Exposure Method and Lithography System

• US 20080259297A1
• Filed: 05/24/2006
• Published: 10/23/2008
• Est. Priority Date: 05/25/2005
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Kawakubo, Masaharu
• Granted Patent: US 8,605,248 B2
• Time in Patent Office: Days
• US Class Current: 355/52
• CPC Class Codes: G03F 7/70425 Imaging strategies, e.g. for increasing throughput or resolution, printing product fields larger than the image field or compensating lithography- or non-lithography errors, e.g. proximity correction, mix-and-match, stitching or double patterning
• CPC Class Codes: G03F 7/70458 Mix-and-match, i.e. multiple exposures of the same area using a similar type of exposure apparatus, e.g. multiple exposures using a UV apparatus

Abstract

In the case where the previous process (X) and the previous process (Y) are different in step 310, only a distortion amount in an X-axis direction is extracted from image distortion data of the previous process (X) in Step 316 and only a distortion amount in a Y-axis direction is extracted from image distortion data of the previous process (Y) in Step 318, and then in Step 320, image distortion data is created by synthesizing the extracted distortion amounts, and the synthesized image distortion data is used for subsequent adjustment of projected images. With this operation, the distortion of projected images can be adjusted per axis and accordingly overlay exposure with high accuracy can be realized.

Claims

1. An exposure method in which overlay exposure to a photosensitive object is performed by overlaying layers, the method including:

a selection process in which a reference layer that serves as a reference to obtain information on overlay exposure of a next layer is selected for each of axes of a two-dimensional orthogonal coordinate system that serves as a reference on overlay, from among at least two layers that have been already exposed, wherein

the information on overlay exposure includes a distortion component of a projected image at the point in time when exposure of the reference layer was performed, in a projection exposure apparatus that was used for the exposure of the reference layer.

2. The exposure method according to claim 1, further including:

a process in which while adjusting an exposure state of a projection exposure apparatus for each of the axes based on information on a formation state of a pattern image on the selected reference layer, overlay exposure of a next layer is performed.

3. The exposure method according to claim 1, wherein

in the selection process, in the case where a plurality of reference layers are selected with respect to at least one of the axes, the distortion component of a projected image in the at least one of the axes is computed by weighted average processing of distortion components of projected images of the plurality of reference layers.

4. The exposure method according to claim 3, wherein

a criterion for deciding weights of the weighted average processing includes a positional relation of the reference layers with a layer subject to exposure, the degree of approximation of pattern linewidth between the reference layers and the layer subject to exposure, and the degree of similarity of process between the reference layers and the layer subject to exposure.

5. An exposure method in which overlay exposure to a photosensitive object is performed by overlaying layers, the method including:

a selection process in which a reference layer that serves as a reference to obtain information on overlay exposure of a next layer is selected for each of axes of a two-dimensional orthogonal coordinate system that serves as a reference on overlay, from among at least two layers that have been already exposed, wherein

the information on overlay exposure includes a nonlinear component of a positional deviation amount of formation positions of a plurality of divided areas with respect to positions, which serve as datum positions when the plurality of divided areas are formed on the photosensitive object, in a projection exposure apparatus that was used for exposure of the reference layer.

6. The exposure method according to claim 5, further including:

a process in which while adjusting an exposure state of a projection exposure apparatus for each of the axes based on information on a formation state of a pattern image on the selected reference layer, overlay exposure of a next layer is performed.

7. The exposure method according to claim 5, wherein

in the selection process, in the case where a plurality of reference layers are selected with respect to at least one of the axes, the nonlinear component corresponding to the at least one of the axes is obtained by weighted average processing of nonlinear components of the plurality of reference layers.

8. The exposure method according to claim 7, wherein

a criterion for deciding weights of the weighted average processing includes a positional relation of the reference layers with a layer subject to exposure, the degree of approximation of pattern linewidth between the reference layers and the layer subject to exposure, and the degree of similarity of process between the reference layers and the layer subject to exposure.

9. A lithography system that performs overlay exposure to a photosensitive object by overlaying layers, the system comprising:

a plurality of projection exposure apparatuses;

a storage unit that stores information on a formation state of a pattern image of a layer that has been already exposed by any one of the plurality of projection exposure apparatuses;

a first selection unit that selects a reference layer that serves as a reference to obtain information on overlay exposure of a next layer for each of axes of a two-dimensional orthogonal coordinate system that serves as a reference on overlay, from among at least two layers that have been already exposed, the information on overlay exposure including a distortion component of a projected image at the point in time when exposure of the reference layer was performed, in a projection exposure apparatus that was used for the exposure of the reference layer;

a second selection unit that selects a projection exposure apparatus that performs overlay exposure of a next layer from among the plurality of projection exposure apparatuses; and

a computation unit that computes information on overlay exposure of a next layer in the selected projection exposure apparatus based on information on an exposure state of the selected reference layer for each of the axes.

10. The lithography system according to claim 9, further comprising:

an adjusting unit that adjusts an exposure state of a projection exposure apparatus for each of the axes based on information on a formation state of a pattern image on the selected reference layer, when overlay exposure of a next layer is performed.

11. The lithography system according to claim 9, wherein

in the case where the first selection unit selects a plurality of reference layers with respect to at least one of the axes, the distortion component of a projected image in the at least one of the axes is computed by weighted average processing of distortion components of projected images of the plurality of reference layers.

12. The lithography system according to claim 11, wherein

a criterion for deciding weights of the weighted average processing includes a positional relation of the reference layers with a layer subject to exposure, the degree of approximation of pattern linewidth between the reference layers and the layer subject to exposure, and the degree of similarity of process between the reference layers and the layer subject to exposure.

13. A lithography system that performs overlay exposure to a photosensitive object by overlaying layers, the system comprising:

a plurality of projection exposure apparatuses;

a storage unit that stores information on a formation state of a pattern image of a layer that has been already exposed by any one of the plurality of projection exposure apparatuses;

a first selection unit that selects a reference layer that serves as a reference to obtain information on overlay exposure of a next layer for each of axes of a two-dimensional orthogonal coordinate system that serves as a reference on overlay, from among at least two layers that have been already exposed, the information on overlay exposure including a nonlinear component of a positional deviation amount of formation positions of a plurality of divided areas with respect to positions, which serve as datum positions when the plurality of divided areas are formed on the photosensitive object, in a projection exposure apparatus that was used for overlay exposure of the reference layer;

a second selection unit that selects a projection exposure apparatus that performs overlay exposure of a next layer from among the plurality of projection exposure apparatuses; and

a computation unit that computes information on overlay exposure of a next layer in the selected projection exposure apparatus based on information on an exposure state of the selected reference layer for each of the axes.

14. The lithography system according to claim 13, further comprising:

an adjusting unit that adjusts an exposure state of a projection exposure apparatus for each of the axes based on information on a formation state of a pattern image on the selected reference layer, when overlay exposure of a next layer is performed.

15. The lithography system according to claim 13, wherein

in the case where the first selection unit selects a plurality of reference layers with respect to at least one of the axes, the nonlinear component corresponding to the at least one of the axes is obtained by weighted average processing of nonlinear components of the plurality of reference layers.

16. The lithography system according to claim 15, wherein

a criterion for deciding weights of the weighted average processing includes a positional relation of the reference layers with a layer subject to exposure, the degree of approximation of pattern linewidth between the reference layers and the layer subject to exposure, and the degree of similarity of process between the reference layers and the layer subject to exposure.