JPH02122613A - Reduction projection-type aligner - Google Patents

Abstract

PURPOSE:To enable easy detection of defocus during aligned exposure processing and suppress the occurrence of inferior pattern formation to the minimum, by memorizing the optimum focal position of each exposure region being at the upsides of wafers, calculating the focal position differences between regions adjoining each other, comparing the differences with the reference value, and displaying the results. CONSTITUTION:During aligned exposure processing of a plurality of wafers, the optimum focal position of the exposure region at the i-row, j-column of the k-th wafer 10 is expressed as kZi, j, and the optimum focal positions of all the exposure regions of the k-th wafer 10 are memorized in a focal position memory section 3. Next, also for the (k+1)-th wafer the optimum focal positions are similarly memorized. Then, the differenced Z1 to Z8 between the optimum focal position of an i-row, j-column region and the optimum focal positions of the adjacent eight exposure regions are calculated at a difference detecting section value 4 of focal positions, they are compared with the reference value Z0 of the differences between adjoining optimum focal positions memorized in a reference value memory section 1, for both the k-th and (k+1)-th wafers, and whether the differences are within the reference allowable Z0 or not is displayed. If the differences exceed Z0, it is judged that there is a foreign substance being the possible cause for defocus in the i-row, j-column region under a semiconductor substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reduction projection type exposure apparatus used in the manufacturing process of semiconductor devices.

[Conventional technology]

Conventionally, automatic focusing mechanisms in reduction projection exposure equipment include a pressure detection method using an air micrometer, a capacitive sensor type, and a reflection imaging method using an optical sensor, all of which are used for semiconductor wafers (hereinafter simply referred to as wafers).
The focal point is determined before performing exposure for each exposure area.

[Problem to be solved by the invention]

In the above-mentioned conventional reduction projection exposure equipment with an automatic focusing mechanism, if there is foreign matter such as dust under the wafer, the flatness of the exposed area on the wafer surface will collapse and the step will become large, resulting in a focus shift. However, there is a drawback that pattern formation defects occur continuously in the same exposure area on a wafer that has been subjected to alignment exposure processing.

[Means to solve the problem]

The reduction projection type exposure apparatus of the present invention includes a reference value storage unit that stores a reference value of a difference in focus positions, and a focus position unit that stores a focus position detected by an automatic focusing mechanism for each exposure area on a semiconductor device. a storage unit, a focus position difference detection unit that extracts focus position data of a target exposure area and focus position data of an adjacent exposure area from the focus position storage unit and detects a difference therebetween; and a comparison section that compares the reference value of the focus position with the difference value from the focus position difference detection section, and a display section that inputs the signal from the comparison section and displays the comparison result.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram for explaining one embodiment of the present invention.

In FIG. 1, a reference value storage unit 1 is composed of a memory, etc., and a reference value zo for the difference in focus position is stored. The focus position for each exposure area is stored in a focus position storage section 3 consisting of a memory or the like. The focus position difference detection unit 4 is composed of an arithmetic circuit, etc., and retrieves the focus position data of the target exposure area and the focus position data of the adjacent exposure area from the focus position storage unit 3, and calculates the difference between them. Zx is detected and sent to the comparison section 5.

A comparison section 5 including a comparison circuit etc. is a focal position difference detection section 4.
The difference ZX sent from the reference value storage unit 1 and the reference value Z from the reference value storage unit 1. The results are sent to the display section 6. A display section 6 consisting of a liquid crystal, an LED, etc. displays the result based on the signal from the comparison section 5.

That is, when the difference Zx between the focus position data of the target exposure area and the adjacent exposure area is compared with the reference value of 2 degrees, it is displayed whether the difference is within the tolerance value or not.

Next, further explanation will be given using a plan view of the wafer shown in FIG. 2 and a sectional view near the reduction projection lens shown in FIG.

As shown in FIG. 2, during alignment exposure processing of multiple wafers, the optimal focus position of the exposure area of the i-th row and j-th column of the wafer 10 is defined as kZi,j, and The optimum focus position is similarly stored for the +1st wafer in the 0th order in which the focus position of the entire exposure area is stored in the focus position storage unit 3. Then, the focus position difference detection unit 4 calculates the differences Z1 to Z8 between the optimum focus position of the i-th row and the j-th column and the optimum focus positions of the eight adjacent exposure areas, and
The reference value Z of the difference between adjacent optimal focus positions is stored in the reference value storage unit 1 for each sheet. If it exceeds , it can be determined that there is a foreign object under the semiconductor substrate in the i-th row and j-th column, causing a focus shift.

In fact, if there is a foreign object under the semiconductor substrate in the i-th row and the j-th column, as shown in FIG. ', the patterns drawn at the outermost exposure periphery B' and C' are on the exposure axes 14, 15 and 16, respectively.
, and passes through the projection lens 17 to form images at positions A, B, and C. The focusing mechanism uses light 19 emitted from the light emitting element 18.
is guided to the light-receiving element 20 so as to be focused at the exposure center point A. At this time, if there is a foreign object 21 between the semiconductor substrate and the stage 20 near point A, the focus will be measured at the height of point A, which will cause a focus shift at point B and point 0, resulting in a pattern formation area. .

〔Effect of the invention〕

As explained above, the present invention stores the optimal focus position for each exposure area on a semiconductor wafer, calculates the difference in focus position between adjacent areas, compares the difference with a reference value, and displays the result. By having this mechanism, it is possible to easily detect defocus during alignment exposure processing, which has the effect of minimizing the occurrence of pattern formation defects in semiconductor devices.

[Brief explanation of drawings]

FIG. 1 is a block diagram for explaining an embodiment of the present invention, and FIGS. 2 and 3 are a plan view of a wafer and a sectional view of the vicinity of a reduction projection lens for explaining an embodiment of the present invention. be. 1... Reference value storage unit, 2... Automatic focusing mechanism, 3
...Focus position storage unit, 4...Focus position difference detection unit,
5... Comparison section, 6... Display section, 10... Wafer, 11... Exposure center axis, 12... Reticle blind, 13... Reticle, 17... Projection lens, 18
... light emitting element, 19 ... light, 20 ... light receiving element,
21...Foreign object.

Claims (1)

[Claims] a reference value storage unit that stores a reference value for the difference in focus positions; a focus position storage unit that stores the focus position detected by the automatic focusing mechanism for each exposure area of the semiconductor wafer; a focus position difference detection unit that extracts focus position data of the exposure area to be exposed and focus position data of an adjacent exposure area and detects the difference therebetween; and a difference detection unit between the reference value from the reference value storage unit and the focus position. 1. A reduction projection type exposure apparatus, comprising: a comparison section for comparing the difference value between the first and second comparison sections; and a display section for inputting a signal from the previous comparison section and displaying the comparison result.