JP2012078184A - Pressure measuring device and pressure measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure measuring device and a pressure measuring method capable of measuring with higher reliability.
SOLUTION: A first detection unit 4 having a first resistance element 13 and outputting an electric signal corresponding to a gas pressure; and disposed in proximity to the first detection unit 4; The second detection element 5 having a small second resistance element 14 that outputs an electric signal corresponding to the pressure of the gas, and the output value of the second detection section 5 from the output value of the first detection section 4. And a calculation unit 8 for subtracting and calculating the pressure of the gas.
[Selection] Figure 1

Description

  The present invention relates to a pressure measuring device and a pressure measuring method for measuring pressure based on a heat loss amount.

  In general, it is known to use a Pirani gauge as a detection unit of a pressure measuring device that measures the pressure of a gas. The Pirani gauge is a device including a resistance element made of a thin metal wire provided on a substrate or the like, and is driven by a method generally called constant temperature driving. During constant temperature driving, a voltage is applied to the resistance element, and the element temperature is maintained at a higher setting value than the surrounding gas by Joule heat generation. At this time, since the amount of heat taken by the gas from the resistance element changes according to the pressure of the surrounding gas, the voltage required to maintain the temperature of the resistance element changes. The pressure can be measured from the voltage value at this time.

  Further, in order to obtain a pressure value based on the voltage value output from the resistance element, the pressure measurement device 101 shown in FIG. 5 is obtained from the Pirani vacuum gauge 102 provided with a resistance element (not shown) and the temperature compensation unit 103. The converted voltage value is converted into a signal via the driver 104 and input to the calculation unit 105, and the pressure value is calculated using a mathematical formula stored in the memory 106 provided in the calculation unit 105.

JP 2005-114574 A

  However, in the conventional pressure measuring apparatus 101, in the high vacuum region, the influence of the solid conduction heat amount (heat amount conducted to the wiring board) that does not contribute to the pressure measurement is more dominant than the heat radiation amount from the resistance element to the surrounding gas. If the initial resistance value of the resistive element changes due to changes in the physical temperature of the resistive element due to environmental temperature, heat generation, or changes in the connection resistance with the substrate wiring, the driving conditions such as the temperature setting value of the resistive element during driving change. The amount of conduction heat changes and the pressure measurement accuracy deteriorates. Therefore, it is difficult to obtain a reliable pressure measurement result in a high vacuum region.

  Therefore, an object of the present invention is to provide a pressure measuring device and a pressure measuring method capable of performing measurement with higher reliability.

  In order to achieve the above object, the pressure measuring device according to the embodiment includes a first resistance element, and is disposed close to the first detection unit and a first detection unit that outputs an electrical signal corresponding to the pressure of the gas, A second detection element having a second resistance element having a smaller surface area than the first resistance element and outputting an electrical signal corresponding to the pressure of the gas, and subtracting the output value of the second detection part from the output value of the first detection part And an arithmetic unit for calculating the pressure of the gas.

  Moreover, the pressure measuring method of embodiment is a pressure measuring method using the pressure measuring apparatus of Claim 1 or Claim 2, Comprising: The process of measuring the pressure of gas by a 1st detection part and a 2nd detection part, The calculating unit includes a step of subtracting the output value of the second detection unit from the output value of the first detection unit to calculate the gas pressure.

1 is a schematic diagram of a pressure measuring device according to an embodiment of the present invention. The top view of the detection part and temperature compensation part of the pressure measuring device which concerns on embodiment of this invention. Sectional drawing of the detection part and temperature compensation part of the pressure measuring apparatus which follow the AA line of FIG. The flowchart which shows the pressure measuring method which concerns on embodiment of this invention. Sectional drawing which shows the conventional wiring board.

  Hereinafter, a pressure measuring device and a pressure measuring method capable of measuring with higher reliability according to an embodiment of the present invention will be described in detail with reference to the drawings.

  First, a pressure measuring device according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3.

  FIG. 1 shows a schematic diagram of a pressure measuring device. A pressure measuring device 1 according to this embodiment includes a power supply unit 2, first and second detection units 4 and 5, and first and second temperature compensation units. 6 and 7, a sensing unit 3, a calculation unit 8, and a display unit 9.

  The power supply unit 2 serves to supply power to the sensing unit 3, which is a constant temperature drive circuit including the first and second detection units 4 and 5 and the first and second temperature compensation units 6 and 7.

And the 1st, 2nd detection part 4 and 5 of the sensing part 3 has played the role which outputs the electric signal corresponding to the pressure of gas to the calculating part 8, and uses the Pirani vacuum gauge. Also,
The first and second detection units 4 and 5 are provided with different surface areas of first and second resistance elements 13 and 14 to be described later.

  Further, the first and second temperature compensation units 6 and 7 of the sensing unit 3 change the driving temperature of the first and second resistance elements 13 and 14 by the same amount as the change of the environmental temperature, and the environmental temperature and the temperature of the resistance element. Temperature compensation is performed by keeping the difference constant. In the present embodiment, the first and second temperature compensation units 6 and 7 are used, but may not be used as long as the environment is temperature controlled.

  The first and second detection units 4 and 5 and the first and second temperature compensation units 6 and 7 of this embodiment will be described in more detail. FIG. 2 is a top view of the present embodiment, and FIG. 3 is a cross-sectional view thereof. The first detection unit 4 and the first temperature compensation unit 6 are provided in parallel, and the second detection unit 5 and the second temperature compensation unit 7 are also provided in parallel. And the 1st temperature compensation part 6 and the 2nd detection part 5 are arranged in parallel. In the present embodiment, the first and second detectors 4 and 5 and the first and second temperature compensators 6 and 7 are provided in parallel, and the first temperature compensator 6 and the second detector 6 are provided in parallel. However, the position is not limited to this, and any position may be used as long as the position has the same environmental temperature.

  Next, the configuration of the first and second detection units 4 and 5 will be described. The first and second detection units 4 and 5 include the wiring substrate 10, first and second supports 11 and 12, first and second resistance elements 13 and 14, first and second protective layers 15, 16.

  As the wiring substrate 10, an insulating layer 18 made of SiO is provided on a substrate 17 made of Si, and an Al wiring 19 is further laminated thereon. Note that the material of the wiring substrate 10, the substrate 17, and the wiring 19 used in this embodiment is not limited, and any material may be used.

  The first and second supports 11 and 12 are 1 μm thick and are made of SiN. Further, the first and second supports 11 and 12 support the first and second resistance elements 13 and 14 from the wiring board 10 at a constant interval, for example, 1 μm in the present embodiment, so that each of the first and second support members 11 and 12 supports 6. Two pillars H are provided to form a bridge and support the first and second resistance elements 13 and 14. Of the six pillars H, two pillars H are formed so as to be in contact with the wiring 19 of the wiring substrate 10, which are the first and second resistors formed on the first and second supports 11 and 12. This is because current is supplied to the elements 13 and 14 via the wiring 19. The remaining four pillars H are formed with first and second supports 11 and 12 so as to be in contact with the insulating layer 18. In this embodiment, SiN is used as the first and second supports 11 and 12. However, the present invention is not limited to this, and any material can be used as long as it is an insulator and has high strength and high thermal resistance. Any material may be used.

  The first and second resistance elements 13 and 14 are made of Ti, arranged in a meander shape on the first and second supports 11 and 12, and electrically connected through the two columns H connected to the wiring 19 of the wiring substrate 10. Touching. In addition, the first resistance element 13 has the same electric resistance value as the second resistance element described later by arranging two wirings having a thickness of about 0.3 μm, a width of about 5 μm, and a length of about 3200 μm in parallel. It is designed to be. Further, the vertical width L1 of the first support 11 is about 350 μm, and the horizontal width S1 excluding the column H is about 350 μm. The second resistance element 14 uses wiring having a thickness of 0.3 μm, a width of 5 μm, and a length of 1800 μm. The vertical width L2 of the second support 12 is about 260 μm, and the horizontal width S2 excluding the column H is It is provided to be about 90 μm. In the present embodiment, Ti is used as the first and second resistance elements 13 and 14, but is not limited to this, and any conductive material having a large temperature coefficient of electrical resistance can be used. You may use the thing of such a material. Further, the thickness, width, length, and the like of the first and second resistance elements 13 and 14 are not limited to this, and the surface area of the first resistance element 13 is larger than the surface area of the second resistance element 14, and the electric resistance value. Should be equal.

  The first and second protective layers 15 and 16 are provided so as to cover the first and second resistance elements 13 and 14 in order to prevent the growth of oxide films due to heat generation of the first and second resistance elements 13 and 14. A SiN film having a thickness of 0.5 μm is formed. In this embodiment, SiN is used as the first and second protective layers 15 and 16, but the present invention is not limited to this, and any material can be used as long as it is an insulator and has a high thermal resistance. May be used. Further, the thickness is not limited to this, and may be determined as appropriate.

  Next, the structure of the 1st, 2nd temperature compensation parts 6 and 7 is demonstrated. The first and second temperature compensation units 6 and 7 are provided on the same wiring substrate 10 as the first and second detection units 4 and 5, and the third and fourth support bodies 20 and 21, the third and fourth resistance elements 22. , 23 and the third and fourth protective layers 24, 25 are laminated in this order.

  The third and fourth supports 20 and 21 share a part of the wiring 19 provided with the pillars H of the first and second detectors 4 and 5 with a part of the third and fourth supports 20 and 21. Is formed. Further, like the first and second supports 11 and 12, it is 1 μm thick and is made of SiN. In the present embodiment, the wiring 19 provided with the pillars H of the first and second detection units 4 and 5 is formed so that a part of the third and fourth support bodies 20 and 21 share. However, the present invention is not limited to this and may not be shared.

  Similarly to the first and second resistance elements 13 and 14, the third and fourth resistance elements 22 and 23 are formed of Ti wirings in a meander shape, and are electrically connected to the wiring 19 of the wiring board 10. It is provided so that it may contact. In addition, the third resistance element 22 includes two wires having a thickness of about 0.3 μm, a width of about 5 μm, and a length of about 3200 μm arranged in parallel, and the vertical width of the third support 20 is about 350 μm. The fourth resistance element 23 has a thickness of 300 nm, a width of 5 nm, and a length of 1800 μm, and the fourth support 21 has a vertical width of about 260 μm and a horizontal width of about 350 μm. It is provided to be 90 μm.

  Similarly to the first and second protective layers 15 and 16, the third and fourth protective layers 24 and 25 also prevent the growth of oxide films due to heat generation of the third and fourth resistance elements 22 and 23. It is provided so as to cover the fourth resistance elements 22 and 23, and is formed of SiN having a thickness of 0.5 μm.

  Returning to FIG. 1, the calculation unit 8 will be described next. The calculation unit 8 is a voltage corresponding to the pressure of the gas output from the first detection unit 4 temperature compensated by the first temperature compensation unit 6 and the second detection unit 5 temperature compensated by the second temperature compensation unit 7. The gas pressure is calculated by subtracting the voltage value input from the second detection unit 5 from the voltage value input from the first detection unit 4 and the calculation result is output to the display unit 9.

More specifically, in the calculation unit 8, first, temperature compensation is performed by the first temperature compensation unit 6, the voltage value V _p1 output from the first detection unit 4, and temperature compensation is performed by the second temperature compensation unit 7, Using the voltage value V _p2 output from the detection unit 5, (V _p1 ² −V _p2 ² ) is calculated. This is to obtain a more accurate gas pressure by canceling the influence of the solid conduction heat quantity Q _sol (heat quantity conducted to the wiring board) occupying most of the first and second joule heat quantities Q _t1 and Q _t2. Because.

That is, the amount of Joule heat generated from the first resistance element 13 is Q _t1 , the amount of heat released to the gas is Q _g1 , the amount of radiant heat is Q _r1 , the amount of Joule heat generated from the second resistance element 14 is Q _t2 , and the amount of radiant heat is Q _r2 , and since the materials of the first and second support bodies 11 and 12 supporting the first and second resistance elements 13 and 14 and the shape of the column H are the same, the solid conduction heat quantity is both Q _sol , Since the resistance values of the first and second resistance elements 13 and 14 are the same design value, assuming that R is Joule heat quantity Q _t1 of the first resistance element 13, the following formula (1), Joule heat quantity Q _t2 of the second resistance element 14 Is expressed by the following equation (2).

Q _t1 = V _p1 ² / R = Q _g1 + Q _r1 + Q _sol (1)
Q _t2 = V _p2 ² / R = Q _g2 + Q _r2 + Q _sol (2)
When the Joule heat _{Q t1} of the first resistive element 13 subtracting joule heat _{Q t2} of the second resistive element 14, the following equation (3). Further, the amount of radiant heat is orders of magnitude smaller than the amount of solid conduction heat, and the influence can be ignored.

Q _t1 −Q _t2 = (V _p1 ² −V _p2 ² ) / R = (Q _g1 −Q _g2 ) + (Q _r1 −Q _r2 ) (3)
Q _t1 −Q _t2 = (V _p1 ² −V _p2 ² ) / R = (Q _g1 −Q _g2 ) (4)
From this, since the solid conduction heat quantity Q _sol can be canceled, it is possible to know a more accurate heat release amount to the gas and to derive the gas pressure.

Thereafter, the gas pressure is calculated from a correspondence table between the result of calculating the voltage value (V _p1 ² -V _p2 ² ) and the pressure value input in advance to the calculation unit 8, and the calculation result of the pressure is displayed on the display unit 9. Is output.

  The display unit 9 outputs and displays the calculation result of the gas pressure output from the calculation unit 8 on, for example, a display.

  Next, a pressure measurement method will be described with reference to FIG.

  First, power is supplied from the power supply unit 2 to the sensing unit 3 (step S1).

Next, the first detection unit after temperature compensation is output from the first detection unit 4 that is temperature-compensated by the first temperature compensation unit 6 and the second detection unit 5 that is temperature-compensated by the second temperature compensation unit 7. 4 and the voltage value _{V p1} of inputs a voltage value _{V p2} of the second detecting portion 5 after temperature compensation computing section 8 (step S2).

Thereafter, the calculation unit 8 subtracts the voltage value V _p2 of the second detection unit 5 after temperature correction from the voltage value V _p1 of the first detection unit 4 after temperature correction (V _p1 ² −V _p2 ^2). ) Is calculated (step S3).

Next, a voltage value (V _sp1 ² −V _sp2 ² ) obtained by subtracting the sample voltage value V _sp2 of the second detection unit 5 from the sample voltage value V _sp1 of the first detection unit 4 input in advance to the calculation unit 8. The gas pressure is calculated with reference to the pressure value correspondence table (step S4). And the calculation result of gas pressure is output to the display part 9, and is displayed on the display part 9 (step S5).

As mentioned above, according to this embodiment, the electric signal according to the pressure of the gas output from the 1st, 2nd detection parts 4 and 5 which comprise the sensing part 3, and the 1st, 2nd temperature compensation parts 6 and 7 is comprised. Is input to the calculation unit 8, and the voltage value V _p1 of the first detection unit 4 corrected in temperature by the first temperature compensation unit 6 and the voltage value of the second detection unit 5 compensated for temperature by the second temperature compensation unit 7. By calculating (V _p1 ² -V _p2 ² ) from V _p2 and referring to a correspondence table of pressure values and voltage values (V _sp1 ² -V _sp2 ² ) input in advance to the calculation unit 8, the gas pressure Is calculated. Thereby, the influence of the physical temperature change of the 1st, 2nd resistance elements 13 and 14 of the 1st, 2nd detection parts 4 and 5 and the physical property change by heat_generation | fever can be reduced, and more accurate gas pressure can be derived. It becomes.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1,101 ... Pressure measuring device 2 ... Power supply part 3 ... Sensing part 4 ... 1st detection part 5 ... 2nd detection part 6 ... 1st temperature compensation part 7 ... 2nd temperature compensation part 8, 105 ... Calculation part 9 ... Display Part 10: Wiring board 11 ... First support 12 ... Second support 13 ... First resistance element 14 ... Second resistance element 15 ... First protection layer 16 ... Second protection layer 17 ... Substrate 18 ... Insulating layer 19 ... Wiring 20 ... third support 21 ... fourth support 22 ... third resistance element 23 ... fourth resistance element 24 ... third protection layer 25 ... fourth protection layer H ... pillars L1, L2 ... vertical widths S1, S2 ... Width 102 ... Pirani vacuum gauge 103 ... Temperature compensation unit 104 ... Driver 106 ... Memory

Claims (4)

A first detector having a first resistance element and outputting an electrical signal corresponding to the pressure of the gas;
A second detection unit disposed adjacent to the first detection unit, having a second resistance element having a smaller surface area than the first resistance element, and outputting an electrical signal corresponding to the pressure of the gas;
A calculation unit that calculates the pressure of the gas by subtracting the output value of the second detection unit from the output value of the first detection unit;
A pressure measuring device comprising:   In addition, a first temperature compensation unit that is disposed in proximity to the first detection unit and performs temperature compensation of the first detection unit, and a first temperature compensation unit that is disposed in proximity to the second detection unit and performs temperature compensation of the second detection unit. The pressure measuring device according to claim 1, comprising at least one of the two temperature compensation units. A pressure measuring method using the pressure measuring device according to claim 1 or 2,
Measuring the pressure of the gas by the first detector and the second detector;
Calculating the pressure of the gas by subtracting the output value of the second detection unit from the output value of the first detection unit in the calculation unit;
A pressure measuring method characterized by comprising:   Further, the method includes at least one of a step of performing temperature compensation of the first detection unit by the first temperature compensation unit and a step of performing temperature compensation of the second detection unit by the second temperature compensation unit. The pressure measurement method according to claim 3.

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