JPH0529204A - Electron beam correction mark - Google Patents

Abstract

PURPOSE:To accurately detect the position and the configuration of a beam by a method wherein the title mark is made of the material having the electron reflectivity different from that of a substrate, and the stepping between the upper surface of the substrate and the mark is formed less than 1mum. CONSTITUTION:In the example (a) mentioned separately, the stepping on a substrate 1 is made small by thinning a mark 2 itself in the amount of 0.05mum, for example. In the example (b), the stepping is eliminated by providing a mark 3, having the ordinary thickness (0.5mum, for example) in the form wherein the recessed part provided on the substrate 1 is filled up. In the example (c), the stepping is eliminated by providing the mark 3, having the ordinary thickness, in the recessed part which is a little larger than the above-mentioned recessed part. Two narrow grooves are formed on the circumference (at least on the part where a beam is scanned) of the mark. As the symmetrization of waveform of the mark detection signal in the above-mentioned three examples is excellent, a highly precise correction can be made possible, and this contributes to the ultramicroscopic formation of the pattern of a semiconductor device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mark structure for correcting the position and shape of an electron beam in an electron beam writing apparatus.

In recent years, semiconductor devices have been made finer in pattern in response to the demand for higher integration and higher density, and it is certain that this tendency will continue in the future. Electron beam lithography technology has already been put to practical use as a technology for forming a fine pattern. When drawing a pattern with an electron beam,
By reading the reference mark provided on the sample surface with the electron beam for exposure, the deflection distortion and drift of the beam are corrected, and the stitching of figures across fields is controlled to maintain the pattern accuracy. There is. Therefore,
In order to draw a finer pattern in the future with high accuracy, it is necessary to improve the mark reading accuracy.

[0003]

2. Description of the Related Art An example of a conventional electron beam correction mark will be described with reference to FIG. 3A and 3B are explanatory views of a conventional example, FIG. 3A is a schematic sectional view, and FIGS. 3B and 3C are diagrams showing the waveform of a mark detection signal. In FIG. 3 (a), 1 is a substrate (silicon wafer, etc.) on which a pattern is drawn, and 3 is a mark. The mark 3 is made of a material having a much higher electron reflectance than the substrate 1, for example, a heavy metal such as gold, and has a thickness of 0.5.
It is about μm.

An electron beam for exposure is irradiated from above the mark 3 to scan the mark 3 and its vicinity, and the reflected electrons are detected by a detector (for example, a PN junction type). On this occasion,
It is inevitable that the electron beam irradiates the mark 3 slightly obliquely. 3B and 3C show waveforms of signals obtained by irradiating the mark 3 with the electron beam vertically and obliquely, respectively. The waveform is symmetric in (b), but asymmetric in (c).

[0005]

When the waveform of the mark detection signal has asymmetry as described above, there is a problem in that an error occurs in the detection of the beam position / shape, and therefore the correction cannot be performed accurately.

An object of the present invention is to solve the above problems and provide an electron beam correction mark capable of accurately detecting the beam position and shape.

[0007]

According to the present invention, the object is [1] a mark made of a material having an electron reflectance different from that of a substrate material, and a step between the mark upper surface and the substrate upper surface is zero. An electron beam correction mark characterized by having a thickness of 0.1 μm or less. [2] An electron according to [1], which is mounted on the upper surface of the substrate and has a thickness of 0.1 μm or less. By using the beam correction mark, [3] the mark material fills the entire recess provided on the substrate surface.
By using the electron beam correction mark described in [1], [4]
This is achieved by using the electron beam correction mark according to [1], characterized in that it is arranged so as to form narrow grooves on both sides in a recess provided on the surface of the substrate.

[0008]

The degree of asymmetry of the waveform of the mark detection signal due to the oblique irradiation of the electron beam becomes smaller as the level difference between the upper surface of the substrate and the upper surface of the mark becomes smaller. Therefore, the smaller the step, the more accurate the beam position / shape can be corrected. As means for eliminating this step, even if the thickness of the mark is thin, or as a dug structure in which a thick mark is sunk in a recess provided in the substrate,
The same effect occurs.

The mark position detection accuracy is required to be about 1/10 of the minimum line width of the pattern to be drawn.
If the step between the upper surface of the substrate and the upper surface of the mark is 0.1 μm or less,
Sufficient detection accuracy can be obtained even for pattern miniaturization expected in the future.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an electron beam correction mark according to the present invention will be described with reference to FIG. FIG. 1 is an explanatory view of an embodiment of the present invention, in which (a), (b) and (c) are schematic sectional views of the first example, the second example and the third example, respectively (aa) and (bb). , (cc) are diagrams showing the waveforms of the mark detection signals of the first example, the second example, and the third example (however, in the case of oblique irradiation). In the figure, 1 is a substrate such as a silicon wafer, and 2 and 3 are marks made of heavy metal such as gold.

FIG. 1 (a) shows a first embodiment of the present invention,
By making the mark 2 itself thin (for example, 0.05 μm), the step difference with the substrate 1 is made small. The waveform of the mark detection signal when the mark 2 is obliquely irradiated with an electron beam is
The symmetry is good as shown in Fig. 1 (aa).

Generally, when the thickness of the mark 2 made of heavy metal is reduced, the intensity of the reflected electrons is reduced. However, according to the experimental result of the present inventor, if the thickness of the mark 2 is not extremely thin,
It was confirmed that the mark signal was sufficiently detected. The results of this experiment are shown in FIG. FIG. 2 is a graph showing the relationship between the mark thickness and the detection signal strength. In the figure, a gold mark on a silicon substrate is irradiated with an electron beam with an acceleration voltage of 30 KeV,
The backscattered electrons are detected by a PN junction type detector. According to the figure, the detection signal intensity is about 40% of the maximum value even when the mark thickness is 0.05 μm, and it is detected even below that.

FIG. 1 (b) shows a second embodiment of the present invention,
The mark 3 having a normal thickness (for example, 0.5 μm) is formed on the substrate 1
It is provided in such a manner that the recess provided in the above is filled to eliminate the step. In order to obtain such marks 3, anisotropic dry etching is performed on the substrate 1 using the patterned resist on the substrate 1 as an etching mask to form recesses, and then the recesses are filled with a mask material by a lift-off method. do it. The waveform of the mark detection signal when the mark 3 is obliquely irradiated with the electron beam has good symmetry as shown in FIG. 1 (bb).

FIG. 1 (c) shows a third embodiment of the present invention,
A mark 3 having a normal thickness (for example, 0.5 μm) is provided in a recess slightly larger than the mark 3 provided on the substrate 1 to eliminate a step. A thin groove 4 is formed around the mark 3 (at least the side where the beam is scanned).
In order to obtain such a mark 3, a resist patterned on the substrate 1 is used as an etching mask, isotropic etching is performed to such an extent that the underside of the resist is undercut to form a concave portion, and then the lift-off method is used to form the concave portion. A mask material may be deposited in the recess. The waveform of the mark detection signal when the mark 3 is obliquely irradiated with an electron beam has good symmetry as shown in FIG. 1 (cc).

As described above, since the waveforms of the mark detection signals have good symmetry in all three examples, highly accurate correction is possible. The present invention is not limited to the above embodiments, and can be implemented with various modifications.

[0016]

As described above, according to the present invention,
It is possible to provide an electron beam correction mark capable of accurately detecting the beam position and shape, which contributes to miniaturization of the pattern of the semiconductor device.

[Brief description of drawings]

FIG. 1 is an explanatory view of an embodiment of the present invention, in which (a), (b),
(c) is a schematic sectional view of the first example, the second example, and the third example,
(aa), (bb), (cc) are diagrams showing the waveforms of the mark detection signals of the first example, the second example, and the third example (however, in the case of oblique irradiation).

FIG. 2 is a graph showing the relationship between mark thickness and detection signal intensity.

FIG. 3 is an explanatory view of a conventional example, (a) is a schematic sectional view,
(b), (c) is a diagram showing a waveform of a mark detection signal.

[Explanation of symbols]

1 substrate A few marks 4 narrow groove

Claims (4)

[Claims] 1. A mark for electron beam correction, wherein the substrate material is a mark made of a material having a different electron reflectivity, and a step between the mark upper surface and the substrate upper surface is 0.1 μm or less. 2. The electron beam correction mark according to claim 1, which is mounted on the upper surface of the substrate and has a thickness of 0.1 μm or less. 3. The electron beam correcting mark according to claim 1, wherein the entire concave portion provided on the surface of the substrate is filled with the mark material. 4. The electron beam correction mark according to claim 1, wherein the recess is provided on the surface of the substrate and is provided so as to form fine grooves on both sides.