JP6253269B2 - Lithographic apparatus, lithographic method, and article manufacturing method using the same - Google Patents

Description

  The present invention relates to a lithographic apparatus, a lithographic method, and an article manufacturing method using the same.

A lithographic apparatus is an apparatus that forms a pattern on a substrate (such as a wafer having a resist layer formed thereon ) using an original plate (reticle, mold, etc.) in a lithography process included in a manufacturing process of a semiconductor device, a liquid crystal display device, etc. ( Pattern forming apparatus ). In recent years, with the progress of miniaturization of patterns formed in the lithography process and the improvement in resolution, there has been a demand for higher accuracy in substrate surface position detection (focus measurement).

  Generally, as a focus detection system for detecting the surface position of a substrate, a focal plane detection device that detects the position of reflected light by irradiating the substrate with detection light obliquely from above is used. However, for example, when a resist layer (thin film) is formed on the surface of the substrate, the light reflected on the surface of the resist layer interferes with the light transmitted through the resist layer and reflected on the surface of the substrate. The interference light beam may form an image on the detection unit. In addition, the focal plane detection device needs to measure the surface of the substrate finely, but when a concavo-convex pattern (for example, a circuit pattern) exists on the substrate, if it is made to follow the concavo-convex pattern one by one, A stage that movably holds the substrate oscillates. Such oscillation may reduce image contrast and is not preferable from the viewpoint of focus accuracy. Therefore, a detection error amount (offset value) caused by the interference light, an offset value caused by the shape of the concavo-convex pattern, and the like are measured in advance and reflected in the detection result. In this connection, Patent Document 1 discloses a surface position detection method for subtracting an offset generated due to a detection error amount and the shape of a concavo-convex pattern from a focus measurement value (surface height of a substrate). In this surface position detection method, the offset value is obtained based on the measured values of the surface height in a plurality of sample shots existing on the substrate.

JP-A-9-45608

  However, if there is a specific area on the surface of the substrate, the offset value as described above may be affected by the measurement value in that area. FIG. 6 is a diagram illustrating a state of a concavo-convex pattern accompanying deformation of a conventional substrate. First, in FIG. 6A, the substrate 201 has a shape close to a secondary paraboloid, and uneven patterns 202 </ b> A to 202 </ b> F are formed on each sample shot on the substrate 201. In this case, in order to obtain an offset value corresponding to the pattern structure, the heights of the concave and convex patterns 202A to 202F are measured. The measurement result 203A is simply averaged to calculate a height distribution (corresponding to the offset value distribution) 203B. In the example shown in FIG. 6A, the arrangement of the concave and convex patterns 202A to 202F is substantially symmetric, so that the offset value is relatively accurately obtained by simply averaging the height measurement results. Can be sought.

  On the other hand, for example, foreign matter exists between the substrate and the holding table (chuck) that holds the substrate, or the substrate warps due to other processes such as heat treatment. The shape of the substrate is not necessarily a parabolic shape as described above. In FIG. 6B, the substrate 204 is warped due to other processes, and uneven patterns 205A to 205F are formed in each sample shot on the substrate 204. In this case, when the heights of the concavo-convex patterns 205A to 205F are measured and the measurement result 206A is simply averaged, the height distribution 206B is affected by the non-uniformity of the substrate shape, as shown in FIG. The shape is inclined to. That is, in this case, since the offset value distribution corresponding to the pattern structure cannot be calculated with high accuracy, the height measurement value of the substrate surface corrected using this offset value cannot be obtained with high accuracy, and the result In particular, the focus accuracy decreases.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a lithographic apparatus that is advantageous for obtaining the surface position of a substrate with high accuracy, for example.

In order to solve the above-mentioned problem, the present invention is a pattern forming apparatus for forming a pattern on a substrate having a plurality of shots, and detecting the height of the surface of a sample shot included in the plurality of shots on the substrate system and obtains a first surface height information by subtracting the offset value from the value of the height of the surface in the detected sample shot by the detection system, the error amount of the offset value generated when calculating the offset value And a controller for subtracting the error amount of the offset value from the first surface height information to obtain the second surface height information.

  According to the present invention, for example, it is possible to provide a lithographic apparatus that is advantageous in obtaining the surface position of a substrate with high accuracy.

It is a figure which shows the structure of the exposure apparatus which concerns on 1st Embodiment of this invention. It is a flowchart which shows the flow of exposure in 1st Embodiment. It is a figure which shows the measurement position in a sample shot. It is a figure which shows arrangement | positioning of the sample shot on a wafer. It is a flowchart which shows the flow of exposure in 2nd Embodiment. It is a figure which shows the state of the uneven | corrugated pattern accompanying a deformation | transformation of a wafer. It is a wafer surface height map after offset value removal.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

(First embodiment)
First, a lithographic apparatus according to a first embodiment of the invention will be described. FIG. 1 is a schematic diagram showing a configuration of an exposure apparatus 100 according to the present embodiment. In the first embodiment, as a lithography apparatus, a projection type that is used in a semiconductor device manufacturing process and exposes (transfers) a pattern formed on a reticle LT on a wafer WF (on a substrate) by a step-and-repeat method. An exposure apparatus will be described. The exposure apparatus 100 includes an illumination system 8, a reticle stage 4, a projection optical system 9, a wafer stage 7, an alignment detection system 10, a focus detection system 11, and a control unit 12. In FIG. 1, the Z axis is taken in parallel to the optical axis of the projection optical system 9 (vertical direction in the present embodiment), and the X axis is taken in the scanning direction of the wafer WF during exposure in a plane perpendicular to the Z axis. The Y axis is taken in the non-scanning direction orthogonal to the X axis. The illumination system 8 adjusts light emitted from a light source (not shown) and illuminates the reticle LT. The reticle LT is an original made of, for example, quartz glass on which a pattern (for example, a circuit pattern) to be transferred is formed on the wafer WF. The reticle stage 4 is movable in the XY axial directions while holding the reticle LT. The projection optical system 9 projects the image of the pattern on the reticle LT illuminated with the light from the illumination system 8 onto the wafer WF at a predetermined magnification (for example, 1/2 to 1/5). The wafer WF is a substrate made of single crystal silicon, for example, having a resist (photosensitive agent) applied on the surface thereof. The wafer stage 7 is movable in the XYZ axial directions while holding the wafer WF. Although not shown, the alignment detection system 10 includes a projection system that projects detection light onto a reference mark on the wafer WF, and a light receiving system that receives reflected light from the reference mark, and the X axis of the wafer WF. And a position in the Y-axis direction (alignment position) are detected. For example, the alignment detection system 10 may be an off-axis alignment detection system that can optically detect a reference mark on the wafer WF without using the projection optical system 9.

  The focus detection system (detection system) 11 is a focal plane detection device, and includes a projection system 11a that projects detection light toward the surface of the wafer WF, and a light receiving system 11b that receives the reflected light. A position (surface position) in the Z-axis direction is detected. The projection system 11a and the light receiving system 11b are provided to face the reference mark for the alignment detection system 10 obliquely upward. The surface position of the wafer WF detected using the focus detection system 11 is an offset value generated by a detection error of the light receiving system 11b as a detection unit or an offset value resulting from the state of the concavo-convex pattern (hereinafter collectively referred to as “offset value”). Is referred to in calculating "."

  The control unit 12 can control the operation and adjustment of each component of the exposure apparatus 100. The control unit 12 is configured with, for example, a computer, and is connected to each component of the exposure apparatus 100 via a line, and can control each component according to a program or the like. The control unit 12 may be configured integrally with other parts of the exposure apparatus 100 (in a common casing), or separate from the other parts of the exposure apparatus 100 (in a separate casing). It may be configured.

  Next, a method for obtaining a measurement value by the focus detection system 11 with high accuracy by obtaining and applying an error of the offset value itself will be described. As described above, the offset value is obtained by measuring the surface (including the concave / convex pattern) of the wafer WF in advance using the focus detection system 11 and averaging the height information of the measured multiple shots (pattern formation regions). Can be calculated. For example, in the case of the so-called single stage type exposure apparatus 100 exemplified in the present embodiment, the offset value is calculated based on the unevenness information in a preselected sample shot. In particular, as described with reference to FIG. 6B, when there is a specific region on the surface of the wafer WF, for example, a portion having an abnormal inclination, the calculated offset value itself is affected. FIG. 7 is a wafer surface height map after offset value removal. The shape of the wafer surface after removing the offset value has a first-order inclination for each shot. When the wafer 301 is warped as shown in FIG. 7, the surfaces 302A to 302F after the offset value removal do not have a smooth shape. Therefore, in the present embodiment, as described below, an error amount that can occur when calculating the offset value is obtained, and the height information of the wafer WF from which the offset value has been removed (subtracted) (the “surface height map” described later). And the same meaning).

  Here, the shape of the wafer WF having no underlying pattern such as a concavo-convex pattern is influenced by the holding table for holding the wafer WF and the warp caused by the process. However, even if affected by the shape of the wafer WF, the amount of variation in the measured value is small when viewed in a local region such as several mm. In recent years, the focus measurement interval has become smaller due to the demand for higher accuracy and the improvement in the response speed of the sensor (detection unit), so that measured values at adjacent measurement points (measurement targets) in consecutive shots. It can be considered that the difference is almost negligible. Therefore, this feature is used to remove the offset error amount.

  FIG. 2 is a flowchart showing the flow of exposure processing in the present embodiment. First, the control unit 12 causes the focus detection system 11 to measure the surface position of the wafer WF and creates a surface height map (step S101). Next, the control unit 12 calculates an offset value related to the focus detection system 11 including information on the concavo-convex pattern (for example, shape information) and a sensor detection error, and subtracts it from the surface height map obtained in step S101. (Step S102). The result obtained at this time is the surface height map (first surface position information) after the offset value removal shown in FIG.

  Next, the control unit 12 calculates the amount of error that can occur when obtaining the offset value, and subtracts it from the surface height map after the offset value removal obtained in step S102 (step S103). Here, the shape 301 of the wafer WF after the offset value is removed is expected to have a smooth shape by removing the uneven pattern due to the uneven pattern and sensor measurement error. Therefore, the step components (step amounts) that can be observed at the boundary positions 303AB to 303EF of each sample shot shown in FIG. 7 are considered to be due to the first-order calculation error component of the offset value.

FIG. 3 is a plan view showing measurement positions in two adjacent sample shots in the present embodiment. In this case, from the following equation (1) using the measurement value difference between the closest measurement points for the adjacent sample shots and the distance L between the two points selected as the closest measurement points in the sample shot, The corrected inclination amount ΔT is calculated.
ΔT = Average (D1, D2, D3,..., D_maximum number of shots) / L (1)
However, (D1, D2, D3,..., D_maximum number of shots) is a measured value difference when D is a step component between adjacent sample shots after the offset value is removed. Two adjacent sample shots illustrated in FIG. 3 (one first sample shot S1 and the other second sample shot S2) include measurement points 401A and 401B and 402A and 402B, respectively, on the surface thereof. Among these, the measurement points 401A and 402A and the measurement points 401B and 402B are set to be the same location in each sample shot of the first sample shot S1 and the second sample shot S2. These measurement points can be appropriately set according to the state of the sample shot, and are not limited to those arranged on the top and bottom of the paper as shown in FIG. 3, but may be those arranged on the left and right of the paper. The distance L is, for example, the length between the measurement points 401A and 401B, and the measurement value difference between the measurement points 401A and 402B is a step component at the shot boundary position. Then, the offset value ΔT that can be generated by the influence of the deformation of the wafer WF, for example, is obtained by subtracting the correction inclination amount ΔT calculated here as an error amount related to the offset value and subtracting it from the surface height map after the offset value removal shown in FIG. Error can be reduced, and highly accurate offset correction can be performed.

  In the single stage type exposure apparatus such as the exposure apparatus according to the present embodiment, the surface of the wafer WF is measured in advance for a plurality of sample shots. Conventionally, in order to cancel the overall shape of the wafer WF on average, the sample shots are distributed over as wide a region as possible on the wafer WF, such as sample shots 501A to 501H illustrated in FIG. Was selected. On the other hand, according to the present embodiment, it is possible to remove the error amount of the offset value that may be generated due to the deformation of the wafer WF. Therefore, for example, as shown in FIG. 4B, a plurality of sample shots 502A to 502I that are adjacent to each other (adjacent) can be set, so that the drive area of the wafer stage 7 is also reduced, and throughput is improved. This is also advantageous from the viewpoint of

  Then, the control unit 12 drives the wafer stage 7 based on the final surface height map (second surface position information) obtained in step S103 to perform exposure processing. The surface height map used at this time has a smooth shape after the error amount of the offset value is removed, and the focus detection system 11 can obtain the surface position of the wafer WF with high accuracy. Thereby, the wafer stage 7 is positioned at a desired position as much as possible, and the exposure apparatus 100 can realize highly accurate exposure as a result.

  As described above, according to the present embodiment, it is possible to provide a lithography apparatus and a lithography method that are advantageous in obtaining the surface position of the substrate with high accuracy.

(Second Embodiment)
Next, a lithographic apparatus according to a second embodiment of the invention will be described. In the first embodiment, it has been described that the arrangement of sample shots on the wafer WF is suitable when they are adjacent to each other as shown in FIG. On the other hand, the lithographic apparatus according to the present embodiment can be applied when the arrangement of sample shots is such that the interval between adjacent sample shots is large, that is, not adjacent, as shown in FIG. is there. If the interval between adjacent sample shots is wide, the difference in the closest measured value between sample shots is affected by the flatness of the wafer WF. Here, it is considered that the shot size (shot angle of view) is generally 26 × 33 mm. In this case, when two adjacent sample shots are arranged exceeding the shot size, it is less affected by the flatness if the error amount of the offset value is calculated from the measured value in the same sample shot. . At this time, from the following equation (2) using a measured value difference at any two measurement points in a certain sample shot and a distance l (lowercase letter L) between the two measurement points, 1 The next corrected inclination amount ΔT is calculated.
Δt = Average (d1, d2, d3,..., D_maximum number of shots) / l (2)
However, (d1, d2, d3,..., D_maximum number of shots) is a measurement value difference when d is a step component between two measurement points after the offset value is removed.

  Note that if two measurement points with an extremely narrow interval are set in one sample shot, the measurement error increases due to the influence of measurement reproducibility of the sensor (detection unit). Therefore, when setting two measurement points, it is desirable to set the distance between the two measurement points to be the longest, for example, the upper and lower ends in the sample shot. In addition, it is conceivable that high detection accuracy cannot be obtained in a sample shot in which the focus fluctuation amount becomes large due to the influence of edge roll-off or foreign matter. Therefore, for sample shots in which the residual or slope of the approximate plane obtained from the measurement results of the sample shots exceeds a preset threshold based on the warpage amount predicted by the process characteristics, the sample to be actually used It may be excluded from the shot.

  FIG. 5 is a flowchart showing a flow of an exposure process as an example in the present embodiment based on the above contents. First, steps S201 and S202 are the same as steps S101 and S102 in FIG. 2 of the first embodiment. Next, the control unit 12 refers to the surface height map obtained in step S202, and compares the closest measurement interval (distance) between adjacent sample shots with the shot size (step S203). Here, when the control unit 12 determines that the measurement interval is smaller than the shot size (Yes), similar to the first embodiment, the vicinity measurement between adjacent sample shots (including the case where the sample shots are adjacent) is performed. An offset calculation error amount is obtained from the point and subtracted (step S204). On the other hand, when the control unit 12 determines that the measurement interval is larger than or equal to the shot size (No), the control unit 12 offsets from the measurement value difference at any two measurement points in one sample shot. A calculation error amount is calculated and subtracted (step S205). Then, the control unit 12 drives the wafer stage 7 based on the final surface height map obtained in either step S204 or S205 to perform an exposure process.

  As described above, according to the present embodiment, the same effect as that of the first embodiment can be achieved most efficiently according to the arrangement and size of the sample shots.

In any of the above-described embodiments, an exposure apparatus that projects a reticle pattern onto a substrate and transfers the pattern as a lithography apparatus (pattern forming apparatus) has been described. However, the present invention is not limited to this. The lithography apparatus may be an electron beam exposure apparatus that transfers (draws) a pattern onto a substrate using an electron beam (charged particle beam). Moreover, the imprint apparatus which transfers a pattern by making the pattern formed in the type | mold contact with the imprint material supplied on the board | substrate as a lithography apparatus may be sufficient.

(Product manufacturing method)
The method for manufacturing an article according to an embodiment is suitable for manufacturing an article such as a micro device such as a semiconductor device or an element having a fine structure. The manufacturing method includes a step of forming a pattern (for example, a latent image pattern) on an object (for example, a substrate having a photosensitive agent on the surface) by using the above-described lithography apparatus, and a processing of the object on which the pattern is formed in the step. (For example, a developing step and a processing step). Further, the manufacturing method may include other well-known steps (oxidation, film formation, vapor deposition, doping, planarization, etching, resist stripping, dicing, bonding, packaging, and the like). The method for manufacturing an article according to the present embodiment is advantageous in at least one of the performance, quality, productivity, and production cost of the article as compared with the conventional method.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

DESCRIPTION OF SYMBOLS 11 Focus detection system 12 Control part 100 Exposure apparatus S1 1st sample shot S2 2nd sample shot WF Wafer

Claims (11)

A pattern forming apparatus for forming a pattern on a substrate having a plurality of shots,
A detection system for detecting a height of a surface of a sample shot included in the plurality of shots on the substrate;
Obtains a first surface height information by subtracting the offset value from the value of the height of said surface in said detected sample shot by the detection system, before Symbol of the offset value generated when calculating the offset value A control unit that obtains an error amount and subtracts the error amount of the offset value from the first surface height information to obtain second surface height information;
A pattern forming apparatus comprising: Each of the sample shots has a plurality of measurement points to be measured by the detection system,
The plurality of measurement points are set to be the same location in each sample shot,
For the two adjacent sample shots, the error amount of the offset value is the first measurement point included in one of the sample shots and the second sample shot closest to the first measurement point. And the distance between the first measurement point and the measurement point corresponding to the position of the second measurement point of the other sample shot in the one sample shot. Is the first-order slope amount
The pattern forming apparatus according to claim 1. Each of the sample shots has a plurality of measurement points to be measured by the detection system,
The error amount of the offset value is a first-order inclination amount obtained from a measurement value difference between two measurement points included in one sample shot and a distance between measurement positions of the two measurement points .
The pattern forming apparatus according to claim 1. The pattern forming apparatus according to claim 3 , wherein the two measurement points have the longest distance among the plurality of measurement points included in the sample shot. The control unit selects whether to calculate the error amount of the offset value using two adjacent sample shots or one sample shot based on the arrangement or size of the sample shots the pattern formation apparatus according to claim 2 or 3, characterized in that. The control unit adjoins the error amount of the offset value when it determines that the distance between the measurement positions of the first measurement point and the second measurement point is smaller than the size of the sample shot. Using two sample shots,
When it is determined that the distance between the measurement positions of the first measurement point and the second measurement point is larger than or equal to the size of the sample shot, the distance is obtained using one sample shot.
The pattern forming apparatus according to claim 5 . Wherein the plurality of measurement points, the pattern forming apparatus according to claim 2 or 3, characterized in that it is set in accordance with the state of the sample shots. The offset value, the pattern forming apparatus according to any one of claims 1 to 7, characterized in that a value generated by the measurement error of the detection system. The offset value, the pattern forming apparatus according to any one of claims 1 to 7, characterized in that a value due to the shape of the concavo-convex pattern in the sample shots detected by the detection system. A pattern forming method for forming a pattern on a substrate having a plurality of shots,
Determining a surface height value in a sample shot included in the plurality of shots on the substrate;
A step of obtaining a first surface height information by subtracting the offset value from the value of the height of said surface,
Obtaining an error amount of the offset value generated when calculating the offset value;
Subtracting an error amount of the offset value from the first surface height information to obtain second surface height information;
And a step of transferring the pattern onto the substrate using the second surface height information. Forming a pattern on a substrate using the pattern forming apparatus according to any one of claims 1 to 9 or the pattern forming method according to claim 10 ;
Processing a substrate on which a pattern is formed;
A method for producing an article comprising:

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