JP3828119B2 - Method for manufacturing halftone phase shift mask - Google Patents

Description

  The present invention relates to a halftone phase shift mask, and more particularly, to a halftone phase shift mask that can be easily manufactured and can form a fine pattern among photomasks used for manufacturing a VLSI.

The halftone phase shift mask is effective for forming a fine pattern, but has the following two problems.
(1) At the time of transfer, there is a problem in that a sub-peak of light intensity is generated in the vicinity of an exposure pattern to be formed on the wafer, which deforms the exposure pattern to be originally generated. This problem is particularly noticeable in the vicinity of a large missing pattern, and the transfer characteristic is inferior to that of a conventional chrome mask in a large missing pattern that can be sufficiently resolved without using a phase shift lithography technique.

  (2) When transfer exposure is performed sequentially by the stepper, an area where adjacent shots (ranges transferred by one exposure) overlap on the wafer is generated. In the case of a conventional chrome mask, if it is not desired to expose this multiple exposure area, if the pattern (black pattern) is left leaving the periphery of the mask, the exposure light is completely blocked and is not exposed. In the shift mask, since the remaining pattern portion is also translucent, it is exposed to repeated multiple exposure.

  Conventionally, the following two methods are known as countermeasures against these problems.

(A) A method of disposing an ultrafine repetitive pattern below the resolution limit in a mask region where it is not desired to transmit exposure light substantially (see Patent Document 1, for example)
JP-A-6-175347

  (B) A halftone phase shift film and a light shielding film or a film capable of obtaining high contrast are laminated, and after processing the whole into a predetermined pattern, a light shielding film or a film capable of obtaining high contrast is required. How to process into a pattern.

  The above solution (A) has the advantage that a mask can be produced by a single lithography process, but the above-mentioned repetitive pattern must be very fine, and it is very difficult to form it. It was difficult. Moreover, although the solution (B) is easy to form a pattern, there is a problem that the plate making essentially needs to be carried out twice and the process becomes long.

  The present invention has been made in view of the above-described problems of the prior art, and its purpose is not to form an ultrafine pattern, but to provide a sub-peak of light intensity that adversely affects image formation during exposure. To provide a halftone phase shift mask having a light-shielding pattern that suppresses and lowers the transmittance in a multiple-exposed region outside an element region.

The method for producing a halftone phase shift mask of the present invention that achieves the above object is the method for producing a halftone phase shift mask having a halftone phase shift pattern comprising a single layer or two or more layers on a transparent substrate. At least one layer in the halftone phase shift pattern is formed of a film composed mainly of a compound of chromium element and fluorine element, and a part of the pattern is irradiated with electromagnetic waves, particle beams, or heat rays. The composition of the film mainly composed of the compound consisting of the chromium element and the fluorine element in the irradiation region is changed to form a film mainly composed of the compound composed of the chromium element and the oxygen element. To do.

  Another halftone phase shift mask manufacturing method of the present invention is the halftone phase shift mask manufacturing method having a halftone phase shift pattern having a single layer or two or more layers on a transparent substrate. At least one layer in the shift pattern is formed from a layer mainly composed of a compound of one or more kinds of metal elements and one or more kinds of elements of oxygen, fluorine, carbon, nitrogen, and chlorine, and the half After masking a partial area of the tone phase shift mask, the entire halftone phase shift mask is exposed to an active atmosphere, and the oxygen, fluorine, carbon, nitrogen, and chlorine contents of the compound in the non-masked area are masked. It is characterized in that it is different from the content of the region.

  In the method of manufacturing a halftone phase shift mask having a halftone phase shift pattern composed of a single layer or two or more layers on a transparent substrate, at least one layer of the halftone phase shift pattern is made of chromium element and fluorine. After forming a film composed mainly of a compound composed of an element and masking a partial region of the halftone phase shift mask, the entire halftone phase shift mask is exposed to an active atmosphere, and the region of the masking region is not masked. It is characterized in that the film is mainly composed of a compound composed of chromium element and oxygen element by changing the composition of the film composed mainly of a compound composed of chromium element and fluorine element.

  Hereinafter, a supplementary description including the operation of the present invention will be given. The transparent substrate is a single layer or a multilayer, and at least one of the layers constituting the single layer or multiple layers includes at least one metal element and at least one of oxygen, fluorine, carbon, nitrogen, and chlorine. A halftone phase shift mask with a halftone phase shift pattern, which is a layer mainly composed of a compound with an element, is exposed repeatedly between adjacent shots during transfer exposure, and is not necessarily a halftone phase shift effect. By changing the content of one or more elements of oxygen, fluorine, carbon, nitrogen, and chlorine in the compound of the above layer in part or all of the pattern that can be sufficiently transferred and formed without using The above problem can be solved by lowering the transmittance for the exposure light in that region.

  Specifically, when the halftone phase shift pattern has a transmittance of 1% to 50% when the transmittance of the transparent substrate is 100%, the above-mentioned problem is caused. Can be solved.

  The change in the composition of the layer constituting the halftone phase shift pattern described above may be changed uniformly in the entire thickness direction of a specific layer, or only a part of the layer may be changed. When the halftone phase shift pattern is composed of multiple layers, it is of course possible to simultaneously change the composition of a plurality of layers.

  Moreover, it is also possible to use together with said conventional solution (A) and (B). Further, the method of the present invention can be used not only in the above-mentioned problem areas, but also when the transmittance needs to be lowered for other reasons.

  The method of changing the composition of the above-mentioned compound is, for example, a method of irradiating a specific region with electromagnetic waves, particle beams, heat rays, etc. in the air, in a vacuum, or in an active atmosphere, or does not want to change the composition. A method of exposing the whole to an active atmosphere after masking the region is possible. As a result, the above-mentioned problems can be solved by a single lithography process without forming an ultrafine pattern below the resolution limit.

  As is apparent from the above description, in the present invention, at least one layer in the halftone phase shift pattern is formed of one or more metal elements and one or more of oxygen, fluorine, carbon, nitrogen, and chlorine. In some areas where the transmittance is low, the content of oxygen, fluorine, carbon, nitrogen, and chlorine in this compound is the content in other areas. Just by making it different, it does not require the formation of ultra-fine patterns, suppresses the sub-peak of light intensity that adversely affects image formation during exposure, and lowers the transmittance in the multiple exposure area outside the element area A halftone phase shift mask having a so-called shading band can be easily obtained.

  The halftone phase shift mask of the present invention is a halftone phase shift mask having a halftone phase shift pattern composed of a single layer or two or more layers on a transparent substrate. By changing the composition of the phase shift layer, the transmittance for the exposure light in that region is changed. Hereinafter, the halftone phase shift mask of the present invention will be described on the basis of an embodiment of a manufacturing method.

  [Embodiment 1] An embodiment for forming a so-called shading zone for preventing the exposure of the multiple exposure portion during transfer according to the present invention will be described with reference to the process diagram of FIG. As shown in FIG. 1A, a half-tone phase shift film 102 for deep ultraviolet (DUV) exposure is formed on a synthetic quartz substrate 101 for photomask having a 6 inch square and a thickness of 0.25 inch under the following conditions. A DUV exposure halftone phase shift mask blank 103 was obtained.

Deposition method: DC magnetron sputtering target: Metal chromium deposition gas and flow rate: Argon 75 sccm + Carbon tetrafluoride 25 sccm
Deposition pressure: about 4 mTorr
Current: 5 amperes Note that the refractive index and extinction coefficient of this film 102 at a wavelength of 250 nm are 1.7 and 0.27, respectively. Therefore, the film thickness required as a phase shift film for DUV exposure (relative to air) The thickness for delaying the phase by 180 ° is about 185 nm. Further, when the film 102 was formed on the quartz substrate 101 with a thickness of about 185 nm, the transmittance was about 10% when the transparent substrate was taken as 100%.

  Next, as shown in FIG. 1B, an electron beam resist 104 is applied on the blank 103 and patterned by a normal electron beam lithography method to form a resist pattern as shown in FIG. 105 was obtained. Using this resist pattern 105 as a mask, the halftone phase shift film 102 whose surface was exposed was dry-etched under the following conditions.

Etching method: high frequency reactive ion etching gas and flow rate: dichloromethane 20 sccm + oxygen 50 sccm
Pressure: about 300mTorr
Electric power: 250W
After completion of the etching, the resist pattern 105 was removed to obtain a DUV exposure halftone phase shift mask 106 as shown in FIG.

  Next, in order to produce a light-shielding band, a laser irradiation apparatus is used to irradiate the area indicated by reference numeral 107 on the outer periphery of the halftone phase shift film that is patterned, as shown in FIG. The transmittance of the region 107 at a wavelength of 250 nm was lowered. In addition, this laser irradiation apparatus improved and used the apparatus normally used when correcting the black defect (chromium leaving defect) of a chromium mask. The laser uses Nb: YAG with a Q switch (wavelength 1.06 μm), an attenuator is installed before entering the condensing optical system from the YAG rod, and the irradiation dose is about 1 of the exposure intensity when correcting the chromium defect. / 10 was set to irradiate a predetermined area. In addition, the relationship between the damage of the chromium compound halftone phase shift film and the harmonics (second harmonic: wavelength 0.53 μm, fourth harmonic: wavelength 0.27 μm) was investigated. Since the transmittance of the film is increased, it is possible to provide a margin for setting conditions that do not cause damage if the harmonics are not used. Furthermore, in the pulse wave and the CW wave, the pulse wave did not damage the phase shift film, and the transmittance could be lowered.

  Therefore, FIGS. 4 and 5 show the analysis results by X-ray photoelectron spectroscopy of the halftone phase shift film before and after irradiation with a pulse wave laser of 1.06 μm, respectively. FIG. 6 shows a comparison of the analysis results before and after laser irradiation for fluorine. The detection results of the composition of the halftone phase shift film before and after laser irradiation based on X-ray photoelectron spectroscopy are shown in the following table.

図４〜図６及び上記の表より、レーザー照射によりフッ素含有量が減り、酸素含有量が増えていることが分かる。

4 to 6 and the above table, it can be seen that the fluorine content is reduced and the oxygen content is increased by laser irradiation.

  FIG. 7 shows spectral transmittance curves of the halftone phase shift film before and after laser irradiation. From this figure, it can be seen that the transmittance at a wavelength in the vicinity of the exposure light (250 nm) is substantially 0% by laser irradiation, which is a good light shielding film.

  [Embodiment 2] An embodiment of a halftone phase shift photomask with reduced influence of sub-peaks according to the present invention will be described below with reference to FIG. A large halftone phase shift film that can be sufficiently resolved without using the halftone phase shift effect in the halftone phase shift mask 201 having a cross section shown in FIG. The periphery 202 of the pattern (FIG. 2B) was irradiated with the same laser irradiation apparatus as in Example 1, and the transmittance of this portion was lowered. This laser irradiation apparatus is normally used for correcting defects in photomasks. Therefore, the transmittance is controlled by irradiating the periphery of an arbitrary pattern on the photomask, such as irradiation position accuracy and irradiation area controllability. Enough to lower. In this embodiment, the region where the transmittance is lowered is about 1 μm from the pattern end.

  Thus, as shown in the cross section in FIG. 2B, a fine pattern that is difficult to resolve with a photomask is usually large enough to be resolved without using the halftone phase shift effect. In the pattern, a halftone phase shift mask with reduced so-called sub-peaks, which is a defect of the halftone phase shift mask, could be obtained.

  [Embodiment 3] Another embodiment for forming a light shielding band according to the present invention will be described below. FIG. 8 shows a configuration of a light shielding band forming apparatus used in this embodiment. In the figure, reference numeral 601 denotes a mask holder, on which a halftone phase shift mask 607 is set. The holder 601 can be cooled by a circulating refrigerant 602. Reference numeral 603 denotes an infrared heater, which heats the halftone phase shift film of the halftone phase shift mask 607. At this time, the infrared light shielding mask 604 blocks the infrared light in the region that is not used as the light shielding band. The infrared light shielding mask 604 can also be cooled by a circulating refrigerant 605 as necessary. The infrared light shielding mask 604 can be detached from the support column 606, and the light shielding band pattern can be arbitrarily changed by replacing the infrared light shielding mask 604 and changing the shape of the light shielding mask.

  Hereinafter, a method of forming a light shielding band using the light shielding band forming apparatus of FIG. 8 will be described with reference to FIG. A halftone phase shift mask 301 having a cross section shown in FIG. 3A produced by the same method as in the first embodiment is set on the holder 601 of the light shielding band forming apparatus as shown in FIG. 3B. To do. At this time, the atmosphere is left as air. Next, an infrared light shielding mask 604 having a necessary shape is attached to the column 606, and the infrared light shielding mask 604 is placed on the surface of the halftone phase shift mask 301 within a range where the infrared light shielding mask 604 does not contact the surface of the halftone phase shift film of the halftone phase shift mask 301. Close. Subsequently, the infrared heater 603 is turned on, and an appropriate amount of cooling water is allowed to flow through the mask holder 601 and the infrared light shielding mask 604 so that the surface temperature of the region not shielded by the infrared light shielding mask 604 is about 450 ° C. By keeping the surface temperature of the substrate at about 250 ° C. and maintaining this state for 60 minutes, a desired light-shielding band 305 as shown in FIG. 3C is obtained. The shading zone obtained by this method was substantially the same as that shown in Example 1.

  As described above, the halftone phase shift mask of the present invention has been described based on several embodiments. However, the present invention is not limited to these embodiments, and various modifications are possible.

It is process drawing which forms the halftone phase shift mask of Example 1 of this invention. 10 is a process diagram for forming the halftone phase shift mask of Example 2. FIG. FIG. 10 is a process diagram for forming the halftone phase shift mask of Example 3. It is a figure which shows the analysis result by the X-ray photoelectron spectroscopy of the halftone phase shift film | membrane before laser irradiation in Example 1. FIG. It is a figure which shows the analysis result by the X-ray photoelectron spectroscopy of the halftone phase shift film | membrane after laser irradiation in Example 1. FIG. It is a figure which compares and shows the analysis result regarding the fluorine before and behind laser irradiation in Example 1. FIG. It is a figure which shows the spectral transmittance spectrum before and behind laser irradiation of the halftone phase shift film of Example 1. It is a figure explaining the structure of the light-shielding zone formation apparatus used in Example 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Synthetic quartz substrate 102 for photomasks ... Halftone phase shift film 103 ... Halftone phase shift mask blank 104 ... Electron beam resist 105 ... Resist pattern 106, 201, 301, 607 ... Halftone phase shift mask 107 ... Outer peripheral area 202 ... periphery of large halftone phase shift film pattern 305 ... light shielding band 601 ... mask holders 602, 605 ... refrigerant 603 ... infrared heater 604 ... infrared light shielding mask 606 ... post

Claims (3)

In a method for producing a halftone phase shift mask having a halftone phase shift pattern composed of a single layer or two or more layers on a transparent substrate,
At least one layer in the halftone phase shift pattern is formed of a film mainly composed of a compound of chromium element and fluorine element, and an electromagnetic wave, particle beam, or heat ray is applied to a partial region of the pattern. Irradiating and changing the composition of the film mainly composed of the compound of chromium element and fluorine element in the irradiated region to form a film mainly composed of the compound of chromium element and oxygen element A method for manufacturing a halftone phase shift mask. In a method for producing a halftone phase shift mask having a halftone phase shift pattern composed of a single layer or two or more layers on a transparent substrate,
At least one layer in the halftone phase shift pattern is formed from a layer mainly composed of a compound of one or more metal elements and one or more elements of oxygen, fluorine, carbon, nitrogen, and chlorine. Then, after masking a partial area of the halftone phase shift mask, the entire halftone phase shift mask is exposed to an active atmosphere, and oxygen, fluorine, carbon, nitrogen, and chlorine content of the compound in the non-masked area A method for producing a halftone phase shift mask, characterized in that the amount is different from the content of the masked region. In a method for producing a halftone phase shift mask having a halftone phase shift pattern composed of a single layer or two or more layers on a transparent substrate,
At least one layer in the halftone phase shift pattern is formed of a film containing a compound composed of chromium element and fluorine element as a main component, and after masking a partial region of the halftone phase shift mask, halftone The entire phase shift mask is exposed to an active atmosphere, and the composition of the film mainly composed of the compound of chromium element and fluorine element in the non-masking region is changed, so that the compound of chromium element and oxygen element is mainly used. A method for producing a halftone phase shift mask, characterized in that the film is a component film.

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