JPH10318921A - Fluid concentration measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accuracy in measuring concentration by suppressing temperature rise caused by the irradiation of light from a light source on the side of a reference medium and to avoid adverse effects caused by scattered light. SOLUTION: A sample cell 11 interposed in a treat water supplying piping 6 and a reference cell 12 arranged in the proximity of the sample cell 11 are irradiated selectively via a switching means 15 with irradiation light from a light source 13 branched via a light branching means 14. The light transmitted through the sample cell 11 and the reference cell 12 is entered into a light detector 17 to measure the concentration of a sample fluid on the basis of a ratio between both intensity of the transmitted light. The first shutter 27 to switch the switching means 15 between in the state of transmitting light and in the state of blocking light by the first air cylinder 26 is provided between the light branching means 14 and the sample cell 11, and the second shutter 29 to switch the switching means 15 between in the state of transmitting light and in the state of blocking light by the second air cylinder 28 is provided between the light branching means 14 and the reference cell 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid concentration measuring device for measuring the concentration of various kinds of fluids such as a treatment solution obtained by mixing a chemical solution and pure water or a chemical solution for treating a substrate such as a semiconductor wafer.

[0002]

2. Description of the Related Art Conventionally, this type of fluid concentration measuring apparatus has been generally configured as shown in a schematic configuration diagram of FIG.

That is, light from one light source 01 is transmitted via a light branching unit 04 to a sample cell 02 provided in a pipe through which a fluid (eg, a chemical solution) as a sample flows and a reference cell 03 as a reference medium. Irradiated and further transmitted through the sample cell 02 and the reference cell 03,
5 so as to be incident on one photodetector 06.

An optical path switching means 7 is provided between each of the sample cell 02 and the reference cell 03 and the optical coupling means 05,
The configuration is such that the transmitted light 03 of the sample cell 02 and the transmitted light of the reference medium are alternately incident on the photodetector 06.

[0005] The photodetector 06 detects the light transmitted through the sample cell 02 and the reference cell 03 and outputs a signal corresponding to the light intensity. Then, the signal is processed by a computer (not shown) connected to the photodetector 06, and the sample cell 02
And a reference cell 03 to calculate the transmittance based on the ratio of the transmitted light intensity to the reference cell 03, and to measure the concentration of the fluid as a sample based on the transmittance.

[0006]

However, in the conventional example, since the branched light is constantly irradiated on the sample cell 02 and the reference cell 03, there are the following disadvantages.
That is, a fluid, which is a new sample, is constantly flowing in the sample cell 02, but there is no such change in the reference cell 03. Therefore, on the reference cell 03 side, the temperature rises due to the constant irradiation of light, the extinction coefficient changes, the basic data itself on the reference cell 03 side fluctuates, and the measurement accuracy of the concentration decreases.

[0007] Each of the sample cell 02 and the reference cell 03 is connected to each of the optical branching means 04 and the optical coupling means 05 by an optical fiber. The cell 02 and the reference cell 03 are often arranged close to each other. When scattered light is generated in each of the sample cell 02 and the reference cell 03, the scattered light from one cell is incident on the other cell, and there is a disadvantage that the measurement accuracy of the concentration is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and it is possible to suppress the temperature rise on the reference medium side due to the irradiation of light from the light source and improve the measurement accuracy of the density. It is another object of the present invention to avoid adverse effects due to scattered light. It is also an object of the present invention to increase the degree of freedom in design and achieve it with an inexpensive configuration, and to improve the concentration measurement accuracy and to perform the measurement process efficiently.

[0009]

The invention according to claim 1 is
In order to achieve the above object, a fluid concentration measurement device that measures the concentration of a fluid that is a sample, a sample cell provided in a pipe through which the fluid flows, and a reference medium having a constant extinction coefficient, A light source that irradiates the sample cell and the reference medium with light, a light branching unit that branches light from the light source into the sample cell side and the reference medium side, and detects light transmitted through the sample cell. A light detecting means for outputting a first signal and detecting a light transmitted through the reference medium and outputting a second signal; and measuring a transmitted light intensity of the sample cell based on the first signal. And a transmitted light intensity measuring means for measuring a transmitted light intensity of the reference medium based on the second signal, and a transmittance based on a ratio of a transmitted light intensity of the sample cell to a transmitted light intensity of the reference medium. Calculate,
Concentration calculating means for calculating the concentration of the fluid based on the transmittance; and a light detecting means provided between the light branching means, the sample cell and the reference medium, and transmitting light detected by the light detecting means through the sample cell. Switching means for switching between the transmitted light and the light transmitted through the reference medium.

According to a second aspect of the present invention, in the fluid concentration measuring apparatus according to the first aspect, the switching means includes a first shutter provided between the light branching means and the sample cell. , A second shutter provided between the light splitting means and the reference medium.

According to a third aspect of the present invention, in the fluid concentration measuring device according to the first or second aspect, the switching means is configured to transmit light to one of the sample cell and the reference medium. The time from when the irradiation is set to zero to when irradiation to the other side is started is set to 1 to 3 seconds.

[0012]

According to the configuration of the first aspect of the invention, when the light detecting means detects the light transmitted through the sample cell, the light applied to the reference medium is blocked, and the light transmitted through the reference medium is blocked. When the light detecting means detects, since the switching means for blocking the light irradiated to the sample cell is provided between the light branching means and the sample cell and the reference medium, any one of the sample cell and the reference medium is used. One side is irradiated with light from the light source, and the influence of scattered light from the other side is eliminated.

According to the second aspect of the present invention, the first shutter provided between the light splitting means and the sample cell, and the second shutter provided between the light splitting means and the reference medium.
The light detected by the light detecting means is switched between the light transmitted through the sample cell and the light transmitted through the reference medium in an individual configuration by the shutter.

According to the third aspect of the present invention, the switching means changes the state from zero light irradiation to one of the sample cell and the reference medium to starting irradiation to the other side. Is set to 1 to 3 seconds, the photodetector is reliably returned to the initial state, and the time required for concentration measurement is reduced.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a substrate processing apparatus using an embodiment of a fluid concentration measuring apparatus according to the present invention, in which a wafer carrier (not shown) containing a plurality of substrates such as semiconductor wafers is immersed. An overflow tank 2 for retaining the processing solution overflowing from the processing tank 1 is provided around the processing tank 1.

A pure water supply source (not shown) is connected to the processing tank 1 via a pure water supply pipe 3 provided with a first flow control valve V1.
Is connected, and pure water is supplied into the processing tank 1 at a predetermined pressure. On the other hand, a chemical liquid tank 5 is connected to the overflow tank 2 via a chemical liquid supply pipe 4 provided with a second flow control valve V2, so that a predetermined amount of the chemical liquid can be supplied into the overflow tank 2. .

The bottom of the processing tank 1 and the overflow tank 2 are connected via a processing liquid supply pipe 6 for circulating the remaining processing liquid. The processing liquid supply pipe 6 includes a pump 7 for circulating the processing liquid, a heater 8 for heating the circulating processing liquid, a temperature sensor 9 for measuring the temperature of the processing liquid, and a circulating processing liquid. A filter 10 for removing particles and the like in the liquid is interposed.

With the above structure, a chemical solution and pure water are mixed and adjusted at a predetermined ratio according to the purpose, and a substrate such as a semiconductor wafer is immersed in the processing liquid (fluid as a sample) having the predetermined concentration. This allows the substrate to be cleaned.

Next, the fluid concentration measuring device will be described. That is, the sample cell 11 is interposed between the filter 10 and the processing tank 1 in the processing liquid supply pipe 6, and the reference cell 1 filled with pure water is provided near the sample cell 11.
2 are arranged in close proximity. Sample cell 11 and reference cell 12
Are configured to have the same optical path length.

Irradiation light from a light source 13 such as a halogen lamp is branched via a light branching means 14, and the branched irradiation light is selectively irradiated on a sample cell 11 and a reference cell 12 via a switching means 15. It is supposed to be.

The light transmitted through the sample cell 11 and the reference cell 12 enters a light detector 17 as light detecting means via a light guide 16, and the light detector 17 corresponds to the light transmitted through the sample cell 11. The first signal and the reference cell 12
The microcomputer 18 outputs a second signal corresponding to the light transmitted through the microcomputer 18 to the microcomputer 18.

The microcomputer 18 includes a transmitted light intensity measurement unit 19, a density calculation unit 20, an optical path switching control unit 21, a temperature control unit 30, a feedback control unit 31, and a supply amount control unit 32.

In the transmitted light intensity measuring section 19, the first signal and the second signal from the photodetector 17 are inputted at a predetermined timing in response to the switching signal from the optical path switching control section 21, and based on the signals, , The transmitted light intensity of the light transmitted through each of the sample cell 11 and the reference cell 12 is measured. The concentration calculator 20 calculates the transmittance based on the ratio of the transmitted light intensity of the sample cell 11 to the transmitted light intensity of the reference cell 12, and calculates and measures the concentration of the processing liquid based on the transmittance. .

As shown in FIG. 2, the light branching means 14 converts the light emitted from the light source 13 into parallel light.
And the first and second condenser lenses 14b and 14c for splitting the irradiation light from the first collimator lens 14a into two.

First and second condenser lenses 14b, 14
The light branched by the first and second optical fibers 2
2a, 22b and second and third collimator lenses 2
Sample cell 11 and reference cell 1 via 3a and 23b
2 is irradiated.

The transmitted light from the sample cell 11 and the reference cell 12 is transmitted to the third and fourth condenser lenses 24a and 24a.
4b, and third and fourth optical fibers 25a, 25b
Then, the light is incident on the light guide 16.

The switching means 15 includes a first condenser lens 14b.
A first shutter 27 for switching between a transmission state and a light-shielding state by a first air cylinder 26 is provided between the second condenser lens 14 c and the reference cell 12. A second shutter 29 is provided for switching between a transmission state and a light shielding state by two air cylinders 28.

The light detector 17 is, for example, GaP or PbS
And GaAsP. The first and second photoelectric conversion elements are used to enhance the operation stability.
The air cylinders 26 and 28 are operated by a switching signal from the optical path switching control unit 21. The operation will be described below with reference to a time chart of FIG.

First, an opening signal is output to the first air cylinder 26, the first shutter 27 is opened by shortening the stroke end, and light from the light source 13 is irradiated only on the sample cell 11 side. Next, the first signal D1 is output after waiting for one second so that the operation of the photodetector 17 is stabilized, and the maximum light intensity in the subsequent one second is transmitted from the photodetector 17 to the transmitted light intensity measurement unit 19. take in. After a lapse of two seconds from opening the first shutter 27, a closing signal is output to the first air cylinder 26 to extend the stroke to the end of the stroke and close the first shutter 27.

After that, in order to eliminate the influence of the light transmitted through the sample cell 11, an open signal is output to the second air cylinder 28 after waiting for one second so that the photodetector 17 returns to the initial state without fail. , The second shutter 27 is opened to the end of the stroke, and the light source 1 is placed only on the reference cell 12 side.
The light from 3 is irradiated. Next, the second signal D2 is output after waiting for one second so that the operation of the photodetector 17 is stabilized, and the maximum light intensity in the subsequent one second is transmitted from the photodetector 17 to the transmitted light intensity measurement unit 19. take in. Second shutter 2
After a lapse of 2 seconds from the opening of the shutter 9, a closing signal is output to the second air cylinder 28, the stroke is extended to the stroke end, and the second shutter 29 is closed. After that, in order to eliminate the influence of the light transmitted through the reference cell 12, the light detector 17 is used.
Waits for one second to ensure that the sample cell returns to the initial state, and then outputs an open signal to the first air cylinder 28, and the sample cell 1
Light from the light source 13 is irradiated only on one side.

These operations are repeated, and the intensity of the light transmitted through the sample cell 11 and the intensity of the light transmitted through the reference cell 12 are taken every three seconds. The concentration of the treatment liquid is calculated and measured by the concentration calculator 20 based on the transmitted light intensity of the reference cell 12.

The temperature control section 30 compares the temperature measured by the temperature sensor 9 with the target temperature while circulating the processing liquid, and turns ON / OFF the heater 8 based on the comparison result.
Then, the temperature of the processing liquid can be maintained at the target temperature.

After the transmitted light intensity measuring section 19 confirms that the temperature of the processing liquid has reached a predetermined temperature, the optical path switching control section 21
And an open signal and a close signal are output from the optical path switching control unit 21 to the first and second air cylinders 26 and 28 at the above-described timing, and the concentration of the processing liquid is calculated and measured. ing.

The feedback controller 31 stores a target concentration set in advance by an input means (not shown), and circulates the processing liquid from the overflow tank 2 to the processing tank 1 through the processing liquid supply pipe 6 by the pump 7. Meanwhile, the target density is compared with the density calculated by the density calculation unit 20, and a control signal corresponding to the difference is output to the supply amount control unit 32.

The supply amount control unit 32 adjusts the first flow control valve V1 of the pure water supply pipe 3 or the second flow control valve V2 of the chemical liquid supply pipe 4 in accordance with a signal from the feedback control unit 31, The concentration of the processing liquid in the processing layer 1 is adjusted.
By repeating these operations, the concentration of the processing liquid can be adjusted to the target concentration.

FIG. 4 is a block diagram showing a schematic configuration of another substrate processing apparatus to which the fluid concentration measuring apparatus according to the present invention is applied. The difference from the previous substrate processing apparatus is as follows.

A pure water supply source (not shown) is connected to the processing liquid supply pipe 33 via a pure water supply pipe 34 provided with a third flow control valve V3, and pure water is supplied at a predetermined pressure. It has become so. Further, a plurality of chemical liquid tanks 35a, 35b, 35c are provided in the processing liquid supply pipe 33 in the fourth and fifth chemical liquid tanks.
And chemical liquid pipes 36a, 36b, 36c provided with sixth flow control valves V4, V5, V6 interposed therebetween, and a predetermined chemical liquid is selected and mixed with pure water to be adjusted to a predetermined temperature and a predetermined concentration. The processing liquid is supplied to the processing tank 1. A drain pipe 37 is connected to the overflow tank 2.

From the supply amount control unit 32, the third flow control valve V3, the fourth, fifth and sixth flow control valves V4, V
5, a signal is output to a predetermined one of V6, and the concentration of the processing liquid can be adjusted to the target concentration. The configuration of the fluid concentration measuring device and other configurations are the same as those of the above-described substrate processing device, and the same reference numerals are assigned and the description is omitted.

The light source 13 is not limited to a halogen lamp that emits infrared rays, but may be a deuterium lamp or a xenon lamp that emits ultraviolet rays.

The present invention is not limited to the case of measuring the concentration of a substrate processing solution composed of pure water and a chemical solution, that is, a gas such as a nitrogen oxide NOx or a sulfur oxide SOx. It is applicable when measuring the concentration of various fluids.

In the above embodiment, after the irradiation of the light to one of the sample cell 11 and the reference cell 12 is stopped,
The time until the start of light irradiation on the other side is set to one second, but this time may be set as appropriate. From the viewpoint of measurement accuracy and measurement processing efficiency, it is preferable to set the time within 1 second or more and within 3 seconds.

In the above embodiment, the reference cell 12 filled with pure water is used. In other words, for example, an optical filter having a predetermined extinction coefficient is used. These are collectively referred to as a reference medium.

[0043]

As apparent from the above description, according to the first aspect of the present invention, since the switching means is provided between the optical branching means and the sample cell and the reference medium, the switching means is provided on the sample cell side. When light is irradiated, the reference medium side is not irradiated with light, but is intermittently irradiated so as to irradiate the reference medium only when necessary. The temperature rise can be suppressed, and the measurement accuracy of the concentration can be improved. In addition, since light is emitted to only one of the sample cell and the reference medium, even if the configuration is such that scattered light is generated in each of the sample cell and the reference medium, it is not affected by the scattered light. In addition, there is an advantage that a light-shielding structure for avoiding the influence of scattered light can be made unnecessary and the structure can be simplified.

According to the second aspect of the present invention, for example, if an attempt is made to provide a light transmission opening of a predetermined length in a rotary plate or a slide plate that moves in a linear direction, the timing of switching the light transmission state can be improved. However, since the position of the sample cell and the reference medium must be restricted, the first and second shutters are individually configured, so that there are few restrictions on the mounting surface and the control surface as described above. The object of the invention according to claim 1 can be achieved with an inexpensive configuration by increasing the degree of freedom in design.

According to the third aspect of the present invention, the state in which the light transmitted through both the sample cell and the reference medium is not incident on the light detecting means is maintained for one second or more, so that the light detecting means is returned to the initial state. After that, the light transmitted through each of the sample cell and the reference medium can be incident to measure the light intensity, and the concentration measurement accuracy can be improved. Further, since the state in which light transmitted through either the sample cell or the reference medium is not incident on the photodetector is set to 3 seconds or less, the time required for concentration measurement can be reduced, and the measurement process can be performed efficiently.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a substrate processing apparatus using an embodiment of a fluid concentration measuring apparatus according to the present invention.

FIG. 2 is a configuration diagram of a main part.

FIG. 3 is a time chart illustrating an operation of an optical path switching control unit.

FIG. 4 is a block diagram showing a schematic configuration of another substrate processing apparatus to which the fluid concentration measuring device according to the present invention is applied.

FIG. 5 is a schematic configuration diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Sample cell 12 ... Reference cell (reference medium) 13 ... Light source 14 ... Light splitting means 15 ... Switching means 17 ... Photodetector (light detection means) 27 ... 1st shutter 29 ... 2nd shutter

Claims (3)

[Claims] 1. A fluid concentration measuring device for measuring the concentration of a fluid as a sample, comprising: a sample cell provided in a pipe through which the fluid flows; a reference medium having a constant extinction coefficient; A light source that irradiates light to a medium; a light branching unit that branches light from the light source to the sample cell side and the reference medium side; and detects light transmitted through the sample cell to generate a first signal. A light detecting means for outputting light, detecting light transmitted through the reference medium and outputting a second signal, and measuring a transmitted light intensity of the sample cell based on the first signal; Transmitted light intensity measuring means for measuring the transmitted light intensity of the reference medium based on the signal of, the transmittance is calculated by the ratio of the transmitted light intensity of the sample cell and the transmitted light intensity of the reference medium, the transmittance Calculates fluid concentration based on Concentration calculating means, provided between the light branching means and the sample cell and the reference medium, the light detected by the light detection means and transmitted through the sample cell and light transmitted through the reference medium. And a switching means for switching to a fluid concentration measuring device. 2. The fluid concentration measuring device according to claim 1, wherein said switching means includes a first shutter provided between said light branching means and said sample cell, and said light branching means. A second shutter provided between the reference medium and the reference medium. 3. The fluid concentration measurement device according to claim 1, wherein the switching unit sets the irradiation of light to one of the sample cell and the reference medium to zero. A time from when the irradiation to the other side is started is set to 1 to 3 seconds.