Phase shift mask for preventing light leakage and application method thereof
By introducing a light leakage protection area into the phase displacement mask, the light leakage problem of the peripheral cutting path edge during the secondary exposure of the phase displacement mask is solved, which improves pattern accuracy and resolution, reduces defect rate, extends the service life of the mask plate, and reduces production costs.
Patent Information
- Application Number
- CN202410242495.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-04
- Publication Date
- 2025-09-05
AI Technical Summary
During the secondary exposure process, the existing phase displacement mask has light leakage at the edge of the peripheral cutting path, resulting in photoresistance remaining and affecting the yield of wafer products.
A light leakage protection area is introduced into the phase displacement mask. A chrome ring protection area is provided on the outer layer of the scribed track area and overlapping the light leakage protection area on adjacent mask plates to compensate for deviations and avoid light leakage.
Improve pattern accuracy and resolution, reduce defect rate, extend the service life of the mask plate, improve production efficiency and reduce production costs.
Smart Images
Figure CN120595530A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of phase shift mask production, in particular to a phase shift mask capable of preventing light leakage. Background Art
[0002] The semiconductor integrated circuit manufacturing process typically requires multiple photolithography steps, such as creating various doping windows and electrode contact holes in the dielectric layer of the semiconductor substrate or etching metal interconnect patterns in the conductive layer. The rapid development of large-scale integrated circuit technology has placed extremely high demands on the quality of photomasks, including various aspects such as mask accuracy, defect density, and durability.
[0003] As the size of semiconductor components continues to shrink, improving the resolution of photolithography processes has become a key issue. In many current resolution enhancement techniques (RIE), phase-shift masks (PSMs) have been one of the key tools used to improve resolution. Phase-shift masks selectively add a phase-shift layer to the pattern itself, eliminating interference effects through destructive interference, thereby significantly improving the resolution of pattern boundaries. However, in actual manufacturing processes, light leakage at the edges of the peripheral cutting paths during the secondary exposure process can cause residual photoresist. This results in a yield loss at the exposed edges of some wafer products compared to the center, significantly impacting the finished product yield of the wafer products.
[0004] Therefore, there is a need in the prior art for improving a phase shift mask that prevents light leakage. Summary of the Invention
[0005] In view of this, the purpose of the embodiments of the present invention is to propose a phase-shift mask for preventing light leakage and its application method. The improved phase-shift photomask designed by the present invention solves the light leakage phenomenon at the edge of the peripheral cutting path during exposure and avoids photoresist residue.
[0006] Based on the above-mentioned purpose, on the one hand, the present invention provides a phase-shift mask for preventing light leakage, the mask including multiple main graphic areas, scribing road areas and light leakage protection areas, each main graphic area including a white area and a pattern area, the scribing road areas including a transparent substrate, a partially transparent layer and an opaque blocking layer from bottom to top, and the light leakage protection area is arranged on the outer layer of the outermost cutting road of the scribing road area to form light leakage protection for the mask.
[0007] In some embodiments, the light leakage protection zone is a chrome ring protection zone.
[0008] In some embodiments, the width of the light leakage protection area is greater than 1 μm.
[0009] In some embodiments, the white region is a quartz glass layer.
[0010] In some embodiments, the partially light-transmitting layer is a molybdenum silicide layer.
[0011] In some embodiments, the light transmittance of the molybdenum silicide layer is 6%.
[0012] In some embodiments, the pattern area is sequentially formed from bottom to top by the quartz glass layer and the molybdenum silicide layer.
[0013] In some embodiments, the light-impermeable layer includes chromium and / or chromium oxide.
[0014] On the other hand, the present invention also provides an application method of a phase shift mask for preventing light leakage, which comprises preparing a wafer and coating it with photoresist, aligning the main graphic areas of multiple phase shift masks with the effective chip area of the wafer, and overlapping the light leakage protection areas of adjacent phase shift masks.
[0015] In some embodiments, the overlapping range of the light leakage protection area is not less than 1 μm.
[0016] The present invention has at least the following beneficial technical effects:
[0017] During the photolithography process, the peripheral cutting paths will overlap and be exposed. When the exposure energy is greater than a certain level, light leakage will occur at the deviation position of the peripheral cutting paths, resulting in residual photoresist. The present invention improves the design of the phase-shift mask by introducing a light leakage protection zone, expanding the protection range of the outer layer of the original peripheral cutting paths, and overlapping the light leakage protection zones of adjacent mask plates to compensate for the original deviation problem. During exposure, light leakage will not occur at the edge of the peripheral cutting paths, and no photoresist will remain, thereby improving pattern accuracy, enhancing resolution, reducing defect rate, improving production efficiency, and extending the service life of the mask, etc., and helping to improve the overall quality and efficiency of semiconductor manufacturing and reduce production costs. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying any creative work.
[0019] Figure 1 is a schematic diagram of an embodiment of a phase-shift photomask in the prior art;
[0020] Figure 2 A schematic diagram of an embodiment of a phase-shift mask for preventing light leakage provided by the present invention;
[0021] Figure 3 A flow chart of the phase shift mask preparation process provided by the present invention;
[0022] Figure 4 A schematic diagram of the phase-shift mask for preventing light leakage provided by the present invention during application.
[0023] Description of reference numerals:
[0024] 10. Main graphics area; 20. Scribing lane area; 30. Light leakage protection area DETAILED DESCRIPTION
[0025] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.
[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which the present invention pertains; the terms used in the specification herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention; for example, the directions or positions indicated by the terms "length", "width", "up", "down", "left", "right", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the directions or positions shown in the accompanying drawings and are for ease of description only and should not be construed as limiting the present technical solution.
[0027] The terms "including," "having," and any variations thereof in the present specification, claims, and accompanying drawings are intended to cover non-exclusive inclusions. The terms "first," "second," and the like in the present specification, claims, and accompanying drawings are used to distinguish between different items, not to describe a particular order. "Multiple" means two or more, unless otherwise expressly specified.
[0028] In the specification and claims of the present invention and the above-mentioned description of the drawings, when an element is referred to as being “fixed to,” “mounted on,” “disposed on,” or “connected to” another element, it may be directly or indirectly located on the other element. For example, when an element is referred to as being “connected to” another element, it may be directly or indirectly connected to the other element.
[0029] Furthermore, references herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute a separate or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.
[0030] As semiconductor device dimensions continue to shrink, improving the resolution of photolithography processes has become a critical issue. Phase-shift masks (PSMs) have long been a key tool for improving resolution in many current resolution enhancement (RIE) techniques. Generally, when the exposure light passes through a traditional mask, the phase of the light source is not shifted. Consequently, some light rays constructively interfere when they reach the wafer surface. This causes areas on the wafer surface that should not be exposed to light due to interference, resulting in a decrease in pattern resolution. A phase-shift mask selectively adds a phase-shifting layer to the pattern itself. When the exposure light passes through the phase-shifting layer of the phase-shift mask, the phase of the light's electric field is shifted by a predetermined angle. This creates a phase difference between the phase of the shifted light source and the previously incident light source, causing destructive interference when the light reaches the wafer surface. This destructive interference cancels out the interference effect, significantly improving the resolution of pattern boundaries.
[0031] like Figure 1 The phase-shift photomask in the prior art is shown to include a main pattern area and a photomask frame area. Due to the chip factory machine's need to calibrate the alignment marks on the photomask frame, the photomask frame area is required to retain an opaque barrier layer (Test-key) on a portion of the transparent layer. In some embodiments, the main pattern area only needs to retain a portion of the transparent layer. During the second exposure, there is a deviation in the opaque barrier layer in the frame area between the two exposure areas, resulting in light leakage problems at the deviation, thereby causing photoresist residue.
[0032] Therefore, in view of the problems in the prior art, the present invention improves the design of the mask to solve the problem of uneven illumination of light at the edge of the cutting path, thereby causing light leakage. The present invention provides a phase shift mask that prevents light leakage, such as Figure 2 As shown, the mask includes multiple main graphic areas 10, scribing street areas 20 and light leakage protection areas 30. Each main graphic area includes a white area and a pattern area. The scribing street areas 20 include a transparent substrate, a partially transparent layer and an opaque blocking layer from bottom to top. The light leakage protection area is arranged on the outer layer of the outermost cutting street of the scribing street area 20 to form light leakage protection for the mask.
[0033] Among them, the main function of the scribe lane area 20 is, on the one hand, to be used for segmentation, dividing the entire mask into multiple independent small pieces or chips, so as to facilitate the subsequent wafer processing process. During the wafer manufacturing process, each chip will be individually aligned and exposed to the wafer to form the required circuit pattern. The scribe lane area provides a physical boundary so that each chip can be accurately cut and separated; on the other hand, it is used for positioning, and the scribe lane area is also used for positioning and alignment during the wafer manufacturing process. The scribe lane area on the mask corresponds to the alignment mark on the wafer, and these marks can ensure that the pattern on the mask is accurately aligned with the specific position on the wafer. This is crucial to ensure the accurate replication of the circuit pattern.
[0034] Furthermore, the light leakage protection zone 30 is a chrome ring protection zone. In some embodiments, the width of the light leakage protection zone is greater than 1 μm. During exposure, the peripheral cutting paths will overlap, and due to the precision of the second writing machine, there will typically be a deviation of approximately 0.3 μm. When the exposure energy exceeds a certain level, light leakage will occur at the deviation position, resulting in photoresist residue and yield loss. In actual processes, it has been found that the photoresist residue caused by light leakage generally only occurs when the exposure energy is greater than 53.5 mJ. Therefore, the present invention provides a light leakage protection zone made of chrome material on the outermost layer of the mask.
[0035] Furthermore, the white area is a quartz glass layer, that is, the entire transparent substrate portion of the mask.
[0036] Furthermore, the pattern area is composed of a quartz glass layer and a molybdenum silicide layer from bottom to top.
[0037] Furthermore, a portion of the light-transmitting layer is a molybdenum silicide layer. In some embodiments, the light transmittance of the molybdenum silicide layer is 6%. Molybdenum silicide has a high refractive index, thermal stability, and good light transmittance. Its high refractive index enables it to produce the desired phase delay in the phase-shift mask. By precisely controlling the thickness of the molybdenum silicide layer, different levels of phase shift can be achieved, thereby improving pattern resolution and contrast. The good light transmittance effectively transmits the exposure light source, ensuring pattern accuracy.
[0038] Furthermore, the light-impermeable layer includes chromium and / or chromium oxide.
[0039] Further, for the structure formation of the mask, please refer to Figure 3From bottom to top, it includes: QZ (transparent substrate), MoSiON (partially light-transmitting layer), Cr / CrOx (opaque blocking layer), and photoresist. After two exposures and development processes, a mask with a specific pattern is formed, on which a light leakage protection zone is formed. Primary and secondary exposures are key steps in the production of phase-shift masks. In primary exposure, the photoresist is exposed primarily through the pattern on the mask, causing a chemical reaction that changes its optical properties. Secondary exposure, based on the primary exposure, further adjusts the optical properties of the photoresist to meet the requirements of a phase-shift mask.
[0040] The purpose of both primary and secondary exposure is to remove unwanted portions of the photoresist, thereby obtaining the desired pattern. Specifically, primary exposure primarily exposes the photoresist to the pattern on the mask, causing a chemical reaction in the exposed portions, rendering them soluble or insoluble. During the development process, these exposed portions are removed, resulting in a pattern corresponding to the mask pattern. Secondary exposure, on the other hand, involves re-exposing the photoresist based on the primary exposure to further adjust its optical properties, such as its refractive index. This secondary exposure and development process results in a mask pattern with the desired phase shift.
[0041] On the other hand, the present invention also provides an application method of a phase shift mask for preventing light leakage, which comprises preparing a wafer and coating it with photoresist, aligning the main graphic areas of multiple phase shift masks with the effective chip area of the wafer, and overlapping the light leakage protection areas of adjacent phase shift masks.
[0042] Furthermore, the overlapping range of the light leakage protection zone is not less than 1 μm.
[0043] like Figure 4 The figure shows a schematic diagram of a phase-shift mask for preventing light leakage during application, in which the wafer surface is divided into a grid of several rectangular areas of equal size according to the exposure area. Shot A and shot B are both separate exposure areas of a mask. In some embodiments, a mask may contain multiple shots, each shot corresponding to a specific position on the wafer. In the embodiment of the present invention, a mask including one shot is used as an example. The effective chip area (effective die) refers to the area on the wafer that is cut and packaged into independent chips. Each effective chip area is defined by an exposure area (shot). Since the improved phase-shift mask for preventing light leakage of the present invention is provided with a light leakage protection area, the light leakage protection areas of adjacent masks partially overlap during application, thereby avoiding light leakage problems.
[0044] Furthermore, the specific application method of the mask provided by the present invention includes the following steps:
[0045] Wafer preparation: First, the wafer to be processed needs to be prepared. The wafer surface needs to be cleaned to remove impurities and contaminants to ensure the quality of subsequent processing.
[0046] Photoresist coating: A layer of photoresist is applied to the wafer surface. Photoresist is a light-sensitive material that undergoes a chemical reaction during exposure to form the desired pattern.
[0047] Soft bake: After applying the photoresist, a soft bake is required. The purpose of soft bake is to make the photoresist more evenly distributed on the wafer surface, remove the solvent, and improve the adhesion and stability of the photoresist.
[0048] Alignment and Exposure: The phase-shift mask is placed in the exposure machine, and the wafer is aligned onto the mask. The light leakage protection areas of adjacent phase-shift masks overlap, ensuring that the overlap is no less than 1μm. The wafer is then exposed by the exposure machine. During the exposure process, the pattern on the phase-shift mask is transferred to the photoresist on the wafer, forming the desired pattern.
[0049] Development: After exposure, development is required. The purpose of development is to remove the chemically reacted portions of the photoresist after exposure, thereby obtaining a pattern corresponding to the phase-shift mask pattern.
[0050] Hard bake: After development is complete, hard bake is required. The purpose of hard bake is to make the photoresist adhere more firmly to the wafer surface and improve the stability and durability of the pattern.
[0051] The present invention improves the design of the phase-shift mask by introducing a light leakage protection zone, expanding the protection range of the outer layer of the original peripheral cutting path, and overlapping the light leakage protection zones of adjacent mask plates to compensate for the original deviation problem. During exposure, no light leakage will occur at the edge of the peripheral cutting path, and no photoresist will remain, thereby improving pattern accuracy, enhancing resolution, reducing defect rate, improving production efficiency, and extending the service life of the mask, etc., and helping to improve the overall quality and efficiency of semiconductor manufacturing and reduce production costs.
[0052] The above are exemplary embodiments disclosed in the present invention, but it should be noted that various changes and modifications may be made without departing from the scope of the embodiments disclosed in the claims. The functions, steps and / or actions of the method claims according to the disclosed embodiments described herein do not need to be performed in any particular order. In addition, although the elements disclosed in the embodiments of the present invention may be described or required in individual form, they may also be understood as multiple unless expressly limited to the singular.
[0053] It should be understood that, as used herein, the singular forms "a" and "an" are intended to include the plural forms as well, unless the context clearly supports an exception. It should also be understood that, as used herein, "and / or" is intended to include any and all possible combinations of one or more of the associated listed items.
[0054] The serial numbers of the embodiments disclosed in the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.
[0055] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples. Within the spirit of the embodiments of the present invention, the technical features of the above embodiments or different embodiments may be combined, and there are many other variations of different aspects of the above embodiments of the present invention, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the scope of protection of the embodiments of the present invention.
Claims
1. A phase shift mask for preventing light leakage, characterized in that: The mask includes multiple main graphic areas, scribing lane areas and light leakage protection areas. Each of the main graphic areas includes a white area and a pattern area. The scribing lane areas include a transparent substrate, a partially transparent layer and an opaque blocking layer from bottom to top. The light leakage protection area is arranged on the outer layer of the outermost cutting lane of the scribing lane area to form light leakage protection for the mask.
2. The phase shift mask for preventing light leakage according to claim 1, wherein: The light leakage protection zone is a chrome ring protection zone.
3. The phase shift mask for preventing light leakage according to claim 2, wherein: The width of the light leakage protection zone is greater than 1 μm.
4. The phase shift mask for preventing light leakage according to claim 1, wherein: The white area is a quartz glass layer.
5. The phase shift mask for preventing light leakage according to claim 1, wherein: The partially light-transmitting layer is a molybdenum silicide layer.
6. The phase shift mask for preventing light leakage according to claim 5, wherein: The light transmittance of the molybdenum silicide layer is 6%.
7. The phase shift mask for preventing light leakage according to claim 1, wherein: The pattern area is composed of a quartz glass area and a molybdenum silicide layer from bottom to top.
8. The phase shift mask for preventing light leakage according to claim 1, wherein: The light-impermeable layer includes chromium and / or chromium oxide.
9. A method for applying a phase shift mask to prevent light leakage, characterized in that: A wafer is prepared and coated with photoresist, and main pattern areas of a plurality of phase-shift masks are aligned with the effective chip area of the wafer, with light leakage protection areas of adjacent phase-shift masks overlapping.
10. The method for applying a phase shift mask for preventing light leakage according to claim 9, wherein: The overlapping range of the light leakage protection zone is not less than 1 μm.