CN100462848C - Sealed control device for liquid supply and recovery in immersion lithography system - Google Patents

Abstract

The invention discloses a sealing control device for liquid supply and recovery in an immersion photolithography system. It is a sealed control device for liquid supply and recovery between the projection lens group in the immersion lithography system and the silicon wafer to be exposed. The sealing control device for liquid supply and recovery is composed of an external pipe connection body of the immersion unit, a cavity of the immersion unit and a working surface of the immersion unit. Double air curtain sealing and double porous medium recovery are adopted. The sealing gas injection and gas-liquid mixed recovery pipelines have a buffer and pressure equalization structure, and an air curtain with stable flow and uniform pressure difference is obtained at the boundary of the gap flow field, which prevents the stepping and scanning strokes In the liquid leakage, at the same time in the liquid recovery part, the increased effective working area reduces the stagnant liquid on the surface of the silicon wafer. At the same time, it has a strong ability to resist the pulsation of gas source supply. The thickness of the sealing air curtain is small, the input power of the gas source is small, the efficiency is high, and the overall back pressure of the silicon wafer is reduced.

Description

Sealed control device for liquid supply and recovery in immersion lithography system

technical field

The invention relates to a liquid supply and recovery sealing control device in an immersion lithography (Immersion Lithography) system, in particular to a liquid in the gap between the near-field end element of the projection lens group (Lens) and the silicon wafer (Wafer). It is a liquid transmission and sealing control device that transports liquid and ensures that the liquid does not leak.

Background technique

Modern lithography equipment is based on optical lithography, which uses an optical system to accurately project and expose the pattern on the mask onto the silicon wafer coated with photoresist. It includes an ultraviolet light source, an optical system, a projection mask composed of chip patterns, an alignment system and a silicon wafer covered with photosensitive photoresist. The immersion lithography system fills the gap between the projection lens and the silicon wafer with some kind of liquid, and increases the numerical aperture (NA) of the projection lens by increasing the refractive index (n) of the medium in the gap, thereby improving the resolution of lithography rate and depth of focus. In the step-scan lithography equipment, the silicon wafer scans at a high speed during the exposure process. This high-speed motion will take the filling liquid out of the gap, which will cause the liquid to leak. The leaking fluid will cause some parts of the lithography equipment to malfunction, such as the interferometers that monitor the position of the silicon wafer. Therefore, in the immersion lithography technology, it is necessary to focus on solving the sealing problem of the filling liquid.

The sealing structure of the current immersion lithography system generally adopts an air-tight member to surround the gap field between the end element of the projection lens group and the silicon wafer. A hermetic seal is formed between the hermetic seal member and the surface of the silicon wafer to hermetically seal liquid in the gap field. However, in the various airtight structures proposed, there are the following problems:

(1) The phenomenon of uneven flow and concentrated pressure at the gas sealing boundary. Uneven air flow is not conducive to liquid sealing on the one hand, and causes leakage during stepping and scanning. On the other hand, it may cause cracking of the gap flow liquid film, causing air bubbles to enter the exposure field between the projection lens and the silicon wafer, thereby affecting imaging. quality.

(2) The air sealing effect is not good, and the liquid on the working surface stays too much. The effective working area of the liquid recovery part is small, and the liquid cannot be recovered in time during the movement stroke of stepping and scanning, resulting in a large amount of retention.

(3) The gas demand for airtight work is too large. Excessive gas demand has high requirements for the supply of the back-end source, which is not suitable for continuous and pulsation-free. At the same time, under high-speed motion, it is not conducive to the uniformity of static pressure on the surface of the silicon wafer and the reduction of the back pressure on the surface of the silicon wafer, which affects the imaging quality.

Contents of the invention

The object of the present invention is to provide a sealing control device for liquid supply and recovery in an immersion photolithography system.

In order to achieve the above object, the technical scheme adopted in the present invention is as follows:

The liquid supply and recovery sealing control device in the immersion lithography system is a liquid supply and recovery sealing control device installed between the projection lens group in the immersion lithography system and the silicon wafer to be exposed; the liquid supply And the recovered sealed control device, which is composed of the external pipeline connection body of the immersion unit, the cavity of the immersion unit and the working surface of the immersion unit; wherein:

1) External piping connection body of the immersion unit:

There is a gas injection pressure buffer chamber, a gas-liquid mixture recovery buffer chamber, and a liquid injection chamber connected to the external channel pipeline;

On the connecting body of the external pipeline of the immersion unit, there are five layers: an outer gas injection pressure buffer chamber, an inner gas injection pressure buffer chamber, an outer gas-liquid mixture recovery buffer chamber, an inner gas-liquid mixture recovery buffer chamber and a liquid injection chamber. A corresponding interface for connecting the ring-shaped cylindrical cavity with the external water supply and gas supply system;

2) Immersion unit cavity:

This part is composed of five consecutive ring-shaped cylindrical cavities nested from the center to the outside, which are the liquid injection cavity, the inner gas-liquid mixture recovery buffer cavity, the inner gas injection pressure buffer cavity, and the outer gas-liquid The mixture recovery buffer chamber and the outer gas injection pressure buffer chamber, the five ring-shaped cylindrical chambers are connected vertically upwards to the external water supply and gas supply system through the corresponding interface of the external pipeline connection body of the immersion unit;

3) Working face of immersion unit:

This part provides the connection channels between the five annular cylindrical cavities in the cavity of the immersion unit and the working space on the upper surface of the silicon wafer:

First, the array of gas injection holes in the outer layer is arranged along the circumferential direction, the direction of the holes is perpendicular to the working surface of the immersion unit, and the array of gas injection holes in the outer layer communicates upward with the buffer cavity of the gas injection pressure in the outer layer;

Second, the array of gas injection holes in the inner layer is arranged along the circumferential direction, the direction of the holes is perpendicular to the working surface of the immersion unit, and the array of gas injection holes in the inner layer communicates upward with the gas injection pressure buffer cavity in the inner layer;

Third, the annular continuous groove where the outer porous medium is located communicates upward with the outer gas-liquid mixture recovery buffer chamber;

Fourth, the annular continuous groove where the inner layer porous medium is located communicates upward with the inner layer gas-liquid mixture recovery buffer chamber.

The joint surface between the external pipe connection body of the immersion unit and the cavity of the immersion unit is a plane, and the joint surface between the cavity of the immersion unit and the working surface of the immersion unit is a plane, and the connection method adopts bonding or bolt fastening.

The beneficial effects that the present invention has are:

(1) Double air curtain sealing and double porous medium recovery methods are adopted. The sealing gas injection and gas-liquid mixed recovery pipelines have buffer and pressure equalization structures, and an air flow curtain with stable flow and uniform pressure difference is obtained at the boundary of the gap flow field, which prevents stepping And the liquid leakage during the scanning stroke, and at the same time in the liquid recovery part, the increased effective working area reduces the stagnant liquid on the surface of the silicon wafer. It can form a uniform and stable slit flow field sealing air curtain on the surface of the silicon wafer, and at the same time has a strong ability to resist the pulsation of the gas source supply. The thickness of the sealing air curtain is small, the input power of the gas source is small, the efficiency is high, and the overall back pressure of the silicon wafer is reduced.

(2) It can effectively recover the injected immersion liquid, reduce the liquid retention in the stepping and scanning motion stroke, and has a high tolerance for speed and acceleration.

(3) The device has no moving parts, the number of parts is small, the disassembly and assembly wear is small, and the installation accuracy is easy to ensure.

Description of drawings

Fig. 1 is the simplified schematic diagram that the present invention is assembled with projection lens group;

Fig. 2 is an explosion sectional view of the present invention;

Fig. 3 is the bottom view of the working surface of the immersion unit of the present invention;

Fig. 4 is a P1-P1 sectional view of the immersion unit cavity;

Fig. 5 is a partially enlarged sectional view of the present invention representing a single-layer sealed control loop;

Fig. 6 is a partially enlarged cross-sectional view of the high-voltage isolation sealing tape of the present invention.

In the figure: 1. Projection lens group, 2. Sealing control device, 2A, Working surface of immersion unit, 2B, Cavity of immersion unit, 2C, External pipeline connection body of immersion unit, 3. Silicon wafer, 4A, Porous medium, 4B , porous medium, 5A, gas injection pressure buffer chamber, 5B, gas injection pressure buffer chamber, 6A, gas-liquid mixture recovery buffer chamber, 6B, gas-liquid mixture recovery buffer chamber, 7, groove, 8A, gas injection hole array, 8B . Air injection hole array, 9. Liquid injection chamber, 10. Slit flow field.

Detailed ways

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

Fig. 1 schematically shows the assembly of the sealing control device and the projection lens group according to the embodiment of the present invention, and the device can be applied in step-and-repeat or step-and-scan lithography equipment. During the exposure process, light from a light source (not shown in the figure) (such as krypton fluoride or argon fluoride excimer laser) passes through an aligned reticle (not shown in the figure), projection lens group 1 and The lens-silicon wafer gap field filled with immersion liquid exposes the photoresist on the surface of the silicon wafer 3 . The immersion unit is connected to the external pipeline connector 2C, the immersion unit cavity 2B, and the immersion unit working surface 2A. The joint surface between the three parts is a plane, and the connection method is bonding or bolt fastening according to the specific working conditions.

As shown in Fig. 1, Fig. 2 and Fig. 3, the immersion unit is composed of three parts: the working surface 2A of the immersion unit, the cavity 2B of the immersion unit, and the connecting body 2C of the external pipeline of the immersion unit. The immersion liquid enters from the liquid injection chamber 9 and fills the gap flow field 10 between the lens group 1 and the silicon wafer 3, and is recovered through two layers of porous media 4A and 4B along the way, and there are two layers of gas injection hole arrays 8A and 8B with circumferential closure The formed air curtain acts as an air seal, which ensures the effective recovery of the immersion liquid, reduces the residue, and enhances the adaptability of the movement state.

As shown in Figure 4 and Figure 5, the high-pressure gas from the gas source pipeline will pass through the circumferential continuous gas injection pressure buffer chambers 5A and 5B before the gas injection hole arrays 8A and 8B, and the position of the pipeline loop is at the gas source inlet of the immersion unit Between 2C and the gas injection hole arrays 8A, 8B, and in the circumferential direction of the immersion unit, the structure of the ring-shaped sealed air chamber is distributed. The gas injection pressure buffer chambers 5A, 5B can balance the high-pressure gas field pressure in the circumferential direction while suppressing the pulsation of the gas source, so that the gas injection hole arrays 8A, 8B can obtain relatively consistent initial injection pressure. The gas blown out by the gas injection hole arrays 8A, 8B forms a gas curtain and splits near the surface of the silicon wafer 3, a part of which is recovered by the porous media 4A, 4B. Part of the immersion liquid in the slit flow field 10 comes from the sealing gas split by the air curtain, before entering the recovery chamber 6A, 6B, it first passes through the porous media 4A, 4B area. The porous media 4A, 4B, which are closely parallel to the gas injection hole arrays 8A, 8B in the circumferential direction and are distributed in a closed circle, effectively reduces the numerical aperture of the recovery pipeline, and suppresses the destruction of the slit flow field by bubble bursting during the recovery process 10 A stable source of vibration. Appropriately increasing the size in the radial direction of the distribution area of the porous medium 4A, 4B can effectively increase the tolerance of the sealing control device 2 to the speed and acceleration during the stepping and scanning process.

As shown in FIG. 6 , the air curtain formed by the air injection hole arrays 8A, 8B distributes a large number of micro-radius through holes (for example, 0.5 mm in diameter and 1.5 mm in pitch) in the circumferential direction of the fixed radius of the immersion unit working surface 2A. The high-pressure gas is blown to the surface of the silicon wafer through the air hole array, forming a circumferentially closed airtight curtain. Between the airtight working area of the inner layer structure (gas injection hole array 8B) and the recovery area of the porous medium 4A of the outer layer structure, there is a groove 7 with a trapezoidal cross-section distributed around the circumference. A high-pressure isolation zone is formed in the groove 7 to further prevent liquid leakage. Double air injection hole arrays 8A, 8B are used to form air curtain seals and double porous media 4A, 4B recovery methods, the sealing gas injection and gas-liquid mixed recovery pipelines respectively have gas injection pressure buffer chambers 5A, 5B and gas-liquid mixture recovery buffer chambers 6A, 6B Buffer and pressure equalization structure, the air flow curtain with stable flow and uniform pressure difference is obtained at the boundary of the slit flow field 10, which prevents liquid leakage during the stepping and scanning strokes, and at the same time in the liquid recovery part, the effective working area of the porous media 4A, 4B is enlarged Reduces entrapped liquid on the wafer surface. The porous medium 4A, 4B recovery area, the porous medium 4A, 4B that is parallel to the gas injection hole array in the circumferential direction at a close distance (such as 2mm) and the circumference is closed, the pipeline loop position is between the gap flow field 10 and the recovery area. Between the buffer cavities 6A and 6B, there is an appropriate size in the radial direction of the distribution area of the porous media 4A and 4B (for example, 8mm). The gas-liquid mixture recovery buffer cavity 6A, 6B, the pipeline loop position is between the immersion unit external pipeline connection body 2C and the gap flow field 10, and the structure of the ring-shaped sealed air chamber is distributed in the circumferential direction of the immersion unit .

To sum up, the present invention is different from the existing gas sealing control structure of the liquid flow field in the literature, and provides a sealing control device for liquid supply and recovery in the immersion lithography system. Double air curtain sealing and double porous medium recovery are adopted, and the sealing gas injection and gas-liquid mixed recovery pipelines have buffer and pressure equalization structures, and the air flow curtain with stable flow and uniform pressure difference is obtained at the boundary of the gap flow field, which prevents the stepping and scanning strokes In the liquid leakage, at the same time in the liquid recovery part, the increased effective working area reduces the stagnant liquid on the surface of the silicon wafer.

Claims (2)

1. the seal control device supplying with and reclaim of the liquid in the immersion lithographic system, be that the seal control device that liquid is supplied with and reclaimed is housed between projection lens set (1) in immersion lithography system and the silicon chip to be exposed (3), it is characterized in that: the seal control device (2) that described liquid is supplied with and reclaimed, form by submergence unit external pipeline connector (2C), submergence unit cavity (2B) and submergence cell operation face (2A); Wherein:

1) submergence unit external pipeline connector (2C):

On submergence unit external pipeline connector (2C), have the corresponding interface that outer gas injection pressure cushion chamber (5A), internal layer gas injection pressure cushion chamber (5B), outer gas-liquid mixture recovery cushion chamber (6A), internal layer gas-liquid mixture recovery cushion chamber (6B) and fluid injection chamber (9) these five ring-type cylindrical cavities are connected with extraneous water and air supply system;

2) submergence unit cavity (2B):

This part is made up of the outside nested successively cylindrical cavity of ring-shaped continuous separately in center by five, be that fluid injection chamber (9), internal layer gas-liquid mixture reclaim cushion chamber (6B), internal layer gas injection pressure cushion chamber (5B), outer gas-liquid mixture recovery cushion chamber (6A) and outer gas injection pressure cushion chamber (5A) successively, five ring-type cylindrical cavities are connected with extraneous water and air supply system by the corresponding interface of submergence unit external pipeline connector (2C) respectively vertically upward;

3) submergence cell operation face (2A):

This part provides in the submergence unit cavity (2B) interface channel of five ring-type cylindrical cavities and silicon chip (3) upper surface work space:

The first, outer injecting hole array (8A) is along the circumferential direction arranged, and the direction in hole is perpendicular to submergence cell operation face (2A), and outer injecting hole array (8A) upwards communicates with outer gas injection pressure cushion chamber (5A);

The second, internal layer injecting hole array (8B) is along the circumferential direction arranged, and the direction in hole is perpendicular to submergence cell operation face (2A), and internal layer injecting hole array (8B) upwards communicates with internal layer gas injection pressure cushion chamber (5B);

The 3rd, the ring-like succeeding vat at outer porous medium (4A) place upwards reclaims cushion chamber (6A) with outer gas-liquid mixture and communicates;

The 4th, the ring-like succeeding vat at internal layer porous medium (4B) place upwards reclaims cushion chamber (6B) with the internal layer gas-liquid mixture and communicates.

2. the seal control device that the liquid in the immersion lithographic system according to claim 1 is supplied with and reclaimed, it is characterized in that: the faying face between submergence unit external pipeline connector (2C) and the submergence unit cavity (2B) is the plane, faying face between submergence unit cavity (2B) and the submergence cell operation face (2A) is the plane, and connected mode adopts bonding or bolted.

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