Method for aligning a substrate, and positioning device

Abstract

The invention relates to a method for aligning a substrate (12) relative to a flat component (14), in particular a mask, comprising the following steps: detecting a component marking (20) of the component (14) using a front-side microscope (16); detecting the component marking (20) or a further component marking (20) of the component (14) using a rear-side microscope (22), wherein the front-side microscope (16) and the rear-side microscope (22) are arranged on different sides (18, 24) of the component (14); detecting a substrate marking (28) of the substrate (12) using the rear-side microscope (22); calculating an adjustment path (36) on the basis of the detected component marking(s) (20) and the detected substrate marking (28); aligning the component (14) relative to the substrate (12) by displacing the component (14) by the adjustment path (36), wherein a movement of the component (14) during the displacement is monitored using the front-side microscope (16). The invention also relates to a positioning device (10).

Description

[0001] Method for aligning a substrate and positioning device

[0002] The present invention relates to a method for aligning a substrate relative to a planar component, in particular a mask. Furthermore, the invention relates to a positioning device.

[0003] To manufacture micro- and / or nanostructured components, it is often necessary to precisely align components relative to each other, for example a substrate relative to a mask.

[0004] Bottom-side alignment is often used for this purpose, where positioning is based on substrate markings located on the back of a substrate. For this purpose, images of mask markings are first taken and the position of the mask is determined. The substrate is then loaded, images of the substrate markings are taken using back-side microscopes, and the position of the substrate is determined. The positions of the mask and substrate are compared, and an alignment movement is carried out. On many manually operated machines, this movement is carried out with the substrate. However, there are also automated machines where the alignment movement is carried out with the mask. In order to be able to check whether this movement was carried out correctly, the back-side microscopes on the automated machines are typically attached to the mask or mask manipulator so that they move with the mask.

[0005] This presents several problems. Since the backside microscopes are located on the mask or mask manipulator, they must be moved during alignment movements. This is mechanically difficult to implement and can cause the microscope images to drift, which in turn can lead to inaccuracies in positioning.

[0006] It is therefore an object of the invention to provide a method and system that enables technically simple and reliable positioning of a substrate relative to a planar component. This object is achieved according to the invention by a method for aligning a substrate relative to a planar component, in particular a mask, comprising the steps:

[0007] Capturing a component marking of the component with a front-side microscope;

[0008] Detecting the component marking or another component marking of the component with a back-side microscope, wherein the front-side microscope and the back-side microscope are arranged on different sides of the component;

[0009] Detecting a substrate mark of the substrate with the backside microscope;

[0010] Calculating an alignment path based on the detected component mark(s) and the detected substrate mark; and

[0011] - Aligning the component relative to the substrate by moving the component by the adjustment path, whereby any movement of the component during the movement is monitored with the front-side microscope.

[0012] The term mask includes photomasks, reticles and / or stencils.

[0013] In addition to a mask, the planar component can also be another substrate, such as a carrier substrate, wafer, and / or similar component. In particular, the planar component can also be another substrate to which the substrate can be bonded.

[0014] The planar component may also be a stamp, in particular a micro- or nano-stamp, with which a specific pattern can be embossed onto the substrate or an embossing material applied to the substrate.

[0015] The basic idea of ​​the invention is to divide the alignment process into the determination of an alignment error or an adjustment path necessary to correct the alignment error on the one hand and a check of the alignment movement on the other hand.

[0016] For this purpose, both the front-side microscope and the back-side microscope are used. The microscopes must be calibrated to each other, which is achieved primarily by capturing the component marking(s) with both the front-side microscope and the back-side microscope.

[0017] The alignment movement can then be monitored with the front-side microscope. This eliminates the need to attach the back-side microscopes to the mask or mask manipulator. This means significantly less mass needs to be moved compared to the conventional method.

[0018] By calibrating the microscopes to each other, not only possible alignment errors but also so-called run-out errors, i.e. errors in which there is a position-dependent misalignment with the component due to, for example, thermal expansion of the substrate, can be detected and compensated.

[0019] In one variant of the process, the position of the substrate is monitored with a backside microscope during alignment. This ensures that the substrate does not move while the component is being moved. Thus, the positions of the component and the substrate are monitored simultaneously during alignment, making the process particularly reliable.

[0020] If monitoring the movement of the component and / or the position of the substrate reveals a deviation from a target value, the alignment of the component relative to the substrate can be adjusted. Alignment errors that occur during the process can thus be corrected quickly and easily.

[0021] Preferably, the method comprises the step of placing the substrate between the backside microscope and the component. This step can be performed, in particular, after the component marking(s) have been detected with the backside microscope to ensure that the component marking(s) are not obscured by the substrate. In the case of a transparent substrate, this step can also be performed before the component marking(s) have been detected with the backside microscope.

[0022] In one embodiment of the method, the use of at least two front-side microscopes and at least two back-side microscopes is provided, with each front-side microscope and back-side microscope forming a microscope pair. At the same time, several component markings are provided laterally distributed across the component, with each of the microscope pairs capturing at least one of the component markings. By using multiple front-side microscopes and back-side microscopes, increased alignment accuracy and reliability of the method can be achieved.

[0023] Furthermore, several spaced-apart substrate markings can be provided, with each of the microscope pairs detecting at least one of the substrate markings. For example, each of the substrate markings can be assigned to one of the component markings and / or one of the microscope pairs. Such a 1:1 assignment is technically comparatively simple and can be implemented with little computational effort.

[0024] The alignment path can then be calculated based on the relative positions of the substrate markings to the component markings. In the simplest case, this can be done by subtracting the coordinates of the substrate markings and the associated component markings, as recorded by the microscope.

[0025] The method may further comprise the following step: determining a run-out error by comparing the relative positions of the substrate markings to the component markings. For example, if different values ​​result from the subtraction of the recorded coordinates of the substrate markings and the associated component markings for different microscope pairs, this may indicate a run-out error.

[0026] This can be quantified and corrected by appropriate countermeasures, such as heating or cooling the substrate. Here, too, the positions of both the substrate markings and the component markings can be recorded and monitored using the respective microscopes.

[0027] In this context, it is conceivable that heating or cooling the substrate could lead to a temperature change and thus a change in the size of the mask. However, this can be detected by the front-end microscopes and taken into account during adjustment. The temperature of the substrate is controlled, for example, by a closed-loop control system, where the relative positions of the substrate markings and the component markings detected by the microscopes, or a value derived from them, serve as the controlled variable, and the temperature is changed as the manipulated variable so that the desired positioning or expansion of the substrate relative to the component is achieved.

[0028] The object of the invention is further achieved by a positioning device for carrying out a method according to the invention for aligning a substrate relative to a planar component, in particular a mask, comprising: at least one front-side microscope arranged on a first side of the component and designed to detect a component marking of the component; at least one back-side microscope arranged on an opposite second side of the component and designed to detect the component marking or a further component marking of the component, and further designed to detect a substrate marking of the substrate; a computing unit designed and configured to calculate an adjustment path based on the detected component marking(s) and the detected substrate marking;and at least one actuator configured to displace the component relative to the substrate by the adjustment path;

[0029] The advantages discussed for the method apply to the positioning device in a corresponding manner.

[0030] Further advantages and features of the invention will become apparent from the following description and the accompanying drawings, to which reference is made. In the drawings:

[0031] Figure 1 schematically shows a positioning device when detecting an alignment mark of a mask; Figure 2 shows the positioning device from Figure 1 when detecting a substrate mark;

[0032] Figure 3 shows the positioning device from Figure 1 when aligning a component relative to a substrate; and

[0033] Figure 4 shows the positioning device of Figure 1 determining a run-out error.

[0034] Figure 1 schematically shows a positioning device 10 with which a method for aligning a substrate 12 relative to a planar component 14 can be carried out. In the exemplary embodiment, the component 14 is a horizontally arranged mask and the substrate 12 is a wafer.

[0035] The positioning device 10 comprises two front-side microscopes 16 arranged on a first side 18 of the component 14. The two front-side microscopes 16 are positioned horizontally spaced from one another and aligned such that they can each capture images of the component 14, in particular of component markings 20 of the component 14. In the exemplary embodiment, the component markings 20 are alignment markings of the mask.

[0036] The component markings 20 can be arranged on a surface of the component 14 or can extend through the component 14. For example, the component markings 20 can be cross-shaped openings in the component 14.

[0037] Furthermore, the positioning device 10 comprises two back-side microscopes 22, which are arranged on a second side 24 of the component 14 opposite the front-side microscopes 16. One front-side microscope 16 and one back-side microscope 22 each form a microscope pair 26. The two back-side microscopes 22 are each designed to detect the same component markings 20 as the front-side microscopes 16 assigned to them (for example, the cross-shaped openings) and / or other component markings 20 of the component 14.

[0038] The backside microscopes 22 are also configured to detect substrate markings 28 of the substrate 12. The positioning device 10 further comprises a computing unit 30, which is configured and configured to calculate an adjustment path based on the detected component markings 20 and the detected substrate markings 28.

[0039] Furthermore, the positioning device 10 has an actuator 32, for example a linear motor or a piezo element, with which the component 14 can be displaced relative to the substrate 12 by the adjustment path.

[0040] In the exemplary embodiment, the positioning device 10 also comprises a temperature control unit 34 for detecting and changing a temperature of the substrate 12.

[0041] The positioning device 10 is intended to carry out a method for aligning a substrate 12 relative to a planar component 14, in particular a mask.

[0042] An example of this procedure is briefly explained below.

[0043] At the beginning of the process, the positioning device 10 is unloaded. Therefore, no substrate 12 is yet arranged in the positioning device 10.

[0044] In a first step of the method, which is schematically shown in Figure 1, the front-side microscopes 16 take top-side images of the component 14 and thereby detect the component markings 20. In the exemplary embodiment, the component markings 20 are several horizontally distributed cross-shaped openings in the mask.

[0045] In a second step of the process, the backside microscopes 22 take images of the underside of the component 14 and thereby capture the same component markings 20.

[0046] In the exemplary embodiment, which is of course not to be understood as limiting, each pair of microscopes 26 detects exactly one of the component markings 20.

[0047] The first and second steps can be performed in parallel or sequentially in any order. The information acquired by the front-side microscopes 16 and the back-side microscopes 22 is transmitted to the processing unit 30. Based on this information, the processing unit can determine both the position of the component 14 and the exact positions of the front-side microscopes 16 and the back-side microscopes 22 relative to each other.

[0048] In a third step of the method, the substrate 12 is arranged between the backside microscopes 22 and the component 14.

[0049] Subsequently, in a fourth step of the process, images of the substrate underside are taken using the backside microscopes 22, thereby detecting substrate markings 28 located on the substrate underside. This is shown schematically in Figure 2.

[0050] In the exemplary embodiment, the substrate 12 has a plurality of spaced-apart substrate markings 28. Each of the substrate markings 28 is assigned to one of the component markings 20 and is detected by one of the back-side microscopes 22 or one of the microscope pairs 26. The information thus obtained is transmitted to the computing unit 30.

[0051] In a fifth step of the method, the computing unit 30 calculates an adjustment path 36 based on the detected component markings 20 and the detected substrate markings 28, in particular their relative positions to one another.

[0052] In a subsequent sixth step, the component 14 is aligned relative to the substrate 12. For this purpose, the actuator 32 displaces the component 14 by the adjustment path 36. This is shown schematically in Figure 3.

[0053] The movement of the component 14 or the component markings 20 is monitored with the front-side microscopes 16.

[0054] At the same time, the position of the substrate 12 is monitored with the backside microscopes 22 as the component 14 is moved. This can be done, for example, by taking images of the substrate markings 28 using the backside microscopes 22 during or after the component movement and comparing them with previously acquired images. Preferably, the substrate 12 does not move as the component 14 is moved.

[0055] In the event that monitoring the movement of the component 14 and / or monitoring the position of the substrate 12 reveals that there is a deviation from a target value, the alignment of the component 14 relative to the substrate 12 is adjusted in a further step.

[0056] If the microscope images reveal that an unintentional substrate displacement has occurred or that the component 14 has been displaced by too little or too much, the computing unit 30 can cause the actuator 32 to correct the deviation from the target state by a corresponding further displacement of the component 14. This ensures precise and error-free positioning.

[0057] Another unique feature of the method is that it can detect and correct not only alignment errors of the substrate 12 with respect to the component 14, but also run-out errors. This is shown schematically in Figure 4.

[0058] In the exemplary embodiment, a further method step is provided for this purpose, in which the relative positions of the substrate markings 28 and component markings 20 are compared with one another. For example, if a first offset 38 of a substrate marking 28 and associated component marking 20 is detected using one of the microscope pairs 26, and a second offset 40 of a substrate marking 28 and associated component marking 20 is detected using a spaced-apart further microscope pair 26, the run-out error can be determined from the offset difference.

[0059] The run-out error is then compensated in a further process step. In the exemplary embodiment, this is done by the computing unit 30 causing the temperature control unit 34 to heat the substrate 12 so that it expands, thereby correcting the run-out error.

[0060] Of course, alternatively, active cooling of the substrate 12 can also be provided for run-out error correction. In the exemplary embodiment, heating or cooling the substrate 12 also causes a temperature change and thus a size change of the planar component 14 (i.e., the mask). This change is recorded with the front-side microscopes 16 and taken into account during adjustment.

Claims

Patent claims 1. A method for aligning a substrate (12) relative to a planar component (14), in particular a mask, comprising the steps: Detecting a component marking (20) of the component (14) with a front-side microscope (16); Detecting the component marking (20) or another component marking (20) of the component (14) with a backside microscope (22), wherein the frontside microscope (16) and the backside microscope (22) are arranged on different sides (18, 24) of the component (14); Detecting a substrate marking (28) of the substrate (12) with the backside microscope (22); Calculating an adjustment path (36) based on the detected component mark(s) (20) and the detected substrate mark (28); Aligning the component (14) relative to the substrate (12) by moving the component (14) by the adjustment path (36), wherein a movement of the component (14) during the movement is monitored with the front-side microscope (16).

2. The method according to claim 1, wherein a position of the substrate (12) is monitored during alignment with the backside microscope (22).

3. The method according to claim 2, wherein, if monitoring the movement of the component (14) and / or monitoring the position of the substrate (12) reveals that there is a deviation from a desired value, the alignment of the component (14) relative to the substrate (12) is readjusted.

4. Method according to one of the preceding claims, comprising the intermediate step: arranging the substrate (12) between the backside microscope (22) and the component (14).

5. Method according to one of the preceding claims, wherein at least two front-side microscopes (16) and at least two back-side microscopes (22) are provided, wherein in each case one front-side microscope (16) and one back-side microscope (22) form a microscope pair (26), wherein several component markings (20) distributed over the component (14) are provided and wherein each of the microscope pairs (26) detects at least one of the component markings (20).

6. The method according to claim 5, wherein a plurality of spaced-apart substrate markings (28) are provided and wherein each of the microscope pairs (26) detects at least one of the substrate markings (28).

7. The method according to claim 6, wherein the adjustment path (36) is calculated based on the relative positions of the substrate markings (28) to the component markings (20).

8. The method according to claim 6 or 7, comprising the step of: determining a run-out error by comparing the relative positions of the substrate markings (28) to the component markings (20).

9. The method according to claim 8, comprising the step of: at least partially compensating for the run-out error, in particular by changing a temperature of the substrate (12).

10. A positioning device for carrying out a method according to one of the preceding claims for aligning a substrate (12) relative to a planar component (14), in particular a mask, comprising: at least one front-side microscope (16) arranged on a first side (18) of the component (14) and configured to detect a component marking (20) of the component (14); at least one back-side microscope (22) arranged on an opposite second side (24) of the component (14) and configured to detect the component marking (20) or another component marking (20) of the component (14), and further configured to detect a substrate marking (28) of the substrate (12); a computing unit (30) configured and configured to calculate an adjustment path (36) based on the detected component marking(s) (20) and the detected substrate marking (28); and at least one actuator (32) which is designed to displace the component (14) relative to the substrate (12) by the adjustment path (36).

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