JP2000107672A - Semiconductor substrate surface impurity recovering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recover not only molecular or ionic impurity metal but also particulate impurity metal that is not dissolved in droplets in a device for recovering metal impurities on a semiconductor substrate by providing a means for giving vibration to a droplet holding means and/or a semiconductor holding means. SOLUTION: After an arbitrary quantity of solution is dropped onto a semiconductor substrate 10 held on a holding means 1 from a solution feeding means 3, a droplet holding means 5 is moved by a scanning means 6 to scan the dropped liquid droplets 4 to recover ionic or molecular impurity metal existing on the semiconductor substrate 10. In such a recovering device, an ultrasonic generator 8 for vibrating the semiconductor substrate 10 from the rear is provided. The generator 8 is installed in pure water 11 and the semiconductor substrate is held so that the surface not to be analyzed thereof is in contact with the pure water. In this way, particulate impurity metal not dissolved in the droplets can be also recovered. As a chemical solution used for recovery, an alkaline solution is preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor substrate surface impurity recovery apparatus for preparing a sample solution for analyzing ultratrace impurities on a semiconductor substrate surface.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional semiconductor substrate surface impurity recovery apparatus.

In FIG. 1, a semiconductor substrate holding means 1 for holding a semiconductor substrate 10, the semiconductor substrate holding means,
Solution supply means 3 for dropping an arbitrary volume of solution
And a droplet holding means 5 for holding the dropped droplet 4
Scanning means 6 for moving the liquid drop holding means to scan the liquid drops dropped on the semiconductor substrate, and a liquid drop collecting container 7 for collecting the liquid drops.

In such a configuration, after the chemical solution 9 is dropped on the semiconductor substrate 10 by the solution supply means 3, the droplet 4 is scanned on the semiconductor substrate 10 by the droplet holding means 5, and The existing ionic and molecular impurity metals are recovered and recovered in the droplet recovery container 7. By measuring the amount of metal contained in the collected droplets using a high-sensitivity analyzer such as a graphite furnace atomic absorption spectrometer or an inductively coupled plasma mass spectrometer, the metal impurity concentration on the semiconductor substrate can be obtained. .

[0005]

As described above, in the prior art, ionic and molecular impurity metals existing on a semiconductor substrate are recovered, but particulate metal impurities that do not dissolve in droplets are removed from the liquid. There is a problem that the amount of the impurity metal on the semiconductor substrate shows a low value because it is not taken in the droplet and remains on the semiconductor substrate. Further, when an organic substance is attached to the surface of the semiconductor substrate, it is difficult to scan the entire surface of the semiconductor substrate.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a device for recovering metal impurities on a semiconductor substrate, which can be used not only in ionic and molecular forms but also in liquid form. It is an object of the present invention to provide an apparatus for recovering particulate impurity metal not dissolved in droplets and performing a recovery operation so that a correct value can be obtained as the impurity metal concentration on a semiconductor substrate.

[0007]

In order to achieve the above object, according to the present invention, in a device for recovering metal impurities on a semiconductor substrate, vibration is applied to a droplet holding means, a semiconductor substrate holding means, or both. By providing the means, the particulate metal is held and collected in the droplet. The vibration applied to the droplet holding means and the semiconductor substrate holding means is controlled to an optimum frequency according to the size and type of particles on the semiconductor substrate. Also, the direction of the vibration is selected to be the optimum direction depending on the particles. Due to these vibrations, the particles in the droplet are not adsorbed on the semiconductor substrate, and the adsorbed particles are separated and held in the droplet. Agglomeration of particles can be prevented, and particles do not remain on the semiconductor substrate. Further, it is possible to stably hold the particles in the droplet by applying a potential to the droplet and the semiconductor substrate or the holding means.

Further, an organic solvent is added to the recovered solution,
By supplying the gas as a gas to the surface of the semiconductor substrate, organic substances adhering to the surface of the semiconductor substrate are dissolved, and the scanning of the recovered liquid is facilitated. Further, by adding a surfactant or the like to the droplet, the particles can be more stably held in the droplet. By the above means, not only ionic and molecular forms, but also particulate impurity metals not dissolved in the droplets are recovered, and a recovery operation is performed so that a correct value can be obtained as the impurity metal concentration on the semiconductor substrate. It becomes possible to provide a device.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to embodiments.

FIG. 1 is a schematic view showing a semiconductor substrate surface impurity recovery apparatus used in an embodiment of the present invention. In the figure, reference numeral 8 denotes an ultrasonic oscillator for vibrating the semiconductor substrate from the back surface, and the frequency and direction of the vibration can be arbitrarily changed. Although a ceramic diaphragm was used here,
Any oscillator made of any material capable of providing vibration at a frequency of 20 kHz to 4 MHz can be used. This oscillator is placed in pure water 11 in the figure, and the semiconductor substrate is held such that the surface not to be analyzed comes into contact with this pure water. In this case, the vibration on the analysis target surface propagates from the non-target surface, so that particles on the analysis target surface side are easily collected.

The frequency is within the above range, especially 300 kHz
A fixed-frequency vibrator may be used in the range of 2 MHz to 2 MHz, but it is preferable to use a plurality of vibrators. Further, it is more preferable that the vibration frequency can be swept.

As the chemical used for recovery, both acidic and alkaline chemicals can be used. Preferably, the use of an alkaline chemical makes it easier to collect particles by making the zeta potentials of the particles in the semiconductor substrate 10 and the droplets 4 uniform. can do. However, if the alkalinity is high, ions in the droplets may precipitate as hydroxides. Therefore, a weakly alkaline chemical having a pH of 8 or less is preferably used. Further, by adding an organic solvent such as acetone or alcohol, an organic substance adhering to the surface of the semiconductor substrate can be dissolved, and scanning of the recovered liquid can be facilitated. Furthermore, if a surfactant or the like is added, the particles can be more stably held in the droplet.

Next, the operation of the apparatus for collecting impurities on the surface of a semiconductor substrate shown in FIG. 1 will be described.

The chemical solution 9 was dropped on the semiconductor substrate 10 held by the semiconductor substrate holding means 1 by the solution supply means 3. The droplet 4 dropped by the droplet holding means 5 is scanned on the semiconductor substrate 10 to collect ionic and molecular impurity metals present on the semiconductor substrate 10. The droplet 4 that has scanned the entire surface of the semiconductor substrate 10 is collected in the droplet collection container 7. The scanning method may be to move the scanning means 6 in the radial direction while rotating the semiconductor substrate holding means 1, or to scan the entire surface of the substrate by moving the scanning means 6 in parallel.

FIG. 2 shows an apparatus for collecting impurities on the surface of a semiconductor substrate provided with a device for directly applying ultrasonic vibration to a droplet and further applying a voltage. In the figure, reference numeral 12 denotes an ultrasonic oscillator for vibrating a droplet on a semiconductor substrate, and the frequency and direction of the vibration can be arbitrarily changed. The vibration frequency and vibration direction can be arbitrarily changed in the same manner as 8 in FIG. The droplet vibration means is provided in the droplet holding means 5 in the figure, and applies ultrasonic vibration to the droplets on the semiconductor substrate via the droplet holding means, thereby facilitating the collection of particles from the semiconductor substrate 10. . In the figure, reference numeral 13 denotes a device for applying a voltage between the semiconductor substrate 10 and the droplet 4, and the applied voltage and the application method can be changed according to the potential of the particles in the droplet. When the particles in the chemical liquid are negatively charged, the droplet holding means is positively charged, and when the particles in the chemical liquid are positively charged, the droplet holding means is negatively charged, whereby the particles are peeled from the semiconductor substrate. , Facilitate recovery.

Example 1 As Example 1, an apparatus for collecting impurities on the surface of a semiconductor substrate as shown in FIG. 1 was used. At this time,
The surface concentration of each of Na, Mg, Al and Ca is 1 × 10 ¹²
Five 8-inch silicon wafers subjected to forced contamination to atoms / cm ² and heat-treated at 1000 ° C. for 10 minutes in a diffusion furnace are prepared. Prior to the collection operation, hydrofluoric acid vapor is placed in a closed container. For 30 minutes to decompose the silicon oxide film on the surface. The silicon wafer is held by the semiconductor substrate holding means 1 and EDTA as a surfactant is added to the hydrochloric acid and hydrogen peroxide solution by the solution supply means 3.
Of 0.1 was dropped on the silicon wafer. The entire surface of the wafer was scanned with the droplets 4 at a speed of 30 mm / sec using the fluororesin droplet holding means 5. At this time,
During the period from the dropping of the droplet 4 to the completion of the scanning, the silicon wafer is subjected to 300 kHz through the pure water 11 from the back surface.
Was irradiated so that the silicon wafer vibrated vertically. The collected droplets 4 were collected from each wafer using an inductively coupled plasma mass spectrometer.
a, Mg, Al, and Ca were quantified.

Comparative Example 1 As Comparative Example 1, the same operation as in Example 1 was performed without performing ultrasonic irradiation.

As a result, in Example 1, as shown in Table 1, a sufficient recovery rate was obtained for the elements present on the silicon wafer as oxide particles, such as Mg, Al, and Ca, and repeated. It was confirmed that the accuracy was excellent. On the other hand, in Comparative Example 1, the recovery of these elements was insufficient and the values were low, and the dispersion between wafers was large.

[0019]

[Table 1] Example 2 As Example 2, an apparatus for collecting impurities on the surface of a semiconductor substrate as shown in FIG. 2 was used. At this time, five 8-inch silicon wafers were prepared in the same manner as in Example 1, and prior to the recovery operation, the silicon oxide film on the surface was decomposed by exposing to a hydrofluoric acid vapor for 30 minutes in a closed container. The silicon wafer was held by the semiconductor substrate holding means 1, and 0.1 ml of the chemical solution 9 containing ammonia was dropped on the silicon wafer by the solution supply means 3. The entire surface of the wafer was scanned with the droplets 4 at a speed of 30 mm / sec using the fluororesin droplet holding means 5. At this time, from the dropping of the droplet 4 to the completion of scanning, the droplet 4 was irradiated with ultrasonic waves of 1 MHz via the droplet holding means 5. Further, voltage applying means 1
3, the droplet holding means 5 was charged to +50 mV. The collected droplets 4 were collected from each wafer using an inductively coupled plasma mass spectrometer.
Ca was quantified.

(Comparative Example 2) As Comparative Example 2, the same operation was performed using the same apparatus as in Example 2 without applying a voltage to the ultrasonic irradiation and the droplet holding means.

As a result, in Example 2, as shown in Table 2, a sufficient recovery rate was obtained for the elements present on the silicon wafer as oxide particles, and the repetition accuracy was excellent. On the other hand, in Comparative Example 2, the recovery of these elements was insufficient and the values were low, and the dispersion between wafers was large.

[0022]

[Table 2]

[0023]

As described above, according to the present invention,
The total amount of metal impurities on the semiconductor substrate can be recovered, and the amount of metal impurities on the semiconductor substrate can be determined.

[Brief description of the drawings]

FIG. 1 is a schematic view of a semiconductor substrate surface impurity recovery apparatus showing one embodiment of the present invention.

FIG. 2 is a schematic view of a semiconductor substrate surface impurity recovery apparatus showing one embodiment of the present invention.

FIG. 3 is a schematic view of a conventional semiconductor substrate surface impurity recovery apparatus.

[Explanation of symbols]

1: semiconductor substrate holding means, 3: solution supply means, 4: droplet, 5: droplet holding means, 6: scanning means, 7: droplet collection container, 8: semiconductor vibrating means, 9: chemical liquid, 10: semiconductor Substrate, 11: pure water, 12: droplet vibration means, 13: voltage application means

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoshihiro Uozumi 8th Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture F-term in Toshiba Yokohama Office 4F042 AA07 DA01 EB25 4M106 AA01 BA12 CA29 DH20 DH53

Claims (6)

[Claims] A semiconductor substrate holding means for holding a semiconductor substrate; a solution supply means for dropping an arbitrary volume of a solution onto the semiconductor substrate; a droplet holding means for holding the dropped solution; Scanning means for moving the liquid drop holding means to scan the liquid drops dropped on the semiconductor substrate, a liquid drop collecting container for collecting the liquid drops, and applying vibration of an arbitrary frequency to the liquid drop holding means An apparatus for collecting impurities on a surface of a semiconductor substrate, comprising: a droplet holding vibrating means. 2. A semiconductor substrate holding means for holding a semiconductor substrate, a solution supply means for dropping an arbitrary volume of solution onto the semiconductor substrate, a droplet holding means for holding the dropped solution, Scanning means for moving the liquid drop holding means to scan the liquid drops dropped on the semiconductor substrate, a liquid drop collecting container for collecting the liquid drops, and a substrate for applying vibration of an arbitrary frequency to the substrate holding means An apparatus for collecting impurities on the surface of a semiconductor substrate, comprising a holding vibration means. 3. The apparatus according to claim 1, further comprising a substrate holding vibrating means for applying vibration of an arbitrary frequency to the substrate holding means.
3. The apparatus for collecting impurities on a surface of a semiconductor substrate according to claim 1. 4. The semiconductor substrate surface impurity recovery apparatus according to claim 1, further comprising a potential applying means for applying an arbitrary potential to the droplet dropped on the semiconductor substrate. 5. The apparatus for collecting impurities on the surface of a semiconductor substrate according to claim 1, further comprising means for supplying an arbitrary organic solvent to droplets dropped on the semiconductor substrate. 6. The semiconductor substrate surface impurity recovery apparatus according to claim 1, wherein an arbitrary surfactant is contained in the droplet dropped on the semiconductor substrate.