JPH11195596A - Method of alignment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of alignment capable of abstaining information of the deformation in a wafer and a shot with a minimum number of alignments by measuring each of a prescribed number or more of alignment mark in a prescribed number or more of a first shot and a relatively different alignment mark of a prescribed number or more in a region for a second shot. SOLUTION: One or more respectively of 3 or more alignment mark points in a first shot and 2 or more alignment mark points relatively different each other in a region for a second shot are measured. A plurality of marks ML1 to ML3 and MR1 to MR3 for alignment are exposed on each chip pattern in the shot region of S1 to SN of the first shot arrangement. During the overlapping exposure, each of a plurality of alignment marks are selected in a plurality of predetermined sample shots selected from among the second shot arrangements SA1 to SAM, and a required parameter is determined. This enables suppression of the number of alignment to be as small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method for performing exposure by a so-called mix-and-match (mix & match) method, and more particularly, to an exposure method on a substrate using two exposure apparatuses having different exposure field sizes. The present invention relates to an exposure method when performing exposure by a mix-and-match method in which mask patterns are exposed in an overlapping manner.

[0002]

2. Description of the Related Art Conventionally, in a factory for manufacturing a semiconductor device such as an VLSI or the like, in order to increase the throughput (productivity) of a manufacturing process, a different exposure apparatus is used for exposing between different layers in a manufacturing process of one kind of device. There are many things to do. For example, for exposure to a rough layer that does not require a very high resolution, a batch exposure type projection exposure apparatus (stepper) having a low reduction ratio or a scanning exposure apparatus for exposing a large area is used as a first exposure apparatus. Exposure to a critical layer requiring resolution is performed by a second batch exposure type projection exposure apparatus (stepper) having a high reduction magnification.
A mix-and-match type of exposure such as the use of
2-90931). Generally, a large-diameter exposure apparatus is used as the first exposure apparatus, and a small-diameter exposure apparatus is used as the second exposure apparatus.
Conventionally, in a match type exposure method, superimposition is performed without considering the in-shot deformation of an exposure result obtained by a large-diameter exposure apparatus.

[0003]

In the prior art described above, sufficient overlay accuracy could not be obtained because the in-shot deformation was not taken into account. However, the in-shot deformation was converted into a shot map for large-diameter exposure. , It was difficult to handle the information necessary to reflect the measurement result to the exposure position. This is because one shot of the superposition by the small-diameter exposure machine is formed by dividing one shot in the first exposure of the large-diameter exposure machine.
This is because a large number of parameters (map center coordinates, step pitch, offset for each shot, etc.) that accurately represent the relative positional relationship between the two shot maps are required.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the exposure throughput by knowing the in-wafer deformation and the in-shot deformation with a minimum number of alignments.

[0005]

In order to achieve the above object, an exposure method according to the first aspect of the present invention uses a first exposure apparatus on a substrate by using a plurality of first exposure apparatuses including alignment marks. A first exposure step of exposing the shots in a first arrangement; a position measurement step of measuring the position of the alignment mark; and after the first exposure step, the first exposure apparatus has an exposure field size. A second exposure step of superposing and exposing a plurality of second shots in a second arrangement using different second exposure apparatuses; the position measurement step includes:
In the plurality of first shots, one or more positioning marks in three or more first shots are respectively set in the second shot, and
Measuring two or more relatively different alignment marks in the shot area; the second exposing step includes the step of measuring the positions of the plurality of first marks based on a measurement value of the position measuring step. Error between the shots and the second
Is determined, and an error in the first shot is calculated based on the position of the second shot as a reference. Based on the calculated error, the second reference in each first shot is calculated. And determining the position of the remaining second shot with reference to the position of the second shot, and exposing the second shot.

In this way, three or more alignment marks in the first shot are each assigned at least one point, and two or more relatively different alignment marks in the second shot area are assigned. Since the measurement step is included, ten parameters required for the alignment of the second shot can be determined, and the positions of the remaining second shots are determined based on the position of the second shot serving as a reference. The economy of correction is achieved, and the second shot can be accurately overlapped with the first shot for exposure.

In this method, the first exposure apparatus is a large-diameter exposure apparatus, the second exposure apparatus is a small-diameter exposure apparatus, and the first shot Is a rectangular large-diameter shot, and the second shot is three rectangular small-diameter shots obtained by equally dividing the rectangular large-diameter shot by two parallel lines cutting two opposing sides, The second shot serving as the predetermined reference may be any one of the three small-diameter shots.

[0008] In this manner, exposure in which a large-diameter shot is divided into three and small-diameter shots are overlapped can be performed accurately and with high throughput. Further, for example, if the second shot serving as a predetermined reference is the central shot of the three small-aperture shots, the amount of correction is relatively small, and more accurate and high-throughput exposure can be performed.

In the method according to the first aspect, the first exposure apparatus is a large-diameter exposure apparatus, the second exposure apparatus is a small-diameter exposure apparatus, The first shot is a rectangular large-diameter shot, and the second shot is
Are four rectangular small-diameter shots obtained by equally dividing the rectangular large-diameter shot by two straight lines passing through the midpoint of each side, and the second shot serving as the predetermined reference May be any one of the four small-diameter shots.

[0010] In this way, exposure in which a large-diameter shot is divided into four crosses by a large-diameter shot and small-diameter shots are overlapped can be performed accurately and with high throughput.

According to a fourth aspect of the present invention, in the exposure method, the first exposure apparatus synchronously scans the mask and the substrate to expose a pattern on the mask to each shot area on the substrate. 4. The exposure apparatus according to claim 1, wherein the second exposure apparatus is a batch exposure type exposure apparatus that collectively transfers a pattern on a mask to each shot area on a substrate. May be used.

In this case, since a scanning exposure type exposure apparatus is used as the first exposure apparatus, exposure with a high resolution and a large exposure field can be performed. Since the position error of the use mark is reduced, the accuracy of the overlay can be improved by exposing the first layer by scanning.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding members are denoted by the same or similar reference numerals, and duplicate description is omitted.

First, an example of an exposure apparatus suitable for carrying out the exposure method according to the present invention will be described with reference to the drawings.

FIG. 18A shows a step-and-scan projection exposure apparatus (hereinafter, referred to as a "scanning exposure apparatus") as a first exposure apparatus used in the embodiment of the present invention.
1 at the time of exposure in FIG.
An excimer laser light source composed of an F excimer laser or an ArF excimer laser, an illumination optical system 2 including a fly-eye lens, a field stop, a condenser lens, and the like for uniformizing the illuminance distribution of exposure light (here, laser light) from the light source. The emitted exposure light IU1 illuminates a slit-shaped illumination area 13 on the reticle 3. Then, the pattern in the illumination area 13 is projected via the projection optical system 4 onto the wafer W coated with the photoresist at a projection magnification β1 (β1 is に, １ ／, etc.). Hereinafter, the Z axis is taken parallel to the optical axis of the projection optical system 4, and the X axis is perpendicular to the plane of FIG. 18A in a plane perpendicular to the Z axis, and is parallel (scanning) to the plane of FIG. 18A. The direction will be described taking the Y-axis.

At this time, the reticle 3 is mounted on the reticle base 6 via the reticle stage 5, and the reticle stage 5 performs continuous movement in the Y direction and fine movement in the X, Y and rotation directions. . The position information of the reticle stage 5 measured by the laser interferometer 7 is supplied to a main control system 8 that controls the overall operation of the apparatus, and the main control system 8 determines the position of the reticle stage 5 (reticle 3) and the Y direction. To control the scanning operation. On the other hand, the wafer W is moved via a wafer holder (not shown) to a Z stage 9 for controlling the position, rotation angle, tilt angle, and the like of the wafer W in the Z direction.
The Z stage 9 is held on the XY stage 10. The XY stage 10 is capable of continuous movement and stepping in the Y direction, and stepping in the X direction. The position information of the Z stage (wafer W) 9 measured by the laser interferometer 11 is supplied to the main control system 8, and the main control system 8 positions the XY stage 10 (wafer W) and performs a scanning operation in the Y direction. Control.

FIG. 18B is a plan view of the reticle 3 in FIG. 18A, and in FIG.
Of the slit-shaped illumination area 13
Is set, and the illumination area 13 is inscribed in the circular effective field IF1 of the projection optical system 4. At the time of scanning exposure, the XY stage 10 of FIG. 18A is synchronized with scanning the reticle 3 in the + Y direction (or -Y direction) at a predetermined speed VR via the reticle stage 5 via the reticle stage 5. The wafer W in the −Y direction (or + Y direction)
By scanning at VR 1, a projected image of the pattern area 14 wider than the illumination area 13 is sequentially exposed on each shot area on the wafer W. In this case, the slit-shaped exposure area on the wafer W conjugate with the illumination area 13 on the reticle 3 is called the “illumination field” of the projection optical system 4 and is the area of the entire pattern image transferred by scanning exposure, that is, An area on the wafer W conjugate to the pattern area 14 on the reticle R is called an “exposure field” of the projection optical system 4. Each shot area formed on the wafer W has the same size as the exposure field.

Further, a plurality of alignment marks are formed together with the circuit pattern in the pattern area 14 of the reticle 3, and at the same time as the circuit pattern image is transferred, the alignment mark images are also transferred. The alignment mark image becomes an alignment mark (wafer mark) in the next layer on the wafer W. In FIG. 18A, the scanning exposure apparatus 1 is provided with an off-axis type and image processing type alignment sensor 12 as an example.

FIG. 19A shows a collective exposure type projection exposure apparatus (hereinafter, referred to as a "collective exposure apparatus") 21 comprising a stepper as a second exposure apparatus used in this embodiment. At the time of exposure at 19 (A), an ultra-high pressure mercury lamp, an optical filter for selecting, for example, an i-line from an emission line from this lamp, a fly-eye lens for uniformizing the illuminance distribution, a variable field stop (reticle blind), a condenser lens, etc. Exposure light IU2 emitted from illumination optical system 22 including illuminates illumination area 33 on reticle 23. The pattern in the illumination area 33 is the projection optical system 2
4 and projected onto the wafer W coated with the photoresist at a projection magnification β2 (β2 is 1/4, 1/5, etc.).
Again, taking the Z axis parallel to the optical axis of the projection optical system 24,
The description will be made with the X axis perpendicular to the plane of FIG. 19A and the Y axis parallel to the plane of FIG. 19A in a plane perpendicular to the Z axis.

At this time, the reticle 23 is held on the reticle stage 25, and the reticle stage 25 is
The reticle 23 is finely moved in the Y direction and the rotation direction. On the basis of the measurement result of the laser interferometer (not shown), the main control system 28 that supervises and controls the operation of the entire apparatus is provided by
(Reticle 23) positioning operation is controlled. On the other hand, the wafer W is placed on the Z stage 2 via a wafer holder (not shown).
9, the Z stage 29 is mounted on the XY stage 30, and the XY stage 30 performs stepping of the Z stage 29 (wafer W) in the X direction and the Y direction. Z stage (wafer W) measured by laser interferometer 31
29 is supplied to the main control system 28, and the main control system 2
Reference numeral 8 controls the positioning operation of the XY stage 30 and the like.

FIG. 19B is a plan view of the reticle 23 shown in FIG. 19A. In FIG. 19B, the pattern area of the reticle 23 substantially coincides with the normally rectangular illumination area 33. The area 33 is inscribed in the circular effective field IF2 of the projection optical system 24. At the time of exposure, the pattern image in the illumination area 33 is transferred to each shot area on the wafer W while the reticle 23 and the wafer W are stationary. In the case of the batch exposure type, the illumination area 33 on the reticle 23
The exposure area on the wafer W conjugate with the projection optical system 2
4 exposure fields. Therefore, if the projection optical systems 4 and 24 have the same effective field at the same projection magnification, the exposure field of the scanning exposure apparatus 1 is wider than the exposure field of the collective exposure apparatus 21. In FIG. 19A, the collective exposure apparatus 21 is also provided with an alignment sensor 32 of an off-axis type and an image processing type as an example, and the detection result of the wafer mark by the alignment sensor 32 is used as the main control system 28. The main control system 28 receives the detected result, for example, from the enhanced global alignment (EG) as described later.
A) The reticle 23 is aligned with each shot area on the wafer W by the method A). The alignment of the EGA method is described in detail in, for example, Japanese Patent Application Laid-Open No. 61-44429 or Japanese Patent Application No. 9-31974.

In this example, the first layer on the wafer W is exposed to the circuit pattern image and the alignment mark image of the reticle 3 using the scanning exposure apparatus 1, and then subjected to processing such as development. After re-coating the photoresist, the collective exposure apparatus 2 is applied to the second layer on the wafer W.
Exposure is performed by a mix-and-match method in which exposure is performed using No. 1. This is because, in the scanning exposure apparatus 1, distortion in an exposure field is disclosed in
As described in JP-A-349702, the batch exposure apparatus 2
This is because the accuracy can be expected to be improved by about 40% as compared with 1, and as a result, the position accuracy of the wafer mark is improved and the overlay accuracy is improved.

In this embodiment, the reticle size is shared between the scanning exposure apparatus 1 and the batch exposure apparatus 21.
As an example, the projection magnification β1 of the scanning type exposure apparatus 1 is 、,
The projection magnification β2 of the batch exposure apparatus 21 is set to １ ／, and the sizes of the reticles 3 and 23 are both 6 inches.
As a result, the exposure field size of the scanning type exposure apparatus 1 is 26 to 30 mm in the X direction and 33 mm in the Y direction (scanning direction), and the exposure field size of the batch type exposure apparatus 21 is about 22 mm square. . Further, in this example, the size of each chip pattern, which is the minimum unit of the semiconductor device formed on the wafer, is set to 22 mm (X direction) × 1 width.
As a 1 mm (Y direction) rectangle, the exposure field size of the scanning exposure apparatus 1 is 22 mm (X direction) × 33 m (width).
It is set so that m (Y direction), that is, three chip patterns can be exposed at one time. In the batch exposure apparatus 21, two chip patterns can be exposed in a 22 mm square exposure field. However, the field of view is limited by a variable field stop, and the exposure field size is 22 mm (X direction) × 11 mm in width.
By setting (Y direction), 1
It is also possible to expose only one chip pattern.

FIG. 1A shows an example of the relationship between a shot by a large-diameter exposure machine and a shot division by a shot by a small-diameter exposure machine. In the first embodiment, the shot S1 by the large-diameter exposure machine is divided into three shots.
C3 is a shot area by the small-diameter exposure machine.

The shot area S1 is a rectangle long in the Y direction with a width XA in the X direction and a width YA in the Y direction (scanning direction), and the area S1 divides two opposing sides of the rectangle in the Y direction into three equal parts. The three parallel lines L1 and L2 are equally divided into three, and shots C1 to C3 are formed by a small-diameter exposure machine.
That is, the shot area S1 has one row in the X direction and 3 rows in the Y direction.
This is a 1 × 3 shot area of a row. In one embodiment, width XA is 22 mm and width YA is 33 mm. In the shot area S1, six sets (points) of alignment marks ML1 to ML3 and MR1 to MR3 are respectively set to C1.
Alignment marks ML and MR of C3 to C3 (FIG. 1B). These are arranged on the left and right of each of the chip patterns C1, C2, and C3 in pairs with the wafer marks MR1, ML1, the wafer marks MR2, ML2, and the wafer marks MR3, ML3.

Here, the six sets are referred to as a set, and these wafer marks MR1 to MR3 and ML1 to ML3 are the same two-dimensional marks. For example, the wafer mark MR1 is
As shown in FIG. 1C, a combination of the uneven line and space pattern 35X arranged in the X direction and the uneven line and space pattern 35Y arranged in the Y direction is formed. Because it is a mark.
Alignment is performed using these wafer marks.

The correspondence between the large-diameter shot and the small-diameter shot on the map is, for example, as shown in FIG. FIG. 2A shows the first exposure using a large-diameter shot (1st print).
(B) is a shot map of the overlay exposure using the small-diameter shot.

First, FIG. 2A shows an example of a shot map when the image of the reticle 3 is exposed on the first layer (layer) on the wafer W using the scanning exposure apparatus 1. In (A), by moving the slit-shaped illumination field relative to the wafer W in a predetermined order, the shot areas S1, S2, S3 are arranged on the wafer W at a predetermined pitch in the X and Y directions. ,..., SN (N = 2 in this example)
4) is formed.

In the present example, five shot areas S1 to S5 are arranged side by side, and the next row has seven shot areas S6 to S1.
2 is a 7-shot area S13 to S19 in the next row.
However, in the last row, the five shot areas S20 to S24 are arranged side by side, and are symmetrically arranged as a whole as a whole.

Then, by performing processing such as development, chip patterns C1, C2, and C3 are respectively formed in the shot areas Si (i = 1 to N) on the wafer,
Wafer marks MR1, ML1,..., MR3, ML3 are formed on both sides of each shot area Si in the X direction.

In this case, the exposure field size of the scanning type exposure apparatus 1 (ie, the size of each shot area Si), information on the shot arrangement in the shot map, and the coordinate system on the wafer W (sample coordinate system) The main control system 2 of the collective exposure apparatus 21 that performs exposure on the second layer via, for example, a host computer, etc., based on design coordinate information of each wafer mark.
8 is supplied.

Further, information such as the size of the exposure field in the previous layer is recorded in a barcode portion on the reticle, and the information is read out by a second layer exposure apparatus via a barcode reader. Alternatively, the exposure field size and the like may be written in advance in the exposure data file of each process of each exposure apparatus as information. Note that for convenience of description, FIG. 1A is displayed in correspondence with FIG. 2A.

FIG. 2B shows an example of a shot map in a case where one batch exposure apparatus 21 is formed on the second layer on the wafer W and the image of the reticle 23 is exposed. ), The shot areas SA1, SA2, SA3,..., SA such that three shot areas are respectively contained in the shot areas Si in the shot arrangement of FIG.
M (M = 72 in this example) are arranged, and each shot area S
One chip pattern image in the reticle 23 is exposed in Ai.

In this example, the five shot areas SA1 to SA5
Are arranged side by side, and the next row also has five shot areas SA6 to SA10, and further has five shot areas SA11 to SA11.
SA15 are arranged side by side.
15 are arranged in 3 rows and 5 columns. In this way, SA1, SA6, and SA11 form a small-diameter shot area overlapping the large-diameter shot area S1. Hereinafter, SA16 to SA57 are similarly arranged in 6 rows and 7 columns, and subsequently, SA58 to SA57 are similarly arranged as SA1 to SA15.
A72 is arranged in 3 rows and 5 columns.

Here, for example, the first exposure using a large-diameter exposure machine
When the print includes a shot rotation (shot rotation), each large-diameter shot is rotated by the rotation angle, and the exposure result is as shown in FIG.

If small-diameter shots are simply superimposed on a small-diameter shot map, even if the exposure position is determined in consideration of the deformation within the shot, each small-diameter shot will have only the previous rotation angle on the small-diameter shot map. Just rotate,
In the exposure result, each small-diameter shot is shifted stepwise as shown in FIG. FIG. 4B is an enlarged view of one shot of the large diameter of FIG. As shown in this figure, if the center of the three small-diameter shots is overlapped with a positive value, the upper and lower adjacent small-diameter shots need only be located in the area indicated by hatching. It shifts to the left and right like the area shown in white. That is, the chip patterns C1, C2, and C3 do not fit in the large-diameter shot S1.
3 is shifted to the right.

Therefore, as shown in FIG. 5 (A), when creating a small-diameter shot map, 3
The divided small-diameter shot at the center is designated as a predetermined shot serving as a reference of the present invention, shot *, the small-diameter shot immediately above the shot * is designated as shot A, and the small-diameter shot below the shot * is designated as shot B. I do.

Here, the shot center coordinates of shot *, shot A, and shot B are represented by ^t (x _* , y _* ),
_{^{t (x A, y A)}} , t (x B, y B) When ^(t denotes the transpose of a matrix), * included in the same large diameter shot, A, for B shot is calculated by the following formula To
^t (V _A , W _A ) and ^t (V _B , W _B ) are constant values.

[0039]

(Equation 1)

^T (V _A , W _A ) and ^t (V _B , W _B ) represent the relative positional relationship between shot * and shot A, and shot * and shot B, respectively. vice versa,
^{If t} (V _A , W _A ) and ^t (V _B , W _B ) are specified in advance, the shot A and the shot B start from the position of the shot *.
You can know the position of. In other words, ^t (V _A ,
From W _A ) and ^t (V _B , W _B ), it is possible to know which small-diameter shot group constitutes one large-diameter shot. ^{That, A = * + t (V} A, W A) B = * + t (V B, W B) of the relationship specified, can be expressed shot A, B, relative to the location of the shot * (FIG. 5 ( B)).

In this way, as shown in FIG. 2A in the scanning exposure apparatus (first exposure apparatus of the present invention) 1 shown in FIG. As shown, the first layer is exposed (first exposure step of the present invention).

Next, for the second layer on the wafer W,
Batch exposure apparatus (second exposure apparatus of the present invention) 2 in FIG.
In order to perform the overlay exposure using the shot map of FIG. 2B using the shot map 1 in FIG. That is, first, a predetermined number of sample shots (EGA shots), which are shot areas to be measured, are selected from the shot map to be exposed in FIG. 2B, and the position measurement step of the present invention is executed. That is, the positions of predetermined wafer marks belonging to these sample shots are detected via the alignment sensor 32 in FIG.

FIG. 6 shows an example of how to determine the alignment execution position. FIG. 6 shows an example of a sample shot selected from the single shot map of FIG. 2B without considering the shot map of the first layer,
In FIG. 6, shot areas SA1 to SA1 to 1
Zero sample shots 43A to 43J are selected. The sample shots 43A to 43J are included in three or more first shots of the present invention, and the number is 10 in this embodiment.

In the example of FIG. 6, 43A to 43J correspond to FIG.
Looking at the inside of the wafer with reference to (B), SA1, SA3,
SA5, SA17, SA21, SA52, SA56, S
A68, SA70, SA72 (these symbols are SA
1, only SA3) are scattered throughout the wafer W. In this example, how to swing reference numerals 43A to 43J is as follows.
Instead of the order of the SA numbers, the wafers are taken clockwise in the wafer W from SA1 (43A) to SA17 (43J).

These sample shots 43A to 43J
Is the first in the shot, as shown in FIG.
Shot areas S1, S3, S in the shot arrangement of the layer
5,..., S24 correspond to the selection of the chip pattern C1 or C3 at random. That is, 43A, 4
3B, 43C, 43D, 43J are C1, 43E, 43
F, 43G, 43H, and 43I correspond to C3. Since the chip patterns C1 and C3 are selected, there are two relatively different points in the present invention.

Each of the sample shots 43A to 43J in FIG. 6 is provided with a pair of wafer marks (one of the wafer marks MR1 to MR3 and ML1 to ML3 in FIG. 1A), for example, to which these wafer marks belong. Design coordinates of the center of the chip pattern in the sample coordinate system (x, y),
The design relative coordinates of the wafer mark with respect to the center thereof are supplied to the main control system 28. In the main control system 28,
The coordinates of the wafer mark to be measured are measured via the alignment sensor 32 on the stage coordinate system (X, Y) composed of the X coordinate and the Y coordinate determined by the measurement values of the laser interferometer 31 in FIG. Position measurement step). Here, for example, the wafer marks MR1 and M of the sample shot 43A are
If L1 is measured, one or more alignment marks in the first shot according to the present invention are measured.
In this example, two points are measured in the shot S1.

When calculating the misregistration correction parameters from the alignment result, a large-diameter shot map is used as shown in FIG. 7, and the alignment marks in the shot A are first and second shots in the large-diameter shot. The alignment mark of the mark and the shot B is treated as the third and fourth marks in the large-diameter shot (MM in FIG. 5B).
1 to MM4).

The following are examples of exposure position shift correction models that also take shot deformation into account. The wafer scaling is (1 + γ _x , 1 + γ _y ), the wafer rotation is θ, the wafer orthogonality is ω, the translation component of the wafer is ^t (Ο _x , Ο _y ), and the shot scaling is (1+
Γ _x , 1 + Γ _y ), shot rotation is Θ, shot orthogonality is Ω,

[0049]

(Equation 2)

Assume that S is a matrix representing in-wafer deformation,
T is a matrix representing the deformation between shots, and C is a vector representing the parallel movement of the wafer. Shot center position of the design ^{_{t (x c, y c)}} , the alignment mark position in the shot as (x _m, y _m),

[0051]

(Equation 3)

Assume that: ^t (x ′, y ′) is an estimated value of the alignment mark position. Therefore, M marks are measured for each of the N shots (where N ≧
3, M ≧ 3),

[0053]

(Equation 4)

Γ _x , γ _y , θ,
ω, Ο _x , Ο _y , Γ _x , Γ _y , Θ, Ω may be determined. Here, ^t (x _ij , y _ij ) is an actually measured value of the j-th mark position of the i-th shot, and ^t (x ′ _ij , y ′ _ij ) is an estimated value thereof.

When this model is applied directly to a small-diameter shot map as shown in FIG. 6, calculation is as follows: N = 10, M =
2 and cannot be calculated, but if it is read as a large-diameter shot map using the relative expression of (Equation 1), it can be transformed into a form that can be calculated. Now, referring to FIG. 1, the coordinates in the shot of the mark MR of each small-diameter shot are represented by (x _m1 ,
y _m1 ) and the coordinates in the shot of the ML are (x _m2 , y _m2 ). Here, in equation (3), the shot * using equation (1), for _{x c = x * y c =} y * x m = x m1 or x _m2 y _m = y _m1 or y _{m @ 2} shots A, for _{x c = x * y c =} y * x m = x m1 + V A or _{x m2 + V A y m =} y m1 + W A or y _m2 + W _A shot _{B, x c = x * y} c = y * x m if = x _m1 + as in V _B or _{x m2 + V B y m =} y m1 + W B or y _m2 + W _B, can be treated as N = 5, M = 4 data in large diameter shot map of FIG. 7 .

The exposure position obtained by applying the S, C, and T obtained as described above to a small-diameter shot map as it is is the position indicated by the mark in FIG. However, since the first pattern is exposed with a large aperture, the actual shot center position is at the position indicated by + in FIG.

The difference between the two shots A and B

[0058]

(Equation 5)

Can be calculated. Therefore, these offsets may be added to the exposure positions obtained by applying S, C, and T as they are to the small-diameter shot map. That is, prior to _{^{exposure, offsetA = T t (V A}} , W A) offsetB = T t (V B, W B) advance is calculated, the exposure position, * shots: normal correction calculation A Shot: Normal Correction calculation + offset AB shot: normal correction calculation + offset B can be calculated (FIG. 8).

FIG. 8 illustrates the correction by the above calculation. FIG. 8 shows a state where the white area described in FIG. 4B is corrected for offsetA and offsetB, and can be moved to the hatched area. In this way, the positions of the remaining shots are determined with reference to the position of the second shot *, which is the reference of the present invention, and the second shot of the second layer is exposed (second exposure step of the present invention).

FIG. 9 shows another example of the shot division by the shot of the small-diameter exposure machine of the shot of the large-diameter exposure machine. In the second embodiment, a square large-diameter shot S
51 are two orthogonal straight lines passing through the midpoint of each side (FIG. 9).
(A) is shown by a broken line), and is divided into four equal portions in the shape of a cross, and is assigned to four square small-diameter shots C51 to C54. In this example, in FIG.
Of the straight lines, the horizontal straight line is the X axis, and the vertical straight line is the Y axis.
Considering a coordinate plane with the axis and its intersection as the origin, the shot area S51 is a square having the same width in the X direction and the width in the Y direction (scanning direction),
1 to C54 are C52 in the first quadrant, C51 in the second quadrant,
C53 is taken in the third quadrant and C54 is taken in the fourth quadrant. In the present example, the shot S51 is a 2 × 2 shot area of a total of four pieces arranged in a cross.

In the shot area S51, four sets of alignment marks MUL, MUR, MLL, and MLR are provided so as to become the alignment marks MZ of C51 to C54, respectively (FIG. 9B). These are arranged in pairs each inside the vicinity of the right side of each of the chip patterns C51, C52, C53 and C54. These wafer marks are the same two-dimensional marks as shown in FIG.

The correspondence on the map is as shown in FIG. 10, for example. FIG. 10 (A) shows a 1st pr by a large diameter shot.
It is a shot map of int. In this example, large-diameter shots S51 and S52 are arranged side by side. Four shots S53 to S56 are arranged in the next row, four shots S57 to S60 are arranged in the next row, and S61 and S62 are arranged in the last row. ing. A total of 12 shots are arranged point-symmetrically with respect to the center of the wafer W (reference numerals S51, S52,
(Only S53, S56, S57, S60, S61, 62 are shown).

FIG. 10B is a shot map of superposition exposure using small-diameter shots. Here, 4
9 are arranged side by side (in FIG. 9B, the small-diameter shots C51 to SA54).
C54 is arranged in a cross in the large-diameter shot S51, but here, the arrangement of SA51 to SA54 is changed to one horizontal row.) Similarly, SA55 to SA58,
SA59-SA66, SA67-SA74, SA75-
SA82, SA83 to SA90, SA91 to SA94,
SA95 to SA98 are arranged side by side in different rows (reference numerals SA51 to SA54 and SA59, SA66, SA83, and SA9 located at the corners of the array).
0, SA95 and SA98 only).

In this case, the deformation in the shot can be calculated by devising the arrangement of the alignment shots, even if only one set of alignment marks is inserted in the small-diameter shots. That is, an arrangement in which C51 to C54 are included as evenly as possible is selected (FIG. 11), and the marks C51 to C54 are interpreted as the first, second, third, and fourth marks of the large-diameter shot, respectively (see FIG. 11). 12) The model of (Equation 1) may be applied to a large-diameter shot map (FIG. 1).
3).

Subsequently, as in the first embodiment, a first exposure step, a position measurement step, and a second exposure step are executed.

FIG. 11 (corresponding to FIG. 6 of the first embodiment)
Shows an example of how to determine the alignment execution position.
FIG. 11 shows an example of a sample shot selected from the single shot map shown in FIG. 9B without considering the shot map of the first layer. Eight sample shots have been selected. These are in three or more (8 in this example) first shots of the present invention.

In the example of FIG. 11, eight sample shots correspond to SA5 in the wafer with reference to FIG.
1, SA54, SA59, SA66, SA83, SA9
0, SA95, and SA98, and are scattered throughout the wafer W.

When these sample shots are viewed in the shot, as shown in FIG. 13, the shot areas S51, S52,.
Chip patterns C51, C52, C5 from 2
3 or C54. That is, in this example, two are each selected equally.
That is, there are two or more relatively different points in the present invention (four points in this example).

Here, as in the first embodiment, for example, when the shot is rotated (shot rotation) at the first print by the large-diameter exposure machine, each large-diameter shot is rotated by the rotation angle and the exposure result is obtained. Is as shown in FIG.

If small-diameter shots are simply superimposed on a small-diameter shot map, even if the exposure position is determined in consideration of the deformation within the shot, each small-diameter shot will have only the previous rotation angle on the small-diameter shot map. Just rotate,
In the exposure result, each small-diameter shot is shifted stepwise as shown in FIG. FIG. 15B is an enlarged view of one shot of the large diameter of FIG. As shown in this figure, 4
Shot C in the upper left (2nd quadrant) of the smaller caliber shots
If you superimpose 51 as positive, it will be on the right (first quadrant)
The small-diameter shot adjacent to and below (third quadrant) and in the diagonal direction (fourth quadrant) may be located in the area indicated by hatching. It shifts in the direction.

Therefore, as shown in FIG. 16A, when a small-diameter shot map is created, the upper-left small-diameter shot divided into four in each large-diameter shot is a predetermined shot * which is a reference of the present invention. , Shot * are designated as shots A, B, and C, respectively, on the right (first quadrant), diagonally (fourth quadrant), and lower (third quadrant). Here, the relationship of A = * + ^t (V _A , W _A ) B = * + ^t (V _B , W _B ) C = * + ^t (V _C , W _C ) is specified. That is, shots A, B,
C is represented by a relative position from the shot * (FIG. 16)
(B)). As in the first embodiment, " ^t " represents the transpose of a matrix.

As in the first embodiment, the alignment of the EGA method is performed in this example, and offset A = T ^t (V _A , W _A ) offset B = T ^t (V _B , ^{_{W B) offset C = T t}} (V C, leave calculated W _C), the exposure position, * shots: normal correction calculation a shot: normal correction calculation + offset a B shots: normal correction calculation + offset B C shot: normal correction calculation + offset C is calculated. (FIG. 17). FIG. 17 illustrates the correction by the above calculation.
It is shown that by correcting t A, offset B, and offset C, it can be moved to the hatched area.

In the first example of FIG. 1, two-point measurement within 10 shots in the small-diameter shot map is analyzed using a four-point measurement model within 10 shots in the large-diameter shot map. However, each mark of the large-diameter shot is measured only for a total of five shots.

Similarly, in the second example of FIG. 9, one point measurement within eight shots in the small diameter shot map is analyzed by a four point measurement model within eight shots in the large diameter shot map. . However, each mark of the large-diameter shot is measured only for a total of two shots.

As described above, in each example, alignment is performed by taking out and measuring marks at two or more points in a shot and three or more shots in a wafer.
Here, two or more points in a shot (in terms of the number of data, four data in the xy direction (see FIG. 1C)) or more mean two different points in a large-diameter shot. However, it suffices if the two points are relatively different. For example, in the second embodiment,
This means that all measurement points must not be the center point on the right side of the shot in the upper left corner of the cross, and at least one point may include the center point on the left side of the shot in the upper left corner of the cross, or Even if they are all the same point at the center of the right side, the shot in the upper left (second quadrant) and the shot in the lower right (fourth quadrant) of the cross may be selected.

The expression “3 or more shots in the wafer” means that three or more different points need only be scattered in the wafer.

Although the number of marks to be measured required in the present invention is three or more, what is important here is the number of data. 3
The dot mark includes a total of 6 data (see FIG. 1C). These data may be measured independently, see FIG.
As shown in (C), it is not necessary to measure an X-direction pattern and a Y-direction pattern which are physically applied to one place as one set. For example, the X-direction pattern of the first mark is measured, and then the second mark physically separated from the first mark is applied.
May be measured in the Y direction. In such a case, the intersection of the patterns in the X and Y directions thus measured may be regarded as one point. The point is that it is sufficient to measure a total of six or more data for three different data in two different directions.

The above description will be further described in the first embodiment. When exposing these alignment marks using the first exposure apparatus 1, each shot area of the first shot array is exposed. Each chip pattern C in (S1 to SN)
A plurality of alignment marks (ML1 to M3 for each of 1 to C3)
L3, MR1 to MR3) are exposed, and when the overlay exposure is performed using the second exposure apparatus 21, each of the predetermined plurality of sample shots selected from the second shot array is used. A plurality of alignment marks are selected, and six parameters (X-direction scaling, Y-direction scaling, rotation angle) corresponding to the linear array error of the shot array are determined based on the positions of the alignment marks thus selected. , Orthogonality, X direction offset, Y direction offset), and 4 corresponding to the linear error in each shot area.
Calculate the number of parameters (X direction shot magnification, Y direction shot magnification, shot rotation angle, intra-shot orthogonality),
Using these ten parameters, the alignment of each shot area of the second shot array can be performed.

The second shot serving as a predetermined reference is the center shot in the first embodiment, but may be the top shot or the bottom shot. In the second embodiment, the upper left shot is used, but the lower left, right, or lower right shot may of course be used. Alternatively, instead of taking any of the small-diameter shots, it is also possible to take a position completely off the large-diameter shot. However, if any small-diameter shot is used as a reference, the number of corrections can be omitted once, which is advantageous in throughput.

As described above, when an alignment shot is selected so that a multi-point EGA in a shot can be performed when viewing a large-diameter shot, the EGA information of the small-diameter shot is actually the multi-point EGA in the shot of the large-diameter shot. Since the information also serves as information and the number of times of alignment can be reduced, the productivity of manufacturing semiconductor devices and the like by exposure can be improved.

As described above, the present invention relates to an alignment and exposure method for calculating the position of a specific shot as a relative position with respect to other shots. In particular, the base shot size differs from the shot size to be superimposed. Sometimes, an alignment and exposure method is used to select an alignment position in consideration of the base shot size. In the present invention, shot division of a large-diameter exposure machine shot is represented by a relative position from a specific shot on a shot map of a small-diameter exposure machine. Then, the arrangement of the alignment shots on the shot map of the small-diameter exposure machine is set such that the deformation in the shot can be calculated by considering the shot map of the large-diameter exposure machine.

In this way, an accurate exposure position can be calculated only by measuring the intra-shot deformation in the large-diameter exposure machine and finely correcting the relative position based on the result.

[0084]

As described above, according to the present invention, a shot correction value can be calculated easily and with a small number of parameters.

[Brief description of the drawings]

FIG. 1A is a plan view showing a 1 × 3 shot area of a scanning exposure apparatus 1, and FIG.
FIG. 3 is a plan view showing a state in which exposure is performed while stepwise moving three shot areas of 1 × 1 piece.

2A is a diagram illustrating an example of a shot map when a first layer on a wafer W is exposed using a scanning exposure apparatus 1, and FIG. 2B is a diagram illustrating one shot map on a second layer on the wafer W; FIG. 4 is a diagram showing an example of a shot map in a case where exposure is performed using a collective type exposure apparatus 21;

FIG. 3 is a plan view of the wafer W in which an exposure state when a shot is rotated when the first layer is exposed by the scanning exposure apparatus is extremely rotated.

FIG. 4 is a plan view of the wafer W showing an exposure state when the second layer is exposed by correcting the rotation of the shot by the batch type exposure apparatus.

FIG. 5 is a diagram illustrating a relationship between a central small-diameter shot and upper and lower adjacent shots when a small-diameter shot divides a large-diameter shot into three parts.

FIG. 6 is a diagram showing an example of a sample shot randomly selected for a second layer in FIG. 2 (B).

FIG. 7 is a diagram illustrating a position of a sample shot in FIG. 2A on a first layer.

FIG. 8 is an enlarged view showing a state where upper and lower adjacent shots are corrected by an offset in the case of three divisions.

FIG. 9A is a plan view showing a 2 × 2 shot area of the scanning exposure apparatus 1 according to the second embodiment, and FIG.
FIG. 4 is a plan view showing a state in which exposure is performed while stepwise moving four 1 × 1 shot areas of the collective exposure apparatus 21.

10A is a diagram showing an example of a shot map when the first layer on the wafer W is exposed using the scanning exposure apparatus 1 in the case of FIG. 9; FIG. FIG. 9 is a diagram illustrating an example of a shot map in a case where exposure is performed on a second layer using a single-piece collective exposure apparatus 21.

11 is a diagram illustrating an example of a sample shot randomly selected for the second layer in FIG. 10B.

FIG. 12 illustrates that a mark on a small-diameter shot is interpreted as a mark on a large-diameter shot.

FIG. 13 is a diagram showing the position of the sample shot in FIG. 10A on the first layer.

FIG. 14 illustrates a first example of the scanning exposure apparatus according to the second embodiment.
FIG. 9 is a plan view of the wafer W, showing an exposure state when the shot is rotated when the layer is exposed, and the exposure state is extremely rotated.

FIG. 15 shows a second embodiment of the collective exposure apparatus according to the second embodiment.
FIG. 4 is a plan view of the wafer W showing an exposure state when a layer is exposed by correcting only a rotation of a shot.

FIG. 16 is a diagram showing a relationship between an upper left small-diameter shot and right, lower right, and lower adjacent shots when the small-diameter shot divides a large-diameter shot into four crosses;

FIG. 17 is an enlarged view showing a state in which shots on the right, lower right, and lower sides are corrected by an offset in the case of four divisions.

18A is a schematic configuration diagram illustrating a scanning exposure apparatus 1, and FIG. 18B is a plan view illustrating a reticle for the scanning exposure apparatus 1. FIG.

19A is a schematic configuration diagram illustrating a collective exposure apparatus 21, and FIG. 19B is a plan view illustrating a reticle for the collective exposure apparatus 21.

[Explanation of symbols]

 Reference Signs List 1 scanning type exposure apparatus (scanning type projection exposure apparatus) 3 reticle 4 projection optical system W wafer 21 batch type exposure apparatus (collective exposure type projection exposure apparatus) 23 reticle 24 projection optical system 32 alignment sensor MR1-MR3, ML1 To ML3 Wafer mark MUL, MUR, MLL, MLR Wafer mark S1 to SN First layer shot area SA1 to SAM Second layer shot area S51 to S62 First layer shot area SA51 to SA98 Second layer shot area 43A ~ 43J Sample shot

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/30 520A 525W

Claims (4)

[Claims] A first exposure step of exposing a plurality of first shots including an alignment mark on a substrate in a first arrangement using a first exposure apparatus; and determining a position of the alignment mark. A position measuring step of measuring; after the first exposure step, a plurality of second shots are superimposed in a second arrangement using a second exposure apparatus having an exposure field size different from that of the first exposure apparatus. A second exposure step of performing alignment exposure; the position measurement step includes, in the plurality of first shots, one or more alignment marks in three or more first shots; Measuring two or more relatively different alignment marks in the shot area; wherein the second exposing step is performed based on a measured value of the position measuring step. The error between shots and the An error in the first shot is calculated based on the position of the second shot as a reference, and the reference in each first shot is calculated based on the calculated error. The position of the remaining second shot is determined with reference to the position of the second shot
The step of exposing a shot; 2. The apparatus according to claim 1, wherein the first exposure device is a large-diameter exposure device, the second exposure device is a small-diameter exposure device, the first shot is a rectangular large-diameter shot,
Shot facing the rectangular large-diameter shot 2
Three rectangular small-diameter shots divided into three equal parts by two parallel lines cutting the side, and the second shot serving as the predetermined reference is any one of the three small-diameter shots. The exposure method according to claim 1, wherein: 3. The first exposure apparatus is a large-diameter exposure machine, the second exposure apparatus is a small-diameter exposure machine, the first shot is a rectangular large-diameter shot, and the second exposure apparatus is a large-diameter shot.
Are four rectangular small-diameter shots obtained by equally dividing the rectangular large-diameter shot by two straight lines intersecting through the midpoint of each side, and the second shot serving as the predetermined reference 2. The exposure method according to claim 1, wherein the shot is any one of the four small-diameter shots. 4. The scanning exposure type exposure apparatus according to claim 1, wherein the first exposure apparatus is a scanning exposure type exposure apparatus that synchronously scans the mask and the substrate to expose a pattern on the mask to each shot area on the substrate. 4. The exposure method according to claim 1, wherein the apparatus is a collective exposure type exposure apparatus that collectively transfers a pattern on a mask to each shot area on a substrate.