JP2023021205A - Apparatus and method for indirect surface cleaning - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve optical characteristics of a photomask.

SOLUTION: A photomask comprises at least one feature disposed thereon. The at least one feature has an associated design location, where a distance between a location of the at least one feature and the associated design location causes a positional error of the at least one feature. A method for improving a performance characteristic of the photomask includes: directing electromagnetic radiation toward the photomask, the electromagnetic radiation having a wavelength that substantially coincides with a high absorption coefficient of the photomask; generating a thermal energy increase in the photomask through incidence of the electromagnetic radiation thereon; and decreasing the positional error as a result of the generation of the thermal energy increase in the photomask.

SELECTED DRAWING: Figure 1A

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present disclosure, or the invention, relates generally to apparatus and methods for cleaning surfaces, and more particularly to apparatus and methods for cleaning surfaces of components, optics, etc. used in the semiconductor industry. The apparatus and methods disclosed in the present invention can be used to extend the useful life of photomask reticles, improve the performance of photomask reticles, or a combination thereof.

[Description of related application]
This patent application is a continuation-in-part of U.S. patent application Ser. This is a continuation-in-part of patent application Ser. 13/657,847 (now U.S. Patent No. 8,613,803), which is a continuation-in-part of U.S. Patent Application Serial No. 12/277, filed November 24, 2008. , 106 (now U.S. Patent No. 8,293,019), which is a continuation-in-part of U.S. Patent Application Serial No. 12/2,055, filed Mar. 25, 2008. 178 (now U.S. Patent No. 7,993,464), which U.S. Patent Application is U.S. Provisional Application No. 60/954,989, filed Aug. 9, 2007. , and these US patent applications are incorporated by reference and the entire disclosures of these US patent applications are incorporated herein by reference.

Photographic manufacturing of semiconductors utilizes a series of photomasks to create features on semiconductor wafers. In each photolithography step, a photomask is imaged onto a preprocessed semiconductor wafer. Once the photomask is imprinted on the wafer, additional processing can be used to modify the semiconductor wafer material in the pattern of the photomask. In a next step, additional photomasks may be imaged onto the wafer. Precise alignment or registration of subsequent photomasks to features made with previous photomasks enhances the quality of structures produced on semiconductor wafers. Metrics for evaluating the quality of structures produced on a semiconductor wafer include the dimensional accuracy of a single feature, the dimensional accuracy of the location of one feature relative to another feature, or a combination thereof. . Some dimensions of features on a photomask are called critical dimensions (CDs), and the placement of features on a photomask with respect to other features is sometimes called overlay. For most critical photomasks, the overlay requirement may be a few nanometers or less over the entire length of the mask.

Photomask properties, such as critical properties and material properties, may vary within ranges as a result of tolerances applied during the manufacturing process. For example, the optical performance characteristics of a film may depend on the material composition of the film and the thickness of the film. In addition, mask CD and overlay may vary depending on the accuracy of the writing tool, the accuracy of the etching process, the number and type of cleaning processes, and the temperature and stress applied to the photomask during fabrication. Variations in raw photomask properties (eg, differences in composition and film stress) can also contribute to final CD and overlay variations by changing the response of the photomask to the manufacturing process.

Differences between masks ultimately lead to variations in the products made using the photomasks. For this reason, limits or ranges of performance criteria are utilized to distinguish defective photomasks from photomasks that are acceptable for use during manufacturing. If the photomask performance is outside acceptable limits, the photomask is discarded (rejected) and another mask made.

In addition to manufacturing variations, photomask performance characteristics may change due to use during manufacturing. During use during manufacturing, photomasks may be exposed to intense radiation, including ultraviolet (UV), deep ultraviolet (DUV), or extreme ultraviolet (EUV) radiation. Radiation can cause photodegradation of photomasks, especially thin films. Photomasks may also require cleaning after use during fabrication over a period of time. These cleaning processes may change the properties of the photomask, and there may be a limit to the number of times the photomask can be recleaned and still meet specifications.

A process that reduces the mask-to-mask variability of one or more of the critical properties of photomasks can potentially improve the overall manufacturing yield of semiconductor fabrication processes that use photomasks. First, making non-standard mask modifications and masks viable for use in manufacturing avoids the manufacturing delays and costs associated with fabricating new photomasks to replace non-standard photomasks. can help you to Second, reducing the variability of one or more performance characteristics can result in a tolerance margin that can be used to extend the tolerance of another characteristic. Thus, reducing variability in critical photomask characteristics can provide the advantage of reducing variability in printed features on product wafers, thereby improving device yield and performance.

As an example, it may be advantageous to improve the overlay of a photomask to improve the accuracy of feature placement on a wafer, and such improved overlay can be used to correct non-standard masks, which This improves mask yield. Additionally, it may be advantageous to reduce mask-to-mask variability during overlay for sets of masks printed on the same wafer. By improving the alignment of features from multiple masks on the wafer, other defect increases in the variability of another critical parameter may become acceptable.

As the technology trend in the photomask industry is toward multiple patterning, the requirements for overlay accuracy between critical mask layers are tightening. In multiple patterning, two or more masks are used in combination to produce feature size reduction on the printed wafer. Reducing feature size may require both reducing individual mask error and reducing overlay error between sets of masks. Therefore, it would be particularly advantageous to develop a process that enhances overlay for photomasks used in multiple patterning.

This background discussion is provided by the inventors to aid the reader and should not be taken as an indication that any of the problems presented are per se known in the art. be understood.

In view of at least the above discussion, it would be advantageous to develop a process that can improve the overlay of the photomask by processing before, during, and after the photomask manufacturing process.

In addition, it would be advantageous to develop a process that could improve the overlay of photomasks to recover from changes caused by use during manufacturing.

Additionally, it would be advantageous to develop novel methods and/or apparatus for modifying photomask overlays that enhance availability, performance, lifetime, or other aspects of use.

In addition, develop novel laser-based methods and/or apparatus that improve photomask overlays that enhance availability, performance, lifetime, or other aspects of use with reduced risk of surface damage. is advantageous.

In addition, it would be advantageous to incorporate methods and/or apparatus for improving photomask overlay into photomask fabrication, wafer fabrication, and/or repair processes.

In addition, it would be advantageous to develop a method and/or apparatus for improving photomask overlay by local or global thermal modification of a partially absorbing film on the photomask surface.

In addition, to improve overlays that cause thermally-assisted removal of surface contamination and also enhance availability, performance, lifetime, or other aspects of use with reduced risk of surface damage. It would be advantageous to develop a new laser-based method and/or apparatus for thermally modifying a photomask.

The above needs are met to a large extent by certain embodiments of the present invention. According to one embodiment of the present invention, one or more properties of the material of the object are modified to affect the optical properties of the material and/or improve the performance or lifetime of the device utilizing the target material. A method of influence is provided. Specifically, a method is provided for improving the overlay of a photomask. The method may include irradiating the substrate to cause thermal energy or heat buildup in the substrate and/or thin film. The resulting increase in temperature in the partially absorbent membrane causes thermal material changes, including changes in composition (e.g., dehydration, oxidation), surface changes (e.g., morphology, roughness). (e.g., annealing, densification), or changes in material properties (eg, annealing, densification).

The method may involve the use of electromagnetic radiation, in particular laser radiation. In the method of the present invention, a reduced risk of thin film damage is obtained by utilizing relatively long pulse widths or by heating the substrate and thin film to comparable temperatures by irradiation. This method allows for improved photomask performance through localized and/or uniform or non-uniform global enhancement of the photomask overlay.

This method can be advantageous for applications where the environment above the substrate is substantially or completely enclosed. In these cases, the method further comprises directing the source of electromagnetic energy into the material provided against the surface and being part of the substrate's environment enclosure. For example, the method of the present invention can be used to improve the overlay of pellicled photomasks.

According to another embodiment of the present invention, an apparatus is provided for laser material modification utilizing the method described above. The apparatus may include metrics for inspection or inspection of photomask overlays. These measurements are advantageously performed before, during or after use of the process and can be used for closed-loop control of the process during use.

The apparatus described above may further include means for monitoring and controlling the temperature of the substrate and/or adjacent materials. Such means may include local temperature control or temperature control over the entire substrate.

According to yet another embodiment of the present invention, a photomask fabrication process utilizing the methods and/or apparatus disclosed herein is provided for improving photomask overlay.

Certain embodiments of the present invention provide the ability to modify materials without surface pretreatment or environmental control above the substrate surface. Certain embodiments allow material modification with reduced risk of substrate damage. Additionally, certain embodiments of the present invention allow for extended lifetime of photomasks used during wafer printing. Certain embodiments of the present invention also allow for improved manufacturing accuracy of photomasks used during wafer printing. In addition, certain embodiments of the present invention provide capabilities that result in reduced wafer manufacturing costs and increased device yields, including increased photomask yields.

Thus, in order that the detailed description of the invention herein may be better understood, as well as the contribution of the invention to the art, certain specific embodiments of the invention may be described. has been outlined quite broadly. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto.

In this regard, before describing at least one embodiment of the present invention in detail, the present invention should be directed to the details of the construction and arrangement of the parts or components whose application is set forth in the following description or illustrated in the drawings. It should be understood that there is no limitation. The invention may be embodied in alternative embodiments to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology and abstract used herein are for the purpose of illustration and should not be construed as limiting the invention.

Therefore, those skilled in the art will appreciate that the technical idea on which the present invention is based can be readily utilized as a basis for designing other structures, methods and systems for achieving some of the objects of the present invention. . It is important, therefore, that the claimed invention be construed to include such equivalents to the extent such equivalents do not depart from the spirit and scope of the present invention.

1 is a schematic illustration of thermal excitation induced externally to a partially absorbing material or substance; FIG. 4B is a side view of an absorbing thin film on top of a substrate; FIG. 2 is a plot of the absorption spectrum of MoSi from the far ultraviolet region to the far infrared region of the electromagnetic spectrum; FIG. 2 is a plot of the absorption spectrum of quartz from the far ultraviolet region to the far infrared region of the electromagnetic spectrum; FIG. 3 is a view of the surface of a photomask with a thin film partial absorber containing a pellicle attached. FIG. 2B is a schematic illustration of a photomask with a pellicle showing a laser beam focused through the pellicle onto a surface; Fig. 4 is a schematic diagram comparing the beam spot size on the pellicle and the beam spot size on the mask produced by focusing; FIG. 2B is a schematic illustration of a photomask with a pellicle showing a laser beam focused through the pellicle onto a surface and a side view of the beam spot on the pellicle; FIG. FIG. 3B is a cross-sectional view of a Gaussian distribution of beam energy and a corresponding resulting temperature profile; FIG. 2B is a cross-sectional view of a top-hat distribution of beam energy and the resulting temperature profile; 1 is a schematic representation of a photomask with a cold plate in contact with the bottom of the mask; FIG. 4 is a schematic diagram showing the cooling of regions on a photomask by forced convection; FIG. Schematic representation of a single pass of a laser beam across a surface to minimize localized heat energy or heat build-up in a single row or column with large lateral spacing between spots. ) is shown. Schematic representation of two passes of a laser beam across a surface to minimize localized thermal energy or heat build-up, with beam spots of the two sets overlapping with a large spacing between the pulse sets. FIG. 11 shows a single row of . Fig. 2 is a schematic representation of multiple laser passes over a region of a substrate to achieve cross-sectional material modification processing of the substrate; Fig. 4 is a schematic illustration of a second dimension of a material change process; Fig. 3 is a schematic representation of the use of non-continuous pulses on the substrate; 1 is a schematic illustration of a partial absorber material on a substrate with a thermocouple or infrared temperature monitor; 1 is a schematic illustration of a partial absorber material on a substrate with imaging, microscopy, spectroscopy, or a combination system for material characterization; Fig. 2 is a schematic representation of a part material on a substrate with a measurement system, showing the measurement system and the laser beam source sharing a common path; FIG. 3 is a system diagram of robotic loading of a substrate to a laser beam and X/Y/Z stage motion; 1 is a plan view of a photomask assembly according to one aspect of the present invention; FIG. 1 is a plan view of a photomask assembly according to one aspect of the present invention; FIG. 1 is a plan view of a photomask assembly according to one aspect of the present invention; FIG. 1 is a plan view of a photomask assembly according to one aspect of the present invention; FIG. 1 is a plan view of a photomask assembly according to one aspect of the present invention; FIG. 1 is a plan view of a photomask assembly according to one aspect of the present invention; FIG. 1 is a plan view of a photomask assembly according to one aspect of the present invention; FIG. 1 is a plan view of a photomask assembly according to one aspect of the present invention; FIG.

Aspects of the present invention will now be described in detail with reference to the drawings, wherein like reference numerals refer to like elements throughout the figures, unless specified otherwise.

Aspects of the present invention provide apparatus and methods for repositioning features on a photomask. FIG. 1A is a schematic representation of thermal excitation originating externally to a partially absorbing material or substance. As shown in FIG. 1A, the excitation device 100 is constructed and arranged to direct the energy beam 2 onto an absorptive thin film 3 provided on a surface of a substrate 4 that is partially or fully transparent. an external energy source 1. A method of excitation according to one aspect of the present invention may involve direct excitation of an absorbing thin film 3 on a substrate by an energy beam 2 generated by an external energy source 1 . Substrate 4 may be a photomask or may form part of a photomask assembly, and the terms "substrate" and "photomask" are used throughout this specification unless otherwise specified. can be used interchangeably through

Unless otherwise specified, the partially absorbing films described herein are specifically made to allow at least a fraction of the lithographic light wavelength to pass through the film to improve wafer printing efficiency. ing. Thus, partially absorbent membranes do not include opaque membranes.

According to one aspect of the invention, the external energy source 1 is an electromagnetic energy source and the energy beam 2 is an electromagnetic beam. According to another aspect of the invention, the external energy source 1 is a light source and the energy beam 2 is a beam of light. According to another aspect of the invention, the external energy source 1 is a laser light source and the energy beam 2 is a beam of laser light. However, it will be appreciated that the external energy source 1 may produce an energy beam 2 embodying other energy forms, such as electron beams, microwave beams, x-ray beams. , sound waves, combinations thereof, or any other beam of energy known in the art.

Interaction of the energy beam 2 with the absorptive thin film 3 or substrate 4 can produce thermal excitation of the absorptive thin film 3, substrate 4, or a combination thereof. According to one aspect of the invention, the interaction of the energy beam 2 with the absorbing film 3 results in an increase in the thermal energy of the material of the absorbing film 3, thereby increasing the temperature of the material of the absorbing film 3. can cause Alternatively or additionally, the interaction of the energy beam 2 with the substrate 4 can result in an increase in the thermal energy of the substrate 4 material, thereby causing an increase in the temperature of the substrate 4 material. If the temperature of the substrate 4 is higher than the temperature of the absorbing thin film 3 , heat can be transferred from the substrate 4 to the absorbing thin film 3 by conduction, convection, radiation, or a combination thereof, thereby increasing the temperature of the absorbing thin film 3 . Thermal energy or temperature is further increased.

As will be appreciated, an increase in thermal energy in the materials described herein may mean an increase in enthalpy (h), an increase in internal energy (u), an increase in temperature, or a combination thereof. .

FIG. 1B is a side view of absorptive thin film 3 on top of substrate 4 . In FIG. 1B, the absorbing thin film 3 is in communication with an external energy source 1 through which some portions of the substrate 4 are provided, while other portions of the substrate are exposed to the external energy source. 1 and in this case patterned so that there is no prior transmission of the energy beam 2 through the absorbing thin film 3 . Thus, heat generated in the portion of the substrate 4 that is in direct communication with the external energy source 1 can be conducted through the substrate 4 and then through the absorptive thin film 3 by conduction, convection, radiation, or a combination thereof. It will be appreciated that the .

According to one aspect of the invention, a method of altering one or more properties of a material to alter the material properties and/or affect the performance or lifetime of a device utilizing the target material. provided. In a non-limiting example, a method of changing the position of features on a substrate is provided. In the case of an absorbing thin film 3 on a photomask 4, this method may be displaced by use during manufacturing, cleaning processes, or external forces applied to the photomask (e.g. attachment of a pellicle to the photomask 4). The usable lifetime of the photomask 4 can be extended by moving the positions of the features in the absorptive thin film 3 . The method may include excitation of the substrate surface to produce a uniform increase in thermal energy or temperature increase in the substrate 4 and the absorbing thin film 3 . The resulting temperature rise in the substrate 4 and/or thin film 3 results in thermal material changes, including compositional changes (e.g., dehydration, oxidation), surface changes (e.g., morphology, roughness), or changes in material properties (eg, annealing, densification). Alternatively or additionally, the thermal material change may be a change in optical performance characteristics of the photomask.

External energy sources 1 other than lasers can be used. For example, the external energy source 1 can include lamps or other fixtures capable of emitting energy along any portion of the electromagnetic spectrum, including microwave, infrared, near-ultraviolet, Deep UV, extreme UV, electron beam generators, X-ray generators, or combinations thereof.

Absorptive thin film 3 and substrate 4 can be made from or include many different materials. According to one aspect of the invention, the substrate 4 may have thin film absorber properties, making such a substrate 4 a target for material modification without an absorbing thin film 3 provided thereon. can be done. An increase in temperature in the absorbent film 3 can cause thermal changes in the material of the absorbent film 3 and/or the properties of the absorbent film 3, such changes as dehydration, oxidation, surface roughness, annealing. , or combinations thereof.

According to aspects of the present invention, the threshold temperature for modifying the absorbing thin film 3 is below the temperature that may cause damage to the material of the substrate 4, thereby causing thermal damage to the substrate 4. is reduced. Aspects of the present invention can also reduce the risk of substrate 4 damage to other substrate or film modification techniques, because the present invention, in some cases, reduces the ubiquitous distribution of multiphoton absorption processes. This is because relatively long pulse widths can be used which can reduce the probability of failure. According to one aspect of the invention, the pulse width of the energy beam 2 may be in the range of 1 microsecond to 10 milliseconds. According to another aspect of the invention, the laser pulse width may exceed 1 microsecond below including continuous wave laser excitation.

The apparatus and method of the present invention may be advantageous for applications in which the environment above the thin film absorber 3 is substantially or completely enclosed. For example, FIG. 4 shows a photomask assembly 102 that includes an absorbent membrane 3 and a pellicle 8 attached to the absorbent membrane 3 . Once the absorptive thin film 3 is encased, the method further includes directing the energy beam 2 into material provided near the outer surface of a pellicle 104 that is part of the substrate's environmental enclosure. good. For example, the apparatus and methods of the present invention can be used to improve the overlay of a pellicle-equipped photomask (see FIG. 5A), where pellicle 104 comprises pellicle membrane 8, pellicle frame 9, and pellicle frame adhesive 10. including.

According to aspects of the present invention, the method comprises the steps of selecting a laser wavelength substantially matching the strong absorbance of the absorbing thin film 3; and setting the pulse width. In some cases, the increased absorbance of the substrate 4 allows lower laser energy to be used for the process, thus reducing laser energy when the laser beam 2 is incident on or reflected from the surface of the substrate 4 . The risk of damage to adjacent materials that may interact with beam 2 can be reduced.

According to another aspect of the invention, a wavelength of the energy beam 2 is selected that is highly absorbed by the substrate 4, which is beneficial when most of the substrate has thin film absorbers removed. I can say. Furthermore, by selecting the wavelength of the energy beam 2 near the strong absorption band of the substrate 4, the thermal or temperature difference between the thin film absorber 3 and the substrate 4 can be reduced, thereby reducing the absorption thin film. The difference in thermal expansion coefficient between 3 and substrate 4 can be reduced. Multiple laser beam wavelengths and/or laser beam energies may be used where multiple thin film absorbers or substrates of more than one material are used. Multiple wavelengths can be produced, for example, by utilizing multiple laser sources or a single tunable laser source or both. Multiple energies can be used by controlling the output energy of each laser source using controls and/or devices located inside or outside each laser source.

Substrates of multiple materials may require consideration of material parameters as well as energy beam 2 parameters, including excitation wavelength selection. According to one aspect of the invention, a laser wavelength is chosen that has a significant absorption in the material of thin film absorber 3 . In some embodiments, the selected wavelength has little absorption in or is highly reflected by other materials on or in substrate 4, resulting in thermal energy increases mainly in the material of the thin-film absorber 3 . This can be particularly useful when the material located adjacent to the thin film absorber is affected by the process temperature. For example, in the case of a pellicle photomask, the pellicle film 8 and the pellicle frame adhesive 10 can be in intimate contact with the thin film absorber film. Reducing the overall thermal energy or temperature build-up or build-up in the system can be important, for example, when pellicle frame adhesive outgassing occurs or the pellicle frame adhesive degrades. Minimizing the total heat energy or temperature rise can also be important when a significant amount of heat is transferred to the environment 7 between the photomask 4 surface and the pellicle film 8, because , because this heat build-up can adversely affect the membrane 8, the adhesive 10, the pellicle frame 9 material, or a combination thereof. In some cases, the process temperature may preferentially be kept below the damage or modification temperature of the substrate 4 material.

In other embodiments, the basis of the material modification process allows any region of substrate 4 to be substantially cooled to the temperature required for typical modification without exceeding the thermal damage threshold of substrate 4 or other adjacent materials. It may be particularly desirable to reach a temperature close to . The laser energy required to bring one of the materials to the material modification process temperature can cause thermal damage to the other material, especially if there is a substantial difference between the materials' absorptances. be. The local fluence of the energy beam 2 may be controlled based on the exposed or exposed material.

In other embodiments, it may be particularly desirable to have different regions of the substrate 4 reach different temperatures and different treatment levels on the basis of the material modification process. Certainly, the rate and extent of material modification may depend on the laser energy. In this case, the local fluence of the beam may be controlled based on the desired amount of material change in different regions of substrate 4 . It is also conceivable that material modification may depend on the number of times the energy source is applied to substrate 4 . In this case, the number of applications of the energy source may vary across the substrate to produce different amounts of material modification in different regions of the substrate 4 .

According to aspects of the present invention, longer laser pulse widths and shorter, including continuous wavelength (CW) lasers, are used to improve thermal equilibrium between materials with significantly different absorption constants. However, the use of such long laser pulse widths results in the highest thermal energy or temperature increase in the overall system, and the material located adjacent to the substrate surface has a thermal damage threshold or other thermal damage below the process temperature. Such long laser pulse widths may not be usable if they have other adverse effects caused by radiation.

According to aspects of the present invention, a laser wavelength is selected that has substantial absorption in some or all of the materials on substrate 4 . The same laser energy can then be used to produce the desired process temperature below, for example, any of the damage thresholds of the substrate material. It is also possible to exploit the transfer of thermal energy or heat between different materials by considering their thermal properties (including diffusivities). In some cases, this allows the substrate 4 and/or thin film absorber to take advantage of the reduced process fluence, especially when the thermal energy or heat flow from the high absorptive material is preferential over the low absorptive material. The desired thermal reforming can be achieved during 3. In this case, the flow of heat from the high-absorption material to the low-absorption material causes the low-absorption material to be processed using a lower process energy than would be required by direct exposure of the low-absorption material by an energy source. Temperature can be increased.

practical example

The following is an example of a method according to one aspect of the invention that may be used to improve the overlay of photomask substrates used in wafer fabrication processes. In this example, thermal processing according to aspects of the present invention can modify the photomask substrate and/or thin film to cause misalignment of features in the thin film relative to other features on the mask. can. This embodiment may be used throughout several aspects disclosed herein.

Control of laser beam parameters may be particularly desirable in aspects related to photomask overlay adjustment. For example, wavelength selection is highly desirable due to the physical structure of typical photomasks. In some cases, the photomask assembly 102 has a quartz substrate 4 with a thin film absorber 3 or partially absorbing film 3 applied over the critical surface of the substrate 4 (see FIGS. 1A and 1B). ). If the absorbing thin film 3 is a metal film, there will typically be a sizable absorption coefficient for most of the laser wavelengths that can be produced. However, in the case of partially absorbing films, there may be wavelength regions where these films absorb less, unlike pure metal films. However, in the case of quartz substrates 4, there may be a limited range of wavelengths for which the substrate has substantial absorption and laser sources are generally available. Thus, certain embodiments can utilize wavelengths that are highly absorbed by thin films, while the substrate is weakly absorbing or transparent to selected wavelengths. This process can minimize the overall temperature rise of the system and reduce the risk of direct absorption damage to the quartz substrate.

In accordance with aspects of the present invention, it may be advantageous to move features of photomask assembly 102 to reduce errors introduced during overlay due to mask making and application processes. FIG. 14 is a plan view of a photomask assembly marked with an array of recesses or design features 110 on the surface of photomask 4 . Although the design feature array 110 shown in FIG. 14 is shown schematically as an array of cross (+) features, it is understood that the cross features so shown are the It simply represents a point on any photomask feature known in the art. Typically, designed feature array 110 is made by patterning thin film 3 onto photomask substrate 4 . However, patterns can be made directly into the substrate surface with or without a thin film on the surface.

In one embodiment, most of the photomask is covered with a thin film absorber 3, sometimes referred to as a so-called "dark field mask", and the individual features of the design feature array 110 are the design features. It is made by removing only the thin film at the location of the part. In another embodiment, the bulk of the photomask has the thin film absorber removed, sometimes referred to as a so-called "clear field mask", and the individual features of design feature array 110 are , is made by leaving only a thin film at the location of the design features. For both dark-field and clear-field photomasks, the actual location of features may vary as a result of feature movement caused, for example, by manufacturing process variations or photomasks used in semiconductor manufacturing processes. , may produce variations from the designed pattern array.

FIG. 15 is a plan view of a photomask assembly 102 according to one aspect of the invention. Similar to FIG. 14, FIG. 15 shows a design array of features 110 marked with cross symbols, but in addition FIG. 15 shows a design array of features 112 marked with diamond (⋄) symbols. Contains the actual array. Each actual feature in the actual array of features 112 may correspond to a designed feature in the designed array of features 110 . Differences between the actual position of a position feature from the array of actual features 112 and the design or intended position for the corresponding design feature in the array of design features 110 may create errors during overlay. There is Depending on the source of the error, the position of the actual pattern relative to the intended pattern may be systematic and/or random.

Errors in the overlay may have a component in first direction 114, a component in second direction 116, or a combination thereof. Furthermore, the overall positional error for all of the real features in the array of real features 112 is defined according to a statistical measure for all of the real features in the array of real features 112. Such measures can include the sum of the errors, the square root of the sum of the squares of the errors, or any other statistical measure of error known in the art.

The dimensions of the process area, the energy of the laser and the number of exposures for each location will vary depending on the response of the photomask to the process. For example, the response to application of the disclosed process to the entire photomask substrate 4 at constant fluence may be a contracting (gradual contraction) radial pattern as shown in FIG.

FIG. 16 is a plan view of the single liver metastasis night photomask assembly 102 of the present invention. In FIG. 16, the cross (+) symbols represent the actual feature array 120 prior to processing the substrate 4 with the external energy source 1, and the diamond (⋄) symbols represent: It represents the actual feature array 122 after processing the substrate 4 with the external energy source 1 . The radial contraction of the pattern towards the center of the photomask can be seen in FIG. This description is only one possible result of applying the disclosed method to the entire photomask substrate 4 and is used for illustrative purposes only. Alternatively, implementation of this process may result in an expanding (gradual expansion) radial distribution or fixed lateral motion at each location, or other relative motion.

FIG. 17 is a plan view of a photomask assembly 102 according to one aspect of the invention. In FIG. 17, the cross (+) symbol represents the designed feature array 110 and the diamond (⋄) symbol represents the actual feature array 112 . The overlay error between the designed feature array 110 and the actual feature array 112 is a pattern of radial gradual expansion from the center of photomask 4 . As will be appreciated, treating photomask 4 with energy beam 2 from external energy source 1 in accordance with aspects of the present invention actually causes feature array 112 to contract radially toward center 124 of photomask 4 . can be made Results are shown in FIG.

FIG. 18 is a plan view of a photomask assembly 102 according to one aspect of the invention. In FIG. 18, the cross (+) symbol represents the designed feature array 110 and the diamond (⋄) symbol represents the actual feature array 112 . As shown in FIG. 18, directing the energy beam 2 onto the photomask substrate 4 in accordance with aspects of the present invention brings the actual feature array 112 closer to the designed feature array 110, thereby resulting in a photomask assembly. 102 overlay error is reduced.

Subsequent impingements of the energy beam 2 on the substrate 4 can have a cumulative effect on the actual feature locations in the actual feature array 112 . FIG. 19 is a plan view of a photomask assembly 102 according to one aspect of the invention. In FIG. 19, the cross (+) symbol represents an array of design features 110 and the diamond (⋄ ) symbol represents the array 112 of actual features. Thus, by performing the process multiple times, the actual feature array 112 can be made closer to the designed feature array 110, thereby further reducing the overlay error of the photomask assembly 102 as shown in FIG. Decrease.

The dimensions of the process area, the energy of the laser, and the number of exposures for each location may vary depending on the original overlay error of photomask 4 . For example, overlay errors may only occur over a portion of photomask 4 as shown in FIG.

FIG. 20 is a plan view of a photomask assembly 102 according to one aspect of the invention. In FIG. 20, the cross (+) symbol represents the designed feature array 110 and the diamond (⋄) symbol represents the actual feature array 112 . As shown in FIG. 20, only the lower right portion 126 of photomask 4 exhibits a significant overlay error. In this case, treating only the lower right portion 126 of the photomask 4 or only the error affected area of the photomask 4 in accordance with aspects of the present invention can be achieved without treating the entire photomask 4 with the energy beam 2. 4 can be advantageous in reducing the overlay error in the lower right portion 126 of FIG.

FIG. 21 is a plan view of a photomask assembly 102 according to one aspect of the invention. In FIG. 21, the cross (+) symbols represent the array of design features 110 and the diamond (⋄) symbols represent the array of design features 110 after processing the photomask 4 with the energy beam 2 in accordance with aspects of the present invention. , represents the actual feature array 112 taken from FIG. As shown in FIG. 21, processing the lower right portion 126 of photomask 4 reduces the overlay error in the lower right portion 126 of photomask 4 .

If the overlay error is more random as shown in FIG. 15, according to aspects of the present invention, the local energy and the number of applications of the energy beam 2 onto the photomask 4, primarily to different regions of the mask It may be advantageous to vary the Due to such localization of the photomask, the area of process (the size of the energy beam 2) is advantageously small relative to the distance between individual adjacent features in the actual feature array 112. It may be adjusted so that the effect of the process is to have a resolution smaller than the distance between individual adjacent features in the actual feature array 112 . For this embodiment, the energy and number of pulses may vary for each location on the mask, so that features further away from their intended or designed It is better to move the feature by a larger amount than the feature near the position of .

Additionally, if the material change that occurs is relatively constant, the average material change can be controlled by treating a large number of spaced apart regions (FIG. 9A) on the substrate surface. In this case, the spacing between treated areas 13 and/or the density of treated areas relative to untreated areas can be used to control the relative amount of material conversion process.

A specific example of a representative method is to alter one or more properties of the absorptive thin film 3 on the photomask substrate 4 using laser excitation to shift features of the absorptive thin film 3. is. For example, in a photomask ₄ in which the absorptive thin film 3 is a molybdenum silicon oxynitride ( _{MowSixOyNz )} film (molybdenum silicon oxynitride may be abbreviated as _MoSi ), the overlay The deviation in may be due to changes in thermal material properties in the MoSi film. Material changes include, but are not limited to, oxidation, annealing, dehydration, or densification of the thin film absorber 3 material. Considering photomask thermal damage levels, the lowest thermal damage point would typically be the melting/reflow point for the base quartz substrate, ie, about 2912 degrees Fahrenheit (1600 degrees Celsius). Depending on the exact material properties of the MoSi film, material change (eg annealing) may occur at temperatures well below the reflow point of the quartz substrate 4 . Therefore, there is a potential process that may occur with temperatures below the damage level of the photomask substrate material for material transformation.

As noted above, the relative absorption of substrate materials is commonly considered due to potential differences in material absorption properties. It may be desirable to choose a wavelength that is highly absorbed by the MoSi film. FIG. 2 is a schematic illustration of an absorption curve for a MoSi partially absorbing photomask film. In this example, the main absorption occurs either below the 0.3 μm wavelength or above the 9 μm wavelength. Shorter wavelengths are not in a particularly desirable wavelength range because they are usually significantly absorbed by air, and they have high photon energies, thus giving rise to multiphoton processes. This is because there is a high possibility that

Choosing wavelengths in the infrared range from 1 μm to 1000 μm may be preferred for DUV, as longer wavelengths reduce the potential for multiphoton processes and environmental absorption. . For MoSi films, it is particularly desirable in accordance with aspects of the present invention to select wavelengths above 9 μm, such as near the 11.5 μm absorption peak, so that typically a High absorption occurs. According to one aspect of the invention, the expression "near the 11.5 μm absorption peak" means wavelengths in the range from 10.5 μm to 12.5 μm, except that other wavelengths in the infrared range are , may be acceptable. By choosing wavelengths within this range, the total thermal energy or heat input to the system can be minimized during use of the present invention by lowering the energy required to cause the material change.

Also, as noted above, consideration of the absorptivity of the quartz substrate may also be made. Quartz substrates used in photomasks may be specially designed to have high transmission in the deep infrared (DUV) wavelength range (see FIG. 3). This is typically accomplished by using synthetic fused silica (silica) substrates that contain very low levels of impurities. According to aspects of the present invention, it may be advantageous to have substantial absorption in MoSi and low absorption in the quartz substrate. As shown in FIG. 3, the absorptivity for the exemplary quartz substrate does not have a significant absorptance of 11.5 μm near the MoSi film absorptance peak. Therefore, processing at wavelengths near 11.5 μm preferentially causes thermal energy accumulation in MoSi over quartz, thereby minimizing heat accumulation in regions of the substrate without the thin film absorber 3. minimizes the total heat input to the system during use of the present invention.

Alternatively, it may be advantageous to choose a wavelength that is highly absorbed by the quartz substrate of photomask 4 so that all areas of the surface of photomask 4 reach the desired processing temperature. Comparing the thermal properties of quartz and the thin film absorber layer, it can be expected that heat transfer between these materials occurs preferentially from the quartz to the absorber layer. The reason this can occur is that quartz has a relatively low thermal diffusivity and thin film absorber films typically include metallic components and therefore have a high thermal diffusivity. This embodiment may be advantageous when the temperature difference between the thin film absorber and the photomask substrate is important. For example, it is conceivable that the difference in coefficient of thermal expansion between the absorbing film 3 and the substrate 4 may cause damage to one or both of these materials. Also, having different material expansion coefficients may weaken the bond between the thin film absorber 3 and the substrate 4 and may result in separation or delamination. If thermal equilibrium between the thin film absorber and the substrate is beneficial, the use of long pulse widths also achieves sufficient time for heat transfer (e.g. heat conduction) between the materials when the process temperature is reached. It can be said that it is advantageous above.

The reason why it may be advantageous to operate at the process wavelength, where quartz has a substantial absorption at the process wavelength, is that thermal energy flow or heat transfer is preferential to the absorptive thin film 3 and over the exposed area. can reach the desired process temperature. The major absorption for these substrates generally occurs at wavelengths either below 0.2 μm or above 8 μm. Short wavelengths may be particularly undesirable, as such wavelengths may be significantly absorbed by air, and these wavelengths have high photon energies, thus giving rise to multiphoton processes. This is because there is a high possibility that As mentioned above, wavelengths in the infrared region from about 1 μm to about 1000 μm may be preferred compared to DUV because the longer wavelengths have the potential for multiphoton processes and environmental absorption. because it reduces

It may be particularly desirable according to aspects of the present invention to select wavelengths above 8 μm, for example near 9 μm quartz absorption, to allow high absorption in the quartz substrate without high environmental absorption. can be generated. According to one aspect of the invention, the expression "near the 9 μm absorption peak" means wavelengths in the range of 8 μm to 10 μm, although other wavelengths within the quartz region may be acceptable. be. This wavelength can also be advantageous for photomasks with partially absorbing film coatings (ie, MoSi). As shown in FIG. 2, the exemplary MoSi material has a reduced state absorptance near 9 μm compared to a peak at 11.5 μm, thus the energy beam from the external energy source 1 2 exhibits a decrease in thermal energy or an increase in temperature caused directly by 2. Generally speaking, the film material temperature reached with a constant energy beam 2 fluence using wavelengths in this range is , should be approximately the same as the film material temperature for quartz. This is also expected to be true even though the partially absorbing film has a relatively high absorption coefficient in this wavelength range due to the expected thermal diffusivity advantage. Selecting other wavelengths within this range improves overall thermal uniformity by changing the relative heat build-up in the material caused by direct absorption of the energy beam 2 from the energy source 1. It is possible to

The type of photomask may also be considered in selecting wavelengths for overlay correction. For example, when using a dark field mask, it may be preferable to choose wavelengths that are highly absorbed in the thin film. Overlay improvement can be best obtained by modifying the thin film, since most of the surface is covered with the thin film. When using a clear field mask, it may be preferable to choose wavelengths that are highly absorbed by the substrate. Overlay improvement can be best obtained by modification of the substrate surface, since most of the surface is not covered with a thin film. In either case, it may be preferable to provide similar thermal modifications in areas of the photomask with the thin film and in areas of the photomask without the thin film, so that the modification spreads over the entire mask surface. Predictable.

The process just described for use in accordance with certain aspects of the present invention renders the photomask 4 usable by correcting for overlay variations resulting from the cleaning process as well as caused by the use of the photomask during fabrication. Lifetime can be extended. Exposure of the photomask during use in manufacturing can degrade the photomask film. These changes in film composition can cause mask overlay misalignment. Use of the present invention to correct overlay variations caused by use in manufacturing can advantageously be embodied via pellicle 8 . This allows the photomask 4 to be returned to production without requiring a new photomask to be produced to replace the deteriorated photomask. In addition, there are times when the photomask must be removed from the manufacturing environment and cleaned for other reasons, including pellicle film damage and haze growth. A conventional cleaning process sequence may require removal of an installed pellicle, cleaning, and then installation of a new pellicle. The act of removing the pellicle from the mask can cause changes in the photomask overlay. In addition, wet cleaning or wet clean processes can degrade the thin film and can adversely affect the photomask overlay. Use of the presently disclosed process can correct feature position and effectively restore feature positioning unaffected by pellicle removal and wet clean. Adding another pellicle to the photomask after cleaning may also change the position of features in the film due to added stress on the photomask. In this case, aspects of the process just described can be advantageously used through pellicle 8 in photomask assembly 102 to correct for photomask 4 overlay.

An additional benefit of improved photomask overlay is improved mask-to-mask variability. The number of wet cleanings that each mask undergoes can vary, and is determined by several of the manufacturing parameters. Typically, photomasks may be wet cleaned during the processes required to create the pattern and following maintenance processes to correct defects in the pattern. The final overlay will depend on the cumulative effect of the fabrication process and the number of wet cleans. This can result in mask-to-mask variability of the overlay prior to use.

Mask-to-mask variability can be improved in accordance with aspects of the present invention. Different amounts of overlay enhancement are applied to various photomasks prior to use so that each mask can be adjusted for the same overlay level. It is possible that by tightening the variability of this aspect of the photomask, the allowable variability of other mask parameters can be relaxed. For example, it is possible that the allowable critical dimension variation in use can be relaxed if each photomask has an accurate overlay. This can be particularly advantageous when combined with repair processing, because the limited dimensional control requirements result in high photomask yields.

Methods according to aspects of the present invention can be used for photomask thin film absorber modifications, and such methods do not require removal of pellicle 8 from photomask assembly 102 . Performing thin film absorber modification after pellicleization provides the advantage of eliminating the need for additional wet cleaning prior to using aspects of the presently disclosed process. For example, laser-assisted overlay enhancement can be performed with the pellicle membrane material 8 without affecting the pellicle membrane properties (see FIG. 4). In this case, typically the absorption of the pellicle film at the process wavelength and the energy density (fluence) of the energy beam 2 at the surface of the pellicle film are considered. As with substrates and substrate films, material modification processes generally do not result in temperature increases in the pellicle membrane above the damage threshold. However, depending on the pellicle film, there may be significant absorption in the pellicle film near the 9 μm absorption peak for the quartz substrate. However, it is still possible to operate near a significant pellicle membrane absorptance, since the pellicle membrane 8 is positioned above the surface of the substrate 4 .

In addition to wavelength selection, the relative temperature increase in the pellicle membrane 8 can be reduced by focusing the laser beam 12 through the pellicle membrane 8 onto the surface of the substrate 4, for example using a lens 11 (Fig. 5A). As shown in Equation 1, the temperature increase in the substrate may be proportional to the fluence of the energy beam 2 applied to the surface.

ΔT~F Formula 1

where ΔT is the temperature change in the material and F is the absorbed laser fluence.

For constant intensity or beam pulse energy, the fluence is proportional to the square of the beam spot radius.

F to E/r ² Formula 2

where F is the fluence, E is the energy, and r is the radius of the beam on the substrate surface.

The ratio of the beam radius 14 at the pellicle 8 to the beam radius 13 on the surface of the photomask 4 is typically increased by focusing the beam 2 through the pellicle 8 and thus compared to the photomask substrate surface. The relative fluence on the pellicle membrane can be reduced (Fig. 5B).

In addition to wavelength considerations, utilizing process parameters (e.g., excessively long pulse lengths or high repetition rates) that produce large temperature increases in the system may be limited by the damage threshold of the pellicle film. be. Pulse width, relative fluence, process duration, and use of external material cooling control schemes are exemplary off-process parameters that can be used to minimize system temperature increase.

In addition to MoSi-based partially absorbing photomask embodiments, aspects of the disclosed process also include fully absorbing photomasks, optical photomasks without thin film absorbers (quartz only), and extreme ultraviolet ( Advantages can be gained for next generation photomasks used for EUV) and nano-imprint lithography (NIL). Optical photomasks without thin film absorbers have features etched directly into the base quartz substrate. Nanoimprint lithography masks also have features fabricated in the substrate, and typically such masks do not comprise thin films. For both of these types of masks, aspects of the disclosed process can be used to provide thermal modification of the substrate, including desired improvements in overlay. In the case of thin film photomasks, aspects of the disclosed processes can be applied to EUV photomasks by modifying the absorber or base substrate. In addition, it is envisioned that thermal modifications to multiple layers can be used to improve overlays. However, the optical damage level of the reflective multilayer must be considered because modifications to the multilayer can adversely affect photomask performance.

pulse shaping

The pulse width, temporal pulse shape, and spatial distribution of the laser can enhance the material transformation process or widen the safe operating range for processing according to certain embodiments of the present invention. A short pulse width can be used to minimize the overall heat input to the system (substrate and environment). A long pulse width can be used to maintain the process temperature for an extended period of time which increases process uniformity and prevents temperature differentials between different materials. Temporal pulse shapes can be used to control the temperature rise in the thin film absorber. Using elevated temperature over an extended period of time can produce an initial effect (eg, annealing) followed by a secondary effect (eg, oxidation). Also, the use of multiple pulses can reduce the desired beam energy for complete processing, thereby further reducing the risk of substrate damage analogously to the use of long pulse widths. The advantage of multiple pulses is that it is possible that localized cooling of one material can prevent damage while still allowing the process to run. For example, the pellicle film may be cooled to prevent heat build-up by multiple pulses while the thin film absorber is uncooled, and inter-pulse heat build-up is used to reach the process temperature in the film.

The spatial distribution of the laser beam can be used to improve process window and process uniformity. For example, FIG. 6A shows a Gaussian spatial distribution 15 that can create a temperature gradient 16 in substrate 4, and FIG. A spatial distribution 17 is shown. This spatial distribution can be used to widen the process window. A flat-top or top-hat spatial distribution can produce a uniform temperature rise within the beam spot, whereas a Gaussian distribution typically produces a temperature gradient within the beam spot. To avoid potential substrate damage, the maximum energy of the beam is typically limited by a Gaussian peak. A Gaussian energy distribution is expected to be more likely to exceed the material damage level compared to a flat top beam when the energy variation is approximately equal to the energy difference between the process and damage energy levels. Also, Gaussian distributions may produce non-uniform material variation effects, and top-hat energy distributions are expected to produce uniform material variation within the working area of the beam.

thermal management

Since aspects of the present invention involve heat-based processes, it is sometimes desirable to manage the overall temperature of the system to avoid damage to heat-sensitive materials located near the processed material. This is especially true for photomask material modification processes where pellicle removal is not performed. Pellicle membranes typically have a low thermal damage threshold. Therefore, in some cases it is useful to avoid global system temperature build-up that can transfer to and/or damage the pellicle material. This includes a pellicle frame and a closed environment between the mask surface and the pellicle membrane.

Managing system temperature can be accomplished in several ways. The examples below show some representative sample cooling methods, and it will be appreciated that other methods may exist. One approach to managing system temperature is through contact cooling. For example, the photomask may be placed in contact with a plate 19, which acts as a heat sink drawing heat generated over the entire surface of the mask toward the back of the mask (see FIG. 7). This reduces heat transfer to the environment overlying the mask surface, the pellicle membrane and the adhesive between the pellicle frame and the mask surface. Cooling can be accomplished in a variety of ways, such as by flowing a cooling liquid or gas other than the heat transfer fluid over the mask and/or pellicle to force the heat transfer fluid through the inlet port 21 and the heat sink outlet port. 20, thermoelectric or laser induced cooling of part or all of the mask and/or pellicle, or combinations thereof. The heat transfer fluid can be water, ethylene glycol, air, nitrogen, combinations thereof, or any other heat transfer fluid known in the art.

Another potential way to control temperature is through forced convection cooling. Directing a stream of filtered and/or cooled gas or liquid over portions of mask 24, over pellicle membrane 23, pellicle frame and/or adhesive region 22 to cause thermal energy or temperature build-up in these materials. can be directly reduced (see FIG. 8). This not only reduces the risk of pellicle membrane damage, but can also reduce the risk of gassing causing contamination from the pellicle frame and pellicle membrane adhesive. In addition to hardware control of heat build-up in the system, it is possible to reduce heat build-up by allowing process times to be extended. By applying a slow pulse rate to the system or allowing delays between successive pulse applications, the injected heat can be removed without raising the overall system temperature above a critical level. can.

The inter-pulse thermal energy or temperature build-up may also be advantageously controlled and may depend on the thermal properties of the thin film absorber, substrate and/or adjacent materials. Generally speaking, pulse-to-pulse heat build-up can be controlled by reducing the number of laser pulses incident on the surface per unit time. This temperature build-up can also be controlled by increasing the distance between adjacent laser pulses. It may be particularly desirable to have large lateral displacements between adjacent pulses, in which case materials (eg, pellicle membrane materials) are particularly susceptible to inter-pulse thermal energy accumulation. In this case, the process typically involves positioning the laser beam 7 at approximately the same location multiple times to obtain the desired material modification of the target surface. For example, a first series of laser pulses is directed at the surface with relatively large lateral separation (see Figure 9A). A second pass over the same area places an additional series of laser pulses slightly offset with respect to the first set of spots (see FIG. 9B). This process continues until the entire area has been exposed to the laser pulse (see Figure 9C). Using overlap in the second direction in accordance with aspects of the present invention, the surface of substrate 4 can be fully exposed (see FIG. 9D). According to aspects of the present invention, if it is desired that the material modification process include multiple pulses for process completion, the entire process is repeated and/or the overlap between passes is increased. Changing the position of the beam relative to the surface as shown can be accomplished by moving the beam and/or moving the substrate. In addition, by applying the pulses across the mask in a systematically distributed manner, the potential for thermal energy or heat accumulation on the photomask 4 can be further reduced (see FIG. 9E).

technology combination

The present invention may be used in conjunction with surface preparation or environmental control techniques to extend reticle lifetime. Some of these techniques require processing prior to pellicle attachment while others are better performed after pellicleization. For example, surface pretreatment methods associated with the present invention may enable improved material modification results. The influence of this process is obtained in this case, for example, due to incorporating another material into the thin-film absorber or increasing the heat build-up in the thin-film absorber.

Environmental control techniques can also be used in conjunction with the method of the present invention. Techniques for controlling the environment inside and outside the pellicle and the environment prior to pellicle attachment can be used in combination with the material modification process of the present invention. One embodiment includes exchanging the environment under the pellicle with a gas that interacts with the thin film absorber material to change the properties of the material. This can be done without pellicle removal by gas exchange through filtered vents in the pellicle frame. Additionally, it may be advantageous to maintain an inert environment inside or outside the pellicle in conjunction with the present invention to enhance bulk absorber properties to surface material alteration processes. These combinatorial processes may increase the direction of relative overlay change or feature displacement, for example.

metrics

Methods according to aspects of the present invention can also be used in conjunction with metrics to monitor critical process parameters and/or evaluate the progress or completion of a material improvement process. Measurement of localized temperature of the substrate material may be used in combination with material change, for example. Temperature measurements can be evaluated prior to process utilization to verify the potential for temperature-related damage. Additionally, these temperatures can be monitored during the material modification process to ensure process control and/or reduce the risk of material damage. For example, according to certain embodiments of the present invention, the temperature of the substrate and/or absorber film is monitored during this process to maintain the desired process or to detect excessive temperature build-up. It has feedback control capability of the energy applied to turn off the process in case. Numerous temperature monitoring devices and methods exist and include contact devices (eg, thermocouples) and methods 30 and non-contact (eg, infrared cameras) devices and methods 29 (see Figure 10).

The metric apparatus 31 and method may also, in accordance with aspects of the present invention, measure the material or performance properties of the substrate and/or the substrate's material or performance characteristics before, during and/or after the energy beam 2 is applied to the substrate 4 and/or the substrate. (Fig. 11). For example, measurements of feature positions on a photomask can be used to calculate overlay error prior to processing. This can determine the level of material modification required to correct local or global overlay errors. It can also be used to determine the exact energy or number of pulses to apply to different areas of the photomask to cause the desired change. This metric can also be used to monitor overlay and feedback information to the process during processing or to stop the process if adjustments are within specified process limits. Additionally, the material properties of the pellicle membrane can be monitored to determine if adverse effects are occurring on the pellicle material. This information can be used before processing to limit the process temperature or during processing to stop the process if damage is observed. For example, one or more ellipsometers can be used to measure the material response of the pellicle film, absorber film and substrate surface. This data can then be used to calculate desired material properties including film thickness, transmittance and phase. The measurement device may share a common optical path with the process energy source (Fig. 12). For example, the energy source 1 may be coupled into the path of the measuring device 31 using a beam splitting device 33 . An additional optical element 2) may also be advantageous in properly correcting the metric data as shown in FIG.

In the case of photomasks, for example, multiple metrics may be incorporated into the material modification process according to certain embodiments of the present invention. For example, by identifying overlay errors across a photomask reticle, process temperature requirements can be defined. Identifying local or global overlay variability on a photomask can provide lateral dimensions for process applications and the number of energy levels required to process different locations/sections across the photomask. Available as you ask. Additionally, it may be beneficial to initially utilize a low energy process and measure the response of the photomask features to the process. Once the response magnitude for a particular mask is measured, additional processing that utilizes this information is finally available. This allows the response per mask to be taken into account when determining the optimum process for correcting the photomask overlay.

Metrics are also used according to certain aspects of the invention to monitor properties of materials located adjacent to the surface being cleaned. For example, monitoring the temperature of the pellicle above the photomask can reduce the risk of pellicle film damage. Permeability properties of pellicle membranes can also be used to determine process performance during or after processing.

As will be appreciated by one of ordinary skill in the art when implementing one or more aspects of the invention, the metric examples described above are not intended to be all inclusive of the present invention. do not have. In contrast, these examples merely illustrate the use of metrics within some methods of the present invention.

The metric device 31, the external energy source 1, or a combination thereof may be operatively coupled to the controller 40 for their control. The controller 40 may be any dedicated processor for operating or controlling the metric device 31, the external energy source, or both. As will be appreciated, the controller 40 may be embodied within a single housing or within multiple housings distributed throughout the excitation and metric system. Additionally, modular controller 310 may include power electronics, pre-programmed logic, data processing circuitry, volatile memory, non-volatile memory, software, firmware, input/exit processing circuitry, combinations thereof, or known in the art. Any other controller structure provided may be included.

As will be appreciated, controller 40 may be configured to perform or control any method or function described herein. Further, as will be appreciated, articles of manufacture encoded with non-transitory machine-readable instructions may be processed by controller 40 to perform any of the methods or functions described herein when such instructions are executed by controller 40 . may be configured to perform or control any of the

Device

Certain methods for material modification according to aspects of the present invention may be practiced using various aspects of the apparatus described herein. An example of such a substrate handling device 130 is one using a robotic handling device 35 of the substrate 4 and/or a translation stage 34 for positioning a sample of the substrate 4 relative to the external energy source 1 as shown in FIG. It further includes motion of substrate 4 along one or more axes of motion. The robotic handling device may include a substrate gripping end effector 36 that transfers the substrate 4 between multiple locations. Apparatus 130 may include, for example, one or more of the metrics described above and/or a way to control the temperature of the substrate and/or adjacent materials during the material modification process. Additionally, the apparatus may include metrics used to align the substrate to the staging system and thus to the laser beam 2 . This metric may further include a computer controlled visual recognition system. Additionally, the apparatus may further utilize computer control of lasers, motion and/or metrics, and the apparatus may allow software-assisted recipe control of the material modification process. Laser energy source control can include, for example, measuring the amount of energy applied at the time of applying a laser pulse and/or during the process.

Reticle fabrication process

Methods and/or apparatus according to aspects of the present invention can be used as part of novel reticle fabrication processes involving improved overlays on photomask surfaces. According to aspects of the present invention, material modification processes can be used to adjust overlay during or following photomask fabrication processes, including photomask repair processes. The photomask may or may not be pellicled prior to processing. Certain embodiments can also be applied to photomasks following a cleaning process. According to aspects of the present invention, material modification can be used to correct overlay changes resulting from wet cleaning processes. As a result, using this process, the overlay can be improved to bring the photomask to the desired specifications, so that the overlay can be used during manufacturing. Another aspect of the invention can be used after the reticle has been used during manufacturing to correct overlay changes caused by use during manufacturing. This process can be utilized through the reticle to correct overlay, thereby avoiding a rereticle cleaning process. In this embodiment, aspects of the disclosed process can extend photomask lifetime beyond what is currently achievable by avoiding additional wet cleaning processes and/or repellicles. Duplicate sets of photomasks are currently required because nonstandard photomasks must be discarded. Thus, the disclosed method also enables cost reduction by extending the useful life of photomasks and reducing the need for the same two masks to complete a single fabrication run.

A novel photomask reticle fabrication method according to certain aspects of the present invention uses apparatus that utilizes one or more of the methods described above to modify the properties of the thin film absorber 3 of the photomask 4. do. A typical reticle fabrication process according to one aspect of the present invention includes multiple wet cleaning processes applied to the photomask during fabrication. The number of wet cleaning processes varies from mask to mask, thus leading to variations in final overlay from mask to mask. One aspect of the present invention utilizes one or more of the material modification methods described above to globally alter the overlay of each photomask by different amounts, resulting in a final overlay variability is reduced. According to another aspect of the invention, using a reticle fabrication process that includes the use of one or more of the disclosed methods reduces overlay errors (globally or locally) to produce photomasks. The useful life of 4 can be extended.

In addition to mask-to-mask optical performance variations, each wet cleaning process may impart variations in material properties across the surface of a single photomask. Variations in overlay on a single photomask can become unacceptable after fabrication and/or wet clean processing. This is especially true as the number of wet cleaning processes increases. In accordance with one aspect of the present invention, a novel photomask reticle fabrication process using equipment that utilizes one or more of the material modification methods described above to improve photomask overlay uniformity. is provided. This may involve creating non-uniform variations across the photomask or one or more localized variations in the overlay. According to certain embodiments of the present invention, non-uniform material variations are used to extend the useful life of the photomask by correcting non-uniformities in the overlay of the photomask.

According to certain embodiments of the present invention, a novel reticle wafer fabrication process reduces the use of additional masks or mask sets for product manufacturing by extending photomask lifetime.

The many features and advantages of the present invention will be apparent from the detailed description, and it is thus intended that all such features and advantages of the invention that fall within the spirit and scope of the invention be covered by the appended claims. intended. Furthermore, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the present invention to the precise construction and operation shown and described; Examples can be taken as included within the scope of the present invention.

Recitations of ranges of values herein are intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise specified herein. merely, each separate value shall be described herein as if it were individually described herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.

Unless otherwise specified, the use of the term "substantially" as used herein means "substantially greater in degree" or "greater in degree but not necessarily to the degree specified". means no.

It will be appreciated that the above description provides examples of the disclosed systems and techniques. However, it is envisioned that other implementations of the invention may differ in detail from the above-described embodiments. All references to the invention or embodiments thereof are intended to refer to the specific embodiments being described at the time, and are not meant to imply any limitation as to the overall scope of the invention. All discriminatory and derogatory terms relating to certain features indicate no preference for those features and do not exclude such terms entirely from the scope of the invention unless otherwise specified. do not have.

Claims (20)

A method of improving performance characteristics of a photomask, wherein at least one feature is provided on the photomask, the at least one feature has an associated design location, and the at least one a distance between one feature location and the associated design location creates an error in the position of the at least one feature, the method comprising:
directing electromagnetic radiation toward the photomask, the electromagnetic radiation having a wavelength substantially matching a high absorption coefficient of the photomask;
generating a thermal energy increase in the photomask due to incidence of the electromagnetic radiation on the photomask;
reducing said position error as a result of said generation of said increase in thermal energy in said photomask. 2. The method of claim 1, further comprising directing the electromagnetic radiation into an object positioned on the photomask. 3. The method of claim 2, wherein the photomask is at least partially housed within a pellicle and the object is a pellicle membrane. 2. The method of claim 1, wherein the laser wavelength is greater than 8 micrometers. 2. The method of claim 1, wherein said photomask is a quartz photomask and said electromagnetic radiation wavelength is about 9 micrometers. 2. The method of claim 1, wherein a thin film is provided on the photomask, and the at least one feature is contained in the thin film. 7. The method of claim 6, wherein said thin film is partially light absorbing. 2. The method of claim 1, wherein said reduction in positional error is the result of at least one of dehydration, oxidation, annealing, and densification. the at least one feature includes a first feature at a first location and a second feature at a second location; is different from the first location, and the method includes:
reducing the positional error of the first feature by a first amount;
2. The method of claim 1, further comprising reducing the positional error of the second feature by a second amount, the first amount being different than the second amount. The photomask includes a plurality of materials, and the electromagnetic radiation is a laser beam, the laser beam having a wavelength substantially matching high absorption coefficients of at least two materials of the plurality of materials. A method according to claim 1. A method for improving optical properties of a photomask, comprising:
directing electromagnetic radiation toward said photomask, wherein said photomask is provided with a partially absorptive thin film, said electromagnetic radiation having a wavelength substantially matching a high absorption coefficient of said photomask; death,
generating an increase in thermal energy in the photomask in response to the electromagnetic radiation incident on the photomask;
A method comprising repositioning a first feature on the photomask relative to a second feature on the photomask. 12. The method of claim 11, wherein said modifying step comprises increasing a distance between said first feature and said second feature. 12. The method of claim 11, wherein said modifying step comprises decreasing a distance between said first feature and said second feature. 12. The method of claim 11, wherein the photomask is at least partially housed within a pellicle, the method further comprising directing the electromagnetic radiation into a pellicle membrane positioned above the photomask. 15. The method of claim 14, wherein said electromagnetic radiation is further directed toward said thin film, said electromagnetic radiation having a wavelength substantially matching a high absorption coefficient of said thin film. A method for improving optical properties of a photomask, comprising:
directing electromagnetic radiation toward a partially absorptive thin film provided on the photomask, wherein the electromagnetic radiation has a wavelength substantially matching a high absorption coefficient of the thin film;
generating a thermal energy increase in the thin film in response to the electromagnetic radiation incident on the thin film;
A method comprising repositioning a first feature on the photomask relative to a second feature on the photomask. 17. The method of claim 16, wherein said modifying step comprises increasing a distance between said first feature and said second feature. 17. The method of claim 16, wherein said modifying step comprises decreasing a distance between said first feature and said second feature. 17. The method of claim 16, wherein the photomask is at least partially housed within a pellicle, the method further comprising directing the electromagnetic radiation into a pellicle membrane positioned above the photomask. 17. The method of Claim 16, wherein said electromagnetic radiation is further directed toward said photomask, said electromagnetic radiation having a wavelength substantially matching a high absorption coefficient of said photomask.

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