GB2224639A

GB2224639A - Vapor cleaning method

Info

Publication number: GB2224639A
Application number: GB8925091A
Authority: GB
Inventors: Yuzo Shibuya; Ryozo Nakamura
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1988-11-15
Filing date: 1989-11-07
Publication date: 1990-05-16
Anticipated expiration: 2009-11-07
Also published as: GB2224639B; KR900007493A; JPH02133925A; GB8925091D0; KR930007614B1; DE3937864A1; JP2544971B2; FR2638984B1; NL8902810A; DE3937864C2; FR2638984A1

Description

VAPOR CLEANING AND DRYING METHOD AND APPARATUS FIELD OF THE INVENTION AND RELATED ART This invention relates to a vapor cleaning and drying method and apparatus for super fine cleaning of an article, usable in a semiconductor device manufacturing process, for example.

Conventionally, a super fine cleaning apparatus for use in a semiconductor device manufacturing process or otherwise includes a processing station for cleaning and drying an article to be cleaned such as, for example, a photomask, a reticle or a semiconductor wafer, and a reservoir station for reserving a medium having high volatility.

The medium within this reservoir station is heated by a heating means to produce vapor, whereby the processing station as a whole is filled with a vapor ambience. An article to be cleaned is introduced into this vapor ambience and the cleaning and drying of the same is effected.

SUMMARY OF THE INVENTION Such conventional cleaning apparatus as described above involves the following inconveniences: (1) A large quantity of medium having high volatility has to be reserved at the reservoir station for a long ti't're. This easily results in deterioration of the purity of the medium and thus leads to a difficulty in attaining super fine cleaning.

(2) A large quantity of vapor has to be produced continuously. This necessitates the provision of a large-capacity heating means.

(3) The evaporated or volatilized medium has to be continuously cooled and condensed so that it can be discharged in the form of liquid. As a consequence, a large quantity of medium is required.

(4) Since a large quantity of medium has to be heated, the initial heating time from start of the heating to the production of vapor is long.

(5) The cleaning effect is low if the article to be cleaned has a surface height change such as by a recess or protrusion.

It is accordingly an object of the present invention to provide a vapor cleaning and drying method and apparatus by which an article to be cleaned can be cleaned and dried super-finely and very efficiently with a reduced quantity of medium.

In accordance with an aspect of the present invention, to achieve this object, a limited quantity of medium is supplied and evaporated and the evaporated medium is discharged against an article to be cleaned to thereby clean the same. Additionally, during this cleaning operation, a small quantity of fresh medium vapor can be supplied continuously. Namely, in this aspect of the present invention, only a predetermined quantity of volatile medium is spread and dropped to a vapor producing station which is heated to a temperature not lower than the boiling point of the medium but not higher than the firing point of the medium, whereby the introduced volatile medium can be evaporated instantaneously. By using a vapor pressure produced at this time, the vapor is introduced to a cleaning and drying station to execute the cleaning and drying of the article to be cleaned.

These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic and diagrammatic view of a major part of a vapor cleaning and drying apparatus according to an embodiment of the present invention.

Figure 2 is a schematic view of a major part of a vapor cleaning and drying apparatus according to another embodiment of the present invention, wherein an article to be cleaned can be conveyed horizontally.

Figure 3 is a schematic and diagrammatic view of a major part of a vapor cleaning and drying apparatus according to a further -embodiment.of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Figure 1 shows, partially in section, a major part of a vapor cleaning and drying apparatus according to an embodiment of the present invention. In this embodiment, a medium. such as, for example, flon or alcohol an example of which is isopropyl alcohol (IPA), is reserved in a medium reservoir 41. A limited quantity of medium can be supplied at a time from a medium supplying station 60 to a vapor producing station 70, whereat the medium can be evaporated and the thus produced vapor medium can be introduced to a vapor introducing station 80.

The medium supplying station 60 includes an inlet valve 1, a gas reservoir 2, a preheater 3 and an outlet valve 4 which are disposed along the path of supply of the medium from the medium reservoir station 41. Each of the valves 1 and 4 comprises an airoperation valve the opening and closing of which can be switched by a pneumatic pressure, the opening/closing being controlled in response to an instruction signal supplied from a controller 40. The controller 40 serves also to control the heat generation at a heater 5, details of which will be described later. The vapor producing station 70 includes this heater 5, an evaporation plate 6, a medium spreading nozzle 7, a dropping funnel 8 and an evaporation chamber 9 in which these components are accommodated.The medium supplied from the medium supplying station 60 goes through the medium spreading nozzle 7 and the funnel 8 and is dropped and spread onto the evaporating plate 6 having stepped surface shape as seen in Figure 1. Due to the heating made by the heater 5, the spread medium is evaporated. The vapor introducing station 80 comprises a vapor introducing tube 10 having an end communicated with the evaporation chamber 9 and having another end branched to provide a plurality of passageways. The vapor introducing station 80 further includes discharging nozzles 12 each being provided at a free end portion of corresponding one of the vapor introducing passageways 10.

The vapor introducing passageways 10 extend into a cleaning and drying chamber 13, in which an article 20 to be cleaned such as, for example, a photomask, a reticle or a semiconductor wafer to be used in semiconductor device manufacturing processes, can be placed. The vapor introducing passageways 10 serve to discharge the vapor of medium, supplied from the vapor producing chamber 70, to the front and rear surfaces of the article 20. The article 20 is not limited to one which is to be used in the semiconductor device manufacturing process, but may be-anything for which super fine cleaning is required. For example, the article 20 may be a glass material.The evaporation chamber 9 and the vapor introducing tube (passageways) 10 as well as the cleaning and drying chamber 13 are covered by a heat insulating material 11, so as to avoid a large change in the inside temperature. Also, a heat retaining means 14 is provided within the cleaning and drying chamber 13.

Denoted at 15 is a vapor trap chamber for collecting ascending vapor from the cleaning and drying chamber 13. Denoted at 16 and 17 are cooling means for cooling the vapor of medium for liquefaction of the same. The medium liquefied in the vapor trap chamber 15 or in the cleaning and drying chamber 13 by the cooling means 16 or 17 is discharged through a discharging tube 18 or 19 to the outside of the apparatus. Each of these discharging tubes 18 and 19 has a U-shaped trap 61 or 62 formed at a mid portion thereof for prevention of leakage of the vapor of medium to the outside of the apparatus. Due to the presence of liquefied medium remaining in these Ushaped traps 61 and 62, the vapor trap chamber 15 and the cleaning and drying chamber 13 are isolated from the outside of the apparatus.

The operation of the cleaning and drying apparatus of the structure described, will now be explained. Under the influence of the controller 40, the valve 4 is closed and, thereafter, the valve 1 is opened. In response, medium is supplied from the medium reservoir 41 into a pipe encircled by the preheater 3. Since the supply of medium is automatically stopped as the pressure in the inert gas reservoir 2 becomes equal to the pressure within the medium reservoir station 41, the controller 40 closes the valve 1 after a certain time corresponding to the stoppage. The evaporating plate 6 is heated to a temperature not lower than the boiling point of the medium but not higher than the firing point thereof, by means of the heater 5 which is being operated in response to an instruction signal supplied from the controller 40.By the heat insulating material 11 and the heat retaining medium 14, the evaporation chamber 9 and the vapor introducing tube (passageways) 10 as well as the cleaning and drying chamber 13 can be maintained at a temperature equal to or slightly higher than the boiling point of the medium.

At a desired moment whereat the vapor supply is desired, the controller 40 supplies an instruction signal to open the valve 4. In response, a certain quantity of medium being preheated to a temperature not higher than its boiling point by means of the preheater 3, being operated in accordance with en instruction signal from ti-le controller 40, is spread from the spreading nozzle 7 to the evaporating plate 6 and, at the same time, the dropping funnel 8 is filled with the medium. The medium spread onto the evaporating plate 6 is instantaneously evaporated, and the thus produced vapor flows through the vapor introducing tube (passageways) 10 and is discharged into the cleaning and drying chamber 13. By this, the inside of the cleaning and drying chamber 13 is filled with a highdensity vapor ambience.On the other hand, the medium filling the funnel 8 drops, little by little, to the evaporating plate 6 to replenish the insufficiency of vapor which results from the condensing and discharging of the vapor during the cleaning and drying process.

By this, the vapor density in the cleaning and drying chamber 13 can be maintained substantially constant for a predetermined time period.

In accordance with an article 20 to be cleaned, the number of the discharging nozzles 12 and/or the shape of each discharging nozzle may be changed to change the cleaning effect to be provided by the vapor pressure of the medium. Further, additional valve means may be provided at the midway of the vapor introducing tube 10, to produce increased vapor pressure as it is discharged.

The cooling means 16 serves to condense and collect the ascending vapor, while the cooling means 17 serves to cool the medium, condensed and collected by the article 20 being cleaned, so as to prevent reevaporation of the same. The collected medium is discharged, by oneself, through the U-shaped discharging tubes 18 and 19 which are designed in consideration of the external pressure.

Figure 2 shows an applied form of the present invention which allows horizontal and intermittent/continuous conveyance of an article 20 to be cleaned and which makes easier the coupling with any other mechanism. The mechanism denoted at 1 - 12 in Figure 1 can be directly coupled to the arrangement shown in Figure 2 and, to the structure of the Figure 1, shutters 21, 22, 21' and 221 and a conveying mechanism 23 as well as an article holder 24 are added.

As the right-hand side shutters 21 and 22 are opened, the article 20 to be cleaned is placed on the article holder 24 and the horizontally conveying mechanism 23, movable leftwardly, and is conveyed into the cleaning and drying chamber 13. Then, the shutters 21 and 22 are closed and, thereafter, vapor is injected from the discharging nozzles 12, whereby the cleaning and drying chamber 13 as a whole is filled with a high-density vapor ambience. After completion of the cleaning and drying process, all the left-hand side and right-hand side shutters or, alternatively, only the left-hand side shutters 22' and 21' are opened in sequence and, by leftward movement of the horizontally conveying mechanism 23, the article- 20 is discharged out of the apparatus and is-conveyed to any associated mechanism.

The structure and function of the remaining part of the Figure 2 example is essentially the same as that of the Figure 1 embodiment.

Figure 3 is a schematic section showing a major part of a vapor cleaning and drying apparatus according to another embodiment of the present invention This embodiment is particularly effective in an occasion where such medium whose vapor, when produced, is relatively heavy. However, the present embodiment is not limited to this, but alcohol such as IPA, flon or otherwise may be used as the cleaning medium. Although in the Figure 3 embodiment two medium supplying stations 60 and two vapor producing stations 70 are provided at the opposite sides of a cleaning and drying chamber 13, one of the two sets may be omitted by using, for example, a branched vapor introducing tube 10, like the Figure 1 embodiment.

In the present embodiment, heating medium reservoirs 36 and 36' are provided around evaporation chambers 9 and 9', respectively. To each of these heating medium reservoirs 36 and 36', a heating medium 50 such as a silicon oil, for example, reserved in a tank 50 is introduced under the influence of a vacuum pressure within a vacuum tank 46. The vacuum tank 46 is communicated through a solenoid valve 43 with the heating medium reservoirs 36 and 36'. Also, through a solenoid valve 44 the vacuum tank 46 can be opened to the atmosphere. Controller 40 is operable to open a solenoid valve 45 while maintaining the solenoid valves 43 and 44 closed, and to actuate a vacuum pump 42. By this, a desired vacuum can be established in the vacuum tank 46. At any time other than this, the solenoid valve 45 is held closed and the vacuum pump 42 is held deactuated.The heating medium reservoirs 36 and 36' are communicated through a solenoid valve 54 with the tank 50. The heating medium 51 within the tank 50 is heated by a heater 52 to a desired temperature not lower than the boiling point of the cleaning medium, within a medium reservoir 41, and not higher than the firing point thereof. Temperature detector 53 detects the temperature of the heating medium 51 in the tank 50 and produces an output which is supplied to the controller 40. On the basis of the applied output, the controller 40 controls the heat generation at the heater 52 to maintain the heating medium 51 at a desired temperature.

Heaters 5 and 5' are provided to heat the heating medium, introduced to the heating medium reservoirs 36 and 36', when the temperature of the introduced heating medium becomes lower than the predetermined temperature. These heaters 5 and 5' are controlled by the controller 40 on the basis of outputs of temperature detectors 37 and 37' which are provided in the heating medium reservoirs 36 and 36', respectively. The cleaning medium spread to evaporating plates 6 and 6' from medium spreading nozzles 7 and 7' is evaporated by the heat of the heating medium in the heating medium reservoirs 36 and 36'. As compared with the heating process wherein the medium is heated directly by a heating means such as a heater, the heating process of this embodiment is preferable in respect to safety particularly in an occasion where a used cleaning medium has ingnitability.First, the position of a holder 24 for holding the article 20 to be cleaned is adjusted so that the cleaning medium evaporated at the evaporating plates 6 and 6' and passing through vapor introducing tubes 10 and 10' is discharged to the upper portion of the article 20. The holder 24 can be moved upwardly and downwardly by means of a driving mechanism 35 and through a rod 30. The driving mechanism 35 is controlled by the controller 40.

Next, the operation of this embodiment will be explained. Like the Figure 1 embodiment, the controller 40 serves to open inlet side air-operation valves 1 and 1' while maintaining outlet side airoperation valves 4 and 4' closed. In response, the cleaning medium is supplied from the medium reservoirs 41 and 41' to the medium supplying stations 60 and 60' until the pressures in gas reservoirs 2 and 2' become equal to those in the medium reservoirs 41 and 41', respectively. Subsequently, the controller 40 operates to close the valves 1 and 1'. On the other hand, as an upper shutter 31 is open, the controller 40 causes the driving mechanism 35 to move the holder 24 upwardly from the illustrated position and, after the holder 24 grasps the article 20, the driving mechanism 35 moves the holder 24 downwardly back to the illustrated position.In this state, an opening formed at the bottom of an inner cylinder casing 33, which defines the cleaning and drying chamber 13, is closed and blocked by a shutter 59 which is formed integrally with the rod 30.

When, after this, the shutter 31 is closed, the controller 40 supplies an instruction signal to each of the air-operation valves 4 and 4' to open it, whereby the whole quantity of the cleaning medium in each of the medium supplying station 60 or 60' is dropped or spread from the nozzle 7 or 7' to the evaporating plate 6 or 6' in the evaporation chamber 9 or 9'. After elapse of a predetermined time corresponding to the completion of the medium dropping or spreading, the valves 4 and 4' are closed.Then, the controller 40 opens the solenoid valves 43 and 54 to allow that the vacuum pressure in the vacuum tank 46 acts through the heating medium reservoirs 36 and 36' on the heating medium 51 in the tank 50, in order that the cleaning medium remaining in the evaporation chambers 9 and 9' is heated to a temperature not lower than its boiling point but not higher than its firing point. By this, the heating medium being heated to a desired temperature not lower than the boiling point of the cleaning medium but not higher than the firing point thereof, is introduced to the heating medium reservoirs 36 and 36' and, as a result, the temperature of the cleaning medium in the evaporation chambers 9 and 9' is increased gradually by the heat of the heating medium, whereby the cleaning medium is evaporated.

The vapor medium flows through the vapor introducing tubes 10 and 10' and is discharged to the article 20 to be cleaned, and the cleaning and drying chamber 13 is filled with the discharged medium vapor.

The portion of the vapor ascending beyond an aperture 32 of the cleaning and drying chamber 13 flows through the aperture 32 into a vapor collecting chamber 15 which is defined by an outer cylinder casing 34.

Exhaust pipe 18 is continuously evacuated by means of an evacuating pump, not shown, such that any excess vapor in the collecting chamber 15 is discharged through the exhaust pipe 18, while being condensed by a cooling tube 16.

After elapse of a time period in which the cleaning medium in the evaporation chambers 9 and 9' is completely evaporated and the cleaning and drying of the article is completed, the controller 40 opens the solenoid valve 44 to open the vacuum tank 46 to the atmosphere, to cause the heating medium in the heating medium reservoirs 36 and 36' to flow back to the tank 50. Thereafter, the controller closes the valves 43, 44 and 45 and, at the same time, opens the valve 45, such that by means of the vacuum pump 42, a desired vacuum is produced again in the vacuum tank 46. On the other hand, in parallel to this, the controller 40 causes the driving mechanism 35 to move the rod 30 upwardly through a half stroke to open the bottom opening of the inside cylinder casing 33, whereby the vapor and liquid filling the cleaning and drying chamber 13 is discharged into the outside cylinder casing 34.At the bottom of the outside cylinder casing 34, cooling means 17 is provided. The vapor and liquid are condensed by this cooling means 17 and are discharged out of the apparatus through a discharging tube 19.

When, after this, the shutter 31 is opened, the controller 40 causes the driving mechanism 35 to move the rod 30 upwardly to its topmost position to allow unloading of the article 20 from the holder 24.

If a fresh particle 20 is set on the holder 24, the above-described operation is repeated. The remaining part of the operation of the present embodiment is essentially the same as that of the Figure 1 embodiment.

In accordance with the present invention, as described hereinbefore, a vapor producing station and a cleaning and drying station are separated from each other and, at a time, a limited quantity of medium is evaporated. As a result, it is not necessary to reserve and heat a large quantity of medium for a long time. Accordingly, it is possible to maintain the purity of the medium high and, therefore, it is possible to ensure precise cleaning and drying.

Further, since the medium is not reserved for a long time, there is no necessity of forming a part, contacting the medium, by using an expensive quartz glass material or otherwise, and the deposition can be minimized even when inexpensive stainless steel, for example, is used. As a result, the manufacturing cost can be decreased.

Further, the medium evaporation chamber can be smali and the heating capacity can be low, and the heating time can be reduced. Therefore, efficient cleaning operation is attainable.

While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1. A vapor cleaning and drying apparatus, comprising: reserving means for reserving a medium; vapor producing means for evaporating the medium to produce vapor; medium supplying means for supplying only a predetermined quantity of medium to said vapor producing means from said reserving means; cleaning and drying means having a cleaning and drying chamber in which an article to be cleaned can be placed; and vapor introducing means for introducing the vapor produced by said vapor producing means into said cleaning and drying chamber for cleaning and drying of the article placed in said cleaning and drying chamber with the vapor produced by said vapor producing means.

2. An apparatus according to Claim 1, wherein said vapor producing means includes an evaporation plate on which the medium is to be dropped, an evaporation chamber for accommodating said evaporation plate, and heating means for heating said evaporation plate from the outside of said evaporation chamber.

3. An apparatus according to Claim 2, wherein said heating means supplies a heating medium, being heated to a predetermined temperature, to a part around said evaporation chamber.

4. An apparatus according to Claim 2, wherein said vapor producing means includes dropping means for dropping, little by little, the medium from said medium supplying means to said evaporation plate.

5. An apparatus according to Claim 2, wherein said vapor introducing means includes a vapor introducing tube having an end communicated with said evaporation chamber and another end branched into plural passageways extending into said cleaning and drying chamber.

6. An apparatus according to Claim 5, wherein each of said evaporation chamber, said cleaning and drying chamber and said vapor introducing tube is covered by a heat insulating material, for retaining the temperature of the vapor.

7. An apparatus according to Claim 1, wherein said medium supplying means includes preheating means for supplying preheat to the medium to be supplied to said vapor producing means.

8. An apparatus according to Claim 1, wherein said cleaning and drying means includes a vapor collecting chamber provided adjacent said cleaning and drying chamber, and cooling means for condensing the vapor in said vapor collecting chamber.

9. An apparatus according to Claim 1, wherein said cleaning and drying chamber has an opening provided with an openable and closable shutter through which opening the article can be loaded into and unloaded out of said cleaning and drying chamber, and wherein said cleaning and drying means includes conveying means for conveying the article horizontally to and from said cleaning and drying chamber through said opening.

10. An apparatus according to Claim 1, wherein said cleaning and drying chamber has an opening provided with an openable and closable shutter through which opening the article can be loaded into and unloaded out of said cleaning and drying chamber, and wherein said cleaning and drying means includes conveying means for conveying the article vertically to and from said cleaning and drying chamber through said opening.

11. A vapor cleaning and drying method, comprising the steps of: supplying a predetermined quantity of cleaning medium from a medium reservoir to an evaporation chamber, by use of medium supplying means; heating the cleaning medium in the evaporation chamber by using heating means, to evaporate the cleaning medium in the evaporation chamber to produce vapor; and introducing the vapor produced in the evaporation chamber through a vapor introducing tube to the cleaning and drying chamber, for cleaning and drying of an article placed in the cleaning and drying chamber with the vapor produced in the evaporation chamber.

12. A method according to Claim 11, wherein a heating medium heated to a predetermined temperature is supplied to a part around the evaporation chamber.

13. A vapor cleaning and drying method wherein volatile cleaning fluid is both dispensed and entirely evaporated at a controlled rate, and as vapor directed upon a body to be cleaned thereby.

14. A vapor cleaning and drying apparatus constructed, adapted and arranged to operate substantially as described hereinbefore with reference to and as shown in any one of Figures 1 to 3 of the accompanying drawings.

15. A vapor cleaning and drying method when performed substantially as described hereinbefore with reference to any one of Figures 1 to 3 of the accompanying drawings.