JP3418703B2 - Moisture content measuring device with sample surface treatment function - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water content measuring device having a sample surface treatment function. For example, to quantify moisture adsorbed on various material surfaces, such as quantification of moisture adsorbed on thin film surfaces such as silicon films and silicon oxide films formed on the surface of highly clean electrolytic polishing pipes, and quantification of moisture adsorbed on metal surfaces. The present invention relates to a water content measuring device which is preferably used and is capable of revealing the water content adsorbed on the surface of various wafers in the semiconductor manufacturing process and the inner surface adsorbed water content of a semiconductor manufacturing apparatus.

[0002]

2. Description of the Related Art Conventionally, when measuring the amount of water adsorbed in a pipe or the like, while baking the pipe, a high-purity gas (for example, water having a water content of 50 ppt or less) is used as a carrier gas in the pipe.
r gas), and the desorbed water is desorbed by an atmospheric pressure mass spectrometer (A
PIMS) or the Karl Fischer method is used.

However, in the method using APIMS, it takes several hours until the water molecules adsorbed on the inner surface of the sample are completely desorbed and the water concentration in the carrier gas returns to the original value. However, high-speed measurement is impossible, and there is a limit to measuring high water concentration. Further, the Karl Fischer method is not a reliable method because it is unknown whether all the water molecules taken in the carrier gas have been absorbed by the solvent, and there is a limit in measuring low water concentrations. The current situation is that there are none. Moreover, since the sample surface-treated by the surface treatment device is installed and measured in the above measuring device,
There is a problem that the surface of the sample is exposed to the atmosphere, and the surface state immediately after the treatment cannot be measured accurately.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus for measuring the amount of adsorbed water immediately after surface treatment or the amount of adsorbed water immediately after surface treatment.

[0005]

The gist of the present invention is an apparatus for measuring the amount of water adsorbed on the surface of a sample, which comprises a storage container for storing a chemical solution having solubility in water, a sample chamber or It has a sample itself and an electric conductivity meter for measuring the electric conductivity of the chemical liquid, and further controls the flow rate of the chemical liquid in the storage container from the storage container to the sample chamber or the sample itself. Means for supplying a chemical solution, means for sending the chemical solution from the sample chamber or the sample itself to the electric conductivity meter, and various types in a completely sealed manner on the surface of the sample or the sample itself installed in the sample chamber And a means for preparing the surface state of the sample, and a device for measuring the amount of water having a sample surface treatment function.

[0006]

[Function] Since the surface treatment function is provided in the water content measuring device, the sample can be kept completely shielded from the atmosphere from the surface treatment to the water content measurement. Alternatively, it becomes possible to measure the amount of adsorbed water immediately after the surface treatment.

As means for producing the surface condition of the present invention, for example, various film deposition means by CVD, surface alteration means by oxidation, nitridation, fluorination reaction, etc., alteration means by various non-aqueous solutions, various electroless plating. -Deterioration means by drying is exemplified. In the present invention, when a chemical solution having a large interaction with water, such as anhydrous hydrogen fluoride, is brought into contact with a solid sample, water molecules adsorbed on the solid surface are immediately absorbed by the chemical solution. The water molecules absorbed in the chemical solution dissociate into ions in the chemical solution, and as a result, the electric conductivity changes according to the amount of water. Therefore, by measuring the electrical conductivity of the drug solution,
It is possible to measure the amount of water adsorbed on the sample surface. Then, by using a chemical solution having a large interaction with water, such as anhydrous hydrogen fluoride, even if the water is adsorbed on the surface in any state, the water is easily dissolved in the chemical solution, so that it can be used for a short time. It becomes possible to measure the adsorbed water content.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is shown in FIG. 1, and an embodiment of the present invention will be described with reference to the drawing. In the figure, 1 is a chemical solution container, 2 is a chemical solution flow rate control means, 3 is a leaktight electric conductivity meter, 4 and 5 are heating means, 6 and 7 are heating temperature control means, 8 is a chemical solution recondensing means, 9 Is a reference tube for keeping the inside of the conductivity meter sensor cell super clean. 10 creates various inner surfaces to adsorb (adhere) moisture
This is a sample tube to be used.

As a method for producing the inner surface condition of the sample tube 10, for example, the following method may be used. Valves 11, 1
Open 2, 13 and 14 and introduce gas (eg oxygen gas in case of forming oxide film) or solution for applying various surface treatments, and bring the heater 5 and the temperature controller 7 to the target treatment temperature. Surface treatment. Next, after introducing a gas containing water to adsorb the water, the valve 11
Close 12, 13, and 14.

To measure the water content, the chemical solution container 1 is heated to a target temperature by the heater 4 and the temperature controller 6,
The valve 15 is opened and the gas corresponding to the vapor pressure of the chemical liquid is liquefied by the condenser 8. After the chemical solution is sufficiently filled, the valve 16 is opened to supply the chemical solution to the pipe. The flow rate of the chemical liquid flowing through the pipe is controlled to a predetermined flow rate by the flow rate control means 2. First, the valves 17 and 18 are opened, and the chemical solution is sent to the electric conductivity meter 3 through the reference tube 9, and the electric conductivity of the chemical solution is measured there.
When the electric conductivity becomes constant, the valves 17 and 18 are closed, and the valves 19, 12, 13 and 20 are opened to introduce the chemical solution into the sample tube 10 to dissolve the adsorbed water in the sample tube, and then the electric conductivity meter. Sent to 3.

The relationship between the time elapsed after the introduction of the chemical solution into the sample tube 10 and the electric conductivity of the chemical solution is shown in the graph of FIG. That is, when the drug solution in which water adsorbed on the inner surface of the sample tube is dissolved reaches the conductivity meter 3, the measured value of the conductivity meter increases and then decreases to the original conductivity of the drug solution. When anhydrous hydrogen fluoride is used as the chemical solution, the water dissolved in the anhydrous hydrogen fluoride is completely dissociated in the anhydrous hydrogen fluoride, so the relationship between the electric conductivity measured by an electric conductivity meter and the water content is As shown in FIG. 3, there is a linear relationship. FIG. 3 shows the values when the temperature of hydrogen fluoride is 0 ° C. It is possible to obtain the number of adsorbed water molecules per unit area adsorbed on the sample tube from the relationship between the electric conductivity and the water content shown in FIG. 3 by integrating the peak portion in FIG.

Solubility in water used in the present invention
A chemical liquid that has water has a large interaction with water and
It mixes even in the following proportions, for example anhydrous fluorinated water
Elementary materials and the like are preferably used. Means 2 for controlling the flow rate of the chemical liquid
Is a stainless steel flow that can be controlled with high accuracy.
A body mass flow controller is preferred. Also electricity
Conductivity meter 3 is 10 ^-7-10^-2Electrical conduction in the S / cm range
It is preferable to be able to measure the degree, especially it can be attached to piping
A capable in-line conductivity meter is preferred.

The means for supplying anhydrous hydrogen fluoride to the sample is
It consists of a piping system connecting the anhydrous hydrogen fluoride container and the sample, and the means for sending anhydrous hydrogen fluoride from the sample to the electric conductivity meter consists of a piping system connecting the sample and the electric conductivity meter. In these piping systems, various metals and alloys can be used because anhydrous hydrogen fluoride does not corrode metals.
Alternatively, plastics such as Teflon can be used, but it is more preferable to use stainless steel whose inner surface is passivated after electrolytic polishing and which has low adsorption of impurity gas and high heat resistance.

A sheath heater of any shape is preferable as the means 4 and 5 for heating the sample tube and the chemical solution container, and a PID controller capable of controlling with precision is preferable as the temperature control means 6 and 7. When anhydrous hydrogen fluoride is used as the chemical liquid, the boiling point of anhydrous hydrogen fluoride is 19.5 ° C., so that the piping system, the flow rate control means, and the electric conductivity meter sensor cell in which the liquid of hydrogen fluoride normally flows are the same. It is desirable to keep the temperature below 5 ° C, for example, 0 ° C. The hydrogen fluoride discharged from the electric conductivity meter 3 is recovered in a closed container cooled to, for example, about -10 to -30 ° C.

The method of measuring the water adsorbed in the pipe has been described above. However, by providing a sample chamber in place of the sample pipe in FIG. 1 and installing a sample therein, not only the pipe but also various shapes can be obtained. For example, the amount of water adsorbed on powder or the like can be measured.

[0016]

EXAMPLES The present invention will be described in detail below with reference to examples. Example 1 As a sample tube of the device shown in FIG. 1, the inner surface was electrolytically polished 1
Using a stainless steel tube having a diameter of / 4 inch and a length of 4 m, the valves 19 and 20 are closed, the valves 11, 12, 13 and 14 are opened, and oxygen gas (amount of water content ppb) is introduced into the sample tube 10. The sample tube was kept at 400 ° C. for 1 hour by the heater 5 and the temperature controller to form an oxidation passivation film.

The result of analysis of the obtained oxidation passivation film by X-ray photoelectron spectroscopy (XPS) is shown in FIG. Also,
FIG. 4B shows the XPS analysis result of the oxidation passivation film produced by the dedicated oxidation passivation film forming apparatus. As is clear from the figure, the compositional changes in the depth direction of both are the same, and it is understood that the passivation film having the same composition was formed. Then, after forming the oxidation passivation film by the method described above, the valves 11 and 14 are closed, the valves 19 and 20 are opened, and anhydrous hydrofluoric acid (electrical conductivity 18 μS / cm) is flown into the sample tube, The water content in hydrofluoric acid was measured with an electric conductivity meter to determine the amount of water adsorbed inside the pipe. On the other hand, the oxidation passivation film formed by the dedicated oxidation passivation film forming device was also attached to the water content measuring device immediately after formation and the water content was measured in the same manner.

The amount of adsorbed water obtained by using the water content measuring device of FIG. 1 was below the detection limit, whereas the conventional measurement showed a high value of 36 × 10 ¹³ molecules / cm ² .
As can be seen from this, according to the present invention, it is possible to accurately measure the water content immediately after the surface treatment. (Example 2) In the same procedure as in Example 1, a silane gas was introduced into the sample tube and pyrolyzed at 500 ° C for 1 hour to deposit a silicon film. The XPS analysis result in the depth direction is shown in FIG.
In addition, XPS of silicon film deposited by a dedicated CVD device
The analysis result is shown in FIG.

As is apparent from the figure, it was found that the deposited films having the same composition were obtained in both cases. In the same manner as in Example 1, the amount of water adsorbed on the silicon deposited film was measured. The result of using the device of the present invention was below the detection limit, and the result of measurement after installation in the moisture measuring device after deposition was 20 × 10 ^13.
It became a molecule / cm ² . That is, the present invention shows that the moisture adsorption amount after silicon deposition can be accurately measured.

(Embodiment 3) As in Embodiment 1, using the apparatus shown in FIG. 1, Ar gas having a water content of 1 ppm was introduced at 25 ° C. after forming an oxidation passivation film, and the contact time was changed. Then, the amount of water adsorbed inside the pipe was measured (Example 3). The results are shown in Table 1. For comparison, after forming an oxidation passivation film with a dedicated oxidation passivation film forming device, attaching it to a water content measuring device and baking (500 ° C., 3 hours),
The measured results are also shown in Table 1 (comparative example).

[0021] As shown in Table 1, one second after contact with Ar gas, the water content in the comparative example was three times as large as that in Example 3. It is considered that this is because water molecules adsorbed when exposed to the atmosphere are not completely removed by baking, and it is difficult to measure accurately trace amounts of water, especially with conventional methods and devices. .

[0022]

According to the present invention, it is possible to provide a measuring apparatus capable of measuring moisture adsorbed on various samples with high accuracy and in a short time in a state immediately after surface treatment of various samples.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a configuration example of a water content measuring apparatus of the present invention.

FIG. 2 is a graph showing the relationship between the elapsed time and the electrical conductivity of the chemical liquid after the chemical liquid was introduced into the sample tube 10.

FIG. 3 is a graph showing the relationship between the water content in hydrogen fluoride and the electrical conductivity (0 ° C.).

FIG. 4 is a graph showing a composition profile in the depth direction of an oxidation passivation film.

FIG. 5 is a graph showing a composition profile in the depth direction of a Si deposited film.

[Explanation of symbols]

1 chemical liquid storage container, 2 chemical liquid flow rate control means, 3 leak tight electric conductivity meter, 4, 5 heating means (heating heater), 6, 7 heating temperature control means (temperature controller), 8 chemical liquid recondensing means, 9 electric Reference tube for keeping the inside of the conductivity meter sensor cell ultra-clean, 10 Sample tubes for making various inner surfaces to adsorb moisture, 11, 12, 13, 14, 15, 16, 17, 18, 1
9, 20 valves.

Claims (2)

(57) [Claims] 1. An apparatus for measuring the amount of water adsorbed on the surface of a sample, comprising: a storage container for storing a chemical solution soluble in water, a sample chamber or the sample itself, and the electrical conductivity of the chemical solution. And an electric conductivity meter for measuring
Further, means for supplying the chemical liquid from the storage container to the sample chamber or the sample itself while controlling the flow rate of the chemical liquid in the storage container, and the electrical conductivity meter for supplying the chemical liquid from the sample chamber or the sample itself. And a means for producing various surface states on the surface of the sample or the sample itself installed in the sample chamber in a completely sealed manner, the moisture having a sample surface treatment function. Quantity measuring device. 2. The sample surface treatment function according to claim 1, wherein the means for producing the surface state comprises at least a heating means for the sample and a means for introducing a gas to the surface of the sample. A water content measuring device having.