JP2001085299A - Method for correcting electron beam device, manufacture thereof and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for correcting an electron beam device capable of performing correction with high accuracy by simple procedures. SOLUTION: A sample 7 having a given crystal orientation face is placed on the sample base 5 of an electron beam device and is irradiated through an electron beam optical system OS with an electron beam EB radiated from an electron beam source 1. Here, the sample 7 is scanned with the electron beam by polarizing the electron beam with a polarizing unit 3 on the sample base 5, and reflective electrons from the sample are detected. The relationship between the incident angle of the electron beam to the sample and the output of the polarizing unit 3 is checked by using a signal reflecting the crystallinity of the sample in the signal of the detected reflective electrons. The beam axis of the electron beam optical system OS is corrected by the use of the check results.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for calibrating an electron beam apparatus such as an electron beam exposure apparatus. In particular, the present invention relates to a method of calibrating an electron beam apparatus capable of performing high-precision calibration by a simple procedure. Further, the present invention relates to a semiconductor device manufacturing method capable of forming a highly accurate pattern using an electron beam apparatus calibrated by such a calibration method.

[0002]

2. Description of the Related Art FIG. 3 is a diagram showing a conventional method for calibrating an incident angle of an electron beam on a sample surface. In the drawing, surfaces 100 and 100 'of a sample (semiconductor wafer or the like) having alignment marks 101 and 101' are shown. Above the sample surface, a deflector 7 for deflecting the electron beam EB
And a backscattered electron detector 72 for detecting backscattered electrons. While scanning the mark 101 with the electron beam EB deflected by the deflector 70, electrons reflected upward from the mark 101 can be detected by the reflected electron detector 72.

Next, a conventional method for calibrating the angle of incidence of an electron beam in this apparatus will be described. First, the calibration sample on which the alignment mark 101 is formed is placed on a sample stage, and the sample surface 100 is set at a certain height. The electron beam EB is irradiated and scanned in this state. An alignment mark position is obtained from a reflected electron signal waveform from the alignment mark 101 obtained at that time. Next, the height of the sample stage is set to △ Z
(The sample surface 101 '), and the position of the same alignment mark 101' is obtained again in the same manner. The angle θ at which the electron beam is incident on the sample surface can be obtained from the change ΔX in the alignment mark position obtained at this time and the changed height ΔZ of the sample stage. Usually, the deflector 70
Since it is desirable that the incident angle θ of the electron beam is zero when the deflection amount is zero, the electron optical system or the sample stage is adjusted so that the angle θ becomes zero.

[0004]

In this calibration method according to the prior art, the detection accuracy of the angle θ is determined by the Z-direction stroke of the sample stage and the detection accuracy of the alignment mark. As a general example, a stroke in the Z direction is 1
When the detection accuracy of the alignment mark is 0 μm and the detection accuracy of the alignment mark is 0.1 μm, the detection accuracy of the angle θ is about 10 mrad, which is not sufficient in many cases. 1 stroke in Z direction
Even if the detection accuracy of the alignment mark is 00 nm and the detection accuracy of the alignment mark is 10 nm, the detection accuracy of the angle θ is about 100 μrad, and it is difficult to detect the angle of about 10 μrad required for the electron beam exposure apparatus.

Generally, it is difficult to further improve the detection accuracy of the Z-direction stroke and the alignment mark, and it is difficult to obtain a detection accuracy of 100 μrad or less. In addition, when the height of the sample stage is changed, it often shifts not only in the normal height but also in the horizontal direction. Therefore, the conventional method includes factors that further deteriorate the detection accuracy.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a method of calibrating an electron beam apparatus capable of performing high-precision calibration by a simple procedure. It is still another object of the present invention to provide a semiconductor device manufacturing method capable of forming a pattern with high accuracy using an electron beam apparatus calibrated by such a calibration method.

[0007]

Means for Solving the Problems and Embodiments of the Invention In order to solve the above problems, a method for calibrating an electron beam apparatus according to the present invention is a method for calibrating an apparatus for irradiating a sample with an electron beam; Irradiating a sample with an electron beam while scanning it, detecting backscattered electrons from the sample, and calibrating the apparatus using a signal that reflects the crystallinity of the sample in the detected backscattered electron signal. And

In one embodiment of the present invention, a method for calibrating an electron beam apparatus comprises placing a sample having a certain crystal orientation plane on a sample stage of an electron beam apparatus, and converting an electron beam emitted from an electron beam source into an electron beam. The sample is irradiated through the line optical system. At this time, the electron beam is scanned on the sample by deflecting the electron beam by the deflector of the electron optical system, and the reflected electrons from the sample are detected.
The angle of incidence of the electron beam on the sample is detected from the relationship between the signal reflecting the crystallinity of the sample in the detected reflected electron signal and the output of the deflector, and the beam axis of the electron beam optical system is calibrated. It is characterized by the following.

According to the present invention, a material having high crystallinity, such as a single crystal silicon wafer, is used as a calibration sample, and the sample is irradiated with an electron beam and scanned. The angle at which the electron beam is incident on the sample surface is detected using the characteristic intensity waveform of the reflected electron signal and the like.
As an example of such a signal, when a surface of a wafer having a certain crystal orientation is irradiated while scanning an electron beam,
In some cases, the intensity of the backscattered electron signal changes depending on the angle of incidence and the angle of emission of the electron beam to the object, and is obtained from development.
This development is presumed to be caused by a difference in ease of passing the electron beam due to crystallinity.

[0010] When the angle of the electron beam incident on the sample surface having such characteristics is changed, development occurs in which the position where the reflected electron signal waveform due to the crystallinity of the sample is detected moves. From the relationship between the waveform detection position and the incident angle of the electron beam, the beam axis in the electron beam optical system can be detected. According to this calibration method, the angle can be detected with higher accuracy than in the related art. Further, since it is not necessary to change the height of the sample table during the calibration operation, it is possible to eliminate the influence of the lateral displacement of the sample table due to the change in the height of the sample table.

An electron beam apparatus according to the present invention comprises: a sample stage on which a sample is placed; an electron beam source; an electron beam optical system for irradiating the sample with an electron beam emitted from the electron beam source;
A backscattered electron detector for detecting backscattered electrons from the sample, and a calibration control unit for calibrating the apparatus using a signal reflecting the crystallinity of the sample in the detected backscattered electron signal, I do.

A semiconductor device manufacturing method according to the present invention is characterized in that exposure in a lithography step is performed using an electron beam apparatus calibrated by the above-described method for calibrating an electron beam apparatus.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically showing a configuration of an electron beam exposure apparatus according to one embodiment of the present invention. The electron beam exposure apparatus shown in FIG. 1 has an electron beam source (electron gun) 1 from which an electron beam EB is emitted. The electron beam EB is applied to the silicon wafer (sample) 7 through the electron beam optical system OS. The wafer 7 is placed on a wafer stage (sample stage) 5. The wafer stage 5 is a movable stage for mounting a wafer when performing electron beam exposure. The electron beam EB incident on the wafer 7 is deflected by the scanning deflector 3 on the exit side of the electron beam optical system OS. The deflector 3 is connected to a controller 4 and the controller 4
The electron beam EB is two-dimensionally scanned on the silicon wafer 7 by controlling the deflector 3.

When the electron beam EB is irradiated on the silicon wafer 7 as described above, backscattered electrons (reflected electrons) are generated from the surface of the wafer 7, and the backscattered electrons are detected by the backscattered electron detector 9. The signal of the backscattered electron detector 9 is transmitted to an interface 8 including an amplifier and an A / D converter.
Is sent to the calibration control unit 10 via With such a configuration, it is possible to observe a change in the intensity of the reflected electron signal when the beam incident on the wafer 7 is scanned. By integrating the reflected electron signal and the deflection angle signal of the deflector 3 and performing image processing, a reflected electron signal pattern as shown in FIG. 2, for example, can be obtained.

In this example, the upper surface of the sample has a plane orientation (1).
11) A single-crystal silicon wafer having a plane. The electron beam is irradiated by deflection scanning while gradually changing the incident angle of the electron beam on the sample. In this case, a reflected electron signal pattern by electron beam diffraction as schematically shown in FIGS. 2A and 2B is obtained.

FIG. 2 is a diagram in which the deflection output of the scanning deflector 3 and the reflected electron intensity signal detected by the reflected electron detector 9 are imaged. The horizontal axis indicates deflection in the X direction, and the vertical axis indicates deflection in the Y direction. A thick solid line in the figure indicates a portion where the level of the reflected electron signal is low. In this example, the reflected electron signal tends to be weak when the X-direction deflection and the Y-direction deflection have a certain linear relationship. Therefore, a pattern in which six straight lines 12 intersect as shown in FIG. 2 can be observed. As described above, this phenomenon is presumed to be caused by the difference in the ease of passing an electron beam due to the crystallinity of the sample.

The positions of the patterns are different between FIGS. 2A and 2B. That is, in FIG.
Correspond to the origin of the XY coordinates. On the other hand, in (B),
The center O 'of the pattern is shifted from the origin of the XY coordinates. Here, the origin of the XY coordinates is the position where the deflection amount of the electron beam EB by the scanning deflector 3 is O. On the other hand, the centers O and O 'of the pattern are on the sample surface (111
This is a point where the electron beam EB is perpendicularly incident on the (surface). Accordingly, the fact that the center O of the pattern coincides with the center of the XY coordinate as shown in FIG. 2A means that the output beam EB from the electron beam optical system OS in a state where the beam is not deflected by the deflector 3.
Means that the light is perpendicularly incident on the sample surface. Usually, such a state is preferable, and the electron beam optical system OS and the sample stage 5 are adjusted so as to make such a state.

Consider the accuracy when the beam axis of the electron beam optical system OS is adjusted by such a method. FIG.
In the case of (B), it is assumed that the distance between the center O ′ of the pattern and the XY coordinates is d _X and d _Y. And, as shown in FIG.
The distance between the center of the scanning deflector 3 and the surface of the sample 7 is h
And The inclination angles when the electron beam EB coming out of the electron beam optical system OS advances straight without being deflected by the scanning deflector 3 are θ _X and θ _Y. There is the following relationship between them. tan θ _X = d _X / h tan θ _Y = d _Y / h

Therefore, by measuring the distances d _X and d _Y between the center of the pattern and the center of the screen, the incident angles θ _X and θ _Y of the electron beam with respect to the sample when the electron beam is not scanned can be measured. Here, the detection accuracy of h = 10 mm and d is 1 μm
Then, the detection accuracy of the angle θ is about 10 μrad, and a desired accuracy can be obtained.

In practice, by adjusting the inclination of the electron optical system and the sample stage while watching the screen showing the relationship between the reflected electron signal and the deflection output, the state shown in FIG. 2A is adjusted. Work efficiency is also high.

Next, an embodiment of a device manufacturing method for performing exposure in a lithography step using an electron beam apparatus calibrated by the above method will be described. FIG. 4 is a flowchart showing an example of the semiconductor device manufacturing method of the present invention. The manufacturing process of this example includes the following main processes. Wafer manufacturing process for manufacturing a wafer (or wafer preparing process for preparing a wafer) Mask manufacturing process for manufacturing a mask to be used for exposure (or mask preparing process for preparing a mask) Wafer processing process for performing necessary processing on a wafer Wafer Chip assembling step of cutting out the chips formed on the chip one by one to make it operable Chip inspecting step of inspecting the resulting chips Each of the steps further includes several sub-steps.

Among these main steps, the main step that has a decisive effect on the performance of the semiconductor device is the wafer processing step. In this step, designed circuit patterns are sequentially stacked on a wafer, and a number of chips that operate as memories and MPUs are formed. This wafer processing step includes the following steps. A thin film forming step (using CVD, sputtering, etc.) for forming a dielectric thin film serving as an insulating layer, a wiring portion, or a metal thin film forming an electrode portion (using CVD or sputtering, etc.) An oxidizing step for oxidizing the thin film layer or the wafer substrate A lithography process of forming a resist pattern using a mask (reticle) in order to selectively process etc. An etching process of processing a thin film layer or a substrate according to a resist pattern (for example, using a dry etching technique) An ion / impurity implantation diffusion process Resist stripping step Inspection step for inspecting the processed wafer Further, the wafer processing step is repeated by a necessary number of layers to manufacture a semiconductor device that operates as designed.

FIG. 5 is a flowchart showing a lithography process which is the core of the wafer processing process of FIG. This lithography step includes the following steps. A resist coating step of coating a resist on a wafer on which a circuit pattern has been formed in the preceding step An exposing step of exposing the resist A developing step of developing the exposed resist to obtain a resist pattern Stabilizing the developed resist pattern An annealing process for using the above-described exposure apparatus in the above-described exposure process improves the accuracy of pattern formation in the lithography process. In particular, the process related to realizing the required minimum line width and the overlay accuracy corresponding thereto is a lithography process, in particular, an exposure process including alignment control, and it has been difficult until now by applying the present invention. Semiconductor devices can be manufactured.

[0024]

As is apparent from the above description, according to the present invention, it is possible to provide a method for calibrating an electron beam apparatus capable of performing high-precision calibration by a simple procedure. Further, it is possible to provide a semiconductor device manufacturing method capable of forming a pattern with high precision using an electron beam apparatus calibrated by such a calibration method.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a configuration of an electron beam apparatus according to one embodiment of the present invention.

FIG. 2 is a diagram in which a deflection output of a scanning deflector 3 and a reflected electron intensity signal detected by an electron beam detector 9 are imaged.

FIG. 3 is a diagram showing a conventional method for calibrating an incident angle of an electron beam with respect to a sample surface.

FIG. 4 is a flowchart illustrating an example of a semiconductor device manufacturing method according to the present invention.

FIG. 5 is a flowchart showing a lithography step which is the core of the wafer processing step shown in FIG. 4;

[Explanation of symbols]

REFERENCE SIGNS LIST 1 electron beam source 3 deflector 4 controller 5 sample table 7 sample (wafer) 8 interface 9 backscattered electron detector 10 calibration controller 12 lines

Claims (5)

[Claims] 1. A method for calibrating a device for irradiating a sample with an electron beam; irradiating a sample having crystallinity with an electron beam while scanning, detecting reflected electrons from the sample, and detecting a detected reflected electron signal. A method for calibrating an electron beam apparatus, wherein the apparatus is calibrated using a signal reflecting the crystallinity of the sample therein. 2. The method for calibrating an electron beam device according to claim 1, wherein the calibration of the device is a calibration of an incident angle of an electron beam with respect to a sample surface. 3. A sample having a certain crystal orientation plane is placed on a sample stage of an electron beam apparatus, and the sample is irradiated with an electron beam emitted from an electron beam source through an electron beam optical system. The electron beam is scanned on the sample by deflecting the electron beam by the system deflector, the reflected electrons from the sample are detected, and the signal reflecting the crystallinity of the sample in the detected reflected electron signal and the deflector A method for calibrating an electron beam apparatus, comprising: detecting an incident angle of an electron beam on a sample from a relationship with an output of the electron beam apparatus; and calibrating a beam axis of the electron beam optical system. 4. A sample stage on which a sample is placed, an electron beam source, an electron beam optical system for irradiating the sample with an electron beam emitted from the electron beam source, and detecting reflected electrons from the sample. An electron beam apparatus, comprising: a backscattered electron detector that performs calibration; and a calibration control unit that performs calibration of the apparatus using a signal reflecting the crystallinity of the sample in the detected backscattered electron signal. 5. A method for manufacturing a semiconductor device, comprising: performing an exposure in a lithography step using an electron beam apparatus calibrated by the method for calibrating an electron beam apparatus according to claim 1, 2 or 3.