A bath supply and recovery device for improving pressure characteristics of an immersion flow field

Abstract

This invention relates to an immersion liquid supply and recovery device for improving the pressure characteristics of an immersion flow field. The invention features a top groove disposed on the top surface of the immersion liquid supply and recovery device. The gap between the surrounding surface and the objective lens side is connected to the top groove. An outer side surface is disposed opposite to the objective lens side surface of the top groove, and this outer side surface is farther from the objective lens side surface than the surrounding surface. The width of the surrounding surface from the objective lens side surface varies circumferentially, making the two ends of the surrounding surface farther from the objective lens side surface in the substrate movement direction than other circumferential positions. This increases the local gap volume between the immersion liquid supply and recovery device and the end objective lens, reducing the rise and fall of the top liquid level caused by local accumulation or reduction of immersion liquid. This suppresses pressure fluctuations and top liquid level sloshing in the immersion flow field, thereby stabilizing the pressure of the immersion flow field, ensuring stable optical properties of the immersion flow field, and guaranteeing exposure quality.

Description

Technical Field

[0001] This invention belongs to the field of immersion liquid recovery technology for immersion lithography machines, and relates to an immersion liquid supply and recovery device that improves the pressure characteristics of the immersion flow field. Background Technology

[0002] A photolithography machine is one of the core pieces of equipment in manufacturing very large-scale integrated circuits. It uses an optical system to precisely project the circuit pattern on a photomask onto a substrate coated with photoresist, and then exposes and modifies the photoresist, thereby leaving the circuit pattern information on the substrate. It includes a laser source, a projection lens system, a projection photomask containing the circuit pattern, and a substrate coated with photosensitive photoresist.

[0003] Compared to dry lithography, which uses a gas as the intermediate medium, immersion lithography equipment fills the space between the last projection lens and the substrate with a high-refractive-index liquid. By increasing the refractive index (n) of this liquid medium, the numerical aperture (NA) of the projection lens is increased, thereby improving the resolution and depth of focus of the lithography equipment. Among current mainstream lithography technologies, immersion lithography is widely used due to its good inheritance from earlier dry lithography. For filling the immersion liquid, the commonly used method is partial immersion, which uses an immersion liquid supply and recovery device to confine the liquid to a local area between the lower surface of the last projection lens and the upper surface of the substrate. Maintaining the optical consistency and transparency of the immersion liquid within the exposure area is crucial for ensuring the exposure quality of immersion lithography. Therefore, existing technologies often use liquid injection and recovery to achieve real-time updates of the immersion flow field, promptly removing photochemical contaminants, localized heat, micro- and nano-bubbles from the core exposure area to ensure the high purity and uniformity of the immersion liquid.

[0004] like Figure 1 and Figure 2As shown, the projection lens system in the immersion lithography machine has an end lens 1 closest to the substrate 2, and a first gap 11 is formed between the end lens 1 and the substrate 2. An immersion liquid supply and recovery device 3 is arranged around the end lens 1. The immersion liquid supply and recovery device 3 supplies immersion liquid LQ into the first gap 11. The immersion liquid supply and recovery device 3 has a central through hole 31 for the exposure laser beam from the end lens 1 to pass through. When the exposure laser beam carrying circuit pattern information passes through the end lens 1, it enters the immersion liquid LQ and is projected onto the substrate 2 after passing through the immersion liquid LQ. For the 193nm wavelength exposure laser beam commonly used in immersion lithography machines, the immersion liquid LQ can be ultrapure water. The refractive index of ultrapure water for 193nm laser is greater than that of air. Therefore, compared with dry lithography machines, the exposure laser beam of the immersion lithography machine can converge into a smaller-scale exposure target area after passing through the end lens 1 and the immersion liquid LQ, thereby forming a smaller-scale circuit pattern on the substrate, thereby improving the exposure resolution of the lithography machine. To prevent the immersion supply and recovery device 3 from transmitting vibration and thermal disturbance to the end objective lens 1 and interfering with its optical properties, the immersion supply and recovery device 3 is designed not to contact the end objective lens 1, thus forming a second gap 12 between the end objective lens 1 and the immersion supply and recovery device 3. Since existing immersion lithography machines move the substrate 3 relative to the end objective lens 1 according to the scanning stepping principle during exposure, the exposure laser beam scans and projects a single circuit pattern onto a single target area of ​​the substrate 2, and steps to project the same circuit pattern onto multiple target areas of the substrate 2; because the substrate 2 moves relative to the end objective lens 1, while the immersion supply and recovery device 3 remains stationary relative to the end objective lens 1, the substrate 2 also moves relative to the immersion supply and recovery device 3, resulting in a third gap 13 between the substrate 2 and the immersion supply and recovery device 3.

[0005] During the exposure process, the laser beam heats the immersion liquid LQ, and the photoresist on the substrate 2 undergoes a photochemical reaction, potentially releasing contaminants into the immersion liquid LQ. Changes in the temperature and cleanliness of the immersion liquid LQ will alter its optical properties. Therefore, an immersion liquid supply and recovery device 3 is installed to continuously flow and refresh the immersion liquid LQ to maintain its temperature and cleanliness. Specifically, the immersion liquid supply and recovery device 3 has a main injection port 4 facing the second gap 12, through which the immersion liquid LQ is supplied to the second gap 12 by the immersion liquid supply system LS. The immersion liquid supply and recovery device 3 also has a main extraction port 5 facing the second gap 12 and located opposite the main injection port 4, through which the main extraction system VM extracts and removes contaminants. Immersion liquid LQ; most of the immersion liquid LQ flows into the second gap 12 through the self-filling port 4, and then into the first gap 11. The immersion liquid in the first gap 11 and the second gap 12 is then pumped out by the main pumping port 5. A portion of the immersion liquid LQ will flow into the third gap 13. In order to avoid a large amount of immersion liquid LQ remaining on the surface of the substrate 2 and causing photolithography defects on the substrate 2, and to avoid the immersion liquid LQ wetting other components and causing damage, the immersion liquid supply and recovery device 3 is provided with a sealed pumping port 6 on the surface facing the substrate 2. The sealed pumping port 6 can be a ring of evenly distributed small holes or an annular slit. The sealed pumping system VC is used to pump out the immersion liquid LQ in the third gap 13 through the sealed pumping port 6. During the scanning and stepping motion, substrate 2 pulls on the immersion liquid LQ. To prevent excessive pulling on the immersion liquid LQ during high-speed movement of substrate 2, which could cause it to break free from the constraint of the sealed extraction port 6, a gas-tight port 7 is provided radially outside the sealed extraction port 6 in the immersion liquid supply and recovery device 3. The gas supply system AS supplies gas flow to the third gap 13 through the gas-tight port 7. Under the increased pressure and purging effect of the gas flow, the constraint capability of the sealed extraction port 6 on the immersion liquid LQ is also enhanced. The main extraction port 5 and the sealed extraction port 6 completely extract the immersion liquid LQ, forming a meniscus 20 between the immersion liquid LQ and the surrounding gas. The immersion liquid space enclosed by the meniscus 20 is the immersion flow field.

[0006] During the scanning and stepping motion of substrate 2, the immersion liquid LQ is pulled, causing pressure increases or decreases in the immersion flow field due to viscous forces. This results in increased pressure in the region facing the direction of substrate 2's movement and decreased pressure in the region away from it. In the second gap 12, the top liquid surface 21 of the immersion flow field exists as a free surface. If the pressure within the immersion flow field increases, it will push the top liquid surface 21 upwards. This upward movement of the top liquid surface 21 poses a risk, on the one hand, that the immersion liquid LQ overflows from the upper surface of the liquid inlet supply and recovery device 3 into other areas of the lithography machine. On the other hand, since the pressure in the immersion flow field is related to the height of the free surface, the rise and fall of the top liquid surface 21 will cause pressure fluctuations within the immersion flow field, affecting exposure quality. For example… Figure 3As shown, the substrate 2 moves in a -X direction 41 relative to the end objective lens 1 and the immersion liquid supply and recovery device 3. Due to the viscous force, the immersion liquid accumulates and the pressure increases in the -X side region of the first gap 11 facing the direction of substrate 2 movement, while the immersion liquid decreases and the pressure decreases in the +X side region facing away from the direction of substrate 2 movement. This causes the top liquid level 21 on the -X side of the second gap 12 to rise and the top liquid level 21 on the +X side to fall. The top liquid level 21 on the -X side may overflow the top of the immersion liquid supply and recovery device 3, causing immersion liquid to remain on the +X side. The top liquid surface 21 may detach from the main pumping port 5, resulting in a reduction in the pumping power of the immersion liquid. In addition, the scanning and stepping motion can generally be regarded as reciprocating. When the substrate 2 performs a stepping motion 41 in the +X direction relative to the end objective lens 1 and the immersion liquid supply and recovery device 3, it will cause the top liquid surface 21 on the -X side of the second gap 12 to drop and the top liquid surface 21 on the +X side to rise. This up-and-down "swaying" phenomenon of the top liquid surface 21 causes a decrease in the working efficiency of the main injection port 4 and the main pumping port 5, as well as introduces unfavorable pressure pulsations into the immersion liquid flow field. Summary of the Invention

[0007] The purpose of this invention is to provide an immersion liquid supply and recovery device that improves the pressure characteristics of the immersion flow field, thereby suppressing the vertical oscillation phenomenon of the top liquid surface.

[0008] The present invention has a surrounding surface that surrounds the side of the objective lens, and the surrounding surface forms a gap with the side of the objective lens. Immersion liquid supply openings and immersion liquid extraction openings are provided at opposite ends on the horizontal cross-section of the surrounding surface. On at least one horizontal cross-section of the surrounding surface, the width between the surrounding surface and the side of the objective lens varies circumferentially.

[0009] The surrounding surface is farther from the objective lens side at both ends in one direction of substrate movement compared to other circumferential positions.

[0010] The surrounding surface is farther from the objective lens side at both ends of the two mutually perpendicular directions of substrate movement compared to other circumferential positions.

[0011] The surrounding surface is farther from the objective lens side than at other circumferential locations near the immersion supply opening and the immersion drain opening.

[0012] The surrounding surface is farther from the objective lens side near both ends of the line connecting the immersion supply opening and the immersion drain opening in the vertical direction compared to other circumferential positions.

[0013] The invention may also have a surrounding surface that surrounds the side of the objective lens, with a gap between the surrounding surface and the side of the objective lens, and an immersion liquid supply opening and an immersion liquid discharge opening provided at opposite ends on the horizontal cross-section of the surrounding surface; it also has a top groove provided on the top surface of the immersion liquid supply and recovery device, with the gap between the surrounding surface and the side of the objective lens communicating with the top groove, and an outer side of the top groove provided opposite to the side of the objective lens, the outer side of the groove being farther away from the side of the objective lens than the surrounding surface.

[0014] Immersion liquid is supplied through the immersion supply opening on the surrounding surface, such that the top liquid level of the immersion liquid is located radially inside the top groove when the substrate is stationary.

[0015] The outer side of the groove is farther from the objective lens side at both ends in one direction of substrate movement compared to other circumferential positions.

[0016] The outer side of the groove is farther from the objective lens side at both ends of the two mutually perpendicular directions of substrate movement compared to other circumferential positions.

[0017] The outer side of the groove is farther from the objective lens side than other circumferential locations near the immersion liquid supply opening and the immersion liquid extraction opening.

[0018] The present invention configures the immersion liquid supply and recovery device such that the width of the surrounding surface of the device from the objective lens side varies in the circumferential direction. This makes the two ends of the surrounding surface farther from the objective lens side in the substrate movement direction than other circumferential positions. This increases the local gap volume between the immersion liquid supply and recovery device and the end objective lens, thereby reducing the rise and fall of the top liquid level when the immersion liquid locally accumulates or decreases. This suppresses the pressure fluctuations in the immersion flow field and the amplitude of the top liquid level sloshing, thus making the pressure of the immersion flow field more stable, ensuring the stability of the optical properties of the immersion flow field, and guaranteeing the exposure quality. Attached Figure Description

[0019] Figure 1 A longitudinal cross-sectional schematic diagram of the immersion liquid supply recovery device and the immersion flow field;

[0020] Figure 2 A bottom view of the liquid recovery unit;

[0021] Figure 3 This is a schematic diagram illustrating the change in the height of the top liquid level caused by substrate pulling.

[0022] Figure 4 The immersion flow field pressure distribution pattern within the first gap when the substrate undergoes a stepping motion;

[0023] Figure 5 This is a schematic diagram of the structure of Embodiment 1 of the present invention;

[0024] Figure 6 This is a schematic diagram of the second gap in Embodiment 1 of the present invention;

[0025] Figure 7 This is a schematic diagram of the second gap in Embodiment 2 of the present invention;

[0026] Figure 8 This is a schematic diagram of the second gap in Embodiment 3 of the present invention;

[0027] Figure 9 This is a schematic diagram of the structure of Embodiment 4 of the present invention;

[0028] Figure 10 This is a schematic diagram of the second gap in Embodiment 4 of the present invention. Detailed Implementation

[0029] Example 1

[0030] Fluid simulation of the immersion flow field revealed that when the substrate undergoes a stepping motion 41 in the -X direction, the pressure distribution in the immersion flow field on the radially inner side of the through-hole 31 exhibits the following characteristics: Figure 4 The shape shown. In Figure 4 In the diagram, isobars 50 depict the pressure distribution in the immersion flow field. A localized high-pressure zone 51 exists on the side of the main injection port 4 facing the substrate movement direction, while a localized low-pressure zone 52 exists on the side of the main extraction port 5 facing away from the substrate movement direction. The substrate pulls the immersion liquid in the first gap 11 towards the -X side. The immersion liquid is blocked by the through-hole 31 and accumulates, causing pressure buildup on the -X side of the through-hole 31, which also raises the top liquid level 21. The substrate pulls the immersion liquid away from the +X side of the first gap 11, causing a decrease in pressure on the +X side of the through-hole 31, which also lowers the top liquid level 21.

[0031] like Figure 5 and Figure 6 As shown, in response to the phenomenon and cause of pressure distribution and top liquid level height fluctuations in the immersion flow field, this invention provides a second gap whose horizontal width varies circumferentially. Specifically, the end objective lens 1 has an objective lens side surface 122, and the immersion liquid supply and recovery device 3 has a surrounding surface 121 facing the objective lens side surface 122, forming a second gap 12 between the surrounding surface 121 and the objective lens side surface 122; as Figure 6As shown, the second gap 12 is cut along the horizontal plane, and the width D of the second gap 12 varies circumferentially. The cross-section of the objective lens side surface 122 is generally circular, but the cross-section of the surrounding surface 121 can be set to be elliptical to obtain a second gap 12 that meets the requirements. The surrounding surface 121 can be farther from the objective lens side surface 122 near the main injection port 4 and the main extraction port 5 than at other circumferential positions of the surrounding surface 121 to obtain a larger local volume. In this way, when the stepping motion 41 causes the immersion liquid near the main injection port 4 and the main extraction port 5 to accumulate or decrease, the top liquid level 21 can rise or fall less, thereby enhancing the buffering effect of the second gap 12 on pressure increases or decreases, and thus making the pressure in the immersion flow field more stable. It can be understood that the horizontal cross-sectional shape of the surrounding surface 121 does not necessarily have to be set to elliptical; it can also be set to a shape with unequal distances from the objective lens side surface 122 at other circumferential positions.

[0032] Example 2

[0033] like Figure 7 As shown, the horizontal cross-section of the surrounding surface 121 is elliptical, and the ends furthest from the objective lens side 122 are further away from the main injection port 4 and the main extraction port 5. Typically, the substrate scanning motion direction 42 is set along the Y-axis, which is perpendicular to the line connecting the main injection port 4 and the main extraction port 5. Furthermore, to achieve higher lithography efficiency, a longer scanning path is desired to have a higher speed than a stepping motion. Therefore, the substrate's pulling effect on the immersion liquid is stronger during scanning, resulting in a stronger effect on raising and lowering the top liquid level 21. A wider second gap 12 in the Y-axis direction helps suppress disturbances to the height of the top liquid level 21 caused by the substrate scanning motion.

[0034] The remaining implementation methods are the same as in Example 1.

[0035] Example 3

[0036] like Figure 8 As shown, the surrounding surface 121 is set in a rhombus shape, wherein the surrounding surface 121 is farther from the objective lens side surface 122 at both ends of the X and Y axes compared to other positions in the circumferential direction. This arrangement suppresses the disturbance of the height of the top liquid surface 21 by the substrate scanning motion and the stepping motion.

[0037] The remaining implementation methods are the same as in Example 1.

[0038] Example 4

[0039] like Figure 9 and Figure 10As shown, a top groove 14 is provided on the top surface of the immersion liquid supply and recovery device 3. The top groove 14 communicates with the second gap 12 and is opposite to the objective lens side 122. The top groove 14 is located above the main injection port 4 and the main extraction port 5. When the substrate is stationary due to the supply of immersion liquid, the top liquid surface 21 is located radially inside the top groove 14. Since the top groove 14 has a wider horizontal width and volume than the second gap 12, the pressure fluctuation of the immersion flow field has a smaller impact on the height of the top liquid surface 21 in the top groove 14. In addition, the top groove 14 can suppress pressure pulsation while keeping the width of the second gap 12 unchanged. In this way, the flow resistance of the immersion liquid discharge path of the main injection port 4 changes less, which makes it easier for the immersion liquid to flow into the second gap 12 and the first gap 11, and can avoid excessively increasing the power of the immersion liquid supplied through the main injection port 4. The top groove 14 has an outer side 123, which forms a top groove width d with the objective lens side 122. The horizontal cross-section of the outer side 123 can be set to a rhombus shape, and it is farther from the objective lens side 122 at both ends of the X and Y axes compared to other circumferential positions, which can better suppress the disturbance of the top liquid surface 21 height by the scanning and stepping motion of the substrate. Of course, similar to Embodiment 1 or Embodiment 2, the horizontal cross-section of the outer side 123 can also be set to an ellipse with both ends farther from the objective lens side 122 in the X direction or both ends farther from the objective lens side 122 in the Y direction, so as to enhance the suppression of pressure pulsation in local positions with large pressure fluctuations in the immersion flow field.

[0040] The above content and structure describe the basic principles, main features, and advantages of the product of this invention, which should be understood by those skilled in the art. The examples and descriptions above are merely illustrative of the principles of this invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A liquid supply and recovery device for improving the pressure characteristics of an immersion flow field, characterized in that: It has a surrounding surface that surrounds the side of the objective lens, forming a gap between the surrounding surface and the side of the objective lens. Immersion supply openings and immersion discharge openings are provided at opposite ends on the horizontal cross-section of the surrounding surface. It also has a top groove provided on the top surface of the immersion supply and recovery device. The gap between the surrounding surface and the side of the objective lens is connected to the top groove. The top groove has an outer side opposite to the side of the objective lens, and the outer side is farther away from the side of the objective lens than the surrounding surface. The outer side of the groove is farther from the objective lens side at both ends in one direction of substrate movement compared to other circumferential positions, or at both ends in two mutually perpendicular directions of substrate movement compared to other circumferential positions, or near the immersion supply opening and immersion drain opening compared to other circumferential positions.

2. The immersion liquid supply and recovery device for improving the pressure characteristics of the immersion flow field as described in claim 1, characterized in that: Immersion liquid is supplied through the immersion supply opening on the surrounding surface, such that the top liquid level of the immersion liquid is located radially inside the top groove when the substrate is stationary.

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