CN100526052C - Imprint lithography with improved monitoring and control and apparatus therefor - Google Patents

Abstract

A process for measuring or monitoring at least one parameter during an imprint lithography process, comprising the steps of: providing a mold having a surface for imprinting a test pattern (block a); imprinting a test pattern on the moldable surface (block B); illuminating the test chart (block C); measuring a component of the scattered, reflected, or transmitted radiation to monitor a parameter of the imprint (block D); and optionally using the measured radiation components to control parameters of the treatment process (square cabinet E).

Description

Imprint lithography with improved monitoring and control and apparatus therefor

Cross Reference Related Applications

This application claims priority to U.S. Provisional Application Serial No. 60/477,161, filed June 9, 2003 by Stephen Y. Chou and Zhaoning Yu and entitled "Method and Apparatus for Monitoring and Controlling of Imprinting Processes and Materials ". This 161 provisional application is incorporated herein by reference.

technical field

The present invention relates to imprint lithography which imprints a pattern of a mold on the surface of a workpiece having a moldable surface by pressing the molded surface into the moldable surface. More particularly, the present invention relates to a method and apparatus for monitoring and controlling imprint lithography, which is particularly useful for imprinting lines with micro- or nano-scales.

Background technique

The method of forming tiny lines on a substrate is very important for fabricating many electronic, magnetic, mechanical, and optical devices, as well as devices for biological and chemical analysis. This method can be used, for example, to define the lines and structures of microcircuits, as well as the structures and working lines of planar optical waveguides and related optical devices.

Optical lithography is a conventional method of forming such lines. A thin layer of photoresist is applied to the surface of the substrate, and selected portions of the photoresist are exposed to a pattern of light. The photoresist is then developed to reveal the desired pattern on the exposed substrate for further processing, such as etching. The challenge with photolithography processing is that the resolution is limited by the wavelength of light, scattering in the resist and substrate, and the thickness and properties of the resist. Thus, making photolithography more difficult as the required line sizes become smaller. Also, the application, development, and removal of photoresist are relatively slow steps that limit the speed of production.

Imprint lithography, on the other hand, is based on a fundamentally different principle, offering high resolution, high throughput, low cost, and potentially large area coverage. In imprint lithography, a mold with fine lines is pressed onto a workpiece with a moldable surface, such as a photoresist-coated substrate. The lines on the mold deform the shape of the plastic photoresist film, deform the shape of the film according to the lines of the mold, and form a raised pattern on the surface of the film. After removal of the mold, the patterned film is processed to remove the thinned portions. This removal step exposes the underlying substrate for further processing. Using mechanical pressure to perform the down-pressing step, this imprint can imprint lines down to 25 nm with a high degree of uniformity over an area on the order of 12 square inches. For more details, see US Patent No. 5,772,905, issued June 30, 1998 to Stephen Y. Chou, which patent is incorporated herein by reference.

Even higher resolution, larger area imprint lithography could be achieved if the tolerance issues presented by high precision mechanical pressure could be overcome. This problem can be solved with positive hydraulic pressure, which pressurizes the mold surface together with the moldable surface. Because the hydraulic pressure is isobaric, there is no significant unbalanced side force during the pressurization step. More details are set forth in US Patent No. 6,482,742 issued to Stephen Y. Chou on November 19, 2002, entitled "Fluid Pressure Imprint Lithography," which is incorporated herein by reference. Apparatus that has worked well for hydraulic imprint lithography is described in US Patent Application Serial No. 10/637,838 filed August 8, 2003 by Stephen Chou et al., which application is incorporated herein by reference.

It is also possible to perform imprint lithography by pressing the mold directly into the substrate surface, for which purpose the workpiece is provided with the substrate surface being a moldable surface. For example, the moldable surface can be a material forming part of the device, such as an organic light-emitting material, an organic conductive material, an insulator, or a low-K dielectric material. As another example, silicon workpieces can be directly imprinted with nanoscale patterns. The molding surface is placed in close proximity to the silicon surface to be molded. The silicon surface is irradiated with laser radiation to soften or liquefy the silicon, and the molded surface is pressed into the softened or liquefied surface. For more details, see U.S. Published Patent Application Serial No. 2004/0046288, filed March 17, 2003 by Stephen Chou, entitled "Laser Assisted Direct Imprint Lithography," which application is incorporated herein by reference.

Due to imprint lithography's potential high-speed, high-resolution ability to produce a large number of important products, it is necessary to monitor and study the imprint lithography process, optimize process parameters, optimize material composition, and control the process in real time process. The present invention provides an efficient way to achieve such monitoring, optimization, and control.

Contents of the invention

According to the invention, at least one parameter is monitored or measured during the method of embossing a mold pattern on the surface of a workpiece. Monitoring or measurement is performed by: a) providing a mold with an embossing surface configured to imprint at least a test pattern for measurement; b) embossing the test pattern by pressing the embossing surface into a moldable surface on the mouldable surface; c) illuminating the test pattern with radiation during at least a portion of the imprint, and monitoring or measuring at least one component of the radiation scattered, reflected, or transmitted from the test pattern to monitor or measure at least one parameter of the imprint . The embossing step generally includes: placing the mold adjacent to the workpiece with the molding surface of the mold next to the moldable surface; pressing the molding surface into the moldable surface; and separating the moldable surface from the moldable surface so that the imprinted image of the molded surface remains on the moldable surface . In many cases, pressing can be effected by heating the moldable surface, while retention of the imprint can be achieved by cooling or solidifying the deformed surface material. In addition, the control of the process can be performed by detecting the radiation component, generating a feedback control signal from the detected signal, and finally the feedback control signal controls the imprint process in real time. The present invention also includes advantageous apparatus for use in the monitoring, measuring, and controlling imprint lithography methods described above.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating one or more preferred embodiments of the invention and should not be considered as limiting the invention.

In the attached picture:

Figures 1A to 1E schematically depict the different stages of the embossing process and material which the metrology method described in the present invention needs to monitor.

Figure 2 schematically illustrates a measuring device according to an embodiment of the invention.

FIG. 3 illustrates a measured structure according to an exemplary embodiment of the present invention.

Fig. 4 is a scanning electron microscope image of an exemplary test pattern used on a mold according to an exemplary embodiment of the present invention.

Figure 5 shows a simplified diagram of an experimental layout, according to an exemplary embodiment of the present invention.

FIG. 6 shows measured data obtained with the experiment shown in FIG. 5 .

Fig. 7 shows a schematic block diagram of a metrology instrument according to an exemplary embodiment of the present invention.

Fig. 8 shows a schematic block diagram of a processing system according to an exemplary embodiment of the present invention.

FIG. 9 is a graph showing measurement data obtained with the layout of FIG. 5 . The figure shows the effect of processing temperature on the speed of the mold penetrating into the photoresist.

FIG. 10 graphically represents measurement data obtained with the layout of FIG. 5 . The figure shows the effect of process pressure on the speed of the mold penetration into the photoresist.

FIG. 11 graphically represents measurement data obtained with the layout of FIG. 5 . The figure shows the effect of pre-imprint photoresist baking conditions on the speed of mold penetration into photoresist.

FIG. 12 graphically represents measurement data obtained with the layout of FIG. 5 . The figure shows the effect of different initial photoresist film thicknesses on the speed of the mold penetrating into the photoresist.

Figure 13A shows the effect (simulated) of different photoresist indices of refraction on measurements according to the layout of Figure 5 . Data were calculated using scalar diffraction theory.

FIG. 13B plots measurement data obtained with the embodiment shown in FIG. 5 . The graph plots the effect of the photoresist index of refraction on the measurement.

FIG. 14 plots measured data obtained with the layout of FIG. 5 . The graph shows the effect of the difference in stencil line (line width in this case) on the speed at which the stencil penetrates the photoresist (with different initial film thicknesses).

FIG. 15 plots measurement data obtained with the layout of FIG. 5 . The figure shows the application of the present invention in the process control of embossing process; and

Figure 16 is a schematic block diagram illustrating the steps involved in monitoring or controlling imprint lithography in accordance with the present invention.

Detailed ways

The present invention relates to methods of monitoring and/or controlling imprint lithography processes and materials. By measuring and analyzing the radiation scattered by a set of microscopic test lines related to imprinting, the parameters of imprinting and the properties of materials can be measured or detected on-site or off-site, and feedback or control signals can be generated to control the imprinting process process and its outcome. The present invention is also directed to methods and apparatus for monitoring imprinting processes and materials on-site or off-site.

These methods include:

1) Provide a mold with at least one group of raised lines on the test surface, the raised lines on the test surface may include gratings, two-dimensional arrays, structures with irregular or arbitrarily defined shapes, or three-dimensional structures;

2) irradiating the pattern of the test surface elevation with radiation (monochromatic or broad-band in the wavelength spectrum) during the embossing process, which usually consists of bringing the mold to the immediate vicinity of the workpiece to be patterned, The mold is pressed into the film coated on the workpiece surface, the film is changed from a viscous state to a non-viscous state (or vice versa), and the mold is separated from the photoresist. In some cases, it is necessary to align an existing image on the workpiece or substrate with a new image to be printed. In this case, the pattern on the mold needs to be aligned with the existing pattern before the embossing step. The radiation can be light (visible, x-ray, ultraviolet, or infrared), electron beam, or ion beam. For simplicity, throughout the description of the invention, the term light is used, but it should be realized that it includes other forms of radiation;

3) measuring light scattered from the illuminated test structure and moldable material, or light transmitted through the illuminated test structure and moldable material (in the case where both the mold and substrate are relatively transparent to this radiation);

4) Extraction of parameters related to the imprint process and material from the measured information. Extraction can be real-time (on-site) or offline (off-site).

5) The extracted information can generate signals for controlling the embossing process and material purpose in an on-site manner.

6) and/or use the extracted information to study the influence of different parameters and materials on the imprint process.

Devices based on this method include:

1) A metrology device that can be used independently, which is based on extracted information about the imprinting process and materials.

2) Processing systems, including: stamping equipment, metrology equipment, and controllers for processing processes and materials. Imprint instruments are suitable for performing imprint lithography according to operational factors. Metrology instruments are suitable for illuminating the mold and substrate with radiation (typically light) and measuring the scattered or transmitted radiation in order to extract information about the imprint process and material. The controller of the embossing process and material generates signals to adjust one or more operating parameters in real time based on the data obtained by the metrology device.

Referring now to the drawings, FIG. 16 is a block diagram schematically illustrating the steps involved in monitoring or measuring and optionally controlling in imprint lithography on a workpiece with a moldable surface. The first step, shown in box A, is to provide a mold with an embossing surface for embossing a test chart for measurement.

Figure 1A shows a mold 10 having a test pattern thereon comprising a plurality of raised lines 16 of the desired shape adjacent to a workpiece having a moldable surface. The workpiece comprises a substrate 14 carrying a thin, moldable film layer 12 . Arrow 20 indicates the direction of movement of the mold relative to the substrate.

The next step (block B of Figure 16) is to imprint the moldable surface. This step generally includes placing the mold adjacent to the workpiece with the molding surface of the mold proximate to the moldable surface; pressing the molding surface into the moldable surface; and separating the molding surface from the moldable surface so that an imprint of the molding surface remains on the moldable surface. Pressurization can be accomplished by high-precision mechanical pressure as described in the aforementioned U.S. Patent No. 5,772,905, by hydraulic pressure as described in U.S. Patent No. 6,482,742, or by using electrostatic or magnetic forces: Heating the mouldable surface facilitates the pressing step, while cooling the mouldable surface facilitates maintaining the imprinted figure in the mouldable surface. The moldable film can be a photocurable material that is liquid or in a deformable state prior to photocuring. The plastic film 12 can be omitted if the substrate material provides a surface that is plastic or can be made plastic, for example a silicon surface can be softened by means of a laser. See aforementioned US Published Patent Application Serial No. 2004/0046288. The moldable surface may be a moldable film or a moldable material forming part of the device. Examples of such plastic materials include semiconductors, insulators, metals, inorganic materials, organic materials, and light emitting materials.

FIG. 1B depicts the mold 10 being pushed into contact with a thin plastic film layer 12 carried by a substrate 14 . The thin moldable film layer 12 may comprise a thermoplastic composition, a curable composition, or a composition of other moldable materials. The thin, moldable film layer 12 is preferably capable of transitioning from a viscous state to a non-viscous state or vice versa through physical change or chemical reaction depending on changes in conditions, such as temperature, polymerization, curing, or radiation. Preferably, the thin moldable film layer 12 is in a viscous state either before or after it is pushed into contact with the mold 10 .

1C and ID depict lines 16 on the mold 10 for pressing in the thin plastic film layer 12 . After the lines 16 have been pressed into the thin plastic film layer 12 to the required depth ( FIG. 1D ), after the embossed film has been allowed or caused to change into a non-viscous state, for example by cooling or solidifying, in this non-viscous state Remove the mold.

FIG. 1E shows the mold 10 detached from the thin plastic film layer 12 . The die exits in the direction indicated by arrow 22 , leaving embossed lines 17 in the film 12 . The test line 17 generally follows the shape of the line depressed on the mold.

Referring back to the third step shown in block C of FIG. 16, which occurs at some part during the imprint process, and usually occurs during the pressing step, this third step is to irradiate with radiation, usually light. At least a portion of the test pattern. The use of relatively transparent molds and/or relatively transparent substrates, for example using fused silica, is advantageous for irradiation. Typically, the imprinted test lines form a test raster pattern in the photoresist. When illuminated with light, the grating scatters, reflects, or transmits the light in a manner that can be analyzed, giving information about the imprinting process. By analysis, this method provides a metrology approach for measuring and studying imprint lithography. Thus, in the step of block D, at least one parameter of the lithographic imprint is monitored, measured, or studied using at least one component of scattered or transmitted radiation.

The next step, shown in Box E, is to move from measurement and research to real-time or offline control of imprint lithography. In this step, the scattered, reflected, or transmitted radiation is measured or analyzed to generate a feedback signal for controlling the imprint. At least one component of the scattered or transmitted radiation is measured and analyzed in order to control at least one parameter of the imprint. It is good practice to use one or more components to generate feedback signals that control various parameters of the imprint.

Figure 2 schematically depicts the metrology method for measuring imprint parameters and material properties. Use radiation beam 34 (such as light beam, electron beam, or ion beam) from radiation source 30 as probe, irradiate at least a part of assembly 18, this assembly 18 comprises mold 10, thin plastic film layer 12 (it also can have multiple layer photoresist structure), and substrate 14 (which may be a flat substrate or a pattern-carrying substrate or structure). For simplicity, the term "light source" or "light" is used throughout the description, but it should be appreciated that it includes other forms of radiation sources.

Light to be detected and analyzed typically includes a reflected component 36 (the so-called "specular" component), a transmitted component 38, and a scattered component 40 (40a, 40b, and 40c). To simplify the discussion, the term "scattered" light encompasses all of these components unless otherwise stated. Detector 32 makes optical measurements, such as measurements of the intensity, phase, or polarization of one or more scattered components.

Light source 30 may use substantially monochromatic light, white light (broadband), or other combinations of certain wavelengths. Light of any polarization or any combination of polarized and non-polarized may be used. Irradiation at any angle of incidence can be used. Although FIG. 2 depicts the assembly 18 illuminated with a beam from the side of the mold 10, the assembly may also be illuminated with a beam from the side of the substrate 14. The light source can be a converging and directed beam or a non-converging broad beam. Useful light wavelength range, from 1nm to 100μm. Useful electron beam wavelength range, from 0.001nm to 10μm. The useful ion beam wavelength ranges from 0.00001nm to 10μm. The dimensions of the probed lines (which may be on the mold, on the substrate, or in the photoresist) typically range from 0.1 nm to 500 μm in width and typically from 0.1 nm to 100 μm in depth.

The scattered light profile (i.e. its angular distribution, intensity, phase, and polarization) depends on: 1) the nature of the incident light 34 (i.e. its angle of incidence, intensity, wavelength, phase, and polarization); 2) the mold 10. The material and composition of the thin plastic film layer 12 and the substrate 14; 3) features of the figure on the mold 10 and the figure in the irradiated thin plastic film layer 12 (i.e. shape, height, mold line extrusion into photoresist depth, arrangement, and relative orientation).

By measuring and analyzing the properties of scattered light, information about the parameters and materials of the imprint process can be extracted. These parameters include, but are not limited to: intrusion of the mold line into the photoresist; speed of movement of the mold relative to the substrate; gap between the mold and the photoresist film; gap between the mold and the substrate; photoresist film condition, hysteresis and degree of polymerization; parallelism between mold and substrate; relative orientation of mold and substrate; coincidence accuracy between mold lines and lines on substrate obtained from previous processing; , substrate, and photoresist shape changes. Photoresist conditions that can be measured include: stress, deformation, composition, viscosity, flow velocity, flow direction, phase transition, degree of polymerization, degree of polymer crosslinking, hardness change, and optical property change.

The above measurements can be performed in real-time and on-site, or off-line and off-site. The information extracted from the above measurements can be used to analyze and control the imprinting equipment, imprinting process, and imprinting materials on-site or off-site.

The information obtained from the above qualifications in the field can be used to control various parameters in real time, such as the relative position between the mold and the substrate (x, y, z, theta, stretch and yaw - all 6 possible free degree), imprint speed, imprint pressure, imprint temperature, mold variation, and local and global alignment between substrate and mold.

The above-described metrology instruments of the present invention can be modified to suit a particular implementation. For example, the lines tested on the die can be designed to enhance the intensity of scattered light in specific diffraction orders, optimizing the measurement of specific parameters, such as die penetration into the photoresist.

Figures 3 to 6 illustrate examples of detection of mold intrusion in photoresist.

FIG. 3 shows a specific example of components irradiated with probe light 34 . Mold 10 is a transparent mold made from a 0.5 mm thick fused silica substrate with a backside finish. The test line is a group of grating primitives with a period of 1 μm and a line width of 650 nm. The depth of the test pattern is about 400nm. The thin plastic film layer 12 is a thermoplastic polymer with an initial film thickness of 60 and a refractive index nr = 1.46, while the photoresist can be transformed into a viscous state at elevated temperatures. Substrate 14 is silicon. Figure 4 is a scanning electron microscope image of a test raster pattern prepared for imprinting on a mold.

Figure 5 shows a simplified diagram of the measurement layout. A He-Ne laser 30 is used as a light source. The probe beam 34 has a wavelength of 632.8 nm and is polarized parallel to the incident plane (the probe beam can also be polarized perpendicular to the incident plane, or other polarization states can be used without significantly changing the results of this embodiment). In this layout, an angle of incidence 80 of 30° is used. Other angles of incidence may be used.

In operation, the mold 10 is brought into contact with the thin plastic film layer 12 carried by the substrate 14 at room temperature. The grating is aligned parallel to the plane of incidence and the assembly 18 is illuminated with the probe beam from the side of the mould. The grating can also be adjusted to other orientations relative to the plane of incidence.

The mold is hydraulically pressed against the substrate from the outside during the entire process. The assembly 18 is heated, and the elevated temperature can convert the photoresist to a viscous state.

Because the test pattern is a periodic array of lines (diffraction grating), the illumination causes many "orders" of light beams scattered from the grating. In this arrangement, there are generally three diffractive orders, including a zero order 30 (also known as a "specular" order) and two first order beams 40a.

The relative intensity of the diffraction orders is strongly dependent on the penetration of the photoresist by the test grating on the mold. When the mold lines are pressed into the photoresist film so that the grooves between the grating lines are filled with a photoresist material with an approximate index of refraction matching, the intensity of the 1st order will drop.

In this embodiment, a photodetector 32 is used to measure the intensity of the primary beam. The time-resolved data obtained from this measurement are shown in the graph of FIG. 6 . This curve demonstrates the sensitivity of the metrology method and the ability to resolve different stages of the imprint process.

The relatively high intensity of the 1st order diffraction at the beginning of the process indicated that although the mold was in contact with the photoresist film under external pressure (a constant pressure of ⁸⁰ psi was applied throughout the process), during the initial stages, The stencil lines are not pressed into the photoresist. The later decrease in diffraction intensity indicates that the mold pressed into the photoresist as the photoresist was heated and softened. At the end of the process, near-zero 1st-order diffraction intensity indicates that the mold lines are fully pressed into the photoresist and that the trenches between the grating lines are filled with an index-matching material.

This example illustrates that the metrology method of the present invention enables the monitoring and study of imprinting processes, either on-site or off-site. Key information for imprinting, such as the penetration of the mold into the photoresist, the detection of start and end points, and the speed of the process, can be deduced from the measurements.

FIG. 7 is a simplified block diagram of a stand-alone device 200 (metrology instrument) that can monitor imprinting processes and materials in accordance with the present invention. The metrology instrument 200 includes: 1) an illumination system 100 for generating one or more probe beams 34; 2) optical hardware 120 for detecting and measuring scattered light; and 3) a data analysis system 140 for processing The data is collected by the optical hardware and the results are output in the desired format.

Figure 8 is a simplified block diagram of a processing system for performing imprint lithography in accordance with the present invention. The processing system includes: 1) Imprint apparatus 100 for performing imprint lithography. Parameters of device handling factors (eg, mold position in all dimensions, substrate position in all dimensions, register alignment between mold and substrate, imprint pressure, and imprint duration) can be preset 2) the metrology instrument 200 as shown in Figure 7; and 3) the processing controller 300, which can receive and analyze the data sent by the metrology instrument 200, and generate real-time control signals.

Figures 9 to 15 illustrate some applications of the embodiment illustrated in Figures 3 to 6 in the quality of the imprint process and photoresist properties, and in the control of the imprint process.

Figure 9 plots the results of experimental measurements regarding the effect of process temperature on imprint speed. In each case, the same photoresist (NP-46) had the same initial film thickness 60 of 210 nm. All impressions were performed at the same pressure of 80 psig but with different process temperatures (30, 40, 50, 60, ⁷⁰ , 80, 100, and 120°C). The data show that processing temperature has a significant effect on die extrusion speed. At low temperatures (30 and 40°C), the photoresist is still strong, and only the applied pressure cannot deform the photoresist. At higher temperatures, the photoresist softens and the mold can be pressed into the photoresist at an increased speed. The data also show that the metrology methods described in the present invention are sufficiently sensitive to detect changes in imprint speed, and changes in photoresist state (from solid to softened state) as a result of temperature changes.

Figure 10 plots experimental measurements of the effect of process pressure on imprint speed. In both cases, the photoresist (NP-46) had the same initial film thickness 60 of 210 nm. The two imprints were performed at the same process temperature of 60°C but different process pressures (80 and 100 psi). Figure 10 shows that at 100 ^psi , the impression takes less time than at the ^lower pressure of 80 psi. The data also show that the metrology method described herein is sufficiently sensitive to indicate changes in imprint speed as a result of pressure changes.

FIG. 11 shows the results of experimental measurements regarding the effects of pre-imprint photoresist baking conditions on imprint speed and on photoresist properties. In each case, the photoresist (NP-46) film had the same initial film thickness 60 of 210 nm. All embossing was performed at 70°C and 80 ^psi . Before embossing, the films were baked with the same temperature of 90°C but different durations. One sample was not baked after spin coating and before embossing; the other three samples were baked for 15, 30, and 60 minutes, respectively. The photoresist drives out the solvent in the spin-coated film because it is baked, so the baking results in a slight change in the properties of the photoresist (eg glass transition temperature T _g ). Figure 11 shows that the longer the bake time, the longer it takes to fully press the mold in. Figure 11 also shows that the metrology method described in the present invention enables detection of the effect of baking on photoresist properties.

Figure 12 plots the effect of initial photoresist film thickness 60 on imprint speed. All embossing was performed at 60°C and 80 ^psi . Photoresist (NP-46) films were available in different initial thicknesses (200, 400, and 600 nm). They were all baked at 90°C for 24 hours before imprinting. With thicker films, more photoresist is available to fill the "voids" in the mold pattern, and the "slit" between the mold and substrate will become larger, making it easier for the photoresist to flow into the mold gaps in the figure. As a result, increasing the initial film thickness 60 helps to increase the speed of the process. This effect can be readily detected using the metrology methods described herein.

Figures 13A and 13B are simulated and experimental curves, respectively, showing the correlation of photoresist index of refraction with imprint test results. When photoresists with different refractive indices are used in imprinting, the refractive index can affect the measured features. The mold depth ratio (R _p ) is defined as the ratio of the photoresist height 76 protruding into the mold trench to the mold trench depth 74 . During imprinting, the mold depth ratio increases from 0 to 1. At the beginning of imprinting, no photoresist protrudes into the grooves of the mold, so the depth ratio is 0; at the end of imprinting, the grooves are completely filled with photoresist, so the depth ratio is 1.

Figure 13A is the simulation results calculated using a scalar diffraction model for two photoresists with different refractive indices (1.46 and 1.58), plotting the simulated 1st order diffraction intensity (normalized) as a function of die depth ratio. When the photoresist refractive index n _r perfectly matches the mold refractive index n _m (n _r =n _m =1.46, as shown by the solid line in Fig. 13A), the diffraction intensity decreases continuously with increasing R _p and is Reached 0 at the end of printing. However, when there is a mismatch between n _r and _nm , the final value of the diffraction intensity corresponding to the end of imprinting (R _p =1.0) is often higher than zero. For example, we have calculated the case at _nr = 1.58 (dashed line in Fig. 13A), which is significantly higher than that of the mold (fused silica, _nm = 1.46). In this case, the diffraction intensity reaches zero when the groove of the mold is partially filled ( _Rp ~ 0.8), but increases slightly towards the end point as _Rp approaches its final value of 1.0.

Figure 13B shows the experimentally measured 1st order diffraction intensity as a function of time during the imprint process for two different refractive index photoresists. In these experiments, the same grating stencil shown in Figure 4 was used. Two types of thermoplastic polymer photoresists were used: No. 1 polymer with a refractive index _nr = 1.46; No. 2 polymer with a refractive index _nr = 1.58 (determined with an ellipsometer). The polymer films had the same initial thickness 60 of ~210 nm in both experiments. Due to their difference in glass transition temperature, the two photoresists were imprinted with different conditions, so that the imprinting processes in both cases had comparable durations in time. The No. 1 polymer was imprinted at 100 psi and a temperature of 60°C ^, while the No. ² polymer was imprinted at 80 psig and a temperature of 80°C. The data show that when n _r matches _nm , the diffraction intensity drops to zero at the end of imprinting (No. 1 polymer, solid line in Fig. 13B). However, when n _r is higher than n _m , the diffraction intensity reaches zero before the grooves of the mold are completely filled, and approaches a non-zero final value at the end of imprinting (No. 2 polymer, in Fig. 13B dotted line). The experiments are consistent with the simulation results given by the scalar diffraction model shown in Fig. 13A.

The metrology method described can also be used to examine the effect of mold pattern lines on imprinting. One such example is illustrated by the data shown in Figure 14. In this experiment, two dies with the same 1.0 μm period 70 and pattern depth 74 of 330 nm, but different pattern line width 72, were used for testing and comparison. One die ("narrow") had a linewidth 72 of ~330 nm, while the other ("wide") had a linewidth 72 of ~660 nm. Figure 14A depicts the experimental results of imprinting a photoresist with an initial thickness of ~220 nm of 60 using these two molds. Figure 14B depicts the experimental results of imprinting a photoresist with an initial thickness 60 of ~350 nm using these two molds. In each case, different die maps produced distinctly different embossing curves. Figures 14A and 14B demonstrate that the present metrology method can be used to examine the effect of test lines (in this case, different line widths) on imprinting in a die pattern. This metrology method can also be used to study other test pattern lines (such as pattern size, depth, density, distribution, two-dimensional versus one-dimensional, and closed versus open patterns) versus imprint and resist flow process impact.

With the application of this metrology method, it is now possible to detect the penetration depth of the mold on site and in real time. For this reason, a processing system as shown in FIG. 8 can be used to carry out more precise control over the embossing process. For example, it is now possible to control the speed of the imprint process and the intrusion of the mold. In Figure 15, pressure was initially applied at a lower temperature (-30°C). At this low temperature, the die extrusion rate is low. This was followed by an increase in temperature (to -80°C). The photoresist softens and the die extrusion speed increases. Figure 15 shows that the present metrology method can provide control of the imprint process in the field by detecting the effect of changes in process conditions that occur during the imprint process. The present metrology method also offers the possibility of stopping the imprinting process when the mold pattern has only to be partially pressed to the depth required by the photoresist, thus enabling the possibility of specifying the depth of penetration 76 .

It should be noted that the method of the present invention is capable of using a wide variety of test patterns, including one-dimensional or two-dimensional periodic arrays containing periods small enough to allow essentially only first order diffraction. The test pattern can also be three-dimensionally structured, or a set of aperiodic lines.

The illuminating radiation may be substantially monochromatic, may include multiple wavelengths, or may include a combination of multiple wavelengths. It can be polarized (linear or elliptically polarized), randomly polarized, or unpolarized. Illumination can be directed at a fixed angle of incidence, scanned at varying angles of incidence, or from multiple sources.

This process can be used effectively to monitor a wide variety of imprint process parameters, including: extrusion of the die in the photoresist, speed of motion of the die relative to the substrate or workpiece, viscosity of the moldable surface, surface The glass transition temperature of the surface material, the compliance of the surface material to the lines on the mold, the curing speed of the surface material, and the degree of curing of the surface material. The process can also provide a measurement of surface material flow rate and, with stress-sensitive surface materials, can provide a measurement of surface material stress. This process indicates the displacement of the mold relative to the substrate, the parallelism of the mold relative to the substrate, and also provides a measure of the uniformity of the imprint process.

The test line of the mold can be the same material as the mold body, or it can be made of a different material, while the moldable surface can be the same material as the substrate, a different material than the substrate, or a composite layer such as multilayer photoresist .

The workpiece can carry one or more line drawings, which are pre-formed as functional lines, or pre-formed as test lines, which can be used in conjunction with mold test patterns. For greater precision or to provide monitoring of various parameters, the tooling can include imprinting various test pattern lines on the workpiece. Measurements can be static or time resolved.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

Claims (39)

1. One kind in the method that the surface of the workpiece that moldable surface is arranged impresses, monitor or measure the method for at least one parameter of this method, the step that this method comprises has:

   Provide the mould on mold pressing surface, be used to impress one group of lines, comprising supplying measuring resolution chart;

   Moldable surface is impressed, comprise the step that the mold pressing surface is pressed into moldable surface;

   At least during a part of imprint step, use the radiation irradiation resolution chart;

   Monitoring or measurement are from least one component of the radiation of resolution chart scattering, reflection or transmission, with at least one parameter of monitoring or measurement impression.
2. 2. the periodic array that comprises one dimension or bidimensional according to the resolution chart that the process of claim 1 wherein.
3. 3. according to the method for claim 2, wherein the cycle of array sufficiently little so that its diffraction has only first-order diffraction.
4. 4. comprise three-dimensional structure according to the resolution chart that the process of claim 1 wherein.
5. 5. comprise one group of acyclic lines according to the resolution chart that the process of claim 1 wherein.
6. 6. be monochromatic according to the radiation that the process of claim 1 wherein.
7. 7. comprise multi-wavelength or the light that makes up by the multi-wavelength according to the radiation that the process of claim 1 wherein.
8. 8. comprise linearly polarized light according to the radiation that the process of claim 1 wherein.
9. 9. comprise elliptically polarized light according to the radiation that the process of claim 1 wherein.
10. 10. comprise non-polarized light or random polarization according to the radiation that the process of claim 1 wherein.
11. 11. according to the process of claim 1 wherein that the incidence angle of the radiation that is used to shine fixes.
12. 12. according to the process of claim 1 wherein that the incidence angle of the radiation that is used to shine changes.
13. 13. comprise light from scanning light source or a plurality of light sources according to the radiation that the process of claim 1 wherein.
14. 14., comprise the intensity of radiation according to the process of claim 1 wherein at least one component of radiation.
15. 15., comprise the phase place of radiation according to the process of claim 1 wherein at least one component of radiation.
16. 16., be the degree of clamp-oning of mould in the photoresist according to the process of claim 1 wherein at least one parameter that impresses.
17. 17., be the movement velocity of mould with respect to substrate according to the process of claim 1 wherein at least one parameter that impresses.
18. 18. method according to claim 1, Ya Yin at least one parameter wherein, be selected from as next group parameter, comprise: the glass transition temperature on the viscosity on surface, surface, surfacing are to the degree of complying with of lines on the mould, the curing rate of surfacing and the curing degree of surfacing.
19. 19., be the flow rate of surfacing according to the process of claim 1 wherein at least one parameter that impresses.
20. 20. according to the method for claim 18, surfacing wherein is the stress sensitive material, and at least one parameter that wherein impresses, and is the stress of surfacing.
21. 21., be the displacement of mould with respect to substrate according to the process of claim 1 wherein at least one parameter that impresses.
22. 22., be the depth of parallelism of mould with respect to substrate according to the process of claim 1 wherein at least one parameter that impresses.
23. 23., be the uniformity of imprint process according to the process of claim 1 wherein at least one parameter that impresses.
24. 24., be to be produced in the material different with the material of forming mould according to the process of claim 1 wherein the resolution chart of mould.
25. 25., comprise the photoresist of multilayer according to the moldable surface that the process of claim 1 wherein.
26. 26. be loaded with one or more figure according to the workpiece that the process of claim 1 wherein, these figure can combine with the lines on the mould, are used to the purpose of monitoring and measuring.
27. 27., comprise the measuring resolution chart of a plurality of confessions according to the process of claim 1 wherein the mold pressing surface.
28. 28. according to the measurement that the process of claim 1 wherein is static measurement.
29. 29. according to the measurement that the process of claim 1 wherein is time-resolved measurement.
30. 30. a meterological apparatus is used for the method that impresses at the surface of the work that moldable surface and one group of lines are arranged, monitors or measure at least one parameter of this method, these group lines comprise that this apparatus comprises for measuring resolution chart:

    Illuminator, this illuminator are at least during a part of imprint step, with radiation irradiation at least a portion resolution chart;

    Radiation detection system is used for monitoring or measure from least one component of radiation of resolution chart scattering, reflection or the transmission of irradiation; With

    Data analysis system is used for the radial component of analyzing and testing, with the measurement of at least one parameter that method for stamping is provided.
31. 31. a lithographic apparatus comprises:

    The impression apparatus is used for the surface of the work that moldable surface and one group of lines are arranged is impressed, and wherein these group lines comprise for measuring resolution chart;

    The described meterological apparatus of claim 30; With

    Processing controller is used to analyze the output of meterological apparatus, and produces output signal, with control impression apparatus.
32. 32. according to the lithographic apparatus of claim 31, have the double duty lighting unit, this double duty lighting unit provides the radiation on the meterological and the radiation that changes moldable surface character is provided.
33. 33. an imprint lithography method is used for that the surface of the work of moldable surface is being arranged, impressing mould figure, and the step that this method comprises has:

    Provide the mould on mold pressing surface, so that impress one group of lines, these group of lines comprises for measuring resolution chart;

    Mould near workpiece is placed in the mode of mold pressing surface next-door neighbour's moldable surface;

    The mold pressing surface is pressed into moldable surface; With

    The mold pressing surface is separated with moldable surface, makes the imprinted pattern on mold pressing surface stay moldable surface,

    Wherein, at least during a part of pressurization steps,, and measure and analyze from least one component of the radiation of resolution chart scattering, reflection or the transmission of irradiation, with at least one parameter of control imprint process with radiation irradiation at least a portion resolution chart.
34. 34. according to the method for claim 33, pressurization wherein produces by mechanical pressure.
35. 35. according to the method for claim 33, pressurization wherein produces by hydraulic pressure.
36. 36. according to the method for claim 33, pressurization wherein is that it is plastic that the surface is become by the radiation of laser instrument to the surface.
37. 37. according to the method for claim 33, pressurization wherein produces with static or magnetic force.
38. 38. according to the method for claim 33, at least one component wherein is used to produce feedback signal, uses at least one parameter of control imprint process.
39. 39. method according to claim 33, at least one parameter in the imprint process wherein, be selected from as next group parameter, comprise: stacking between die location, the location of workpiece, mould and the workpiece aimed at, imprint temperature, impression pressure and impression duration.

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