JP2006108364A - Droplet holder and impurity collection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a droplet holder and an impurity recovery method having high droplet-holding ability on the surface of a substrate and capable of extending the range of a sample from which an impurity can be collected. <P>SOLUTION: This droplet holder has a tubular shape, and has an opening at least at one end thereof with an opening area of ≤40 mm<SP>2</SP>, and this end has a tapered end surface 302, and the droplet holder is composed of a fluorine-contained resin having acid resistance and water repellency. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a droplet holder and an impurity recovery method using the droplet holder, and more particularly to a suitable one for analyzing impurities present on the surface of a semiconductor substrate or in a thin film.

  VPD (Vapor Phase Decomposition) and WSA (Wafer Surface Analysis) are widely known as methods for chemically analyzing trace impurities in the surface of a semiconductor substrate and in a thin film, as described in Non-Patent Document 1 described later. ing.

  In these methods, a semiconductor substrate is exposed to hydrofluoric acid vapor to dissolve a thin film and a natural oxide film, and the substrate surface is made hydrophobic, whereby a substrate surface or a thin film with a small amount (100 to 200 μl) of an acid solution is used. Impurities can be recovered.

  Specifically, the recovered droplets are dropped on a substrate exposed to hydrofluoric acid vapor, and the recovered droplets are moved by a cylindrical dedicated holder to recover the impurities.

However, even if the contact angle between the recovered droplet and the substrate surface is 90 degrees or less, such as the ion-implanted substrate surface, which is subsequently hydrophobized by exposure to hydrofluoric acid vapor, The recovered droplet could not be retained. For this reason, there has been a problem that the range of samples capable of collecting impurities is narrowly limited.
New version of silicon wafer surface cleaning technology, Section 3 Wafer surface metal contamination analysis and evaluation technology, May 2000 publication, Realize issue, supervision Jun Hattori JP-A-6-224275 JP-A-6-249769 JP-A-9-72836

  SUMMARY OF THE INVENTION In view of the above circumstances, the present invention has an object to provide a droplet holder and an impurity recovery method capable of expanding the range of a sample capable of recovering impurities by enhancing droplet retention on a substrate surface. And

A droplet holder according to an aspect of the present invention includes:
It has a tubular shape, has an opening having an opening area of 40 mm ² or less at least at one end, and is provided with a taper on the end face of the one end,
It is made of a fluorine resin having acid resistance and water repellency.

An impurity recovery method according to an aspect of the present invention includes:
Exposing the semiconductor substrate to acid vapor for a predetermined time;
Scanning the surface of the semiconductor substrate using the droplet holder according to claim 1 or 2 in a state where the dropped droplet is in contact with the surface of the semiconductor substrate;
It is characterized by providing.

  According to the droplet holder and the impurity recovery method of the present invention, the droplet retention on the substrate surface is improved, and the range of samples capable of recovering impurities is expanded.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(1) Embodiment 1
As shown in FIG. 1, the hydrofluoric acid vapor introduced into the container 101 as indicated by the arrow from the introduction port 101 a toward the discharge port 101 b on the surface of the semiconductor substrate 102 accommodated in the container 101. 103, the natural oxide film 104 existing on the surface of the semiconductor substrate 101 is dissolved, and the surface of the semiconductor substrate 102 is made hydrophobic.

  As a result, as shown in FIG. 2, the natural oxide film 104 existing on the surface of the semiconductor substrate 102 is dissolved (film 104a).

Thereafter, for example, 2% wtHF / 2% wtH ₂ O ₂ is dropped as a small amount (100 to 200 μl) of an acid solution on the surface of the semiconductor substrate 102, and the recovered droplet is moved using a droplet holder. Thus, impurities are recovered.

  Here, in the cylindrical droplet holder 201 as shown in FIGS. 3 and 4 as a comparative example, the lower end face is formed perpendicular to the longitudinal direction.

  As shown in FIG. 3, when the contact angle θ between the surface of the semiconductor substrate 102 and the recovered droplet is 90 degrees or more, the recovered droplet 202 is held on the substrate surface by the droplet holder 201. Can be scanned.

  However, as shown in FIG. 4, the surface of the semiconductor substrate 102 and the recovery droplets 202 are formed even after being exposed to hydrofluoric acid vapor to make it hydrophobic, such as the ion-implanted substrate surface. When the contact angle θ is less than 90 degrees, the recovered droplet 202 cannot be held. For this reason, when the droplet holder 201 according to the comparative example is used, the range of samples from which impurities can be recovered is limited.

On the other hand, the droplet holder 301 according to the present embodiment shown in FIG. 5 has the following configuration.
1) It is produced using a fluororesin (PTFE) which is a material excellent in acid resistance and water repellency.
2) It is cylindrical and has an opening having an area A of 40 mm ² or less in at least one place.
3) A taper 302 having an angle θ1 from an end surface perpendicular to the longitudinal direction of more than 0 degree and less than 90 degrees is provided on the end face of the lower portion of the opening.

  Accordingly, as indicated by arrows in FIGS. 6 and 7, the surface of the semiconductor substrate 102 on which the dissolved natural oxide film 104 a exists is scanned while the recovered droplet 202 is held by the droplet holder 301. To do.

  Thereby, impurities present in the semiconductor substrate 102 or in the dissolved natural oxide film 104 a are dissolved in the recovery droplet 302.

  By analyzing the impurities contained in the recovered droplets 302 using an analyzer (not shown), it is possible to analyze a very small amount of impurities present on the substrate surface or in the natural oxide film.

  Analyzes such as atomic absorption spectrometers, inductively coupled plasma mass spectrometers, inductively coupled plasma emission spectrometers, ion chromatograph analyzers, fluorescent X-ray analyzers or total reflection X-ray fluorescence analyzers, etc. Anything can be used as long as it can be analyzed.

  FIG. 8 shows the dependency of the droplet retention rate on the opening area in the droplet holder.

  More specifically, for each of a plurality of droplet holders 301 having different opening areas, a process of dissolving a natural oxide film in an unprocessed semiconductor substrate (bareSi) not subjected to the above-described ion implantation (hereinafter referred to as process A). 2 shows the droplet retention rate when the impurity recovery scanning operation is performed for those subjected to the above process and those subjected to the process A and then the process of dissolving the natural oxide film.

  Here, the droplet holding ratio is (distance that can be scanned while holding the recovered droplet) / (wafer entire surface scanning distance) × 100. That is, when the entire surface of the substrate can be scanned, it becomes 100%.

  As is clear from FIG. 8, the dependency of the droplet retention rate on the opening area of the droplet holder is low for an unprocessed semiconductor substrate.

  In the case of an untreated substrate, when the natural oxide film is dissolved by exposure to hydrofluoric acid vapor or the like, the substrate surface becomes hydrophobic. For this reason, it is possible to hold the recovered droplets relatively easily by using a droplet holder made of a water-repellent PTFE material.

However, in the semiconductor substrate subjected to the process A, the contact angle between the recovered droplet and the scanning substrate is about 40 degrees even after exposure to hydrofluoric acid vapor. The force between the two is relatively large, and the recovered droplet is likely to fall under the droplet holder. For this reason, it is difficult to hold the recovered liquid droplets unless the opening area is 40 mm ² or less.

  Therefore, it is necessary to make the opening area smaller and to increase the force for pulling the recovered droplet upward than the semiconductor substrate not subjected to the process A.

Therefore, in the first embodiment, by setting the aperture ratio of the droplet holder 301 to 40 mm ² or less, the force that pulls the recovered droplet upward due to the capillary effect is increased to improve the retention force. Drop retention is improved.

  FIG. 9 shows the jig shape dependency of the droplet retention rate in the droplet holder. More specifically, the droplet holder 301 according to the first embodiment in which the lower end face is tapered with respect to the semiconductor substrate that has been processed in the process A and then processed to dissolve the natural oxide film is used. The results of measuring the respective droplet retention rates in the case of using the droplet holder 201 according to the comparative example in which the taper is not formed are shown.

  From FIG. 9, it can be seen that the droplet holder 301 according to the first embodiment provided with a taper further improves the droplet retention rate.

  In the droplet holder 201 according to the comparative example, the lower end surface of the droplet holder 201 is perpendicular to the longitudinal direction as shown in FIG. The recovered droplet 202 leaks from the gap between the two, and the retention rate decreases.

  On the other hand, in the droplet holder 301 according to the first embodiment, since the taper 302 is formed on the lower end surface, the recovered droplet 202 is difficult to leak from the gap between the semiconductor substrate 102 and the lower end surface of the droplet holder 301. , The retention rate is improved.

  Thus, according to the droplet holder of the first embodiment and the impurity recovery method using the same, since the droplet retention is high, it is possible to expand the range of samples from which impurities can be recovered. .

(2) Embodiment 2
A droplet holder according to Embodiment 2 of the present invention and an impurity recovery method using the same will be described.

  The droplet holder 301 according to the first embodiment is provided with a taper 302 that is inclined outward at the lower end surface.

  On the other hand, as shown in FIG. 12, the droplet holder 401 according to the second embodiment is provided with a taper 402 that is inclined inward at the lower end surface.

  Such a second embodiment can also improve the droplet retention.

(3) Embodiment 3
FIG. 13 shows a configuration of a droplet holder according to Embodiment 3 of the present invention.

The droplet holder 701 according to the third embodiment has a two-stage opening structure, with a narrow tube portion 701 (opening area 7 mm ² ) aimed at the capillary effect at the top, and a recovered droplet 202 and a semiconductor substrate 102 at the bottom. In order to shorten the scanning time by increasing the contact area (opening area A2), the large tube part 702 having an opening area larger than that of the thin tube part 701 is provided.

  FIG. 14 shows the dependency of the droplet retention rate on the maximum opening area A2.

From FIG. 8, when the maximum opening area A2 exceeds 80 mm ² , the opening area becomes too large with respect to the droplet amount (100 to 200 μl) of the recovery droplet 202 and the recovery droplet 202 cannot be held. I understand that.

Therefore, the maximum opening area A2 in the thick tube portion 702 according to the third embodiment is set to 80 mm ² or less.

On the other hand, when the opening area A2 is less than 10 mm ² , the time for scanning the substrate surface becomes long and the working efficiency decreases. Therefore, the area of the opening area A2 is set to 10 mm ² or more and 80 mm ² or less.

  The above-described embodiments are merely examples and do not limit the present invention, and various modifications can be made within the technical scope of the present invention.

The longitudinal cross-sectional view which showed the process which melt | dissolves the natural oxide film on a semiconductor substrate. The longitudinal cross-sectional view which showed the dissolved natural oxide film. The longitudinal cross-sectional view which shows the droplet holding state when the angle which a collection | recovery droplet contacts a board | substrate is 90 degree | times or more using the droplet holder by a comparative example. The longitudinal cross-sectional view which shows the droplet holding state when the angle which a collection | recovery droplet contacts a board | substrate is less than 90 degree | times using the droplet holder by a comparative example. 1 is a longitudinal sectional view showing a configuration of a droplet holder according to Embodiment 1 of the present invention. The perspective view which showed a mode that the collection | recovery droplet was hold | maintained using the droplet holder, and the surface of a semiconductor substrate was scanned. The perspective view which showed a mode that the collection | recovery droplet was hold | maintained using the droplet holder, and the surface of a semiconductor substrate was scanned. The graph which shows the opening area dependence of the droplet retention in a droplet holder. The graph which shows the shape dependence of the holder of the droplet retention rate in a droplet holder. The longitudinal cross-sectional view which shows the state which hold | maintained the collection | recovery droplet using the droplet holder by a comparative example. The longitudinal cross-sectional view which shows the state holding the collection | recovery droplet using the droplet holder by the said Embodiment 1. FIG. The longitudinal cross-sectional view which showed the structure of the droplet holder by Embodiment 2 of this invention. The longitudinal cross-sectional view which showed the structure of the droplet holder by Embodiment 3 of this invention. The graph which shows the maximum opening area dependence of the droplet retention rate in a droplet holder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Sealed container 102 Semiconductor substrate 103 Hydrofluoric acid vapor 104 Natural oxide film 104a Dissolved natural oxide film 202 Collected droplets 301, 401, 701 Droplet holders 302, 402 Taper
702 Narrow tube
703 Thick pipe section

Claims (5)

It has a tubular shape, has an opening having an opening area of 40 mm ² or less at least at one end, and is provided with a taper on the end face of the one end,
A droplet holder made of a fluorine-based resin having acid resistance and water repellency. The opening is provided with a first tube portion and a second tube portion along the longitudinal direction from the end face,
The first tube portion has an opening area in a range of 10 mm ² or more and 80 mm ² or less,
The droplet holder according to claim 1, wherein the second tube portion has an opening area smaller than that of the first tube portion and is 40 mm ² or less. Exposing the semiconductor substrate to acid vapor for a predetermined time;
Scanning the surface of the semiconductor substrate using the droplet holder according to claim 1 or 2 in a state where the dropped droplet is in contact with the surface of the semiconductor substrate;
An impurity recovery method comprising:   4. The impurity recovery method according to claim 3, wherein the acid vapor includes at least one selected from the group consisting of hydrofluoric acid, nitric acid, hydrochloric acid, hydrogen peroxide solution, sulfuric acid, phosphoric acid, and ozone.   5. The impurity according to claim 3, wherein the droplet includes at least one selected from the group consisting of hydrofluoric acid, nitric acid, hydrochloric acid, hydrogen peroxide solution, sulfuric acid, phosphoric acid, and ozone water. Collection method.

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