JPH05275314A - Stepper - Google Patents

Abstract

PURPOSE:To enhance resolution of pattern by inputting irradiation position information of a wafer irradiated with an auto-focus beam to an input section thereby eliminating error from a focus value. CONSTITUTION:The stepper comprises an input section 1 of coordinates on a wafer being irradiated with a beam, an operating section 2 comprising a focus control operating circuit 2b performing operation under control of a stepper main CPU 2a, a section 3 for irradiating a beam based on an operation result, and a section 4 for detecting a reflected light beam. Coordinate on the wafer being irradiated with an auto-focus beam is then key inputted to the beam irradiation input section 1. According to the constitution, profile of the wafer is obtained and thereby a focus offset input value is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepper having an autofocus function.

[0002]

2. Description of the Related Art In a conventional stepper having an autofocus function, a center of a wafer or a specific hardware point is irradiated with an autofocus beam, a focus value is calculated from the reflected light, and a focus value is calculated based on the focus value. The position is controlled.

[0003]

By the way, in the prior art, the beam for autofocus is irradiated to a certain specific point and the autofocus value is calculated by the reflected light thereof to control the focus. In this case, an error occurs in the focus value due to the deviation of the beam irradiation position between the upper part and the lower part. Due to this error, the pattern resolution is remarkably lowered, and becomes more and more fatal with the miniaturization of the LSI.

The present invention has been made in view of the above points, and an object of the present invention is to provide a stepper having an autofocus function capable of eliminating the error of the focus value and improving the pattern resolution.

[0005]

In order to achieve the above object, a stepper of the present invention comprises an input section for inputting irradiation position information of a wafer irradiated with an autofocus beam,
A cross-sectional shape of the wafer at the beam irradiation point obtained based on the position information, a calculation unit that calculates the autofocus value based on the focus offset input value obtained by the cross-sectional shape, and the calculation result of the calculation unit. Based on the above-mentioned reflection signal, the beam irradiation unit for irradiating the beam for autofocus on the wafer and the detection unit for detecting the reflection signal of the reflection beam which reflects the wafer. It is characterized by being configured to perform focus control by the calculated autofocus value.

[0006]

By inputting the irradiation position information of the wafer on which the autofocus beam is irradiated to the input section, the sectional shape of the wafer at that position can be obtained. Therefore,
A focus offset value corresponding to the sectional shape and an autofocus value based on the sectional shape are obtained.

Further, the autofocus value is obtained again based on the reflection signal of the reflected beam of the beam emitted according to the autofocus value, and the focus control is performed, so that the optimum focus control without error is performed.

[0008]

FIG. 1 is a block diagram of an embodiment of the present invention. Embodiments of the present invention will be described with reference to the drawings.

The stepper of the present invention comprises a beam irradiation coordinate input section 1 for inputting coordinate points on a wafer for beam irradiation.
An arithmetic unit 2 having a focus control arithmetic circuit 2b that performs an operation under the stepper main CPU 2a, an irradiation unit 3 that irradiates a beam based on the operation result, and a reflected beam detection unit that detects a reflected beam of the emitted light. Four
It is composed of and.

The operation of the embodiment of the present invention having the above configuration will be described below. First, in the beam irradiation input unit 1, the coordinates of the irradiation point of the wafer to which the beam for autofocus is irradiated are keyed. The cross-sectional shape of the wafer at the beam irradiation point is obtained from the input value of this input coordinate, and the focus offset input value is obtained from the cross-sectional shape.
Under the stepper main CPU 2, the focus control calculation circuit 2b calculates the autofocus value based on the sectional shape and the focus offset input value. This autofocus value is obtained based on the wafer cross-sectional shape at the irradiation point and the focus offset input value. Further, in the auto-focus beam irradiation unit 4, the focus position is controlled based on the calculation result, and the auto-focus beam is irradiated. Then, the reflected beam detection unit 5 detects the reflected signal of the reflected beam reflected by the beam irradiated on the wafer, and the reflected signal is again detected by the focus control arithmetic circuit 2b under the stepper main CPU 2 again. The autofocus value is calculated, and the previously obtained calculated value is corrected, resulting in optimum focus control without error.

In this embodiment, even if there is a step difference in the underlying layer, its cross-sectional shape becomes clear, and the focal length of the beam to be irradiated can be obtained from the difference between the upper part and the lower part. In this way, the focus value can be calculated at any point.

[0012]

As described above, according to the stepper of the present invention, by inputting the positional information of the irradiation point of the wafer to which the beam for autofocus is irradiated, the sectional shape at that point becomes clear, Since the focus control is performed by obtaining the focus value according to the shape, the focus value error can be improved. Further, since the autofocus value is obtained again based on the reflection signal of the reflected beam of the beam emitted according to the focus value and the focus control is performed, the optimum focus control without error can be performed. As a result, the obtained pattern has an improved resolution, and can correspond to the miniaturization of the LSI.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

[Explanation of symbols]

 1 ... Beam irradiation coordinate input unit 2 ... Calculation unit 2a ... Stepper main CPU 2b ... Focus control calculation circuit 3 ... Autofocus beam irradiation unit 4 ... Reflection Beam detector

Claims (1)

[Claims] 1. An input unit for inputting irradiation position information of a wafer to which an autofocus beam is irradiated, a cross-sectional shape of the wafer at the beam irradiation point obtained based on the position information, and the cross-sectional shape. A calculation unit that calculates the autofocus value based on the focus offset input value, a beam irradiation unit that irradiates an autofocus beam on the wafer based on the calculation result of the calculation unit, and the beam that irradiates the wafer. A stepper configured to include a detection unit that detects a reflection signal of a reflected reflection beam, and to perform focus control with an autofocus value calculated based on the reflection signal.