JPH07193110A - Oxygen concentration measurement device - Google Patents

Abstract

PURPOSE:To raise measurement accuracy of an oxygen concentration measurement device by, based on the signal from a temperature sensor that senses the temperature in a sample chamber, controlling a heating device which heats the second gas supply system that supplies the sample chamber with inactive gas, with a control circuit device. CONSTITUTION:An oxygen concentration measurement device of FT-IR method is provided with a temperature sensor 11, gas supply system 12, heating device 13, and control circuit device 14, so, the inert gas controlled to a constant temperature, such as nitrogen gas, is fed to a sample chamber 5, thus, the temperature in the sample chamber 5 is kept constant, for reduced variation in oxygen concentration. As a result, measurement accuracy of an oxygen concentration measurement device is raised. In addition, by covering the sample chamber 5 with an insulation material 15, the heat generated at an optical system 1 is prevented from conveyed to the inactive gas in the sample chamber 5 due to the heat of optical system 1 is prevented, for further raised measurement accuracy. Further, a switch 16 provided at a communication hole 4 raise measurement accuracy as well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen concentration measuring device, and more particularly to a technique effective when applied to an FT-IR (Fourier Transform Infrared Spectroscopy) type oxygen concentration measuring device.

[0002]

2. Description of the Related Art In semiconductor manufacturing technology, for example, FT is used as a measuring device for measuring the oxygen concentration in a semiconductor wafer.
There is an -IR (Fourier transform infrared spectroscopy) type oxygen concentration measuring device. This type of oxygen concentration measuring device comprises an optical chamber in which an optical system is arranged, a gas supply system for supplying an inert gas to the optical chamber, and a sample chamber connected to the optical chamber via a communication hole. The oxygen concentration is measured by irradiating the semiconductor wafer (measurement sample) arranged in the sample chamber with the measurement light emitted from the optical system.

Regarding the FT-IR type oxygen concentration measuring device, for example, an electronic material (E
lectornic Parts and Materials, 1989, November issue,
Vol. 28, No. 11).

[0004]

In the FT-IR type oxygen concentration measuring apparatus, the temperature inside the sample chamber in which the semiconductor wafer is placed is as shown in FIG. (Characteristic diagram shown)
It fluctuates in response to the temperature of the room where the measuring device is placed.
There is a close relationship between the temperature variation in the sample chamber and the measured oxygen concentration of the semiconductor wafer. When the temperature in the sample chamber rises with respect to a predetermined reference temperature (for example, 25 [° C.]), the measured oxygen concentration value decreases, and when the temperature in the sample chamber falls, the measured oxygen concentration value increases. That is, there is an inverse correlation phenomenon between the temperature in the sample chamber and the measured oxygen concentration. For example, the temperature inside the sample chamber is ± 2 relative to the reference temperature.
When a variation of [° C.] or more occurs, as shown in FIG. 5 (characteristic diagram showing weekly variation in measured value variation corresponding to temperature variation in FIG. 4), the measured oxygen concentration value is also an absolute value (reference value). A variation of ± 0.5 [%] or more occurs in 2δ with respect to the measured value at temperature). Regarding the temperature dependence of the measured value of the oxygen concentration, as shown in FIG. 6 (a characteristic diagram showing the relationship between the temperature variation in the sample chamber and the oxygen concentration variation), the measured value of the oxygen concentration and the temperature in the sample chamber are A negative correlation phenomenon is seen between and. That is, there is a problem in that the measured value of the oxygen concentration varies with the temperature change in the sample chamber, and thus the measurement accuracy of the oxygen concentration measuring device deteriorates.

The oxygen concentration in a semiconductor wafer is one of the important parameters in semiconductor manufacturing technology. Since the measurement accuracy required for absolute values is becoming stricter year by year,
Variation in measured value with respect to absolute oxygen concentration (variation rate)
Is based on 2δ = ± 0.5 [%].

An object of the present invention is to provide a technique capable of increasing the measurement accuracy of an oxygen concentration measuring device.

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

[0008]

Of the inventions disclosed in the present application, a representative one will be briefly described below.
It is as follows.

(1) An optical chamber for arranging an optical system, a first gas supply system for supplying an inert gas to the optical chamber, and a sample chamber connected to the optical chamber via a communication hole, In the oxygen concentration measuring device for measuring the oxygen concentration by irradiating the measurement sample arranged in the sample chamber with the measurement light emitted from the optical system, a temperature sensor for sensing the temperature in the sample chamber and the sample chamber A second gas supply system that supplies an inert gas, a heater that heats the second gas supply system, and a control circuit device that controls the heater based on a signal from the temperature sensor are provided.

(2) The sample chamber is covered with a heat insulating material.

(3) A switch for separating the optical chamber and the sample chamber is provided in the communication hole.

[0012]

According to the above-mentioned means (1), since the temperature in the sample chamber can be kept constant, it is possible to reduce the variation in the measured value of the oxygen concentration. As a result, the measurement accuracy of the oxygen concentration measuring device can be improved.

According to the above-mentioned means (2), the heat generated from the optical system can be blocked, so that the temperature fluctuation in the sample chamber due to the heat of the optical system can be prevented. As a result, the measurement accuracy of the oxygen concentration measuring device can be further improved.

According to the above-mentioned means (3), since the inert gas filled in the optical chamber can be prevented from entering the sample chamber, the temperature fluctuation in the sample chamber due to the inert gas in the optical chamber can be prevented. As a result, the measurement accuracy of the oxygen concentration measuring device can be further improved.

[0015]

EXAMPLES The constitution of the present invention will be described below together with an example in which the present invention is applied to an oxygen concentration measuring apparatus of the FT-IR system.

In all the drawings for explaining the embodiments, parts having the same function are designated by the same reference numerals, and the repeated description thereof will be omitted.

FIG. 1 (perspective view) and FIG. 2 show a schematic configuration of an FT-IR type oxygen concentration measuring apparatus which is an embodiment of the present invention.
(Block diagram).

As shown in FIGS. 1 and 2, the FT-IR type oxygen concentration measuring apparatus supplies an optical chamber 2 in which an optical system 1 is arranged, and an inert gas (for example, nitrogen gas) is supplied to the optical chamber 2. A gas supply system 3, a sample chamber 5 connected to the optical chamber 2 through a communication hole 4, a wafer transfer system 7 for transferring a semiconductor wafer (measurement sample) 6 from the cassette jig into the sample chamber 5, and a cassette jig. It is composed of a cassette stage 8 for mounting a monitor, a monitor 9 and the like. In this FT-IR type oxygen concentration measuring apparatus, a semiconductor wafer 6 arranged in a sample chamber 5 is irradiated with measuring light (infrared light) 1B emitted from an optical system 1 of an optical chamber 2, and this semiconductor wafer is irradiated. The measuring light 1B that has passed through 6 is analyzed by the analyzer 10 to measure the oxygen concentration.

As shown in FIG. 2, the FT-IR type oxygen concentration measuring apparatus supplies a temperature sensor 11 for detecting the temperature in the sample chamber 5 and an inert gas (for example, nitrogen gas) to the sample chamber 5. Gas supply system 12 and this gas supply system 1
A heater 13 that heats the heater 2 and a control circuit device 14 that controls the heater 13 based on a signal from the temperature sensor 11 are provided. In this way, the temperature sensor 11 and the gas supply system 1
2. Since the inert gas whose temperature is controlled to a constant temperature can be supplied to the sample chamber by providing the heater 13, and the control circuit device 14, the temperature in the sample chamber can be kept constant, so that variations in oxygen concentration can be reduced. . As shown in FIG. 3 (characteristic diagram showing weekly variation in measured value variation), the measured value variation (variation rate) with respect to the absolute value of oxygen concentration is 2δ.
Within ± 0.5 [%]. As a result, the measurement accuracy of the oxygen concentration measuring device can be improved.

The sample chamber 5 is covered with a heat insulating material 15. As described above, by covering the sample chamber 5 with the heat insulating material 15, it is possible to block the heat generated from the optical system 1 from being transferred to the inert gas in the sample chamber 5, so that the sample chamber due to the heat of the optical system 1 is blocked. The temperature fluctuation within 5 can be prevented. As a result, the measurement accuracy of the oxygen concentration measuring device can be further improved.

The communication hole 4 is provided with an opening / closing device (air shutter) 16 for separating the optical chamber 2 and the sample chamber 5. In this way, by providing the switch 16 in the communication hole 4, the inert gas supplied into the optical chamber 2 can be stored in the sample chamber 5.
Since it can be prevented from entering the inside, it is possible to prevent the temperature change in the sample chamber 5 due to the inert gas supplied into the optical chamber 2. As a result, the measurement accuracy of the oxygen concentration measuring device can be further improved.

As described above, the invention made by the present inventor is
Although the present invention has been specifically described based on the above-mentioned embodiments, the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made without departing from the scope of the invention.

[0023]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.

The measurement accuracy of the oxygen concentration measuring device can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic configuration of an FT-IR type oxygen concentration measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram of the oxygen concentration measuring device.

FIG. 3 is a characteristic diagram showing weekly fluctuations in measured value variations.

FIG. 4 is a characteristic diagram showing weekly temperature fluctuations in a room and sample room temperature in a conventional oxygen concentration measuring apparatus.

FIG. 5 is a characteristic diagram showing weekly variations in measured value variations corresponding to temperature variations in FIG.

FIG. 6 is a characteristic diagram showing a relationship between room temperature fluctuation and oxygen concentration fluctuation in a conventional oxygen concentration measuring device.

[Explanation of symbols]

1 ... Optical system, 1A ... Laser light, 1B ... Infrared light (measurement light), 2 ... Optical chamber, 3 ... Gas supply system, 4 ... Communication hole, 5 ...
Sample chamber, 6 ... Semiconductor wafer, 7 ... Wafer transport system, 8
... cassette stages 8, 9 ... monitors, 10 ... analyzers,
11 ... Temperature sensor, 12 ... Gas supply system, 13 ... Heater, 14 ... Control circuit device, 15 ... Heat insulating material, 16 ... Switch.

Claims (3)

[Claims] 1. An optical chamber for arranging an optical system, a first gas supply system for supplying an inert gas to the optical chamber, and a sample chamber connected to the optical chamber via a communication hole, In an oxygen concentration measuring device for measuring an oxygen concentration by irradiating a measurement sample placed in a sample chamber with measurement light emitted from the optical system, a temperature sensor for sensing the temperature in the sample chamber and A second gas supply system for supplying active gas, a heater for heating the second gas supply system, and a control circuit device for controlling the heater based on a signal from the temperature sensor are provided. Oxygen concentration measuring device. 2. The oxygen concentration measuring device according to claim 1, wherein the sample chamber is covered with a heat insulating material. 3. A switch for separating the optical chamber and the sample chamber is provided in the communication hole.
Alternatively, the oxygen concentration measuring device according to claim 2.