JPH0680413B2 - Photo detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a photodetection technique, and particularly to a technique effective when applied to a photodetection technique in which a plurality of adjacent photoelectric conversion elements receive light at the same time.

[Prior Art] Regarding the photodetection technology including a plurality of photoelectric conversion elements such as a diode array, see Ohmsha Publishing Co., Ltd.
It is described in "Semiconductor / IC Term Encyclopedia," P129, issued March 20, 1993.

By the way, the present inventor causes the photodetector composed of a plurality of photoelectric conversion elements such as a diode array to receive scattered light generated when the inspection object is irradiated with inspection light such as a laser spot. We examined the adjustment of the detection sensitivity of the foreign substance inspection device that inspects foreign substances adhering to the surface of the inspection object. The following is a technology that has not been publicly known but has been studied by the present inventor, and the outline thereof is as follows.

That is, by manually adjusting the amplification factors of the plurality of amplifiers connected to the individual photodiodes individually, variations in the characteristics of the individual photodiodes forming the diode array and the incident light in the array direction of the photodiodes can be suppressed. The detection sensitivity of scattered light from foreign matter is constant in all photodiodes without being affected by the deviation of the light amount.

[Problems to be Solved by the Invention] However, as described above, in the method of manually adjusting the amplification factors of the individual amplifiers, for example, when the number of photodiodes forming the diode array is large, the adjustment is performed. The present inventor has found that there is a problem that it takes a long time to perform, and there is a problem that the adjustment result varies due to individual differences among workers.

An object of the present invention is to provide a photodetection technique capable of quickly and stably adjusting the detection sensitivity of each of a plurality of photoelectric conversion elements.

The above and other objects and novel characteristics of the present invention are
It will be apparent from the description of this specification and the accompanying drawings.

[Means for Solving the Problems] The outline of the representative one of the inventions disclosed in the present application will be briefly described as follows.

That is, according to the output value of each amplification unit via the first and second switching units on the output side and the control line of each of the amplification units connected to each of the plurality of photoelectric conversion elements. By connecting the control unit for adjusting the amplification factor and synchronizing the switching operation of the connection between the control unit and the individual amplification units by the first and second switching units, the output value of each amplification unit can be adjusted. The adjustment of the amplification factor is automatically performed.

[Operation] According to the above-mentioned means, it is possible to automatically adjust the detection sensitivity of each of the plurality of photoelectric conversion elements in a relatively short time, as compared with, for example, manual work.
It is possible to quickly and stably adjust the detection sensitivity of each of the plurality of photoelectric conversion elements.

[Embodiment] FIG. 1 is an explanatory view showing a main part of a photodetector according to an embodiment of the present invention.

Light such as a plurality of photodiodes arranged adjacent to each other
The electrical conversion elements D ₁ , D ₂ , D ₃ , ... Dn include, for example, a plurality of amplification units A ₁ , A ₂ , A ₃ ,.
, Are connected via a plurality of input lines IN ₁ , IN ₂ , IN ₃ ,.

Then, the photocurrent, the photoelectromotive force, etc. generated according to the light amount of the light P incident on each of the plurality of photoelectric conversion elements D ₁ , D ₂ , D ₃ , ... _{a 1, a 2, a 3} , ‥‥ each of the control lines C ₁ to An, C _2, C _3, is amplified at a predetermined amplification factor corresponding to the voltage applied to ‥‥ Cn, a plurality of output lines OUT ₁ , OUT ₂ , OU
It is output to T ₃ , OUTn.

In this case, the plurality of output lines OUT ₁ , OUT ₂ , OUT ₃ , ... OUTn of the plurality of amplifiers A ₁ , A ₂ , A ₃ , ... An are connected to the plurality of inputs of the _first switching unit M _1. line _{LIN 1, LIN 2, LIN 3} , ‥‥ LINn are respectively connected, by a command from the outside to the first switching unit M _1, a plurality of input lines _{LIN 1, LIN 2, LIN 3} , ‥‥ LINn Any one of them is connected to the output line LOUT of the _first switching unit M ₁ .

In addition, the control lines for each of the plurality of amplifiers A ₁ , A ₂ , A ₃ , ...
_{C 1, C 2, C 3} , the ‥‥ Cn, a plurality of command voltage holding section H _1, H _2,
A plurality of output lines LO of the second switching unit M ₂ via H ₃ , ..., Hn
UT ₁ , LOUT ₂ , LOUT ₃ , ... LOUTn are connected, and a plurality of output lines are output in response to an external command to the second switching unit M ₂ .
Any one of LOUT ₁ , LOUT ₂ , LOUT ₃ , ... LOUTn is the second
It is configured to be connected to the input line LIN of the switching unit M ₂ .

Further, the output line LOUT of the _first switching unit M ₁ and the input line LIN of the _second switching unit M ₂ are connected from the microprocessor or the like via the analog-digital converter ADC and the digital-analog converter DAC, respectively. Is connected to the control unit C.

Then, the control unit C issues a command to the first switching unit M ₁ and the second switching unit M ₂ for the synchronization signal S, so that the plurality of amplification units A ₁ , A ₂ , A ₃ ,. Connect any one of a plurality of output lines OUT ₁ , OUT ₂ , OUT ₃ , ... OUTn and a plurality of control lines C ₁ , C ₂ , C ₃ , ... Cn corresponding to any one of An. Select at the same time and output multiple output lines OU of multiple amplifiers A ₁ , A ₂ , A ₃ , ...
By controlling the voltage applied to the control lines C ₁ , C ₂ , C ₃ , ... Cn according to the individual output values of T ₁ , OUT ₂ , OUT ₃ ,. The amplification factors of the sections A ₁ , A ₂ , A ₃ , ..., An are adjusted individually.

The operation of this embodiment will be described below.

For example, the inspection light of a laser spot or the like having a predetermined diameter is applied to the surface of an object to be inspected (not shown), and the light P scattered by foreign matters existing on the surface of the object to be inspected is used by the photodetector of this embodiment. A foreign matter inspection device that detects the foreign matter will be described.

Normally, in a laser spot, etc., the distribution of the amount of light has a nearly normal distribution around the optical axis, so the intensity of scattered light from foreign matter at the center and peripheral portions of the laser spot is the same for the foreign matter. But it is different.

Therefore, a plurality of photoelectric conversion elements D ₁ and D ₁ as in this embodiment
_When simultaneously detecting the light P such as scattered light of a predetermined width from the irradiation area of the laser spot by ₂ , D ₃ ,.
Along with variations in individual characteristics of the plurality of photoelectric conversion elements D ₁ , D ₂ , D ₃ , ..., Dn, the plurality of photoelectric conversion elements D ₁ , D ₂ ,
It is necessary to adjust the variation in the detection sensitivity caused by the uneven distribution of the light quantity of the inspection light in the array direction of D ₃ , ..., Dn.

First, light P such as scattered light from a standard object to be inspected, on which fine irregularities are uniformly formed, is incident on a plurality of photoelectric conversion elements D ₁ , D ₂ , D ₃ , ... Dn. Then, from the plurality of photoelectric conversion elements D ₁ , D ₂ , D ₃ , ..., Dn, the plurality of amplifiers A ₁ , A ₂ ,
Multiple output lines OUT ₁ , OUT ₂ , OUT ₃ , ... via A ₃
A predetermined output value is obtained at OUTn, and at this time, the control unit C causes the first switching unit M ₁ and the second switching unit M ₂ to act on the synchronization signal S to cause the first switching unit M _{1 to} operate. output lines a plurality of input lines LIN ₁ for LOUT, LIN _2, LIN _3, a selective connection operation ‥‥ Linn, a plurality of output lines to the second switching input line LIN in section M ₂ LOUT _1, LOUT ₂ , LOUT ₃ , ... Selective connection operation is performed in synchronization.

Then, for example, when the output line OUT ₁ of the amplification unit A ₁ is connected to the control unit C via the input line LIN ₁ and the output line LOUT of the first switching unit M ₁ and further the analog-digital converter ADC. At the same time, the control line C ₁ of the amplifier a ₁ is the command voltage holding section H ₁
And the output line LOUT ₁ and the input line LIN of the second switching unit M ₂ ,
Furthermore, the control unit C is connected to the control unit C via a digital-analog DAC, and the control unit C moves from the photoelectric conversion element D ₁ to the amplification unit.
The output value of the electrical signal such as the photoelectromotive force or photocurrent output to the output line OUT ₁ via A ₁ is set to a predetermined value that is set in advance, that is, a plurality of opto-electric The command voltage holding unit H ₁ connected to the control line C ₁ of the amplification unit A ₁ so that the detection sensitivities of the conversion elements D ₁ , D ₂ , D ₃ ,.
The operation of appropriately adjusting the voltage etc. set to is automatically performed, and the operation of adjusting the detection sensitivity is performed by sequentially switching the first switching section M ₁ and the second switching section M ₂ which are operated in synchronization. , A plurality of photoelectric conversion elements D ₁ , D ₂ , D ₃ ,.
And a plurality of amplification units A ₁ , A ₂ , A ₃ , ... An for all sequences quickly.

After that, for normal inspection objects such as semiconductor wafers,
Light P such as scattered light having a predetermined width from the surface of the object to be inspected when the inspection light such as a laser spot is irradiated is generated by a plurality of light beams.
By allowing the electric conversion elements D ₁ , D ₂ , D ₃ , ..., Dn to receive light, for example, light P such as scattered light from a foreign substance is converted into a plurality of light-electric conversion elements D ₁ , D ₂ , D ₃ ,. The detection sensitivity does not vary regardless of whether Dn is detected or not, and the reliability of the foreign matter inspection device equipped with the photodetector of this embodiment is improved.

In the above description, a plurality of photoelectric conversion elements D ₁ , D ₂ ,
The case where the sensitivity adjustment is performed in the state where the light P incident on D ₃ , ..., Dn has a statistical predetermined variation due to the light source or the like has been described, but depending on the use of the photodetector, for example, In the state where the light P having a uniform distribution of the amount of light in each portion in the cross section perpendicular to the optical axis, such as sunlight, is incident on the plurality of photoelectric conversion elements D ₁ , D ₂ , D ₃ , ... The sensitivity adjustment operation may be performed.

As described above, in the present embodiment, the following effects can be obtained.

(1). A plurality of light - electric conversion element _{D 1, D 2, D 3} , ‥‥ plurality of amplifier section A ₁ which is connected to each of the Dn, A _2, A _3, a plurality of output lines OUT ₁ of ‥‥ An, OUT ₂ , OUT ₃ , OUTn and multiple control lines
C ₁ , C ₂ , C ₃ , ... Cn has a first switching unit M ₁ and a second switching unit
The control unit C is connected via M ₂ , and the first switching unit M ₁ and the second switching unit M ₂ are operated in synchronization, so that a plurality of photoelectric conversion elements D ₁ , D ₂ , D _The control unit C adjusts the amplification factor according to each output value of the plurality of amplification units A ₁ , A ₂ , A ₃ , ... An connected to each of Dn. Since it is automatically performed, a plurality of photoelectric conversion elements D ₁ , D ₂ , D ₃ ,.
The detection sensitivity of each of Dn can be automatically adjusted in a relatively short time, and a plurality of photoelectric conversion elements D ₁ , D ₂ ,
It becomes possible to quickly and stably adjust the detection sensitivity of each of D ₃ ,.

(2). As a result of the above (1), for example, the inspection light such as a laser spot having a predetermined diameter is applied to the surface of the inspection object, and the light P scattered from the foreign matter present on the surface of the inspection object is the light of this embodiment. In a foreign matter inspection apparatus that detects using a detection apparatus, the time required for adjustment of the apparatus prior to the inspection is shortened, and the reliability of the detection result of the foreign matter adhered to the inspection object is improved. The productivity in the foreign matter inspection is improved.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Nor. For example, the opto-electric conversion element is not limited to a photodiode or the like, and may be any other opto-electric conversion element. Further, the amplification unit is not limited to the voltage control type amplifier or the like, and is not limited to the one from the outside. Any one can be used as long as the amplification factor can be controlled by the command.

[Effects of the Invention] The effects obtained by the representative one of the inventions disclosed in the present application will be briefly described as follows.

That is, a plurality of photoelectric conversion elements arranged adjacent to each other, and an electric signal from the photoelectric conversion element connected to each of the photoelectric conversion elements, which is connected to each of the photoelectric conversion elements by a command from the outside via a control line. A plurality of input lines connected to each output side of the amplification unit and one output line, and a plurality of output lines to the one output line according to a command from the outside. A first switching unit for switching the connection of the input lines, a plurality of output lines and one input line connected to each control line of the amplifying unit, and the plurality of output lines connected to each other according to an external command. A second switching unit that switches the connection of one input line to the output line is connected to the output line of the first switching unit and the input line of the second switching unit, and the first switching unit is connected.
And a control unit for individually setting the amplification factor of each of the plurality of amplification units on the basis of each output value by controlling the switching operation in the second switching unit in synchronization with each other. Compared to work, etc., the detection sensitivity of each of the plurality of photoelectric conversion elements can be automatically adjusted in a relatively short time, and the detection sensitivity of each of the plurality of photoelectric conversion elements can be adjusted. It becomes possible to carry out quickly and stably.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a main part of a photodetector according to an embodiment of the present invention. D ₁ , D ₂ , D ₃ , ・ ・ ・ Dn …… Optical-electric conversion element, A ₁ , A ₂ , A ₃ , ・ ・ ・
…… An …… Amplifier, IN ₁ , IN ₂ , IN ₃ ,… INn …… Input line, OU
T ₁ , OUT ₂ , OUT ₃ , ・ ・ ・ OUTn …… Output line, C ₁ , C ₂ , C ₃ , ・ ・ ・ Cn
...... Control line, H ₁ , H ₂ , H ₃ , ・ ・ ・ Hn …… Command voltage holding unit, M ₁
...... First switching unit, M ₂ ...... Second switching unit, LIN ₁ , LIN ₂ , LI
N ₃ , LINn ...... Input line of the first switching unit, LOUT ...... First
Output line of the switching section, LOUT ₁ , LOUT ₂ , LOUT ₃ , ... LOUTn ...
Output line of the second switching unit, LIN ... Input line of the second switching unit, ADC ... Analog-digital converter, DAC ... Digital-analog converter, C ... Control unit, S ... Synchronization signal .

Claims (4)

[Claims] 1. A plurality of opto-electrical conversion elements arranged adjacent to each other, and the opto-electrical conversion elements connected to each of the opto-electrical conversion elements, in response to a command from the outside through a control line. Of an electric signal having a variable amplification factor, a plurality of input lines and one output line connected to each output side of the amplification unit, and the one output line according to a command from the outside. To a plurality of output lines and one input line connected to each control line of the amplifying unit, and a first switching unit for switching connection of a plurality of input lines to the A second switching unit for switching connection of one input line to the plurality of output lines, the output line of the first switching unit and the input line of the second switching unit are connected, Synchronizing and controlling the switching operation in the first and second switching units Ri, photodetector, characterized in that comprising a controller for individually set based on the amplification factor of each of the plurality of amplifying parts to each of the output values. 2. The amplifier is a voltage control type amplifier whose amplification factor is variable according to a command voltage applied to a control line from the outside, and the control line of each of the amplifiers has a command to hold the command voltage. The photodetector according to claim 1, wherein the photodetector is connected to the second switching unit via a voltage holding unit. 3. The photodetector according to claim 1, wherein the plurality of photoelectric conversion elements are diode arrays formed by linearly arranging a plurality of photodiodes. . 4. The photodetector according to claim 1, wherein the photodetector is a photodetector of a foreign matter inspection device.