Multi-photoetching photoetching plate capable of manually registering and freely adjusting overlay size

Abstract

The utility model discloses a photoetching plate used for multiple photoetching and capable of manually registering and freely adjusting the overlay size, and belongs to the field of semiconductor manufacturing equipment. According to the utility model, the primary photolithography mask and the overlay mask which are matched for use are designed, and the surfaces of the primary photolithography mask and the overlay mask are respectively provided with two marking characteristic pattern masks, namely the coordinatometer mask and the positioning mark mask, besides the chip unit masks; a coordinatometer which can be clearly observed through a microscope is obtained at the non-chip position of the wafer after one-time front photoetching, and the coordinatometer is reserved on the wafer through wet etching. Therefore, in the overlay process, during manual operation, the overlay feature points can be adopted to be randomly adjusted on the coordinate scale according to the target overlay size, and the overlay position can be positioned, and after a multiple photoetching method is adopted, the overlay size can be freely adjusted, and a required chip pattern can be obtained.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor manufacturing equipment, and in particular relates to a photolithography plate for multiple photolithography with manual plate alignment and free adjustment of overlay size. Background Art

[0002] With the rapid development of the semiconductor industry, the requirements for chip manufacturing technology are increasing. As one of the key technologies in semiconductor manufacturing, secondary overlay technology plays a vital role in the manufacture of precision chips. The secondary overlay process requires a set of matching mask plates, namely the primary photomask and the overlay plate. The basic principle of the secondary overlay process is: first, the initial pattern is formed on the chip through the primary photomask, and then the overlay plate is used for secondary overlay. Through precise alignment and exposure, the new pattern is superimposed on the original pattern, thereby constructing a more complex pattern on the surface of the silicon wafer.

[0003] However, although the secondary overlay technology has achieved remarkable results in semiconductor manufacturing, there are still some problems that need to be solved in the prior art. The most prominent defect is the customization of the overlay plate size. In the existing secondary overlay technology, each overlay needs to customize the size of the mask according to the structural design requirements on the specific chip, which leads to an increase in production costs and an extension of the production cycle. Due to the diversity and variability of circuit design, it is impossible to provide a universal mask size, so that each overlay needs to be redesigned and produced, which greatly limits the flexibility and adaptability of the secondary overlay technology. Summary of the invention

[0004] The purpose of the present invention is to solve the problems existing in the prior art that the size of the overlay plate is completely dependent on customization and the manufacturing cost is high, and to provide a multi-photolithography photolithography plate with manual alignment and free adjustment of the overlay size.

[0005] The specific technical solutions adopted by the present invention are as follows:

[0006] A multi-lithography photoresist with manual alignment and free adjustment of overlay size, comprising a primary photoresist and an overlay plate for use in combination, both of which have square chip mask units, the primary photoresist has at least three identical coordinate ruler masks, the centers of the three coordinate ruler masks are not on the same straight line; each coordinate ruler mask contains a coordinate origin and multiple square rings; the centers of different square rings coincide with the coordinate origin, but the side lengths of different square rings are different; the posture direction of all square rings in the primary photoresist is consistent with the posture direction of the chip mask unit;

[0007] The overlay plate is provided with positioning mark masks which are the same in number and correspond one to one with the coordinate ruler masks, and each positioning mark mask comprises a positioning dot and a positioning ring whose center coincides with the positioning dot;

[0008] When the chip mask units in the primary lithography plate correspond one-to-one with the chip mask units in the overlay plate and their centers completely overlap, the positioning dots in each positioning mark mask just overlap with the coordinate origin in the corresponding coordinate ruler mask.

[0009] Preferably, the coordinate ruler mask also has an XY coordinate axis constructed with the coordinate origin, and the X coordinate axis is parallel to one side of the square ring.

[0010] Preferably, in the primary lithography plate, all the coordinate ruler masks are located in a peripheral non-chip mask area surrounding all the chip mask units.

[0011] Preferably, in the primary photolithography plate, the coordinate ruler masks are divided into four groups, distributed in four directions of the primary photolithography plate, namely, east, south, west and north, and each group includes at least two adjacent coordinate ruler masks.

[0012] Preferably, each square ring in the coordinate ruler mask carries a scale size mark corresponding to the square ring.

[0013] Preferably, the positioning ring in the positioning mark mask is a circular ring.

[0014] Preferably, the chip mask unit in the primary photolithography plate is a light-transmitting material area, and the chip mask unit in the overlay plate is a light-opaque material area.

[0015] Preferably, the coordinate ruler mask on the primary photolithography plate is constructed into a desired shape through a combination of a light-transmitting material area and an opaque material area.

[0016] Preferably, the positioning mark mask on the overlay plate is constructed into a desired shape by combining a light-transmitting material area and an opaque material area.

[0017] Preferably, the outer contours of the primary photolithography plate and the overlay plate are both circles with equal diameters.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The utility model designs a primary photolithography plate and an overlay plate for matching use. In addition to the chip unit mask, the surfaces of the two plates are respectively provided with two types of marking characteristic pattern masks, namely, a coordinate ruler mask and a positioning mark mask, so that the non-chip position of the wafer after the primary front photolithography can obtain a coordinate ruler that can be clearly observed through a microscope, and the coordinate ruler is retained on the wafer through wet etching. Therefore, during the overlay process, the characteristic points of the overlay can be used to adjust and locate the overlay position on the coordinate ruler according to the target overlay size during manual operation. After adopting the multiple photolithography method, the overlay size can be freely adjusted to obtain the required chip pattern.

[0020] The utility model can be applied to the case of manual plate alignment, and can freely adjust the overlay size on the microscope according to the actual size of the product, and perform photolithography for multiple photolithography. The utility model can be used for the metallization table processing technology in the production process of semiconductor diode GPP tube core. When manually operated under a microscope, only one photolithography plate is needed, and different metallization tables (i.e. welding lead hole tables) can be freely adjusted and obtained according to the actual target specification requirements, thereby adjusting the product's current capacity so that some parameters affected by the table size (such as forward voltage drop, forward surge, etc.) match the performance requirements and process capabilities, methods and methods of the packaging end. The greatest advantage of the utility model is that it greatly improves the utilization rate of the photolithography plate, effectively reduces the cost of raw materials, and further improves the economic benefits of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of a primary photolithography plate in an embodiment of the present invention;

[0022] Figure 2 for Figure 1 A magnified image of the coordinate ruler mask at position A in the middle;

[0023] Figure 3 is a schematic diagram of a coordinate ruler mask with offset marks;

[0024] Figure 4 A schematic diagram of an overlay plate in an embodiment of the present invention;

[0025] Figure 5 for Figure 4 A magnified image of the positioning mark mask at position B in the middle;

[0026] Figure 6 A simplified diagram of a marking feature pattern mask and a chip mask unit on a primary lithography plate;

[0027] Figure 7 A simplified diagram of a positioning mark mask and a chip mask unit on an overlay;

[0028] Figure 8It is a schematic diagram of a first alignment state of a primary lithography plate and an overlay plate;

[0029] Fig. 9 is a schematic diagram of a second alignment state of a primary lithography plate and an overlay plate;

[0030] Fig.10 It is a schematic diagram of the third alignment state of the primary photolithography plate and the overlay plate;

[0031] Fig.11 Schematic diagram of the unexposed pattern after double photolithography with offset.

[0032] The colors in some of the above figures are only used for better distinction for display purposes, and do not require that the mask on the photolithography plate be of the corresponding color. DETAILED DESCRIPTION

[0033] In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation mode of the present invention is described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. The technical features in each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0034] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for the purpose of distinguishing descriptions, and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features.

[0035] In a preferred embodiment of the present invention, a multi-photolithography photomask with manual alignment and free adjustment of the overlay size is provided. Similar to the photomask assembly of the traditional overlay process, it also includes a set of primary photomask and overlay plates for matching use, and both the primary photomask and overlay plates have square chip mask units. The chip mask units on the primary photomask and overlay plates are arranged in an array according to conventional practices. The outer contours of the primary photomask and overlay plates are generally circles of equal diameter, and the outer contours of the internal chip mask units are generally square. The primary photomask and overlay plates form mask patterns on a transparent substrate with an opaque light-shielding film, and the patterns are transferred to a wafer by exposure. The masks on the transparent substrates of the two can be processed according to existing technologies. For example, a thin layer of metal (usually chromium) can be plated on a glass substrate, and then the desired pattern can be etched on the metal layer by photolithography.

[0036] In a preferred embodiment of the present invention, the primary photomask and the overlay plate are different from the conventional method in that, in addition to the chip mask unit, both of them also have a marking feature pattern mask for indicating coordinates and positioning. The marking feature pattern mask on the primary photomask and the overlay plate is introduced below.

[0037] The primary photolithography plate has at least three identical coordinate scale masks, and the centers of the three coordinate scale masks are not on the same straight line, but are located at the three corner points of a triangle, thereby satisfying the principle of three-point positioning. Figure 1 As shown, in the embodiment of the present invention, the number of coordinate ruler masks is 8, two by two form a group, and the 8 coordinate ruler masks are divided into four groups, which are distributed in the four directions of the southeast, northwest, and northeast of the primary photolithography plate. Since the field of view of the microscope is limited during the alignment, although theoretically three coordinate ruler masks can meet the positioning requirements, the efficiency of finding these three coordinate ruler masks under the microscope is low, and the above four-group arrangement can improve the alignment efficiency during use. After finding any coordinate ruler mask, another nearby coordinate ruler mask can be found, and then alignment can be performed quickly.

[0038] like Figure 2 As shown, each coordinate ruler mask includes a coordinate origin and multiple square rings. The centers of different square rings coincide with the coordinate origin, but the side lengths of different square rings are different. Thus, with the coordinate origin as the center, multiple levels of concentric nested square rings of different sizes are formed, and these square rings are used to indicate different offset coordinates respectively. Moreover, in the embodiment of the present invention, in addition to the square rings for indication, the XY coordinate axis constructed with the coordinate origin can also be marked in the coordinate ruler mask, and the X coordinate axis is parallel to one set of opposite sides of the square ring, and the Y coordinate axis is parallel to another set of opposite sides.

[0039] It should be noted that the posture direction of all square rings in the primary photomask is consistent with the posture direction of the chip mask unit. Since the square ring has the ability to rotate around the center point on the two-dimensional primary photomask plane, the posture direction of the square ring here is consistent with the posture direction of the chip mask unit, which means that on the primary photomask plane, the two opposite sides of the square ring are parallel to the two opposite sides of the outer contour of the chip mask unit, and the other two opposite sides of the square ring are parallel to the other two opposite sides of the outer contour of the chip mask unit. Each square ring in the coordinate ruler mask corresponds to an offset scale size. In order to facilitate manual confirmation, each square ring in the coordinate ruler mask is marked with the scale size corresponding to the square ring. For example, Figure 3As shown, in the embodiment of the present invention, there are 4 square rings, whose side lengths are 4mil, 10mil, 20mil, and 40mil, respectively. Therefore, the offsets of the corner points of the four square rings relative to the coordinate origin in the X-axis direction (horizontal side direction of the square ring) or the Y-axis direction (vertical side direction of the square ring) are 2mil, 5mil, 10mil, and 20mil, respectively. Therefore, the offset corresponding to each of the above square rings can be marked in the coordinate ruler mask for quick confirmation. Of course, the marking of these offset values ​​is not necessary. When the number of square rings is small, the marking of the offset value can be omitted.

[0040] In the present invention, in addition to the marking feature pattern mask on the primary photolithography plate, the overlay plate also has a positioning mark mask, and the number of the positioning mark masks is the same as the number of the coordinate scale masks on the primary photolithography plate, and the positioning mark masks on the overlay plate correspond to the coordinate scale masks on the primary photolithography plate. Figure 4 As shown, in the embodiment of the present invention, four groups of 8 positioning mark masks are also set on the overlay. Each positioning mark mask includes a positioning dot and a positioning ring whose center coincides with the positioning dot. The positioning dot is used as the center when aligning the overlay, and the positioning ring is mainly for easy finding under a microscope. The positioning ring can be found in advance and then the positioning dot can be found in the center of the positioning ring. The overlay can be adjusted to align the positioning dot with the point specified by the coordinate ruler mask. Figure 5 As shown, in the embodiment of the present invention, the positioning ring in the positioning mark mask is preferably a circular ring. Of course, in other embodiments, a rectangular or other polygonal positioning ring may also be used.

[0041] In the primary photolithography plate and overlay plate used in combination, the chip mask units in the primary photolithography plate correspond one-to-one with the chip mask units in the overlay plate. When the centers of all corresponding chip mask units on the two plates completely overlap, the positioning dot in each positioning mark mask just overlaps with the coordinate origin in the corresponding coordinate ruler mask.

[0042] In order to prevent the marking feature pattern mask from affecting the chip mask area in the primary lithography, all coordinate scale masks should be located as far as possible in the peripheral non-chip mask area surrounding all chip mask units.

[0043] The coordinate ruler mask on the primary photomask is constructed into a desired shape by combining a light-transmitting material area and an opaque material area. Similarly, the positioning mark mask on the overlay plate is constructed into a desired shape by combining a light-transmitting material area and an opaque material area. The specific processing method of these marking feature pattern masks in the primary photomask and the overlay plate is consistent with the processing method of other chip mask units, and the only difference is the shape.

[0044] In order to demonstrate the specific principle of the present invention that the primary lithography plate with the marking feature pattern mask and the overlay plate are combined to manually align the plates and freely adjust the overlay size, the marking feature pattern mask and the chip mask unit on the primary lithography plate are simplified as follows: Figure 6 As shown, only one marking feature pattern mask and four chip mask units are shown; similarly, the positioning mark mask and chip mask unit on the overlay are simplified as follows Figure 7 As shown, only one positioning mark mask and four chip mask units are shown. Taking the scenario of forming the metallized mesa of the diode chip by overlay as an example, the lithography method with adjustable overlay size is as follows:

[0045] 1) First, use a primary photomask for photolithography. The photolithography process is the same as the existing technology. The primary photomask pattern is transferred to the wafer surface coated with the photomask through the photolithography machine. The coordinate ruler mask and chip mask unit patterns on the primary photomask are transferred to the silicon wafer surface, followed by wet etching, leaving the coordinate ruler on the wafer surface. Then the wafer goes through the steps of debonding, powdering, sintering, etc. to the second photolithography (DP scraping method is the second photolithography, PG photoresist method is the third photolithography), that is, the stage of overlay to obtain the metalized table.

[0046] 2) When overlay is required after completing one lithography, after installing the overlay plate, the position of the circular positioning ring in the positioning mark mask can be quickly found manually through a microscope, and then the central positioning circle is aligned with the corresponding offset point on the corresponding coordinate scale mask to adjust the overlay size. After at least three sets of coordinate scale masks and positioning mark masks are aligned, all center points should be aligned according to the principle that three points determine the plane. Multiple lithography can be performed after inspection.

[0047] For example, the chip mask unit of the currently used overlay is the common size of S155 mil. If the chip table size to be overlaid is exactly S155 mil, then the positioning dot in the positioning mark mask of the primary lithography just coincides with the coordinate origin in the corresponding coordinate ruler mask. Figure 8 As shown in the figure, it can be ensured that the chip mask unit in the primary lithography plate corresponds to the chip mask unit in the overlay plate one by one and the centers are completely overlapped. However, if the chip table size smaller than S155mil needs to be overlaid, it is necessary to use the overlay plate for two lithography. For example, when the target chip table size is S151 mil, the first lithography is performed by aligning the positioning circle in the positioning mark mask with the upper right corner of the square with an offset of 2mil in the coordinate ruler mask, and the result is as follows Fig. 9 The pattern shown in FIG. 1 is then etched for the second time by aligning the positioning circle in the positioning mark mask with the lower left corner of the square with an offset of 2 mil in the coordinate ruler mask. Fig.10The pattern shown in Figure 1. After two such photolithography, the overlapping part of the two patterns is as shown in Figure 1. Fig.11 As shown, the overlapping part is exactly the target chip of S151 mil. Therefore, in order to meet the overlay size adjustment requirements of the present invention, the chip mask unit in the above-mentioned primary photomask can be a light-transmitting material area, while the chip mask unit in the overlay can be an opaque material area. When the mesa of the diode chip is formed by overlay, the photoresist coated on the surface of the wafer adopts a negative photoresist, and the overlapping part of the chip mask unit of the two photolithography in the overlay link is completely not exposed. The unexposed photoresist can be removed from this area by subsequent development and fixing operations, and a window that meets the target metallization mesa size is obtained on the surface of the diode chip by wet etching in the subsequent process.

[0048] In addition, if the size of the overlay needs to be changed, different square rings in the above-mentioned coordinate ruler mask can be selected as positioning points, so that the overlay size can be flexibly adjusted through the same set of overlay plates. In addition, some special specifications can also be estimated by using the square rings and XY coordinate values. For example, if the target table is S140 mil, the calculated offset should be 7.5 mil. Then, at least three center points are first aligned with the middle position of the line connecting the upper right corner points of the square with offsets of 5 mil and 10 mil for the first lithography, and then aligned with the middle position of the line connecting the lower left corner points of the square with offsets of 5 offset and 10 offset for the second lithography. The final table size obtained is about 140 mil square.

[0049] It should be noted that in the above embodiments, the offset designed on the coordinate ruler mask is just a summary of the more commonly used sizes, but in theory the minimum scale and division value of the coordinate ruler can be modified arbitrarily.

[0050] The above-described embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A photoresist for multiple photolithography with manual alignment and free adjustment of overlay size, comprising a primary photoresist and an overlay plate used in conjunction with each other, both the primary photoresist and the overlay plate having square chip mask units, characterized in that: The primary lithography plate carries at least three identical coordinate ruler masks, the centers of the three coordinate ruler masks are not on the same straight line; each coordinate ruler mask contains a coordinate origin and multiple square rings; the centers of different square rings coincide with the coordinate origin, but the side lengths of different square rings are different; the posture direction of all square rings in the primary lithography plate is consistent with the posture direction of the chip mask unit; The overlay plate is provided with positioning mark masks which are the same in number and correspond one to one with the coordinate ruler masks, and each positioning mark mask comprises a positioning dot and a positioning ring whose center coincides with the positioning dot; When the chip mask units in the primary lithography plate correspond one-to-one with the chip mask units in the overlay plate and their centers completely overlap, the positioning dots in each positioning mark mask just overlap with the coordinate origin in the corresponding coordinate ruler mask.

2. The photoresist for multiple photolithography with manual alignment and free adjustment of overlay size as claimed in claim 1, characterized in that: The coordinate ruler mask also has an XY coordinate axis constructed with the coordinate origin, and the X coordinate axis is parallel to one side of the square ring.

3. The photoresist for multiple photolithography with manual alignment and free adjustment of overlay size as claimed in claim 1, characterized in that: In the primary photolithography plate, all the coordinate ruler masks are located in the peripheral non-chip mask area surrounding all the chip mask units.

4. The photoresist for multiple photolithography with manual alignment and free adjustment of overlay size as claimed in claim 3, characterized in that: In the primary photolithography plate, the coordinate ruler masks are divided into four groups, which are distributed in the four directions of the primary photolithography plate, namely, east, south, west and north, and each group contains at least two adjacent coordinate ruler masks.

5. The photoresist for multiple photolithography with manual alignment and free adjustment of overlay size as claimed in claim 1, characterized in that: Each square ring in the coordinate ruler mask carries a scale size mark corresponding to the square ring.

6. The photoresist for multiple photolithography with manual alignment and free adjustment of overlay size as claimed in claim 1, characterized in that: The positioning ring in the positioning mark mask is a circular ring.

7. The photoresist for multiple photolithography with manual alignment and free adjustment of overlay size as claimed in claim 1, characterized in that: The chip mask unit in the primary photolithography plate is a light-transmitting material area, and the chip mask unit in the overlay photolithography plate is a light-opaque material area.

8. The photoresist for multiple photolithography with manual alignment and free adjustment of overlay size as claimed in claim 1, characterized in that: The coordinate ruler mask on the primary photolithography plate constructs a desired shape through a combination of a light-transmitting material area and a light-opaque material area.

9. The photoresist for multiple photolithography with manual alignment and free adjustment of overlay size as claimed in claim 1, characterized in that: The positioning mark mask on the overlay plate is constructed into a desired shape by combining a light-transmitting material area and an opaque material area.

10. The photoresist for multiple photolithography with manual alignment and free adjustment of overlay size as claimed in claim 1, characterized in that: The outer contours of the primary photolithography plate and the overlay plate are both circles with equal diameters.

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