Pattern forming unit and method and apparatus for alignment

Abstract

Alignment marks are effectively detected in alignment performed in a pattern forming device such as an exposure device. The exposure device (10) is equipped with a table (45) on which a substrate (W), which is a silicon wafer, is placed, and an alignment measuring device (60), and a plurality of openings (AT) are installed on the substrate placement surface (45S) of the table (45). The openings (AT) have opening sizes in which pattern areas (dies) (PT) and alignment marks (AR) are placed in a grid shape parallel to each other on the substrate (W).

Description

Technology Field

[0001] The present invention relates to alignment of a pattern forming device such as an exposure device, and in particular to the detection of an alignment mark from the back side of a substrate. Background Technology

[0003] In a pattern forming device such as an exposure device, an alignment mark formed on a substrate is captured, and alignment is performed based on the measured mark position. For example, in a process for manufacturing a stacked device, a circuit is formed that conducts between the surface side of the substrate and the back side of the substrate, and a metal layer is formed as an intermediate layer, so an alignment mark is formed not only on the surface side of the substrate but also on the back side or the intermediate layer.

[0004] When an alignment mark formed on the back side of the substrate or on an intermediate layer is captured from the back side of the substrate, i.e., the table side of the stage, an optical system for detecting the alignment mark is placed inside the table (stage) on which the substrate is mounted (see Patent Documents 1 and 2). The alignment mark is illuminated, and the reflected light is formed into an image using a camera or a microscope to detect the image of the alignment mark. Prior art literature

[0006] Japanese Patent Publication No. 2002-280299 and Japanese Patent Publication No. 2019-158926 The problem to be solved

[0007] The size of the alignment mark is determined to enable high-precision positioning. Meanwhile, the size of the die (chip) that forms the pattern area on the substrate is determined by the characteristics and specifications of the pattern forming device, the manufacturing process of the preceding process, etc.

[0008] For example, when a reticle pattern is transferred to a silicon wafer by a projection exposure device, the size of the chip (die) formed on the silicon wafer depends on the reticle size. For example, if the reticle size is 6 inches, it is possible to make the size up to 26 mm × 33 mm.

[0009] Therefore, when detecting alignment marks installed on a substrate mounted on a table from the back side of the substrate, the size of the alignment marks is minute compared to the pattern area, so a situation occurs where they fall outside the imageable range. It is necessary to adjust the position of the substrate to a location where the alignment marks can be detected, making it difficult to perform efficient and high-precision alignment. In addition, there are cases where the placement of the die (chip) must be restricted so that the placement range of alignment marks, such as scribe lines, comes into an imageable position.

[0010] Therefore, in alignment performed in a pattern forming device such as an exposure device, it may be required to be able to effectively detect alignment marks. means of solving the problem

[0012] An alignment device, which is one embodiment of the present invention, can be applied to a pattern forming device such as an exposure device or a laser processing device.

[0013] The alignment device comprises a table having at least one opening on the substrate mounting surface and a substrate mounting surface having a plurality of pattern areas, and an alignment mark measuring unit capable of capturing an alignment mark formed on the substrate from the substrate mounting surface side of the table through the opening.

[0014] The formation location of alignment marks varies. For example, alignment marks can be formed outside the pattern area of ​​the substrate. Additionally, the pattern area can be set to be aligned in a grid shape.

[0015] The substrate can be composed of a semiconductor wafer. In addition, the aperture size of the aperture can be determined according to the reticle size, the reduction ratio of the projection optical system, etc. For example, it can be configured to be larger than the size of the pattern area according to the maximum size of the reticle. The maximum size of the pattern area is determined based on the manufacturing process including the semiconductor front-end process, and for example, in the case of a projection ratio of 1 / 4 and a reticle of 6 inches, it is determined to be 33mm × 26mm.

[0016] In the present invention, the opening has an opening size that includes a pattern area and a boundary portion around it along at least one direction. For example, when the substrate is composed of a silicon wafer, the scribe line corresponds to the boundary portion.

[0017] The configuration of the shape and location of the openings varies under conditions that satisfy the opening size. For example, the opening size can be made such that the width along one direction of the opening is larger than the sum of the width along one direction of the pattern area and the width along one direction of the alignment mark. In addition, it is possible to form at least three openings in the table so that global alignment can be performed.

[0018] An alignment device in another embodiment of the present invention comprises a table having at least one opening installed on the substrate mounting surface, a table having a substrate having a plurality of pattern areas, an alignment mark measuring unit that captures an alignment mark formed on the substrate through the opening from the substrate mounting surface side of the table, and an alignment correction amount calculating unit that calculates an alignment correction amount based on position information of the alignment mark, wherein the opening has an opening size that includes a pattern area and a surrounding boundary portion along at least one direction.

[0019] Another embodiment of the present invention is an alignment method in which, for a table having a substrate having a plurality of pattern areas, at least one opening is provided on the substrate mounting surface, the substrate is mounted on the table, an alignment mark formed on the substrate is captured through the opening from the substrate mounting surface side of the table, and alignment is performed based on the position of the image of the alignment mark, wherein the opening has an opening size that includes a pattern area and a surrounding boundary portion along at least one direction. Effects of the invention

[0021] According to the present invention, alignment marks can be effectively detected in alignment performed in a pattern forming device such as an exposure device. Brief explanation of the drawing

[0023] FIG. 1 is a schematic block diagram of a projection exposure apparatus according to the present embodiment. Figure 2 is a diagram illustrating the schematic configuration of an alignment measuring device. Figure 3 is a top view of a table on which a substrate is placed. Figure 4 is a drawing illustrating a modified example of an opening. Figure 5 is a drawing illustrating another variation of the opening. Specific details for implementing the invention

[0024] Hereinafter, an alignment measuring device and a pattern forming device equipped with the same will be described with reference to the drawings.

[0025] FIG. 1 is a schematic block diagram of a projection exposure apparatus according to the present embodiment.

[0026] The exposure device (10) is a projection exposure device that transfers a reticle pattern formed on a reticle (R) to a substrate (work) (W) according to a step and repeat method, and is equipped with a light source (20), a reticle stage (30), a projection optical system (34), and a substrate stage (40). The substrate (W) is, in this case, composed of a silicon wafer.

[0027] Illuminating light emitted from the light source (20) enters the integrator (24) through the mirror (22). The illuminating light, with its light intensity made uniform, enters the collimator lens (28) through the mirror (26). As a result, parallel light enters the reticle (R).

[0028] A mutually orthogonal XYZ coordinate system is defined in the stage (30) where the reticle (R) is placed and the stage (40) where the substrate (W) is placed. The reticle stage (30) and the substrate stage (40) are movable in the X direction and the Y direction, and are driven by the reticle stage driving unit (32) and the substrate stage driving unit (42), respectively. In addition, the reticle stage (30) and the substrate stage (40) are rotatable around the Z axis perpendicular to the XY plane.

[0029] The pattern light transmitted through the reticle (R) is formed on the photosensitive surface of the substrate (W) by the projection optical system (34). The substrate stage (40) is moved according to the step-and-repeat method to sequentially transfer the reticle pattern to the pattern area (shot area) that forms the pattern. The projection magnification of the projection optical system (34) is set to 1x here.

[0030] The alignment measuring device (60) captures an alignment mark installed on the substrate (W) according to an off-axis method. The alignment measuring device (60) is equipped with an imaging device (65) configured by a camera or microscope and an alignment optical system (70), and captures the alignment mark from the back side of the substrate (W), i.e., the stage (40) side.

[0031] The imaging device (65) can be moved in the X and Y directions by means of an actuator not shown. The image processing unit (80) detects the position coordinates of the alignment mark based on the image signal sent from the alignment measurement device (60).

[0032] The control unit (50) controls the lamp driving unit (21), the reticle stage driving unit (32), and the substrate stage driving unit (42), and performs an exposure operation according to the step & repeat method. In addition, the control unit (50) controls the driving of the imaging device (65) of the alignment measurement device (60) and moves the imaging device (65) to a position where an alignment mark can be captured.

[0033] FIG. 2 is a diagram illustrating the schematic configuration of an alignment measuring device (60).

[0034] An alignment mark (AR) is formed on the back side of the substrate (W), that is, on the substrate mounting surface (45S) where the substrate (W) contacts the table (45). Additionally, an alignment mark (AR) is formed on the intermediate layer of the substrate (W).

[0035] The alignment optical system (70) of the alignment measuring device (60) comprises a first alignment optical system (72) that forms a relay optical system with the optical system of the imaging device (65), and a second alignment optical system (74) that is positioned below the table (45) of the stage (40) and forms a relay optical system with the first alignment optical system (72).

[0036] An opening (AT) is formed on the substrate mounting surface (45S) of the table (45). The alignment optical system (70) transmits or reflects light from the lighting device (76) and illuminates the alignment mark (AR) installed on the substrate (W) through the opening (AT).

[0037] Light reflected by illumination of the alignment mark (AR) enters the second alignment optical system (74) through the aperture (AT). The light entered into the second alignment optical system (74) passes through the second alignment optical system (74) and the first alignment optical system (72) and forms an image on the imaging surface of the imaging device (65). By doing so, an image of the alignment mark (AR) is detected.

[0038] By detecting the alignment mark (AR) from the substrate mounting surface (45S), the alignment mark (AR) can be captured even if a metal layer or the like is formed on the intermediate layer of the substrate (W).

[0039] In addition, instead of the off-axis method, the alignment mark (AR) may be detected by the TTL (through the lens) method. Also, the second alignment optical system (74) may be configured as a mirror, or an optical system combining a mirror and a prism.

[0040] FIG. 3 is a top view of a table (45) on which a substrate (W) is placed. Using FIG. 3, an opening (AT) formed in the table (45) will be described.

[0041] In the table (45), a plurality of openings (AT) (here, 4) are formed to correspond to the position where the substrate (W) is placed. The plurality of openings (AT) are all of the same size and are formed at positions facing the four corners of the substrate (W). A plurality of alignment measuring devices (60) (here, 4) are installed to correspond to the number of openings (AT).

[0042] As shown in FIG. 3, dies (chips) (PTs) are formed in a grid shape on a substrate (W) composed of a silicon wafer. In an exposure device (10), batch exposure is performed on the dies (PTs) as a shot area (hereinafter, the dies (PTs) are referred to as pattern areas).

[0043] A scribe line (SB) serving as a boundary area is formed between adjacent pattern areas (PT). Additionally, a cross-shaped alignment mark (AR) is installed on the scribe line (SB). The alignment mark (AR) may have a shape other than a cross.

[0044] The size of the pattern area (PT) is determined according to the reticle size, the reduction ratio of the projection optical system (34), etc. For example, in the case of a 6-inch reticle, the maximum size of the pattern area (PT) is set to 33 mm × 26 mm. However, the projection ratio is set to 1 / 4.

[0045] The opening (AT) is larger than the pattern area (PT) that becomes the maximum size and has an opening size that accommodates the pattern area (PT). Therefore, with respect to the X direction in which the alignment mark (AR) is parallel, the width (W3) of the opening (AT) is greater than the sum of the width (W1) of the pattern area (PT) along the X direction and the width (W2) of the alignment mark (AR).

[0046] The size of the alignment mark (AR) is very small compared to the size of the pattern area (PT). Therefore, the opening size of the opening (AT) can be set to be slightly larger (e.g., about 1 or 2 mm) than the maximum size of the pattern area (PT) in the X direction. For example, the opening (AT) can be set to a size that does not overlap with an adjacent pattern area.

[0047] By determining the opening size of the opening (AT) in this way, when the substrate (W) is placed at a predetermined position on the table (45), at least one alignment mark (AR) enters the opening (AT). Accordingly, the imaging device (65) can detect the alignment mark (AR) of the substrate (W) through the opening (AT).

[0048] Since the imaging device (65) accurately detects alignment marks (AR) of a micro-size of several µm to several hundred µm, the camera field of view is set to a very narrow range (e.g., 1 mm or less). As described above, since at least one alignment mark (AR) is located in a position that enters the opening (AT), the alignment mark (AR) can be captured without reinstalling the substrate (W).

[0049] Meanwhile, since the size of the opening (AT) is not large enough to capture two adjacent pattern areas, the camera movement range of the imaging device (65) is suppressed. Additionally, when the pattern area (PT) is smaller than the maximum size of the reticle, it is naturally possible to capture the alignment mark (AR).

[0050] Also, even if alignment marks (AR) are installed on the pattern area (PT), at least one alignment mark (AR) is positioned to enter the opening (AT) so that it can be captured.

[0051] A reference mark that is not shown is installed on the table (45). The reference mark is captured by the imaging device (65), and the reference position of the alignment measurement device (60) is corrected. The control unit (50) detects the misalignment of straightness in the global alignment area, rotational error, and scaling error caused by linear stretching of the substrate (W) based on the position coordinates of the alignment mark sent from the image processing unit (80). Then, the alignment correction amount (offset value, scaling value, rotational correction amount) is calculated, and the positions of the reticle stage (30) and the substrate stage (40) are adjusted.

[0052] The alignment measuring device (60) is installed in four units according to the position of the opening (AT) here, but it is also possible to configure it so that one alignment measuring device (60) is moved. For example, it is good to arrange four second alignment optical systems (74) according to the position of the opening (AT) and share the first alignment optical system (72) and the imaging device (65).

[0053] Regarding the number of openings (AT), it is preferable to have a configuration in which at least three are installed to enable global alignment. Alternatively, it is possible to adopt a die-by-die method instead of global alignment, and it is preferable to have at least one opening (AT). The formation position of the opening (AT) should be determined so that it overlaps with at least a portion of one die when the substrate (W) is mounted.

[0054] FIGS. 4 and 5 are drawings illustrating variations of the opening. In FIG. 4, the opening (AT') is formed in a circular shape. In FIG. 5, the opening (AT") is formed in a rectangular shape, and with respect to the X direction, the width (W3) of the opening (AT") is larger than the width (W1) of the pattern area (PT) and the width (W2) of the alignment mark (AR).

[0055] The opening (AT) does not have an opening size that surrounds the entire pattern area (PT), but has an opening size that allows a part of the scribe line (SB) to enter with respect to the X direction in which the alignment marks (AR) are lined up, so the alignment marks (AR) can be detected by the imaging device (65). Also, when installing multiple openings (AT), different shapes or sizes may be combined.

[0056] As described above, the exposure apparatus (10) of the present embodiment is equipped with a table (45) on which a substrate (W), which is a silicon wafer, is placed, and an alignment measuring device (60), and a plurality of openings (AT) are installed on the substrate placement surface (45S) of the table (45). The openings (AT) have opening sizes that accommodate pattern areas (dies) (PT) and alignment marks (AR) arranged in a grid shape on the substrate (W).

[0057] With this configuration, various die arrangements are possible, and even when global alignment is performed, the die arrangement is not limited by the position or size of the opening (AT).

[0058] Regarding the substrate (W), it is possible to configure it with a substrate other than a silicon wafer (semiconductor wafer), for example, a printed circuit board. In addition to the pattern area (die), it is preferable to form an opening so that an alignment mark installed at the boundary of an adjacent pattern area can be captured.

[0059] It is possible to apply the above-described alignment measurement device (60) to a pattern forming device (e.g., a laser processing device) other than the projection exposure device (10). In this case, it is preferable to determine the opening size of the opening according to the pattern area size (especially the maximum size) determined by the characteristics or specifications of the pattern forming device or the manufacturing process. Explanation of the symbols

[0061] 10 Exposure device 40 stages 45 tables 50 control unit 60 alignment measuring device 70 alignment optical system 80 Image processing unit AT opening PT pattern area

Claims

Claim 1 A pattern forming device comprising a table having at least one opening installed on the substrate mounting surface and a substrate mounting surface having a plurality of pattern areas, and an alignment mark measuring unit capable of capturing an alignment mark formed on the substrate from the substrate mounting surface side of the table through the opening, wherein the opening has an opening size that includes the pattern area and the surrounding boundary portion along at least one direction. Claim 2 A pattern forming device according to claim 1, characterized in that the width along one direction of the opening is greater than the sum of the width along one direction of the pattern area and the width along one direction of the alignment mark. Claim 3 A pattern forming device according to claim 1, characterized in that at least three openings are formed in the table. Claim 4 An alignment device according to claim 1, characterized in that the substrate is a semiconductor wafer. Claim 5 A pattern forming device according to claim 1, characterized in that the opening size of the opening is larger than the size of the pattern area according to the maximum size of the reticle. Claim 6 A pattern forming device according to claim 1, characterized in that the alignment mark is formed outside the pattern area of ​​the substrate. Claim 7 A pattern forming device according to claim 1, characterized in that the pattern area is arranged in a grid shape. Claim 8 A pattern forming device characterized by being an exposure device in any one of claims 1 to 7. Claim 9 A pattern forming device characterized by being a laser processing device in any one of claims 1 to 7. Claim 10 An alignment device comprising: a table having at least one opening installed on the substrate mounting surface, a table having a substrate with a plurality of defined pattern areas; an alignment mark measuring unit that captures an alignment mark formed on the substrate from the substrate mounting surface side of the table through the opening; and an alignment correction amount calculating unit that calculates an alignment correction amount based on position information of the alignment mark, wherein the opening has an opening size that includes the pattern area and the surrounding boundary portion along at least one direction. Claim 11 An alignment method comprising, for a table having a substrate having a plurality of defined pattern areas, at least one opening on the substrate mounting surface, mounting the substrate on the table, capturing an alignment mark formed on the substrate through the opening from the substrate mounting surface side of the table, and performing alignment based on the position of the alignment mark, wherein the opening has an opening size that includes the pattern area and the surrounding boundary portion along at least one direction.

Images