JP2005217092A - Method and equipment for exposing semiconductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten the transition time from some sample shot processing to next sample shot processing, and the transition time from sample shot processing to exposure processing. <P>SOLUTION: Processing order of sample shot of global alignment is determined to shorten the stage movement distance from the last shot of global alignment to the first shot of exposure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exposure method, a device manufacturing method, and an exposure apparatus that perform exposure after performing one or a plurality of sample shot processes on a substrate to be exposed such as a wafer.

  Wafer processing for producing an exposed wafer mainly includes sample shot processing and exposure processing such as pre-alignment and global alignment for positioning the wafer. Conventionally, efforts have been made to shorten the time required for each process in order to improve the productivity of exposed wafers, that is, the throughput (Patent Document 1).

  In pre-alignment, the wafer stage is moved to each sample shot to measure the position of the pre-alignment mark, and the wafer is preliminarily positioned based on the result.

  Each device has one dedicated sample shot automatic selection means that can select the best shot for the conditions used for each application so that the best and recommended shot for the purpose can be selected. According to the selection means, it is possible to automatically select the optimum sample shot for the conditions used for the application.

As a diagram showing a sample shot, the one shown in FIG. 1A is used.
Here, the numbers in parentheses indicate the processing order of each shot.

  In FIG. 1A, in pre-alignment, first, the mark position of PA2 is measured, and then PA1 is measured to preliminarily position the wafer.

  When the preliminary positioning of the wafer is performed, global alignment, which is the final positioning of the wafer, is performed.

  Global alignment currently measures several shots (sample shots) in a wafer from the standpoint of the productivity of IC and LSi and the alignment accuracy.

  For example, an example of global alignment sample shot placement that has been considered optimal is to be placed as far as possible outside the outer periphery of the wafer so that it is distributed almost symmetrically from the wafer center and the circumference is evenly distributed. select.

  In FIG. 1A, in the global alignment, the mark positions (not shown) are measured in the order of G1, G2, G3, and G4 in the counterclockwise direction, and the wafer is finally positioned.

  When the main positioning is completed, the wafer stage is driven to the exposure first shot E1 to perform exposure. Similarly, each shot exposure is performed while driving the wafer stage.

  Here, the OAS high / low magnification switching process for performing pre-alignment and global alignment will be described with reference to FIGS.

  2A, 2B, and 2C are written by shifting the stage in the Z direction in each measurement order with respect to the G1 to G4 measurement positions and the exposure position E1.

  2A, 2B, and 2C, UL is a projection optical system, and OAS is an off-axis scope for performing alignment measurement.

  The OAS in FIGS. 2 (a), 2 (b), and 2 (c) can perform pre-alignment low magnification observation and global alignment high magnification observation.

  Hereinafter, OAS in FIGS. 2A, 2B, and 2C will be described with reference to FIG.

  A light beam irradiated from an alignment lighting fixture (not shown) that irradiates illumination light (non-exposure light) passes through the half prism 3, and illuminates the wafer W through the objective lens by the bending mirror 2. The speed of light reflected from the wafer mark passes through the objective lens 1 again and through the half prism by the bending mirror.

  Here, the switching mirror 4 can perform an optical path switching operation by entering and exiting the mirror (IN / OUT). When the switching mirror 4 is IN, the speed of light reflected from the wafer mark is a low-magnification observation relay lens. 5 and reach the half prism 7.

  When the switching mirror 4 is OUT, the speed of light reflected from the wafer mark reaches the half prism 7 through the relay lens 6 for high magnification observation.

  At this time, it is necessary to wait for the stability of the switching mirror so that the mirror drive accuracy does not appear at the time of fine examination for performing high magnification observation (during global alignment).

  The speed of light that has passed through the half prism 7 is taken into the positional deviation detection device 9 through the erector lens 8, and the positional deviation of the irradiated mark can be detected.

  Here, the wafer is carried in by a wafer transfer system (not shown) and pre-alignment is performed, but the wafer delivery position differs from the right and left of the wafer transfer system.

  In the right transport system, the pre-alignment is measured in order of PA2 and PA1, and the processing time from wafer transfer to pre-alignment is shorter than PA1 and PA2.

  In the left transport system, the pre-alignment is measured in the order of PA2 and PA1, and the processing time from wafer transfer to pre-alignment is shorter than that of PA2 and PA1.

  Conventionally, if a 200 mm wafer is used, the movement from PA2 to the G1 shot has been completed within a waiting time so that the driving accuracy for OAS switching is not achieved.

For this reason, there was no difference in throughput between the left and right transport systems.
JP 2001-093817 A

  However, when a 300 mm wafer, which has been increasing in recent years, is used, the moving distance from PA2 to G1 is extended.

  When pre-alignment was performed in the order of PA1 and PA2, the stage steps could not be completed within the time for OAS switching.

  That is, when the measurement is performed in the order of PA1, PA2, the throughput is reduced as compared with the case where the measurement is performed in the order of PA2, PA1.

  Referring to FIG. 4, in FIG. 4A, the stage step amount from the pre-alignment final shot to the global alignment first shot (G1) ends within the OAS high / low magnification switching time. In (b), the OAS high / low switching time is not over. As a result, FIG. 4B has a longer global alignment time than FIG.

  When a 300 mm wafer is used, the global alignment time is often extended as described above, depending on how the pre-alignment and global alignment sample shots are taken because the stage step distance increases.

  Further, when viewing FIG. 1 (a), the final shot G4 of the global alignment is close to the first exposure shot E1 in the layout, but when viewing the stage from G4 to E1 when viewing the stage from FIG. 2 (a), the OAS center Since there is a difference in the Y direction between the center of the projection optical system UL, it can be seen that the stage drive amount is large.

  The problem to be solved by the invention is to improve the throughput with respect to the time to shift from one sample shot process to the next sample shot process and the time to shift from the sample shot process to the exposure process (hereinafter referred to as “transfer time”). In order to reduce the above-mentioned transition time.

  In an exposure method in which each shot is exposed after performing a plurality of sample shots on the substrate to be exposed, the global alignment sample is set so that the stage moving distance from the last shot to the first shot of the global alignment is shortened. The processing order of shots is determined.

  Further, in the processing order of the sample shot processed last in the global alignment, a distance (baseline) between the center of the off-axis and the center of the projection optical system is considered.

  Furthermore, in the processing order of the sample shot to be processed last in the global alignment, with respect to the distance between the global alignment shot position and the exposure first shot position, the maximum value of the X-direction distance and the Y-direction distance drawn from the baseline is A global alignment shot that satisfies the minimum condition is used as the final shot of the global alignment.

  As described above, according to the present invention, the distance between the final shot of one sample shot process and the first shot of the next sample shot process, or the distance between the final shot of the sample shot process and the first shot of the exposure process. This makes it possible to shorten the transition distance, and to shorten the moving time of the stage that moves the transition distance. Accordingly, the processing time per one substrate to be exposed can be shortened, and the productivity of exposed wafers, that is, the throughput can be improved.

  Hereinafter, preferred embodiments of the present invention will be described using examples.

  Hereinafter, an example of a semiconductor exposure method and apparatus using the semiconductor exposure apparatus of the present invention will be described with reference to FIGS.

  5 and 6 show a sequence flow for determining the processing order of sample shots in each sample shot processing for a wafer having a shot layout as shown in FIG.

  The shot layout to be processed in the sequence and the number and position of the sample shots in the sample shot process can be selected. In this embodiment, it is assumed that they are selected as shown in FIG.

  In the drawing, PA1 and PA2 are sample shots for pre-alignment (2 shots), G1, G2, G3, and G4 are sample shots for global alignment (4 shots), and E1 is an exposure shot. The parentheses indicate the measurement order of sample shots, and the exposure shot E1 is exposed after G4.

  When the sequence starts, first, the wafer is carried in step S001.

  As shown in the figure, when wafer processing is started, sample shot processing is performed in the order of pre-alignment (S002) and global alignment (S003) on the wafer placed on the wafer stage.

  Finally, an exposure process is performed (S004). When the exposure process is completed, the wafer is unloaded (S005), and the next wafer is loaded (S001).

  When all the wafers are finished (S006), the sequence is finished.

Before the present invention is applied, the pre-alignment shots in FIG. 1B are in the order of PA1 and PA2. (Left transport system)
Further, the processing order of the sample shot for global alignment before applying the present invention is G1, G2, G3, G4.

  All sample shot operations such as alignment and exposure are performed based on this layout.

  However, in this embodiment, the sample shot is processed counterclockwise.

  Instead of processing sample shots counterclockwise, other rules may be used.

  Here, the off-axis scope OAS is used for the measurement for both the pre-alignment and the global alignment.

  Next, the movement of pre-alignment and global alignment will be described using the flow of FIG.

In S002 pre-alignment, first, a stage step is performed on the mark of the pre-alignment first shot PA1 of FIG. 1B while driving the switching mirror 4 of FIG. 3 to IN (SA001), and the position at a low magnification is obtained. Measure the deviation. (SA002)
When the measurement is completed, a stage step is performed on the mark of the pre-alignment first shot PA2 in FIG. 1B (SA003), and the position deviation measurement is performed at a low magnification. (SA004)
In SA005, correction amounts of X, Y, and θ are obtained from the positional deviation amounts obtained in steps SA002 and SA004.

Next, while driving the switching mirror 4 of FIG. 3 to OUT, a stage step is performed on the mark of the global alignment first shot G1 of FIG. 1B in consideration of the pre-alignment correction value obtained in SA005 ( SA006), the positional deviation measurement at high magnification is performed. (SA007)
After the position shift measurement at high magnification (SA007), it is determined whether or not the final shot is completed (SA008). If it is not the final shot, a stage step is performed to the global alignment next shot G2 in FIG. (SA009)
After performing SA007 to SA009 in the same procedure, when the final shot (G4) is completed (SA008), the process proceeds to SA010 correction amount calculation. (The method of calculation in global alignment is a well-known fact and will be omitted.)
Here, FIG. 4 shows SA001 to SA010 as a timing chart.

  According to the present invention, the first shot of AGA is selected so that the pre-alignment final shot stage step time (B) is within the OAS switching time (A).

  Assuming that OAS high / low magnification switching time: to [msec] when mirror driving accuracy is not mounted during high-precision observation for high magnification observation, the circle of R1 in FIG. It is obtained from the formula.

  In this embodiment, the speed v is an average in the xy direction, but the stage drive range may be obtained separately for the xy direction.

  That is, in this embodiment of FIG. 1, the stage drive range that can be driven to time is a circle with a radius R1, but it may not be a circle when the XY drive speed is different.

  In the present embodiment of FIG. 1, the center of the stage drive range that can be driven to time is the PA2 shot center, but the mark position of PA2 may be the center.

  Further, within the stage drive range, the stage drive range may be obtained in consideration of acceleration / deceleration and profiles such as acceleration.

  Further, an actual driving time measured in advance by a preliminary operation may be applied without using a calculation calculated.

  Here, G3 and G4 can be options for the global alignment first shot.

  Hereinafter, it is determined which of G3 and G4 is selected as the first shot of global alignment.

  FIG. 7 is a diagram showing the shot position of the wafer in this embodiment.

  When G3 is selected as the first shot of global alignment, exposure processing is performed in the order of G3, G4, G1, G2, and the exposure first shot E1.

  When G4 is selected as the first shot of global alignment, exposure processing is performed in the order of G4, G1, G2, G3 and exposure first shot E1.

  However, as shown in FIG. 7, G2, which is the final global alignment shot, is farther from the first exposure shot E1 than G4 described in the prior art.

  2 (a) (b) and FIG. 2 (c), the distance for driving the stage in the Y direction from the global alignment final shot to the exposure first shot E1 is clearly the largest in FIG. 2 (c). Few.

  That is, the global alignment final shot position is optimally the shot G3 that minimizes the stage drive amount from the global alignment final shot position to the exposure first shot position.

  The first global alignment shot for selecting G3 as the global alignment final shot is G4.

  In other words, considering FIGS. 2A, 2B, and 2C, it is desirable to consider the baseline.

Here, the Y direction difference between the OAS measurement center and the exposure center of the projection optical system is defined as BLY. To write a specific selection method that takes into account the baseline,
Set the exposure first shot position to (E1X, E1Y),
Global alignment last shot position is (AGA_X, AGA_Y)
given that,
MAX (| E1X-AGA_X |, | E1Y-AGA_Y-BLY |)… (A)
Is to make the shot that minimizes the global alignment final shot position.

When G2 (G2X, G2Y) is selected as the last shot, the value of G2MAX (> 0) is (A).
G2MAX = MAX (| E1X-G2X |, | E1Y-G2Y-BLY |)
= MAX (Xa, Ya)
= Xa = | E1X-G2X |… (B)
Represented as:

When G3 (G3X, G3Y) is selected as the final shot, the value of G3MAX (> 0) is (A).
G3MAX = MAX (| E1X-G3X |, | E1Y-G3Y-BLY |)
= MAX (Xb, Yb)
= Yb = | E1X-G2X |… (C)
Represented as:

In this embodiment, Xa> Yb.
G2MAX> G3MAX… (D)
It is. From (B), (C), and (D), the global alignment final shot that minimizes the expression (A) can be selected as G3.

  In this embodiment, since the X direction difference BLX = 0 between the OAS measurement center and the exposure center of the projection optical system, the description about the X direction is omitted, but the same applies to the case where BLX ≠ 0. I can think.

  Further, although the mark is calculated as being in the center of the shot, it may be calculated using the mark coordinates.

It is a figure which shows the shot position of the wafer in connection with this invention. It is the principal part schematic of the Example which can be set | placed on this invention. It is an example (off-axis scope) of the measurement system in the Example of this invention. It is a timing chart of pre-alignment time and global alignment time in the example of the present invention. It is a flowchart in the Example of this invention. It is a flowchart of the pre-alignment and global alignment in the Example of this invention. It is a figure which shows the shot position of the wafer in the Example of this invention.

Explanation of symbols

PA1, PA2 Pre-alignment shot
G1-G4 Global alignment shot
E1 First exposure shot
W wafer
Stage Wafer stage (1) to (4) Processing order of each sample shot and exposure shot UL projection optical system OAS Off-axis scope for performing measurement for alignment
Distance between R0 PA2 and G1
Range where stage can be driven during R1 OAS high / low switching
R2 R0-R1
E1X x coordinate in E1
E1Y y coordinate in E1
X coordinate in G2X G2
Y coordinate in G2Y G2
X coordinate in G3X G3
Y coordinate in G3Y G3
Difference between BLY UL center and OAS center (baseline)
Xa | E1X-G2X |
Ya | E1Y-G2Y-BLY |
Xb | E1X-G3X |
Yb | E1Y-G3Y-BLY |

Claims (6)

  In an exposure method in which each shot is exposed after performing a plurality of sample shots on the substrate to be exposed, the global alignment sample is set so that the stage moving distance from the last shot to the first shot of the global alignment is shortened. A semiconductor exposure method characterized by determining a processing order of shots.   2. The semiconductor exposure method according to claim 1, wherein the processing order of the sample shot to be processed last in the global alignment takes into account the distance (baseline) between the center of the off-axis and the center of the projection optical system.   In the processing order of the sample shot to be processed last in the global alignment, the maximum value of the distance in the X direction and the distance in the Y direction with the baseline is the minimum with respect to the distance between the global alignment shot position and the exposure first shot position. 2. The semiconductor exposure method according to claim 1, wherein a global alignment shot that satisfies such a condition is used as a final shot of the global alignment.   In an exposure apparatus that performs exposure of each shot after performing a plurality of sample shots on the substrate to be exposed, the global alignment sample is set so that the stage movement distance from the last shot to the first exposure shot is reduced. A semiconductor exposure apparatus that determines a processing order of shots.   The semiconductor exposure apparatus according to claim 1, wherein a distance (baseline) between the center of the off-axis and the center of the projection optical system is considered in the processing order of the sample shot to be processed last in the global alignment.   In the processing order of the sample shot to be processed last in the global alignment, the condition that the maximum value of the distance drawn by the baseline is the minimum with respect to the distance between the global alignment shot position and the exposure first shot position is satisfied. 2. The semiconductor exposure apparatus according to claim 1, wherein the global alignment shot is a final shot of global alignment.

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