Controlled environment photoresist analysis system

Abstract

Controlled Environment Photoresist Analysis System A tool (10) for evaluating photoresist chemical changes during lithographic processes, comprising: a radiation exposure station (20) for exposing photoresist samples (15) to radiation; a thermal processing station (30) for thermally processing photoresist samples (15); an intermediate analysis station (40) separate from the exposure station (20) and the thermal processing station (30), the intermediate analysis station (40) comprising a system (42) configured for analyzing photoresist samples (15), and environmental isolation means (60) between the stations enabling independent environments in each station during operation; an atmosphere control system (70) configured to establish different atmospheric conditions in each station, and a sample transfer system (80) for transferring photoresist samples (15) between the stations while maintaining environmental isolation.

Description

[0001] Controlled Environment Photoresist Analysis System

[0002] Field of the Invention

[0003] The present invention relates to the field of semiconductor lithography metrology, and more specifically to equipment for studying photoresist chemistry during lithographic processing.

[0004] Background of the Invention

[0005] Photolithography is a cornerstone technology in the semiconductor manufacturing industry, enabling the creation of ever-smaller and more complex integrated circuits. At the heart of this process are photoresists, specialized materials designed to undergo chemical transformations when exposed to specific wavelengths of light. These transformations ultimately allow for the transfer of intricate patterns onto semiconductor substrates.

[0006] The lithographic process involves several distinct steps. Typically, photoresist is applied to a wafer through wet deposition methods using solvents or through dry techniques such as chemical vapor deposition (CVD). The coated wafer is then exposed to light of specific wavelengths, including KrF, ArF, or extreme ultraviolet (EUV) radiation. Following exposure, the wafer undergoes one or more baking steps, known as post-exposure bakes (PEB), and finally a development step that may be wet or dry in nature. Throughout this sequence, the photoresist undergoes complex molecular transformations that ultimately determine the quality and precision of the resulting patterns.

[0007] In semiconductor manufacturing facilities, wafers may be exposed to cleanroom atmosphere during transfers between process steps.

[0008] Understanding the precise nature of chemical changes in photoresists is challenging in production environments. When evaluating lithographic outcomes, manufacturers typically assess the final results after the complete process has been executed. The quality of lithographic patterns is generally evaluated through metrics such as critical dimension (CD) process window, CD uniformity, feature roughness, and the presence of stochastic failures. However, these measurements do not directly reveal the underlying molecular changes that occurred during each processing step.

[0009] The photoresist's molecular composition can be significantly influenced by the surrounding atmospheric environment. This is particularly evident during the times between process steps when the wafer may be exposed to varying conditions. For instance, some photoresists, including metal oxide resists (MOR) used in EUV lithography, have shown sensitivity to environmental factors such as humidity levels and airborne contaminants. These environmental variables can introduce inconsistencies in the lithographic process.

[0010] This sensitivity is particularly evident during delay times between processing steps. For instance, there is a direct correlation between the duration of the post-coating delay (PCD) and the deviation from the target critical dimension (CD) (S. Kim et al., "An investigation on the process control for the solid application of EUV MOR," Proc. SPIE 12494, 2023). This deviation has been linked to environmental factors such as ambient humidity, which can alter the photoresist film's properties before it even reaches the exposure step. Similarly, the post-exposure delay (PED), the time between exposure and post-exposure bake (PEB), is another critical window for environmental influence. As shown in Fig. 8, both humidity and the concentration of airborne molecular contaminants (AMCs) during PED can significantly alter the dose-dependent chemical reactions, such as fractional ligand cleavage (S. Castellanos et al., "EUV metal oxide resists: impact of the environment composition on CD during post-exposure delay," Proc. SPIE 12957, 2024). Fig. 9 schematically illustrates how these ambient molecules, like water (H2O) and AMCs, can infiltrate the resist structure during the PED and PEB stages, leading to unintended chemical changes and degrading the performance and stability of these sensitive materials.

[0011] The chemical transformations within photoresists are multifaceted. While a primary chemical reaction may dominate, numerous secondary reactions can occur simultaneously. These parallel processes can impact the final lithographic result, yet distinguishing between them and quantifying their relative contributions presents significant difficulties.

[0012] Challenges remain in developing comprehensive approaches for investigating photoresist behavior

[0013] Summary of the Invention

[0014] It is an object of embodiments of the present invention to enable precise characterization of molecular changes occurring in photoresists during lithographic processes. This objective is accomplished by the aspects of the present invention.

[0015] In a first aspect, the present invention relates to a tool for evaluating photoresist chemical changes during lithographic processes, comprising a radiation exposure station for exposing photoresist samples to radiation; a thermal processing station for thermally processing photoresist samples; an intermediate analysis station separate from the exposure station and the thermal processing station, the intermediate analysis station comprising a system configured for analyzing photoresist samples, and environmental isolation means between the stations enabling independent environments in each station during operation; an atmosphere control system configured to establish different atmospheric conditions in each station, and a sample transfer system for transferring photoresist samples between the stations while maintaining environmental isolation.

[0016] In a second aspect, the present invention relates to a method for evaluating photoresist chemical changes during lithographic processes in a tool according to the first aspect, comprising exposing a photoresist sample to radiation in the radiation exposure station under a first controlled atmosphere; transferring the exposed photoresist sample to the intermediate analysis station while maintaining environmental isolation; performing analysis of the photoresist sample in the intermediate analysis station under a second controlled atmosphere; transferring the analyzed sample to the thermal processing station while maintaining environmental isolation; thermally processing the photoresist sample in the thermal processing station under a third controlled atmosphere; and transferring the thermally processed sample back to the intermediate analysis station while maintaining environmental isolation, and performing further analysis of the photoresist sample in the intermediate analysis station under a fourth controlled atmosphere, wherein the first, second, third, and fourth controlled atmospheres are independently controlled. In a third aspect, the present invention relates to a system comprising the tool according to the first aspect, and a controller for carrying out at least some steps of the method according to the second aspect.

[0017] In a fourth aspect, the present invention relates to a computer program comprising instructions which, when executed by the controller of the system of the third aspect, cause the controller to carry out the method according to the second aspect.

[0018] In a fifth aspect, the present invention relates to a computer-readable medium having stored thereon the computer program of the fourth aspect.

[0019] In a sixth aspect, the present invention relates to a method for optimizing lithographic process conditions for a photoresist material, comprising evaluating photoresist chemical changes using the method of the second aspect under multiple sets of process conditions; correlating the photoresist chemical changes with lithographic performance metrics; and identifying optimal process conditions based on the correlations.

[0020] It is an advantage of embodiments of the present invention that step-specific investigation of photoresist chemistry can be performed without interruption by uncontrolled ambient exposure.

[0021] It is a further advantage of embodiments of the present invention that a single platform allows samples to remain in continuously isolated environments while moving between processing stations.

[0022] It is a further advantage of embodiments of the present invention that independent atmospheric conditions may be established for each process step, thereby enabling systematic exploration of environmental variables.

[0023] It is a further advantage of embodiments of the present invention that in-situ spectroscopic and analytical measurements can be carried out at multiple stages of the lithographic workflow.

[0024] It is a further advantage of embodiments of the present invention that molecular-level data acquired during processing can be directly correlated with downstream lithographic performance metrics.

[0025] It is a further advantage of embodiments of the present invention that the need for off-line metrology is reduced, shortening experimental cycles and limiting sample handling errors.

[0026] It is a further advantage of embodiments of the present invention that reproducibility of chemical characterization is enhanced through temperature-stable measurement conditions.

[0027] It is a further advantage of embodiments of the present invention that users can rapidly screen process parameters such as gas composition, humidity and delay time within a single controlled sequence.

[0028] It is a further advantage of embodiments of the present invention that diverse resist chemistries, including next-generation EUV materials, can be studied under identical, well-defined conditions.

[0029] It is a further advantage of embodiments of the present invention that transfer mechanisms designed for minimal contamination support high-fidelity analysis of trace chemical events.

[0030] It is a further advantage of embodiments of the present invention that modular architecture permits future integration of additional processing or measurement units without redesigning the entire system.

[0031] It is a further advantage of embodiments of the present invention that quantitative insight obtained from the platform can guide optimisation of industrial lithography processes. It is a further advantage of embodiments of the present invention that experimenters gain flexibility to apply either vacuum, inert, oxidative or humid ambients on demand during thermal or radiative treatments.

[0032] It is a further advantage of embodiments of the present invention that multiple samples or multiple exposure conditions can be evaluated in a single run, improving research throughput.

[0033] It is a further advantage of embodiments of the present invention that consistent environmental control minimises variability, thereby increasing confidence in comparative studies across different laboratories or timeframes.

[0034] Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims.

[0035] The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. This description is given for the sake of example only, without limiting the scope of the invention. The reference figures quoted below refer to the attached drawings.

[0036] Brief description of the drawings

[0037] Fig. 1 is a schematic view of a tool for evaluating photoresist chemical changes during lithographic processes according to embodiments of the present invention.

[0038] Fig. 2 illustrates a schematic representation of a particular embodiment of the atmosphere control system (70) according to embodiments of the present invention.

[0039] Fig. 3 is a comparative view of the system implementation showing integration of EUV exposure, FTIR module, and bake chamber components in a controlled environment according to embodiments of the present invention.

[0040] Fig. 4 is a schematic view of a multi-chamber system for evaluating photoresist chemical changes during lithographic processes according to embodiments of the present invention.

[0041] Fig. 5 is a schematic diagram of a multi-chamber system for in-situ FTIR and bake processes according to embodiments of the present invention.

[0042] Fig. 6 is a schematic cross-sectional view of an intermediate chamber with in-situ FTIR capabilities within a multi-chamber processing system according to embodiments of the present invention.

[0043] Fig. 7 is a schematic diagram of a bake chamber configured for evaluating photoresist chemical changes during lithographic processes according to embodiments of the present invention.

[0044] Fig. 8 is a schematic view of a tool for evaluating photoresist chemical changes during lithographic processes according to embodiments of the present invention.

[0045] Fig. 9 is a schematic view of a tool system for evaluating photoresist chemical changes during lithographic processes according to embodiments of the present invention. Fig. 10 is a flowchart of a method for evaluating photoresist chemical changes during lithographic processes under independently controlled atmospheres according to embodiments of the present invention.

[0046] Fig. 11 is a diagram of a system for evaluating photoresist chemical changes during lithographic processes according to embodiments of the present invention.

[0047] Fig. 12 is a flowchart of a method for optimizing lithographic process conditions by evaluating chemical changes, correlating with performance metrics, and identifying optimal conditions according to embodiments of the present invention.

[0048] Fig. 13 is a schematic representation of chemical processes occurring in photoresist during postcoating delay (PCD) and post-exposure delay (PED) according to embodiments of the present invention.

[0049] Fig. 14 is a schematic representation of model metal oxide resists (MORs) with various counterions used in tool qualification according to embodiments of the present invention.

[0050] Fig. 15 is a schematic representation of chemical processes occurring in a metal oxide resist during lithographic processing stages according to embodiments of the present invention.

[0051] Fig. 16 is a comparative graphical representation of absorbance spectra showing photoresist stability in controlled versus non-controlled environments according to embodiments of the present invention.

[0052] Fig. 17 is a graphical representation of the relationship between delay time and moisture uptake in a photoresist sample during post-exposure delay according to embodiments of the present invention.

[0053] Fig. 18 is a graph showing the relationship between post-exposure bake temperature and chemical changes in a photoresist sample, depicting ligand and SnO signals according to embodiments of the present invention.

[0054] Fig. 19 (left) is an FTIR spectrum of an unexposed photoresist sample showing characteristic absorption peaks including H2O absorption at 3400 cm according to embodiments of the present invention. Fig. 19 (right) is a bar chart representation of OH signal levels in photoresist samples at different processing stages according to embodiments of the present invention.

[0055] Fig. 20 is a bar chart illustrating the effect of different atmospheric conditions on ligand signal retention after exposure and post-exposure bake according to embodiments of the present invention.

[0056] Fig. 21 is a set of bar charts showing the effects of different post-exposure bake environments and humidity conditions on ligand cleavage and SnO condensation in metal oxide resists according to embodiments of the present invention.

[0057] Fig. 22 is a composite diagram showing chemical analysis of photoresist during lithographic processing via tool, comprising process flow, FTIR spectra, and differential spectra according to embodiments of the present invention.

[0058] Fig. 23 is a graph illustrating the relationship between film thickness and exposure dose for a BMOR sample, showing thickness plateauing around 20 nm and indicating a dose-to-gel threshold according to embodiments of the present invention.

[0059] Fig. 24 is a composite view showing a process flow diagram and comparative FTIR spectra demonstrating dose-dependent chemical changes in a BMOR-coated sample before and after EUV exposure according to embodiments of the present invention. Fig. 25 (left) is a graph depicting the relationship between ligand cleave fraction and exposure dose for a photoresist material according to embodiments of the present invention. Fig. 25 (right) is a graph depicting the dose-dependent ligand cleavage and moisture reduction according to embodiments of the present invention.

[0060] Fig. 26 is a composite view illustrating the effect of post-exposure bake temperature on ligand removal in EUV-exposed metal-organic resist samples according to embodiments of the present invention.

[0061] Fig. 27 is a comparative diagram of chemical changes in BMOR and OSMO model resist materials upon radiation exposure as revealed by FTIR spectroscopy according to embodiments of the present invention.

[0062] Fig. 28 is a comparative illustration of thermal behavior in BMOR and OSMO model resists showing FTIR spectra and chemical changes after post-exposure bake at different temperatures according to embodiments of the present invention.

[0063] Fig. 29 is a set of graphs showing EUV irradiation effects on counter-ions in MOR materials and resulting acid formation according to embodiments of the present invention.

[0064] Fig. 30 is a set of FTIR spectral graphs showing the effect of relative humidity levels during postexposure bake on photoresist chemical composition according to embodiments of the present invention.

[0065] In the different figures, the same reference signs refer to the same or analogous elements.

[0066] Detailed description of Illustrative Embodiments

[0067] The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.

[0068] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner, ft is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

[0069] Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein. ft is to be noticed that the term "comprising", used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps, ft is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. The term "comprising" therefore covers the situation where only the stated features are present and the situation where these features and one or more other features are present. Thus, the scope of the expression "a device comprising means A and B" should not be interpreted as being limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

[0070] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

[0071] Similarly it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

[0072] Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0073] Furthermore, some of the embodiments are described herein as a method or combination of elements of a method that can be implemented by a processor of a computer system or by other means of carrying out the function. Thus, a processor with the necessary instructions for carrying out such a method or element of a method forms a means for carrying out the method or element of a method. Furthermore, an element described herein of an apparatus embodiment is an example of a means for carrying out the function performed by the element for the purpose of carrying out the invention.

[0074] In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

[0075] The following terms are provided solely to aid in the understanding of the invention.

[0076] As used herein, and unless otherwise specified, the term "photoresist sample" refers to any substrate or wafer portion upon which a photoresist fdm has been applied, including but not limited to semiconductor wafers, glass substrates, or other materials suitable for lithographic processes. Examples of such substrates include silicon wafers used in microfabrication, quartz wafers used in photomask fabrication, or other materials that accept a photoresist coating. As used herein, and unless otherwise specified, the term "photoresist film" refers to a layer formulated with light-sensitive or radiation-sensitive compounds deposited over a substrate, and intended to undergo chemical or physical changes upon exposure to radiation or after specific process steps. Examples of photoresist films include chemically amplified resists suitable for extreme ultraviolet (EUV) lithography, deep ultraviolet (DUV) lithography, or electron beam lithography, as well as non- chemically amplified resists.

[0077] As used herein, and unless otherwise specified, the phrase "radiation exposure station" refers to any subsystem of the tool configured to direct and apply radiation to a photoresist sample. It typically enables control over parameters such as dose, wavelength, and exposure duration. Examples of radiation sources used in such a station include extreme ultraviolet (EUV) light sources, deep ultraviolet (DUV) light sources, electron beam emitters, or (lab-scale) radiation sources such as discharge produced plasma light sources designed to replicate production lithography wavelengths.

[0078] As used herein, and unless otherwise specified, the term "stage" refers to any platform or mechanism on which a photoresist sample is placed for positioning, alignment, or movement relative to a radiation beam or measurement beam. Examples of such stages include two-dimensional XY stages enabling precise lateral motion, rotary stages enabling rotation of the sample, or combined XY-rotary stages for multiaxis positioning.

[0079] As used herein, and unless otherwise specified, the phrase "thermal processing station" refers to a subsystem of the tool configured to subject a photoresist sample to controlled heating or cooling, thereby enabling processes such as post-exposure bake (PEB), post-application bake (PAB), soft bake, or other temperature-dependent treatments of the photoresist. Examples of thermal processing elements include hot plates designed to reach temperatures from 20 °C up to about 300 °C, chill plates for maintaining cool temperatures, and associated sensors to measure environmental parameters such as humidity or gas concentration during the thermal process.

[0080] As used herein, and unless otherwise specified, the phrase "intermediate analysis station" refers to a subsystem of the tool separate from other stations, configured for in-process or post-process analysis of the photoresist sample’s properties. It comprises a system configured for analyzing photoresist samples. For instance, this station can host measurement instruments for chemical analysis, thickness measurement, optical characterization, or thermal property evaluation. Examples include Fourier Transform Infrared (FTIR) spectrometers, ellipsometers, reflectometers, or other analytical devices.

[0081] As used herein, and unless otherwise specified, the phrase "system configured for analyzing photoresist samples" refers to any apparatus or collection of apparatuses intended to measure or detect chemical, optical, physical, or other properties of a photoresist sample. This can be performed, for instance, by spectroscopic, mechanical, or other methods. Examples of such systems include FTIR spectrometers for infrared spectroscopic measurements, ellipsometers for measuring film thickness and optical constants, or mass spectrometry instruments for outgas analysis.

[0082] As used herein, and unless otherwise specified, the phrase "sample tilting mechanism" refers to a device or assembly that can adjust the angle of a photoresist sample relative to an incoming beam of radiation or analysis light. An example is a goniometer that allows fine angular positioning of the sample to modify path lengths or angles of incidence, optimizing measurement conditions such as FTIR transmission. As used herein, and unless otherwise specified, the phrase "environmental isolation means" refers to structures, features, or components designed to preserve distinct atmospheric or vacuum conditions in separate subsystems of the tool, preventing cross-contamination or pressure equalization among them. Examples include valves, gate mechanisms, seals, or isolation chambers arranged to allow sample transfer without compromising the environment in each station.

[0083] As used herein, and unless otherwise specified, the phrase "atmosphere control system" refers to a combination of hardware, and optionally software or firmware implementing operational methods, that manage the composition, pressure, humidity, and other environmental characteristics within the tool’s stations. Examples of atmospheres provided by such a system include high vacuum, low vacuum, inert gas environments (e.g., nitrogen, argon), reactive gas environments (e.g., oxygen), or controlled humidity environments achieved with devices such as humidity control units or bubblers.

[0084] As used herein, and unless otherwise specified, the term "high vacuum" refers to an environment where the pressure is maintained at or below a level on the order of 1 x 106mbar or lower, so as to minimize gaseous molecule presence. In contrast, the term "low vacuum" refers to a less stringent vacuum level, typically in the mbar to IO3mbar range.

[0085] As used herein, and unless otherwise specified, the term "clean air (CA)" refers to an environment substantially free from airborne molecular contaminants or particulate matter, maintained through filtration and circulation methods to reduce contamination within a station.

[0086] As used herein, and unless otherwise specified, the term "sample transfer system" refers to a subsystem, including but not limited to robotic arms or manual handlers, configured to move a photoresist sample between stations without exposing that sample, or the stations, to undesired environmental changes. Examples include motorized transfer arms coordinated via a central control or manually operated stage-transfer devices, each capable of sealing off or isolating station environments during transport.

[0087] As used herein, and unless otherwise specified, the phrase "resist coat station" refers to any subsystem configured to deposit or apply a photoresist material onto a substrate, thereby forming a photoresist film. Examples include spin-on systems using spinning to spread fluid resist solutions evenly over the substrate, and dry deposition systems using vapor-phase or other non-liquid methods to deposit the photoresist.

[0088] As used herein, and unless otherwise specified, the phrase "developer station" refers to any subsystem configmed to remove exposed or unexposed portions of a photoresist film, depending on whether the resist is positive- or negative-tone, so as to create the desired pattern. Examples include wet systems such as puddle or spin-off development using aqueous or solvent-based developers, as well as dry systems employing plasma processes to selectively etch or remove parts of the resist film.

[0089] As used herein, and unless otherwise specified, the phrase "post-application bake (PAB)" refers to a thermal treatment stage conducted after a photoresist film has been applied to a substrate, intended to remove residual solvents, promote adhesion, or achieve partial crosslinking. An example includes placing the freshly coated substrate onto a hot plate at a defined temperature and duration aligned with the resist formulation’s recommended bake profile.

[0090] As used herein, and unless otherwise specified, the phrase "post-exposure delay (PED)" refers to the time interval between the exposure of the photoresist film to radiation and the subsequent processing step (such as a bake or development), during which the sample may be stored or held under controlled conditions. Examples of controlled conditions include inert atmospheres like nitrogen or vacuum environments intended to minimize undesired chemical changes that could alter the resist profde.

[0091] As used herein, and unless otherwise specified, the term "outgas analysis" refers to methods or procedures used to detect and characterize gaseous species released from a photoresist film during or after exposure or thermal treatment. An example includes monitoring by a residual gas analyzer (RGA) to identify volatile byproducts or contaminants.

[0092] As used herein, and unless otherwise specified, the term "thermal desorption analysis" refers to measuring substances that emerge from a photoresist film or substrate during heating, typically by increasing temperature and detecting the outgassed components. An example includes connecting a heated chamber to a mass spectrometer or RGA, so that substances released at each temperature ramp can be identified.

[0093] As used herein, and unless otherwise specified, the term "residual gas analyzer (RGA)" refers to an instrument that detects and measures partial pressures of gases and vapors in a vacuum environment, enabling identification of chemical species outgassing from a photoresist film. An example includes a quadrupole mass spectrometer capable of analyzing gas composition in real time during exposure or thermal processing.

[0094] As used herein, and unless otherwise specified, the phrase "temperature-controlled stage" refers to a platform on which a photoresist sample is placed that can regulate temperature to a desired setpoint. Examples include chill plates configured to cool substrates for stabilizing their properties, as well as heated stages maintaining a constant elevated temperature during analysis.

[0095] As used herein, and unless otherwise specified, the phrase "chill plate" refers to a specific type of temperature-controlled stage designed to lower or stabilize the temperature of a photoresist sample, typically to lessen thermal diffusion or unwanted chemical changes before, during, or after measurement. An example might be a refrigerant-based plate capable of maintaining sub-ambient temperatures.

[0096] As used herein, and unless otherwise specified, the term "hot plate" refers to a heating apparatus for raising the temperature of a photoresist sample within a controlled range, typically from room temperature up to an upper setpoint. Examples include conduction-based plates with embedded heaters, or contactless thermal systems with precisely regulated heat transfer surfaces.

[0097] As used herein, and unless otherwise specified, the term "humidity control unit" refers to a device that adjusts and controls the level of water vapor present in a station’s atmosphere. An example includes a bubbler that passes a carrier gas through water to achieve a defined relative humidity (RH), thereby allowing processes to be carried out under controlled moisture conditions.

[0098] As used herein, and unless otherwise specified, the phrase "airborne molecular contaminants (AMCs)" refers to gaseous or vapor-phase impurities that can chemically react with or otherwise affect a photoresist film, such as amines or volatile organic compounds (VOCs). Examples include ammonia, diisopropylamine, or other basic compounds that may cause photoresist deprotection, as well as volatile organics that may deposit or alter the resist surface.

[0099] As used herein, and unless otherwise specified, the phrase "controller" refers to a computing device or collection of computing resources arranged for carrying out at least some steps of the method. This may include coordinating sample transfers, controlling environmental parameters, executing method steps measurement, and / or executing processing sequences. Examples include a programmable logic controller (PLC), a personal computer running dedicated software, or an integrated control system configured to handle lithographic process recipes.

[0100] The invention will now be described by a detailed description of several embodiments of the invention. It is clear that other embodiments of the invention can be configured according to the knowledge of persons skilled in the art without departing from the technical teaching of the invention, the invention being limited only by the terms of the appended claims.

[0101] In a first aspect, the present invention relates to a tool (10) for evaluating photoresist chemical changes during lithographic processes. This tool (10) comprises a radiation exposure station (20) for exposing photoresist samples (15) to radiation; a thermal processing station (30) for thermally processing photoresist samples (15); and an intermediate analysis station (40) separate from the exposure station (20) and the thermal processing station (30). The intermediate analysis station (40) comprises a system (42) configured for analyzing photoresist samples (15), and environmental isolation means (60) between the stations enabling independent environments in each station during operation. The tool (10) also includes an atmosphere control system (70) configured to establish different atmospheric conditions in each station, and a sample transfer system (80) for transferring photoresist samples (15) between the stations while maintaining environmental isolation.

[0102] Figure 1 illustrates a schematic view of an embodiment of this tool (10) for evaluating photoresist chemical changes during lithographic processes. The depicted embodiment of the tool (10) comprises three main stations: a radiation exposure station (20) (here with measurement capabilities), an intermediate analysis station (40), and a thermal processing station (30). Each station is connected by a sample transfer system (here transfer arms) (80) for moving the photoresist samples (15) between them while maintaining environmental isolation. The radiation exposure station (20) includes an optional sample stage for holding the photoresist sample (15) and, in the depicted embodiment, is equipped with an optional in-situ measurement system (170), such as a residual gas analyzer (RGA) for monitoring outgassing during exposure. The radiation exposure station is designed to expose the sample to radiation, such as EUV, under a controlled environment. The intermediate analysis station (40) features an optional chill plate (150) to cool down the sample and / or maintain a constant sample temperature until the start of analysis. It is equipped with system (42) configured for analyzing photoresist samples (15). For instance, it can be equipped with a Fourier Transform Infrared (FTIR) spectrometer (42) for analyzing the chemical changes in the photoresist. The station can be purged with an inert gas or maintained under vacuum to suppress atmospheric absorption peaks.

[0103] In embodiments, the measurement chamber of the intermediate analysis station may be arranged to alternately expose a sample to at least two different atmospheres and to perform spectroscopic analysis after each atmosphere change. For instance, the intermediate analysis station may comprise gas in- and outlets, a vacuum pump, and automated valves that may permit sequential switching between a vacuum condition and a selected gas condition without opening the station to ambient air. This may permit controlled, repeatable simulation of real-world post-exposure delay conditions without removing the sample (15) from the protected cluster environment. Preferably, this is performed while the sample remains thermally stabilized, for instance within ±1 °C. As an example, in the intermediate analysis station (40), a programmable valve manifold may switch the chamber between <1 x 10"1mbar and a nitrogen atmosphere at 45% RH in cycles of not more than 2 minutes, each cycle being followed by an FTIR transmission measurement on the sample (15) held at 20 °C, thereby enabling time-resolved studies of post-exposure delay phenomena.

[0104] The thermal processing station (30) typically contains a hot plate for thermally processing the samples (15), for instance, at temperatures between 20°C and 300°C. It may include sensors (34) for measuring environmental parameters such as humidity and gas concentration. The station may be configured for in-situ analysis of the photoresist sample (15) during thermal processing, for instance by enabling outgas analysis and / or FTIR spectroscopy.

[0105] Environmental isolation means (60) are positioned between each of the stations, allowing for independent environments in each station during operation. An atmosphere control system (70) is configured to establish different atmospheric conditions in each station. Such atmospheric conditions may for instance be high vacuum, low vacuum, clean air (CA), and various gases. The entire setup may be under a controlled environment to ensure precise evaluation of photoresist chemical changes.

[0106] Figure 2 illustrates a schematic representation of a particular embodiment of the atmosphere control system (70), specifically designed to enable precise control over the atmospheric environment during post-exposure delay (PED) and post-exposure bake (PEB) steps. The diagram on the right shows the context within the overall lithographic workflow, indicating that after the EUV exposure step is performed in vacuum within the tool (10), the sample is subjected to PED and PEB under the controlled atmosphere provided by this system.

[0107] As shown in the diagram on the left of Figure 2, the system may be configured to mix multiple gases to create a desired process atmosphere. In this embodiment, input lines for a carrier or inert gas, such as nitrogen (N2), and a reactive gas, such as oxygen (O2), are provided. Each gas line may be equipped with a valve for on / off control and a mass flow controller (MFC) for precisely regulating the flow rate of the respective gas. By adjusting the setpoints of the MFCs, a gas mixture with a predetermined and repeatable ratio of oxygen to nitrogen can be created, allowing for the study of environments ranging from fully inert to oxygen-rich.

[0108] Downstream of the gas mixing point, the combined gas stream may be passed through a humidity control unit (%RH), such as a humidifier (224), to introduce a controlled amount of water vapor and achieve a target relative humidity. In embodiments where a completely dry atmosphere is required (e.g., 0% RH), a bypass line (dashed line), which may be manually or automatically controlled, can be included to route the gas mixture around the humidity control unit. This ensures that a true dry condition can be achieved without residual moisture from the humidity control unit affecting the process. A final valve controls the delivery of the fully conditioned gas mixture into the appropriate station of the tool (10), such as the thermal processing station (30) or intermediate analysis station (40), where the PED or PEB steps are performed.

[0109] This embodiment of the atmosphere control system (70) is particularly advantageous for executing the methods of the invention. It allows for the systematic evaluation of how reactive gases (e.g., oxygen) and humidity levels during post-exposure processing steps affect the photoresist's chemical transformations, such as ligand cleavage and network condensation. The controller (300) may be configured to automate the operation of the valves and MFCs to execute pre-programmed recipes, ensuring high precision and repeatability for experiments designed to optimize lithographic process conditions.

[0110] To provide a more concrete illustration of the invention, a specific embodiment of the tool (10) will now be described in detail. This embodiment corresponds to the system used to generate the data in the Examples section that follows and is illustrated in Figures 3 to 7.

[0111] The multi-chamber design of this embodiment is shown schematically in the top section of Figure 3. The tool (10) comprises three primary chambers connected in sequence: a radiation exposure station (20), an intermediate analysis station (40), and a thermal processing station (30). The first station (20) contains a sample stage for exposing a photoresist sample (15) to a radiation source (22) under vacuum conditions. The second, intermediate station (40) features an optional chill plate (150) for temperature stabilization and is equipped with a system (42) configured for analysis, here an FTIR spectrometer with a source and detector for in-situ measurements. The third station (30) includes a hot plate (32) for thermal processing up to 300°C and is equipped with connections for the atmosphere control system (70) to introduce controlled gases and humidity. Each station is separated by valves (60), enabling independent environmental control and ensuring the sample remains in a controlled atmosphere throughout processing and analysis. While the simplified illustration in Figure 3 (top) shows the sample on the chill plate during measurement, in this embodiment the analysis is performed away from the chill plate and the system (42) further comprises a sample tilting mechanism (110) as depicted in Figure 6.

[0112] The physical implementation of this integrated tool (10) is shown in Figure 3. This implementation is obtained from the modification of a prior art system, comprising an EUV exposure chamber with an EUV source, a sample entry loadlock, and a residual gas analyzer (RGA) (170) for outgas measurement. Figure 3 (bottom) shows the 3D model of the fully integrated tool (10) according to an embodiment of the present invention. The original radiation exposure station (20) has been extended with the addition of the intermediate analysis station (40), which contains the FTIR module (42), and the thermal processing station (30) for controlled baking.

[0113] The sample handling pathways of this embodiment is further illustrated in the top view of Figure 8. Figures 3 (bottom) and Figure 8 show a modular configuration where the stations are connected by cylindrical conduits, enabling sequential processing. The top-down view in Figure 8 illustrates a potential sample path, wherein a sample (15) is transferred from a multi-sample holder in the exposure station (20) to a sample storage unit or garage (160) located within the intermediate station (40), and then moved to the analysis position before proceeding to the thermal processing station (30). The integration of the FTIR spectrometer (42) with a goniometer (110) for sample tilting is highlighted in Figures 8. This setup optimizes the optical path length for transmission measurements. The integration of the atmosphere control system (70) with the bake chamber (30) is also shown in these figures, which details the connections for bulk gases and the humidity control unit (224) for precise humidity control.

[0114] Further details of the individual chambers of this embodiment are provided in Figures 5 to 7. Figure 5 shows a schematic of the complete three-chamber system, indicating the placement of FTIR components, outgas analysis ports (170), sample stages (chill stage 150, hot stage), and transfer arms (80). A detailed view of the intermediate analysis station (40) is provided in Figure 6. It shows the arrangement of the FTIR system (42), the goniometer (110) for tilting the sample (15), the chill plate (150), and the sample Stocker (160) for holding multiple samples. A detailed schematic of the thermal processing station (30) is shown in Figure 7, illustrating the bake stage, integrated in-situ FTIR and optional ellipsometry capabilities, outgas analysis port (170), and sensors (34) for monitoring humidity and gas concentration.

[0115] In embodiments, the atmosphere control system (70) may be arranged to deliver predetermined quantities of reactive trace gases in addition to bulk gases to any station of the tool (10). This capability may allow systematic evaluation of resist sensitivity to airborne molecular contaminants (AMCs).

[0116] In embodiments, the atmosphere control system (70) may comprise mass-flow-controlled lines for different gases (e.g., for NO and NO2). In embodiments, atmosphere control system (70) may have dilution capability down to sub-ppm levels. In embodiments, the atmosphere control system (70) may comprise an exhaust scrubber to prevent cross-contamination of neighboring chambers. As an example, during post-exposure bake, the bake chamber (30) may receive a 100 ppm O2 / N2 mixture at 1 bar and 30% RH for 60 s, after which the chamber may be purged with dry N2; inline electro-chemical sensors may verify O2 concentration within ±10 ppm.

[0117] The radiation exposure station (20) may be configured to expose photoresist samples (15) to radiation selected from the group consisting of extreme ultraviolet radiation, deep ultraviolet radiation, and an electron beam. This allows for compatibility with different lithography technologies.

[0118] The radiation exposure station (20) may comprise a radiation source, such as a discharge produced plasma light source. The radiation source is preferably for generating radiation having the same wavelength as used in production lithography tools. This enables realistic simulation of production conditions in a research environment.

[0119] The radiation exposure station (20) may comprise a stage, such as an XY or rotary stage, for positioning the photoresist sample (15) to allow for multiple exposure conditions on a single sample (15). This increases efficiency by allowing multiple test conditions on a single sample (15).

[0120] The system configured for analyzing photoresist samples in the intermediate analysis station (40) may comprise a Fourier Transform Infrared (FTIR) spectrometer (42). This provides detailed molecular-level analysis of chemical changes in the photoresist.

[0121] The system configured for analyzing photoresist samples (42) may be configured for FTIR spectrometry transmission measurements through a photoresist sample (15). This allows for more accurate analysis of chemical changes throughout the entire thickness of the film.

[0122] The system (42) configured for analyzing photoresist samples (15) may further comprise a sample tilting mechanism, such as a goniometer (110), for tilting the photoresist sample (15) to increase the optical path length for transmission measurements. This improves signal-to-noise ratio and measurement sensitivity for thin films.

[0123] As shown in Figure 8, this schematic illustrates the configuration for adjusting the orientation of a sample (15) to the infrared (IR) beam using a goniometer (110). The standard IR beam is depicted entering the system, where the goniometer (110) is employed to precisely align the sample (15) for optimal IR beam interaction. The schematic also indicates a potential upgrade path to enable FTIR measurements during the bake process, as shown by a dashed line leading to a designated area.

[0124] Figure 6 illustrates an intermediate chamber with several key components and functionalities. At the top, an “IR in” source and an “IR out” detector (42) are shown, indicating the path of the infrared beam used for analysis. A sample (15) is positioned on a stage, which is tilted using a goniometer (110) to increase the optical path length for transmission measurements.

[0125] The atmosphere control system (70) may be configured to purge the intermediate analysis station (40) with an inert gas or to maintain it under vacuum during measurements to suppress atmospheric absorption peaks. This reduces interference from atmospheric components and improves measurement accuracy. This is particularly relevant for FTIR measurements.

[0126] The intermediate analysis station (40) may further comprise an ellipsometer. This enables additional film thickness and optical property measurements.

[0127] The intermediate analysis station (40) may comprise a temperature-controlled stage (150). This ensures consistent measurement conditions by preventing temperature-induced variations.

[0128] The temperature-controlled stage (150) may be a chill plate (150) configured to maintain a constant sample temperature until the start of an analysis. This provides temperature stability for accurate and reproducible measurements. The analysis itself may be performed away from the temperature-controlled stage (150). The sample may be returned to the temperature-controlled stage (150) between analysis.

[0129] The thermal processing station (30) may comprise a hot plate configured to heat samples (15) to a temperature between 20°C and 300°C. This allows for simulation of the full range of post-exposure bake conditions used in production.

[0130] In embodiments, the thermal processing station (30) may be capable of heating a substrate to a temperature of at least 300°C. In embodiments, the thermal processing station (30) may comprise a radiative or inductive heater enabling said heating. In embodiments, the atmosphere control system may comprise a gas manifold for supplying inert or reducing gases at pressures between 5 Pa and atmospheric pressure, to the thermal processing station (30). In embodiments, the thermal processing station (30) may comprise optical ports for in-situ spectroscopic monitoring. As an example, the thermal processing station may be fitted with IR-transparent sapphire windows that allow in-situ FTIR reflection measurements and residual-gas analysis of desorbed hydrocarbons.

[0131] The thermal processing station (30) may comprise sensors (34) for measuring environmental parameters such as humidity and gas concentration. This enables precise monitoring and control of the processing environment.

[0132] The thermal processing station (30) may be configured for in-situ analysis of the photoresist sample (15) during thermal processing. The analysis may, for instance, be selected from the group consisting of outgas analysis, thermal desorption analysis, FTIR spectroscopy, and ellipsometry. This allows real-time monitoring of chemical changes during thermal processing.

[0133] The environmental isolation means (60) may comprise valves positioned between each of the stations. This provides effective isolation between different environments to prevent crosscontamination.

[0134] The tool (10) may further comprise a sample storage unit (160), e.g., in the intermediate analysis station (40), such as a garage or Stocker (160), connected to the sample transfer system (80) for holding one or more samples (15) under a controlled environment. This enables time-delay studies under controlled conditions. As shown in Figure 4, the system includes a sample table for the exposure of multiple samples and a sample store unit (160) for stacking multiple samples (15). The system is equipped with a series of valves (60) that provide environmental isolation between the chambers, allowing for independent atmospheric conditions in each section. The sample store unit (160) is also shown in Figure 6 where a sample storage unit (160) is shown on the left, here within in the intermediate station (40), capable of holding multiple wafer samples (15), with one sample (15) being moved from the sample store unit (160) to the chill plate (150).

[0135] The radiation exposure station (20) may further comprise a residual gas analyzer (RGA) (170) for monitoring outgassing from the photoresist sample (15) during exposure. This provides insight into volatile reaction products during exposure.

[0136] The atmosphere control system (70) may be configured to independently provide in any of the stations, atmospheres selected from the group consisting of high vacuum, low vacuum, clean air (CA), carbon dioxide (CO2), oxygen (O2), inert gases such as nitrogen (N2), and mixtures thereof. This allows testing under a wide range of environmental conditions.

[0137] The atmosphere control system (70) may be configured to provide a gas environment comprising oxygen to one or more of the stations. This enables studies of oxygen effects on resist chemistry, particularly important for metal oxide resists.

[0138] In embodiments, the atmosphere control system (70) may comprise:

[0139] * at least a first gas inlet for an inert gas (e.g., N2) and a second gas inlet for a reactive gas (e.g., O2); and

[0140] * a mass flow controller (MFC) connected to each of the first and second gas inlets, wherein the mass flow controllers are configured to independently control the flow rate of each gas to create a gas mixture with a predetermined composition for introduction into one of the stations (e.g., into the intermediate analysis station and / or into the thermal processing station).

[0141] The atmosphere control system (70) may further comprise a humidity control unit (224) for controlling relative humidity (RH) within one or more stations. This enables studies of moisture effects on resist chemistry. Such a humidity control unit is visible in Figure 3.

[0142] In embodiments, the atmosphere control system (70) may further comprise:

[0143] * a humidity control unit (224) positioned downstream of the mass flow controllers, configured to receive the gas mixture and introduce a controlled amount of humidity; and

[0144] * a bypass line configured to selectively route the gas mixture around the humidity control unit to provide a dry atmosphere to one of the stations.

[0145] The atmosphere control system (70) may be configured to provide an inert gas, not interfering with the analysis, to the intermediate analysis station (40). This minimizes interference during analytical measurements.

[0146] The atmosphere control system (70) may be configured to provide a high vacuum environment below 1 x 106mbar in the radiation exposure station (20). This simulates the vacuum conditions of production EUV exposure tools.

[0147] The atmosphere control system (70) may be further configured to dose controlled amounts of airborne molecular contaminants (AMCs), such as amines or volatile organic compounds (VOCs). This allows investigation of contaminant effects on resist performance. The sample transfer system (80) may comprise one or more transfer arms (80) configured for manual or automated transfer of samples (15). This provides flexibility in operation and sample handling.

[0148] The tool (10) may further comprise a resist coat station (90) connected to the sample transfer system (80), the resist coat station (90) configured for applying a photoresist film to a sample (15). This enables a more complete process flow study from the coating on. A tool comprising such a resist coat station is depicted in Figure 9.

[0149] The resist coat station (90) may be a spin-on system or a dry deposition system. This accommodates different types of resist application methods.

[0150] The tool (10) may further comprise a developer station (100) connected to the sample transfer system (80), the developer station (100) being configured for developing an exposed photoresist film. This allows complete end-to-end process evaluation. A developer station (100) is also visible in Figure 9.

[0151] The developer station (100) may be a wet system for puddle and spin-off development or a dry system using a thermal and / or plasma-based process. This supports both traditional and advanced development techniques.

[0152] When both a resist coat station (90) and a developer station (100) is present in the tool (10), the intermediate analysis station (40) is preferably centrally located so as to enable a direct connection to every other station. This allows the intermediate analysis station (40) to serve as a hub for transferring samples (15) between different processing stages.

[0153] In Figure 9 is illustrated a comprehensive tool (10) for evaluating photoresist chemical changes during lithographic processes, incorporating a resist coat station (90) and a developer station (100). The system is designed to maintain a controlled environment throughout the process. The tool (10) comprises several interconnected stations, each serving a specific function in the lithographic process. The exposure and measurement station (20) is depicted on the left, where a sample (15) is exposed to radiation. This station (20) is connected to a loadlock / intermediate analysis station (40), which includes an optional chill plate (150) for stabilizing the sample (15) temperature. The intermediate analysis station (40) is, in this example embodiment, centrally located and serves as a hub for transferring samples (15) between different processing stages. Above the intermediate station (40) is the resist coat station (90) connected to the sample transfer system (80), which applies a photoresist layer to the sample (15). In the depicted embodiment, this station (80) is equipped with an optional spin-on system for resist application. Below the intermediate station (40) is the develop station, which processes the exposed photoresist. This station can handle both wet and dry development processes. To the right of the intermediate station (40) is the thermal processing station (30), featuring an optional hot plate for postexposure baking. This station (30) is advantageous for inducing chemical changes in the photoresist after exposure. Transfer arms of a sample transfer system (80) are depicted on either side of the system (10), facilitating the movement of samples (15) between stations while maintaining environmental isolation. Environmental isolation means (e.g., valves (60)) are placed between stations to ensure independent atmospheric conditions can be maintained in each chamber.

[0154] Any feature of the first aspect may be as correspondingly described in any of the other aspects. In a second aspect, the present invention relates to a method for evaluating photoresist chemical changes during lithographic processes in a tool (10) according to the first aspect. As illustrated in Figure 10, this method comprises exposing a photoresist sample (15) to radiation in the radiation exposure station (20) under a first controlled atmosphere; transferring the exposed photoresist sample (15) to the intermediate analysis station (40) while maintaining environmental isolation; performing analysis of the photoresist sample (15) in the intermediate analysis station (40) under a second controlled atmosphere; transferring the analyzed sample (15) to the thermal processing station (30) while maintaining environmental isolation; thermally processing the photoresist sample (15) in the thermal processing station (30) under a third controlled atmosphere; and transferring the thermally processed sample (15) back to the intermediate analysis station (40) while maintaining environmental isolation, and performing further analysis of the photoresist sample (15) in the intermediate analysis station (40) under a fourth controlled atmosphere, wherein the first, second, third, and fourth controlled atmospheres are independently controlled.

[0155] Performing analysis in the method may comprise performing Fourier Transform Infrared spectroscopy (42) in a transmission mode. This provides detailed molecular information about chemical changes in the resist.

[0156] The second and fourth controlled atmospheres may be selected from the group consisting of an inert gas atmosphere and a vacuum to minimize interference with the analysis. This ensures measurement accuracy by reducing environmental interference.

[0157] The third controlled atmosphere may comprise a reactive gas, such as oxygen, and / or a controlled level of humidity. This allows investigation of specific environmental effects on thermal processing.

[0158] In embodiments, providing the third controlled atmosphere for the thermal processing step (e) may comprise:

[0159] * independently controlling the flow rates of at least a first gas and a second gas using respective mass flow controllers to create a gas mixture with a predetermined ratio; and

[0160] * introducing said gas mixture into the thermal processing station (30). In embodiments, the first gas may be an inert gas, such as nitrogen, and the second gas may be a reactive gas, such as oxygen. In embodiments, the thermal processing station (30) may further comprise one or more gas sensors (34) for providing real-time information on the concentration of specific atmospheric components, such as O2 or H2O. this permits to verily and actively control the composition of the third controlled atmosphere. In embodiments, this data can be used by the controller (300) in a feedback loop to dynamically adjust the mass flow controllers, ensuring the atmospheric composition is maintained at a precise setpoint throughout the thermal processing step. In embodiments, the method may further comprise, before introducing the gas mixture into the thermal processing station (30), selectively performing one of the following steps:

[0161] * passing the gas mixture through a humidity control unit to achieve a predetermined relative humidity; or

[0162] * routing the gas mixture through a bypass line that circumvents the humidity control unit to provide an atmosphere with substantially zero relative humidity. The method may further comprise monitoring outgassing from the photoresist sample (15) using a residual gas analyzer (RGA) (170) during the exposing step. This provides additional information about volatile reaction products.

[0163] The method may further comprise, after transferring to the intermediate analysis station (40) and before performing analysis, storing the exposed photoresist sample (15) in a sample storage unit (160) for a defined post-exposure delay period under a controlled delay atmosphere. This enables controlled investigation of delay effects.

[0164] This is exemplified in example 1.

[0165] The method may further comprise, before exposing, coating a sample (15) with a photoresist in a resist coat station (90) connected to the sample transfer system (80); transferring the coated sample (15) to the thermal processing station (30); and performing a post-application bake on the coated sample (15). This enables a more complete process flow evaluation from the coating on.

[0166] The method may further comprise, after performing the further analysis of step g, transferring the sample (15) to a developer station; and developing the photoresist. This enables evaluation of the final patterning results.

[0167] Any feature of the second aspect may be as correspondingly described in any of the other aspects.

[0168] In a third aspect, the present invention relates to a system (320) comprising the tool (10) according to any embodiment of the first aspect, and a controller (300) for carrying out at least some steps of the method according to any embodiment of the second aspect.

[0169] As shown in Figure 11, this illustrates a diagram of a system (320) for evaluating photoresist chemical changes during lithographic processes. The system (320) comprises two main components: a tool (10) and a controller (300). The tool (10) is depicted as a rectangular block on the left side of the figure, while the controller (300) is shown as a separate rectangular block on the right side. A connecting line between the two blocks indicates a communication or control link. The entire setup is enclosed within a larger rectangular boundary, representing the system (320) as a whole.

[0170] The controller (300) may be configured to automate the transfer of photoresist samples (15) and the execution of a pre-programmed sequence of exposing, analyzing, and thermal processing steps. This improves reproducibility and efficiency of experiments.

[0171] The controller (300) may be configured to record analysis data from the analysis system (42) and correlate said data with the controlled atmospheres and processing parameters of each step. This enables comprehensive data analysis and process optimization.

[0172] The controller (30) may be configured to pilot the atmosphere control system (70) to independently provide in any of the stations, atmospheres selected from the group consisting of high vacuum, low vacuum, clean air (CA), carbon dioxide (CO2), oxygen (O2), inert gases such as nitrogen (N2), and mixtures thereof.

[0173] The controller (300) may be configured to pilot the atmosphere control system (70) to maintain the oxygen at a controlled concentration in the one or more of the stations during at least one postexposure thermal processing step. This improves contrast and reduces EUV dose requirements for metal oxide photoresists.

[0174] Any feature of the third aspect may be as correspondingly described in any of the other aspects. In a fourth aspect, the present invention relates to a computer program comprising instructions which, when executed by the controller (300) of the system (320) of the third aspect, cause the controller (300) to carry out the method according to the second aspect.

[0175] Any feature of the fourth aspect may be as correspondingly described in any of the other aspects.

[0176] In a fifth aspect, the present invention relates to a computer-readable medium having stored thereon the computer program of the fourth aspect.

[0177] Any feature of the fifth aspect may be as correspondingly described in any of the other aspects.

[0178] In a sixth aspect, the present invention relates to a method for optimizing lithographic process conditions for a photoresist material. As illustrated in Figure 37, this method comprises evaluating photoresist chemical changes using any embodiment of the method of the second aspect under multiple sets of process conditions; correlating the photoresist chemical changes with lithographic performance metrics; and identifying optimal process conditions based on the correlations.

[0179] Figure 12 illustrates a flowchart detailing the method for optimizing lithographic process conditions for a photoresist material. The process begins with evaluating chemical changes under varied conditions, as indicated in step (a). This is followed by correlating these changes with lithography performance metrics, as shown in step (b). Finally, step (c) involves identifying optimal process conditions based on the correlations.

[0180] The lithographic performance metrics may be selected from the group consisting of critical dimension, CD uniformity, line-edge roughness, line-width roughness, and stochastic failures. This focuses optimization on industrially relevant performance parameters.

[0181] The evaluating step may be performed by varying at least one parameter selected from the group consisting of radiation exposure dose, thermal processing temperature, thermal processing duration, post-exposure delay duration, and the composition and humidity of the first, second, third, and fourth controlled atmospheres, enabling comprehensive process window exploration and optimization.

[0182] Examples:

[0183] The following examples illustrate the use and capabilities of the tool (10) of the present invention. The experiments demonstrate how the integrated, controlled-environment system enables an unprecedented level of insight into the complex chemical transformations of advanced photoresist materials during lithographic processing.

[0184] Metal Oxide Resists (MORs) represent a significant advancement in semiconductor lithography, offering the potential for high-resolution patterning required for next-generation integrated circuits. The excellent lithographic performance of these materials allows achieving precise high- resolution patterning. Achieving this consistently in a manufacturing environment requires a deep understanding of the underlying resist chemistry.

[0185] The high performance of MORs is rooted in a complex series of chemical transformations. As illustrated in the reaction diagrams of Figure 13, MORs can consist of a central metal-oxo core or cage surrounded by organic ligands. During the lithographic process, exposure to radiation initiates photoreactions that lead to condensation, forming a robust, cross-linked network.

[0186] A critical challenge in working with MORs is their pronounced sensitivity to the surrounding atmospheric environment at multiple stages of the process. The Sn-oxo cage structure of a model MOR (see Figure 14) can readily interact with ambient molecules, particularly water (H2O). This sensitivity impacts the entire lithographic workflow, as depicted schematically in Figure 15, which shows the evolution of the MOR from its initial coated state, through activation by EUV radiation, and finally to condensation during the post-exposure bake (PEB) phase.

[0187] The necessity of specific environmental conditions for successful MOR processing is further emphasized by the fact that, after initial activation by light, the MOR units can be held in a stable state in a vacuum environment, but the critical solid-phase condensation step to form the final oxo-network requires the presence of components from cleanroom air. Similarly, Figure 15 highlights the importance of the PEB atmosphere, showing how an oxygen-rich environment is crucial for facilitating further chemical reactions and enhancing the cross-linking of the MOR units after the initial exposure. These examples underscore that the environment is not merely a source of contamination but can be an essential reactant in the desired chemical pathway.

[0188] Conventional analytical approaches, which rely on separate, standalone tools for exposure, baking, and measurement, fail to capture these dynamic changes.

[0189] The conventional photoresist process begins with the spin-coating of a resist layer onto a silicon wafer, forming a film. This is followed by the exposure step, where extreme ultraviolet (EUV) light is reflected off of a multilayer mask on a low thermal expansion substrate to pattern the resist (15). This step can be assisted by subsequent bake. The development step comes next, showing two possible outcomes: in a positive tone process, the exposed resist (15) is removed, while in a negative tone process, the unexposed resist (15) is removed. The final step is etching, where the patterned resist (15) protects the underlying film during the etching process, resulting in the desired pattern on the silicon substrate.

[0190] Transferring a sample between different tools inevitably exposes it to uncontrolled cleanroom ambients, altering its chemical state and making it impossible to distinguish the effects of a specific process step from the effects of environmental exposure. This creates a critical gap in understanding and optimizing MOR process conditions.

[0191] To overcome these limitations, the experiments described herein were performed using the tool (10) of the present invention. As illustrated in the schematic in Figure 3 (top), the tool provides a comprehensive, multi-chamber platform designed for step-by-step lithographic processing and analysis.

[0192] The system comprises three main stations — a radiation exposure station (20), an intermediate analysis station (40) equipped with a Fourier Transform Infrared (FTIR) spectrometer, and a thermal processing station (30) — all connected by a sample transfer system (80). Environmental isolation means (60) and a comprehensive atmosphere control system (70) allow for independent, precisely defined atmospheric conditions (e.g., high vacuum, inert gas, controlled humidity, reactive gases) to be maintained in each station. This integrated design allows, for the first time, a photoresist sample to undergo sequential processing and analysis steps without being exposed to uncontrolled ambient conditions, enabling a direct and unambiguous investigation of molecular transformations as they occur at each stage of the lithographic process.

[0193] The capabilities of the tool (10) are demonstrated in the following experimental case studies using several model photoresist systems. The primary focus is on tin-oxo based MORs with various counter-ions, whose molecular structures are shown in Figure 14, including MOR-[OH], MOR-[Ac], and MOR-[Piv]. While MORs are the main subject, it is noted that the tool is equally suited for studying other advanced material platforms, such as the Chemically Amplified Resists (CARs), showcasing the versatility of the invention. The chemically amplified resist (CAR) mechanism is impacted by environmental factors during the lithographic process.

[0194] During exposure, a photo acid generator (PAG) is present, which releases an acid (H+) upon exposure to light. This acid initiates the deprotection of the protection group (PG) of a polymer chain, altering the solubility of the resist (15).

[0195] During PEB this reaction continues. The acid further catalyzes the removal of the PG during the baking process. The presence of airborne amines can neutralize the acid, inhibiting the deprotection reaction and affecting the critical dimension (CD) control.

[0196] Environmental conditions play an important role in the process. Controlling amine levels is advantageous to ensure consistent lithographic performance.

[0197] Through its comprehensive capabilities for controlled environment processing and analysis, this tool (10) provides a valuable platform for evaluating photoresist chemical changes during lithographic processes, enabling optimization of process conditions and improved understanding of resist chemistry under various environmental conditions.

[0198] All FTIR spectroscopic data presented in the following examples were processed to ensure accuracy and repeatability. Raw transmittance spectra were converted to absorbance spectra, and a baseline correction was applied to remove noise and create a flat baseline. This process allowed for the clear resolution of characteristic absorption peaks, such as those for water (H2O) and C-H bonds in ligands, with a high signal-to-noise ratio.

[0199] Example 1: Investigation of Post-Exposure Delay Effects on Metal Oxide Resist Chemistry

[0200] Multiple MOR-[Ac] coated coupons with 25 nm film thickness were prepared and loaded into the system's sample garage (160) located in the intermediate chamber. Each coupon was individually processed through the exposure chamber (20) at an EUV dose of 35 mJ / cm2. After exposure, the samples were subjected to different post-exposure delay (PED) conditions to study the impact of the ambient environment.

[0201] A first sample was immediately analyzed by FTIR in the intermediate chamber (40) under vacuum conditions to establish a baseline. Another sample (Sample 1) was stored in the controlled environment (CE) of the sample garage (160) under vacuum (~1 * 102mbar) for periods of up to four hours. A separate, identical sample (Sample 2) was removed from the tool and exposed to a noncontrolled cleanroom (CR) atmosphere with 45% relative humidity (RH) for the same time intervals before being reintroduced to the tool for FTIR analysis. For all measurements, the FTIR chamber was purged with N2 to prevent atmospheric interference during analysis.

[0202] The results of this comparative study are clearly shown in Figure 16. For the sample maintained in the controlled vacuum environment (CE, middle pane), the overlaid FTIR spectra at various delay times showed minimal changes. This demonstrated excellent control over the sample's chemical state. In stark contrast, the sample exposed to the non-controlled cleanroom air (Non-CE, right pane) showed a significant and time-dependent increase in the OH peak around 3400 cm '. indicating progressive moisture uptake. The high sensitivity of the tool allowed for an even more detailed analysis of the resist's stability, as demonstrated in Figure 16 (left and middle panes). A closer examination of the exposed sample held in the controlled environment revealed extremely subtle but consistent changes over time in the C-H ligand peaks. A control experiment on an unexposed sample showed no such changes, confirming that this minor instability was a real, exposure-induced phenomenon and showcasing the system's excellent sensitivity.

[0203] The moisture uptake from the non-controlled environment was quantified by integrating the OH signal over time, as plotted in Figure 17. The graph shows a clear upward trend that begins to level off, indicating that the resist film was becoming saturated with water from the ambient air. The significance of this chemical change stems from the correlation between moisture uptake during PED and critical dimension (CD) variations. This confirms that the molecular-level changes measured by the tool have a direct impact on final lithographic performance.

[0204] After the delay -period characterization, all samples were transferred to the bake chamber (30) and subjected to a post-exposure bake (PEB). Post-bake FTIR analysis revealed that samples exposed to cleanroom air during the delay period showed different degrees of Sn-O-Sn condensation compared to those maintained in vacuum. This experiment successfully demonstrated the tool's ability to precisely measure and quantify how environmental exposure during post-exposure delay drives chemical changes that are directly linked to lithographic outcomes.

[0205] Example 2: Step-by-Step Optimization of the Post-Exposure Bake Process

[0206] A series of experiments was conducted to demonstrate the tool's capability to systematically investigate and optimize the post-exposure bake (PEB) process by decoupling the effects of temperature, moisture, and atmospheric composition on the key chemical reactions in a metal oxide resist.

[0207] First, the tool was used to quantify the fundamental kinetics of the PEB step as a function of temperature. A MOR-[OH] sample was exposed to a uniform EUV dose of 35 mJ / cm2. The sample was then subjected to a PEB in the thermal processing station (30) at various temperatures ranging from 140°C to 260°C under a controlled N2 / 45%RH atmosphere. The results, plotted in Figure 18, highlight the unique analytical power of the integrated system. The in-situ FTIR measurements allowed for the simultaneous tracking of two critical, opposing reactions: as the PEB temperature increased, the relative ligand signal clearly decreased, indicating thermally induced ligand cleavage. Concurrently, the SnO signal, corresponding to the formation of the Sn-O-Sn network, showed a distinct increase. This demonstrates the tool’s ability to provide quantitative data on both ligand removal and network condensation, which is essential for optimizing the bake temperature to achieve the desired resist chemistry.

[0208] The tool was also used to track the stability and removal of moisture, a critical environmental factor, throughout the lithographic sequence. An initial FTIR measurement of an unexposed M0R-[0H] sample after coating and post-application bake (PAB), shown in Figure 19 (left), revealed a significant H2O absorption peak, establishing the baseline moisture content. Figure 19 (right) presents a bar chart summarizing the OH signal at subsequent processing stages. It shows that while vacuum steps can reduce moisture levels when performed at 80 °C, higher-temperature steps on the order of a typical PEB are most effective at removing the majority of the moisture from the fdm. This confirms the tool's ability to monitor and verify the conditioning of the resist film at each stage. Building on this understanding of thermal and moisture effects, a comprehensive experiment was conducted to determine the impact of different atmospheric compositions during a fixed PEB. A series of identical MOR-[Ac] coupons was exposed to 35 mJ / cm2EUV and baked at 180°C under various environments. The results, shown in the bar chart in Figure 20, demonstrated that the atmospheric composition had a significant impact on ligand cleavage, with oxygen-containing environments (CA and Air) being the most effective. This conclusion was strongly reinforced by a dedicated study on the MOR-[Piv] resist, with results shown in Figure 21. As seen in Figure 21(a), the ligand loss was again most significant in the dry Clean Air (CA) environment, confirming that the presence of oxygen strongly enhances thermal ligand cleavage. Concurrently, Figure 21(b) shows that the Sn-0 condensation signal was also most pronounced in the CA atmosphere. Interestingly, the presence of humidity (30% RH) appeared to slightly facilitate the Sn-0 condensation reaction, suggesting that while oxygen is key for ligand removal, water plays a role in the network formation. This detailed analysis, made possible by the tool's precise environmental control, allows for the fine-tuning of the PEB atmosphere to optimize both critical reactions simultaneously.

[0209] To further dissect the specific role of humidity during the PEB, another experiment was performed as detailed in Figure 30. A BMOR sample was exposed to 35 mJ / cm2EUV radiation and then subjected to a PEB at a fixed temperature of 180°C, but with the relative humidity (RH) varied from 30% to 70% in a controlled N2atmosphere. The FTIR spectra taken before the bake confirmed the initial samples were identical. After the bake, the spectra suggested a potential trend where samples baked at lower RH had a slightly lower final OH signal, indicating less residual moisture. However, the graph of ligand cleave fraction versus the PEB humidity level showed that the extent of ligand removal was consistently high (around 80%) and virtually unaffected by the humidity level during the bake. This experiment, enabled by the tool’s integrated humidity control, indicates that for this specific temperature, water vapor in the baking ambient does not significantly inhibit or enhance the primary thermal ligand cleavage reaction, although it may influence the final film hydration. Such studies are advantageous for defining robust process windows and identifying subtle environmental sensitivities.

[0210] Example 3 : Step-by-Step Chemical Analysis of a Full Lithographic Process A detailed analysis of the chemical changes in a photoresist was performed at various stages of the lithographic process using the tool, as illustrated in Figure 22.

[0211] The experiment followed the process flow shown in section (a) of the figure. A photoresist sample was prepared by coating and performing a post-application bake (PAB). The sample was then loaded into the tool, and an initial FTIR measurement was taken to establish a baseline. The sample was subsequently transferred to the exposure station and exposed to EUV radiation at a dose of 35 mJ / cm2. Following exposure, a second FTIR measurement was performed. The sample then underwent a postexposure delay (PED) before being transferred to the thermal processing station for a post-exposure bake (PEB) at 180°C in a controlled nitrogen environment with 70% relative humidity (N2 / 70%RH). A final FTIR measurement was conducted after the bake step.

[0212] The results are presented in sections (b) and (c) of Figure 22. Section (b) shows the FTIR spectra collected at three key stages: after coating (top line), after EUV exposure (middle line), and after the post-exposure bake (bottom line). The changes in the spectral regions corresponding to water (OH), ligands (CH), counter-ions, and Sn-0 bonds clearly indicated that significant chemical transformations, such as ligand removal and Sn-0 condensation, occurred at each step.

[0213] To better emphasize these changes, differential spectra were calculated, as shown in section (c). The spectmm calculated by subtracting the unexposed spectrum from the exposed spectrum (top line) revealed negative peaks for ligands and OH, confirming their loss during exposure. The differential spectmm comparing the post-bake state to the post-exposure state (bottom line) showed a further loss of ligands and OH, coupled with a distinct positive peak corresponding to the gain of Sn-0 bonds. This experiment successfully demonstrated the tool's capability to track specific molecular transformations throughout a complete, environmentally controlled lithographic process.

[0214] Example 4: Systematic Investigation of Dose and Temperature Effects

[0215] A series of experiments was conducted to demonstrate the tool's core capability to systematically decouple and quantify the chemical impacts of EUV dose and post-exposure bake (PEB) temperature on a model Metal Oxide Resist (BMOR).

[0216] Part A: EUV Dose-Dependent Chemical Changes

[0217] A preliminary experiment was performed to determine the resist's dose-to-gel (D2G) threshold. As shown in Figure 23, the remaining fdm thickness of the BMOR sample was measured after exposure to a range of EUV doses. The film thickness was observed to plateau around 20 nm at a dose of approximately 35 mJ / cm2, which was identified as the D2G threshold and selected as the standard dose for subsequent thermal studies.

[0218] Next, the dose-dependent chemical changes were directly measured using the tool (10). A BMOR-coated sample was prepared, and a baseline FTIR measurement was taken. The sample was then exposed to a range of EUV doses from 0 to 100 mJ / cm2in the controlled vacuum environment of the exposure station (20). A final FTIR measurement was performed in the intermediate analysis station (40). The results, presented in Figure 24, showed a clear, dose-dependent chemical response. As the EUV dose increased, the intensity of the C-H stretching peaks associated with the resist's ligands decreased, providing direct evidence of ligand removal. This relationship was quantified in Figure 25 (left), which plots the ligand cleave fraction as a function of exposure dose, showing a clear trend of increased ligand removal with higher doses.

[0219] A more comprehensive view of the chemical kinetics during exposure is provided in Figure 25 (right). This figure simultaneously tracks the relative signal change for both the organic ligands (CH) and the water content (OH) as a function of EUV dose. The top line confirms the gradual cleavage of ligands, consistent with the data in Figure 25 (left), illustrating how the remaining fraction provides insights into exposure kinetics. More strikingly, the bottom line reveals a rapid and significant decrease in the OH signal, indicating that the EUV exposure process itself is highly effective at removing moisture from the resist film. The D2G threshold dose (around 35 mJ / cm2, highlighted) corresponds to a point where nearly 40% of the initial moisture has been removed. Without being bound by theory, it is believed that at 0 mJ / cm2, the Sn-cages are surrounded by numerous ligands and water molecules. As the dose increases to 35 mJ / cm2and then to 100 mJ / cm2, both the number of ligands and, more dramatically, the number of water molecules decrease. This demonstrates the tool's powerful ability to monitor multiple, simultaneous chemical changes within the resist film as a direct consequence of the exposure step, distinguishing between the primary photoreaction (ligand cleavage) and secondary effects (moisture removal).

[0220] Part B: Post-Exposure Bake (PEB) Temperature-Dependent Chemical Changes

[0221] To isolate the effects of thermal processing, a BMOR sample was first exposed to a uniform EUV dose of 35 mJ / cm2. The sample was then transferred to the thermal processing station (30) and subjected to a PEB in a controlled environment at temperatures ranging from 100°C to 260°C. FTIR analysis was performed after each bake. The results, shown in Figure 26, demonstrated a strong correlation between PEB temperature and further ligand removal. The intensity of the C-H stretching peaks continued to decrease significantly as the PEB temperature increased.

[0222] The data confirmed that both exposure dose and PEB temperature drive ligand cleavage, but their kinetics could be independently quantified. Furthermore, the tool allowed for the simultaneous tracking of other chemical changes, such as Sn-0 condensation, providing a complete picture of the resist chemistry.

[0223] Example 5: Comparative Analysis of Different MOR Formulations

[0224] To showcase the tool's utility for material screening and comparative studies, two different model metal oxide resists, BMOR and OSMO, were analyzed under identical processing conditions.

[0225] The objective was to directly compare the chemical response of BMOR (with hydroxide counter-ions) and OSMO (with acetate counter-ions) to both EUV radiation and post-exposure bake.

[0226] Samples of both BMOR and OSMO were prepared and loaded into the tool (10). Each sample was subjected to an identical process flow: an initial FTIR scan, followed by exposure to a range of EUV doses, and a subsequent FTIR scan. A separate set of exposed samples was then subjected to a PEB at various temperatures (100°C, 220°C, and 260°C) followed by a final FTIR analysis.

[0227] The comparative response to EUV exposure is shown in Figure 27. Both resists exhibited similar dose-dependent ligand removal, as evidenced by the decreasing intensity of the C-H peaks in their respective FTIR spectra. This indicated that the fundamental photo-cleavage mechanism was consistent between the two formulations.

[0228] The comparative thermal behavior is shown in Figure 28. Again, both resists displayed similar trends, with significant ligand removal occurring as the PEB temperature increased. The changes observed in the OSMO spectra were noted to be in line with those of BMOR, suggesting comparable thermal stability and ligand removal patterns.

[0229] This experiment demonstrated the tool's exceptional value for generating high-fidelity, directly comparable data on different material formulations. By ensuring that all processing and measurement conditions are identical and free from environmental variability, the tool enables researchers to confidently attribute observed differences in chemical behavior directly to the molecular structure of the resists themselves.

[0230] Example 6: In-Situ Analysis of Counter-Ion Transformations During EUV Exposure

[0231] The tool (10) was utilized to investigate the transformation of counter-ions during EUV irradiation, a subtle but important chemical event. The study focused on the MOR- [Ac] and MOR-[Piv] model resists, which have distinct counter-ions.

[0232] As shown in Figure 29(a), FTIR measurements of the C=O stretching signal around 1550 cm were used to quantify the counter-ion presence. After exposure to an EUV dose of 35 mJ / cm2, both materials exhibited a clear and similar decrease in the C=0 signal, indicating a loss or transformation of the counter-ions.

[0233] To further investigate this, the integrated residual gas analyzer (RGA) in the exposure station (20) was used to perform outgas measurements during irradiation. The mass-to-charge spectrum, shown in Figure 29(b), revealed that while most outgassing peaks corresponded to butyl-related ligand fragments for both materials, specific masses showed distinct differences. The MOR-[Piv] sample exhibited a significantly higher peak at m / z = 102, corresponding to pivalic acid, while the MOR-[Ac] sample showed a stronger signal at m / z = 60, related to acetic acid. These combined FTIR and RGA findings strongly suggest that the counter-ions undergo protonation during EUV exposure, converting into their respective volatile acids. This experiment demonstrates the tool's unique capability to correlate changes within the film (via FTIR) with volatile byproducts (via RGA) in a single, controlled process sequence.

[0234] It is to be understood that although preferred embodiments, specific constructions and configurations, as well as materials, have been discussed herein for devices according to the present invention, various changes or modifications in form and detail may be made without departing from the scope of this invention. For example, any formulas given above are merely representative of procedures that may be used. Functionality may be added or deleted from the block diagrams and operations may be interchanged among functional blocks. Steps may be added or deleted to methods described within the scope of the present invention.

[0235] List of Reference Numbers

[0236] 10 - Tool

[0237] 15 - Photoresist samples

[0238] 20 - Radiation exposure station

[0239] 22 - Radiation source

[0240] 30 - Thermal processing station

[0241] 32 - Hot plate

[0242] 34 - Sensors

[0243] 40 - Intermediate analysis station

[0244] 42 - System configured for analyzing photoresist samples / Fourier Transform Infrared (FTIR) spectrometer

[0245] 60 - Environmental isolation means

[0246] 70 - Atmosphere control system

[0247] 80 - Sample transfer system

[0248] 90 - Resist coat station

[0249] 100 - Developer station

[0250] 110 - Sample tilting mechanism / Gonio meter

[0251] 150 - Temperature-controlled stage

[0252] 160 - Sample storage unit (e.g., garage or stacker)

[0253] 170 - Residual gas analyzer (RGA) - Humidity control unit - Controller - System

Claims

29Claims1. A tool (10) for evaluating photoresist chemical changes during lithographic processes, comprising: a) a radiation exposure station (20) for exposing photoresist samples (15) to radiation; b) a thermal processing station (30) for thermally processing photoresist samples (15); c) an intermediate analysis station (40) separate from the exposure station (20) and the thermal processing station (30), the intermediate analysis station (40) comprising a system (42) configured for analyzing photoresist samples (15), d) environmental isolation means (60) between the stations enabling independent environments in each station during operation; e) an atmosphere control system (70) configured to establish different atmospheric conditions in each station, and f) a sample transfer system (80) for transferring photoresist samples (15) between the stations while maintaining environmental isolation.

2. The tool (10) of claim 1, wherein the system (42) configured for analyzing photoresist samples (15) in the intermediate analysis station (40) comprises a Fourier Transform Infrared (FTIR) spectrometer (42).

3. The tool (10) of claim 2, wherein the FTIR spectrometer (42) is configured for transmission measurements through a photoresist sample (15).

4. The tool (10) of claim 3, further comprising a sample tilting mechanism (110) for tilting the photoresist sample (15) to increase the optical path length for transmission measurements.

5. The tool (10) according to any one of the preceding claims, wherein the intermediate analysis station (40) comprises a temperature-controlled stage (150).

6. The tool (10) according to any one of the preceding claims, further comprising a sample storage unit (160), such as a garage or Stocker, connected to the sample transfer system (80) for holding one or more samples (15) under a controlled environment for defined periods.

7. The tool (10) according to any one of the preceding claims, wherein the radiation exposure station (20) further comprises a residual gas analyzer (RGA) (170) for monitoring outgassing from the photoresist sample (15) during exposure.

8. The tool (10) according to any one of the preceding claims, wherein the atmosphere control system (70) is configured to independently provide in any of the stations, atmospheres selected from the group consisting of high vacuum, low vacuum, clean air (CA), carbon dioxide (CO2), oxygen (O2), inert gases such as nitrogen (N2) and argon (Ar), and mixtures thereof.

9. The tool (10) of claim 8, wherein the atmosphere control system (70) is configured to provide an inert gas, not interfering with the analysis, to the intermediate analysis station (40).

10. The tool (10) according to any one of the preceding claims, wherein the atmosphere control system (70) further comprises a humidity control unit (224) for controlling relative humidity (RH) within one or more stations.

11. The tool (10) according to any one of the preceding claims, wherein the atmosphere control system (70) is further configured to dose controlled amounts of airborne molecular contaminants (AMCs), such as amines or volatile organic compounds (VOCs).

12. A method for evaluating photoresist chemical changes during lithographic processes in a tool (10) according to any one of claims 1 to 11, comprising: a) exposing a photoresist sample (15) to radiation in the radiation exposure station (20) under a first controlled atmosphere; b) transferring the exposed photoresist sample (15) to the intermediate analysis station (40) while maintaining30 environmental isolation; c) performing analysis of the photoresist sample (15) in the intermediate analysis station (40) under a second controlled atmosphere; d) transferring the analyzed sample (15) to the thermal processing station (30) while maintaining environmental isolation; e) thermally processing the photoresist sample (15) in the thermal processing station (30) under a third controlled atmosphere; and f) transferring the thermally processed sample (15) back to the intermediate analysis station (40) while maintaining environmental isolation, and g) performing further analysis of the photoresist sample (15) in the intermediate analysis station (40) under a fourth controlled atmosphere, wherein the first, second, third, and fourth controlled atmospheres are independently controlled.

13. A system (320) comprising the tool (10) according to any one of claims 1 to 11, and a controller (300) for carrying out at least some steps of the method according to claim 12.

14. A computer program comprising instructions which, when executed by the controller (300) of the system (320) of claim 13, cause the controller (300) to carry out the method according to claim 12.

15. A computer-readable medium having stored thereon the computer program of claim 14.

16. A method for optimizing lithographic process conditions for a photoresist material, comprising: a) evaluating photoresist chemical changes using the method of claim 12 under multiple sets of process conditions; b) correlating the photoresist chemical changes with lithographic performance metrics; and c) identifying optimal process conditions based on the correlations.

Images