JPH06132376A - Wafer analyzer - Google Patents

Abstract

PURPOSE:To obtain an excellent total reflection fluorescent x-ray analytical specimen by a method wherein a wafer analyzer is composed of a wafer holding member and a hood having an opening with a removable lid and attached detachably to the holding member to enclose a wafer. CONSTITUTION:A board 2, a suction piece 3, a hood 4, and a lid 6 are cleaned in a clean booth, and the opening 4 of the hood 4 is covered with the lid 6. A wafer 1 is placed on the board 2, and as the rear side of the wafer 1 and the front side of the board 2 are both smooth, they come into close contact with each other. Then, the suction piece 3 is made to bear against the board 2 so as to make its infrared transmitting window 3a confront the hole 2a of the board 2 and depressurized to stick to the board 2. The wafer 1 placed on the board 2 is covered with the hood 4 with the lid 6, and when the hood 4 and the board 2 are closely fitted to each other, the wafer 1 is enclosed in a space surrounded with the board 2, the hood 4, and the lid 6 and kept free from contamination. By this setup, an excellent total reflection fluorescent x-ray analytical specimen can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a wafer analysis instrument. More specifically, the present invention relates to a wafer analysis instrument used for collecting impurities on the surface of a wafer and collecting an analysis sample.

[0002]

2. Description of the Related Art Conventional semiconductor substrates (hereinafter called wafers)
Is widely used for manufacturing semiconductor devices by surface treatment. The concentration of impurities, especially heavy metal impurities, contained in the surface of the wafer is a very important factor in order to obtain a good semiconductor device with a high yield by subjecting the wafer to a surface treatment together with a shape factor such as flatness. For this reason, it is necessary to analyze a very small amount of impurities with high sensitivity, and it is indispensable to collect impurities on the surface of a wafer while avoiding contamination by dust or the like in the atmosphere.

Atomic absorption analysis (AAS), total reflection X-ray fluorescence analysis (TXRF) and the like are used for the analysis of these impurities. In particular, the analysis of heavy metal impurities on the surface of a wafer by the total reflection X-ray fluorescence analysis method is widely used because the lower limit of quantification is 1 × 10 ¹⁰ (atoms / cm ² ).

Conventionally, in order to collect an analytical sample for atomic absorption spectrometry, hydrofluoric acid HF is dropped on the surface of a wafer and dissolved together with a natural oxide film (silicon oxide SiO ₂ ) on the surface of the wafer to recover impurities. A method of using a recovered liquid as an analysis sample is adopted.

Japanese Patent Laid-Open No. 4-133427 discloses a hermetically sealed container, a container installed outside the hermetically sealed container for storing at least one medicine connected to the hermetically sealed container by a gas supply audit corporation, and the medicine. And a means for heating and cooling the container for storing the semiconductor substrate, and means for holding and cooling the semiconductor substrate in the closed container, and further stores the decomposition solution received in the receiver inside the closed container through a pipe. There is disclosed a device for recovering impurities on the surface of a wafer by vapor of hydrogen fluoride, which is provided with a concentrating container and a heating means for heating the concentrating container.

[0006]

However, in the above-mentioned conventional technique, hydrogen fluoride is dropped on the surface of the wafer to form a natural oxide film (silicon oxide Sio) formed on the surface of the wafer.
_The impurities are recovered by dissolving with ₂ ), but in order to obtain a sample for total reflection X-ray fluorescence analysis, this recovered solution must be dropped on the sample and dried to dryness. Contamination of the water sometimes impaired the accuracy of the analytical values.

The impurities on the surface of the wafer recovered by the apparatus disclosed in Japanese Patent Laid-Open No. 4-133427 were suitable as a sample for atomic absorption analysis concentrated while avoiding contamination from the atmosphere. However, in order to dry it to obtain a sample for total reflection X-ray fluorescence analysis, contamination from the atmosphere cannot be avoided.

Then, according to the conventional method, in the step of drying the collected liquid at the time of collecting the sample for total reflection fluorescent X-ray analysis,
Since vapor such as hydrogen fluoride is generated, expensive equipment such as a clean draft is required, but there is a problem that this is not common in ordinary chemical analysis rooms.

In view of the above problems, it is an object of the present invention to provide a wafer analysis instrument used for collecting an impurity analysis sample of a wafer while easily avoiding contamination from the atmosphere.

[0010]

DISCLOSURE OF THE INVENTION The present invention is a wafer analysis instrument comprising a holding member for holding a wafer and a hood which is detachable from the holding member and which is capable of covering and sealing the wafer and having an opening with a lid. Is. A preferable holding member is composed of a perforated plate on which the wafer is placed and a suction member which sucks and holds the wafer on the perforated plate. Further, for drying, infrared rays radiated from the infrared heater pass through the infrared transmission window of the adsorption member provided at a position corresponding to the hole of the perforated plate to heat the wafer.

[0011]

[Action] was dropped on the wafer surface hydrofluoric acid HF, impurities wafer surface was collected and dissolved with a silicon oxide film Si0 _2, the recovery liquid Thereafter, dryness causes on the wafer. For this purpose, the wafer is first attached to the wafer analyzing instrument in the clean booth, and then the wafer analyzing instrument is transferred to the draft. Then, the dropping of hydrofluoric acid, the dissolution of the silicon oxide film, the recovery of the recovered liquid, and the drying process are performed in the same sealed wafer analysis instrument, so that the wafer is free from contamination from the atmosphere. The recovered liquid on the wafer is dried and solidified by infrared heating or the like.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. The first embodiment relates to a method for obtaining a total reflection X-ray fluorescence analysis sample. 1 is a sectional view of the first embodiment, and FIG. 2 is a sectional view of the first embodiment including a pedestal. The wafer 1 is placed on a so-called donut-shaped plate 2 made of fluororesin and having a large hole in the center, and the hole 2a is formed.
In, the vacuum suction device 3 made of quartz glass sucks and is fixed. A portion of the suction tool 3 corresponding to the hole 2a of the plate 2 is an infrared transmission window 3a. A hood 4 made of quartz glass is detachably fitted to the plate 2 so as to cover the plate 2, and an opening 5 is covered with a lid 6 made of fluororesin. When the lid 6 is covered, the plate 2, the hood 4, and the lid 6 form a closed space.

The plate 2 is supported by three columns 8 standing on a table 7, and each column 8 is provided with a screw 8a so that the inclination of the plate 2 can be changed and the wafer 1 can be leveled. ing. A base plate 9 is movably installed on the base 7, and the base plate 9
A condensing infrared lamp 10 is placed on the above. The focus position of the condensing infrared lamp 10 can be adjusted by changing the number of the base plates 9.

Next, the operation of this embodiment will be described. First, the plate 2, the suction tool 3, the hood 4, and the lid 6 are cleaned in the clean booth, and the opening 5 of the hood 4 is covered with the lid 6. When the wafer 1 is placed on the plate 2, both the back surface of the wafer 1 and the front surface of the plate 2 are extremely smooth, so that they are in close contact with each other. Next, the suction tool 3 is provided so that the infrared ray transmitting window 3a corresponds to the hole 2a of the plate 2, and the pressure is reduced by a vacuum pump (not shown) to suck the suction tool 3 onto the plate 2. At this time, the central portion of the wafer 1 is pulled by the reduced pressure and becomes lower than the peripheral portion.

The wafer 1 placed on the plate 2 is covered with a lid 6
When the hood 4 and the plate 2 are tightly fitted and the assembly is completed, the wafer 1 is sealed in the space formed by the plate 2, the hood 4, and the lid 6 and is not polluted by the atmosphere. It becomes a state.

Next, the assembled plates 2 and the like are transferred onto a pedestal in the draft. Then, the three columns 8 are rotated, the wafer 1 is leveled by the screws 8a, and the base plate 9 is adjusted to adjust the position of the condensing infrared lamp 10.

Then, the lid 6 is removed and the opening 5 is opened.
Hydrogen fluoride 11 is dropped onto the surface of the wafer 1 through the opening 5 with a pipette, and the lid 6 is covered again. The oxide film formed on the surface of the wafer 1 is dissolved by hydrogen fluoride, and the impurities enter the solution. The dropped hydrogen fluoride scans the surface of the wafer 1 in a vertical direction, a horizontal direction, and a spiral shape as shown in FIGS. 3 (1), 3 (2), and 3 (3), and then scans the surface of the wafer 1 thoroughly. Collected as a recovery liquid in the center.
Since the central part of the wafer 1 is lower than the peripheral part,
The scanning is stable and it is easy to collect the collected liquid in the center.

Next, the condensing infrared lamp 10 is turned on and heated, and volatile substances such as hydrogen fluoride, silicon fluoride and water are evaporated from the recovered liquid to dryness, and the fluoride as an impurity is formed on the surface of the wafer 1. It remains as a residue in the center. In this way, a total reflection X-ray fluorescence analysis sample is obtained at the center of the surface of the wafer 1. During this period, only the opening 5 is opened during the dropping of hydrogen fluoride, and the other wafers 1 are all placed in the closed space,
No pollution from the atmosphere.

A second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a sectional view of the second embodiment. Detailed description of the same or similar points to those of the first embodiment will be omitted. The hood 4a of this embodiment is provided with a gas inlet 4b and a gas outlet 4c, and the gas outlet 4c is further provided with a valve 4d. When pure dry nitrogen N ₂ is introduced through the gas inlet 4b and discharged through the gas outlet 4c, hydrogen fluoride vapor does not condense on the inner surface of the hood 4a, and the inner surface of the quartz glass hood 4a is fluorinated. Less erosion by hydrogen.

At this time, dry nitrogen N is closed with the valve 4d closed.
_When hydrofluoric acid is dropped while ₂ is introduced from the gas introduction port 4b, the internal pressure of the hood 4a increases and dry nitrogen is discharged from the opening 5. This prevents contaminants from entering the inside of the hood 4a from the atmosphere against the flow of dry nitrogen in the opening 5.

A third embodiment of the present invention will be described with reference to FIGS. The third embodiment is a method of obtaining a total reflection X-ray fluorescence analysis sample by a gas phase decomposition method. 5 and 6 are sectional views of the third embodiment. Detailed description of the same or similar points to those of the first embodiment will be omitted. The silicon wafer 1 is sucked and fixed under the plate 2 by the suction tool 3, the hood 4 is detachably fitted to the plate 2 so as to cover the plate 2, and the fluororesin container 6a is fitted into the opening 5 thereof. , The plate 2, the hood 4, and the container 6a form a closed space.

Next, the operation of this embodiment will be described. First, in the clean booth, the plate 2, the suction tool 3, the hood 4, and the container 6a are cleaned, and the wafer 1 is placed under the plate 2 to hold the suction tool 3
Then, the hood 4 is attached to the plate 2. The opening 5 of the hood 4 is faced downward, and an empty container 6a is fitted into the opening 5 from below and the lid is closed.

Next, the assembled plates 2 and the like are moved into a draft, the container 6a is once removed, hydrogen fluoride 12 is put therein, and the container 6a is fitted into the opening 5 of the hood 4 from below. Hydrogen fluoride vapor diffuses from the container 6a, fills the hood 4, and condenses on the silicon oxide film formed on the surface of the wafer 1. The condensed hydrogen fluoride dissolves the silicon oxide film, and the impurities dissolve therein. At this time, if this jig is installed on the pedestal as shown in FIG. 6, the hydrofluoric acid can be heated by the concentrating infrared lamp 10, and the silicon oxide film can be rapidly dissolved.

When the reaction is completed, the container 6a is removed, the hydrogen fluoride 12 therein is discarded, the clean lid 6 is fitted into the opening 5, and the top and bottom are turned upside down to the state shown in FIG. 6, similar to the first embodiment. The wafer 1 is transferred onto the pedestal as shown in FIG.
Then, the position of the condensing infrared lamp 10 is adjusted.

Then, the lid 6 is removed to open the opening 5,
Ultrapure water 13 is dropped on the surface of the wafer 1 with a pipette. Then, when scanned with ultrapure water, the condensed solution of hydrogen fluoride is collected in the center of the surface of the wafer 1 as a recovery liquid. Then, the recovered liquid is heated with infrared rays to dryness. In this way, a total reflection X-ray fluorescence analysis sample by the gas phase decomposition method is obtained at the center of the surface of the wafer 1. During this time, the hydrogen fluoride 12 is put in the container 6a, and the opening 5 is only opened while the ultrapure water 11 is dropped, and the other wafers 1 are all placed in the closed space and may be contaminated by the atmosphere. Absent.

Needless to say, the donut-shaped plate can be formed of a resin such as polyethylene other than the fluororesin. The heating can be performed with a nichrome wire or the like instead of using an infrared heater.

[0027]

As described above, when the wafer analysis instrument according to the present invention is used, the wafer is attached to the wafer analysis instrument in the clean booth, the hydrofluoric acid is dropped, the silicon oxide film is dissolved, and the recovered liquid is recovered. Since the dry-drying process is performed in the same sealed wafer analysis instrument, the analysis sample can be easily produced by avoiding contamination from the atmosphere, and a good total reflection X-ray fluorescence analysis sample can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment.

FIG. 2 is a sectional view of the first embodiment including the pedestal of the first embodiment.

FIG. 3 is a diagram showing how a recovered liquid of the first embodiment scans a wafer surface.

FIG. 4 is a sectional view of a second embodiment.

FIG. 5 is a sectional view of a third embodiment.

FIG. 6 is a sectional view of a third embodiment.

[Explanation of symbols]

 1 Wafer 2 Plate 2a Hole 3 Adsorption Tool 3a Infrared Transmission Window 4, 4a Hood 4b Gas Inlet 4c Gas Outlet 4d Valve 5 Open 6 Lid 6a Container 7 Units 10 Infrared Lamp

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[Procedure amendment]

[Submission date] March 30, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

Japanese Patent Laid-Open No. 4-133427 discloses a closed container, a container which is installed outside the closed container and which stores at least one medicine connected to the closed container by a gas supply pipe, and the medicine. A means for heating the container to be stored, a means for holding and cooling the semiconductor substrate in the hermetically sealed container, and further storing the decomposing solution received in a receiver in the hermetically sealed container through a pipe. An apparatus for recovering impurities on a wafer surface by vapor of hydrogen fluoride equipped with a concentrating container and a heating means for heating the concentrating container is disclosed.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

Next, the condensing infrared lamp 10 is turned on and heated, and volatile substances such as hydrogen fluoride, silicon fluoride and water are evaporated from the recovered liquid to dryness, and the fluoride as an impurity is formed on the surface of the wafer 1. It remains as a residue in the center. In this way, a total reflection X-ray fluorescence analysis sample is obtained at the center of the surface of the wafer 1. During this period, only the opening 5 is opened during the dropping of hydrogen fluoride, and the other wafers 1 are all placed in the closed space,
No pollution from the atmosphere. Next, an example of total reflection fluorescent X-ray analysis using this embodiment will be described. Sample (a) is a wafer that is Cu-contaminated in a cleaning liquid SCl containing a trace amount of copper ions (Cu ions), and sample (b) is a natural oxide film formed on the surface after cleaning in a clean hydrochloric acid cleaning liquid. The wafer was removed by hydrogen fluoride treatment and was further contaminated with Cu in pure water to which a trace amount of copper ions (Cu ions) were added. Both Cu contaminations have a surface concentration of Cu ions of about 1 × 10 ¹¹ atoms / cm ³ .
The cleaning liquid SC1 used was a cleaning liquid for wafers, N
It is an alkaline / oxidizing mixed solution of H ₄ OH: H ₂ O ₂ : H ₂ O = 0.25: 1: 5. The analysis example (A) is an example in which the sample (a) is analyzed by the analysis method using this embodiment (referred to as the HF dropping method), and the analysis example (B) is an analysis method using this embodiment (referred to as the HF dropping method). ), The sample (b)
The analysis example and the analysis example (C) are comparative examples in which the sample (a) is analyzed by the analysis method (referred to as the HF vapor method) disclosed in Japanese Patent Laid-Open No. 4-133427 for comparison. . As shown in FIG. 7 for each analysis example, in the analysis example (A) by the HF dropping method, about 80% of the copper taken into the natural oxide film was recovered, but by the HF vapor method ( In C), the copper taken into the native oxide film was hardly recovered. Also, in the analysis example (B) by the HF dropping method, the recovery rate of the copper adsorbed on the wafer surface is about 1
It was only 0%. This is because the HF dropping method drops hydrogen fluoride on the native oxide film formed on the surface of the wafer to dissolve it, and dissolves contaminants together with the native oxide film to concentrate it in the recovery liquid. This shows that even if the dropping method is used, if the natural oxide film is not formed, the pollutants directly adsorbed on the wafer surface cannot be dissolved. Further, it is shown that this example is suitable for the analysis of the sample in which the natural oxide film is formed. Also, by the method of dropping hydrogen fluoride on the natural oxide film to dissolve it, compared to the case where the wafer analysis instrument according to the present embodiment is used, the influence of environmental pollution is obviously caused when it is not used. Is recognized. An analysis example (A) using the wafer analysis instrument according to the present example and an analysis example (D) simply analyzed in the clean draft chamber without using the wafer analysis instrument for samples similar to those described above in FIG. As shown in the analysis value of), in the analysis example (A), the copper recovery rate is about 80% and the variation is small, whereas in the analysis example (D), the copper recovery rate is about 80%. It shows a value considerably exceeding 100% and has a large variation. This indicates that environmental pollution is large unless the wafer analysis instrument according to the present example is used.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

Further, at this time, when hydrofluoric acid is dropped with the dry nitrogen N ₂ being introduced from the gas introduction port 4b with the valve 4d closed, the internal pressure of the hood 4a is increased and the dry nitrogen is opened 5 Emitted from. This prevents contaminants from entering the inside of the hood 4a from the atmosphere against the flow of dry nitrogen in the opening 5. Total reflection X-ray fluorescence analysis was performed using this example, and the same results as the analysis results in the first example were obtained.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0025

[Correction method] Change

[Correction content]

Next, the lid 6 is removed, the opening 5 is opened, and ultrapure water 13 is dropped on the surface of the wafer 1 with a pipette. Then, when scanned with ultrapure water, the condensed solution of hydrogen fluoride is collected in the center of the surface of the wafer 1 as a recovery liquid. Then, the recovered liquid is heated with infrared rays to dryness. In this way, a total reflection X-ray fluorescence analysis sample by the gas phase decomposition method is obtained at the center of the surface of the wafer 1. During this time,
While the hydrogen fluoride 12 is put in the container 6a and the opening 5 is only opened while the ultrapure water 11 is dropped, all the other wafers 1 are placed in the closed space and are not contaminated by the atmosphere. Total reflection X-ray fluorescence analysis was performed using this example, and the same results as the analysis results in the first example were obtained.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 7

[Correction method] Added

[Correction content]

FIG. 7 is a diagram showing analysis results using the first embodiment.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] Figure 8

[Correction method] Added

[Correction content]

FIG. 8 is a diagram showing analysis results using the first embodiment.

[Procedure Amendment 7]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 7

[Correction method] Added

[Correction content]

[Figure 7]

[Procedure Amendment 8]

[Document name to be corrected] Drawing

[Correction target item name] Figure 8

[Correction method] Added

[Correction content]

[Figure 8]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiji Takahashi 1-297 Kitabukuro-cho, Omiya City, Saitama Prefecture Central Research Laboratory, Mitsubishi Materials Co., Ltd.

Claims (3)

[Claims] 1. A wafer analysis instrument comprising: a holding member for holding a wafer; and a hood which is detachable from the holding member and which is capable of being covered and sealed to cover the wafer and having an opening with a lid. 2. The wafer according to claim 1, wherein the holding member includes a perforated plate on which the wafer is placed, and a suction member that sucks and holds the wafer on the perforated plate. Analytical instrument. 3. The infrared ray radiated from the infrared heater is transmitted through an infrared ray transmitting window of the adsorption member provided at a position corresponding to the hole of the perforated plate to heat the wafer. The wafer analysis instrument according to claim 2.