A surface modified substrate holder and preparation method thereof

Abstract

The present invention provides a surface-modified substrate holder and a preparation method thereof, the preparation method comprising: S1, depositing a modified layer on a substrate after rough polishing, the modified layer being a material that is easy to etch; S2, fine polishing the modified layer, the flatness achieved by fine polishing being greater than the flatness achieved by rough polishing; S3, forming a wear-resistant layer on the finely polished modified layer; S4, forming a photoresist layer on the wear-resistant layer, exposing and developing the photoresist layer to obtain a first graphic structure; S5, growing a metal mask layer on the developed photoresist layer, then stripping and removing the photoresist layer, and obtaining a second graphic structure in the metal mask layer; S6, transferring the second graphic structure to the modified layer by reactive ion etching, removing the metal mask layer, and obtaining a surface-modified substrate holder. The method disclosed in the present invention can simply and efficiently process a high-precision substrate holder to meet the needs of high-process processing.

Description

Technical Field

[0001] The present invention relates to the technical field of precision photolithography wafer holders, and in particular to a surface-modified substrate holder and a preparation method thereof. Background Art

[0002] At present, the substrate holders in advanced process systems mostly adopt a columnar lattice suction cup structure, with a large number of cylindrical structures arranged on the surface, which become contacts with the substrate under the action of vacuum, and play the role of supporting the back of the substrate and fixing the substrate; the top of the cylindrical structure frequently contacts the back of the substrate when the substrate holder is working, and there is wear after long-term use. In order to extend the service life of the substrate holder, the cylindrical structure usually adopts silicon carbide, aluminum oxide, silicon nitride, boron nitride and other materials with high hardness and good wear resistance that are consistent with the substrate holder substrate; however, these materials have high chemical inertness, which limits the supporting processing methods. In order to process the lattice contact structure on the surface of these substrate materials, a series of processing steps such as grinding and polishing are required, which can easily cause mechanical damage or material degradation. In addition, it is difficult to detect the flatness of discrete lattice structures, which further limits the improvement of the flatness of the substrate holder. Summary of the invention

[0003] 1. Technical issues to be resolved

[0004] In view of the above problems, the present disclosure provides a surface-modified substrate holder and a preparation method thereof, which are used to solve technical problems such as easy wear or great processing difficulty of traditional substrate holders.

[0005] (II) Technical solution

[0006] On the one hand, the present disclosure provides a surface-modified substrate holder and a preparation method thereof, comprising: S1, depositing a modified layer on a roughly polished substrate, wherein the modified layer is a material that is easy to etch; S2, fine-polishing the modified layer, wherein the flatness achieved by the fine polishing is greater than the flatness achieved by the rough polishing; S3, forming a wear-resistant layer on the fine-polished modified layer; S4, forming a photoresist layer on the wear-resistant layer, exposing and developing the photoresist layer to obtain a first graphic structure; S5, growing a metal mask layer on the developed photoresist layer, and then stripping and removing the photoresist layer to obtain a second graphic structure in the metal mask layer; S6, transferring the second graphic structure to the modified layer by reactive ion etching, and removing the metal mask layer to obtain a surface-modified substrate holder.

[0007] Furthermore, before S1, it also includes: S0, performing mechanical structure processing on the substrate, and the mechanical structure at least includes ventilation holes, side holes and a mounting structure.

[0008] Furthermore, the rough polishing method of the substrate after the rough polishing in S1 includes grinding and ring polishing; the fine polishing method in S2 includes one of ion beam polishing and magnetorheological polishing.

[0009] Furthermore, the material of the substrate in S1 includes one of silicon carbide, aluminum oxide, silicon nitride, and boron nitride; the material of the modified layer in S1 includes one of silicon and silicon dioxide; and the thickness of the modified layer is 0.2 mm to 1 mm.

[0010] Furthermore, the method for forming the wear-resistant layer in S3 includes one of magnetron sputtering deposition, thermal evaporation and chemical vapor deposition; the material of the wear-resistant layer includes one of silicon carbide, diamond-like carbon-based and graphene; the thickness of the wear-resistant layer is 30nm to 200nm.

[0011] Furthermore, the method for forming the photoresist layer in S4 is spin coating; the material of the photoresist layer includes one of AR and Az series photoresists; and the thickness of the photoresist layer is 1 μm to 20 μm.

[0012] Furthermore, the method for growing the metal mask layer in S5 includes one of plasma enhanced chemical vapor deposition, magnetron sputtering deposition and thermal evaporation deposition; the material of the metal mask layer includes one of aluminum, chromium and copper; the thickness of the metal mask layer is 50nm to 400nm.

[0013] Furthermore, the second graphic structure obtained in S5 includes a columnar lattice structure and a sealing ring structure, wherein the width dimension of the columnar lattice structure is 0.2mm~0.5mm, the height dimension is 0.05mm~0.1mm, and the period dimension is 1mm~10mm; the arrangement method of the columnar lattice structure includes one of a square arrangement and a triangular arrangement.

[0014] Further, the reactive ion etching gas combination in S6 includes a group selected from C4F8 / SF6, SF6 / O2, and SF6 / CF6.

[0015] Another aspect of the present disclosure provides a surface-modified substrate holder, which is prepared according to the above-mentioned method for preparing a surface-modified substrate holder.

[0016] (III) Beneficial effects

[0017] The surface-modified substrate holder and preparation method thereof disclosed herein, by depositing a modified layer on a substrate, the modified layer being a material that is easy to etch, fine-polishing the modified layer before etching, breaking through the limitation of the traditional mode on the substrate material of the substrate holder, and the processed columnar lattice structure better maintains the flatness of the modified layer, and can simply and efficiently process high-precision substrate holders to meet the needs of high-process processing; and a wear-resistant layer is added on the modified layer, the wear-resistant layer increases the wear resistance of the surface of the substrate holder, and extends the service life of the substrate holder. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The schematic diagram of the structure of the substrate holder according to the embodiment of the present disclosure is shown;

[0019] Figure 2 A flow chart schematically shows a surface-modified substrate holder and a method for preparing the same according to an embodiment of the present disclosure;

[0020] Figure 3 A schematic diagram showing a comparison between isotropic and anisotropic etching effects according to an embodiment of the present disclosure is shown;

[0021] Figure 4 The schematic diagram of the cross-sectional structure after the modified layer is deposited on the substrate according to the embodiment of the present disclosure is shown;

[0022] Figure 5 The schematic diagram of the cross-sectional structure after forming the wear-resistant layer on the modified layer according to the embodiment of the present disclosure is shown;

[0023] Figure 6 The schematic diagram of the cross-sectional structure after a photoresist layer is formed on the wear-resistant layer according to an embodiment of the present disclosure is shown;

[0024] Figure 7 A schematic diagram of the cross-sectional structure of a photoresist layer after exposure and development according to an embodiment of the present disclosure is shown;

[0025] Figure 8 The schematic diagram of the cross-sectional structure after the metal mask layer is grown according to the embodiment of the present disclosure is shown;

[0026] Fig. 9 The schematic diagram of the cross-sectional structure after the photoresist layer is stripped and removed according to the embodiment of the present disclosure is shown;

[0027] Fig.10 A schematic diagram of a cross-sectional structure after the second graphic structure is transferred to the modified layer by reactive ion etching according to an embodiment of the present disclosure is shown;

[0028] Fig.11The schematic diagram of the cross-sectional structure after the metal mask layer is removed according to the embodiment of the present disclosure is shown;

[0029] Description of reference numerals:

[0030] 1. substrate; 2. substrate holder; 21. upper surface; 211. sealing ring; 212. columnar lattice structure; 22. step surface; 221. substrate holder mounting structure; 23. vent hole; 24. side hole; 25. base plate; 26. modified layer; 27. wear-resistant layer; 28. photoresist layer; 29. ​​metal mask layer; 3. machine platform. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0032] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0033] It should be noted that if directional indication is involved in the embodiments of the present disclosure, the directional indication is only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0034] Figure 1 The schematic diagram of the structure of the substrate holder in the present disclosure is shown in FIG. The substrate holder 2 is generally a cylindrical substrate with a stepped surface, including main structures such as an upper surface 21, a stepped surface 22, a vent hole 23 and a side hole 24, wherein the upper surface 21 includes a large number of regularly arranged columnar lattice structures 212 and a sealing ring 211, and the stepped surface 22 includes a substrate holder mounting structure 221.

[0035] When the substrate holder 2 is working normally, it is connected to the machine table 3 through the mounting structure 221 on the step surface 22. The mounting connection method is adapted to the machine table interface form according to different usage scenarios, which can be Figure 1The screw installation method shown can also be vacuum adsorption installation, pressure ring installation, etc. The lower surface of the substrate 1 is in contact with the columnar lattice structure 212 and the sealing ring 211, and a relatively closed cavity is formed around the columnar lattice. The cavity is connected to the side hole 24 through the vent hole 23, and a relative negative pressure is generated by the external vacuum source connected to the side hole 24, while the upper surface of the substrate 1 is at normal atmospheric pressure, which generates a pressure difference. Under the action of the pressure difference, the substrate 1 is firmly adsorbed on the upper surface 21 of the substrate holder 2, and the back of the substrate 1 is in close contact with the columnar lattice structure 212. The diameter of the sealing ring 211 is slightly smaller than the outer diameter of the substrate 1, ensuring the airtightness of the cavity.

[0036] From the above working principle, it can be seen that when the substrate 1 is in normal working condition, its back side is tightly fitted with the columnar lattice structure 212 on the surface of the substrate holder 2. The flatness of the upper surface of the substrate holder 2 will be reflected in the surface accuracy of the substrate 1 after adsorption. Therefore, the flatness of the substrate holder 2 determines the flatness index of the substrate 1 after adsorption, which is closely related to the semiconductor process.

[0037] For columnar lattice substrate holders, the current traditional processing method is to first machine the surface columnar structure and then directly perform grinding, polishing and other processing steps on the surface columnar structure, which can easily cause mechanical damage or material degradation; at the same time, since the surface of the substrate holder is a large number of discrete columnar structures, there is a lack of high-precision flatness detection methods, which limits the improvement of processing accuracy; and since the substrate holder base material is mostly made of chemically stable materials such as silicon carbide, aluminum oxide, and silicon nitride, it is difficult to directly perform etching processing on its surface.

[0038] Based on this, the present disclosure provides a method for preparing a surface-modified substrate holder, such as Figure 2 As shown, the preparation method includes: S1, depositing a modified layer 26 on a substrate 25 after rough polishing, wherein the modified layer 26 is a material that is easy to etch; S2, fine polishing the modified layer 26, wherein the flatness achieved by the fine polishing is greater than the flatness achieved by the rough polishing; S3, forming a wear-resistant layer 27 on the modified layer 26 after fine polishing; S4, forming a photoresist layer 28 on the wear-resistant layer 27, exposing and developing the photoresist layer 28 to obtain a first graphic structure; S5, growing a metal mask layer 29 on the developed photoresist layer 28, then stripping and removing the photoresist layer 28, and obtaining a second graphic structure in the metal mask layer 29; S6, transferring the second graphic structure to the modified layer 26 by reactive ion etching, removing the metal mask layer 29, and obtaining a substrate holder with a modified surface.

[0039] The cross-sectional schematic diagram of the preparation process is shown in Figures 4 to 11As shown, a modified layer 26 is deposited on a substrate 25, and the modified layer 26 is finely polished and then etched to obtain a substrate holder 2 with a columnar lattice structure 212; since the modified layer 26 is a material that is easy to etch, it breaks through the limitation of the traditional mode on the substrate material of the substrate holder. Compared with directly optically processing the columnar lattice, the etching processing method can obviously more simply process a substrate holder with better flatness, has significant economic benefits, and can meet the needs of higher processes. At the same time, the columnar lattice structure 212 prepared by this process can better inherit the flatness of the modified layer 26, because the wear-resistant layer 27 is plated on the surface of the modified layer 26 and the dry etching process will hardly destroy the surface shape accuracy of the modified layer 26. And since the modified layer 26 is a continuous plane before etching, the difficulty of surface shape detection and fine polishing is significantly lower than directly detecting and processing the discrete cylindrical lattice. At the same time, since the hardness of the wear-resistant layer 27 is usually much greater than that of the modified layer 26, the wear resistance of the surface of the substrate holder 2 is increased, and the service life of the substrate holder is extended. It should also be noted that the reason why the present disclosure does not adopt the method of directly etching the modified layer 26 to obtain the second graphic structure and then forming the wear-resistant layer 27 is that the upper surface area of ​​the cylinder is usually very small, and directly coating the top of the cylinder will cause problems such as difficulty in film formation, poor uniformity of film thickness, and poor adhesion of the film layer. On the basis of the above embodiment, before S1, it also includes: S0, performing mechanical structure processing on the substrate 25, and the mechanical structure at least includes a vent hole 23, a side hole 24 and a mounting structure 221.

[0040] like Figure 1 As shown, before the surface modification step is performed, it is first necessary to select suitable materials for processing the mechanical structure of the substrate 25, including the internal structure of the cavity and the mounting structure of the substrate 25 and the machine table 3, etc.

[0041] On the basis of the above embodiment, the rough polishing method of the substrate 25 after the rough polishing in S1 includes grinding and ring polishing; the fine polishing method in S2 includes one of ion beam polishing and magnetorheological polishing.

[0042] The upper surface 21 of the substrate 25 is ground and roughly polished to prepare for the next step of modification. Before modification, the substrate 25 needs to have good flatness and roughness, which is conducive to the close bonding of the modified layer 26 and the substrate 25. The flatter and smoother the substrate 25 is, the stronger the bonding force between the two. In this step, the substrate 25 needs to be processed to a flatness PV < 1 / 4λ (for example, λ = 632.8nm) and a roughness Ra < 5nm, which can generally be achieved by grinding and whole-plate ring polishing.

[0043] The modified layer 26 is finely polished. The polishing accuracy of this step directly determines the final flatness index of the substrate holder. Therefore, the flatness after polishing needs to reach PV<1 / 10λ. Advanced polishing methods such as ion beam polishing and magnetorheological polishing can be used.

[0044] Based on the above embodiment, the material of the substrate 25 in S1 includes one of silicon carbide, aluminum oxide, silicon nitride, and boron nitride; the material of the modified layer 26 in S1 includes one of silicon and silicon dioxide; and the thickness of the modified layer 26 is 0.2 mm to 1 mm.

[0045] The material of the substrate 25 needs to have the characteristics of high rigidity, low thermal expansion coefficient, and no introduction of metal contamination, and ceramic materials such as silicon carbide, aluminum oxide, silicon nitride, and boron nitride are preferred.

[0046] The modified layer 26 is deposited on the substrate 25 by physical vapor deposition, chemical vapor deposition or magnetron sputtering. Figure 4 As shown, the selection of the material of the modified layer 26 needs to consider the following points: ① Thermal expansion coefficient: It needs to be close to the thermal expansion coefficient of the substrate 25 material to avoid the modified layer 26 from falling off due to inconsistent thermal deformation during the subsequent process; ② Machinability: It is easy to perform optical processing such as high-precision grinding and polishing, has high processing efficiency, and can achieve high flatness; ③ Process adaptability: It is suitable for the subsequent processing of the columnar lattice structure 212 by etching, and adapts to the requirements of related processes; ④ Environmental adaptability: It meets the standard requirements of the semiconductor production environment, such as not introducing additional metal ion pollution, non-toxic and harmless, etc. Considering the above factors, the material of the modified layer 26 is preferably silicon, silicon dioxide, etc.

[0047] Based on the above embodiments, Figure 5 As shown, the method for forming the wear-resistant layer 27 in S3 includes one of magnetron sputtering deposition, thermal evaporation and chemical vapor deposition; the material of the wear-resistant layer 27 includes one of silicon carbide, diamond-like carbon (DLC), and graphene; the thickness of the wear-resistant layer 27 is 30nm to 200nm.

[0048] The wear-resistant layer 27 is plated on the surface of the modified layer 26 to increase the hardness and wear resistance of the substrate holder surface and extend the service life of the substrate holder. The wear-resistant layer 27 should not be too thick to avoid affecting the subsequent etching process. Therefore, the thickness of the wear-resistant layer is preferably within the above range. The selection of the material of the wear-resistant layer 27 needs to consider the following points: ① Hardness: It has a higher hardness to improve the wear resistance of the substrate holder surface; ② Thermal expansion coefficient: It is close to the thermal expansion coefficient of the modified layer 26, with strong bonding force to avoid falling off; ③ Environmental adaptability: It meets the standard requirements of the semiconductor production environment, such as not introducing additional metal ion pollution, non-toxic and harmless, etc. Considering the above factors, the material of the wear-resistant layer 27 is preferably silicon carbide, DLC, graphene, etc.

[0049] Before applying the photoresist in step S4, the substrate 25 needs to be cleaned to ensure that the subsequent spin coating of the photoresist proceeds smoothly. A solvent such as acetone, alcohol, isopropyl ketone, etc. can be used for ultrasonic cleaning. At this point, the substrate holder substrate is prepared, and the surface columnar lattice structure will be prepared later.

[0050] Based on the above embodiments, Figure 6 As shown, the method for forming the photoresist layer 28 in S4 is spin coating; the material of the photoresist layer 28 includes one of AR and Az series photoresists; the thickness of the photoresist layer 28 is 1 μm to 20 μm.

[0051] A layer of photoresist is spin-coated on the surface of the silicon wafer by a spin coater to form a photoresist layer 28. After the spin coat, the substrate 25 is dried; the photoresist can be AR-P6200, Az9260, Az3100 and other AR, Az series photoresists.

[0052] like Figure 7 As shown, exposure is performed using photolithography technology, and a first graphic structure is developed on the photoresist, and the first graphic structure is complementary to the second graphic structure; wherein the photolithography technology can be ultraviolet lithography, laser direct writing lithography, electron beam direct writing lithography, etc.

[0053] Based on the above embodiments, Figure 8 As shown, the method for growing the metal mask layer 29 in S5 includes one of plasma enhanced chemical vapor deposition, magnetron sputtering deposition and thermal evaporation deposition; the material of the metal mask layer 29 includes one of aluminum, chromium and copper; the thickness of the metal mask layer 29 is 50nm to 400nm.

[0054] A metal mask layer 29 is grown to perform pattern transfer. The function of the metal mask layer 29 is to resist the etching gas so that the modified layer 26 covered by it is not etched, while the uncovered part is exposed to the etching gas, thereby achieving selective etching to obtain the target columnar lattice structure 212 and the sealing ring structure 211.

[0055] Further, if Fig. 9 As shown, the photoresist is removed by chemical reaction between the stripping solution and the photoresist, so as to facilitate the subsequent etching process. The stripping solution can be selected to match the photoresist.

[0056] Based on the above embodiment, the second graphic structure obtained in S5 includes a columnar lattice structure 212 and a sealing ring structure 211, wherein the width dimension of the columnar lattice structure 212 is 0.2mm~0.5mm, the height dimension is 0.05mm~0.1mm, and the period dimension is 1mm~10mm; the arrangement method of the columnar lattice structure 212 includes one of a square arrangement and a triangular arrangement.

[0057] The height of the columnar lattice structure 212 is less than 1 / 2 of the thickness of the modified layer 26. A too high ratio will cause the strength of the root of the columnar lattice to decrease. The outer diameter of the sealing ring structure 211 is 1 to 5 mm smaller than the diameter of the substrate 1, and the width can be equal to the maximum width of the column. The height of the sealing ring structure 211 is consistent with the height of the columnar lattice structure 212. If the height of the sealing ring structure 211 is too low, it will cause air leakage. If it is too high, the columnar lattice structure 212 cannot play a supporting function, and the edge will warp. The columns in the columnar lattice structure 212 are usually cylinders, but they can also be triangular prisms, quadrangular prisms, hexagonal prisms, etc. The arrangement of the columnar lattice is a square arrangement (such as Figure 1 As shown), a triangular arrangement, of course, other feasible arrangements are also possible.

[0058] Based on the above embodiment, the gas combination for reactive ion etching in S6 includes a group selected from C4F8 / SF6, SF6 / O2, and SF6 / CF6.

[0059] like Fig.10 As shown, reactive ion etching is performed to transfer the second graphic structure to the modified layer 26. Reactive ion etching belongs to dry etching and is a physical and chemical processing process. During the processing, there are both physical processes of plasma bombardment and chemical processes of etching gas chemical corrosion. It is very suitable for the preparation of the surface modification disclosed in the present invention; in the early stage of etching, there is still a wear-resistant layer 27 on the surface of the modified layer 26. The wear-resistant layer 27 is generally chemically stable and it is difficult to undergo chemical reactions for etching. At this stage, the physical bombardment process of plasma is dominant. Therefore, the wear-resistant layer 27 mentioned above should not be too thick to prevent the wear-resistant layer 27 from not being etched through, resulting in low processing efficiency; in the middle and late stages of etching, the wear-resistant layer 27 in the non-graphic area has been etched through. At this stage, the physical and chemical processes work together to etch the modified layer 26, and finally a columnar lattice structure 212 and a sealing ring structure 211 are obtained.

[0060] This step should not be replaced by wet etching, mainly for the following two reasons: First, the chemical properties of the wear-resistant layer 27 are stable and it is not easy to react chemically with the corrosive solution, which has a shielding effect on wet etching; in order to use the wet etching method, the wear-resistant layer 27 can only be abandoned, which will aggravate the wear on the surface of the substrate holder and shorten the service life of the substrate holder. Second, wet etching is an isotropic etching method. Compared with anisotropic dry etching (such as Figure 3 As shown in the figure, there are problems such as inaccurate etching dimensions and rough and not steep side walls, which will increase the risk of crack expansion on the side walls and fracture of the cylinder after long-term use, shortening the service life of the substrate holder. Therefore, wet etching is obviously not as advantageous as dry etching in the preparation of the surface-modified substrate holder disclosed in the present invention.

[0061] Further, if Fig.11 As shown, removing the metal mask layer 29 includes: removing the metal mask layer 29 remaining in the pattern area after etching, and alternately cleaning with a cleaning solution composed of an organic solvent and an inorganic solvent, and finally obtaining a surface-modified substrate holder that can be put into use.

[0062] The present disclosure also provides a surface-modified substrate holder, which is prepared according to the above-mentioned preparation method of the surface-modified substrate holder.

[0063] The surface-modified substrate holder disclosed in the present invention has a simple and efficient preparation process and has significant economic benefits; the processed substrate holder has very high flatness accuracy and can be applied to semiconductor processing with higher process steps; and by using reactive ion etching, a dry etching method, the processed columns have better quality and a lower risk of column breakage.

[0064] The present disclosure is further described below through specific implementations. The above-mentioned surface-modified substrate holder and its preparation method are specifically described in the following examples. However, the following examples are only used to illustrate the present disclosure, and the scope of the present disclosure is not limited thereto.

[0065] This embodiment provides a surface-modified substrate holder and a method for preparing the same. Figures 4 to 11 As shown, in this embodiment, the substrate holder is a suction cup, and the substrate is a wafer. The entire processing flow includes two parts: suction cup substrate preparation and suction cup columnar lattice structure processing. The following steps are performed in sequence:

[0066] Step 1, processing of the suction cup substrate: Select appropriate materials to process the mechanical structure of the substrate 25. The structures such as the vent hole 23, the side hole 24 and the mounting structure 221 are all processed in this step. The material of the substrate 25 is preferably a ceramic material such as silicon carbide, aluminum oxide, silicon nitride, boron nitride, etc.; equivalent to the above step S0.

[0067] Step 2, optical processing of substrate: complete the grinding and rough polishing of the upper surface 21. In this step, the substrate 25 needs to be processed to a flatness PV < 1 / 4λ (for example, λ = 632.8nm) and a roughness Ra < 5nm, which can generally be achieved by grinding and whole-plate ring polishing.

[0068] Step 3, substrate surface modification: depositing a modified layer 26 on the upper surface 21 of the chuck by physical vapor deposition, chemical vapor deposition or magnetron sputtering, etc., the thickness of the modified layer 26 is 0.2 mm to 1 mm. The material of the modified layer 26 is preferably silicon, silicon dioxide, etc.; equivalent to the above step S1.

[0069] Step 4, fine polishing: fine polishing is performed on the modified layer 26. The flatness after fine polishing needs to reach PV<1 / 10λ. Advanced polishing methods such as ion beam polishing and magnetorheological polishing can be used; this is equivalent to the above step S2.

[0070] Step 5, plating a wear-resistant layer: Plating a wear-resistant layer 27 on the surface of the modified layer 26, the thickness of the wear-resistant layer 27 is 30nm to 200nm. The material of the wear-resistant layer 27 is preferably silicon carbide, DLC, graphene, etc.

[0071] Step 6, cleaning the substrate to ensure that the subsequent spin coating of the photoresist proceeds smoothly, and ultrasonic cleaning can be performed using solvents such as acetone, alcohol, isopropyl ketone, etc.; this is equivalent to the above step S3.

[0072] At this point, the suction cup substrate is prepared, and the surface columnar lattice structure will be prepared later.

[0073] Step 7, spin coating photoresist: Spin coating a layer of photoresist on the surface of the silicon wafer using a spin coating machine, the thickness of the photoresist is 1μm to 20μm, and after spinning, the substrate 25 is dried; the photoresist can be AR, Az series photoresist such as AR-P6200, Az9260, Az3100, etc.

[0074] Step 8, exposure and development: exposure is performed using photolithography technology, and the first pattern structure is developed on the photoresist. The photolithography technology may be ultraviolet lithography, laser direct writing lithography, electron beam direct writing lithography, etc.; this is equivalent to the above step S4.

[0075] Step 9, metal mask growth: grow a metal mask layer 29 to perform pattern transfer. The material of the metal mask layer 29 is aluminum, chromium, copper or other metals.

[0076] Step 10, stripping: removing the photoresist by chemical reaction between the stripping solution and the photoresist, the stripping solution can be selected to match the photoresist, and after stripping, a second graphic structure is obtained in the metal mask layer 29; equivalent to the above step S5.

[0077] Step 11, reactive ion etching: Reactive ion etching is performed to transfer the second graphic structure to the modified layer 26 to obtain a columnar lattice structure 211 and a sealing ring structure 212, wherein the columnar lattice structure 211 is a cylinder, the width of the cylinder is 0.2mm-0.5mm, the height is 0.05mm-0.1mm, and the height of the cylinder is less than 1 / 2 of the thickness of the modified layer 26; the cylinder period size is 1mm-10mm; the outer diameter of the sealing ring structure 212 is 1mm-5mm smaller than the diameter of the wafer, and the width can be equal to the maximum width of the cylinder; the arrangement of the cylinder is a square arrangement, a triangular arrangement, etc. The depth of reactive ion etching is determined by the height of the cylinder, and the etching can be performed once or multiple times. The gas combination used for etching can be: C4F8 / SF6, SF6 / O2, SF6 / CF6.

[0078] Step 12, removing the mask and cleaning the suction cup: soak in a removal solution for 30 to 60 minutes to remove the metal mask layer 29 remaining in the graphic area after etching. The removal solution is selected according to the type of material of the metal mask layer 29, and can be sulfuric acid, nitric acid, hydrochloric acid or a combination thereof; after removing the metal mask, use a cleaning solution composed of an organic solvent and an inorganic solvent to alternately clean the residual removal solution or other impurities, and finally obtain a surface modified suction cup that can be put into use; this is equivalent to the above-mentioned step S6.

[0079] According to the above steps 1 to 12, a specific embodiment is provided below.

[0080] Embodiment 1:

[0081] The surface modified suction cup processing method in this embodiment has the following specific implementation steps:

[0082] (1) Silicon carbide is selected as the material of the suction cup substrate 25, and a reaction sintering (Rb-SiC) method is used to prepare a blank of the substrate 25, and then the vent hole 23 and the side hole 24 are machined.

[0083] (2) The upper surface 21 of the suction cup blank is rough-machined by grinding. After the flatness is processed to about 10 μm, it is transferred to a ring polishing machine for optical polishing until the flatness PV is 1 / 4λ and the roughness Ra is about 5 nm.

[0084] (3) Figure 4 As shown, a modified layer 26 is deposited on the upper surface 21 of the roughly machined silicon carbide suction cup by physical vapor deposition (PVD). The modified layer 26 is made of silicon and has a thickness of 0.3 mm. At this time, the upper surface has a certain degree of flatness and roughness and can be tightly combined with the modified layer 26.

[0085] (4) Fine polishing is performed on the modified layer 26. Since the silicon modified layer is softer than silicon carbide, the processing removal efficiency is higher and it is easier to achieve a higher surface accuracy. The flatness of the suction cup surface can be improved to more than 1 / 10λ by using the iterative method of ring polishing and ion beam processing.

[0086] (5) Figure 5 As shown, a wear-resistant layer 27 is plated on the surface of the modified layer 26 by magnetron sputtering. The material of the wear-resistant layer 27 is DLC with a thickness of 50 nm. The DLC film layer is a diamond-like carbon-based thin film material with high hardness and wear resistance. The specific preparation method of the DLC film layer is as follows: a clean suction cup sample is dried and placed in a vacuum chamber to evacuate the vacuum chamber. When the vacuum is evacuated to 10 -3 Pa, argon gas was introduced into the vacuum chamber as a protective atmosphere; then the power was turned on to make Ar + Bombard the surface of the suction cup for about 20 minutes to further remove the dirt on the surface of the suction cup and activate the surface; then introduce C2H2 into the vacuum chamber until the pressure in the cavity reaches above 0.3Pa, maintain the flow rates of argon and C2H2 at 50seem and 130seem respectively, set the negative bias voltage to 120V, the target power to 1.1KW, and the deposition time to 25 minutes; after the deposition is completed, turn off all power supplies and let the sample cool naturally with the vacuum chamber. Since the surface activity of the newly prepared film is high and it is easy to be contaminated, argon can still be continuously introduced during the cooling process to protect the surface of the film. When the temperature cools to below 50°C, take out the sample and cool it to room temperature.

[0087] (6) Clean the suction cup after depositing the DLC film layer to ensure the subsequent spin coating of the photoresist is carried out smoothly. Soak the suction cup in acetone and alcohol and ultrasonically clean it for more than 30 minutes to ensure that there are no impurities and pollutants on the surface.

[0088] (7) Figure 6 As shown, after cleaning, AR-P6200 photoresist is dropped in the center of the suction cup and placed in a spinner for even coating. The spinner parameters are set to 2000 rpm and the coating time is 2 minutes. After even coating, a 2μm thick photoresist coating can be obtained. The evenly coated suction cup is then placed on a hot plate at 150°C and baked for 10 minutes to ensure that the moisture in the photoresist is evaporated to enhance the adhesion of the photoresist to the silicon substrate.

[0089] (8) Figure 7 As shown, the surface of the chuck after spin coating the photoresist is exposed and developed, and the exposure is performed using an electron beam exposure device, with an electron beam current of 100 pA and a dose of 300 μC / cm 2The diameter of the columnar lattice structure 212 is 0.5 mm, and the period is 3 mm. The developer AR600-546 and the fixer AR600-56 are used for development. The suction cup must be first immersed in the developer for 70 seconds and then immersed in the fixer for 30 seconds to complete the development.

[0090] (9) Figure 8 As shown, PECVD is used to grow the metal mask layer 29, which is made of aluminum and has a growth thickness of 160 nm, which is thick enough to resist etching.

[0091] (10) Fig. 9 As shown, use stripping liquid AR600-71 to remove the aluminum film and photoresist in the non-graphic area, pour the stripping liquid into the culture dish, then put the suction cup sample in, and soak for 5 hours. In order to prevent part of the aluminum film from still adhering to the surface of the suction cup, the suction cup can be placed in an ultrasonic cleaner for 1 to 2 minutes.

[0092] (11) Fig.10 As shown, the suction cup is placed in a reactive ion etching device for etching, the pressure of the reaction chamber is 4mTorr, the ICP power is 20W, the forward power is 850W, the etching gas is SF6, the passivation gas is C4F8, the etching / passivation gas ratio is 1:1, the gas flow rate is 24sccm, the etching thickness is set to 0.1mm, and the etching time is 90 minutes.

[0093] (12) Fig.11 As shown, the chuck is soaked and corroded with concentrated nitric acid to remove the aluminum film remaining on the surface of the chuck. The corrosion time is about 30 minutes. After the corrosion is completed, the chuck is ultrasonically cleaned for 10 minutes with an alcohol-acetone mixed solution, and then rinsed with deionized water and dried with a nitrogen gun. The entire processing process of the surface modified chuck is completed.

[0094] The suction cup material of the surface modified substrate holder disclosed in the present invention is composed of two groups of different materials, the substrate and the modified layer. The substrate material can still use silicon carbide, aluminum oxide, silicon nitride, boron nitride and other materials to make the suction cup as a whole have good rigidity and thermal stability; the modified layer uses silicon, silicon dioxide and other materials that are easy to etch and process, breaking through the limitations of the substrate material on the processing method. The etching process can be carried out simply and efficiently to obtain a columnar lattice structure with higher dimensional accuracy and better side wall quality. The preparation process of the entire columnar lattice structure has little effect on the flatness of the suction cup surface, and the columnar lattice structure can inherit the flatness of the modified layer surface to a high degree. A wear-resistant layer is plated on the surface of the modified layer to extend the service life of the substrate holder.

[0095] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A method for preparing a surface-modified substrate holder, characterized in that: include: S1, depositing a modified layer (26) on a roughly polished substrate (25), wherein the modified layer (26) is a material that is easy to etch; S2, performing fine polishing on the modified layer (26), wherein the flatness achieved by the fine polishing is greater than the flatness achieved by the rough polishing; S3, forming a wear-resistant layer (27) on the modified layer (26) after fine polishing; S4, forming a photoresist layer (28) on the wear-resistant layer (27), exposing and developing the photoresist layer (28) to obtain a first pattern structure; S5, growing a metal mask layer (29) on the developed photoresist layer (28), and then stripping and removing the photoresist layer (28), thereby obtaining a second graphic structure in the metal mask layer (29); S6, using reactive ion etching to transfer the second graphic structure into the modified layer (26), removing the metal mask layer (29), and obtaining a surface-modified substrate holder.

2. The method for preparing a surface-modified substrate holder according to claim 1, characterized in that: The S1 also includes: S0, performing mechanical structure processing on the substrate (25), wherein the mechanical structure at least includes a vent hole (23), a side hole (24) and a mounting structure (221).

3. The method for preparing a surface-modified substrate holder according to claim 1, characterized in that: The rough polishing method of the substrate (25) after rough polishing in S1 includes grinding and ring polishing; The fine polishing method in S2 includes one of ion beam polishing and magnetorheological polishing.

4. The method for preparing a surface-modified substrate holder according to claim 1, characterized in that: The material of the substrate (25) in S1 includes one of silicon carbide, aluminum oxide, silicon nitride and boron nitride; The material of the modified layer (26) in S1 includes one of silicon and silicon dioxide; the thickness of the modified layer (26) is 0.2 mm to 1 mm.

5. The method for preparing a surface-modified substrate holder according to claim 1, characterized in that: The method for forming the wear-resistant layer (27) in S3 comprises one of magnetron sputtering deposition, thermal evaporation and chemical vapor deposition; The material of the wear-resistant layer (27) includes one of silicon carbide, diamond-like carbon-based and graphene; The thickness of the wear-resistant layer (27) is 30nm-200nm.

6. The method for preparing a surface-modified substrate holder according to claim 1, characterized in that: The method of forming the photoresist layer (28) in S4 is spin coating; The material of the photoresist layer (28) includes one of AR and Az series photoresists; The thickness of the photoresist layer (28) is 1 μm to 20 μm.

7. The method for preparing a surface-modified substrate holder according to claim 1, characterized in that: The method for growing the metal mask layer (29) in S5 comprises one of plasma enhanced chemical vapor deposition, magnetron sputtering deposition and thermal evaporation deposition; The material of the metal mask layer (29) includes one of aluminum, chromium and copper; The thickness of the metal mask layer (29) is 50nm-400nm.

8. The method for preparing a surface-modified substrate holder according to claim 1, characterized in that: The second graphic structure obtained in S5 comprises a columnar lattice structure (212) and a sealing ring structure (211), wherein the columnar lattice structure (212) has a width dimension of 0.2 mm to 0.5 mm, a height dimension of 0.05 mm to 0.1 mm, and a period dimension of 1 mm to 10 mm; The arrangement of the columnar lattice structure (212) includes one of a square arrangement and a triangle arrangement.

9. The method for preparing a surface-modified substrate holder according to claim 1, characterized in that: The reactive ion etching gas combination in S6 includes a group consisting of C4F8 / SF6, SF6 / O2, and SF6 / CF6.

10. A surface-modified substrate holder, characterized in that: The surface-modified substrate holder is prepared according to the method for preparing a surface-modified substrate holder according to any one of claims 1 to 9.

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