TW201831993A - Apparatus and method for contamination identification - Google Patents

Abstract

Method and apparatus for identifying a contaminant on a substrate. Identification of a contaminant removed from a substrate can be useful in identifying and eliminating or reducing the source of the contamination and tailoring the removal method to minimize the potential for substrate damage. The methods and apparatus for identification of the contaminant provide liberation of molecules of the contaminant from the surface of the substrate, accounting for different geometries and substrate materials, sample preparation, and chemical analysis of the contaminant.

Description

Apparatus and method for identifying pollution

This patent application is a continuation of the U.S. Patent Application Serial No. 15/048,774, filed on Jun. 16, s. The continuation of the continuation of US Patent Application No. 14/294,728 (now US Patent No. 8,986,460) filed on June 3, 2014, filed on November 11, 2013 U.S. Patent Application Serial No. 14/077,028 (now U.S. Patent No. 8,741,067), which is incorporated herein by reference. The continuation of U.S. Patent Application Serial No. 12/277,106 (now U.S. Patent No. 8,293,019), filed on Nov. 24, 2008, which is issued on March 25, 2008. Continuation of U.S. Patent Application Serial No. U.S. Patent No. Serial No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. The aforementioned documents are cited by way of reference. Wen incorporated herein.

The present invention generally relates to apparatus and methods for cleaning surfaces. More particularly, the present invention relates to apparatus and methods for cleaning surfaces for components typically used in the semiconductor industry, optical components, and the like. The disclosed device and method are used to extend the service life of the reticle marking.

Electromagnetic radiation has long been used for surface cleaning. Examples of such processes include the removal of surface contamination, the removal of a coating of a thin layer of paint, or the removal of oil from a metal work surface. Some of the earliest examples utilized flash source. These systems may be limited in applications due to the achievable peak power.

Lasers have been increasingly used in these types of processes because of the high peak power, high energy stability, and wavelength selectivity that are achievable. These features allow for highly localized, improved material selectivity, and depth control of cleaning effects. Laser surface cleaning processes can be broadly classified into surface contamination layer removal and particle removal. The removal of the surface contamination layer is usually achieved by laser ablation. Particle removal involves removing overall contamination.

Both types of cleaning processes can benefit from the use of pulsed laser radiation to provide higher peak power. Short pulsed radiation provides particularly improved processing. Short pulse radiation has been shown to reduce the heat affected zone in laser ablation processing. This allows for improved localization of ablation removal and finer removal depth control. Short pulsed radiation also enhances particle removal by increasing the rate of heat increase within the particles and/or substrate, thereby increasing the acceleration of particle removal.

Substrate damage can be a problem for both ablation and particle removal processes and several techniques have been developed to minimize these effects. For ablative processes, selecting a wavelength that increases the absorption of contaminants reduces flux requirements and thus reduces substrate damage. In addition, the use of multiple pulses for total contaminant removal reduces the flux required. However, substrates with high absorption at selected wavelengths may ablate with contamination, even along with wavelength selection and multiple pulse removal processes. In these cases, the ability to terminate the removal process at the substrate interface will be limited. This problem is significantly increased for smaller size contamination because the absorption cross section for contamination is reduced relative to the substrate.

Like the ablation removal process, the particle removal process can also cause substrate damage for sensitive substrates and substrates that have high absorption at processing wavelengths. This problem is increased for small particle removal because of the increased adhesion between the particles and the substrate and the self-focusing of the laser below the particles. Apparatus and methods for reducing the risk of substrate damage for particle cleaning processes involve controlling the environment above the contaminated surface. Examples of particulate laser processes that allow for reduced flux levels include wet laser cleaning, water vapor laser cleaning, and increased humidity cleaning. Combinations of lasers and other cleaning processes, including etching, organic solvents, and ultrasonics, have been shown to increase cleaning and reduce the risk of substrate damage. However, in addition to the dry laser cleaning process, all of the described particle removal processes require an environment that is close to the surface of the substrate. This may not be practical for some systems.

Alternative dry laser particle cleaning processes have been developed. Laser sonic cleaning and laser shock cleaning have also been evaluated for dry laser cleaning methods for particle cleaning. Laser acoustic cleaning involves the high probability of directing the excited state to the substrate and thus suffering from substrate damage, particularly for the small particles discussed. Laser shock cleaning has been shown to enhance particle removal and reduce the risk of substrate damage by focusing the laser over the surface of the substrate and relying on the interaction of the seismic wave with the particles. This technique will also have increased difficulties when applied to small particle removal. In addition, shock waves can damage other sensitive features on or near the surface of the substrate. This is especially true if sensitive materials are above the surface of the substrate, since the generation of seismic waves requires a relatively high laser intensity to focus on the substrate.

In the case where the environment above the proximity surface is impractical (eg, a closed system), even the latest dry laser technology can be limited. For a closed system, the removal process will only move the particles to different locations on the substrate as the particles are removed from the surface as a whole. Typically these techniques utilize additional control devices and methods to completely remove particles from the substrate to be cleaned. Such methods include directing air flow, using reduced pressure (vacuum) or gravity, most of which require open proximity to the environment above the surface of the substrate.

Semiconductor manufacturing is one of the major industrial areas that utilize surface cleaning processes including laser cleaning methods. Many of the cleaning processes required have a strict tolerance to the extent of substrate damage. In addition, the small product features make it necessary to remove very small particles to avoid product failure. Cleaning is a problem in multiple wafer processing steps and includes extended contamination layers (eg, photoresist removal) and particulate contamination removal.

Surface cleaning is also a requirement for optical components (eg, reticle) used in wafer fabrication processes. Especially for reticle, contamination growth is observed during normal use of the mask in the wafer printing process. These masks are exposed to deep ultraviolet (DUV) radiation during normal processing for printing mask patterns onto the wafer. Exposure to this radiation produces contaminated growth in the form of small particles that absorb the illuminating radiation. This growth is commonly referred to as haze.

For wafer printing processes, turbidity is a problem because it blocks more light from passing through the reticle as the particle size increases. Eventually the turbid contamination absorbs enough light to cause defects in the printed image of the reticle on the wafer. The reticle surface must be cleaned before turbidity pollution reaches this level. This cleaning requirement has the effect of reducing the useful life of the reticle since the process currently used to remove turbidity degrades the absorbing film on the mask. For partial absorbent films, current cleaning methods reduce film thickness and thus the transmission and phase properties of the film. By varying the size and shape of the printed features on the wafer beyond acceptable tolerance, phase and/or transmission changes reduce the life of the reticle. Once the useful life of the reticle is exceeded, a replicated collection of reticle must be made to continue manufacturing. When the contaminated reticle is cleaned, a copy set is also required. There are several daytime requirements before the mask is cleaned and verified, as the cleaning process is typically performed at different facilities. As feature sizes for semiconductor manufacturing are reduced, the size of turbid growth that produces print defects is also reduced. This increased sensitivity to turbid growth indicates that the latest reticle will need to be cleaned more often and will have a shorter usable life.

In addition, the composition and source of turbidity and most of the contaminants on semiconductor substrates are often difficult to identify. To this end, it would be beneficial to develop tools and methods that not only remove contaminants but also allow the user to identify the physical and chemical properties of the contaminants. This can be accomplished by collecting contaminants for analysis when the contaminants are removed from the substrate. The collection and subsequent analysis of contaminants will help to identify the source of the contaminants. This information can then be used to slow or even eliminate contamination problems in the semiconductor manufacturing process, saving both process time and manufacturing cost.

The chemical or elemental composition of the particles on the surface of the identification substrate is limited by the resolution of the techniques and instruments used for the analysis. Contaminants can also be small, as individual particles or thinly distributed along the surface of the film, so many chemical analysis techniques do not have the resolution to detect or identify chemical composition. For example, the contaminants remaining after each wash may not be chemically or detected by particle inspection on the reticle used in the photomicrography of multiple washes exposed to different chemical compositions. Outdated and always exposed to energy and molecular pollution carried by the surrounding air, these remaining molecules tend to stick and grow on the surface. These molecules are of the nanometer grade, sometimes of the micron scale, and are not detectable by standard chemical analysis tools. However, it exists and has grown to a size that can be observed by particle inspection equipment down to tens of nanometers. As these molecules grow, they hinder the ability to make wafers, especially when the molecules grow into sufficiently large defects that they can be broken down onto the wafer. In such cases, identifying the composition of the molecules on the reticle will allow for the manufacture of a source of confirmation.

The application of an alternative cleaning method to remove the turbidity of the reticle surface is hampered by the use of a pellicle attached to the reticle surface. The surface layer consists of a frame that is adhesively bonded to the surface of the reticle and a film that stretches across the surface frame. The skin layer is used to prevent externally generated particles from depositing onto the surface of the reticle where it may affect the printing process. The externally generated particles are deposited onto the film above the surface of the mask where it has a significantly reduced impact on the printing process. In addition to the small filter valve on the skin frame allowing pressure equalization, the top surface of the reticle is effectively sealed to separate the local environment by surface attachment.

The currently accepted method for turbidity removal requires the wafer manufacturer to ship the contaminated reticle back to the mask maker or to a third party. Here, the surface frame is removed from the reticle, the mask is cleaned, the defect is inspected, and a new surface layer is attached to the reticle, and in many cases, the particle defect inspection is again masked before it is shipped back to the wafer manufacturer. cover. This typically takes a few days to complete, increasing the cost of the mask due to additional processing and reducing the quality of the mask due to the cleaning process. In addition, since the adhesive is removed from the surface layer and dropped onto the printable area of the reticle, there is a small possibility that the reticle will be damaged when the turbid removal process is used.

Because of the difficulty associated with thorough surface cleaning, current efforts to improve the problems associated with turbid growth on reticle have focused on processes that can be performed prior to the addition of the skin. These efforts have primarily focused on the use of alternative chemicals in surface preparation and cleaning processes. The latter has been shown to alter turbid pollutant species but does not eliminate their growth. Both regions, at best, show a reduction in growth rate and do not eliminate the need for cleaning. More recently, the use of an inert environment has been shown to reduce the growth rate of turbidity formation on the reticle. Applying this method requires control of all environments exposed by the reticle, including all process equipment. As with other methods of development, this process has the potential to reduce growth rates but does not eliminate the need for cleaning and the deleterious effects of cleaning.

In one aspect of the invention, a method for cleaning the surface of a substrate is provided. The method includes the steps of directing a laser toward a substrate having contaminating particles disposed thereon; creating a temperature increase in the substrate; and transferring thermal energy from the substrate to the particles to decompose the particles. The laser has a wavelength that is substantially the same as the local maximum of the absorption spectrum of the substrate.

In another aspect of the invention, a method of increasing the useful life of a reticle substrate is provided. The method includes the steps of directing electromagnetic radiation through a protective material toward a substrate having contaminating particles disposed thereon; creating a temperature increase in the substrate; and transferring thermal energy from the substrate to the particles to decompose the particles. The radiation has a wavelength that is substantially the same as the local maximum of the absorption spectrum of the substrate.

In a further aspect of the invention, a method of cleaning a surface of a substrate at least partially enclosed within a skin layer is provided. The method includes the steps of directing a laser through a surface film toward a substrate having a layer of contaminating particles thereon; creating a temperature increase in the substrate; and transferring thermal energy from the substrate to the particle layer to decompose at least a portion of the particle layer. The laser has a wavelength that is substantially the same as the local maximum of the absorption spectrum of the substrate.

In another aspect of the invention, a non-destructive method for the release and analysis of surface contamination is provided. The method can be performed using a substrate under atmospheric conditions, allowing in situ detection and analysis of the substrate, the substrate having one or more portions that are incompatible with the vacuum. The method focuses on releasing molecules from the substrate to form airborne molecularly contaminated (AMC), which is then more sensitively detected or analyzed. The method consists of a source of electromagnetic radiation impinging on the substrate to release surface contamination. The released AMC is then delivered to a metrology system for detection or analysis. Alternatively, the released contamination can accumulate on the secondary collection substrate to concentrate the contamination for internal analysis or for delivery to an external metrology system. Partial partial vacuum can be used to assist in the collection of molecules or particles released from the surface.

The specific embodiments of the invention have been broadly described in order to provide a better understanding of the embodiments thereof Of course, there are additional embodiments of the invention, which will be described below and which will form the subject matter of the appended claims.

In this regard, before explaining at least one embodiment of the invention, it is understood that the invention is not limited by the details of The invention includes embodiments other than those described and can be implemented and carried out in various ways. It is also to be understood that the phraseology and terminology used herein and in the claims

Therefore, those of ordinary skill in the art will recognize that the concept of the present disclosure can be used as a basis for designing other structures, methods, and systems for the purpose of performing the various embodiments of the invention. Therefore, it is important that the scope of the patent application is to be construed as including such equivalent constructions as long as they do not depart from the spirit and scope of the invention.

The invention will now be described with reference to the drawings, in which like reference numerals refer to the like. In accordance with certain embodiments of the present invention, a method for laser surface cleaning with reduced risk of substrate damage is provided.

1A illustrates an embodiment of the present invention in which an excited state energy 2 is derived from an energy source such as laser 1 and directed toward the surface of the contaminated substrate 4, causing heat to transfer from the surface of the substrate 4 to the contaminating particles 3 or Contaminated layer (eg, by convection or conduction). However, energy sources other than lasers can also be used (eg, lamps and other devices that can always illuminate energy along the electromagnetic spectrum, including generators or x-rays, microwaves, infrared radiation, near-ultraviolet radiation, etc., can be used, etc. ). Also, the surface can be any material (eg, the surface of a germanium wafer). The increase in temperature caused by contamination typically produces a heat based removal and its effect is shown in Figure 1B, including but not limited to sublimation or evaporation material 6 and decomposition material 5. Further, the contaminating fine particles 3 can be found on the reticle, as shown in Fig. 2, which shows the contaminating fine particles 3 on the substrate 4 and on the film absorbent 7.

According to a particular embodiment of the invention, the method has a reduced risk of substrate damage because the temperature typically used to create surface cleaning is lower than the level of thermal damage of the material 4 of the substrate 4. The risk of substrate damage is also typically reduced compared to other techniques because in some cases it can utilize a relatively long pulse width, which often reduces the likelihood for multiple photon absorption processes.

The exemplary methods discussed above generally provide improved small contaminant/particle removal because of its minimal dependence on particle size. The method may be particularly advantageous for applications where the environment above the contaminated substrate is substantially or completely enclosed. In these cases, the method can also include directing the beam of light through the opposing surface of the material that is part of the substrate environment enclosure. For example, the method of the present invention can be used to clean turbid contamination from the surface of a reticle.

Decomposition of contaminant species has been suggested to be an advantage in laser surface cleaning processes. However, prior to the development of embodiments of the present invention, there has been no disclosure of laser heating using a substrate to create a process based on thermal surface cleaning.

In accordance with a particular embodiment of the present invention, the method includes selecting a laser wavelength that is substantially consistent with the strong absorption of the substrate and setting the laser energy and pulse width to produce a desired cleaning effect. In some instances, the increased absorption in the substrate allows for lower laser energy for the cleaning process. The possibility of damage to adjacent materials that may interact with the laser when the laser is directed to or from the surface is thus reduced. Although not required, in accordance with certain embodiments of the present invention, the selection is also a wavelength at which the contaminant or contaminants are highly absorbed, as this may improve the desired heat removal effect. The use of multiple laser wavelengths and/or laser energy can be used in the cleaning process, especially when the substrate is composed of more than one material. Multiple laser energies can also be used for the same component, typically undergoing material or material property changes during the first step of the desired cleaning process. Multiple wavelengths can be generated, such as by utilizing multiple laser sources or a single tunable laser source or both. Multiple energies can be used by controlling the output energy of the laser source for internal or external control of the laser. Practical example

The following is an example of a method in accordance with one embodiment of the present invention applied to cleaning turbid contamination from a reticle substrate surface used in a wafer fabrication process. This example can be used to discuss all of the additional embodiments of the method of the invention.

Particular embodiments of the invention are applicable to surface cleaning of wafers (e.g., germanium wafers). The type of turbid growth has also been observed for these substrates and may become a problem in some instances if not removed prior to wafer printing. Environmental controls have been suggested to control turbid growth on germanium wafers. However, certain embodiments of the present invention are useful, for example, for turbidity reduction or other types of contamination removal on the surface of a germanium wafer. More specifically, in accordance with certain embodiments of the present invention, turbidity can be removed by laser excitation of the germanium wafer substrate to below a thermal damage threshold.

The method according to certain embodiments of the present invention can clean contaminated precursor materials because such methods typically do not rely on direct absorption of the material placed on the substrate. In this manner, the method according to certain embodiments of the present invention can be used as a surface preparation technique to reduce the rate of contamination formation. The opaque growth of the mask can be reduced, for example, by applying the method according to the invention prior to use in a wafer fabrication process and removing or resetting the turbid growth precursor material (eg, acid residue, water, etc.) or nucleation sites. . Other techniques may be used in conjunction with the current invention to further alleviate regrowth or reformation of turbidity after treatment of the reticle with the present invention. For example, by reducing the regrowth or re-formation rate of turbidity, environmental control prior to, during, or after surface preparation prior to surface layering can increase the life of the reticle.

Applying a method in accordance with certain embodiments of the present invention to a substrate comprised of a plurality of materials may require consideration of material parameters and beam parameters, including excitation state wavelength selection. The basis of the cleaning process makes it particularly desirable that all contaminated areas of the substrate reach a temperature substantially close to the temperature required for removal without exceeding the thermal damage threshold of the substrate. Bringing one of the materials to the laser energy typically required for process temperature may result in thermal damage in other materials, especially if there is a significant difference between material absorption. The local flux of the beam can be controlled based on the exposed material.

In accordance with certain embodiments of the present invention, longer laser pulse widths, up to and including continuous wave (CW) lasers, are used to improve the thermal balance between materials having significantly different absorption constants. However, using such longer laser pulse widths produces the highest thermal increase in the system, and may be useless if the material of the adjacent substrate surface has a thermal damage threshold below the process temperature.

In accordance with certain embodiments of the present invention, a laser wavelength having significant absorption in all of the materials on the substrate is selected. The same laser energy can then be used, for example, to produce a desired process temperature below any substrate material damage threshold. Thermal transfer between different materials can be benefited by considering thermal properties, including diffusivity. In some cases, this allows the use of reduced process throughput to achieve removal on the entire substrate, particularly if the thermal energy flow from the higher absorbent material is prioritized to the lower absorbent material.

Control of the beam parameters is particularly desirable in embodiments of the invention where the turbidity of the associated turbid contamination is cleaned. Due to the physical structure of a typical reticle, for example, wavelength selection is highly desirable. Referring to Fig. 2, the photomask is usually composed of a quartz substrate 4 having a thin absorption film 7 on a critical surface. In the case of metal films, a significant absorption coefficient will typically be typical for most of the laser wavelengths that can be generated. However, for quartz substrates, there will typically be a limited range of wavelengths in which the substrate has significant absorption and a common source of laser light can be obtained. Considering the thermal properties of the quartz relative metal layer, a particular process in accordance with embodiments of the present invention will utilize wavelengths that are highly absorbed by the quartz substrate material because heat transfer between the materials will occur preferentially from the quartz to the metal layer.

The above discussion is also substantially true for the case of partially absorbing the mask film. In general, for a reticle having a partially absorbing film, heat flow will preferentially occur from quartz to the film because the film typically contains metal components and quartz has relatively low thermal diffusivity. However, there may be wavelength regions in which these films do not absorb significantly, unlike pure metal films. This has the potential to increase the range of wavelengths that can be used to preferentially excite the quartz portion of the substrate. In addition to heat flow, heat-induced material changes (eg, oxidation, annealing, etc.) must be considered for a portion of the absorbing film. The phase and transmission characteristics of these materials are critical to their function and can be altered by heat treatment. If thermal material changes adversely affect film performance, it may be necessary to limit the maximum temperature at which the process is removed. If thermal material changes have a beneficial effect, it may be necessary to control the uniformity of the process by pulse shaping or pulse overlap.

A specific example of a representative method in accordance with the present invention is the removal of ammonium sulphate turbidity from the surface of the reticle. Temperature and other areas – It is expected that ammonium sulfate will decompose at temperatures above 280 °C. The lowest thermal damage point for a typical reticle will typically be the melting/reflow point for the base quartz substrate (i.e., about 1600 ° C). Thus, there are possible processes in which the temperature for contamination removal/cleaning can occur below the extent of damage to the substrate material.

It is important to note that the exact species to be removed from the reticle typically only determines process temperature requirements. Although it may be advantageous to have significant absorption in the contamination, it is not a requirement. As discussed above, due to possible differences in material absorption characteristics, the relative absorption of the substrate material is generally considered. In particular, quartz substrates having significant absorption at the process wavelength are desirable, primarily because heat flow will preferentially precede the absorber film.

Quartz substrates for reticle are typically specifically designed to have high transmission in the deep ultraviolet (DUV) wavelength range, as shown by the quartz absorption spectrum in Figure 3. This is typically achieved by using a substrate formed by synthesis that has a very low level of impurities. In addition to having relatively weak absorption at wavelengths near 3 μm, these materials typically also have high transmission in the infrared region. The primary absorption for these substrates occurs substantially at wavelengths below 0.2 μm or above 8 μm. Shorter wavelengths are not in the particularly desirable wavelength range because they are typically absorbed by air and because they have higher photon energies and are more likely to produce multiple photon processes.

According to a particular embodiment of the invention, it is particularly desirable to select a wavelength above 8 μm, such as near 9 μm quartz absorption. This typically produces high absorption in the quartz substrate without high environmental absorption. In particular, if the reticle has a metal film layer (e.g., chrome), this wavelength has an additional benefit because the reflection of the metal film increases with increasing wavelength in this region. This typically reduces the available light to be absorbed by the film and substantially improves the deviation from the thermally excited state of the quartz. Because of the relatively high absorption coefficient for quartz, this wavelength also provides an advantage to a reticle having a portion of the coated coating (ie, MoSi). In general, the temperature of the film material that reaches a constant flux should be similar to that for quartz due to high quartz absorption and higher thermal diffusivity than a portion of the absorber of quartz. This can be expected to be true even if the partially absorbing film has a relatively high absorption coefficient in this wavelength range.

The process described in accordance with certain embodiments of the present invention typically increases the useful life of the reticle by replacing the cleaning process currently used to remove turbidity from the reticle surface. Unlike typical chemical cleaning processes for turbid cleaning, the laser removal process in accordance with certain embodiments of the present invention does not substantially reduce the thickness of the absorbent and/or the line width of the absorbent film. There is a limit to the number of conventional "cleaning processes" that can be performed before the reticle will no longer be usable, as material loss is a consequence of these processes. This is especially true for reticles having a partial absorbing film because loss of material causes phase loss and increased transmission through the film. By design, the performance of a partially absorbing film reticle is strictly dependent on the transmission of the phase and film. In accordance with the laser cleaning process in accordance with the present invention, an unlimited number of cleaning cycles can be used.

It has been determined that using temperatures below the critical range can result in material changes in the partially absorbing film. For example, the effect of partially absorbing the MoSi film at the first temperature annealing and annealing film is to reduce the phase delay or significant transmission loss of the light penetrating film, and the cleaning process must be operated below this first temperature. Otherwise, the life of the partial absorbing film reticle will be reduced as it utilizes the nominal wet "cleaning process" currently used for turbid removal. However, by adjusting the energy supplied to the surface (e.g., control pulse period, pulse amplitude, CW energy, etc.) and thus circumventing the critical temperature tolerance of the film, the temperature of the process of the present invention can be finely controlled.

However, if the effect of the annealed film is an increase in phase retardation and minimal or no transmission loss of the light penetrating film, it may be advantageous to operate the cleaning process above the annealing temperature. The standard wet "cleaning process" is integrated into the reticle production and produces an unacceptably low phase delay for a portion of the absorbing film, even before use. Furthermore, a wet cleaning process may be required in addition to using the current invention. For example, if a non-turbidity related defect is present or appears on the reticle, a wet cleaning process may be required. By restoring the phase delay losses caused by the wet cleaning process, material changes in the partially absorbing film during the cleaning process of the present invention can extend the life of the reticle. It is also possible to modify the heat of the partial absorbing film by using the method of the present invention to extend the life of the reticle marking by itself (without requiring turbid cleaning) by restoring the phase loss during the wet cleaning process.

One of the reasons for using an aggressive wet cleaning process is the fact that the surface frame is removed from the reticle leaving adhesive residue. The wet cleaning process will generally affect the adhesive residue, causing the adhesive to contaminate the working area of the mask because they are generally difficult to localize. However, some of the laser cleaning processes described herein can be positioned away from the adhesive residue so that they are unaffected. Controlled Removal of the Surface Frame and Most Adhesives The laser cleaning process in accordance with embodiments of the present invention allows for subsequent surface attachment without the need for wet cleaning (aggressive or otherwise). This is especially true if the laser cleaning process in accordance with embodiments of the present invention is used in combination with multiple skin layers, multiple skin layers will utilize alternative bonding methods or will not require exposure of the adhesive for surface exchange.

The method according to a particular embodiment of the invention can be applied to the opaque cleaning of the reticle without the need to remove the skin. These laser cleaning methods, which are typically performed through the skin film material without affecting the characteristics of the skin film, are illustrated in Figure 4, which shows the skin layer 8, the skin frame 9, and the substrate skin adhesive 10.

In this case, the absorption of the surface film 8 at the process wavelength and the energy density (flux) on the surface of the substrate 4 are typically considered. Like the substrate 4 and the substrate film coating 7, the cleaning process does not substantially produce a temperature increase above the damage threshold in the skin film. However, depending on the surface film, there may be significant absorption in the surface film for the quartz substrate at an absorption peak close to 9 μm. However, it is still possible to operate in areas where significant surface film absorption occurs because the surface film system is placed over the surface of the substrate.

FIG. 5A illustrates that the focused excited state energy 2 passes through the focusing lens 11 to produce a convergent beam 12 passing through the surface film to the substrate film coating 7 on the surface of the substrate 4 to remove the contaminating particles 3. The wavelength and convergence properties allow for focusing at different heights and reducing the relative temperature increase in the skin film 8. The temperature increase in any substance is proportional to the flux applied to the surface; ΔT ~ F Equation 1 where ΔT is the temperature change within the material and F is the absorbed laser flux.

For a constant intensity or beam pulse energy, the flux is inversely proportional to the square of the spot radius. F ~ E / r2 Equation 2 where F is the flux, E is the energy, and r is the radius of the beam on the surface of the substrate.

Figure 5B illustrates the spot beam size on the surface layer. The ratio of the radius of the surface beam (surface beam 14) to the radius of the beam (mask beam 13) on the mask surface 4 is typically increased by the focused beam passing through the surface layer, and thus the relative flux on the surface film is compared to light. The cover substrate surface can be reduced. Figure 5C is a side view showing the unconvergent energy of the convergence of the mask beam 13 at the surface 4 with respect to the entry point of the surface layer 9 (the surface beam 14).

In addition to wavelength considerations, processes that generate large temperature increases in the system (eg, long pulse length or high repetition rate) may be limited by the damage threshold of the superficial film. This is typically lower than the process temperature requirements for many reticle haze components. Pulse shaping

In accordance with certain embodiments of the present invention, the pulse width, temporal pulse shape, and spatial distribution of the laser can be used to enhance the cleaning process or to increase the safe operating range for processing. A shorter pulse width can be used to minimize the overall heat input to the system (substrate and contamination). Longer pulse widths can be used to maintain process temperatures for extended periods of time, improving the integrity of the heat removal process. Time pulse shapes can be used to control temperature rise within contaminating species. A long temperature rise can be used to produce an initial effect (eg, melting) that is followed by a secondary effect (eg, decomposition). In some cases, a shorter rise time promotes evaporation of contaminants while limiting the decomposition process. Combinations of short and long pulse shapes can also be used to optimize the removal process. The use of multiple pulses can also be used to reduce beam energy, which is desirable for complete cleaning, thereby further reducing the risk of substrate damage.

The spatial distribution of the laser beam can be used to increase the process window. By way of example, Figure 6A shows a typical Gaussian spatial distribution 15 that produces a temperature gradient in the substrate 16, while Figure 6B illustrates a flat top or high top spatial distribution 17, allowing for a more uniform temperature rise within the substrate 4. Spatial distribution can be used to increase the process window. For example, having a flat top or high top spatial distribution allows for a uniform temperature rise within the spot, while a Gaussian distribution typically produces a temperature gradient within the spot. To avoid the risk of substrate damage, the maximum energy in the beam is typically limited by the peak of the Gaussian distribution. As previously mentioned, when more than one material is present on the substrate, a longer pulse width can be used to allow for thermal equilibrium between the substrate materials. Thermal management

Because certain embodiments of the invention relate to heat-based processes, it is sometimes desirable to manage the overall temperature of the system to avoid damage to materials that are thermally sensitive or susceptible to contamination. This is especially true in the case where the reticle is turbid and clean without surface removal. The skin film typically has a low heat damage threshold. Therefore, it is sometimes useful to avoid the overall system temperature buildup that can be transferred to and/or damaged the skin material. This includes the surface frame and the enclosed environment between the surface of the mask and the surface film.

Managing system temperatures can be done in several ways. The following examples illustrate representative methods of several sample cooling, and it is to be understood that other methods exist. One method of managing system temperature is through contact cooling. The reticle, for example, can be placed in contact with the plate 17, as illustrated in Figure 7, the plate 17 acts as a heat sink to attract heat generated on the front surface of the mask toward the back of the mask and includes the heat exchange tubes 18 and 19. This reduces the heat transfer to the environment above the mask surface, the surface film, and the adhesive between the skin frame and the surface of the mask. Cooling can be accomplished in a variety of ways, including thermoelectric cooling or laser induced cooling of a portion or the entirety of water or other cooling liquid or gas, mask, and/or skin layer over the mask and/or skin.

It is also possible to control the temperature by forced convection cooling. The filtered and/or cooled gas or liquid stream is typically directed onto the mask portion, the skin film, the frame and/or the adhesive region to directly reduce heat buildup in these materials, as shown in FIG. . The top stream 20, side stream 21 or underflow 22 of the coolant can be used to control the temperature. This typically not only reduces the risk of surface film damage, but also typically reduces the risk of contaminated outgassing from the surface layer and superficial film adhesives. In addition to the hardware control of thermal stacking of the system, thermal buildup can be reduced by allowing for increased process time. Applying a lower rate pulse to the system or allowing a delay between series of pulse applications may allow the injected heat to be removed without causing the total system temperature to rise above a critical level.

Pulse-to-pulse thermal stacking can also be advantageously controlled and can depend on the thermal characteristics of the contamination, substrate, and/or adjacent materials. In general, pulse-to-pulse thermal stacking can be controlled by reducing the number of times a laser pulse hits the surface per unit time. This temperature buildup can be controlled by increasing the distance between adjacent laser pulses. It may be particularly desirable to have a large lateral displacement between adjacent pulses, where the material is particularly sensitive to pulse-to-pulse heat buildup (eg, skin film material). In this case, the process typically involves multiple positioning of the laser beam at approximately the same location to achieve complete cleaning of the target surface. For example, a first series of laser pulses 13 having a relatively large lateral separation as shown in Figure 9A is exposed to surface 4. As shown in Figure 9B, a second scan over the same area places a further series of laser pulses 13 that are slightly offset relative to the first set of spots. As shown in Figure 9B, this process continues until the entire area has been exposed to the laser pulse 13. As shown in Figure 9D, in accordance with certain embodiments of the present invention, the overlap in the second direction can be used to completely expose the substrate surface 4. In accordance with certain embodiments of the present invention, this overall process repeat and/or overlap between scans is increased, particularly if the cleaning process is desired to include multiple pulses for complete removal. Changing the position of the opposing surface of the beam as illustrated can be accomplished by moving the beam and/or moving the substrate. Moreover, applying a pulse traverse mask in a more systematic manner reduces the likelihood of further thermal buildup on the mask, as illustrated in Figure 9E. Residue control

According to a particular embodiment of the invention, the laser cleaning method may create residual material on the surface of the reticle, depending on the decomposition product of the contamination. Even though the residue no longer affects the use of the substrate material (ie, even if the substrate is effectively cleaned), there may be reasons to control their position or concentration. In accordance with certain embodiments of the present invention, conventional methods for controlling residue formation may be used, such as, for example, applying a directed gas flow, a water flow, or a reduced pressure over a substrate to be cleaned. However, for the case of a closed system, such as, for example, a surfaced reticle, these environmental controls are typically not desired to be used. Thus, in accordance with certain embodiments of the present invention, an alternative method of controlling the position of residual material is used for a closed system. For example, in accordance with certain embodiments of the present invention, the pattern of laser pulses is controlled. For example, Figure 10 shows an embodiment in which the pattern of laser pulses 13 begins at the center of the surface of the substrate 4 and is directed into the progressively increasing diameter or progressively shaped square pattern 23, with the residual material preferentially Move towards the edge of the substrate as shown in Figure 10. An additional method of controlling residue in accordance with certain embodiments of the present invention is to utilize gravity. The reticle is placed with its surface facing down as shown in Fig. 11A, or at the slanted position 24 as shown in Fig. 11B, allowing the residue material to be preferentially deposited onto the surface film or the side of the reticle, respectively. In an additional method, in conjunction with a particular embodiment of the invention, the reticle can be rotated (i.e., spin) to move residual material away from the center of the mask and/or to the inactive area of the reticle. Moreover, in accordance with certain embodiments of the present invention, the temperature of the regions of the reticle, skin, and skin frame is reduced to form a residue material preferentially deposited onto the surface, as this material may be produced when the vapor phase is converted to a liquid or solid, as shown in FIG. Shown in . For example, these cooling methods can include, but are not limited to, flowing water, other liquids or gases, thermoelectric cooling, or laser induced cooling in and/or around the preferred deposition area. Reduce turbid growth and reformation

Current inventions can be used in conjunction with surface preparation or environmental control techniques to extend the life of the reticle. Some of these techniques will need to be processed before the surface layer is set, while others can be executed after the surface layer. For example, the surface preparation method along with the present invention can increase the time between cleaning prior to surface layering. This may be important if there is a limited number of cleaning methods of the present invention before additional cleaning (e.g., wet cleaning) may be required. One embodiment of the method of the present invention places a seed crystal or other nucleating material beneath the surface layer in the inactive region of the reticle. These seed crystals can be used as a dominant growth site for turbidity. This effectively reduces the concentration of the residue and the precursor material available in the active region of the reticle and reduces the growth rate in these regions. Another embodiment of the method is to coat the surface of the mask with a material that reacts with the residue and the precursor material prior to release of the cleaning process and/or neutralizes the residue and releases the precursor material prior to the cleaning process of the present invention. This also reduces the turbid growth rate in the active area on the mask by limiting the available reactive species.

The back skin technology can also be used in combination with the present invention. For example, environmental control or regulation within and outside the surface layer can be used in combination with the present cleaning process invention. One embodiment would include exchanging the environment under the surface layer with the non-reactive gas after the cleaning process. This can be performed by gas exchange through the filter vents on the skin frame without the need to remove the skin. It may be additionally advantageous to maintain an inert environment outside the skin along with the present invention to mitigate turbid regrowth or reformation. With the method of the present invention, these combined processes can extend the time between cleaning processes and can be important if a limited number of cleaning processes can be used.

Additional post-surface, environmentally controlled embodiments of the present invention will evacuate the environment below the surface layer and introduce or exchange the environment with materials that react or neutralize the turbid residue and/or precursor. This process can be performed before, during or after the cleaning process. In all cases, the turbid residue and/or precursor species released during the cleaning process will react with the introduced/exchanged material to form a non-turbidity forming species.

Additional post-layering techniques can be used in conjunction with the present invention to mitigate turbid regrowth or reformation. These techniques will utilize the thermal effects of the present invention to alter the surface profile and/or substrate composition to inhibit turbid growth and reformation. For example, operation at or near the quartz reflow temperature can result in a change in the state or morphology of the material of the quartz substrate. This can reduce or eliminate active sites believed to cause crystal turbid growth nucleation and thus reduce turbid growth rate or reformation. An alternative embodiment combines a combined surface preparation or environmental control method with the thermal impact of the method of the invention to modify or eliminate the active/nucleating sites. The precursor material can be activated by heat treatment or reacted with the surface in a thermally excited state to reduce turbid growth and reformation. Weights and Measures (Metrology)

Methods in accordance with certain embodiments of the present invention may also be used in conjunction with metrology to monitor critical process parameters and/or to assess the progress or completeness of a cleaning process. The measurement of the temperature generated locally by the substrate material can be used, for example, in combination with a cleaning process. Temperature measurements can be evaluated to verify the risk of temperature-related damage before applying the cleaning process. In addition, these temperatures can be monitored during the cleaning process to confirm process control and/or reduce the risk of material damage. For example, in accordance with certain embodiments of the present invention, the temperature of the substrate and/or absorber film is monitored during processing and has feedback control capabilities of the applied energy to maintain the desired process or if too much temperature is detected Turn off the cleaning process when stacking. The multiple temperature monitoring methods present are shown in Figure 12 and include contacts, such as thermocouples 26, and non-contact, such as infrared camera 25 technology.

In accordance with certain embodiments of the present invention, metrology is also used to analyze contamination for material properties before, during, and/or after the removal process, as shown in FIG. The identification of contaminants can be used prior to the cleaning process to set the desired processing parameters. This allows the use of a minimum process temperature, thereby reducing the risk of substrate damage. Monitoring contamination can also be used during the process to assess the integrity of the cleaning process based on the strength of the measurement signal as the cleaning process proceeds. In addition, monitoring of alternative materials can be used during the process to indicate when the process produces different contamination and/or cause unwanted changes in the substrate material. This information can be used to control the process and/or reduce the risk of substrate damage and/or poor cleaning results.

There are many methods available for determining the chemical or elemental composition of particles on a surface. Methods include, but are not limited to, spectroscopy, mass spectrometry, electrochemical analysis, thermal analysis, separation, hybrid technology (including more than one technique), microscopy. In embodiments of the devices discussed herein, spectroscopy, mass spectrometry, or both are used. It should be understood that reference to the metrology techniques herein is intended to broadly cover the various sub-sets of such techniques. For example, the techniques contained in the spectroscopy method include Fourier transform infrared spectroscopy (FTIR), infrared spectroscopy, Raman spectroscopy, laser induced collapse spectroscopy, electron paramagnetic resonance spectroscopy (EPR), and nuclear magnetic resonance spectroscopy. (NMR), Aojie Electron Spectroscopy, X-ray Photoelectron Spectroscopy, Energy Dispersive X-ray Spectroscopy (EDS or EDX), Electron Energy Loss Spectroscopy (EELS), Attenuated Total Reflex (ATR) and Fluorescence Spectroscopy . Common techniques for identifying the chemical composition of particles on a substrate in photolithography are EDX, time-of-flight secondary ion mass spectrometry (TOF-SIMS), Raman spectroscopy, FTIR, and liquid chromatography mass spectrometry (MS-MS). LC-MS).

Liquid chromatography is a separation process that uses an absorbing material to separate particles from a solvent containing a sample mixture. Depending on the compound, the solvent and sample mixture are dispersed across the absorbent material at different rates. This allows the compound to be isolated in different regions of the absorbent material. Liquid chromatography can be used in conjunction with mass spectrometry to more accurately identify molecules.

Mass spectrometry is a chemical analysis technique that uses ionized particles and categorized by mass to establish a spectrum based on mass and ionic charge, which determines the exact chemical composition. Mass spectrometry techniques are destructive. Common techniques include quadrupole mass filters and TOF-SIMS.

A quadrupole mass filter (QMF) uses an ion source to ionize the particles and then use an ion accelerator to accelerate the ions in the beam. The ion paths are concentrated to and travel along four parallel rods that are used to generate pulsed electromagnetic waves. These rods are divided into two groups of 180° out of phase effects. This causes the ions to be radially displaced along the beam in an oscillating manner as the ions travel along the axial direction of the rod. The ions are not accelerated along the beam axis. At the end of the rod there is a detector that will identify the radial position of the ions. The radial position of the ions on the detector is based on the mass-to-charge ratio of the ions passing through the quadrupole. One advantage of QMF is that it is relatively inexpensive compared to other mass spectrometry tools. There are several disadvantages to using a quadrupole mass filter. Quadrupole mass filters have limited resolution, peak to mass response must be adjusted, and are not suitable for pulse ionization.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is a technique that utilizes primary beam ions to bombard the surface of the substrate. Secondary ions are released and collected by the detector. Based on the impact time of the primary ion beam and the time at which the secondary ions are detected, the mass spectrum of the current compound can be identified. This is the most sensitive method currently available, with a resolution of one part per billion. However, there are some limitations. TOF-SIMS must be performed in a vacuum to avoid contamination from the surrounding atmosphere. This method is also destructive, and the released ions are often part of the parent material of the substrate rather than just the particles situated on top of the substrate. For some applications, such as photolithography, this will damage the pattern on the reticle and make the reticle useless. This method is most often used for qualitative purposes and often results vary depending on the operator of the device.

Raman spectroscopy uses monochromatic light (one wavelength) to bombard molecules with photons. Energy is exchanged between incident photons and molecules, which cause energy and the wavelength of the emitted photons to change. This phenomenon is called scattering. Different molecules have different energy exchanges with photons and cause wavelength changes and spectra to identify molecules. The latest and most advanced technology for Raman is Surface Enhanced Raman Spectroscopy (SERS). Technology can detect a single molecule. This technique typically requires a silver or gold colloid or substrate. The sample is often prepared as a plasmonic surface constructed of a nanostructure consisting of silver/gold on a porous tantalum wafer. Samples can be expensive and take a considerable amount of time to manufacture.

There are many advantages to using standard Raman spectroscopy. Raman can be used on solids and liquids without sample preparation, water does not interfere with the analysis, and it is non-destructive. This technology can identify chemicals with very high confidence and the analysis for this method is very fast. Raman analysis can be used on relatively small sample sizes (<1 um) and is more easily detected by Raman than IR spectroscopy inorganics. One of Raman's greatest strengths is that this type of analysis can be performed in standard atmospheric conditions.

Fourier transform infrared (FTIR) spectroscopy is a technique that relies on the vibrational response of chemical bonds when a compound is exposed to the IR spectral range. Depending on the technology, the infrared spectrum is observed or absorbed for solids, liquids or gases during exposure to the IR spectrum and is used to identify compounds. Compared to Raman, FTIR has the advantage that it has fewer interfering objects, such as fluorescent light. However, FTIR generally requires minimum thickness, uniformity, and dilution.

In accordance with certain embodiments of the present invention, metrology is also used to analyze or monitor material properties of materials on substrate 4 and/or substrates or adjacent substrates before, during, and/or after removal of the process, as shown in FIG. . For example, the measurement of the material properties of a portion of the absorbent film on the substrate can be used to calculate the phase delay of the material prior to processing. This can be used to determine the process temperature for cleaning to induce an appropriate phase delay in the absorber film. This weight can also be used to monitor phase and feedback information during processing to the process or to stop the process when the process limits are exceeded. Material property analysis of the substrate can be used to determine the correct energy to induce a desired surface material or morphological change. In addition, the material properties of the skin film can be monitored to determine if adverse effects are occurring to the skin material. This information can be used prior to processing to limit process temperature or to use this information during processing to stop the process if damage is observed. For example, one or more ellipsometers or cameras 31 can be used to measure the material response of the skin film, absorber film, and substrate surface. This data can then be used to calculate the desired material properties, including film thickness, transmission, and phase.

In accordance with certain embodiments of the present invention, an alternative metrology can be used to monitor the presence and amount of surface contamination before, during, and/or after the cleaning process. For example, in accordance with certain embodiments of the present invention, a metrology to detect the presence of contamination can be used to determine if a laser pulse is to be applied to the area of the measured substrate. This information can then be used to minimize the number of pulses applied to the overall substrate, which reduces the total thermal energy applied to the system as well as the overall cleaning process time.

Weights and measures for measuring the lateral size/size, position, number, density, and/or height (thickness) of contaminating or contaminating particles may also be used in accordance with a particular embodiment of the invention in combination with a cleaning process. These measurements can be used, for example, to define the efficiency and integrity of the process by measurements prior to and/or after the cleaning process. These measurements can be used during the process to evaluate the in-situ efficiency of the process. For example, if multiple laser pulses are used for complete removal, the detection of residual contamination can be used to assess whether the number of pulses required for removal and additional pulses are necessary. In accordance with certain embodiments of the present invention, in this case, the metrology is constructed to view the area being cleaned as the cleaning process occurs. This is typically done by imaging the area being exposed by laser imaging, and may include the use of the same optical elements as for laser delivery, as shown in FIG. Through the partial mirror 29, the imaging lens 32 allows for detailed monitoring of the contaminating particles 3, allowing simultaneous monitoring and cleaning.

In accordance with embodiments of the present invention, there are multiple methods for detecting particles and assessing particle size. These methods include, for example, reflected and transmitted light intensity measurements, imaging, low angle scattered light detection, interferometry, scanning electron beam, scanning tunneling microscopy, near field microscopy, atomic force microscopy, and the like. Multiple methods can be combined with specific embodiments in accordance with the present invention to provide additional information.

In accordance with certain embodiments of the present invention, in the case of a reticle, for example, multiple metrology scales can be incorporated into the laser cleaning process. Identifying the presence of particular contamination (eg, ammonium sulfate) on the reticle, for example, defining decomposition temperature requirements and sometimes allowing the selection of laser energy to be just high enough to perform a cleaning process.

According to a particular embodiment of the invention, the transmitted light intensity is measured and the result is compared to a programmed structure for the absorbing film on the surface of the reticle. The difference between the programming features and the detection features is then used to identify the contamination. Moreover, in accordance with certain embodiments of the present invention, aerial imaging measurements are used to evaluate the printed features of the reticle. This method is typically used to assess the effect of contamination on the performance of the reticle. This measurement can also be used in situ to detect damage to the absorber layer from the cleaning process. This is particularly relevant to a portion of the absorbent film in which the thickness of the film is directly related to the performance of the reticle. In accordance with certain embodiments of the present invention, combined detection of scattered light detection and transmitted light detection improves contamination by detecting irregular surface topography that is different from the typical smooth surface of the reticle and the reticle film.

In accordance with certain embodiments of the present invention, metrology is also used to monitor features of materials adjacent to the surface to be cleaned. For example, the temperature of the superficial film above the reticle can be monitored to reduce the risk of damage to the superficial film. The transmission characteristics of the skin film can also be used to limit the effects of the cleaning process during or after the cleaning process. In addition, particle detection on the inside of the surface film can be performed prior to performing the cleaning process and/or can be used to detect the loss of these particles during the process and/or whether it is better to limit the energy used in the process to prevent surface layer and / or risk of damage to the substrate material.

It will be appreciated by those of ordinary skill in the art that, when one or more embodiments of the present invention are implemented, the above-described embodiments of the present invention are not intended to be exhaustive. Rather, these examples are merely illustrative of the use of weights and measures within the methods of the present invention. Pollution identification

As previously described, the reticle substrate is typically comprised of a base substrate that is transparent to the radiation used in the lithographic exposure process and that is a thin optical film that partially or completely absorbs the exposed radiation. Because the optical properties of these substrates are critical to their performance, it is important that their surfaces be as free of chemical contamination as possible. Because of the energy and wavelength of the exposed radiation, it is also critical that there is no contamination against these surfaces. This radiation can cause decomposition of residual surface contamination and, in some cases, progressive defects (turbidity) that affect the performance of the mask.

A lot of effort is put into the reticle cleaning process to minimize surface contamination, but there is always some degree of residual contamination and the degree can vary from mask to mask. In addition to residual surface contamination, it can also accumulate in a polluted environment. Variations in the surface contamination of the reticle used in wafer fabrication can result in variations in performance and lifetime in reticle production. Therefore, it would be advantageous to be able to detect the presence and extent of surface contamination and analyze its chemical composition.

Identifying contaminants removed from a reticle or other contaminated substrate can have sources for identifying and eliminating or reducing contamination as well as customized removal methods to minimize the likelihood of substrate damage. The identification of contaminants involves the release of molecules from the surface of the contaminated substrate, illustrating the different geometries and substrate materials, sample preparation, and chemical analysis of contaminants.

Several methods for performing this identification will now be described in connection with Figure 17, in which the surface of the contaminated substrate 4 is excited in each method, for example by laser 31 using photons to bombard the surface of the contaminated substrate, by moving from photons to a molecule, a light or thermal bond that is broken by a bond between a contaminant and a surface of a substrate, a photon-induced chemical reaction in which a molecule collapses or forms, or a thermal collapse or formation caused by heat generated from a substrate, and Causes the release of molecules. In one embodiment, when contaminants are released, the temperature of the reticle is maintained below a critical temperature to prevent damage to the reticle. In all methods, the molecules are in the gas phase near the substrate. Approaching the surface of the substrate 4 can create a pressure differential to move the released molecules away from the substrate where they are then collected or captured for analysis. It will be appreciated by those of ordinary skill in the art that it is advantageous to create a pressure differential in a localized region of the substrate, particularly in the region of the laser that illuminates the substrate. In one embodiment, a cylindrical tube 38 is provided around the excitation source 31 and extends to the surface of the substrate 4. A sensor 39 above the substrate can be employed to provide input to the gas analysis tool 40 to identify contaminants. Alternatively, a pressure differential can be generated in the cylindrical tube 38 and used to push any free-floating molecules into the analytical tool or to the collection device 43 by, for example, a vacuum pump 41. The detection or chemical analysis method may vary depending on whether the molecules to be identified and the contaminants 3 are directly pushed into or accumulated by the collection device 40.

The release of molecules from the surface of the self-contaminated substrate can be carried out using a number of methods including: thermal evaporation, thermal decomposition, or physical kinetic energy transfer, photochemical bond cleavage or other photochemical means of releasing surface contamination. The preferred embodiment uses a laser. The laser wavelength can vary based on the material of the substrate and the contamination to be analyzed. At a particular wavelength, the material can be transparent, representing no effect on the substrate as it passes through the substrate. At other wavelengths, the substrate and/or contaminants may act as a partial or complete blackbody, absorbing some or all of the photons and energy from the excitation source. This will cause an increase in the temperature of the substrate and/or contaminants. At high enough energy, photon density, and appropriate wavelengths, this can result in the release of contaminants from the surface of the substrate. In a preferred embodiment, the wavelength of the electromagnetic wave is substantially the same as the local maximum of the absorption spectrum of the reticle.

The pollution identification methods described herein can analyze airborne molecular contaminants (AMCs) when they are released directly from the contaminated substrates or after they are accumulated in the collection device 43. Any type of sensor 39 and gas analysis tool 40 may be employed for the AMC released into the atmosphere above the contaminated substrate. Alternatively, the AMC released from the contaminated substrate may be accumulated in the collection tank 44 or on the collection substrate 45. The AMC released from the contaminated substrate may be trapped in the tank 44 or concentrated on a surface of the collection substrate 45 to a concentrated state. Prior to performing the analysis, the collection device 43 can collect AMCs from individually contaminated substrates or from multi-contaminated substrate samples, and in the case of collecting substrates 45, can be analyzed using multiple surface analysis methods.

In one embodiment, the collection substrate 45 can be a cold plate below 0 C° to make condensation of vapor phase contaminants more likely to occur. For example, the substrate can be cooled using liquid N2 to -195 ° C or cooled to the desired temperature using a Peltier cooling device. A pressure differential can be created to push the AMC toward the cold collection substrate from the environment above the contaminated substrate 4, increasing the likelihood of condensation and accumulation of the AMC.

In other embodiments, the collection trough 44 can be a closed volume having an inlet and an outlet weir. This volume can be internally cooled to below 0 °C to make condensation of gaseous phase contaminants more likely to occur. A pressure differential can be created to push the AMC through the inlet enthalpy into the enclosed volume from the environment above the contaminated substrate 4, increasing the likelihood of condensation and accumulation of the AMC.

When cooling the collection device, it is very important to understand that all of the condensable gases generated by the pressure differential in the draw will condense on the collection substrate 45 or in the collection trough 44. This includes any air product produced by the humidity in the environment surrounding the collection device 43. For this reason, it is recommended to place the contaminated substrate surface and collection device 43 in an environment in which the humidity has been reduced by this point, more commonly referred to as a dry environment.

A dry environment can be achieved by replacing the contaminated substrate with the air surrounding the collection device with a dry gas, preferably a dry inert gas such as nitrogen, argon or helium. The dryness of the environment can be monitored by measuring the dew point that should be maintained below -10 °C. This will minimize the amount of water from the atmosphere condensing on the collection substrate or in the collection tank and improve the signal-to-noise ratio of the weights and measures performed on the contaminants during identification and quantification.

It will also be appreciated by those of ordinary skill in the art that it is important to have a cooled collection device near the surface of the contaminated substrate. The closer the collection device is to the contaminated substrate surface, the more AMC will be accumulated by the collection device. This is important when dealing with small amounts of contaminants.

After the AMCs are accumulated in the collection device, they can then be analyzed using mass spectrometry such as mass spectrometry. AMC can also be re-evaporated and analyzed in the gas phase and using various gas phase spectroscopy.

Methods for analysis include, but are not limited to, spectroscopy, mass spectrometry, electrochemical analysis, thermal analysis, separation, hybrid technology (including more than one technique), and microscopy. Some analytical techniques have many advantages for reticle substrates, such as spectroscopy, mass spectrometry, separation, and hybrid technology.

The design of the pollution identification device according to aspects of the present invention may also vary depending on the geometry. Some applications are available on the surface of a flat substrate. In this application, a fixed excitation source and a collection tube surrounding the excitation surface and the excitation source may be employed. Other applications may have geometric obstructions and equipment available with adjustable focusing optics and telescopic collection tubes. In the case where the contaminated substrate contains dissimilar materials, the device can utilize excitation sources of varying wavelengths. The preferred embodiment will consider varying geometry and multiple material substrates.

The application of the method of the invention for analyzing the surface contamination of a reticle will depend on the point of manufacture of the reticle. When the mask is first produced, the entire substrate surface is exposed to the atmosphere. At this stage in the production of the reticle, a source of electromagnetic radiation can be applied to the entire reticle. Radiation can expose the entire reticle at a time or the source of radiation can be focused toward the surface of the substrate and the surface and source are scanned relative to each other. The released AMC contamination can be directly propelled from the atmosphere above the contaminated substrate and analyzed directly by a metrology tool such as a mass spectrometer. Alternatively, the AMC can be collected by the collection device for subsequent analysis.

For a particular embodiment of the invention, analyzing AMC when directly producing AMC over a reticle substrate has advantages. For example, in one aspect of the present disclosure, the presence, relative amount, and identification of contaminants are determined when the laser is first applied to the substrate. The degree of contamination can then be compared to the average level of reticle collection or the nominal value of the contamination. The degree of contamination and the type of contamination can be used to determine if the markings are clean enough to be used in production. The reticle can be rejected or sent to another cleaning process to further reduce surface contamination. By identifying contaminants, the overall reticle manufacturing process can be adjusted to remove such contaminants and improve overall production quality. The disclosed process can be applied to the reticle a second time and thus the extent and identification of the contamination is determined. This measurement can be used in comparison to previous levels and in the process of the invention to determine if the cleaning process reduces surface contamination. The cleaning process and contamination identification process can be used repeatedly until the desired level of surface contamination is achieved.

This approach has advantages over other direct metrology techniques. The disclosed process is not limited to a single analytical technique. Gas and substrate samples can be easily prepared, enabling the use of many powerful analytical tools. The method used to release the AMC is non-destructive and therefore does not render the product, such as a reticle, useless. The disclosed method does not require a vacuum chamber to perform the analysis. Most analytical techniques are limited by sample size. The process of the invention is per-energizing-pulse local process limited by the process area. However, with continuous pulsed and mobile contaminated sample substrates, sample size is not limited, especially when incorporated into high precision platforms.

In other aspects of the present disclosure, electromagnetic radiation to detect the presence, extent, and identification of the AMC can be used to help clean the surface of the reticle. In this case, it is expected that the degree of surface contamination is reduced when radiation is applied to the surface. Monitoring of the degree of contamination of the repeated exposure of some or all of the reticle surface combination can be used to determine when the reticle is sufficiently clean to be used in production.

At the later portion of the reticle production, a skin layer is added to the top surface of the reticle substrate. The surface layer is composed of a hollow rectangular frame that is bonded to one side of the substrate and has a thin fluoropolymer film (surface layer) across the top. The presence of the skin layer renders the reticle incompatible with the vacuum system. For example, applying a vacuum to the reticle will release volatiles from the skin frame and the glue, which will otherwise contaminate the reticle surface. The application of the process of the present invention can be applied to the area outside the surface frame on the top surface of the reticle or to the area of the back side of the reticle that does not contain the skin. Alternatively, electromagnetic radiation can be applied across the skin. However, only AMC species that penetrate the superficial membrane may be detected and identified. Immediately after the production of the reticle, the method of the present invention can be applied to the reticle, or after the reticle has been in production for a period of time, the method of the present invention can be applied to the reticle. The extent to which the AMC is measured immediately after the application of the skin layer and the identification allow the degree of surface contamination to be confirmed before being used in production. Analysis of the degree of surface contamination after the reticle has been used in production allows for confirmation of the extent and type of exposure of the reticle to environmental pollution during production use. This allows for early detection and identification of surface contamination buildup prior to failure of the line in production, while allowing the manufacturer to adjust the process to prevent further contamination.

Due to the low degree of contamination typically on the reticle, it may be advantageous to collect the contamination released from the single reticle. The accumulation of material released from the reticle improves the ability to measure the presence, extent and identification of contamination. In addition, chemical analysis of surface contamination typically requires a larger sample volume than separate detection. Depending on the degree of contamination, the collection of released AMC from multiple reticle substrates onto a single collection substrate to accumulate large amounts of residual surface contamination can be very useful for identifying contaminants and locating sources.

Those of ordinary skill in the art will recognize that the apparatus and method of contamination identification disclosed herein allows analysis of contaminants on a substrate in situ or distally. This analysis can be destructive or non-destructive and can be used in chemical analysis, gaseous or surface analysis methods. Multiple analysis types can be used simultaneously for more accurate identification or self-calibration. Those of ordinary skill in the art will also recognize that the collected samples may be much higher in concentration than the contaminated substrate surface, allowing for lower levels of contaminant detection. Chemical analysis can be performed over the surface of multiple contaminated substrates and chemical analysis can be monitored over time, as well as chemical analysis can be performed on multiple contaminated substrates with varying materials and geometries. device

A particular method in accordance with embodiments of the present invention is incorporated into an apparatus for performing a laser surface cleaning process. An example of such a device is shown in Figure 15, additionally including a robotic arm 35 and a platform 34 for processing substrate material, the robot arm 35 having a robotic arm end effector to accurately position the substrate material, and the platform 34 for one or A multi-action axis is used to position the substrate sample relative to the laser beam. The apparatus may, for example, contain one or more weights as previously described and/or may include methods of controlling the temperature of the substrate and/or adjacent materials during the cleaning process. In addition, the apparatus may include a metrology to register the substrate to a staging system and thus to the laser beam. This weight can also include a computer-controlled visual identification system. In addition, the device can also utilize computer control using lasers, motion and/or metrology, and software-based recipe control for cleaning processes. Laser control may, for example, include controlling when a laser pulse is applied and controlling the amount of energy applied during the cleaning process. Wafer manufacturing process

Methods and/or apparatus in accordance with certain embodiments of the present invention can be used as part of a novel wafer fabrication process that includes removing turbidity formation from a surface layer of the reticle. Typically, the reticle is removed from the wafer printing process when the degree of turbidity becomes insufficient to adversely affect the wafer printing process. The time prior to removal of the reticle is typically determined by direct detection of the level of high turbidity contamination or based on a predetermined period and/or extent for use in the wafer fabrication process. Typically, the reticle is routed to a different facility to remove the skin, the reticle is cleaned, and the additional skin is attached to the reticle. These other facilities (eg, masking workshops) maintain the equipment needed to perform these tasks and perform additional inspections that are not required for reticle repair and wafer fabrication facilities. The replicated collection of reticle is typically used during the time required for the reticle to be cleaned and attached to the new skin. These additional reticle add significant cost to the overall wafer printing process due to the high material requirements and setup and evaluation costs required.

The novel wafer fabrication method in accordance with certain embodiments of the present invention incorporates cleaning of the turbid reticle surface using one or more of the methods discussed above. A typical wafer fabrication process in accordance with an embodiment of the present invention illustrates the use of a wet cleaning process to remove the reticle contamination system as shown in Figure 16A. An alternative method that also falls within the scope of certain embodiments of the present invention utilizes one or more of the above-described laser cleaning methods to perform a cleaning operation at a wafer fabrication facility without the need for surface removal, as shown in Figure 16B. In the flow chart. This can minimize or eliminate additional skin costs and/or degradation of the photomask film caused by current wet cleaning processes.

In accordance with certain embodiments of the present invention, the novel wafer fabrication process eliminates the use of additional masks or mask sets for manufacturing, while the original set is cleaned. In this manufacturing process, the original reticle is placed back into production immediately after the cleaning process, as shown in the flow chart of Figure 16C. This has the potential to eliminate duplicate mask sets and reduce the set time required to use a repeat mask set. Using inspection weights to confirm the cleaning process can advantageously be used before returning the mask to production. This measurement can be incorporated, for example, into the device or provided by another device at wafer fabrication or other facility. Regardless of the weights and measures, the overall process time for mask opacity removal will be reduced.

The features and advantages of the invention are apparent from the Detailed Description of the invention. In addition, the present invention is not limited to the precise construction and operation of the invention described and described, and thus all suitable modifications and equivalents may be It is within the scope of the invention.

1‧‧ ‧ laser

2‧‧‧Excited state energy

3‧‧‧Contaminant particles

4‧‧‧Substrate

5‧‧‧Decomposing materials

6‧‧‧Evaporation materials

7‧‧‧Absorbing film

8‧‧‧Face

9‧‧‧ surface frame

10‧‧‧Adhesive

11‧‧‧focus lens

12‧‧‧Converging beam

13‧‧‧Mask beam

14‧‧‧ surface beam

15‧‧‧ Spatial distribution

16‧‧‧Substrate

17‧‧‧ Spatial distribution

18‧‧‧Heat exchange tube

19‧‧‧Heat exchange tube

20‧‧‧ top flow

21‧‧‧ sidestream

22‧‧‧ Underflow

23‧‧‧ pattern

24‧‧‧ tilt position

25‧‧‧ camera

26‧‧‧ thermocouple

29‧‧‧Partial mirror

31‧‧‧ camera

32‧‧‧ imaging lens

34‧‧‧ platform

35‧‧‧ Robotic arm

38‧‧‧ cylindrical tube

39‧‧‧ Sensors

40‧‧‧Analytical tools

41‧‧‧Vacuum pump

43‧‧‧Collection equipment

44‧‧‧ collection trough

45‧‧‧Collecting substrates

A number of drawings illustrating various embodiments of the invention are provided.

Figure 1a illustrates a schematic diagram of the laser excited state and surface contamination.

Figure 1b illustrates a schematic of the surface of the substrate illustrating the removal of contamination. According to particular embodiments of the invention, multiple species may be removed from the mask and the species may be in the form of a gas, liquid, solid, or the like.

Figure 2 illustrates an illustration of the surface of the reticle with the film absorber on top, including contamination on the film and on the substrate.

Figure 3 is a graph showing the quartz absorption spectrum of the electromagnetic spectrum from the deep ultraviolet light to the far infrared light region.

Figure 4 illustrates an illustration of a reticle surface with a film absorber, including a skin attached to the surface. According to a particular embodiment of the invention, there may be contamination on the film and/or on the substrate.

Figure 5a illustrates a schematic view of a reticle with a skin layer showing the laser beam focused through the surface layer and onto the surface.

Figure 5b illustrates a schematic representation of the size of the spot on the opposite mask on the surface layer resulting from focusing.

Figure 5c illustrates a schematic view of a reticle having a skin layer showing a side view of the laser beam focused on the surface layer and onto the surface of the laser beam and the surface layer.

Figure 6a illustrates a cross-sectional view of the Gaussian beam energy distribution and the corresponding temperature profile produced.

Figure 6b illustrates a cross-sectional view of the energy distribution of the high top beam and the corresponding temperature profile produced. According to a particular embodiment of the invention, a Gaussian, flat top, and/or high top energy distribution may be used.

Figure 7 illustrates a pattern of a reticle having a cold plate that contacts the bottom of the mask. According to a particular embodiment of the invention, the point of contact may be, for example, water (or other liquid or gas) flowing through the cold plate, or electrical contact for thermoelectric cooling.

Figure 8 illustrates an illustration showing the force air cooling of the area above the reticle. According to a particular embodiment of the invention, the air flow is guided at the surface frame.

Figure 9a illustrates an illustration showing a single scanning laser beam across the surface to minimize localized thermal buildup. A single column or row with a large lateral spacing between the spots is illustrated.

Figure 9b illustrates an illustration showing two scanned laser beams across the surface to minimize localized thermal buildup. A large interval overlap between a single column with two sets of spots and a pulse group is illustrated.

Figure 9c illustrates an illustration showing multiple scanning of the laser over the area of the substrate to achieve complete cleaning of the substrate portion.

Figure 9d illustrates an illustration of the second dimensional surface cleaning.

Figure 9e illustrates an illustration showing the use of discontinuous pulses on the surface.

Figure 10 illustrates an illustration of the use of a laser pulse pattern to control the position of the residual material.

Figure 11a illustrates an illustration of the use of gravity to control the position of the residual material.

Figure 11b illustrates an illustration of the use of gravity to control the position of the residual material.

Figure 12 illustrates a schematic of the surface of a contaminated substrate with a thermocouple or infrared temperature monitoring device.

Figure 13 illustrates a schematic of a contaminated substrate surface with imaging, microscopy, spectroscopy, or a combination system for contamination analysis.

Figure 14 illustrates a schematic diagram of a contaminated substrate surface with an imaging system in which the imaging system and the laser beam are delivered in a common optical path.

Figure 15 illustrates a system diagram showing the mechanical loading and X/Y/Z segment motion of the substrate relative to the laser beam.

Figure 16a illustrates a block diagram of a typical wafer fabrication process using a photomask wet cleaning process.

Figure 16b illustrates a block diagram of a wafer fabrication process flow incorporating a laser reticle cleaning without surface removal.

Figure 16c illustrates a block diagram of a wafer fabrication process flow that incorporates a laser reticle cleaning without the use of an additional mask set during the cleaning process.

Domestic deposit information (please note according to the order of the depository, date, number)

Foreign deposit information (please note in the order of country, organization, date, number)

Claims (37)

A method of identifying contaminants on a surface of a reticle, the method comprising the steps of: directing electromagnetic waves toward a reticle having a contaminating particle disposed thereon, the electromagnetic waves having substantially absorption with the reticle a local maximum of the spectrum having the same wavelength; generating a temperature increase in the reticle; transferring thermal energy from the reticle to the contaminant to release molecules of the contaminant from the surface of the reticle; A pressure differential is created above to move the released contaminant molecules away from the reticle; molecules that capture the released contaminants; and analyze the composition of the contaminants. The method of claim 1, wherein the electromagnetic waves are laser light. The method of claim 2, wherein the laser wavelength is greater than 8 microns. The method of claim 1 wherein the reticle comprises at least one film layer. The method of claim 4, wherein the film layer is patterned and includes a void region below which portions of the reticle are exposed. The method of claim 1, further comprising the step of maintaining a temperature of the reticle below a critical temperature to prevent damage thereto. The method of claim 1, wherein the reticle comprises at least two materials and the laser wavelength is substantially the same as a local maximum of one of the absorption spectra of the substrate. The method of claim 1 wherein the pressure differential is positioned less than the entire reticle. The method of claim 8, wherein the pressure differential is located to a region where the laser is applied to the reticle. The method of claim 1 wherein the pressure differential is generated in the collection tube in a collection tube surrounding the source of the electromagnetic waves. The method of claim 1, wherein the step of capturing molecules of the released contaminants comprises the steps of: cooling the collection substrate to below 0 o C and using a pressure differential to direct the molecules of the released contaminants To the collection substrate. The method of claim 11, wherein the reticle and the collection substrate are exposed to atmospheric pressure in a dry environment. The method of claim 1, wherein the step of analyzing the composition of the contaminant utilizes spectroscopy. The method of claim 1, wherein the step of analyzing the composition of the contaminant utilizes mass spectrometry. The method of claim 1, wherein the step of analyzing the composition of the contaminant determines the extent and type of the contaminant. The method of claim 1, wherein the step of analyzing the composition of the contaminant further comprises the step of comparing the extent and type of the contaminant with a reference for one of the reticle. A method for identifying contaminants on a surface of a substrate, the method comprising the steps of: directing electromagnetic waves toward a substrate on which a contaminating particle is placed in a dry environment at atmospheric pressure, the electromagnetic waves having substantial a wavelength at the same local maximum as one of the absorption spectra of the substrate; generating a temperature increase in the substrate; transferring thermal energy from the substrate to the contaminant to release molecules of the contaminant from the surface of the substrate; A molecule that captures the released contaminants in a cooled collection device. The method of claim 17, further comprising the step of maintaining a temperature of the substrate below a critical temperature to prevent damage thereto. The method of claim 17, wherein the cooled collection device is a cold plate. The method of claim 17, wherein the cooled collection device is cooled to below 0oC. The method of claim 17, wherein the cooled collection device is in close proximity to a surface of the substrate. The method of claim 17, wherein the cooled collection device is a closed volume having one of an inlet and an outlet port for cooling. The method of claim 22, wherein a pressure differential is generated between the cooled enclosed volume and the dry environment such that the released contaminant molecules move through the inlet port into the cooled enclosed volume . The method of claim 17, wherein the dry environment has a dew point of less than -10oC. The method of claim 17, wherein the dry environment is an inert gas environment. The method of claim 25, wherein the inert gas is nitrogen. A method for cleaning a surface of a substrate, the method comprising the steps of: directing an electromagnetic wave to a substrate having a contaminant disposed thereon in a dry environment toward atmospheric pressure, the electromagnetic wave having substantially absorption with the substrate a wavelength at which one of the spectra has the same local maximum; a temperature increase is generated in the substrate; and thermal energy is transferred from the substrate to the contaminant to decompose the contaminant. The method of claim 27, wherein the electromagnetic waves are laser light. The method of claim 27, wherein the laser wavelength is greater than 8 microns. The method of claim 27, wherein the substrate comprises at least one film layer. The method of claim 30, wherein the film layer is patterned and includes a void region below which portions of the substrate are exposed. The method of claim 27, further comprising the step of maintaining a temperature of the substrate below a critical temperature to prevent damage thereto. The method of claim 27, wherein the substrate comprises at least two materials and the laser wavelength is substantially the same as a local maximum of one of the absorption spectra of the substrate. The method of claim 27, wherein the dry environment has a dew point of less than -10oC. The method of claim 27, wherein the dry environment is an inert gas environment. The method of claim 35, wherein the inert gas is nitrogen. The method of claim 27, wherein the substrate is placed in a dry environment at atmospheric pressure prior to the start of surface cleaning.