KR19990026083A - Deformed lighting device and its formation method - Google Patents

Abstract

The present invention discloses a modified illumination device and a method of forming the same. The modified lighting apparatus according to the present invention includes a complex illumination system aperture combined with a multi-point illumination system and a ring illumination system having light transmission. Such apertures can increase the resolution of the lighting apparatus, obtain a deep DOF, and increase the exposure dose incident on the wafer. Therefore, the use of such a modified illumination device is advantageous not only for the formation of a simple pattern but also for the formation of a complex and directional pattern.

Description

Deformed lighting device and its formation method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deformed lighting device and a method of forming the same. In particular, the present invention relates to an annular illumination effect to improve both resolution, depth of focus (hereinafter referred to as DOF), and light intensity compared to simple lighting. It relates to a deformed lighting device and a method of forming the same that can exhibit a multi-point lighting effect.

The lighting device used in the manufacturing process of the semiconductor device has a high resolution and a deep DOF while having a sufficient amount of light to expose the photoresist, since the light intensity is determined when the light source is determined.

On the other hand, as the integration of semiconductor devices is advanced, there is a need for lighting devices having higher resolution and deeper DOF. In other words, as the semiconductor devices are highly integrated, the device density per unit area is increasing. Therefore, the pitch between the patterns formed on the wafer is narrower than before, and the vertical height of the pattern is higher. Therefore, in order to form such a pattern, the resolution of the lighting apparatus exposing the photoresist film must be higher than that of the conventional lighting apparatus, and the DOF must be deeper.

To this end, the prior art provides a deformation lighting apparatus that exhibits high resolution and deep DOF by modifying an aperture provided between a fly's eye lens and a condenser lens among lighting apparatuses. Such apertures include ring illumination apertures, dead spot illumination apertures, or two-point illumination apertures.

Hereinafter, a deformation lighting apparatus according to the related art and an aperture used therein will be described in detail with reference to the accompanying drawings.

1 is a view showing a part of a modified lighting apparatus according to the prior art,

FIG. 2 is a plan view of an aperture used in the modified illumination device of FIG. 1. FIG.

Referring to FIG. 1, the conventional lighting apparatus includes the following components. That is, a projection lens 12 is provided at a spaced distance upward from the wafer 10. The chrome layer pattern mask 14 is positioned above the projection lens 12. The chromium layer pattern mask 14 is formed on the light transmissive substrate 14a with a chromium layer pattern 14b defining a light shielding area. A light source (not shown) is provided above the chromium layer pattern mask 14 and is below the fly's eye lens 20. The aperture 18 and the condenser from the fly's eye lens 20 toward the chrome layer pattern mask 14 are provided. A condenser lens 16 is provided. The aperture 18 is divided into a light shielding region 18a and a light transmitting region 18b. The aperture 18 may be either a four-point illumination system aperture as shown in FIG. 2, or a two-point illumination system or a ring illumination aperture. Referring to FIG. 2, in the dead-point illumination system aperture, circular light transmitting areas 22a are formed in four groups of light blocking areas 22, and these light transmitting areas 22a are symmetrically formed with respect to the center of the aperture.

By using such a deformed aperture 18 in the lighting device, the deformed lighting device according to the prior art becomes an incident lighting device. That is, the aperture 18 blocks light incident to the center portion of the condenser lens 16 among the light coming from the fly's eye lens 20 and passes only the light incident to the edge. Accordingly, the light passing through the edge of the condenser lens 16 is incident on the chromium layer pattern mask 14 at an incident angle larger than the light passing through the center. As a result, the diffraction angle α of light diffracted from the chromium layer pattern mask 14 becomes larger than the diffraction angle of light incident perpendicularly to the chromium layer pattern mask 14. As a result, 0th order light (0) of the diffracted light passes through one edge of the projection lens 12, and + 1th order light (+1) and -1 are distributed symmetrically around the 0th order light (0). Of the light shield (-1), the -light shield (-1) light leaves the projection lens 12, and the +1 light shield (+1) passes through the opposite edge of the projection lens 12, and the 0 light shield (0) Focus on the wafer together. Reference numeral α is a diffraction angle of +1 order light (+1) with respect to 0 order light (0).

As described above, the modified illumination apparatus according to the related art may increase the resolution of the illumination apparatus and deepen the DOF by realizing the incident illumination that excludes the light passing through the central portion of the projection lens 12, but is illustrated in FIG. 2. As described above, most of the aperture blocks most of the light coming from the fly's eye lens into the light shielding region, resulting in a decrease in the amount of light incident on the wafer. As a result, the photosensitivity of the photoresist film is incomplete, and the formation of the pattern is incomplete. For example, in the case of forming the contact hole, the contact hole is incompletely opened or does not open at all. This problem can be solved by widening the light transmitting region 22a of the aperture, but the problem of deterioration in resolution and DOR appears at that time.

Accordingly, the technical problem to be achieved by the present invention is to provide a deformed illumination device that can increase the amount of light incident on the wafer while improving the resolution and DOF in order to solve the problems shown in the prior art described above.

Another object of the present invention is to provide an aperture for use in the modified illumination device.

Another object of the present invention is to provide a method of forming the modified illumination device.

1 is a view showing a part of a modified lighting apparatus according to the prior art.

FIG. 2 is a plan view of an aperture used in the modified illumination device of FIG. 1. FIG.

3 is a view showing a part of a modified lighting apparatus according to an embodiment of the present invention.

4 is a plan view of the aperture used in FIG. 3.

* Explanation of symbols for main parts of the drawings

40: Wafer. 42: projection lens.

44: Mask. 46: condenser lens.

48: Aperture. 50: Paris eye lens.

52: Shading area. 54, 56: first and second light transmitting regions.

48a: Multi-point illumination aperture. 48c: ring illuminator aperture.

In order to achieve the above technical problem, the deformed lighting device according to the present invention comprises a fly-eye lens for flattening the light coming from the light source; A condenser lens and a projection lens provided in parallel with the fly's eye lens; An aperture provided between the fly's eye lens and the condenser lens; In the modified illumination device having a mask or the like provided between the condenser lens and the projection lens, the aperture is characterized in that the composite illumination system aperture combined with at least two illumination systems.

According to an embodiment of the present invention, the composite illumination system aperture is a ring illumination system and a multi-point illumination system are combined.

According to an embodiment of the present invention, the composite illumination system aperture has a ring illumination aperture in the center, and a multi-point illumination system is provided around it.

According to an embodiment of the present invention, the multi-point illumination system is any one selected from a four-point or two-point illumination system.

In order to achieve the above technical problem, the deformed lighting device according to the present invention comprises a fly-eye lens for flattening the light coming from the light source; A condenser lens and a projection lens provided in parallel with the fly's eye lens; An aperture provided between the fly's eye lens and the condenser lens; And a mask provided between the condenser lens and the projection lens, wherein the aperture is formed of a light blocking area, a first light transmitting area, and a second light transmitting area.

According to an embodiment of the present invention, the light blocking area surrounds the circumference of the second light transmitting area, and the first light transmitting area is rotationally symmetrically distributed about the second light transmitting area.

According to an embodiment of the present invention, the first light-transmitting region is formed in the light-shielding region and is selected from among a four-point hole or a two-point hole forming rotation symmetry around the second light-transmitting region.

According to the embodiment of the present invention, the second light-transmitting region is formed with grooves that are concentrically outward from the center thereof at predetermined intervals.

In order to achieve the above another technical problem, the aperture according to the present invention is provided with a light-transmissive diffraction grating at the center of the opaque substrate, characterized in that it has a plurality of through-holes having rotational symmetry around the center.

According to an embodiment of the present invention, the light-transmissive diffraction grating has a circular shape, and grooves having a predetermined distance to the outside with the center thereof as the axis are formed concentrically.

In addition, the number of the through holes is two or four.

In order to achieve the above another technical problem, the method of forming a modified lighting apparatus according to the present invention is as follows.

That is, a convex lens and a projection lens provided in parallel with and parallel to the fly's eye lens to planarize light from a light source, an aperture provided between the fly's eye lens and the condenser lens, and between the condenser lens and the projection lens. In the method of forming a modified illumination device having a mask or the like provided in the, the aperture is formed by combining at least two different illumination system apertures as a composite illumination system aperture.

According to an embodiment of the present invention, the aperture is formed by combining the ring illumination aperture and the multipoint illumination aperture.

According to an embodiment of the present invention, the aperture forms the ring illumination aperture in the center and forms the multi-point illumination aperture around the center so as to be rotationally symmetrical.

The modified lighting apparatus according to the present invention includes at least two illumination systems, for example, a composite aperture formed by combining a ring illumination system and a dead point illumination system. In the case of illuminating the wafer using such a deformation lighting apparatus, it is possible to increase the amount of light incident on the wafer while maintaining high resolution and deep DOF, which are advantages of the deformation lighting apparatus. In addition, by using the multi-point illumination system and the ring illumination system together, there is an advantage in forming not only a simple pattern but also a complicated and directional pattern.

Hereinafter, with reference to the accompanying drawings, a modified illumination device and a method for forming the same according to an embodiment of the present invention will be described in detail.

3 is a view showing a part of a modified lighting apparatus according to an embodiment of the present invention, Figure 4 is a plan view of the aperture used in FIG.

Referring to FIG. 3, the deformation lighting apparatus according to the exemplary embodiment of the present invention includes the following components to expose the wafer 40 to be exposed.

Specifically, the light source of the lighting apparatus used in the manufacturing process of the semiconductor device emits divergent light instead of convergent light. The position at which the wafer 40 is loaded is placed on the focal plane of the final optics of the illumination device. Therefore, in order to illuminate the wafer, it is preferable to inject light having parallel waves to the optical system located on the front surface of the wafer. For this purpose, the fly's eye lens 50 is provided in the illumination device. An optical system including a plurality of lenses is provided between the fly's eye lens 50 and the wafer 40. For example, the condenser lens 46 and the projection lens 42 are arranged in parallel to each other from the fly's eye lens 50 toward the wafer 40. An aperture 48 is provided between the fly's eye lens 50 and the condenser lens 46.

The aperture 48 can be described in two ways.

First, the aperture 48 is described according to a coupling method. Specifically, the aperture 48 is a complex illumination system aperture in which at least two illumination systems are combined. That is, the aperture 48 has a form in which the multi-point illumination system aperture 48a and the ring illumination system aperture 48c indicating the transmissivity provided in the light shielding area at the center thereof are combined. In this case, the multi-point illumination system aperture 48a is any one selected from four-point or two-point illumination system apertures.

The multi-point illumination system aperture 48a is arranged to be rotationally symmetrical about the translucent ring illumination aperture 48c. 3 shows a four-point illumination system aperture as the multi-point illumination system aperture 48a of the aperture 48.

Originally, the ring illumination system itself has a light shielding area and a light transmitting area. However, the annular illumination aperture 48c of the aperture 48 is entirely a light transmitting area. However, the light passing through the annular illumination aperture 48c has the same effect as passing through the annular illumination system provided as a normal light shielding region and a light transmitting region. This effect is made possible by forming the annular illumination system aperture 48c in the form of a circular diffraction grating. To this end, one side of the ring illumination aperture 48c, for example, grooves having a predetermined depth are provided on the side of the fly's eye lens 50 at predetermined intervals. The groove is provided outward from the center of the ring illumination aperture 48c. The groove is formed concentrically around the center of the ring illumination aperture 48c. By this groove, the light passing through the ring illumination aperture 48c exhibits the same effect as when passing through the conventional ring illumination aperture. Specifically, as the groove is formed in the ring illumination aperture 48c, the ring illumination aperture 48c has two thicknesses, that is, the first thickness D1 and the second thickness, as shown in the right side of FIG. 3. Thickness D2 is present. The first thickness D1 is a thickness of a portion where the groove is not formed, and the second thickness D2 is a thickness of a portion where the groove is formed. The difference D1-D2 between the first and second thicknesses D1 and D2 corresponds to the depth of the groove. Depending on the depth of the groove, the ring illumination system aperture 48c plays the same role as a conventional ring illumination system.

On the other hand, the following equation 1 is established between the transparent medium having a refractive index n and the thickness D and the wavelength of light passing through the medium.

According to Equation 1, the depth D1-D2 of the groove must be equal to the half wavelength of light in order for the ring illumination aperture 48c to serve as a conventional ring illumination aperture. In this case, the light having passed through the portion having the first thickness D1 of the ring illumination aperture 48c and the light having passed through the portion having the second thickness D2 have the ring illumination aperture 48c. A phase difference of 180 ° appears between the lights that go straight vertically. Therefore, these lights cancel and disappear. Therefore, the light passing through the annular illumination aperture 48c becomes the same light as the light passing through the annular illumination system consisting of the light blocking region and the light transmitting region sequentially and concentrically.

As a result, the light passing through the aperture 48 is equal to the sum of the light passing through the dead point illumination aperture and the light passing through the loop illumination aperture so that more light is incident on the condenser lens 46. do. This does not result in lower resolution or shallower DOF.

In FIG. 3, reference numeral β denotes an angle between homogeneous light diffracted through the second light-transmitting region 48c.

Second, the aperture 48 is divided into regions. Specifically, the aperture 48 is a method described by an aperture having a first light transmitting region, a second light transmitting region, and a light blocking region. Here, the light blocking area is a light blocking area of the multi-point illumination system aperture 48a, and the first light transmitting area corresponds to the light transmitting area 48b of the multi-point illumination system aperture 48a. The second light transmitting area corresponds to the ring illumination system aperture 48c indicating the light transmitting property.

The second description can be clarified by referring to FIG. 4. Specifically, in FIG. 4, reference numeral 52 denotes a light blocking area of the aperture 48, 54 denotes a first light transmitting area as a light transmitting area formed in the light blocking area 52, and 56 denotes the aperture 48. The second light-transmitting region provided at the center of the light-shielding region of the? The first light transmitting region 54 is distributed so as to be rotationally symmetrical about the second light transmitting region 56. The second light-transmitting region 56 is shown as first and second concentric circles 56a and 56b, of which different markings of the first concentric circles 56a and the second concentric circles 56b pass through the respective regions. This is to indicate that the phase of the light is shifted by 180 degrees. Therefore, the first concentric circles 56a are not light blocking regions.

In FIG. 4, reference numeral R denotes the diameter of the first light-transmitting region 54.

Subsequently, a mask 44 is provided between the condenser lens 46 and the projection lens 42. The mask 44 has a chromium layer pattern 44b formed on a transparent quartz substrate 44a. The chromium layer pattern 44b not only defines a light blocking region but also forms a pattern to be formed on the wafer 40.

Next, a modified illumination method using the deformed lighting device, that is, the incident lighting method will be described.

Referring to FIG. 3, light emitted from a light source that emits light in an i-Line or a deep ultraviolet region having a shorter wavelength is transformed into a plane wave while passing through the fly's eye lens 50. It is incident perpendicular to the aperture 48. By using the complex illumination system aperture as described above (or an aperture having two different light transmission characteristics) as the aperture 48, more light can be passed than when using a single illumination aperture. Can be. Therefore, the amount of light passing through the aperture increases. Light passing through the fly's eye lens 50 passes through the light-transmitting region 48b of the multi-point illumination system aperture 48a of the aperture 48 and the light-transmissive ring illumination aperture 48c. The light passing through the light-transmitting region 48b of the multi-point illumination system aperture 48a has a diameter of the light-transmitting region much larger than the light wavelength, so that diffraction of light passing through the light-transmitting region 48b can be ignored. Will be joined.

On the other hand, in the ring illumination aperture 48c, as described above, a groove having a depth corresponding to half wavelength of the light passing through is formed. The grooves are formed at predetermined intervals so that the annular illumination aperture 48c has the same identity as the annular illumination aperture provided with alternating light shielding areas and light transmitting areas alternately, and the ring illumination apertures 48c It forms concentrically outward from the center. In addition, the groove may be formed on the side surface of the condenser lens 46, as shown in the figure.

The light that is not diffracted in the light passing through the ring illumination aperture 48c, that is, the light traveling perpendicular to the ring illumination aperture 48c cancels each other and cancels. Further, an additional path difference is generated between the light diffracted at the predetermined diffraction angle β by light diffraction, and light whose path difference reaches half the wavelength of the light is cancelled by interference. As a result, only the light causing the constructive interference among the diffracted light passing through the ring illumination aperture 48c is incident on the condenser lens 46.

On the other hand, according to the following equation (2), the diffraction angle β of the light passing through the ring illumination aperture 48c depends on the pitch of the groove carved into the ring illumination aperture 48c.

(Where p is the pitch of the inscribed groove of the diffraction grating, λ is the wavelength of light passing through the diffraction grating, and β and n are the diffraction angle and the refractive index of the diffraction grating, respectively.)

In other words, when the pitch between the grooves of the annular illumination aperture 48c is narrow, the diffraction angle β becomes large, and when it is wide, it becomes small. Therefore, the diffraction angle β of the light passing through the annular illumination aperture 48c can be arbitrarily adjusted.

Light passing through the aperture 48 is collected by the condenser lens 46 and is incident on the mask 44 lying on the focal plane of the condenser lens 46. The mask 44 has a chrome layer pattern 44b defining a light shielding area. The mask 44 acts as a diffraction grating by the chromium layer pattern 44b. Therefore, the light incident on the mask 44 is diffracted at a predetermined diffraction angle γ according to the diffraction law. At this time, the incident light incident on the mask 44 is not incident perpendicularly to the mask 44 but is inclined. Accordingly, the zeroth order light 0 of the diffracted light is further diffracted by the angle corresponding to the incident angle of the incident light, and is incident on the edge of the lens which is out of the center of the projection lens 42. Further, the + 1st order light (+1) symmetrically distributed about the 0th order light (0) of the diffracted light and the -1st order light (-1) of the -1st order light (-1) are diffracted greatly to make the projection lens It is outside the scope of (42). In addition, the high-order diffracted light of +1 or -1 order or more also has a large diffraction angle, thereby leaving the projection lens 42. As a result, the light incident on the projection lens 42 is 0th order light (0) and + 1th order light (+1). These lights are concentrated at one point of the wafer lying on the focal plane of the projection lens 42, and the photosensitive film applied thereon is exposed.

As described above, the modified illumination device according to the present invention includes a complex illumination system aperture combined with a multi-point illumination system and a ring illumination system having a light transmission. Such apertures can increase the resolution of the lighting apparatus, obtain a deep DOF, and increase the exposure dose incident on the wafer. Therefore, the use of such a modified illumination device is advantageous not only for the formation of a simple pattern but also for the formation of a complex and directional pattern.

The present invention is not limited to the above embodiments, and it is apparent that many modifications can be made by those skilled in the art within the technical idea of the present invention.

Claims (25)

A fly's eye lens to flatten the light coming from the light source; A condenser lens and a projection lens provided in parallel with the fly's eye lens; An aperture provided between the fly's eye lens and the condenser lens; In the modified illumination device comprising a mask or the like provided between the condenser lens and the projection lens, The aperture is a modified illumination device, characterized in that the at least two illumination system combined illumination aperture. The modified illumination device according to claim 1, wherein the complex illumination system aperture is an aperture combined with a ring illumination system and a multi-point illumination system. The modified illumination device of claim 1, wherein the complex illumination system aperture has a ring illumination aperture at the center thereof, and a multi-point illumination system is provided at the periphery thereof. The apparatus of claim 2 or 3, wherein the ring illumination aperture is a light transmitting circular diffraction grating. The deformed illumination device according to claim 4, wherein the circular diffraction grating is formed with grooves concentrically outward from the center thereof at predetermined intervals. The deformed illumination device according to claim 5, wherein the groove is formed on the side of the fly's eye lens of the diffraction grating. 6. The modified illumination apparatus of claim 5, wherein the groove has a depth equal to a half wavelength of light passing through the diffraction grating. The modified illumination apparatus according to claim 2 or 3, wherein the multi-point illumination system is any one selected from a dead point or a two-point illumination illumination system. A fly's eye lens to flatten the light coming from the light source; A condenser lens and a projection lens provided in parallel with the fly's eye lens; An aperture provided between the fly's eye lens and the condenser lens; And In the modified illumination device comprising a mask or the like provided between the condenser lens and the projection lens, The aperture is modified illumination device, characterized in that consisting of the light shielding area, the first light-transmitting area and the second light-transmitting area. 10. The apparatus of claim 9, wherein the light blocking area surrounds the circumference of the second light transmitting area, and the first light transmitting area is symmetrically distributed about the second light transmitting area. The deformed lighting apparatus according to claim 10, wherein the first light transmitting area is one selected from a dead point hole or a two point hole which is formed in the light blocking area and forms rotationally symmetry around the second light transmitting area. 12. The deformed lighting device according to claim 11, wherein the second light-transmitting region is provided with grooves concentric with the center thereof outwardly at predetermined intervals. 13. The modified illumination apparatus according to claim 12, wherein the groove is formed on the side of the fly's eye lens of the second light-transmitting region. 13. The modified illumination apparatus of claim 12, wherein the groove has a depth equal to a half wavelength of light passing through the aperture. An aperture comprising a transmissive diffraction grating at the center of the opaque substrate, and a plurality of through holes having rotational symmetry around the opaque substrate. The aperture as claimed in claim 15, wherein the transmissive diffraction grating is a circular diffraction grating, and grooves having a predetermined distance outwardly from the center thereof are formed concentrically. 16. The aperture of claim 15 wherein the number of through holes is four. 18. The aperture of claim 15 wherein the number of through holes is two. A condenser lens and a projection lens provided in parallel with and parallel to the fly's eye lens, and an aperture provided between the fly's eye lens and the condenser lens, and provided between the condenser lens and the projection lens. In the forming method using a deformed lighting device having a mask or the like, The aperture is a complex illumination system aperture, characterized in that formed by combining at least two different illumination system aperture. 20. The method of claim 19, wherein the aperture is formed by combining a ring illumination aperture and a multipoint illumination aperture. 21. The method of claim 20, wherein the aperture forms the ring illumination aperture at a center thereof and forms the multi-point illumination aperture around the center so as to be rotationally symmetrical. 21. The method of claim 20, wherein the ring illumination aperture is formed by a transmissive circular diffraction grating. 23. The method according to claim 22, wherein the circular diffraction grating is formed with concentric grooves outwardly about its center. 24. The method of claim 23, wherein the groove is formed such that its depth is half the wavelength of light passing through the aperture. 22. The method according to claim 21, wherein the multi-point illumination system aperture is any one selected from a dead point or a two-point illumination system.