JP7607423B2 - METHOD FOR CONTROLLING A LITHOGRAPHIC APPARATUS, ... AND METHOD FOR MANUFACTURING AN ARTICLE - Patent application - Google Patents

Description

The present invention relates to a method for controlling a lithography apparatus, a lithography apparatus, and a method for manufacturing an article.

Patent document 1 discloses a technique for registering an arbitrary pattern as a mark and measuring the position of a substrate using the registered pattern.

JP 2006-032521 A

When the shape of the pattern registered as a mark is arbitrary, depending on the shape, the measurement accuracy may decrease due to the influence of lens aberration in the measurement system. In particular, when the pattern shape is distributed asymmetrically with respect to the measurement center, it is affected by distortion due to lens aberration that spreads isotropically with respect to the measurement center. In other words, when the pattern shape is asymmetric with respect to the measurement center, the amount of distortion generated on one side of the pattern differs from the amount of distortion generated on the other side. Therefore, the amount of distortion of the pattern changes depending on the position of the pattern being sent in, and the measurement linearity decreases. Also, when the amount of information of the pattern that can be recognized as a mark is small, it is affected by electrical noise, etc., and both the measurement repeatability and measurement linearity decrease.

The present invention provides technology that is advantageous for improving the accuracy of substrate position measurement, for example.

According to one aspect of the present invention, there is provided a control method for a lithography apparatus, comprising: an acquisition step of acquiring an image by capturing an image of a measurement area of a substrate using an imaging unit; a calculation step of calculating an evaluation value relating to the entropy of the acquired image; and a registration step of registering information about the image as information for position measurement of the substrate if the calculated evaluation value satisfies a predetermined criterion, wherein the calculation step includes a step of calculating the entropy of an image in each of a plurality of areas obtained by dividing the image; and a step of calculating the evaluation value based on the calculated entropy of the image in each of the areas .

The present invention can provide a technology that is advantageous for improving the accuracy of substrate position measurement, for example.

FIG. 1 is a diagram showing the configuration of an exposure apparatus. FIG. 13 is a flowchart of a mark registration process. 13 is a flowchart of a mark registration process. 13 is a flowchart of an entropy evaluation value calculation process. FIG. 1 is a diagram showing an example of image region division. FIG. 2 is a diagram showing an example of dividing an area into subareas. 5A to 5C are diagrams for explaining a process of determining a driving amount of the substrate stage. Area reduction layout diagram used in this embodiment 13 is a flowchart of a mark registration process. 1A and 1B are diagrams illustrating an example of region division based on a design region of a reticle.

The following embodiments are described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe multiple features, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicate explanations are omitted.

The present invention relates to a lithography apparatus that forms a pattern of an original on a substrate. Below, an example will be described in which the present invention is applied to an exposure apparatus, which is one example of a lithography apparatus. However, the lithography apparatus is not limited to an exposure apparatus, and may be other lithography apparatus. For example, the lithography apparatus may be a drawing apparatus that draws on a substrate (or a photosensitive agent thereon) using a charged particle beam. Alternatively, the lithography apparatus may be an imprint apparatus that forms a pattern on the substrate by molding an imprint material on the substrate with a mold.

FIG. 1 is a diagram showing the configuration of an exposure apparatus according to an embodiment. FIG. 2 is a diagram showing the layout of a substrate W processed by the exposure apparatus of FIG. 1. In FIG. 2, a plurality of shot areas arranged in a matrix are formed on the substrate W. In one predetermined shot area, a measurement area RA is formed having a pattern that can be registered as a mark for measuring the position of the substrate W. In another predetermined shot area, a measurement area RB is formed having a pattern that can be registered as a mark for measuring the position of the substrate W. A notch N used in mechanical pre-alignment is formed in a part of the outer periphery of the substrate W. Note that an orientation flat may be formed instead of the notch N.

In FIG. 1, the reticle stage RS is a stage that holds and moves the reticle R, which is an original (mask). The illumination optical system I illuminates the reticle R held by the reticle stage RS. A pattern (e.g., a circuit pattern) to be transferred to a substrate W is drawn on the reticle R. The projection optical system P projects the pattern of the reticle R onto the substrate W.

The substrate transport unit WF loads and unloads the substrate W into and from the device. The mechanical pre-alignment unit MA detects the notch N of the substrate W and performs pre-alignment to adjust at least one of the position and rotation angle of the substrate W. The substrate stage STG is a holder that holds and moves the substrate W. A chuck CH that holds the substrate W is installed on the substrate stage STG. The alignment scope AS may include a half mirror M and an imaging unit C. Light from the illumination unit LI is reflected by the half mirror M to illuminate the substrate W. The light reflected by the substrate W is incident on the imaging unit C via the half mirror M. The imaging unit C captures the incident light with an imaging element to generate an image signal. The image signal is transferred to the processing unit IP.

The processing unit IP performs mark position measurement, for example, using template matching technology, based on the image acquired by the alignment scope AS. The processing unit IP may be a computer device including a CPU and memory MEM1 (not shown). The control unit MC performs overall control of each unit regarding the exposure process. For example, based on the position measurement from the processing unit IP, the control unit MC drives the substrate stage STG, aligns the substrate W, and executes exposure processing in which the pattern of the reticle R is exposed onto the substrate W via the projection optical system P. The control unit MC may be a computer device including a CPU and memory MEM2 (not shown). Note that the processing unit IP and the control unit MC may be configured as separate devices, or the functions of the processing unit IP and the control unit MC may be realized by a single computer device.

The mark registration process in this embodiment will be described with reference to the flowcharts of Figures 3 to 5. In S31, the substrate W is carried into the exposure apparatus by the substrate transport unit WF and placed on the mechanical pre-alignment unit MA. The mechanical pre-alignment unit MA performs mechanical pre-alignment, which adjusts the position or rotation angle of the substrate W by detecting the notch N of the substrate W. In S32, the substrate W is placed on the chuck CH of the substrate stage STG by the substrate transport unit WF. The chuck CH holds the placed substrate W, for example, by vacuum suction.

In S33, the controller MC controls the substrate stage STG to send the center coordinates of the measurement area RA of the substrate W to the center of the field of view of the alignment scope AS.

In S34, the processing unit IP executes a mark registration process. FIG. 4 shows a detailed flowchart of the mark registration process in S34. In S401, the control unit MC turns on the illumination unit LI to illuminate the substrate W. This allows the imaging unit C to image the measurement area RA of the substrate to obtain an image (pattern image). Specifically, light reflected by the substrate W enters the alignment scope AS and reaches the imaging unit C via the half mirror M. The imaging unit C captures the incident light with an imaging element to generate an image signal of the pattern image. The image signal is transferred to the processing unit IP and stored, for example, in the memory MEM1.

In S402, the processing unit IP executes a step of calculating an evaluation value related to the entropy of the obtained image (calculation step). FIG. 5 shows a detailed flowchart of the calculation step in S402. In S51, the processing unit IP sets region division of the image. Here, for example, as shown in FIG. 6, the image is divided into a plurality of regions (for example, four regions). However, the number of divided regions is not limited to four.

Here is a set of equations that will be used in the following steps: where E _i is the entropy in region i, and P _k is the probability of occurrence of intensity value k within the region.

In S52, the processing unit IP calculates the overall entropy E _sum , which indicates the sum of the entropy of the image in each region, using the following formulas (1) and (2). Here, since the image is divided into four regions as shown in FIG. 6, i takes values from 1 to 4. Also, the brightness value k takes values from 0 to 255 assuming 8-bit gradation, but the range of k is not limited to this. The overall entropy E _sum represents the amount of information in the entire image, and the larger E _sum indicates the greater the overall amount of information.

In S53, the processing unit IP calculates the image entropy _Ei for each region using formula (1). In S54, the processing unit IP calculates the entropy variance value _Evar, which indicates the variance of the entropy of the image for each region, using formulas (3) and (4). The entropy variance value _Evar indicates the bias of the distribution of the pattern shown in the image, and the smaller the entropy variance value _Evar , the more even (less biased) the distribution of the pattern is.

In S55 and S56, the processing unit IP obtains the difference in the entropy of the image of the region that is symmetrical with respect to the center of the image among the multiple regions. For example, in S55, the processing unit IP obtains the entropy difference value _Ediff1 between the upper region (regions 1 and 2 in FIG. 6) and the lower region (regions 3 and 4 in FIG. 6) using formulas (5), (6), and (9). The smaller the entropy difference value _Ediff1 , the higher the symmetry of the patterns of the upper region and the lower region. In S56, the processing unit IP obtains the entropy difference value Ediff2 between the left region (regions 1 and 3 in FIG. 6) and the right region (regions 2 and 4 in FIG. 6) using formulas (7), (8), and (10). The smaller _{the entropy difference value Ediff2 ,} the higher the symmetry of the patterns of the left region and the right region.

In S57, the processing unit IP applies the total entropy E _sum , the entropy variance value E _var , and the entropy difference values E _diff1 and E _diff2 calculated in S52 to S56 to formula (11) to obtain an entropy evaluation value E _total . The first term on the right side of formula (11), which is the evaluation formula, indicates that the higher the total entropy E _sum , the higher the evaluation value. As described above, the total entropy E _sum indicates the amount of information in the entire pattern image. Since the greater the amount of information, the higher the measurement accuracy (equivalent to the greater number of marks), the higher the total entropy E _sum , the higher the evaluation value. The second term on the right side of formula (11) indicates that the smaller the entropy variance value E _var, the higher the evaluation value. The smaller the entropy variance value E _var , the more even (unbiased) the pattern distribution is, and the smaller the effect of the aberration of the measurement system is. The third and fourth terms on the right side of equation (11) indicate that the smaller the entropy difference values _Ediff1 and _Ediff2 , respectively, the higher the symmetry of the pattern, and the higher the evaluation value.

This completes the sub-process in S402.

Returning to FIG. 4, in S403, the processing unit IP judges whether the entropy evaluation value E _total calculated in S402 satisfies a predetermined criterion. For example, the processing unit IP judges whether the entropy evaluation value E _total calculated in S402 is equal to or greater than a predetermined threshold. If the entropy evaluation value E _total is equal to or greater than the threshold, the processing unit IP proceeds to S404 and registers the image information obtained in S401 as information for measuring the position of the substrate. The "image information" may be the image itself or a feature amount of the image. The image information may also include information on the position of the image on the substrate. Here, the processing unit IP registers the image obtained in S401 as a mark image of the measurement area RA on the substrate. The registered image is stored, for example, in the memory MEM2 of the control unit MC.

Returning to FIG. 3, in S35, the controller MC controls the substrate stage STG to send the central coordinates of the measurement region RB of the substrate W to the center of the field of view of the alignment scope AS. Then, in S36, a mark registration process is executed for the measurement region RB. This mark registration process is the same processing as the mark registration process in S34 described above, so a description thereof will be omitted.

Next, a case where it is determined in S403 of FIG. 4 that the entropy evaluation value E _total is not equal to or greater than the threshold (i.e., does not satisfy a predetermined standard) will be described. In this case, the process proceeds to S405. In S405, the processing unit IP divides the area 1 in FIG. 6 into four subareas 1-1, 1-2, 1-3, and 1-4 as shown in FIG. 7, calculates the entropy of the image of each subarea according to the flowchart of FIG. 5, and obtains the entropy evaluation value of the area 1. Note that, although each area is further divided into four subareas in the example of FIG. 7, the number of divisions is not limited to this. Thereafter, in S406, S407, and S408, the processing unit IP similarly obtains the entropy evaluation values for the areas 2, 3, and 4.

In S409, the control unit MC determines the drive amount of the substrate stage STG based on the entropy evaluation value calculated in S405 to S408. For example, the control unit MC selects the area in which the entropy evaluation value calculated in S405 to S408 is the maximum. FIG. 8 shows the division layout of the image corresponding to FIG. 7. In FIG. 8, the number of pixels in the horizontal direction of the image is XPIX, and the number of pixels in the vertical direction is YPIX. As an example, assume that the entropy evaluation value of area 4 in FIG. 6 is the maximum. In this case, the drive amount for sending the center OFS of area 4 to the image center ORG (the center of the field of view of the alignment scope AS (imaging unit C)) in FIG. 8 can be Δ(1/4)XPIX, Δ(1/4)YPIX.

In S410, the control unit MC drives the substrate stage STG by the drive amount determined in S409. In this way, the position of the substrate stage STG is adjusted so that the center of the area with the maximum entropy evaluation value is located at the center of the field of view of the imaging unit C.

Then, the process returns to S401, and the mark image is registered again using the same process. This makes it possible to determine the area of the image that maximizes the entropy evaluation value.

Second Embodiment
In the above-described first embodiment, a detailed flow of the mark registration steps (S34, S36) in FIG. 3 is shown in FIG. 4, but an alternative example to FIG. 4 is shown in FIG.

S1001, S1002, S1003, and S1004 in FIG. 10 are the same as S401, S402, S403, and S404 in FIG. 4, respectively. In FIG. 10, if it is determined in S1003 that the entropy evaluation value E _total is not equal to or greater than the threshold, the process proceeds to S1005. In S1005, the processing unit IP changes the target area for which the entropy evaluation value E _total is to be calculated to the partial area MAR of the area OAR of the original image, as shown in FIG. 9. Then, the process returns to S1002. In S1002, the processing unit IP calculates the entropy evaluation value for areas 1 to 4 in the partial area MAR according to the flow of FIG. 5. Then, if the entropy evaluation value is equal to or greater than the threshold in S403, the image of the partial area MAR is registered as a mark image in S404. The registered image is stored, for example, in the memory MEM2 of the control unit MC.

Third Embodiment
11 shows a design area in the reticle R where a pattern such as a circuit pattern to be exposed on a substrate is formed. Here, the dimension in the X direction of the design area of the reticle R is RXNM, the dimension in the Y direction is RYNM, and the dimensions in the X direction of the image captured by the imaging unit C are XNM and YNM. The processing unit IP divides the design area of the reticle R into a plurality of areas each of which is equal to or smaller than the dimensions XNM and YNM of the image, and calculates an entropy evaluation value for each divided area. Then, based on the calculated entropy evaluation value for each area, the processing unit IP determines a position in the design area where a pattern that can be registered as a mark is to be formed. For example, the processing unit IP determines whether the entropy evaluation value for each divided area is equal to or greater than a threshold value. If the entropy evaluation value is equal to or greater than the threshold value, the divided area is determined to be an area of the design area of the reticle R suitable for measurement and suitable for forming a pattern that can be registered as a mark.

This makes it possible to determine in advance a position suitable for measurement on the design area of reticle R (a position suitable for forming a pattern that can be registered as a mark).

<Embodiment of an article manufacturing method>
The article manufacturing method according to the embodiment of the present invention is suitable for manufacturing articles such as microdevices such as semiconductor devices and elements having fine structures. The article manufacturing method according to the present embodiment includes a step of transferring a pattern of an original to a substrate using the above-mentioned lithography apparatus (exposure apparatus, imprint apparatus, drawing apparatus, etc.) and a step of processing the substrate to which the pattern has been transferred in the above step. Furthermore, the manufacturing method includes other well-known steps (oxidation, film formation, deposition, doping, planarization, etching, resist stripping, dicing, bonding, packaging, etc.). The article manufacturing method according to the present embodiment is advantageous in at least one of the performance, quality, productivity, and production cost of the article compared to conventional methods.

The invention is not limited to the above-described embodiment, and various modifications and variations are possible without departing from the spirit and scope of the invention. Therefore, the following claims are appended to disclose the scope of the invention.

W: substrate, R: reticle, MA: mechanical pre-alignment unit, STG: substrate stage, CH: chuck, AS: alignment scope, IP: processing unit, MC: control unit

Claims (14)

1. A method for controlling a lithographic apparatus, comprising the steps of:
an acquisition step of acquiring an image by capturing an image of a measurement region of the substrate using an imaging unit;
a calculation step of calculating an evaluation value related to the entropy of the obtained image;
a registration step of registering information of the image as information for substrate position measurement when the calculated evaluation value satisfies a predetermined criterion;
having
The calculation step includes:
Calculating the entropy of the image in each of a plurality of regions obtained by dividing the image;
calculating the evaluation value based on the calculated entropy of the image of each region;
A control method comprising: 1. A method for controlling a lithographic apparatus, comprising the steps of:
an acquisition step of acquiring an image by capturing an image of a measurement region of the substrate using an imaging unit;
a calculation step of calculating an evaluation value related to the entropy of the obtained image;
a registration step of registering information of the image as information for substrate position measurement when the calculated evaluation value satisfies a predetermined criterion;
having
the evaluation value is a value for evaluating at least one of a bias in distribution of a pattern represented in the image and a symmetry of the pattern,
The calculation step includes:
Calculating the entropy of the image in each of a plurality of regions obtained by dividing the image;
calculating the evaluation value based on the calculated entropy of the image of each region;
A control method comprising : The control method according to claim 1, characterized in that the evaluation value is a value for evaluating at least one of the information amount of the image, the bias of the distribution of the pattern represented in the image, and the symmetry of the pattern. 4. The control method according to claim 3 , wherein the evaluation value includes a total entropy indicating a sum of entropies of the images of the calculated respective regions, the total entropy being a value representing the amount of information. The control method according to claim 3, characterized in that the evaluation value includes an entropy variance value that indicates the variance of the entropy of the image of each of the calculated regions, which is a value that represents the bias. 4. The control method according to claim 3 , wherein the evaluation value includes a difference in entropy of images in areas symmetrically positioned with respect to a center of the image, the difference being a value representing the symmetry. The evaluation value is
A term including a total entropy indicating the sum of the entropies of the images of the calculated regions, which is a value representing the amount of information;
a term including an entropy variance value indicating the variance of the entropy of the image of each of the calculated regions, the entropy variance value being a value representing the bias;
A term including a difference in entropy of an image in a region located symmetrically with respect to the center of the image, the difference being a value representing the symmetry;
The control method according to claim 3 , characterized in that the calculation is performed using an evaluation formula including: 8. The control method according to claim 1 , wherein the registration step registers the image as an image of a mark for measuring a position of the substrate when the calculated evaluation value satisfies a predetermined criterion. a step of calculating an entropy of an image in each of a plurality of sub-regions obtained by further dividing each of the plurality of regions when the calculated evaluation value does not satisfy the predetermined criterion;
calculating an evaluation value for the entropy of each of the plurality of regions based on the calculated entropy of each of the subregions;
adjusting a position of a stage that holds the substrate so that a center of the region among the plurality of regions in which the evaluation value is maximum is located at a center of a field of view of the imaging unit;
8. The method according to claim 1, further comprising : If the calculated evaluation value does not satisfy the predetermined criterion, the method further includes a step of changing a target region for obtaining the evaluation value in the calculation step to a partial region of the image,
The control method according to claim 1 , wherein the calculation step and the registration step are executed again for the partial region. Dividing a design area of the reticle into a plurality of areas, each of which is equal to or smaller than the image, and calculating an evaluation value relating to the entropy of the image in each of the plurality of divided areas;
determining a position in the design area where a pattern that can be registered as a mark is to be formed based on the calculated evaluation value of each area;
11. The method according to claim 1, further comprising: A holder for holding the substrate;
an imaging unit that images a measurement region of the substrate held by the holding unit;
A processing unit that processes an image obtained by the imaging unit,
the processing unit is configured to calculate an evaluation value relating to an entropy of the image, and, when the calculated evaluation value satisfies a predetermined criterion, register information of the image as information for substrate position measurement;
The processing unit includes:
Calculating the entropy of an image in each of a plurality of regions obtained by dividing the image;
calculating the evaluation value based on the calculated entropy of the image of each region;
13. A lithography apparatus comprising: A holder for holding the substrate;
an imaging unit that images a measurement region of the substrate held by the holding unit;
A processing unit that processes an image obtained by the imaging unit,
the processing unit is configured to calculate an evaluation value relating to an entropy of the image, and, when the calculated evaluation value satisfies a predetermined criterion, register information of the image as information for substrate position measurement;
the evaluation value is a value for evaluating at least one of a bias in distribution of a pattern represented in the image and a symmetry of the pattern,
The processing unit includes:
Calculating the entropy of an image in each of a plurality of regions obtained by dividing the image;
The evaluation value is calculated based on the calculated entropy of the image of each region.
13. A lithography apparatus comprising: forming a pattern on a substrate using a lithographic apparatus according to claim 1 ,
processing the substrate on which the pattern is formed;
and manufacturing an article from the substrate on which the processing has been performed.

Images