/reception with the slave side. 
     The slave side also comprises an interface  112 , transmitter/receiver  114 , board controller  116 , and the like. The control signals of a matching box  10 , cooling jacket  42 , and pressure control valve  18 , their return signals, and the like can be communicated between the salve and host sides. Note that  FIG. 7  illustrates only one slave-side I/O board. In practice, a plurality of slave-side I/O boards are parallel-connected, and each I/O board can individually, independently communicate data to the host side. 
     The self-diagnostic circuit as the feature of the present invention is arranged in the I/O circuit system having the above arrangement. 
     More specifically, tie switches  118 A,  118 B, and  118 C which connect the transmission digital channels  104 A to  104 C and reception digital channels  106 A to  106 C are interposed between the transmitter/receiver  102  and the respective terminals  108  on the I/O board. 
     Self-diagnostic switches  120 A,  120 B, and  120 C are respectively interposed between the nodes of the tie switches  118 A to  118 C on one side and the respective terminals  108  on the transmission digital channels  104 A to  104 C. Self-diagnostic switches  122 A,  122 B, and  122 C are respectively interposed between the nodes of the tie switches  118 A to  118 C on the other side and the respective terminals  108  on the reception digital channels  106 A to  106 C. 
     The tie switches  118 A to  118 C integrally operate to be in a nonconductive state in normal operation (transmission/reception) and in a conductive state in self-diagnosis. The self-diagnostic switches  120 A to  120 C and  122 A to  122 C integrally operate to be in a conductive state in normal operation and in a nonconductive state in self-diagnosis. The tie switches  118 A to  118 C and the self-diagnostic switches  120 A to  120 C and  122 A to  122 C can use either semiconductor switches such as FETs or relay switches. 
     Self-diagnostic operation using serial communication in the I/O circuit system having this arrangement will be explained. 
     In normal operation (transmission/reception), i.e., to operate the semiconductor manufacturing apparatus  2 , the tie switches  118 A to  118 C are in a nonconductive state, and the self-diagnostic switches  120 A to  120 C and  122 A to  122 C are in a conductive state.  FIG. 7  shows a normal operation state. In this state, necessary data is exchanged between the host-side main controller  14  and the slave side. 
     Self-diagnosis is performed when whether the I/O circuit is properly connected is to be checked at the start of operation after a wiring cable is temporarily disconnected for maintenance or repair of the semiconductor manufacturing apparatus and then connected, or when any electrical fault occurs in the I/O circuit and the I/O circuit must be checked to detect the faulty portion. 
     In self-diagnosis, the tie switches and self-diagnostic switches are switched to be in an opposite state to those in normal operation. More specifically, the self-diagnostic switches  120 A to  120 C and  122 A to  122 C are in a nonconductive state to disconnect the slave side. All the tie switches  118 A to  118 C are in a conductive state to construct loopback. As a result, the transmission digital channels  104 A to  104 C and reception digital channels  106 A to  106 C are electrically connected. 
     The main controller  14  outputs, e.g., self-diagnostic signals of pulse sequence codes as shown in  FIGS. 8A  to  8 C to the transmission digital channels  104 A to  104 C. The main controller  14  reads return signals which appear in the reception digital channels  106 A to  106 C. 
     These self-diagnostic signals have different codes for the respective transmission digital channels  104 A to  104 C. For example, a code shown in  FIG. 8A  is sent to the first transmission digital channel  104 A. A code shown in  FIG. 8B  is sent to the second transmission digital channel  104 B. A code shown in  FIG. 8C  is sent to the third transmission digital channel  104 C. If a channel is disconnected or suffers a defective element, a return signal from the channel is not detected. 
     If the channels are short-circuited, pulse sequences different from the above-mentioned codes are obtained as return signals in the channels. Thus, short-circuiting or generation of a defective element can be quickly, easily recognized and detected for every channel. 
     In this case, self-diagnostic signals are simultaneously sent, but the sending timings of these signals may be changed. In this case, when channels are short-circuited, the channels which are short-circuited can be easily detected. Note that the number of channels is three in this embodiment, but is not limited to this. This embodiment has exemplified a single-wafer processing type semiconductor manufacturing apparatus. The present invention is not limited to this, and can also be easily applied to a batch processing type semiconductor manufacturing apparatus. 
     The object to be processed is not limited to a semiconductor wafer, and can also be a glass substrate, LCD substrate, and the like. 
     As has been described above, the self-diagnostic circuit of the I/O circuit system according to the present invention can exhibit the following excellent operation effects.
         In self-diagnosis, the self-diagnostic switches which are connected to the load side and power supply side are in a nonconductive state to disconnect the load and sensor. The tie switches are in a conductive state to electrically connect the input digital channels and output digital channels. Digital self-diagnostic signals are supplied to these channels, and their return signals are detected. An electrically defective portion can be quickly, easily detected.   Since the self-diagnostic switches are commonly used, the number of self-diagnostic switches arranged can be reduced.   In self-diagnosis, the self-diagnostic switches which are connected to the load side and power supply side are in a nonconductive state to disconnect the load and an object to be controlled. The tie switches are in a conductive state to electrically connect the input digital channels and output digital channels. Digital self-diagnostic signals are supplied to these channels, and their return signals are detected. An electrically defective portion can be quickly, easily detected.   Since channels are simultaneously diagnosed, the self-diagnostic time can be shortened. The voltage value of an analog self-diagnostic signal is changed. Whether gain adjustment of an amplifier is appropriate can be more accurately self-diagnosed.   A portion where an electrical defect exists in a transmission digital channel or reception digital channel can be quickly, easily detected.
 
Industrial Applicability
       

     The present invention can provide a self-diagnostic circuit for an I/O circuit system that can quickly, easily detect an electrically defective portion in the circuit arrangement of an apparatus. 
     According to the present invention, an I/O circuit system incorporated in the controller of a semiconductor manufacturing apparatus or the like comprises a self-diagnostic circuit in which tie switches are interposed between output channels which output control signals in order to drive and control apparatus-side driving portions constructed on an I/O board, and input channels which input return signals in response to the control signals, and self-diagnostic switches which are arranged on power supply lines for supplying power to the driving portions of the apparatus and stop power supply to the driving portions are arranged. In normal operation, the tie switches are in a nonconductive state, and the self-diagnostic switches are in a conductive state, outputting signals to apparatus-side building portions via the output digital channels. Return signals from the building portions or sensor signals from sensors attached to the building portions are input to the main controller via the input channels, controlling the building portions. In self-diagnosis, the self-diagnostic switches are in a nonconductive state, and all the tie switches are in a conductive state to electrically disconnect the apparatus. The loopbacks of the output and input channels are constructed. If a return signal corresponding to a self-diagnostic signal output from the main controller is returned, no electrical fault is determined to occur. If no return signal is returned, an electrical fault is determined to have occurred.