JPH06273918A - Method for correcting residual defect of phase shift mask and device therefor - Google Patents

Abstract

PURPOSE:To correct the residual defects of the phase shifters of a phase shift mask. CONSTITUTION:The device for correcting the mask by utilizing a sputtering effect of a focused ion beam is provided with plural secondary charge particle detectors 8 in order to correct the residual defects of the phase shifters of the phase shift mask. The three-dimensional shapes of the residual defects of the phase shifters are recognized by the outputs of the plural secondary charge particle detectors 8 and a map of ion irradiation quantities meeting the three-dimensional shapes of the defects is formed. Etching is executed in accordance with this map. Then, the surface of the mask after removal of the residual defects is smoothed and this mask is usable as the phase shift mask.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for repairing pattern defects of phase shift masks and reticles used in the manufacture of semiconductor integrated circuits, especially residual defects of phase shifters.

[0002]

2. Description of the Related Art As disclosed in Japanese Patent Laid-Open No. 58-17374, a phase shift mask (phase shift reticle) uses a phase difference of light as well as an amplitude distribution of light. It is intended to improve the resolution of. A photolithography method (phase shift method) using a phase shift mask will be described with reference to FIGS. 5 (a), (b), (c), and (d). FIG. 5A is a cross-sectional view of the phase shift mask, and a light shielding pattern 62 made of Cr is formed on the surface of the glass substrate 61. One shading pattern 62
The next light-shielding pattern 62 is formed very close to, and an opening 63 is formed between the adjacent light-shielding patterns. These are repeatedly formed. Also,
In every other opening 63, a transparent film is formed, which is called a phase shifter 64. The material of the phase shifter 64 is a transparent material, and includes inorganic substances such as magnesium fluoride, titanium dioxide, and silicon dioxide, and organic substances such as polymer materials. It is also useful to use a resist material.

In FIG. 5A, coherent light emitted from above passes through each opening 63 and forms an image on a wafer directly or through a lens optical system. The light passing through the phase shifter 64 has a phase change of 180 degrees as compared with the light passing through a portion without the phase shifter 64. The amplitude distribution of the light passing through the opening 63 of the mask is shown in FIG.
As shown in (b). That is, the light passing through the opening 63 having the phase shifter 64 and the light passing through the opening 63 having no phase shifter 64 are 180 degrees out of phase with each other. Further, since the light passing through the opening 63 is diffracted, the diffracted light reaches the wafer corresponding to the shaded portion of the light shielding pattern 62. Therefore, the amplitude intensity of the light reaching the wafer is as shown in FIG. Lights diffracted by a shadow portion of a certain light shielding pattern 62 and sneaking from the left and right openings 63 are out of phase with each other by 180 degrees. That is,
They cancel each other out, and the intensity distribution of the light irradiated on the wafer is as shown in FIG. 5 (d). That is, the image of the opening is separated.

Here, in order to realize the phase shift method,
Although the phase shifter 64 must be surely present at a predetermined position, a residual defect of the phase shifter often occurs as shown in FIG. The residual defects 65a of the phase shifter of the phase shift mask are those in which the phase shifter material remains in the opening 63 having no phase shifter on the glass substrate 61. In order to remove the residual defect 65a,
It is conceivable to irradiate only the partial area of the residual defect 65a with the focused ion beam while repeatedly scanning it and to scatter it by ion sputtering.

[0005]

The phase shifter residual defects 65a generally have a three-dimensional shape, as shown in FIG. When the focused ion beam is irradiated to remove all the residual defects, the thin portion of the phase shifter, which is the residual defect 65a, especially the peripheral portion is immediately removed by the focused ion beam irradiation and is ground to the glass substrate 61. Will end up.

As described above, when the glass substrate 61 is damaged, the plate thickness at that portion is different from that at the other portion, and the irradiation light passing through that portion is the light passing through the portion having the normal plate thickness. And the phase will be different. As a result, a fine pattern cannot be accurately transferred.

Therefore, in reality, there is no method for accurately removing the residual defect 65a of the phase shifter.

[0008]

According to the present invention, a region including a phase shifter defect region formed on a sample surface is irradiated with a focused ion beam while scanning with a deflection electrode,
With a plurality of secondary charged particle detectors, secondary charged particles generated from the sample by the focused ion beam irradiation are detected, and a secondary charged particle detection intensity detected by the plurality of secondary charged particle detectors is detected. Based on the thickness of the phase shifter defect corresponding to the sample plane position of the phase shifter defect recognized by the arithmetic device, the dose map of focused ion beam irradiation is recognized based on the three-dimensional shape of the phase shifter defect based on the arithmetic device. Is produced by the computing unit, and the defect correction method and apparatus for a phase shift mask are characterized by irradiating the phase shifter defect with the ion beam according to a dose map of the focused ion beam irradiation. .

[0009]

When the sample is irradiated with the focused ion beam, secondary charged particles are emitted from the sample. The intensity of the secondary charged particles detected by the secondary charged particle detector is determined by measuring the incident angle, which is the angle between the focused ion beam and the sample surface, and the secondary charged particles, if the focused ion beam intensity and the material of the sample are constant. It changes depending on the detection angle, which is the angle between the detection direction and the sample surface. Here, the detection intensity is highest when the incident angle and the detection angle are 90 degrees, and becomes zero when they are 0 degrees.

The irradiation direction of the focused ion beam and the secondary charged particle detection direction are substantially the same at any position in the residual defect region. Therefore, the secondary charged particle intensity detected by the secondary charged particle detector changes depending on the surface shape of the residual defect, and the three-dimensional shape of the residual defect can be detected and confirmed by detecting the change. can do. Since the material of the residual defects is already known, the amount of sputtering per unit time by the focused ion beam irradiation is fixed. Here, the focused ion beam irradiation amount (time) at each position is determined from the thickness (Zi) at each position (Xi, Yi) of the residual defect. Therefore, a dose (time) map of focused ion beam irradiation can be created.

By irradiating each position (Xi, Yi) of the residual defect with the focused ion beam in accordance with the dose (time) map of the irradiation of the focused ion beam, the residual defect of the phase shifter can be flattened. it can.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic block diagram and a circuit block diagram of a defect correction device for a phase shift mask. Since the focused ion beam irradiation system for irradiating the focused ion beam 6 is widely known, detailed description thereof will be omitted. An ion source 1 generates ions. Reference numeral 2 is a focusing lens, and 5 is an objective lens. Both are lenses for focusing the ions. Three
Is a blanking electrode, which works when the sample 9 is not irradiated with the focused ion beam 6. The sample 9 is placed on a sample stage 10 that can move in the YX directions. A scanning electrode 4 scans the surface of the sample 9 with the focused ion beam 6. The rectangular area on the surface of the sample 9 is normally scanned by the scanning electrode 4 by the focused ion beam 6, and the blanking electrode 3 is operated at a position in the scanning area where irradiation of the focused ion beam 6 is not necessary, The area is irradiated with a focused ion beam. The ion source 1, the focusing lens 2, the blanking electrode 3, the scanning electrode 4, and the objective lens 5 form a focused ion beam irradiation means.

Reference numeral 8 denotes a secondary electron detector as a secondary charged particle detector, which detects secondary electrons 7 as secondary charged particles generated from the sample 9 by irradiation of the focused ion beam.
A plurality of secondary electron detectors 8 are provided, and their detection windows are directed to the irradiation position of the sample 9 with the focused ion beam 6.

In this embodiment, two secondary electron detectors 81 and 82 are arranged at symmetrical positions and angles with respect to the focused ion beam axis. First, residual defects 65 of the phase shifter on the surface of the sample 9 are focused by the focused ion beam 6.
Irradiation is performed while scanning the area including the area with the deflection electrode.
The secondary electrons 7 generated from the sample 9 by the irradiation of the focused ion beam 6 are detected by the secondary electron detectors 81 and 82.
The output of each secondary electron detector 81, 82 is A / D
After the A / D conversion by the converter 11, the arithmetic unit 12 detects and confirms the three-dimensional shape of the residual defect 65.

A method of detecting and confirming the three-dimensional shape of the residual defect 65 will be described below. First, terms will be described with reference to FIG. The angle of incidence of the focused ion beam 6 on the surface of the sample 9 is referred to as an incident angle 25. Further, the angles detected by the two secondary electron detectors 81 and 82 with respect to the sample surface are set as detection angles 26 and 27, respectively. Further, the detection directions of the secondary electrons are 36 and 37, respectively.

Next, a method of detecting a three-dimensional shape will be described with reference to FIGS. The emission intensity of secondary electrons generated when the surface of the sample 9 is irradiated with the focused ion beam 6 becomes stronger as the incident angle 25 approaches 90 degrees,
Also, the closer the detection angles 26 and 27 are to 90 degrees, the more secondary electrons are detected. The secondary electron amounts detected by the two secondary electron detectors 81 and 82 are equal when the detection angles 26 and 27 are the same, and more secondary electrons are detected when the detection angles 26 and 27 are closer to 90 degrees. To detect. Therefore, when the surface of the sample 9 and the secondary electron detections 81 and 82 are given as shown in FIG. 2B, the signal 2 obtained by the two secondary electron detectors 81 and 82 is obtained.
9 and 30 are as shown in FIGS. 2C and 2D, respectively. That is, more secondary electrons from the inclined surface of the sample surface are detected by the secondary electron detector (eg, 81) on that side, and secondary electrons from the opposite surface are detected by the other secondary electrons. Many are detected by the electronic detector 82. When the difference between these two signals is obtained, the signal 31 of FIG. 2 (e) is obtained. Further, by integrating the difference signal 31 in the scanning direction of the focused ion beam 6, the data 32 of the height (Z direction) of the sample (here, the residual defect 65) in the scanning direction (X direction) is obtained as shown in FIG. It is obtained as in (f). This focused ion beam 6
The three-dimensional shape of the residual defect 65 can be detected / confirmed by repeating the scanning of the above with a slight shift in the Y direction.
These calculations are performed by the calculation device 12.

Next, a method of irradiating the focused ion beam 6 according to the three-dimensional shape of the residual defect 65 will be described with reference to FIG. It is assumed that the three-dimensional shape of the residual defect 65 is given as shown in the plan view and side view of FIG. A focused ion beam dose map is created from this information. A contour line 44 is drawn with the amount of etching per unit time (the thickness 42 of the residual defect 65) as a unit, and only the region surrounded by the contour line 44 is sequentially scanned with the focused ion beam 6 from the top. Irradiate from. That is, at first, the area indicated by 65a is not scanned with the focused ion beam 6 for a unit time, and irradiation is performed.
Next, the area shown by 65b is irradiated with the focused ion beam 6 without scanning for a unit time, and then the area shown by 65c is irradiated. By sufficiently shortening the unit time described above, the residual defect 65 can be removed without damaging the surface of the glass substrate 51.

The contour line 44 corresponds to the focused ion beam dose map, which is also created by the arithmetic unit 12.
Will be held in. The focused ion beam dose map and the shape of the residual defect 65 are displayed on the display device 14. Each element of the focused ion beam irradiation system is controlled via the ion optical system control power supply 13 based on the focused ion beam irradiation amount map calculated by the calculation device 12.

[0019]

As described above, according to the present invention,
By providing a plurality of secondary charged particle detectors and processing the outputs thereof, the three-dimensional shape of the residual defect is obtained, and a focused ion beam irradiation map is created from the obtained three-dimensional shape of the residual defect. By irradiating the focused ion beam according to the map, the residual defects of the phase shift mask and the reticle can be removed without damaging the substrate. As a result, residual defects of the phase shift mask and the reticle that could not be conventionally corrected can be corrected.

[Brief description of drawings]

FIG. 1 shows a schematic block diagram and a circuit block diagram of a phase shift mask defect repairing apparatus of the present invention.

2A and 2B are plan views showing the relationship among a focused ion beam, a secondary electron detector, and a sample surface.
(C) is a graph showing the detection signal 29 of the secondary electron detector 81. (D) is a graph showing the detection signal 30 of the secondary electron detector 82. (E) is a graph showing a difference 31 between the detection signal 29 and the detection signal 30. (F) is
6 is a graph obtained by integrating a difference 31 between a detection signal 29 and a detection signal 30.

3A and 3B are a plan view and a side view showing a three-dimensional shape of a residual defect 65 and a dose map.

FIG. 4 is a cross-sectional view showing a residual defect.

FIG. 5A is a sectional view of a phase shifter mask.
(B) A graph showing a light amplitude distribution on a mask.
(C) A graph showing a light amplitude distribution on a wafer.
(D) A graph showing a light intensity distribution on a wafer.

[Explanation of symbols]

 1 Ion Source 2 Focusing Lens 4 Scanning Electrode 6 Focused Ion Beam 9 Sample 11 A / D Converter 12 Calculator 13 Ion Optical System Control Power Supply 42 Etching Amount per Unit Time 44 Contour Line 61 Glass Substrate 62 Shading Pattern 63 Opening 64 Phase Shifter 65 Residual defect 81, 82 Secondary electron detector

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location // H01L 21/302 D 9277-4M

Claims (2)

[Claims] 1. An area including a phase shifter residual defect area formed on a sample surface is irradiated with a focused ion beam while scanning with a deflection electrode, and a plurality of secondary charged particle detectors are used to detect the area. The secondary charged particles generated from the sample by focused ion beam irradiation are detected, and the three-dimensional shape of the phase shifter defect is calculated by the arithmetic device based on the secondary charged particle detection intensities detected by the plurality of secondary charged particle detectors. Recognize, create a dose map of the focused ion beam irradiation based on the thickness of the phase shifter residual defects corresponding to the sample plane position of the phase shifter residual defects recognized by the arithmetic unit, in the arithmetic unit, Residual defects in a phase shift mask, wherein the ion beam is applied to the phase shifter residual defects according to a dose map of focused ion beam irradiation. How to fix. 2. A focused ion beam irradiation means for irradiating a region including a phase shifter residual defect region formed on a sample surface while scanning with a deflection electrode, and a secondary ion beam generated from the sample by the focused ion beam irradiation. A plurality of secondary charged particle detectors for detecting charged particles, and recognizing the three-dimensional shape of the phase shifter residual defect based on the secondary charged particle detection intensities detected by the plurality of secondary charged particle detectors, and the recognition The calculator for creating a dose map of focused ion beam irradiation based on the thickness of the phase shifter residual defects corresponding to the sample plane position of the phase shifter residual defects, and the dose map of the focused ion beam irradiation. Accordingly, the residual phase shift mask comprises an ion optical system control means for irradiating the phase shifter residual defects with the ion beam. Residual defect repair device.