JPH03102207A - Height detecting apparatus for sample surface - Google Patents

Abstract

PURPOSE:To measure with high accuracy by providing a detecting apparatus which obtains the height of the surface of a sample on the basis of detecting signals of a detector from two marks obtained through scanning. CONSTITUTION:An electron beam 1 projected from an electron beam generating apparatus 20 forms a reduced image of a source of the electron beams via a reducing lens 2 and a focus correcting lens 3 at a position 4. This image is formed on the surface of a sample 11 by an objective lens 7. A reflecting electron from the sample 11 is detected by an electron detector 10, amplified by an amplifier 13 and input to a control apparatus 14. Then, the apparatus 14 generates a control command based on the design data input from an input device 15 to a sample movement control apparatus 16 so that the center of a predetermined registration mark is found on the axis of an electro-optical system. As a result, a current to be fed to deflection coils 5, 6 is controlled to scan the registration mark with respect to a position 9 as the center of deflection. By taking an output of the amplifier 13 in synchronization with the scanning, the distance between the position 9 and the surface of the sample 11 can be measured.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an apparatus for measuring the height of a sample surface using an electron beam. [Prior Art] For example, conventionally, when measuring the height of a sample surface with an electron beam imaging device, an optical system is separately provided near the objective lens, and light is incident obliquely on the sample surface. The height of the sample surface was measured from the imaging position of the reflected light. There is also a method that calculates the height of the sample from the focusing conditions of the electron beam for drawing without using a special optical system for measuring light. [Problem to be solved by the invention] However, in devices that use light to detect height, it is necessary to install an insulator such as glass near the electron optical system, which is essential for the optical system of the measurement light. The electrostatic charge caused by the beam causes positional drift or astigmatism of the electron beam, and it also requires a light optical system in addition to the electron optical system, making the device complex and expensive. Additionally, conventional devices that use a special measurement light can accurately measure heights when the drawing surface is flat and has no pattern.
There was a problem that accurate height measurements could not be made in areas with patterns with different reflectances or in cases where the drawing surface was uneven. On the other hand, the method in which the height of the sample is determined from the focusing conditions of the electron beam has the problem that the measurement takes a long time because the current of the objective lens needs to be changed several times.

Therefore, the present invention provides a height measuring device for a sample surface that can measure the height of a sample with high precision and high speed using an electron optical system without using light for height measurement. The purpose is to [Means for Solving Problem I] In order to solve the above problems, the present invention first provides a focusing lens system that focuses an electron beam from an electron beam generator on a sample, and a focusing lens system that focuses the electron beam on a sample. a deflection device for deflecting and scanning the sample; a detector for detecting a signal from the sample; A sample characterized in that it is provided with a control device for scanning, and a detection device for determining the height of the sample surface based on a detection signal of the detector that detects a signal obtained from the mark by the scanning. It is a surface height measuring device, and also includes a focusing lens system that focuses an electron beam from an electron beam generator on a sample, a deflection device that deflects and scans the electron beam on the sample, and a deflection device that deflects and scans the electron beam on the sample. A height detecting device for an electronic WTI imaging device having at least a detector for detecting a signal from In addition to providing a deflection means for scanning by a line,
A height measuring device for a sample surface, further comprising: a detection device that determines the height of the sample surface based on a detection signal of the detector that detects a signal obtained from the mark; The measuring device is characterized by a two-stage coil for axis alignment. [Function] In the present invention, since the distance between the deflection fulcrum and the sample surface is made small (approximately 1/10 of the image point distance of the objective lens), two marks at a certain distance on the sample can be scanned. The deflection angle becomes larger. In other words, oblique incidence scanning with a large angle is performed. Therefore, the deflection angle between marks changes greatly with a slight vertical movement of the sample, allowing highly accurate measurements. Furthermore, since measurement can be performed by scanning two marks at once, even when considering the time required to bring the two marks to a predetermined position in relation to the scanning position, rapid measurement can be performed.

〔Example〕

FIG. 1 is an explanatory diagram of an embodiment in which the present invention is applied to a drawing apparatus using an electron beam. Electrons &? emitted from the electron beam generator 20? At t 1 , a reduced image of the electron beam source of the electron beam generator 20 is formed at position 4 through the reduction lens 2 and the focus correction lens 3 . This image is shown by the objective lens 7
An image is formed on the surface of sample 11 by . The conditions of incidence on the objective lens 7 are determined by the alignment coils 5 and 6, and a preliminary scan is performed by the drawing deflector 8 to produce a positive image.
The sample 11 is composed of a plurality of chips, and each chip is provided with a registration mark 12, as shown in FIG. Then, the sample 11 is transferred to the sample moving device W16.
Movement is controlled by The backscattered electrons from the sample 11 are detected by the backscattered electron detector 10, and the output signal of the detector IO is amplified by the amplifier 13 and input to the control device 14.

The control device 14 receives operator commands from the human power device 15,
Input the design values of the pattern on the surface of the sample l1, etc., and proceed to the electron beam generator 20, the reduction lens 2, the focus correction lens 3, the alignment coils 5, 6, the drawing deflector 8, the objective lens 7, and the sample moving device 16. control. Since the alignment coils 5 and 6 are two-stage deflectors, the electron beam 1 can be controlled to scan over the sample using the alignment coils 5 and 6, and the current ratio flowing through each can be controlled. By setting the deflection fulcrum to an appropriate value,
It can be set to position 9 just above the surface of 1. This embodiment utilizes this property of the alignment coils 5 and 6 to mark the registration marks 12a and 12 on the sample 1l.
Scan b. The trajectory of the electron beam 1 in this case is shown by reference numeral 17 in FIG.

The control device 14 selects predetermined registration marks 12a, 12 based on the design information input from the input device 15.
A control command is given to the sample movement control device l6 so that the center of point b is on the axis of the electron optical system, and a control command is given to the alignment coils 5 and 6 to scan the registration marks 12a and 12b using position 9 as a deflection fulcrum. Controls the current value flowing to each.

When the electron beam 1 is emitted from the electron beam generator 20, the electron beam 1 scans the registration marks 12a and 12b as shown in FIG. By capturing the output of the amplification r&13 in synchronization with scanning, the distance from the deflection fulcrum 9 to the surface of the sample 11 can be determined.
That is, the interval 2L between the registration marks 12a, 12b is known in advance, and when the electron beam 1 is scanned, the distance 2L between the registration marks 12a, 12b is known.
By reading the signal obtained from 2b from the output of the amplifier 13, the angle e at which the two registration marks 12aS and 12b are viewed from the deflection fulcrum 9 can be found.
The distance HD between the deflection center 9 and the surface of the sample 11 can be determined. That is, D=L/Lane. Then, the control device l4 controls the current value to be applied to the objective lens 7 so that the determined distance D becomes a predetermined position, and when the distance D reaches a predetermined value, the two measured registration marks 1
The current flowing through the drawing deflector 8 is controlled in order to perform drawing according to the design value on the chips 2a and 12b.

When the skin drawing is completed, the sample moving device 16 is controlled according to the design value, and the same process is repeated. Next, we will discuss measurement accuracy with reference to Figure 3. If the distance between the deflection fulcrum 9 and the surface of the sample 11 is D, the interval between the registration marks 12a and 12b is 2L, the required Z measurement accuracy is dZ, and the mark measurement sensitivity is dL, then the second
The following relationship is obtained from the two similar triangles in the figure.

D L dZ dL For example, 2L=100IIm, dL=0.02pm
, D=2M, dZ=2 μm is obtained.

That is, if the deflection fulcrum (center) of the two deflection coils is adjusted to a position 2+w above the sample and the mark interval can be measured in one scan, the measurement can be performed with an accuracy of 2 μm. Also, the deflection angle when the deflection fulcrum is set below the sample and the deflection fulcrum 9 is set above the sample 11, and the distance between the registration marks 12a and 12b when the deflection center is at the fulcrum 9' below the sample 1l. Find the conditions under which the values are the same, and try 1411 between them.
It may be calculated if there is a position of . Also, Z in the range where the surface of the sample 1l may change
Calibration marks are provided at two Z positions outside the position, and the deflection fulcrum is set so that the mark near the lens can be measured in one scan when the maximum current is applied to the deflector. The side marks and marks at all sample surface positions become detectable. The reliability of the measurement can be improved by interpolating between the measured values at the two calibration marks and performing the Z measurement on any sample surface.

In the above explanation, an example has been given in which the present invention is applied to an electron beam lithography system. However, the present invention is not limited to an electron beam lithography system, but can be applied to a wide range of devices for detecting the height of a sample surface using an electron beam. It can be captured. In the above embodiment, the two alignment coils 5 and 6 of the electron optical system were used to perform scanning for height detection, but the alignment coil 5,
6 is not necessarily required, and it is of course possible to provide a scanning means exclusively for height detection. [Effects of the Invention] As described above, according to the present invention, (]) Since the light optical system is not required, the electron optical system is simplified, and there is no adverse effect caused by the insulator of the light optical system, so that the beam (2) Change the lens current of the objective lens to adjust Z from the focusing condition.
(3) Measurement accuracy can be improved because the deflection fulcrum is set near the sample surface. It has the following effects. Furthermore, according to the embodiment of the present invention, by measuring from data obtained when deflection supports are provided in front and behind the sample surface, it is possible to perform even more accurate measurement, and it is also possible to perform measurements with even higher accuracy. By referring to the data obtained when the calibration mark is scanned at a certain position, the reliability of the measured value can be improved.

[Explanation of symbols of main parts]

5, 6...Axis alignment coil, 9...Deflection fulcrum, lO・
... Backscattered electron detector, l4... Control device.

Claims (3)

[Claims] (1) A focusing lens system that focuses an electron beam from an electron beam generator on a sample, a deflection device that deflects and scans the electron beam on the sample, and a detector that detects a signal from the sample. , a control device that causes the electron beam to scan two marks whose distance is known in advance on the sample surface using the vicinity of the surface of the sample as a deflection fulcrum; and the detection device that detects a signal obtained from the marks by the scanning. A detection device for determining the height of the sample surface based on a detection signal of the sample surface. (2) A focusing lens system that focuses the electron beam from the electron beam generator on the sample, a deflection device that deflects and scans the electron beam on the sample, and a detector that detects the signal from the sample. In a height detection device for an electron beam lithography apparatus having at least the following, a deflection means is provided that causes the electron beam to scan two marks on the sample surface whose distance is known in advance, using the vicinity of the surface of the sample as a deflection fulcrum. A height measuring device for a sample surface, further comprising a detection device that determines the height of the sample surface based on a detection signal from the detector that detects a signal obtained from the mark. (3) The measuring device according to claim 2, wherein the deflection means is a two-stage coil for axis alignment.