JPH0695509B2 - Cleaning method and its apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is used, for example, in the case of cleaning a photomask blank or a photomask in a semiconductor process, or a semiconductor substrate or the like that requires high cleanliness. The present invention relates to a suitable cleaning method and its apparatus.

[Conventional technology]

Conventionally, as this type of cleaning device, for example, Japanese Patent Laid-Open No. 59-12
There are known cleaning devices disclosed in JP 1938, JP-A-58-210624 and the like. In all of these cleaning devices, the cleaning liquid in the cleaning tank is made to flow from the supply side to the discharge side, and the object to be cleaned is released from the object to be cleaned by moving it from the cleaning liquid discharge side to the supply side against the flow of the cleaning solution. This is to prevent the reattachment of foreign matter and improve the cleaning quality.

[Problems to be solved by the invention]

However, in the above-mentioned conventional cleaning device, foreign matter such as metal particles having a larger specific gravity than the cleaning liquid separated and removed from the object to be cleaned is difficult to be removed because it is deposited and accumulated on the bottom wall of the cleaning tank as it is. There was a problem that the quality could not be improved. Further, since it takes a long time to replace the contaminated cleaning liquid near the bottom wall with a clean cleaning liquid, the amount of the cleaning liquid used is large, which is uneconomical.

[Means for solving problems]

The cleaning method according to the present invention has been made to solve the above-mentioned problems, in which the bottom wall of the cleaning tank is inclined toward the cleaning liquid discharge side, and a laminar flow of the cleaning liquid is formed along the inclined bottom wall. The object to be cleaned is moved against the flow of the cleaning solution for cleaning.

Further, the cleaning apparatus according to the present invention includes a cleaning tank, a cleaning liquid discharging means and a supplying means provided at positions facing each other in the cleaning tank, and an object to be cleaned from the cleaning liquid discharging side of the cleaning tank to the cleaning liquid supplying side. And a means for moving the cleaning tank, wherein the area of the part of the side wall of the cleaning tank that is immersed in the cleaning solution is smaller than the area of the part of the side wall of the cleaning solution that is immersed in the cleaning solution, and the bottom wall of the cleaning layer is It is inclined so as to descend from the cleaning liquid supply side toward the cleaning liquid discharge side.

[Action]

In the present invention, the slanted bottom wall and the laminar flow formed along the bottom wall reliably and promptly move and discharge the foreign matter having a specific gravity larger than that of the cleaning solution deposited and accumulated on the bottom wall to the cleaning solution discharge side. be able to.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a sectional view showing an embodiment of a cleaning apparatus according to the present invention, and FIG. 2 is a plan view of a cleaning tank. In these drawings, the cleaning device 1 includes a cleaning tank 2 provided with an overflow tank 3 and a spare tank 4. The cleaning tank 2 is
The tank is composed of a pair of side walls 5A and 5B facing each other in the longitudinal direction, that is, the left-right direction, front and rear walls 5C and 5D facing each other in the direction orthogonal to the longitudinal direction, that is, the front-rear direction, and a bottom wall 5E. The right side wall 5A constitutes a supply side wall by forming supply ports 6 and 7 for supplying the two kinds of cleaning liquids A and B into the cleaning tank 2. On the other hand, the left side wall 5B constitutes a discharge side side wall because the overflow tank 3 is provided. The bottom wall 5E is inclined to the left at an appropriate angle (eg, 15 °), and a discharge port 8 for discharging the cleaning liquids A and B is provided in the vicinity of the boundary between the side wall 5B and the bottom wall 5E. That is, the supply ports 6 and 7, the overflow tank 3 and the discharge port 8 are provided in substantially the same direction, and the cleaning liquids A and B flow in a laminar flow in this direction, and part of them is on the side wall. Five
Overflow from B to overflow tank 3. Further, since the bottom wall 5E is inclined, a laminar flow is more easily generated on the side wall 5A side, and the metal particles (contaminants) in the cleaning liquids A and B are guided to the discharge port 8. The area of the part of the side wall 5A provided in the cleaning liquid is 20
0mm (H ₁ ) x 150mm (W ₁ ), side wall 5B area 440mm (H ₂ )
Smaller than × 150 mm (W ₁ ).

Further, the cleaning device 1 holds the article to be cleaned 10 and moves the cleaning tank 2 from the discharge side of the cleaning liquid to the supply side thereof, and the pipe 12 for supplying the cleaning liquids A and B to the cleaning tank 2. , 13, the pipes 14 and 15 for discharging the cleaning liquid in the cleaning tank 2 and the overflow tank 3, and the pipes 16 and 17 for connecting the pipes 14 and 15 to the auxiliary tank 4 and the pipe 13 Pipe 18, valve 1 installed on pipes 12, 13, 14, 15, 16, 18
9,20,21,22,23,24,25, pump 26 and filter 27 provided in pipe 13, ultrasonic generator 30 provided on the discharge side from about half the longitudinal direction of bottom wall 5E Is equipped with. The auxiliary tank 4 stores the cleaning liquid B, and one end of the pipe 13 is connected to the tank 4. The reason for providing the ultrasonic wave generation device 30 on the discharge side of the bottom wall 5E is to prevent the cleaning liquid on the supply side from being affected by the contaminated cleaning liquid on the discharge side due to the propagation of ultrasonic waves.

Next, the cleaning operation according to this example will be described.

First, a clean regenerated cleaning solution is supplied to the cleaning tank 2 to efficiently replace the contaminated cleaning solution on the discharge side to reduce the contaminated concentration of the cleaning solution on the discharge side to a certain value or less, or particles in the cleaning solution. The following operation is performed in order to prevent redeposition on the object to be cleaned 10 (however, only when the cleaning liquid A is used). That is, the valve in FIG.
19, 20, 22, 23 are opened, valves 21, 24 are closed, and the cleaning liquid A is supplied from the supply port 6 to the cleaning tank 2 through the pipe 12. A part of the cleaning liquid A supplied to the cleaning tank 2 is discharged from the discharge port 8 and, at the same time, overflows into the overflow tank 3, and the pipes 14, 15, 17
Through the pump 26 to the pipe 13, and the filter 27
After passing through, the gas is returned to the cleaning tank 2 through the supply port 7. The valve 19 may be closed when the cleaning liquid starts to be supplied to the cleaning tank 2 from the supply port 7. The object to be cleaned 10 is held by the moving means 11 and immersed in the cleaning liquid A along the discharge side wall 5B of the cleaning tank 2, and after cleaning for a certain time by rocking or ultrasonic irradiation, the regenerated cleaning liquid is supplied. It is moved toward the supply side wall 5A and pulled up from the cleaning tank 2. At this time, since the regenerated cleaning liquid is moving from the supply side to the discharge side opposite to the object to be cleaned 10, the contaminated cleaning liquid near the surface of the object to be cleaned is moved to the discharge side by the clean regenerated cleaning liquid. As a result, liquid replacement is performed. Also,
When the article to be cleaned 10 is pulled up on the supply side, it is possible to prevent reattachment of the contaminated cleaning liquid, and a high quality cleaning effect can be obtained.

Next, two types of cleaning solutions A with different specific gravities that do not dissolve each other,
A method of continuously supplying B (specific gravity: dA <dB) to one cleaning tank 2 to clean the object to be cleaned 10 will be described.

First, close valves 20, 22, and 23, open valve 19, and wash solution A
Is supplied to the cleaning tank 2 through the supply port 6 to clean the object to be cleaned 10. After washing for a certain period of time, close valve 19 and open valves 20, 21.
And the cleaning liquid B in the auxiliary tank 4 is supplied to the cleaning tank 2 from the supply port 7 via the pump 26 and the filter 27. Then, since the specific gravity of the cleaning liquid A is smaller than that of the cleaning liquid B, the cleaning liquid A is pushed up and overflows into the overflow tank 3 as shown in FIG. Then, the cleaning liquid A overflowing into the overflow tank 3 is removed through the pipe 18 by opening the valve 25, and when completely removed from the cleaning tank 2, the valve 25 is closed again.

After filling the cleaning tank 2 with the cleaning solution B, the valve 22 or 23 is opened and the valve 21 is closed, and the cleaning solution B discharged from the discharge port 8 or overflowing into the overflow tank 3 is pumped.
After passing through the filter 27, it is returned to the cleaning tank 2 through the supply port 7 and circulated. After cleaning for a certain time with the cleaning liquid B,
The object to be cleaned 10 is moved from the cleaning liquid discharge side of the cleaning tank 2 to the supply side, and then pulled up. The valves 22 or 23, 24 are opened and the cleaning liquid B in the cleaning tank 2 is collected in the spare tank 4.
At this time, the pump 26 is stopped. Then, the valves 20, 22, 23, and 24 are closed and the valve 19 is opened to wash the next object to be washed, and the washing liquid A is supplied again.

Next, a specific example of cleaning the photomask substrate using the cleaning device will be described.

Example 1 (when using one type of cleaning liquid) A photomask substrate 10 having a surface size of 152 mm square and a thickness of 2.3 mm is held by a moving means 11 and supplied to the cleaning tank 2 as a cleaning liquid. Immersion is performed on the discharge side of the IPA so that the main surface (front and back surfaces) of the substrate 10 is parallel to the moving direction of the cleaning liquid. A part of IPA overflows into the overflow tank 3, is circulated again to the cleaning tank 2 by the pump 26, and is over-regenerated by the filter 27 having a pore diameter of 0.2 μm in the middle thereof.
The reason for making the photomask substrate 10 parallel to the moving direction of the cleaning liquid is to effectively remove dirt. Items to be cleaned
Shake 10 in IPA for 1 minute, ultrasonically clean, move from discharge side to supply side, leave at that position for 1 minute, and then lift from cleaning tank 2. Next, IPA vapor is used for vapor drying, and the cleaning of the photomask substrate 10 is completed.

After cleaning, the substrate surface was irradiated with a condenser lamp and inspected, and it was confirmed that a clean photomask substrate was obtained.

Example 2 (when two kinds of cleaning liquids are used) As the cleaning liquid A in FIGS. 1 and 3, a 10: 1 mixed liquid of ultrapure water and IPA (specific gravity 0.79) was cleaned from the supply port 6 through the pipe 12. Supply to tank 2. This mixed solution was regenerated by 20 l / min by a pump and a filter (not shown) and circulated and supplied to the cleaning tank 2. In the mixed solution, the above-mentioned embodiment (1) was used.
Similarly, the photomask substrate 10 is immersed, and ultrasonic cleaning is performed for 1 minute while rocking up and down.

Next, the valve 19 was closed while the photomask substrate 10 was immersed in the mixed solution, and the valves 20 and 21 which were closed were opened, and the cleaning solution B (1.1.2-trichloro-) contained in the spare tank 4 was opened. 1.2.2-Trifluoroethane, trade name: Freon TF, specific gravity 1.58) is introduced by a pump 26 into a filter 27 having a pore size of 0.2 μm, and then supplied to the cleaning tank 2 through the supply port 7. Figure 3 shows this situation.
In a freon ternary mixture system of about 10: 1: 10 (note that a part of IPA dissolves in freon), ultrapure water and freon do not dissolve in each other but separate from the solubility curve.

When Freon is injected into the cleaning tank 2, the ultrapure water-IPA liquid phase overflows from the cleaning tank 2 into the overflow tank 3. Then, a part of the Freon filling the cleaning tank 2 overflows to be circulated and over-regenerated, and in this state, the photomask substrate 10
The substrate is cleaned by ultrasonically cleaning the substrate for a certain period of time while swinging it up and down, then moving from the discharge side of the cleaning tank 2 to the supply side, pulling it up, and drying it. As a result, a clean photomask substrate was obtained.

In addition, as the cleaning liquid A of Example (1), ultrapure water, Freon, methylene chloride or the like was used instead of IPA, and as the cleaning liquid of Example (2), liquids which were not soluble in each other (for example, ultrapure water-methylene chloride (specific gravity 1.33), n-hexane (specific gravity 0.66) -ultra pure water, n-hexane-dimethyl sulfoxide (specific gravity 1.10)) are all right.

In addition, although the present embodiment has been described with respect to the case where it is applied to a cleaning device with a single tank type cleaning tank, the present invention is not limited to this, and a plurality of tanks may be connected. In this case, any one cleaning tank can select a cleaning liquid different from the other cleaning tanks.

Also, for example, as the size of the object to be cleaned increases, such as a photomask substrate having a surface dimension of 178 mm square, the contaminated liquid on the surface of the object to be cleaned and its vicinity can be replaced with a clean cleaning liquid on the supply side of the cleaning tank. In addition, it is desirable to increase the number of supply ports (for example, the number of circulating systems) in the vertical direction of the supply side wall. The reason for this is that a plurality of laminar flows are generated immediately after the cleaning liquid is supplied from the supply port and can be effectively replaced by the plurality of laminar flows.

Further, although the overflow tank 3 is additionally provided in each of the present embodiments, it is needless to say that only the cleaning tank 2 may be provided. However, when the overflow tank 3 is provided, it is easier to generate a laminar flow, and it is effective and effective in removing dirt.

〔The invention's effect〕

As described above, according to the cleaning method and the apparatus therefor of the present invention, the object to be cleaned is moved against the flow of the cleaning solution, the bottom wall of the cleaning tank is inclined toward the discharge side of the cleaning solution, and the bottom wall is moved along the bottom wall. Since the laminar flow is formed by the laminar flow, it is possible to reliably and promptly move and discharge the foreign matter having a large specific gravity that precipitates and accumulates on the bottom wall to the cleaning liquid discharge side. As a result, it is possible to improve the cleaning quality, because the object to be cleaned can be finally pulled up on the cleaning liquid supply side where there is almost no foreign material, without the foreign matter separated and removed from the object to be reattached. It takes no time to replace the contaminated cleaning liquid near the bottom wall with a clean cleaning liquid, and the amount of cleaning liquid used is small, which is economical.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing an embodiment of a cleaning apparatus according to the present invention, FIG. 2 is a plan view of a cleaning tank, and FIG. 3 shows a state in which two kinds of cleaning tanks are supplied. FIG. 1 ... Cleaning device, 2 ... Cleaning tank, 3 ... Overflow tank, 4 ... Spare tank, 5A ... Supply side wall, 5B ... Discharge side wall, 5E ... Bottom wall, 6,7 ... Supply Mouth, 8 ... outlet, 1
0 …… Item to be cleaned, 11 …… Transportation means.

Claims (2)

[Claims] 1. A bottom wall of a cleaning tank is inclined toward a cleaning liquid discharge side,
A cleaning method characterized in that a laminar flow of the cleaning liquid is formed along the inclined bottom wall, and the object to be cleaned is moved against the flow of the cleaning liquid for cleaning. 2. A cleaning tank, a cleaning liquid discharge means and a supply means provided at positions facing each other in the cleaning tank, and a means for moving an object to be cleaned from the cleaning liquid discharge side of the cleaning tank to the cleaning liquid supply side. The area of the portion of the side wall of the cleaning tank that is immersed in the cleaning solution is smaller than the area of the portion of the side wall of the cleaning solution discharge side that is immersed in the cleaning solution, and the bottom wall of the cleaning tank is supplied from the side of the cleaning solution to the cleaning solution. A cleaning device that is inclined so as to descend toward the discharge side.