JPS6159506B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for correcting image defects that occur during the manufacture of photomasks for photoetching used in the manufacture of transistors, integrated circuits, and other semiconductor devices.

Conventionally, emulsion masks using silver emulsions have been used as photomasks for photoetching semiconductor devices, but emulsion masks have low surface strength and are prone to scratches because their surfaces are composed of a gelatin layer. Because it is easy to use, it has the disadvantage of extremely poor durability.

On the other hand, in order to improve durability, hard masks, in which a thin film of metal or the like is vapor-deposited or sputtered on a transparent glass substrate and patterned by photo-etching, have recently been widely used. The light-shielding film of the hard mask is made of a single layer or a laminate of two or more layers of metals such as metal chromium, chromium oxide, iron oxide, germanium oxide, and inorganic materials such as metal oxides, and has high mechanical strength and durability. It also has the advantage of being very flexible.

However, these hard masks have a problem in that various defects occur on the mask when forming an inorganic light-shielding film pattern. In other words, image defects that occur on the hard mask can occur when the inorganic light-shielding film layer exists as a residual area (black area) that is unnecessary due to the design, or when a necessary area is missing due to the design and falls off (white area). There are two types of cases in which people get used to it.
If a photomask with such defects is used, for example, in semiconductor manufacturing, these defects will be transferred onto the surface of a wafer, which is a semiconductor material, resulting in defective products and lower yields and characteristics. Therefore, a photomask having more image defects than is allowed by design cannot be used. Therefore, establishing a method for correcting image defects occurring in photomasks is of extremely important industrial significance. Regarding a method for repairing unnecessary residual portions (black portions) such as mutual short circuits between wiring patterns, a repair device using laser light has recently been developed and put into practical use, and has achieved remarkable effects in the production of photomasks.

However, the current situation is that no effective method for repairing the missing parts (white parts) has yet been found.
There are many types of image defects of missing parts (white parts) in the inorganic light-shielding film 1 provided on the transparent substrate, as shown in Fig. 1. (shows an example)
For example, this occurs unavoidably in photomask manufacturing for the following reasons. Images of semiconductor components are minute and ultra-precise, and the photoresist used in photomask manufacturing must have high resolution.For this reason, the photoresist film is made as thin as possible, and because the film is thin, there are no parts that fall off. (white area) is likely to occur. Also, garbage,
Foreign matter or the like gets mixed into the photoresist or is transferred to the photoresist, resulting in drop-off areas (white areas).
In addition, there are flaws and contamination due to force majeure during handling.

In order to eliminate the above-mentioned drawbacks, conventional methods pay close attention to the materials used, manufacturing equipment, operating environment, operating conditions, etc. when manufacturing photomasks. ) It is extremely difficult to produce a photomask without such defects, and in recent years, with the increase in the integration density of ICs and LSIs, the tolerance for image defects in photomasks has become increasingly strict. Incidentally, there is a method called a lift-off method as a method for correcting such a defect in the fallen part (white part). That is, a photoresist is applied onto a photomask having a defect, only the photoresist on the defective area is removed, metal is deposited on the photomask by a method such as vapor deposition or sputtering, and then the photoresist is peeled off to remove the photoresist over the defective area. In this method, an inorganic light-shielding film layer is again formed only on top.

However, the lift-off method described above has the disadvantage that the process is long and new defects are generated accordingly.

The present invention improves the conventional drawbacks as described above, and also provides a photomask having a defect in which a necessary part as shown in FIG. This relates to a method of correcting the design pattern shape 8, and it is possible to use a photomask with a defective part (white part) as a practical photomask, which was conventionally treated as a defective product and treated as a mere glass plate. This improvement not only improves the production efficiency in photomask manufacturing, but also aims to make effective use of valuable resources.

Hereinafter, the photomask repair method of the present invention will be explained with reference to the drawings.

FIG. 3 is a cross-sectional view showing the main steps of a conventional hard mask manufacturing method. In FIG.
A photoresist layer 11 is formed to a thickness of about 5000 Å by vapor deposition or sputtering, and is then patterned as shown in FIG. 3b by a normal photoprocess.
That is, it is formed through processes such as coating, pre-baking, exposure, development, and post-baking. Next, as shown in FIG. 3c, the inorganic light shielding film layer 10 is etched away using a suitable etching solution using the photoresist layer 11 as a protective film to form a patterned inorganic light shielding film layer 12.

Next, the photoresist layer 11 is removed to obtain a photomask patterned as shown in FIG. 3d. However, the photomask shown in FIG. 3d has a defect such as a drop-off part (white part) as shown in FIG. 3e, for example.

FIG. 4 is related to the present invention, and for example, a third case having a defect of a falling part (white part) as shown in FIG. 3e is shown.
As shown in FIG. 4a, a photoresist is applied onto the photomask shown in FIG. 4 by a method such as spinner coating and prebaked to obtain a photoresist layer 13 having a thickness of 1000 to 4000 Å. The prebaking conditions may be set to predetermined conditions for each photoresist.

The positive photoresist is diazide-based AZ-1350 manufactured by Shipley, and the negative resist is rubber-based AZ-1350 manufactured by Tokyo Ohka Kogyo Co., Ltd.
Photoresists generally used for photoetching semiconductor devices, such as OMR and Way Coat manufactured by Hunt, can be used.

Next, as shown in FIG. 4b, the photoresist is selectively exposed using a spot exposure device so as to sufficiently cover only the defective parts of the fallen parts (white parts), and then developed.
Post-baking is performed to form a photoresist layer 14 that sufficiently covers only the defective portions. In order to selectively expose minute portions of photoresist, a spot exposure correction machine commercially available for semiconductor devices is most suitable. Exposure, development, and post-bake conditions may follow predetermined conditions for each resist.

In this state, the photoresist layer 14 on the photomask shown in FIG. It has high transmittance.

Next, as shown in FIG. 4C, the photomask obtained in FIG. Accelerate 15 with an energy of 120KeV or more, a dose of 3
The photoresist layer 14 at ×10 ¹⁵ ions/cm ² or more
Once implanted in the photoresist layer 14, the photoresist layer 14 is shown in FIG.
The photoresist layer 16 is hardened and transformed into an ion-implanted photoresist layer 16 as shown in FIG.

The high-energy particles 15 to be implanted at this time include, for example, atomic ions such as ¹¹ B ⁺ , ³¹ P ⁺ , ⁴⁰ Ne ⁺ ,
There are molecular ions such as ⁴⁰ Ar ⁺ , ⁴⁹ BF ₂ ⁺ , ⁷⁰ B ₂ O ₃ ^+, etc., and even those that are ions during acceleration and become neutral particles immediately before implantation can also be used. or,
The high-energy particles 15 do not necessarily need to be mass-separated, and it is possible to use all the ions generated from the ion source, and both positive ions and negative ions can be used.

The ion-implanted photoresist layer 16 on the photomask obtained in FIG. In addition to exhibiting optical strength, it also provides optical density of 2 or more and sufficient light-shielding properties against ultraviolet and visible light. In addition, chemical resistance such as acid resistance is greatly increased, and no abnormality occurs in the repaired portion even when cleaning is performed with a photomask cleaning solution such as a chromic acid mixture. Therefore, the photomask in which the defect shown in FIG. 4d is corrected (the top view of which is shown in FIG. 4e) has the same characteristics as a normal hard mask without defects and can be used under similar conditions. This method is extremely effective as a method for correcting image defects in missing areas (white areas) that occur during the manufacturing process of reticle masks, master masks, copy masks, etc. in photomask manufacturing.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Photoresist OMR-83 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) was applied onto a hard mask with a cleaned surface having an IC pattern with pinhole-like defects formed from a thin metal chromium film deposited with a thickness of 800 Å on a glass plate. ) was applied using a spinner, and then prebaked at 90°C for 20 minutes to obtain a film thickness of 3500 Å. Next, only the photoresist on the pinhole-like defect area is selectively exposed to light using a spot exposure device to photocure, developed with a specified developer and rinse solution, and host baked at 140°C for 30 minutes. A photoresist image is formed only on the area. Next, ³¹ P ⁺ ions were implanted into the photoresist using an ion implantation device at an acceleration energy of 120 KeV and a dose of 3×10 ¹⁵ ions/cm ² to completely repair the pinholes. A pinhole-free hard mask was obtained.

Example 2 1000Å consisting of two layers of metallic chromium and chromium oxide
Az-1350 is coated on a patterned hard mask having a defect of device dropout to a film thickness of 3000 Å, and then prebaked at 80° C. for 30 minutes to provide a film thickness of 3000 Å. Next, using a spot exposure device, only the photoresist other than the defective areas due to the element falling off is selectively exposed to light to be photodecomposed, developed with a specified developer and rinse solution, and post-baked at 140°C for 30 minutes to remove the defective areas. Form a photoresist only on top. Next, the hard mask on which the photoresist image was formed was implanted using an ion implanter at an acceleration energy of 150 KeV and a dose of 4.
⁴⁰ Ar ⁺ ions were implanted into the resist at ×10 ¹⁵ ions/cm ² to obtain a defect-free hard mask.

[Brief explanation of the drawing]

FIG. 1 is a plan view schematically showing the types of appearance defects that occur in a photomask, and FIG. 2 is a plan view schematically showing the state in which the defects shown in FIG. 1 have been corrected according to the present invention. 3a to 3d are schematic cross-sectional views showing the conventional hard mask manufacturing process, FIG. 3e is a schematic plan view of the manufactured photomask, and FIG.
-d are schematic cross-sectional views showing the method for correcting image defects according to the present invention, and FIG. 4e is a schematic plan view of the corrected photomask. 1... Patterned inorganic light-shielding film layer on glass, 2... Scratch, 3... Disconnection, 4... Pinhole, 5... Chip, 6... Edge, 7...
Element falling off, 8... Inorganic light-shielding film layer with defect corrected, 9... Transparent glass substrate, 10... Inorganic light-shielding film layer, 11... Patterned photoresist layer, 12... Patterned Inorganic light shielding film layer, 1
3... Photoresist layer, 14... Photoresist layer covering the defective portion, 15... High energy particles, 16... Photoresist layer into which ions were implanted.

Claims (1)

[Claims] 1. A photoresist layer is formed on the surface including the pattern of a photomask having an inorganic light-shielding film pattern including the image defective portion of the drop-off portion on a transparent substrate, and then the portion of the photoresist layer corresponding to the image defective portion is spot-exposed. After selective exposure using an apparatus, the method is developed to form a photoresist image that sufficiently covers only the defective portion of the image, and then particles accelerated to high energy are injected into the photoresist image. A photomask image defect correction method.