JP4960055B2 - Contamination measurement method - Google Patents

Description

The present invention relates to how you measure the presence or dusting of contamination such as dust contained in the atmosphere in the closed space such as a clean room.

  Currently, in the manufacturing process of semiconductor elements and precision equipment and in the medical field, contaminants such as fine dust contained in the atmosphere inside the space and contamination impurities caused by acid and base molecules in the atmosphere are forcibly removed. Thus, so-called clean rooms with high atmosphere cleanliness are often used. Recently, a super clean room with the cleanliness raised to the limit has come to be used, and the measurement management of contamination contained in the atmosphere in the space is regarded as important.

  Conventionally, the following method has been used as a method for measuring the contamination in such an atmosphere. First, a certain amount of the atmosphere in the space where the contamination measurement is desired is sampled, the sampled atmosphere is passed through various filters, the contamination corresponding to each filter is collected, and the contamination in the filter is extracted into the solution. Analyze the components and measure the quantity using a particle counter.

  Another measurement method is to use laser light and scan the sample atmosphere with the laser light. If there is contamination such as dust in the atmosphere, the laser light hits the contamination and the scattered light. Is generated. A method is also used in which the scattered light is detected by a CCD camera, and the total amount of contamination in the measured space is derived by calculation based on the number of scattered light detected from the sample.

Contamination measurement methods as described above are disclosed in the following prior art documents.
JP 2000-180348 A JP-A-7-209146 Japanese Patent Laid-Open No. 7-229826

  In addition, the applicant has not found any prior art documents related to the present invention by the time of filing of the present application other than the prior art documents specified by the above prior art document information.

  However, the contamination measurement method as described above is effective for measuring the content and amount of contamination, but an atmospheric sample containing the contamination is collected and the sample is applied to an analyzer to measure the contamination. Therefore, it takes time to obtain measurement results, and it is difficult to immediately measure the presence or absence of contamination. In addition, in the measurement method using a laser, the measurement system itself needs to be incorporated in a clean room or the like in advance, and the measurement system becomes large-scale, which may lead to an increase in cost and complexity of the measurement itself.

The present invention has been made to solve the above problems, and in a method for measuring the presence or absence of contamination in a measured atmosphere, the piezoelectric vibration element is lower than the measured atmosphere in the measured atmosphere. Shutter means that is mounted in a space inside a container that is airtightly sealed with atmospheric pressure, forms external connection terminals that are electrically connected to excitation electrodes formed on the front and back main surfaces of the piezoelectric vibration element, and blocks the inside and outside of the container And a step A for preparing a measurement terminal body having a control unit for controlling the opening / closing mode of the shutter means, and a measurement terminal body in which a piezoelectric vibration element is mounted and the shutter means is closed to make the space in the container airtight. At least one or more terminals are arranged in the measurement atmosphere, and the external connection terminal and the predetermined terminal of the control unit are electrically connected to the measurement control analysis processing electronic device and / or electronic computer. Degree and B, by connecting the electronic device and / or computer, a piezoelectric vibrating element of the measuring device body, the drive current value of the piezoelectric vibrating element as a reference - a step C of measuring the characteristic data values between the crystal impedance value, A control signal is input from the connected electronic device or / and the electronic computer to the control unit, the shutter means is opened, and the process D for causing the measured atmosphere to flow into the measurement terminal body, and after a predetermined time, the connected electronic device or / and the electronic computer, from the piezoelectric vibrating element of the measuring device body, compared drive current value subject to the piezoelectric vibrating element - a and step E of determining characteristic data values between the crystal impedance value, the reference obtained in the step C piezoelectric drive current value of the vibration element characteristics - and data values between the crystal impedance value, the piezoelectric to be compared obtained in the step (E) Drive current value of the dynamic element - comparatively analyzed the characteristic data values between the crystal impedance value, characterized by including a determining step F whether tangible contaminants into the atmosphere to be measured from the difference of the data value This is a contamination measuring method.

  In the method for measuring contamination according to the present invention, when a substance adheres to the surface, a measurement terminal in which a measurement terminal is arranged by the action of a piezoelectric vibration element whose characteristics such as resonance frequency and crystal impedance (hereinafter referred to as CI) value change. Because it is possible to immediately detect changes in characteristics when contamination such as dust in the atmosphere and contamination impurities due to acid and base molecules in the atmosphere adhere to the surface of the piezoelectric vibration element in the measurement terminal. The presence and occurrence of contamination can be measured in real time.

  In addition, the size of the measurement terminal body is a size of a roughly rectangular parallelepiped of several centimeters, and a plurality of measurement terminal bodies can be arranged in the measurement space, so that the measurement configuration can be made smaller than before. Therefore, the cost of the measurement itself can be reduced and simplified, and the measurement terminal body is small, so that it is possible to measure the contamination in the atmosphere in the narrow space in the manufacturing apparatus for semiconductor elements and the like. .

  In addition, since the piezoelectric vibration element for detecting contamination is mechanically vibrated, the contamination attached to the surface of the piezoelectric vibration element can be removed by higher vibration by increasing the vibration level. Therefore, the measurement terminal can be reused.

  Therefore, according to the present invention, there is provided a contamination measuring method that can immediately measure the presence / absence or occurrence of contamination in the atmosphere in the space desired to be measured, and that can be easily formed on a small scale and at low cost. There is an effect that can be done.

Hereinafter, an embodiment of a method for measuring contamination according to the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a measurement system used in a contamination measurement method according to the present invention. FIG. 2 illustrates the measurement terminal body shown in FIG. 1, (a) is a plan view of the half viewed from the opening forming surface side, and the other half is an internal structure diagram. It is sectional drawing at the time of cut | disconnecting between the virtual cutting lines AA 'of (a) description. FIG. 3 is a characteristic graph between the drive current and the CI value, showing the change in the characteristics of the piezoelectric vibration element when contamination adheres to the piezoelectric vibration element in the measurement terminal. The form of the change is shown in FIG. It is the graph shown to (b) and (c).
In each of the drawings, a part of the structure is not shown, and some dimensions are exaggerated for the sake of clarity. In particular, the thickness dimension of each part is exaggerated.

  First, the measurement terminal body 20 used for the contamination measuring method in the present invention will be described. The inside of the container body 22 constituting the measurement terminal body 20 is hermetically sealed at a lower pressure than the atmosphere to be measured in the space to be measured 10 in the state before measurement, and the main space in the container body 22 has a substantially circular main shape. A plate-like piezoelectric vibration element 21 having a surface outer shape is mounted. In the present embodiment, an example using a crystal as a piezoelectric material constituting the piezoelectric vibration element is illustrated.

  Excitation electrodes 23 having a circular outer shape concentric with the piezoelectric vibration element 21 are formed on the front and back main surfaces of the piezoelectric vibration element 21, and directions different from each excitation electrode 23 by 180 ° between the front and back main surfaces. An extraction electrode 24 extending toward the edge of the piezoelectric vibration element 21 is formed, and the two extraction electrodes 24 are made of metal and are opposed to each other with the piezoelectric vibration element 21 interposed therebetween. At the same time as being electrically connected to each support portion 25, a part of the outer peripheral edge portion of the piezoelectric vibration element 21 is fitted into the slit portion 26 provided in each support portion 25, thereby the piezoelectric vibration element 21. Is held at a predetermined position in the container body 22. The support portion 25 is led out of the container body 22 via a support portion base 27 in the container body 22 and connected to the element connection electrode terminal.

  For example, in the case where crystal is used as the piezoelectric material, the piezoelectric vibration element 21 has a pair of excitation elements as described above on both main surfaces of a circular flat plate crystal piece cut and polished from a crystal crystal at a so-called AT cut angle. When the electrode 23 is deposited and an alternating voltage from the outside is applied to the crystal piece via the pair of excitation electrodes 23, vibration with the thickness-shear vibration mode as the main vibration occurs at a predetermined frequency.

  In the container body 22 in which the piezoelectric vibration element 21 as described above is mounted, a plane of the container body 22 facing one main surface of the piezoelectric vibration element 21 is concentric with the piezoelectric vibration element 21 and excited. An opening 28 having substantially the same size as the electrode 23 is formed. On the inner surface of the container body 22 in the vicinity of the opening 28, shutter means 29 for blocking the inside and outside of the container body 22 by closing the opening 28. Is provided. The container body 22 is also provided with a control unit 30 for controlling the opening / closing mode of the shutter means 29. The control signal electrode terminal provided in the control unit 30 for inputting and outputting the control signal for controlling the element connecting electrode terminal and the shutter means 29 is an electrode terminal unit 31 provided in the container body 22. It is the form put together in one set.

Hereinafter, a method for measuring contamination using the measurement terminal body 20 described above will be described.
First, as the process A, a plurality of measurement terminal bodies 20 are prepared.
Next, as step B, the shutter unit 29 is placed in the measurement atmosphere in the measurement space 10 where there is a concern about the occurrence of contamination of a plurality of measurement terminal bodies 20 having the above-described form, such as a clean room. The space inside the container body 22 of the measurement terminal body 20 is hermetically sealed, and the electrode terminal unit 31 is electrically connected to an electronic computer 40 for measurement control analysis processing provided outside the space to be measured 10. To do. In this embodiment, the signal cords connected to the electrode terminal units of the plurality of measurement terminals 20 arranged in the measured space 10 are all connected to the relay unit 11 provided in the measured space 10. A form in which another signal cord is connected from the relay unit 11 to the outside of the measured space 10 is used.

  Next, as step C, the excitation drive current value applied to the piezoelectric vibration element 21 of the piezoelectric vibration element 21 in each measurement terminal body 20 is swept from 10 μA to 1 mA by the connected electronic computer 40, and further from 1 mA. Measure CI value data when swept to 10 μA. The characteristic data acquired at this time is a reference characteristic data value when the contamination is not attached to the piezoelectric vibration element.

  Next, as step D, a control signal is input from the connected electronic computer 40 to the control unit 30 of each measurement terminal body 20, the shutter means 29 is opened, and the measurement atmosphere in the measurement space 10 is changed to the measurement terminal body 20. It flows into the container body 22. Since the pressure inside the container before the opening of the shutter means 29 is set slightly lower than the pressure inside the measured space 10 outside the container body, the measured atmosphere in the measured space 10 varies as soon as the shutter means 29 opens. If the measurement terminal body 20 automatically flows into the container body 22 and contamination is contained in the atmosphere to be measured, the measurement terminal body 20 enters the container body 22 together with the flowing gas, and enters the container body 22. It will adhere to the surface of the mounted piezoelectric vibration element 21.

  Next, as step E, after opening the shutter means 29, the connected electronic computer 40 applies the piezoelectric vibration element 21 in each measurement terminal body 20 arranged at various locations in the measured space 10 to the piezoelectric vibration element 21. CI value data when the excitation drive current value to be swept from 10 μA to 1 mA is swept from 1 mA to 10 μA is measured as needed.

  Next, in step F, the measurement characteristic data acquired in step E and the reference characteristic data measured when the shutter unit 29 is closed are compared and analyzed in real time. At this time, if there is no difference between the measured characteristic data and the reference characteristic data, there is no contamination in the measured atmosphere in the measured space 10. However, when there is contamination in the measured atmosphere in the measured space 10 and it adheres to the piezoelectric vibration element 21 in the measurement terminal body 20, the adhered contamination inhibits the vibration of the piezoelectric vibration element 21. Thus, there is a difference between the characteristic data as described in each graph of FIG. Due to the difference between the characteristic data, it is determined that contamination exists in the measured atmosphere in the measured space 10.

  In addition, the measurement terminal body 20 with the shutter means 29 opened is placed in the measured space 10 and the above characteristic data is continuously acquired, so that the contamination in the measured space 10 for some reason. In the case where the nation has occurred, the contamination adheres to the piezoelectric vibration element 21 in the measurement terminal body 20, so that the acquired characteristic data changes, and the occurrence of contamination on the electronic computer 40 occurs. Can be notified in real time.

  In addition, this invention is not limited to the above-mentioned embodiment, A various change, improvement, etc. are possible in the range which does not deviate from the summary of this invention. For example, in the above-described embodiment, the measurement terminal body using crystal as the piezoelectric material constituting the piezoelectric vibration element has been described. However, as the piezoelectric material, lithium niobate, lithium tantalate, or piezoelectric ceramics is used. It doesn't matter what you have. In addition, as the characteristic data acquired from the piezoelectric vibration element, the characteristic data between the excitation drive current value and the crystal impedance value is used. In addition, the characteristic data between the excitation drive current value and the resonance frequency value, and the resonance frequency value − Even if the characteristic data between the equivalent reactance values is used, the same effect as the present invention can be obtained. Furthermore, in the above-described embodiment, a form using an electronic computer as an apparatus for measuring and analyzing the characteristic data of each measurement terminal body has been disclosed. However, in the case where an electronic device such as an impedance analyzer or a network analyzer is used instead of the electronic computer Alternatively, a measurement system constructed by combining these electronic devices and electronic computers may be used.

FIG. 1 is a configuration diagram of a measurement system used in a contamination measurement method according to the present invention. FIG. 2 illustrates the measurement terminal body shown in FIG. 1, (a) is a plan view of the half viewed from the opening forming surface side, and the other half is an internal structure diagram. It is sectional drawing at the time of cut | disconnecting between the virtual cutting lines AA 'of (a) description. FIG. 3 is a characteristic graph between the drive current and the CI value, showing the change in the characteristics of the piezoelectric vibration element when contamination adheres to the piezoelectric vibration element in the measurement terminal. The form of the change is shown in FIG. It is the graph shown to (b) and (c).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Measuring space 20 ... Measurement terminal body 21 ... Piezoelectric vibration element 22 ... Container body 23 ... Excitation electrode 24 ... Extraction electrode 25 ... Support part 26 ... Slit part 27 ... Supporting part base 28 ... Opening part 29 ... Shutter means 30 ... Control part 31 ... Electrode terminal unit 40 ... Computer

Claims (1)

In a method for measuring the presence or occurrence of contamination in the atmosphere to be measured,
A piezoelectric vibration element is mounted in a space in a container hermetically sealed at a lower air pressure than the measurement atmosphere in the measurement atmosphere, and is electrically connected to the excitation electrodes respectively formed on the front and back main surfaces of the piezoelectric vibration element. Step A of preparing a measurement terminal body having a shutter means for forming an external connection terminal to be connected and blocking the inside and outside of the container and a control unit for controlling the opening / closing mode of the shutter means;
At least one or more measurement terminal bodies each having a piezoelectric vibration element mounted therein and the shutter means closed and the space inside the container being hermetically sealed are disposed in the atmosphere to be measured, and the external connection terminal and the predetermined control unit Step B for electrically connecting the terminal to an electronic device or / and an electronic computer for measurement control analysis processing;
A step C of measuring a characteristic data value between a drive current value and a crystal impedance value of a reference piezoelectric vibration element from the piezoelectric vibration element in the measurement terminal by a connected electronic device or / and an electronic computer;
A step D of inputting a control signal to the control unit from the connected electronic device or / and electronic computer, opening the shutter means, and allowing the atmosphere to be measured to flow into the measurement terminal body;
A step of measuring a characteristic data value between a drive current value and a crystal impedance value of a piezoelectric vibration element to be compared from the piezoelectric vibration element in the measurement terminal by a connected electronic device or / and electronic computer after a predetermined time. E and
Drive current value of the piezoelectric vibrating element as a reference obtained in the step C - and the characteristic data values between the crystal impedance value, the drive current value of the piezoelectric vibrating elements to be compared obtained in the step E - between the crystal impedance value of A method of measuring contamination, comprising: a step F of comparing and analyzing characteristic data values and determining the presence or absence of a tangible contaminant in the atmosphere to be measured from the difference between the data values.

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