JPS5893233A - Pattern matching apparatus with automatic focal plane alignment - Google Patents

Abstract

PURPOSE:To accurately transfer a pattern by detecting a focus on a wafer and setting the focus through a half mirror between a wafer and upper projecting optical system, shifting them keeping the relative location and by aligning a mask pattern and projected pattern on the wafer. CONSTITUTION:A picture of a mask 2 having passed a projecting optical systems 6, 6' is not focused when there is no wafer surface at the focusing position 12. Therefore, a half mirror 7 is moved vertically while operating a focus detecting circuit 8 and thereby it is shifted to the position where the picture of wafer 1 becomes most clear in order to detect the focus. While keeping the relative position of the wafer 1 and half mirror 7, a support 3 and a mirror 7 are shifted simultaneously and they are stopped when a projected picture on the wafer 1 becomes most clear. Thereby, the surface of wafer 1 and projected picture of mask 2 perfectly match, the mask 2 is projected most clearly on the wafer 1, and even when there is a temperature change on the projecting optical systems 6, 6' and mask 2, a focused accurately pattern can be transfered by accurately setting the upper surface of wafer to the picture focusing position.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is one of semiconductor manufacturing equipment, and relates to an apparatus for aligning a mask pattern image with a wafer when forming a circuit on a semiconductor wafer.

In a projection-type mask pattern and wafer alignment device that is one of semiconductor manufacturing equipment, it is necessary to accurately position the image formation position of the mask pattern on the wafer surface.

FIG. 1 schematically shows and explains a conventional pattern matching device.

In FIG. 1, the light emitted from the light source 4 causes the mask 2 to
The image drawn above is transmitted to the foot position 5 through the projection optical system 66'.
to form an image. By moving the wafer table 3, the upper surface of the wafer 1 was aligned with the set position 5, and the mask pattern was transferred to the wafer by IK.

In such a conventional device, even if a deviation occurs between the position where the mask projection image is formed and the set position due to thermal expansion of the mask 2 and the projection optical systems 6, 6, the deviation cannot be corrected. The pattern was transferred while the pattern was not in focus, resulting in an out-of-focus image being transferred. This has caused defects in the circuits on the wafer, leading to a decrease in product yield.

The present invention aims to provide a pattern matching device that improves the conventional technology as described above and can improve the yield of products by performing more accurate positioning.

In order to achieve the above-mentioned object, the present invention provides means for providing an objective optical system that can be raised and lowered between the L-shape and the projection optical system, and detecting the focal point of the projected image on the L-shape through the objective optical system. and is constructed so that the target optical system and the target optical system can be moved while maintaining a fixed relative position, and the image is projected onto the wafer based on information from the focus detection means of the target optical system. This is like focusing an image.

Next, an embodiment of the present invention will be described with reference to FIG.

In FIG. 2, 1 is the wafer to be transferred, 2 is the wafer 1
3 is a wafer table that can be raised and lowered, 4
6 is a light source, and 6.6 is a projection optical system that receives light from the light source 4 through the mask 2, so that the wafer 1 is positioned at the imaging position 12.
If the wafer l is at any other position, it will appear as an image, but if the wafer l is at any other position, only an out-of-focus image will appear.

In the present invention, an objective optical system 7 consisting of a half mirror or the like is provided between the projection optical system ``6'' and the sea urchin 1, and a mask 2 is projected onto the L fly through the entire objective optical system 7. a focus detection circuit 8 capable of detecting the focal point of an image of
, 11. If the projected image of the mask 2 that has passed through the projection optical system 6.6 has an imaging plane position 12VcxLc plane, it will appear as an image.
If there is another wafer surface, only an out-of-focus image will appear. Therefore, while operating the focus detection circuit 8, the objective optical system 7 is moved up and down to a position where the image of the wafer 1 is the clearest and focused. While maintaining the relative positional relationship between the wafer 1 and the objective optical system 7 in this state, the wafer table 3 and the objective optical system 7 are simultaneously moved by VC to the position where the projected image on the wafer 1 is the clearest VC in the same way as above. make it stop.

By doing this, the surface of the p-wafer 1 and the projection image plane of the mask 2 are completely aligned, and the image of the mask 2 is projected onto the sea urchin-1 in the clearest state.

Therefore, even if the temperature of the projection optical system 6.6 and the mask 2 changes, the top surface of the wafer can be accurately aligned with the image plane position.
It is possible to transfer patterns without defocusing.

As described above, the pattern matching device with automatic focusing of the present invention includes an objective optical system consisting of a half mirror or the like between the wafer and the projection optical system located above the wafer, and a focal point on the wafer through the objective optical system. A means for detecting the urchin is used to focus on the sea urchin, and the objective optical system is moved while maintaining the relative position of the urchin.The pattern drawn on the mask and the mask projected onto the wafer are then By aligning the patterns with each other using a focus detection means, accurate transfer can be performed and the yield of products can be improved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an overview of a conventional pattern matching device;
FIG. 2 is an explanatory diagram showing an example of a pattern matching device to which the present invention is applied. 1... 1 ha, 2... mask, 3... 1 no%
f-pull, 4... Light source, 6, 6'... Projection optical system, 7... Objective optical system, 8... Focus detection circuit, 9...
- Control circuit, 1o... Wafer table operation signal, 11
...Objective optical system operation signal, 12...Imaging plane. Agent Patent Attorney Tadashi Akimoto Jichiji Figure j Figure 2

Claims (1)

[Claims] In an apparatus for projecting and transferring an image of a first sample onto a second sample, an objective optical system that can be raised and lowered is provided between the second sample and the projection optical system, and an image of the first sample is transferred onto the second sample through the objective optical system. means for detecting the focal point of the projected image of the objective optical system and the second sample is configured to be movable while keeping the objective optical system and the second sample at a constant relative position; 1. A pattern matching device with automatic focusing, characterized in that the pattern matching device is configured to focus a pattern projected onto a second sample from the source.