CN103454865A - Deep ultraviolet photoetching lighting system - Google Patents

Abstract

A deep-ultraviolet lithography illumination system includes a diffraction element and a condenser lens group; a quartz rod is located on the optical path of the condenser lens group, and the light converged by the condenser lens group enters through the incident end of the quartz rod and exits through the exit end; the quartz rod control device is responsible for The control quartz rod has a rotation axis perpendicular to the optical axis, the two ends of the quartz rod can be exchanged by rotating around the rotation axis, and different quartz rods can be placed on the optical axis by moving along the rotation axis. The rotation of the quartz rod control device is controlled by a high-precision rotary table, and the axial movement is controlled by a high-precision one-dimensional translation table; the conical prism group is located on the outgoing light path of the collimating mirror group; the collimating mirror group is located behind the control device, and the quartz rod On the outgoing light path; behind the collimating mirror group, the fly-eye lens array is responsible for decomposing the light beam into multiple secondary light sources and illuminating the mask surface through the subsequent imaging system. The invention realizes the multi-level change of the coherence factor by using a simple method, simplifies the design complexity of the zoom lens, and achieves the purpose of simplifying the structure and reducing the cost.

Description

A deep ultraviolet lithography illumination system

technical field

The invention relates to the field of lithography, in particular to a deep ultraviolet lithography illumination system.

Background technique

Optical projection lithography is an optical exposure process that uses the principle of optical projection imaging to transfer the integrated circuit (IC) pattern on the reticle to the rubber-coated silicon wafer in a step-by-step or step-and-scan manner. .

According to different exposure requirements when the lithography machine is actually working, different numerical apertures or coherence factors are required on the silicon wafer.

The existing technology is mainly to adjust the coherence factor of the lighting system by combining the zoom lens group with the upper conical prism.

For example, US Pat. No. 6,452,662 adopts the method of adjusting the coherence factor of the illumination system by combining a zoom lens group with a tapered prism. Figures 1a and 1b are diagrams of the system: the system mainly includes a beam expander and shaping system 10, a tapered prism and a zoom module 12, a homogenizer and a projection optical system 14. An optical axis 16, a pupil plane 18 and a modulation plane 20 are defined in the system. The module 12 includes a conical prism group and a zoom lens group with adjustable spacing, wherein the former of the aconic prisms 22 is a negative cone, and the latter is a positive cone. After passing through the beam expander and shaping system 10 in the light illumination system, the light emitted by the laser light source enters the module 12 composed of conical prisms and zoom mirrors, and finally enters the homogenizer and projection optical system module 14 to illuminate the modulation plane. FIG. 2 shows the available light energy distribution on the pupil plane 18 after being adjusted by the conical prism 22 and the zoom lens group 24 . Wherein when the pupil shape is changed from A to shape B, the interval of the conical prisms is set to zero, and the focal length of the zoom lens group 24 is enlarged; The interval of 22 is enough. The above process is to adjust the coherence factor of the lighting system.

However, when it is desired to obtain a wide range of coherence factors for the above-mentioned lighting system, the focal length ratio of the zoom lens group will be larger, and the control structure will become more complicated.

Contents of the invention

The technical solution of the present invention is to overcome the deficiencies of the prior art and provide a deep ultraviolet lithography lighting system, which can change the coherence factor of the lighting system in a simple way, simplify the zoom lens group, improve the efficiency of the lithography machine, and reduce the cost.

The technical solution of the present invention: a deep ultraviolet lithography lighting system, firstly, the virtual straight line passing through the center of each component of the lighting system is defined as the optical axis of the system, and the positive direction along the Z axis is the positive direction of the optical axis, and each component of the lighting system The centers of are all on the optical axis;

The lighting system also includes:

Diffraction element: located on the front-end illumination optical path of the illumination system, it shapes the incident beam into a corresponding shape, and obtains the energy distribution of the corresponding shape on the pupil plane;

The condenser lens group is located on the optical path of the illumination system behind the diffraction element, and converges the parallel light obtained by beam expansion and shaping near the incident port of the quartz rod;

The quartz rod is located on the optical path of the illumination system behind the condenser lens group. The light emitted by the condenser lens group enters through the incident end of the quartz rod and exits from its exit end; there are multiple quartz rods in the system; any two The diameter ratio of the two ends of the quartz rod is not the same;

The quartz rod control device is installed on the mechanical housing of the lighting system to fix the plurality of quartz rods. The quartz rod control device has a rotation axis perpendicular to the optical axis, and the quartz rod control device moves along the rotation axis to adjust the quartz rods. Place the designated quartz rod in the optical path of the lighting system to participate in the adjustment of the coherence factor of the lighting system, and the quartz rod can also be used to adjust the coherence factor of the lighting system around the rotation axis of the quartz rod control device;

Collimating lens group: located on the optical path of the lighting system behind the control device, responsible for collimating the beam emitted by the quartz rod;

Conical prism group: located behind the optical path of the illumination system of the collimator group, it is composed of two conical prisms. By adjusting the distance between the conical prisms, the height of the inner and outer edges of the beam can be changed at the same time, and the width and angle of the beam remain unchanged;

Fly-eye lens array: located on the optical path behind the tapered prism, it decomposes the light beam into multiple sub-light sources, and adjusts the uniformity of illumination on the mask surface of the illumination system;

Compound eye imaging system: multiple secondary light sources decomposed into the fly eye lens array illuminate the mask surface through the compound eye imaging system;

After the light beam passes through the system's diffraction element, condenser lens group, quartz rod, condenser lens group, and conical prism, a specific pupil shape formed by the diffraction element is formed on the front surface of the fly eye lens group. This surface is the pupil surface of the system.

The calibers at both ends of the quartz rod are different;

The control device is controlled by a one-bit translation stage with an adjustment accuracy of micron level to control the axial movement, and the rotation is controlled by a high-precision rotary stage with a resolution > 0.0001°, a one-way repeatability > 0.0005°, and an absolute control accuracy of 0.01°. The control accuracy meets the alignment requirements of the lighting system.

The collimator lens group must be a zoom lens group to collimate the incident light rays at different heights adjusted by the tapered prism.

The pyramidal prism group can be a positive pyramidal prism and a negative pyramidal prism or two pyramidal prisms. The tapered prism with concave tapered surface is negative tapered prism, and the tapered tapered prism with convex tapered surface is positive tapered prism. When positive and negative tapered prisms are combined, the negative tapered prism is placed on the light path of the lighting system after the collimator group, and the positive tapered prism is placed behind the negative tapered prism. There is enough axial distance between the forward conical prism and the collimating lens group to move the conical prism; when two positive conical prisms cooperate, the direction of the cone surface must be opposite to ensure that the beam only changes the beam size after passing through the prism group without changing the beam divergence angle. The combinations of the conical surfaces of the two conical prisms are as follows: the positive conical surface of the forward conical prism faces the negative direction of the optical axis, and the positive conical surface of the rearward conical prism faces the positive direction of the optical axis or the front one The positive cone of the positive tapered prism faces the positive direction of the optical axis, and the positive cone of the rearward tapered prism faces the negative direction of the optical axis. When the positive and negative tapered prisms are combined, the axial distance required to adjust the same beam size is smaller than the axial distance required for the combination of two positive tapered prisms, but the negative tapered prism is more difficult to process than the positive tapered prism; two When the positive tapered prisms are matched, the axial distance between the tapered prisms is larger than that of the positive and negative tapered prisms when the same beam size is adjusted.

Compared with the prior art, the present invention has the advantages that: the present invention utilizes a plurality of quartz rods with different aperture ratios, and uses a control device to control the quartz rods. The control device only needs to translate along the rotation axis or rotate around the vertical rotation axis to realize the multi-level numerical aperture of the lighting system, that is, the change of multi-level coherence factor. For an illumination system in which a specific quartz rod is placed on the light path, adjusting the distance between the conical prism groups can be adjusted between the minimum and maximum coherence factors of the illumination system determined by the specific quartz rod. Compared with adjusting the coherence factor of the lighting system only through the zoom lens group and the conical prism group, this method only needs to adjust the quartz rod control device once, and the control structure and process are simpler.

Description of drawings

Fig. 1a and Fig. 1b are the lighting system using zoom lens group and conical prism to adjust the coherence factor of the system in the U.S. patent US6452662, wherein Fig. 1a is the implementation diagram of the lighting system using quartz rod uniform light; light lighting system;

Fig. 2 is a schematic diagram of using a zoom lens group and a conical prism to adjust the energy distribution of the pupil plane in US Patent No. 6,452,662;

Shown in Fig. 3a, 3b, 3c is the diagram of the control device in the present invention. Fig. 3a is a projection diagram of the control device in the XZ plane, Fig. 3b is a projection diagram of the control device in the YZ plane, and Fig. 3c is a projection diagram of the control device in the XY plane;

Figures 4a, 4b, 4c, and 4d are schematic diagrams of the lighting system of the embodiment of the present invention, wherein Figure 4a is a schematic diagram of the implementation of the lighting system in which the quartz rod 301 is placed in the optical path of the lighting system, and Figure 4b is a schematic diagram of the lighting system after the control device is adjusted. The implementation diagram of the lighting system in which the rod 302 is placed in the optical path of the lighting system, Fig. 4c is a schematic diagram of the implementation of the lighting system in which the quartz rod 303 is placed in the optical path of the lighting system, and Fig. 4d is the implementation diagram of the lighting system in which the quartz rod 304 is placed in the optical path of the lighting system sketch;

Figures 5a, 5b, 5c, and 5d show a schematic diagram of the lighting system scheme after the quartz rod control device shown in Figure 4 is rotated 180° around the rotation axis in the embodiment of the present invention, wherein Figure 5a shows that the quartz rod 304 is placed in the lighting system The implementation diagram of the lighting system in the optical path of the system, Fig. 5b is the implementation diagram of the lighting system in which the quartz rod 303 is placed in the optical path of the lighting system after adjusting the control device, Fig. 5c is the implementation diagram of the lighting system in which the quartz rod 302 is placed in the optical path of the lighting system A schematic diagram, Figure 5d is a schematic diagram of the implementation of the lighting system in which the quartz rod 301 is placed in the light path of the lighting system;

Figures 6a, 6b, 6c, 6d, and 6e are schematic diagrams of adjusting the beam size with a quartz rod and a conical prism in the present invention, wherein Figures 6a, 6b, 6c, and 6d are respectively placing quartz rods 201, 202, 203, and 204 in the lighting system In the light path, the height of light emitted from the exit end of the quartz rod in the lighting system varies with the aperture ratio of the quartz rod. Figure 6e is a schematic diagram of the light emitted from the quartz rod being adjusted by the axicon;

Fig. 7 a, 7b, 7c show that can be used in the conical prism structural form of the present invention, and wherein Fig. 7 a is the schematic diagram that positive and negative conical prisms adjust beam height, and Fig. 7 b shows that two positive cones are adjusted in the first way The schematic diagram of the beam height, Fig. 7c shows the schematic diagram of two positive cones adjusting the beam height in the second way;

Detailed ways

The specific implementation manner of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific examples.

The invention can realize multi-level coherence factor transformation with a simple method, simplify the zoom lens group, and improve exposure efficiency.

The present invention first utilizes multiple quartz rods with different diameter ratios at the two ports, and through the control device, the specific quartz rods are placed on the optical path of the lighting system in different ways to participate in the adjustment of the coherence factor of the lighting system, and multiple numerical apertures, that is, the coherence factor can be realized. The change. Then the conical prism is used to change the overall height of the light beam and increase the adjustable range of the coherence factor. Compared with adjusting the coherence factor of the lighting system only through the zoom lens group and the conical prism group, this method only needs to adjust the quartz rod control device once, the control structure and process are simpler, and the multi-level coherence factor can be obtained. The control device is driven by a high-precision rotary table, which can achieve high rotation accuracy.

A measure of the ability of an optical system to collect light is a Laplace invariant:

L＝nhu (1)

In the formula, n, h and u respectively represent the refractive index of the medium, the height of the object and the angle of view;

Since formula (1) is an approximation to an optical system with a small angle, using sinu instead of u in a large-angle system can obtain a Laplace invariant closer to the real system. According to the Lagrangian invariant at the incident end and the outgoing end of the quartz rod, it can be obtained:

hnsinu=h'n'sinu' (2)

h, n, and u respectively represent the diameter of the entrance port of the quartz rod, the refractive index of the medium at the entrance end, and the angle of the edge light at the entrance end; h', n', and u' represent the diameter of the exit port of the quartz rod, the refractive index of the medium at the exit end, and the The angle of the edge rays.

It is more convenient in the description of this system to use the diameter D of the port of the quartz rod instead of h in the formula. The Lagrangian invariants at both ends of the quartz rod remain unchanged, and nsinu is the numerical aperture (NA) of the system, namely:

D ₁ NA ₁ =D ₂ NA ₂ (3)

In the formula, D ₁ and NA ₁ are the diameter and the incident numerical aperture of the incident end of the quartz rod, and D ₂ and NA ₂ are the diameter and the exit numerical aperture of the exit end.

The exit end face of the quartz rod is k times the diameter of the entrance end face, that is, D ₂ =kD ₁ , and NA ₁ =kNA ₂ can be obtained from the above formula, that is, the numerical aperture of the exit end is 1/k of the numerical aperture of the entrance end.

Fig. 4 and Fig. 5 show the schematic diagrams of adjusting the coherence factor of the lighting system according to the embodiment of the present invention. The present invention includes: the optical axis 08 of the lighting system passing through the center of each component in the lighting system, the diffraction element 01 is located at the front end of the lighting system, and is used to change the shape of the incident light beam; the condenser lens group 02 is responsible for converging the light beam shaped by the diffraction element 01 to the vicinity of the incident end face of the quartz rod; the control device 03 is used to fix the quartz rod 301a, the quartz rod 302b, the quartz rod 303c and the quartz rod 304d with different aperture ratios, and through translation along the rotation axis perpendicular to the optical axis or around the rotation axis Rotate to control the position of the quartz rod in the lighting system; the module 04 composed of the collimating lens group and the conical prism is responsible for collimating the beam and then adjusting the height of the beam. The fly-eye lens array 05 decomposes the adjusted and collimated beam into multiple secondary light sources, and uniformly illuminates the mask surface 07 through the fly-eye imaging system 06; in the lighting system, the front surface of the fly-eye lens 05 is defined as the Pupil face 09. After the light beam passes through the diffraction element 01, the condenser lens group 02, the quartz rod 03, the conical prism group and the collimating lens group 04, the pupil as shown in Figure 2 is formed on the pupil plane 09 by the diffraction element 01 shape.

In this embodiment, the diameter of one port of the quartz rod 301 is 6 mm, the diameter of the other port is 10 mm, and the length of the quartz rod 301 along the Z-axis direction is 50 mm.

Assuming that the beam is shaped by the diffraction element 01 and then converged by the condenser lens 02, the numerical aperture at the incident end face of the 301 quartz rod is 0.05.

The diameter of the exit end of the quartz rod 301 in Fig. 4a is 1.67 times the diameter of the entrance port. Since the numerical aperture of the condenser lens is 0.05, the numerical aperture of the exit end of the quartz rod is 0.03 according to formula (3).

Define the coherence factor σ as the ratio of the numerical aperture of the illumination system to the numerical aperture of the projection optical system, expressed as:

σ=NA _ill /NA _po (4)

It can be seen from the above formula that when the object-side numerical aperture of the projection optical system is fixed, adjusting the image-side numerical aperture of the illumination system can adjust the coherence factor of the illumination system.

The image-side numerical aperture of the illumination system can be adjusted by moving the control device 03 along the axis of rotation. In addition to the quartz rod 301, three other quartz rods are fixed in the control device 02, which are respectively 302, 303 and 304. The diameter of one end of the remaining three quartz rods is also 6mm, and the diameters of the other end are 9mm, 8mm, and 7mm respectively. Both ends of the quartz rod are square. In order to ensure the convenience of adjustment and the adjacent quartz rods do not affect each other, the distance between the centers of two adjacent quartz rods is 15mm.

Move the control device in Fig. 4a along the negative X-axis direction by 15mm, and place the quartz rod 302 in the light path of the lighting system, as shown in Fig. 4b. The diameter of the entrance port of the quartz rod is 6 mm, and the diameter of the exit port is 9 mm. The numerical aperture at the entrance is still 0.05, and the numerical aperture at the exit becomes 0.0333.

Move the control device in Fig. 4b along the negative X-axis direction by 15mm, and place the quartz rod 302 in the light path of the lighting system, as shown in Fig. 4c. The diameter of the entrance port of the quartz rod is 6 mm, and the diameter of the exit port is 8 mm. The numerical aperture at the entrance end is still 0.05, and the numerical aperture at the exit end becomes 0.0375.

Move the control device shown in Fig. 4c by 15mm along the negative X-axis direction, and place the quartz rod 302 in the light path of the illumination system, as shown in Fig. 4d. The diameter of the entrance port of the quartz rod is 6 mm, and the diameter of the exit port is 7 mm. The numerical aperture at the entrance is still 0.05, and the numerical aperture at the exit becomes 0.0429.

Turn the control device 180° around its rotation axis, and after the two ends of the quartz rod are reversed, the quartz rod 304 is in the optical path at this time, as shown in Figure 5a. The numerical aperture of the incident light is still 0.05, the diameter of the entrance port is 7 mm, the diameter of the exit port is 6 mm, and the numerical aperture of the exit port is 0.0583.

The control device in Fig. 5a is moved 15mm along the positive direction of the X axis, and the quartz rod 303 is placed in the optical path, as shown in Fig. 5b. The incident diameter of the quartz rod is 8mm, and the exit diameter is 6mm. The numerical aperture of the incident light is still 0.05, and the numerical aperture of the exit end is 0.0667.

The control device in Fig. 5b is moved 15mm along the positive direction of the X-axis, and the quartz rod 302 is placed in the optical path, as shown in Fig. 5c. The incident diameter of the quartz rod is 9mm, and the exit diameter is 6mm. The numerical aperture of the incident light is still 0.05, and the numerical aperture of the exit end is 0.075.

Move the control device in Fig. 5c for 15mm along the positive direction of the X-axis, and place the quartz rod 302 in the optical path, as shown in Fig. 5d. The incident diameter of the quartz rod is 10mm, and the exit diameter is 6mm. The numerical aperture of the incident light is still 0.05, and the numerical aperture of the exit end is 0.083.

The collimated beam height is linear to the incident light numerical aperture: as the incident light numerical aperture increases, the collimated beam height also increases.

The illumination system is designed so that when the numerical aperture of the exit end of the quartz rod is 0.03, the ratio of the collimated light beam to the aperture of the tapered prism is about 0.27. Since the light-passing size of the conical prism 402 determines the light-passing area of the fly-eye lens array 05, when the axicon distance is 0 mm, the ratio of the height of the light beam on the fly-eye lens array 05 to the light-passing aperture is also approximately 0.27.

The image-side numerical aperture of the illumination system is determined by the incident height of the light beam on the fly-eye lens array 05: the numerical apertures of light rays at different incident heights on the mask surface are different and proportional. When the incident height of the light is exactly equal to the effective aperture of the fly-eye lens array, the numerical aperture of the light on the mask surface is the maximum value of the theoretical numerical aperture of the illumination system, which is equal to the object space of the projection optical system in the lithography system numerical aperture.

When the incident beam is incident on the fly-eye lens array 05 with a relative aperture of 0.27, the ratio of its numerical aperture on the mask surface to the maximum numerical aperture of the illumination system is also 0.27, and the coherence factor of the illumination system can be obtained from formula (4) is 0.27.

Move the control device in Fig. 4a along the negative direction of the X axis by 15mm, place the quartz rod 303 in the optical path, as shown in Fig. 4b, the corresponding coherence factor of the illumination system is 0.3.

Move the control device in Fig. 4b along the negative direction of the X axis by 15mm, place the quartz rod 303 in the optical path, as shown in Fig. 4c, the corresponding coherence factor of the illumination system is 0.34.

Move the control device in Fig. 4c along the negative direction of the X axis by 15mm, place the quartz rod 303 in the optical path, as shown in Fig. 4d, the corresponding coherence factor of the illumination system is 0.39.

After rotating the control device in Figure 4d by 180°, the structure of the lighting system is shown in Figure 5a, and the coherence factor of the lighting system is 0.53.

Move the control device in Figure 5a by 15mm along the positive direction of the X-axis, the lighting system is shown in Figure 6b, and the corresponding coherence factor of the lighting system is 0.6.

Move the control device in Figure 5b by 15mm along the positive direction of the X-axis, the lighting system is shown in Figure 6c, and the corresponding coherence factor of the lighting system is 0.675.

Move the control device in Figure 5c by 15mm along the positive direction of the X-axis, the lighting system is shown in Figure 6d, and the corresponding coherence factor of the lighting system is 0.75.

From the above adjustment process, it can be seen that only by adjusting the control device, 8 levels of coherence factors can be obtained.

The principle of adjusting the beam height by the tapered prism is shown in Figure 6. Assuming that the half-cone angle of the cone surface is θ, the refractive index of the material is n, and the light is incident on the cone surface parallel to the optical axis, the angle θ’ of the light relative to the cone surface is:

θ′＝arcsin(n*sinθ) (5)

The angle between the outgoing ray and the optical axis is:

φ＝θ′-θ (6)

The height at which the beam changes is Δh=Δl*cosφ, where Δl is the distance between the tapered prisms 402a and 402b. In order to ensure no loss of light energy, the semi-diameter of the prism should be larger than the image height of the collimator group. As shown in FIG. 6 , the distance between the tapered prisms 402 is determined by the numerical aperture of the outgoing light of the quartz rod. The larger the numerical aperture of the outgoing light of the quartz rod, the smaller the movable interval of the conical prism and the smaller the corresponding adjustable range of the coherence factor under the premise of ensuring no loss of light energy.

The coherence factors obtained above are all obtained when the distance between the conical prisms 402 is 0, and changing the distance between the conical prisms 402 can also change the coherence factor of the system. For an illumination system with a coherence factor of 0.27, adjust the distance between the conical prisms 402 and change the height of the light beam to continuously change the coherence factor in the range of [0.27,0.9]; when the coherence factor is 0.3, adjust the distance between the conical prisms 402 , changing the height of the beam can make the coherence factor change continuously in the range of [0.3,0.9]; when the coherence factor is 0.34, adjust the interval of the conical prism 402, and change the height of the beam can make the coherence factor in [0.34,0.9] Continuous change in the range of; when the coherence factor is 0.34, adjusting the interval of the conical prism 402, changing the height of the light beam can make the coherence factor change continuously in the range of [0.39,0.9];

After rotating the control device, the coherence factor of the lighting system can be adjusted in the ranges of [0.53,0.9], [0.6,0.9], [0.675,0.9] and [0.75,0.9] respectively.

By adjusting the control device 03, the coherence factor of the system can be changed in 8 steps, and coupled with the conical prism 402, the coherence factor of the system can be changed in a wider range. The control device is driven by a high-precision rotary table, which can obtain high precision. The high-precision rotary table can rotate 360° around the rotation axis. The rotary table with a maximum rotation speed of 30° is selected in the system, and the exchange of the quartz rod port can be completed in 6 seconds.

As shown in Figure 7, there are two types of conical prisms, concave inward and convex outward, among which the conical prism with concave conical surface is a negative conic prism, and the conical prism with convex conical surface is a positive conical prism. conical prism.

For the conical prism group composed of positive and negative conic prisms shown in FIG. 7 a , when the air space between the conical prisms 702 a and 702 b is 0 mm, the beam size does not change. When the air gap is greater than 0, the height of the beam changes. Assuming that the opening angle of the tapered prism is 140°, when light is incident on the tapered prism parallel to the optical axis, the incident angle of the light on the tapered surface is 20°. According to the law of refraction n ₁ *sini ₁ =n ₂ *sini ₂ at the cone, where n1 and i1 are the refractive index of the conical prism and the incident angle of light on the cone, n2 and i2 are the refractive index and The angle at which light emerges in air. i ₁ is 20°, assuming that the refractive index of the cone prism is 1.5608, it can be calculated that i ₂ =32.25°, and the angle between the outgoing light and the optical axis i3=i2-(90-140/2)=12.25°. The distance between two conical prisms is L, the exit height of the light relative to the optical axis after passing through the negative conic prism is h ₁ , and the height on the positive conical prism is h ₂ , h ₂ -h ₁ =L*tan( i ₃ ). Assuming that the aperture of the tapered prism is D, when the beam is incident at a height of D/2, when the beam fills the aperture of the positive tapered prism, the distance between the two tapered prisms is L=D/(2*tan(i ₃ )).

The conical prism group composed of two positive conical prisms shown in Figure 7b and 7c must make the most epitaxial light beam incident parallel to the optical axis converge on the optical axis and then pass through the rearward positive conic prism to be collimated. straight. The distance between the two tapered prisms is also L, the exit height of light relative to the optical axis after passing through the negative tapered prism is h ₁ , and the height on the positive tapered prism is h ₂ . Assuming that the semi-diameter of the tapered prism is D, when the beam is incident at a height of D/2, h ₂ -h ₁ =L*tan(i ₃ )-D/2, the incident beam is reversed up and down with the optical axis as the symmetry axis , when the light beam fills the clear aperture of the forward tapered prism, the distance between two tapered prisms is L=3*D/(2*tan(i ₃ )).

It can be seen that when the height of the light beam is adjusted by D/2, the axial distance between the two positive conical prisms is greater than the axial distance between the positive and negative conical prisms by D/tan(i ₃ ), increasing the The axial length of the lighting system, but the machinability of the positive tapered prism is better than that of the negative tapered prism, so the two solutions have their own advantages.

It is simple and easy to change the numerical aperture and coherence factor of the system by adopting the invention, and only needs to adjust the quartz rod control device once during adjustment, which is simpler than the control structure and process of zooming and tapered prism.

To sum up, the present invention uses the rotation control device to control the quartz rods with different areas at both ends to be placed in the optical path of the lighting system, and the numerical aperture and exposure field of view can be changed by operating the control device to place the designated quartz rod in the optical path of the lighting system .

Compared with the method of adjusting the coherence factor of the lighting system with the zoom lens group and the conical prism, the present invention uses a high-precision rotary table drive control device to place different quartz rods in the optical path to adjust the coherence factor of the lighting system, which can achieve high precision. . When the numerical aperture and coherence factor of the system are adjusted through the quartz rod alone, multiple changes can be obtained. Cooperating with the conical prism, a wider range of coherence factor adjustment can be realized. The lighting system has a simple structure, low cost and high efficiency.

Parts not described in detail in the present invention belong to the well-known technology in the art.

The above are only some specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be covered within the protection scope of the present invention.

Claims (4)

1. A deep ultraviolet lithography lighting system, characterized in that: firstly, the virtual straight line passing through the center of each component of the lighting system is defined as the optical axis of the system, and the positive direction along the Z axis is the positive direction of the optical axis, and each component of the lighting system The centers of are on the optical axis; the lighting system includes: Diffraction element: located on the front-end illumination optical path of the illumination system, it shapes the incident beam into a corresponding shape, and obtains the energy distribution of the corresponding shape on the pupil plane; The condenser lens group is located on the illumination optical path of the illumination system, and converges the parallel light obtained by beam expansion and shaping near the incident port of the quartz rod; A quartz rod is located on the optical path of the condenser lens group, and the light emitted by the condenser lens group enters through the incident end of the quartz rod and exits from its exit end; there are multiple quartz rods in the system; any two quartz rods have two The diameter ratio of the end is not the same; The quartz rod control device is installed on the mechanical housing of the lighting system to fix the plurality of quartz rods. The quartz rod control device has a rotation axis perpendicular to the optical axis, and the quartz rod control device moves along the rotation axis to adjust the quartz rods. Place the designated quartz rod in the optical path of the lighting system to participate in the adjustment of the coherence factor of the lighting system, and the quartz rod can also be used to adjust the coherence factor of the lighting system around the rotation axis of the quartz rod control device; Collimating lens group: located on the optical path of the lighting system behind the control device, responsible for collimating the beam emitted by the quartz rod; Conical prism group: located behind the optical path of the illumination system of the collimator group, it is composed of two conical prisms. By adjusting the distance between the conical prisms, the height of the inner and outer edges of the beam can be changed at the same time, and the width and angle of the beam remain unchanged; Fly-eye lens array: located on the optical path behind the tapered prism, it decomposes the light beam into multiple sub-light sources, and adjusts the uniformity of illumination on the mask surface of the illumination system; Compound eye imaging system: multiple secondary light sources decomposed into the fly eye lens array illuminate the mask surface through the compound eye imaging system; After the light beam passes through the system's diffraction element, condenser lens group, quartz rod, condenser lens group, and conical prism, a specific pupil shape formed by the diffraction element is formed on the front surface of the fly eye lens group. This surface is the pupil surface of the system. 2. A deep ultraviolet lithography illumination system according to claim 1, characterized in that: the diameters of the two ends of the quartz rod are different, and both ends are square. 3. A deep ultraviolet lithography illumination system according to claim 1, characterized in that: the control device is controlled by a one-dimensional translation stage whose adjustment accuracy is in the order of microns to move axially, and the resolution is >0.0001°, The unidirectional repeatability > 0.0005°, the absolute control accuracy reaches 0.01° The high-precision rotary table controls the rotation, and the control accuracy meets the alignment requirements of the lighting system. 4. A deep ultraviolet lithography illumination system according to claim 1, characterized in that: the two prisms in the conical prism group can be negative conical prisms combined with positive conical prisms, or can be positive conical prisms The prism cooperates with the positive conical prism; the conical prism with the concave conical surface is the negative conical prism, and the conical prism with the convex conical surface is the positive conic prism; Placed on the optical path of the illumination system behind the collimating lens group, the positive conical prism is placed behind the negative conical prism; it can be moved to the negative direction of the optical axis through the negative conical prism or the positive conical prism can be moved along the positive direction of the optical axis way to change the height of the beam; when the lighting system uses two positive conical prisms to adjust the height of the beam, the orientation of the two positive conical surfaces must be opposite to ensure that the beam only changes in height after passing through the conical prism group without changing the divergence of light angle; the combinations of the conical surfaces of the two conical prisms are as follows: the positive conical surface of the forward conical prism faces the negative direction of the optical axis and the positive conical surface of the posterior conical prism faces the positive direction of the optical axis, or the position The positive cone of the forward tapered prism faces the positive direction of the optical axis and the positive cone of the rearward tapered prism faces the negative direction of the optical axis.

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