JP2909052B2 - Projection exposure equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure method, and more particularly to a projection exposure apparatus suitable for manufacturing a highly integrated semiconductor. 2. Description of the Related Art A highly integrated semiconductor is manufactured by sequentially transferring a plurality of original patterns onto an object to be exposed. Then, a pattern of a plurality of original images is sequentially transferred onto an object to be exposed, for example, a wafer, set on a two-dimensionally movable XY stage by a projection exposure system including an illumination optical system. At this time, the detection mark previously transferred to the object to be exposed is detected by the pattern detector, and the relative position with respect to the next original image is obtained based on the mark detected by the pattern detector, and the error amount is corrected. Then, the pattern of the original picture in the next stage is superimposed. FIG. 1 shows an apparatus used for carrying out such a projection exposure method. In FIG.
An XY stage that is step-and-repeat in the XY directions, is driven in the XY directions by drive motors 3 and 4,
The position is controlled by the laser measuring system 5 and has a positioning accuracy of about 0.05 μm.
6 is an exposure illumination system, 7 is a condenser lens, 8 is a reduction lens, and 9 is a pattern original (reticle) mounted on an original mounting table 10. 11 and 12 are pattern detection systems, 11a and 12a are detection system illumination systems, 11b and 12b are pattern detectors, 11c and 12c are half mirrors, 11
d and 12d are mirrors, and 11e and 12e are collimators. To perform projection exposure using this apparatus, X
The wafer 2 is mounted on the Y stage 1 and the original mounting table 10
After the first reticle 9 is installed, the light generated by the exposure illumination system 6 and condensed through the condenser lens 7 passes through the reticle 9, passes through the reduction lens 8, and passes through the XY stage 1.
The pattern of the reticle 9 is imaged on the wafer 2. [0005] Next, after the pattern of the reticle 9 is transferred onto the wafer 2 in this manner, a different pattern of the reticle 9 is transferred thereon, and the reticle transferred onto the wafer 2 is transferred. In order to transfer the pattern of the next stage reticle 9 with high accuracy on the pattern 9 and transfer it, the lights from the detection system illumination systems 11 and 12 are respectively reflected by half mirrors 11c, 12c, mirrors 11d and 1d.
Irradiation is performed on the wafer 2 through a reduction lens 8 through a hole provided in the reticle 9 via 2d, an image of the detection pattern 13 on the wafer 2 is formed on the reticle 2, and an enlarged image of the image is used as a mirror. 11d, 12d, and pattern detectors 11b, 12 via half mirrors 11c, 12c.
Then, the X and Y coordinates of the position of the wafer detection pattern are obtained by the pattern detectors 11b and 12b, and the relative error between the position of the wafer 2 and the position of the reticle 9 is obtained from the measurement of two chips on the wafer 2. The transfer is performed by feeding back the relative error to the control of the XY stage. [0006] Generally, a wafer is subjected to distortion by going through various processes, and this distortion appears as transfer distortion. This transfer distortion is not completely irregular, but rather regular. 2 to 6 show examples of transfer distortion. In each of the figures, the horizontal axis and the vertical axis have the X and Y axes, respectively. In the case of FIG. 2 and FIG. 3, when a transfer distortion occurs as if the chip arrangement had an arc-shaped undulation,
4 and 5 show a case where a transfer distortion (pitch error) occurs as if the chip array extends or contracts in the X and Y directions, and FIG. 6 shows a transfer distortion where an XY orthogonality error occurs. These various errors may occur alone or in combination, and the alignment error may be particularly large in a 1: 1 projection type projection exposure apparatus, and may be 1 μm or more. There is known a so-called global alignment in which two chip positions on a transferred wafer are detected, and the detected chip positions are used as reference positions for overlay exposure. This alignment method is very effective for improving the throughput, but is insufficient in accuracy when there is a transfer distortion as described above. There is also chip alignment for performing position detection and alignment for each chip. This alignment method has a serious problem in terms of throughput. In addition, with respect to alignment accuracy, when a certain chip is misaligned for some reason when the chip is aligned, the chip may be shifted as it is. SUMMARY OF THE INVENTION An object of the present invention is to provide a projection exposure apparatus capable of expecting mutually contradictory advantages of high throughput and high precision alignment. According to the present invention, there is provided a stage for moving an object to be exposed, and a projection lens for exposing an original image pattern on the object to be exposed. In a projection exposure apparatus for exposing the original pattern onto the object to be exposed, a detection mark provided in correspondence with the first original pattern transferred to the object to be exposed is detected, and the position of the detection mark is detected.
A pattern detector for detecting the position of the first original pattern transferred to the object to be exposed, and at least four selected positions that are not on a straight line based on the output of the pattern detector. Detecting means for calculating a target position so as to correct the orthogonality error of the array of the transferred first original pattern based on the detected position; and calculating means for calculating a target position based on an output of the pattern detector. Having stage control means for moving the stage so that the object to be exposed is at the target position,
The stage is sequentially moved to expose the object to be exposed via the projection lens so that a second original pattern is superimposed on the transferred first original pattern. Things. According to the present invention, since at least three of the first original patterns transferred to the object to be exposed are selected and their positions are detected, the selected original image is selected. Exposure takes longer than global alignment by the number of patterns, but higher throughput can be expected than chip alignment. Also, regarding the alignment accuracy, since at least three original patterns are selected, the original pattern arrangement can be obtained with high accuracy. In addition, the alignment of one original pattern is slightly shifted due to the averaging effect. However, the influence can be reduced by compensating for the other original patterns.
Even if the transferred original image pattern includes a distortion of orthogonality, it is possible to perform the overlay transfer with high accuracy. Thus,
According to the present invention, there is provided a projection exposure apparatus in which mutually contradictory advantages of high throughput and high precision alignment can be expected. As an example, as shown in FIGS.
When the chips are arranged in 5 rows and 5 columns, the center chip and the five chips selected from the center chip with one chip placed in each of the X-axis direction and the Y-axis direction are used as detection chips. Can be. In this case, the coordinates of the center chip are (x ₀ , y ₀ ), the coordinates of the two chips in the X-axis direction are (xa, ya), (xb, yb), and the coordinates of the two chips in the Y-axis direction are respectively (Xc, yc), (xd,
yd), and in the case of the arc-shaped undulation shown in FIG. 2, (x ₀ , y ₀ ), (xa, ya), (x
By obtaining (x ₁ , y ₁ ) and (x ₂ , y ₂ ) from the detected coordinates of the three points (b, yb) using the well-known least square method, the chip array of 5 rows and 5 columns is obtained. The chip arrangement can be determined in the same way as in the case of FIG. 2 in the case of the undulation shown in FIG. In addition, as shown in FIG. 4, when there is elongation in the X direction, x is calculated from the coordinates of three points (x ₀ , y ₀ ), (xa, ya), and (xb, yb) obtained by detection. _1, the chip sequence of five rows and five columns by determining the x ₂ can be determined. The arrangement is determined in the same manner in the case where there is an extension in the Y direction shown in FIG. Further, when there is the orthogonality error shown in FIG. 6, (xa, ya), (xb, y)
When the coordinates of four points b), (xc, yc) and (xd, yd) are obtained, the following equation is obtained from these coordinates. As a result, an orthogonality error is obtained, and an arrangement of 5 rows and 5 columns is determined. Therefore, when the pattern of the next original image is transferred onto the chips arranged as described above, the XY stage on which the object to be exposed is mounted is moved to transfer the pattern of the next original image to the preceding stage. Can be transferred to the correct position on the original pattern. FIG. 7 is a schematic explanatory view of a main part of an embodiment of the projection exposure apparatus. Reference numerals 14 and 15 denote wafers, each of which is a chip when five chips are used. An array,
The position of the chip at which the position of the detection mark is detected by this method is shown, and the five chips are in a direction perpendicular to each other with respect to the chip located at the center, and from this chip. It consists of four equidistantly located. The position of the mark is obtained by the pattern detectors 11b and 12b of the illumination systems 11 and 12 of the projection exposure apparatus of FIG. In addition, the code | symbol attached to the chip is FIGS.
It is the same as And 16 is (xc, yc), (x
₀ , y ₀ ) and (xd, yd) data, and an X-direction undulation error correction calculation circuit for obtaining an X-direction undulation error, 17
Is a Y-direction pitch error correction calculation circuit for similarly calculating the Y-direction pitch error, and 18 is (xa, ya), (x ₀ , y ₀ ),
The (xb, yb) data is input and the Y-direction undulation error correction calculation circuit for obtaining the undulation error in the Y-direction.
The X-direction pitch error correction calculation circuit for calculating the pitch error in the direction, 20 includes (xd, yd), (xc, yc), (x
a, ya), (xb, in Cartesian degree error correction calculation circuit data seeks Cartesian degree error type of yb), obtaining the final stage target position by the calculation result obtained by these calculation circuit. When the final stage target position is obtained in this way, the deviation between the final stage target position and the position of the next original image is adjusted by moving the XY stage using the drive motors 3 and 4, so that the The pattern of the next original picture can be superimposed on the pattern of the previous original picture transferred to the chip. Although this target determination has been described by taking as an example the case of a 1: 1 projection having an array of rows × columns = 5 × 5, in general, an array of rows × columns = n × n, or
As shown in FIG. 8, the same idea can be applied to a case where a part of the array of row × column = n × n on the wafer 2 is limited due to the shape of the wafer 2 and omitted. The correction formula and method to be used vary depending on the model of the 1: 1 projection and the arrangement of rows and columns, but can be similarly applied in any case. If so, it can be appropriately selected. Further, this method is not limited to the method in which the former stage is transferred by the 1: 1 projection exposure method, and is applicable to the case where the former stage is transferred and formed by any other type of exposure method. According to the present invention, even when the transferred original image pattern includes a distortion of orthogonality, it is possible to perform overlay transfer with high accuracy, and to achieve high throughput and high precision alignment. The present invention can provide a projection exposure apparatus that can be expected to have conflicting advantages, and has a great industrial effect.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of a projection exposure apparatus used for projection exposure. FIG. 2 is an explanatory diagram showing an arrangement of chips on a wafer for explaining the principle of the projection exposure method of the present invention. FIG. 3 is an explanatory view showing an array of chips on a wafer. FIG. 4 is an explanatory view showing an arrangement of chips on a wafer. FIG. 5 is an explanatory view showing the arrangement of chips on a wafer. FIG. 6 is an explanatory view showing an array of chips on a wafer. FIG. 7 is a schematic explanatory view of a main part of an embodiment of the projection exposure apparatus of the present invention. FIG. 8 is a plan view showing another example of an arrangement of chips on a wafer. [Description of References] 1 ... XY stage, 2 ... Wafer, 3, 4 ... Drive motor,
5: Laser measuring system, 6: Exposure illumination system, 7: Condenser lens, 8: Reduction lens, 9: Pattern original (reticle), 10: Original mounting table, 11, 12: Pattern detection system, 13: Detection pattern

Continuation of the front page (56) References JP-A-10-261586 (JP, A) JP-A-59-54225 (JP, A) JP-A-57-17132 (JP, A) JP-A-57-80724 (JP) JP-A-55-41739 (JP, A) Patent 2675528 (JP, B2) JP 7-66905 (JP, B2) JP 4-74854 (JP, B2) Solid State Technology, Vol. 25, No. 5, (1982-5), p. 111-115 (58) Field surveyed (Int. Cl. ⁶ , DB name) H01L 21/027

Claims (1)

(57) [Claims] A stage for moving the object to be exposed, and a projection exposure apparatus having a projection lens for exposing the original pattern to the object to be exposed, and sequentially moving the stage to expose the original pattern to the object to be exposed, Detecting a detection mark provided in correspondence with the first original pattern transferred to the object to be exposed;
該検hoax - detecting the position of the click patterns - and emissions detector, wherein the four positions selected not to at least a straight line of the first original pattern the transferred on an exposure object pattern - emission detection Calculating means for detecting based on the output of the device, and calculating a target position based on the detected position so as to correct the orthogonality error of the array of the transferred first original pattern;
A stage control means for moving the stage based on the output of the pattern detector so that the object to be exposed is at the target position; and sequentially moving the stage to transfer the second original pattern. A projection exposure apparatus configured to expose the object to be exposed through the projection lens so as to overlap the first original pattern.