JP2000106338A - Method and device for projection aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection aligner capable of conducting high-accuracy alignment, while its alignment errors are prevented. SOLUTION: A wafer substrate 12 for a sample shot is irradiated with a diffracted light from an alignment light source of an alignment optical device 14. Intensity of the alignment signal waveform is discriminated by an alignment detector of the alignment optical device 14. A contrast which is the ratio, (a-b)/(a+b) between a maximum value a and a minimum value b of the alignment signal waveform is discriminated, and that with the contrast of a specified value or higher is detected as an alignment mark. Only the alignment marks having contrast of a specified value or above is employed, and alignment is carried out. Since alignment is performed using only the alignment mark of high contrast, accuracy in positioning by alignment is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a projection exposure method and apparatus for performing alignment using a signal waveform of an alignment mark.

[0002]

2. Description of the Related Art Conventionally, this type of projection exposure method includes:
For example, a configuration described in Japanese Patent Publication No. 5-17692 is known.

In the device disclosed in Japanese Patent Publication No. Hei 5-17692, the alignment is performed by changing the resist film thickness to obtain a signal waveform of an alignment mark having good contrast.

[0004]

However, in the projection exposure method described in the above-mentioned conventional Japanese Patent Publication No. 5-17692, the optimum exposure amount changes by changing the resist film thickness, and the dimensional accuracy decreases. There is.

In addition, when there are steps on the wafer substrate, there is another problem that the dimensional relative relationship changes between patterns on each step.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a projection exposure method and apparatus capable of preventing alignment errors and performing highly accurate alignment.

[0007]

According to a first aspect of the present invention, there is provided a projection exposure method for performing alignment by alignment of a wafer substrate, wherein an intensity ratio of an alignment signal waveform among sample shots for alignment is not less than a predetermined value. The alignment is performed using only the data of the alignment mark. The projection exposure method according to claim 2,
In the projection exposure method according to the first aspect, when the number of alignment marks whose intensity ratio of the alignment signal waveform is equal to or more than a predetermined value is insufficient, a part of the alignment marks that does not reach the predetermined value is used. According to a third aspect of the present invention, in the projection exposure method according to the second aspect, among the alignment marks not reaching the predetermined value, an alignment mark having a value closest to the predetermined value is employed. 5. The projection exposure apparatus according to claim 4, wherein the alignment optical apparatus detects an alignment mark whose intensity ratio of an alignment signal waveform is equal to or greater than a predetermined value among alignment sample shots. And performing alignment using only alignment mark data that is equal to or greater than the predetermined value detected by the alignment optical device. According to a fifth aspect of the present invention, in the projection exposure apparatus according to the fourth aspect, the alignment optical device does not reach a predetermined value when the number of alignment marks whose intensity ratio of the alignment signal waveform is equal to or more than a predetermined value is insufficient. A part of the alignment mark is used.
According to a sixth aspect of the present invention, in the projection exposure apparatus according to the fifth aspect, the alignment optical device employs an alignment mark having a value closest to the predetermined value among a part of the alignment marks not reaching the predetermined value. Things.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the configuration of a projection exposure apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG.
, The projection exposure apparatus includes a first reflector 3 that reflects exposure light 2 from a light source 1. Further, the projection exposure apparatus includes a fly-eye lens 4 for making the exposure light 2 reflected by the first reflection plate 3 uniform. Further, the projection exposure apparatus sets an aperture stop 5 for forming a secondary light source from the exposure light 2 uniformized by the fly-eye lens 4 and an illumination range on the reticle from the exposure light 2 passing through the aperture stop 5. Reticle blind 6 to be decided
It has. Further, the projection exposure apparatus includes a second reflecting plate 7 that reflects the exposure light 2 formed by the reticle blind 6.
And a condenser lens 8 for illuminating the exposure light 2 reflected by the second reflection plate 7 on a reticle.

The projection exposure apparatus includes a reticle stage 10 provided with a reticle 9 on an upper surface to which the exposure light 2 is irradiated.
It has. Further, the projection exposure apparatus includes a reduction projection lens 13 for projecting and exposing a pattern on the reticle 9 and forming a pattern on a wafer substrate 12 mounted on an upper surface of a wafer stage 11 movable in a substantially horizontal direction. Is provided. Further, the projection exposure apparatus includes an alignment optical device 14 of a diffraction light detection type.

As shown in FIG. 2, the alignment optical device 14 includes an alignment light source (not shown) and a half mirror 16 for irradiating the alignment light 15 from the alignment light source onto the wafer substrate 12. Further, the alignment optical device 14 is located in the vertical direction of the half mirror 16, respectively, and collects the alignment light 15 reflected by the half mirror 16 to irradiate the wafer substrate 12 with the first condensing lens 17; , Wafer substrate 1
A second condenser lens 18 is provided for condensing the alignment light 15 reflected and diffracted at 2 and transmitted through the first condenser lens 17 and the half mirror 16. Further, the alignment optical device 14 includes a filter 19 that cuts only the zero-order light of the alignment light 15 diffracted by the alignment mark, and receives an alignment signal that receives only the zero-order light by the filter 19. A detector 20 is provided.

Next, the operation of the projection exposure apparatus will be described.

First, an alignment sample shot is performed. That is, the alignment light 15 is condensed from the alignment light source of the alignment optical device 14, reflected by the half mirror 16, and condensed by the first condensing lens 17,
The alignment light 15 is applied to the wafer substrate 12 placed on the wafer stage 11. By irradiating the wafer substrate 12 with the alignment light 15, the alignment light 15
Is reflected and diffracted and transmitted through the first condenser lens 17, the half mirror 16, and the second condenser lens 18, and the filter 1
At 9, only the zero-order light is cut off and detected by the alignment signal detector 20. A signal of the diffracted light is generated by the diffraction grating-like alignment mark on the wafer, but as the alignment light scans near the alignment mark,
By driving the wafer stage and scanning the wafer, diffracted light by the alignment mark is detected, and the position of the alignment mark is recognized. This alignment signal detector 20
The diffracted alignment light 15 detected at is recognized as an alignment signal waveform.

Then, the intensity of the alignment signal waveform which is the diffracted alignment light 15 detected by the alignment detector 20 is determined. That is, the wafer substrate 12
The contrast of the alignment light 15 diffracted by the alignment mark on the wafer substrate 12 due to the background noise caused by the variation in the thickness of the underlayer and the surface step, ie, as shown in FIGS. Of the maximum value a and the minimum value b of (a−
b) / (a + b) varies. Therefore, the ratio (a) between the maximum value a and the minimum value b of the alignment signal waveform
−b) / (a + b) is detected as a contrast, and those having a contrast equal to or more than a predetermined value are detected as alignment marks S as shown in FIG.

In this manner, each position of the wafer substrate is irradiated with the alignment light 15, and only the alignment marks S having a contrast equal to or more than a predetermined value are adopted as shown in FIG.

That is, if the alignment is performed using an alignment mark having a low contrast, the noise component may be increased in the alignment signal waveform, and high-accuracy alignment may not be performed. Since the alignment is performed using only the high-contrast alignment marks, the accuracy of the alignment by the alignment can be improved.

If the number of high-contrast alignment marks S in the sample shot is insufficient, the alignment mark which is not adopted as low-contrast and has a value closest to a predetermined value which is a high-contrast adopted value. What is necessary is just to employ | adopt an alignment mark as an alignment mark (S) of a sample shot instead.

As described above, in the above-described embodiment, since the alignment is performed by using only the data of the alignment mark S having a predetermined contrast or more among the sample shots, the accuracy of the alignment can be improved.

If the number of high contrast sample shots equal to or more than the predetermined value is insufficient, among the alignment marks which are not adopted as low contrast, the alignment mark with the value closest to the predetermined value which is the adopted value of high contrast is replaced with the sample shot. Alignment mark (S)
By adopting as, there is obtained an effect that it is possible to prevent a decrease in alignment accuracy due to a shortage of sample shots in alignment.

[0019]

According to the present invention, since the alignment is performed by using only the data of the alignment marks having a predetermined contrast or more among the sample shots, the accuracy of the alignment can be improved.

In the case where a high-contrast sample shot equal to or more than a predetermined value is insufficient, an alignment mark having a value closest to the predetermined value among the alignment marks which are not adopted as a low-contrast is adopted as an alternative sample shot alignment mark. In addition, it is possible to prevent a decrease in alignment accuracy due to a shortage of sample shots in alignment.

[Brief description of the drawings]

FIG. 1 is a block diagram of a projection exposure apparatus showing an embodiment of the present invention.

FIG. 2 is a block diagram showing an alignment optical device according to the first embodiment;

FIG. 3 is a graph showing a relationship between coordinates obtained by alignment sample shots and the intensity of an alignment signal waveform in the case of high contrast.

FIG. 4 is a graph showing a relationship between coordinates obtained by sample shots of alignment and alignment signal waveform intensity in the case of low contrast.

FIG. 5 is an explanatory view showing a wafer substrate on which a sample shot has been performed;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light source 2 exposure light 3 first reflector 4 fly eye lens 5 aperture stop 6 reticle blind 7 second reflector 8 condenser lens 9 reticle 10 reticle stage 11 wafer stage 12 wafer substrate 13 reduction projection lens 14 alignment optical device 15 Alignment light 16 Half mirror 17 First condenser lens 18 Second condenser lens 19 Filter 20 Alignment signal detector

Claims (6)

[Claims] 1. A projection exposure method for performing alignment by alignment of a wafer substrate, wherein alignment is performed using only alignment mark data having an intensity ratio of an alignment signal waveform of a predetermined value or more among alignment sample shots. Characteristic projection exposure method. 2. The projection exposure according to claim 1, wherein when the number of alignment marks whose intensity ratio of the alignment signal waveform is equal to or greater than a predetermined value is insufficient, a part of the alignment marks that does not reach the predetermined value is used. Method. 3. The projection exposure method according to claim 2, wherein an alignment mark having a value closest to the predetermined value is employed among a part of the alignment marks not reaching the predetermined value. 4. A projection exposure apparatus for performing alignment by alignment of a wafer substrate, comprising: an alignment optical apparatus for detecting, among sample shots of alignment, an alignment mark having an intensity ratio of an alignment signal waveform of a predetermined value or more; A projection exposure apparatus, wherein alignment is performed using only data of an alignment mark equal to or greater than the predetermined value detected by the apparatus. 5. The alignment optical device according to claim 1, wherein when the number of alignment marks whose intensity ratio of the alignment signal waveform is equal to or more than a predetermined value is insufficient, a part of the alignment marks that does not reach the predetermined value is used. 5. The projection exposure apparatus according to 4. 6. The projection exposure apparatus according to claim 5, wherein the alignment optical device employs an alignment mark having a value closest to the predetermined value among a part of the alignment marks not reaching the predetermined value.