JP2891219B2 - Exposure apparatus and element manufacturing method using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus and a device manufacturing method using the same, and more specifically, to appropriately illuminate a pattern on a reticle surface with a so-called stepper, which is a semiconductor device manufacturing apparatus, to obtain a high resolution. It is intended to be easily obtained.

[0002]

2. Description of the Related Art Recent developments in semiconductor device manufacturing technology have been remarkable, and the accompanying fine processing technology has also advanced remarkably.
In particular, the optical processing technology has reached the fine processing technology having a submicron resolution since the manufacture of 1MDRAM semiconductor devices. As a means for improving the resolution, the exposure wavelength is often fixed and the NA (numerical aperture) of the optical system is increased.
Was used. However, recently, various attempts have been made to change the exposure wavelength from g-line to i-line and to improve the resolution by an exposure method using an ultra-high pressure mercury lamp.

[0003] With the development of the method using g-line or i-line as the exposure wavelength, the resist process has also been developed. Together, the optics and the process have led to rapid advances in optical lithography.

It is generally known that the depth of focus of a stepper is inversely proportional to the square of NA. Therefore, when trying to obtain a submicron resolution, there arises a problem that the depth of focus becomes shallower.

On the other hand, various methods have been proposed for improving the resolving power by using light having a shorter wavelength typified by an excimer laser. It is known that the effect of using light of a short wavelength generally has an effect inversely proportional to the wavelength, and the depth of focus becomes deeper as the wavelength is shortened.

Various methods using a phase shift mask (phase shift method) have been proposed as a method of improving the resolving power in addition to using light having a shorter wavelength. According to this method, a thin film which gives a phase difference of 180 degrees with respect to passing light is formed on a part of a conventional mask to improve the resolving power, and the Levenso of IBM (USA) is used.
n et al. The resolving power RP is generally represented by the formula RP = k ₁ λ / NA, where λ is the wavelength, k _{1 is} the parameter, and NA is the numerical aperture. Usually 0.7-0.8 parameter k ₁ is a practical range is known to be significantly improved to about 0.35, according to the phase shift method.

[0007] Various types of phase shift methods are known, for example, Nikkei Micro Devices, July 1990.
It is described in detail in the article by Fukuda et al.

However, there are still many problems in improving the resolving power by using a spatial frequency modulation type phase shift mask. For example, the following are the problems at present. (I). The technology to form a phase shift film has not been established. (B). Development of the optimal CAD for the phase shift film has not been established. (C). Existence of a pattern without a phase shift film. (D). In connection with (c), a negative resist must be used. (E). Inspection and repair technology not established.

Therefore, there are various obstacles in actually manufacturing a semiconductor device using a phase shift mask, and it is very difficult at present.

On the other hand, the applicant of the present invention has proposed an exposure apparatus having an improved resolution without using a phase shift mask, as disclosed in Japanese Patent Application No. Hei.
No. 8631 (filed on Feb. 22, 1991).

[0011]

On the other hand, Japanese Patent Application Laid-Open No. 61-9 / 1986
In Japanese Patent Application Publication No. 1662/1989, a special stop having an aperture shape different from the uniform stop is inserted after the optical integrator in place of the normal uniform stop, so that the shape (of the intensity distribution) of the secondary light source as the effective light source is changed to the peripheral intensity. Discloses an exposure apparatus that converts the intensity into an intensity higher than the central portion and improves the resolution performance.

However, if an aperture having an off-axis aperture is used, it becomes difficult to make the illuminance distribution uniform on the reticle surface.

An object of the present invention is to provide an exposure apparatus capable of improving the illuminance distribution on the reticle surface even when using a stop having an off-axis aperture, and an object manufacturing method using the same.

[0014]

According to the present invention, there is provided an exposure apparatus comprising:
-1) irradiating light from a light source to a first optical integrator and illuminating the first object with a light beam from the first optical integrator, thereby projecting a pattern of the first object onto a second object by a projection optical system. In the exposure apparatus, before the first optical integrator or
An aperture stop having an aperture outside the optical axis is provided at a rear or conjugate location , and a second optical integrator and a light beam from the second optical integrator are provided between the light source and the first optical integrator by the first optical integrator. And an optical system for irradiation.

[0015] In particular, the use of the first aperture comprises only four openings off the optical axis as (1-1-1) the aperture stop.

(1-1-2) One of a plurality of stops including the first stop and a second stop having one aperture on the optical axis .
Having a throttle selection means for selectively inserting the diaphragm into the optical path.

(1-1-3) The aperture selecting means is configured to:
A disk having second apertures arranged at different positions and a driving means for rotating the disk;

(1-1-4) The four apertures respectively have two directions orthogonal to each other corresponding to the main directions related to the apparatus as the x-axis and y-axis directions, respectively, and centered on the position of the optical axis. The xy coordinate system described above is provided in the first to fourth quadrants when the second iris is assumed. And so on.

The element manufacturing method of the present invention is characterized in that (2-1) a step of projecting and transferring a circuit pattern onto the second object by using the exposure apparatus of the constitutional requirement (1-1). .

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of a main part of a first embodiment of the present invention. In the figure, reference numeral 11 denotes a light source such as an ultra-high pressure mercury lamp, the light emitting point of which is arranged near the first focal point of the elliptical mirror 12. The light emitted from this ultra-high pressure mercury lamp 11 is an elliptical mirror 1
2 collects light. 13 is a mirror for bending the optical path, and 14 is a shutter for limiting the amount of light passing therethrough. 71
Is a relay lens system that efficiently collects light from the ultra-high pressure mercury lamp 11 to the second optical integrator 72 via the wavelength selection filter 16 as wavelength selection means. The optical integrator 72 has a configuration in which a plurality of minute lenses are two-dimensionally arranged as described later.

In the present embodiment, the state of image formation on the optical integrator (integrator) 72 may be either critical illumination or Koehler illumination.
It may be one that forms an image. Wavelength selection filter 1
Numeral 6 selects and transmits only light of a necessary wavelength component from the wavelength components of the light beam from the ultrahigh pressure mercury lamp 11.

Reference numeral 73 denotes a relay lens (optical system).
The light beam from the optical integrator 72 is applied to the first optical integrator 74.

In the present embodiment, each of the minute lens groups constituting the second optical integrator 72 is connected to the first optical integrator 72 via the relay lens 73 by the action of the integrator.
The optical integrator 74 overlaps each other. As a result, a uniform illuminance distribution is obtained at the entrance 74a of the first optical integrator 74.

Reference numeral 18 denotes a diaphragm shape adjusting member as a selecting means (aperture selecting means), which is constituted by arranging a plurality of irises in a turret type, and arranged after the first optical integrator 74. The aperture shape adjusting member 18 selects a predetermined minute lens from a plurality of minute lenses constituting the optical integrator 74 according to the shape of the first optical integrator 74. That is,
In this embodiment, an illumination method suitable for a pattern shape of a semiconductor integrated circuit, which will be described later, in which exposure is performed by driving the aperture shape adjusting member 18 by an aperture drive system (drive device) 50 is selected. The selection of the plurality of micro lenses at this time will be described later.

In the present embodiment, each of the elements 18 and 50 constitutes one element of a changing means for changing the shape of the effective light source used for exposure.

Reference numeral 19 denotes a mirror for bending the optical path, and reference numeral 20 denotes a lens system, which collects a light beam passing through the diaphragm shape adjusting member 18. The lens system 20 plays an important role in controlling illumination uniformity. Reference numeral 21 denotes a half mirror, which divides a light beam from the lens system 20 into transmitted light and reflected light. The light reflected by the half mirror 21 is guided to a photodetector 40 via a lens 38 and a pinhole 39. The pinhole 39 is located at a position optically equivalent to the reticle 30 having a pattern to be exposed, and the light passing therethrough is detected by the photodetector 40 to control the amount of exposure.

Reference numeral 22 denotes a mechanical blade for performing so-called masking, and the position is adjusted by a drive system (not shown) according to the size of a pattern portion of the reticle 30 to be exposed. 23 is a mirror, 24 is a lens system,
25 is a mirror, 26 is a lens system, and the reticle stage 37 receives light from the ultra-high pressure mercury lamp 11 through these members.
The reticle (first object) 30 mounted thereon is illuminated.

In this embodiment, each element 20, 22, 2
Reference numerals 4 and 26 constitute one element of irradiation means for irradiating the reticle with a light beam from the effective light source.

Reference numeral 31 denotes a projection optical system which projects and forms a pattern on the reticle 30 onto a wafer (second object) 32. The wafer 32 is adsorbed on the wafer chuck 33, and the wafer chuck 33 is further attached to the laser interferometer 3.
6 on a stage 34 controlled by.
A mirror 35 is mounted on the wafer stage 34 and reflects light from a certain laser interferometer (not shown).

In the present embodiment, the exit surface 74b of the optical integrator 74 has the components 19, 20, 23,
A pupil plane 31a of the projection optical system 31 via the radiators 24, 25, 26
And a substantially conjugate relationship. That is, an effective light source image corresponding to the exit surface 74b is formed on the pupil surface 31a of the projection optical system 31.

Here, each element 20, 24, 26
The effective light source formed on the projection optical system 31
This constitutes one element of the effective light source forming means formed in a.

Next, the pupil plane 3 of the projection optical system 31 will be described with reference to FIG.
1a and the emission surface 74b of the optical integrator 74
Will be described. The shape of the optical integrator 74 corresponds to the shape of the effective light source formed on the pupil plane 31a of the projection optical system 31. FIG. 2 shows this state, in which the shape of the effective light source image 74c of the exit surface 74b formed on the pupil plane 31a of the projection optical system 31 is overlaid. The diameter of the pupil 31a of the projection optical system 31 is set to 1.0 for normalization, and a plurality of minute lenses constituting the optical integrator 74 form an image in the pupil 31a to form an effective light source image 74c. In the case of the present embodiment, each of the minute lenses constituting the optical integrator has a square shape.

Here, orthogonal axes, which are main directions used when designing a pattern of a semiconductor integrated circuit, are taken as x and y axes. This direction coincides with the main direction of the pattern formed on the reticle 30, and substantially coincides with the direction of the outer shape of the reticle 30 having a square shape.

The illumination system with high resolution exerts its power when the above-mentioned k ₁ factor takes a value near 0.5.

Therefore, in this embodiment, the aperture shape adjusting member 1
Out of a plurality of micro lenses constituting the optical integrator 74 by the aperture 8, only a light beam passing through a predetermined micro lens according to the pattern shape on the reticle 30 surface is used for illumination of the reticle 30.

Specifically, a micro lens is selected so that a light beam passes through a plurality of areas other than the center area on the pupil plane 31a of the projection optical system 31.

FIGS. 3A and 3B show a pupil plane when only a light beam passing through a predetermined minute lens is selected by the stop of the stop shape adjusting member 18 from among a plurality of minute lenses constituting the optical integrator 74. It is the schematic on 31a. In the figure, a black area indicates a light-shielded area, and a white area indicates an area through which the light passes.

FIG. 3A shows a pupil plane 31 when the direction in which resolution is required in the pattern is the x and y directions.
5 shows an effective light source image on a. Assuming that a circle representing the pupil plane 31a is x ² + y ² = 1, the following four circles are considered.

(X-1) ² + y ² = 1 x ² + (y-1) ² = 1 (x + 1) ² + y ² = 1 x ² + (y + 1) ² = 1 The pupil plane 31a is defined by these four circles. Is decomposed into eight regions 101 to 108.

In the present embodiment, the illumination system having a high resolution and a large depth in the x and y directions gives priority to the microlens groups existing in the even-numbered areas, that is, the areas 102, 104, 106 and 108. This is achieved by choosing to allow the light to pass through. Since the microlens near x = 0 and y = 0, which is the origin, is largely effective in improving the depth of a coarse pattern, whether or not to select a part near the center is a choice determined by the pattern to be printed.

FIG. 3A shows an example in which the micro lens near the center is excluded. Note that a portion outside the optical integrator 74 is shielded from light by an integrator holding member (not shown) in the illumination system. FIG. 3
7A and 7B, the pupil 31a and the effective light source image 74c of the optical integrator are overlaid to make it easy to understand the relationship between the microlens to be shielded and the pupil 31a of the projection lens.

On the other hand, FIG. 3B shows the shape of the stop when high resolution is required for a pattern in the ± 45 ° direction. 3A shows the relationship between the pupil 31a and the effective light source image 74c of the optical integrator 74 as in the case of FIG. Same as before for ± 45 ° pattern

[0043]

(Equation 1) The four circles shown in FIG.
As in the case of (A), the pupil 31a is divided into eight regions 111 to 118. In this case, the regions represented by odd numbers, that is, the regions 111, 113, 115, and 117 contribute to the high resolution of the pattern in the ± 45 ° direction.
Optical integrator 7 existing in this area
± 45 ° by preferentially selecting 4 microlenses
The directional pattern has a significant increase in the depth of focus when the k ₁ factor is around 0.5.

FIG. 4 shows each stop 18 of the stop shape adjusting member 18.
It is the schematic which performs switching of a-18d. As shown in FIG. 4, a turret type exchange system is employed. Second
The aperture 18a, used when burning one or more is not so fine pattern in k _1. Second diaphragm 18
Reference numeral a denotes a fixed stop which has the same configuration as that of a conventionally known illumination optical system, and which is set so as to shield a portion outside a minute lens group constituting the optical integrator 74 as necessary. . The diaphragms 18b to 18d are various diaphragms as first diaphragms according to the present embodiment.

As a general tendency, in the case of an illumination system for high resolution, the optical integrator 74 has a higher spatial frequency if it is used up to the outer region on the pupil plane than the size required in the conventional illumination system. Is advantageous. For example, in a conventional illumination system, it is preferable to use a microlens group having a radius of 0.5 or less, whereas in a high-resolution illumination system, a microlens at the center is not used.
It may be preferable to use up to a minute lens group within a circle within 75.

For this reason, the optical integrator 74
And the effective diameter of the other parts of the illumination system are preferably set in advance in consideration of both the conventional type and the high-resolution type. Further, it is preferable that the light intensity distribution at the entrance 74a of the optical integrator 74 is large enough to perform its function even when a stop is inserted. The reason that the aperture 18a may shield the outer minute lens group from light for the above reason is that, for example, the optical integrator 74 may be prepared up to a radius of 0.75, but the aperture 18a may have a radius from among them. For example, a part within 0.5 is selected.

As described above, if the shape of the stop is determined in consideration of the specificity of the pattern of the semiconductor integrated circuit to be exposed, an optimal exposure apparatus according to the pattern can be constructed. The selection of these apertures is automatically made, for example, given from the control computer of the entire exposure apparatus. FIG. 4 shows an example of the aperture shape adjusting member 18 equipped with such an aperture. In this case, it is possible to select four types of aperture 18a to 18d patterns. Of course, this number can easily be increased.

When the aperture is selected, the illuminance unevenness may change according to the selection of the aperture. Therefore, in the present embodiment, the optical integrator is provided in two stages and the reticle 3
The illuminance distribution on the zero plane is not made non-uniform.
In the present embodiment, the illuminance unevenness in such a case is finely adjusted by adjusting the lens system 20. It has already been shown by the applicant of the present application that the fine adjustment of the illuminance unevenness can be adjusted at intervals in the optical axis direction of the individual element lenses constituting the lens system 20. A driving mechanism 51 drives an element lens (movable lens) of the lens system 20. The adjustment of the lens system 20 is performed according to the selection of the aperture. In some cases, the lens system 20 itself can be completely replaced with another interchangeable lens according to a change in the shape of the stop. In such a case, a plurality of lens systems corresponding to the lens system 20 are prepared, and the lens systems are exchanged so as to be changed to a turret type according to the selection of the shape of the diaphragm.

In this embodiment, an illumination system is selected according to the characteristics of the pattern of the semiconductor integrated circuit by changing the shape of the stop. Also, in the case of the present embodiment, when the illumination system for high resolution is used, when the entire effective light source is viewed largely, the light source itself is divided into four regions. The important factor in this case is the balance between the intensity of these four regions. However, in the system shown in Fig. 1, the ultra-high pressure mercury lamp 1
One cable shadow can adversely affect this balance. Accordingly, in the illumination system for high resolution using the aperture shown in FIG. 3, it is desirable to set the linear portion which becomes the shadow of the cable so as to correspond to the position of the minute lens which is shielded by the optical integrator 74.

That is, in the case of the diaphragm of FIG. 3A, the direction of pulling the cable 11a is x as shown in FIG. 5A.
Alternatively, it is preferable to set in the y direction.
5B, the direction in which the cable 11a is pulled is ± 45 ° with respect to the x and y directions as shown in FIG.
Is preferably set to. In the present embodiment, it is preferable that the direction in which the cable of the ultra-high pressure mercury lamp is pulled is also changed in accordance with the change in the aperture.

The example described above uses one ultra-high pressure mercury lamp conventionally used. However, the present invention can of course be applied to a case where a plurality of light sources are used or an excimer laser is used as a light source. In the case of an illumination system using an excimer laser, there is a method in which the position of the laser is scanned temporally on the optical integrator. FIG. 3 shows that the scanning range is changed according to the pattern to be printed. Such an effective light source distribution can be easily realized.

Although not described in the above embodiments, in an illumination system for high resolution, it is also important to balance the four parts which are largely divided by the diaphragm. The monitoring of the distribution of the effective light sources divided into four or the correction method has already been described in the previous application, so that the description is omitted here.

In the embodiment of the present invention, the stop is inserted at the rear side of the last optical integrator, but may be inserted at the front side of the optical integrator. If there is another surface conjugate with the optical integrator in the illumination system, the aperture operation may be performed there.

[0054]

According to the exposure apparatus of the present invention, the illuminance distribution can be improved even if a stop having an off-axis aperture is used, whereby a semiconductor device having a high-resolution pattern can be easily obtained. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a main part of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a pupil of a projection optical system and an optical integrator.

FIG. 3 is an explanatory diagram showing a pupil plane of the projection optical system.

FIG. 4 is a detailed view of an aperture used in the present invention.

FIG. 5 is a diagram showing how to pull out a cable from an ultra-high pressure mercury lamp.

DESCRIPTION OF SYMBOLS 11 Ultra-high pressure mercury lamp 12 Elliptical mirror 13 Mirror 14 Shutter 15 Lens 16 Wavelength selection filter 18 Mechanical aperture 19 Mirror 20 Lens 21 Half mirror 22 Masking blade 23,25 Mirror 24,26 Lens 30 Reticle 31 Projection optical system 32 Wafer 33 Wafer chuck 34 Wafer stage 35 Laser interferometer mirror 36 Laser interferometer 37 Reticle stage 38 Lens 39 Pinhole 40 Photodetector 50 Aperture drive system 51 Lens drive system 71, 73 Relay lens 72 Second optical integrator 74 First optical Integrator

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-155843 (JP, A) JP-A-61-91662 (JP, A) JP-A-61-267722 (JP, A) JP-A-62 52929 (JP, A) JP-A-62-134650 (JP, A) JP-A-63-12135 (JP, A) JP-A-4-329623 (JP, A) JP-A 9-186081 (JP, A) JP-A-9-190974 (JP, A) Patent 2363091 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 21/027

Claims (6)

(57) [Claims] A first optical integrator that emits light from a light source and illuminates a first object with a light beam from the first optical integrator;
In an exposure apparatus for projecting a pattern of an object onto a second object by a projection optical system, an aperture stop having an aperture outside the optical axis is provided before or after the first optical integrator or at a conjugate place, and the light source and the first optical integrator are provided. A second optical integrator between the optical integrators,
An optical system for irradiating a light beam from the second optical integrator onto the first optical integrator. 2. The apparatus according to claim 1, wherein a first aperture having only four apertures outside the optical axis is used as said aperture stop.
Exposure equipment. 3. A diaphragm for selectively inserting one of a plurality of diaphragms including the first diaphragm and a second diaphragm having one aperture on the optical axis into the optical path. 3. The exposure apparatus according to claim 2, further comprising a selection unit. 4. An exposure apparatus according to claim 3, wherein said aperture selecting means includes a disk having said first and second apertures arranged at different positions, and a driving means for rotating said disk. 5. The four apertures each have two mutually orthogonal directions corresponding to the main direction associated with the device, x.
Axis, claims 2 to 4, characterized in that xy coordinate system centered on the position of the to and the optical axis direction of the y-axis is provided to the first to fourth quadrants when it is assumed on the second aperture Exposure equipment. 6. An element manufacturing method, comprising a step of projecting and transferring a circuit pattern onto the second object using the exposure apparatus according to any one of claims 1 to 5.