JP3357037B2 - Semiconductor substrate cleaning method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a washing <br/> purification method of a semiconductor board.

[0002]

2. Description of the Related Art Conventionally, cleaning of a semiconductor substrate is performed by adding an ultrasonic vibrator to a pure water tank or a chemical tank to propagate ultrasonic waves in pure water or a chemical, and immersing the semiconductor substrate in the tank for cleaning. It is carried out.

[0003]

However, in the above-described cleaning method, since the ratio of ultrasonic waves absorbed in pure water or a chemical solution is large, the ultrasonic waves are applied to the semiconductor substrate (object to be cleaned).
, And the cleaning effect is low.

Further, if the ultrasonic power is increased to enhance the cleaning effect, there is a problem that the semiconductor substrate is damaged.

Further, organic solvents (IPA, ethyl alcohol, etc.) which are pure water or chemicals, and acids (H ₂ SO ₄ , H
₂ O ₂ , NH ₄ OH, etc.) and alkali solutions, etc., float in the liquid after the contaminants on the semiconductor substrate are removed by ultrasonic cleaning because of good wettability with the semiconductor substrate to be cleaned. The so-called re-adhesion phenomenon in which the contaminants adhere to the semiconductor substrate again cannot be avoided.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and can eliminate the above-mentioned conventional disadvantages. For example, the present invention can be applied to a method of cleaning a semiconductor substrate to achieve ultra-clean semiconductor substrates without causing damage. It is intended to provide a cleaning method.

[0007]

SUMMARY OF THE INVENTION The present invention provides a liquid and
Liquefied nitrogen on the surface of the semiconductor substrate with the particles attached
Solidifying the liquid by attaching come spray, this clotting
The particles expand from the surface due to the volume expansion effect
This is to remove the file.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a first embodiment of the present invention.

In this figure, reference numeral 31 denotes a tank formed of a heat insulating material and filled with liquid nitrogen 32. An ultrasonic vibrator 33 is attached to the bottom of the tank 31, and is connected to an ultrasonic oscillator (power supply) 34.

A partition 35 is provided in the tank 31.
The liquid nitrogen 32 overflows from the partition 35 to the discharge side. The overflowed liquid nitrogen 32 is pressurized by a pump 37 through an outlet 36,
It circulates through a filter 38.

When cleaning the semiconductor substrate 39, the carrier 40 accommodating the semiconductor substrate 39 is immersed in liquid nitrogen 32, and ultrasonic waves are transmitted to the liquid nitrogen 32 to irradiate the semiconductor substrate 39 with ultrasonic waves. Then, the contaminants on the substrate 39 are frozen and brittle by the liquid nitrogen 32, and furthermore, the contaminants are shrunk, and the contaminants are reduced by the ultrasonic vibration.
And is cleaned.

At this time, since the liquid nitrogen 32 has a very high surface tension, it is possible to prevent contaminants floating in the liquid nitrogen 32 from adhering to the semiconductor substrate 39 again after being removed from the substrate 39. After cleaning in this manner, when the semiconductor substrate 39 was pulled out of the liquid nitrogen 32, no contaminants (particles) were adhered.

The use of the liquid nitrogen 32 shortens the wavelength of the ultrasonic wave and decreases the energy per phonon, so that the semiconductor substrate 39 is not damaged by the ultrasonic wave. This damage is caused by liquid nitrogen
It is also considered that this does not occur because 9 is cooled.

The ultrasonic vibrator 33 may be vibrated in order to apply ultrasonic waves to the substrate 39 without unevenness. Although liquid nitrogen was used, for example, helium (H
The same effect can be obtained by using another liquefied gas such as e). Further, objects to be cleaned other than the semiconductor substrate can be cleaned in the same manner.

FIG. 2 is a view for explaining a second embodiment for cleaning one to several semiconductor substrates one by one.

In this embodiment, three tanks, a first tank 51, a second tank 52, and a third tank 53, are provided as tanks for filling the liquid nitrogen 54. The second tank 52 is a main tank for cleaning the semiconductor substrate 55 by ultrasonic waves.

The first tank 51 is a tank in which the semiconductor substrate 55 accommodated in the carrier 56 before cleaning is immersed in liquid nitrogen 54, and the cleaning of the semiconductor substrate 55 in the second tank 52 is completed. After the semiconductor substrate 55 is transferred to the third tank (recovery tank) 53, the semiconductor substrate 55 in the first tank 51 is transferred to the second tank 52. The first tank 51 is provided with an injection port 57 for injecting the liquid nitrogen 54, and clean liquid nitrogen is injected.

The injected liquid nitrogen 54 further fills the second tank 52 and the third tank 53 through the partition of each tank, and is discharged from an outlet 58 provided in the third tank 53. The first, second, and third tanks 51, 52, and 53 may be provided with inlets and outlets, respectively, so that the injection and discharge of liquid nitrogen may be performed independently of each tank.

An XY scanner 5 is provided in the second tank 52.
9 are provided. The XY scanner 59 includes two motors 60a and 60b, and the motors 60a and 60b.
And two sets of gear mechanisms 61a and 61b connected to
The table on which the semiconductor substrate 55 is placed can be moved vertically and horizontally.

The vertical movement is used to adjust the distance between the ultrasonic transducer described later and the semiconductor substrate 55 to eliminate the influence of the standing wave of the ultrasonic wave. On the other hand, the movement in the left-right direction is used to irradiate the entire surface of the semiconductor substrate 55 with ultrasonic waves.

An ultrasonic vibrator 62 is provided above the second tank 52.
Are connected to the ultrasonic oscillator 63. FIG. 3 shows a specific shape of the ultrasonic vibrator 62.

The ultrasonic vibrator 62 has an elongated shape. Therefore, the XY scanner 59 moves the semiconductor substrate 55 in the right and left direction orthogonal to the ultrasonic vibrator 62, so that the entire surface of the semiconductor substrate 55 is Can be irradiated with ultrasonic waves.

In this embodiment, the ultrasonic vibrator 62
The cleaning can also be performed by irradiating ultrasonic waves radially with a spherical ultrasonic transducer.

Further, it is possible to irradiate the whole surface of the semiconductor substrate with ultrasonic waves by scanning a rectangular ultrasonic transducer in the left-right direction and the front-back direction. Further, the ultrasonic vibrator may cover a portion in contact with liquid nitrogen with a heat insulating material to protect it from low temperatures.

Thus, in the second embodiment,
The semiconductor substrate 55 accommodated in the carrier 56 is immersed in the liquid nitrogen 54 of the first tank 51, and the semiconductor substrates 55 are sent, for example, one by one to the second tank 52, and subjected to ultrasonic cleaning with liquid nitrogen, Then, the semiconductor substrate 55 is sent to the third tank 53 and accommodated in the carrier 56, and pulled up from the liquid nitrogen 54.

Also in the second embodiment, a clean surface can be obtained as compared with the conventional chemical or pure water cleaning. Conventionally, at least a few particles existed, but in the present embodiment, there were no particles.

Next, a third embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. In the third embodiment, first, chemical (concentrated nitric acid) cleaning is performed, then pure water cleaning is performed, and finally, liquid nitrogen cleaning is performed. No ultrasonic waves are used in the liquid nitrogen cleaning section.

First, as shown in FIG.
Reference numeral 1 denotes a concentrated nitric acid tank.
Is filled. Further, the partition plate 1 is provided in the chemical tank 11.
The concentrated nitric acid 12 overflows on the partition plate 13 and flows into the effluent 14 to form the outlet 1
5b.

On the other hand, new concentrated nitric acid is injected into the chemical tank 11 through the injection port 15a at the bottom of the chemical tank 11, and the concentrated nitric acid 12 in the chemical tank 11 circulates. Semiconductor substrate 17 which is placed in carrier 16 as indicated by arrows A ₁ and 4 (b) of FIG. 4 (a), it is immersed in concentrated nitric acid in the chemical tank 11.

Next, the semiconductor substrate 17 and the carrier 16
Is pulled up from the chemical tank 11 as shown by arrow A ₂ in FIG. 4 (b), it is placed in a deionized water tank 18 as indicated by arrow A ₃ in FIG. 5 (a). The pure water tank 18 in FIG. 5A is filled with pure water 18a.

The pure water 18a is injected from an inlet 18b at the bottom of the pure water tank 18, overflows from an upper part of a partition plate 18c provided in the pure water tank 18, and is discharged as a drain 18d from an outlet 18e. And pure water 1
8a circulates in the pure water tank 18.

By immersing the semiconductor substrate 17 together with the carrier 16 in pure water 18a in the pure water tank 18 as shown in FIG. 5B, the chemicals adhered to the semiconductor substrate 17 in the pure water tank 18 are washed.

The semiconductor substrate 17 is washed with pure water 18a is pulled up from the pure water tank 18 as indicated by the arrow A ₄ of FIG. 5 (b), then, as shown by arrow A ₅ shown in FIG. 6 (a) It is put in a liquid nitrogen tank 19.

The liquid nitrogen tank 19 is thermally separated from the liquid nitrogen 19a inside by a heat insulating tank 19f. Similarly to the pure water tank 18 and the chemical tank 11, the liquid nitrogen 19a is injected from the injection port 19b, overflows from the upper part of the partition plate 19c, and is circulated as the discharge liquid 19d from the discharge port 19e.

The liquid nitrogen 1 in such a liquid nitrogen tank 19
During 9a, immersing the semiconductor substrate 17 as shown in arrows A ₅ and in FIG. 6 (a) 6 (b) .

FIG. 7A is an enlarged sectional view of a part of one semiconductor substrate 17 immersed in liquid nitrogen 19 a in a liquid nitrogen tank 19. As shown in FIG. 7A, the surface of the semiconductor substrate 17 is exposed to water 21
And particles 22 are attached.

As shown in FIG. 6B, the semiconductor substrate 17 to which the water 21 and the particles 22 are adhered is immersed in liquid nitrogen 19a in a liquid nitrogen tank 19, whereby the liquid nitrogen 19a Moisture 2 as shown in b)
1 becomes ice pieces 23, which are separated from the semiconductor substrate 17a together with the particles 22 by the expanding action at that time, and the surface of the semiconductor substrate 17 is dried in a clean state.

Thereafter, as shown in FIG. 6C, the semiconductor substrate 17 is pulled up from the liquid nitrogen tank 19, thereby completing all the steps.

In the third embodiment, the liquid nitrogen 19a in the liquid nitrogen tank 19 is circulated through a pump and a filter outside the tank to filter out water (ice) and particulate contaminants separated from the semiconductor substrate. It is even better if you collect it at

In the third embodiment, the liquid nitrogen tank 19
Although the semiconductor substrate 17 is immersed in the semiconductor substrate 17, liquid nitrogen may be sprayed on the semiconductor substrate 17 instead of the liquid nitrogen tank 19.

[0041]

As described above in detail, according to the present invention, liquefied nitrogen is sprayed on the surface of the semiconductor substrate, so that contaminants on the semiconductor substrate can be removed satisfactorily and reliably.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the present invention.

FIG. 3 is a perspective view illustrating a specific shape of an ultrasonic transducer according to a second embodiment.

FIG. 4 is a sectional view showing a part of a third embodiment of the present invention.

FIG. 5 is a sectional view showing a part of a third embodiment of the present invention.

FIG. 6 is a sectional view showing a part of a third embodiment of the present invention.

FIG. 7 is a cross-sectional view showing a state of removing attached matter according to a third embodiment of the present invention.

[Explanation of symbols]

 16 Semiconductor substrate 18 Pure water tank 18a Pure water 19 Liquid nitrogen tank 19a Liquid nitrogen 31 tank 32 Liquid nitrogen 33 Ultrasonic vibrator 39 Semiconductor substrate 51 First tank 52 Second tank 53 Third tank 54 Liquid nitrogen 55 Semiconductor substrate 56 Ultrasonic wave Vibrator

Claims (1)

(57) [Claims] 1. A semiconductor to which liquid and particles adhere.
The liquid by attaching can spray the liquid nitrogen to the surface of the body substrate
Coagulates the body, and the volume expansion effect during coagulation
Removing the particles from the surface.
Cleaning method for semiconductor substrates .