Diaphragm monitoring apparatus and method and lithographic apparatus

Abstract

A monitoring subsystem for monitoring a septum for use in a lithographic apparatus, the monitoring subsystem comprising: a light source configured to illuminate the septum, the septum being arranged between a first region and a second region of the lithographic apparatus; a light detector configured to measure a total power of light incident on a field of view of the light detector, the light being emitted from the light source and reflected by the diaphragm; and a controller configured to determine a degradation level of the diaphragm based at least in part on a measured total power of light incident on a field of view of the light detector.

Description

Cross-references to related applications

[0001] This application claims priority to EP application 23196628.4, filed on September 11, 2023, which is incorporated herein by reference in its entirety. Technical Field

[0002] This invention relates to a technique for detecting the degradation level of diaphragms (such as dynamic gas lock (DGL) diaphragms or surface films) in photolithography equipment. Background Technology

[0003] A photolithography apparatus is a machine configured to apply a desired pattern onto a substrate. Photolithography apparatus can be used, for example, to manufacture integrated circuits (ICs). A photolithography apparatus can project a pattern from a patterning apparatus (e.g., a mask) onto a radiation-sensitive material (resist) layer disposed on a substrate.

[0004] To project a pattern onto a substrate, a photolithography apparatus can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the feature that can be formed on the substrate. Compared to a photolithography apparatus that can use, for example, radiation with a wavelength of 193 nm, a photolithography apparatus using extreme ultraviolet (EUV) radiation in the range of 4–20 nm (e.g., 6.7 nm or 13.5 nm) can be used to form smaller features on the substrate.

[0005] Once EUV radiation is generated, it is guided by multiple mirrors through the lithography equipment to the patterned surface of the patterning apparatus, which imparts the desired pattern to the EUV radiation.

[0006] In EUV lithography, a dynamic gas-lock (DGL) diaphragm can be used to filter out multiple wavelengths (such as deep ultraviolet (DUV) and / or infrared (IR) radiation), which can affect overlap or critical dimensional uniformity (CDU) in the product. The DGL diaphragm also prevents substrate contaminants and / or debris from entering the projection optics cassette of the lithography apparatus. The DGL diaphragm is a thin, nearly transparent membrane located between the substrate and the projection system. In some embodiments, the DGL diaphragm replaces the dynamic gas-lock structure that relies on airflow to achieve the same result. The DGL diaphragm is a self-supporting diaphragm supported at its periphery by a boundary attached to a frame. The DGL diaphragm has a film thickness that maximizes EUV transmittance. For example, the DGL diaphragm has at least 65% EUV transmittance, preferably at least 75%, more preferably at least 85%, and even more preferably at least 95% EUV transmittance.

[0007] The DGL separator should be as thin as possible (e.g., approximately 10 nm to 50 nm thick) to minimize optical power loss. However, the nanoscale makes the DGL separator fragile and prone to breakage. Since the DGL separator filters out multiple wavelengths, a broken separator can affect product overlap or CDU. A broken separator cannot prevent contaminants from entering the projection optics cassette, thus requiring replacement with a new separator. Furthermore, once contaminants are allowed to diffuse in the area surrounding the substrate W, it may be necessary to shut down the lithography equipment and perform a lengthy cleaning process. A conservative approach might be to develop a DGL separator replacement plan to replace the separator early enough to ensure that it is never allowed to deteriorate to a level where the risk of breakage becomes significant. However, this often results in premature replacement of the DGL separator, leading to increased hardware costs and unnecessary maintenance downtime. Summary of the Invention

[0008] Therefore, the object of this invention is to improve the usability of lithography equipment. Another object of this invention is to utilize the diaphragm's lifespan more effectively while limiting the risk of breakage.

[0009] According to the present invention, a monitoring subsystem for monitoring a diaphragm used in a photolithography apparatus is disclosed, the monitoring subsystem comprising: A light source configured to irradiate the diaphragm, the DGL diaphragm being disposed between a first region and a second region of the photolithography apparatus; A photodetector configured to measure the total power of light incident on the field of view of the photodetector, the light being emitted from the light source and reflected by the diaphragm; and A controller configured to determine the level of degradation of the diaphragm based at least in part on the measured total power of light incident on the field of view of the photodetector. Attached Figure Description

[0010] Embodiments of the invention will now be described by way of example only, with reference to the accompanying schematic diagrams, wherein corresponding reference numerals denote corresponding parts.

[0011] Figure 1 An embodiment of a photolithography apparatus is schematically depicted.

[0012] Figure 2 An embodiment of the dynamic airlock is schematically depicted.

[0013] Figure 3 An embodiment of the monitoring subsystem when the DGL diaphragm is in the nominal position is schematically depicted.

[0014] Figure 4a and Figure 4bAn embodiment of the monitoring subsystem when the DGL diaphragm bulges is schematically depicted.

[0015] Figure 5 The possible evolution of the detector signal level over time is schematically depicted.

[0016] Figure 6a and Figure 6b This is a graph of detector signal level data obtained using a functional model of an embodiment of the monitoring subsystem.

[0017] Figure 7 An embodiment of the monitoring subsystem is illustrated schematically.

[0018] The features shown in the figures are not necessarily drawn to scale, and the dimensions and / or arrangements depicted are not limited. It should be understood that the figures include optional features that may not be essential to the invention. Furthermore, not all features of the device are depicted in every figure, and the figures may only show some parts relevant to describing a particular feature. Detailed Implementation

[0019] Figure 1 A lithography system including a radiation source SO and a lithography apparatus LA is shown. The radiation source SO is configured to generate an EUV radiation beam B and provide the EUV radiation beam B to the lithography apparatus LA. The lithography apparatus LA includes an irradiation system IL, a support structure MT configured to support a pattern forming apparatus MA (e.g., a mask), a projection system PS, and a substrate stage WT configured to support a substrate W.

[0020] The irradiation system IL is configured to adjust the EUV radiation beam B before it is incident on the pattern forming apparatus MA. Therefore, the irradiation system IL may include a faceted field mirror device M0 and a faceted pupil mirror device M1. Together, the faceted field mirror device M0 and the faceted pupil mirror device M1 provide the EUV radiation beam B with a desired cross-sectional shape and a desired intensity distribution. The irradiation system IL may include other mirrors or devices besides or replacing the faceted field mirror device M0 and the faceted pupil mirror device M1.

[0021] After this adjustment, the EUV radiation beam B interacts with the patterning apparatus MA. This interaction produces a patterned EUV radiation beam B'. A projection system PS is configured to project the patterned EUV radiation beam B' onto the substrate W. For this purpose, the projection system PS may include multiple mirrors M3, M4, configured to project the patterned EUV radiation beam B' onto the substrate W held by the substrate stage WT. The projection system PS may apply a reduction factor to the patterned EUV radiation beam B', thereby forming an image with features smaller than the corresponding features on the patterning apparatus MA. For example, a reduction factor of 4 or 8 may be applied. Although in Figure 1 The projection system PS shown has only two mirrors M3 and M4, but the projection system PS may include a different number of mirrors (e.g., six or eight mirrors).

[0022] The substrate W may include a previously formed pattern. In this case, the photolithography apparatus LA aligns the image formed by the patterned EUV radiation beam B' with the pattern previously formed on the substrate W.

[0023] A relative vacuum, i.e., a small amount of gas (e.g., hydrogen) at a pressure much lower than atmospheric pressure, can be provided in the radiation source SO, the irradiation system IL, and / or the projection system PS.

[0024] The radiation source SO can be a laser-generated plasma (LPP) source, a discharge-generated plasma (DPP) source, a free-electron laser (FEL), or any other radiation source capable of generating EUV radiation.

[0025] Figure 2This is a schematic diagram of the boundary between a first region and a second region in a lithography apparatus. For example, the boundary can be between a substrate W and a projection system PS in the lithography apparatus. As shown, this boundary may include a dynamic gas lock (DGL) 22. The DGL 22 may include a DGL diaphragm 21. Another suitable boundary may be the boundary between a pattern forming apparatus MA and a projection system PS in the lithography apparatus. At this boundary, a diaphragm similar to the DGL diaphragm 21 can be provided to protect the pattern forming apparatus MA from contamination; in this case, the diaphragm is also referred to as a surface film. Moreover, this surface film is supported by a boundary and connected to a frame, allowing it to be attached to a self-supporting surface film of the pattern forming apparatus. Furthermore, the EUV surface film has an EUV transmittance of at least 65%, preferably at least 75%, more preferably at least 85%, and even more preferably at least 95%. Therefore, it should be understood that the disclosure herein regarding the DGL diaphragm 21 can also be applied to other diaphragms used in different locations in the lithography apparatus, such as diaphragms present at the boundary between the pattern forming apparatus MA and the projection system PS in the lithography apparatus. Furthermore, the disclosure of the DGL diaphragm 21 herein can also be applied to diaphragms used in inspection or measurement equipment, or even to diaphragms in transport cases, or generally to any device that requires inspection of the deterioration and / or integrity of the diaphragm.

[0026] An airflow can be generated around the DGL diaphragm 21 to displace or remove contaminants and debris that may fall onto the DGL diaphragm 21. Specifically, the DGL 22 may include an airflow flowing downwards from the DGL diaphragm 21 to the substrate W. The DGL 22 may also include an airflow above the DGL diaphragm 21 to maintain pressure at a certain level.

[0027] DGL 22 and DGL diaphragm 21 can be located adjacent to the substrate stage WT (e.g., a location separating the substrate compartment from the projection system PS). Therefore, one side of DGL diaphragm 21 can face the projection system PS, and the other side can face the substrate W and substrate stage WT. DGL diaphragm 21 can prevent contamination of the substrate W by creating a physical barrier between the interior of the projection system PS and the area surrounding the substrate W and substrate stage WT. DGL can allow a patterned beam B' to pass through to reach the substrate W.

[0028] The DGL separator 21 can be fabricated in a variety of ways. For example, the DGL separator 21 can be fabricated by depositing multiple layers on a polycrystalline silicon core, wherein these layers are deposited (stacked) one at a time on top of each other. For example, the core film can be about 25 nm thick, while the multiple layers can each be about 2 nm to 4 nm thick. The multiple layers can include different functional layers, such as layers that can block and / or allow radiation of a predetermined wavelength range to pass through the separator. In some aspects, for example, the layers in the stack of the DGL separator 21 can include one or more capping layers containing an oxide barrier, and one or more suppression layers or active layers for a specific wavelength. In particular, the capping layer can be the outermost layer and can provide an oxide barrier for the inner layers.

[0029] Due to the nanometer-thickness of the DGL separator 21, it is potentially fragile and therefore prone to breakage. For example, in some applications, the expected lifespan of the DGL separator 21 is approximately six months, and it may need to be replaced due to performance degradation. Degradation of the DGL separator 21 can lead to various performance degradations in the lithography equipment. For instance, over time, degradation in EUV transmission rate loss and / or a decrease in EUV transmission uniformity may occur, which could affect target performance and machine yield. In more severe cases, the DGL separator 21 may degrade significantly enough to break. If the DGL separator 21 is allowed to degrade to the point of breakage, the physical barrier between the projection system PS and the substrate W will be lost, and contaminants from the projection system PS may reach and deposit on the substrate W, resulting in defects. The loss of the physical barrier may also allow contaminants from areas surrounding the substrate W (e.g., the wafer stage compartment) to flow in and contaminate the projection system PS. Furthermore, contaminants will diffuse in the area surrounding the substrate W. Consequently, the lithography equipment will have to be shut down and thoroughly cleaned, resulting in unnecessary downtime and maintenance costs.

[0030] While known systems exist to detect when the DGL diaphragm 21 ruptures, this may be too late to prevent contaminants from spreading to the area surrounding the substrate W. A conservative approach might be to establish a DGL diaphragm 21 replacement program, ensuring that the diaphragm 21 is replaced early enough to guarantee that it never deteriorates to a level where the risk of rupture becomes significant. However, this typically results in premature replacement of the DGL diaphragm 21, leading to increased hardware costs and unnecessary maintenance downtime.

[0031] As discovered by the inventors, the DGL diaphragm 21 can exhibit observable changes during operation of the photolithography equipment, making it possible to determine the level of degradation of the DGL diaphragm 21. Furthermore, the degree of degradation of the DGL diaphragm 21 can be used to determine whether the DGL diaphragm 21 is degraded or at or nearing the end of its lifespan and requires replacement. Therefore, the DGL diaphragm 21 can be safely used until it truly needs replacement without the risk of breakage.

[0032] When a new DGL diaphragm 21 is installed in a DGL 22, the DGL diaphragm 21 can be generally flat and smooth, or it can be in its nominal / resting position, without any power or pressure and ignoring the effects of gravity. During operation of the lithography apparatus, a pressure difference may exist across the DGL diaphragm 21. This pressure difference may cause the DGL diaphragm 21 to bulge, i.e., to take on a curved / dome shape. During different operations of the lithography apparatus, the pressure difference across the diaphragm 21 may vary in magnitude and / or direction, causing the DGL diaphragm 21 to bulge to varying degrees, either bulging into the projection system PS or bulging towards the substrate W. Even when the DGL diaphragm 21 is brand new, some degree of bulging of the DGL diaphragm 21 can be expected.

[0033] As the inventors have discovered, the DGL diaphragm 21 deteriorates with increasing usage time or cumulative exposure time to the patterned beam B'. This deterioration can be caused by a variety of factors. For example, repeated exposure to the patterned beam B', chemical reactions with gases present on both sides of the DGL diaphragm 21, and mechanical stress resulting from repeated changes in the pressure difference across the diaphragm 21 can all contribute to the deterioration of the DGL diaphragm 21. As the DGL diaphragm 21 deteriorates, it has been found that it may become less taut. Therefore, in the presence of a pressure difference, the DGL diaphragm 21 may exhibit a gradually increasing degree of bulging as deterioration progresses. This gradually increasing degree of bulging in the DGL diaphragm 21 can be considered a major effect observable as the DGL diaphragm 21 deteriorates.

[0034] As the inventors have discovered, in addition to or as a substitute for protrusions, the DGL diaphragm 21 may become wrinkled as degradation progresses. Furthermore, it has been found that the degree of wrinkling (qualitatively) may also be affected by the magnitude of the pressure difference across the diaphragm 21. Specifically, wrinkles or creases appear to be more likely to appear when the pressure difference across the diaphragm 21 is small or nonexistent, and the DGL diaphragm 21 may become less wrinkled as the pressure difference across the diaphragm 21 increases. This is thought to be because the pressure difference across the diaphragm 21 tends to stretch the DGL diaphragm 21, which in turn can more or less flatten the wrinkles.

[0035] Given the observable degradation effect of the DGL diaphragm 21 described above, the degradation level of the DGL diaphragm 21 can be measured.

[0036] like Figure 3 As shown, in an embodiment of the present invention, a monitoring subsystem 1 may be provided. The monitoring subsystem 1 can be used in a photolithography apparatus. As shown, the monitoring subsystem 1 may include a light source 11. The light source 11 may be configured to illuminate the DGL diaphragm 21. The light source 11 may be configured to emit visible light. For example, the light source 11 may be configured to emit light including light within a spectral band of 430 nm to 630 nm, or 480 nm to 580 nm, or 500 nm to 550 nm (such as 530 nm). It should be understood that, additionally or alternatively, the light source 11 may emit light outside the visible spectrum, such as infrared light. The light source 11 may employ an LED source or other suitable type of light generation technology.

[0037] As described above, the DGL diaphragm 21 can be disposed on the substrate W of the photolithography equipment. Figure 3 (not shown in the image) and the projection optics in the projection system PS ( Figure 3 (Not shown in the text)

[0038] The monitoring subsystem 1 may also include a photodetector 12. The photodetector 12 may be configured to measure light emitted from the light source 11 and reflected by the DGL diaphragm 21. The photodetector 12 may have a field of view 120. The photodetector 12 may be configured to measure the total power of the light incident on the field of view 120 of the photodetector 12.

[0039] Any type of light detector 12 can be used, as long as it is capable of measuring the total power of light incident on its field of view 120. Suitable light detection techniques include photodiodes, phototransistors, photoresistors, photomultiplier tubes, charge-coupled devices (CCDs), and complementary metal-oxide-semiconductor (CMOS) sensors. Furthermore, the light detector 12 may include focusing optics, such as one or more lenses and / or one or more apertures. For simplicity, the light detector 12 may be non-spatially resolved (i.e., the light detector does not have multiple pixels). Specifically, the light detector 12 may have a single voltage output representing a measurement of the total power of light incident on the field of view 120 of the light detector 12. It should be understood that spatially resolved light detectors (such as image sensors) may also be used so that pixel values ​​can be accumulated to provide a measurement of the total power of light incident on the field of view 120 of the light detector 12, but spatial resolution is not necessary for implementing certain embodiments of the invention.

[0040] Monitoring system 1 may also include controller 15 (see Figure 7The controller 15 can be configured to determine the degradation level of the DGL diaphragm 21. The controller 15 can determine the degradation level based at least in part on the measured total power of the light incident on the field of view 120 of the photodetector 12. The controller 15 can be placed anywhere within the lithography apparatus. The controller 15 can be placed within the atmospheric pressure region of the lithography apparatus. This may facilitate maintenance.

[0041] Light source 11 can operate at a known or predetermined power level. For example, controller 15 can control the power level of light source 11. Because the power level of light source 11 can be known or predetermined, the measured total power of the light incident on the field of view 120 of photodetector 12 can be compared with the power level of light source 11. The power level of light source 11 can also be assumed to be constant, so that the measured total power of the light incident on the field of view 120 of photodetector 12 can be used directly without comparison with the power level of light source 11. For example, the degradation level of DGL diaphragm 21 can be based at least in part on the absolute value of the measured total power of the light incident on the field of view 120 of photodetector 12.

[0042] like Figure 3 As shown, the light source 11 can be positioned to emit light toward the DGL diaphragm 21 at an incident angle θ. As illustrated, the incident angle θ can be measured from the normal to the DGL diaphragm 21. Specifically, the incident angle θ can be defined assuming the DGL diaphragm 21 is perfectly flat and smooth. The photodetector 12 can also be positioned accordingly to receive light reflected from the DGL diaphragm 21. The positioning of the light source 11 and the photodetector 12 (including the incident angle θ) can be selected based on the available space near the DGL 22 in the lithography apparatus. For example, the incident angle θ may be approximately 30°, 40°, 50°, or 60°. In one arrangement, the incident angle θ can be approximately 48°. The light source 11 and the photodetector 12 can be located on the same side of the DGL diaphragm 21. For example, the light source 11 and the photodetector 12 can be placed inside the projection system PS such that light from the light source 11 is incident on the side of the DGL diaphragm 21 facing inwards from the projection system PS. Alternatively, light sources 11 and 12 can be placed on opposite sides of the DGL diaphragm 21 (i.e., outside the projection system PS), such that light from light source 11 is incident on the side of the DGL diaphragm 21 facing the substrate W and the substrate stage WT.

[0043] exist Figure 3 In the diagram, the DGL diaphragm 21 is shown as smooth and flat, or in its nominal / resting position. Therefore, the DGL diaphragm 21 can function as a (partially reflective) flat mirror for light emitted by the light source 11. Figure 3As shown, the light emitted by the light source 11 can have a specific beam profile 110, such as a circular profile. The beam emitted by the light source 11 can be parallel, converging, or diverging. Therefore, as light is emitted from the light source 11, reflected by the DGL diaphragm 21, and travels toward the photodetector 12, the beam profile can change or remain constant. If the beam is parallel and the DGL diaphragm 21 is flat and smooth, the beam profile can always remain constant, such that the beam profile 119 at the photodetector 12 can be substantially the same as the beam profile 110 at the light source 11.

[0044] refer to Figure 4a When the DGL diaphragm 21' bulges towards the light source 11 and the photodetector 12, the size and / or shape of the beam profile 119' at the photodetector 12 may change. When the pressure on the side of the DGL diaphragm 21' facing the light source 11 and the photodetector 12 is lower than the pressure on the opposite side of the DGL diaphragm 21', the DGL diaphragm 21' may transform into a (partially reflective) convex mirror. The DGL diaphragm 21' may have a generally rectangular or elliptical shape. Therefore, when the DGL diaphragm 21' bulges under pressure differential, the DGL diaphragm 21' may exhibit different curvatures along the major and minor axes of its generally rectangular or elliptical shape. In particular, due to the generally rectangular or elliptical shape of the DGL diaphragm 21', the DGL diaphragm 21' may act as an astigmatic mirror, i.e., it may have unequal optical power in different directions. Therefore, as shown, after light from the light source 11 is reflected by the DGL diaphragm 21', the beam profile may become gradually distorted until the light reaches the detector 12. This is illustrated by beam profile 115' (immediately following reflection), beam profile 117' (approximately halfway between DGL diaphragm 21' and photodetector 12), and beam profile 119' (at photodetector 12). As shown, the beam profiles become increasingly elliptical. It should be understood that... Figure 4a The distortion of the bundle profile shown is only one of many possibilities; the actual distortion will depend on a variety of factors, including the geometry of the DGL diaphragm 21', the level of degradation, the instantaneous pressure difference, the angle of incidence θ, the material properties, and so on. The DGL diaphragm 21' may also degrade in a spatially non-uniform manner (and its mechanical properties may change) (e.g., the diaphragm and its mechanical properties may vary non-uniformly across its area), which may also lead to distortion.

[0045] In addition to beam profile distortion, the protrusions of the DGL diaphragm 21' can also cause the reflected beam to deflect. For example, when the DGL diaphragm 21 is flat and smooth or in its nominal / resting position (see...). Figure 3 The photodetector 12 can be positioned such that the beam profile 119 is centered relative to the field of view 120 of the photodetector 12; however, when the DGL diaphragm 21' bulges toward the light source 11 and the photodetector 12 (see...). Figure 4aThe beam profile 119' at photodetector 12 may deviate from the center of the field of view 120 of photodetector 12. Specifically, the beam profile 119' at photodetector 12 may be offset relative to the field of view 120 of photodetector 12 in the same direction as the protrusion of DGL diaphragm 21'. If the protrusion of DGL diaphragm 21' continues to increase, the beam offset may become so severe that the beam may completely deviate from the field of view 120 of photodetector 12. In cases where the protrusion of DGL diaphragm 21' is less pronounced, the beam profile 119' at photodetector 12 may partially fall within the field of view 120 of photodetector 12.

[0046] exist Figure 4a In the scenario shown, where the DGL diaphragm 21' bulges to become a convex mirror, the cross-sectional area of ​​the beam profile typically increases as light travels from the DGL diaphragm 21' toward the photodetector 12. Therefore, as the beam profile increases, the light intensity may decrease. This decrease in light intensity may translate into a reduction in the measured total power of the light incident on the field of view 120 of the photodetector 12. As mentioned above, beam deflection may result in less reflected beam falling into the field of view 120 of the photodetector 12, and thus may also lead to a reduction in the measured total power of the light incident on the field of view 120 of the photodetector 12.

[0047] As described above, it has been found that the degree of bulging of the DGL diaphragm 21' may increase with the degree of degradation of the DGL diaphragm 21'. Therefore, for a given pressure difference on opposite sides of the DGL diaphragm 21', the degree of bulging may be related to the degree of degradation, and the degree of bulging may affect the total power of the measured light incident on the field of view 120 of the photodetector 12.

[0048] Figure 4b The diagram illustrates a case of pressure reversal, where the pressure on the side of the DGL diaphragm 21'' facing the light source 11 and the photodetector 12 is greater than the pressure on the opposite side of the DGL diaphragm 21''. In this case, the DGL diaphragm 21'' may transform into a (partially reflective) concave mirror. As previously mentioned, if the DGL diaphragm 21'' has a generally rectangular / elliptical shape, it may behave as a concave mirror with different optical powers in different directions.

[0049] As shown, because the DGL diaphragm 21'' acts as a concave mirror, the beam reflected from the DGL diaphragm 21'' may converge (or diverge less than before reflection). For example, as shown, the beam profile 115'' immediately following reflection may be smaller than the original beam profile 110. When the bulge is slight, the beam profile may continue to decrease as the light travels from the DGL diaphragm 21'' toward the photodetector 12. In some cases, the beam may be sufficiently converged so that it falls entirely within the field of view 120 of the photodetector 12, and thus the total measured power of the light incident on the field of view 120 of the photodetector 12 may be maximum at that point.

[0050] However, as Figure 4b As shown, with increasing convexity, the beam may converge to a focal point before reaching the photodetector 12. As illustrated, at a certain distance from the DGL diaphragm 21'', the beam profile 116'' converges to a focal point in one direction. Beyond this point, the beam may diverge in one direction, causing the beam profile 117'' to become wider downstream of the optical path. By the time the light reaches the photodetector, the beam profile 119'' may have become wider than the field of view 120 of the photodetector 12. Simultaneously, due to astigmatism, the beam profile may remain convergent in another direction until it reaches the photodetector 12.

[0051] and Figure 4a As shown, when the DGL diaphragm 21'' becomes as... Figure 4b When using a concave mirror as shown, the reflected beam may also be deflected relative to the photodetector 12. As shown, the beam profile 119'' at the photodetector 12 may be deflected relative to the field of view 120 of the photodetector 12 in the same direction as the protrusion of the DGL diaphragm 21''.

[0052] Therefore, from such Figure 3 Starting with the flat and smooth DGL diaphragm 21 shown, the degree of bulging increases as... Figure 4b As the convexity increases in the indicated direction, it is expected that the total power of the light incident on the field of view 120 of the photodetector 12 may initially increase (slightly) or remain constant. However, as the convexity continues to increase, causing the focal point on at least one optical axis to move closer to the DGL diaphragm 21'', it is expected that the total power of the light incident on the field of view 120 of the photodetector 12 will decrease. Deflection of the reflected beam may also cause a decrease in the total power of the light incident on the field of view 120 of the photodetector 12.

[0053] As described above, the protrusions in the DGL diaphragm 21 are likely the primary observable effect of degradation, while secondary observable effects may arise from wrinkling of the DGL diaphragm 21. Wrinkles in the DGL diaphragm 21 can cause light scattering. Therefore, as the DGL diaphragm 21 becomes more wrinkled, the reflected beam may become more diffuse, and the reflected beam profile may become less sharp. It is expected that this may result in a reduction in the total power of the measured light incident on the field of view 120 of the photodetector 12.

[0054] It should be understood that while the effect of DGL diaphragm 21 degradation on the degree of protrusion and / or wrinkling can be qualitatively described, the precise behavior of DGL diaphragm 21 may depend on many factors, such as the geometry, size, pressure differential, temperature, and material properties of DGL diaphragm 21. Similarly, the precise effect of protrusion and / or wrinkling on the reflected beam, and therefore on the precise effect on the total power of the measured light incident on the field of view 120 of photodetector 12, may also depend on many factors that may be difficult to quantify. However, it is generally not necessary to model each of these effects according to first principles. Instead, the determination of the degradation level of DGL diaphragm 21 can be based on empirical relationships that can be established for the specific design of the lithography apparatus, the specific operating mechanism, and the properties of the DGL diaphragm 21 used, etc.

[0055] However, some general trends can be established. (Reference) Figure 5 As the DGL diaphragm 21 deteriorates over time due to changes in stress or material properties, in some embodiments, it is expected that the detector signal (i.e., the measured total power of the light incident on the field of view 120 of the photodetector 12) will generally decrease. For example, the detector signal may initially decrease steadily, and then decrease more sharply before the DGL diaphragm 21 breaks. Once the DGL diaphragm 21 breaks, it is expected that little or no light emitted by the light source 11 will reach the photodetector 12 because the DGL diaphragm 21 may no longer be present.

[0056] Specifically, through empirical measurements, it can be observed that the total power of the light incident on the field of view 120 of the photodetector 12 may drop to a specific low level before breaking. Therefore, as Figure 5As shown, a predetermined threshold can be defined to indicate that the DGL diaphragm 21 has deteriorated but not broken. Specifically, the predetermined threshold can be defined as a value higher than the detector signal level at the break point. Since the prediction of breakage can be statistically significant, if the predetermined threshold is defined too close to the detector signal level at the break point, the DGL diaphragm 21 may sometimes break before the detector signal drops below the predetermined threshold. However, to optimally utilize the lifetime of the DGL diaphragm 21, it is generally desirable to define the predetermined threshold close to the detector signal level at the break point. For example, one option for the predetermined threshold could be a balance between the maximum lifetime of the DGL diaphragm 21 and the risk of breakage of the DGL diaphragm 21 during operation of the lithography apparatus, or alternatively, a predetermined threshold such as one used to maintain a balance threshold during operation and minimize the risk of breakage at the expense of a shorter lifetime of the DGL diaphragm could be selected.

[0057] Given a predetermined threshold, controller 15 can be configured to compare the measured total power of light incident on the field of view 120 of photodetector 12 with the predetermined threshold. Specifically, controller 15 can be configured to indicate that the DGL diaphragm 21 has deteriorated when the measured total power of light incident on the field of view 120 of photodetector 12 drops below the predetermined threshold. Based on this indication, the operator of the lithography equipment can decide to shut down the lithography equipment and replace the DGL diaphragm 21.

[0058] While the present invention can help prevent the DGL diaphragm 21 from breaking, breakage can still occur in principle. For example, if an operator decides to continue manufacturing the device despite warnings that the DGL diaphragm 21 may deteriorate, the DGL diaphragm 21 may eventually break. Other unusual external conditions may also cause the DGL diaphragm 21 to break suddenly. Therefore, the controller 15 can be effectively configured to detect whether the DGL diaphragm 21 is intact or present, rather than detecting whether it is broken or absent. The controller 15 can do this similarly based on the measured total power of the light incident on the field of view of the photodetector 12. In particular, when the DGL diaphragm 21 is broken or completely absent, the photodetector 12 will pick up almost no light from the light source 11. Any light that is still picked up is typically light scattered near the light source 11 and the detector 12. Therefore, when the measured total power of the light incident on the field of view of the photodetector 12 is zero (or less than nominal zero), it can be concluded that the DGL diaphragm 21 has broken or is absent.

[0059] As described above, the degree of bulging and / or wrinkling of the DGL diaphragm 21 can depend not only on the degree of deterioration of the DGL diaphragm 21, but also on the pressure difference across the opposite sides of the DGL diaphragm at any given time. Therefore, the controller 15 can also be configured to adjust a predetermined threshold based on a measurement of the pressure difference across the two sides of the DGL diaphragm 21. For example, the controller 15 can store an empirical relationship between the predetermined threshold and the measured pressure difference across the two sides of the diaphragm 21.

[0060] The pressure difference across diaphragm 21 can be measured or obtained using any suitable method. For example, such as Figure 7 As shown, monitoring subsystem 1 may include pressure sensors 13 and 14 located on both sides of the DGL diaphragm 21, and the pressure difference can be obtained by subtracting the signals from pressure sensors 13 and 14. Alternatively, a single pressure sensor may be provided across the boundary between the interior of the projection system PS and the area surrounding the substrate W and the substrate stage WT, and the pressure difference across the diaphragm 21 can be directly determined based on the signal from this pressure sensor. It should be understood that monitoring subsystem 1 does not necessarily need to be as described above. Figure 7 The pressure sensor shown is a dedicated one. Instead, the pressure sensor can be shared with other subsystems of the lithography apparatus. Alternatively or additionally, the pressure difference across the diaphragm 21 can be obtained in ways other than real-time measurement. For example, the pressure difference for one or more states of the lithography apparatus can be known in advance, allowing the pressure difference to be inferred from the state of the lithography apparatus at any given time. The pressure difference in various states of the lithography apparatus can be measured during system verification (i.e., before the lithography apparatus is put into operation) using pressure sensors, or determined through flow modeling (e.g., during the design phase of the lithography apparatus). It should be understood that the pressure difference can be obtained through any one of real-time pressure measurement, pre-measurement, and flow modeling determination, or any combination of these methods.

[0061] Figure 6a and Figure 6b These are graphs of data points obtained from the functional model of monitoring subsystem 1. These graphs show the detector signal level (i.e., the measured total power of the light incident on the field of view 120 of photodetector 12) and various differential pressure values ​​across the diaphragm 21. Figure 6a and Figure 6b In each of these series, data series 31 was obtained using a brand new DGL diaphragm 21; data series 32 was obtained using a degraded DGL diaphragm 21; and data series 39 was obtained in the absence of a DGL diaphragm. As confirmed by experiments, the absence of the DGL diaphragm 21 is an accurate representation of a ruptured DGL diaphragm 21. Figure 6b It shows the relationship with Figure 6a The same data, but amplified to the pressure difference between -10 Pa and +10 Pa. Figure 6a and Figure 6b According to the definition, when the DGL diaphragm 21' bulges into a convex mirror, the pressure difference is positive, and when the DGL diaphragm 21'' bulges into a concave mirror, the pressure difference is negative.

[0062] like Figure 6a As shown, when the DGL diaphragm 21 is brand new and substantially wrinkle-free, the detector signal decreases as the differential pressure increases from 0 Pa to 150 Pa and above. When the differential pressure decreases from 0 Pa to -150 Pa, the detector signal is observed to remain approximately constant at approximately -35 Pa and then decrease. As shown in data series 32, when the DGL diaphragm 21 deteriorates, the detector signal is lower than that of a brand new DGL diaphragm across all differential pressure values. In this example, the predetermined threshold mentioned above can be set according to data series 32 and can also be adjusted as a function of the differential pressure according to data series 32. That is, the controller 15 can continuously monitor the detector signal and the differential pressure, and if the detector signal drops below data series 32 at an instantaneous differential pressure value, the controller can indicate that the DGL diaphragm 21 has deteriorated.

[0063] like Figure 6b As shown, a local minimum is observed in data series 32 at zero differential pressure. This is thought to be caused by wrinkles in the DGL diaphragm 21. When no differential pressure acts on the DGL diaphragm 21, there is no force to flatten the wrinkles. As the magnitude of the differential pressure increases (regardless of direction), it can be assumed that the wrinkles will gradually flatten, causing the detector signal to initially increase when the differential pressure changes away from zero. It can be seen that, apart from the local minimum observed at zero differential pressure, data series 32 follows the general shape of data series 31, except that data series 32 is offset downwards. For completeness, it can be seen from data series 39 that the detector signal is practically zero when the DGL diaphragm is missing / ruptured.

[0064] The light source 11 and the photodetector 12 can be configured such that, when the DGL diaphragm is smooth and flat, or when the DGL diaphragm is in its nominal / rest position, the light incident on the photodetector 12 has a spot size comparable to the field of view 120 of the photodetector 12. The spot size can be larger than or slightly larger than the field of view 120 of the photodetector 12, such as... Figure 3 The bundle profile 119 is shown in the figure.

[0065] In addition to monitoring subsystem 1, this disclosure also envisions a lithography apparatus including monitoring subsystem 1. This disclosure also envisions a method for monitoring the condition of the DGL diaphragm 21 using the above-described technology, and a method for manufacturing a device including the method for monitoring the DGL diaphragm 21. This disclosure also envisions a method for manufacturing a device using the above-described lithography apparatus.

[0066] While specific reference may be made herein to the use of lithography equipment in IC manufacturing, it should be understood that the lithography equipment described herein may have other applications, such as fabricating integrated optical systems, guiding and detecting patterns for magnetic domain memory, flat panel displays, liquid crystal displays (LCDs), thin-film magnetic heads, etc. Those skilled in the art will understand that in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered synonymous with the more general terms “substrate” or “target portion,” respectively. The substrates mentioned herein may be processed before or after exposure in, for example, tracks (typically tools for applying a resist layer to the substrate and developing the resist after exposure), metrology tools, and / or inspection tools. Where applicable, the disclosure herein may be applied to these and other substrate processing tools. Furthermore, the substrate may be processed more than once, for example, to form a multilayer IC, such that the term “substrate” as used herein may also refer to a substrate that already contains one or more processed layers.

[0067] Although the use of embodiments of the invention may have been specifically referenced above in the context of optical lithography, it should be understood that the invention can be used in other applications.

[0068] The aspects of the present invention are described in the following numbered items. 1. A monitoring subsystem for monitoring a diaphragm used in a photolithography apparatus, the monitoring subsystem comprising: A light source configured to irradiate the diaphragm, the diaphragm being disposed between a first region and a second region of the photolithography apparatus; A photodetector configured to measure the total power of light incident on the field of view of the photodetector, the light being emitted from the light source and reflected by the diaphragm; and A controller configured to determine the level of degradation of the diaphragm based at least in part on the measured total power of light incident on the field of view of the photodetector. 2. The subsystem according to item 1, wherein the first region is configured to include a substrate, the second region includes projection optics of the lithography apparatus, and the diaphragm is a dynamic gas lock (DGL) diaphragm. 3. The subsystem according to clause 1 or clause 2, wherein the light source is configured to emit visible light. 4. The subsystem according to clause 1 or clause 2, wherein the light source is configured to emit light, the light comprising light in a spectral band of 430 nm to 630 nm, or 480 nm to 580 nm, or 500 nm to 550 nm. 5. The subsystem according to any one of the preceding clauses, wherein the controller is configured to compare the measured total power of light incident on the field of view of the photodetector with a predetermined threshold indicating that the diaphragm has deteriorated but not broken. 6. The subsystem according to item 5, wherein the controller is configured to indicate that the diaphragm has deteriorated when the total power of the measured light incident on the field of view of the photodetector drops below the predetermined threshold. 7. The subsystem according to item 5, wherein the controller is configured to adjust the predetermined threshold based on a measurement of the pressure difference between the two sides of the diaphragm. 8. The subsystem according to any one of the preceding clauses, wherein the controller is configured to determine, at least in part, i) whether the diaphragm is intact or present, or ii) whether the diaphragm is broken or absent, based on the measured total power of light incident on the field of view of the photodetector. 9. The subsystem according to any one of the preceding clauses, wherein the photodetector includes a light-collecting optics. 10. The subsystem according to any one of the preceding clauses, wherein the photodetector is non-spatial resolved. 11. The subsystem according to any one of the preceding clauses, wherein the photodetector has a single voltage output representing a measurement of the total power of light incident on the field of view of the photodetector. 12. The subsystem according to any one of the preceding clauses, wherein when the diaphragm is smooth and flat, the spot size of the light incident on the photodetector is larger than the field of view of the photodetector. 13. A lithography apparatus comprising a subsystem according to any one of the preceding clauses. 14. A method comprising: The diaphragm positioned between the first and second regions of the photolithography equipment is illuminated using a light source. Measure the total power of light incident on the field of view of the photodetector, said light being emitted from the light source and reflected by the diaphragm; and The level of degradation of the diaphragm is determined at least in part based on the measured total power of the light incident on the field of view of the photodetector. 15. The method according to clause 13, wherein the first region is configured to include a substrate, the second region includes projection optics of the lithography apparatus, and the diaphragm is a dynamic gas lock (DGL) diaphragm. 16. The method according to clause 14 or clause 15, wherein the light source emits visible light. 17. The method according to clause 14 or clause 15, wherein the light source emits light, the light comprising light in a spectral band of 430 nm to 630 nm, or 480 nm to 580 nm, or 500 nm to 550 nm. 18. The method according to any one of clauses 14 to 17 further comprises comparing the total power of the light incident on the field of view of the photodetector with a predetermined threshold indicating that the diaphragm has deteriorated but not broken. 19. The method according to clause 18, further comprising indicating that the diaphragm has deteriorated when the total power of the measured light incident on the field of view of the photodetector drops below the predetermined threshold. 20. The method according to clause 19 further includes adjusting the predetermined threshold based on a measurement of the pressure difference between the two sides of the diaphragm. 21. The method according to any one of clauses 14 to 20 further comprises determining, at least in part, i) whether the diaphragm is intact or present, or ii) whether the diaphragm is broken or absent, based on a measurement of the total power of light incident on the field of view of the photodetector. 22. The method according to any one of clauses 14 to 21, wherein the photodetector has a single voltage output representing a measurement of the total power of light incident on the field of view of the photodetector. 23. The method according to any one of clauses 14 to 22, wherein when the diaphragm is smooth and flat, the spot size of the light incident on the photodetector is larger than the field of view of the photodetector. 24. A method of manufacturing a device, the method comprising the method according to any one of claims 12 to 19. 25. A method for manufacturing a device using the photolithography apparatus according to clause 11.

[0069] Although specific embodiments of the invention have been described above, it will be understood that the invention may be practiced in ways other than those described.

[0070] The above description is intended to be illustrative and not restrictive. Therefore, it will be apparent to those skilled in the art that modifications can be made to the described invention without departing from the scope of the claims set forth below.

Claims

1. A monitoring subsystem for monitoring a diaphragm used in a photolithography apparatus, the monitoring subsystem comprising: A light source configured to irradiate the diaphragm, the diaphragm being disposed between a first region and a second region of the photolithography apparatus; A photodetector configured to measure the total power of light incident on the field of view of the photodetector, the light being emitted from the light source and reflected by the diaphragm; and A controller configured to determine the level of degradation of the diaphragm based at least in part on the measured total power of light incident on the field of view of the photodetector.

2. The subsystem of claim 1, wherein a) the first region is configured to include a substrate, the second region includes projection optics of the lithography apparatus, and the diaphragm is a dynamic gas lock (DGL) diaphragm, and / or b) the first region is configured to include a pattern forming apparatus, the second region includes projection optics of the lithography apparatus, and the diaphragm is a surface film.

3. The subsystem according to claim 1 or claim 2, wherein the light source is configured to emit visible light.

4. The subsystem according to claim 1 or claim 2, wherein the light source is configured to emit light, the light comprising light within a spectral band of 430 nm to 630 nm, or 480 nm to 580 nm, or 500 nm to 550 nm.

5. The subsystem according to any one of the preceding claims, wherein the controller is configured to compare the measured total power of light incident on the field of view of the photodetector with a predetermined threshold indicating that the diaphragm has deteriorated but not broken.

6. The subsystem of claim 5, wherein the controller is configured to indicate that the diaphragm has deteriorated when the total power of the measured light incident on the field of view of the photodetector drops below the predetermined threshold.

7. The subsystem of claim 5, wherein the controller is configured to adjust the predetermined threshold based on a measurement of the pressure difference between the two sides of the diaphragm.

8. The subsystem according to any one of the preceding claims, wherein the controller is configured to determine, at least in part, i) whether the diaphragm is intact or present, or ii) whether the diaphragm is broken or absent, based on the measured total power of light incident on the field of view of the photodetector.

9. The subsystem according to any one of the preceding claims, wherein the photodetector comprises a light-collecting optics.

10. The subsystem according to any one of the preceding claims, wherein the photodetector is non-spatial resolved.

11. The subsystem according to any one of the preceding claims, wherein the photodetector has a single voltage output representing a measurement of the total power of light incident on the field of view of the photodetector.

12. The subsystem according to any one of the preceding claims, wherein when the diaphragm is smooth and flat, the spot size of the light incident on the photodetector is larger than the field of view of the photodetector.

13. A lithography apparatus, the lithography apparatus comprising a subsystem according to any one of the preceding claims.

14. A method, the method comprising: The diaphragm positioned between the first and second regions of the photolithography equipment is illuminated using a light source. The total power of light incident on the field of view of the photodetector, the light being emitted from the light source and reflected by the diaphragm, is measured. as well as The level of degradation of the diaphragm is determined at least in part based on the measured total power of the light incident on the field of view of the photodetector.

15. The method of claim 13, wherein a) the first region is configured to include a substrate, the second region includes projection optics of the lithography apparatus, and the diaphragm is a dynamic gas-lock (DGL) diaphragm, and / or b) the first region is configured to include pattern forming apparatus, the second region includes projection optics of the lithography apparatus, and the diaphragm is a surface film.

16. The method of claim 14 or claim 15, wherein the light source emits visible light.

17. The method of claim 14 or claim 15, wherein the light source emits light, the light comprising light within a spectral band of 430 nm to 630 nm, or 480 nm to 580 nm, or 500 nm to 550 nm.

18. The method according to any one of claims 14 to 17, further comprising comparing the total power of the light incident on the field of view of the photodetector with a predetermined threshold indicating that the diaphragm has deteriorated but not broken.

19. The method of claim 18, further comprising indicating that the diaphragm has deteriorated when the total power of the measured light incident on the field of view of the photodetector drops below the predetermined threshold.

20. The method of claim 19, further comprising adjusting the predetermined threshold based on a measurement of the pressure difference between the two sides of the diaphragm.

21. The method according to any one of claims 14 to 20, further comprising determining, at least in part, i) whether the diaphragm is intact or present, or ii) whether the diaphragm is broken or absent, based on a measurement of the total power of light incident on the field of view of the photodetector.

22. The method according to any one of claims 14 to 21, wherein the photodetector has a single voltage output representing a measurement of the total power of light incident on the field of view of the photodetector.

23. The method according to any one of claims 14 to 22, wherein when the diaphragm is smooth and flat, the spot size of the light incident on the photodetector is larger than the field of view of the photodetector.

24. A method of manufacturing a device, the method comprising the method according to any one of claims 12 to 19.

25. A method for manufacturing a device using the photolithography apparatus according to claim 11.

Images