JPH02167491A - Sensor device - Google Patents

Abstract

PURPOSE:To decrease faults which are caused by an electrolyte by applying a voltage which is lower than an operating voltage to a light source or photoelectric converting element in the off period of a sensor and covering the surface of the sensor with a transparent coating material. CONSTITUTION:When a specific current flows from a power source 33, the LED 31 of the photosensor 21 illuminates. The collector of the phototransistor(PT) 32 of the sensor 21 is connected to the base of a transistor(TR) 35 and the emitters of the PT 32 and TR 35 are grounded to obtain an output corresponding to the quantity of photodetection at the collector of the PT 32 and the inverted output at the collector of the TR 35. Consequently, even when the PT 32 is off, the base-emitter voltage of the TR 35 is applied between the collector and emitter of the PT 32 and this voltage is lower than the operating voltage, so even if the electrolyte enters the gap between a mold part and the PT 32, its electrolytic reaction is not active; and the surface of the sensor 21 is covered with the transparent coating film to make the electrolyte hard to enter the sensor, thereby reducing trouble.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a sensor device suitable for installation in a place where an electrolytic solution such as a developing solution is used.

[Conventional technology]

When developing a semiconductor wafer, a photosensor detects the semiconductor wafer being transported, and when the semiconductor wafer is detected, the semiconductor wafer is vacuum-adsorbed onto a chuck and the development process is started. FIG. 5 shows the external appearance of an example of the photosensor 10 used in this case. 11 is a light emitting diode, 12 is a phototransistor, and these light emitting diode 11 and phototransistor 12 are molded. The terminals of the lead wires led out to the outside and the terminals of the aluminum wiring of the light emitting diode 11 and the phototransistor 12 are bonded, for example, with gold wire or the like. Conventionally, the surface of the phototransistor 12 is not coated because it receives light from the light emitting diode 11. Conventionally, as a detection circuit for a semiconductor wafer using this photosensor 10, a circuit shown in FIG. 6 has been generally used. In this case, the light emitting diode 11 and the phototransistor 1
2 is arranged so as to sandwich the semiconductor wafer when detecting the semiconductor wafer. In this example, a constant current is supplied to the light emitting diode 11, and the light emitting diode 11 emits light with a constant amount of light. The emitter of the phototransistor 12 is grounded, and the collector is connected to, for example, +5■ through a variable resistor 13.
It is connected to the power supply terminal 14 of. The voltage Vl obtained at the connection point between the collector of the phototransistor 12 and the variable resistor 13 is supplied to one input terminal of an operational amplifier 15 that constitutes a comparator. Further, the power supply terminal 14 is grounded via resistors 16 and 17, and the power supply voltage +Vcc is connected to the connection point of the resistors 16 and 17.
The divided voltage vth can be obtained. This divided voltage vth is
It is supplied to the other input terminal of the operational amplifier 15 as a comparison threshold value. Note that the resistors 18 and 19 are
The comparison circuit 15, which constitutes a feedback circuit, has a hysteresis characteristic, but in the following explanation, for the sake of simplicity, it is assumed that there is no hysteresis. In the above circuit, when the semiconductor wafer is between the light emitting diode 11 and the phototransistor 12, the amount of light incident on the phototransistor 12 from the light emitting diode 11 is reduced by the amount of light that is blocked, so the phototransistor 12 is in the non-conducting direction. Since the voltage Vl is high and exceeds the threshold value vth, the output SD of the operational amplifier 15 becomes "1". On the other hand, when there is no semiconductor wafer, the light emitting diode 1
1, the amount of light incident on the phototransistor 12 increases. Therefore, since the phototransistor 12 becomes conductive, the voltage Vl becomes low, and the threshold value vth
Therefore, the output SD of the operational amplifier 15 is r
□.

[Problem to be solved by the invention]

By the way, heretofore, the photosensor used in this development processing apparatus to detect the presence or absence of a semiconductor wafer has often broken down. The applicant investigated the cause of this failure and discovered the following facts. That is, conventionally, the surface of the photosensor, especially the phototransistor 12, has not been coated.
The developer sometimes adhered to this phototransistor 12 as well. The developer is a surfactant and enters the gap between the phototransistor 12 of the photosensor 10 and the mold. Since the developer is a liquid with low volatility, the liquid that has entered will accumulate in this gap. Since the developing solution is also an electrolytic solution, the accumulated solution causes an electrolytic reaction and the conductive wire inside the sensor is engraved. As shown in FIG. 6, in the conventional discrimination circuit, when the phototransistor is off, the power supply voltage of 5V is applied directly to the phototransistor.
is applied, and the electrolytic reaction takes place relatively actively. Electrolytic reactions can corrode the terminals, leading to disconnections or short circuits, which can also cause failures. In view of the above points, the present invention aims to provide a sensor device that can reduce failures caused by electrolyte.

[Means to solve the problem]

In this invention, in a sensor device comprising a light source and a photoelectric conversion element provided to receive light from the light source, at least one of the light source and the photoelectric conversion element is supplied with a voltage lower than an operating voltage during a non-operating period. so that it is applied. Additionally, the surface of the sensor device is covered with a transparent coating material.

[Effect]

This invention provides at least one of a light source and a photoelectric conversion element,
During the non-operating period, a voltage lower than the operating voltage is applied, so that even when used in an electrolytic treatment section, the electrolytic reaction does not occur as actively as in the conventional case. Furthermore, since the surface of the sensor device is coated with a coating material, it is possible to prevent electrolyte from entering, reducing failures and further extending the lifespan.

【Example】

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings, taking as an example a case in which it is applied to a device for detecting the presence or absence of a wafer in a semiconductor wafer development process. In FIG. 3, 20 is a semiconductor wafer, 21 is a photosensor, 22 is a chuck for fixing the semiconductor wafer 20, and 23 is a pin for regulating the position of the semiconductor wafer in the transport direction. The semiconductor wafer 20 is conveyed as indicated by the arrow in the figure, hits the pins 23, and stops. At this position, when the wafer 20 is detected by the photosensor 21, the wafer 20 is placed on the chuck 22 and vacuum suctioned. FIG. 4 is a view of the device shown in FIG. 3 viewed from the side of the chuck 22. In this case, the photosensor 21, as shown in FIG.
It has the same structure as the photosensor shown in FIG. 5, and a transparent coating film 24 is formed on the entire surface of the sensor. FIG. 1 is a circuit diagram of an example of a sensor circuit according to the present invention. A light source of the photosensor 21, for example, a light emitting diode 31, is connected to a resistor 3 from a power terminal 33 to which a DC voltage of 5 cm is supplied.
A predetermined current flows through the light emitting diode 31
or emit light. The collector of the phototransistor 32 of the photoelectric conversion element, for example, the photosensor 21, is connected to the base of a transistor 35 that constitutes a low voltage circuit with a voltage lower than the operating voltage, and the collector of the phototransistor 32 and the base of the transistor 35 are connected. The point is connected to the power supply terminal 33 via a resistor 36. Phototransistor 32
The emitters of the six transistors 35 and the emitters of the transistors 35 are commonly connected, and an output corresponding to the light reception output of the photosensor 21 is obtained from the collector of the six transistors 35 which are grounded. The rest of the structure is the same as the example shown in FIG. In this circuit, an output corresponding to the amount of light received from the light emitting diode 31 is obtained at the collector side of the phototransistor 32, and an inverted output thereof is obtained at the collector side of the transistor 35. In this case, the base-emitter voltage of the transistor 35, for example 0.4V, is applied between the collector and emitter of the phototransistor 32 even when the phototransistor 32 is off. Therefore, even when the phototransistor 32 is off, the conventional +
A lower voltage is applied compared to the voltage of 5V. Therefore, even if the electrolytic solution enters the gap between the mold part and the phototransistor, the applied pressure of the phototransistor 32 is low, so the electrolytic reaction is not active, and the life of the phototransistor is extended. Note that this invention is not limited to development processing of semiconductor wafers;
Needless to say, the present invention is applicable to all cases where a photosensor is installed in a place where an electrolytic solution is used. As explained above, since the surface of this photosensor is coated, it becomes difficult for the electrolyte to enter this photosensor. Even if an intrusion occurs, a low voltage will be applied to the Fol-transistor even when it is off, so
Electrolytic reaction is weak. Therefore, the life of the photosensor becomes longer.

【Effect of the invention】

As described above, according to the present invention, since a voltage lower than the operating voltage is applied to one of the light source and the photoelectric conversion element during the off period of the sensor, electrolytic reactions can be suppressed. Furthermore, since the entire surface of the sensor is coated with a coating material, it becomes difficult for the electrolyte to enter the sensor, reducing failures.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an example of a sensor circuit of a sensor device according to the present invention, FIG. 2 is a diagram showing an external appearance of an example of a photosensor used in the device of this invention, and FIGS. 3 and 4 are diagrams of an example of a sensor circuit according to the present invention. FIG. 5 is a diagram showing an example of a photosensor used in a conventional device, and FIG. 6 is a circuit diagram of an example of a conventional sensor circuit. 21; Photo sensor 24; Transparent coating film 31: Light emitting diode 32; Photo transistor 35; Transistor representative as an example of a low voltage circuit Patent attorney Tadashi Sato Miya visit figure 6-799=

Claims (2)

[Claims] (1) In a sensor device consisting of a light source and a photoelectric conversion element provided to receive light from the light source, a voltage lower than the operating voltage is applied to at least one of the light source and the photoelectric conversion element during its non-operation period. A sensor device characterized by: (2) The sensor device according to claim (1), wherein the sensor device is entirely coated with a transparent coating material.