Mask and roughness optimization method thereof

Abstract

The invention discloses a mask plate and a roughness optimization method thereof, and the method comprises the following steps: providing a mask plate, the mask plate sequentially comprises a transparent substrate, a protection layer and a light shielding layer from a bottom layer, the protection layer covers the surface of the transparent substrate, the light shielding layer is composed of a light shielding area and a reserved light transmission area, and the protection layer is arranged below the reserved light transmission area; depositing a shading material with a first preset thickness on the side wall of the shading layer through atomic layer deposition so as to at least partially fill the pits in the side wall of the shading layer; a shading material with a second preset thickness is etched on the side wall of the shading layer through atomic layer etching, so that the protrusions of the shading layer are at least partially removed; detecting the roughness of the side wall of the shading layer, and comparing the detected roughness of the side wall of the shading layer with a preset roughness set value; and when the detected roughness of the side wall of the shading layer reaches a roughness set value, removing the protection layer below the reserved light-transmitting area. According to the invention, the line edge roughness of the mask can be effectively reduced.

Description

Technical Field

[0001] The invention relates to the technical field of integrated circuit manufacturing, and in particular to a mask and a roughness optimization method thereof. Background Art

[0002] With the development of integrated circuit technology, the critical dimension (CD) of semiconductor devices is getting smaller and smaller, and the exposure wavelength has also developed from ultraviolet (UV), deep ultraviolet (DUV) to extreme ultraviolet (EUV). Therefore, in order to meet the requirements of high-precision chip preparation, the mask for lithography needs to be precisely processed during its preparation.

[0003] At present, the characteristic size (CD) of the chip has been reduced to a few nanometers, but its line edge roughness (LER) does not decrease in the same proportion as the CD decreases. In the process of mask manufacturing, especially in the process of patterning the light shielding layer of the mask, the side wall of the light shielding layer will appear uneven, which is called line edge roughness (LER), and its influence on device performance is becoming more and more prominent. For example, when the gate characteristic size of the CMOS field effect transistor is less than 100nm, the gate line edge roughness in the range of 5nm will cause a significant change in the effective conductive channel length of the device, causing the performance of the device to degrade or fluctuate: the leakage current increases, the driving current decreases, and the turn-on voltage Vth changes. Therefore, the control of LER is one of the basic problems that urgently need to be solved in chip manufacturing. LER mainly comes from the photolithography process and etching process, such as the diversity of polymer molecular structure, the fluctuation of spatial imaging, the acid diffusion of photoresist, and the process conditions of production and preparation (such as the thickness of the glue coating, the drying temperature, the exposure dose, and the uniformity of the light intensity of the light source). If the LER of the mask is unqualified, it will be directly transferred to the wafer and cause defects in the wafer.

[0004] In general, in order to reduce the line edge roughness (LER) of the mask in the existing technology, the LER is mainly reduced by optimizing the lithography and etching processes. For example, using a shorter wavelength light source, a higher precision lithography machine, a finer mask, etc. In addition, multiple exposures and etchings can be performed to gradually approach the ideal line accuracy. Although existing solutions can reduce LER to a certain extent, these methods are often costly, inefficient, and difficult to meet the needs of higher precision in the future. In addition, these methods may be limited by physical limits when processing very fine lines, making it difficult to further improve accuracy.

[0005] Therefore, a new technical solution is urgently needed to optimize the mask and its roughness. Summary of the invention

[0006] The object of the present invention is to provide a mask and a roughness optimization method thereof, so as to solve the technical problem of high line edge roughness of the existing mask light shielding layer.

[0007] In order to solve the above technical problems, the present invention provides a mask and a roughness optimization method thereof, comprising: A mask plate comprises a transparent substrate, a protective layer and a light-shielding layer from the bottom layer in sequence. The protective layer covers the entire surface of the transparent substrate. The light-shielding layer consists of a plurality of light-shielding areas and reserved light-transmitting areas. The reserved light-transmitting areas are provided with a protective layer below.

[0008] In another aspect, a roughness optimization method is provided, comprising: A mask is provided, which includes a transparent substrate, a protective layer and a light shielding layer in order from the bottom layer, wherein the protective layer covers the entire surface of the transparent substrate, the light shielding layer is composed of a plurality of light shielding areas and reserved light transmission areas, and the reserved light transmission area has a protective layer below; Depositing a light-shielding material of a first preset thickness on the sidewall of the light-shielding layer of the mask by atomic layer deposition to at least partially fill the pits on the sidewall of the light-shielding layer and reduce the roughness of the sidewall of the light-shielding layer; Etching a second preset thickness of light shielding material on the sidewall of the light shielding layer of the mask by atomic layer etching to at least partially remove protrusions on the light shielding layer and reduce the roughness of the sidewall of the light shielding layer; Detecting the roughness of the side wall of the light shielding layer, and comparing the detected roughness of the side wall of the light shielding layer with a preset roughness setting value; When the detected roughness of the side wall of the light shielding layer reaches a set roughness value, the protective layer below the reserved light-transmitting area is removed.

[0009] The above-mentioned mask and roughness optimization method thereof first provide a mask, the mask includes a transparent substrate, a protective layer and a light-shielding layer from the bottom layer in sequence, wherein the protective layer covers the entire surface of the transparent substrate, the light-shielding layer is composed of a light-shielding area and a reserved light-transmitting area, and a protective layer is provided below the reserved light-transmitting area, the protective layer covers the entire surface of the transparent substrate, so that the protective layer can protect the transparent substrate from the influence of the following deposition and etching; then, a light-shielding material of a first preset thickness is deposited on the side wall of the light-shielding layer of the mask by atomic layer deposition, and the physical property of conformal growth of atomic layer deposition is utilized, the pits on the side wall of the light-shielding layer are easy to grow light-shielding material in the pits due to their inwardly concave shape, especially when the thickness of the light-shielding material grown at the pits is half of the spacing between the two sides of the pits, the pits can be completely filled, so the thickness of the light-shielding material grown at the pits is greater than the first preset thickness, and the light-shielding material at the protrusions is greater than the first preset thickness. The thickness of the material growth is less than the first preset thickness, so the pits on the side walls of the light-shielding layer can be at least partially filled, thereby reducing the roughness of the side walls of the light-shielding layer; then, the side walls of the light-shielding layer of the mask are etched with a second preset thickness of light-shielding material by atomic layer etching, and the physical property of conformal removal of atomic layer etching is utilized. Since the protruding area protrudes outward due to its shape, it is easy to remove the light-shielding material in the protruding area. Therefore, the thickness removed at the protrusion is greater than the second preset thickness, and the thickness removed at the pit is less than the second preset thickness. Therefore, the protrusions on the light-shielding layer can be at least partially removed, thereby reducing the roughness of the side walls of the light-shielding layer; finally, the roughness of the side walls of the light-shielding layer is detected, and the detected roughness of the side walls of the light-shielding layer is compared with the preset roughness setting value. When the detected roughness of the side walls of the light-shielding layer reaches the roughness setting value, the protective layer is removed to complete the roughness optimization of the light-shielding layer of the mask.

[0010] The above method can, on the basis of protecting the transparent substrate, make the pits and protrusions on the side walls of the mask light-shielding layer gradually flat during atomic layer deposition and atomic layer etching, thereby reducing the roughness of the side walls of the mask light-shielding layer, and effectively solving the technical problem of low line edge roughness of the mask in the prior art.

[0011] Optionally, the material of the protective layer of the mask is SiNx.

[0012] Optionally, in the method for optimizing the roughness of the mask, after the step of detecting the roughness of the side wall of the light shielding layer and comparing the detected roughness of the side wall of the light shielding layer with a preset roughness setting value, the method further includes: When the detected roughness of the side wall of the light-shielding layer does not reach the preset roughness setting value, repeat the steps of depositing a first preset thickness of light-shielding material on the side wall of the light-shielding layer of the mask by atomic layer deposition to the step of comparing the detected roughness of the side wall of the light-shielding layer with the preset roughness setting value.

[0013] Optionally, in the method for optimizing the roughness of a mask, after the step of depositing a light-shielding material of a first preset thickness on the sidewall of the light-shielding layer of the mask by atomic layer deposition, the following steps are included: Detecting the roughness of the side wall of the light shielding layer, and comparing the detected roughness of the side wall of the light shielding layer with a preset roughness setting value; When the detected roughness of the side wall of the light shielding layer reaches a set roughness value, the protective layer below the reserved light-transmitting area is removed.

[0014] Optionally, in the method for optimizing the roughness of the mask, the material of the protective layer is SiNx.

[0015] Optionally, in the method for optimizing the roughness of the mask, the thickness of the protective layer is no greater than half the thickness of the light shielding layer.

[0016] Optionally, in the method for optimizing the roughness of the mask, the temperature of the atomic layer deposition is not less than 100°C.

[0017] Optionally, in the method for optimizing the roughness of the mask, the first preset thickness is no greater than 10 nm.

[0018] Optionally, in the method for optimizing the roughness of the mask, the second preset thickness is no greater than 10 nm.

[0019] The above method can, on the basis of protecting the transparent substrate, make the pits and protrusions on the side walls of the mask light-shielding layer gradually flat during atomic layer deposition and atomic layer etching, thereby reducing the roughness of the side walls of the mask light-shielding layer, and effectively solving the technical problem of low line edge roughness of the mask in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of a process for optimizing the roughness of a mask according to an embodiment of the present invention; Figure 2 A mask structure diagram according to an embodiment.

[0021] Description of reference numerals: 1-light shielding layer, 2-protective layer, 3-transparent substrate. DETAILED DESCRIPTION

[0022] In the following description, a large number of specific details are given in order to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some technical features known in the art are not described. It should be understood that the present invention can be implemented in different forms and should not be interpreted as being limited to the embodiments presented here. On the contrary, providing these embodiments will make the disclosure thorough and complete, and fully convey the scope of the present invention to those skilled in the art. The same reference numerals represent the same elements from beginning to end. It should be understood that when a layer is referred to as being formed on other layers, it can be directly formed on other layers, or there can be an intervening film layer. Among them, the orientation or positional relationship indicated by the terms "upper", "lower", "front", "back" and the like is based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention, wherein "longitudinal" can be understood as a direction perpendicular to the substrate surface, and "lateral" can be understood as a direction parallel to the substrate surface. When used herein, the singular forms "a", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the term "include" is used to determine the presence of features, steps, operations, elements and / or parts, but does not exclude the presence or addition of one or more other features, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items. The terms "same", "equal" and "consistent" include completely equal and identical meanings, and may also include approximately the same or approximately equal meanings under allowed process errors. The terms "first" "second" and the like in the specification are used to distinguish between similar elements, and are not necessarily used to describe a specific order or time sequence. It is to be understood that, where appropriate, these terms used in this way are interchangeable, for example, so that the embodiments of the present invention described herein can be operated in other orders different from those described or shown herein. Similarly, if the method described herein includes a series of steps, the order in which the steps are presented herein is not necessarily the only order in which the steps can be performed, and some of the steps described may be omitted and / or some other steps not described herein may be added to the method. If components in a certain figure are the same as components in other figures, although these components can be easily identified in all figures, in order to make the description of the figures clearer, this specification will not mark all the same component numbers in each figure.

[0023] The present invention is described more clearly and completely below by way of embodiments in conjunction with the accompanying drawings, but the present invention is not limited to the scope of the following embodiments.

[0024] The present invention discloses a mask and a roughness optimization method thereof, which can optimize the mask and the line edge roughness of the mask to meet the high-precision chip manufacturing requirements. The method can be used to optimize various masks in semiconductor manufacturing processes, including but not limited to binary masks, OMOG masks, etc.

[0025] See also Figure 1 A method for optimizing the roughness of mask lines, characterized in that it comprises the following steps: Step S1: providing a mask, which includes a transparent substrate, a protective layer and a light-shielding layer from the bottom layer in sequence, wherein the protective layer covers the entire surface of the transparent substrate, the light-shielding layer is composed of a plurality of light-shielding areas and reserved light-transmitting areas, and there is a protective layer below the reserved light-transmitting areas.

[0026] Specifically, a mask base is provided, which includes a transparent substrate, a protective layer, a light-shielding layer and a photoresist layer in sequence from the bottom layer. The mask base is subjected to electron beam direct writing and development to pattern the photoresist layer. The light-shielding layer is etched using the patterned photoresist layer as a mask, and the pattern of the photoresist layer is transferred to the light-shielding layer. Then, the photoresist layer is removed to form a mask. Therefore, the mask includes a transparent substrate, a protective layer and a light-shielding layer. The protective layer covers the entire surface of the transparent substrate. A light-shielding layer is provided above the protective layer. The light-shielding layer is composed of a plurality of light-shielding areas and a reserved light-transmitting area. The light-shielding layer is formed above the protective layer. The light-shielding layer is formed after electron beam direct writing, development and etching. The required part of the light-shielding layer is left on the transparent substrate to form a light-shielding area, and the unnecessary part of the light-shielding layer is removed by development and etching to expose the protective layer below the light-shielding layer, thereby forming a reserved light-transmitting area.

[0027] Furthermore, the material of the transparent substrate may be a quartz glass substrate, an ultra-low expansion glass substrate, etc.; or any substrate for a mask known to those skilled in the art. The patterned light-shielding layer is composed of light-shielding patterns such as dots, lines or figures of different shapes, and the light-shielding layer is a thin film composed of a metal substance of a transition metal. Preferably, the material of the light-shielding layer may be, but is not limited to, silicon compounds, chromium compounds and chromium metals, such as MoSi, MoSiON, MoSiCON, CrN, CrO, CrCO, CrCN, Cr, etc. Of course, in other embodiments, the material of the light-shielding layer may also be selected from other light-shielding materials known to those skilled in the art, and this embodiment does not specifically limit this.

[0028] Step S2: depositing a light-shielding material of a first preset thickness on the sidewalls of the light-shielding layer of the mask by atomic layer deposition to at least partially fill the pits on the sidewalls of the light-shielding layer and reduce the roughness of the sidewalls of the light-shielding layer.

[0029] Specifically, a light-shielding material of a first preset thickness is deposited on the side wall of the light-shielding layer of the mask through atomic layer deposition. Atomic layer deposition is a technology that deposits the light-shielding material on the surface layer by layer in the form of a single atomic film based on chemical vapor. The physical characteristics of conformal growth of atomic layer deposition are utilized. The pits on the side wall of the light-shielding layer are concave inwardly due to their shape, and it is easy for the light-shielding material to grow in the pits. In particular, when the thickness of the light-shielding material grown at the pits is half of the spacing between the two sides of the pits, the pits can be completely filled. Therefore, the thickness of the light-shielding material grown at the pits is greater than the first preset thickness, and the thickness of the light-shielding material grown at the protrusions is less than the first preset thickness. Therefore, the pits on the side wall of the light-shielding layer can be at least partially filled to reduce the roughness of the side wall of the light-shielding layer. Of course, the light-shielding material is used to repair the roughness of the side wall of the light-shielding layer. Therefore, the composition of the light-shielding material is set to perform the same function as the light-shielding layer. Preferably, for the light-shielding layer composed of chromium compounds, the light-shielding material can be metallic chromium or carbon, etc.

[0030] In a specific embodiment, the atomic layer deposition of the light-shielding material chromium has a thickness of 10 nm, 0.08 Å / cycle, a chamber pressure of 8 mbar-12 mbar, a temperature of 180° C., and is performed in an environment of 99.9995% purity of nitrogen.

[0031] Step S3: etching the sidewalls of the light shielding layer of the mask plate with a second preset thickness of light shielding material by atomic layer etching to at least partially remove the protrusions on the light shielding layer and reduce the roughness of the sidewalls of the light shielding layer.

[0032] Specifically, the side walls of the light-shielding layer of the mask are etched with a second preset thickness of light-shielding material through atomic layer etching. Atomic layer etching is a technology that uses a series of self-limiting reactions to etch thin films, which is similar to the concept of layer-by-layer growth of atomic layer deposition. As the reverse process of atomic layer deposition technology, atomic layer etching is a technology that removes material layer by layer. The physical property of conformal removal of atomic layer etching is utilized. The light-shielding material in the protruding area is easily removed due to its outward protruding shape. Therefore, the thickness removed at the protrusion is greater than the second preset thickness, and the thickness removed at the pit is less than the second preset thickness. Therefore, the protrusions on the light-shielding layer can be at least partially removed, thereby reducing the roughness of the side walls of the light-shielding layer.

[0033] In a specific embodiment, the thickness of the chromium light shielding material is 10 nm, the cycle is 20 s / cycle, and the chamber bottom pressure is 2.0×10 -5 Torr, the process pressure is 2.0 mTorr, and the chamber environment is 50 sccm of O2 and 50 sccm of Cl2.

[0034] Step S4: detecting the roughness of the side wall of the light shielding layer, and comparing the detected roughness of the side wall of the light shielding layer with a preset roughness setting value.

[0035] Specifically, the line edge roughness of the side wall of the light shielding layer is detected by using a characteristic size scanning electron microscope, and the detected line edge roughness of the side wall of the light shielding layer is compared with a preset roughness setting value.

[0036] Furthermore, for the process node of 22nm chip manufacturing, the line edge roughness of the mask light shielding layer is no more than 4nm, and for the process node of 14nm chip manufacturing, the line edge roughness of the mask light shielding layer is no more than 0.5nm.

[0037] Step S5: When the detected roughness of the side wall of the light shielding layer reaches the set roughness value, the protective layer below the reserved light-transmitting area is removed.

[0038] Specifically, when the detected line edge roughness of the light shielding layer reaches the preset roughness setting value, the line edge roughness of the light shielding layer has met the requirements, and finally the protective layer under the reserved light-transmitting area of ​​the light shielding layer is removed to expose the transparent substrate under the reserved light-transmitting area. Furthermore, the protective layer is removed by reactive ion etching, using 17sccm of CF4, 3sccm of H2, a chamber pressure of 10mT, and a power of 100w.

[0039] Furthermore, while using a feature size scanning electron microscope to detect the line edge roughness of the side walls of the light-shielding layer, the feature size of the mask is also detected. If there is a deviation in the feature size of the mask, atomic layer deposition and atomic layer etching of the light-shielding material can be performed on the side walls of the light-shielding layer of the mask to make the feature size of the mask meet the requirements.

[0040] The above-mentioned mask and roughness optimization method thereof provide a mask that has a protective layer formed on a transparent substrate when the mask base is formed, and then electron beam direct writing, development and etching and other steps are performed to form the mask, so that the protective layer completely covers the transparent substrate to protect the transparent substrate from the influence of the deposition and etching of the following shading material, and then the shading material of a first preset thickness is deposited on the side wall of the shading layer of the mask by atomic layer deposition, and the physical property of conformal growth of atomic layer deposition is utilized, and the pits on the side wall of the shading layer are easy to grow shading material in the pits due to their inward concave shape, especially when the thickness of the shading material grown at the pits is half of the spacing between the two sides of the pits, the pits can be completely filled, so the thickness of the shading material grown at the pits is greater than the first preset thickness, and the thickness of the shading material grown at the protrusions is less than the first preset thickness. degree, so the pits on the side walls of the light-shielding layer can be at least partially filled, thereby reducing the roughness of the side walls of the light-shielding layer; then, the side walls of the light-shielding layer of the mask are etched with a second preset thickness of light-shielding material by atomic layer etching, and the physical property of conformal removal of atomic layer etching is utilized. Since the protrusion area protrudes outward due to its shape, it is easy to remove the light-shielding material in the protrusion area. Therefore, the thickness of the protrusion removed is greater than the second preset thickness, and the thickness of the pit removed is less than the second preset thickness. Therefore, the protrusions on the light-shielding layer can be at least partially removed, thereby reducing the roughness of the side walls of the light-shielding layer; finally, the roughness of the side walls of the light-shielding layer is detected, and the detected roughness of the side walls of the light-shielding layer is compared with a preset roughness setting value. When the detected roughness of the side walls of the light-shielding layer reaches the roughness setting value, the protective layer is removed to complete the roughness optimization of the light-shielding layer of the mask. The above method can make the pits and protrusions on the side walls of the mask light-shielding layer gradually flat during atomic layer deposition and atomic layer etching, reduce the roughness of the side walls of the mask light-shielding layer, and effectively solve the technical problem of low line edge roughness of the mask in the prior art.

[0041] In one embodiment, after the step of detecting the roughness of the side wall of the light shielding layer and comparing the detected roughness of the side wall of the light shielding layer with a preset roughness setting value, the following steps are also included: When the detected roughness of the side wall of the light-shielding layer does not reach the preset roughness setting value, repeat the steps of depositing a first preset thickness of light-shielding material on the side wall of the light-shielding layer of the mask by atomic layer deposition to the step of comparing the detected roughness of the side wall of the light-shielding layer with the preset roughness setting value.

[0042] Specifically, when the line edge roughness of the side wall of the light-shielding layer detected by a feature-size scanning electron microscope does not reach a preset roughness setting value, steps S3, S4 and S5 are repeated to further reduce the line edge roughness of the side wall of the light-shielding layer until it meets the preset roughness setting value. More specifically, when the preset roughness setting value cannot be met after atomic layer deposition of a first preset thickness of the light-shielding material and atomic layer etching of a second preset thickness on the mask light-shielding layer, the atomic layer deposition of a first preset thickness of the light-shielding material and atomic layer etching of a second preset thickness on the mask side wall can be repeated to further reduce the roughness of the side wall of the mask light-shielding layer until the detected roughness of the side wall of the mask light-shielding layer reaches the preset roughness setting value.

[0043] Furthermore, the first preset thickness of the first atomic layer deposition of light-shielding material on the sidewall of the light-shielding layer is d1, the second preset thickness of the first atomic layer etching of the light-shielding material on the sidewall of the light-shielding layer is d2, the first preset thickness of the second repetition of atomic layer deposition of light-shielding material on the sidewall of the light-shielding layer is d1', the second preset thickness of the second repetition of atomic layer etching of the light-shielding material on the sidewall of the light-shielding layer is d2', the first preset thickness of the third repetition of atomic layer deposition of light-shielding material on the sidewall of the light-shielding layer is d1'', the second preset thickness of the third repetition of atomic layer etching of the light-shielding material on the sidewall of the light-shielding layer is d2'', and so on, wherein the thicknesses of d1, d1' and d1'' may be the same or different, preferably, d1 is greater than d1', and d1' is greater than d1'', wherein the thicknesses of d2, d2' and d2'' may be the same or different, preferably, d2 is greater than d2', and d2' is greater than d2''.

[0044] Furthermore, each time the atomic layer deposition and atomic layer etching of the light shielding material are performed on the sidewall of the light shielding layer, the first preset thickness and the second preset thickness are both set so as not to affect the characteristic size of the mask.

[0045] In one embodiment, after the step of depositing a light shielding material of a first preset thickness on the sidewall of the light shielding layer of the mask by atomic layer deposition, the following steps are included: Detecting the roughness of the side wall of the light shielding layer, and comparing the detected roughness of the side wall of the light shielding layer with a preset roughness setting value; When the detected roughness of the side wall of the light shielding layer reaches a set roughness value, the protective layer below the reserved light-transmitting area is removed.

[0046] Specifically, after a first preset thickness of shading material is deposited on the side wall of the shading layer of the mask through atomic layer deposition, due to the physical characteristics of conformal growth of atomic layer deposition, the pits on the side wall of the shading layer are easy to grow shading material in the pits because of their inward concave shape, especially when the thickness of the shading material grown at the pits is half of the spacing between the two sides of the pits, the pits can be completely filled. Therefore, the thickness of the shading material grown at the pits is greater than the first preset thickness, and the thickness of the shading material grown at the protrusions is less than the first preset thickness. The pits and protrusions on the side wall of the shading layer gradually tend to be flat, so the roughness of the side wall of the shading layer is reduced. At this time, the roughness of the side wall of the shading layer is detected by a characteristic dimension scanning electron microscope. If the detected roughness of the side wall of the shading layer reaches the set value, the protective layer under the reserved light-transmitting area is removed to complete the roughness optimization of the shading layer. After the atomic layer deposition of the side wall of the shading layer is performed, the roughness detection is performed. If the roughness meets the requirements at this time, the protective layer under the reserved light-transmitting area can be removed, thereby simplifying the roughness optimization process and saving resources.

[0047] More specifically, the process of detecting the roughness of the side walls of the mask's light-shielding layer can be added to before and after the steps of depositing a first preset thickness of light-shielding material on the side walls of the mask's light-shielding layer by atomic layer deposition and etching a second preset thickness of light-shielding material on the side walls of the mask's light-shielding layer by atomic layer etching. When the roughness of any of the above detections reaches the roughness set value, the protective layer under the reserved light-transmitting area is removed to complete the roughness optimization of the light-shielding layer. This can simplify the roughness optimization process and help improve the roughness optimization efficiency.

[0048] In one embodiment, the material of the protective layer is SiNx. Specifically, the material of the protective layer needs to have a large etching selectivity with the transparent substrate, and the transparent substrate below the light-transmitting area can be unaffected during the deposition and removal of the protective layer. Since SiNx has a good etching selectivity with respect to quartz, a conventional transparent substrate material, the material of the protective layer is preferably SiNx. If there are other materials with a good etching selectivity with respect to the transparent substrate, they can also be used, which will not be described in detail here. In a specific embodiment, the method of depositing SiNx is ICPCVD (inductively coupled plasma chemical vapor deposition), the power is 800W, the pressure is 5Pa-15Pa, the temperature is 80℃-130℃, the chamber environment is 7sccm to 20sccm of NH3, 146sccm of SiH4 (doped with 5% He), 139sccm of Ar, and the time is 38nm / min-52nm / min; the method of removing SiNx is to use reactive ion etching, using 17sccm of CF4, 3sccm of H2, the chamber pressure is 10mT, and the power is 100w.

[0049] In one embodiment, the thickness of the protective layer is no greater than half of the thickness of the light shielding layer. Specifically, the protective layer is finally left below the light shielding area of ​​the mask light shielding layer. In order not to affect the performance of the light shielding layer, the thickness of the protective layer is no greater than half of the thickness of the light shielding layer, and various parameters of the protective layer are set according to the performance of the light shielding layer to ensure that the protective layer below the light shielding area of ​​the mask light shielding layer does not affect the various performances of the light shielding layer.

[0050] In one embodiment, the temperature of the atomic layer deposition is not less than 100° C. Specifically, when the temperature of the atomic layer deposition is 100° C. and above, water vapor, which is usually used as one of the reactants, evaporates quickly from the substrate and the wall, so when the temperature of 100° C. and above is used, the circulation speed between the precursors will be faster and the effect of the atomic layer deposition will be better.

[0051] In one embodiment, the first predetermined thickness is no greater than 10 nm.

[0052] Specifically, the first preset thickness of the atomic layer deposited light-shielding material is not greater than 10 nm. Since the roughness optimization is performed on the side wall of the light-shielding layer, the thickness of the deposited light-shielding material cannot exceed the distance between any two light-shielding layer patterns to be optimized (that is, the characteristic size of the mask). Therefore, the thickness of the deposited light-shielding material is not greater than 10 nm, and the first preset thickness is set according to the characteristic size of different light-shielding layers.

[0053] In one embodiment, the second predetermined thickness is no greater than 10 nm.

[0054] Specifically, the second preset thickness of the atomic layer etching light-shielding material is not greater than 10nm. Since the roughness optimization is performed on the side wall of the light-shielding layer, the thickness of the etched light-shielding material cannot exceed the distance between any two light-shielding layer patterns to be optimized (that is, the characteristic size of the mask). Therefore, the thickness of the etched light-shielding material is not greater than 10nm, and the second preset thickness is set according to the characteristic size of different light-shielding layers.

[0055] See also Figure 2 A mask, characterized in that the mask includes a transparent substrate, a protective layer and a light-shielding layer from the bottom layer in sequence, the protective layer covers the entire surface of the transparent substrate, the light-shielding layer is composed of a plurality of light-shielding areas and reserved light-transmitting areas, and there is a protective layer under the reserved light-transmitting area.

[0056] Specifically, a mask substrate is provided, which includes a transparent substrate, a protective layer, a light-shielding layer and a photoresist layer in sequence from the bottom layer. The mask substrate is subjected to electron beam direct writing and development to pattern the photoresist layer. The patterned photoresist layer is used as a mask to etch the light-shielding layer, and the pattern of the photoresist layer is transferred to the light-shielding layer. Then, the photoresist layer is removed to form a mask. Therefore, the mask substrate includes a transparent substrate, a protective layer and a light-shielding layer in sequence from the bottom layer. The protective layer covers the entire surface of the transparent substrate. A light-shielding layer is provided above the protective layer. The light-shielding layer is composed of a plurality of light-shielding areas and a reserved light-transmitting area. The light-shielding layer is formed above the protective layer. The light-shielding layer is formed after electron beam direct writing, development and etching. The required part of the light-shielding layer is left on the transparent substrate to form a light-shielding area, and the unnecessary part of the light-shielding layer is removed by development and etching to expose the protective layer below the light-shielding layer, thereby forming a reserved light-transmitting area.

[0057] In one embodiment, the material of the mask protective layer is SiNx. Specifically, the material of the protective layer needs to have a large etching selectivity with the transparent substrate, and the transparent substrate below the light-transmitting area can be unaffected during the deposition and removal of the protective layer. Since SiNx has a good etching selectivity with respect to quartz, a conventional transparent substrate material, the material of the protective layer is preferably SiNx. Other materials that have a good etching selectivity with respect to the transparent substrate can also be used, which will not be described in detail here.

[0058] The above-mentioned mask and its roughness optimization method reduce the roughness of the side walls of the mask light-shielding layer by making the pits and protrusions on the side walls of the mask light-shielding layer gradually flat during atomic layer deposition and atomic layer etching, thereby effectively solving the technical problem of low line edge roughness of the mask in the prior art.

[0059] The above description is only a description of the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any changes and modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of the technical solution of the present invention.

Claims

1. A mask, characterized in that: The mask plate includes a transparent substrate, a protective layer and a light-shielding layer in sequence from the bottom layer. The protective layer covers the entire surface of the transparent substrate. The light-shielding layer consists of a plurality of light-shielding areas and reserved light-transmitting areas. There is a protective layer below the reserved light-transmitting area.

2. The mask according to claim 1, characterized in that: The material of the protection layer is SiNx.

3. A roughness optimization method, characterized in that: include: A mask is provided, wherein the mask comprises a transparent substrate, a protective layer and a light shielding layer in order from the bottom layer, wherein the protective layer covers the entire surface of the transparent substrate, the light shielding layer is composed of a plurality of light shielding areas and reserved light transmission areas, and the reserved light transmission area has a protective layer below; Depositing a light-shielding material of a first preset thickness on the sidewall of the light-shielding layer of the mask by atomic layer deposition to at least partially fill the pits on the sidewall of the light-shielding layer and reduce the roughness of the sidewall of the light-shielding layer; Etching a second preset thickness of light-shielding material on the sidewall of the light-shielding layer of the mask by atomic layer etching, so as to at least partially remove protrusions on the light-shielding layer and reduce the roughness of the sidewall of the light-shielding layer; Detecting the roughness of the side wall of the light shielding layer, and comparing the detected roughness of the side wall of the light shielding layer with a preset roughness setting value; When the detected roughness of the side wall of the light shielding layer reaches the roughness setting value, the protective layer below the reserved light-transmitting area is removed.

4. The roughness optimization method according to claim 3, characterized in that: After the step of detecting the roughness of the side wall of the light shielding layer and comparing the detected roughness of the side wall of the light shielding layer with a preset roughness setting value, the method further includes: When the detected roughness of the side wall of the light-shielding layer does not reach the preset roughness setting value, repeat the step of depositing a first preset thickness of light-shielding material on the side wall of the light-shielding layer of the mask by atomic layer deposition to the step of comparing the detected roughness of the side wall of the light-shielding layer with the preset roughness setting value.

5. The roughness optimization method according to claim 3, characterized in that: After the step of depositing a light-shielding material of a first preset thickness on the sidewall of the light-shielding layer of the mask by atomic layer deposition, the following steps are included: Detecting the roughness of the side wall of the light shielding layer, and comparing the detected roughness of the side wall of the light shielding layer with a preset roughness setting value; When the detected roughness of the side wall of the light shielding layer reaches the roughness setting value, the protective layer below the reserved light-transmitting area is removed.

6. The roughness optimization method according to any one of claim 3, characterized in that: The material of the protection layer is SiNx.

7. The roughness optimization method according to any one of claim 3, characterized in that: The thickness of the protective layer is no greater than half of the thickness of the light shielding layer.

8. The roughness optimization method according to claim 3, characterized in that: The temperature of the atomic layer deposition is not less than 100°C.

9. The roughness optimization method according to claim 3, characterized in that: The first preset thickness is no greater than 10 nm.

10. The roughness optimization method according to claim 3, characterized in that: The second preset thickness is no greater than 10 nm.

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