JP2006091667A - Photomask, and method and device for cleaning the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photomask configured to attach and detach two half pellicle frames without using a magnetic body. <P>SOLUTION: The photomask has a mask substrate where an electronic circuit pattern used to manufacture a semiconductor device is drawn, a lower frame bonded onto the mask substrate to surround the electronic circuit pattern, an upper frame provided detachably to the lower frame, and a pellicle films fitted to the upper frame, the lower frame and upper frame having means of holding them in contact with each other with dynamic stress. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photomask on which an electronic circuit pattern used for manufacturing a semiconductor device is drawn, a cleaning method thereof, and a cleaning apparatus.

  When manufacturing a semiconductor device, selective processing is performed on an underlayer such as a semiconductor substrate by etching or ion implantation. At this time, for the purpose of selectively protecting the part to be processed of the underlayer, a pattern of a composition that is sensitive to actinic rays such as ultraviolet rays, X-rays, and electron beams, a so-called photosensitive photoresist film (hereinafter referred to as photoresist). Is formed on the underlayer. In order to form such a resist pattern, reduction projection exposure using a photomask is performed.

  A photomask is a glass mask substrate in which an electronic circuit pattern is formed of a light-shielding film such as chromium (Cr) or molybdenum silicide (MoSi), and is also called a reticle. Here, when a foreign substance adheres to the surface of the photomask on which the electronic circuit pattern is drawn, it is transferred to the photoresist as a pattern defect. Therefore, a pellicle is provided to protect the electronic circuit pattern. The pellicle includes a pellicle frame provided so as to surround the electronic circuit pattern surface, and a highly transparent pellicle film attached to the pellicle frame.

  As a light source for exposure, a g-line (wavelength 436 nm), i-line (wavelength 365 nm), or KrF excimer laser (wavelength 248 nm) of a mercury lamp is used. Furthermore, due to the recent demand for circuit pattern miniaturization, an ArF excimer laser (wavelength: 193 nm) has come to be used in the manufacture of devices after the 90 nm node.

  Here, an example of the pattern forming method will be described. First, a commercially available organic antireflection film of 85 nm is applied on the substrate to be processed, and baking is performed at 200 ° C. for 90 seconds, a commercially available ArF resist is applied at 300 nm, and baking is performed at 130 ° C. for 60 seconds. Next, exposure is performed using a scanner set exposure apparatus using ArF excimer laser light as a light source through a photomask on which a wiring pattern is drawn. The illumination condition is NA 0.70, and an off-axis method using a 2/3 annular illumination aperture is used. Subsequently, after performing a 60-second bake (PEB: Post Exposure Bake) at 130 ° C., development is performed for 60 seconds using a 2.38 wt% aqueous solution of tetramethylammonium hydroxide (TMAH). Thus, a resist pattern corresponding to the reticle pattern is obtained.

Then, after exposing about 3,000 8-inch wafers with an energy of 40 mJ / cm ² , the surface of the photomask was observed. As a result, clouding was observed in the portion irradiated with ArF light. When observed using an optical microscope and an electron microscope, crystalline foreign substances as large as about 10 μm were observed. When the exposed wafer was inspected using this mask, a large number of pattern defects to which foreign matter on the mask was transferred were confirmed.

  Components of this crystalline foreign material were analyzed using Raman spectroscopy and micro-Auger, and were identified as ammonium sulfate and ammonium phosphate. It has been found that these substances can be removed by washing with pure water. However, when the photomask is washed with pure water, it is necessary to remove the pellicle so that the pellicle film is not broken.

  However, in the conventional photomask, since the pellicle frame is fixed to the mask substrate with an adhesive, the residue of the adhesive remains on the photomask when the pellicle is removed, causing foreign matter. In order to remove the adhesive residue, cleaning with a chemical such as strong acid or strong alkali is required, which damages the light shielding film. In particular, in the case of a halftone phase shift mask formed of a MoSi film, a change in transmittance and phase difference occurs due to cleaning, which affects the pattern resolution characteristics.

  In view of this, a photomask has been proposed in which the pellicle frame is divided into two parts and removable using a magnetic material so that the pellicle film can be removed during cleaning (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 6-2336022

  However, when a magnetic material is used for the pellicle frame, there is a problem in that it affects the linear motor that drives the reticle stage in the scanning exposure apparatus. In addition, when a permanent magnetic material such as an iron-based material is used in order to give a strong fixing force, there is a problem that distortion occurs on the photomask surface due to the weight.

  Also, the conventional photomask has a square frame-shaped pellicle frame, and when cleaning, the cleaning liquid is introduced and discharged from the upper side of the pellicle frame, so that contaminants remain in the inner corner of the pellicle frame. There was a problem.

  The present invention has been made to solve the above-described problems, and a first object of the present invention is to provide a photomask capable of detachably configuring a pellicle frame divided into two without using a magnetic material, and the photomask. It is to obtain a cleaning method and a cleaning apparatus. A second object is to provide a photomask that can be cleaned without leaving contaminants inside the pellicle frame, a cleaning method thereof, and a cleaning apparatus.

  A photomask according to the present invention includes a mask substrate on which an electronic circuit pattern used for manufacturing a semiconductor device is drawn, a lower frame bonded so as to surround the electronic circuit pattern on the mask substrate, and a detachable from the lower frame. It has an upper frame provided and a pellicle film attached to the upper frame, and the lower frame and the upper frame have means for holding them in close contact with each other by mechanical stress.

  Another photomask according to the present invention is a mask substrate on which an electronic circuit pattern used for manufacturing a semiconductor device is drawn, a pellicle frame bonded to surround the electronic circuit pattern on the mask substrate, and attached to the pellicle frame The pellicle frame has a water supply port for supplying the cleaning liquid inside and a drain port for discharging the cleaning liquid from the inside. Other features of the present invention will become apparent below.

  The photomask according to the present invention can be configured so that the divided pellicle frame can be attached and detached without using a magnetic material. In addition, another photomask according to the present invention can be cleaned without leaving contaminants inside the pellicle frame.

Embodiment 1 FIG.
A photomask according to Embodiment 1 of the present invention is shown in FIG. As shown in the figure, an electronic circuit pattern 11 used for manufacturing a semiconductor device is drawn on a mask substrate 12. A square frame-like lower frame 13 is adhered to the mask substrate 12 with an adhesive so as to surround the electronic circuit pattern 11. Further, an upper frame 14 is provided so as to be detachable from the lower frame 13. The lower frame 13 and the upper frame 14 are divided pellicle frames, and are formed of aluminum or plastic in order to prevent distortion of the photomask due to weight.

  A pellicle film 15 is attached to the upper frame 14. The pellicle film 15 is made of an extremely thin organic film or glass. As the pellicle film, a film using an organic film such as a cellulose polymer or a fluorine polymer is called a soft pellicle, and a film using a glass such as synthetic quartz glass is called a hard pellicle.

  The lower frame 13 and the upper frame 14 have screw holes 16 and 17 provided at positions corresponding to each other. Then, by inserting the screws 18 into the screw holes 16 and 17, the lower frame 13 and the upper frame 14 are held in close contact with each other. Thus, since the lower frame 13 and the upper frame 14 are held in close contact with each other by mechanical stress, the pellicle frame divided into two can be configured to be detachable without using a magnetic body.

  In order to clean the photomask, first, the upper frame 14 is removed from the lower frame 13. In this state, the electronic circuit pattern 11 is cleaned with a cleaning liquid such as pure water.

Embodiment 2. FIG.
A photomask according to Embodiment 2 of the present invention is shown in FIG. Constituent elements similar to those in FIG. As shown in the figure, the lower frame 13 is provided with a protrusion 22 at a portion that contacts the upper frame 14 along two opposing sides. The upper frame 14 is provided with a groove 21 at a portion that contacts the lower frame 13 along two opposing sides.

  Then, by fitting the projection 22 into the groove 21, the lower frame 13 and the upper frame 14 are held in close contact with each other. Side views of the lower frame 13 and the upper frame 14 are shown in FIGS. 3 shows a case where the cross-sectional shapes of the groove 21 and the protrusion 22 are T-shaped, FIG. 4 shows a case where the cross-sectional shape is an inverted triangle, and FIG. 5 shows a case where the cross-sectional shape is an L-shape. In either case, the lower frame 13 and the upper frame 14 are detachable by sliding the upper frame 14 in the horizontal direction.

  Thus, since the lower frame 13 and the upper frame 14 are held in close contact with each other by mechanical stress, the pellicle frame divided into two can be configured to be detachable without using a magnetic body.

  Contrary to the above example, the same effect can be obtained when the groove 21 is provided in the lower frame 13 and the protrusion 22 is provided in the upper frame 14. That is, it is only necessary that a groove is provided on one of the lower frame 13 and the upper frame 14 and a protrusion is provided on the other.

  In order to clean the photomask, as in the first embodiment, the electronic circuit pattern 11 is cleaned with a cleaning liquid such as pure water with the upper frame 14 removed from the lower frame 13.

Embodiment 3 FIG.
A photomask according to Embodiment 3 of the present invention is shown in FIG. Constituent elements similar to those in FIG. As shown in the figure, a square frame-like pellicle frame 31 is adhered to the mask substrate 12 with an adhesive so as to surround the electronic circuit pattern 11. The pellicle frame 31 is made of aluminum or plastic in order to prevent distortion of the photomask due to weight. A pellicle film 15 is attached to the pellicle frame 31.

  The pellicle frame 31 has a water supply port 32 for supplying the cleaning liquid on the inner side and a drain port 33 for discharging the cleaning liquid from the inner side. The water supply port 32 and the drain port 33 are wider than the electronic circuit pattern 11 and are provided at positions facing each other across the electronic circuit pattern 11. When the photomask is used for exposure, lids 34 and 35 are respectively attached to the water supply port 32 and the drain port 33 in order to prevent foreign matter from entering the pellicle.

  Further, in order to clean the inside of the photomask, the lids 34 and 35 are removed, a cleaning liquid such as pure water is supplied from the water supply port 32 at an appropriate flow rate, the electronic circuit pattern 11 is cleaned with the cleaning liquid, and the drain port Drain the cleaning solution from 33. Further, the outer portion of the photomask may be simultaneously cleaned with the cleaning liquid.

  As described above, the water supply port and the drain port are provided in the pellicle frame, so that the electronic circuit pattern can be cleaned without removing the pellicle, and cleaning is performed without leaving contaminants inside the pellicle frame. be able to. In addition, the water supply port and the drain port are wider than the electronic circuit pattern and are provided at positions facing each other across the electronic circuit pattern. The entire circuit pattern can be cleaned uniformly.

  FIG. 7 is a side view showing a cleaning apparatus for cleaning the photomask. As shown in the figure, a chamber 41 is provided for cleaning the photomask inside. A stand 42 for placing a photomask is provided in the chamber 41. As shown in FIG. 8, the table 42 is provided with a notch 42 a for placing the mask substrate 12. Further, the base 42 may be made of Teflon (registered trademark) or the like, and the mask substrate 12 may be sandwiched from both sides as shown in FIG.

  When the photomask is placed on the table 42, the surface on which the electronic circuit pattern 11 is drawn is turned upside down, and the side where the water supply port 32 is provided is slanted so as to be higher than the side where the drainage port 33 is provided. Placed on. However, a photomask may be placed vertically on the table 42. As a result, the cleaning liquid supplied to the water supply port 32 automatically drains from the drain port 33 by gravity after cleaning the electronic circuit pattern 11.

  Supply means 43 is provided to supply the cleaning liquid to the water supply port 32 of the photomask, and discharge means 44 is provided to discharge the cleaning liquid discharged from the drain port 33 out of the chamber 41. The discharge means 44 is provided with a measuring unit 45 that measures the amount of contaminant contained in the cleaning liquid drained from the drain port 33. When the amount of contaminants measured by the measurement unit 45 is less than a predetermined value, the control unit 46 controls the supply of the cleaning liquid from the supply unit 43 to stop. Accordingly, it is possible to detect that the photomask has been sufficiently cleaned and automatically stop the cleaning.

  Further, if the nozzle 47 for ejecting the cleaning liquid toward the pellicle film 15 and the nozzle 48 for ejecting the cleaning liquid from the lower direction toward the mask substrate 12 are provided, not only the inside of the photomask but also the outside can be cleaned at the same time. it can.

Embodiment 4 FIG.
A photomask according to Embodiment 4 of the present invention is shown in FIG. Constituent elements similar to those in FIG. As shown in the figure, the pellicle frame includes a lower frame 51 bonded to the mask substrate 12 and an upper frame 52 that is detachably attached to the lower frame 51 and to which the pellicle film 15 is attached. The lower frame 51 and the upper frame 52 are made of aluminum or plastic in order to prevent distortion of the photomask due to weight.

  The lower frame 51 is two linear frames bonded on the mask substrate 12 so as to be parallel to each other at positions facing each other across the electronic circuit pattern 11. The spaces between the right ends and the left ends of the two linear frames serve as a water supply port 53 and a drain port 54, respectively. That is, a water supply port 53 and a drain port 54 are provided on the lower frame 51 side.

  The upper frame 52 has a convex portion 55 that closes the water supply port 53 and the drain port 54 while being attached to the lower frame 51. As a result, when the upper frame 52 is mounted on the lower frame 51 in order to use the photomask for exposure, the water supply port 53 and the drain port 54 are simultaneously closed by the convex portion 55, thereby preventing foreign matter from entering the pellicle. Can do. When the upper frame 52 is removed from the lower frame 51 in order to clean the photomask, the water supply port 53 and the drain port 54 are opened at the same time, so that the cleaning can be performed without leaving contaminants inside the pellicle frame. .

  In order to clean the photomask, as in the first embodiment, a cleaning liquid such as pure water is supplied from the water supply port 53 of the photomask with the upper frame 52 removed from the lower frame 51, and the electron The circuit pattern 11 is washed with the washing liquid, and the washing liquid is drained from the drain port 54. At this time, the cleaning apparatus of Embodiment 3 can be used.

Embodiment 5 FIG.
FIG. 11 is a side view showing a cleaning apparatus according to Embodiment 5 of the present invention. Constituent elements similar to those in FIG.

  The cleaning device is provided with a supply means 61 for supplying water vapor into the chamber 41 at an appropriate flow rate. As this supply means, for example, an apparatus for generating water vapor by ultrasonic vibration can be used. However, when cellulose or the like is used as the pellicle film 15, the temperature of the water vapor is set to 60 ° C. or lower, preferably 50 ° C. or lower, in order to prevent the pellicle film 15 from being damaged. Therefore, a decompression unit 62 is provided. By reducing the pressure in the chamber 42 by the pressure reducing means 62, water vapor can be generated at a low temperature.

  Water vapor that has entered the pellicle frame 31 from the water supply port 32 is condensed on the photomask, and the water generated by the dew condensation is automatically drained from the drain port 33 by gravity after washing the electronic circuit pattern 11.

  By washing the photomask with water vapor in this way, damage to the electronic circuit pattern 11 and the pellicle film 15 can be reduced as compared with the case where pure water is used.

  In addition, the table 42 is provided with cooling means for lowering the temperature of the mounted photomask below that of water vapor. As a result, water vapor tends to condense on the photomask, and the cleaning efficiency increases.

  As the cooling means, it is possible to use a structure that cools the mounted photomask by circulating cold water through the table 42 to cool the table 42 itself. Further, a nozzle 63 that ejects a cleaning liquid having a temperature lower than that of water vapor can be used on the lower surface of the photomask placed on the table 42. Thereby, not only the photomask can be cooled, but also the lower surface of the photomask can be cleaned at the same time.

It is a perspective view which shows the photomask which concerns on Embodiment 1 of this invention. It is a perspective view which shows the photomask which concerns on Embodiment 2 of this invention. It is a side view of a pellicle frame when the cross-sectional shape of a groove part and a projection part is T shape. It is a side view of a pellicle frame when the cross-sectional shape of a groove part and a projection part is an inverted triangle. It is a side view of a pellicle frame when the cross-sectional shape of a groove part and a projection part is L-shaped. It is a perspective view which shows the photomask which concerns on Embodiment 3 of this invention. It is a side view which shows the washing | cleaning apparatus which concerns on Embodiment 3 of this invention. It is a perspective view which shows an example of the stand for mounting a photomask. It is a perspective view which shows another example of the stand for mounting a photomask. It is a perspective view which shows the photomask which concerns on Embodiment 4 of this invention. It is a side view which shows the washing | cleaning apparatus which concerns on Embodiment 5 of this invention.

Explanation of symbols

11 Electronic circuit pattern 12 Mask substrate 13, 51 Lower frame (pellicle frame)
52,14 Upper frame (pellicle frame)
15 Pellicle membrane 16, 17 Screw hole 18 Screw 21 Groove 22 Projection 31 Pellicle frame 32, 53 Water supply port 33, 54 Drain port 34, 35 Lid 41 Chamber 42 Base 42a Notch 43, 61 Supply unit 44 Discharge unit 45 Measurement unit 46 Control part 47,48,63 Nozzle 55 Convex part 62 Suction means

Claims (15)

A mask substrate on which an electronic circuit pattern used for manufacturing a semiconductor device is drawn; and
A lower frame bonded to surround the electronic circuit pattern on the mask substrate;
An upper frame detachably provided with the lower frame;
A pellicle membrane attached to the upper frame;
The photomask according to claim 1, wherein the lower frame and the upper frame have means for holding them in close contact with each other by mechanical stress.   The lower frame and the upper frame have screw holes provided at positions corresponding to each other, and are held in close contact with each other by inserting screws into the screw holes. The photomask described.   A groove is provided on one of the lower frame and the upper frame, and a protrusion is provided on the other. The lower frame and the upper frame are held in close contact with each other by fitting the protrusion into the groove. The photomask according to claim 1, wherein: A mask substrate on which an electronic circuit pattern used for manufacturing a semiconductor device is drawn; and
A pellicle frame adhered on the mask substrate so as to surround the electronic circuit pattern;
A pellicle membrane attached to the pellicle frame;
The photomask characterized in that the pellicle frame has a water supply port for supplying the cleaning liquid to the inside and a water discharge port for draining the cleaning liquid from the inside.   5. The photomask according to claim 4, wherein the water supply port and the drain port are wider in width than the electronic circuit pattern and are provided at positions facing each other with the electronic circuit pattern interposed therebetween. The pellicle frame has a lower frame bonded to the mask substrate, and an upper frame that is detachably attached to the lower frame and has the pellicle film attached thereto.
The water supply port and the drain port are provided in the lower frame,
5. The photomask according to claim 4, wherein the upper frame has a convex portion that closes the water supply port and the drain port when the upper frame is attached to the lower frame.   7. The photo according to claim 6, wherein the lower frame includes two linear frames bonded on the mask substrate so as to be parallel to each other at positions facing each other across the electronic circuit pattern. mask. A method for cleaning the photomask according to any one of claims 1 to 3, 6, and 7,
A photomask cleaning method, wherein the electronic circuit pattern is cleaned with a cleaning liquid in a state where the upper frame is removed from the lower frame. A method for cleaning the photomask according to any one of claims 4 to 7,
A photomask cleaning method comprising: supplying a cleaning liquid from the water supply port; cleaning the electronic circuit pattern with the cleaning liquid; and draining the cleaning liquid from the drain port. A method for cleaning the photomask according to any one of claims 4 to 7,
A photomask cleaning method, wherein water vapor is introduced from the water supply port, the electronic circuit pattern is washed with the water vapor, and the water vapor is discharged from the drain port. An apparatus for cleaning the photomask according to any one of claims 4 to 7,
A table on which the surface on which the electronic circuit pattern is drawn is placed on the photomask, and the side where the water supply port is provided is higher than the side where the drainage port is provided,
A photomask cleaning apparatus comprising: supply means for supplying a cleaning liquid to a water supply port of the photomask. A measurement unit for measuring the amount of contaminants contained in the cleaning liquid drained from the drain port;
12. The photomask according to claim 11, further comprising a control unit configured to control the supply of the cleaning liquid from the supply unit when the amount of the contaminant measured by the measurement unit is less than a predetermined value. Cleaning device. An apparatus for cleaning the photomask according to any one of claims 4 to 7,
A chamber for cleaning the photomask inside;
A table on which the surface on which the electronic circuit pattern is drawn is placed on the photomask, and the side where the water supply port is provided is higher than the side where the drainage port is provided,
Supply means for supplying water vapor into the chamber;
A photomask cleaning apparatus, comprising: a decompression unit that decompresses the inside of the chamber.   The photomask cleaning apparatus according to claim 13, wherein the table includes a cooling unit that lowers the temperature of the mounted photomask than the water vapor. The photomask cleaning apparatus according to claim 13, further comprising a nozzle that ejects a cleaning liquid having a temperature lower than that of the water vapor on a lower surface of the photomask placed on the table.

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