Film deposition with variable film thickness gradient

Abstract

The present invention provides a film deposition apparatus for depositing a sample with a film or membrane that can change the film thickness gradient. [Solution] The apparatus comprises a sample carrier, a source, a shadow mask, and a deposition drive unit, the source comprising a plurality of targets such as a first target and a second target. The source is positioned to deposit at least one sample contained in the sample carrier, the shadow mask is positioned on the line of sight between the sample carrier and the source, the shadow mask is positioned so that the first target provides a contribution to the first deposition, and further positioned so that the second target provides a contribution to the second deposition, the contribution to the second deposition being different from the contribution to the first deposition. At least one of the contributions to the first and second depositions is non-uniform in the first dimension of the sample. The deposition drive unit is positioned to independently control the contributions to the first and second depositions so that the thickness gradient of the film in a first direction is variable.

Description

Technical Field

[0001] The present disclosure relates to a film forming apparatus and a film forming method. More specifically, the present disclosure relates to a film forming apparatus and method for forming films on a plurality of samples. Even more specifically, the present disclosure relates to a film forming apparatus configured to provide a film or a film having a variable film thickness gradient, and a method for forming a film on a sample with a film or a film having a variable film thickness gradient. The present disclosure also relates to a waveguide and a method for forming a waveguide with a material or film having a gradient or a stepped thickness.

Background Art

[0002] Light scattered from an object has information on both amplitude and phase. This amplitude and phase information is captured, for example, on a photosensitive plate using well-known interference techniques to form a holographic record consisting of interference fringes, that is, a "hologram". This hologram is reconstructed by irradiating it with appropriate light to form a two-dimensional or three-dimensional holographic reconstruction image, that is, a reproduced image, that reproduces the original object.

[0003] Computer-generated holography can numerically simulate the interference process. Computer-generated holograms are calculated by techniques based on mathematical transforms such as Fresnel transform and Fourier transform. These types of holograms are called Fresnel / Fourier transform holograms, or simply Fresnel / Fourier holograms. Fourier holograms can be considered as the Fourier domain / Fourier plane representation of an object, or the frequency domain / frequency plane representation of an object. Computer-generated holograms may also be calculated by methods such as the coherent ray tracing method and the point cloud method.

[0004] Computer-generated holograms can be encoded on a spatial light modulator arranged to modulate the amplitude and phase of incident light. The optical modulation can be realized, for example, using an electrically addressable liquid crystal, an optically addressable liquid crystal, or a micromirror.

[0005] A spatial light modulator typically consists of multiple individually addressable pixels (also called cells or elements). The modulation scheme can be binary, multi-level, or continuous. Alternatively, if the device is continuous (i.e., not composed of pixels), the modulation is continuous throughout the device. Spatial light modulators can also be reflective, in which case the modulated light is reflected and output. Similarly, spatial light modulators can be transmissive, in which case the modulated light is transmitted and output.

[0006] The system described herein can be used to provide a holographic projector. Such projectors are used in head-up displays (HUDs). [Overview of the project]

[0007] The aspects of this disclosure are defined in the attached independent claims.

[0008] Overview of Holographic Projection and Wavefront Replication Broadly speaking, this disclosure relates to image projection. The present invention relates to an image projection method and an image projector comprising a display device. This disclosure also relates to a projection system comprising an image projector and an observation system. The image projector projects or relays light from a display device to an observation system. This disclosure is equally applicable to monocular and binocular observation systems. The observation system comprises the observer's eye(s). The observation system comprises an optical element having optical power (e.g., the lens of the human eye) and an observation surface (e.g., the retina of the human eye). The projector is sometimes called an “optical engine”. The display device and the image formed (or perceived) using the display device are spatially separated from each other. The image is formed on the display surface or perceived by the observer. In some embodiments, the image is a virtual image, and the display surface is sometimes called a virtual image surface. In other embodiments, the image is a real image formed by holographic reconstruction and projected or relayed to the observation surface. The image is formed by illuminating a diffraction pattern (e.g., a hologram) displayed on the display device.

[0009] Display devices are composed of pixels. Pixels in a display device diffract light. According to well-known optical theory, the magnitude of the maximum diffraction angle is determined by the size of the pixel (and other factors such as the wavelength of light).

[0010] In some embodiments, the display device is a spatial light modulator, such as a liquid crystal on silicon (LCOS) spatial light modulator (SLM). Light propagates from the LCOS towards an object / system to be observed, such as a camera or an eye, over a range of diffraction angles (e.g., from zero to the maximum diffraction angle). In some embodiments, magnification techniques can be used to extend the range of usable diffraction angles beyond the conventional maximum diffraction angle of the LCOS.

[0011] In some cases, the image (formed from the displayed hologram) is transmitted to the eye. For example, spatially modulated light obtained from a screen or other light-receiving surface between the display device and the viewer, or from an intermediate holographic reconstruction image formed in free space, is transmitted to the viewer.

[0012] In some other examples, the hologram (or its light) itself is transmitted to the observer's eye. For example, the spatially modulated light of the hologram (holographic reconstruction, i.e., what has not yet been fully converted into an image) (informally, it could also be said to be "encoded" by the hologram) is transmitted directly to the observer's eye. The observer can perceive a real or virtual image. In these embodiments, no intermediate holographic reconstruction / image is formed between the display device and the observer. In these embodiments, it may be said that the lens of the eye performs the conversion or transformation from hologram to image. A projection system, or light engine, can be configured so that the observer effectively looks directly at the display device.

[0013] According to well-known optical principles, the angular range of light emitted from a display device and observed by the eye or other observation object / system varies with the distance between the display device and the observation object. For example, at an observation distance of 1 meter, the angle range in which rays from an LCOS can pass through the pupil of the eye and form an image on the retina at a particular eye position is limited. The angular range of rays emitted from the display device that can pass through the pupil of the eye and form an image on the retina determines the portion of the image that the observer "sees." In other words, not all parts of the image are visible from any point on the observation plane (for example, any eye position at any point within an observation window such as an eye movement box).

[0014] In some embodiments, the image perceived by the viewer is a virtual image appearing upstream of the display device. That is, the viewer perceives the image as being farther away than the display device. Conceptually, one can think of the viewer as seeing the virtual image through a "display device-sized window." This window is very small, for example, 1 cm in diameter, and is viewed from a relatively far distance, for example, 1 meter. The viewer is then viewing this display device-sized window through an equally small pupil. Consequently, the field of view is narrow, and the range of angles that can be seen varies greatly depending on the position of the eye at a given time.

[0015] Pupil dilators address the challenge of how to expand the angular range over which light rays propagating from a display device can pass through the pupil of the eye and form an image. Display devices are generally (relatively) small, and the projection distance is (relatively) large. In some embodiments, the projection distance is at least one order of magnitude, e.g., at least two orders of magnitude, greater than the diameter or width of the entrance pupil of the display device and the aperture (i.e., the size of the pixel array).

[0016] The use of a pupil dilator expands the field of view (i.e., the viewer's eye box) laterally, allowing the viewer to move their eyeballs to some extent while continuing to view the image. As those skilled in the art will understand, in an imaging system, the field of view (viewer's eye box) is the area in which the observer's eye can perceive the image. This disclosure relates particularly to virtual image distances other than infinity, i.e., near-field virtual images, but is equally applicable to virtual images formed at infinity, or real images formed downstream of a display device / hologram.

[0017] The display device may have an active area or display area whose first dimension is less than 10 cm, e.g., less than 5 cm, or less than 2 cm. The propagation distance between the display device and the observation system may exceed 1 m, e.g., more than 1.5 m, or more than 2 m. The optical propagation distance in the waveguide may be up to 2 m, e.g., more than 1.5 m, or up to 1 m. This method can receive an image and determine a corresponding hologram of sufficient quality in less than 20 ms, e.g., less than 15 ms, or less than 10 ms.

[0018] In general, this specification discloses systems that provide pupil dilation of an input optical field or wavefront. The input optical field may be a diffracted optical field or a holographic optical field containing a diverging beam of light rays, and the display system can be described as hologram-to-eye. In this case, the input optical field is spatially modulated according to the hologram of the image. Alternatively, the input optical field may be an image, and the display system may comprise a screen, such as a diffuser plate, positioned to form an image on it. In this case, the input optical field is spatially modulated according to the image. In either case, the input optical field is replicated to form a one-dimensional or two-dimensional replica array. To avoid doubt, this disclosure is equally applicable to both arts. In particular, the films or thin films according to this disclosure, or methods for forming them, are equally applicable to the guidance and replication of holograms or images.

[0019] In this disclosure, the term “replica” is used solely to reflect the fact that spatially modulated light is split such that its complex field or wavefront is directed along multiple different optical paths. The term “replica” is used to refer to each generation or instance of the complex field or wavefront after a replication event, such as partial reflection-transmission by a pupil dilator. Each replica travels along a different optical path. Some embodiments of this disclosure relate to the propagation of light encoded in a hologram rather than an image; that is, to light spatially modulated in a hologram of an image, rather than the image itself. Those skilled in the art of holography will understand that the complex field associated with the propagation of hologram-encoded light changes with respect to propagation distance. The use of the term “replica” in this specification is independent of propagation distance, and therefore two light branches or paths associated with a replication event are called “replicas” of each other, even if the lengths of the branches are different. In other words, the complex field evolves differently along each path. That is, two complex fields are considered “replicas” according to this disclosure, even if their propagation distances are different. However, this is conditional on them originating from the same replication event or a series of replication events.

[0020] As described above, an optical waveguide used as a pupil dilator can guide or direct an optical field or wavefront between a pair of parallel surfaces. This can be achieved by internal reflection between the parallel surfaces. Of the pair of surfaces, the first surface may be partially transmission-reflective, and the second surface may be reflective. Thus, the optical field is divided with each internal reflection on the first surface, and multiple replicas of the optical field pass through the region of the first surface that forms the output port of the waveguide. In this way, the observation window (and eye box) is enlarged by the waveguide.

[0021] The intensity and spectrum of each consecutive replica emitted from the waveguide are required to be substantially constant between replicas. For example, the integral value of the light intensity of each replica may be substantially constant, the average value of the light intensity of each replica may be substantially constant, or the distribution of the light intensity of each replica may be substantially constant. Replicas having substantially constant intensity and spectrum are referred to herein as spatially uniform, and a waveguide emitting such replicas is referred to herein as providing spatially uniform emission. Spatially uniform replicas favorably reduce or minimize variations in the brightness of the image (or different areas thereof) perceived by an observer moving around a (magnified) observation window. Furthermore, especially if the hologram contains light of multiple different wavelengths, the overall quality of the hologram received by the observer (or the resulting image perceived by the observer) can be improved.

[0022] The intensity of light guided between the first and second surfaces of a waveguide decreases each time the light field is divided by the first surface. A suboptimal waveguide typically has a first surface with constant reflectivity. As a result, the intensity of each replica decreases. In other words, such conventional waveguides do not provide spatially uniform radiation.

[0023] By applying a gradient film or thickness gradient film to a waveguide, a first surface can be provided in which the reflectance, and therefore the transmittance, changes. In particular, the film can be arranged so that the transmittance of the first surface increases along the waveguide direction. The gradient film can be arranged so that the increase in transmittance of the first surface in the waveguide direction compensates (e.g., at least partially compensates) for the decrease in the intensity of the guided light. However, current gradient films often result in large absorption losses of guided light. Furthermore, these films usually have very limited control over their spectral characteristics, which is particularly disadvantageous when the guided light contains multiple wavelengths. There are some improved gradient films, but these are expensive, time-consuming, complex to manufacture, and generally cannot be manufactured reliably. For example, such films consist of multiple layers (often 20 or more) of dielectric material, where the thickness of each layer changes at different rates from the first end to the second end of the layer. Such complex layered structures may be necessary to provide substantially spatially uniform emission across the entire visible spectrum, but they are time-consuming to manufacture and difficult to produce reliably (for example, they may require a mobile grader to be placed inside the deposition chamber).

[0024] Overview of waveguide membranes In general, this disclosure addresses the technical challenge of providing spatially uniform emission from a waveguide pupil expander, with each replica having substantially similar intensity and spectrum. This disclosure proposes an improved waveguide pupil expander that provides substantially uniform emission at least at specific wavelengths such as red, green, and blue. The first surface of the waveguide comprises multiple alternating layers of first and second dielectrics with different refractive indices. In some examples, each layer has an intrinsic rate of change in thickness. In some examples, each dielectric layer has a rate of change in thickness.

[0025] The multilayer structures obtained by conventional design methods are very complex and not suitable for scale-up on an industrial scale. This complexity is partly due to the need to achieve uniformity at three different wavelengths. This design process was rethought, with a focus on relaxing the constraints in a way that simplifies the necessary manufacturing methods and does not affect the imaging (e.g., holographic) process. In particular, emphasis was placed on reducing the number of hardware changes that occur during film formation and improving the speed. This is because opening the film formation chamber, such as re-evacuating the chamber, may require time-inefficient processes.

[0026] According to an embodiment, a waveguide is provided. The waveguide includes a pair of parallel / complementary surfaces arranged to form a waveguide therebetween. The first surface of the pair of parallel surfaces includes a plurality of first dielectric layers and a plurality of second dielectric layers arranged alternately. Each layer of the first and second dielectrics has a first end and a second end. The first end can be an (optical) input end, and the second end can be the (optical) output end of the final replica or the end of an output port / window. The rate of change of the thickness of each layer from the first end to the second end has one of a plurality of discrete (e.g., acceptable) values. The total number of layers of the first and second dielectrics is greater than the total number of discrete values. The difference in refractive index between the first dielectric and the second dielectric is greater than 0.4 and optionally greater than 0.5.

[0027] As used herein, the "rate of change of thickness" of a layer, unless otherwise specified, refers to the rate of change of the thickness of the layer from the first end to the second end of the layer. The rate of change of the thickness of a layer is represented by 100×(t f -t i ) / t i . Here, t i is the thickness at the first end of the layer, and tf is the thickness at the second end of the layer.

[0028] In general, each layer of a plurality of layers may be parallel to the other layers. The first edge of each layer may be aligned with the first edge of the other layer, and the second edge of each layer may be aligned with the other layer. In other words, each layer may have substantially the same length and width as the other layers, but may differ in thickness or depth. Multiple layers of the first and second dielectrics are sometimes called a stack of layers, or simply a dielectric stack.

[0029] As used herein, the “alternating configuration” of the first dielectric layer and the second dielectric layer means that each layer of the first dielectric is separated from the next nearest layer of the first dielectric by a layer of the second dielectric, and vice versa.

[0030] In some examples, two or more, optionally four or more, optionally six or more, optionally eight or more, and optionally ten or more layers may have the same rate of change in thickness from their first end to their second end (and thus these layers may be associated with the same discrete value). In some examples, layers having the same rate of change in thickness are layers of the same dielectric (i.e., all layers with a particular rate of change in thickness are either the first dielectric layer or the second dielectric layer).

[0031] Each of the first or second dielectric layers may have an increasing or decreasing thickness along the waveguide direction. The first direction may be defined from the first end to the second end of each of the multiple layers. A pair of parallel planes may be arranged to guide light in the first direction. In other words, light guided by the pair of planes may interact with the first end before interacting with the second end. Furthermore, each of the first or second dielectric layers may have an increasing or decreasing thickness along the first direction.

[0032] The minimum thickness of each of the multiple layers of the first and second dielectrics, as well as the discrete values ​​of the rate of change of thickness, can be selected to give the waveguide desired optical properties, in particular, desired transmission behavior that produces spatially uniform light emission. These parameters may depend (among others) on the material properties of the first and second dielectrics (especially the refractive index), the angle of incidence of the light incident on the waveguide, the wavelength of the incident light, and the distance between a pair of parallel surfaces of the waveguide. As will be understood by those skilled in the art, there are multiple (usually quite a few) arrangements of multiple layers that give the waveguide desired optical properties. However, the advantage common to all of these arrangements is that the layered structure of the first surface gives the desired optical properties and can be manufactured quickly, inexpensively, and reliably.

[0033] One example of a rapid, inexpensive, and reliable method for manufacturing the first and second dielectric layers is to form the layers by depositing each dielectric material onto a waveguide substrate. A shadow mask can be used to control the flow of the dielectric material onto the substrate. Preferably, a trapezoidal shadow mask can be used. The rate of change in the thickness of each layer is determined by the shape of the mask, and the overall thickness of each layer is determined by the time it takes for the dielectric material to flow. If the mask is trapezoidal, the rate of change in the thickness of each layer can correspond to the rate of change from the short base to the long base of the trapezoidal shape of the shadow mask. A different mask can be associated with each discrete value. For example, if there are first to fourth rates of change, four different masks can be used to manufacture each layer of the film. Waveguide substrates have the advantage of being easily moved between different material sources having different masks.

[0034] Preferably, the rate of change in the thickness of each layer is constant. In other words, each layer has a linear profile. Dielectric layers with a linear profile may be easier to manufacture. Furthermore, those skilled in the art will understand that for laminates with a linear profile, it is easier to calculate / determine discrete tolerances.

[0035] In some embodiments, the first surface may comprise a plurality (n) of light emission zones for light guided between the first surface and the second surface. The plurality of light emission zones may be distributed along the length of the first surface in the guidance direction. A replica of the input wavefront is generated in each emission zone. The first edge of each layer of the first and second dielectric layers may be located in or adjacent to the first light emission zone. The second edge of each layer of the first and second dielectric layers may be located in or adjacent to the nth light emission zone.

[0036] The internal incidence angle in each emission zone can be in the range of 0 to 70 degrees, preferably in the range of 10 to 50 degrees.

[0037] At other wavelengths (i.e., wavelengths other than the first, second, and third visible wavelengths), the transmittance of the first surface may or may not increase in the waveguide direction. As described above, the waveguides of this disclosure may be particularly advantageous when guiding discrete wavelength light rather than light having a continuous spectrum. The inventors have recognized that parameters such as the thickness and rate of change of the thickness of the multiple layers of the first and second dielectrics can be selected so that the desired transmittance change behavior is obtained only at the first, second, and third wavelengths, and that the layers do not need to exhibit the same transmittance behavior at other wavelengths. The inventors have found that by limiting the transmittance change behavior to specific wavelengths, the desired transmittance behavior can be obtained with a film containing multiple layers with the same rate of change of thickness, and that, as described above, it can be manufactured inexpensively, quickly, and reliably while maintaining acceptable transmission characteristics.

[0038] The first wavelength mentioned above is preferably in the range of 630 to 670 nm. The second wavelength is preferably in the range of 500 to 540 nm. The third wavelength is preferably in the range of 430 to 470 nm. In other words, the first wavelength corresponds to red visible light. The second wavelength corresponds to green visible light. The third wavelength corresponds to blue visible light.

[0039] Preferably, the transmittance T(n) of the first surface at each emission point can satisfy the following equation: T(n) = (T(n-1)) / ([1-T(n-1)] × [1-L]), where L is the optical loss coefficient of the waveguide material.

[0040] The first dielectric may be a first oxide, fluoride, sulfide, or nitrate of a first transition metal or semiconductor. The second dielectric may be a second oxide, fluoride, sulfide, or nitrate of a second transition metal or semiconductor. In some embodiments, the first dielectric includes silicon, titanium, tantalum, or hafnium. In some embodiments, the second dielectric includes any of silicon, titanium, tantalum, or hafnium.

[0041] The thickness of each layer can be in the range of 2 to 300 nm. The thickness of each layer must not be outside this range at any point between the first and second edges. In some embodiments, the thickness of each layer can be in the range of 20 to 300 nm.

[0042] The minimum thickness of each layer can be 2 to 300 nm, or arbitrarily 20 to 300 nm. The maximum thickness of each layer can be 2 to 300 nm, or arbitrarily 20 to 300 nm. The minimum thickness of each layer is less than the maximum thickness of that layer. The minimum or maximum thickness of each layer may be the thickness at the first edge of that layer. The other of the minimum or maximum thickness of each layer may be the thickness at the second edge of that layer.

[0043] At least one of the rates of change in thickness can be positive. At least one of the rates of change in thickness can be negative.

[0044] Each percentage change in thickness ranges from -150% to +150%.

[0045] The number of layers in a set of layers may be at least 10, optionally at least 15, or optionally at least 20. The number of layers in a set of layers may also be in the range of 10 to 30, or optionally 15 to 25.

[0046] Overview of the improved waveguide membrane In summary, this disclosure relates to a method for forming a permeable film consisting of multiple layers. This specification discloses a method for providing an unlimited number of film thickness gradients using the same hardware. This disclosure is based on a dual target and a shadow mask that provides different coating contributions from each target, and significantly changes the film thickness gradient with minor adjustments without opening the deposition chamber, thus increasing design flexibility.

[0047] This disclosure is in conjunction with the methods described in U.S. Patent No. 11,852,832 and UK Patent Application GB 2402387.1, which are incorporated herein by reference in their entirety. U.S. Patent No. 11,852,832 discloses an improved method for fabricating a gradient film on a waveguide. This patent discloses that the rate of change in thickness from the first to the second end of each layer of the film has one of several discrete tolerances, and the total number of layers is greater than the total number of discrete tolerances. UK Patent Application GB 2402387.1 discloses a method for measuring deviations in the deposition function and modifying the film design based on those deviations to optimize a film without making hardware changes in the deposition chamber, such as changing the deposition target.

[0048] The method of this disclosure may include step a, which determines first deposition parameters and a deposition function for each layer in order to optimize the transmittance for multiple different wavelengths at multiple locations along a waveguide. The deposition function is selected from a plurality of acceptable deposition functions. Next, in these examples, there is step b, which involves forming multiple layers using the determined deposition parameters and deposition functions. Next, there is step c, which involves measuring the thickness of at least one layer at each of the multiple locations. The measurement indicates that the deposition function deviates from the one selected during the optimization in step a. Finally, there is step d, which involves determining second deposition parameters for at least one layer by repeating the optimization in step a using the deposition function derived from the measurement in step c. The deposition function is not adjusted; that is, the deposition function determined in step a is retained in step d. However, this disclosure is not limited to these steps.

[0049] Aspects and embodiments of this disclosure A first aspect of this disclosure is a film deposition apparatus comprising a sample carrier, a source (e.g., a film material source), a shadow mask, and a film deposition drive unit. The source comprises a plurality of targets, such as a first target and a second target. The source is positioned to deposit at least one sample contained within the sample carrier. The shadow mask is positioned on the line of sight between the sample carrier and the source. The shadow mask is positioned (e.g., molded and / or positioned) so that the first target provides a contribution to a first film deposition. The shadow mask is further positioned (e.g., molded and / or positioned) so that the second target provides a contribution to a second film deposition. The contribution to the second film deposition is different from the contribution to the first film deposition (e.g., the magnitudes of the deposition rate or deposition rate are not equal). At least one of the contributions to the first and second film deposition is non-uniform in the first dimension (on the surface) of the sample. The deposition drive unit (e.g., a power supply or multiple power supplies) is arranged to independently control the contribution to the first deposition and the contribution to the second deposition, so that the thickness gradient of the film in the first direction is variable. The deposition apparatus may further include a vacuum chamber arranged to be filled with a gas that promotes deposition, such as a physical vapor deposition method such as sputtering. The vacuum chamber can house a sample carrier, a source, and a shadow mask. The vacuum chamber may also house other components that can be controlled externally (e.g., without opening the vacuum chamber) by the deposition drive unit.

[0050] The deposition apparatus described in the embodiments is typically used to deposit a uniform optical film on a sample. Significant resources are expended to enhance the uniformity of the film formed by such apparatus. This disclosure describes a method different from conventional uses of such deposition apparatus. This specification discloses a method for operating a deposition apparatus designed to provide a uniform film and easily forming multiple different deposition gradients (i.e., heterogeneous films with thickness varying in one direction or having a thickness gradient in one direction) using the same hardware, specifically the same light source and the same shadow mask. This method is characterized by using multiple targets and a shadow mask that generates multiple different deposition contributions using the multiple targets. More specifically, the shadow mask generates different deposition contributions from each target. At least one of the deposition contributions is heterogeneous. The inventors have found that when multiple different deposition contributions are generated, the total deposition contribution (e.g., thickness gradient) can be varied using software-controlled means, where the total deposition contribution is the sum of the different deposition contributions. To avoid doubt, this cannot be achieved if the deposition contributions of the different targets are identical. According to this disclosure, an unlimited number of film gradients can be achieved (within a certain range). This expands design flexibility, as there are an unlimited number of selectable gradients, even when the number of available different shadow masks is limited. New film designs become easier. While this is beneficial for research and development, mass production capacity decreases if the target without a shadow mask is not operating at 100% power. Yield during mass production improves. Shadow masks degrade during continuous deposition, requiring frequent maintenance, for example, in line with machine maintenance schedules. This can be compensated for by fine-tuning the gradient (adjusting the target without a shadow mask). Another technological advancement provided by this disclosure is that the target is consumed uniformly.

[0051] The light source can be positioned to deposit multiple samples, such as at least six samples contained within a sample carrier.

[0052] The shadow mask may comprise a first shadow mask component (e.g., a first non-uniform opening) aligned with a first target to provide a contribution to a first film deposition. The shadow mask may also comprise a second shadow mask component (e.g., a second non-uniform opening) aligned with a second target to provide a contribution to a second film deposition, either additionally or alternatively. The second shadow mask component may be omitted. In other words, in some embodiments, the shadow mask comprises a first shadow mask component aligned with a first target to provide a contribution to a first film deposition and a second shadow mask component aligned with a second target to provide a contribution to a second film deposition (e.g., the first shadow mask component is different from the second shadow mask component), while in alternative embodiments, the shadow mask comprises a first shadow mask component aligned with a first target to provide a contribution to a first film deposition, and the second shadow mask component is absent.

[0053] The first shadow mask component can define a first deposition aperture whose size varies along the first dimension of the sample. Alternatively, or additionally, the second shadow mask component can define a second deposition aperture whose size varies along the first dimension of the sample.

[0054] The first deposition opening may consist of alternating first and second sections. Each first section may have an increasing (e.g., linear) opening size. Each second section may have a decreasing (e.g., linear) opening size. To avoid doubt, the disclosure is not limited to a linear gradient, and the first / second sections may consist of a non-linear thickness gradient.

[0055] An increase in the opening size of the first section may be equivalent to a decrease in the opening size of the second section, and may be in opposite directions.

[0056] Each of the first and second sections can correspond to individual samples of multiple samples.

[0057] The deposition drive unit may include at least one selected from the group consisting of a magnetic bar control unit that changes the strength of the magnetic field at multiple positions of the source, a pressure control unit that changes the gas pressure of the deposition apparatus, and a magnet swing that controls the deposition direction.

[0058] The film deposition drive unit can be configured to change the contribution to the first film deposition and / or the second film deposition by 20% or less, for example, 10% or less.

[0059] The material of the first target may be different from the material of the second target; in this case, the film will be a mixed target formed by mixing the materials of the first and second targets. The material of the first target may also be the same as the material of the second target.

[0060] The first and second targets may be spatially separated.

[0061] The deposition direction of the deposition apparatus may be substantially perpendicular to the first dimension of the sample.

[0062] The deposition of the sample film may include sputtering the target material.

[0063] The light source can be positioned to rotate around an axis parallel to the first dimension.

[0064] A second aspect of this disclosure is a method for varying the thickness gradient of a film formed by a source including a first target and a second target. This method includes the steps of (shadow) masking, deposition (or deposition), and software control. The masking step includes positioning or setting a shadow mask on the line of sight between the source and the sample carrier such that the first target provides a contribution to a first deposition and the second target provides a contribution to a second deposition that is different from the contribution to the first deposition. At least one of the first and second deposition contributions is non-uniform in a first dimension of the sample(s) contained in the sample carrier. The deposition step includes guiding the material from the first target and the film material from the second target toward the sample carrier (through the shadow mask) (e.g., by deposition or evaporation, such as by physical vapor deposition). This method further includes the step of software-controlling the first and / or second deposition contributions by changing the operating conditions or parameters of the deposition drive unit. According to this method, the film thickness gradient in the first direction is variable, such as continuously changing, at least within the operating range.

[0065] Overview of Terms The term “hologram” is used to refer to a record containing amplitude information, phase information, or a combination thereof, about an object. The term “holographic reconstruction” is used to refer to the optical reconstruction of an object formed by illuminating a hologram. Systems disclosed herein are described as “holographic projectors” because the holographic reconstruction is a real image and is spatially separated from the hologram. The term “reconstruction field” is used to refer to the two-dimensional region in which the holographic reconstruction is formed and fully focused. When a hologram is displayed on a spatial light modulator containing pixels, the reconstruction field is repeated in the form of multiple diffraction orders, each diffraction order being a copy of the zeroth reconstruction field. The zeroth reconstruction field is the brightest reconstruction field and therefore generally corresponds to the preferred or primary reconstruction field. Unless otherwise specified, the term “reconstruction field” is interpreted to refer to the zeroth reconstruction field. The term “reconstruction plane” is used to refer to a plane in space containing all reconstruction fields. The terms “image,” “reconstruction image,” and “image region” refer to the region of the reconstruction field illuminated by the light of the holographic reconstruction. In some embodiments, the “image” may consist of discrete spots called “image spots” or, for convenience, “image pixels.”

[0066] The terms “encoding,” “writing,” or “addressing” are used to describe the process of providing multiple control values ​​to multiple pixels of an SLM, each determining the modulation level of that pixel. It can be said that the pixels of the SLM are configured to “display” an optical modulation distribution in response to the reception of these control values. Therefore, it can be said that the SLM “displays” a hologram, which can be thought of as an array of optical modulation values ​​or levels.

[0067] It has been discovered that a holographic reconstruction of acceptable quality can be formed from a “hologram” containing only phase information related to the Fourier transform of the original object. Such holographic recordings are sometimes called phase-only holograms. Although the embodiments relate to phase-only holograms, this disclosure also applies to amplitude-only holography.

[0068] This disclosure is also applicable to forming holographic reconstructions using amplitude and phase information associated with the Fourier transform of the original object. In some embodiments, this is achieved by complex modulation using a so-called fully complex hologram, which includes both amplitude and phase information associated with the original object. Such a hologram is sometimes called a fully complex hologram because the value (gray level) assigned to each pixel of the hologram has both amplitude and phase components. The value (gray level) assigned to each pixel can be represented as a complex number having both amplitude and phase components. In some embodiments, a fully complex computer-generated hologram is computed.

[0069] The terms phase value, phase component, phase information, or simply phase may be used as an abbreviation for “phase delay” when referring to the phase of a pixel in a computer-generated hologram or spatial light modulator. That is, the phase value is actually a numerical value (e.g., in the range of 0 to 2π) that represents the amount of phase delay provided by that pixel. For example, a pixel in a spatial light modulator described as having a phase value of π / 2 delays the phase of the received light by π / 2 radians. In some embodiments, each pixel in a spatial light modulator can operate at any of several possible modulation values ​​(e.g., phase delay values). The term “gray level” may be used to refer to multiple available modulation levels. For example, the term “gray level” may be used for convenience to refer to multiple available phase levels in a phase-only modulator, even if different phase levels do not provide different shades of gray. The term “gray level” may also be used for convenience to refer to multiple available complex modulation levels in a complex modulator.

[0070] Therefore, a hologram consists of a grayscale array, i.e., an array of optical modulation values ​​such as phase delay values ​​or complex modulation values. A hologram can also be considered a diffraction pattern, as it is a pattern that is displayed on a spatial light modulator and causes diffraction when illuminated with light of a wavelength equivalent to, or usually shorter than, the pixel pitch of the spatial light modulator. This specification refers to combining holograms with other diffraction patterns, such as diffraction patterns that function as lenses or gratings. For example, a diffraction pattern that functions as a grating can be combined with a hologram to translate the reconstructed field on the reconstructed plane, or a diffraction pattern that functions as a lens can be combined with a hologram to focus the holographic reconstruction on the near-field reconstructed plane.

[0071] In the following detailed description, different embodiments and groups of embodiments may be disclosed individually, but any feature of any embodiment or group of embodiments can be combined with other features or combinations of features of any embodiment or group of embodiments. In other words, all possible combinations and permutations of the features disclosed herein are assumed. [Brief explanation of the drawing]

[0072] Specific embodiments are described only as examples, with reference to the following diagram. [Figure 1] Figure 1 is a schematic diagram showing a reflective SLM that generates a holographic reconstruction on a screen. [Figure 2] Figure 2 shows a perspective view of a pair of wavefront replicators arranged for two-dimensional replication. [Figure 3] Figure 3 shows a schematic cross-sectional view of the first waveguide according to this disclosure. [Figure 4] Figure 4 shows a schematic cross-sectional view of a portion of the first waveguide in Figure 3, magnified. [Figure 5] Figure 5 shows a graph illustrating the ideal increase in the transmittance of the waveguide in the waveguide direction. [Figure 6] Figure 6 is a schematic cross-sectional view showing part of the apparatus for manufacturing a waveguide according to the present disclosure, illustrating how the waveguide substrate passes beneath a source of dielectric material. [Figure 7] Figure 7 is a schematic diagram of the shadow mask of the apparatus shown in Figure 6, which has four openings, and its cross-section lies in a plane perpendicular to the plane of the cross-section in Figure 6. [Figure 8] Figures 8A, 8B, 8C, and 8D show schematic cross-sectional views of four different waveguide substrates, each having a layer of dielectric material formed on a first surface using the mask of Figure 7, with each layer formed using a different opening in the mask. [Figure 9] Figures 9A, 9B, and 9C show the cumulative effect when two targets are deposited simultaneously using different masks. [Figure 10] Figure 10 shows an example of a film deposition apparatus according to several embodiments.

[0073] The same reference number is used throughout the drawing to refer to the same or similar parts. [Modes for carrying out the invention]

[0074] The present invention is not limited to the embodiments described below, but extends to the entire scope of the appended claims. That is, the present invention can be implemented in various forms and should not be construed as being limited to the embodiments described for illustrative purposes.

[0075] Unless otherwise specified, singular terms may include their plural forms.

[0076] Structures described as being formed on or below other structures, or above or below other structures, are interpreted to include cases where structures are in contact with each other, and even cases where a third structure is positioned between them.

[0077] When describing temporal relationships, for example, if the temporal order of events is described using terms such as "after," "successor," "next," or "before," this disclosure should be interpreted as including both consecutive and discontinuous events unless otherwise specified. For example, unless expressions such as "just after," "immediately following," or "directly following" are used, non-consecutive cases should also be interpreted as being included in this disclosure.

[0078] In this specification, terms such as "first," "second," etc., may be used to describe various elements, but these terms do not limit these elements. These terms are used solely to distinguish one element from another. For example, without departing from the scope of the appended claims, the first element may be called the second element, and similarly, the second element may be called the first element.

[0079] Features of different embodiments can be linked or combined with each other, either partially or entirely, and can operate in conjunction with each other in various ways. Some embodiments can be executed independently of each other, or together in an interdependent manner.

[0080] Conventional optical configurations of holographic projection Figure 1 shows an embodiment of encoding a computer-generated hologram on a single spatial light modulator. The computer-generated hologram is the Fourier transform of the object for reconstruction. Therefore, the hologram can be said to be a Fourier domain, frequency domain, or spectral domain representation of the object. In this embodiment, the spatial light modulator is a reflective liquid crystal on silicon (LCOS) device. The hologram is encoded on the spatial light modulator, and a holographic reconstruction image is formed on a light-receiving surface, such as a screen or diffuser, in the reproduction field.

[0081] A light source 110 (e.g., a laser or laser diode) is positioned to illuminate the SLM 140 via a collimator lens 111. The collimator lens makes the wavefront of the light incident on the SLM nearly planar. In Figure 1, the direction of the wavefront is deviated from the perpendicular (e.g., 2-3 degrees from true orthogonality with respect to the plane of the transparent layer). However, in other embodiments, the nearly planar wavefront is provided with perpendicular incidence, and the input and output optical paths are separated by a beam splitter arrangement. In the embodiment shown in Figure 1, light from the light source is reflected off the mirrored back of the SLM and is positioned to interact with the optical modulation layer to form the output wavefront 112. The output wavefront 112 is applied to an optical system including a Fourier transform lens 120 focused on the screen 125. More specifically, the Fourier transform lens 120 receives the modulated light beam from the SLM 140 and performs a frequency-space transformation to generate a holographic reconstruction on the screen 125.

[0082] It is noteworthy that in this type of holography, each pixel of the hologram contributes to the overall reconstruction. There is no one-to-one correlation between a specific point (or image pixel) on the reconstruction field and a specific optical modulator (or hologram pixel). In other words, the modulated light emitted from the optical modulation layer is distributed throughout the entire reconstruction field.

[0083] In these embodiments, the spatial position of the holographic reconstruction is determined by the refractive power (focusing power) of the Fourier transform lens. In the embodiment shown in Figure 1, the Fourier transform lens is a physical lens. That is, the Fourier transform lens is an optical Fourier transform lens, and the Fourier transform is performed optically. While any lens can function as a Fourier transform lens, the accuracy of the Fourier transform is limited by the performance of the lens. Those skilled in the art understand how to perform an optical Fourier transform using a lens.

[0084] In the example in Figure 1, an image is formed on screen 125 by holographic reconstruction or transformation. The image can be replicated by the waveguide of the present disclosure. In this example, the waveguide receives and replicates a wavefront containing spatially modulated light in accordance with the image. In other examples of the present disclosure, the image is not formed on a screen, but instead the hologram is propagated directly to the viewer. This is referred to as hologram-to-eye, and at least conceptually, it can be said that the lens of the viewer's eye performs the hologram-to-image transformation. In these examples, it can be said that the waveguide receives and replicates a wavefront containing spatially modulated light in accordance with the hologram of the image.

[0085] Hologram calculation In some embodiments, the computer-generated hologram is a Fourier transform hologram, or simply a Fourier hologram or Fourier transform type hologram, in which the image is reconstructed in the far field using the Fourier transform properties of a positive lens. The Fourier hologram is computed by a Fourier transform that returns the desired light field at the reconstruction plane to the lens plane. Computer-generated Fourier holograms can be computed using the Fourier transform. Embodiments relate to Fourier holography and the Gerchberg-Saxton algorithm, but these are illustrative only. This disclosure is equally applicable to Fresnel holography and Fresnel holograms, which can be computed in a similar manner. In some embodiments, the hologram is a phase hologram or a hologram of phase only. However, this disclosure is also applicable to holograms computed by other methods, such as those based on point cloud methods.

[0086] In some embodiments, the hologram engine is configured to exclude the contribution of light blocked by the limiting aperture of the display system from the hologram calculation. UK Patent Application No. 2101666.2, filed 5 February 2021 and incorporated herein by reference, discloses a first hologram calculation method that uses eye-tracking and ray tracing to identify subregions of a display device in order to calculate a point cloud hologram with ghost images removed. The subregions of the display device correspond to the aperture in this disclosure and are used to exclude the light path from the hologram calculation. UK Patent Application No. 2112213.0, filed 26 August 2021 and incorporated herein by reference, discloses a second method based on a modified Gerchberg-Saxton algorithm, which includes a step of cropping the light field in accordance with the pupil of the optical system during the hologram calculation. The cropping of the light field corresponds to the determination of the limiting aperture in this disclosure. Filing on 23 December 2021 and incorporated herein by reference, UK Patent Application No. 2118911.3 discloses a third method for calculating a hologram, the method comprising the step of determining a region of a so-called extended modulator formed by a hologram replicator. This region of the extended modulator is also, according to the present disclosure, an aperture.

[0087] In some embodiments, a real-time engine is provided that receives image data and computes holograms in real time using an algorithm. In some embodiments, the image data is a video containing a series of image frames. In other embodiments, the holograms are pre-computed, stored in computer memory, and called upon as needed to be displayed on the SLM. In other words, in some embodiments, a repository of predetermined holograms is provided.

[0088] Two-dimensional pupil dilation or wavefront duplication Figure 2 shows a perspective view of system 200, which includes two pupil dilators or replicators 204, 206 arranged to dilate the pupil or to replicate the wavefront 202 in two dimensions.

[0089] In the system 200 of Figure 2, the first replicating device 204 comprises a first pair of surfaces stacked parallel to each other and arranged to provide replicating, i.e., pupil dilation. The first pair of surfaces are similar (and possibly identical) in size and shape to each other and are substantially elongated in one direction. The wavefront 202 is directed toward the input of the first replicating device 204. The wavefront contains light spatially modulated according to an image or a hologram of that image. As is well known to those skilled in the art, the light of the wavefront 202 is replicated in a first direction along the length of the first replicating device 204 by the processes of internal reflection between the two surfaces and partial transmission of light from each of a plurality of output points on one of the surfaces (the top surface as shown in Figure 2). Thus, a first plurality of replicated wavefronts 208 are radiated from the first replicating device 204 toward the second replicating device 206.

[0090] The second duplicator 206 comprises a second pair of surfaces stacked parallel to each other and positioned to receive each of the parallelized light beams of the first plurality of wavefronts 208, and further positioned to provide duplication, i.e., pupil dilation, by expanding each of these light beams in a second direction substantially perpendicular to the first direction. The first pair of surfaces are similar (and possibly identical) in size and shape to each other and are substantially rectangular. The second duplicator has a rectangular shape so that it has a length along the first direction to receive the first plurality of wavefronts 208 and a length along the second orthogonal direction to provide duplication in the second direction. Due to internal reflection between the two surfaces and partial transmission of light from each of the plurality of output points on one of the surfaces (the top surface as shown in Figure 6), the light of each light beam in the first plurality of wavefronts 208 is duplicated in the second direction. Thus, the second plurality of wavefronts 210 are emitted from the second duplicator 206. Here, the second set of wavefronts 210 includes copies of wavefront 202 along the first and second directions, respectively. Therefore, the second set of wavefronts 210 can be considered to include a two-dimensional grid or array of the copied wavefronts. Thus, it can be said that a two-dimensional replicating device (or "two-dimensional pupil dilation device") is constructed by combining the first and second replicating devices 204 and 205 in Figure 2.

[0091] Improved waveguide As explained in relation to Figure 2, light within a waveguide is reflected between the reflecting surfaces of the waveguide. The light may undergo one or more reflections or bounces between the two reflecting / reflecting / transmitting planes, and at each bounce point on the partial-transmitting surface, a portion of the light is radiated out of the waveguide, while the remaining (usually larger) portion is reflected and continues to propagate between the two surfaces of the waveguide. Thus, the partial-transmitting surface of the waveguide provides multiple (n) light-emitting regions for the light guided between the first and second surfaces. After each bounce point / emitting region, the intensity of the light propagating within the waveguide decreases. In other words, the intensity of light propagating within the waveguide decreases along the direction of guidance.

[0092] It is desirable that the intensity of light emitted from the waveguide be substantially the same in each of the n emission zones. This can be achieved by providing an improved waveguide that applies a layered film to the semi-transparent surface of the waveguide, thereby reducing the transmittance of the semi-transparent surface along the waveguide direction. This reduces the intensity of the propagating light in the waveguide direction.

[0093] Figure 3 is a schematic cross-sectional view of a waveguide 308 according to the present disclosure. The waveguide 308 comprises a first surface 302 and a second surface 304. The diagram shows how a light field or wavefront 306 (represented by a single ray in Figure 3) propagates through the waveguide 308. The second surface 304 includes an input port positioned to receive the light field. The first surface 302 is partially transparent and partially reflective and comprises a film 303. The term “film deposition” is used herein for convenience only, and those skilled in the art will understand that any component described as “film deposition” may be formed by any method including, but not limited to, a film deposition process. The second surface 304 is substantially entirely reflective (except for the input surface). Figure 3 shows the path of the light field or wavefront as it passes through the waveguide, reflecting between the first and second surfaces. Each time a reflection occurs on the first surface, the light field is divided, with a portion radiating from the first surface and the remainder being reflected and propagating between the first and second surfaces. Thus, a substantially radiating region is formed at each reflection point. Six radiating regions are shown in Figure 3, but those skilled in the art will understand that the number of reflection and radiating regions can, of course, be more or less than this. Figure 3 is merely illustrative.

[0094] In some embodiments, the film 303 is constructed by alternately stacking multiple layers of a first dielectric and multiple layers of a second dielectric, as shown in Figure 4. Each layer of the film is referred to herein by number, with the layer in contact with the first surface 302 being the first layer (layer 401). Layer 402 lies above layer 401, and layer 403 lies above layer 402. The layer furthest from the first surface 302, i.e., the layer above layer 403, is the fourth layer 404. In this example, layers 401 and 403 are formed of silicon dioxide (SiO2), and layers 402 and 404 are formed of titanium dioxide (TiO2), with these layers being alternately stacked so that subsequent SiO2 layers (first dielectric) are separated by TiO2 layers (second dielectric).

[0095] Each of layers 401 to 404 has a thickness that changes along the waveguide direction (from left to right in Figure 4), and in this embodiment, it has a linear profile as an example. In other words, the rate of change of thickness of each layer is constant. The profile of each layer can be characterized using the rate of change of thickness. Each layer has a first end 406 and a second end 408. The rate of change of thickness is defined as the change in thickness from the first end 406 to the second end 408 divided by the thickness of the first end 406 and multiplied by 100. In the case of the first layer 401, the rate of change of thickness is 100 × (final thickness 412 - initial thickness 410) / initial thickness 410.

[0096] The rate of change in the thickness of layer 403 is the same as that of layer 401. Furthermore, the rate of change is positive for both layer 401 and layer 403 (i.e., the thickness of the layer increases from the first end 406 to the second end 408). The rates of change of layer 402 and layer 404 are different from each other, and from layer 401 to layer 403. Furthermore, the rate of change is negative for both layer 402 and layer 404 (i.e., the thickness of the layer decreases from the first end 406 to the second end 408).

[0097] It was found that by alternately stacking an appropriate number of first and second dielectric layers, and appropriately setting the thickness of each layer and the rate of change of thickness from the first end to the second end, it is possible to realize the first surface of a waveguide in which the transmittance increases along the direction of the waveguide. As a result, the intensity of the light field emitted from each light-emitting region (i.e., the intensity of each replica emitted from each light-emitting region) becomes substantially constant. This makes it possible to advantageously achieve substantially spatially uniform light emission from the waveguide.

[0098] Figure 5 shows the ideal exponential increase in transmittance of the first surface 302. This is a graph with transmittance on the Y axis and position on the first surface 302 on the X axis. The numbers on the X axis represent the nth light-emitting region. Specifically, the transmittance increases according to the following equation: T(n) = (T(n-1)) / ([1 - T(n-1)] × [1 - L]), where L is the optical loss coefficient of the waveguide material.

[0099] Manufacturing method Figures 6, 7, 8A, 8B, 8C, 8D, 9A, 9B, 9C, and 10 show different examples of deposition apparatus that can be used to carry out the methods and apparatus disclosed herein. Figures 6, 7, 8A, 8B, and 8C show a first example of a planar deposition apparatus in which the sample moves on the XZ plane. Figures 9A, 9B, 9C, and 10 show a second example of a so-called drum deposition apparatus. This disclosure is not limited to any particular film shape, and only two embodiments are described herein as examples.

[0100] The advantage of the multilayer films of this disclosure is that they can be manufactured in an inexpensive, rapid, and reliable manner. While this specification discloses one such method, those skilled in the art will understand that other methods are also possible.

[0101] An apparatus for carrying out this method comprises two sources of a first dielectric material (e.g., SiO2), two sources of a second dielectric material (e.g., TiO2), a shadow mask having first to fourth trapezoidal openings, and means for moving a waveguide substrate relative to the shadow mask. Each opening in the shadow mask is associated with a source of dielectric material. During the production of each layer, dielectric material from one of the sources is configured to pass through one of the openings in the shadow mask. The waveguide substrate is moved relative to the shadow mask (or vice versa) such that the shadow mask is positioned between the sources and the waveguide substrate. The waveguide substrate passes under the openings, and a layer of dielectric material is formed on the surface of the waveguide substrate.

[0102] Figure 6 is a schematic cross-sectional view showing a part of a waveguide manufacturing apparatus according to the present disclosure, the cross-section being in the XY plane. The part of the apparatus shown in Figure 6 comprises a first SiO2 supply source and a shadow mask 640 having a first opening 601. A waveguide substrate 600 (in the form of a glass or Perspex block or slab) is also shown. The SiO2 material is configured to flow out from the first supply source 620 and pass through the first opening 601 of the shadow mask 640. The material flow is in the negative Y direction. The shape of the first opening 601 determines the shape of the SiO2 flow downstream of the shadow mask 640. Figure 6 is not drawn to scale.

[0103] Means for moving the waveguide substrate 600 (not shown) are configured to move the waveguide substrate 600 in a first plane perpendicular to the Y direction so that the waveguide substrate 600 passes under the first opening 601. In some embodiments, the movement is entirely in the X direction. However, in other embodiments, the waveguide substrate 600 rotates in the first plane and moves in both the X and Z directions.

[0104] In Figure 6, the waveguide substrate 600 has not yet passed under the first aperture 601, and therefore no film layer has been formed on the waveguide substrate 600. When the waveguide substrate passes under the first aperture 601 (in the X direction), a dielectric film is deposited on the substrate. Generally, to form a complete layer, the waveguide substrate 600 needs to pass under the first aperture 601 multiple times until the desired thickness is reached.

[0105] Once the first layer is formed, the waveguide substrate 600 is moved under one of the sources of the second dielectric material, and a second layer of the second dielectric material is formed on top of the first layer of the first dielectric material.

[0106] Figure 7 is a schematic diagram of a shadow mask photographed in the XZ plane (i.e., a plane perpendicular to the plane in Figure 6). The shadow mask comprises four openings, namely, a first opening 701 (see above), a second opening 702, a third opening 703, and a fourth opening 704. For example, the first opening 701 and the third opening 703 can be associated with a first source(s) of a first dielectric material. For example, the second opening 702 and the fourth opening 704 can be coupled with a second source(s) of a second dielectric material. Each opening has a trapezoidal shape including a short base and a long base, forming a film with a thickness gradient in the Z direction.

[0107] The waveguide substrate 700 is movable so that it is positioned sequentially under different openings (e.g., translated and / or rotated as shown by the dashed arrow 750). The order of the layers can be controlled depending on the order of the openings over which the waveguide substrate 700 moves. The waveguide substrate 700 is moved relative to the shadow mask (e.g., translated and / or rotated in the x-direction) and passes sequentially under different openings. This causes the waveguide substrate 700 to pass under each opening with the short and long bottoms of the openings spaced apart in the Z direction. In this example, since the shadow mask is rotatable, the waveguide substrate 700 forms a film with a thickness gradient (in the Z direction) through one opening at a time. In Figure 7, the first opening 701 is positioned to be active, i.e., to provide the film. In this way, the thickness of each deposited layer changes in the Z direction. The rate of change in the thickness of the layer from the first end to the second end (in the Z direction) depends on the rate of change in the short and long bottom widths of each opening. Figure 7 shows linear movement of the substrate and rotation of the shadow mask, but the disclosure is not limited to this arrangement and includes any method for engaging or disengaging different openings one by one with the substrate. The different openings may correspond to different film materials.

[0108] Figures 8A, 8B, 8C, and 8D are schematic cross-sectional views of four different first layers formed on the waveguide substrate 800. Figure 8A shows the first layer 801 formed when the waveguide substrate 800 passes under the first opening 701. Figure 8B shows the second layer 802 formed when the waveguide substrate 800 passes under the second opening 702. Figure 8C shows the third layer 803 formed when the waveguide substrate 800 passes under the third opening 703. Figure 8D shows the fourth layer 804 formed when the waveguide substrate 800 passes under the fourth opening 804. As will be understood by those skilled in the art, the thickness profiles of each of the first to fourth layers 801 to 804 correspond to the shape of the respective openings.

[0109] In particular, as shown in Figure 7, when the openings and waveguide substrate are aligned, the widths of the first and third openings 701 and 703 increase in the Z direction, resulting in a positive gradient from left to right. The rate of change in the thickness of the third layer 803 is greater than that of the first layer 801. This is because the rate of change in the width from the short bottom to the long bottom of the third opening 703 is greater than that of the first opening 701. As shown in Figure 7, when the shadow mask and waveguide substrate are rotated and aligned, the widths of the second and fourth openings 702 and 704 decrease in the Z direction, resulting in a negative gradient from left to right. The rate of change in the thickness of the second layer 802 is greater than that of the fourth layer 804. This is because the rate of change in the width from the short bottom to the long bottom of the second opening 702 is greater than that of the fourth opening 704.

[0110] As can be understood, the arrangement of a shadow mask having four different shaped openings, two of which are connected to a first dielectric material source and two of which are connected to a second dielectric material source, provides means for manufacturing a plurality of alternately arranged first dielectric layers and a plurality of second dielectric layers. Each layer of the first dielectric layer has a thickness change rate equal to either a first or second value, all layers having the first value are associated with, for example, a first dielectric material source 701, and all layers having the second value are associated with, for example, a second dielectric material source 702. Each layer of the second dielectric layer has a thickness percentage change equal to either a third or fourth value, all layers having the third value are associated with, for example, a third dielectric material source 703, and all layers having the fourth value are associated with, for example, a fourth dielectric material source 704.

[0111] The advantage of this manufacturing method is that multiple alternating layers of first and second dielectric materials can be formed by quickly and easily moving / rotating the waveguide substrate and passing it under the openings of the shadow mask as needed. The number of unique masks with different shapes determines the number of discrete values ​​of the rate of change of the layer thickness available, and thus the rate of change of any layer thickness can be controlled simply by selecting the order of the openings. The absolute thickness of any layer can be controlled by controlling the speed at which the waveguide substrate passes under a particular shadow mask 604 or by controlling the flow velocity of the material.

[0112] It should be understood that the manufacturing methods disclosed herein are not limited to four openings and two dielectric material sources. For example, increasing or decreasing the number of masks of different shapes only increases or decreases the discrete number of allowable percentage changes in the available layer thickness.

[0113] Improved film coating method and UK patent application GB 2402387.1 The present invention relates to a film design method comprising the following steps. 1. In the design of the base structure, a multilayer mirror with an RGB window is typically used and placed at the lowest T% position. The gradient is not considered in this step. 2. Apply a linear gradient to the multilayer base structure and optimize the gradient so that the membrane transmittance at different locations can meet all requirements.

[0114] The basic idea is to use the gaps between the RGB (red, green, blue) windows as design flexibility to stably and synchronously increase the transmittance within the RGB windows. Therefore, this design is highly susceptible to the effects of gradients, and even a slight change (a few percent) can significantly alter the transmittance of the film.

[0115] In practice, it can be difficult to adjust the mask to achieve the gradient thickness as designed. There are several challenges. • Adjusting the mask is a time-consuming process and requires precise metal machining. There is no simple relationship between the thickness of the gradient and the physical gradient of the mask opening. To achieve a linear gradient thickness, it is usually necessary to introduce nonlinearity into the mask. Approaching the desired gradient typically involves several iterations of trial and error. • In mass production, masks deteriorate within a few weeks, requiring maintenance and readjustment. This increases the likelihood of slight variations in the thickness of the gradient.

[0116] Typically, gradient masks are close to the design but not perfectly accurate. To avoid such imperfect gradient masks, this specification discloses a “post-process” film optimization. This optimization does not require hardware changes and can significantly improve film performance. This method consists of the following elements: • The gradient ("deposition function") is fixed as is. In other words, small deviations are accepted, and no further optimization is performed. • Find the optimal combination of multilayer thicknesses that can "fully utilize" the fixed gradient ("membrane function").

[0117] Dual target This specification discloses a film deposition apparatus comprising a source with two targets. The source is a source of material for forming a film. Thus, the source comprises two components called two targets. Each target supplies the film material. The composition of the first target may be the same as or different from the composition of the second target. Figures 9A, 9B, 9C, and 10 illustrate, but are not limited to, a drum film deposition apparatus. Film configurations or shapes (including planar film shapes) that can accommodate the two targets and two masks, respectively, are compatible with this disclosure.

[0118] Figure 9A shows a first target 902 and a first mask 904 positioned on a substrate 906 to form a first film 908. The film is a gradient film whose thickness varies according to the first mask. In the upper view of Figure 9A, the deposition direction is out of the plane of the paper. The lower view of Figure 9A shows an orthogonal plane. The left side of the first film 908 is thicker than the right side, according to the shape of the mask. The mask has an opening, as shown in Figures 7, 8A, 8B, 8C, and 8D, and the first film 908 has a negative thickness gradient.

[0119] Figure 9B shows a second target 912 positioned on the substrate 916 to form a second film 918. The second film 918 has a uniform thickness because there is no mask.

[0120] In a dual-target configuration, the first target 902 and the second target 912 can deposit film on the substrate simultaneously. For example, the first target 902 and the second target 912 may be adjacent to each other in the deposition chamber, as shown in Figure 9C. The inventors recognize that this technique and the use of different masks for the two targets allow for an infinite number of different gradients to be utilized, albeit within a certain range. It will be understood that "simultaneously" depositing the substrate means that the contributions to the first and second depositions from the first and second targets are output from the targets simultaneously (i.e., at the same time or in the same first time). However, due to the rotational characteristics of the film configuration, both the contributions to the first and second depositions may not occur on the substrate exactly at the same time (although the contributions to deposition may occur on the substrate simultaneously for at least a portion of the rotation of the substrate or shadow mask).

[0121] For example, suppose a first target 902 fitted with a first mask 904 forms a first film 908 with a film thickness gradient from 1.0 to 0.5. When a second target 912 without a mask is operating at 100% power, its thickness is uniform and 1.0. In this case, the combined gradient is from 1.5(0.5+1) to 2(1+1), which corresponds to 0.75 to 1. When a second target 912 without a mask is operating at 0% power, its thickness is uniform and 0. The gradient remains from 0.5 to 1.

[0122] Therefore, by controlling the output of the second target 912 without using a mask, the thickness gradient of each film layer (the layer deposited by this target pair) can be freely varied from "0.5 to 1" to "0.75 to 1". This is the principle of the present disclosure, which enables an unlimited number of gradients. It is noteworthy that this is achieved using the same hardware, that is, without changing the targets or masks. This is described as a "hardware change" rather than a "software change" achieved by changing the power of the deposition process, as mentioned above. This is achieved by having two masks with different gradients, or by using only one mask. The mask gradient is the rate of change of the size of the mask opening in relation to the dimensions of the substrate, which may correspond to the approximate direction of the waveguide during use.

[0123] By achieving unlimited gradients within a certain range, the number of selectable gradient types becomes unlimited despite the limited number of shadow masks, significantly increasing design flexibility. This makes new film designs easier. While this brings the greatest benefit to the design process, mass production capacity decreases if the target without a shadow mask is not operating at 100% output. This leads to improved yield during mass production. Shadow masks degrade with continuous deposition, requiring frequent maintenance. This problem can be compensated for by fine-tuning the gradient (adjusting the target without a shadow mask).

[0124] Figure 10 shows a deposition chamber for a deposition apparatus of the present disclosure. Figure 10 shows a sample carrier 1010 containing a plurality of individual samples, such as a first sample 1011. Figure 10 shows a dual rotating source 1020 containing a first target 1021 and a second target 1022. Figure 10 further shows a gas control unit 1030 providing 10 adjustment positions along its entire length, and a remotely adjustable magnetic "RAM" bar 1040 also providing 10 adjustment positions along its entire length. The shadow mask 1050 comprises a first mask 1051 aligned with the first target 1021 and a second mask 1052 aligned with the second target 1022. In this figure, the first mask 1051 and the second mask 1052 are the same, but in embodiments, the first mask 1051 and the second mask 1052 are different. More specifically, the gradient of the first mask 1051 is different from the gradient of the second mask 1052. More specifically, the rate of change in the aperture size of the first mask 1051 (the required gradient, i.e., in the Z direction) is different from the rate of change in the aperture size of the second mask 1052. Figure 10 shows how each mask is composed of multiple sections that alternately form positive and negative gradients. Each section corresponds to a different sample. The film thickness gradient 1060 of the film formed on the sample by the first and second targets is shown in Figure 10.

[0125] According to this disclosure, by using a dual target with different gradient masks, small changes to the deposition environment or parameters result in useful changes to the deposition gradient. This specification discloses a method for simultaneously depositing an unlimited number of films with different thickness gradients on multiple relatively small samples using a deposition apparatus designed to provide highly uniform films. These small changes are controlled by software and can be achieved without opening the chamber or changing the process shadow mask. The following three paragraphs illustrate three software-driven methods for changing the thickness gradient as examples.

[0126] In the first example, the RAM bar 1040 directly changes the magnetic field of the deposition process. For example, the deposition process may include sputtering, such as magnetron sputtering. There are multiple adjustment positions, i.e., drive levels or operating levels, such as 10 adjustment positions, which are insufficient to give appropriate gradients to, for example, six samples along the entire length. This function is typically provided to facilitate the formation of uniform thickness films rather than films with film thickness gradients. In other words, this function is provided for uniformity adjustment. However, according to the embodiment, this function is also used to provide relatively small adjustments to the deposition parameters in order to access different gradients from dual target sources without changing the shadow mask.

[0127] In the second example, the gas pressure in the chamber is adjusted. In some embodiments, the gas is argon, and Ar+ ions collide with the target, ejecting the film material toward the sample carrier. The gas control unit 1030 has multiple adjustable positions, drive levels, or operating levels, such as 5 or 10 steps. This is also insufficient to give a proper gradient to, for example, six slabs, but is effective for uniform film formation and uniformity adjustment. This function is usually provided to facilitate the formation of a uniform thickness film rather than a film with a film thickness gradient. In other words, this function is provided for uniformity adjustment. However, in some embodiments, this function is also used to make relatively small adjustments to the film deposition parameters to access different gradients from dual target sources without changing the shadow mask.

[0128] In the third example, slightly adjusting the so-called magnetic swing changes the direction of deposition.

[0129] These three examples involve control parameters in addition to gradient shadow masks, which physically block deposition to create a gradient. Dual rotating targets may have two sets of masks (one for each). While gradient shadow masks can reduce target utilization (depending on the design), the material cost in deposition is practically negligible. The relatively small adjustments in the three examples above are relatively small compared to the effect of the masks. These relatively small adjustments are achieved through software control rather than hardware control such as changing the mask in the chamber. The gradient shadow mask is the main source of the gradient, and software control methods are well-suited for improving yield through small adjustments.

[0130] In some embodiments, the dual rotating target is composed of two different materials. Two sets of gradient masks for this dual rotating target can also be composed of different materials. This effectively generates a gradient refractive index mixed material in which the gradient direction is parallel to the dual rotating target during sputtering. Mixed material sputtering is more stable when performed with a single set of dual rotating targets than when using two physically separated targets. In some embodiments, inline ellipsometry without vacuum breakage is used to quickly adjust the gradient refractive index to within the specified range. In some embodiments, optical monitoring is also used.

[0131] Additional features The methods and processes described herein can be implemented on computer-readable media. The term “computer-readable media” includes media configured to store data temporarily or permanently, such as random access memory (RAM), read-only memory (ROM), buffer memory, flash memory, and cache memory. The term “computer-readable media” also includes any medium or combination of media capable of storing instructions executed by a machine, and when such instructions are executed by one or more processors, the machine can execute one or more of the methodologies described herein, in whole or in part.

[0132] The term “computer-readable medium” also includes cloud-based storage systems. The term “computer-readable medium” includes, but is not limited to, one or more tangible, non-temporary data repositories (e.g., data volumes) in the form of solid-state memory chips, optical discs, magnetic discs, or any suitable combination thereof. In some embodiments, execution instructions may be transmitted by a carrier medium. Examples of such carrier media include temporary media (e.g., propagating signals that transmit instructions).

[0133] It will be apparent to those skilled in the art that various modifications and variations are possible without departing from the scope of the appended claims. This disclosure encompasses all modifications and variations within the scope of the appended claims and their equivalents.

Claims

1. Sample carrier and A source comprising a first target and a second target, the source being arranged to form a film on a sample contained in the sample carrier, A shadow mask provided between the sample carrier and the source, wherein the first target provides a contribution to first film formation and the second target provides a second contribution to film formation that is different from the first contribution to film formation, and at least one of the first contribution to film formation and the second contribution to film formation is non-uniform in the first dimension of the sample, A film deposition apparatus comprising: a film deposition drive unit arranged to independently control the first contribution to film deposition and the second contribution to film deposition so as to change the film thickness gradient of the film in a first direction.

2. The film deposition apparatus according to claim 1, wherein the source is arranged to deposit films on a plurality of samples, for example, at least four or six samples, contained in the sample carrier.

3. The film deposition apparatus according to claim 1 or 2, wherein the shadow mask comprises a first shadow mask component aligned to the first target to provide the first contribution to film deposition, and / or a second shadow mask component aligned to the second target to provide the second contribution to film deposition.

4. The film deposition apparatus according to claim 3, wherein the first shadow mask component defines a first film deposition aperture whose size changes in the first dimension of the sample, and / or the second shadow mask component defines a second film deposition aperture whose size changes in the first dimension of the sample.

5. The film deposition apparatus according to claim 4, wherein the first film deposition opening comprises alternating first and second sections, each first section including an increase in the size of the opening and each second section including a decrease in the size of the opening.

6. The film deposition apparatus according to claim 5, wherein the increase in the size of the opening of the first section is equal to and opposite to the decrease in the size of the opening of the second section.

7. The film deposition apparatus according to claim 5 or 6, as referenced to claim 2, wherein each first section and each second section corresponds to each of the plurality of samples.

8. The film deposition apparatus according to any one of claims 1 to 7, wherein the film deposition drive unit comprises at least one selected from the group consisting of a magnetic bar control unit arranged to change the magnitude of the magnetic field at a plurality of positions of the source, a pressure control unit arranged to change the gas pressure of the film deposition apparatus, and a magnet rotating unit arranged to control the direction of deposition (in a plane perpendicular to the vertical).

9. The film deposition apparatus according to any one of claims 1 to 8, wherein the film deposition drive unit is arranged to change the contribution to the first film deposition and / or the contribution to the second film deposition by 20% or less, for example, 10% or less.

10. The film deposition apparatus according to any one of claims 1 to 9, wherein the material of the first target is different from the material of the second target, such that the film is a mixed target comprising the materials of the first target and the second target.

11. The film deposition apparatus according to any one of claims 1 to 10, wherein the material of the first target is the same as the material of the second target.

12. The film deposition apparatus according to any one of claims 1 to 11, wherein the first target and the second target are spatially separated.

13. The film deposition apparatus according to any one of claims 1 to 12, wherein the film deposition direction of the film deposition apparatus is substantially perpendicular to the first dimension of the sample.

14. A film deposition apparatus according to any one of claims 1 to 13, wherein forming a film on the sample includes sputtering the target material.

15. The film deposition apparatus according to any one of claims 1 to 14, wherein the source is arranged to rotate about an axis parallel to the first dimension.

16. A method for changing the film thickness gradient of a film formed by a source comprising a first target and a second target, Shadow masking is performed by arranging or providing a shadow mask on a direct viewing path between the source and the sample carrier such that the first target provides a contribution to first film formation and the second target provides a second contribution to film formation different from the first contribution to film formation, wherein at least one of the first contribution to film formation and the second contribution to film formation is non-uniform in a first dimension of one or more samples contained in the sample carrier. The process involves depositing material from the first target onto the sample carrier via the shadow mask, and forming a film of material from the second target. A method comprising: software-controlling the contribution to the first film formation and / or the contribution to the second film formation by changing the operating conditions or parameters of the film formation drive unit of the film formation apparatus so that the film thickness gradient of the film in the first direction can be continuously changed.

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