JPH04204737A - Mask and projection exposure device and pattern forming method - Google Patents

Abstract

PURPOSE:To obtain sufficient resolution and the depth of a focus in the case of a solid element pattern by using a phase shift mask and a multiple image- forming exposure method, and forming plural images of mask patterns at different positions in the optical axis direction. CONSTITUTION:The phase shift masks are used and the multiple image-forming exposure method is operated especially, under highly coherent illumination, and the distance between the same phase patterns opposite to each other across a light-shielding part is set to a prescribed distance or more in accordance with a space coherency and whether the multiple image-forming exposure method is applied or not. The illumination light to be used has high coherency in the repeated directions of the repeated patterns and comparatively low coherency in the directions perpendicular to the above directions. The form of an effective light source in the face of a secondary light source of a reduction projection exposure device is set to a small one in the repeated directions of the repeated patterns and to a large one in the direction perpendicular to the above directions, thus permitting sufficient resolution and the sufficient depth of the focus to be obtained.

Description

[Detailed Description of the Invention] [Industry [, Benefits JIS Field 1] The present invention is applicable to various [) ■: For the formation of a fine pattern of body and substance (1) Pattern formation method using reduction projection method , and the mask used for this, the projection fi world, and the mounting.

[Prior Art] In order to improve the degree of integration and the speed of movement of a solid element f- such as 7SI, the minute i of the path pattern is MA.

Currently, the reduction projection exposure method, which is excellent in mass production and resolution performance, is widely used for forming these patterns1.The resolution of this method is proportional to the exposure wavelength G, and the projection edge Opening 1
] It is inversely proportional to the number (NA). Traditionally, the resolution limit has been improved by increasing the numerical aperture (iglNA) (51), but these methods only reduce the depth of focus. 4 ÷ Approaching the limit due to trouble in the technique -, ) There are.

On the other hand, in the conventional reduction projection exposure method, the resolution [I
A phase shift method has been proposed as a method for further increasing W. This method uses adjacent open [-] descendants:.

The ability to invert the phases of the light passing through each other greatly improves the resolution of the reduction projection exposure method by 1-1. In particular, it is possible to invert the phases of the light that passes through the lens repeatedly. In the case of exposure light (mask illumination HFi field).

21 To increase the spatial coherence (coherence), the spatial frequency response of the optical system can be increased up to 2
Doubly so, the y depth of focus can also be increased significantly (1.5 to 2 times or more). In this method, an ear phase shifter plate (phase shifter) with an appropriate refractive index is selectively provided in a predetermined aperture of each transmission type mass, and an effective optical path difference is created for light passing through adjacent apertures. Adding 6' further inverts the phase of the light. Regarding the phase shift method, for example,
Devices ED-29 volume Nα12. Pages 1828 to 1835 (19821 (IEEE Trans.
ction on Electron Devices,
Voi, El)-29, No, 12. pp-! 828-
1835 (1982)) 1 (discussion I-), and the depth of focus in the conventional reduction projection B y (, method CJ9), and (in the multiple imaging plane exposure method ( Common name)'L-F', X method, j-Xocus' Lat
itude enhance+++entL-Xp (
・sor+・) has been proposed by the present inventors. This method is based on the exposure of the same exposure area of the substrate-1 by imaging the number of images of the same mask pattern at different positions in the optical axis direction. For the multiple imaging plane n-light method, which is carried out using
Volume, Nre 4. Pages 179 to 180 (198711
(IEEE Electron Device Let
,t,erS,VC++.

EDL-8, No, 4. pp, 179-180 (19
87)) discuss C) lie.

[Problems to be Solved by the Invention] As mentioned above, the 5-phase shift method has a special C
5 Great effects can be obtained. Actual LSI patterns include various complex patterns (e.g., peripheral circuit parts in memory LSIs) in addition to simple repeating patterns (e.g., memory mat part in memory LSIs). All the various parts, especially the isolated pattern G
On the other hand, the phase shift method does not always have a sufficient effect; that is, it has the problem that sufficient resolution and depth of focus cannot be obtained for patterns other than the repetitive pattern portion.

On the other hand, the multiple imaging exposure method uses two contact holes.
Arcs such as (when using a positive type 1. Cyst), single lie], pattern (J knee 6 go when using a negative type cyst), and 7 (.Tan light batting? - are effective But repeatedly,
There was a problem in that a pattern with a large exposed area ratio of 57", such as a pattern, would reduce the contrast of the optical image.

Furthermore, when the general C spatial copy ratio is made high, the optical proximity effect (inter-penetration interaction effect) that occurs between adjacent patterns becomes noticeable.・Te is the design mask pattern ζ, J,
It is known that the fidelity of optical images or resists for repeated patterns is degraded. 2 = ;> When I is high < 15, -1 for mask patterns with complex shapes other than repeating pattern parts.
-There is the problem of deterioration of pattern fidelity mentioned in -.
).1 The purpose of the present invention is to provide relatively simple repetition5. A general 1. '1. ．． ■ (li! path) For a solid elementary f pattern such as ζ tan (・, (ζ phase mi ″7 S ;l
';'';<Apply (-if it is, Toshiki ←) θ) Part now) Peta 1.-χ Earth Hi-komo +-5, De resolution and Jiaotun deep demon 4 pass/sai ] 5. I'm in the middle of the day.

In addition, another object of the present invention is that a complex-shaped mass outside the space of 7 L high heights, a cow, and a repeated 7 L height of 5 cm. , mask 'i-(
-E m To obtain an optical device [Means of M) for solving the problem] The above purpose is to obtain a phase shift, .
In the projection exposure method, a special feature is the multiplex imaging method.
High coherence lighting F (Yoshikei)
Actor: Apply when σ is o, 'qrtr). T- and IJ-1 will be achieved.

Also, the above purpose is +! , ] S-7t, Gua, υf,
,, ,p',l L,f-In the projection exposure method, it is intercepted by Mi,' and Guto, W=Zazo8:・1000(τThe distance between opposing in-phase bars/2 Knee L and the above-'1-Lf connection g, a light method]〆) For) Otsu, Cal=, <4. Depending on how, separate by a certain distance 71'
ll',! Achieved by okisumi and tsuba.

Further, the above object is achieved by using illumination light having high coherency in the repeating direction of the repeating pattern and relatively low copying coherency in the direction perpendicular to the repeating direction.

Furthermore, the L-multiplying method is achieved by setting the shape of the effective light source on the secondary light source surface of the reduction projection exposure apparatus to be small with respect to the repeating direction of the J-note repeating pattern and large with respect to the direction perpendicular to this. achieved.

[Effect]

Next, the operation of the present invention will be explained using the drawings.

Figures 1 (a) and (b) show the dependence of the distribution of the maximum light intensity in the optical axis direction on the distance Δ between the imaging planes when the multiple imaging exposure method is applied to an isolated space pattern (isolated linear transparent part). (a)
9, which is shown for high = 1 coherence (σ2 0.1) and (b) low coherence condition (σ = 0.5).
In addition, Fig. 1 (c) and (d) are r, / S bat'')
Figures (a) and (b) show the dependence of the distribution in the optical axis direction of the image cocitrus 2t on the distance Δ between the imaging planes when the phase shift method and the multiple imaging exposure method are applied together at L: The position in the optical axis j5 direction and the distance between the image forming planes are both λ
/NA" is expressed as a unit (,2. In addition, L /
The dimensions of the S pattern were 0.3Xλ/NA (however, λ
is the wavelength and NA is the numerical aperture). In addition, in the case of an isolated space pattern, even if the line width on the mask is made smaller than O25×λ/NA, the spread of the light intensity distribution 1j hardly changes, and only the light intensity decreases (,,(,Mautanu, Space line width is 0.5×λ/
/N, ;8 and ta.

When the coherency is low, the width of the peak of the light intensity of the isolated space pattern and the image contrast of the L/S pattern similarly widens in the light @ direction as Δ increases. but,
At the same time, the absolute value of image contrast/trust decreases (to 1.7). On the other hand, when copy density is high, there is no significant difference in the effect of multiple imaging exposure method on isolated space patterns. For this, the phase shift method is used.■2
．． /"S Papayu can obtain a strong image contrast in a wide range in the optical axis direction (7) regardless of △, and it becomes h6-like 4 (
The reason for h is as follows: τ is 7 degrees, the high space is about 1 piece, and the condition is 71'!,')
: When using the phase one method, the depth of focus becomes significantly larger. In this case, a relatively small distance between image planes Δ (usually 1
Even if the multiple imaging exposure method is applied using 66 to 2.0×λ/NA), the optical image obtained by the phase shift method is hardly affected. Therefore, for repetitive patterns, the phase shift method C
The effect of the multiple imaging exposure method can be selectively obtained only for isolated space patterns while maintaining a large depth of focus and a high contrast optical image. It can be seen that this makes it possible to secure the necessary depth of focus for both the isolated pattern and the repeated pattern due to phase shift. In addition, in order to obtain the above effect in -F, it is preferable that the coherence factor -σ of the exposure light is 0.3 or less.

In the method described below, high coherence conditions are used, in which case optical proximity effects occur due to the increased interference between adjacent patterns, as described above. The interaction between a pair of antiphase patterns always works in the direction of weakening the light intensity between the patterns, that is, in the direction that is favorable for increasing the degree of separation between the patterns, but in the case of the same phase, it works in the opposite direction, that is, in the direction of increasing the degree of separation between the patterns. This acts in the direction of deteriorating the degree of separation. Since the second interaction increases with defocusing, the multi-imaging exposure method in which large defocused images are superimposed becomes particularly large. In an actual LSI pattern, it is assumed that the patterns are in the same phase or are 1.Iauds facing each other through a light shielding part. Therefore,
Measures are required to suppress the proximity effect between same-phase patterns.

Figure 2 (a) shows the defocus dependence of the light intensity distribution when two isolated linear transparent space patterns of the same phase exist in close proximity, and the difference between the edges of the two patterns. The distance and the coherence factor σ are shown by changing. The light intensity distribution created by the two patterns is the sum of the light intensity distributions when each pattern exists in an incident, plus the interaction (interaction strength) between the two patterns.4, Figure 2 In addition to the actual light intensity distribution, this interaction strength is also shown. , the distance between patterns is small,
As the spatial coherence increases and the number of defocus stations increases, the phase pressure effect between patterns, that is, the proximity effect increases, and 2
It can be seen that a third light intensity peak appears between the two patterns.

Figure 2(b) shows (
It is a figure similar to a). Compared to (a), it can be seen that the light intensity peaks corresponding to the two patterns are maintained even with large defocus, and the depth of focus is increased by the multiple imaging exposure method.

However, if the distance between patterns is small and the spatial coherence is large, a third light intensity peak will still appear between the two patterns over a wide focal range.

In order to sufficiently suppress these in-phase proximity effects, it is necessary to set the distance between patterns (expressed in λ/NA as a unit) within the range shown by the shaded area in Figure 3 according to the coherence factor. preferable.

On the other hand, in order to obtain the full effect of the phase shift method,
It is preferable that the distance between the opposite phase patterns is set below the solid line in FIG. 3 (the part without diagonal lines).

Therefore, by increasing the distance between the same phase patterns that face each other via the light shielding part 7, it is possible to suppress the proximity effect between the same phase patterns under the high coherence condition F. Furthermore, an LSI in which the repeating direction of fine patterns is limited
In patterns, etc., by increasing the effective spatial coherence of the exposure light only in one direction and suppressing the spatial coherence in a direction perpendicular to this direction, the proximity effect in the latter direction can be suppressed.

[Example] First example Next, one embodiment of the present invention will be described.

Figure 4(a) shows a typical LSI wiring mask pattern, and Figures 4(1:) to (d) show the mask pattern in (a) under high coherence illumination (a=0.2). Defocus dependence of the optical image obtained when using the phase shift method (defocus value 0/, Lm, 11zm.

1.5 μm) is shown by the contour lines of the light intensity distribution.2. It is something that The light source used was a KrF excimer laser (wavelength 24
8 nm), and the open 11 number i:io of the projection lens is 45. Note that a phase shifter for inverting the phase of transmitted light was provided for each striped pattern. As the image is defocused, an image remains in the L/S portion, but an image in the peripheral portion (projection portion) disappears.

FIGS. 4(e) to 4(g) are examples in which the same phase shift masks as those shown in FIGS. 4(b) to 4(d), each having the same defocus value, are exposed using the multiple imaging exposure method. However, here, the amount of defocus in the multiple imaging exposure method is defined as the amount of deviation of the two imaging planes from the average plane.

Further, the distance between the image forming planes was set to 2 μI'n. As a result, although constrictions can be seen at the thinner protrusions and the bent parts of the pattern, even when defocused, ■, /S
It can be seen that not only the image of the area but also the peripheral area (projection area) is maintained.

Second example Next, another embodiment of the present invention will be described.

FIG. 5(a) shows another typical 1. ,, SI wiring mask pattern, Fig. 5(t)) ~ (l is the defocus value O
Figure 5 (2) when pm, 171m, 1.5μm L
This is an example in which the phase shift method and the multiple imaging exposure method are applied to the mask pattern 1) under high coherence illumination. The conditions of the optical system are the same as in the first embodiment. The light spreads between the same-phase patterns facing each other through the light shielding part (for example, between the third and fifth wires from the left), and the two connect (for example, at the tip of the third wire from the left). 4.Therefore, in order to separate the in-phase patterns that are directly opposed to each other through the light shielding part as much as possible in the direction of the wiring pattern, the wiring pattern was changed as shown in Figure 4(a) (: This made it possible to suppress the interaction between the same-phase patterns.The above-mentioned change in pattern design is simply a matter of geometrical arrangement and does not affect the function of the LSI at all.

Embodiment 3 FIG. 6(a) shows the phase shift mask pattern of FIG. 4(a) with some corrections, and FIG. 6(b)...
~(d) is an example of exposing the 7 snow patterns shown in FIG. 6 (43) using the multiple imaging exposure method. An illumination with a relatively low coherence (equivalent to σ = 0.7) in the direction perpendicular to this (equivalent to σ - 0,1) with a high "7F" · -Lance (equivalent to σ - 0,1) in the repetition direction of Light was used.Other optical system conditions were the same as in the first example.Isodirectional coherence was used in Figs.
Compared to g), an image more faithful to the mask pattern could be obtained with a deeper depth of focus.

Generally, when the multiple imaging exposure method is applied to a pattern including an isolated line pattern and an I, /S pattern due to a phase shift, as shown in FIG. 4(a), the light intensity of the isolated line pattern is relatively reduced. The pattern correction shown in FIG. 6(a) is mainly to widen the line width of the isolated line pattern in order to solve this imbalance of light intensity. The spread of the light intensity distribution of the isolated line pattern hardly changes when the line width is 0.7×λ/N, A or less, so the light intensity can be adjusted by changing the line width λ.

In order to obtain illumination light having the above coherence anisotropy, an aperture (open [-]) as shown in FIG. 7 is provided on the secondary light source surface of the illumination optical system of the reduction projection exposure apparatus.
J. The effective light source is defined by the - aperture.

Fourth Embodiment Next, a reduction projection exposure apparatus according to an embodiment of the present invention will be described. FIG. 8 is a schematic diagram of the illumination optical system of the reduction projection exposure apparatus according to the present invention. A plurality of apertures having different shapes are installed on a disk placed on the secondary light source surface of the illumination optical system.

By rotating the disk, one of the plurality of apertures can be set on the optical path of the illumination optical system and the secondary light source surface. Thereby, the shape of the effective light source can be set in various ways.

Fifth Embodiment FIG. 9 is a schematic diagram of an illumination optical system of another reduction projection exposure apparatus according to the present invention. The secondary light source surface of the illumination optical system has a Fi'T aperture that has the function of making the vertical and horizontal widths variable. The length and width of the aperture are set to be parallel to the orientation flat of the wafer exposed by the reduction projection exposure apparatus. This allows the shape of the effective light source to be set to a rectangular shape C7-2 with various sizes and vertical heights.
For example, it can be stacked with the circular Aba-Chiya, and is variable molded. By making the size of the aperture larger than the circular aperture, the shape of the effective light source can be made into a chevron shape, for example. 2 and Z, which use both the method and the multiple imaging exposure method under high coherence conditions.
``The relatively simple 2-patashi part, and the part)''
In a general solid-state r pattern that includes both complex patterns such as L-lyshi, the solid state of either part of C or F is
1' provides superior resolution and depth of focus)
Sleep.

In addition, it is possible to spatially copy the distance between the same-phase butterflies facing each other via the light shielding part in the Z-cross route l-1, and arrange them a certain distance apart depending on the situation or the like, or to repeat the mismatched pattern. (For the −U direction, use C-crystalline coherency. 2. Use illumination light with relatively low coherency for stiff and straight force surfaces. 5. From the binding, in-phase pattern 65
By suppressing the proximity force W of
1: These make it possible to apply the reduction projection exposure method, which is excellent in mass production and reliability, to pattern line widths of 0.3 μn1 or less.

[Brief explanation of the drawing]

Figures 1, 2 (a) and 2 (b) are characteristic diagrams showing the effects that form the principle of the present invention, Figure 3 is a characteristic diagram showing the scope of application of the present invention, and Figure 4 (a). ) is a schematic diagram of a typical LSI pattern, Figures 4(F) to 4(d) are optical images obtained by the conventional garden method, and Figures 4(c) to 4(e) are the optical images of the conventional FIG. 3 is a diagram showing an optical image according to an embodiment of the invention. Figure 5 (a
) is another typical 1. , SI pattern schematic diagram 1, FIG. 5(1) to (j) are FIG. 73 showing the problems of another embodiment of the present invention. FIG. 6(a) is a typical i pattern. ,+
Schematic diagram of sr pattern, No. 6] (b) ~ ((1)
FIG. 6 is a diagram showing an optical image according to another embodiment of the present invention. 1 is a schematic diagram showing a part of an n-light device for an embodiment of the present invention; and 81 and 9 are illumination optics of a reduction projection exposure device according to the present invention. Type of V! Figure (a7) Space “y,:’ (C) L/s
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Name of the No. Invention: Mask, projection exposure device, and relationship to the case involving a person correcting a pattern forming method Patent Applicant Name (5)
10) Subject of Hitachi Manufacturing Co., Ltd. Correction: The darkness in the simple explanation of the drawings in the specifications.

Claims (1)

[Claims] 1. In a method of forming a pattern by projecting and exposing a pattern on a mask onto a substrate using an optical system, the mask controls the phase of light passing through closely adjacent aperture patterns. This is a phase shift mask that includes a function such that the patterns are reversed each other, and the exposure is performed using a multiple imaging exposure method to produce multiple images of the mask pattern on the same exposure area on the substrate in different optical axis directions. A pattern forming method characterized by forming an image at a certain position. 2. In the pattern forming method using the above phase shift mask, the distance between the patterns having the same phase that are arranged opposite to each other on the mask through the light shielding part is determined by the multiple imaging of the light used for the exposure. The pattern forming method according to claim 1, wherein the pattern forming method is arranged at a distance of a certain distance or more depending on whether an exposure method is applied or not or the spatial coherency of the light used for the exposure. 3. In a phase shift mask that includes a function in which the phases of light passing through closely adjacent aperture patterns are inverted, there is a difference between patterns having the same phase that are placed opposite each other on the mask through a light shielding part. A mask characterized in that the masks are arranged at a distance of a certain distance or more depending on whether the multiple imaging exposure method is applied or not or the coherency. 4. In the pattern forming method according to claim 1, the mask according to claim 3 is used, and the spatial coherence factor of the light used for the exposure is 0.3 or less. Characteristic pattern formation method. 5. In a method of forming a pattern by projecting and exposing a pattern on a mask onto a substrate using an optical system, the mask has a repeating pattern, and the light illuminating the mask is directed toward the repeating direction. A pattern forming method characterized by having high spatial coherency and relatively low spatial coherency in a direction perpendicular to the spatial coherency. 6. A pattern forming method according to claim 3, characterized in that the mask according to claim 3 and the mask illumination light according to claim 5 are used. Method. 7. A projection exposure apparatus characterized in that the shape of the effective light source on the secondary light source surface of the reduction projection exposure apparatus is set to be small with respect to the repeating direction of the repeating pattern and large with respect to the direction perpendicular thereto. 8. The projection exposure apparatus according to claim 7, which is equipped with a plurality of apertures that regulate the shape of the effective light source, and has a function of selecting an arbitrary aperture from the plurality of apertures. 9. The projection exposure apparatus according to claim 7, which has a function of varying the shape of an aperture that regulates the shape of the effective light source.