JPH0515055B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a semiconductor printing apparatus that prints a circuit pattern drawn on a mask (or reticle) onto a wafer by step-and-repeat.
More specifically, the present invention relates to a semiconductor printing apparatus that can visually confirm any abnormality detected in the alignment between a mask and a wafer prior to exposure.

[Description of Prior Art] In this type of conventional semiconductor printing apparatus, alignment marks on a mask and a wafer are scanned with a laser beam, etc., and the scattered light is photoelectrically converted into electrical pulses. It is widely practiced to measure this pulse position with a counter or the like for alignment.

For example, an alignment mark M as shown in FIG. 2a is used as a mask, a mark W as shown in b is drawn on the wafer, and an apparatus having the configuration as shown in FIG. Scanning M and W with a laser beam to detect the relative position, that is, the amount of deviation, between the mask 1 and the wafer 2;
By driving at least one of the mask 1 and the wafer 2 according to this amount of deviation, the mask 1 and the wafer 2 are aligned relative to each other, as shown in FIG. 2c.

The alignment marks M are formed one each on the left and right sides of the mask, that is, on the outside of the circuit pattern of the mask, and the alignment marks W are formed on both sides of each corresponding shot on the wafer.

FIG. 3 is a plan view showing a portion of each shot area and alignment mark on the wafer. In the figure, S (and Sn) each indicate an area (one shot) in which a circuit pattern is exposed in one step. W1 and W2 are alignment marks placed on the left and right sides of each exposure area. In particular, W1n and W2n are alignment marks in the exposure area Sn. These marks are arranged in a Y-shape so that adjacent marks do not overlap.
It is placed at a position offset from the direction. Assuming that alignment marks M1 and M2 are arranged on the left and right sides of the mask, if the exposure shot is Sn, the marks M1 and W1n on the mask are aligned, and the marks M2 and W2n are aligned. .

FIG. 4 shows the configuration of a semiconductor printing apparatus which is a conventional example and is also an example to which the present invention is applied. The semiconductor printing apparatus shown in FIG. 1 uses a step-and-repeat method to reduce and project a circuit pattern on a mask onto a wafer placed on a stage and print the pattern.

In the figure, 1 is a mask on which a circuit pattern is drawn, 2 is a wafer which is an object to be exposed, and 3 is a wafer stage. 4 is a laser tube that generates a laser beam for alignment, 5 is a polygon mirror, 6 is a motor, 7 is a prism, 8 is a beam splitter,
9 is an objective lens, and 10 is a mirror. Also, 1
1 is a projection lens, 12 is a photoelectric detector, 13 is a control circuit, 14 is a binarization circuit, 15 is a measurement circuit, 16
1 is a stage drive circuit, and 17 is a motor. 18
1 is an input/output terminal, 19 is a display of the terminal, and a shot layout 20 of the wafer 2 is graphically displayed on the display 19. Reference numeral 21 is a display showing each exposure (shot) area of the wafer 2, which is filled in with a specific color (for example, green) each time the exposure of each step is completed.

Alignment marks M1 and M2 are arranged on the mask 1. Further, alignment marks W1 and W2 are arranged on the wafer 2 for each exposure area. For convenience of explanation, M1 and W1
The system for detecting the set of marks M2 and W2 will be called the left visual field system, and the system for detecting the set of marks M2 and W2 will be called the right visual field system.

In the apparatus shown in the figure, a laser beam emitted from a laser tube 4 passes through a polygon mirror 5 rotated by a motor 6, and is divided by a prism 7 into a left viewing system and a right viewing system. The divided laser beams pass through a beam splitter 8, an objective lens 9, and a mirror 10, and scan alignment marks M1, M2 on the mask and alignment marks W1, W2 on the wafer, respectively. Scattered light from each mark passes through a mirror 10, an objective lens 9, and a beam splitter 8 and enters a photoelectric detector 12. The photoelectric detector 12 photoelectrically converts this incident light and outputs it as an electrical signal. This output is 2 in the control circuit 13.
The data is binarized by the digitization circuit 14. Further, the measuring circuit 15 calculates the relative position of each mark (the amount of deviation between M1 and W1 and the amount of deviation between M2 and W2) from this binary output. The control circuit 13 calculates the amount of movement of the stage 3 based on this amount of deviation, and instructs the stage drive circuit 16 to move the stage 3 in order to arrange the mask 1 and wafer 2 in the correct positional relationship. Stage 3 has its movement direction (X, Y)
The control circuit 13 controls the motor 17 to move the stage by the correct amount while monitoring the amount of movement data from the laser interferometer. Drive control.

When the alignment is completed, exposure is performed, and then, among the shot layouts 20 of the wafer 2 displayed on the display 19 of the terminal 18,
Portion 21 corresponding to the shot position where exposure was performed
Fill it with a specific color. Furthermore, the stage 3 is moved to the next exposure shot.

Here, the stage to be driven for positioning is
Drive amount in XY direction (amount of misalignment between mask and wafer)
is obtained by calculating the average value of the amount of deviation between the alignment marks M1 and W1 and the amount of deviation between M2 and W2. Furthermore, regarding the rotational direction, the difference in the amount of deviation in the Y direction between W1 and M1 and the amount of deviation in the Y direction between W2 and M2 is taken to determine the amount of deviation in the rotational direction. To compensate for this deviation in the rotational direction, the mask or wafer is rotated and aligned using a rotation mechanism (not shown).

By the way, in actual wafers, marks W1 and W2 on the wafer may not be formed correctly due to etching failure, dust, and other influences during the process. FIG. 5a is a cross-sectional view of a properly formed alignment mark, and such a mark produces a confusion signal as shown in FIG. 5b. In addition, figure c is an example (cross-sectional view) of an alignment mark that was not formed correctly due to a failure such as etching.
d in the figure shows the signal from this mark.
The signal obtained from the mark here is
It is an electrical signal obtained by scanning a mark with a laser beam or the like and detecting its reflected or scattered light with a photoelectric element or the like.

In this way, the alignment mark W1 or W
If one of the two marks is not formed correctly, the conventional device cannot measure the signal from that mark or the measured value is abnormal, so the shot cannot be aligned. It was hot. Further, even when a signal is obtained, the error between the measured mark deviation amount and the true deviation amount may become large due to signal distortion caused by the edges of the mark not being formed correctly. As described above, the amount of deviation between the mask and the wafer is determined as the average of the amount of deviation in the left mark set and the deviation amount in the right mark set.
Therefore, for example, even if the left mark is measured correctly, if the error in the amount of deviation measured by the right mark is large, the error in alignment using the average value will be large. It was hot.

Therefore, in order to solve the above problems, the present inventors invented the following alignment device and previously filed a patent application. The alignment operation in the apparatus of this prior application will be described with reference to the flowchart of FIG.

In the alignment and exposure sequence, first the gain of the amplifier of the signal detection system is adjusted (step S101). Next, the alignment mark is detected and the amount of deviation between the mask and the wafer is measured (step S102). Next, it is determined whether or not both the left and right marks have been measured in the measurement at step S102 described above (step S103), and if the measurement has been completed, the process proceeds to step S104; if either one has not been measured, the process proceeds to step S108. Branch out.

In step S104, the measured value of the left visual field system and the measured value of the right visual field system are each independently checked to determine whether the amount of deviation measured in step S102 is larger than a predetermined upper limit value. The upper limit value of this deviation amount is input in advance through the input/output terminal 18 and stored in a memory (not shown) in the control circuit 13. This upper limit value consists of the upper limit value of the amount of deviation in the XY direction and the upper limit value of the amount of deviation in the rotational direction.

In the check at step S104, if this measured value exceeds the upper limit value for both the left and right visual field systems, an error is determined. Furthermore, if the measured values are within the upper limit for both viewing systems, it is determined whether the amount of deviation is within the tolerance (step S105),
If not, the amount of drive of the stage is calculated (step S106), and the stage is driven (step S10).
7). Thereafter, the process returns to step S102.

On the other hand, if it is not possible to measure either the left or right mark in step S103,
Furthermore, it is determined whether it was not possible to measure both the left and right visual field systems, or whether only one of them could not be measured (step S108). Here, if there is a measurement error in both the left and right sides, it is determined as an error, and if only one side has a measurement error, the process branches to step S110. Further, if in step S104 only the single-field system exceeds the upper limit value, the process branches to step S110. That is, the process branches to step S110 when only one of the left and right visual fields can be measured within the upper limit value.

In step S110, the measurement execution flag corresponding to one of the visual field systems in which the upper limit value of the deviation amount has been exceeded or in which an error has occurred in measurement is cleared. That is, the measurement execution flag corresponding to the visual field system for which the measurement value is normal remains on, and the other measurement execution flag is cleared. Thereafter, the driving amount calculation (step S106) is performed without using the measurement data of the visual field system for which the measurement execution flag has been cleared.
This is performed using measurement data only from the single-view system with the flag turned on. Thereafter, the stage is driven (step S107), and the process returns to step S102 to perform positioning again, and measurement is performed, but in this case, measurement is also performed only with the single-field system with the flag turned on.

In step S105, when the amount of deviation is within the tolerance, the alignment is finished. Thereafter, exposure is performed (step S111), and a graphic is displayed in a specific color on the terminal at the same time as the exposure is completed to indicate the completion of exposure for that shot (step S113). For example, fill in the part corresponding to that shot with green. Furthermore, the stage is moved to the next shot (step S114), and alignment and exposure are performed again from the beginning.

By the way, even if only one field of view system is aligned as described above during the alignment of each shot, all the graphic displays on the terminal will be filled with the same color at the end of step-and-repeat. Therefore, it was not known in what shot and to what extent the alignment mark was abnormal. That is, although abnormalities in alignment marks are often caused by the effects of resist coating or etching processes, and it is important to know the shots, there is a drawback that it is not possible to know the shot where the abnormality occurs.

[Object of the Invention] In view of the above-mentioned problems, the present invention provides a semiconductor printing apparatus that prints a circuit pattern on a mask or reticle onto a wafer by step-and-repeat. The purpose is to make it possible to check the alignment status of shots at a glance using a terminal, etc.

[Description of Embodiment] Next, the operation of a semiconductor printing apparatus according to an embodiment of the present invention will be described with reference to the flowchart of FIG. In this embodiment, the present invention is applied to a semiconductor printing apparatus having the configuration shown in FIG.

Here, steps S1, S2, . . . in FIG. 1 are replaced by steps S101, S102, . . . in the conventional example in FIG.
The operation of each step is the same as that shown in FIG. Furthermore, the difference between the flowchart of FIG. 1 and the flowchart of FIG. 6 is that steps S9 and S12 are newly added.

In FIG. 1, if there is a measurement error in only one of the left and right visual field systems in step S8, or if only one visual field system exceeds the upper limit value in step S4, the process branches to step S9. In step S9, the CPU (not shown) in the control circuit 13 in FIG. 4 sets a flag in the memory (not shown) in the control circuit 13 to indicate which error has occurred and its type. When the alignment is completed, after the exposure is completed (step S11), the flag in the memory is checked in step S12 to determine whether the alignment prior to this exposure was performed normally or if there was any abnormality. Check what's going on. If the alignment is correct, the shot on the graphic display on the terminal is filled in with normal green color, and if there is any abnormality, the shot is filled in, for example, with yellow-green color. By using this method, if you look at the display on the terminal at the end of the step-and-repeat,
You can see at a glance how the alignment was performed. If you wish to keep it as a record, you can record the graphic display of the terminal using a graphic printer or the like.

In the above embodiment, the graphic display had only two colors for normal and abnormal alignment, but
It is also possible to display the details of the abnormality in more detail by adding other colors. In this case, more detailed information can be obtained regarding the content of the abnormality in the shot in which the positioning was abnormal at the end of the step-and-repeat. For example, using four display colors, the first color is used for normal shots, the second color is used when there is an error in the right visual system, the third color is used when there is an error in the left visual system, and the third color is used for both visual systems. If an error occurs in the 4th color, it is possible to know in which viewing system the error occurred.

Also, even if you use a monochrome monitor (terminal) instead of a color one, fill in the shots with a mesh, etc., and change the mesh of the bright spots or black spots for the shots that are out of alignment with the normal shots. A similar effect can be achieved by

Further, by step-and-repeat only the position measurement prior to the alignment-exposure operation by step-and-repeat, and by displaying a graphic display, the position information for wafer exposure can be known before exposure.

[Effects of the Invention] As explained above, according to the present invention, in a semiconductor printing apparatus that prints a circuit pattern drawn on a mask or reticle onto a wafer by step-and-repeat, the mask or reticle and the wafer are connected. Shots for which an abnormality was detected during relative positioning are displayed graphically on a terminal, etc. so that they can be distinguished from shots for which normal positioning was performed. You can check the alignment status at a glance.

[Brief explanation of the drawing]

FIG. 1 is a flowchart for explaining the operation of a semiconductor printing apparatus according to an embodiment of the present invention, FIG. 2 is a diagram showing alignment marks applied to a mask and a wafer, and FIG. 3 is a diagram showing alignment marks applied to a wafer. FIG. 4 is a plan view showing a part of the exposure area and alignment mark above, FIG. 4 is a configuration diagram of a semiconductor printing apparatus which is a conventional example and an example to which the present invention is applied, and FIG. 5 is a cross-sectional view of the alignment mark and its FIG. 6 is a flowchart for explaining the operation of a conventional semiconductor printing apparatus. 1: Mask, 2: Wafer, 3: Wafer stage, 12: Photoelectric detector, 13: Control circuit, 14:
Binarization circuit, 15: Measurement circuit, 16: Stage drive circuit, 17: Motor, 18: Input/output terminal, 19: Display, 20: Shot layout, 21: Display showing each shot, M (M1,
M2,...): Alignment mark on mask, W (W
1, W2,...): Alignment mark on the wafer.

Claims (1)

[Scope of Claims] 1. A semiconductor printing apparatus that prints a circuit pattern drawn on a mask or reticle onto a wafer by step-and-repeat, and in each step, prior to exposure, the mask or reticle and the wafer are printed. means for relatively aligning the images, means for detecting an abnormality that occurs during the above alignment, means for graphically displaying which shot is currently being exposed for each exposure, and a means for detecting an abnormality by the above detection means. 1. A semiconductor printing apparatus comprising: display control means for causing the graphic display means to separately display shots that have been properly aligned and shots that have been properly aligned. 2. The graphic display means is a color type graphic display means, and the display control means displays a shot in which an abnormality has been detected and a shot in which normal alignment has been performed in different colors. A semiconductor printing apparatus according to scope 1. 3. The graphic display means is a monochrome graphic display means, and the display control means displays a shot in which an abnormality has been detected and a shot in which normal alignment has been performed by changing the mesh of bright dots or black dots. A semiconductor printing apparatus according to claim 1. 4. The alignment means aligns the mask or reticle and the wafer by detecting and relatively aligning two or more sets of alignment marks provided on the mask or reticle and the wafer, respectively. At the same time, when there is an undetectable mark, alignment is performed based on the marks excluding the set of marks, and the detection means detects as an abnormality when at least one mark is undetectable. A semiconductor printing apparatus according to claim 1, 2 or 3. 5. The alignment means sets a measured value of the relative deviation amount between the mark provided on the mask or reticle and the mark provided on the wafer to a predetermined upper limit value for each set of the two or more sets of marks. The alignment is performed based only on the measured values that do not exceed the upper limit, and the detection means also detects as an abnormality when at least one of the measured values exceeds the upper limit. A semiconductor printing apparatus according to claim 4. 6. The semiconductor printing apparatus according to claim 5, wherein the step-and-repeat position alignment--prior to the exposure operation, only the position measurement is step-and-repeat and graphically displayed.