JPH07183360A - Reference mark for device calibration of electron beam exposure device and method for calibrating the device - Google Patents

Abstract

PURPOSE:To improve S/N and to prevent the deterioration of an electron beam exposure device configuration accuracy without reducing the intensity (peak value) of a reflected electronic signal obtained from a reference mark (step of metal) used when calibrating the electron beam exposure device. CONSTITUTION:By forming a heavy metal thin film 9 which is approximately 0.5-1.0mum thick on a flat part 8 of a substrate 11 of a light element, a reflected electron signal from a flat part 8 causing background noise is reduced to S/N ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a calibration reference mark used for calibrating an electron beam exposure apparatus.

[0002]

2. Description of the Related Art In an electron beam exposure apparatus for obtaining a desired pattern using electron beam exposure, the calibration of the electron beam exposure apparatus carried out before the electron beam exposure has been conventionally performed as shown in FIG. A reference mark (3) for calibration of heavy metal, which is installed on a stage (2) for moving a target wafer, reticle, etc. (1) and which has uneven steps as shown in FIGS. 5 and 6. In addition, the backscattered electron signal (5) obtained by scanning (deflecting) the incident electron beam (4) is detected by the detector (6). That is, this reference mark (3)
The position of the stage is measured from the backscattered electron signal (5) obtained from the above, and the deflection distortion at the time of electron beam deflection necessary in the actual exposure is calibrated. The beam size was detected and the beam size was calibrated. However, when these calibration reference marks (3) are used, the reflected electron signal (5) from the stepped portion is used.
Since the backscattered electron signal (5) ratio (S / N ratio) from the flat portion is low, the accuracy of stage position detection, beam size detection, etc. is low, and there is a drawback that the accuracy of the apparatus calibration is deteriorated.

[0003]

FIG. 5 and FIG. 6 show the structure of an apparatus calibration reference mark used in a conventional electron beam exposure apparatus. In the case of the reference mark structure for device calibration shown in FIG. 5, since the material of the step portion (projection portion) (7) and the flat portion (8) are the same heavy metals such as W and Ta (9), the flat portion (8 The reflected electron signal (5) from () is detected to the same extent as the signal (5) of the stepped portion (7), the peak value of the first-order differential waveform (10) of the reflected electron signal (5) is low, and the flat portion ( Since the reflected electron signal (5) from 8) becomes background noise, the S / N ratio becomes low.

The reference mark structure for device calibration as shown in FIG. 6 is known as a method for avoiding a decrease in peak value which is a defect of the mark structure shown in FIG. This is known as a reference mark for detecting an exposure position at the time of actual exposure, which is not for device calibration but is described in Japanese Patent Application Laid-Open No. 62-1011, "Method for Manufacturing Integrated Element". However, Si, Al different from the stepped portion (7) which is a heavy metal (9) such as W or Ta
Since the light element (11) such as is used for the flat portion (8), the peak value intensity of the first-order differential waveform (10) is improved, but the reflected electron signal (5) from the flat portion (8) is shown in FIG. Since it is detected as background noise as in the case of the mark structure, a significant improvement in the S / N ratio cannot be expected.

[0005]

In order to solve the above problems, the present invention exposes a resist film, which is provided on a semiconductor substrate or a thin film and absorbs and reacts with electron beam energy, with an electron beam, When calibrating the electron beam exposure apparatus that forms a pattern of, the underlying substrate of a light element, which enables highly accurate calibration, is covered with a thin film of heavy metal, and a structure with the same heavy metal step is provided. A reference mark for calibrating a device, a light element base substrate is Si or Al, and a heavy metal thin film is W or Ta.
In addition, the apparatus calibration method is characterized in that the apparatus calibration of the electron beam exposure apparatus is performed using the calibration reference mark.

[0006]

In the present invention, the apparatus calibration reference mark structure of the electron beam exposure apparatus is characterized in that a light element base substrate is covered with an optimal heavy metal thin film and further has the same heavy metal step. That is, by covering the flat portion with a heavy metal film that is the same material as the step portion having the optimum film thickness, the reflected electron signal from the flat portion that causes background noise is reduced, It is possible to improve the S / N ratio.

[0007]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows the structure of an apparatus calibration reference mark that is an embodiment of the present invention. When calibrating the device, incident electrons (4) are scanned (deflected) in the X-axis direction shown in FIG. 1, a reflected electron signal (5) is detected by a detector (6), and this reflected electron signal ( 5) The position of the center of the step is detected from the peak value of the first-order differential waveform (10), and the beam size is detected from the peak value. Then, based on these, the deflection distortion during electron beam scanning (deflection) and the beam size of the incident electron beam (4) are quantified to calibrate the electron beam exposure apparatus.

In the present invention, a thin film of W, Ta, etc. (9), which is the same heavy metal as the step (7), is formed on the flat part (8) on the base substrate (11) which is a light element such as Si, Al. The incident electron (4) is transmitted through the heavy metal thin film (9) and is injected into the base substrate (11) which is a light element by forming the film with an optimum film thickness (about 0.5 to 1.0 μm). The incident electrons (4) injected into the base substrate (11) are scattered inside the base substrate (11) and also at the interface with the heavy metal thin film (9), and the incident energy disappears. Therefore, the backscattered electron signal (5) re-entered the heavy metal thin film (9) and detected from the surface of the flat portion (8) almost disappears.

That is, the reflected electron signal (5) from the flat portion (8) which causes the background noise can be reduced, and the S / N ratio can be improved. That is, by using the calibration reference mark having this structure, accurate device calibration can be performed. here,
The optimum film thickness of the heavy metal thin film (9) is determined by the acceleration voltage of the incident electrons (4), the film density of the heavy metal thin film (9), and the like. For example, the acceleration voltage of the incident electrons (4) is 50
kV, and when W is used for the heavy metal film (9), the maximum range of the incident electrons (4) into W is about 3.0 μm, and the incident electrons (4) to the bulk material are Since the stationary probability distribution is usually expressed as a Gaussian distribution, the optimum film thickness is about 1
When it is set to 0.6 μm which is / 5, about 90% or more of electrons pass through the W film (9).

Next, a manufacturing process of the apparatus calibration reference mark according to the present invention will be described. 2 and 3 show an example of the production flow of the reference mark for device calibration. In FIG. 2 (a),
A heavy metal such as W or Ta (9) is formed on a substrate (11) such as Si or Al which is a light element by CVD or a sputtering method.
The film is formed with a sufficient film thickness. Next, etching is performed as shown in FIG. 2B using a resist or a mask of SiO ₂ or the like (12). At this time, as shown in FIG. 2C, it is necessary to leave a heavy metal film having an optimum film thickness on the flat portion. Although the heavy metal has been described as W and Ta, other heavy metals may be used, and naturally, Mo and Cr may be used.

In the manufacturing example of FIG. 3, first, as shown in FIG. 3A, a heavy metal (9) is first formed with an optimum film thickness on a base substrate (11) which is a light element by CVD or sputtering. To do.
Next, a film of SiO ₂ or Si ₃ N ₄ etc. (13) is formed as shown in FIG.
A film is formed and etched as shown in FIG. Finally, as shown in FIG. 3C, the heavy metal (9) is embedded by selective CVD, sputtering, etc., and finally SiO ₂ , Si ₃ N
₄ Remove the film (13).

[0012]

As described above, according to the present invention,
Equipment calibration reference mark By coating the flat part with a heavy metal film with an optimal film thickness similar to that of the step part, the reflected electron signal from the step part and the reflection from the flat part can be achieved without reducing the intensity of the reflected signal. It has an effect of greatly improving the electron signal ratio (S / N ratio), and as a result, improves the position measurement accuracy and beam size detection accuracy by electron beam scanning (deflection), which are necessary when calibrating the electron beam exposure apparatus. Can be done. That is, by using this calibration reference mark, it is possible to calibrate the electron beam exposure apparatus with high accuracy.

[Brief description of drawings]

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

FIG. 2 is a flowchart for explaining a calibration reference mark manufacturing process of the present invention.

FIG. 3 is a flowchart for explaining a calibration reference mark manufacturing process of the present invention.

FIG. 4 is an explanatory diagram of a device calibration method for explaining a conventional example.

FIG. 5 is a diagram illustrating a conventional example.

FIG. 6 is a diagram illustrating a conventional example.

[Explanation of symbols]

1 wafer, reticle, etc. 2 stage 3 device calibration reference mark 4 incident electron 5 reflected electron signal 6 detector 7 step of calibration reference mark 8 flat part of calibration reference mark 9 heavy metal such as W, Ta 10 reflected electron signal (5) First-order differential waveform 11 Light element substrate such as Si and Al 12 SiO ₂ , mask such as resist 13 SiO ₂ and mask such as Si ₃ N ₄

Claims (4)

[Claims] 1. A method for exposing a resist film, which is provided on a semiconductor substrate or a thin film and absorbs and reacts with electron beam energy, with an electron beam to expose a resist film to form a desired pattern. A reference mark for device calibration, which is characterized by a structure in which an undersubstrate of a light element that enables accurate calibration is covered with a thin film of heavy metal and further has a step of the same heavy metal. 2. The reference mark for device calibration according to claim 1, wherein the base substrate of the light element is Si or Al. 3. The reference mark for device calibration according to claim 1, wherein the heavy metal thin film is W or Ta. 4. An apparatus calibration method, which comprises calibrating an electron beam exposure apparatus using the calibration reference mark according to claim 1. Description: