JPH0782987B2 - Electron beam writer - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam drawing apparatus, and more particularly, to easily detect a registration mark on a wafer when it is difficult to detect it with an electron beam. The present invention relates to means for accurately determining a drawing position.

[Conventional technology]

In the electron beam drawing apparatus, a mark formed as unevenness on the wafer surface or as a combined portion of dissimilar metals is scanned with an electron beam, a change in the amount of reflected electrons is detected, and the drawing position is determined.

As an example of this type of conventional technology, Miyauchi, Yuasa “Electronic exposure apparatus and its application” (“Electronics”, Showa 42
December, pp1364-1372).

[Problems to be Solved by the Invention]

The detection method using the electron beam is effective when the mark on the wafer is exposed, but when the semiconductor surface is flattened or the resist film becomes extremely thick, the electron beam scanning method is used. It may be difficult to detect the mark position by.

In order to solve this problem, a method has been proposed, such as Japanese Utility Model Laid-Open No. 56-29953, which uses a mark that can be detected by optical means.

In this conventional technique, the mark used for the optical transfer method so-called stepper is diverted without forming the mark for the electron beam on the wafer, and the optical detection capable of detecting the stepper mark in the electron beam drawing apparatus. Add a new system,
Marks are detected for matching drawing. That is, it is premised that the mark detection is always performed by the optical system, and the alignment of the coordinate axes of the optical system and the electronic drawing system is discussed.

However, if the mark is always detected by the optical system in this way, even if the mark can be clearly read by the electron beam, the stage must be moved to the reading position by the optical system and then moved to the drawing position by the electron beam. It will be. To this extra stage movement time, the detection time of the optical system, which is generally 100 ms or more, and a certain amount of time required for switching between the optical detection system and the electronic drawing system are added, and the recent demand for high-speed drawing There was a problem that there was a case that could not be met.

[Means for Solving the Problems]

In order to achieve the above object, the present invention provides an electron beam deflection system for changing an electron beam irradiation position, a stage drive system for moving a stage on which a wafer is mounted, and a reflection electron from an electron beam irradiation object. In an electron beam drawing apparatus including an electron beam position detection system for detecting the position of an object by means of a laser interferometer and a laser interferometer for detecting the position of the stage, it is possible to detect the position of either the electron beam or the light on the stage surface. A standard mark is provided, and an optical position detection system for detecting the standard mark position and the mark position on the wafer by light is provided, and the standard mark position detection value by the electron beam and the standard mark position detection value by the light are drawn before writing. The difference is calculated and stored, and when the mark position on the wafer can be detected by the electron beam, the stage is driven based on the value to draw and Proposes a electron beam lithography system provided with means for driving the stage drawing on the basis of said difference which has been stored mark position on the detected wafer by light only when undetectable by the beam.

[Action]

In the surface treatment process of a semiconductor wafer, even if it is difficult to detect a mark by scanning with an electron beam, when light is used, the mark position may be easily detected due to a phenomenon such as coloring or polarization.

Therefore, in the present invention, a standard mark, such as gold deposited in advance on a silicon wafer, which can be easily detected by any means of light and electron beam, is formed on the stage, and the standard mark is used. The difference between the standard mark position detection values of the optical method and the electron beam method is obtained. Next, the mark on the wafer is detected by the electronic method, and if it can be detected normally, the stage is driven based on the value and the circuit pattern is drawn at the desired position on the wafer, making it difficult to detect by the electronic method. Only in such a case, if the mark position on the wafer is determined by the optical method, the stored difference is corrected, and the mark is written, the mark can be detected with high accuracy and the mark can be drawn at high speed.

In the above prior art, since the mark detection is always performed by the optical system, even if the mark position can be clearly read by the electron beam, the stage must be moved to the reading position by the optical system, and then the writing by the electron beam is performed. Had been moved to the position. To this extra stage movement time, an optical system detection time of 100 ms or more and a certain amount of time required to switch between the optical detection system and the electronic drawing system are added to meet the recent demand for high-speed drawing. As mentioned above, there are cases where there is no such case.

On the other hand, in the present invention, in general, when the mark position detection of the electron beam method, which is completed generally in 20 ms or less, is normally performed, the operation directly shifts to electronic drawing, and detection by the electron beam is difficult. Only in this case, the process moves to the detection of the mark position by the light, which takes a relatively long time, so that it is possible to satisfy both the requirements for highly accurate and reliable mark position detection and high-speed drawing.

〔Example〕

 Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an embodiment of an electron beam drawing apparatus according to the present invention. In the figure, 1 is an electron gun, 2 is an electron lens for obtaining a desired electron beam shape and current density,
3 is a deflector for deflecting the electron beam, 4 is a reflection electron detector for detecting electrons from an object irradiated with the electron beam, 5 is a light source of an optical mark position detection system, and 6 is this reflection light. An image sensor for detecting, 7 is a standard mark provided on the stage and well reflecting both light and electron beam, 8 is a laser mirror for detecting the stage position, 9 is a stage drive system including a servo mechanism for driving the stage 10, 11 is A light source of a laser interferometer, which precisely measures the position of the stage 10 in units of 0.01 μm using the laser mirror 8, 12 is its light receiver,
Reference numeral 13 denotes a stage control circuit that gives a drive instruction to the stage drive system 9 based on the length measurement result, and 14 gives a deflection instruction of an electron beam to the deflector 3 via a deflection control circuit 15.
A CPU that calculates the stage and wafer positions based on signals from the electron beam type position detection circuit 16 and the optical type position detection circuit 17 and sends them to the stage control circuit, 18 is a wafer mounted on the stage 10, and 19 is an actual drawing It is a mark formed on the wafer 18 which serves as a reference reference for determining the position.

FIG. 2 is a diagram showing an example of the arrangement of standard marks and marks to be detected by the electron beam method and the optical method. The laser mirror 8 is installed in both the X and Y axis directions of the stage 10, and the standard mark 7 is provided between the laser mirror 8 and the wafer 18 mounting area. The mark 19 is provided on the wafer 18 near the circuit pattern to be drawn.

FIG. 3 is a view showing standard mark position detection by an electronic method. When the standard mark 7 that sufficiently reflects both light and electrons on the stage 10 (for example, made of Au on Si) is scanned with an electron beam, the reflected electron detector 4 shows the same as in FIG.
A backscattered electron signal such as Appropriate threshold E _TH
Is set and the standard mark symbols P ₁ and P ₂ are loaded. If the average value (P ₁ + P ₂ ) / 2 = Pe of these values is defined as the beam deflection amount from the electron beam deflection amount 0 position Pφe, the distance Le from the origin position of the stage drive to the position Pφe is the laser interferometer. Therefore, the standard mark position Me obtained by the electron beam method is Me = Le + Pe (1).

FIG. 4 is a diagram showing standard mark position detection by the optical method. The light from the light source 5 is applied to the periphery of the standard mark 7 by the lens 20, and is imaged on the image sensor 6 by the lens 21.
The image sensor 6 has a dot matrix as shown in FIG. _4B, and detects the amount of deviation P _OPt from the center position Pφ _OPt . As a detection method using light,
In addition to this, a method of scanning and detecting light using a mirror,
There is a method of detecting the polarized component and the scattered component of the reflected light.
Since L _OPt to the center position P.PHI _OPt the image sensor 6 can be measured by a laser gauge interferometer, standard mark position M _OPt obtained by the optical _{system, M OPt = L OPt + P} OPt (2) mark detected in the electron beam system FIG. 5 shows an example of an object which is difficult to detect but can be easily detected by an optical method. When a mark as shown in FIG. 5 (a) is scanned by an electron beam, the obtained signal waveform is extremely weak as shown in FIG. 5 (b).
On the other hand, when detecting the reflected light by the optical method, the refractive index of the resist and the oxide film is usually equal to about 1.5, and as shown in (c),
Since interference occurs, an extremely remarkable mark waveform is obtained as shown in (d).

In this way, the mark 19 that is difficult to detect with the electron beam method
Is detected by the optical method, the difference M _OPt −Me of the above equations (1) and (2) for the standard mark 7 is stored in the CPU 14, etc., and the position m _OPt of the mark 19 detected by the light is stored. On the other hand, the calculation of me = m _OPt − (M _OPt −Me) (3) is executed, and me is set to the position of the mark 19. When actually writing, the electron beam is deflected with reference to the position of the mark 19.

However, in the present embodiment, it is already possible to switch to the optical method only when it is difficult to detect the mark by the electron beam method in the normal state and it is difficult to detect the mark by the electron beam method. As stated.

The drawing process will be described with reference to FIG. First, the position e of the standard mark 7 is detected by the electron beam method. Next, the stage is moved and the position M _OPt of the standard mark 7 is moved by the optical method.
To detect. The difference between these positions, M _OPt −Me, is _calculated by, for example, CPU1.
Remember in 4. Further, the stage is moved to detect the position me of the mark 19 by the electron beam method. As a result, when the detection is normally performed, the stage movement amount necessary for actual drawing is calculated, the stage is moved to the drawing position, and drawing is executed. On the other hand, the stage is moved only when the detection cannot be made by the electron beam method and the mark is made by the optical method.
Detect position 19 m _OPt . Using the value, the stage movement amount is calculated by the equation (3). The stage is moved to the position thus obtained, and drawing is executed. The procedure after the detection of the mark me by the electron beam method is repeated until all the drawing on the wafer is completed.

〔The invention's effect〕

According to the present invention, the mark position is usually detected by the electron beam method, and only when it is difficult to detect the mark by the electron beam method, the optical system is switched to a relatively time-consuming optical method. An electron beam drawing apparatus that satisfies both the position detection and the demand for high-speed drawing can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of an electron beam drawing apparatus according to the present invention, FIG. 2 is a diagram showing an example of standard marks to be detected by an electron beam and light, and an example of arrangement of the marks, and FIG. FIG. 4 is a diagram showing a standard mark position detection method of a beam system, FIG. 4 is a diagram showing a standard mark position detection method of an optical system, FIG.
FIG. 6 is a diagram showing an example of a mark that can be easily detected by light even if it is difficult to detect with an electron beam, and FIG. 6 is a flow chart showing a process of electron beam drawing by the apparatus of the present invention. 1 ... electron gun, 2 ... electron lens, 3 ... deflector, 4 ...
… Reflected electron detector, 5 …… Light source, 6 …… Image sensor, 7 …… Standard mark, 8 …… Leather mirror, 9 …… Stage drive system, 10 …… Stage, 11,12 …… Laser interferometer , 13 …… Stage control circuit, 14 …… CPU, 15 ……
Deflection control circuit, 16 ... Electron beam mark position detection circuit, 17 ... Light position detection circuit, 18 ... Wafer, 19
……mark.

Claims (1)

[Claims] 1. An electron beam deflection system for changing an electron beam irradiation position, a stage drive system for moving a stage on which a wafer is mounted, and a position of an object is detected by reflected electrons from the electron beam irradiation object. In an electron beam drawing apparatus including an electron beam position detection system and a laser interferometer that detects the position of the stage, a standard mark that can detect the position of either the electron beam or light is provided on the stage surface, An optical position detection system that detects the standard mark position and the mark position on the wafer by light is provided, and the difference between the standard mark position detection value by the electron beam and the standard mark position detection value by the light is calculated and stored prior to writing. If the mark position on the wafer can be detected by the electron beam, the stage is driven based on that value to draw the image. Electron beam lithography apparatus characterized in that a means for driving the stage drawing on the basis of said difference which has been stored with the mark position on the detected wafer by light only when not out.