Exposure method and lithography system

• US 8,605,248 B2
• Filed: 05/24/2006
• Issued: 12/10/2013
• Est. Priority Date: 05/25/2005
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Kawakubo, Masaharu
• Primary Examiner(s): Kim, Peter B
• Assistant Examiner(s): Persaud, Deoram
• Application Number:
  US11/915,504
• Publication Number:
  US 20080259297A1
• Time in Patent Office: 2,757 Days
• Field of Search: 438/763, 438/725, 438/942, 430/22, 430/30, 430/312
• 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 on the object, the method comprising:

a selection process in which a reference layer on the object that serves as a reference to obtain information on overlay exposure of a next layer on the object is selected for a first axis and a second axis, respectively, of a two-dimensional orthogonal coordinate system that serves as a reference on overlay, from among at least two layers on the object 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 selected reference layer was performed, in a projection exposure apparatus that was used for the exposure of the selected reference layer,

the selection process includes selecting a plurality of reference layers on the object for at least one of the first axis and the second axis so that a reference layer selected for the first axis and a reference layer selected for the second axis are different, and

the distortion component of the projected image of the axis for which the plurality of reference layers have been selected is computed by computation processing using distortion components of projected images of the selected plurality of reference layers,

wherein the computation processing is weighted average processing.

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

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 a selected reference layer, overlay exposure of a next layer is performed.

3. The exposure method according to claim 1, wherein

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

4. An exposure method in which overlay exposure to a photosensitive object is performed by overlaying layers on the object, the method comprising:

a selection process in which a reference layer on the object that serves as a reference to obtain information on overlay exposure of a next layer on the object is selected for a first axis and a second axis, respectively, of a two-dimensional orthogonal coordinate system that serves as a reference on overlay, from among at least two layers on the object 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 object, in a projection exposure apparatus that was used for the exposure of the selected reference layer,

the selection process includes selecting a plurality of reference layers on the object for at least one of the first axis and the second axis so that a reference layer selected for the first axis and a reference layer selected for the second axis are different, and

the nonlinear component of the positional deviation amount of the plurality of divided areas that corresponds to the axis for which the plurality of reference layers have been selected is computed by computation processing using nonlinear components of positional deviation amounts of the formation positions of the plurality of divided areas with respect to the datum positions in the selected plurality of reference layers,

wherein the computation processing is weighted average processing.

5. The exposure method according to claim 4, further comprising:

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 a selected reference layer, overlay exposure of the next layer is performed.

6. The exposure method according to claim 4, wherein

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

7. A lithography system that performs overlay exposure to a photosensitive object by overlaying layers on the object, 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 on the object that has been already exposed by any one of the plurality of projection exposure apparatuses;

a first selection unit that selects a reference layer on the object that serves as a reference to obtain information on overlay exposure of a next layer on the object for a first axis and a second axis, respectively, of a two-dimensional orthogonal coordinate system that serves as a reference on overlay, from among at least two layers on the object 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 selected reference layer was performed, in a projection exposure apparatus that was used for the exposure of the selected reference layer,

the first selection unit selects a plurality of reference layers on the object for at least one of the first and second axis so that a reference layer selected for the first axis and a reference layer selected for the second axis are different;

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

a computation unit that computes information on overlay exposure of the 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, and computes the distortion component of the projected image of the axis for which the plurality of reference layers have been selected, by computation processing using distortion components of projected images of the selected plurality of reference layers,

wherein the computation processing is weighted average processing.

8. The lithography system according to claim 7, 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 a selected reference layer, when overlay exposure of the next layer is performed.

9. The lithography system according to claim 7, wherein

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

10. A lithography system that performs overlay exposure to a photosensitive object by overlaying layers on the object, 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 on the object that has been already exposed by any one of the plurality of projection exposure apparatuses;

a first selection unit that selects a reference layer on the object that serves as a reference to obtain information on overlay exposure of a next layer on the object for a first axis and a second axis, respectively, of a two-dimensional orthogonal coordinate system that serves as a reference on overlay, from among at least two layers on the object 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 object, in a projection exposure apparatus that was used for overlay exposure of the selected reference layer,

the first selection unit selects a plurality of reference layers on the object for at least one of the first axis and the second axis so that a reference layer selected for the first axis and a reference layer selected for the second axis are different;

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

a computation unit that computes information on overlay exposure of the 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, and computes the nonlinear component of the positional deviation amount of the plurality of divided areas that corresponds to the axis for which the plurality of reference layers have been selected, by computation processing using nonlinear components of positional deviation amounts of the formation positions of the plurality of divided areas with respect to the datum positions in the selected plurality of reference layers,

wherein the computation processing is weighted average processing.

11. The lithography system according to claim 10, 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 a selected reference layer, when overlay exposure of the next layer is performed.

12. The lithography system according to claim 10, wherein

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

13. An exposure method in which overlay exposure to a photosensitive object is performed by overlaying layers on the object, the method comprising:

selecting a plurality of reference layers on the object that serve as a reference to obtain information on overlay exposure of a next layer on the object for a first axis of a two-dimensional orthogonal coordinate system that serves as a reference on overlay, from among at least two layers on the object that have been already exposed, where the information on overlay exposure includes a distortion component of a projected image at a point in time when exposure of the selected plurality of reference layers was performed, in a projection exposure apparatus that was used for the exposure of the selected plurality of reference layers, and the distortion component of the projected image of the first axis for which the plurality of reference layers have been selected is computed by weighted average processing using distortion components of projected images of the selected plurality of reference layers; and

selecting at least one reference layer on the object to obtain information on overlay exposure of the next layer on the object for a second axis of the two-dimensional orthogonal coordinate system, from among the at least two layers on the object that have already been exposed, so that at least one reference layer on the object selected for one of the first axis and the second axis is not selected for the other of the first axis and the second axis, where the information on overlay exposure of the next layer on the object for the second axis includes a distortion component of a projected image at a point in time when exposure of the selected at least one reference layer on the object to obtain information on overlay exposure of the next layer on the object for the second axis was performed, in a projection exposure apparatus that was used for the exposure of the selected at least one reference layer on the object to obtain information on overlay exposure of the next layer on the object for the second axis.

14. The exposure method according to claim 13, wherein the selected plurality of reference layers and the selected at least one reference layer together are layers that are overlaid sequentially on the object.

15. An apparatus in which overlay exposure to a photosensitive object is performed by overlaying layers on the object, the apparatus comprising:

a selection unit which

selects a plurality of reference layers on the object that serve as a reference to obtain information on overlay exposure of a next layer on the object for a first axis of a two-dimensional orthogonal coordinate system that serves as a reference on overlay, from among at least two layers on the object that have been already exposed, where the information on overlay exposure includes a distortion component of a projected image at a point in time when exposure of the selected plurality of reference layers was performed, in a projection exposure apparatus that was used for the exposure of the selected plurality of reference layers, and the distortion component of the projected image of the first axis for which the plurality of reference layers have been selected is computed using distortion components of projected images of the selected plurality of reference layers, and

selects at least one reference layer on the object to obtain information on overlay exposure of the next layer on the object for a second axis of the two-dimensional orthogonal coordinate system, from among the at least two layers on the object that have already been exposed, so that at least one reference layer on the object selected for one of the first axis and the second axis is not selected for the other of the first axis and the second axis, where the information on overlay exposure of the next layer on the object for the second axis includes a distortion component of a projected image at a point in time when exposure of the selected at least one reference layer on the object to obtain information on overlay exposure of the next layer on the object for the second axis was performed, in a projection exposure apparatus that was used for the exposure of the selected at least one reference layer on the object to obtain information on overlay exposure of the next layer on the object for the second axis,

wherein the distortion component of the projected image is computed using averaging processing of the selected plurality of reference layers or by weighted average processing in which weight is added to each of the selected plurality of reference layers,

wherein the distortion component of the projected image is computed using averaging processing of the selected plurality of reference layers or by weighted average processing in which weight is added to each of the selected plurality of reference layers.

16. The apparatus according to claim 15, wherein the selected plurality of reference layers and the selected at least one reference layer together are layers that are overlaid sequentially on the object.