JPH0259615B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for aligning two objects.

[Prior art]

Generally, transparent electrodes are used in various display boards including liquid crystal display boards, and these display boards are used in optical equipment, electronic equipment, dials of watches, etc., large LCD TV displays, thermometers, etc. It covers a wide range of fields. In such display boards, two substrates are used to encapsulate materials such as liquid crystal, and transparent electrodes are formed on each substrate, but the performance of the product depends on whether the patterns of these transparent electrodes match accurately. It becomes important.

Conventionally, this type of alignment has been carried out by printing an alignment mark 20 on one substrate and a similar mark 21 on the other substrate, as shown in FIG. If it falls within the mark 20, it is determined that the alignment of the two boards has been completed, but this judgment is done by visual inspection, which results in poor work efficiency and a problem with alignment accuracy. Ta.

On the other hand, in a semiconductor printing apparatus, as a step before printing the semiconductor integrated circuit pattern of the mask onto the wafer, there is a step of accurately aligning the mask and the wafer.

In the conventional alignment process, alignment marks are formed on the mask and wafer in advance, and the marks are scanned with a laser beam and the scattered light from the marks is detected to detect the relative positional misalignment between the wafer and the mask. Measuring. Then, move the wafer by the amount of this measured positional deviation,
The mask and wafer are precisely aligned. However, since the wafer is coated with a photoresist film, this method of detecting scattered light is affected by reflection and refraction, interference between scattered light from marks, and the influence of dust. It has the disadvantage that it is easily damaged and cannot perform accurate positioning.

〔the purpose〕

The purpose of the present invention is to eliminate the drawbacks of the above-mentioned conventional examples,
The purpose of the present invention is to provide a highly accurate alignment method.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing the principle of alignment used in one embodiment of the present invention, and FIG.
2A and 2B partially illustrate cross sections of glass substrates 1 and 2 on which circular alignment marks 1a and 2a of different sizes are formed, respectively, and are made of a transparent electrode material. As shown in FIG. 3, the reflectance of the marks 1a and 2a (curve 18) gradually decreases as the wavelength of the illumination light increases, while the reflectance of the glass substrates 1 and 2 (curve 19) decreases as the wavelength of the illumination light increases. Increase gradually. Note that in this embodiment, the glass substrates 1 and 2 have marks 1a and 2.
A material with lower reflectance than a is used. Here, at least the mark 1a is translucent, and when it is illuminated from the direction shown in FIG.
The portion C where a and 2a overlap exhibits the highest light intensity due to the addition of the reflection from the mark 1a on the upper substrate 1 and the reflection from the mark 2a on the lower substrate 2. And 2
Marks are formed on only one of the two boards.
The intensity of the reflected light gradually decreases from part b' to part a' of only the substrate 2 (see FIG. 2C). In other words, the part C where marks 1a and 2a of the two boards overlap, and the part C where mark 2a is attached to one of the boards.
It is possible to clearly distinguish the part b' from the part a', which is only the substrate, and to confirm the respective sizes and shapes of the two marks 1a and 2a, as well as their relative positions. Therefore, by scanning the observed reflected light in the direction 3 in FIG. 2B via a video signal or the like and detecting the difference in light intensity, the substrates 1 and 2
positioning becomes possible. The following description will be made assuming that accurate positioning of the two substrates is performed when the centers of the two marks coincide. FIG. 4 is a schematic diagram of an apparatus for aligning the glass substrates 1 and 2 at the bottom of the figure, according to an embodiment of the present invention. The glass substrates 1 and 2 are held parallel to each other with a gap of several microns apart by a stage mechanism (not shown). Two circular alignment marks 1R and 1L, 2R and 2L made of transparent electrode material are formed on the glass substrates 1 and 2, respectively.
R and 1L correspond to marks 2R and 2L, respectively.

To explain the configuration of the device shown in FIG. 4, the light source 9R,
Along the optical path of 9L, filters 10R and 10L each block infrared light, and a condenser lens 11.
R, 11L, half mirrors 14R, 14L are arranged, and along the optical path reflected by the half mirrors 14R, 14L, apertures 13R, 13L, respectively.
Imaging lenses 12R and 12L are arranged, and the light beams transmitted through the imaging lenses 12R and 12L are imaged on glass substrates 1 and 2, respectively. Note that, as shown in FIG. 3, the glass substrate and mark used in this example exhibit a high luminous intensity difference in reflected light with short wavelength illumination light, so a filter 10 for blocking infrared light is used.
R, 10L is used. Furthermore, this illumination system employs a bright field illumination method. Bright-field illumination involves placing apertures 13R and 13L at the focal positions behind the imaging lenses 12R and 12L to form a telecentric optical system for the illumination light, which illuminates objects using specularly reflected light from the illumination light. This is a lighting method for observation.

Along the optical paths reflected by the substrates 1 and 2, half mirrors 14R and 14L and image pickup tubes 15R and 1 are installed, respectively.
5L is arranged, and the images taken by the image pickup tubes 15R and 15L are sent to the camera control unit 1.
6, one screen is divided into two and taken out on the monitor television 17.

The video signals from the image pickup tubes 15R and 15L are input to a central processing unit (CPU) 18 that detects the relative positions of the substrates 1 and 2, as will be described later, and the motor 19 is activated according to the calculation results of the central processing unit 18. The substrates 1 and 2 are aligned by driving a stage mechanism (not shown) that holds the substrates 1 and 2, respectively.

To explain the operation of the above configuration, the substrates 1 and 2 are
First, the marks 1R and 2 are roughly aligned in advance.
If the marks R, marks 1L and 2L are placed within the projection fields of the imaging lenses 12R and 12L, respectively, and a positional error occurs, the monitor television 17 will display the fifth mark.
Marks 1R and 1L on board 1 as shown in the upper part of the figure.
The image is taken with a misalignment between the marks 2R and 2L on the substrate 2. Mark 1 to simplify the explanation below
The relationship between R and 2R will be described.

Two scan lines Sm of the video signal of the above image,
When Sn is detected by the central processing unit 18, a high voltage signal is obtained over a predetermined time period according to the difference in intensity of the reflected light from the marks 1R and 2R, as shown in the lower part of FIG. The distance of the first reflected part from only mark 2R on scanning line Sm is
l ₁ , the distance of the overlapping part of marks 1R and 2R is l ₂ , and the distance of the part finally reflected only from mark 2R is detected as l ₃ , and on the other hand, similarly for the scanning line Sn, l' ₁ , If l' ₂ and l' ₃ are detected, marks 1R and 2
The position error △Xr in the X direction and the position error △Yr in the y direction of R are as follows: △Xr=l ₃ −l ₁ /2=l′ ₃ −l′ ₁ /2 △Yr=(M ² −M′ ² ) −(l ² / ₂ −l′ ² / ₂ )/8L. In addition, in the above formula, M=l ₁ +l ₂ +l ₃ , M′=l′ ₁ +l′ ₂ +l′ ₃ ,
L
is the distance between scanning lines Sm and Sn. Similarly, substrate 1,
Regarding the marks 1L and 2L on the left side of 2, the position error ΔXl in the X direction and the position error ΔYl in the Y direction can also be detected.

Next, if the distance between marks 1R, 2R and 1L, 2L is R, the relative positional error between substrates 1 and 2 is: △X=△Xr+△Xl/2 △Y=△Yr+△Yl/2 △ It can be detected by θ=−tan ⁻¹ (ΔYl−ΔYr)/R.

The central processing unit 18 performs the above calculation and calculates △
When X, ΔY, and Δθ are detected, the motor 19 drives the stage mechanism that holds the substrates 1 and 2 according to the calculation results, thereby accurately aligning the substrates 1 and 2.

Note that if the two marks are placed parallel to the X direction, alignment will be completed in one alignment operation, but if the two marks are at an angle that is in the X direction, the actual drive amount and calculated value may differ. Because of the difference, alignment cannot be completed in one operation. However, repeating the same operation several times completes the alignment.

In the embodiment described above, two circular marks of different sizes have been described, but the same applies to marks of the same size, and alignment is also possible for marks of other shapes. Figure 6 shows isosceles triangle marks (6 and 7), respectively.
The larger mark 6 has an isosceles triangular hole 8 having sides parallel to the outer sides of the mark 6. The positional error of the marks (6 and 7) shown in Figure 6 is as follows: △X = (L ₁ - L ₂ ) + (L ₄ - L ₅ )/4 △Y = - (L ₁ - L ₂ ) + (L ₄ −L ₅ )/4.

Further, the present invention can also be used for aligning a mask and a wafer in a semiconductor printing apparatus, but in this case, since the wafer has a nearly mirror surface, a layer with a low reflectance is placed on the wafer 5 as shown in FIG. By forming the portion 2b, the reflected light distribution shown in the lower part of FIG. 7 can be formed. In the figure, 4 is a mask, and 1b is a mark formed of a transparent electrode material.

〔effect〕

As described above, according to the present invention, accurate alignment of two objects is possible by detecting specularly reflected light from a mark. Further, during positioning, unlike the conventional example, a signal is obtained over a predetermined period of time, so even if dust or the like adheres to a part of the mark, stable positioning can be performed. Although the present invention has been described with reference to an embodiment using a scanning system, it is also possible to measure the lengths of the weight part and non-weight part, for example, without using the scanning system.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a conventional mark for alignment, Fig. 2 is an explanatory diagram showing the principle of the present invention, and Fig. 3 is an alignment mark used in an embodiment of the present invention. FIG. 4 is a schematic configuration diagram of an alignment device according to an embodiment of the present invention; FIG. 5 is an explanatory diagram of alignment marks used in FIG. 4; FIG. 6 is an explanatory diagram of an alignment mark according to another embodiment of the present invention, and FIG. 7 is an explanatory diagram of an embodiment applied to a semiconductor printing apparatus. 1, 2...Substrate, 1a, 2a, 1R, 1L, 2
R, 2L, 1C, 2b, 6, 7... Marks for positioning.

Claims (1)

[Claims] 1. A first object having translucency and a second object are illuminated with a light beam from an illumination system, and the relative positions of both objects are optically detected. In the alignment method, a first mark having translucency and reflectivity is formed on the first object, a second mark having reflectivity is formed on the second object, and The first object and the second object are arranged in order from the illumination system side, and based on the difference in light intensity between the light reflected from one of the marks and the light reflected from the overlapping part of both the marks. , the relative position of the first object and the second object is detected, and the first object and the second object are relatively moved to align the positions based on the detected position information. A positioning method characterized by: