JPH0710244Y2 - Optical shape measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to an optical profile measuring apparatus, and improves the measurement accuracy of the optical profile measuring apparatus.

<Prior Art> FIG. 2 is a block diagram showing an example of a conventional optical shape measuring apparatus of this type.

In FIG. 2, 10 is a laser diode, 11 is a collimator lens, 12 is a polarization beam splitter, 13 is a λ / 4 plate, and 14
Is an objective lens, 15 is an object to be measured, 16 is a beam splitter,
Reference numeral 17 is an array element for measuring the light intensity pattern of the reflected light from the object to be measured 15, and 18 is arithmetic processing by a signal from the array element 17 according to the light intensity pattern of the reflected light from the object to be measured 15. Calculation processing unit, 19 is a focus error detection optical system for obtaining a focus error signal from the reflected light from the object to be measured 15, 20 is a focus error signal obtained from the focus error detection optical system 19 from the calculation processing unit 18 It is a calculation processing unit that corrects according to the calculation result.

In such a configuration, the light emitted from the laser diode 10 is collimated by the collimator lens 11 and reflected by the polarization beam splitter 12. The reflected light passes through the λ / 4 plate 13, is condensed by the objective lens 14, and is irradiated onto the object to be measured 15. The irradiated light is reflected by the DUT 15 and the objective lens
After passing through the beam splitter 14, the λ / 4 plate 13 and the polarization beam splitter 12, the beam splitter 16 splits the beam into two. One light is incident on the array element 17, becomes a signal according to the light intensity pattern of the reflected light from the object to be measured 15, is sent to the arithmetic processing unit 18, and after the arithmetic processing, the light such as the groove width which is the measurement data. The pattern signal in the spot is obtained and sent to the arithmetic processing unit 20. The other light is incident on the focus error detection optical system 19 and is sent to the arithmetic processing unit 20 as a focus error signal.
The arithmetic processing unit 20 corrects the focus error signal based on the measurement data from the arithmetic processing unit 18.

<Problems to be Solved by the Invention> However, in the optical shape measuring device shown in the above-mentioned prior art, it is possible to measure a groove width pattern smaller than the light spot diameter, but it is possible to measure one light spot. The data obtained is of a very narrow range,
Since the data for sufficiently grasping the state around the measurement point such as the inclination of the surface of the is not obtained, there is a problem that the measurement data and the focus error signal cannot be corrected sufficiently.

The present invention has been made in view of the above-mentioned problems of the prior art.By capturing the data around the measurement point, the state around the measurement point such as the inclination of the surface of the DUT can be grasped, and the measurement data and focus error can be grasped. The object is to provide an optical shape measuring device capable of surely correcting signals and the like.

<Means for Solving the Problems> The configuration of the present invention for solving the above problems is to drive an objective lens in the focus direction to focus a light spot on an object to be measured and to form a light intensity pattern of the reflected light. Is an optical device including a measurement optical system for measuring the shape of an object to be measured by performing measurement processing with an array element and a focus error detection optical system for obtaining a focus error signal from the reflected light from the object to be measured. In the profile measuring apparatus, a defocus signal generator is provided, and the defocus signal obtained from the defocus signal generator and the focus error signal detected by the focus error detection optical system are added to defocus the light spot. It is characterized by including a defocusing device for creating a state.

<Example> Hereinafter, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an optical shape measuring apparatus according to the present invention. In FIG. 1, the same elements as those in FIG. 2 are designated by the same reference numerals, and duplicate description will be omitted.
In FIG. 1, reference numeral 30 indicates that the objective lens 14 or the object to be measured 15 is displaced in the optical axis direction from the state where the light spot is focused on the object to be measured 15 (hereinafter, simply referred to as just focus state). A defocus device for creating a state in which light is not focused on the DUT 15 (hereinafter, simply referred to as a defocus state), 31 is a defocus signal generator that generates a defocus signal, and 32 is a focus error signal. And a summing amplifier for adding the defocus signal, 33
Is a focus control circuit for driving the objective lens 14 by a signal from the addition amplifier 32.

Here, as the operation of the defocusing device 30 for creating the defocused state of the light spot, the objective lens 14 is moved in the optical axis direction from the just focused state by adding the defocus signal to the focus error signal. It is done by.

In such a configuration, the light emitted from the laser diode 10 is collimated by the collimator lens 11 and reflected by the polarization beam splitter 12. The reflected light passes through the λ / 4 plate 13 and irradiates the object to be measured 15 focused by the objective lens 14. The irradiated light is reflected by the DUT 15, passes through the objective lens 14, the λ / 4 plate 13 and the deflection beam splitter 12, and is split into two by the beam splitter 16. One light is incident on the array element 17, becomes a signal according to the light intensity pattern of the reflected light from the object to be measured 15, is sent to the arithmetic processing unit 18, and after the arithmetic processing, the light such as the groove width which is the measurement data. The pattern signal in the spot is obtained and sent to the arithmetic processing unit 20. The other light is incident on the focus error detection optical system 19 and is sent to the arithmetic processing unit 20 as a focus error signal. The arithmetic processing unit 20 corrects the focus error signal based on the measurement data from the arithmetic processing unit 18, sends it to the focus control circuit 33 via the addition amplifier 32, and drives the objective lens 14 in the focusing direction. Further, the defocus signal generated by the defocus signal generator 31 is added to the focus error signal in the adding amplifier 32,
It is sent to the focus control circuit 33 to drive the objective lens 14 in the defocus direction. The means for creating the defocused state of the light spot is configured such that the output of the focus control circuit 33 is input to the DUT 15, and the objective lens 14 is fixed at the position of the just focus state, and the DUT 15 is set to the optical axis. You may go by moving in the direction.

In the above configuration, when measuring the defocus state, a defocus signal is generated from the defocus signal generator 31 and added to the focus error signal from the arithmetic processing unit 20 by the addition amplifier 32. At the same time, the arithmetic processing unit 18,
This measurement state is also sent to 20 and correction is performed. Further, when measuring the just focus state, the defocus signal is set to 0V, the measurement state is sent to the arithmetic processing units 18 and 20, and the measurement data of the defocus state is also added for correction.

The arithmetic processing contents of the arithmetic processing units 18 and 20 include a light and dark pattern stored in a characteristic shape in the just focus state and the defocus state (edge in the former, inclination in the latter, etc.) and a measurement pattern. Take the correlation of.

The measurement data in the just-focused state is corrected based on the calculation result in the defocused state.

The focus error signal is corrected using the measurement data in the defocus state and the just focus state.

<Effects of the Invention> As described above in detail with reference to the embodiments, according to the present invention, a defocus device for creating a defocused state of the light spot is provided, and not only the just focused state but also the defocused state is provided. By measuring the light intensity pattern in the focused state, the data around the measurement point can also be captured to measure the state of the measurement surface, such as inclination.
Since it is possible to correct the measurement data and the focus error signal with certainty, it is possible to realize an optical shape measuring device capable of highly accurate measurement.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an optical shape measuring apparatus according to the present invention, and FIG. 2 is a view showing a conventional example. 10 ... Laser diode, 11 ... Collimator lens, 12
...... Polarizing beam splitter, 13 …… λ / 4 plate, 14 …… Objective lens, 15 …… Measurement object, 16 …… Beam splitter, 17
...... Array element, 18, 20 …… Arithmetic processing unit, 19 …… Focus error detection optical system, 30 …… Defocus device, 31
...... Defocus signal generator, 32 …… Summing amplifier, 33
...... Focus control circuit.

Claims (1)

[Scope of utility model registration request] 1. A shape of an object to be measured by driving an objective lens in a focus direction to condense a light spot on the object to be measured and measuring a light intensity pattern of the reflected light with an array element to perform arithmetic processing. In the optical shape measuring device, which comprises a measuring optical system for measuring the object and a focus error detecting optical system for obtaining a focus error signal from the reflected light from the object to be measured, the defocus signal generator is provided. An optical system comprising a defocus device for adding a defocus signal obtained from a generator and a focus error signal detected by the focus error detection optical system to create a defocused state of the light spot. Type shape measuring device.