JPS59220604A - Method for detecting position between two objects opposed each other with minute gap therebetween - Google Patents

Abstract

PURPOSE:To enable mutual positional alignment with high accuracy by determining an error, using a position aligning jig obtained by providing a transparent layer on the reflective layer provided on a substrate while providing the pattern of a detection body on said layer. CONSTITUTION:A position aligning jig is obtained by providing a reflective layer 27 on a substrate 26 being a mirror wafer while providing a transparent layer 28 on said layer 27. The pattern 29 of an optical detection body is provided on the transparent layer 28. Three patterns 29 of the detection body per one place are arranged to a position capable of being detected at once by the objective lens of a microscope provided to a constant position. Shift amounts delta, delta of an optical axis of which the image forming position is not changed even if magnification is changed and the optical axes 30 formed by connecting the patterns 29 of the detection body of a real image detected by the objective lenses 11a, 11b of the microscope and the pattern 29' of the detection body of a virtual image can be detected and the detected values come to the erroneous amounts generated by the inclination of the optical axes 30 of the objective lenses 11a, 11b of the microscope. By adding correction to the detection values of alignment marks 22, 24 according to a method for calculating the shift amounts deltaa, deltab or changing the inclination angle of the optical axis, mutual positional alignment can be realized with high accuracy.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a position detection force method between two objects facing each other with a minute gap between them, and furthermore, the present invention relates to a position detection force method between two objects facing each other with a minute gap between them. As shown in FIG.
The present invention relates to a method for detecting the position between two opposing proboscises with a minute gap through which the amount can be measured.

[Background of the invention]

In the conventional method of aligning the mask and wafer with a microscopic gap between them, the alignment marks are aligned on the same axis. To obtain the detection error, exposure and development are performed and estimation is made from the results. However, because of l and 1', this method includes errors due to other factors, and has the disadvantage that it is difficult to know the detection error due to the tilt of the microscope objective lens to within 1 m.

This point will be explained in more detail with reference to FIGS. 1 to 6.

The conventional method for detecting the relative position of the mask and wafer is
Figure 1 (shown here).

In the position detection method shown in FIG.
and 3 perform automatic focusing on the X, Y, and θ axes.

The details will be explained based on the detection optical system 1.

Illumination light 6 that passes through the optical fiber 5 from the light source 4 is condensed by a condenser lens 7, and is then condensed by a mirror 8, a half prism 9, and a mirror 1.
0, the light passes from the microscope objective lens 11 to the mask 12 in accordance with the arrow shown by the broken line in FIG.

The light reflected from the mask 12 and the wafer 13 enters the microscope objective lens 115 again, passes through the mirror IO and the half prism 14 according to the solid arrow in FIG. It passes through forming an optical path that is symmetrical to the optical path that it passed through earlier. Error correction due to movement of the prism 14 is performed by forming this optical path.

The light passing through the prism 14 is reflected by a mirror 16 and separated into two optical paths by a half prism 17.

One of the optical paths that has passed by WLg passes through the relay lens 18 and forms an image on the linear sensor 19 .

The other separated optical path passes through the relay lens 20 and forms an image on the TV imaging screen 21, which is used for visual viewing.

The type of house to be imaged depends on the optical path length from the microscope objective lens 11 to the linear sensor 19 or the TV imaging screen 21.

For this purpose, the prism 14 is moved in the direction of arrow a, the optical path length is changed to an arbitrary length, and an image of the alignment mark on the mask 12 or wafer 13 is formed on the linear sensor 19 to detect the respective positions.

The detection principle is shown in FIGS. 2 and 3.

Mask 12 located at a distance a from the microscope objective lens 11
The alignment mark 22 forms an alignment mark image 23 at a distance of m from the microscope objective lens 11. Also, from the a-fine objective lens 11, 0. ．． The alignment mark 24 of the wafer 13, which is at a distance of 7, forms an alignment mark image 258 at a distance of W) from the microscope objective lens 11. The alignment mark images 23 and 25 of this mask 12 and wafer 13, the aforementioned Fulism 14
The optical path length ff is changed by the movement of , and the respective images are formed on the linear sensor 19 for position detection.

However, due to the imaging law of the optical lens, the magnification of the image formed on the linear sensor 19 differs.

Therefore, the relative position of the mask 12 and wafer 13 is determined by the alignment mark 1g22325 of the mask 12 and wafer 13.
The distance from the optical axis 30, which is the axis where the imaging position does not change even when the magnification changes (lL, m), to the position where the alignment mark 25 of the wafer 13 is imaged is determined by the imaging magnification difference (gyn 79) Multiply (LWX ('-=-iζ)), 71)n
n,! The relative position of ZIF frame 12 and wafer 13 is determined.

Originally, in detecting the relative positions of the mask 12 and the wafer 13, the mask 12 and the wafer 13 are arranged parallel to each other as shown in FIG. 4, and the microscope objective lens 11. ．． It is clear that accurate relative positions cannot be determined unless the optical axes 30 are arranged and detected so that eleven optical axes 30 are formed.

However, in reality, as shown in FIGS. 5 and 6, it is difficult to accurately align the optical axes 30 of multiple microscope objective lenses 1 and 11 perpendicular to the mask 12 or wafer 13, and The current situation is that it is still being used.

At this time, the microscope objective lens 11er-
The detection error δ caused by +I li can be expressed as δ=IlJLmθ1-11 or δ=9·shiθ2-11 in the specifications shown in FIGS. 5 and 6.

Conventionally, the only way to determine this error was to perform exposure and development and estimate it from the results. However, this method has the disadvantage that it contains many errors due to other factors, making it difficult to produce accurate hani.

In addition, in FIG. 5, 19.19 indicates a linear sensor.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art and provide a method for detecting a position between two objects facing each other with a minute gap in between, which can accurately measure the error cover caused by the inclination of the optical axis of a microscope objective lens.

There is a particular thing.

[Summary of the invention]

The present invention uses an alignment jig in which a reflective layer such as an aluminum vapor-deposited film is provided on a substrate, a transparent layer such as a polyimide film is provided on this reflective layer, and an optical character detector pattern is provided on this transparent layer. By detecting the optical detector pattern and a virtual image of the optical detector pattern reflected on the reflective layer, the amount of error caused by the inclination of the optical axis of the microscope objective lens is accurately measured.

[Embodiments of the invention]

An embodiment of the present invention will be described based on FIGS. 7 to 13.

FIG. 7 shows an alignment jig that serves as a reference for relative alignment of the mask 12 and wafer 13.

In the alignment jig used in the present invention, a reflective J@27 is provided on a substrate 26 which is a mirror wafer, a transparent layer 28 is provided on this reflective layer 27, and a transparent layer 28 is provided on this reflective layer 27. An optical detection object pattern (hereinafter referred to as detection object pattern) 29 is provided on the top.

The reflective layer 27 is provided by depositing an aluminum vapor-deposited film or the like.

The transparent layer 28 is provided by attaching a transparent polyimide film or the like onto the reflective layer 27 by spin coating. The film thickness by spin coating is approximately determined by the viscosity of the coating material and the number of rotations, and it is possible to coat only about 0.8 to 1 μm in one coating.

Generally, the variation in film thickness due to spin coating is 0.01μ
ms degree, so even if it is applied several times, variations in film thickness will not be a problem. The relationship between the thickness t of the transparent layer 28 and the gap J between the mask 12 and the Ueno X 13 can be expressed by the following formula\, = H* Ji+ where, n-...Transparent layer (polyimide film) is the refractive index of

Generally, in an X-ray exposure apparatus using a point light source, master 2
and Ueno X13 @y is 5-40 due to penumbra blur issue
It is about μm. In addition, since the refractive index n of the polyimide film as the transparent layer 28 is about 1.5, in the case of a polyimide film, the thickness t of the transparent layer 28 is often 3.75 to 40 μm as calculated from the mJ notation. used.

In this embodiment, as shown in FIG. 7, 31 of the detection body patterns 29 are provided at the same location on the transparent layer 28, and three detection body patterns 29 are arranged at each location. Further, this detection object pattern 29 can be provided by substantially the same process as the LSI manufacturing process. Next, the specifications of the detection object pattern 29 will be explained.

Using the microscope objective lens 11, epi-illumination is used to illuminate the back side of the detection object pattern 29 (the detection object pattern 29 is located on the transparent layer 2).
8), the illumination light 31 from the microscopic sharp objective lens 11 passes through the reflective layer 2 as shown in FIG.
The reflected light 32 that is reflected by the object pattern 29 and reflected again by the reflective layer 27 is reflected by the microscope objective lens 11.
have to go back to. However, the detection object pattern 29
If the 0 width W is too wide, a problem arises in that the light that has been reflected on the back surface of the detection object pattern 29 returns to the back surface of the detection object pattern 29 and does not return to the Me jump objective lens 11, making it impossible to detect it. Can not. For this reason, the width W of the detection body pattern 290 and the gap S between the detection body pattern 290 and the adjacent detection body pattern 29 must be set within an excessive pressure range.

As shown in FIG. 13, the maximum value of the distance W of the detection object pattern 29 is determined by the thickness t of the polyimide film that is the transparent layer 28, the refractive index n, and the numerical aperture NA of the microscope objective lens 11. You can find it in the next 2.

w=2・t−1 (knee 1 (Δ戊)) Furthermore, the minimum gap S between adjacent detection object patterns 29 is
It can be determined using the same formula as the formula for determining the maximum width W of the detection object pattern 29.

・ -I NA S=2・t-&L(-()) However, if the width of the detection object patterns 290 is sufficiently small, the gap between adjacent detection object patterns 29 will be a value smaller than the calculated minimum gap S. However, detection is possible.

Next, the reflectance of the detection object pattern 290 will be explained.

When the alignment jig used in the present invention is detected by epi-illumination, almost all of the illumination light 31 is reflected by the reflective layer 27 and returns to the microscope objective lens, so the field of view becomes very bright.

Therefore, in order to add contrast, the detection object pattern 29 is required to have a low reflectance and be close to black.

For this reason, the detection object pattern 29 is made of, for example, chromium oxide.

In addition, the detection object pattern 29, which targets three objects per location, can be detected by the microscope objective lens 11 installed at a predetermined position.
It is placed in a position where it can be detected at any time.

The positioning jig shown in FIGS. 9, 10, and 11
As shown in the figure, when detected with a microscope objective lens "a+117," the mask 12 and the wafer 13 are ideally aligned with each other with a gap g.
A real image detection object pattern 29 corresponding to the alignment mark 22 on the wafer 13 and a virtual image detection object pattern 29' corresponding to the alignment mark 24 on the wafer 13 can be detected.

At this time, as shown in FIG. 10, the optical axis does not change the imaging position even if the magnification (optical path length) changes, and the object pattern 2 of the real image detected by the microscope objective lenses 11 and 11J.
9 and the optical axis 30 connecting the virtual image detection object pattern 29' can be detected.

This detection value is determined by each microscope objective lens.

O is the error amount caused by the optical axis 30 of 11 degrees, and the deviation δ9. After the detection of δl, when actually aligning the mask 12 and the wafer 13 relative to each other, the detection of the respective alignment marks 22 and 24 and the value ζ
On the other hand, this slippage δ4. Calculate δ or 1 of the optical axis
By correcting by changing the roll angle, etc., it is possible to achieve relative positioning with a higher degree of rotation.

Note that in FIGS. 9 and 10, 19.19 indicates a linear sensor.

Furthermore, the materials of the substrate 26, reflective layer 27, and transparent layer 28 of the positioning jig are limited to those of the above-mentioned embodiments.
The number of 90 pieces is not limited to the above embodiment.

Further, the present invention is not limited to detecting the positions of the mask 12 and the wafer 13, but can be applied to detecting the positions of two similar objects.

〔Effect of the invention〕

According to the present invention described above, a reflective layer is provided on the substrate,
A transparent layer is provided on the reflective layer, and an alignment jig with a detecting object pattern provided on this transparent layer is used to measure the amount of error due to the inclination of the optical axis of the microscope objective lens. It has the effect of being able to accurately measure the amount, grasping the amount of error, and making corrections when actually aligning two objects, so it has the derivative effect of realizing high-precision relative alignment. be.

[Brief explanation of the drawing]

Figures 1 to 6 show the prior art. Figure 1 is a diagram showing the position detection optical system between two objects, Figure 2 is a diagram showing the principle of position detection, and Figure 3 is Figure 2. 4 and 5 are diagrams showing position detection when the optical axis of the microscope objective lens is straight and when it is tilted.
FIGS. 7 to 13, which are enlarged views of the v1 portion of the figure, show one embodiment of the method of the present invention, and FIG. 7 is a perspective view of the positioning jig used in the method of the present invention, and FIG. is ■− in Figure 7.
■ Line enlarged vertical cross-sectional views, Figures 9 and 10 are diagrams showing detection using a positioning jig for cases where the optical axis of the microscope objective lens is straight and tilted,
FIG. 11 is a partially enlarged view of the same detection state, and FIGS. 12 and 13 are explanatory views when setting a gap of two widths between the detection object patterns of the positioning jig. 11LL, IIJ...Microscope objective lens 12.
13...Mask and wafer as two objects facing each other with a minute gap 26...Substrate 27 of alignment jig...Same reflection J@ 28...Same transparent layer 2
9...Detection object pattern 29'...Virtual image of the detection object reflected on the reflective surface of the reflective layer Turn 30...Towards the optical axis of the microscope objective lens, δ...Magnification (optical path length) The amount of deviation between the optical axis, which does not change the convergence position even if the position changes, and the optical axis that connects the real image of the object pattern on the alignment jig and the virtual image reflected on the reflective surface. 2nd 膓萬 4n Taku 7ro dōmura 720

Claims (1)

[Claims] 1. A reflective layer is provided on the substrate, a transparent layer is provided on the reflective layer,
Using a positioning jig with an optical detector pattern provided on this transparent layer, Th! A method for detecting a position between two objects facing each other with a minute gap between them, characterized by determining an error cover due to the inclination of the optical axis of a mirror objective lens. 2. The transparent holes of the positioning jig are made of a polyimide film and have a diameter of 3.75 to 40 μm.
A method for detecting the position between objects. 3. Width of the optical detection object pattern of the alignment jig -
2. A method for detecting a position between two objects facing each other with a minute gap as claimed in claim 1, wherein W is made narrower than a value expressed by the following calculation formula. , -I NA W=s 2 ·t -y (4(-7-)) However, t...Thickness of the transparent film n...Refractive index of the transparent film NA...Detection of the optical detector pattern Numerical aperture of the microscope objective lens used for