JP2005003422A - Total reflection fluorescent x-ray analyzing method and gaseous phase decomposition treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a total reflection X-ray analyzing method which enables a gaseous phase decomposition-total reflection fluorescent X-ray analyzing method capable of a quantitative measurement of higher sensitivity and precision, and an analyzer therefor. <P>SOLUTION: The thin film or natural oxidation film formed on the surface of a wafer is decomposed in a hydrofluoric acid gaseous phase (1a and 1b). Next, a recovery liquid for recovering a decomposed substance produced by the decomposition in the hydrofluoric acid gaseous phase is dripped on the surface of the wafer to be scanned over the whole surface of the wafer (2). Subsequently, the recovery liquid is dried on the surface of the wafer to form a dry mark (3). Then, the dry mark is measured by the total reflection fluorecent X-ray analysis (4). Herein, a gaseous decomposition is accelerated at a temperature lower than the liquefying temperature of hydrofluoric acid when the thin film or natural oxidation film on the surface of the wafer is decomposed and a sample stage on which the wafer is held in a vacuum state is subsequently heated to accelerate the separation of residue for lowering the analytical precision of a very small amount of impurities (1b). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a highly sensitive analysis method and a vapor phase decomposition apparatus using a total reflection X-ray fluorescence analyzer which is a surface analyzer for analyzing trace impurities on the surface of a semiconductor wafer.
[0002]
[Prior art]
With the recent miniaturization of semiconductor devices, analysis of trace impurities on the surface of a semiconductor wafer has become very important. This is to change the electrical characteristics of the transistor, such as reducing the breakdown voltage of the gate oxide film even with a very small amount of metal impurities. Therefore, in order to improve the electrical characteristics of the semiconductor device, it is necessary to reduce impurities on the wafer surface as much as possible. Therefore, it is necessary to analyze the amount of impurities on the wafer surface with high sensitivity and accuracy.
[0003]
As a highly sensitive composition analysis method for the wafer surface, there is a method in which trace impurities on the wafer surface are concentrated and collected and then measured with a total reflection X-ray fluorescence spectrometer (for example, Patent Documents 1 and 2). This analysis method is called gas phase decomposition-total reflection X-ray fluorescence analysis.
[0004]
FIG. 4 shows a flowchart of the measurement method of the vapor phase decomposition-total reflection fluorescent X-ray analysis method. As shown in FIG. 4, the gas phase decomposition-total reflection X-ray fluorescence analysis method is
(1) A step of vapor-phase decomposition of a thin film on a wafer surface or a natural oxide film in hydrofluoric acid vapor,
(2) a step of recovering the vapor-phase decomposed oxide film with a recovery liquid;
(3) drying the recovered liquid;
(4) a step of measuring a trace of dried recovered liquid by total reflection X-ray fluorescence analysis,
It consists of the above four steps.
[0005]
By doing so, contaminants on the entire surface of the wafer are collected in one place and measured by vapor phase decomposition-total reflection X-ray fluorescence analysis, so that high sensitivity analysis is possible.
[0006]
[Patent Document 1]
JP 2000-9615 A [Patent Document 2]
Japanese Patent Laid-Open No. 2001-201442
[Problems to be solved by the invention]
However, the vapor phase decomposition-total reflection X-ray fluorescence analysis method has a problem that the shape of the drying mark affects the measurement accuracy as described below.
[0008]
Generally, in total reflection X-ray fluorescence analysis, it is known that the quantitative analysis value fluctuates depending on the shape of the measurement target part as described in JP-A-6-207889 and JP-A-8-327766. ing. In other words, in the vapor phase decomposition-total reflection X-ray fluorescence analysis, since the contaminants on the wafer surface are collected and then dried, the shape of the drying mark changes depending on the collection and drying conditions, and the quantitative analysis value is There are changing problems. Especially in the measurement of trace impurities in oxide film, the oxide film is decomposed, recovered, and dried, so the dry trace contains a lot of Si residue and the shape of the dry trace becomes large, and the fluctuation of quantitative analysis value is a significant problem. It becomes.
[0009]
In view of the above problems, an object of the present invention is to provide a total reflection X-ray analysis method and an analysis apparatus that enable a gas phase decomposition-total reflection X-ray fluorescence analysis method capable of quantitative measurement with higher sensitivity and accuracy. There is to do.
[0010]
[Means for Solving the Problems]
In order to solve the above-described problems, a total reflection X-ray fluorescence analysis method of the present invention is a total reflection X-ray fluorescence analysis method for analyzing a trace amount of impurities on a wafer surface, which is a thin film or natural oxidation formed on the wafer surface. A step of decomposing the film in a hydrofluoric acid gas phase; and a recovery liquid for recovering a decomposition product generated by the decomposition in the hydrofluoric acid gas phase is dropped on the wafer surface, and the recovered liquid is applied to the entire surface of the wafer surface. Scanning the collected liquid on the surface of the wafer to form a drying mark, and measuring the drying mark by total reflection X-ray fluorescence analysis. In the step of decomposing the natural oxide film, the step of accelerating vapor phase decomposition at a temperature lower than the temperature at which hydrofluoric acid liquefies, the sample stage holding the wafer under reduced pressure is heated, and the analysis accuracy of the trace impurities Reducing residue Comprising the step of promoting desorption.
[0011]
By adopting such a configuration, unnecessary residues in the drying trace can be removed, and a decomposition product for obtaining a drying trace suitable for total reflection X-ray fluorescence analysis can be obtained, with high sensitivity and high accuracy. Analysis becomes possible.
[0012]
In the total reflection X-ray fluorescence analysis method of the present invention, it is preferable that the step of promoting vapor phase decomposition and the step of promoting desorption of the residue are repeated a plurality of times.
[0013]
By adopting such a configuration, unnecessary residues in the drying trace can be removed more sufficiently, and a decomposition product for obtaining a drying trace suitable for total reflection X-ray fluorescence analysis can be obtained. Highly accurate analysis is possible.
[0014]
Further, in the total reflection fluorescent X-ray analysis method of the present invention, the step of promoting the vapor phase decomposition is performed by performing the temperature of the sample stage at 20 ° C. or less and the atmosphere in the container in a hydrofluoric acid atmosphere, and removing the residue. In the step of promoting the temperature, the temperature of the sample stage is preferably 40 ° C. or higher and the pressure in the container is preferably 100 Pa or lower.
[0015]
By adopting such a configuration, dry traces in which Si residue that is an obstacle to measurement in total reflection X-ray fluorescence analysis is reduced, and high-sensitivity and high-accuracy total reflection X-ray fluorescence analysis is possible.
[0016]
Further, the vapor phase decomposition processing apparatus of the present invention supplies a hydrofluoric acid in a gas state to the sealed container having a sample stage for holding the wafer and controlling the temperature of the wafer and an open / close valve. A chemical bottle, an exhaust pump that exhausts the inside of the sealed container, a control device that controls the atmosphere in the sealed container by opening and closing the open / close valve and operating the exhaust pump, and temperature control of the sample stage; And when decomposing the thin film or the natural oxide film on the wafer surface, the control apparatus controls the atmosphere in the sealed container and the temperature control of the sample stage at a temperature equal to or lower than the temperature at which the hydrofluoric acid is liquefied. A step of promoting vapor phase decomposition and a step of heating the sample stage holding the wafer in a reduced pressure state to promote desorption of residues that reduce the analysis accuracy of trace impurities Carry out.
[0017]
With such a configuration, it is possible to perform sample processing to reduce residues that reduce the analysis accuracy of trace impurities, and to obtain drying traces suitable for total reflection X-ray fluorescence analysis through recovery and drying steps after vapor phase decomposition. Therefore, high-sensitivity and high-accuracy total reflection X-ray fluorescence analysis is possible.
[0018]
Further, in the gas phase decomposition processing apparatus of the present invention, the step of promoting the gas phase decomposition and the desorption of the residue are promoted by the atmosphere control in the sealed container and the temperature control of the sample stage by the control device. It is preferable to repeat the process several times.
[0019]
This configuration enables sample processing to reduce residues that reduce the analysis accuracy of trace impurities, and is suitable for total reflection X-ray fluorescence analysis by repeating collection and drying steps after vapor phase decomposition. Drying traces can be obtained, and further, highly sensitive and highly accurate total reflection X-ray fluorescence analysis can be performed.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
A first embodiment of the present invention will be described with reference to FIG.
[0021]
FIG. 1 is a flowchart of an analysis method according to the first embodiment of the present invention. The process of collecting the decomposition product on the wafer surface, the process of drying the collected liquid, and the process of total reflection X-ray fluorescence analysis shown in the flowchart of FIG. 1 are the same as in the conventional example.
[0022]
The analysis method of the present invention is characterized in that in the vapor phase decomposition step, the temperature of the sample stage and the atmosphere in the vapor phase decomposition vessel are processed under a plurality of conditions and repeated as necessary.
[0023]
In this embodiment, first, the sample stage temperature is set to 15 ° C., the inside of the gas phase decomposition vessel is set to a hydrofluoric acid atmosphere, and this state is maintained for 3 minutes. Subsequently, the sample stage is heated to 40 ° C. Is set to a vacuum of 100 Pa, and this state is maintained for 2 minutes. This process is repeated three times.
[0024]
The comparison result between this embodiment and the conventional example is shown below.
[0025]
FIG. 2 shows a case where 5 pg of Fe, Ni, Cu standard reagent is dropped on a 500 nm-thickness Si oxide film and analyzed by vapor phase decomposition-total reflection X-ray fluorescence analysis according to the conventional method and the present invention. It is the result of obtaining the lower limit of detection of each element from the measurement result.
[0026]
As shown in FIG. 2, it can be seen that the detection limit is improved in the method of the present invention. This is because the Si residue is reduced in the present invention and the shape of the drying mark is reduced, so that the peak intensity of each element is increased and the background intensity is also reduced, so the lower detection limit is improved. is there.
[0027]
As described above, by using the vapor phase decomposition-total reflection X-ray fluorescence analysis method of the present invention, the sample stage is cooled in a hydrofluoric acid atmosphere to promote vapor phase decomposition with hydrofluoric acid water droplets, and the sample stage is heated during vacuum evacuation. By repeating the process for urging the removal of the Si residue, the Si residue can be reduced and the shape of the drying mark can be reduced, so that highly sensitive total reflection X-ray fluorescence analysis can be performed.
[0028]
(Second Embodiment)
An embodiment of a vapor phase decomposition sample processing apparatus according to the second embodiment of the present invention will be described with reference to FIG.
[0029]
In FIG. 3, 5 is a wafer to be subjected to vapor phase decomposition processing, 6 is a sample stage on which the wafer 5 is set, 7 is a sealed container, 8 is an upper lid of the sealed container 7, 9 is a chemical bottle, and 10 is placed in a chemical bottle 9. A hydrofluoric acid, 11 is an open / close valve for introducing the gas of hydrofluoric acid 10 into the sealed container, and 12 is an exhaust pump for introducing hydrofluoric acid gas into the sealed container 7 and evacuating the inside of the sealed container 7.
[0030]
Next, a measurement procedure for performing total reflection X-ray fluorescence analysis using this vapor phase decomposition sample processing apparatus will be described.
[0031]
First, the wafer 5 is set on the sample stage 6 whose temperature can be controlled. Next, when the wafer 5 is set, the upper lid 8 of the sealed container 7 is closed. Next, when the temperature of the sample stage 6 is set to 15 ° C., the open / close valve 11 is opened and the exhaust pump 12 is operated, and the gas of hydrofluoric acid 10 contained in the chemical bottle 9 is introduced into the sealed container 7. Thereby, the inside of the airtight container 7 becomes a hydrofluoric acid atmosphere. Next, after an elapse time set in advance, the sample stage temperature is set to 40 ° C., the open / close valve 11 is closed, the inside of the sealed container 7 is evacuated to about 10 Pa, and this state is maintained for a preset time. This two-stage sample processing is repeated a set number of times, and the vapor phase decomposition processing is completed. Thereafter, the process proceeds to the next collection process.
[0032]
As described above, in the vapor phase decomposition sample processing apparatus of the present embodiment, the wafer cooling in the hydrofluoric acid atmosphere and the wafer heating in the vacuum atmosphere can be repeated, the decomposition of the Si oxide film due to the attachment of hydrofluoric acid water droplets, and the Si And the desorption of the compound of fluorine and fluorine from the wafer surface is carried out efficiently.
[0033]
As a result, the Si residue in the drying trace by the recovery after the vapor phase decomposition step and the drying step can be reduced and the shape of the drying trace can be reduced, so that highly sensitive total reflection X-ray fluorescence analysis can be performed.
[0034]
【The invention's effect】
According to the total reflection X-ray fluorescence analysis method and the vapor phase decomposition apparatus according to the present invention, it is possible to reduce the residue due to the compound of Si and fluorine generated in the vapor phase decomposition process of the Si oxide film. Since the shape of the drying mark can be reduced, highly sensitive total reflection X-ray fluorescence analysis can be performed.
[0035]
As a result, it is possible to perform an appropriate contamination evaluation in the semiconductor device manufacturing process, and it is possible to produce a stable semiconductor device.
[Brief description of the drawings]
FIG. 1 is a flowchart illustrating an analysis method of the present invention. FIG. 2 is a diagram comparing detection limits of the present invention with a conventional method. FIG. 3 is a diagram illustrating a gas phase decomposition sample processing apparatus according to the present invention. ] Flowchart explaining conventional analysis method [Explanation of symbols]
1 Gas phase decomposition process 2 Collection process 3 Drying process 4 Total reflection fluorescent X-ray analysis process 5 Wafer 6 Sample stage 7 Sealed container 8 Upper lid 9 Chemical bottle 10 Hydrofluoric acid 11 Opening and closing valve 12 Exhaust pump

Claims (5)

A total reflection X-ray fluorescence analysis method for analyzing trace impurities on a wafer surface,
Decomposing a thin film or a natural oxide film formed on the wafer surface in a hydrofluoric acid gas phase;
A step of dropping a recovery liquid for recovering decomposition products generated by decomposition in the hydrofluoric acid gas phase onto the wafer surface and scanning the recovery liquid over the entire surface of the wafer;
Drying the recovered liquid on the wafer surface to form drying marks;
Measuring the drying mark by total reflection X-ray fluorescence analysis,
In the step of decomposing the thin film or natural oxide film on the wafer surface,
Accelerating vapor phase decomposition at a temperature below the temperature at which hydrofluoric acid liquefies;
A total reflection X-ray fluorescence analysis method comprising a step of heating a sample stage holding the wafer in a depressurized state to promote desorption of a residue that reduces the analysis accuracy of the trace impurities. The total reflection X-ray fluorescence analysis method according to claim 1, wherein the step of promoting the gas phase decomposition and the step of promoting the desorption of the residue are repeated a plurality of times. The step of promoting the vapor phase decomposition is performed at a temperature of the sample stage of 20 ° C. or less and the atmosphere in the container is a hydrofluoric acid atmosphere, and the step of promoting the desorption of the residue is performed at a temperature of the sample stage of 40 ° C. The total internal reflection X-ray fluorescence analysis method according to claim 1 or 2, wherein the pressure in the container is 100 Pa or less. A sealed container having a sample stage for holding the wafer and controlling the temperature of the wafer, a chemical bottle for supplying hydrofluoric acid in a gas state into the sealed container via an on-off valve, and exhausting the sealed container An exhaust pump, and a control device that controls the atmosphere in the sealed container by opening and closing the open / close valve and operating the exhaust pump, and temperature control of the sample stage,
When decomposing the thin film or natural oxide film on the wafer surface, vapor phase decomposition is performed at a temperature lower than the temperature at which the hydrofluoric acid is liquefied by controlling the atmosphere in the sealed container by the control device and controlling the temperature of the sample stage. And a step of heating the sample stage holding the wafer in a reduced pressure state and promoting the desorption of residues that reduce the analysis accuracy of trace impurities. apparatus. The step of promoting the vapor phase decomposition and the step of promoting the desorption of the residue are repeated a plurality of times by controlling the atmosphere in the sealed container and the temperature control of the sample stage by the control device. Item 5. The gas phase decomposition treatment apparatus according to Item 4.

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