JP2008258325A - Exposure equipment - Google Patents

Abstract

The measurement accuracy of the surface position of a substrate is improved.
An exposure apparatus that has a projection optical system that projects light from an original and exposes a substrate through the projection optical system, and includes a measuring instrument and a controller. The measuring instrument measures the position of the surface of the substrate in the direction of the optical axis of the projection optical system with respect to the measurement points in the shot arranged on the substrate. For each of a plurality of sizes of measurement points, the controller causes the measurement device to measure the position of the surface in a plurality of shots arranged on the substrate. And a measuring device calculates the parameter | index which shows the reproducibility of measurement about each of several magnitude | size based on the measured position, and determines the magnitude | size of a measurement point based on the calculated parameter | index.
[Selection] Figure 1

Description

  The present invention relates to an exposure apparatus.

  When manufacturing fine semiconductor elements or liquid crystal display elements using photolithography technology, a projection exposure system that projects the circuit pattern drawn on the reticle (mask) onto the substrate by the projection optical system and transfers the circuit pattern is used. Has been. In a projection exposure apparatus, as the integration of semiconductor elements increases, it is required to project and expose a reticle circuit pattern onto a substrate with higher resolution. The minimum dimension (resolution) that can be transferred by the projection exposure apparatus is proportional to the wavelength of light used for exposure and inversely proportional to the numerical aperture (NA) of the projection optical system. Therefore, the shorter the wavelength, the better the resolution. For this reason, the light source in recent years has changed from an ultra-high pressure mercury lamp (g-line, i-line) to a KrF excimer laser or ArF excimer laser having a short wavelength, and the practical application of the immersion exposure apparatus is also being studied. Furthermore, further expansion of the exposure area is also required.

  To achieve these requirements, scanners are becoming mainstream instead of steppers. A stepper is a step-and-repeat type exposure apparatus that reduces a substantially square-shaped exposure region to a substrate and performs batch exposure. The scanner is a step-and-scan type exposure apparatus that exposes a large screen with high accuracy by relatively scanning the reticle and the substrate with a rectangular slit shape as an exposure area.

  The scanner measures the surface position at the predetermined position of the substrate by the focus tilt measurement system before the predetermined position of the substrate reaches the exposure slit area during exposure, and the substrate surface is optimized when exposing the predetermined position. Correction is performed to match the exposure image formation position. Also, in order to measure not only the height (focus) of the surface position of the substrate but also the tilt (tilt) of the surface, the exposure slit area, including the longitudinal direction of the exposure slit (direction perpendicular to the scanning direction) It has multiple measurement channels. Such a focus and tilt measurement method is described in Patent Document 1.

A conventional method for measuring an offset will be described with reference to FIG. FIG. 2A shows sample shots for focus measurement in the substrate 40 (eight shots in FIG. 2A). FIG. 2B shows an example of measurement channels and measurement points in a sample shot. In FIG. 2B, each of the measurement channels is assumed to have a plurality of measurement marks (not shown) for the purpose of averaging effect. Focus measurement using a plurality of measurement marks is performed on a predetermined sample shot on the substrate 40 at a predetermined interval (for example, 1 mm) in the scanning direction. Next, in the sample shot, a reference plane is created from the focus measurement value at the measurement point serving as the reference of the reference measurement channel. As shown in FIG. 2 (c), the average of the difference between the focus measurement value at each measurement point Pj (j = 1, 2, 3,..., M) and the reference plane is sample shot. Obtained as an offset at the measurement point Pj. Using the offset, the focus measurement value from the next substrate is corrected, and the surface position (focus and tilt) of the substrate is measured.
JP-A-6-260391

  However, in recent years, the exposure light has been shortened and the projection optical system has a higher NA, the depth of focus has become extremely small, and the accuracy of aligning the substrate surface to be exposed to the best imaging plane, the so-called focus accuracy, has become more severe. Has been demanded. In particular, recently, measurement errors of the surface position measuring instrument due to the density of the pattern on the substrate and the unevenness of the thickness of the resist applied to the substrate cannot be ignored.

  The measurement error due to the uneven thickness of the resist is smaller in the vicinity of the peripheral circuit pattern and the scribe line than the depth of focus, but a large step is generated for focus measurement. For this reason, the inclination angle of the resist surface to be applied is increased, and the reflected light measured by the surface position measuring instrument is deviated from the regular reflection angle by reflection or refraction, resulting in a measurement error (offset).

  FIG. 3 shows measurement errors caused by the density of the pattern on the substrate. For example, the reflectance of the substrate is high in a region where the pattern is rough, and the reflectance is low in a region where the pattern is dense. For this reason, the reflection intensity of the reflected light measured by the surface position measuring instrument changes, and an asymmetry occurs as in the signal waveform B with respect to the original signal waveform A when there is no pattern density. In such signal processing, a measurement error (offset) occurs.

  FIG. 4 is a diagram showing a positional relationship between a measurement mark at a certain measurement point, a pattern on the substrate base, and a measurement error (offset) caused thereby. Depending on the positional relationship between the substrate base pattern and the measurement mark, the measurement area A includes the measurement area up to the point where the offset is small but the measurement area B has a large offset. Further, there is a slight step at the boundary between the high reflectance and the low reflectance, and when the resist application state varies depending on the sample shot, it is conceivable that the offset changes depending on the sample shot.

  FIG. 5 is a diagram showing an offset from a reference plane with respect to a measurement point in a certain measurement channel. In FIG. 5, the variation between offset sample shots is indicated by up and down arrows. In FIG. 5, for example, it can be seen that the offset at the measurement point P4 has a larger variation than the other measurement points and lacks the stability (reproducibility) of the offset. When the variation in offset is larger than the allowable range of flatness of the substrate, even if correction is performed with the offset obtained at the measurement point P4, defocus exceeding the allowable range occurs depending on the shot, and the focus accuracy is deteriorated. As a result, the CD (Critical Dimension, line width) may be out of the allowable range.

  An object of the present invention is to improve the measurement accuracy of the surface position of a substrate.

  The present invention relates to an exposure apparatus that has a projection optical system for projecting light from an original plate and exposes a substrate through the projection optical system, and relates to measurement points in a shot arranged on the substrate. A measuring instrument that measures the position of the surface of the substrate in the direction of the optical axis, and for each of multiple sizes of measurement points, the measuring instrument measures the position of the surface in multiple shots placed on the substrate, and the measured position And a controller that calculates an index indicating the reproducibility of measurement for each of a plurality of sizes and determines the size of the measurement point based on the calculated index.

  According to the present invention, for example, the measurement accuracy of the surface position of the substrate can be improved.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[Embodiment of exposure apparatus]
FIG. 20 is a view showing the overall configuration of a semiconductor exposure apparatus according to the present invention. The exposure apparatus 1 is a scanning exposure apparatus that exposes a circuit pattern formed on a reticle 20 on a substrate 40 by a step-and-scan method. Such an exposure apparatus 1 is suitable for a lithography process of submicron or quarter micron or less. The exposure apparatus 1 includes an illumination device 10, a reticle stage 25 on which the reticle 20 is placed, a projection optical system 30, a substrate stage 45 that holds and moves the substrate 40, a focus tilt measurement system 50, and an alignment measurement system. 70 and a controller 60. The controller 60 includes a CPU and a memory, and is electrically connected to the illumination device 10, the reticle stage 25, the substrate stage 45, the focus tilt measurement system 50, and the alignment measurement system 70, and controls the operation of the exposure apparatus 1.

  The illumination device 10 illuminates a reticle 20 on which a transfer circuit pattern is formed, and includes a light source unit 12 and an illumination optical system 14. The light source unit 12 uses laser light. For example, an ArF excimer laser having a wavelength of about 193 nm, a KrF excimer laser having a wavelength of about 248 nm, or the like can be used. However, the type of the light source is not limited to the excimer laser, and an F2 laser having a wavelength of about 157 nm or EUV (Extreme Ultraviolet) light having a wavelength of 20 nm or less may be used.

  The illumination optical system 14 is an optical system that illuminates the surface to be illuminated using the light beam emitted from the light source unit 12, and illuminates the reticle 20 by forming the light beam into an exposure slit having a predetermined shape optimum for exposure. The illumination optical system 14 includes a lens, a mirror, an optical integrator, a diaphragm, and the like. For example, a condenser lens, a fly-eye lens, an aperture diaphragm, a condenser lens, a slit, and an imaging optical system are arranged in this order. The illumination optical system 14 can be used regardless of on-axis light or off-axis light. The optical integrator includes an integrator configured by stacking a fly-eye lens and two sets of cylindrical lens array (or lenticular lens) plates, but may be replaced by an optical rod or a diffractive element.

  The reticle 20 is made of, for example, quartz, and a circuit pattern to be transferred is formed thereon, and is supported and driven by the reticle stage 25. The diffracted light emitted from the reticle 20 passes through the projection optical system 30 and is projected onto the substrate 40. The reticle 20 and the substrate 40 are arranged in an optically conjugate relationship. The pattern of the reticle 20 is transferred onto the substrate 40 by scanning the reticle 20 and the substrate 40 at the speed ratio of the reduction ratio. The exposure apparatus 1 is provided with a not-illustrated light oblique incidence type reticle measuring instrument, and the position of the reticle 20 is measured by the reticle measuring instrument and placed at a predetermined position. The reticle stage 25 supports the reticle 20 via a reticle chuck (not shown) and is connected to a moving mechanism (not shown). A moving mechanism (not shown) is composed of a linear motor or the like, and can move the reticle 20 by driving the reticle stage 25 in the X-axis direction, the Y-axis direction, the Z-axis direction, and the rotation direction of each axis. The projection optical system 30 has a function of forming a light beam from the object plane on the image plane, and forms an image on the substrate 40 of diffracted light that has passed through the pattern formed on the reticle 20.

  The substrate 40 is an object to be processed, and a photoresist is applied on the substrate. The substrate 40 is also a measurement target for the alignment measurement system 70 and the focus tilt measurement system 50 to perform position measurement. The alignment measurement system 70 is for measuring the XY position shift of the substrate 40. In the figure, the alignment measurement system 70 is arranged on an optical axis different from the optical axis of the exposure projection optical system and uses so-called off-axis light. The method is shown. The substrate stage 45 supports the substrate 40 by the substrate chuck 46. At least three or more substrate chuck marks are arranged on the substrate chuck 46, and the Z height information can be obtained by the focus tilt measurement system 50, and the XY position information can be obtained by the alignment measurement system. Similarly to the reticle stage 25, the substrate stage 45 uses the linear motor to move the substrate 40 and the substrate chuck 46 in the X-axis direction, the Y-axis direction, the Z-axis direction, and the rotation direction of each axis. The position of the reticle stage 25 and the position of the substrate stage 45 are monitored by, for example, a laser interferometer, and both the stages 25 and 45 are driven at a constant speed ratio. The substrate stage 45 is provided on a stage surface plate supported on a floor or the like via a damper, for example, and the reticle stage 25 and the projection optical system 30 are, for example, on a base frame placed on the floor or the like. It is provided on a lens barrel surface plate (not shown) that is supported via a damper.

  Next, the focus tilt measurement system 50 in the exposure apparatus 1 of FIG. 20 will be described. The focus tilt measurement system 50 measures position information on the position of the surface of the substrate 40 during exposure in the direction of the optical phrase of the projection optical system 30 (Z-axis direction) using an optical measuring instrument. The projection optical system 30 is used to project the surface of the substrate 40 at a high incident angle, and the light receiving optical system is used to re-image the projected image of the focus measurement slit-shaped measurement mark on a photoelectric conversion element such as a CCD. The surface position of the substrate 40 is measured using the signal waveform from the photoelectric conversion element.

  In the scanner, the focus tilt measurement system 50 measures the surface position at a predetermined position of the substrate before the predetermined position of the substrate reaches the exposure slit region, and when exposing the predetermined position, the substrate surface Is corrected to match the optimal exposure image formation position. Further, in order to measure not only the height (focus) of the surface position of the substrate but also the tilt (tilt) of the surface, the exposure slit region including the longitudinal direction of the exposure slit (ie, the direction orthogonal to the scanning direction) is included. Has a plurality of measurement channels.

[Measurement area optimization]
FIG. 1 is a flowchart for explaining the outline of the focus measurement method of the present invention. In step 100, the controller 60 obtains position information on the substrate surface, which is a measurement result measured in a different measurement area at each of a plurality of measurement points in a plurality of shots provided on the substrate 40 by the focus tilt measurement system 50. Get multiple. In step 110, the controller 60 first calculates an index of an offset from the reference plane (an index indicating the reproducibility of measurement) for each of the different measurement areas based on the acquired plurality of position information. In step 120, the controller 60 determines an optimal measurement region based on the offset index in the different measurement region calculated in step 110.

  In this specification, “measurement channel” is defined as a measurement unit of a light receiving element such as a CCD arranged in the non-scanning direction, and “measurement point” is defined as a measurement point in the scanning direction of the same CCD. The “measurement area” is defined as an area in the scanning direction when the measurement mark at each measurement point scans the substrate during focus measurement. Hereinafter, an embodiment related to a measurement region optimization technique will be described.

[First Embodiment]
FIG. 6 is a flowchart showing a first embodiment relating to optimization of a measurement region.

  In step 200, the preceding substrate is loaded. In step 210, the controller 60 performs initial setting of a measurement area for focus measurement. In step 220, the controller 60 causes the focus tilt measurement system 50 to perform focus measurement on a shot with a substrate, and the controller 60 acquires the measured surface position information. If the controller 60 determines in step 230 that focus measurement has not been completed for all the set sample shots, the controller 60 changes the sample shot to the focus tilt measurement system 50 in step S240 to focus. Make measurements. If the controller 60 determines in step 250 that all focus measurements of the assumed measurement area have not been completed, the controller 60 changes the measurement area in step 260. Details of the method of changing the measurement area in step 260 will be described below.

  FIG. 8 is a diagram showing an example of the measurement region in the present embodiment, and it is assumed that the stage is scanning in the downward direction on the paper surface. If the measurement area A1 in FIG. 8 is an initial measurement area, the measurement area A1, A3,..., And the measurement area Ak are sequentially changed from the measurement area A1. As a method for changing the measurement region, there are (1) a method for changing the scanning speed of the substrate stage and (2) a method for changing the accumulation time of the CCD. In this embodiment, the above (1) and ( Any of 2) may be changed. The measurement point is often determined in advance as a predetermined position in the shot. When matching the measurement points regardless of the measurement area, the timing of the CCD accumulation time is adjusted so that the measurement areas A1 to Ak are in the vertical direction of the drawing with respect to the predetermined measurement points as shown in FIG. What is necessary is just to make it change symmetrically.

  Returning to FIG. 6, when the controller 60 determines in step 250 that the focus measurement has been completed in all measurement areas from A1 to Ak in all sample shots, the process proceeds to step 270. In step 270, the controller 60 calculates the difference from the reference plane in each measurement region Ai as an offset.

  FIG. 7 is a flowchart showing details of step 270. In step 300, the controller 60 designates a measurement channel as a reference and a measurement point as a reference for obtaining a reference plane. For example, it is assumed that the reference measurement channel in this embodiment is ch3 in FIG. 2B, and the reference measurement point is P3 in FIG. 2B. In step 310, the controller 60 sets one measurement area Ai among the different measurement areas, and in step 320, calculates a reference plane in the measurement area Ai. Specifically, paying attention to the reference measurement channel ch3, the focus measurement value in the designated measurement area Ai is acquired for the sample shot (8 shots in FIG. 2A) at the reference measurement point P3. Approximation is performed based on the acquired focus measurement values for 8 shots to obtain a reference plane. The reference plane may be approximated by a plane, or may be approximated by a curved surface using a higher-order polynomial in order to obtain a more detailed reference plane of the substrate.

  In step 330, the controller 60 calculates the difference from the reference plane at each measurement point Pj (j = 1, 2,... M) of each measurement channel ch1, ch2,. The sample shot is calculated as an offset. If the controller 60 does not determine in step 340 that the offset has been calculated in all the measurement areas Ai, the controller 60 changes the measurement area Ai in step 350 and repeats the process in step 320. If controller 60 (decision unit 62) determines that step 270 in FIG. 6 has been completed, in step 280, controller 60 optimizes the measurement region.

  FIG. 9 is a diagram illustrating an example in which the measurement region is optimized at a specific measurement point in step 280. 9A shows the offset from the reference plane at the measurement point Pj (j = 1, 2,..., M) in a measurement channel in the measurement regions A1, A2,... Ak in FIG. It is the figure which showed the dispersion | variation between sample shots. The variation of the offset between sample shots is an index indicating the reproducibility of measurement. Note that FIG. 9A shows a predetermined tolerance. This tolerance is determined by the substrate process design rules. This tolerance can be defined, for example, as 50 nm in the case of a 65 nm Node W-CMP process and 30 nm in the case of a Cu dual damascene process.

  FIG. 9B is a diagram in which the measurement points P1 and P4 exceeding the tolerance among the sample shot variations in the current measurement area A1 are plotted for each measurement area. In this example, with respect to the measurement point P1, it is indicated that the variation between the offset sample shots is smaller than a predetermined tolerance only in the measurement region A3, and the measurement region A3 is set as an optimal measurement region instead of the current measurement region A1. You only have to set it. The measurement point P4 is shown to be smaller than a predetermined tolerance in the plurality of measurement areas A3 and A4. In particular, from the viewpoint that the focus accuracy is improved as the offset shot-to-shot variation is smaller, the measurement region A4 having the smallest shot-to-shot variation (an index indicating the reproducibility of measurement) may be set as the optimum measurement region.

[Second Embodiment]
FIG. 10 is a diagram illustrating a second embodiment related to optimization of a measurement region, and is a diagram in which optimization is performed at all measurement points. The second embodiment is particularly effective when focusing on each measurement channel and when it is desirable that the CCD accumulation time is constant in the same scan. In FIG. 10A, sample shots of offsets in measurement areas A1, A2,... Ak obtained by setting the scanning speed of the substrate stage constant and setting a plurality of CCD accumulation times in a certain measurement channel. It shows the variation between the two. Note that the timing of the accumulation start time of the CCD is adjusted so that the measurement points Pj coincide with each other regardless of the measurement areas Ai. FIG. 10A shows a predetermined tolerance determined by the design rule of the substrate process described above. In the current measurement region A1, the average of variations between offset sample shots for the measurement channel exceeds the tolerance. ing. FIG. 10B shows a plot of an average value of variations between offset sample shots (an average value of an index indicating measurement reproducibility) for each measurement region including the current measurement region A1. In this example, in FIG. 10B, the measurement area A4 in which the average value of the variation (index) between the sample shots of the offset is smaller than a predetermined tolerance is set as the optimum measurement area common to all measurement points in the measurement channel. You only have to set it.

[Third Embodiment]
FIG. 11 is a flowchart showing the third embodiment. In the third embodiment, focus measurement is performed in advance in a measurement region of the minimum unit, a focus measurement value in a longer measurement region is estimated, and then the measurement region is optimized based on the result. . In step 200, after loading the preceding substrate, in step 215, the controller 60 sets a minimum measurement area for focus measurement. In step 220, focus measurement is performed in advance only in the minimum measurement region, and in step 250, moving the sample shot in step 260 is repeated until focus measurement in the sample shot is completed. Subsequently, in step 265, the focus measurement value in each measurement area Ai is estimated based on the focus measurement value in the minimum measurement area.

  FIG. 12 is a diagram illustrating a measurement region in the third embodiment, and is an example in which measurement points are matched regardless of the measurement region. A method of estimating the focus measurement value in each measurement area Ai from the focus measurement value in the minimum measurement area will be described with reference to FIG. In FIG. 12, for example, the measurement area A1 corresponds to four minimum measurement areas, and the measurement area A2 corresponds to six minimum measurement areas. Accordingly, the focus measurement value in the measurement area A1 can be obtained by integrating the four focus measurement values in the minimum measurement area corresponding to A1. Further, the focus measurement value in the measurement area A2 can be obtained by integration of the six focus measurement values in the minimum measurement area corresponding to A2.

  Next, similarly to the embodiments described so far, in step 270, the offset at each measurement channel and each measurement point in each measurement region is calculated, and in step 280, the measurement region is optimized. .

[Fourth Embodiment]
FIG. 13 is a diagram illustrating a measurement area Ai according to the fourth embodiment. In the embodiments so far, the case where the position of the measurement point Pj is not changed by the measurement region Ai has been described. However, the position of the measurement point Pj may be slightly shifted. FIG. 13 shows, for example, a case where the CCD accumulation start time is matched and the accumulation end time is changed without changing the scanning speed of the stage. In the measurement area Ai, the measurement start position coincides with the measurement end position. Is different. In this case, the measurement point is slightly shifted with the change of the measurement area Ai, but it is effective to cancel the influence of the substrate process only in the vicinity of the measurement end position.

  FIG. 14A shows the current measurement point Pj of a certain measurement channel, and FIG. 14B shows the measurement point Pj ′ and offset obtained by optimization of the measurement region according to the present invention. In particular, in the case of a twin stage, the focus measurement is performed in detail at the measurement station to obtain the flatness of the entire substrate in advance, and the height of the reference mark on the stage is only measured at the exposure station to determine the height between the exposure slit and the substrate Control. Therefore, the measurement points do not necessarily need to be equally spaced during focus measurement at the measurement station, and the measurement area optimization according to the present invention can be applied.

  As shown in FIG. 14B, it is assumed that the measurement points Pj ′ are at unequal intervals. Even in such a case, if the offset correction is performed on the focus measurement value at the measurement point Pj ′ as shown in FIG. 14C after calculating the offset at the measurement point Pj ′, the measurement point Pj ′ is Defocuser exceeding the allowable range is less likely to occur. Then, while the substrate stage is swapped (moved) or moved between the exposure station and the measurement station, a substrate necessary for exposure control is obtained by a statistical method such as linear interpolation or cubic spline interpolation. It is possible to calculate the surface shape (height distribution).

[Fifth Embodiment]
FIG. 15 is a diagram showing a measurement area Ai in the fifth embodiment. FIG. 15 corresponds to the case where the measurement start positions of the focus measurement are matched in each measurement region in the third embodiment. The estimation of the focus measurement value in each measurement area Ai from the focus measurement value in the minimum measurement area will be described with reference to FIG. In FIG. 15, for example, the measurement area A1 corresponds to three minimum measurement areas, and the measurement area A2 corresponds to four minimum measurement areas. Accordingly, the focus measurement value in the measurement area A1 can be obtained by integration of the three focus measurement values in the minimum measurement area corresponding to A1. Further, the focus measurement value in the measurement area A2 can be obtained by integrating the four focus measurement values in the minimum measurement area corresponding to A2.

  The fifth embodiment of the present invention is also a case where the position of the measurement point is slightly shifted, but it is effective if the same optimization as in the fourth embodiment is applied to the case of the twin stage.

[Sixth Embodiment]
FIG. 16 is a diagram showing a measurement area Ai in the sixth embodiment. In all the embodiments described so far, the case where the width of the measurement region Ai (hereinafter referred to as the measurement width) has been described has been described. However, the present invention is not limited to this, and the measurement points are minute even when the measurement width is constant. As a result, the measurement area can be shifted.

  FIG. 16 is a diagram illustrating an example of a measurement region in which the measurement width is constant and the measurement points are measured by being slightly shifted in the stage scanning direction. Specifically, it can be realized by changing the timing of the accumulation start time without changing the scanning speed of the stage or the total accumulation time of the CCD. In the present embodiment, in order to cope with a minute shift of the measurement point Pj in each measurement region, as shown in FIG. 16, the measurement point Pj in the measurement region Ai is described as Pj (Ai) and distinguished. .

  FIG. 17A is a diagram showing variation between offsets of sample shots in the measurement area Ai in FIG. Here, regarding the measurement points, the measurement points P1 in the measurement region A1 and the measurement region A2 are distinguished as P1 (A1) and P1 (A2). FIG. 17B focuses on the current measurement area A1, and offsets P1 (A1), P1 (A2),... P1 (Ak) at different measurement areas Ai for measurement points P1 exceeding a predetermined tolerance. The sample shot variation is plotted for each measurement region. In FIG. 17B, since the variation between sample shots (an index indicating the reproducibility of measurement) is smaller than a predetermined tolerance in the measurement area A3, the measurement area A3 is selected at the measurement point P1 instead of the current measurement area A1. do it.

[Seventh Embodiment]
The seventh embodiment is an embodiment showing an application example of optimization of the focus measurement area. FIG. 18 is a flowchart in the case of applying a measurement region optimization technique during so-called FEM (Focus Exposure Matrix) exposure in which exposure conditions are determined by changing the focus and exposure amount before actual exposure. At the time of FEM exposure, since it is necessary to finely shake and set the exposure amount, the scanning speed of the substrate stage is often performed at a lower speed than that at the time of actual exposure. Therefore, in step 400, the focus measurement of the present invention is performed at a low scanning speed, and the measurement area is optimized in advance. In step 410, exposure conditions are set by FEM exposure. Thereafter, in step 420, the CCD accumulation time corresponding to the scanning speed of the substrate stage in the actual exposure faster than that in the FEM exposure is set so that the measurement regions optimized in step 400 are matched. In step 430, focus measurement is performed on the substrate used in actual exposure using the set CCD accumulation time, and exposure processing is performed in step 440.

[Eighth Embodiment]
In all the embodiments described so far, the measurement area is optimized only for the preceding substrate. However, the measurement area is not limited to this, and the measurement area is optimized for each substrate to be exposed even during the actual exposure. You may go. FIG. 19 is a flowchart showing the eighth embodiment. First, after the substrate to be actually exposed is loaded in Step 500, focus measurement is performed in a set measurement region with a predetermined sample shot in Step 510, and the variation between the sample shots of the offset is acquired. If this variation exceeds a predetermined tolerance set in advance in step 530, a sequence of optimizing the measurement region again in step 540 is possible. Thereafter, an exposure process is performed in step 550, the substrate is unloaded in step 560, and the process is repeated until all the substrates are exposed in step 570.

[Device Manufacturing Embodiment]
With reference to FIGS. 21 and 22, an embodiment of a device manufacturing method using the above-described exposure apparatus 1 will be described. FIG. 21 is a flowchart for explaining how to fabricate devices (ie, semiconductor chips such as IC and LSI, LCDs, CCDs, and the like). Here, the manufacture of a semiconductor chip will be described as an example. In step 1 (circuit design), the device circuit is designed. In step 2 (mask production), a mask (also referred to as an original plate or a reticle) on which the designed circuit pattern is formed is produced. In step 3 (wafer manufacture), a wafer (also referred to as a substrate) is manufactured using a material such as silicon. Step 4 (substrate process) is called a pre-process and is a process for forming a semiconductor chip using a mask and a substrate, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device created in step 5 are performed. Through these steps, the semiconductor device is completed and shipped (step 7).

  FIG. 22 is a detailed flowchart of the substrate process in Step 4. In step 11 (oxidation), the surface of the substrate is oxidized. In step 12 (CVD), an insulating film is formed on the surface of the substrate. In step 13 (electrode formation), an electrode is formed on the substrate by vapor deposition or the like. In step 14 (ion implantation), ions are implanted on the substrate. In step 15 (resist process), a photosensitive agent is applied to the substrate. In step 16 (exposure), the exposure apparatus 1 is used to expose the substrate through the pattern formed on the mask. In step 17 (development), the exposed substrate is developed. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), the resist that has become unnecessary after the etching is removed. By repeatedly performing these steps, multiple circuit patterns are formed on the substrate.

The flowchart explaining the outline | summary of the measuring method of this invention. The figure explaining the offset measuring method. The figure explaining the measurement error by the reflectance difference of the pattern on a board | substrate. The figure explaining the offset in a measurement field. The figure which showed the dispersion | variation between shots of the offset in each measurement point. The flowchart which shows 1st Embodiment. The flowchart which shows the method of calculating the offset from the reference plane in 1st Embodiment. The figure which showed an example of the measurement area | region in 1st Embodiment. The figure which showed the method of optimizing the measurement area | region in 1st Embodiment. The figure which showed the method of optimizing the measurement area | region in 2nd Embodiment. The flowchart which shows 3rd Embodiment. The figure which showed an example of the measurement area | region in 3rd Embodiment. The figure which shows an example of the measurement area | region in 4th Embodiment. The figure which showed 4th Embodiment. The figure which shows an example of the measurement area | region in 5th Embodiment. The figure which shows an example of the measurement area | region in 6th Embodiment. The figure which showed the method of optimizing the measurement area | region in 6th Embodiment. FIG. 4 is a flowchart when focus measurement according to the present invention is applied during FEM exposure. The flowchart which shows 8th Embodiment. It is a figure explaining the whole structure of the semiconductor exposure apparatus which concerns on this invention. The flowchart explaining the device manufacturing process which concerns on this invention. The flowchart explaining the board | substrate process which concerns on this invention.

Claims (9)

An exposure apparatus having a projection optical system for projecting light from an original, and exposing a substrate through the projection optical system,
A measuring instrument that measures the position of the surface of the substrate in the direction of the optical axis of the projection optical system with respect to the measurement points in the shot arranged on the substrate;
With respect to each of the plurality of sizes of the measurement points, the measurement device is caused to measure the position of the surface in a plurality of shots arranged on the substrate, and based on the measured position, measurement of each of the plurality of sizes is performed. A controller that calculates an index indicating reproducibility and determines the size of the measurement point based on the calculated index;
An exposure apparatus comprising:   The exposure apparatus according to claim 1, wherein the controller sets a plurality of measurement points in the shot and determines the size of each of the plurality of measurement points.   The controller sets a plurality of the measurement points in the shot, calculates an average value of the index at the plurality of measurement points for each of the plurality of sizes, and based on the calculated average value, The exposure apparatus according to claim 1, wherein a size of a common measurement point is determined for the measurement points.   The controller sets a unit of size of the measurement point, causes the measurement unit to measure the position of the surface for each unit, and based on the position of the surface measured for each unit, The position of the surface is calculated for each of the sizes, and the index is calculated for each of the plurality of sizes based on the calculated position of the surface. The exposure apparatus according to item 1.   The controller calculates an offset corresponding to the measurement point for each of the plurality of shots based on the position of the surface measured by the measuring instrument for each of the plurality of shots. The exposure apparatus according to claim 1, wherein a variation in offset is calculated as the index.   6. The exposure apparatus according to claim 5, wherein the controller selects one of the plurality of sizes that minimizes variation in the offset.   The exposure apparatus according to any one of claims 1 to 5, wherein the exposure apparatus is a scanning exposure apparatus.   The substrate stage that holds and moves the substrate, and the measuring instrument measures the position of the surface of the substrate held on the moving substrate stage. Exposure device. A step of exposing the substrate using the exposure apparatus according to claim 1;
Developing the exposed substrate;
A device manufacturing method comprising:

Images