Cross-photoetching-field copper interconnection process mask plate structure
By optimizing the design of the photomask for the copper interconnect process across photolithography fields, the photoresist is exposed only once in two exposure processes, which solves the problem of narrowing line width and spacing of copper interconnects and improves the reliability of copper interconnects.
Patent Information
- Application Number
- CN202610088016.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-22
- Publication Date
- 2026-03-06
AI Technical Summary
During the cross-lithography mask splicing process, the linewidth of copper metal interconnects in the copper interconnect process becomes wider and the spacing becomes narrower, leading to a decrease in the reliability of the interconnects.
Design a mask structure for cross-lithography field copper interconnect process so that the photoresist in the cross-lithography field metal interconnect region is exposed only once in two exposure processes. By adjusting the layout of the transparent and opaque areas of the mask, damage to the photoresist from secondary exposure can be avoided.
It effectively prevents the copper interconnect line width from widening and the spacing from narrowing, thus improving the reliability and quality of the interconnect.
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Figure CN121613670A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a mask structure for a cross-lithographic field copper interconnect process. Background Technology
[0002] The size of traditional chips is fundamentally limited by the single exposure area of the lithography machine, the core equipment in semiconductor manufacturing. The lithography machine projects circuit patterns onto the wafer using a mask, but the physical characteristics of its optical system dictate that the area that can be covered in a single exposure is limited. Currently, the maximum area covered in a single exposure using advanced lithography technology is limited to a rectangular area of 26mm × 33mm.
[0003] When the chip area exceeds 26mm×33mm, such as in advanced packaging interposers, adapters, integrated substrates, and large-area detector arrays, photomask splicing technology is needed to avoid the limitation of photomask size on chip size and to achieve cross-field metal interconnection.
[0004] Metal interconnects refer to the connection of different devices to form circuits by forming wires using conductive metallic materials. Metal interconnect technology needs to consider factors such as the resistivity of the interconnect material, the step coverage and surface smoothness of the deposition process, electromigration, and stress. Due to their low resistivity, aluminum (Al) and copper (Cu) are widely used as metal interconnect materials in the back-end interconnect processes of semiconductor manufacturing.
[0005] Early integrated circuits used aluminum (Al) as the metal interconnect material. The aluminum interconnect process adopted a process flow of deposition followed by etching: (1) depositing an aluminum layer on the entire wafer surface; (2) removing the unwanted aluminum through photolithography and etching techniques to form a metal wire pattern; (3) finally filling the gaps with insulating materials such as silicon dioxide.
[0006] With the development of process technology, RC delay has seriously affected the performance of integrated circuits. In process technologies of 0.13μm and below, the semiconductor industry uses copper (Cu), a metal with lower resistivity and higher electromigration resistance, instead of aluminum (Al) as the metal interconnect material. Unlike the implementation process of aluminum interconnects, the implementation process of copper damascus structure is as follows: (1) Through-holes and interconnect trenches are formed in the inter-metal dielectric layer (IMD) by etching technology; (2) Then, barrier layers of tantalum (Ta) and tantalum nitride (TaN) are deposited; (3) Copper seed layer is deposited by ionized metal plasma and copper is deposited in large quantities by chemical electroplating (ECP); (4) Finally, copper outside the trench is removed by chemical mechanical polishing (CMP) technology to achieve planarization, while preventing short circuits between copper interconnects.
[0007] During the cross-field photomask splicing process, with each step exposure, the side of each photomask field (i.e., the photomask splicing area) is repeatedly exposed twice, known as the secondary exposure zone. The pattern located within the secondary exposure zone will be damaged with each additional exposure. When using positive photoresist, the exposed photoresist area is dissolved and, after development, becomes the etching window. Because the implementation processes of aluminum interconnects and copper interconnects differ, the impact of secondary exposure on the metal interconnects also differs.
[0008] For aluminum interconnect processes, in order to preserve the pattern of aluminum interconnect lines, the photoresist in the area containing the aluminum interconnect lines must not be exposed. Therefore, the area corresponding to the aluminum interconnect lines on the photomask is opaque. If a cross-photolithography field photomask splicing technology is developed on the aluminum interconnect process platform, secondary exposure will damage the edges of the photoresist corresponding to the aluminum interconnect line pattern, ultimately resulting in narrower aluminum interconnect lines and increased interconnect resistance.
[0009] For copper interconnect processes, in order to etch the copper plating trenches (i.e., the copper interconnect area), the photoresist in the trench area (i.e., the copper interconnect area) needs to be exposed. Therefore, the area corresponding to the plating trenches on the mask (i.e., the copper interconnect area) is transparent, while the area corresponding to the "copper interconnect isolation," i.e., the "copper interconnect trench etching hard mask pattern," is opaque. Therefore, the mask pattern for copper interconnects in the copper interconnect process is actually the pattern of "copper interconnect isolation," i.e., the pattern of the "copper interconnect trench etching hard mask."
[0010] If cross-photolithography field photomask splicing technology is developed on the copper interconnect process platform, secondary exposure will damage the photoresist edge of the corresponding "copper metal interconnect isolation pattern" (i.e. "copper metal interconnect trench etching hard mask pattern"), resulting in wider copper metal interconnects and narrower interconnect spacing, which may even cause short circuits.
[0011] Therefore, in order to reduce the adverse consequences of mask splicing in cross-lithography copper interconnect processes and improve the reliability of copper metal interconnects, the study of mask structures for cross-lithography copper interconnect processes has become an important topic, which is of great significance for realizing cross-lithography metal interconnects using copper interconnect processes. Summary of the Invention
[0012] The purpose of this invention is to provide a mask structure for copper interconnect processes across photolithography fields, so as to solve the problem that the interconnect width becomes wider and the spacing becomes narrower when copper metal interconnects are spliced across photolithography fields.
[0013] To solve the above technical problems, the present invention provides a mask structure for cross-lithography field copper interconnect process, wherein the mask structure is located in the cross-lithography field splicing region; The cross-lithography field splicing region is located on the top, bottom, left, and right sides of a single photomask, and is used to form copper metal interconnects between adjacent lithography fields in wafer-level integrated copper interconnect processes; wherein, The left and right photolithography fields overlap within the dashed frame, forming a copper metal interconnect region across the photolithography fields. The left and right photolithography fields are interconnected through copper metal interconnect lines within the cross-photolithography field metal interconnect region. The upper and lower photolithography fields overlap within the dashed frame, forming a copper metal interconnect region across the photolithography fields. The upper and lower photolithography fields are interconnected through copper metal interconnect lines within the copper metal interconnect region across the photolithography fields.
[0014] In one embodiment, the light-transmitting area of the left cross-lithography field splicing area mask does not overlap with the light-transmitting area of the right cross-lithography field splicing area mask; the light-transmitting area of the upper cross-lithography field splicing area mask does not overlap with the light-transmitting area of the lower cross-lithography field splicing area mask.
[0015] In one embodiment, the union of the transparent area of the left cross-lithography field splicing area mask and the transparent area of the right cross-lithography field splicing area mask constitutes the target shape of the cross-lithography field copper interconnect; the union of the transparent area of the upper cross-lithography field splicing area mask and the transparent area of the lower cross-lithography field splicing area mask constitutes the target shape of the cross-lithography field copper interconnect.
[0016] In one embodiment, apart from the left, right, top, and bottom light-transmitting areas of the cross-lithography field splicing area mask, the other positions of the cross-lithography field splicing area mask are all opaque areas.
[0017] In one embodiment, the cross-photolithography field copper interconnect process mask structure is used for positive photoresist lithography; wherein, positive photoresist refers to the photoresist area not covered by the mask undergoing a chemical reaction, with the exposed portion dissolving in the developer; the photoresist area covered by the mask is insoluble in the developer.
[0018] The present invention provides a mask structure for cross-lithography field copper interconnect process. In the two exposure processes, the photoresist corresponding to the exposure area of the cross-lithography field metal interconnect region (i.e. the subsequent copper electroplating trench region) is exposed only once, eliminating the problem of the copper metal interconnect line width becoming wider and the interconnect line spacing becoming narrower due to the second exposure. This is of great significance for realizing cross-lithography field metal interconnect using copper interconnect process. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of a copper metal interconnect across a photolithography field.
[0020] Figure 2 This is a schematic diagram of the copper interconnect process.
[0021] Figure 3 This is a schematic diagram of a typical cross-photolithography field copper interconnect process mask.
[0022] Figure 4 This is a schematic diagram after the photoresist coating, exposure, and development process of the cross-photolithography field copper interconnect.
[0023] Figure 5 This is a schematic diagram of a typical cross-photolithography field copper interconnect process.
[0024] Figure 6 This is a schematic diagram of the cross-photolithography field copper interconnect process of this patent.
[0025] Figure 7 This is the first mask structure for the cross-photolithography field copper interconnect process of this patent.
[0026] Figure 8 This is the second mask structure for the cross-photolithography field copper interconnect process in this patent. Detailed Implementation
[0027] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a more detailed explanation of the photomask structure for cross-lithography field copper interconnect processes proposed in this invention. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of this invention.
[0028] The cross-photolithography copper interconnect process mask structure in this invention is used for positive photoresist lithography; positive photoresist refers to the photoresist area (exposure area) not covered by the mask undergoing a chemical reaction, with the exposed part dissolving in the developer; the photoresist area covered by the mask does not dissolve in the developer.
[0029] like Figure 1 The diagram shows a cross-lithography field copper interconnect. The left and right lithography fields overlap within the dashed frame, forming a cross-lithography field copper interconnect region. The left and right lithography fields are interconnected through copper interconnect lines within this "cross-lithography field interconnect region." The diagram also illustrates the interconnection of two adjacent lithography fields through copper interconnect lines within the "cross-lithography field interconnect region." Figure 1 Similarly, it is sufficient to arrange the two photolithography fields vertically and overlap the photomask splicing areas on the adjacent upper and lower sides of the two photolithography fields. This embodiment will not be given further details.
[0030] Figure 2 This is a schematic diagram of the copper interconnect process. Figure 2 (a) represents IMD deposition; Figure 2 (b) indicates metal layer photolithography; Figure 2 (c) indicates metal hard mask etching; Figure 2 (d) indicates through-hole photolithography; Figure 2(e) indicates through-hole etching; Figure 2 (f) indicates that metal etching is performed again using a hard mask; Figure 2 (g) represents the deposited copper seed layer; Figure 2 (h) indicates electroplated copper; Figure 2 (i) indicates copper planarization.
[0031] Figure 2 (b) D is the location of the remaining photoresist after photolithography exposure and development, and C is the location where the photoresist was removed; Figure 2 (c) In this case, the D pattern is transferred to the hard mask retention position, and C is the position where the hard mask is etched away. Figure 2 (f) Use a hard mask to perform metal etching again. Position D is the unetched position, and the pattern C is transferred to become a copper metal interconnect trench. Figure 2 (i) After metal planarization, the C pattern eventually becomes a copper metal interconnect.
[0032] Figure 3 This is a schematic diagram of a typical cross-field copper interconnect (CTI) photomask. From... Figure 3 As can be seen, the areas with graphics on the mask are opaque, while the blank areas are translucent. Furthermore, the left and right edges of the mask have identical shapes, and the top and bottom edges have identical shapes.
[0033] Figure 4 This is a schematic diagram showing the process after photoresist coating, exposure, and development in a cross-field copper interconnect process. (Example:) Figure 4 As shown, the areas where the photoresist is retained are the patterns isolating the copper interconnects, i.e., the patterns of the hard mask etched into the copper interconnect trenches. The areas where the photoresist is removed (the exposed areas) are the patterns of the copper interconnects.
[0034] Figure 5 This is a schematic diagram of a typical cross-photolithography field copper interconnect process. Figure 5 (a) and Figure 2 (a), Figure 5 (c) and Figure 2 (c), Figure 5 (d) and Figure 2 (d), Figure 5 (e) and Figure 2 (e), Figure 5 (f) and Figure 2 (f), Figure 5 (g) and Figure 2 (g), Figure 5 (h) and Figure 2 (h), Figure 5 (i) with Figure 2(i) Identical means that the cross-photolithography copper interconnect process and the ordinary copper interconnect process are indistinguishable in the processes of IMD deposition, metal hard mask etching, through-hole lithography, through-hole etching, metal etching again using a hard mask, deposition of copper seed layer, copper electroplating, copper planarization, etc.
[0035] The only difference between cross-photolithography copper interconnect technology and ordinary copper interconnect technology is the metal layer photolithography process. Figure 5 (b) The cross-lithography field copper interconnect process metal layer photolithography is decomposed into three smaller images, in which... Figure 5 (b1) indicates the first exposure after applying the adhesive. Figure 5 (b2) indicates the second exposure after applying the adhesive. Figure 5 (b3) indicates that development is completed after two exposures.
[0036] from Figure 5 As can be seen, Figure 5 (b1) and Figure 5 The masks in (b2) are exactly the same shape, meaning the opaque position D and the transparent position C are identical, and position C is exposed twice. The final result is as follows: Figure 5 As shown in (b3), after development, C becomes wider and D becomes narrower, which in turn affects the subsequent hard mask etching and the final width and spacing of the copper metal interconnects.
[0037] Figure 6 This is a schematic diagram of the cross-photolithography field copper interconnect process of the present invention. Figure 6 and Figure 5 The difference is that, Figure 6 (b1) and Figure 6 (b2) The shapes of the masks used for the two exposures are different.
[0038] Figure 6 (b1) The mask position is the target mask shape, where D1 is the target shape of the metal etching hard mask, and C1 is the target shape of the metal interconnect. After Figure 6 (b1) After exposure, the photoresist in the exposed area has degenerated.
[0039] Figure 6 (b2) The entire mask area is black (D2). In the second exposure, this area is completely covered, avoiding the adverse effects of the second exposure.
[0040] go through Figure 6 (b1) and Figure 6 (b2) After two exposures, the area where the photomask is stitched together is actually only exposed once. Therefore, Figure 6 (b3) The widths of the remaining photoresist D1 and the photoresist removal location D2 obtained after development are normal and do not deviate from the target width due to secondary exposure.
[0041] In order to achieve Figure 6 To achieve the goal of transforming a two-stage exposure into a single-stage exposure, this invention incorporates a mask design for cross-photolithography field copper interconnect processes, such as... Figure 7 and Figure 8 As shown.
[0042] Figure 7 This is the first mask structure proposed in this invention for cross-photolithography field copper interconnect process. For example... Figure 7 As shown, one of the two cross-lithography field splicing areas on the left and right retains its original pattern, while the other is changed to a completely black version; similarly, one of the two cross-lithography field splicing areas on the top and bottom retains its original pattern, while the other is changed to a completely black version. In this case, whether the left and right or top and bottom lithography plates are spliced, the spliced area will only be exposed once.
[0043] Figure 8 This is the second type of mask structure for cross-photolithography field copper interconnect process proposed in this invention. For example... Figure 8 As shown, in the left and right cross-lithography field splicing areas, half of each area retains the original pattern, while the other half is changed to a completely black plate, with the position of the black plate exactly reversed; in the top and bottom cross-lithography field splicing areas, half of each area retains the original pattern, while the other half is changed to a completely black plate, with the position of the black plate exactly reversed. In this case, whether the left and right lithography plates are spliced or the top and bottom lithography plates are spliced, the splicing area of the lithography plates will only be exposed once.
[0044] In practice, this invention only requires that after the left and right cross-lithography field splicing areas overlap, the blank areas (i.e., the exposure areas) have no overlap and are merged into the target exposure area (i.e., the target shape of the cross-lithography field copper metal interconnect). There are no regulations regarding the proportion of the left and right cross-lithography field splicing areas that retain the original pattern or the proportion that is changed to a completely black version. The same applies to the top and bottom cross-lithography field splicing areas.
[0045] Theoretically, using the cross-lithography field copper interconnect process mask described in this invention (such as...) Figure 7 , Figure 8 ) and using a mask for general cross-photolithography field copper interconnect process (such as Figure 3 The copper metal interconnects obtained after exposure, development, etching, and electroplating are all like... Figure 1 As shown.
[0046] However, in the actual two-exposure process, a typical cross-photolithography field copper interconnect process mask (such as...) is used. Figure 3 The photoresist corresponding to the exposure area (i.e., the electroplating trench area) across the photolithography field metal interconnect area is exposed twice, which inevitably affects the quality of the photoresist and causes it to decline.
[0047] During the two exposure processes, the cross-lithography field copper interconnect process mask described in this invention (such as...) is used. Figure 7 , Figure 8 The photoresist corresponding to the exposure area (i.e., the electroplating trench area) across the photolithography field metal interconnect area is exposed only once, eliminating the problem of the copper metal interconnect line width becoming wider and the spacing becoming narrower due to secondary exposure.
[0048] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.
Claims
1. A cross-lithographic field copper interconnect process mask set structure, characterized by, The mask structure is located in the cross-lithography field splicing area; The cross-lithography field splicing area is located on the upper, lower, left and right sides of a single mask, and is used to form copper metal interconnection lines between adjacent lithography fields in a wafer-level integrated copper interconnection process; wherein, The left-side lithography field and the right-side lithography field overlap in the dashed-line frame to form a cross-lithography field copper metal interconnection area, and the left-side lithography field and the right-side lithography field are interconnected by the copper metal interconnection lines in the cross-lithography field metal interconnection area. The upper-side lithography field and the lower-side lithography field overlap in the dashed-line frame to form a cross-lithography field copper metal interconnection area, and the upper-side lithography field and the lower-side lithography field are interconnected by the copper metal interconnection lines in the cross-lithography field metal interconnection area.
2. The cross-lithographic field copper interconnect process mask set structure of claim 1, wherein, The transparent area of the left-side cross-lithography field splicing area mask has no intersection with the transparent area of the right-side cross-lithography field splicing area mask; and the transparent area of the upper-side cross-lithography field splicing area mask has no intersection with the transparent area of the lower-side cross-lithography field splicing area mask.
3. The cross-lithographic field copper interconnect process maskwork structure of claim 2, wherein, The union of the transparent area of the left-side cross-lithography field splicing area mask and the transparent area of the right-side cross-lithography field splicing area mask is the target shape of the cross-lithography field copper interconnection lines; and the union of the transparent area of the upper-side cross-lithography field splicing area mask and the transparent area of the lower-side cross-lithography field splicing area mask is the target shape of the cross-lithography field copper interconnection lines.
4. The cross-lithographic field copper interconnect process maskwork structure of claim 2 or 3, wherein, In addition to the left, right, upper and lower transparent areas of the cross-lithography field splicing area mask, other positions of the cross-lithography field splicing area mask are non-transparent areas.
5. The cross-lithographic field copper interconnect process maskwork structure of claim 4 wherein, The cross-lithography field copper interconnection process mask structure is used for positive photoresist lithography; wherein, the positive photoresist refers to that the photoresist area not covered by the mask reacts chemically, and the exposed part dissolves in the developing solution; the photoresist area covered by the mask is insoluble in the developing solution.