Planarization of spin-on films

Abstract

A method of planarizing a substrate includes receiving a substrate having microfabricated structures of varying height on a working surface of the substrate defining an uneven topography; depositing a first layer including a solubility-altering agent on the working surface of the substrate in an uneven manner by spin-on deposition; exposing the first layer to a first pattern of actinic radiation based on the topography; developing the first layer using a predetermined solvent; and depositing a second layer on the working surface of the substrate, the second layer having a greater planarity than the first layer prior to developing the first layer. The first radiation pattern alters the solubility of the first layer such that upper regions of the uneven topography of the first layer are soluble in the predetermined solvent.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefits of U.S. Provisional Application No. 62 / 990,823, filed March 17, 2020, and U.S. Non-Provisional Application No. 17 / 122,898, filed December 15, 2020, which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to semiconductor manufacturing and related processes, including the planarization of spin-coated thin films. Background Technology

[0004] Semiconductor fabrication involves forming multiple layers of material on a semiconductor substrate. Some integration schemes may involve 70 or more stages to complete the design. Each stage includes multiple process steps involving patterning various thin films with different geometries and aspect ratios. These patterning processes can result in uneven topography, which can affect the integrity of spin-coated films used in standard semiconductor device processes.

[0005] Photoresist is a fundamental spin-coating material used to pattern most semiconductor layers using photolithography. Since variations in material thickness significantly impede the critical dimensional resolution of photolithography processes, it is crucial to apply photoresist films uniformly onto the wafer. However, uniform application of photoresist films can be challenging due to morphology. This is because the mechanisms of the spin-coating process can lead to varying thicknesses or coating defects when the resist interacts with features of different heights / depths. Summary of the Invention

[0006] According to an embodiment of the present invention, a method of forming a device includes: receiving a substrate having microfabricated structures at different heights relative to each other in a direction perpendicular to a working surface of the substrate, such that the microfabricated structures define an uneven topography on the working surface of the substrate; depositing a first layer on the working surface of the substrate by spin coating, the first layer comprising a solubility modifier, the deposition of the first layer producing an uneven film; exposing the first layer to a first photochemical radiation pattern based on the topography of the substrate, the first photochemical radiation pattern modifying the solubility of the first layer such that upper regions of the uneven topography of the first layer are soluble in a predetermined solvent, while lower regions of the uneven topography of the first layer are insoluble in the predetermined solvent; developing the first layer using the predetermined solvent such that soluble portions of the first layer are removed; and depositing a second layer on the working surface of the substrate by spin coating, wherein the top surface of the second layer has a greater flatness than the top surface of the first layer before developing the first layer.

[0007] According to another embodiment of the present invention, a method of forming a device includes: receiving a substrate having an uneven surface, wherein the substrate has a first surface and a second surface, the first surface having a larger z-height compared to the second surface; depositing a first layer comprising a solubility modifier on a working surface of the substrate by spin coating, the first layer forming an uneven film covering both the first surface and the second surface; exposing the first layer to a first photochemical radiation pattern based on the coordinate positions of the first surface and the second surface, the first photochemical radiation pattern altering the solubility of the first layer such that a portion of the first layer on the first surface is soluble in a predetermined solvent, while a portion of the first layer on the second surface is insoluble in the predetermined solvent; developing the first layer using the predetermined solvent such that the soluble portion of the first layer is removed; and depositing a second layer on the working surface of the substrate by spin coating, wherein the top surface of the second layer has greater uniformity compared to the top surface of the first layer before developing the first layer.

[0008] According to another embodiment of the present invention, a method of forming a device includes: receiving a substrate including a first set of device features and a second set of device features formed on a main surface of the substrate, the first set of device features having a greater height than the second set of device features, wherein the height difference between the first set of device features and the second set of device features forms an uneven topography on the main surface of the substrate; spin-coating a first intermediate layer on the substrate; exposing the substrate to a first local radiation pattern, wherein the first local radiation pattern is projected using a direct-write photolithography method; developing the first intermediate layer to reduce the height difference between the first set of device features and the second set of device features; and measuring a topography metric on the main surface of the substrate. Attached Figure Description

[0009] To gain a more complete understanding of the invention and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:

[0010] Figures 1A to 1D Cross-sectional views of a semiconductor device during various manufacturing stages according to embodiments of this application are shown, wherein Figure 1A Semiconductor devices with non-flat topography were demonstrated. Figure 1B The device is shown after depositing a first intermediate layer and exposing the first intermediate layer to a radiation pattern. Figure 1C The device is shown after the first intermediate layer has been developed, and Figure 1D The device was demonstrated after the material was coated with a second material;

[0011] Figure 2 This is a flowchart of a method for planarizing the working surface of a substrate according to an embodiment of the present invention;

[0012] Figures 3A to 3B Cross-sectional views of a semiconductor device during various manufacturing stages according to embodiments of this application are shown, wherein Figure 3A A semiconductor device was demonstrated after the second intermediate layer was exposed to a radiated pattern, and Figure 3B The device is shown after the second intermediate layer has been developed. Detailed Implementation

[0013] The emergence of the Internet of Things (IoT) has revived the fabrication of unique designs and device integration, from smart sensors to biotechnology to MEMS. Many of these devices have large topographic geometries inherent in their design, operating at the micrometer scale.

[0014] The given morphology directly affects the fabrication of semiconductor devices, particularly spin-coated thin films. One such thin film is photoresist, a fundamental spin-coating material used to pattern most semiconductor layers using photolithography. During photoresist coating, interactions with the morphology result in thickness variations on the wafer. These thickness variations can cause problems for subsequent steps in semiconductor manufacturing processes. For example, photolithography imaging is often used as part of a process to pattern the surface of semiconductor devices during manufacturing. Examples of photolithography processes include: depositing photoresist on a substrate; partially exposing the photoresist through a patterned etch mask; developing the exposed photoresist to define a mask pattern within the photoresist; and then etching the photoresist to form a pattern in the substrate.

[0015] Because variations in material thickness significantly impede the critical size resolution of photolithography processes, it is crucial to apply the photoresist film uniformly onto the substrate. The critical size resolution of feature patterning depends on the high variability of the photoresist film thickness. Photolithography exposure systems are highly sensitive to focal point variations. As the photoresist thickness on the substrate surface changes, the integrity of the subsequent feature patterning also changes. Therefore, uneven photoresist layers can cause variations in the critical size, thickness, profile, and / or roughness of the imaged feature patterns. It is generally important that the feature patterns of a device are defined uniformly, as their dimensions affect device performance / yield.

[0016] The embodiments of this disclosure describe a method for planarizing an uneven surface on a substrate for subsequent photolithographic patterning.

[0017] Embodiments of this disclosure include improved techniques for planarizing thin films deposited on substrates with varying morphologies. Embodiments of this disclosure include applying an intermediate layer on the substrate and selectively exposing the intermediate layer to improve the flatness of the substrate.

[0018] Figures 1A to 1DCross-sectional views of a semiconductor device during various manufacturing stages according to embodiments of this application are shown, wherein Figure 1A Semiconductor devices with non-flat topography were demonstrated. Figure 1B The device is shown after depositing a first intermediate layer and exposing the first intermediate layer to a radiation pattern. Figure 1C The device is shown after the first intermediate layer has been developed, and Figure 1D The device was shown after the material was coated with a second material.

[0019] refer to Figure 1A The semiconductor device 100 has an uneven topography including microfabricated structures. In one or more embodiments, the microfabricated structures may include a structure 104 defining a recess 106 and a top surface 108 on the working surface of the substrate 102. Although this disclosure describes a “recess,” it should be understood that other suitable features, including lines, holes, opening regions, trenches, vias, and / or other suitable structures, may be formed in the semiconductor layer. Structure 104 and recess 106 may be formed using conventional photolithography processes.

[0020] Substrate 102 generally refers to the workpiece being processed according to embodiments of the present invention. Substrate 102 may include any material portion or structure of a device, particularly a semiconductor or other electronic device, and may be, for example, a base substrate structure, such as a semiconductor wafer, a photomask, or a layer, such as a thin film, on or over a base substrate structure. Therefore, substrate 102 is not limited to any particular base structure, lower layer, or upper layer, whether patterned or unpatterned, but is contemplated to include any such layer or base structure, and any combination of layers and / or base structures.

[0021] The substrate 102 may be a bulk substrate (e.g., a bulk silicon substrate), a silicon-on-insulator substrate, or various other semiconductor substrates, including germanium substrates, silicon carbide substrates, gallium nitride (GaN) substrates, including GaN-on-silicon substrates, gallium arsenide substrates, etc.

[0022] In one or more embodiments, the heights of the microfabricated structures differ from one another. For example, in one or more embodiments, the recess in the z-direction has a first height 103 and structure 104 and top surface 108 have a second height 105. In one or more embodiments, the height difference between the microfabricated structures and each other can be between 10 nm and 100 nm, for example, greater than 50 nm. In other embodiments, the height difference can be greater than 5 micrometers, especially in the case of deep openings / trenches. The height (or depth) of each microfabricated structure can be measured using scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS), or wafer optical scattering.

[0023] Figure 1BA cross-sectional view of a semiconductor device after a first intermediate layer 110 has been deposited on the working surface of substrate 102 using spin coating is shown. The first intermediate layer 110 may include a photosensitive material, such as a positive, negative, or mixed photoresist. In one example, the first intermediate layer 110 includes a phenolic resin or a diazonaphthoquinone-based resin. In one or more embodiments, the first intermediate layer 110 may include a chemically amplified resist. In another embodiment, the first intermediate layer 110 includes a non-chemically amplified resist material, such as polymethyl methacrylate (PMMA) or hydrogen silsesquioxane (HSQ).

[0024] A specific material (e.g., a first intermediate layer 110) is deposited on substrate 102 via spin coating or spin deposition. The substrate is then rotated at a relatively high speed, for example, 2000 to 8000 rpm, causing centrifugal force to move the deposited material toward the edge of substrate 102, thereby coating the substrate 102. Excess material is rotated away from substrate 102. Among other factors, the thickness of the photoresist is determined by the resist viscosity and the rotational speed of the substrate during rotation.

[0025] After spin coating deposition, the photoresist is baked to form the first intermediate layer 110. For example, a soft baking process can be used to evaporate residual solvents in the photoresist and densify it. The soft baking process involves heating the photoresist over a narrow temperature range, for example, between 75°C and 100°C.

[0026] When substrate 102 comprises an uneven topography of densely packed microfabricated structures, this density can push the deposited material upwards and control how much material (mass fraction) fills the recesses 106. In other words, the deposited material interacts with the uneven surface of substrate 102 (e.g., the different heights between microfabricated structures). This results in the deposited material being deposited at different film thicknesses (e.g., different z-heights on the substrate).

[0027] refer to Figure 1B A first intermediate layer 110 is deposited using a spin-coating deposition process, thereby creating a film thickness of varying thickness on the uneven surface of the substrate 102. In one or more embodiments, the first intermediate layer 110 may be deposited with a thicker film thickness in the recess 106, and with a thinner film thickness on the structure 104 and the top surface 108 (or vice versa). The morphology of the first intermediate layer 110 is merely an example, and the actual variation in morphology may differ from deposition, even for substrates with a morphology similar to that of the substrate 102.

[0028] Advantageously, in one or more embodiments, the first intermediate layer 110 is exposed to a localized radiative pattern prior to the formation of the microfabrication structure to improve the planarization of the working surface of the substrate 102.

[0029] Refer again Figure 1B The first intermediate layer 110 is exposed to a localized radiation pattern 112. Before exposure to radiation 112, the substrate 102 is aligned with a tool used to expose the substrate 102 to radiation. In various embodiments, the alignment may depend on the stack being patterned. For example, in one embodiment, metal material at the back end of a production line may be used to align the tool. In another embodiment, optical alignment with alignment marks may be used. In yet another embodiment, the morphology of the first intermediate layer 110 may be used to align the substrate 102.

[0030] After aligning the substrate 102 with the tool, the morphology of the first intermediate layer 110 is measured. The morphology of the first intermediate layer can be measured using measuring tools such as atomic force microscopy (AFM), profilometers, or optical thickness measurement tools.

[0031] The exposure pattern of the radiation pattern 112 is then determined based on the morphology and tone of the first intermediate layer 110. Because the expected morphology is determined by the layout, the exposure pattern can be predetermined in some embodiments. In one or more embodiments, the radiation pattern 112 is positioned such that a portion of the first intermediate layer 110 covering the higher / greater microfabrication structure (e.g., structure 104 and top surface 108) is removed, and the portion of the first intermediate layer 110 filling the recess 106 remains after the subsequent development step.

[0032] In one or more embodiments, the radiation pattern 112 may include photochemical radiation, such as ultraviolet radiation projected using a maskless lithography tool such as a direct-write lithography tool. In one or more embodiments, the exposure pattern of the radiation pattern 112 may be formed using a direct-write lithography method such as digital light projection (DLP), grating light valve lithography, electron beam lithography, plasma lithography, focused ion beam (FIB) lithography, or nanoimprint lithography. For example, the radiation pattern 112 may include photochemical radiation with wavelengths between 365 nm and 405 nm and may be formed and projected using a direct-write lithography process in a dedicated direct-write machine. Direct-write lithography uses computer-controlled optics to project the exposure radiation pattern instead of using a conventional mask. Traditionally, exposing a substrate to a radiation pattern requires: designing a mask using computer-aided design (CAD) software, constructing the mask, and exposing the substrate through the mask. However, because direct-write lithography utilizes computer-controlled optics to project radiation, the computer-controlled optics can form the radiation pattern directly from a CAD file.

[0033] In one or more embodiments, the first intermediate layer 110 deposited on the same substrate can have different morphologies during high-volume manufacturing. Therefore, to planarize the same substrate, separate radiation patterns must be formed. Advantageously, as described above, direct-write lithography is a maskless radiation method that allows the radiation pattern 112 to be programmed digitally. One advantage of this is that a separate mask does not need to be built for each exposure of the first intermediate layer 110, thus saving process time and manufacturing costs.

[0034] See again Figure 1B In one or more embodiments where the first intermediate layer 110 is a positive photoresist, the radiating pattern 112 is located above the structure 104 and the top surface 108. In this way, the portion of the first intermediate layer 110 covering the structure 104 and the top surface 108 becomes soluble in a solvent, such as a developer fluid, while the portion of the first intermediate layer 110 filling the recess 106 remains insoluble in the solvent.

[0035] In one or more embodiments where the first intermediate layer 110 is a negative photoresist, the radiation pattern 112 is located above the recess 106. In this way, the portion of the first intermediate layer 110 covering the recess becomes insoluble in the solvent, while the portion of the first intermediate layer 110 covering the structure 104 and the top surface 108 is soluble in the solvent.

[0036] After exposure to photochemical radiation, a hard baking process can be performed to stabilize and harden the photoresist. The hard baking process can be performed at higher temperatures than the soft baking process, for example, between 100°C and 150°C.

[0037] Figure 1C The semiconductor device is shown after a portion of the first intermediate layer 110 has been removed.

[0038] refer to Figure 1C Then, a development step is performed to remove the soluble portion of the first intermediate layer 110 deposited on structure 104 and top surface 108. In one or more embodiments, when the first intermediate layer 110 is a positive resist, it can be removed by exposure to a developer solution, which may include a phenol-based stripper, acetone, trichloroethylene, etc. In one or more embodiments, when the first intermediate layer 110 is a negative resist, it can be removed by exposure to a developer solution, which may include methyl ethyl ketone, methyl isobutyl ketone, etc.

[0039] Advantageously, in one or more embodiments, a portion of the first intermediate layer 110 is retained within the recess 106. One advantage of doing so is that retaining a portion of the first intermediate layer 110 reduces the relative height difference between the recess 106 and the structure 104 and the top surface 108 (i.e., the first height 103 is increased due to the first intermediate layer). Therefore, the difference between the first height 103 and the second height 105 is reduced, thereby improving the morphology.

[0040] In various embodiments, after the development step, topographic metrics of the substrate can be measured. Topographic metrics may include, for example, the flatness or uniformity of the first intermediate layer 110. Optical metrology techniques can be used to measure these topographic metrics. For example, the thickness of the intermediate layer 110 can be measured at different locations, or the height of the top surface of the intermediate layer 110 relative to a horizontal plane can be measured at different locations. A statistical distribution can then be used to obtain a measure of the flatness or uniformity of the intermediate layer 110. Other less commonly used metrics for measuring topography may include surface techniques, such as measuring the surface roughness of the substrate 102.

[0041] In one or more embodiments, the topography metric can be compared with a target topography metric. In one embodiment, if the measured topography metric meets the target topography metric, subsequent microstructure patterns can be formed on the substrate using conventional photolithography processes. In other embodiments, if the topography metric does not meet the target topography metric, the above process can be repeated until the target topography metric is met.

[0042] refer to Figure 1D The second material 114 is deposited onto the substrate using spin-coating deposition. For example... Figure 1D As shown, the second material 114 is deposited in a more planar manner than the deposition of the first intermediate layer 110. The composition of the second material 114 depends on whether the target topography metric was met in the previous step. In one or more embodiments where the target topography metric was met, the second material 114 may contain photoresist for forming subsequent microfabrication structure patterns in the photolithography process. In one or more embodiments where the target topography metric was not met, the second material 114 may be a second intermediate layer containing the same material as the first intermediate layer 110, designed to further planarize the working surface of the substrate 102.

[0043] Figure 2 This is a flowchart illustrating an exemplary process flow for planarizing the working surface of a substrate according to an embodiment of the present invention.

[0044] As shown in box 200 and referenced Figure 1A As described, substrate 102 has microfabricated structures formed on the working surface of substrate 102 with varying heights relative to each other. The height difference between the microfabricated structures defines an uneven topography on the working surface of substrate 102.

[0045] As shown below in box 202 and referenced Figure 1B As described, a first intermediate layer 110 is deposited on a substrate using spin-coating deposition. This is shown next in box 204 and referenced. Figure 1B As described, the first intermediate layer 110 is exposed to the radiation pattern 112.

[0046] As shown below in box 206 and referenced Figure 1C The description describes developing the first intermediate layer to remove portions of the first intermediate layer 110 deposited on the structure 104 and the top surface 108.

[0047] Advantageously, as described above, removing a portion of the first intermediate layer 110 deposited on the higher surface while leaving that portion in the recess reduces the relative height between the microfabricated structures. One advantage of doing so is improved flatness of the working surface of the substrate 102.

[0048] As shown below in box 208 and referenced Figure 1C The description describes measuring a topographic metric on the working surface of substrate 102. As shown below in box 210, the measured topographic metric is compared with a target topographic metric. In various embodiments, the target topographic metric may be a surface height relative to a horizontal plane, such as measured using optical or electron microscopy techniques. In one or more embodiments, this surface height may be defined based on the tolerance level of the process equipment used (e.g., the depth of focus of a photolithography imaging tool). In one or more embodiments, the standard deviation of the surface height of the top surface may be compared with a target standard deviation, and topology outside the target standard deviation may be marked as not satisfying the topographic metric. In other embodiments, the target topographic measurement may be defined as the uniformity of the first intermediate layer 110. The flatness or uniformity of the first intermediate layer 110 may be measured using optical metrology techniques. If the measured topographic metric satisfies the target topographic metric, the method proceeds to box 212 and subsequent microstructure patterning can be formed on substrate 102 using conventional photolithography processes.

[0049] If the measured topography measure does not meet the target topography measure, the method proceeds to box 214.

[0050] As shown next in box 213, after the subsequent microfabrication device pattern is formed, the topography metric of the subsequent microfabrication device pattern is compared with a threshold topography metric. In response to determining that the topography metric of the subsequent microfabrication device pattern is greater than the threshold topography metric, the process proceeds to box 214.

[0051] Conversely, in response to determining that the topography metric is less than or equal to the threshold topography metric, the process proceeds to block 216 and continues with standard semiconductor device fabrication.

[0052] As shown below in box 214 and referenced Figure 1D As described, if the target topography metric does not meet the measured topography metric, an additional intermediate layer is deposited on the substrate using spin-coating deposition. In one or more embodiments, the additional intermediate layer may comprise the same material as the first intermediate layer 110. After depositing the additional intermediate layer, the method is repeated in blocks 204-212 until the target topography metric is met.

[0053] Figures 3A to 3B An example is shown where substrate planarization is further performed if the measured topography metric does not meet the target topography metric. Therefore, Figures 3A to 3B from Figures 1A to 1D continue.

[0054] Figures 3A to 3B Cross-sectional views of a semiconductor device during various manufacturing stages according to embodiments of this application are shown, wherein Figure 3A A semiconductor device was demonstrated after the second intermediate layer was exposed to a radiated pattern, and Figure 3B The device is shown after the second intermediate layer has been developed.

[0055] refer to Figure 3A A second intermediate layer 314 is deposited on the substrate using spin-coating and exposed to the radiation pattern 112. For example... Figure 3A As shown, due to the reduced relative height difference between the microstructures, the second intermediate layer 314 is deposited with improved flatness compared to when the first intermediate layer 110 is deposited. In one or more embodiments, the second intermediate layer 314 may comprise the same material as the first intermediate layer 110. The radial pattern may comprise the same material and may be... Figure 1B It is formed in the same way described in the text.

[0056] refer to Figure 3B The second intermediate layer 314 undergoes a developing step to remove the portion of the second intermediate layer 314 covering the structure 104 and the top surface 108. The developing step may include the same material and may be performed using... Figure 1C It is performed in the same manner as described in [the document / document].

[0057] like Figure 3B As shown, due to the reasons described above, the relative height difference between the recess 106 and the structure 104 and the top surface 108 is further reduced by the second intermediate layer 314. This results in a further improved planarization of the substrate 102.

[0058] Exemplary embodiments of the invention are summarized herein. Other embodiments may also be understood from the entire specification and the claims set forth herein.

[0059] Example 1. A method for planarizing a substrate, the method comprising: receiving a substrate having microfabricated structures at different heights relative to each other in a direction perpendicular to a working surface of the substrate, such that the microfabricated structures define an uneven topography on the working surface of the substrate; depositing a first layer on the working surface of the substrate by spin coating, the first layer comprising a solubility modifier, the deposition of the first layer producing an uneven film; exposing the first layer to a first photochemical radiation pattern based on the topography of the substrate, the first photochemical radiation pattern modifying the solubility of the first layer such that upper regions of the uneven topography of the first layer are soluble in a predetermined solvent, while lower regions of the uneven topography of the first layer are insoluble in the predetermined solvent; developing the first layer using the predetermined solvent such that soluble portions of the first layer are removed; and depositing a second layer on the working surface of the substrate by spin coating, wherein the top surface of the second layer has a greater flatness than the top surface of the first layer before developing the first layer.

[0060] Example 2. The method as described in Example 1, wherein the first photochemical radiation pattern is projected using a direct writing system.

[0061] Example 3. The method as described in either Example 1 or 2, wherein these microfabricated structures have a relative height difference of more than five micrometers.

[0062] Example 4. The method described in any one of Examples 1 to 3, wherein these microfabricated structures have a relative height difference of more than 50 nanometers.

[0063] Example 5. The method of any one of Examples 1 to 4 further includes: exposing the second layer to the first photochemical radiation pattern, wherein the second layer includes the solubility-changing component, the first photochemical radiation pattern changing the solubility of the second layer such that the upper region of the second layer is soluble in a predetermined solvent, while the lower region of the second layer is insoluble in the predetermined solvent; and developing the second layer using the predetermined solvent such that the soluble portion of the first layer is removed.

[0064] Example 6. A method for planarizing a substrate, the method comprising: receiving a substrate having a non-planar surface, wherein the substrate has a first surface and a second surface, the first surface having a greater z-height than the second surface; depositing a first layer comprising a solubility modifier on a working surface of the substrate by spin coating, the first layer forming a non-planar film, the first layer covering both the first surface and the second surface; exposing the first layer to a first photochemical radiation pattern based on the coordinate positions of the first surface and the second surface, the first photochemical radiation pattern altering the solubility of the first layer such that a portion of the first layer on the first surface is soluble in a predetermined solvent, while a portion of the first layer on the second surface is insoluble in the predetermined solvent; developing the first layer using the predetermined solvent such that the soluble portion of the first layer is removed; and depositing a second layer on the working surface of the substrate by spin coating, wherein the top surface of the second layer has greater uniformity than the top surface of the first layer before developing the first layer.

[0065] Example 7. The method as described in Example 6, wherein the first photochemical radiation pattern is projected using a direct write system.

[0066] Example 8. The method as described in Example 6 or 7, further comprising: exposing the second layer to the first photochemical radiation pattern, the first photochemical radiation pattern being based on the coordinate positions of the first surface and the second surface, the first photochemical radiation pattern altering the solubility of the second layer such that a portion of the second layer on the first surface is soluble in the predetermined solvent, while a portion of the second layer on the second surface is insoluble in the predetermined solvent; and developing the second layer using the predetermined solvent such that the soluble portion of the second layer is removed.

[0067] Example 9. The method as described in any one of Examples 6 to 8, wherein the first surface has a z-height greater than 5 micrometers compared to the second surface.

[0068] Example 10. The method as described in any one of Examples 6 to 9, wherein the first surface has a z-height greater than at least 50 nm compared to the second surface.

[0069] Example 11. The method as described in any one of Examples 6 to 10, wherein the first photochemical radiation pattern has a wavelength between 193 nm and 405 nm.

[0070] Example 12. A method of forming a device, the method comprising: receiving a substrate including a first set of device features and a second set of device features formed on a main surface of the substrate, the first set of device features having a greater height than the second set of device features, wherein the height difference between the first set of device features and the second set of device features forms an uneven topography on the main surface of the substrate; spin-coating a first intermediate layer on the substrate; exposing the substrate to a first localized radiation pattern, wherein the first localized radiation pattern is projected using direct-write photolithography; developing the first intermediate layer to reduce the height difference between the first set of device features and the second set of device features; and measuring a topography metric on the main surface of the substrate.

[0071] Example 13. The method of Example 12 further includes: comparing the topography measure with a target topography measure; and, in response to determining that the topography measure satisfies the target topography measure, forming a subsequent device feature pattern using a conventional photolithography process.

[0072] Example 14. The method as described in Example 12 or 13 further includes: comparing the topography measurement with a target topography measurement; and in response to determining that the topography measurement is different from the target topography measurement, spin-coating a second intermediate layer on the substrate, exposing the substrate to the local radiation pattern, and developing the second intermediate layer to further reduce the height difference between the first set of device features and the second set of device features.

[0073] Example 15. The method as described in any one of Examples 12 to 14, wherein the first intermediate layer comprises a positive photoresist and the localized radiative pattern is formed over the first set of device features.

[0074] Example 16. The method as described in any one of Examples 12 to 15, wherein the first intermediate layer comprises a negative photoresist and the localized radiation pattern is formed over the second set of device features.

[0075] Example 17. The method as described in any one of Examples 12 to 16, wherein the first radiation includes photochemical radiation.

[0076] Example 18. The method as described in any one of Examples 12 to 17, wherein the first radiation has a wavelength between 193 nm and 405 nm.

[0077] Example 19. The method as described in any one of Examples 12 to 18, wherein the height difference between the first set of device features and the second set of device features is greater than five micrometers.

[0078] Example 20. The method as described in any one of Examples 12 to 19, wherein the height difference between the first set of device features and the second set of device features is greater than 50 nm.

[0079] In the foregoing description, specific details, such as the particular geometry of the processing system and the description of the various components and processes used therein, have been set forth. However, it should be understood that the techniques described herein may be practiced in other embodiments departing from these specific details, and such details are for illustrative purposes and not for limitation. Embodiments disclosed herein have been described with reference to the accompanying drawings. Similarly, specific figures, materials, and configurations have been set forth for illustrative purposes to provide a thorough understanding. However, embodiments may be practiced without such specific details. Components having substantially the same functional construction are indicated by similar reference numerals, and therefore any redundant description may be omitted.

[0080] Various techniques have been described as multiple discontinuous operations to aid in understanding the various embodiments. The order of the description should not be construed as implying that these operations are necessarily order-dependent. In fact, these operations do not need to be performed in the presented order. The described operations may be performed in a different order than the described embodiments. In additional embodiments, various additional operations may be performed and / or the described operations may be omitted.

[0081] Those skilled in the art will also understand that many changes can be made to the technical operations described above, while still achieving the same objectives of the invention. The scope of this disclosure is intended to cover these changes. Therefore, the foregoing description of embodiments of the invention is not intended to be limiting. Rather, any limitations on embodiments of the invention are set forth in the appended claims.

Claims

1. A method for planarizing a substrate, the method comprising: A receiving substrate having microfabricated structures at different heights relative to each other in a direction perpendicular to the working surface of the substrate, such that the microfabricated structures define an uneven topography on the working surface of the substrate, the uneven topography including recesses. A first layer comprising a solubility modifier is deposited on the working surface of the substrate by spin coating. The deposition of the first layer produces an uneven film in which the first layer does not completely fill the depression. The first layer is exposed to a first photochemical radiation pattern based on the morphology of the substrate. The first photochemical radiation pattern changes the solubility of the first layer, such that the upper region of the uneven morphology of the first layer is soluble in a predetermined solvent, while the lower region of the uneven morphology of the first layer is insoluble in the predetermined solvent. The first layer is developed using a predetermined solvent, thereby removing the soluble portion of the first layer. This development produces a wet-treated top surface of the substrate. A second layer is deposited on the wet-treated top surface of the substrate by spin coating, wherein the top surface of the second layer has greater flatness compared to the top surface of the first layer before development. The method also includes: In the case that the second layer includes a solubility modifier, The second layer is exposed to the first photochemical radiation pattern, which alters the solubility of the second layer, making the upper region of the second layer soluble in a predetermined solvent, while the lower region of the second layer is insoluble in the predetermined solvent; and The second layer is developed using a predetermined solvent, thereby removing the soluble portion of the second layer.

2. The method according to claim 1, wherein, The first photochemical radiation pattern is projected using a direct write system.

3. The method according to claim 1, wherein, The relative height difference of these microfabricated structures is greater than five micrometers.

4. The method according to claim 1, wherein, The relative height difference of these microfabricated structures is greater than 50 nanometers.

5. A method for planarizing a substrate, the method comprising: A substrate having an uneven surface is received, wherein the substrate has a first surface, a second surface and a recess formed by the first surface and the second surface, and the first surface has a larger z-height than the second surface; A first layer comprising a solubility modifier is deposited on the working surface of the substrate by spin coating. The deposition of the first layer produces an uneven film that covers both the first surface and the second surface but does not completely fill the depression. The first layer is exposed to a first photochemical radiation pattern, which is based on the coordinate positions of the first surface and the second surface. The first photochemical radiation pattern changes the solubility of the first layer, such that the portion of the first layer located on the first surface is soluble in a predetermined solvent, while the portion of the first layer located on the second surface is insoluble in the predetermined solvent. The first layer is developed using a predetermined solvent, thereby removing the soluble portion of the first layer, and the development produces a wet-treated top surface of the substrate; as well as A second layer is deposited on the wet-treated top surface of the substrate by spin coating, wherein the top surface of the second layer has greater uniformity compared to the top surface of the first layer before development. The method also includes: The second layer is exposed to the first photochemical radiation pattern, which is based on the coordinate positions of the first and second surfaces. The first photochemical radiation pattern alters the solubility of the second layer, making the portion of the second layer on the first surface soluble in a predetermined solvent, while the portion on the second surface is insoluble in the predetermined solvent. The second layer is developed using a predetermined solvent, thereby removing the soluble portion of the second layer.

6. The method according to claim 5, wherein, The first photochemical radiation pattern is projected using a direct write system.

7. The method according to claim 5, wherein, Compared to the second surface, the first surface has a z-height greater than 5 micrometers.

8. The method according to claim 5, wherein, Compared to the second surface, the first surface has a z-height greater than 50 nm.

9. The method according to claim 5, wherein, The first photochemical radiation pattern has a wavelength between 193 nm and 405 nm.

10. A method of forming a device, the method comprising: A receiving substrate includes a first set of device features and a second set of device features formed on the main surface of the substrate, the first set of device features having a greater height than the second set of device features, wherein the height difference between the first set of device features and the second set of device features forms an uneven topography on the main surface of the substrate, the uneven topography including a depression. A first intermediate layer is spin-coated onto the substrate, wherein the first intermediate layer does not completely fill the depression; The substrate is exposed to a first local radiation pattern, wherein the first local radiation pattern is projected using direct-write photolithography. The first intermediate layer is developed using a wet process to reduce the height difference between the first set of device features and the second set of device features, and the development produces a wet-treated top surface of the substrate; and The topography of the main surface of the substrate was measured. The method also includes: Compare the current shape measurement with the target shape measurement; and In response to determining that the topography measure is different from the target topography measure, a second intermediate layer is spin-coated on the substrate, the substrate is exposed to the first local radiation pattern, and the second intermediate layer is developed to further reduce the height difference between the first set of device features and the second set of device features.

11. The method of claim 10, further comprising: In response to the determination that the topography metric satisfies the target topography metric, a conventional photolithography process is used to form subsequent device feature patterns.

12. The method according to claim 10, wherein, The first intermediate layer includes a positive photoresist and the first localized radiation pattern is formed over the first set of device features.

13. The method according to claim 10, wherein, The first intermediate layer includes a negative photoresist and the first localized radiation pattern is formed over the second set of device features.

14. The method of claim 10, wherein, The first local radiation pattern includes photochemical radiation.

15. The method according to claim 10, wherein, The first local radiation pattern has a wavelength between 193 nm and 405 nm.

16. The method of claim 10, wherein, The height difference between the first group of device features and the second group of device features is greater than five micrometers.

17. The method according to claim 10, wherein, The height difference between the first set of device features and the second set of device features is greater than 50 nm.

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