JP2002090206A - Liquid level detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid level detector capable of accurately detecting the level of a liquid under test with the liquid surface being fluidic. SOLUTION: The liquid level meter 10 comprises detectors 15, 16 having sheaths 13, 14 enclosing thermosensitive elements 11, 12, respectively. The sheath 13 of the detector 15 has a conical and needle-like top end 13b coupled with the lower end of a cylindrical tube 13a with its steeple directed down. The top end 13b is made of a material having a lower heat conductivity than the tube 13a. The tube 13a is heated by a heater 17. Such substantially heat insulation of the top end 13b prevents wrong recognition of the liquid level of a raw material liquid 90. If this liquid 90 deposits to the sheath 13, its effect on the liquid level detection can be effectively eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level detecting device, and more particularly, to a liquid level detecting device for detecting a liquid level of a test liquid stored in a container.

[0002]

2. Description of the Related Art Conventional liquid level detecting devices include, for example,
A heat-sensitive liquid level sensor installed in a container for storing a liquid organometallic raw material used in semiconductor manufacturing is exemplified. FIG. 3 is a schematic diagram showing an example of a conventional liquid level detection device, and FIG. 4 is a schematic diagram showing a part thereof. The liquid level sensor 80 includes two detecting portions 85 and 86 having substantially cylindrical sheaths 83 and 84 in which the heat-sensitive elements 81 and 82 are respectively housed.
0 is fixedly installed in a container 91 in which 0 is stored. One of the detection units 85 and 86 is externally heated.

According to the liquid level sensor 80, the difference between the intensity of the electric signals output from the thermosensitive elements 81 and 82 in the state of being immersed in the raw material liquid 90 and the liquid level of the raw material liquid 90 are exposed above the liquid level L. The distance between the liquid level L and the detection units 85 and 86 is detected based on the difference between the electric signal strengths output from the thermosensitive elements 81 and 82 in the state, and thereby the level (liquid level) of the liquid level L is detected. Is detected.

[0004]

By the way, the raw material liquid 90
Is usually stirred (bubbled) by aeration or aeration, and the entire container 91 containing the raw material liquid 90 is heated and maintained at a predetermined temperature. When the stirring is performed, the liquid level L of the raw material liquid 90 tends to flow so as to vibrate strongly. The present inventors examined the conventional liquid level sensor 80 in this stirring state in detail, and found that FIG.
As shown in FIG.
It was found that the droplets 99 tended to adhere.

[0005] In this case, although the detectors 85 and 86 are exposed above the liquid level L, it is as if the sheaths 83 and 86 were exposed.
There is a possibility that the tip of 84 is detected as being in the raw material liquid 90 and the level of the liquid level L is erroneously recognized. Also,
Depending on the shapes of the sheaths 83 and 84 and their thermal conductivity, it may be difficult to accurately detect the level of the liquid level L even when the droplets 99 do not adhere. Specifically, for example, the liquid level levels L0, L1, and L2 shown in FIG.

Accordingly, the present invention has been made in view of such circumstances, and a liquid level detecting device capable of accurately detecting a liquid surface position (liquid level) of a test liquid in which the liquid surface can flow. The purpose is to provide.

[0007]

Means for Solving the Problems In order to solve the above problems, the present inventors have conducted intensive studies, and as a result, the droplets 99 adhere to the sheaths 83, 84, and the detection portions 85, 8 are detected.
Further, the present inventors have further found that the heat capacity of No. 6 has changed, and this has contributed to the fact that an electric signal having a strength corresponding to the liquid level was not output from the thermosensitive elements 81 and 82, and the present invention has been reached.

That is, the liquid level detecting device according to the present invention comprises:
A first temperature sensor for detecting a liquid level of the test liquid stored in the container and outputting a first electric signal according to an ambient temperature, and a first temperature sensor are provided. First
Coating member, a first detection unit having a heat source connected to the first coating member, a second temperature sensor that outputs a second electric signal according to an ambient temperature, and a second temperature sensor And a second covering member provided with the first member, wherein the first covering member has a first structure made of a first material having thermal conductivity, and a thermal conductivity higher than that of the first structure. And a second structure provided on the first structure and made of a small second material.

In the liquid level detecting device configured as described above, even if the droplet of the test liquid adheres to the end of the first covering member constituting the first detecting section, the liquid is detected at the end. Since the provided second structure has a lower thermal conductivity than the first structure, it is difficult for heat to be transmitted to the first temperature sensor in the first detection unit. Therefore, even if the liquid droplets adhere, the heat capacity of the first detection unit does not change significantly, and an electric signal having the intensity as when the end of the first detection unit is in the test liquid is erroneously output. Hardly ever. Further, when the liquid surface moves up and down at the joining position (point, surface, etc.) between the first structure and the second structure, the difference between the electric signal intensities output from the first and second temperature sensors is different. Clearly change. Therefore, the joining level between the first structure and the second structure is always determined to be the liquid level.

The first structure has a substantially cylindrical shape or a substantially columnar shape, and the second structure has a substantially conical shape, a substantially rod-like shape, a substantially needle-like shape, or a substantially linear shape. It is preferable that it is connected to the end of the structure. With this configuration, even if the test liquid adheres to the end of the second structure that forms the first covering member, the test liquid is transmitted to the second structure more than the first structure. Since the test liquid easily falls, it is difficult for the test liquid to remain as droplets at the first detection unit. Therefore, the influence of the test liquid can be eliminated, and the strength as in the case where the end of the first detection section is in the test liquid when the first detection section is exposed above the test liquid. Erroneous output of the electric signal can be sufficiently prevented.

Further, it is more preferable that the diameter of the second structure is gradually reduced from the coupling end to the first structure toward the other end. In this case, the effect of eliminating the liquid droplets at the tip of the first detection unit is enhanced.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. Note that the same components are denoted by the same reference numerals, and redundant description will be omitted. Unless otherwise specified, the positional relationship such as up, down, left, and right is based on the positional relationship shown in the drawings.

FIG. 1 is a schematic diagram showing an outline of a preferred embodiment of a liquid level detecting device according to the present invention, and FIG. 2 is a schematic diagram showing a main part thereof. Liquid level meter 10 (liquid level detection device)
Is a detecting unit 15 (first covering member) having a sheath 13 (first covering member) in which the thermal element 11 (first temperature sensor) is housed.
And a detecting unit 16 (second detecting unit) having a substantially cylindrical sheath 14 (second covering member) in which the thermal element 12 (second temperature sensor) is accommodated. In addition, the sheath 13 of the detection unit 15 has a substantially cylindrical body 13a (first body 13a).
Of the conical and needle-shaped tip 13
b (the second structure) is connected with the spire section facing downward. The tip portion 13b is formed of a material having a lower thermal conductivity than the body portion 13a, preferably a heat insulating material. As shown in FIG. 1, the sheath 13 as the first covering member and the sheath 14 as the second covering member are provided at substantially the same level.

These detecting sections 15 and 16 are fixed substantially vertically in a container 21 in which a raw material liquid 90 (test liquid) of an organic metal such as tetradimethylaminotitanium (hereinafter referred to as “TDMAT”) is stored. is set up. This TDM
AT is used in semiconductor manufacturing by the CVD method,
It is suitable as a raw material of a TiN film as a barrier metal formed on a substrate such as a silicon wafer.

The body 13 of the sheath 13 of the detection unit 15
A heater 17 as a heat source is connected to a, so that the body 13a and the thermosensitive element 11 are heated. Further, the thermosensitive elements 11 and 12 are connected to a measurement calculation unit 18, and each voltage signal (first and second electric signals) output from the thermosensitive elements 11 and 12 according to the ambient temperature is measured and calculated. Input to the unit 18.

The container 21 further includes a heater 22.
Is connected, and the entire container 21 containing the raw material liquid 90 is heated. A diffuser tube (both not shown) connected to a bubbling gas supply system is provided at the inner bottom of the container 21. Although the upper part of the container 21 is sealed, the illustration is omitted.

The entire container 21 in which the liquid level gauge 10 having the above-described structure is installed is heated by the heater 22 in a state in which the raw material liquid 90 is stored.
0 and the space in the container 21 are maintained at a predetermined temperature. Further, a bubbling gas is supplied to the raw material liquid 90, and the raw material liquid 90 is stirred by aeration.

In the liquid level meter 10 having the above-described configuration, voltage signals corresponding to the ambient temperature are continuously output from the thermosensitive elements 11 and 12, and the difference ΔT between the voltage signals is measured by the measurement calculation unit 18. The calculation is performed substantially continuously, and the difference (variation) of ΔT is calculated over time. This ΔT
Represents the temperature difference between the detectors 15 and 16, so to speak, and the liquid level meter 10 constantly monitors the temperature difference.

Here, the liquid level of the raw material liquid 90 is at the level Lu.
(See FIG. 1), that is, when the lower ends of the sheaths 13 and 14 are immersed in the raw material liquid 90,
The system including the container 21 and the sheaths 13 and 14 is in a thermal steady state. This is because, although the detection unit 15 is heated by the heater 17,
Is sufficiently larger than the liquid level meter 10.
In this case, a voltage signal corresponding to the temperature of the raw material liquid 90 is output from the thermosensitive elements 11 and 12. At this time, ΔT calculated by the measurement calculation unit 18 is assumed to be ΔTu here.

On the other hand, when the liquid level of the raw material liquid 90 is at the level L1 (see FIG. 1), that is, when the lower ends of the sheaths 13 and 14 are exposed from the raw material liquid 90, the above-described thermal steady state Is broken. In the illustrated state, the distal end 13b of the sheath 13 is in contact with the raw material liquid 90. However, since the thermal conductivity of the distal end 13b is sufficiently smaller than that of the body 13a, the heater 13 The amount of heat supplied to the body 13a is hardly transmitted to the raw material liquid 90. As a result, the ambient temperature of the trunk 13a and, consequently, the thermal element 11 rises. Therefore, if ΔT calculated by the measurement calculation unit 18 at this time is ΔTl, the ΔTl and the above-mentioned ΔTu are significantly different values. Therefore, the level Lu and the level Ll of the liquid surface of the raw material liquid 90 can be reliably discriminated.

More specifically, the level of the raw material liquid 90 shown in FIG.
ΔT changes significantly and clearly at the position of the junction 13c with the point b, that is, at the time when the level Lm rises and falls (the above-mentioned ΔTu
To ΔTl or vice versa). Therefore,
It can be accurately detected that the liquid level is at the level Lm. Further, even if the liquid surface of the raw material liquid 90 is at the level Ll and the liquid surface is wavy due to bubbling and adheres to the tip portion 13b, the tip portion 13b is unlikely to conduct heat as described above. Does not change substantially. Therefore, erroneous recognition of the liquid level can be sufficiently prevented.

Further, even if the raw material liquid 90 adheres to the lower end of the body 13a of the sheath 13, the raw material liquid easily falls down along the needle-like tip 13b. This is because the surface tension acting on the droplets of the raw material liquid 90 attached to the lower end of the body 13a without the tip 13b differs from the surface tension acting on the tip 13b.
This is presumed to be due to the fact that the surface tension acting when there is a difference. In particular, as shown in FIG.
In the case of a thin needle shape smaller than the diameter of 3a, it is considered that the effect that the attached raw material liquid 90 is hardly maintained as a droplet is extremely enhanced. However, the operation is not limited to these.

As described above, according to the liquid level meter 10, since the sheath 13 is provided with the tip 13b at the tip of the body 13a, the liquid level of the raw material liquid 90 flows so as to be wavy by bubbling. Even so, the liquid level (liquid level) can be accurately detected. In addition, the liquid level is the body portion 13a and the tip portion 1
It can be detected with high precision that it is at the level Lm corresponding to the junction 13c with 3b.

Further, since the tip portion 13b is provided, even if the raw material liquid 90 adheres to the tip portion 13b, the effect can be effectively eliminated, and erroneous recognition of the liquid level can be further suppressed. Further, the tip portion 13b has a needle shape, and
Since the diameter is gradually reduced from 3c toward the lower end, even if the droplet of the raw material liquid 90 adheres to the lower end of the body portion 13a, the raw material liquid 90 easily falls down smoothly. Therefore, the effect of the raw material liquid 90 being attached can be removed, and erroneous recognition of the liquid level can be further suppressed.

The shape of the body 13a of the sheath 13 and the shape of the sheath 14 are not particularly limited. However, from the viewpoint of effective use of the installation space, operability, and the like, a cylindrical shape, a rectangular cylindrical shape, a cylindrical shape, a prismatic shape, and the like. Alternatively, a shape in which these are combined is desirable. Further, the material of the trunk 13 a is the tip 1 of the sheath 13.
The material is not limited as long as it has a higher thermal conductivity than 3b. For example, a metal material is preferable because sensitivity can be improved. Further, the shape of the distal end portion 13b of the sheath 13 is
The shape may be a cone, a bar, or a line.

Further, the tip portion 13b is connected to the body portion 13a.
And the lower end of the tip portion 13b may be located below the lower end of the body portion 13a. Furthermore, the sheaths 13 and 14 do not have to be installed vertically. Further, a plurality of detection units 15 and 16 may be provided. In addition, a plurality of pairs of the detection units 15 and 16 may be provided. For example, in the case where two pairs are provided, there is an advantage that one of the pairs can be used for an alarm by installing such that one lower end is higher than the other lower end.

[0027]

As described above, according to the liquid level detecting device of the present invention, the liquid surface position (liquid level) of the test liquid at which the liquid surface can flow can be accurately detected, and the liquid level can be detected as compared with the prior art. The detection accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an outline of a preferred embodiment of a liquid level detecting device according to the present invention.

FIG. 2 is a schematic view showing a main part of a preferred embodiment of a liquid level detecting device according to the present invention.

FIG. 3 is a schematic diagram showing an example of a conventional liquid level detection device.

FIG. 4 is a schematic view showing a part of an example of a conventional liquid level detection device.

[Explanation of symbols]

10: liquid level meter (liquid level detecting device), 11: heat sensitive element (first
12) Thermal element (second temperature sensor), 13 ... sheath (first covering member), 13a ... trunk (first structure), 13b ... tip (second structure) ),
14 ... sheath (second covering member), 15 ... detection unit (first
, 16 ... detecting section (second detecting section), 17 ... heater (heat source), 21 ... container, 90 ... raw material liquid (test liquid).

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yumi Suzuki 14-3 Shinzumi, Narita-shi, Chiba Pref. In Applied Materials Japan Co., Ltd. Applied Materials Japan Co., Ltd. (72) Inventor Yuji Murayama 14-3 Shinizumi, Narita-shi, Chiba Pref. Nomohira Industrial Park Applied Materials Japan Co., Ltd. F-term (reference) 2F014 AA07 AB02 CA00

Claims (3)

[Claims] 1. A liquid level detecting device for detecting a liquid level of a test liquid stored in a container, comprising: a first temperature sensor for outputting a first electric signal according to an ambient temperature; A first covering member on which the first temperature sensor is installed, and a first covering member having a heat source connected to the first covering member.
, A second temperature sensor that outputs a second electric signal according to an ambient temperature, and a second temperature sensor provided with the second temperature sensor.
Wherein the first covering member has a first structure made of a first material having thermal conductivity, and a first structure having a smaller thermal conductivity than the first structure. And a second structure provided on the first structure and comprising a second material. 2. The first structure has a substantially cylindrical shape or a substantially columnar shape, and the second structure has a substantially weight shape, a substantially rod shape, a substantially needle shape, or a substantially linear shape. The liquid level detecting device according to claim 1, wherein the liquid level detecting device is connected to an end of the third structure. 3. The method according to claim 1, wherein the diameter of the second structure is gradually reduced from a coupling end to the first structure toward the other end. The liquid level detecting device as described in the above.