Methods for changing etching parameters

Abstract

A method for changing an etching parameter of a substrate etching process, the method comprising: performing a first measurement of a first metric related to a structure on the substrate before etching; performing a second measurement of a second metric related to the structure on the substrate after etching; and changing the etching parameter based on a difference between the first measurement and the second measurement.

Description

[0001] This application is a divisional application of the international application PCT / EP2017 / 078288, which entered the Chinese national phase on November 6, 2017, with application number 201780074864.X and invention name “Method for changing etching parameters”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of European application No. 16201848.5 filed on December 2, 2016 and European application No. 17181816.4 filed on July 18, 2017, which are hereby incorporated by reference in their entirety. Technical Field

[0004] The present invention relates to a method for a photolithography process, in particular to a method for changing etching parameters of a substrate etching process. The present invention also relates to a computer program product for implementing a part of the method. Background Art

[0005] A lithographic apparatus is a machine that applies a desired pattern to a substrate, typically to a target portion of the substrate. For example, a lithographic apparatus may be used in the manufacture of integrated circuits (ICs). In this case, a pattern forming device, alternatively referred to as a mask or reticle, may be used to generate a circuit pattern to be formed on a single layer of the IC. The pattern may be transferred to a target portion (e.g., including a portion of a die, one or several dies) on a substrate (e.g., a silicon wafer). The transfer of the pattern is typically performed by imaging the pattern onto a layer of radiation-sensitive material (resist) disposed on the substrate. Typically, a single substrate will include a network of adjacent target portions that are patterned successively. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing the entire pattern to the target portion at once; and so-called scanners, in which each target portion is irradiated by scanning the pattern with a radiation beam in a given direction (the "scanning" direction) while simultaneously scanning the substrate in a direction parallel or antiparallel to the direction.

[0006] A key performance parameter of the lithography process is the overlay error. This error (often simply referred to as "overlay") is the error in placing product features in the correct location relative to features formed in the previous layer. As device structures become smaller, overlay specifications become more and more stringent.

[0007] Overlay errors may be introduced in one or more of the several stages of the development of the structure on the substrate. For example, overlay errors may be introduced during irradiation in the lithographic apparatus by misalignment of the substrate in the lithographic apparatus. Overlay errors may also be introduced in steps after irradiation, such as in an etching step.

[0008] Metrology tools can be used to measure overlay errors on a substrate. If overlay errors are detected before etching and / or depositing other layers on a substrate, metrology tools that measure overlay errors in a non-destructive manner (e.g., metrology tools based on diffraction measurements) allow reworking of the substrate.

[0009] Etching performed by modern etching equipment allows one or more etching parameters to be set to control various aspects of the etching. Trial and error methods can be used to set the best etching parameters for a given situation. Summary of the invention

[0010] The present invention aims to reduce the overlap introduced by etching by providing a method of changing etching parameters of a substrate etching process.

[0011] According to one aspect of the present invention, a method for changing etching parameters of a substrate etching process is provided, the method comprising: performing a first measurement of a first metric related to a structure on the substrate before etching; performing a second measurement of a second metric related to the structure on the substrate after etching; and changing the etching parameters based on a difference between the first measurement and the second measurement, wherein the first metric and the second metric are metrics representing one or more of the following: an overlay error between two or more layers on the substrate, a placement error of an edge of a feature of one layer of the substrate relative to an edge of a feature of another layer of the substrate, an asymmetry in a property of a feature measured at one or more locations on the substrate.

[0012] According to one aspect of the present invention, a method for controlling etching parameters of a substrate etching process is provided, the method comprising: providing a relationship between a first variable representing an effect introduced by etching and the etching parameter; determining an initial value of the etching parameter; performing the substrate etching process on a first group of substrates using the initial value of the etching parameter; and determining an actual first variable with respect to a substrate in the first group of substrates, and changing the etching parameter of the substrate etching process for subsequent substrates by an amount predicted by the relationship to result in a desired substrate etching process.

[0013] According to one aspect of the present invention, a method for changing etching parameters of a substrate etching process is provided, the method comprising: measuring an etched structure on a substrate; and changing the etching parameters based on asymmetry in a result of the measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

[0015] Figure 1 depicts a lithographic apparatus configured to operate according to an embodiment of the present invention;

[0016] Figure 2 Schematically depicts Figure 1 The lithographic apparatus is used together with other equipment constituting a production facility for semiconductor devices;

[0017] Figure 3 The sources of etching-induced overlay errors are schematically shown;

[0018] Figure 4 On the right hand side the difference between a first measurement made before etching (left hand side) and a second measurement made after etching (center) is shown;

[0019] Figure 5 A perspective view schematically showing etching parameters that may be varied according to the present invention;

[0020] Figure 6 On the left hand side is shown a model of overlay error on the y-axis as a function of distance from the substrate edge along the x-axis, and on the right hand side is shown the relationship between variables associated with the model on the y-axis and etching parameters plotted on the x-axis;

[0021] Figure 7 On the left hand side is shown a plan view of a plot of the associated overlay error versus distance before changing the etching parameters, and on the right hand side is shown the same measurement after changing the etching parameters; and

[0022] Figure 8 Examples of measurement layouts and distributions are shown. DETAILED DESCRIPTION

[0023] Before describing the embodiments of the present invention in detail, it is instructive to provide an example environment in which the embodiments of the present invention may be implemented.

[0024] Figure 1 A lithographic apparatus LA is schematically depicted. The lithographic apparatus comprises:

[0025] an illumination system (illuminator) IL configured to condition a radiation beam B (e.g., ultraviolet (UV) radiation or extreme ultraviolet (EUV) radiation);

[0026] a support structure (e.g., mask table) MT configured to support a patterning device (e.g., mask or reticle) MA and connected to a first positioner PM configured to accurately position the patterning device according to specific parameters;

[0027] a substrate table (eg, wafer stage) WT configured to hold a substrate (eg, a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate according to specific parameters; and

[0028] A projection system PS, eg a refractive projection lens system, is configured to project the pattern imparted to the radiation beam B by the patterning device MA onto a target portion C of the substrate W (eg comprising one or more dies).

[0029] The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, to direct, shape, or control the radiation.

[0030] The support structure supports the patterning device, i.e. bears the weight of the patterning device. The support structure holds the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions such as, for example, whether the patterning device is held in a vacuum environment. The support structure can ensure that the patterning device is in a desired position (e.g. relative to a projection system). Any use of the terms "reticle" or "mask" herein may be considered synonymous with the more general term "patterning device".

[0031] The term "patterning device" as used herein should be broadly understood to mean any device that can be used to impart a pattern to a radiation beam in its cross-section so as to produce a pattern on a target portion of a substrate. It should be noted that the pattern imparted to the radiation beam may not completely correspond to the desired pattern on the target portion of the substrate (for example if the pattern includes phase-shifting features or so-called auxiliary features). Typically, the pattern imparted to the radiation beam will correspond to a specific functional layer in a device (or many devices) formed on the target portion, such as an integrated circuit. The patterning device can be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels.

[0032] The term "projection system" as used herein should be broadly interpreted as including any type of projection system, which may include refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate to the exposure radiation used, or to other factors such as the use of immersion liquid or the use of a vacuum. Any use of the term "projection lens" herein may be considered synonymous with the more general term "projection system".

[0033] As depicted here, the device is transmissive (eg, employing a transmissive mask). Alternatively, the device may be reflective (eg, employing a programmable mirror array of the type described above, or employing a reflective mask).

[0034] The lithographic apparatus may be of a type having two ("dual stage") or more substrate tables (and / or two or more mask tables). In such a "multi-stage" machine, the extra tables may be used in parallel, or preparatory steps may be carried out on one or more tables while one or more other tables are being used for exposure.

[0035] The lithographic apparatus may also be of a type in which at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, such as water, so as to fill the space between the projection system and the substrate. Immersion liquid may also be applied to other spaces in the lithographic apparatus, such as between the mask and the projection system. It is well known in the art that immersion techniques can be used to increase the numerical aperture of the projection system. The term "immersion" as used herein does not mean that the structure (such as the substrate) must be immersed in the liquid, but rather "immersion" only means that the liquid is located between the projection system and the substrate during the exposure process.

[0036] An illuminator IL receives a radiation beam from a radiation source SO. The radiation source and the lithographic apparatus may be separate entities (for example when the source is an excimer laser). In this case, the source is not considered to form part of the lithographic apparatus, and the radiation beam is transferred from the source SO to the illuminator IL with the aid of a beam delivery system BD comprising, for example, suitable directional mirrors and / or a beam expander. In other cases, the source may be an integral part of the lithographic apparatus (for example when the source is a mercury lamp). The source SO and the illuminator IL, and the beam delivery system BD provided if necessary, may be referred to together as a radiation system.

[0037] The illuminator IL may comprise an adjuster AD for adjusting the angular intensity distribution of the radiation beam. Typically, at least the outer and / or inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in a pupil plane of the illuminator may be adjusted. Furthermore, the illuminator IL may comprise various other components, such as an integrator IN and a condenser CO. The illuminator may be used to condition the radiation beam to have a desired uniformity and intensity distribution in its cross-section.

[0038] The radiation beam B is incident on the patterning device (e.g. mask MA) held on a support structure (e.g. mask table MT) and is patterned by the patterning device. After having passed through the mask MA, the radiation beam B passes through a projection system PS which focuses the beam onto a target portion C of the substrate W. With the aid of a second positioner PW and a position sensor IF (e.g. interferometer device, linear encoder or capacitive sensor), the substrate table WT can be accurately moved, for example in order to position different target portions C in the path of the radiation beam B. Similarly, the first positioner PM and a further position sensor ( Figure 1 The first positioner PM is a first positioner (not explicitly shown) for accurately positioning the mask MA relative to the path of the radiation beam B. Typically, movement of the mask table MT can be achieved with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning) forming part of the first positioner PM. Similarly, movement of the substrate table WT can be achieved using a long-stroke module and a short-stroke module forming part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the mask table MT may be connected only to a short-stroke actuator, or may be fixed. Mask MA and substrate W may be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks shown occupy dedicated target portions, they may be located in the space between target portions (fields) and / or between device areas (die) within a target portion. These are known as scribing alignment marks because individual product dies will eventually be cut from each other by scribing along these lines. Similarly, in the case where more than one die is set on the mask MA, the mask alignment marks may be located between the dies.

[0039] The depicted device can be used in at least one of the following modes:

[0040] 1. In step mode, the mask table MT and the substrate table WT are held substantially stationary while an entire pattern imparted to the radiation beam is projected at once onto a target portion C (i.e. a single static exposure). The substrate table WT is then shifted in the X and / or Y direction so that a different target portion C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure.

[0041] 2. In scan mode, the mask table MT and substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (i.e. a single dynamic exposure). The speed and direction of the substrate table WT relative to the mask table MT may be determined by the (de-)magnification and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width of the target portion in a single dynamic exposure (in the non-scanning direction), while the length of the scanning movement determines the height of the target portion (in the scanning direction).

[0042] 3. In another mode, the mask table MT holding the programmable patterning device is held substantially stationary and the substrate table WT is moved or scanned whilst a pattern imparted to the radiation beam is projected onto a target portion C. In this mode, a pulsed radiation source is typically employed and the programmable patterning device is updated as required after each movement of the substrate table WT or between successive radiation pulses during a scan. This mode of operation may be readily applicable to maskless lithography using a programmable patterning device, such as a programmable mirror array of the type described above.

[0043] Combinations and / or variations on the above described modes of use, or entirely different modes of use, may also be employed.

[0044] In this example, the lithographic apparatus LA is of a so-called dual-platform type having two substrate tables WTa, WTb and two stations - an exposure station and a measuring station - between which the substrate tables can be exchanged. While one substrate on one substrate table is being exposed at the exposure station EXP, another substrate is loaded onto another substrate table at the measuring station MEA so that various preparatory steps can be performed. The preparatory steps may include mapping the surface height of the substrate using a height sensor LS and measuring the position of alignment marks on the substrate using an alignment sensor AS. The measurement is time-consuming and the provision of two substrate tables achieves a substantial increase in the throughput of the apparatus. If the position sensor IF cannot measure the position of the substrate table when the substrate table is at the measuring station and at the exposure station, a second position sensor may be provided to track the position of the substrate table at the two stations.

[0045] The device also includes a lithographic device control unit LACU 206 that controls all movements and measurements of the various actuators and sensors described. LACU also includes signal processing and data processing capabilities for implementing the desired calculations associated with the operation of the device. In practice, the control unit LACU will be implemented as a system of many subunits, each of which handles real-time data acquisition, processing and control of subsystems or components within the device. For example, a processing subsystem can be dedicated to the servo control of a substrate positioner PW. Separate units can handle rough and precise actuators, or different axes. Another unit may be dedicated to the readout of a position sensor IF. The overall control of the device can be controlled by a central processing unit, which communicates with these subsystem processing units, communicates with an operator, and communicates with other devices involved in the lithographic manufacturing process.

[0046] Figure 2 At 200 is shown a lithographic apparatus LA in the context of an industrial production facility for semiconductor products. Within the lithographic apparatus (or "lithography tool" 200 for short), a measurement station MEA is shown at 202 and an exposure station EXP is shown at 204. A control unit LACU is shown at 206. Within the production facility, the apparatus 200 forms part of a "lithography cell" or "lithography cluster" which also contains a coating apparatus 208 for applying photoresist and other coatings to substrates W for patterning or forming patterns by the apparatus 200. At the output side of the apparatus 200, a baking apparatus 210 and a developing apparatus 212 are provided for developing the exposed pattern into a physical resist pattern.

[0047] Once the pattern has been applied and developed, the patterned substrate 220 is transferred to other processing equipment such as shown at 222, 224, and 226. Various processing steps are implemented by various equipment in a typical manufacturing facility. In this embodiment, equipment 222 is an etching station, and equipment 224 performs post-etching cleaning and / or annealing steps. Additional physical and / or chemical processing steps are applied in additional equipment 226, etc. Many types of operations may be required to manufacture real devices, such as material deposition, modification of surface material properties (oxidation, doping, ion implantation, etc.), chemical mechanical polishing (CMP), etc. In fact, equipment 226 can represent a series of different processing steps performed in one or more equipment.

[0048] As is well known, the manufacture of semiconductor devices involves many repetitions of such processing to build up device structures with appropriate materials and patterns layer by layer on a substrate. Thus, the substrates 230 arriving at the lithography cluster may be newly prepared substrates, or they may be substrates that have been previously processed in the cluster or in another device entirely. Similarly, depending on the processing required, substrates 232 leaving device 226 may be returned for subsequent patterning operations in the same lithography cluster, they may be designated for patterning operations in a different cluster, or they may be finished products (substrates 234) to be sent for slicing and packaging.

[0049] Each layer of the product structure requires a different set of process steps, and the type of equipment 226 used at each layer can be completely different. In addition, different layers require different etching processes, such as chemical etching, plasma etching, depending on the details of the material to be etched and specific requirements (such as, for example, anisotropic etching).

[0050] The previous and / or subsequent processes may be performed in other lithographic equipment (as just mentioned), and may be performed in different types of lithographic equipment. For example, some layers in the device manufacturing process that are very demanding on parameters such as resolution and overlay may be performed in more advanced lithographic tools than other layers that are less demanding. Thus, some layers may be exposed in an immersion type lithographic tool, while other layers are exposed in a "dry" tool. Some layers may be exposed in a tool operating at a DUV wavelength, while other layers are exposed by using EUV wavelength radiation.

[0051] The entire facility may be operated under the control of a supervisory control system 238, which receives metrology data, design data, process recipes, and the like. The supervisory control system 238 sends commands to each of the equipment to perform a manufacturing process on one or more batches of substrates.

[0052] Figure 2Also shown is a metrology device 240, which is arranged to measure product parameters at desired stages in the manufacturing process. A common example of a metrology device in a modern lithography production facility is a scatterometer, such as an angle-resolved scatterometer or a spectral scatterometer, and which can be applied to measure the properties of the developed substrate at 220 before etching in the device 222. By using the metrology device 240, it can be determined that important performance parameters such as overlay or critical dimension (CD) do not meet the accuracy requirements specified in the developed resist. Prior to the etching step, there is an opportunity to strip the developed resist and reprocess the substrate 220 by the lithography cluster. In addition, as is well known, the measurement results 242 from the device 240 can be used in an advanced process control (APC) system 250 to generate a signal 252 to maintain accurate performance of the patterning operation in the lithography cluster by making small adjustments over time through the control unit LACU 206, thereby minimizing the risk of manufacturing defective products and requiring rework. The metrology equipment 240 and / or other metrology equipment (not shown) may be employed to measure properties of the processed substrates 232 , 234 and the incoming substrate 230 .

[0053] Advanced process control (APC) system 250 can be configured to calibrate a single lithography device and allow different devices to be used more interchangeably. Recently, improvements in the focus and overlap (layer-to-layer or layer-by-layer alignment) of the device have been achieved by implementing a stability module, resulting in an optimized process window for a given feature size and chip application, and enabling the continued production of smaller and more advanced chips. In one embodiment, the stability module automatically resets the system to a predefined baseline regularly (e.g., every day). More details of lithography and measurement methods including stability modules can be found in US2012008127A1. A known exemplary APC system implements three main process control loops. The first loop provides local control of the lithography device by using a stability module and a monitoring wafer. The second APC loop is used for local scanner control on the product (determining the focus, dose, and overlap on the product wafer).

[0054] The etching controller 223 is configured to input at least one etching parameter into the etching station 222. The at least one etching parameter may be one or more of the following: a desired thermal pattern across the substrate, a desired chemical concentration pattern in the plasma used in the etching process, a desired electric field pattern around the substrate during the etching process, a voltage applied to one or more electrodes during the etching process. Each of these etching parameters may be varied so as to vary the etching direction and / or etching rate and / or another etching factor in a position-dependent manner. By varying at least one of the etching parameters, the etching process may be optimized to reduce or eliminate any overlay errors and / or target and / or alignment mark asymmetries introduced during the etching process.

[0055] Figure 3 Shown is how the etching process may introduce overlay errors. Figure 3 It is specifically shown how an overlay error may be introduced at the edge of the substrate. However, the etching process may introduce an overlay error over the entire substrate or in areas other than or in addition to the edge region of the substrate. The overlay error may be introduced by the etching process in an asymmetric manner.

[0056] like Figure 3 As shown in the upper left side of , the substrate 220 typically includes a lower layer 310 with a pattern embedded therein. One or more device layers 320 are applied on top of the lower layer 310. Before applying the photoresist layer 340, one or more other layers 330 may be applied, on which the pattern is irradiated by the device 200 and developed into a physical resist pattern by the developing device 212. As shown, there is no overlay error between the physical resist pattern and the pattern in the lower layer 310.

[0057] In the etching station 222, a chemical substance such as a plasma etches the device layer 320 and any other layers 330 in the gaps in the physical resist pattern of the photoresist layer 340. Figure 3 As shown in the top center of , if the etching direction, as indicated by arrow 350, is not completely perpendicular to the top surface of substrate 220, layers 320, 330 are not etched as rectangles, but are etched as parallelograms. The parallelograms correspond in position to the physical resist pattern at their upper ends, but the parallelograms do not match the pattern of lower layer 310 at their lower ends, although there is no overlay error between the physical resist pattern and the pattern in lower layer 310. Therefore, when layers 330, 340 are removed (by further equipment 226) to obtain a final substrate 234 or substrate 232 for application of further layers, an overlay error is introduced between the pattern in lower layer 310 and the pattern etched in device layer 320, as shown in FIG. Figure 3 is shown in the right-hand side view.

[0058] Therefore, in Figure 3 The overlay shown on the right hand side of FIG. 3 is the overlay error introduced by the etching station 222, which would not exist if the etching direction 350 was completely perpendicular to the top surface of the substrate 220. Figure 3 The middle lower view in FIG. 3 shows how an imperfect etching direction 350 may be introduced. For example, at the edge of substrate 220, the electric field 360 used during the etching process may change from being perfectly vertical at the surface of substrate 220 (which is located at the center of substrate 220) to being angled relative to the vertical direction of the top surface of substrate 220 at the edge of substrate 220.

[0059] One etching parameter that may be varied to change the direction of the electric field (and thus the etching direction 350) is the voltage that may be applied to the electrodes around the outer edge of the substrate 220 (see Figure 5 1 and the related description below). This voltage is an example of an etching parameter that can be varied to change the etching process (i.e., the etching direction 350 at the outer edge of the substrate 220) to reduce the overlay error. For example, similar concepts are disclosed in US6,767,844, which relates to a temperature controlled focus ring around a substrate during etching, and in US2006 / 0016561, which discloses an edge ring member for achieving a uniform etching rate across the entire surface of a substrate.

[0060] Other causes of etching-induced overlay errors may include local variations in the concentration of chemical etchants over the surface of substrate 220 during etching, thermal patterns present in substrate 220 during etching, etc. By varying etching parameters, variations in the etching direction over the surface of substrate 220 can be reduced or eliminated. The present invention provides a way to adjust or change etching parameters, thereby reducing etching-induced overlay errors.

[0061] The present invention aims to strongly reduce (or even eliminate) the contribution of etching on the overlay error (asymmetry and / or displacement) by optimizing at least one etching parameter in the etching station 222. The idea is to use a plot of the difference between the measured values ​​(e.g., overlay) before and after etching the substrate 220 for this purpose. The plot is free of any overlay error contribution of the lithography apparatus 200 and the mask MA, and contains only the contribution from the etching station 222. Depending on the correction capabilities of the etching station 220, the differences in the plot are reduced and / or minimized or (if possible) reduced to zero. Thus, both the target asymmetry and the introduced offset across the substrate 220 can be eliminated, resulting in improved edge placement error performance.

[0062] In the present invention, the developed substrate 220 is transferred to the metrology device 240 (path 410) before moving to the etching station 222. The metrology device 240 performs a first measurement using a first metric related to the structure on the substrate 220 before etching. The first metric can represent one or more of the following: an overlay error between two or more layers on the substrate (e.g., between a pattern in the lower layer 310 and a physical resist pattern 340), a placement error of an edge of a feature of one layer of the substrate 220 (e.g., an edge of a feature in the pattern in the lower layer 310) relative to an edge of a feature of another layer (e.g., a feature in the physical resist pattern 340), a difference between an expected size of a feature and a measured size of the feature (e.g., a critical dimension (CD)), or an asymmetry of a property measured at one or more locations on the substrate 220.

[0063] Only a single measurement of the first metric may be performed, or multiple measurements of the first metric may be performed at different locations on the substrate 220. In an embodiment, multiple measurements may be performed at the same location on the substrate 220. In an embodiment, the first metric is a statistic involving multiple single measurements. The statistic may be one or more of the following: a fit of the first metric to a model of the first metric, an average of multiple single measurements, a standard deviation of multiple single measurements, a mathematical function fitted to multiple single measurements. The first measurement of the first metric may be performed with respect to multiple structures on the substrate 220.

[0064] In an embodiment, as described above, the metrology results 242 from the metrology equipment 240 can be used in an advanced process control (APC) system 250, or the product can be transferred for rework (if the metrology results 242 indicate that rework is desired). Otherwise, the substrate 220 is transferred to the etching station 222, where the substrate 220 is etched under the control of the etching controller 223. After the substrate has been etched (immediately after leaving the etching station 222 (path 420), or after leaving the post-etch cleaning and / or annealing station 224 (path 421), or after leaving another downstream processing equipment 226 (path 422)), the etched substrate 232 / 234 is transferred to the metrology equipment 240 again.

[0065] Then, after being etched, a second measurement of a second metric related to a structure on the substrate 232 / 234 is performed. In an embodiment, the second measurement is a measurement of the same type as the first measurement. In an embodiment, the second metric is a metric of the same type as the first metric. In an embodiment, the structure on which the second measurement is performed is the same as the structure on which the first measurement is performed. In an alternative embodiment, the structure on which the second measurement is performed is a structure different from the structure on which the first measurement is performed. In the case where the second measurement is performed on a structure different from the structure on which the first measurement is performed, it may be necessary to fit a function to the measurement before subtracting the first measurement (value) from the second measurement (value), because the locations on the substrate for the first and second measurements are not exactly the same. Additionally or alternatively, even if the first and second measurements are performed on the same structure, it may be desirable to map the first measurement location and the second measurement location to a common grid (because the rotational alignment of the substrate when the substrate is placed in the measurement device 240 for the first measurement and the rotational alignment of the substrate when the substrate is placed in the measurement device 240 for the second measurement may be different).

[0066] In an embodiment, the first measurement is a measurement representing the overlay error between the pattern in the lower layer 310 and the physical resist pattern 340. The second measurement is a measurement of the overlay error between the pattern in the lower layer 310 and the pattern in the device layer 320. The measurements may be made on the same features of the pattern in the lower layer 310 for both the first measurement and the second measurement, or the measurements may be made on different features of the pattern in the lower layer 310.

[0067] In an embodiment, the features in both the lower layer 310, the physical resist pattern 340, and the pattern in the device layer 320 are patterns of a specifically designed target portion for measurement of overlay error (or difference metric). In an embodiment, the features in both the lower layer 310, the physical resist pattern 340, and the pattern in the device layer 320 used in the first measurement and the second measurement are gratings.

[0068] Preferably, the first measurement and the second measurement are performed on the same substrate, so there is no need to consider the overlap error variation from substrate to substrate. However, this is not necessary, and if the overlap error caused by the process upstream of the etching is small compared to the overlap error caused by the etching, the first measurement and the second measurement can be performed on different substrates. This is particularly suitable for a rough improvement in at least one etching parameter. This has the advantage of increasing throughput, because while the second measurement is performed on the first substrate, the substrate after the substrate on which the first measurement is performed is not retained before being etched. If the first measurement and the second measurement are performed on different substrates, it may be desirable to include additional steps to determine whether the difference between the first measurement and the second measurement is the result of substrate-to-substrate variation, or whether it can be attributed to the effect of the etching process in the etching station 220.

[0069] The result of the second measurement will include the effects of steps applied to the substrate before the substrate 220 is first passed to the metrology station 240 (i.e. as measured in the first metrology), as well as any changes in that metric introduced by the etching process in the etching station 220 (and, as described above, any further downstream steps in the apparatus 224, 226 through which the substrate may be passed before being passed back to the metrology apparatus 240). The difference between the first and second measurements is therefore indicative of the effects of processes applied to the substrate between the first and second measurements, and in particular the effects of the etching process in the etching station 220 on the metric.

[0070] exist Figure 4 An embodiment is shown in FIG. 1 in which a first measurement representing an overlay error is performed on the substrate 220 after leaving the developing device 212 (at Figure 4 The length of the line represents the overlay error at that location on substrate 220. A second measurement is then made of substrates 232, 234 after substrate 220 has been etched in etching station 222 (at Figure 4 By subtracting the first measurement from the second measurement, Figure 4 These results show the effect on the overlay error of processes performed on the substrate 220 after leaving the development device 212 and before reaching the metrology device 240 for the second time (ie, after being etched).

[0071] Based on the difference between the first measurement and the second measurement, at least one etching parameter used by the etching controller 223 can be changed for etching the subsequent substrate 220. This is achieved by the metrology device 240 transmitting the results of the first measurement and the second measurement (alternatively or additionally, only the difference between the first measurement and the second measurement, or instructions on how to change at least one etching parameter) to the etching controller 223 via a signal. The signal from the metrology device 240 to the etching controller 223 can be routed directly or indirectly via the APC 250 and / or via the supervisory control system 238.

[0072] The method described above uses a metrology device 240 that is non-destructive or non-intrusive for taking the first and second measurements. Preferably, the entire process is performed automatically, for example under the control of a supervisory control system 238. The first and second measurements may be performed only on the first substrate of a batch of substrates (for high throughput) or may be performed more or less frequently. In an embodiment, the frequency with which the first and second measurements are performed depends on the difference between the most recent first and second measurements and whether the difference is below a predetermined maximum expected difference.

[0073] This technique may be applied to keep the difference between the first measurement and the second measurement to a minimum over time by dynamically adjusting available etching parameters, thereby mitigating the effects of drift and / or wear of components of the etching station 222 .

[0074] The difference between the first measurement and the second measurement on which the change in the etching parameter is based may be one or more of: a magnitude of the difference between the first measurement and the second measurement, an asymmetry between the first measurement and the second measurement, a location of the difference between the first measurement and the second measurement.

[0075] The first measurement and the second measurement can be overlay measurements based on diffraction.

[0076] The results of the overlay metrology may be calibrated based on SEM analysis of a cross section of the substrate from which the diffraction based overlay measurement is subtracted.

[0077] In an embodiment, the measurement device performs the first measurement and the second measurement by measuring the first order and / or higher order diffraction patterns of the incident radiation. For this purpose, the substrate may be provided with one or more test gratings on which the measurement device can perform the first measurement and the second measurement. The first measurement and the second measurement may be performed using radiation of the same or different wavelengths and / or the same or different polarization states. Changing the wavelength and / or polarization state may enable different types of measurements to be measured, for example, an asymmetry may be measurable at a first wavelength and / or polarization but not at a second wavelength and / or polarization. In the case of zero overlap, it would be expected that the difference between the first measurement and the second measurement for each wavelength and each polarization state would tend toward zero.

[0078] In the method described above, the first measurement and the second measurement are non-destructive. This is preferred because the process can be fully automated and does not require destruction of the substrate. However, some types of defects introduced by the etching process in the etching station 220 may not be detected in a non-destructive manner. For example, edge placement errors can be best determined by dimensional and / or geometric measurements of the cross-section of the respective substrate. In this case, it may be necessary to obtain a cross-section of the substrate and examine it under a microscope such as a scanning electron microscope to facilitate dimensional and / or geometric measurements.

[0079] exist Figure 4 In the example, it can be seen that Figure 4 The difference between the first measurement (left hand side) and the second measurement (middle) shown on the right hand side of is the increased difference in overlay error measured at the edge of the substrate. This may be a reference Figure 3 A result of the overlay error introduced by etching of the type explained. One way to reduce this difference could be to change the etching parameters representing the voltages applied to electrodes positioned around the edge of the substrate W, for example during the etching process in the etching station 220 .

[0080] The manner in which the etching parameters are changed based on the difference between the first measurement and the second measurement can be determined in any manner. For example, a rule involving the observed difference between the first measurement and the second measurement and which etching parameter and / or how to change the etching parameter can be determined experimentally by repeating the first measurement and the second measurement on multiple substrates and varying the etching parameter and observing the change in the difference between the first measurement and the second measurement. Additionally or alternatively, the rule can be one or more theory-based rules.

[0081] The method may vary one or more etching parameters, and the rules for varying the etching parameters may include rules for which etching parameters to vary depending on the observed difference between the first measurement and the second measurement (e.g. in terms of the magnitude or position of the difference or the asymmetry of the measured quantity). The first metric and the second metric may be based on statistics, e.g. involving multiple single measurements.

[0082] As an alternative to basing the variation of an etching parameter on the difference between a first measurement and a second measurement, exclusive use of post-etch measurements relating to properties of any suitable structure may be used. For example, after exposure using a lithographic apparatus and development of the resist, a grating structure is formed in a resist layer on a substrate. After a subsequent etching step using an etcher, the grating structure is formed in one or more layers on the substrate. Measurements performed on the etched grating structure may reveal whether the etching parameters associated with the etching step are correct, or whether debugging is required. For example, the electric field 360 used during the etching process may vary from being perfectly vertical at the surface of the substrate 220 (which is located at the center of the substrate 220) to being angled at the edge of the substrate 220 relative to a direction perpendicular to the top surface of the substrate 220. This may result in the formation of a non-rectangular etched grating structure; essentially, the sides of the elements forming the grating (see Figure 3 ) may not be perpendicular to the top surface of the substrate. This will cause (as explained previously) overlay errors between features in different layers on the substrate. Measurements representing the asymmetry of the etched grating structure can be used to change one or more parameters of the etching step. In such a situation the asymmetry is related to the deviation of the etched structure from a rectangular shape. For example, measurements of the geometry of a cross section of the etched grating structure can reveal the direction of (plasma) etching at the edge of the substrate, which is indicative of the direction of the electric field 360. Alternatively, measurements of first order and / or higher order diffraction patterns of radiation incident on the etched grating structure can be used to determine the asymmetry (a method known as scatterometry). Typically, the asymmetry of the etched structure will cause an asymmetry in intensity between the diffraction orders (e.g. between the first order and the negative first order) of the radiation diffracted from the etched structure. However, the measurement method utilized is not limited to the determination of the geometry of the diffraction pattern and / or cross section, and any suitable measurement method and / or results of the measurement method suitable for the reconstruction of the measurement of asymmetry associated with the etched structure may be used. The etched structure is typically a grating structure, but may be any suitable structure, such as any of the following: isolated lines, isolated contacts, two-dimensional array structures, product structures.

[0083] The measurements may not be limited to just one etched structure, but may include measurements performed at multiple locations on the substrate and / or multiple types of etched structures (e.g. etched grating structures with different pitches). This may improve the accuracy of controlling the etching equipment; the determined changes in the etching parameters will be more representative of the substrate and / or structure of interest.

[0084] In an embodiment, a method of changing an etching parameter of a substrate etching process is disclosed, the method comprising: measuring an etched structure on a substrate; and changing the etching parameter based on an asymmetry of a result of the measurement.

[0085] In another embodiment, the measuring is based on scatterometry.

[0086] Figure 5-8 and the related description below explain one way in which rules can be used to change etching parameters. Figure 5-8 The described method can be used in combination with the above-described method of performing the first measurement and the second measurement, or can be applied in a method for changing an etching parameter, which method requires a measurement step that may be different from the measurement step described above. In any case, the rule may involve a predetermined relationship between the difference and the etching parameter as described above. In an embodiment, the rule involves a trend of a first variable related to the effect introduced by etching as the etching parameter changes, as described below.

[0087] like Figure 4 As shown, to increase throughput, it may be desirable to perform the first and second measurements primarily or exclusively around edge portions of the substrate (eg, where it is desired to observe etch-induced overlay errors).

[0088] In an embodiment, the etching parameters are only changed if the difference between the first measurement and the second measurement is greater than a predetermined minimum difference.

[0089] The process described above can be repeated as often as desired. In an embodiment, the process is repeated until the difference between the first measurement and the second measurement tends to a predetermined level (close to zero). The process can then be repeated only at predetermined time intervals (e.g., time-based, or based on the number of substrates) depending on the (expected) stability of the etching station 220 to ensure the performance of the stable etching station 222. The predetermined time interval can vary depending on the difference of the most recent measurement between the first measurement and the second measurement. Alternatively or additionally, the predetermined time interval can be reduced based on a statistical method, such as a trend over time based on the difference between the first measurement and the second measurement. In another or alternative embodiment, the predetermined time interval is based on completely different measurements, such as a direct or indirect measurement of the drift of the etching station. In this way, the degradation of the components in the etching station 220 can be monitored and steps can be taken to compensate for the degradation of the components or to warn the operator that the components need to be replaced. One such component is a voltage ring with a limited life around the outer edge of the substrate.

[0090] The method can be used to optimize more than one etching parameter. For example, the property of the difference between the first measurement and the second measurement can be used to indicate that one of the plurality of etching parameters should be changed, while the remaining etching parameters should remain the same or be changed by different amounts.

[0091] Figure 5 Schematically shows an etching parameter which may be varied, for example to change the direction of the electric field at the edge of the substrate W and thus change the etching direction (see Figure 3 ). Figure 5 A substrate W and an electrode 500 are shown. The electrode 500 is in the form of a ring. The electrode 500 surrounds the edge of the substrate W. A bias voltage may be applied to the electrode 500.

[0092] exist Figure 5 One etching parameter that may vary in the arrangement of is the distance H of the electrode 500 from the substrate W in a direction perpendicular to the plane of the top surface of the substrate W. As the electrode 500 wears during use, the optimal distance H will change. Another or alternative etching parameter that may vary is the bias voltage applied to the electrode 500.

[0093] In one embodiment, when changing the etching parameters, the predetermined relationship between the difference between the first measurement and the second measurement described above and the etching parameters can be used. One way to establish this predetermined relationship is described below. In fact, the way to use the established relationship is described to facilitate changing the etching parameters, for example, after the electrode 500 is worn.

[0094] The inventors have determined that overlay errors introduced by a non-optimal choice of distance H can be modeled. Figure 6On the left hand side a model of the overlay error OV on the y-axis as a function of the distance d from the edge of the substrate W is shown. That is, for example, according to the above reference Figure 4 The described method measures the overlay error OV caused by the etching process and plots the measured overlay error OV on a graph as a function of the distance d from the edge of the substrate W. The function can be fitted to the data plotted on the graph of the distance d from the edge on the x-axis and the overlay error OV on the y-axis. The function can have the form of 1 / e distance (d0) and having an amplitude a. The inventors have found that the 1 / e distance does not change with distance H, while the amplitude a changes linearly with H. This is due to the fact that in Figure 6 The experimental results are shown in the right hand graph.

[0095] Other models can be used to model the measured overlap error OV caused by the etching process. For example, a hyperbolic edge model or a cubic B-spline model can be used. The function is an exponential decay. In an embodiment, the function is fitted to the data by changing the first variable. In this way, the first variable represents the effect introduced by etching (for example, the first variable characterizes the fingerprint of the effect introduced by etching). In an embodiment, the first variable is an amplitude a representing the amplitude of the measurement of the structure on the substrate W (for example, the overlap error OV introduced by the etching process).

[0096] Used in Figure 6 The information in the figure on the right hand side can determine the etching parameters (distance H I ) to achieve the desired value of the first variable (amplitude a). Figure 6 In the case of a model with , an amplitude of zero is expected since this indicates zero overlap.

[0097] To determine the relationship, a number of test samples were subjected to a first measurement before etching and a second measurement after etching, with different values ​​of distance H. For each of those samples, a graph showing the etch-induced OV error as a function of the distance d from the edge of the substrate W can be found in Figure 1. Figure 6 The results of the difference between the first measurement and the second measurement are plotted on the left hand side of FIG. 1 (the same as shown on the left hand side of FIG. 1 ). A model can be fitted to those experimental results to determine the first variable (amplitude (a)) for each substrate (and therefore for each value of the etching parameter (i.e., distance H)). The results of each of the measurements at different values ​​of distance H can then be plotted on the right hand side of FIG. 1 according to Figure 6 on the right-hand side of the graph.

[0098] After several etching processes have been completed, it is expected that the electrode 500 will have worn. Such wear is expected to result in an overlay error that is caused by a changed etching process. Unexpectedly, the inventors have found that it is possible to correct for the etching-induced overlay error caused by the wear of the electrode 500 using the result of a predetermined relationship between the etching-induced overlay error OV and the non-worn electrode 500. The way to do this is by establishing a trend for the first variable (amplitude a) (which of course is related to the amount of etching-induced overlay error) as the etching parameter (distance H) changes. In an embodiment, the trend may be Figure 6 If the amplitude of the overlay error introduced by etching is measured, a N , then suppose the distance H is increased by a value H I (The initial value of the H parameter) minus the distance H A (which is the most recently measured amplitude a that would have resulted under the non-worn electrode 500 N distance H). That is, the distance H increases by H I -H A . Thus, the overlay error introduced due to wear of the electrode ring 500 is reduced. Therefore, the etching parameters of the substrate etching process for the subsequent substrate are changed by the amount predicted by the trend (the slope in such a case) to cause the actual first variable (amplitude a) to change to the desired value of the first variable (zero in the case of the overlap amplitude). This process can be followed, for example, when an overlay error (etching introduced) above a predetermined maximum value is measured. When the process is repeated, assuming Figure 6 The relationship (ie, trend or slope) is maintained even though electrode 500 has worn.

[0099] Figure 7 The results that can be achieved using this method are shown. Figure 7 The left hand side of FIG. 5 shows the overlap measurements made before applying the correction to the distance H in the case of a worn electrode 500, which was initially operating at a low overlap of measurements before being worn. The left hand plot shows the difference between the first measurement and the second measurement in the plane (i.e., similar to Figure 4 ), Figure 7 The left-hand graph of is a graph with the overlay measurement plotted as a function of the distance d from the edge of the substrate W (i.e., Figure 6 ). By calculating the first variable (amplitude a) and changing the actual parameters of the substrate etching process for the next substrate by the amount predicted by the relationship, resulting in the actual first variable change being zero, the result in the case of Figure 7 On the right hand side of Figure 7It can be seen from both the plan view and the graph on the right hand side that the overlay error is greatly reduced compared to before changing the parameters based on the previously established relationship.

[0100] Thus, the inventors have discovered a way to compensate for overlay errors introduced by etching over time.

[0101] For fitting a function to the overlay data, it has been found that good results can be effectively achieved if more measurements are taken at distances close to the edge of the substrate than at distances further away from the edge of the substrate. Figure 4 A typical measurement layout and distribution that may be used with the present invention is shown.

[0102] Although the method of establishing a relationship and using the relationship to change an etching parameter has been described in conjunction with the etching parameter being the distance H between the electrode 500 and the substrate W, the same method can be used for other etching parameters, including but not limited to: a bias voltage applied to the electrode 500, a thermal pattern across the substrate W, a chemical concentration pattern in the plasma used for the etching process, etc.

[0103] As described above, the relationship can be established using a method for determining the overlay error introduced by etching, the method comprising: taking a first measurement and a second measurement before and after etching, respectively, and calculating the difference between the first measurement and the second measurement (as described above with reference to Figure 4 ). However, the variables may be variables representing different etch-induced errors, such as placement errors of edges of features in one layer of the substrate relative to edges of features in another layer of the substrate, differences between expected dimensions of features and measured dimensions of features (e.g., critical dimensions), asymmetries in properties measured at one or more locations on the substrate, and deviations from expected shapes for errors introduced by etching a first layer of a structure, measurements of, for example, critical dimensions and / or asymmetries made only after etching.

[0104] exist Figure 6 In the embodiment of FIG. 1 , it is assumed that the relationship is linear. However, the present invention is not limited thereto, and the change of the first variable related to the structure on the etching substrate with the change of the etching parameter can be modeled as any other function.

[0105] In an embodiment, the etching parameters are only changed if the actual first variable being measured differs from the expected value of the first variable by more than a predetermined maximum value.

[0106] Although the above description seems to be used to determine the relationship between the etching and the initial value H of the etching parameter (distance H) IThe subsequent etching and the etching chamber that is the same as the etching after the etching parameters are changed based on the relationship can be performed, but this is not required. For example, the relationship can be determined in a given etching chamber and applied to other etching chambers. The relationship (i.e., trend or slope) will be maintained in other etching chambers, but the amplitude for a given etching parameter may not be maintained. This means that it may not be possible to use the relationship to accurately select the initial value of the etching parameter to achieve the desired etching parameter. However, the relationship can be used to adjust the etching parameter to result in the desired value of the first variable.

[0107] It will be appreciated that the etching process may be used to compensate for effects introduced by the lithographic apparatus during imaging of the substrate W. In such a case, the goal may not be to minimize etching effects, but rather to achieve a desired etching process that results in at least partial correction of effects introduced by the lithographic apparatus during imaging. Thus, the method does not necessarily have to compensate for etching introduced errors and reduce them as low as possible, but it may be used to reduce errors in the substrate W caused by both the imaging step and the etching step.

[0108] Further embodiments of the invention are disclosed in the following list of numbered embodiments:

[0109] 1. A method for changing etching parameters of a substrate etching process, the method comprising:

[0110] taking a first measurement of a first metric associated with a structure on the substrate prior to etching;

[0111] taking a second measurement of a second metric associated with the structure on the substrate after etching; and

[0112] The etching parameter is changed based on a difference between the first measurement and the second measurement.

[0113] 2. The method of embodiment 1, wherein the first metric and the second metric are metrics representing one or more of the following:

[0114] Overlay errors between two or more layers on the substrate, placement errors of edges of features on one layer of the substrate relative to edges of features on another layer of the substrate, differences between expected dimensions of features and measured dimensions of the features, asymmetries in properties measured at one or more locations on the substrate.

[0115] 3. The method of embodiment 1 or 2, wherein the first measurement and the second measurement are performed mainly around an edge portion of the substrate, preferably, wherein the first measurement and the second measurement are performed exclusively around an edge portion of the substrate.

[0116] 4. The method of embodiment 1, 2 or 3, wherein the etching parameters are one or more of the following:

[0117] A thermal pattern across the substrate, a chemical concentration pattern in the plasma used in the etching process, an electric field pattern surrounding the substrate during the etching process, a voltage applied to one or more electrodes during the etching process.

[0118] 5. The method of any one of embodiments 1-4, wherein the first measurement and the second measurement are non-destructive.

[0119] 6. The method of any one of embodiments 1-5, wherein the first measurement and the second measurement are performed on the same substrate.

[0120] 7. The method of any one of embodiments 1-6, wherein the first measurement and the second measurement are performed on different structures.

[0121] 8. The method of any one of embodiments 1-7, wherein the first measurement comprises a plurality of first measurements across the substrate and the second measurement comprises a plurality of second measurements across the substrate.

[0122] 9. The method as described in Example 8 further includes performing function fitting on the multiple first measurements and / or performing function fitting on the multiple second measurements.

[0123] 10. The method of embodiment 8 or 9 further comprises transposing the plurality of first measurements into a common grid, and transposing the plurality of second measurements into the common grid.

[0124] 11. The method of any one of embodiments 1-10, wherein the first measurement and the second measurement include measuring first order and / or higher order diffraction patterns of incident radiation.

[0125] 12. A method as described in Example 11, wherein the wavelength of the incident radiation is changed during the first measurement and / or the second measurement, and the first measurement and / or the second measurement are determined based on the difference in the first order and / or higher order diffraction patterns at different wavelengths and / or polarizations of the incident radiation.

[0126] 13. The method of any one of embodiments 1-10, wherein the first measurement and the second measurement comprise dimensional and / or geometric measurements of a cross section of each of the substrates.

[0127] 14. The method of any one of embodiments 1-13, wherein if the difference is greater than a predetermined minimum difference, the etching parameter is changed.

[0128] 15. The method of any one of embodiments 1-14, wherein the first metric and / or the second metric is a statistic related to a plurality of individual measurements.

[0129] 16. The method of any one of embodiments 1-15, wherein if the difference is less than a predetermined maximum difference, the etching parameter is kept unchanged, preferably if there is no difference between the first measurement and the second measurement, the etching parameter is kept unchanged.

[0130] 17. The method of any one of embodiments 1-16, wherein the changing occurs based on a predetermined relationship between the difference and the etching parameter.

[0131] 18. The method of embodiment 17, wherein the predetermined relationship is determined experimentally.

[0132] 19. A method for etching a batch of substrates using a substrate etching process, comprising:

[0133] Using a first substrate in the batch of substrates to perform the method of any one of embodiments 1-18, thereby changing the etching parameters; and

[0134] The remaining substrates in the batch of substrates are etched using the changed etching parameters.

[0135] 20. The method for etching a batch of substrates using a substrate etching process as described in embodiment 19, further comprising performing the method of any one of embodiments 1-18 a second time after an interval.

[0136] 21. The method of embodiment 20, wherein the interval is one of the group consisting of:

[0137] scheduled time;

[0138] a predetermined number of substrates to be etched;

[0139] a period of time determined by measurement;

[0140] Depends on the time period of the difference.

[0141] 22. The method of any one of embodiments 1-21, further comprising: if the difference between the first measurement and the second measurement results in changing the etching parameter, performing an additional step on the substrate where the second measurement was taken.

[0142] 23. The method of embodiment 22, wherein the further step is a step of reshaping the structure.

[0143] 24. A computer program product comprising machine readable instructions for causing one or more processors to control a measurement system to make the first measurement and the second measurement according to any one of embodiments 1-23 and to change the etching parameters of a substrate etching process.

[0144] 25. A method for controlling etching parameters of a substrate etching process, the method comprising:

[0145] providing a relationship between a first variable representing an effect introduced by etching and said etching parameter;

[0146] Determining an initial value of the etching parameter;

[0147] performing the substrate etching process on a first set of substrates using the initial values ​​of the etching parameters; and

[0148] An actual first variable on a substrate of the first group of substrates is determined, and the etching parameter of the substrate etching process for a subsequent substrate is changed by an amount predicted by the relationship to result in a desired substrate etching process.

[0149] 26. The method of embodiment 25, wherein the etching parameter is one selected from the group consisting of:

[0150] the position of an electrode around an edge of a substrate relative to the substrate during the substrate etching process;

[0151] A bias voltage is applied to electrodes around the edge of the substrate during the substrate etching process.

[0152] 27. The method of embodiment 25 or 26, wherein providing a relationship comprises:

[0153] Prior to etching, measuring, for a plurality of substrates, a first metric associated with a structure on the substrate;

[0154] measuring a second metric associated with the structure on the substrate after the structure on the substrate of each of the plurality of substrates has been etched by the substrate etching process using different values ​​of the etching parameter; and

[0155] A function is fit to the difference between the first measurement and the second measurement for each substrate, wherein the function includes the first variable as a variable.

[0156] 28. The method of embodiment 27, wherein each of the first measurement and the second measurement comprises a plurality of individual measurements, the radial distance from the edge of the substrate to the location of the measurement being the variable in the function.

[0157] 29. The method of embodiment 27 or 28, wherein the measurements are performed primarily around an edge portion of the substrate, preferably wherein the number of measurements increases as the distance from the center of the substrate increases.

[0158] 30. The method of embodiment 27, 28 or 29, wherein the function has the form of the first variable multiplied by 1 divided by e raised to the power of the radial distance d from the edge of the substrate to the measured location.

[0159] 31. The method of embodiment 27, 28, 29 or 30, wherein the first metric is a metric representing one or more of the following:

[0160] Overlay errors between two or more layers on the substrate, placement errors of edges of features on one layer of the substrate relative to edges of features on another layer of the substrate, differences between expected dimensions of features and measured dimensions of the features, asymmetry of properties measured at multiple locations on the substrate, deviations from expected shapes.

[0161] 32. The method of any one of embodiments 27-31, wherein the etching of the substrate etching process by the providing step occurs in an etching chamber different from an etching chamber in which the performing etching process occurs.

[0162] 33. The method of any one of embodiments 25-32, wherein the relationship is assumed to be linear.

[0163] 34. A method for changing etching parameters of a substrate etching process, the method comprising:

[0164] measuring an etched structure on a substrate; and

[0165] The etching parameters are varied based on the asymmetry in the measured results.

[0166] 35. The method of embodiment 34, wherein the measuring is based on scatterometry.

[0167] in conclusion

[0168] The different steps described above can be implemented by respective software modules running on one or more processors in the pattern forming system. These processors can be parts of an existing lithographic apparatus control unit, or additional processors added for the purpose. On the other hand, if necessary, the functions of the steps can be composed in a single module or process, or can be subdivided or combined in different sub-steps or sub-modules.

[0169] Embodiments of the present invention may be implemented using a computer program comprising one or more sequences of machine-readable instructions describing a method of recognizing characteristics in position data obtained by an alignment sensor and applying corrections, as described above. The computer program may be executed, for example, to Figure 2 The computer program may be stored in the control unit LACU206 or in some other controller. A data storage medium (eg semiconductor memory, magnetic disk or optical disk) may also be provided in which the computer program is stored.

[0170] The terms "radiation" and "beam" as used herein include all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g., having a wavelength equal to or about 365, 355, 248, 193, 157 or 126 nm) and extreme ultraviolet (EUV) radiation (e.g., having a wavelength in the range of 5-20 nm), as well as particle beams, such as ion beams or electron beams.

[0171] The term "lens," where the context allows, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic, and electrostatic optical components.

[0172] The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

1. A method for determining etching parameters used in configuring a substrate etching process, the method comprising: providing a relationship between a first variable representing an effect introduced by etching and said etching parameter; obtaining a first variable from a substrate after being subjected to said substrate etching process configured by said initial value of said etching parameter; as well as The etching parameter is determined from the relationship and the obtained first variable.

2. The method of claim 1 , wherein the etching parameter is one selected from the group consisting of: a) a position of an electrode near an edge of the substrate during the substrate etching process; and / or b) a bias voltage applied to an electrode near an edge of the substrate during the substrate etching process.

3. The method of claim 2, wherein providing a relationship comprises: Prior to etching, measuring a first metric associated with a structure on a substrate for a plurality of substrates; measuring a second metric associated with the structure on the substrate after the structure on the substrate of each of the plurality of substrates has been etched by the substrate etching process using different values ​​of the etching parameter; and A function is fit to the difference between the first measurement and the second measurement for each substrate, wherein the function includes the first variable as a variable.

4. The method of claim 3, wherein each of the first measurement and the second measurement comprises a plurality of individual measurements, the radial distance from the edge of the substrate to the location of the measurement being the variable in the function.

5. The method of claim 3, wherein the function has the form of the first variable multiplied by 1 divided by e raised to the power of the radial distance d from the edge of the substrate to the measured location.

6. The method of claim 3, wherein the first metric is a metric representing one or more of the following: Overlay errors between two or more layers on the substrate, placement errors of edges of features on one layer of the substrate relative to edges of features on another layer of the substrate, differences between expected dimensions of features and measured dimensions of the features, asymmetry of properties measured at multiple locations on the substrate, deviations from expected shapes.

7. A method for determining etching parameters used in configuring a substrate etching process, the method comprising: obtaining measurements of etched structures on a substrate; and The etching parameters are determined based on the asymmetry in the obtained measurements.

8. The method of claim 7, wherein the measurements are obtained by scatterometry.

9. A computer program stored on a computer readable recording medium, the computer program comprising machine readable instructions for causing one or more processors to: Obtaining a relationship between a first variable of etching-induced effects and etching parameters used in configuring the substrate etching process; obtaining a first variable from a substrate after being subjected to said substrate etching process configured by said initial value of said etching parameter; as well as The etching parameter is determined from the relationship and the obtained first variable.

10. A computer program stored on a computer readable recording medium, the computer program comprising machine readable instructions for causing one or more processors to: obtaining measurements of etched structures on the substrate; and Etching parameters are determined based on the asymmetry in the obtained measurements.

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