Lithographic method and lithographic apparatus

Abstract

The application discloses a photoetching method and a photoetching machine. The photoetching method comprises the following steps: obtaining flatness information of a wafer surface and bending information of a photo mask; determining position information of the wafer at different positions of the wafer surface when a focus plane of a photo mask pattern is under a condition that the photo mask is not bent according to the flatness information; compensating the position information based on the bending information to obtain new position information; and photoetching the wafer at a position indicated by the new position information by using the photo mask. The application can accurately compensate the bending of the photo mask, thereby eliminating the influence of the bending of the photo mask on the uniformity of a critical dimension in an exposure unit and the uniformity of an alignment deviation compensation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor manufacturing, and particularly relates to a photolithography method and a photolithography machine. BACKGROUND

[0002] The two ends of the photomask on the photolithography machine are vacuum-sucked on the guide rails, and the middle part of the photomask sags under the action of gravity, so that the photomask is curved. The amplitude of the photomask curvature increases with the increase of the use time of the photomask, as shown in FIG. 1. The photomask used for the wafer exposed later has a larger curvature amplitude, Figure 1 the dashed line in FIG. 1 indicates a horizontal line, the photomask used for the wafer exposed for the first time is not curved, and the curvature amplitudes of the photomasks used for the wafers exposed for the second time to the Nth time (N is an integer greater than 2) increase in turn. The focusing points formed on the wafer surface by different regions of the curved photomask when light passes through will change differently compared with the focusing points formed by the non-curved photomask, which leads to different critical dimensions (CD) at different positions in the exposure shot and different overlay shift compensation values at different positions in the exposure shot. Figure 1 In the prior art, the photolithography machine can detect the height data of multiple positions on the surface of the photomask and fit the curvature information of the surface of the photomask by using the detected height data, and then adjust the height difference of the guide rails to which the two ends of the photomask are sucked by a vibration-proof device to compensate for the curvature indicated by the flatness information, so that the deformation of the photomask is corrected. Specifically, if

[0003] the left edge of the photomask is sucked on the first guide rail and the right edge is sucked on the second guide rail, as shown in FIG. 2, the first guide rail is controlled to be lower than the second guide rail by the vibration-proof device when the pattern of the left half of the photomask is used for photolithography, and the first guide rail is controlled to be higher than the second guide rail by the vibration-proof device when the pattern of the right half of the photomask is used for photolithography, so as to compensate for the curvature indicated by the flatness information. Figure 1

[0004] However, the vibration-proof device is not directly in contact with the guide rail sucking the photomask, the guide rail sucking the photomask moves under the drive of the motor in the way of air floating, and there is an air floating medium between the vibration-proof device and the guide rail sucking the photomask and a substrate for supporting the guide rail when the air floating support is not present, so that the compensation by the vibration-proof device has errors and the compensation effect is poor. SUMMARY

[0005] In view of the above problems, the present application provides a photolithography method and a photolithography machine, which aims to accurately compensate for the curvature of the photomask, so as to eliminate the influence of the photomask curvature on the uniformity of the critical dimensions in the exposure shot and the uniformity of the overlay shift compensation values.

[0006] According to a first aspect of the present application, a photolithography method is provided, comprising:​

[0007] obtaining flatness information of a wafer surface and curvature information of a mask;

[0008] determining position information of the wafer at different positions of the wafer surface when a focus plane of a mask pattern under a condition that the mask is not curved according to the flatness information;

[0009] compensating the position information based on the curvature information to obtain new position information;

[0010] performing photolithography on the wafer at a position indicated by the new position information using the mask.

[0011] Optionally, compensating the position information based on the curvature information comprises:

[0012] determining a focus surface of the mask under a condition that the mask is curved according to the curvature information;

[0013] obtaining critical dimension shift information of a first focus pattern relative to a second focus pattern, the first focus pattern being a focus pattern of a mask pattern on the focus surface under a condition that the mask is curved, and the second focus pattern being a focus pattern of the mask pattern on the focus plane under a condition that the mask is not curved;

[0014] in a case that the first focus pattern has the critical dimension shift information relative to a third focus pattern of the mask pattern under the condition that the mask is curved, compensating position shift information of a surface where the third focus pattern is located relative to the focus surface to the position information, the third focus pattern being a focus pattern of the mask pattern on a compensation surface under the condition that the mask is curved.

[0015] Optionally, the photolithography method further comprises:

[0016] determining whether the position shift information of the surface where the third focus pattern is located relative to the focus surface is greater than one half of a focus depth of a photolithography lens;

[0017] in a case that the position shift information of the surface where the third focus pattern is located relative to the focus surface is greater than one half of the focus depth, compensating the position shift information of the surface where the third focus pattern is located relative to the focus surface to the position information.

[0018] Optionally, the photolithography method further comprises: in a case that the position shift information of the surface where the third focus pattern is located relative to the focus surface is not greater than one half of the focus depth, performing photolithography on the wafer at the position indicated by the position information using the mask.

[0019] Optionally, the method further comprises: obtaining a detection signal for detecting the height of the wafer surface; filtering noise in the detection signal; and determining the flatness information of the wafer surface according to the detection signal after filtering the noise.

[0020] Optionally, the method further comprises: determining the flatness information of the wafer surface according to the detection signal after filtering the noise.

[0021] Optionally, the method further comprises: determining whether the detection signal after filtering the noise comprises a first sub-signal, the first sub-signal indicating that a position of the wafer surface detected protrudes and a protruding height of the position is greater than a height threshold.

[0022] Optionally, the method further comprises: in a case where the detection signal after filtering the noise comprises the first sub-signal, eliminating the first sub-signal from the detection signal after filtering the noise; and determining the flatness information of the wafer surface according to the detection signal after eliminating the first sub-signal.

[0023] Optionally, the method further comprises: determining the flatness information of the wafer surface according to the detection signal after filtering the noise.

[0024] Optionally, the method further comprises: determining whether the detection signal after filtering the noise comprises a second sub-signal, the second sub-signal indicating that a position of the wafer surface detected protrudes and a continuous width of the protruding position is greater than a width threshold.

[0025] Optionally, the method further comprises: in a case where the detection signal after filtering the noise comprises the second sub-signal, eliminating the second sub-signal from the detection signal after filtering the noise; and determining the flatness information of the wafer surface according to the detection signal after eliminating the second sub-signal.

[0026] Optionally, the method further comprises: obtaining the bending information of the mask comprises:

[0027] Optionally, the method further comprises: obtaining height data of a plurality of positions of the mask.

[0028] Optionally, the method further comprises: calculating a difference between the height data and a height reference value of the mask, the height reference value being a height of a preset plane of the mask.

[0029] Optionally, the method further comprises: fitting a profile curve of the mask including the bending information by using the plurality of calculated differences.

[0030] Optionally, the mask is supported by a first edge and a second edge opposite to the first edge to be in the preset plane, the mask comprises a first region from the first edge to a middle boundary line and a second region from the second edge to the middle boundary line.

[0031] The height data of the plurality of positions of the mask includes height data of a plurality of positions in a target region, the target region being the first region or the second region.

[0032] The plurality of difference values are used to fit a profile curve of the mask including the bending information, including: the plurality of difference values are used to fit a profile curve of the target region, and the profile curve of the mask is determined according to the profile curve of the target region.

[0033] According to a second aspect of the present application, a lithography machine is provided, including a processor, a memory, and a program stored in the memory and executable on the processor, when the program is executed by the processor, the steps of any one of the lithography methods according to the first aspect are implemented.

[0034] The unexpected technical effects of the present application are:

[0035] The lithography method provided by the present application includes: obtaining flatness information of a wafer surface and bending information of a mask; determining position information of the wafer at different positions on the wafer surface when a focusing plane of a mask pattern under a condition that the mask is not bent is determined according to the flatness information; compensating the position information based on the bending information to obtain new position information; and performing lithography on the wafer at the positions indicated by the new position information using the mask. Thus, the bending information of the mask is directly compensated into the position information of the wafer determined according to the flatness information of the wafer surface, the positions of the wafer in the lithography process are adjusted according to different positions on the wafer surface, the bending of the mask is accurately compensated, and the influence of the bending of the mask on the uniformity of the critical dimension and the alignment deviation compensation in the exposure unit is eliminated. BRIEF DESCRIPTION OF DRAWINGS

[0036] The above and other objects, features and advantages of the present application will become more apparent from the following description of embodiments of the present application taken in conjunction with the accompanying drawings, in which:

[0037] Figure 1 A schematic view showing the change of the bending amplitude of a mask with the increase of the use time of the mask;

[0038] Figure 2 A schematic view showing part of the structure of an exemplary lithography machine;

[0039] Figure 3 A flowchart showing a lithography method provided by an embodiment of the present application;

[0040] Figure 4 A schematic view showing a plurality of grids divided by a wafer according to an embodiment of the present application;

[0041] Figure 5An exemplary curved mask is shown according to an embodiment of the present application.

[0042] Figure 6a A protruding area of a wafer surface and its corresponding exemplary detection signal are shown according to an embodiment of the present application.

[0043] Figure 6b A noise signal present in a detection signal is shown according to an embodiment of the present application.

[0044] Figure 6c A first sub-signal present in a detection signal is shown according to an embodiment of the present application.

[0045] Figure 6d A second sub-signal present in a detection signal is shown according to an embodiment of the present application.

[0046] Figure 7 An exemplary mask pattern is compensated for mask curvature information according to an embodiment of the present application.

[0047] Figure 8 An exemplary Poisson curve is shown according to an embodiment of the present application.

[0048] BRIEF DESCRIPTION OF DRAWINGS DETAILED DESCRIPTION

[0049] The present application will be described in more detail with reference to the drawings. Like elements in the drawings are denoted by like reference numerals. Each part in the drawings is not drawn to scale for the sake of clarity. Further, some well-known parts can not be shown.

[0050] The present application can take various forms. Some examples will be described below.

[0051] In a semiconductor manufacturing process, a circuit design is first performed, and then a layout design is performed to form a layout pattern based on the circuit design. The layout pattern is then transferred to a mask. After the pattern is formed on the mask, a photolithography process is used to transfer the mask pattern to a photoresist on a wafer surface. Then, the pattern on the photoresist is transferred to the wafer by etching. By combining ion implantation and metal material deposition processes, a desired semiconductor integrated circuit can be formed on the wafer.

[0052] Figure 2 An exemplary partial structure of a photolithography machine is shown. As shown in FIG. 1, a laser light source 11 is used to generate a laser beam. A beam expander 12 is used to expand the laser beam. A lens 14 is used to focus the expanded laser beam. A mask 13 is used to form a pattern on the laser beam. A wafer 15 is used to receive the patterned laser beam. Figure 2As shown, the photolithography machine 10 comprises a laser light source 11, a beam expander 12, a photomask 13, a lens 14 and a carrier platform 15. The parallel light emitted by the laser light source 11 is expanded by the beam expander 12 and then irradiates the photomask 13. The light beam passing through the photomask 13 is focused by the lens 14 onto a wafer 16 carried by the carrier platform 15, so that the photoresist on the surface of the wafer 16 is exposed. The photomask 13 comprises light-shielding regions and light-transmitting regions. The photoresist is divided into positive photoresist and negative photoresist according to the reaction mode. The exposed part of the positive photoresist is removed during development to form an opening region. The exposed part of the negative photoresist is retained during development to form a shielding region. Thus, the opening region of the positive photoresist corresponds to the light-transmitting region of the photomask 13, and the opening region of the negative photoresist corresponds to the light-shielding region of the photomask 13. Therefore, the pattern formed by the light-shielding regions and the light-transmitting regions on the photomask 13 is projected onto the photoresist on the surface of the wafer 16.

[0053] Generally, the pattern on the photomask 13 is projected onto the photoresist on the surface of the wafer 16 in a reduced manner. The distance between the photomask 13 and the lens 14 is fixed to achieve a fixed reduction ratio. In the case where the size of the photomask 13 is 5 inches or 6 inches and the reduction ratio is 4 times or 5 times, the exposure area obtained by one-time exposure is less than 50 mm, and is generally about 30 mm square. For a wafer 16 with a size of 2 inches to 12 inches, one-time exposure cannot complete the exposure of the entire area. Therefore, multiple exposures are required to cover the entire wafer 16. Thus, the wafer 16 is divided into multiple exposure units (shots). One-time exposure realizes the exposure of one exposure unit. The carrier platform 15 moves in the xy plane to drive the wafer 16 to move in the xy plane, so that the multiple exposure units are exposed in turn.

[0054] In the photolithography machine 10, the two ends of the photomask 13 are vacuum-sucked to the guide rails. Under the action of gravity, the middle part of the photomask 13 sags, so that the photomask 13 presents a curved state. Moreover, the curvature of the photomask 13 will increase with the increase of the service time of the photomask 13. As shown, the photomask 13 is not curved when it is used to expose a wafer for the first time, but it is curved when it is used to expose wafers afterwards, and the curvature increases more and more. Figure 1 When the photomask 13 is curved, the focusing points of different regions on the photomask 13 on the surface of the wafer 16 will change differently compared with the case where the photomask 13 is not curved. This leads to different critical dimensions at different positions in the exposure unit, and the alignment offset compensation values at different positions in the exposure unit will also be different with the change of the critical dimensions.

[0055] In the prior art, the placement mode of the photomask 13 is adjusted by adjusting the height difference of the guide rails to which the two ends of the photomask 13 are adsorbed by a shockproof device, so as to compensate for the curvature of the photomask 13. However, the shockproof device is not directly in contact with the guide rails adsorbing the photomask 13. Therefore, the compensation by the shockproof device has errors and the compensation effect is poor.

[0056] In view of this, one embodiment of the present application provides a photolithography method, which directly compensates bending information representing the bending degree of a mask into position information of a wafer determined according to flatness information of the wafer surface, adjusts the position of the wafer in a photolithography process for different positions on the wafer surface so that the mask bending is accurately compensated, and thus the influence of mask bending on the critical dimension uniformity and alignment deviation compensation uniformity in an exposure unit is eliminated.

[0057] Figure 3 Fig. 1 shows a flowchart of a photolithography method provided by an embodiment of the present application. As shown in the figure, the photolithography method comprises the following steps. Figure 3

[0058] In step S110, flatness information of the wafer surface and bending information of the mask are acquired.

[0059] Specifically, the flatness information of the wafer surface can be composed of height data of different positions on the wafer surface. The wafer can be divided into a plurality of grids as shown in the figure, each grid has a height data, and the more grids, the more accurate the flatness information composed of height data of the plurality of grids can reflect the flatness of the wafer surface. The height data in the flatness information is associated with the position of the wafer surface represented by the height data, and thus the flatness information can also be called a leveling map. Figure 4 The bending information of the mask can be composed of bending data of different positions on the mask. The bending data of a position on the mask is the difference between the height data of the position on the mask and the height reference value of the mask. The height reference value is the height of the preset plane of the mask, and the height of the guide rail in the case of adsorbing the mask at both ends of the guide rail is the height of the preset plane. Similarly, the bending data in the bending information is associated with the position of the mask topography represented by the bending data. For the mask shown in the figure, the bending is represented as having different heights along the x-axis, and thus the bending data is the difference between the height data z(x) of the position x and the height reference value h0. The height data z(x) of the entire mask is a function relationship of z changing with x.

[0060] Figure 5

[0061] In step S120, position information of the wafer at different positions on the wafer surface when the focusing plane of the mask pattern is on the wafer surface under the condition that the mask has no bending is determined according to the flatness information. In other words, according to the flatness information, the axial compensation amount to be applied to the wafer so that the focusing plane formed by the mask pattern on the image side coincides with each local area of the wafer surface under the condition that the mask has no bending is calculated, and the axial compensation amount is taken as the position information of the wafer.

[0062] ​​​It should be noted that the focusing plane of the mask pattern in the case of no bending of the mask is the imaging plane of the mask pattern in the case of no bending of the mask. Since the distance between the preset plane of the mask on the photolithography machine and the lens is fixed, the focusing plane of the mask pattern in the case of no bending of the mask is also fixed. In the case of knowing the distance between the preset plane of the mask and the lens and the focal length of the lens, the focusing plane can be determined according to the imaging formula.

[0063] The position information of the wafer can be composed of position data of the wafer carrying platform when different positions on the wafer surface are in the focusing plane. The wafer is placed on the surface of the carrying platform, and the carrying platform moves to drive the wafer to move as a whole. In the case of determining the position of the carrying platform, the position of the wafer is also uniquely determined. However, if the wafer surface is not flat, the distance between different positions on the wafer surface and the lens is different. Therefore, in the case of the wafer surface being not flat, the position data of the wafer carrying platform when different positions on the wafer surface are in the focusing plane is also different.

[0064] The focusing point of the mask pattern on the focusing plane in the case of no bending of the mask in the embodiment of the present application is also called automatic focus. The above position information can be considered as the position of the automatic focus point obtained by compensating the flatness information.

[0065] In step S130, the position information is compensated based on the bending information to obtain new position information.

[0066] It should be noted that in the process of compensating the position information based on the bending information, there is a one-to-one correspondence between the bending data in the bending information and the position data in the position information. Specifically, the patterns at different positions on the mask are configured to be projected to different preset positions on the wafer surface. The position of the mask is associated with the bending data, and the position of the wafer surface is associated with the position data. Therefore, the bending data associated with a position on the mask and the position data associated with the preset position to which the pattern at the position on the mask is to be projected are one-to-one corresponding.

[0067] The compensation of the position information based on the bending information is to use the new position information obtained after the compensation to make the photoresist at different positions on the wafer surface be etched to have a uniform critical dimension pattern. Since the critical dimension of the projected pattern of the mask pattern on the focusing plane in the case of no bending of the mask is usually the designed critical dimension, the above uniform critical dimension can be selected as the critical dimension of the projected pattern of the mask pattern on the focusing plane in the case of no bending of the mask.

[0068] In step S140, the wafer at the position indicated by the new position information is photolithographed by using the mask.

[0069] Specifically, the new position information is obtained after compensation of the position information, and the position information is composed of position data of the wafer supporting platform when the wafer surface is at different positions of the focusing plane, and thus the new position information is composed of new position data corresponding to different positions of the wafer surface. In this way, when the photoresist at different positions of the wafer surface is exposed, the wafer supporting platform is moved to the position indicated by the new position data corresponding to the position of the wafer surface.

[0070] It should be noted that, since the bending data in the bending information and the position data in the position information have a one-to-one correspondence, the new position data in the new position information also has a one-to-one correspondence with the bending data in the bending information. In this way, the association data between the new position data in the new position information and the bending data in the bending information can be set, so that when the pattern at a position on the mask is used for photolithography, the new position data is determined based on the association data between the bending data at the position and the new position data. In practice, the size of the area on the mask whose pattern shares one new position data for one exposure can be determined according to the size of the bending range of the mask, so as to ensure that the critical dimensions at different positions in the same exposure unit on the wafer surface are substantially the same, and the critical dimensions in different exposure units are also substantially the same.

[0071] The photolithography method provided by the embodiments of the present application compensates for the bending of the mask by adjusting the position of the wafer, and the bending information of the mask is directly compensated into the position information of the wafer determined according to the flatness information of the wafer surface, so that the bending of the mask is accurately compensated, and the influence of the bending of the mask on the uniformity of the critical dimensions in the exposure unit and the uniformity of the alignment offset compensation can be eliminated.

[0072] In an optional embodiment, the process of obtaining the bending information of the mask in step S110 includes: obtaining bending data of a plurality of positions of the mask, and fitting a topography curve of the mask including the bending information by using the obtained plurality of bending data. In this way, it is not necessary to strictly obtain the bending data of each position on the mask to obtain the topography curve. Specifically, the number of the obtained bending data is determined according to the bending range of the mask. The greater the bending range, the more bending data. Thus, it is ensured that the plurality of bending data can more accurately fit the topography curve of the mask. Figure 5 For the mask with a smaller bending range as shown in the figure, one bending data can be collected from each of the five dashed boxes K0 to K4 to fit the topography curve of the mask.

[0073] Further, in the case that the mask is supported by the opposite first edge and second edge to be in the preset plane, the profile of the mask is in a symmetrical state and the symmetry axis is a middle dividing line of the mask which does not intersect with the first edge and the second edge of the mask, the mask comprises a first region from the first edge to the middle dividing line and a second region from the second edge to the middle dividing line, the obtaining of the plurality of position bending data of the mask can obtain the height data of a plurality of positions in any one of the first region and the second region to obtain the difference, and the region providing the height data of the plurality of positions is referred to as a target region, and the fitting of the profile curve of the mask by using the obtained plurality of bending data can comprise: fitting the profile curve of the target region by using the plurality of bending data obtained by the difference and determining the profile curve of the mask according to the profile curve of the target region, and specifically, the profile curve of the mask can be determined according to the profile curve of the target region by using the symmetry. For Figure 5 As shown in the mask, one height data can be collected from the region where the dashed box K0 is located on the right side of the z axis and from each of the dashed boxes K1 and K2, and height data does not need to be collected from the five dashed boxes K0 to K4, thereby facilitating the reduction of collected data.

[0074] In another optional embodiment, the obtaining of the wafer surface flatness information in step S110 comprises: obtaining a detection signal for detecting the height of the wafer surface, filtering noise in the detection signal, and determining the flatness information of the wafer surface according to the detection signal after filtering the noise, so that the determined flatness information of the wafer surface is more accurate.

[0075] Specifically, a sufficient number of focus sensors can be arranged to detect the height of the wafer surface, and the detection signal is an optical signal. In practice, the number of focus sensors is the number of grids divided on the wafer, and one focus sensor detects the height data of one grid. For example, the size of the grid divided on the wafer is 1 mm x 1 mm, in which case one focus sensor detects the height of a 1 mm x 1 mm region on the wafer surface. The detection signals detected by the plurality of focus sensors are signals distributed on a two-dimensional plane, the horizontal coordinate of the signal represents the position of the wafer surface, and the vertical coordinate of the signal is obtained by transforming (for example, taking the first derivative or higher derivative) the height of the corresponding detection position on the wafer surface as the signal amplitude, according to the detection signal, the height distribution map of the wafer surface can be obtained, and the accuracy of the height distribution map is in the nanometer level. In this application, the height distribution map is also referred to as the initial distribution map of the wafer surface height.

[0076] Since the wafer surface protrusion will exhibit a more obvious height change in at least one direction of the wafer surface, the detection signal has more obvious abnormal signal characteristics representing the wafer surface protrusion in at least one direction. Figure 6aThe protruding area of the wafer surface and the corresponding exemplary detection signal are shown, such as Figure 6a As shown, the protruding area of the wafer surface includes a height rising area between points Q1 and Q2, a height maintaining area between points Q2 and Q3, and a height falling area between points Q3 and Q4, and the corresponding detection signal includes a first signal trough near point P1, a first signal peak near point P2, a second signal peak near point P3, a second signal trough near point P4, and a signal segment between the first signal peak and the second signal peak in the direction of the height change of the protruding area, wherein point P1 is the signal obtained by detecting point Q1 of the wafer surface, point P2 is the signal obtained by detecting point Q2 of the wafer surface, point P3 is the signal obtained by detecting point Q3 of the wafer surface, and point P4 is the signal obtained by detecting point Q4 of the wafer surface. The protruding area of the wafer surface is an area protruding compared to the flat area of the wafer, and the signal peak and the signal trough are the signal amplitudes compared to the flat area of the wafer. The greater the protruding height of the protruding area, the greater the peak value of the signal peak.

[0077] The above filtering of noise in the detection signal can be determining whether a section of the detection signal has an abnormal signal characteristic, and if so, the section of the detection signal is a noise signal, and then filtering the noise signal from the detection signal. For example, the abnormal signal characteristic can be that the signal segment does not have a signal trough but has a signal peak in the direction of the height change of the wafer surface, and the peak value of the signal peak is greater than a peak value threshold. Figure 6a The abnormal signal characteristic is shown. Figure 6b The detection signal without a signal trough but with a signal peak in the direction of the height change of the wafer surface and the peak value of the signal peak being greater than a peak value threshold is a noise signal.

[0078] Further, the above determining the flatness information of the wafer surface according to the detection signal after filtering the noise can include: determining whether the detection signal after filtering the noise includes a first sub-signal, the first sub-signal indicating that the position of the wafer surface detected protrudes and the protruding height is greater than a height threshold; in the case that the detection signal after filtering the noise includes the first sub-signal, eliminating the first sub-signal from the detection signal after filtering the noise, and determining the flatness information of the wafer surface according to the detection signal after eliminating the first sub-signal. In this way, the subsequent determination of the new position data of the position of the wafer surface detected by the first sub-signal is not performed, and the position of the wafer surface detected by the first sub-signal is not suitable for manufacturing a semiconductor integrated circuit. The position of the wafer surface detected by the first sub-signal can be marked and informed to the producer through an alarm mode so as to improve the process subsequently.

[0079] For example, the abnormal signal characteristic can be that the signal segment between point S3 and point S4 in the direction of the height change of the wafer surface is a first sub-signal. Figure 6a The abnormal signal characteristic is shown. Figure 6c The signal segment between point S3 and point S4 in the direction of the height change of the wafer surface is a first sub-signal. Figure 6cThe signal segment shown includes a left signal trough located right to point S1 and adjacent to the left of point S1, a right signal trough located left to point S2 and adjacent to the right of point S2, and a signal segment between the left trough and the right trough, which represents that the detected wafer surface includes two protruding points compared to the wafer flat area and a protruding flat plane between the two protruding points and further protruding compared to the two protruding points, and the position of the protruding flat plane detected by the signal segment between point S1 and point S2 is greater than the height threshold compared to the protruding height of the wafer flat area.

[0080] Further, the above determining the flatness information of the wafer surface according to the detection signal after filtering out the noise can include: judging whether the detection signal after filtering out the noise includes a second sub-signal, the second sub-signal representing a position of the detected wafer surface protruding and a continuous width of the protruding position being greater than a width threshold; in the case that the detection signal after filtering out the noise includes the second sub-signal, eliminating the second sub-signal from the detection signal after filtering out the noise, and determining the flatness information of the wafer surface according to the detection signal after eliminating the second sub-signal, so that the position of the wafer surface detected by the second sub-signal is not determined for new position data in the subsequent, and the position of the wafer surface detected by the second sub-signal is not suitable for manufacturing semiconductor integrated circuits as an abnormal area.

[0081] For Figure 6a The abnormal signal feature shown, Figure 6d The signal segment between point S5 and point S6 in the height change direction of the wafer surface shown is a second sub-signal, and the wafer surface area detected by the second sub-signal is uneven compared to the wafer flat area. The width w of the second sub-signal shown in the figure corresponds to the continuous width of the detection area in the height change direction.

[0082] In some examples, the determination of the flatness information of the wafer surface according to the detection signal after filtering out the noise can be to eliminate both the first sub-signal and the second sub-signal from the detection signal after filtering out the noise, and then determine the flatness information of the wafer surface according to the detection signal after eliminating the first sub-signal and the second sub-signal.

[0083] In another optional embodiment, the compensation of the position information based on the bending information in step S130 includes: determining a focusing surface of the mask under the bending condition of the mask according to the bending information; obtaining key dimension offset information of the first focusing pattern compared to the second focusing pattern, the first focusing pattern being a focusing pattern of the mask pattern on the focusing surface under the bending condition of the mask, and the second focusing pattern being a focusing pattern of the mask pattern on the focusing plane under the non-bending condition of the mask; and in the case that the first focusing pattern has the key dimension offset information compared to a third focusing pattern of the mask pattern under the bending condition of the mask, compensating position offset information of the curve surface (hereinafter also referred to as compensation curve surface) where the third focusing pattern is located compared to the focusing surface to the position information.

[0084] It should be noted that the first focus pattern and the second focus pattern obtained by focusing the patterns at different positions on the mask in the case of mask bending have different critical dimension shift data, and thus the first focus pattern obtained by focusing the pattern at a position on the mask and the third focus pattern obtained by focusing the pattern at the position on the mask have the critical dimension shift data between the first focus pattern and the second focus pattern obtained by focusing the pattern at the position on the mask, so that the position information is compensated by offsetting the position of the third focus pattern obtained by focusing the pattern at the position on the curved surface to the position data associated with the preset position on the wafer to be projected by the position.

[0085] In the example of the mask pattern shown in Figure 7 The above compensation process is described in detail, wherein the mask pattern is reduced and projected onto the photoresist on the wafer surface, and thus Figure 7 The mask pattern shown in the lens object side is located outside the double focal length of the lens, Figure 7 The image side focal point F of the lens is marked in the figure, and the focus pattern on the image side and the mask pattern on the object side are both shown by black squares, but this does not mean a specific limitation on the shape of the mask pattern.

[0086] Referring to Figure 7 The mask pattern A(r) on the object side of the lens is the pattern at position r on the mask in the case of no mask bending, and the mask pattern A(r) is changed to the mask pattern B(r) after the mask is bent. The mask pattern A(r) and the mask pattern B(r) are, for example, light transmission regions on the mask, so that for positive photoresist, the mask pattern A(r) and the mask pattern B(r) can respectively expose the photoresist to light to etch corresponding opening regions on the photoresist.

[0087] Figure 7 In the figure, the focus pattern A'(r) on the image side of the lens is the focus pattern of the mask pattern A(r) on the focusing plane, i.e. the second focus pattern obtained by focusing the pattern at position r on the mask in the case of no mask bending; the focus pattern B'(r) on the image side of the lens is the focus pattern of the mask pattern B(r) on the focusing plane, i.e. the first focus pattern obtained by focusing the pattern at position r on the mask in the case of mask bending. The focus pattern B'(r) is larger than the focus pattern A'(r) because it is closer to the position of the double focal length. Correspondingly, the critical dimension of the focus pattern B'(r) is larger than that of the focus pattern A'(r), and the critical dimension of the mask pattern B'(r) minus the critical dimension of the mask pattern A'(r) gives the critical dimension shift data CD 0 bias(r). Since the focus pattern A'(r) and the focus pattern B'(r) are determined based on the imaging principle, the size of each of the focus pattern A'(r) and the focus pattern B'(r) can be determined based on the imaging principle, and then the critical dimension shift data CD of the focus pattern A'(r) compared to the focus pattern B'(r) can be determined. 0 bias (r).

[0088] Further, the focus pattern B''(r) of the lens side is the focus pattern of the mask pattern B(r) on the compensation curved surface, i.e. the third focus pattern obtained by focusing the pattern at the position r on the mask. The critical dimension shift data of the focus pattern B'(r) compared to the focus pattern B''(r) can be determined according to the Poisson curve of the Focus-Energy Matrix (FEM).

[0089] The Focus-Energy Matrix is a test method used to determine the optimal exposure condition. Specifically, when the photoresist on the wafer surface is exposed, the focus value is changed in one direction with a fixed step size and the exposure energy is changed in another direction with another fixed step size, and then the critical dimension of each exposure unit and the focus value and the exposure energy are taken as inputs, so that the so-called Poisson curve can be obtained. Figure 8 An exemplary Poisson curve is shown, in which each Poisson curve corresponds to an exposure energy, the horizontal axis represents the focus value, and the vertical axis represents the measured width of the independent line etched on the photoresist, which can represent the critical dimension. Figure 8 The Poisson curve shown in the figure can be represented by the following formula (1), where CD represents the critical dimension; X represents the focus value, which can be understood as the position in the direction of the optical axis of the lens, and can be represented as the position X of the focus point n and the defocus value Y n ; A, B and C are constants determined when fitting the Poisson curve by the Focus-Energy Matrix.

[0090] CD = AX 2 + BX + C = A (X n + Y n ) 2 + B (X n + Y n ) + C (1)

[0091] It should be understood that formula (1) can be transformed into formula (2) shown below, where A', B' and C' are constants determined according to the constants A, B and C in formula (1) and the position X n of the focus point. In addition, if the position X n of the focus point is 0, formula (1) can be transformed into formula (3) shown below.

[0092] CD = A'Y n 2 + B'Y n + C' (2)

[0093] CD = AY n 2 + BY n + C (3)

[0094] Thus, the position X of the focus point of the focus pattern B'(r) along the optical axis of the lens is determined according to the imaging principle, and the focus pattern B'(r) is obtained according to the formula (1) to (3). n Then, the critical dimension of the focus pattern B'(r) is calculated by using one of the formula (1) to (3), and then the critical dimension of the focus pattern B'(r) is subtracted by the critical dimension offset data CD 0 bias (r) to obtain the critical dimension of the focus pattern B''(r), and then the defocus value Y is calculated according to one of the formula (1) to (3). n Here, the defocus value Y n is the offset value of the focus pattern B''(r) compared with the focus pattern B'(r) in the direction of the optical axis of the lens. It should be understood that the focus surface as the focus surface of the mask in the case of mask bending can be understood as the image of the mask through the lens in the case of mask bending, so that the focus pattern B'(r) theoretically has Figure 8 the critical dimension at the vertex of the Poisson curve as shown, and the critical dimension of the focus pattern B''(r) is reduced compared with the focus pattern B'(r), so that the focus pattern B''(r) can achieve compensation.

[0095] Further, the photolithography method provided by the embodiment of the application can further include: judging whether the position offset information of the third focus pattern relative to the focus surface is greater than one half of the focus depth of the photolithography lens, wherein if the position offset information of the third focus pattern relative to the focus surface is greater than one half of the focus depth, the position offset information of the third focus pattern relative to the focus surface is compensated to the position information to obtain new position information, and then the step S140 is performed by using the new position information, otherwise, the wafer at the position indicated by the position information is directly photolithographed by using the mask, that is, the corresponding compensation process is omitted to simplify the photolithography process in the case that the mask bending does not affect the photolithography precision of the wafer surface photoresist.

[0096] In practice, the same mask will be used in turn for the photolithography process of the surface photoresist of a plurality of wafers, and the photolithography process required by each wafer is performed according to the photolithography method described above.

[0097] Corresponding to the photolithography method provided by the above embodiments, another embodiment of the present application further provides a photolithography machine, which comprises a processor, a memory, and a program stored in the memory and executable on the processor, and the program, when executed by the processor, implements the steps of any one of the photolithography methods provided by the above embodiments. In some embodiments, the processor and the memory can be integrated into a microprocessor for use in the photolithography machine. In addition, the photolithography machine can also comprise a laser light source, a beam expander, a photomask, a lens, and a carrier platform as shown in Figure 2 It is emphasized that the carrier platform in the photolithography machine provided by the embodiments of the present application is movable in three-dimensional directions, thereby driving the wafer to move in three-dimensional directions, so that the plurality of exposure units on the wafer are exposed in turn while also having a uniform critical dimension after being compensated for the bending information of the photomask.

[0098] The embodiments of the present disclosure no longer "straighten" the photomask, but rather actively fit the wafer to the image plane of the curved photomask.

[0099] That is, the photomask bending information is directly converted into a "position compensation amount" of the wafer in the Z direction, which is superimposed with the original flatness compensation amount of the wafer, so that the wafer always falls on the actual focusing surface corresponding to the curved photomask at each local part, thereby eliminating the systematic unevenness of CD and overlay at one time.

[0100] It should be noted that in the description of each embodiment in the present specification, the difference from other embodiments is mainly explained, and the same or similar parts between the embodiments can be mutually understood. For this embodiment of the photolithography machine, since it is basically similar to the method embodiment, the relevant parts can be referred to the description of the method embodiment part.

[0101] According to the embodiments of the present application as described above, these embodiments do not describe all the details, nor limit the present application to only the specific embodiments described. Obviously, many modifications and changes can be made according to the above description. The present specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present application, so that those skilled in the art can well utilize the present application and make modifications and uses on the basis of the present application. The present application is limited only by the claims and their entire scope and equivalents.

Claims

1. A photolithography method, comprising: Obtain information on the flatness of the wafer surface and the curvature of the photomask; Based on the flatness information, the axial compensation amount that needs to be applied to the wafer to make the focal plane formed by the photomask pattern in the image side coincide with each local area on the wafer surface when the photomask is not bent is calculated, and the axial compensation amount is used as the wafer position information. The position information is compensated based on the curvature information to obtain new position information; The wafer at the position indicated by the new position information is photolithographically etched using the photomask.

2. The photolithography method according to claim 1, wherein, Compensating the position information based on the curvature information includes: The focusing surface of the photomask under bending conditions is determined based on the bending information; Obtain key dimensional offset information of the first focusing pattern relative to the second focusing pattern. The first focusing pattern is the focusing pattern of the photomask on the focusing surface when the photomask is bent, and the second focusing pattern is the focusing pattern of the photomask on the focusing plane when the photomask is not bent. When the third focusing pattern of the photomask pattern has the key dimension offset information compared to the first focusing pattern when the photomask is bent, the position offset information of the surface where the third focusing pattern is located compared to the focusing surface is compensated to the position information. The third focusing pattern is the focusing pattern of the photomask pattern on the compensated surface when the photomask is bent.

3. The photolithography method according to claim 2, further comprising: Determine whether the positional offset information of the surface where the third focusing pattern is located relative to the focusing surface is greater than half of the focusing depth of the photolithography lens; If the depth of focus is greater than half of the depth of focus, the position offset information of the surface where the third focus pattern is located relative to the focus surface is compensated to the position information.

4. The photolithography method according to claim 3 further includes: When the positional offset information of the surface where the third focusing pattern is located relative to the focusing surface is not greater than half of the focusing depth, the wafer at the position indicated by the position information is photolithographically etched using the photomask.

5. The photolithography method according to claim 1, wherein, Obtaining wafer surface flatness information includes: acquiring a detection signal for detecting the height of the wafer surface, filtering out noise in the detection signal, and determining the wafer surface flatness information based on the noise-filtered detection signal.

6. The photolithography method according to claim 5, wherein, Determining the flatness information of the wafer surface based on the detection signal after noise filtering includes: Determine whether the detection signal after noise filtering includes a first sub-signal, wherein the first sub-signal indicates that the detected wafer surface protrudes and the protrusion height is greater than a height threshold; If the detection signal after noise filtering includes the first sub-signal, the first sub-signal is removed from the detection signal after noise filtering, and the flatness information of the wafer surface is determined based on the detection signal after removing the first sub-signal.

7. The photolithography method according to claim 5, wherein, Determining the flatness information of the wafer surface based on the detection signal after noise filtering includes: Determine whether the detection signal after noise filtering includes a second sub-signal, wherein the second sub-signal indicates that the detected wafer surface has a protruding position and the continuous width of the protruding position is greater than a width threshold. If the detection signal after noise filtering includes the second sub-signal, the second sub-signal is removed from the detection signal after noise filtering, and the flatness information of the wafer surface is determined based on the detection signal after removing the second sub-signal.

8. The photolithography method according to claim 1, wherein, Obtain the bending information of the photomask, including: Obtain height data at multiple locations of the photomask; Calculate the difference between the height data and the height reference value of the photomask, where the height reference value is the height of the preset plane of the photomask; The morphology curve of the photomask, including the bending information, is fitted using multiple calculated differences.

9. The photolithography method according to claim 8, wherein, The photomask is supported by opposing first and second edges to be positioned on the preset plane, and the photomask includes a first region from the first edge to the middle boundary line and a second region from the second edge to the middle boundary line; Acquiring height data at multiple locations of the photomask includes: acquiring height data at multiple locations within a target area, wherein the target area is either the first area or the second area; Fitting the topography curve of the photomask, which includes the bending information, using multiple calculated differences includes: fitting the topography curve of the target region using multiple calculated differences, and determining the topography curve of the photomask based on the topography curve of the target region.

10. A lithography machine, comprising: A processor, a memory, and a program stored in the memory and executable on the processor, wherein the program, when executed by the processor, implements the steps of the photolithography method as described in any one of claims 1-9.

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