JPH01140727A - Cleaning of substrate - Google Patents

Abstract

PURPOSE:To clean and remove a fine particle efficiently by a method wherein, prior to a wiping and cleaning process or an ultrasonic cleaning process, the outer surface of a substrate is cleaned by using a cleaning liquid containing hydrogen peroxide or ozone. CONSTITUTION:An ammonia hydrogen peroxide solution as a cleaining liquid containg hydrogen peroxide is supplied to both the surface and the rear of a wafer W; a contamination of an organic substance on both the surface and the rear of the wafer W is oxidized and decomposed by using hydrogen peroxide. Then, while pure water as the cleaning liquid is being supplied to both the surface and the rear of the wafer W, both the surface and the rear of the wafer W is wiped and cleaned by actuating wiping materials 1, 2 composed of porous materials or the like; mainly a large particle is cleaned and removed. Then, while an ultrasonic vibration is being applied, pure water as the cleaning liquid or pure water containing ozone is supplied to both the surface and the rear of the wafer W and an ultrasonic cleaning operation is executed; also a fine particle is cleaned and removed. By this setup, the fine particle is stripped off from the substrate effectively; it is cleaned and removed.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for cleaning various substrates such as liquid crystal glass substrates and semiconductor substrates. The present invention relates to a substrate cleaning method including a wiping cleaning step of cleaning the outer surface and an ultrasonic cleaning step of applying a cleaning liquid while applying ultrasonic vibration to clean the outer surface of the substrate.

<Prior Art> The following methods are known as conventional substrate cleaning methods.

(A) First Conventional Example As disclosed in Japanese Unexamined Patent Publication No. 57-119347, a mechanical cleaning method of scrubbing with gauze or a nylon brush while using a detergent, a phenolic resist stripper, acetone, trichlorethylene, nitric acid,
Chemical cleaning methods involve continuous use of sulfuric acid, etc., or steam cleaning; a solvent such as acetone or Freon is placed in a container that generates ultrasonic waves, and the attached dirt is peeled off by ultrasonic waves. The photomask is cleaned using two or more methods simultaneously: an ultrasonic cleaning method for cleaning, and a dient spray cleaning method for removing attached dust by jetting high-pressure pure water or the like from a nozzle.

(B) Second Conventional Example As disclosed in Japanese Unexamined Patent Application Publication No. 59-19329, an ultrasonic cleaner that cleans by applying ultrasonic vibration while supplying a cleaning liquid to the surface of a rotating workpiece to be cleaned. a sonic cleaning process;
The substrate is cleaned by a wiping cleaning process in which the substrate is scrubbed with a brush while spraying a cleaning liquid, and an ultrasonic cleaning process in which cleaning is performed by applying ultrasonic vibration while supplying the cleaning liquid.

<Problems to be Solved by the Invention> However, in both of the cleaning methods of the first and second conventional examples, the particle size attached to the outer surface of the substrate is 2 μm.
Although particles larger than 100 yen can be removed well, particles with a particle size of 2 μ-
Particles smaller than 100% cannot be effectively removed and remain attached to the substrate even after cleaning. For example, during photoetching, the remaining attached fine particles may enter the photoresist film and impair the quality of the photoresist film. There have been drawbacks such as deterioration and product defects, and short circuits and disconnections between wires when forming wires.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method that can effectively wash and remove particles having a particle size of less than 2 μm.

Means for Solving the Problems> In order to achieve the above object, the present invention provides a wiping cleaning process in which the outer surface of the substrate is cleaned by operating a wiping member while supplying a cleaning liquid, and this wiping cleaning process. After the step, in a substrate cleaning method including an ultrasonic cleaning step of cleaning the outer surface of the substrate by applying a cleaning liquid while applying ultrasonic vibration, prior to the wiping cleaning step or the ultrasonic cleaning step, Clean the outer surface of the substrate with a cleaning solution containing hydrogen peroxide or ozone.

<Operation> According to the above configuration, at least before the ultrasonic cleaning process, dirt such as organic matter on the outer surface of the substrate is oxidized and decomposed by a cleaning solution containing hydrogen peroxide or ozone, and particles are easily separated from the substrate. (Since, in the ultrasonic cleaning process, when ultrasonic imaging is applied to vibrate the fine particles attached to the outer surface of the substrate, the fine particles are effectively peeled off from the substrate and cleaned and removed. Note that the wiping cleaning process is performed before or after cleaning with a cleaning solution containing hydrogen peroxide or ozone, and large particles are washed away during the wiping cleaning process, regardless of whether it is before or after the cleaning.

<Example> Next, an example of the present invention will be described in detail based on the drawings.

First Embodiment> FIG. 1 is a schematic vertical sectional view of a first embodiment of a substrate cleaning apparatus that implements the method of the present invention.

In this figure, L is a loader, which takes out and supplies wafers W as substrates housed in multiple stages in a cassette CI.

UL is an unloader that sends and receives wafers W after cleaning processing, and cassette C! It is designed to be housed in multiple stages inside.

Between the loader L and the unloader UL, there is a first processing unit P1 that cleans both the front and back surfaces of the wafer W with a cleaning liquid containing hydrogen peroxide or ozone, and a wiping member 1.2 acts on the wafer W while supplying the cleaning liquid. A second processing unit P2 for wiping and cleaning both the front and back sides of the wafer W, and a third processing unit P3 for ultrasonically cleaning both the front and back sides of the wafer W by applying a cleaning liquid while applying ultrasonic vibrations are provided in series, Then, between the loader L and the first processing unit P1, between the first processing unit P1 and the second processing unit P2, between the second processing unit P2 and the third processing unit P3, and between the third processing unit P3 and the unloader UL. , wafer transport means TI, T2. T3 and T4 are provided to constitute a substrate cleaning apparatus.

In the method of the present invention, the above-mentioned substrate cleaning apparatus is used to clean the wafer W.
While transporting the wafer W, the following steps are sequentially performed to clean both the front and back surfaces of the wafer W to remove attached particles, which will be described in detail below.

■ Cleaning process An ammonia-hydrogen peroxide solution containing ammonia, hydrogen peroxide, and pure water mixed in a weight ratio of 1:1:8 is supplied as a cleaning solution containing hydrogen peroxide to both the front and back surfaces of the wafer W. Hydrogen peroxide oxidizes and decomposes dirt such as organic matter on both the front and back sides of the paper. If necessary, a step of spraying pure water at high pressure may be added. As the cleaning liquid in this step, a sulfuric acid hydrogen peroxide solution using sulfuric acid instead of ammonia or pure water containing ozone may be used.

Further, an aqueous sulfuric acid solution containing ozone may be used as the cleaning liquid.

■ Wiping cleaning process While supplying pure water as a cleaning liquid to both the front and back surfaces of the wafer W, a wiping member 1.2 made of a porous material such as polyvinyl alcohol resin is applied thereto. Wipe and clean both sides to mainly remove large particles. In this step, the aforementioned ammonia hydrogen peroxide solution or ozone-containing pure water may be used as the cleaning liquid instead of pure water.

■Ultrasonic cleaning process Ultrasonic cleaning is performed by supplying pure water, ozone-containing pure water, or ammonia-hydrogen peroxide solution as a cleaning liquid to both the front and back surfaces of the wafer W while applying ultrasonic vibrations, thereby cleaning fine particles as well. Remove.

After that, both the front and back sides of the wafer W are cleaned by supplying pure water,
Furthermore, with the pure water supply stopped, the wafer W is rotated at high speed to perform draining drying, and after the drying process, the wafer W is
is taken out and stored in the cassette C2 of the unloader UL.

In the above treatment, after the drying treatment, the cleaning step may be performed again, and the series of cleaning treatments may be repeated two or more times to further enhance the cleaning effect.

Next, each part constituting the substrate cleaning apparatus will be explained.

Although not shown, the loader L is provided with an elevator that moves the cassette CI up and down, and is equipped with an elevator that moves the cassette CI up and down.
The height of the cassette C1 is detected, a predetermined portion of the cassette C1 is positioned at the transport height, and the lowest wafer W accommodated in the cassette C1 is taken out.

Although not shown, the unloader UL is also provided with an elevator that moves the cassette C2 up and down, detects the height of the cassette C2 using an optical sensor, etc., and positions a predetermined location of the cassette C2 at the transport height. The cassette C2 is configured to accommodate the wafers W after the cleaning process from the top inside the cassette C2.

The wafer transport means Tl, T2. T3. Each T4 is provided with a first arm that can be freely driven and rotated around the vertical axis by a rotational drive means such as an electric motor, and
A second arm is connected to the tip of the first arm so as to be rotatable around the vertical axis, the rotational movement of the first arm is transmitted to the second arm by a rotation transmission mechanism, and the wafer W is placed on the tip of the second arm. A device configured to place the wafer W by suction and move it in the horizontal direction to transport the wafer W (Utility Model No. 60-17654)
Various means are adopted, such as (see Publication No. 8).

The first processing unit P1 is provided with a rotating member 3 driven and rotated around a vertical axis by an electric motor or the like, and the rotating member 3 is a plurality of members extending radially from the upper end of the rotating shaft. A clamping claw 4 is provided on the tip side of each of the clamping claws 4, and a predetermined one of the clamping claws 4...
It is configured to be movable horizontally toward and away from the opposing clamping claws 4, and the wafer W is inserted between the opposing clamping claws 4 with a large gap between them, while the opposing clamping claws By making the interval 4.4 small, the inserted wafer W is held between the holding claws 4 .

A nozzle 5.5 for spraying a cleaning liquid is provided on each of the upper and lower sides of the rotating member 3, and while the wafer W is driven and rotated, a cleaning liquid such as the above-mentioned ammonia-hydrogen peroxide solution is sprayed onto each of the front and back surfaces of the wafer W. It is configured.

In the second processing unit) P2, base plates 6.6 are provided on the upper and lower sides of the wafer W transport path, respectively, and are rotatably driven by electric motors in opposite directions around the vertical axis. .6 each is provided with a sponge-like wiping member 1.2.

A cleaning liquid supply path R is formed on each support shaft 6a of the base plate 6.6, and the cleaning liquid is alternately supplied through the supply paths R and R to the wiping member 1 to which the cleaning liquid is not supplied.
or 2, while holding the wafer W, the front and back surfaces of the wafer W are alternately cleaned.

The third processing unit P3 is provided with a rotating member 7 and clamping claws 8 having the same configuration as the first processing unit P1.
Nozzles 9, 9 for spraying cleaning liquid are provided on the upper and lower sides of the rotating member 7, respectively, and an ultrasonic vibrator 10 is attached to each of the nozzles 9, 9 for spraying the cleaning liquid. , is configured to spray and supply a cleaning liquid to which ultrasonic vibrations have been applied to each of the front and back surfaces for cleaning. The cleaning liquid may be supplied to both the front and back surfaces of the wafer W at the same time, or may be supplied alternately. The frequency of the ultrasonic waves generated by the ultrasonic vibrator 10 is 800 KHz, which is suitable for cleaning and removing fine particles.
It is preferable to do the above.

Next, the results of an experiment conducted using the substrate cleaning apparatus of the first embodiment will be explained.

The frequency of the ultrasonic transducer 10 in the third processing unit P3 is set to 800KH2, and a series of cleaning processes is performed only once, and before the processing (indicated by A), the second processing unit 1
- After the processing in P2 (indicated by B) and after the processing in the third processing unit 1-P3 (indicated by C),
The number of dust particles attached to the wafer W is 0.2 to 0.3 t.
tm (1'), 0.3~0.4am (I[)
, 0.4-2.0 pm (III), 2.0 am
When measuring each particle size (rV) and determining the total number of particles (V), results were obtained as shown in the following table and the semi-logarithm graph in FIG. 2.

(Hereinafter, blank space) From the above results, as shown in the graph of Figure 2, 90% of particles with a particle size of 2 μm or more can be removed through the wiping and cleaning process, but particles with a particle size of less than 2 μm can be removed. It is clear that the number of such cases is extremely small.

However, by going through an ultrasonic cleaning process that is preceded by cleaning with a cleaning solution containing hydrogen peroxide, nearly 80% of the particles are removed, even if the particle size is 0.2 to 0.3 μm. It was clear that the removal rate was extremely high at 84% in total.

Note that when a series of cleaning steps are repeated, particles attached to the wafer W can be removed at a rate close to that shown in the table above.

Second Embodiment FIG. 3 is a schematic vertical sectional view of a second embodiment of a substrate cleaning apparatus that implements the method of the present invention.

The substrate cleaning apparatus of the second embodiment performs a cleaning process by immersing the wafer W in a cleaning liquid. A second processing unit P20 wipes and cleans both the front and back surfaces of the wafer W by applying a wiping member 1.1.12 consisting of a rotating brush while immersed in the cleaning solution of the processing unit PIO1, and a second processing unit P20 that wipes and cleans both the front and back surfaces of the wafer W while being immersed in the cleaning solution. A third processing unit P30 performs ultrasonic cleaning on both the front and back surfaces of the wafer W by immersing it in the medium, and a fourth processing unit P performs a drying process on the wafer W after the cleaning process by blowing air.
40 are provided in series, and the first processing unit P
10, 2nd processing unit) P2O, 3rd processing unit 1-P
2O and the fourth processing unit P40, a feed loader 13 is provided so as to be able to freely rotate forward and backward.

The first processing unit P10 is equipped with an immersion tank 14 and a receiving tank 15, and nozzles 16 are arranged in parallel above and below the feed roller 13 in the immersion tank 14, and the nozzles 16... * and the receiving tank 15 are connected to each other via a liquid supply pipe 19 in which a pump 17 and a filter 18 are interposed.

Further, an inlet-side shutter mechanism 20 and an outlet-side shutter mechanism 21 are provided at the inlet and outlet of the immersion tank 14, respectively, and a discharge pipe 23 having a valve 22 interposed therein is communicatively connected to the immersion tank 14, and Wafer detection sensors 24 and 25 for detecting wafers W are provided near the entrance and exit, respectively.

As a result, in the initial stage, the valve 22 is opened to discharge the cleaning liquid in the immersion tank 14 to the receiving tank 15, and the amount of cleaning liquid is reduced to a position below the lower end level of each of the inlet and outlet, and in this state, Entrance side shutter mechanism 20
is opened and the wafer W is carried into the dipping tank 14. after that,
When the wafer detection sensor 24 detects that the wafer W has been carried into the immersion tank 14, the artificial side shutter mechanism 20 is closed, the pump I7 is driven, and the feed roller 13 is driven.
While reciprocating the wafer W in the horizontal direction, a cleaning solution containing hydrogen peroxide or ozone, such as an ammonia-hydrogen peroxide solution, is sprayed and supplied from the nozzle 16, and the water is kept in the cleaning solution for a certain period of time. Before immersing the wafer W, both the front and back surfaces of the wafer W are cleaned to remove dirt such as organic matter adhering to the wafer W.

After the cleaning process, stop driving the pump 17 and close the valve 2.
2 to drain the cleaning liquid in the immersion tank 14 into the receiving tank 15,
The amount of cleaning liquid is reduced to a position below the lower end level of each of the inlet and outlet, and then the feed rollers 13 and
... carries out the wafer W, and as the wafer detection sensor 25 detects that the wafer W is ready to be carried out from the immersion tank 14, the exit side shutter mechanism 2
1 is opened, and the wafer W is transferred to the second processing (2) P2O.

A receiving gutter 26 is attached around the immersion tank 14, and the immersion tank 14
It is configured to receive the cleaning liquid overflowing from the tank 15 and collect it in a receiving tank 15.

The second processing unit P20 is equipped with an immersion tank 27 and a receiving tank 28 similar to those in the first processing unit PLO, and the immersion tank 27 has an inlet shutter mechanism 29 and an outlet shutter mechanism as described above. 30, wafer detection sensors 31, 32, a discharge pipe 34 with a valve 33 interposed therein, and a receiver! 35 are provided.

The immersion tank 27 and the receiving tank 28 are connected to each other via a liquid supply pipe 38 having a pump 36 and a filter 37 interposed therebetween, and wiping members using rotating brushes are installed above and below the feed rollers 13 in the immersion tank 27, respectively. 11.12 are installed in parallel,
Immersion W in the same manner as in the first processing unit I-PIO
! The wiping member 11.1 carries the wafer W into the cleaning solution 27, and while the wafer W is reciprocated in the horizontal direction by the feed rollers 13, the wafer W is immersed in the cleaning liquid for a certain period of time.
2 is applied to wipe and clean both the front and back surfaces of the wafer W, and mainly particles having a particle size of 2 μm or more adhering to the wafer W are removed. The above-mentioned wiping member 11.12 includes:
The sponge-like material used in the first embodiment may also be used.

The third processing unit P30 includes the second processing unit 1 described above.
- An immersion tank 39 and a receiving tank 40 similar to those in P2O are provided, and the immersion tank 39 is connected via an artificial side shank mechanism 41, an outlet side shank mechanism 42, wafer detection sensors 43, 44, and a valve 45, as described above. A discharge pipe 46, a liquid supply pipe 49 with a pump 47 and a filter 48 interposed therebetween, and a receiving gutter 50 are provided.

Ultrasonic oscillators 51 and 52 are provided on the upper and lower sides of the feed rollers 13 in the dipping tank 39, respectively.
The wafer W is loaded into the immersion bath 39 in the same manner as in PLO, and the wafer W is reciprocated in the horizontal direction by the feed rollers 13 while applying ultrasonic vibration to the cleaning liquid for a certain period of time. Both the front and back surfaces of the wafer W are subjected to ultrasonic cleaning to remove even particles with a particle diameter of less than 2 μm attached to the wafer W.

The fourth processing unit P40 includes feed PJ rollers 13...
Air knives 53 and 54 are provided above and below, respectively, and an intake fan 55 is connected in communication with the air knives 53 and 54 to supply air to both the front and back sides of the wafer W being transported by the feed rollers 13. The wafer W after the spraying and cleaning process is dried. For this drying process, for example, the rotation holding structure of the first processing unit PI and the third processing unit P3 of the first embodiment may be adopted, and the drying may be carried out by cutting waves due to the centrifugal force.

As shown in the schematic cross-sectional view of the main part of FIG. A flange 56 for regulating the placement position of the wafer W is connected to the feed roller 13, and the wafer W is configured to be placed on both sides of the wafer W in the width direction and transported.

As a configuration for transporting the wafer W, for example, a nozzle that sprays a cleaning liquid from both the front and back surfaces of the wafer W may have directionality, and non-contact transport may be performed using the jetting force of the cleaning liquid.

In the above embodiment, cleaning is performed using a cleaning solution containing hydrogen peroxide or ozone prior to the wiping cleaning process, but in the present invention, after the wiping cleaning process and prior to the ultrasonic cleaning process, hydrogen peroxide is used. Alternatively, cleaning may be performed using a cleaning liquid containing ozone.

Further, in the above embodiment, a dedicated first processing unit P is used for cleaning with a cleaning liquid containing hydrogen peroxide or ozone.
1, but the first processing unit P1 is eliminated and, for example, the second processing unit P2 or the third processing unit P3 is used to perform cleaning with a cleaning solution containing hydrogen peroxide or ozone at the initial stage. You can also do it. Note that in order to include ozone in the cleaning liquid, ozone may be bubbled into the cleaning liquid.

<Effects of the Invention> As explained above, according to the present invention, organic matter, which is a major cause of particles adhering to the outer surface of a substrate, is oxidized and decomposed using hydrogen peroxide or ozone, and then fine particles are removed. Since cleaning is performed using an ultrasonic cleaning process suitable for the substrate, ultrasonic vibrations can be applied to particles that are easily detached from the outer surface of the substrate, including particles with a particle size of 2 μm or more. , the particle size is 2
Even fine particles with a size of less than μm can be efficiently washed and removed.
It is possible to avoid quality deterioration caused by residual adhering particles and obtain high-quality products with a high yield.

[Brief explanation of the drawing]

The drawings show an embodiment of the substrate cleaning method according to the present invention, FIG. 1 is a schematic vertical cross-sectional view of the first embodiment of the substrate cleaning apparatus that implements the method of the present invention, and FIG. Graph showing the relationship between the change in the number of attached particles and the particle size, 3rd
The figure is a schematic longitudinal cross-sectional view of a second embodiment of a substrate cleaning apparatus that implements the method of the present invention, and FIG. 4 is a schematic cross-sectional view of the main part of FIG. 3. 1.2, 11.12... Wiping member P1. PLO: First processing unit P2. that performs cleaning containing hydrogen peroxide or ozone. P2O...Second processing unit P that performs wiping and cleaning
3. P2O...Third processing unit W that performs ultrasonic cleaning...Wafer as a substrate

Claims (1)

[Claims] (1) A wiping cleaning process in which the outer surface of the substrate is cleaned by applying a wiping member while supplying a cleaning liquid, and after the wiping cleaning process, the outer surface of the substrate is applied with the cleaning liquid while applying ultrasonic vibrations. An ultrasonic cleaning step for cleaning the substrate, the outer surface of the substrate being cleaned with a cleaning solution containing hydrogen peroxide or ozone prior to the wiping cleaning step or the ultrasonic cleaning step. Substrate cleaning method.