JP7631176B2 - Exposure method, exposure apparatus, and article manufacturing method - Google Patents

Description

The present invention relates to an exposure method and exposure apparatus that projects and transfers a pattern from an original such as a reticle or mask onto a substrate such as a wafer via a projection optical system.

Among the semiconductor devices manufactured by the above-mentioned exposure method and apparatus, for example, memory devices have not only fine circuit line widths but also have stacked circuits, which are called 3DNA N D, in order to increase memory capacity. In this 3DNA N D, multiple circuit layers are formed in a stepped shape, and lead lines are connected to each step. To form such a stepped stacked circuit structure, for example, a trapezoidal resist profile is formed, etched, the resist is then etched (slimmed), and the process of etching is repeated. At this time, it is necessary to thicken the resist, which is an etching mask, but the shape of the resist, i.e., the profile, is also important.

The resist profile can be controlled by changing the exposure dose and focal position, but these alone make it difficult to control the nonlinearity of the profile according to the position on the wafer. Control of the nonlinearity of the profile can be achieved, for example, by tilting one of the stages with respect to the scanning direction when scanning exposure is performed by moving the stage carrying the wafer and the stage carrying the reticle. In addition, as disclosed in Patent Document 1, it can also be achieved by multi-focal exposure, in which the focus is shifted from the best focusing position and exposure is performed at multiple focal positions.

Japanese Unexamined Patent Publication No. 7-153658

However, if the resist profile is nonlinear, the amount of etching during etching will not be uniform in the height direction, resulting in different heights for each step in the stepped stacked circuit structure. The resist profile also changes due to resist unevenness, such as uneven thickness when the resist is applied and uneven development during development. For this reason, it is necessary to reduce the effects of these resist unevenness so that the resist profile is uniform within the wafer.

The present invention provides an exposure method and exposure apparatus that can make the resist profile within a substrate closer to uniform.

An exposure method according to one aspect of the present invention is used when exposing a pattern formed on an original onto a substrate . The method includes a first step of acquiring first data indicating a relationship between a tilt amount of a stage holding the original or the substrate , or multiple focal positions in multifocal exposure , and a resist profile, a second step of acquiring second data indicating nonlinearity of the profile that changes due to unevenness in the thickness of the resist applied to the substrate or unevenness in the development of the resist that occurs when the resist is developed, at multiple positions on the substrate, and a step of correcting the tilt amount or the focal position according to the position on the substrate based on the first data and the second data and performing exposure . Note that a program that causes a computer to execute processing according to the exposure method also constitutes another aspect of the present invention.

An exposure apparatus according to another aspect of the present invention performs exposure to transfer a pattern of an original onto a resist on a substrate via a projection optical system. The apparatus is characterized by having an acquisition means for acquiring first data indicating the relationship between the amount of tilt of a stage carrying an original or substrate relative to the scanning direction in stage tilt exposure or the relationship between multiple focal positions of the projection optical system in multifocal exposure and the profile of the resist after exposure, and second data indicating the nonlinearity of the profile that changes due to resist unevenness at multiple positions in the substrate, and a correction means for correcting the amount of tilt or focal position for each position or region in the substrate using the first and second data. Note that a method for manufacturing an article, which includes a step of exposing a substrate using the exposure apparatus and a step of manufacturing an article from the exposed substrate, also constitutes another aspect of the present invention.

The present invention makes it possible to make the resist profile within the substrate more uniform.

4 is a flowchart showing a resist profile correction sequence in the embodiment. FIG. 4 is a diagram showing an example of an exposure layout in the embodiment. FIG. 4 is a diagram showing an example of a resist profile in an embodiment. 11A and 11B are diagrams showing the relationship between the stage tilt amount and the nonlinearity of the resist profile in an embodiment. FIG. 11 is a diagram showing an example of another exposure layout in the embodiment. FIG. 13 is a diagram showing the relationship between the position on the wafer and the nonlinearity of the resist profile in an embodiment. 13A and 13B are diagrams showing the relationship between a position on a wafer and a corrected amount of stage tilt in an embodiment. FIG. 2 is a diagram showing an exposure apparatus in the embodiment. 4A to 4C are diagrams showing stage tilt exposure in an embodiment. FIG. 4 is a diagram showing multifocal exposure in an embodiment.

The following describes an embodiment of the present invention with reference to the drawings.

Figure 8 shows an exposure apparatus 10 according to an embodiment of the present invention. The exposure light guided from the illumination system 1 is diffracted by the circuit pattern of the reticle (or mask) 2 serving as an original, and is focused by the lens 4 serving as a projection optical system to form an image on the wafer 5 serving as a substrate. In the exposure apparatus of this embodiment, the reticle stage 3 carrying the reticle 2 and the wafer stage 6 carrying the wafer 5 move synchronously in the Y direction in the figure relative to the lens 4, thereby scanning the reticle 2 and the wafer 5 with respect to the exposure light. This causes the pattern of the reticle 2 to be transferred to the resist applied to the wafer 5.

Figure 9 shows stage tilt exposure performed in exposure apparatus 10. By moving the wafer stage 6 at an angle relative to the horizontal scanning direction (Y direction), the wafer 5 moves at an angle relative to the reticle 2 as shown. As a result, the wafer 5 is exposed while the position of the wafer 5 relative to the focal position of the lens 4 changes in multiple stages. Note that instead of the wafer stage 6, the reticle stage 3 may be tilted relative to the scanning direction.

Figures 10(a) and (b) show multifocal exposure performed in exposure apparatus 10. In multifocal exposure, the wafer 5 is exposed with the focal position of the lens 4 shifted from the best position (in-focus position) in the +z direction (Figure 10(a)) and in the -z direction. Figures 10(a) and (b) show the case where the focal position is shifted to two positions from the in-focus position, but exposure may be performed with the focal position shifted to more positions.

As shown in FIG. 8, the exposure apparatus 10 has a controller 100 as a control means for controlling exposure while appropriately setting the tilt amount of the wafer stage 6 in stage tilt exposure and multiple focal positions in multifocal exposure. The controller 100 functions as an acquisition means and a correction means.

The flowchart in FIG. 1 shows the process (exposure method) executed by the controller 100 in this embodiment. The controller 100, which is configured by a computer, executes this process according to a program. The "S" in the diagram indicates a step.

In step 101 (first step), the controller 100 performs these test exposures while changing the conditions of stage tilt exposure and multifocal exposure. Specifically, in stage tilt exposure, the tilt amount (angle θ: hereinafter referred to as stage tilt amount) of the wafer stage 6 relative to the scanning direction, which is a condition, is changed. For example, while changing the stage tilt amount within the wafer 5, the target pattern on the reticle 2 is exposed by changing the position on the resist previously applied to the wafer 5. Also, in multifocal exposure, while changing the focal position, which is a condition, the target pattern is exposed by changing the position on the resist applied to the wafer 5. In the test exposure, it is desirable to perform exposure at multiple positions close to each other within the wafer 5 so as to be less susceptible to processes such as resist application or development within the wafer 5.

2 shows an example of exposure positions on a wafer in a test exposure. A resist (not shown) is applied to the entire wafer 201. Exposure is performed with different stage tilt amounts (i.e., nine conditions) for nine positions close to each other near the center of the wafer 201. The number of conditions is not limited to nine, and the exposure positions 202 do not have to be near the center of the wafer 201 as long as they are close to each other.

After the test exposure, development is performed and the cross-sectional shape of the resist corresponding to the target pattern, i.e., the resist profile, is measured for each stage tilt amount or focus position.

3 shows examples of resist profiles under three conditions with different stage tilt amounts. 301 indicates a wafer as a substrate to be exposed, and 302 to 304 indicate resist profiles. The left side of each resist profile is shown as a simple vertical surface. The degree of nonlinearity of the right side of the resist profiles 302 to 304 differs depending on the stage scanning amount. The resist profile may be measured using, for example, a cross-sectional SEM (Scanning Electron Microscope), scatterometry, or AFM (Atomic Force Microscope).

The degree of nonlinearity of the resist profile obtained by measurement can be quantified, for example, by approximating the profile data with a polynomial and using the coefficients. FIG. 4 shows an example of the relationship between the stage tilt amount and the nonlinearity of the resist profile. The controller 100 stores the first data thus obtained, which indicates the relationship between the stage tilt amount or focal position and the nonlinearity of the resist profile, in a memory (not shown).

The quantification of the degree of nonlinearity of the resist profile is not limited to the polynomial approximation described above. For example, the deviation of the resist profile from the linearity may be calculated as the square sum, and this may be quantified as the nonlinear component. Alternatively, the resist profile may be divided in the height direction, each part may be approximated by a trapezoid, and the sidewall angle and height of the resulting trapezoid may be used to quantify the degree of nonlinearity.

Next, in step 102 (second step), the controller 100 acquires resist profiles at multiple positions on the wafer that change due to resist unevenness that occurs in the resist process in which resist is applied to the wafer and the exposed resist is developed. The resist unevenness here refers to uneven resist thickness and development unevenness. At this time, unlike step 101, the controller 100 performs exposure at multiple positions on the wafer while keeping the stage tilt amount and focal position constant, for example, setting the stage tilt amount to 0 and the focal position to the best focus position.

During this exposure, in order to capture with good sensitivity the resist profile that changes due to resist unevenness, the target pattern of the reticle is exposed at positions on the wafer that are not close to each other (farther apart than the multiple positions in step 101). Figure 5 shows an example of the exposure positions at this time. In this example, multiple exposure positions 502 are set on the resist applied to the wafer 501, spaced apart from each other in the wafer radial direction (from the center to the periphery). The exposure positions may be set in a matrix pattern within the wafer instead of being set in the wafer radial direction as in Figure 5.

After that, the resist profile for each exposure position is measured, and the nonlinearity of the resist profile depending on the position within the wafer is obtained from the measurement results as shown in FIG. 6. The controller 100 stores second data indicating this nonlinearity in memory. Note that the order of steps 101 and 102 may be reversed.

Next, in step 103, the controller 100 reads (acquires) the second data from the memory. Then, it calculates an appropriate correction amount for the stage tilt amount or the focal position to correct the nonlinearity of the resist profile due to the position in the wafer indicated by the second data (to make the resist profile in the wafer closer to uniformity). At this time, the controller 100 reads (acquires) the first data stored in the memory. Then, it calculates the correction amount for each position in the wafer or for each area including multiple positions from the relationship between the stage tilt amount or focal position indicated by the first data and the nonlinearity of the resist profile. Then, it stores the obtained correction amount in the memory. Figure 7 shows an example of the stage tilt amount corrected for each position in the wafer. In this example, the corrected stage tilt amount increases from the center to the periphery of the wafer.

Next, in step 104, the controller 100 performs exposure on the corresponding exposure position or exposure area on the wafer (resist) using the optimal conditions (stage tilt amount or focal position) corrected by the correction amount for each position or area calculated in step 103.

When exposure is performed by changing the amount of stage tilt for each position or region in step 101 or step 104, the distribution of focal positions in the exposure aperture after exposure, i.e., the distribution of the image plane and aberration, changes according to the amount of stage tilt due to the asymmetry of the exposure aperture. For this reason, it is desirable to perform exposure while correcting the image plane position and aberration calculated in advance according to the amount of stage tilt using a correction mechanism in the projection optical system.

In addition, when controlling the nonlinearity of the resist profile by the amount of stage tilt, it is possible to control it in the scanning direction but not in the non-scanning direction. To control the nonlinearity of the resist profile in the non-scanning direction as well, the wafer stage can be tilted around an axis extending in the scanning direction, and the amount of this tilt can be changed for each exposure position in the non-scanning direction, as in multi-focal exposure.

According to the present embodiment described above, the resist profile within the wafer can be made closer to uniform.
Other Examples
The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions.

The method for manufacturing an article using the exposure apparatus and exposure method described in the above embodiment is suitable for manufacturing articles such as, for example, microdevices such as semiconductor devices, elements having fine structures, and flat panel displays. This manufacturing method includes a step of exposing a substrate using the above-mentioned exposure apparatus, and a step of manufacturing an article from the substrate exposed in this step. Furthermore, this manufacturing method may include well-known steps (exposure, oxidation, film formation, deposition, doping, planarization, etching, resist stripping, dicing, bonding, packaging, etc.). This manufacturing method is advantageous in at least one of the performance, quality, productivity, and production cost of the article compared to conventional methods.

The above-described embodiments are merely representative examples, and various modifications and variations are possible when implementing the present invention.

2 reticle 3 reticle stage 4 projection optical system 5 wafer 6 wafer stage 10 exposure apparatus 100 controller

Claims (9)

1. An exposure method for exposing a pattern formed on an original onto a substrate , comprising the steps of:
a first step of acquiring first data indicating a relationship between a tilt amount of a stage holding the original or the substrate , or a plurality of focal positions in multi-focal exposure , and a resist profile;
a second step of acquiring second data indicating nonlinearity of the profile that changes due to unevenness in the thickness of the resist applied to the substrate or unevenness in development of the resist that occurs when developing the resist, at a plurality of positions on the substrate ;
and performing exposure by correcting the tilt amount or the focus position according to a position on the substrate based on the first data and the second data . 2. The method according to claim 1, wherein the profile is a cross-sectional shape of the resist. Exposure method. 2. The exposure method according to claim 1, wherein in the second step , the second data is acquired by performing exposure at the plurality of positions while keeping the tilt amount or the focus position constant. In the first step , exposure is performed at a plurality of positions on the substrate that are close to each other;
4. The exposure method according to claim 1, wherein in the second step , exposure is performed at a plurality of positions on the substrate that are spaced apart from one another more than the plurality of positions in the first step. 5. The exposure method according to claim 1 , further comprising the step of correcting an aberration of a projection optical system which changes in accordance with the amount of tilt when performing exposure by changing the amount of tilt . 6. An exposure method according to claim 1, wherein when exposure is performed by changing the amount of tilt , the amount of tilt around an axis extending in the scanning direction is changed depending on the exposure position in the non-scanning direction of the stage. A program for causing a computer to execute a process according to the exposure method according to any one of claims 1 to 6. An exposure apparatus that exposes a pattern formed on an original onto a substrate , comprising:
an acquisition means for acquiring first data indicating a relationship between a tilt amount of a stage holding the original or the substrate , or multiple focal positions in multifocal exposure , and a resist profile, and second data indicating nonlinearity of the profile that changes at multiple positions on the substrate due to unevenness in the thickness of the resist applied to the substrate or unevenness in development of the resist that occurs when the resist is developed ;
a correction unit that corrects the tilt amount or the focus position in accordance with a position on the substrate based on the acquired first data and second data . a first step of acquiring first data indicating a relationship between a tilt amount of a stage holding an original or a substrate, or a plurality of focal positions in multi-focal exposure , and a resist profile;
a second step of acquiring second data indicating nonlinearity of the profile that changes due to unevenness in the thickness of the resist applied to the substrate or unevenness in development of the resist that occurs when developing the resist, at a plurality of positions on the substrate;
performing exposure by correcting the tilt amount or the focal position according to a position on the substrate based on the first data and the second data ;
and producing an article from the exposed substrate .