JPH0346320A - Exposure of fine pattern - Google Patents

Abstract

PURPOSE:To simply and surely align a beam with an optical axis by specifying data on a deflection amount which are given to a third deflection means and a fourth deflection means on the radiation side of a stencil mask. CONSTITUTION:The following are installed: a third deflection means 15c which directs a beam having passed through a mask 20 to an optical axis again; a fourth deflection means 25d which deflects the beam directed to the optical axis in such a way that the beam travels on the optical axis. Data on a deflection are given in such a way that individual deflection angles theta3, theta4 satisfy the following formulae: theta3=-theta1<s>-thetap<s>+alphatheta<b> and theta4=+theta1<s>+thetap<s>+betatheta<b> (in these formulae, theta1s is a deflection angle corresponding to D1<s>, thetap<s> is that corresponding to Dp<s> and theta<b> is that corresponding to D<b>; the deflection data D1<s> is decided by a desired position on a mask sheet through which the beam is passed; the data Dp<s>, D<b> for deflection correction use are decided by the D1<s>; alpha and beta are constants). The beam which has been patterned by the mask sheet 20 is returned again on the optical axis to execute an exposure operation. Thereby, the beam which has passed the mask can again accurately be put on the optical axis, and a fine pattern can accurately and surely be exposed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary of the Invention] Regarding a method of exposing a fine pattern using a charged particle beam, particularly a deflection method of an exposure apparatus, the third part on the output side of a stencil mask is provided. The purpose is to make the deflection amount data given to the fourth deflection means appropriate so that the beam can be easily and reliably aligned with the optical axis, and a plurality of devices that shape the cross-sectional shape of the charged particle beam. A mask plate having an aperture of and third deflection means on the output side of the mask plate for directing the beam that has passed through the mask back toward the optical axis; In a fine Bakun exposure method using an exposure apparatus having a fourth deflection means that deflects the light so as to run on the optical axis, the third and fourth deflection means each have a deflection angle θ1. θ4 is the following formula, θ,=-θ--θ1+αθ5 θ4=10θ+θ1+βθゝHere, θ- becomes D-, θ1 becomes D P', θ5 becomes D1'
At a deflection angle corresponding to The beam patterned by the mask plate returns to the optical axis again by providing deflection data to perform exposure.

[Industrial application field]

The present invention relates to a method for exposing fine patterns using a charged particle beam, and particularly to a method for deflecting an exposure apparatus.

In recent years, with the increase in the density of integrated circuits, new exposure methods using charged particle beams, particularly electron beams, have been investigated in place of photolithography, which has been the mainstream method for forming fine patterns for many years.
It has come to be actually used.

[Conventional technology]

A conventional electron beam exposure apparatus is a drawing apparatus that deflects an electron beam and draws a pattern on a sample wafer based on a huge amount of pattern data. This type of device has a pattern generation function that creates a pattern (hardware) from software (pattern data), but since the exposure is so-called one-stroke writing, there is a problem that high throughput cannot be obtained. there were.

Possible methods for improving throughput include creating a variable rectangular beam, patterning using a stencil, and creating a dot pattern using a flanking aperture array.

Recent semiconductor devices that require ultra-fine patterns, such as 16 M-DRAMs, are often fine, but most of the exposed area is a repeating pattern. The stencil transfer exposure method focuses on this point, that is, in semiconductor devices formed with ultra-fine patterns, repeated portions occupy the majority of the desired exposure pattern, and extracts only the repeated pattern portions from the entire desired pattern. For the repeating pattern, separate the basic cells that form the basis of the repeating pattern and hold them on a transparent mask.
An area in which the cell is configured, a so-called basic unit unit, is irradiated with an electron beam and exposed, and other areas are exposed using a variable rectangle.

FIG. 5 shows an outline of this stencil transfer exposure apparatus. (
(a) is a partial view, (b) is an overall view, and (C) is a cross-sectional view of the stencil mask 20. The electrons emitted from the electron gun are shaped into a rectangular shape by the first rectangular aperture 14, and then deflected to the stencil mask 20 by the aperture selection deflector 25.
Any repeating basic pattern part (basic cell part) above
is irradiated. Thereafter, the patterned electrons are reduced by reduction lenses 19 and 22, and further deflected onto the wafer W by a deflection system for exposure. A variable rectangular aperture (cutting slit without a pattern) 20a is also provided on the mask 20 for a non-repeating pattern.

The pattern forming portion of the stencil mask has a stencil shape as shown in (C). The pattern portion may be formed at any position on the mask as long as it can be irradiated with electrons by the aperture selection deflector. Moreover, it is not limited to a stencil-like part made of a thin film of silicon (St), etc., but may be any basic cell made of one cell/several cells in one block on a metal plate or the like.

In this figure, 11 is a cathode, 12 is a grid, and 13 is an anode, which constitute an electron gun.

Reference numerals 15, 17, 19, 22, and 23 are lenses, 16° and 18 are deflectors, 21 is an aperture, and 24 is a stage movable in the X-Y directions. 20b.

20c, . . . are (parts of) patterns that often appear in the IC, 20e is the aperture selection deflector 2
5 is a mark pattern for adjustment. The coil marks in the figure are alignment coils, stag coils, refocus coils, etc.

[Problem to be solved by the invention]

In a stencil transfer exposure apparatus, it is desirable to be able to arrange as many different types of basic patterns as possible on a stencil mask. By beam deflection irradiation, one pattern is extracted from this pattern group.
Each pattern is selected and exposed, but when one basic pattern is selected, the basic patterns are spaced apart from each other by a distance of -window or more so that the beam does not leak from other pattern areas. need to be placed. Therefore, the beam must be able to pass through the stencil mask at a position that is significantly (2 to 3 degrees) away from the central axis. For this purpose, for example, as shown in FIGS. 6(a) and 6(b), one or more beam deflecting means 25a, 25b are arranged on the mask incident side to allow the beam to pass through a required position. (a) is one piece, and (b) is two pieces. Even with just one, the beam B can be deflected to pass through the desired position, but in this case the beam will be obliquely incident on the mask 20. If two pieces are provided as shown in (b), and one is swung by θ with one 25a and the other is returned by θ, it is possible to pass through the desired position vertically.

However, with the current X, the beam is far away from the central axis of the optical system after passing through the mask, so the image formation position on the sample surface is significantly different from when the beam passes near the central axis of the optical system. It's going to be different. Regarding this point,
It is preferable to provide a beam deflection means on the exit side of the mask to return the deviated electron beam B to the optical axis again.

In the present invention, the electron beam is deflected on the incident side of the stencil mask by the first deflection means so as to pass through a desired position of the mask, and the electron beam is deflected perpendicularly to the mask by the second deflection means. In an exposure apparatus, the beam is deflected so as to be incident on the mask, and on the mask output side, a third deflection means deflects the beam so as to return to the optical axis, and a fourth deflection means further deflects the beam so that it runs on the optical axis. , the third one on the exit side of the stencil mask. It is an object of the present invention to provide appropriate deflection amount data to the fourth deflection means so that the beam can be easily and reliably aligned with the optical axis.

[Means to solve the problem]

As shown in FIG. 1, in the present invention, deflection data Dc (=- D--DPI+αDl,) is data whose deflection angle θ3 is θ,=-θ1S-θ,$+αθb, and the fourth deflection means 25 on the output side
Deflection data given to d D d (= +D I' +D
F'10βDb) is data such that the deflection angle θ4 is θ4=+θ, 1+θP′+βθ1. Here, θ1$ is the deflection data DIs
, θ1 is the deflection angle corresponding to the same DPI, and θゝ is the deflection angle corresponding to the same Db. Deflection data D,' is determined by the desired position on the mask plate (the aperture) through which the beam passes, and data D, ", D' for deflection correction is determined by D-. Note that the subscripts s and b distinguish different types of deflection. Things (S is for shifting,
b is the initial letter of bending), and the subscript 1+
P is given to the same kind of deflection, but the latter is attached to the correction term with a subscript. α/β is a constant, and the mask 20 and the third . It is determined by the distance from the fourth deflection means.

[Effect]

Third. When the deflection data given to the fourth deflection means 25c and 25d is as described above, the beam B passing through the mask 20 is
can be moved back up the optical axis. That is, assuming that the beam B exits the mask 20 perpendicularly (parallel to the optical axis), the first deflection means 25c bends (deflects) it by θ, and the beam B is deflected by the second deflection means. By bending the beam B by the same amount θ3 in the opposite direction (θ4=θ3) at 25d, the beam B can be made parallel to the optical axis. And the third. The fourth deflection means is the first deflection means on the incident side of the mask 20. second deflection means 25a,
25b, and this axis of symmetry is symmetrical to the mask 20), the first.
When the deflection angle is set to be the same as the deflection angle θ1°θ2 of the second deflection means (θ3=θ2.θ4=θ1), the beam B returns to the beam optical axis again. θ- represents the deflection angle at which the beam is deflected (on the incident side) and returned (on the outgoing side).

If the beam exiting the mask 20 is tilted by φ from the vertical direction due to some reason such as misalignment or misalignment of the deflection coil,
Third. The fourth deflection means θ,=−θ2. θ4=10θ1$
Even if the beam is deflected by 1, the beam will not return to the optical axis. −θ, S+
αθb, +θ, and S+βθb correct this and return the beam correctly to the optical axis.

That is, when the light is incident at an angle of φ as shown in the figure, not only the angle of incidence changes, but also the position of incidence compared to the case of vertical incidence. The latter is corrected by θ and ゛, and the former is corrected by θ5, so that the beam returns to the optical axis correctly even when the incidence is oblique.

In the case of electromagnetic deflection, the deflection angle is adjusted by the current flowing through the deflection coil. Therefore, θ1. The current corresponding to θ, 3 is the third. and αθ using the known value α/β.
1. By adding a current corresponding to βθ, the beam can be easily returned to the optical axis.

The exposure device has an aperture 21, and if the beam B is not on the optical axis, it cannot pass through the aperture.
, the current in the path of the electrode on the stage 24 becomes zero. While monitoring this current, the current corresponding to θ1 is set to 1. In accordance with that of the second deflection means, θ1. αθ5. 3. While adjusting the current corresponding to βθ5. When the current is applied to the fourth deflection means, the above-mentioned current can be observed, and the current is set at θ1 so that the current reaches its peak. αθ1. By setting the current corresponding to βθ1, the beam B can be aligned on the optical axis.

θ, ゛ is the third. Since the fourth deflection means has opposite polarity, θ is the same polarity, and α/β is a constant, two-dimensional adjustment with two adjustment parameters is sufficient. Adjustment can be easily carried out by changing one of θ, 1 and θ5 to maximize the current, and then changing the other to increase its maximum value.

Beam alignment on the optical axis is one of the troublesome operations in an exposure apparatus, and it is of great practical benefit to be able to do this easily.

〔Example) The coil arrangement near the mask 20 is shown in FIG.

Focusing lenses 17a and 17b, deflection coils 25a and 25d, and 25b and 25c are arranged symmetrically with respect to the stencil mask 20. Also, the optical axis is the central axis of axial symmetry. If this arrangement is ideally established and the beam B is incident on the optical axis, the deflection coils 25a and 25b have the same size and opposite direction at a deflection angle θ1. By giving −θ y, the beam can be made to pass through a desired position off the optical axis on the mask and parallel to the optical axis, and the deflection coils 25c and 25d have the same size but opposite directions. By giving a deflection angle of −81,θ, the beam can be returned to the optical axis again.

However, in reality, due to reasons such as the fact that the optical system is not ideally configured or arranged, the beam is not always incident strictly parallel to the optical axis, but is slightly oblique as shown in Figure 3. It may also be incident. In this case, if the beam is deflected at the ideal beam deflection angle shown by the dotted line, it will not be able to cope with the positional deviation δ at the incident point and the deviation angle φ from the vertical, and the beam will not return to the optical axis on the mask exit side. Can not. Note that this problem of inappropriate deflection also occurs on the incident side of the mask 20, but in this case, the desired pattern on the mask 20 is selected.
Therefore, it is assumed that the bias up to pattern selection is appropriately corrected.

The correction for the fact that the beam B passing through the mask 20 is tilted from the optical axis is as shown in FIG.
Let us consider the case (b) in which there is no deviation from the optical axis and the angle is only φ deviated from the vertical. The correction in (a) is made by the deflection means 25c and 25d, with the same angle and opposite direction -θδ
, +θδ only. Further, the correction of 0)) can be made by setting the incident angle to φ, deflecting the beam by αφ to direct it toward the optical axis, and deflecting the beam by βφ by the deflection means 25d so that it runs on the optical axis. Deflection angle θ1 in the ideal case of Fig. 2
Combining these, the deflection means 25c and 25d can deflect as follows: θ, = -θ1 - θδ + αφ θ4 = θ1 + θδ + βφ. Of course this θ.

corresponds to θ in the above equation, θδ corresponds to θ1, and φ corresponds to θb.

The mask may be a blanking aperture array or the like in addition to a stencil mask.

Correction amount θ1. Since θ5 changes depending on the beam passing position on the mask, this correction amount is obtained in advance to the exposure equipment and stored in a memory etc., and the corresponding correction amount is adjusted according to the beam passing position (selected pattern). It is preferable to read it out and apply it to the deflection means.

〔Effect of the invention〕

As explained above, according to the present invention, the beam after passing through the mask can be correctly placed on the optical axis again, and exposure of a fine pattern can be performed accurately and reliably.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the principle of the present invention, Fig. 2 is a detailed explanatory diagram of the present invention, Figs. 3 and 4 are explanatory diagrams of the operation of Fig. 2, and Fig. 5 is an explanatory diagram of the conventional example. FIG. 6 is an explanatory diagram of the operation of FIG. 5. In FIG. 1, 20 is a mask, 25c and 26d are third and fourth deflecting means, B is a beam, and L is an optical axis.

Claims (1)

[Claims] 1. A mask plate (20) having a plurality of apertures for shaping the cross-sectional shape of the charged particle beam is provided, and on the incident side of the mask plate, the beam passes through a desired position on the mask plate. It has a first deflection means for deflecting the deflected beam from the optical axis, and a second deflection means for making the deflected beam parallel to the optical axis. a third deflection means (25c) for directing the beam toward the optical axis again; and a fourth deflection means (25c) for deflecting the beam directed toward the optical axis so that it runs on the optical axis.
25d), the third and fourth deflection means each have a deflection angle θ_3θ_
Deflection data D_l^s, D_ so that 4 becomes the following formula
A fine pattern exposure method characterized by applying p^sD^b so that a beam patterned by a mask plate returns to the optical axis and performs exposure. θ_3=-θ_l^s-θ_p^s+αθ^bθ_4=
θ_l^s + θ_p^s + βθ^b Here, θ_l^s is D_l^s, θ_p^s is D_p^s, and θ^b is D
At the deflection angle corresponding to ^b, the deflection data D_l^s is determined by the desired position on the mask plate through which the beam passes, the data for deflection correction D_p^s and D^b are determined by D_l^s, and α/β is constant.