JPH0267713A - Multiple exposure process - Google Patents

Abstract

PURPOSE:To enable the alignment with high precision to be maintained for effecting the printing process with high precision by a method wherein the alignment of a negative and a substrate is done for printing once again if necessary between respective exposures time-divided. CONSTITUTION:Alignment marks made on a mask 1 and a wafer 2 are irradiated with alignment beams 5 to detect the position shifted amounts by an alignment optical system 4 for transmitting the amounts as position shifting signals 32 to a control circuit 11. The control circuit 11 starts a wafer stage driving device 13 to transmit driving signals 33 so that a wafer stage 3 may be driven to align the patterns of the mask 1 and the wafer 2 with each other for making alignment. Next, the control circuit 11 starts a shutter driving device 12 to transmit the other driving signals 31 so that a shutter 8 may be opened to perform the first exposure and then closed after lapse of specified time. The control circuit 11 checks if the mask 1 and the wafer 2 are irradiated with the light quantity required for the shot, if necessary amount of light has been cast, the exposure of the shot is terminated, and makes realignment if any more exposure is required.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a multiple exposure method used in semiconductor device manufacturing etc. that requires multiple exposures over a long period of time. The present invention relates to a multiple exposure method that precisely maintains the positional relationship with a substrate such as a sea urchin.

[Prior art] With the recent increase in the integration of semiconductor devices such as ICs and LSIs,
The exposure equipment used to manufacture these devices is also required to be more precise. A common method for aligning the circuit pattern on the mask and the circuit pattern on the wafer is to align them through a projection lens using alignment marks provided on the mask and the wafer as a reference. Exposure is then performed. The exposure time is adjusted depending on the intensity of the exposure light source, the sensitivity of the resist, etc. When the light source is weak or the sensitivity of the resist is low, it is necessary to lengthen the exposure time, but there are cases where long-time exposure is not possible due to factors such as shutter control. In this case, a multiple exposure method has been proposed in which one shot is time-divided and exposed two or more times.

[Problems to be Solved by the Invention] However, when multiple exposure is performed, the exposure time for one shot becomes longer. That is, the time from when alignment is achieved using the alignment marks on the mask and the wafer until the exposure for that shot is completed becomes longer, and the effective time for alignment becomes a problem.

Factors that can cause the once aligned alignment to shift due to long exposure are: (1) When applying servo during exposure to maintain the current position, - Extension from the servo system measurement position to the shot position due to changes in aura, etc. - Changes in aura, etc. (2) When the servo is turned off during exposure to lock the position, ■ Misalignment due to vibrations generated from other systems ■ Distortion due to thermal expansion, etc. ■ Occurs from the limit of mechanical position maintenance ability There may be a discrepancy.

Even if highly accurate alignment can be performed and the processed line width is sufficiently thin, the printing accuracy will deteriorate due to these deviations.

In view of the problems of the prior art, an object of the present invention is to
An object of the present invention is to provide a multiple exposure method capable of maintaining high printing accuracy even when long-time exposure is required.

[Means and effects for solving the problem] In order to achieve the above object, the present invention aligns the original plate and the substrate so that they face each other, and exposes the original plate in two or more times in a time-sharing manner. In a multiple exposure method for transferring a pattern of 1 to a substrate, the original and the substrate are repositioned between each time-divided exposure to perform printing.

According to this, the deviations caused by the above-mentioned causes are corrected for each time-divided exposure, and even in printing that requires long exposure, printing can be performed while maintaining high printing accuracy.

[Example] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 shows a multiple exposure method according to an embodiment of the present invention.
This is a flowchart for shots, and FIG. 2 is a schematic diagram showing an example of an exposure apparatus that performs exposure using this method. In FIG. 2, 1 is a mask, 2 is a wafer, 3 is a wafer stage equipped with a moving mechanism that holds and moves the wafer 2, 4 is an alignment optical system for aligning the mask 1 and the wafer 2, and 5 is an alignment device. 6 is an exposure light source, 7 is a luminous flux emitted by the exposure light source 6, 8 is a shutter which is a means for blocking the light from the light source, 9 is a lens, 11 is a control circuit that controls the operation of the apparatus, 12 is a shutter 8 13 is a wafer stage drive device that drives the wafer stage 3.

Next, FIG. 1 shows the procedure for exposing the mask 1 and the wafer 2 to each other in the exposure apparatus having this configuration and performing one shot exposure.
This will be explained with reference to a).

First, in step 101, the alignment light 5 is irradiated onto the alignment marks provided on the mask 1 and the wafer 2, and the amount of positional deviation between them is detected using the alignment optical system 4. It is sent to the control circuit 11 as a positional deviation signal 32. Upon receiving this signal, the control circuit 11 starts the wafer stage drive device 13 based on this signal to transmit a wafer stage drive signal 33, and drives the wafer stage 3 so that the patterns of the mask 1 and the wafer 2 match. Perform alignment.

Next, in step 102, the control circuit 11 starts the shutter drive device 12, transmits the shutter drive signal 31, opens the shutter 8, and performs the first exposure. Close the shutter 8. Here, the control circuit 11 manages the exposure time based on data specific to the apparatus or data set in advance.

Then, in step 103, it is determined whether the shot has been irradiated with the necessary amount of light, and if further exposure is required, the process returns to step 101 and alignment is re-performed.

The necessary amount of light has already been irradiated and the exposure for that shot is finished.

The procedure shown in Figure 1(b) is such that two exposures are performed in one alignment, and the other steps are as shown in Figure 1(a).
It is similar to The selection of either the method shown in FIG. 4A or the method shown in FIG. 2B is made by considering one exposure time and alignment effective time. One exposure time is unique to the apparatus, and the effective alignment time is determined by the factors that cause the alignment to shift as described above, so it is necessary to estimate these in advance.

In addition to using the shutter 8, there is a method of blinking the light source itself as a means of interrupting the exposure. Further, in this embodiment, the mask 1 and the wafer 2 are aligned by moving the wafer 2, but there is also a method of aligning the mask 1 by moving the mask 1.

FIG. 3 is a flowchart for one shot showing a multiple exposure method according to another embodiment of the present invention, and FIG. 4 is a schematic diagram showing an example of an exposure apparatus related to the embodiment. In this exposure apparatus, the exposure light source 6 is an X-ray source, so there is no lens, but the same applies even when ultraviolet rays are used. 614 is a monitoring device that monitors the atmosphere and vibrations.

In the exposure method shown in FIG. 3, after aligning and exposing in steps 121 and 122 in the same manner as in the method shown in FIG. 1, it is determined in step 123 whether or not the exposure necessary for one shot has been performed. make a judgment. Here, if the exposure necessary for one shot has been performed, the exposure is finished; if the exposure is still insufficient, step 124
Proceed to step 3 to determine whether or not it is necessary to re-align. The above-mentioned alignment valid time is used as a criterion for this judgment, but in this embodiment, the control circuit 11 makes the judgment by taking information from the monitoring device 14 into consideration with factors specific to the device.

According to this method, unlike the method shown in Figure 1, where alignment is recalibrated with safety in mind without estimating atmospheric fluctuations, it is possible to determine whether alignment is necessary or not based on actual fluctuations. Alignment redundancy is eliminated and exposure time is reduced.

[Effects of the Invention] As explained above, by using the method of the present invention, it is possible to perform long-time exposure while maintaining the relative positional relationship between the original and the substrate after alignment. It is possible to maintain alignment and realize highly accurate printing that takes advantage of the workability of minute line widths.

FIG. 2 is a schematic diagram of an exposure apparatus according to an embodiment of the present invention, and FIG. 3 is a one-shot flowchart showing a multiple exposure method according to another embodiment of the present invention. FIG. 4 is a schematic diagram of an exposure apparatus according to another embodiment of the present invention.

1: Mask, 2: Wafer, 3: Wafer stage, 4: Alignment optical system, 5: Alignment light, 6: light source, 7: Luminous flux, 8: Shutter, 9: Lens, 11: control circuit, 12: shutter drive device, 13: Wafer stage drive device, 14: Atmosphere, vibration monitoring device, 31: shutter drive signal, 32: positional deviation signal, 33: Wafer stage drive signal.

(b) No. figure No. figure

Claims (1)

[Claims] (1) In a multiple exposure method in which the pattern of the original is transferred to the substrate by aligning the original and the substrate so that they face each other and exposing one shot in two or more times in a time-divided manner, each exposure is time-divided. A multiple exposure method characterized by re-aligning the original and the substrate as necessary between exposures.