JP2018194304A - Particle counter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a measurement error between a plurality of channels in a particle counting device and enable accurate particle counting. SOLUTION: A correction value of each digital output data created based on a difference in digital output data of each signal processing circuit 262 when a signal of the same intensity is output from each photodiode 142 in advance is held in a memory 265. Let me do it. When actually counting particles, this correction data is added to the output from each photodiode 142. As a result, individual differences in each signal processing circuit 262 due to various factors can be absorbed, accurate data can be obtained from the output signal of each photodiode 142, and correct particle counting can be performed. [Selection diagram] Fig. 6

Description

  The present invention relates to a particle counter that measures the number of particles floating or passing through a specific place such as a chamber of a semiconductor manufacturing apparatus or an exhaust pipe.

  Particles such as dust generated in the semiconductor processing process and floating in the processing chamber cause the performance of the product to deteriorate. Therefore, in the semiconductor processing apparatus, in order to suppress the generation of particles, the inside of the processing chamber (chamber) is placed in a high vacuum state, and a particle counting device that measures particles floating in the processing chamber in real time is installed.

  An example of the configuration of a conventional particle counter is shown in FIG. The particle counting apparatus 100 includes a casing 110, a pipe 120 provided so as to penetrate the casing 110, a laser light source 130 provided at one end of the casing 110, and a direction perpendicular to the laser light source 130 with respect to the pipe 120. The light detection unit 140 is provided.

  The laser light source 130 irradiates the laser beam B toward the other end side of the housing 110, and a passage hole (not shown) is provided at a location where the laser beam B passes through the pipe 120. ing. Further, openings (not shown) for allowing scattered light to pass through are also provided in a direction perpendicular to the path of the laser beam B in the pipe 120, that is, in the direction of the light detection unit 140. At both ends of the pipe 120, flanges 121 and 122 for attaching the particle counting apparatus 100 to the pipe to be measured are provided.

  The light detection unit 140 includes a large number of photodiodes (light detection elements) 142, and the large number of photodiodes 142 are arranged in parallel to the laser beam B (Patent Document 1).

  The housing 110 and the pipe 120, the laser light source 130 and the light detection unit 140 constitute a measurement head 150. The measuring head 150 is connected to the control unit 160, and a personal computer 170 is further connected to the control unit 160.

  The measurement principle of the particle counter 100 will be described with reference to FIG. A pipe 120 of the particle counter 100 is attached to a pipe to be measured, and a laser beam B is emitted from the laser light source 130 toward the pipe 120. When the particle p flowing in the pipe 120 passes through the optical path of the laser beam B, the particle p scatters the laser light, and the scattered light R is detected by one or a plurality of photodiodes (PD) 142 of the light detection unit 140. The Output signals from the respective photodiodes 142 are constantly observed in the control unit 160, and when the particles p pass through the laser beam B, output signals from several photodiodes 142 are as shown in FIG. A peak indicating the detection of scattered light R appears. When the output signal from each photodiode 142 exceeds a predetermined threshold TH, it is determined that the particle p has passed through the pipe 120 and counted.

JP 2016-065833 A

  As described above, the light detection unit 140 of the particle counting apparatus 100 includes a plurality of photodiodes 142, and a measurement signal is output from each photodiode 142 to the control unit 160. As shown in FIG. 4, the control unit 160 is provided with a signal processing circuit 162 for each channel corresponding to each photodiode 142 (PD01, PD02, PD03,...), And receives a signal from the corresponding photodiode 142. To process. The output of each signal processing circuit 162 is sent to a determination unit 164 provided in the control unit 160, and the determination unit 164 determines whether or not the particle p is detected based on the output from all the signal processing circuits 162.

  As described above, the plurality of signal processing circuits 162 provided in the control unit 160 are provided with the same circuit in order to process the signal from the corresponding photodiode 142. Each circuit includes electrical elements such as resistors and capacitors. Since these electrical elements necessarily have individual differences, even if the same signal is input to the signal processing circuit 162 of each channel, signal processing is performed. Differences may occur in the output from circuit 162. Such an error in the output from the signal processing circuit 162 affects the determination in the determination unit 164 and causes an error in the particle count value.

  The present invention has been made in view of the above points, and an object of the present invention is to eliminate measurement errors between a plurality of channels in a particle counter and to enable accurate particle counting.

The particle counter according to the present invention, which has been made to solve the above problems,
a) a photoelectric conversion unit comprising a plurality of photoelectric conversion elements;
b) a signal processing unit including a signal processing circuit that generates digital output data corresponding to the intensity of the output signal from the output signal of each photoelectric conversion element of the photoelectric conversion unit;
c) a correction data holding unit holding predetermined positive or negative correction data to be added to each digital output data of the plurality of signal processing circuits;
d) A correction unit that adds correction data held by the correction data holding unit to digital output data generated by each signal processing circuit of the signal processing unit.

  In the particle counting device according to the present invention, the difference in digital output data of each signal processing circuit of the signal processing unit when signals of the same intensity are output from the photoelectric conversion elements of the photoelectric conversion unit to the correction data holding unit in advance. The correction value of the digital output data of each photoelectric conversion element created based on this is held. Thereby, the individual difference of each signal processing circuit of the signal processing unit due to various factors can be absorbed, accurate data can be obtained from the output signal of each photoelectric conversion element of the photoelectric conversion unit, and correct particle counting can be performed. .

The correction data to be held in the correction data holding unit can be prepared by the particle counting device of the present invention. That is, the particle counter according to the present invention further includes
e) a correction signal input unit that accepts an external signal to be input to each signal processing circuit of the signal processing unit;
f) an input switching unit that switches an external signal input from the correction signal input unit to an output signal of each photoelectric conversion element of the photoelectric conversion unit and inputs the signal to each signal processing circuit;
g) a correction data generation unit that generates the correction data based on digital output data of each signal processing circuit when an external signal is input to each signal processing circuit by the input switching unit;
h) A correction data writing unit that writes the correction data in the correction data holding unit may be provided.

  In the particle counting device of this aspect, the correction data generation unit and the correction data writing unit may be provided in an external data processing device (for example, a personal computer connected to the particle counting device). It may be provided inside.

  According to the particle counter according to the present invention, since the correction data created in advance is added to the digital output data generated by each signal processing circuit of the signal processing unit, resistors, capacitors, etc. included in each signal processing circuit Therefore, it is possible to absorb the difference in the characteristics of the signal processing circuits due to individual differences of the electric elements, and to correctly measure the outputs from the plurality of photoelectric conversion elements of the photoelectric conversion unit. This eliminates measurement errors between a plurality of channels in the particle counter, and enables accurate particle counting.

The schematic block diagram of the conventional particle counter. Explanatory drawing of the principle of the particle count in the said particle counter. The graph which shows an example of the output signal of the measuring head of a particle coefficient apparatus. The schematic block diagram which shows the structure of each channel of a particle counter. The schematic block diagram of the signal processing system of the 1st Example of the particle counting device which concerns on this invention. The schematic block diagram of the signal processing system of the 2nd Example of the particle counter which concerns on this invention. The graph which compared the count number before and behind the correction | amendment of the particle counter of 1st Example. The flowchart of the correction data creation process in the particle counting device of the 2nd example.

  A first embodiment of the particle counter according to the present invention will be described with reference to FIG. As shown in FIG. 5, the particle counting apparatus of the present embodiment is roughly composed of a measuring head 150, a control unit 160, a personal computer 170, and the like. The configuration of the measuring head 150 is the same as that shown in FIG.

  The measurement head 150 is provided with a predetermined number of photodiodes 142, and each photodiode 142 detects incident light and converts it into an electrical signal. When the laser beam projected on the pipe 120 is scattered by the particles p passing through the pipe 120 and enters one of the photodiodes 142, the photodiode 142 outputs a high detection signal, and the other photodiodes. 142 outputs a low value (background value) as usual.

  The output signals of these photodiodes 142 of the measuring head 150 (shown collectively as one line in FIG. 5) are respectively input to the same number of signal processing circuits 162 provided in the control unit 160. Each signal processing circuit 162 amplifies the signal from each photodiode 142 and quantizes it with a predetermined frequency and resolution to create digital output data. These digital output data created by each signal processing circuit 162 (in FIG. 5, similarly shown as one line. Hereinafter, each photodiode 142 and each signal processing included in these one line) The portion corresponding to the circuit 162 is called a channel.) In the adder 166, correction data of each channel held in the memory 165 is added, and the added data (corrected measurement data) is sent to the determination unit 164. Sent. The determination unit 164 determines whether or not the particle p is detected based on the output from the all signal processing circuit 162. This determination result is sent to the personal computer 170 via the interface 167. The personal computer 170 processes the data sent by a predetermined particle counter data processing program installed in advance and displays it on the display unit 171 in a form that is easy for the user to understand. At this time, in the particle counter according to the present embodiment, the difference in characteristics of each signal processing circuit 162 due to individual differences among the electric elements included in the plurality of signal processing circuits 162 is absorbed, and the signal from the plurality of photodiodes 142 is absorbed. In order to measure the output correctly, accurate particle counting and data processing based on it are possible.

  FIG. 7 is a graph plotting the voltage (scattered light voltage) output from a certain photodiode 142 of the light detection unit 140 and the appearance frequency (count number) within a predetermined time in the particle counter of the present embodiment. Shown in Before correction (broken line), the peak of the count number is around 150 mV, and the count number is very small at a scattered light voltage lower than that, but this does not match the actual situation. Therefore, based on such a graph, the correction data is set to -50 mV and added to the output of the photodiode 142 (that is, by storing such correction data in the memory 165 in advance). As shown in the graph after correction (solid line), the graph can be a graph that matches the actual situation that the count number increases as the scattered light voltage approaches zero.

  In addition to the particle counting function described above, the determination unit 164 of the particle counting device of the present embodiment may have a function (abnormality detection function) for determining whether or not each photodiode 142 is operating normally. it can. That is, since the determination unit 164 constantly monitors the output from each photodiode 142 through each signal processing circuit 162, when the output from any one of the photodiodes 142 is abnormally high, or for an unusual long time. If no output is sent, it can be determined that the photodiode 142 is abnormal. In this case, an alarm device (lamp, buzzer, etc., not shown) provided in the control unit issues an alarm or sends information to that effect to the personal computer 170 via the interface 167 to perform data processing including abnormal data. You can prevent it from happening.

  A second embodiment of the particle counter according to the present invention will be described with reference to FIG. In FIG. 6, elements corresponding to those in FIG. 5 representing the first embodiment are the same or numbered with 2 in the 100s. The basic configuration of the particle counter of this embodiment is the same as that of the first embodiment shown in FIG. 5, but in the particle counter of this embodiment, correction data to be stored in the memory is stored in the control unit 260. It has a function to generate itself. That is, an interface 268 for inputting a signal from an external signal generator such as the function generator 180 (external signal input interface, which corresponds to a correction signal input unit), and the external signal from the photodiode 142 of the measuring head 150. Is provided with a changeover switch 269 (corresponding to an input switching unit) for inputting to each signal processing circuit 262 in place of the signal from, and the determination unit 264 has the following functions.

  Processing for creating correction data in the particle counter of the present embodiment will be described with reference to the flowchart of FIG. First, the user connects the function generator 180 to the external signal input interface 268 of the control unit 260 (step S1). Then, the control unit is switched to the correction value creation mode (step S2). As a result, the selector switch 269 is switched to connect the external signal input interface 268 and each signal processing circuit 262. Further, the adder 266 stops operating. In this state, the user sequentially inputs the signal of the function generator 180 to each signal processing circuit 262 (step S3). The determination unit 264 receives the digital output data from each signal processing circuit 262 as it is and sequentially stores it (step S4). When digital output data from all the signal processing circuits 262 is obtained, correction data for each channel is determined based on all the data (step S5. The determination unit 264 that performs this processing corresponds to the correction data generation unit). ). The determination unit 264 stores the determined correction data in the memory 265 (step S6. The determination unit 264 that performs this process corresponds to the correction data writing unit).

DESCRIPTION OF SYMBOLS 100 ... Particle counter 110 ... Case 120 ... Piping 121, 122 ... Flange 130 ... Laser light source 140 ... Photodetector 142 ... Photodiode 150 ... Measuring head 160, 260 ... Control unit 162, 262 ... Signal processing circuit 164, 264 Determining units 165, 265 ... Memory 166, 266 ... Adders 167, 267 ... Interface 170 ... Personal computer 171 ... Display unit 180 ... Function generator 268 ... External signal input interface 269 ... Changeover switch

Claims (3)

a) a photoelectric conversion unit comprising a plurality of photoelectric conversion elements;
b) a signal processing unit including a signal processing circuit that generates digital output data corresponding to the intensity of the output signal from the output signal of each photoelectric conversion element of the photoelectric conversion unit;
c) a correction data holding unit holding predetermined positive or negative correction data to be added to each digital output data of the plurality of signal processing circuits;
d) A particle counting apparatus comprising: a correction unit that adds correction data held by the correction data holding unit to digital output data generated by each signal processing circuit of the signal processing unit. Furthermore,
e) a correction signal input unit that accepts an external signal to be input to each signal processing circuit of the signal processing unit;
f) an input switching unit that switches an external signal input from the correction signal input unit to an output signal of each photoelectric conversion element of the photoelectric conversion unit and inputs the signal to each signal processing circuit;
g) a correction data generation unit that generates the correction data based on digital output data of each signal processing circuit when an external signal is input to each signal processing circuit by the input switching unit;
The particle counter according to claim 1, further comprising: a correction data writing unit that writes the correction data to the correction data holding unit.   The particle counter according to claim 1, further comprising an abnormality detection unit that detects an abnormality in operation of each photoelectric conversion element based on an output signal of each photoelectric conversion element.

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