High-molecular compound coated photomask

Abstract

The invention provides a high-molecular compound coated photomask 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 adhered to 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 coating glue 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 fluorine-containing high polymer material is coated on the surface of the membrane frame, so that release of sulfate radicals and ammonium radicals is effectively blocked, and generation of mist is inhibited.

Description

Technical Field

[0001] The invention relates to the field of semiconductor mask materials, and in particular to a photomask coated with a polymer compound. 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 have sulfate (SO 4 2- ) and ammonium (NH 4 + ) 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 anodic oxidation process, and the electrolyte used contains H 2 SO 4 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 such 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 fog-like substances.

[0007] From the perspective of the prior art, the aluminum frame plays a crucial role in supporting and protecting 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, traditional coatings are prone to peeling or decomposition in high-temperature environments and cannot continuously provide effective protection for the aluminum frame. On the other hand, during the coating application process, it is also necessary to avoid having an adverse impact on the adhesion between the aluminum frame and the protective film, otherwise it will lead to a decrease in the stability of the protection 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 problems such as high cost and low production efficiency, which undoubtedly increase the production cost of enterprises and reduce the production efficiency, and are 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 in order to improve the overall level and economic benefits of semiconductor manufacturing. Summary of the Invention

[0009] The present invention provides a photomask coated with a high molecular compound, which is characterized by including:

[0010] A transparent substrate, the transparent substrate including an intermediate region and an edge region surrounding the intermediate region;

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

[0012] A film frame, an annular frame adhered to the edge region of the transparent substrate, the annular frame surrounding the circuit pattern to form an enclosed space, and one or more fluorine-containing polymer coatings are applied on the film frame to block the release of sulfate radicals and ammonium radicals;

[0013] A protective film, covering the film frame and forming an enclosed space with the film frame, 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 film frame is made of aluminum.

[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 photomask frame coated with a polymer compound, which is characterized by including:

[0022] Removing oil stains, oxide layers, dust and impurities on the surface of the film frame to ensure the adhesion of the coating;

[0023] Preparing the fluorine-containing polymer coating glue;

[0024] Coating one to several layers of fluorine-containing polymer coating glue on the film frame;

[0025] Crosslinking the polymer resin into a film to improve hardness and chemical resistance;

[0026] Performing detection and functional verification.

[0027] 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:

[0028] Spraying method: Uniformly spray the surface of the film frame through a spray gun, control 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;

[0029] Brushing method: Dip a brush or roller into the coating material and uniformly brush it on the surface of the film frame, and achieve multiple-layer coating through multiple thin coatings;

[0030] Immersion method: Completely immerse the film frame in the coating tank, keep it for a certain time, slowly lift the film frame, control the dripping to avoid too thick a coating layer, and drain and dry it.

[0031] In an embodiment of the present invention, the detection and functional verification include:

[0032] Visually or microscopically observe the coating uniformity, without bubbles, cracks or uncoated areas;

[0033] Use the cross - cut method to evaluate the adhesion between the coating and the film frame;

[0034] Detect the ammonium sulfate residue through IC testing.

[0035] The present invention focuses on the field of semiconductor mask plate materials, aiming to solve the problem of sulfate and ammonium ion release from the protective frame film of high - end photomasks. By coating a fluorine - containing polymer glue on the aluminum frame, it shows significant advantages in terms of structure and function, effectively improving the performance and reliability of the photomask. It has the following beneficial effects:

[0036] (1) Effectively block the release of ammonium sulfate: Coating one to several layers of fluorine - containing polymer glue on the aluminum frame forms a physical barrier, structurally preventing the release of ammonium sulfate from the aluminum frame. This design specifically addresses the root cause of the problems caused by sulfate and ammonium residue in the protective frame film, providing a basic guarantee for the stable use of the photomask. Experiments have shown that this solution can lock the aluminum frame release substances in the glue. For an aluminum frame with an ammonium sulfate content exceeding 200 ppb in the original IC test (ammonium ion detection), after being coated with fluorine - containing polymer glue, the ammonium sulfate can reach an undetected level. This achievement greatly reduces problems such as the accumulation of foggy substances and short - circuit of circuits in the photomask caused by ammonium sulfate residue, significantly improving the yield rate of chips.

[0037] (2) Flexible coating methods: Provide various coating methods such as spraying, brushing, and soaking, which can be flexibly selected according to the shape, size of the aluminum frame and actual production requirements. The processing temperature range from room temperature to 400 degrees Celsius adapts to the requirements of different materials and production environments. Different coating surface designs, such as full - coverage on all four sides, two - side coating on the inner and outer sides, and single - side coating on the outer side, meet diverse application scenarios, ensuring both the protection effect and compatibility with other components. This solution has 3 usage states, and different coating methods correspond to different ammonium sulfate release levels. The full - coverage on all four sides has the best coating property, with ammonium sulfate release being undetected or < 2 ppb; for the two - side coating on the inner and outer sides, considering that there are other bonding glues on the upper and lower sides and avoiding coating them, the ammonium sulfate release is undetected or < 5 ppb; for the single - side coating on the outer side, considering that there are other bonding glues on the upper, inner and lower three sides and avoiding coating them, the ammonium sulfate release is undetected or < 10 ppb. This characteristic enables the product to operate stably under different working conditions and environments, improving the applicability and reliability of the photomask. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Shows the phenomenon diagram of fog formation in the photomask in the prior art;

[0039] Figure 2 shows a schematic diagram of a photomask structure coated with a polymer compound in an embodiment of the present invention; and

[0040] Figure 3 shows a flowchart for manufacturing a photomask frame coated with a polymer compound in an embodiment of the present invention.

[0041] Specific implementation details

[0042] In the following description, the present invention is described with reference to the 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 points of the present invention. Similarly, for purposes of explanation, specific quantities, materials, and configurations are set forth to provide a thorough understanding of the embodiments of the present invention. However, the present invention is not limited to these specific details.

[0043] In the present invention, each embodiment is merely intended to illustrate the solution of the present invention and should not be construed as restrictive.

[0044] In this specification, the reference to "an embodiment" or "the embodiment" means that the specific features, structures, or characteristics described in connection with the embodiment are included in at least one embodiment of the present invention. The phrase "in an embodiment" appearing throughout this specification does not necessarily refer to the same embodiment.

[0045] In addition, the numbering of the steps of the 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.

[0046] The present invention will be further described below in conjunction with the specific implementation manners with reference to the accompanying drawings.

[0047] Figure 2 shows a schematic diagram of a photomask structure coated with a polymer compound in an embodiment of the present invention.

[0048] As Figure 2 shown, a photomask coated with a polymer compound in an embodiment of the present invention includes:

[0049] 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:

[0050] High light transmittance: The light transmittance to 193 nm deep ultraviolet light needs to be >90%, ensuring effective transmission of the exposure energy.

[0051] Low coefficient of thermal expansion: close to fused silica (0.55×10 -6 / °C), avoiding pattern distortion caused by temperature changes.

[0052] Chemical stability: resistant to etching solutions (such as H 2 SO 4 、HF) and cleaning solvents.

[0053] Surface flatness: nanometer-level precision (such as TTV < 50 nm), ensuring the uniformity of the circuit pattern.

[0054] The circuit pattern 20 is located in the middle area of the transparent substrate 10 and is a geometric pattern formed by an opaque material, 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.

[0055] The film frame 30 is an annular frame adhered to the edge area of the transparent substrate 10, and the annular frame surrounds the circuit pattern 20 to form a sealed space. A layer or multiple layers of fluorine-containing polymer photoresist are coated on the film frame 30 to block the release of sulfate and ammonium ions.

[0056] The protective film 40 covers the film frame and forms a sealed space with the film frame to prevent the surfaces of the middle area of the photomask frame 30 and the circuit pattern 20 from coming into contact with the outside world.

[0057] 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 circuit pattern 20 of the photomask. Its material needs to meet strict requirements such as high bonding strength, high temperature resistance, chemical corrosion resistance, and low volatility. Usually, acrylate adhesives, silicone adhesives, epoxy resin adhesives, or fluoropolymer adhesives are used.

[0058] In the prior art, the accumulation process of ammonium sulfate crystallization is specifically divided into four steps:

[0059] Oxidation of sulfide ions: The sulfate residue in the aluminum frame or protective film decomposes into sulfide ions and is oxidized to sulfur dioxide under the irradiation of 193 nm light.

[0060]

[0061] Generation of reactive oxygen species: The energy of 193 nm light decomposes oxygen molecules into reactive oxygen atoms, which further oxidize sulfur dioxide to sulfur trioxide.

[0062] SO 2 (adsorbed state) + O (gaseous state) → SO 3 (adsorbed state).

[0063] Formation of sulfuric acid: SO3 Combines with water vapor in the air to form sulfuric acid.

[0064] SO 3 (adsorbed state) + H 2 O (gaseous phase) → H 2 SO 4 (adsorbed state).

[0065] Ammonium sulfate crystallization: Sulfuric acid reacts with ammonia (NH 3 ) in the environment to form white ammonium sulfate crystals.

[0066] H 2 SO 4 (adsorbed state) + 2NH 3 (gaseous phase) → (NH 4 ) 2 SO 4 (crystals).

[0067] In the present invention, by coating the surface of the aluminum frame with a fluorine-containing polymer material, the release of sulfate and ammonium ions can be effectively blocked, thereby inhibiting the occurrence of the above reactions.

[0068] Figure 3 Shows the manufacturing flow chart of a photomask frame coated with a polymer compound in an embodiment of the present invention.

[0069] As Figure 3 shown, the manufacturing process of the photomask frame coated with a polymer compound is as follows:

[0070] Film frame pretreatment 100:

[0071] Surface cleaning: Remove impurities such as oil stains, oxide layers, and dust on the surface of the aluminum frame to ensure the adhesion of the coating. The operation process is as follows:

[0072] Use an alkaline solution (such as NaOH) or an organic solvent (such as acetone) for ultrasonic cleaning to remove grease;

[0073] Rinse with deionized water and dry.

[0074] In an embodiment of the present invention, this step further includes surface roughening: increasing the surface roughness of the aluminum frame to improve the mechanical bonding force of the coating. The operation process is as follows:

[0075] Chemical etching (such as H 2 SO 4 + HNO 3 mixed solution) or sandblasting;

[0076] Clean and dry again.

[0077] Preparation of Fluorine-containing Polymer Coating 200: Fluorine-containing polymers are usually polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), fluorinated acrylate polymers, 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] Coating of Membrane Frame 300:

[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] Spray the surface of the aluminum frame evenly, 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] Brushing method, suitable for small-sized or complex-shaped membrane frames. The process is as follows:

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

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

[0087] Immersion method, suitable for batch processing or membrane frames that require a uniform coating. The process is as follows:

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

[0089] Slowly lift the aluminum frame, controlling the dripping to avoid excessive coating thickness;

[0090] Drain and then dry.

[0091] Curing Treatment 400: Put the coated membrane frame into an oven or a curing furnace, process it according to the set temperature and time, and take it out after cooling to room temperature.

[0092] The purpose is to crosslink the polymer resin into a film, improving hardness and chemical resistance. The temperature can be selected according to the material (such as PVDF can be cured at room temperature, and PTFE requires sintering at 375°C). The time-consuming is usually 30 minutes to 2 hours.

[0093] Post-treatment and Testing 500:

[0094] Surface inspection, visually or microscopically observe the coating uniformity, without bubbles, cracks or missed coating.

[0095] Adhesion test, use the cross - hatch method (ASTM D3359) to evaluate the adhesion of the coating to the film 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 where the protective film 40 formed by the fluorine - containing polymer coating covers the film frame 30:

[0098] Full coverage on all four sides: Glue needs to be applied to all outer surfaces of the film frame 30 (including the four sides of up, down, left and right).

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

[0100] Single - side coverage on the outer side: Only coat the outer side of the film 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 only as examples and not as limitations. It is obvious to those skilled in the relevant art that various combinations, deformations and changes can be made without departing from the spirit and scope of the present invention. Therefore, the width and scope of the present invention disclosed herein should not be limited by the above - disclosed exemplary embodiments, but should be defined only by the appended claims and their equivalents.

Claims

1. A photomask coated with a polymer compound, 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, an annular frame 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 polymer glue are coated on the film frame 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 polymer compound-coated photomask 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 polymer compound-coated photomask 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 polymer compound-coated photomask frame according to claim 1, wherein: The film frame is made of aluminum.

5. The polymer compound-coated photomask according to claim 1, wherein: 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 photomask frame coated with a polymer compound, characterized in that: include: 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 photomask frame coated with a polymer compound 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 photomask frame coated with a polymer compound 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