Mask calibration mark double exposure process method

Abstract

The present invention discloses a calibration mark double exposure process method for a mask, the method comprising: after setting a photoresist layer, using a standard exposure dose and a single exposure mask pattern to expose the entire mask substrate as a whole; using a preset exposure dose and a double exposure mask pattern to partially expose the mask substrate, the double exposure mask pattern only includes the calibration mark area. As the photoresist at the edge of the mask substrate is thick, the standard dose mode (DOSE) cannot expose thoroughly. After the first conventional exposure, only the calibration mark area with thick photoresist is partially exposed using a specific exposure dose. Finally, all the calibration mark areas can be normally transparent, and the alignment operation of the NikonI8 exposure machine will not be affected.

Description

Technical Field

[0001] The present application relates to the field of semiconductor production technology, and in particular to a method for secondary exposure of calibration marks of a mask. Background Art

[0002] The photolithography mask (also known as the photomask), referred to as the mask, is a graphic master used in the photolithography process commonly used in micro-nano processing technology. The mask pattern structure is formed on the transparent substrate by an opaque light-shielding film, and the graphic information is transferred to the product substrate through the exposure process. The mask to be processed is composed of a glass / quartz substrate, a chrome layer and a photoresist layer. Its graphic structure can be obtained through platemaking processing, and the commonly used processing equipment is direct-write photolithography equipment, such as laser direct-write photolithography machines, electron beam photolithography machines, etc. Masks are widely used, and masks are needed in fields involving photolithography processes, such as IC (integrated circuit), FPD (flat panel display), PCB (printed circuit board), MEMS (micro-electromechanical system), etc.

[0003] For example, the Nikon I8 series lithography machine is one of the mainstream exposure machines for the 6-inch semiconductor production line, equipped with a 5-inch mask. The design of the mask drawing mainly consists of two parts: architecture and chip graphics. The architecture is mainly used for loading and aligning the mask in the exposure machine. Only after these two steps can the chip graphics be exposed on the wafer. The core design of the architecture graphics is the calibration mark used for alignment. The calibration mark of Nikon I8 consists of three marks, each of which has a square light-transmitting area and a cross mark in the center. Figure 1 As shown: The three marks are close to the edge of the mask, 2mm, which exceeds the effective quality area of ​​the raw material substrate used to make the mask. The effective quality area refers to the area where effective patterns can be resolved during photolithography. When the mask substrate is coated with photoresist, it is limited by the limitations of the uniform coating process, and a relatively thick photoresist will be formed at the edge. When the mask is photolithographic, a standard exposure dose is usually used to obtain a higher level of precision in the chip area. However, this exposure dose cannot be thoroughly exposed in the area where the edge photoresist is thicker, and finally a residual metal chromium layer will be formed in this area, causing light blocking.

[0004] At present, the effective area of ​​a 5-inch (127*127mm) mask is the middle range of 122*122mm, that is, the 2.5mm edge area cannot properly resolve the pattern. Therefore, under normal process conditions, the calibration mark of this model will theoretically have a 0.5mm width area that cannot properly transmit light, which will affect the alignment of the exposure machine and cause the Nikon I8 exposure machine to fail to operate.

[0005] The existing process methods to solve the above problems are mainly to optimize the coating process of the mask substrate. For example, after the photoresist is coated, a chemical solvent is used to clean off the excess thick photoresist at the edge. There are also methods such as optimizing the coating parameters to minimize the thickness of the edge photoresist. However, such methods cannot accurately eliminate the thickness difference of the photoresist or may bring some difficulties in defect control. Summary of the invention

[0006] The main purpose of the present invention is to propose a mask secondary exposure alignment method, aiming to solve the technical problem that the calibration mark part cannot transmit light normally after one exposure, thereby affecting the alignment of the exposure machine.

[0007] In order to solve the above technical problems, the present invention provides a first aspect of a mask secondary exposure alignment method, the method comprising:

[0008] After the photoresist layer is set, the entire mask substrate is exposed as a whole using a standard exposure dose and a single exposure mask pattern;

[0009] The mask substrate is partially exposed using a preset exposure dose and a secondary exposure mask pattern, wherein the secondary exposure mask pattern only includes an area of ​​the calibration mark.

[0010] Specifically, the single exposure mask pattern includes all chip pattern areas and architecture pattern areas.

[0011] Specifically, the preset exposure dose is greater than or equal to a minimum dose required for the area of ​​the calibration mark to be completely transparent after secondary exposure.

[0012] Optionally, the area where the secondary exposure mask pattern only includes the calibration mark specifically includes:

[0013] Secondary exposure blocks are respectively arranged corresponding to the three square areas of the calibration mark, the length of each secondary exposure block is greater than or equal to the side length of the square area, and the width of the secondary exposure block abuts against the outer edge of the square area.

[0014] Optionally, the area where the secondary exposure mask pattern only includes the calibration mark specifically includes:

[0015] Secondary exposure blocks are respectively set corresponding to the three square areas of the calibration mark, the length of each secondary exposure block is greater than or equal to the side length of the square area, and the width of the secondary exposure block covers the part of the square area falling outside the effective area of ​​the mask.

[0016] Optionally, the area where the secondary exposure mask pattern only includes the calibration mark specifically includes:

[0017] Secondary exposure blocks are respectively set corresponding to the three square areas of the calibration mark, the length of each secondary exposure block is greater than or equal to the side length of the square area, and the width of the secondary exposure block covers the square area.

[0018] Optionally, the area where the secondary exposure mask pattern only includes the calibration mark specifically includes:

[0019] Secondary exposure blocks are respectively set corresponding to the three square areas of the calibration mark, and the center of the secondary exposure block in the horizontal direction is on the same horizontal line with the cross mark of the square area; the center of the secondary exposure block in the vertical direction is on the same vertical line with the cross mark of the square area.

[0020] Optionally, the area where the secondary exposure mask pattern only includes the calibration mark specifically includes:

[0021] The three square areas corresponding to the calibration mark are respectively provided with secondary exposure blocks, the length of the secondary exposure block is 6 mm, the width is 1 mm, and the distance between the center line of the secondary exposure block and the edge of the mask is 1.5 mm.

[0022] Beneficial effects of the technical solution of the present invention:

[0023] The calibration mark double exposure process method of the mask plate of the embodiment of the present invention is for the thick photoresist at the edge of the mask substrate, and the standard dose mode (DOSE) exposure cannot be fully exposed. After the first conventional exposure, only the calibration mark area with thick photoresist is partially exposed using a specific exposure dose. Finally, the entire calibration mark area can be normally transparent, and will not affect the alignment operation of the Nikon I8 exposure machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a graphic structure diagram of a single exposure mask plate for implementing an embodiment of the present invention;

[0025] Figure 2 This is a flow chart of a mask secondary exposure alignment method provided by an embodiment of the present invention;

[0026] Figure 3 It is a graphic structure diagram of a double exposure mask provided by an embodiment of the present invention;

[0027] Figure 4 It is a schematic diagram of a first double-exposure mask pattern exposure process provided by an embodiment of the present invention;

[0028] Figure 5 It is a schematic diagram of a second double-exposure mask pattern exposure process provided by an embodiment of the present invention;

[0029] Figure 61 is a schematic diagram of a third double-exposure mask pattern exposure process provided by an embodiment of the present invention;

[0030] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0031] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0032] Example 1

[0033] like Figure 2 , 3 As shown, an embodiment of the present invention provides a mask secondary exposure alignment method, the method comprising:

[0034] S101, after providing a photoresist layer, using a standard exposure dose and a single exposure mask pattern to expose the entire mask substrate as a whole;

[0035] S102, locally exposing the mask substrate using a preset exposure dose and a secondary exposure mask pattern, wherein the secondary exposure mask pattern only includes an area of ​​the calibration mark.

[0036] like Figure 1 As shown, the single exposure mask pattern includes all chip pattern areas and architecture pattern areas.

[0037] Specifically, the preset exposure dose is greater than or equal to a minimum dose required for the area of ​​the calibration mark to be completely transparent after secondary exposure.

[0038] like Figure 4 As shown, the area where the double-exposure mask pattern only includes the calibration mark specifically includes:

[0039] Secondary exposure blocks are respectively arranged corresponding to the three square areas of the calibration mark, the length of each secondary exposure block is greater than or equal to the side length of the square area, and the width of the secondary exposure block abuts against the outer edge of the square area.

[0040] like Figure 5 As shown, the area where the double-exposure mask pattern only includes the calibration mark specifically includes:

[0041] Secondary exposure blocks are respectively set corresponding to the three square areas of the calibration mark, the length of each secondary exposure block is greater than or equal to the side length of the square area, and the width of the secondary exposure block covers the part of the square area falling outside the effective area of ​​the mask.

[0042] like Figure 6As shown, the area where the double-exposure mask pattern only includes the calibration mark specifically includes:

[0043] Secondary exposure blocks are respectively set corresponding to the three square areas of the calibration mark, the length of each secondary exposure block is greater than or equal to the side length of the square area, and the width of the secondary exposure block covers the square area.

[0044] Optionally, the area where the secondary exposure mask pattern only includes the calibration mark specifically includes:

[0045] Secondary exposure blocks are respectively set corresponding to the three square areas of the calibration mark, and the center of the secondary exposure block in the horizontal direction is on the same horizontal line with the cross mark of the square area; the center of the secondary exposure block in the vertical direction is on the same vertical line with the cross mark of the square area.

[0046] Optionally, the area where the secondary exposure mask pattern only includes the calibration mark specifically includes:

[0047] The three square areas corresponding to the calibration mark are respectively provided with secondary exposure blocks, the length of the secondary exposure block is 6 mm, the width is 1 mm, and the distance between the center line of the secondary exposure block and the edge of the mask is 1.5 mm.

[0048] The calibration mark double exposure process method of the mask plate of the embodiment of the present invention is for the thick photoresist at the edge of the mask substrate, and the standard dose mode (DOSE) exposure cannot be fully exposed. After the first conventional exposure, only the calibration mark area with thick photoresist is partially exposed using a specific exposure dose. Finally, the entire calibration mark area can be normally transparent, and the alignment operation of the Nikon I 8 exposure machine will not be affected.

[0049] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0050] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0051] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, a magnetic disk, or an optical disk), and includes a number of instructions for enabling a terminal device (which can be a mobile phone, a computer, a server, an air conditioner, or a network device, etc.) to execute the methods described in each embodiment of the present invention.

[0052] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A mask secondary exposure alignment method, characterized in that: The method comprises: After the photoresist layer is set, the entire mask substrate is exposed as a whole using a standard exposure dose and a single exposure mask pattern; Partially exposing the mask substrate using a preset exposure dose and a secondary exposure mask pattern, wherein the secondary exposure mask pattern only includes an area of ​​the calibration mark; The area where the double-exposure mask pattern only includes the calibration mark specifically includes: Secondary exposure blocks are respectively set corresponding to the three square areas of the calibration mark, the length of each secondary exposure block is greater than or equal to the side length of the square area, and the width of the secondary exposure block covers the part of the square area falling outside the effective area of ​​the mask.

2. The mask secondary exposure alignment method according to claim 1, characterized in that: The single exposure mask pattern includes all chip pattern areas and architecture pattern areas.

3. The mask secondary exposure alignment method according to claim 1, characterized in that: The preset exposure dose is greater than or equal to a minimum dose required for the area of ​​the calibration mark to be completely transparent after secondary exposure.

4. The mask secondary exposure alignment method according to claim 1, characterized in that: The area where the double-exposure mask pattern only includes the calibration mark specifically includes: Secondary exposure blocks are respectively set corresponding to the three square areas of the calibration mark, and the center of the secondary exposure block in the horizontal direction is on the same horizontal line with the cross mark of the square area; the center of the secondary exposure block in the vertical direction is on the same vertical line with the cross mark of the square area.

5. The mask secondary exposure alignment method according to claim 4, characterized in that: The area where the double-exposure mask pattern only includes the calibration mark specifically includes: The three square areas corresponding to the calibration mark are respectively provided with secondary exposure blocks, the length of the secondary exposure block is 6 mm, the width is 1 mm, and the distance between the center line of the secondary exposure block and the edge of the mask is 1.5 mm.

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