JPS5833837A - Structure for charge beam location detecting mark - Google Patents

Abstract

PURPOSE:To prevent charging on detection mark by promoting diffusion of charges on the mark forming region by making the mark conductive and also by providing a conductive route on the substrate so that charges can escape from the marked portion. CONSTITUTION:The substrate 1 is of the semi-insulated gallium-arsenic substrate, while the resist 2 is provided as the electron beam resist and the electron beam ?is used as the beam for scanning 4. An impurity element is introduced to the substrate 1 and thereby the conductive region 6 of mark on which the conductive layer consisting of a low resistance layer is provided. When the location detecting mark 3 is scanned by the charge beam 4, the charges injected into the area near the mark of substrate is diffused from such area through the conductive route, not giving influence on the scanning beam.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention prevents charging of a position detection mark used to correct the irradiation position of a charged beam in pattern formation using charged particles such as electron beam exposure used in the manufacturing process of semiconductor devices. The present invention relates to a method for improving pattern formation accuracy.

In pattern formation using charged particles, generally, charged particles are irradiated onto desired positions of a resist film coated on a substrate on which a pattern is to be formed, and only the charged particle irradiated portions of the resist film are left behind through development processing, or are dissolved. The resist pattern is removed to leave an unirradiated area, and then the substrate is etched using the resist pattern as a mask to form a pattern. In order to accurately irradiate the desired area with charged particles, a position detection mark for the charged beam with a concave, convex, or V-shaped cross section is formed in advance on the substrate (usually formed by photolithography), and the signal is detected from the position detection mark. The beam position is corrected by In this case, the board is insulating (or high resistance)
In this case, it is difficult for the charge irradiated on the substrate to escape, and when a pre-formed position detection mark is scanned with a charged particle, the charge accumulates near the mark and bends the particle beam, resulting in incorrect position information. However, there was a drawback that it was easy for the drawing position to shift.

FIG. 1 is a perspective view showing an example of the configuration of a conventional position detection mark. In the figure, 1 is the substrate, 2 is the resist, 3
4 is a position detection mark, 4 is a scanning beam, and 5 is an arrow indicating an example of a scanning direction.

In the example shown in FIG. 1, the substrate 1 is semi-insulating gallium arsenide (
The resistivity is 107Ω・cm), and the position detection mark 3 is a 0.6 μm deep sea formed on the gallium arsenide substrate 1, and the position is determined by scanning the groove with an electron beam (scanning beam 4). Detect. After the position detection is completed, electron irradiation is performed to form a desired pattern at a desired position.

Figure 2 is a graph showing the positional deviation results (based on actual measurements) of drawing using detection marks in the conventional configuration, where the horizontal axis is the deviation (μm) of the pattern position from the desired position, and the vertical axis is the frequency. . The right side of the scale shows the deviation in the X direction, and the left side shows the deviation in the Y direction.

As is clear from the figure, the shift caused by the aforementioned charging occurs.

In order to eliminate the above-mentioned drawbacks, the present invention prevents the detection mark from being charged, makes the mark conductive, and promotes the diffusion of charges in the mark formation area so that accurate position information can be obtained by position detection. Moreover, a conductive path is provided on the substrate so that the electric charge can escape from the mark part.

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 3 is a perspective view showing an embodiment of the position detection mark of the present invention. The substrate 1 is made of semi-insulating gallium arsenide (GaA
s) The substrate and resist 2 are electron beam resists, and the scanning beam 4 is an electron beam.

6 is a portion (conductive region of the mark) where an impurity element is introduced into the substrate 1 and a conductive layer (low resistance layer) is formed. In this example, Si was used as an impurity element and was implanted into the substrate by ion implantation to form an n-type conductive layer. To give an example of Si ion implantation, the accelerating voltage is 1.00 kV and 60 kV.
It is carried out in two stages of kV, and both doses are I
X 1013/ciff, and the implantation depth is 0.2 to 0.
．． It was 3 μm.

Note that the impurity element introduced into the GaAs substrate is Si.
Not limited to D, S, Se, Sn, Te, Be,
Examples include Mg, Zn, and Cd, and they may be introduced not only by ion implantation but also by diffusion.

Also, instead of forming an n-type (or n-type) conductive layer, T
i, AI! A similar effect, that is, the effect of promoting charge diffusion in the mark forming region, can be obtained by depositing a thin layer of a metal such as , W, Pt, or Mo or a low resistance semiconductor such as polycrystalline Si on the surface.

FIG. 4 shows another embodiment of the present invention, and is a plan view of the structure of the position detection mark. In the figure, 7 is a conductive path for diffusing charges, 8 is a region for exposing a desired pattern, 3A, 3B, and 3C are three sets of detection marks on a certain chip; 3'A, 3'B .

3'C indicates a detection mark on the chip on the right side in the figure.

Position detection marks 3 (3A, 3B) using charged beams.

3C), the charge injected into the vicinity of the mark on the substrate diffuses from the vicinity of the mark through the conductive path 7 and no longer affects the scanning beam.

The method of forming the conductive region 6 and the conductive path 7 of the mark in this embodiment is the same as that described with reference to FIG.

Note that if the insulation of the substrate 1 is good and the accumulation of charge is significant, it is desirable that one end of the conductive path 7 be grounded.

FIG. 5 is a graph showing the result of positional deviation in drawing using the detection mark configuration of the present invention, where the horizontal axis is the deviation (μm) and the vertical axis is the frequency. X direction on the right side of the scale, Y direction on the left side
Indicates a shift in direction.

The experimental results are for the configuration shown in FIG.
Line width 1 to 0 with an exposure of about 3 x 10-' Coulomb shoulder
．． A pattern of 5 μm was drawn, and the deviation of the drawing position from the desired position was measured. The amount of deviation is kept extremely small compared to the case of a substrate in which the conductive treatment in the vicinity of the detection mark is not performed (see FIG. 2).

As explained above, if the method for configuring a position detection marker of the present invention is used, a region of low resistance can be selectively formed in a part of a substrate in position detection on a substrate using charged particles such as an electron beam. By doing so, it is possible to prevent the detection mark from being charged and to reduce the deviation of the drawing position. This method is extremely effective in directly writing patterns with a charged beam on substrates that are easily charged, such as semi-insulating gallium arsenide.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an example of the configuration of a conventional position detection mark, Fig. 2 is a graph showing the positional deviation results of drawing by the conventional detection mark, and Figs. 3 and 4 respectively. FIG. 5 is a perspective view and a plan view showing the structure of the position detecting mark of the present invention, and a graph showing the result of positional deviation in drawing by the detecting mark structure of the present invention. 1...Substrate 2-...Resist 3...
Mark for position detection 4...Scanning beam 5...Arrow indicating an example of scanning direction 6...Conductive area of mark 8...Pattern exposure area Patent applicant Junnosuke Nakamura, Patent attorney for Nippon Telegraph and Telephone Public Corporation

Claims (2)

[Claims] (1) A step of forming a position detection mark for a charged beam at a predetermined position on a substrate where a pattern is to be formed, and ionizing a selected impurity element to the substrate so as to reduce the resistance of the substrate near the position detection mark forming area. The above-mentioned position detection mark includes a step of introducing a low resistance layer into the substrate by an injection method or a diffusion method and selectively forming a low resistance layer near the surface, or a step of selectively forming a thin layer of metal or a low resistance semiconductor on the surface of the substrate. A method for configuring a position detection mark for a charged beam, characterized in that a means for promoting the diffusion of charges in a formation region is provided. (2) The method for configuring a position detection mark for a charged beam as set forth in claim 1, wherein a conductive path is formed by connecting to the position detection mark area as a means for promoting the diffusion of the charges.