JPH01264220A - Reduction projection aligner - Google Patents

Abstract

PURPOSE:To obtain a high-accuracy apparatus which does not expose a substrate in a deformed state by automatically detecting a foreign body which has adhered to a substrate stage by referring to a changed amount of a focal distance during an exposure operation. CONSTITUTION:When a foreign body 5 adheres to a substrate stage 7, a mountain is formed on a wafer 6. At a shot position of this time, a flat part of the wafer is in focus by means of an autofocus optical system 4. At a next shot operation, a wafer chuck 7 is raised or lowered by DELTAl by using a driving gear 8 because the mountain of the wafer is situated in the center of this shot operation. When this value DELTAl exceeds a standard value delta, the existence of the foreign substance is recognized and an alarm is given.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reduction projection exposure apparatus for LSI manufacturing.

[Conventional technology]

As shown in FIG. 2, the reduction projection exposure apparatus projects a reduced reticle pattern onto a wafer (6) coated with resist. The projected area is, for example, a maximum of 15 x 15 ff" with a Nikon stepper, and 30 to 40 shots are performed on a 5-inch wafer using the step-and-repeat method. Autofocus focuses on the center of the shot for each shot, and Even if the thickness of the image increases or decreases, the center of the shot remains in focus.

[Problem to be solved by the invention]

In the conventional reduction projection exposure apparatus, when a foreign object (5) is attached to the substrate mounting table (7) as shown in FIG. Draw the ups and downs. Since only the center of the rat is in focus, if there is a height difference between the center and the periphery, the periphery will be out of focus. Moreover, it was difficult to discover this product, and there was a problem in that during mass production, a large amount of products were processed without being defocused.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a reduction projection exposure apparatus that can automatically detect foreign objects on a mounting table using an autofocus mechanism.

[Means to solve the problem]

The reduction projection exposure apparatus according to the present invention uses an autofocus mechanism to measure the flatness of a substrate placed on a substrate mounting table by vacuum suction, and automatically detects foreign objects on the mounting table. be.

[Effect]

The automatic detection of a foreign object on a substrate mounting table according to the present invention confirms the presence of a foreign object when the displacement of the focal point exceeds a certain value during exposure using the step-and-repeat method.

[Embodiments of the invention]

An embodiment of the present invention will now be described with reference to the drawings. 1st
In the figure, (1) is the light source, (2) is the mask percentage, (3) is the reduction lens, (4) is the autofocus optical system that detects the height of the sea urchin, and (5) is the foreign matter attached to the wafer chuck. (61 is a wafer, (7) is a wafer chuck that fixes the wafer by vacuum suction, (8) is a drive device that moves the chuck up and down according to the height of the sea urchin, and (9) is a place where there is no foreign object and a place where there is This is the displacement Δl of the focal length when focusing.

As shown in figure m1, there is a foreign object (5) on the wafer chuck (n).
Attached! Then, a mountain forms on the wafer (6). At this shot position, the autofocus optical system (4) focuses on the flat part of the wafer. In the next shot, there is a mountain of wafers in the center of the shot, so the FB drive device 8
) to raise and lower the wafer chuck (7) by Δl to focus. When this value Δ1 (9) exceeds the standard value δ, the presence of a foreign object is recognized and an alarm is issued.

〔Effect of the invention〕

As described above, according to the present invention, foreign matter adhering to the substrate mounting table can be automatically detected using the autofocus mechanism, so that highly accurate reduction projection exposure can be performed without exposing the substrate in a defocused state. A device is obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a reduction projection exposure apparatus according to an embodiment of the present invention, and FIG. 2 is a perspective view of a conventional reduction projection exposure apparatus. FIG. 3 is a sectional view of a conventional reduction projection exposure apparatus. (1) is a light source, (2) is a mask, (3) is a reduction lens,
(4) is autofocus optical system, (5) is foreign object, f6
'l is for sea urchin, (7) is for wafer chuck, (8) is for chuck aufi! , (9) is the displacement Δl, αG is the projected shot, and α is the height difference. The same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] A reduction projection exposure apparatus that is equipped with a function to automatically adjust the focal length with the substrate and is characterized in that during exposure, foreign matter attached to the substrate mounting table is automatically detected based on the amount of change in the focal length.