Photomask with crystalline thermoplastic polymer film frame structure

Abstract

The invention provides a photomask with a crystalline thermoplastic polymer film frame structure, which comprises a transparent substrate, and the transparent substrate comprises a middle area and an edge area surrounding the middle area; the circuit pattern is located in the middle area of the transparent substrate, is a geometric pattern formed by a light-proof material and is used for defining a circuit structure of the semiconductor device; the film frame is an annular frame which is made of a crystal type thermoplastic high polymer material and is adhered to the edge area of the transparent substrate, the annular frame surrounds the circuit pattern to form a closed space, and one or more layers of fluorine-containing high polymer glue are coated on the film frame and are used for blocking release of sulfate radicals and ammonium radicals; and the protective film covers the film frame, forms a closed space with the film frame, and is used for isolating the circuit pattern from the external environment. The crystalline thermoplastic polymer is used for manufacturing the film frame, so that the defect that sulfate radical factors contained in the surface layer of the film frame cannot be removed completely due to the fact that a traditional aluminum frame manufacturing process comprises anodic oxidation and electrolyte contains sulfate radicals is overcome.

Description

Technical Field

[0001] The invention relates to the field of semiconductor mask plate materials, and in particular to a photomask with a crystalline thermoplastic polymer film frame structure. Background Art

[0002] In the field of semiconductor manufacturing, photomasks are key components of the photolithography process. The finished product structure consists of the photomask itself and the protective frame film tightly attached to it. In the current production and manufacturing of high-end photomasks, it is necessary to avoid the residual sulfate and ammonium radicals. This is because, during the use of the back-end mask, as the number of uses increases, these residual sulfate and ammonium radicals will undergo a photochemical reaction, gradually transform into mist, and gradually gather on the pattern of the photomask. Figure 1 As shown in the figure, the generation of photomask mist can be clearly seen. The presence of these mists will seriously damage the circuit structure of the mask plate, causing circuit short circuit failures, and ultimately causing a large number of chips to be scrapped due to failure to work properly, causing huge economic losses to semiconductor manufacturers.

[0003] In-depth investigation of the reasons, during the photomask manufacturing process, both the photomask body and the protective frame film contain sulfate (SO4 2- ) and ammonium ion (NH4 + ) Risk of residual ions. In the photomask body, the sulfuric acid-based solution used in the etching process will inevitably leave residues on its surface. During the etching process, the sulfuric acid-based solution reacts chemically with the material of the photomask body, and some sulfate ions will be embedded in the microstructure of the material, which is difficult to completely remove with subsequent conventional cleaning operations.

[0004] As for the protective frame film, it is usually manufactured using an anodizing process, and the electrolyte used contains H2SO4. During the anodizing process, a series of complex chemical reactions will occur on the surface of the aluminum frame, causing sulfate ions to be firmly adsorbed on the surface of the aluminum frame. These adsorbed sulfate ions become potential hazards for subsequent photochemical reactions.

[0005] During the subsequent use of the mask, after multiple exposures, the residual sulfate and ammonium ions will undergo a series of complex photochemical reactions under the action of light, eventually generating ammonium sulfate crystals. These ammonium sulfate crystals will continue to accumulate in the graphic area, and over time, gradually lead to the emergence of line short circuit problems. Especially in the 193nm process, this phenomenon has a particularly significant impact on the chip yield. Relevant data show that the chip yield of the 193nm process may drop to below 50%, seriously restricting the production efficiency and quality of semiconductor products.

[0006] More problematically, chemical bonds will form between sulfate radicals and the aluminum oxide layer. The existence of these chemical bonds makes it impossible to completely remove sulfate radicals using traditional cleaning methods, such as cleaning with deionized water. Moreover, the enclosed space formed between the protective film of the photomask and the photomask provides favorable conditions for the deposition of reaction products. In this relatively closed environment, the ammonium sulfate crystals formed by the reaction cannot effectively diffuse and can only accumulate continuously, thereby accelerating the formation of foggy substances.

[0007] From the perspective of the prior art, the aluminum frame plays a crucial supporting and protecting role in the photomask structure. Therefore, it must have good rigidity and heat resistance to ensure stable physical properties during the exposure process (the temperature can be as high as 150 °C during exposure). However, there are many insurmountable problems when traditional coating technologies are applied to the aluminum frame. On the one hand, since the manufacturing process includes anodic oxidation and its electrolyte contains sulfate radicals, sulfate radical factors cannot be completely removed from the surface layer of the frame. On the other hand, during the application of the coating, it is also necessary to avoid having an adverse impact on the adhesion between the film frame and the protective film, otherwise it will lead to a decrease in the stability of the protective structure. Taking the parylene evaporation coating technology as an example, although this technology can provide protection for the aluminum frame to a certain extent, it has the problems of high cost and low production efficiency, which undoubtedly increases the production cost of enterprises and reduces the production efficiency, and is greatly limited in large-scale production applications.

[0008] In summary, in the face of the many problems existing in the current photomask manufacturing process, there is an urgent need for a new and effective solution to solve a series of problems brought about by sulfate radical and ammonium radical residues, so as to improve the overall level and economic benefits of semiconductor manufacturing. Summary of the Invention

[0009] The present invention provides a photomask with a crystalline thermoplastic polymer film frame structure, which is characterized by including:

[0010] A transparent substrate, the transparent substrate includes a middle region and an edge region surrounding the middle region;

[0011] A circuit pattern, located in the middle region of the transparent substrate, is a geometric pattern formed by an opaque material, and is used to define the circuit structure of a semiconductor device;

[0012] A film frame, the film frame is made of a crystalline thermoplastic polymer material, and is adhered to the annular frame of the edge region of the transparent substrate. The annular frame surrounds the circuit pattern to form an enclosed space. One or more fluorine-containing polymer photoresists are coated on the film frame to block the release of sulfate radicals and ammonium radicals;

[0013] A protective film, covering the film frame, forms an enclosed space with the film frame, and is used to isolate the circuit pattern from the external environment.

[0014] In an embodiment of the present invention, it further includes an adhesive layer for fixing the film frame on the transparent substrate and fixing the protective film on the film frame.

[0015] In an embodiment of the present invention, the fluorine-containing polymer coating glue is:

[0016] Fully coated on all four sides, the fluorine-containing polymer coating glue is coated on all outer surfaces of the film frame; or

[0017] Coated on both the inner and outer sides, the fluorine-containing polymer coating glue is coated on the inner and outer sides of the film frame, avoiding the upper and lower sides; or

[0018] Coated on the outer side only, the fluorine-containing polymer coating glue is coated on the outer side of the film frame, avoiding the other three sides.

[0019] In an embodiment of the present invention, the surface of the film frame is treated by a plasma surface treatment machine to improve the bonding performance.

[0020] In an embodiment of the present invention, the fluorine-containing polymer coating glue includes polytetrafluoroethylene, polyvinylidene fluoride, fluorinated acrylate or any other polymer coating glue with a fluorine content higher than 20%.

[0021] The present invention also provides a method for manufacturing a crystalline thermoplastic polymer film frame, which is characterized by including:

[0022] Manufacturing the film frame with a crystalline thermoplastic polymer;

[0023] Treating its surface with a plasma surface treatment machine;

[0024] Removing oil stains, oxide layers, dust and impurities on the surface of the film frame to ensure the adhesion of the coating;

[0025] Preparing the fluorine-containing polymer coating glue;

[0026] Coating one to several layers of fluorine-containing polymer coating glue on the film frame;

[0027] Crosslinking the polymer resin into a film to improve hardness and chemical resistance;

[0028] Conducting detection and functional verification.

[0029] In an embodiment of the present invention, the coating of one to several layers of fluorine-containing polymer coating glue on the film frame includes:

[0030] Spraying method, evenly spraying the surface of the film frame through a spray gun, controlling the thickness of a single coating layer. If multiple layers need to be coated, each layer needs to be dried before coating the next layer;

[0031] Brushing method: Use a brush or roller to dip the coating material and evenly brush it on the surface of the membrane frame. Achieve multi-layer coating through multiple thin coatings.

[0032] Immersion method: Completely immerse the membrane frame in the coating tank, keep it for a certain time, slowly lift the membrane frame, control the dripping to avoid too thick coating, and dry it after draining.

[0033] In an embodiment of the present invention, the detection and function verification include:

[0034] Visually or microscopically observe the coating uniformity, without air bubbles, cracks or missed coating.

[0035] Use the cross-cut method to evaluate the adhesion between the coating and the membrane frame.

[0036] Detect the ammonium sulfate residue through IC testing.

[0037] The present invention has the following beneficial effects:

[0038] (1) Effectively block the release of ammonium sulfate. Replace the traditional aluminum frame with a crystalline thermoplastic polymer material, which has high mechanical strength, high temperature resistance, impact resistance, flame retardancy, acid and alkali resistance, hydrolysis resistance, wear resistance, fatigue resistance, radiation resistance and good electrical properties. Successfully avoid that the traditional aluminum frame contains sulfate radicals on the surface layer that cannot be removed cleanly because the production process includes anodic oxidation and its electrolyte contains sulfate radicals.

[0039] (2) Use a plasma surface treatment machine to perform surface treatment on the crystalline thermoplastic polymer membrane frame, which can effectively improve the bonding performance.

[0040] (3) Coating one to several layers of fluorine-containing polymer glue on the aluminum frame to form a physical barrier and structurally prevent the release of ammonium sulfate on the aluminum frame. This design specifically solves the root cause of the problem caused by the sulfate radical and ammonium radical residues in the protective frame film, providing a basic guarantee for the stable use of the photomask. Description of the Drawings

[0041] Figure 1 Shows the generation phenomenon diagram of the fog on the photomask in the prior art;

[0042] Figure 2 Shows the schematic structural diagram of the photomask with the crystalline thermoplastic polymer membrane frame structure in an embodiment of the present invention; and

[0043] Figure 3 Shows the manufacturing flow chart of the crystalline thermoplastic polymer membrane frame in an embodiment of the present invention. Detailed Embodiments

[0044] In the following description, the present invention is described with reference to various embodiments. However, those skilled in the art will recognize that the embodiments can be implemented without one or more specific details or in combination with other alternative and / or additional methods, materials, or components. In other cases, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring the inventive aspects of the present invention. Similarly, for purposes of explanation, specific quantities, materials, and configurations are set forth in order to provide a thorough understanding of the embodiments of the present invention. However, the present invention is not limited to these specific details.

[0045] In the present invention, the embodiments are merely intended to illustrate the solutions of the present invention and should not be construed as restrictive.

[0046] In this specification, the reference to "an embodiment" or "the embodiment" means that the specific features, structures, or characteristics described in connection with that embodiment are included in at least one embodiment of the present invention. The phrase "in an embodiment" that appears throughout this specification does not necessarily all refer to the same embodiment.

[0047] In addition, the numbering of the steps of the various methods of the present invention does not limit the execution order of the method steps. Unless otherwise specified, the method steps can be executed in a different order.

[0048] The present invention will be further described below in conjunction with the specific embodiments with reference to the accompanying drawings.

[0049] Figure 2 A schematic diagram of a photomask structure coated with a polymer compound in an embodiment of the present invention is shown.

[0050] As Figure 2 shown, in an embodiment of the present invention, the photomask coated with a polymer compound includes:

[0051] A transparent substrate 10, the transparent substrate including an intermediate region and an edge region surrounding the intermediate region. In this embodiment, quartz glass is used as the material of the transparent substrate 10, which has the following advantages:

[0052] High light transmittance: The light transmittance to 193 nm deep ultraviolet light needs to be > 90%, ensuring the effective transmission of exposure energy.

[0053] Low thermal expansion coefficient: Close to quartz glass (0.55×10 -6 / °C), avoiding pattern distortion caused by temperature changes.

[0054] Chemical stability: Resistant to corrosion by etching solutions (such as H2SO4, HF) and cleaning solvents.

[0055] Surface flatness: Nanometer-level precision (such as TTV < 50 nm), ensuring the uniformity of the circuit pattern.

[0056] The circuit pattern 20 is located in the middle area of the transparent substrate 10 and is a geometric pattern formed of light-blocking material, which is used to define the circuit structure of the semiconductor device. It is usually made of metal materials such as chromium (Cr) and molybdenum silicide (MoSi), and is deposited on the transparent substrate 10 through sputtering or evaporation processes.

[0057] The film frame 30 is made of crystalline thermoplastic polymer and adheres to the annular frame in the edge area of the transparent substrate 10. The annular frame surrounds the circuit pattern 20 to form a sealed space. One or more layers of fluoropolymer coating glue are applied on the film frame 30. The film frame is made of crystalline thermoplastic polymer, avoiding the problem that the surface of the traditional aluminum frame contains sulfate radicals that cannot be completely removed because the production process of the aluminum frame includes anodizing and the electrolyte contains sulfate radicals.

[0058] The protective film 40 covers the film frame and cooperates with the film frame to form a sealed space, preventing the surfaces of the middle area of the photomask frame 30 and the circuit pattern 20 from contacting the outside world.

[0059] The bonding adhesive layer 50 is used to fix the protective film 40 on the film frame 30 and fix the film frame 30 on the transparent substrate 10 to form a sealed space to protect the photomask circuit pattern 20. Its material needs to meet strict requirements such as high bonding strength, high temperature resistance, chemical corrosion resistance, and low volatility. Usually, acrylate glue, silicone glue, epoxy resin glue, or fluoropolymer glue is used.

[0060] In the prior art, the accumulation process of ammonium sulfate crystallization is specifically divided into four steps:

[0061] Oxidation of sulfide ions: The sulfate radicals remaining in the aluminum frame decompose into sulfide ions and are oxidized to sulfur dioxide under the irradiation of 193nm light.

[0062]

[0063] Generation of active oxygen: The energy of 193nm light decomposes oxygen molecules into active oxygen atoms, which further oxidize sulfur dioxide to sulfur trioxide.

[0064] SO2(adsorbed state)+O(gaseous state)→SO3(adsorbed state).

[0065] Formation of sulfuric acid: SO3 combines with water vapor in the air to form sulfuric acid.

[0066] SO3(adsorbed state)+H2O(gaseous state)→H2SO4(adsorbed state).

[0067] Crystallization of ammonium sulfate: Sulfuric acid reacts with ammonia (NH3) in the environment to form white ammonium sulfate crystals.

[0068] H2SO4 (adsorbed state) + 2NH3 (gaseous phase) → (NH4)2SO4 (crystalline).

[0069] In the present invention, a membrane frame is made of a crystalline thermoplastic polymer, avoiding the problem that the surface layer of a traditional aluminum frame contains sulfate radicals that cannot be completely removed because the manufacturing process of the aluminum frame includes anodic oxidation and its electrolyte contains sulfate radicals.

[0070] As Figure 3 shown, the manufacturing process of the crystalline thermoplastic polymer membrane frame is as follows:

[0071] Membrane frame manufacturing 100: A membrane frame is made of a crystalline thermoplastic polymer.

[0072] Surface roughening 200: The surface of the membrane frame is treated with a plasma surface treatment machine gun head flame to improve the bonding performance.

[0073] Membrane frame pretreatment 300:

[0074] Surface cleaning: Remove impurities such as oil stains, oxide layers, and dust on the surface of the membrane frame to ensure the adhesion of the coating. The operation process is as follows:

[0075] Use an alkaline solution (such as NaOH) or an organic solvent (such as acetone) for ultrasonic cleaning to remove grease;

[0076] Rinse with deionized water and dry.

[0077] Preparation of fluorine-containing polymer coating 400: Fluorine-containing polymers are usually polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), fluorinated acrylic polyester, or any other polymer coating with a fluorine content higher than 20%. Selection should be based on heat resistance, adhesion, cost, etc. For example: PTFE is heat-resistant (up to 260 °C), but requires high-temperature sintering. PVDF has good chemical resistance and can be cured at room temperature. The specific process is as follows:

[0078] Dissolve the fluorine-containing polymer resin in a solvent (such as NMP, DMF) to prepare a solution with a concentration above 20%. If powder coatings are used, electrostatic spraying or fluidized bed dipping is required.

[0079] Membrane frame coating 500:

[0080] Spraying method, suitable for complex shapes, is carried out by an air spray gun or an electrostatic spray gun. The process is as follows:

[0081] Adjust the spray gun pressure (such as 0.3 - 0.5 MPa) and the coating flow rate;

[0082] Uniformly spray the surface of the membrane frame, controlling the single-layer coating thickness (usually 5 - 20 μm);

[0083] If multiple layers of coating are required, each layer needs to be dried before applying the next layer.

[0084] The brushing method is applicable to membrane frames with small sizes or complex shapes, and the process is as follows:

[0085] Dip a brush or roller into the coating material and evenly brush it on the surface of the membrane frame;

[0086] Achieve multi-layer coating through multiple thin coatings.

[0087] The immersion method is applicable to batch processing or membrane frames that require a uniform coating, and the process is as follows:

[0088] Completely immerse the membrane frame in the coating tank and keep it for a certain period of time (such as 1 - 5 minutes);

[0089] Slowly lift the membrane frame and control the dripping to avoid excessive coating thickness;

[0090] Drain and then dry.

[0091] Curing treatment 600: Place the coated membrane frame in an oven or curing furnace, process it according to the set temperature and time, and take it out after cooling to room temperature.

[0092] Its purpose is to crosslink the polymer resin into a film and improve hardness and chemical resistance. The temperature can be selected according to the material (for example, PVDF can be cured at room temperature, and PTFE needs to be sintered at 375 °C). The time consumption is usually 30 minutes to 2 hours.

[0093] Post-treatment and testing 700:

[0094] Surface inspection: Visually or microscopically observe the uniformity of the coating, and there are no bubbles, cracks or missed coatings.

[0095] Adhesion test: Use the cross-cut method (ASTM D3359) to evaluate the bonding force between the coating and the membrane frame.

[0096] Function verification: Detect the ammonium sulfate residue according to the IC test method to ensure no detection or < 10 ppb.

[0097] In an embodiment of the present invention, there are three cases for the protective film 40 formed by the fluorine-containing polymer coating covering the membrane frame 30:

[0098] Full four-sided coating: All outer surfaces of the membrane frame 30 (including the four sides of top, bottom, left and right) need to be coated with glue.

[0099] Two-sided coating on the inner and outer sides: Only coat the inner and outer sides of the membrane frame 30, avoiding the upper and lower sides (if there is a need for tape sticking).

[0100] Single-sided coating on the outer side: Only coat the outer side of the membrane frame 30, avoiding the other three sides.

[0101] Although the embodiments of the present invention have been described above, it should be understood that they are presented by way of example only and not as a limitation. It will be apparent to those skilled in the relevant art that various combinations, modifications, and changes can be made thereto without departing from the spirit and scope of the present invention. Therefore, the breadth and scope of the present invention disclosed herein should not be limited by the above-described exemplary embodiments, but should be defined only in accordance with the appended claims and their equivalents.

Claims

1. A photomask having a crystalline thermoplastic polymer film frame structure, characterized in that: include: A transparent substrate, the transparent substrate comprising a middle region and an edge region surrounding the middle region; A circuit pattern, located in the middle area of ​​the transparent substrate, is a geometric pattern formed by an opaque material and is used to define the circuit structure of the semiconductor device; A film frame, wherein the film frame is made of a crystalline thermoplastic polymer material and is adhered to an annular frame at the edge area of ​​the transparent substrate, the annular frame surrounds the circuit pattern to form a closed space, and the film frame is coated with one or more layers of fluorine-containing polymer glue to block the release of sulfate and ammonium; as well as A protective film covers the film frame and forms a closed space with the film frame to isolate the circuit pattern from the external environment.

2. The photomask of the crystalline thermoplastic polymer film frame structure according to claim 1, characterized in that: It also includes a bonding adhesive layer, which is used to fix the film frame on the transparent substrate and to fix the protective film on the film frame.

3. The photomask of the crystalline thermoplastic polymer film frame structure according to claim 1, characterized in that: The fluorine-containing polymer coating is: Fully covered on all four sides, with fluorine-containing polymer glue applied to all outer surfaces of the film frame; or Coating on both the inside and outside, with fluorine-containing polymer glue applied to the inside and outside of the film frame, avoiding the upper and lower sides; or The outer side is coated on one side, and the fluorine-containing polymer glue is applied to the outer side of the membrane frame, avoiding the other three sides.

4. The photomask of the crystalline thermoplastic polymer film frame structure according to claim 1, characterized in that: The film frame is surface treated by a plasma surface treatment machine to improve the bonding performance.

5. The photomask of the crystalline thermoplastic polymer film frame structure according to claim 1, characterized in that: The fluorine-containing polymer coating includes polytetrafluoroethylene, polyvinylidene fluoride, fluorine-containing acrylate or any other polymer coating containing a fluorine content higher than 20%.

6. A method for manufacturing a crystalline thermoplastic polymer film frame, characterized in that: include: The film frame is made of crystalline thermoplastic polymer; Use a plasma surface treatment machine to treat its surface; Remove oil, oxide layer, dust and impurities on the surface of the membrane frame to ensure the adhesion of the coating; Preparation of fluorine-containing polymer coating; Coating the film frame with one or several layers of fluorine-containing polymer glue; Cross-link polymer resin to form film, improve hardness and chemical resistance; Perform testing and functional verification.

7. The method for manufacturing a crystalline thermoplastic polymer film frame according to claim 6, characterized in that: The step of coating the film frame with one or more layers of fluorine-containing polymer adhesive comprises: Spraying method: spray the film frame surface evenly with a spray gun to control the thickness of a single coating. If multiple layers of coating are required, each layer must be dried before applying the next layer; Brushing method: use a brush or roller to dip the paint and evenly apply it on the surface of the film frame, and achieve multi-layer coating through multiple thin coatings; Immersion method: immerse the film frame completely in the coating tank, keep it for a certain period of time, slowly lift the film frame, control dripping to avoid excessive coating, drain and dry.

8. The method for manufacturing a crystalline thermoplastic polymer film frame according to claim 6, characterized in that: The detection and functional verification include: Observe the uniformity of the coating visually or under a microscope, and check for bubbles, cracks or missing coating; Use the cross-hatch method to evaluate the bonding strength between the coating and the film frame; Ammonium sulfate residue was detected by IC test.

Images