JP7114370B2 - Exposure apparatus and article manufacturing method - Google Patents

Description

The present invention relates to an exposure apparatus and an article manufacturing method.

2. Description of the Related Art An exposure apparatus that exposes a shot area on a substrate with exposure light from a projection optical system is known as one of the apparatuses used in the lithography process, which is one of the manufacturing processes of semiconductor devices and the like. In such an exposure apparatus, the surface position of the substrate is measured prior to exposure, and the height of the substrate is adjusted based on the focus measurement result, which is the measurement result.

Also, there is known a technique for determining whether or not foreign matter exists on the substrate surface or the like from the result of focus measurement. If a foreign substance exists on the substrate surface or the like, the result of focus measurement will change greatly. Therefore, the presence or absence of a foreign substance and the size of the foreign substance can be determined based on the change in the result of focus measurement.

Japanese Patent Application Laid-Open No. 2002-200002 discloses a technique for determining whether or not a foreign object exists between a substrate and a substrate stage based on the result of focus measurement on the substrate. In Cited Document 1, focus measurement is performed in a plurality of shot areas on a substrate, an approximate plane is obtained from the results of the plurality of focus measurements, and the focus measurement results in each shot area are compared with the approximate plane to detect foreign matter. I am making a decision as to whether or not

Here, for example, when focus measurement is performed in a shot area located in the peripheral area of the substrate, there is a possibility that the focus measurement accuracy may be degraded because some focus measurement positions are located outside the substrate. For this reason, it is generally known to perform focus control by excluding the focus measurement result in the focus measurement area including the focus measurement position.

JP 2003-257847 A

In Patent Document 1, the presence or absence of foreign matter is determined by comparing the focus measurement result and the approximate plane. Therefore, the presence or absence of foreign matter is determined in an area corresponding to the focus measurement area excluded from the focus measurement result. can't

SUMMARY OF THE INVENTION It is an object of the present invention to realize an exposure apparatus capable of expanding the region in which the presence or absence of foreign matter can be determined while maintaining focus accuracy.

An exposure apparatus as one aspect of the present invention for solving the above problems is an exposure apparatus that exposes a shot area on a substrate, wherein the height of the substrate is measured in a plurality of focus measurement areas included in the shot area. and a control unit that controls the height of the substrate and determines the presence or absence of foreign matter in the shot area based on the result of measuring the height of the substrate by the measurement unit, the measurement unit comprising: a light projecting unit that projects a measurement mark onto each of a plurality of measurement positions included in the focus measurement area; and a light receiving unit that receives the light projected by the light projecting unit and reflected by the substrate, When part of the measurement marks projected by the light projecting unit are reflected by the focus measurement area and received by the light receiving unit, the control unit is configured to reflect the measurement marks by the focus measurement area. When the number of the measurement marks received by the light receiving unit satisfies a predetermined standard, the height of the substrate is controlled excluding the measurement result in the focus measurement area, and the The presence or absence of foreign matter in the focus measurement area is determined using the measurement result .

According to the present invention, it is possible to obtain an exposure apparatus capable of expanding the region in which the presence or absence of foreign matter can be determined while maintaining focus accuracy.

1 is a schematic diagram showing the configuration of an exposure apparatus; FIG. FIG. 4 is a diagram showing the relationship between a focus measurement area and an irradiation area; It is a figure which shows the signal strength detected by a photoelectric conversion part. FIG. 4 is a diagram showing a positional relationship between a focus measurement area and a substrate; 4 is a flow chart showing an exposure sequence on a substrate;

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, in each drawing, the same reference numerals are given to the same members or elements, and overlapping descriptions are omitted.

An exposure apparatus according to the present invention will be described. FIG. 1 is a schematic diagram showing the configuration of an exposure apparatus 100 of this embodiment. The exposure apparatus 100 is, for example, a so-called scan-and-repeat type exposure apparatus that relatively scans the shot area of the substrate with the light emitted from the projection optical system to perform scanning exposure of the shot area. exposure equipment).

The exposure apparatus 100 can include an illumination system 106 , a mask stage 103 , a projection optical system 101 , a substrate stage 105 , a measurement section 102 and a control section 104 . Here, in FIG. 1, the axis parallel to the optical axis AX of the projection optical system 101 is the Z-axis, and the two axes orthogonal to each other in the plane perpendicular to the Z-axis are the X-axis and the Y-axis. Further, in this embodiment, the scanning direction of the mask M and the substrate W (that is, the scanning direction of the irradiation area on the substrate) is the Y direction.

The illumination system 106 illuminates the mask M by adjusting light emitted from a light source (not shown) such as an excimer laser. The mask M is made of quartz glass, for example, and has a pattern (for example, a circuit pattern) to be transferred onto the substrate. The mask stage 103 includes a chuck that holds the mask M, and is movable in at least the X and Y axial directions. During exposure of the substrate W, the mask stage 103 scans at a constant speed in the Y-axis direction (arrow 103a), which is the planar direction perpendicular to the optical axis AX of the projection optical system 101 .

Positional information of the mask stage 103 in each axial direction can be constantly measured using a bar mirror 120 installed on the mask stage 103 and a first interferometer 121 for position detection of the mask stage 103 .

The projection optical system 101 projects the light transmitted through the mask M onto the substrate at a predetermined projection magnification (for example, 1/2 times). The image plane (focus plane) of the projection optical system 101 is perpendicular to the Z-axis direction. The substrate W is, for example, a single crystal silicon substrate, and a resist (photosensitive agent) can be applied on the surface thereof.

The substrate stage 105 includes a chuck that holds the substrate W, and can move (rotate) in the directions of the X, Y, and Z axes, and further in the directions of rotation of the axes, ie, θx, θy, and θz directions. When exposing the substrate W, the substrate stage 105 scans at a constant speed in the Y-axis direction (arrow 105a), which is the planar direction perpendicular to the optical axis AX of the projection optical system 101 . Positional information of the substrate stage 105 in each axial direction can be constantly measured using a bar mirror 123 installed on the substrate stage 105 and a second interferometer 124 for detecting the position of the substrate stage 105 .

The measurement unit 102 measures the position or inclination of the surface of the substrate W held by the substrate stage 105 in the Z-axis direction (hereinafter these may be collectively referred to as "surface position" or "surface height"). measure. The measurement unit 102 of the first embodiment is an oblique incidence type that irradiates the substrate W with light obliquely. and a light receiving portion that receives a light beam reflected by the substrate W (reflected light beam).

The light projecting unit can include, for example, a light source 110, a collimator lens 111, a slit member 112, a light projecting optical system 113, and a mirror 114. The light source 110 has, for example, a lamp or a light-emitting diode, and emits a light beam with a wavelength that does not sensitize the resist on the substrate. The collimator lens 111 converts the light flux emitted from the light source 110 into parallel light with a substantially uniform cross-sectional light intensity distribution.

The slit member 112 is composed of a pair of prisms bonded together so that the slopes thereof face each other. The projection optical system 113 is a double-side telecentric optical system, and causes a plurality of light beams individually passing through a plurality of openings formed in the slit member 112 to enter the substrate via a mirror 114 . At this time, the plane having the plurality of apertures and the plane including the surface of the substrate W can be configured to satisfy the Scheimpflug condition for the projection optical system 113 .

In this embodiment, the incident angle (the angle formed with the optical axis) when each light beam from the light projecting section is incident on the substrate W is 70° or more. In addition, a plurality of light beams emitted from the light projecting unit are arranged so that the surface height at the position where each light beam is incident can be measured independently of each other in the XY plane from the X direction by θ° (for example, 22.5 °) Incident at different positions on the substrate from the rotated direction.

The light receiving section can include, for example, a mirror 115 , a light receiving optical system 116 , a correcting optical system 117 , and a photoelectric conversion section 118 . The mirror 115 guides the plurality of light fluxes reflected by the substrate W to the light receiving optical system 116 . The light-receiving optical system 116 is a double-side telecentric optical system, and a stopper diaphragm provided in common for a plurality of light beams filters out high-order diffracted light (noise light) caused by the pattern formed on the substrate. ) is cut.

Correction optical system 117 has a plurality of lenses so as to correspond to a plurality of light fluxes, and converts a plurality of light fluxes having optical axes parallel to each other after passing through light receiving optical system 116 to photoelectric converter 118 . An image is formed on the light-receiving surface so as to form spotlights having the same size. The photoelectric conversion unit 118 can include, for example, multiple photoelectric conversion elements so as to correspond to multiple light beams.

Each photoelectric conversion element includes a CCD line sensor or the like, detects the intensity (light intensity) of the luminous flux incident on the light receiving surface, and outputs it to the processing unit 126 (arithmetic circuit). The light receiving optical system 116, the correcting optical system 117, and the photoelectric conversion unit 118 are tilt-corrected in advance so that each measurement position on the substrate and the light receiving surface of the photoelectric conversion unit 118 are conjugate with each other. Therefore, there is no change in the position of the pinhole image on the light-receiving surface due to the local inclination of each measurement point, and the height change in the optical axis direction AX of each measurement point is responded to on the light-receiving surface. The position of the pinhole image at . Here, the photoelectric conversion unit 118 of the present embodiment is configured by a one-dimensional CCD line sensor, but a device in which a plurality of two-dimensional position measurement elements are arranged may be used.

The controller 104 can include, for example, a main controller 127 , a mask position controller 122 , a substrate position controller 125 and a processor 126 . The main control unit 127 is composed of, for example, a computer including a CPU and a memory, is connected to each component of the exposure apparatus 100 (control unit for controlling these components, etc.) via a line, and controls each component according to a program. Overall control of operations.

The mask position control section 122 controls the operation of the mask stage 103 based on commands from the main control section 127 . The substrate position controller 125 controls the operation of the substrate stage 105 based on commands from the main controller 127 . The processing unit 126 obtains the surface position of the substrate W at each measurement point based on the output from the photoelectric conversion unit 118 .

The main controller 127 relatively scans the mask stage 103 and the substrate stage 105 at a speed ratio corresponding to the projection magnification of the projection optical system 101 while synchronizing them. As a result, the irradiation area irradiated with the light from the projection optical system 101 (that is, the area where the pattern image of the mask M is projected by the projection optical system 101) is scanned on the substrate, and the pattern of the mask M is projected onto the substrate. It can be transferred to the shot area. By sequentially performing such scanning exposure for each of the plurality of shot areas on the substrate W while moving the substrate stage 105 in steps, the exposure processing for one substrate W can be completed.

Next, the relationship between the focus measurement area and the exposure light irradiation area 22 in one shot area 21 included in the substrate W will be described with reference to FIG. Here, five focus measurement areas 23 to 27 exist in the irradiation area 22, and five measurement marks M are projected on each focus measurement area. Each measurement mark M is projected at a focus measurement position set in the focus measurement area.

A light beam for measurement is projected from the light projection unit of the measurement unit 102 to the focus measurement position of each focus measurement area, and the light beam reflected at the position on the substrate W corresponding to each focus measurement position is received by the measurement unit. The light is received by a light receiving portion 102 . By moving the substrate W in the scanning direction (Y-axis direction) by the substrate stage 105 , the focus measurement area moves in the Y-axis direction of the shot area 21 .

Specifically, a measurement mark is projected onto each focus measurement position by the light projecting unit, and an image is formed on the photoelectric conversion unit 118 . FIG. 3 shows the signal intensity distribution when the measurement marks projected onto five focus measurement positions in one focus measurement area are imaged on the photoelectric conversion section 118 . If the difference between the surface position of the substrate W and the image plane position of the projection optical system 101 is within the depth of focus of the projection optical system 101, as shown in FIG. Pa to Pe) appear corresponding to the intervals of the focus measurement positions.

Since the interval between the peaks in FIG. 3 changes with the change in defocus, which is the difference between the surface position of the substrate W and the image plane position of the projection optical system 101, the substrate can be detected by detecting the change in the interval. The displacement of the surface position of W can be detected. The substrate position control unit 125 aligns the surface position of the substrate W with the image plane position of the projection optical system 101 by moving the substrate stage 105 in the Z-axis direction so as to reduce the defocus amount. The operation of matching the surface position of the substrate W and the image plane position of the projection optical system 101 is referred to as focus control.

Here, the measurement accuracy of the measurement mark at each focus measurement position may not satisfy the accuracy required for focus control. In this case, by averaging the measurement values of the measurement marks at each focus measurement position, the focus measurement accuracy in the focus measurement area can be improved.

For example, if the accuracy required for focus control is 30 nm and the measurement accuracy of the measurement marks at each focus measurement position is 50 nm, the measurement values of the measurement marks at the four focus measurement positions are averaged. As a result, as shown in the following formula, the focus measurement accuracy in the focus measurement area can be improved beyond the accuracy required for focus control.

By increasing the number of measurement marks to be measured in this manner, the focus measurement accuracy in the focus measurement area can be improved. However, when the number of measurement marks to be measured is small, it becomes difficult to sufficiently improve focus measurement accuracy. Therefore, when the number of measurement marks to be measured is small, the measurement result in the focus measurement area including the focus measurement position is not used for focus control. This can avoid the occurrence of defocus.

For example, when the number of measurement marks to be measured is less than a predetermined number, it is conceivable not to use the measurement result in the focus measurement area for focus control. Here, when the number of measurement marks to be measured is a predetermined number or more, the focus accuracy can be improved by reflecting the measurement result in the focus measurement area in the focus control.

The predetermined number is preferably set according to the accuracy required for focus control. If the accuracy required for focus control is high, it is conceivable to increase the predetermined number. Further, since the flatness of the substrate height may vary depending on the position of the shot area on the substrate W, it is preferable to set the predetermined number as appropriate according to the position of the shot area on the substrate W. FIG.

Next, a foreign matter detection method using the measurement values of the measurement marks will be described. For example, the focus measurement results in each focus measurement area on the substrate W are obtained, and the average value of these focus measurement results is calculated. Then, by comparing the average value with the measurement results in each focus measurement area, it is possible to determine the presence or absence of foreign matter in each focus measurement area.

As an example, the difference between the average value of focus measurement results in each focus measurement area and the measurement value in each focus measurement area is obtained, and if the difference is greater than a preset threshold value, it is determined that a foreign object exists in the focus measurement area. do. Various other determination methods can be used as the method for determining the presence or absence of foreign matter.

Next, the positional relationship between the focus measurement area and the substrate W will be described with reference to FIG. FIG. 4A shows a situation where the entire shot area 21 is positioned on the substrate W. FIG. In the example of FIG. 4A, in each focus measurement area included in the shot area 21, the photoelectric conversion unit 118 can detect measurement marks corresponding to all five focus measurement positions. Therefore, as described above, the measurement results of the measurement marks in the focus measurement areas 41 to 45 are used to perform focus control in the illumination area 4a and to determine the presence or absence of a foreign object in the illumination area 4a.

FIG. 4B shows a situation in which part of the shot area 21 is located outside the substrate W, and one of the focus measurement areas 46 to 50 included in the illumination area 4b. The focus measurement position of the part does not exist in the area on the substrate W. Specifically, three focus measurement positions out of the five focus measurement positions included in the focus measurement area 46 are not located in the area above the substrate W. FIG.

Here, it is assumed that the above-described "predetermined number" is three in consideration of the accuracy required for focus control. At this time, since only two measurement marks are projected onto the substrate W in the focus measurement area 46 and detected by the photoelectric conversion unit 118, the focus measurement result in the focus measurement area 46 is excluded, and the irradiation area Focus control in 4b is performed.

On the other hand, the focus measurement accuracy used for foreign matter presence/absence determination is generally lower than the focus measurement accuracy used for focus control. Therefore, when determining the presence or absence of foreign matter, the presence or absence of foreign matter is determined based on the detection results of the two measurement marks located in the area on the substrate W included in the focus measurement area 46 . As a result, it is possible to determine the presence or absence of foreign matter even in the outermost peripheral region of the substrate W. FIG.

Although an example in which the "predetermined number" is 3 is shown here, the "predetermined number" may be set to 5. As a result, when there is even one measurement mark that is not detected by the photoelectric conversion unit 118, focus control is performed excluding the focus measurement result in the focus measurement area. Such a focus control method is effective when the required focus accuracy is high.

As described above, when the shot areas are arranged as shown in FIG. is used. On the other hand, the measurement results of the measurement marks in the five focus measurement areas 46 to 50 are used as the second number for determining the presence or absence of foreign matter. As a result, it is possible to determine the presence or absence of foreign matter over a wide range on the substrate W while maintaining the focus accuracy in the irradiation area 4b.

Next, the exposure sequence according to this embodiment will be described using the flowchart of FIG. The exposure sequence is executed by the control unit 104 . When the exposure process is started in step S501, first, in step S502, a focus measurement area corresponding to the area where the exposure process is to be performed is determined. In the example of FIG. 4B, focus measurement areas 46 to 50 are specified as focus measurement areas. Subsequently, in step S503, a measurement mark is projected onto each focus measurement position in the focus measurement area, and the photoelectric conversion unit 118 detects the measurement mark.

Furthermore, in step S504, it is determined whether or not the measurement value in each focus measurement area is to be used for focus control. Here, an example is shown in which the determination is made based on whether or not the number of detected marks is 3 or more. The number of marks detected by the photoelectric conversion unit 118 among the measurement marks projected onto each focus measurement area can be known in advance based on the position on the substrate W of each focus measurement area. Therefore, the determination in step S504 can be made based on the arrangement information of each focus measurement area on the substrate W. FIG.

If the number of detected marks is 3 or more, the process advances to step S505, and the measurement result in the focus measurement area is used for focus control. On the other hand, if the number of detected marks is less than 3, the process proceeds to step S506, and the measurement result in the focus measurement area is not used for focus control.

Subsequently, in step S507, based on the number of marks detected by the photoelectric conversion unit 118 among the measurement marks projected on each focus measurement area, whether to use the measurement value in each focus measurement area for foreign matter detection. determine whether or not Here, an example is shown in which the determination is made based on whether or not the number of detected marks is one or more.

If even one mark is detected, the process advances to step S508, and the measurement result in the focus measurement area is used for foreign matter detection. On the other hand, if the detected mark does not exist, the process advances to step S509, and the measurement result in the focus measurement area is not used for foreign matter detection. Note that the determination processing in step S504 and the determination processing in step S507 may be executed in parallel.

Then, based on the determination result in step S504, in step S510, focus control is executed based on the measurement result in each focus measurement area, and then exposure processing is performed. Further, based on the determination result in step S507, in step S511, the presence or absence of a foreign object in each focus measurement area is detected. Foreign matter presence/absence detection may be performed in parallel with focus control and exposure processing in step S510, or may be performed before focus control.

(Modification)
In the above example, if even one mark is detected, the measurement result in the focus measurement area is used for foreign matter detection. Here, in the case where an erroneous determination of the presence or absence of foreign matter is likely to occur, such as when the surface shape of the substrate is uneven, the detection accuracy of foreign matter can be improved by increasing the threshold value in step S507. For example, in step S507, it is conceivable to determine the presence or absence of a foreign object based on whether or not the number of detected marks is equal to or greater than a predetermined number. At this time, when the number of detected marks is less than the predetermined number, the foreign matter presence/absence determination in the focus area is not performed. An integer of 2 or more can be set as the predetermined number.

The present invention can also be applied to a stepper that projects the pattern of the mask M onto the substrate W with the mask M fixed.

(Product manufacturing method)
Next, a method for manufacturing an article (semiconductor IC element, liquid crystal display element, etc.) using the aforementioned exposure apparatus will be described. Such an article can be manufactured by a process of forming a pattern on a substrate using the exposure apparatus described above, a process of processing (development, etching, etc.) the substrate having the pattern formed thereon, and a process (development, etching, etc.) of the substrate having the pattern formed thereon. etc.). The manufacturing method of the present article is advantageous in at least one of performance, quality, productivity and production cost of the article as compared with conventional methods. Alternatively, the aforementioned exposure apparatus can provide articles such as high-quality devices (semiconductor IC elements, liquid crystal display elements, etc.) with high throughput and economically.

Although the preferred embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist.

Claims (7)

An exposure apparatus that exposes a shot area on a substrate,
a measurement unit that measures the height of the substrate in a plurality of focus measurement areas included in the shot area;
a control unit that controls the height of the substrate and determines the presence or absence of foreign matter in the shot area based on the result of measurement of the height of the substrate by the measurement unit ;
The measuring unit includes a light projecting unit that projects a measurement mark onto each of a plurality of measurement positions included in the focus measurement area, and a light receiving unit that receives light projected by the light projecting unit and reflected by the substrate. including the part
When part of the measurement marks projected by the light projecting unit are reflected by the focus measurement area and received by the light receiving unit, the control unit is configured to reflect the measurement marks by the focus measurement area. and when the number of the measurement marks received by the light receiving unit satisfies a predetermined standard, height control of the substrate is performed excluding the measurement result in the focus measurement area, and the An exposure apparatus that determines the presence or absence of foreign matter in a focus measurement area using a measurement result . The light receiving unit includes a photoelectric conversion element,
3. The control unit performs at least one of height control of the substrate and presence/absence determination of the foreign matter based on an intensity distribution of signals of the measurement marks detected by the photoelectric conversion element. 1. The exposure apparatus according to 1. Among the measurement marks projected onto the plurality of measurement positions included in the focus measurement area, the number of measurement marks detected by the light receiving unit is less than a predetermined number and satisfies the predetermined criterion. 3. The exposure apparatus according to claim 1 , wherein the control unit does not determine the presence or absence of a foreign object in the focus measurement area when the focus measurement area is not present. further comprising a projection optical system for projecting exposure light onto a shot area on the substrate;
4. The method according to any one of claims 1 to 3 , wherein the control unit controls the height of the substrate so that the image plane position of the projection optical system and the height position of the substrate are aligned. Exposure equipment. The control unit compares the height measurement result of the substrate in the focus measurement area and the height measurement result of the substrate in a plurality of shot areas on the substrate to determine the presence or absence of the foreign matter. 5. The exposure apparatus according to any one of claims 1 to 4 , characterized in that: The predetermined reference is a range of a first reference value or more and a second reference value or less,
When the number of the measurement marks reflected by the focus measurement area and received by the light receiving unit is larger than a second reference value, the height control of the substrate and the foreign matter are performed using the measurement result in the focus measurement area. Determine the presence or absence of
When the number of the measurement marks reflected by the focus measurement area and received by the light receiving unit is smaller than a first reference value, the height control of the substrate using the measurement result in the focus measurement area and the 2. An exposure apparatus according to claim 1, wherein the presence/absence of foreign matter is not determined. forming a pattern on a substrate using the exposure apparatus according to any one of claims 1 to 6 ;
and a step of manufacturing the article by processing the patterned substrate.

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