CN108345079B - Projection objective for exposure and photoetching system - Google Patents
Projection objective for exposure and photoetching system Download PDFInfo
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- CN108345079B CN108345079B CN201710060955.XA CN201710060955A CN108345079B CN 108345079 B CN108345079 B CN 108345079B CN 201710060955 A CN201710060955 A CN 201710060955A CN 108345079 B CN108345079 B CN 108345079B
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- objective
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
- G02B7/02—Mountings, adjusting means, or light-tight connections, for optical elements for lenses
- G02B7/021—Mountings, adjusting means, or light-tight connections, for optical elements for lenses for more than one lens
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/20—Exposure; Apparatus therefor
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- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
- Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)
Abstract
The invention provides a projection objective for exposure and a photoetching system using the projection objective for exposure, which sequentially comprise a plurality of objective chambers from top to bottom, wherein a gas guide device is arranged at the top of the objective chamber at the top layer, gas outlet holes are arranged at the objective chamber at the bottom layer, and gas flows into all the objective chambers from top to bottom from the gas guide device and flows out from the gas outlet holes. The invention leads the external gas to enter the objective chamber of the projection objective from the gas guiding device, thus changing the flowing direction of the gas, changing the pressure applied when the gas flows, avoiding the generation of flowing dead angles and reducing the probability of polluting the projection objective lens.
Description
Technical Field
The present invention relates to the field of semiconductors, and in particular, to a projection objective for exposure and a lithography system.
Background
In the prior art, as shown in fig. 1, a support frame 1 supports an illumination system 2, a mask stage 3, a projection objective 4 and a wafer stage 6, and a silicon wafer 5 coated with photosensitive photoresist is placed on the wafer stage 6. Referring to fig. 2, the projection objective 4 is composed of a plurality of outer lens holders 41 and inner lens holders 42 (dashed lines). The flow field model of the projection objective 4 is: a vent 430 is provided in the outer lens holder 41 for supplying a gas source, preferably an inert gas or a neutral gas, into the interior of the objective chamber, preferably helium or nitrogen, in order to avoid oxidation of the gas in the objective chamber due to exposure. Referring to fig. 2, the length direction of the vent 430 is a horizontal direction, gas enters the objective chambers (401, 402, 403, 404) between the outer ring lens holder 41 and the inner ring lens 42 in the horizontal direction, each inner ring lens 42 and the outer ring lens holder 41 which is coaxial form a group, each group of inner ring lens 42 and the upper and lower adjacent inner ring lens 42 are hermetically installed through the lens holder assembly, in order to communicate each objective chamber, a through hole 44 is drilled on the outer ring lens holder 41 installed on each group, a vent pipe 45 is arranged between the outer ring lens holders 41 of the two adjacent objective chambers to connect the corresponding through hole 44, and the gas enters the next objective chamber through the through hole 44.
When the projection objective works, in order to prevent the lens group from causing oxidation pollution due to heat influence generated by exposure or prevent introduced gas from polluting photoresist due to retention, the interior of the objective needs to maintain a flowing overpressure environment, a flow field in the objective desirably flows uniformly as much as possible, the expected value of the internal overpressure is 100 +/-1 Pa, and the expected value of the flow field speed range is 0-0.3 m/s. The device can prevent the invasion of the external environment, study the flow field and pressure distribution of the ventilation process of the internal structure of the objective lens through the flow field analysis of the internal structure of the objective lens, and prevent the pollution of the lens through the overpressure design of the internal structure of the objective lens.
The inlet pressure distribution, calculated at a flow rate of 12L/h, of about 0.000004kg/s, can be calculated according to the following equation:
wherein: poIs total pressure, PsIn order to be at a static pressure,
is a dynamic pressure, related to the gas density ρ and the flow velocity v.
In order to ensure that the objective chamber maintains a certain overpressure, the through hole 44 is designed to be 100 Pa, and the flow field and the pressure distribution state are checked after the flow field of the objective chamber is stable.
Referring to fig. 4, the flow field vector diagram distribution of the objective lens chamber shows that the gas entering from the vent 430 flows through the lower three chambers, namely chambers 402, 403 and 404, and the flow field velocity is relatively uniform and the distribution range is about 0-0.05 m/s. The gas flows in from the chamber 402 and forms a circular vortex in the chamber 402, meets the lower layer of through holes 44 and flows downwards, thereby forming the flow velocity distribution in the figure. As can be seen from fig. 3, the gas flow in chamber 402 is relatively strong, chamber 403 times, the flow rate toward chamber 404 gradually becomes zero due to the sudden increase of the volume of chamber 404, and the probability of flowing toward chamber 401 is about zero, so that the gas in chamber 401 can only exchange through molecular diffusion, and the surface of inner ring lens 42 adjacent to chamber 401 is easily contaminated due to gas retention or exposure reaction.
Through simulation experiments, the flow field distribution in the lens area is calculated to be uniform, the pressure distribution range is 100.13-100.00 Pa, but the gas flow speed and the pressure fluctuation at the inlet position are large.
Further, the above structure still faces the problems of: due to the design of the structure of the vent 430, the structure of the chamber 402, and the design of the through holes 44, a certain dead-angle area of the flow field is formed, and due to the existence of the dead-angle area of the flow field, the positions of the through holes 44 are designed exactly, so that the gas cannot flow into the chamber 401 from the dead-angle position. Through simulation, it can be seen from the gas flow lines entering from the inlet 430 that the uniform flow of the gas in the objective chamber formed by the design of the through holes 44 in the projection objective 4 is poor, and the utilization of the design is poor because 80% of the through holes 44 have no gas circulation.
The diffusion of gas molecules in the chamber 401 is experimentally verified to be related to the time, when nitrogen enters the projection objective 4 from the vent 430, a dissolved oxygen sensor is connected to the position of the through hole 44 for measuring the concentration content of oxygen inside the projection objective 4, and the time taken for the nitrogen to completely exhaust the air inside the projection objective 4 is calculated by monitoring the concentration content of oxygen, and the result shows that: when the oxygen concentration is zero, the time required is more than 1 hour, i.e. the time for the gas molecules inside the projection objective 4 to diffuse is more than 1 hour, consuming a lot of time for the objective to stabilize the overpressure state, reducing the yield to some extent.
Disclosure of Invention
In order to solve the above problems, the present invention provides a projection objective lens for exposure and a lithography system, which are used to solve the problem that the objective lens is easily infected by gas.
In order to achieve the above object, the present invention provides a projection objective for exposure, which comprises a plurality of objective chambers from top to bottom, wherein a gas guiding device is arranged at the top of the objective chamber at the top layer, and gas outlets are arranged at the objective chamber at the bottom layer, and gas flows into all the objective chambers from top to bottom from the gas guiding device and flows out from the gas outlets.
Preferably, the gas guiding device is an air duct communicated with the objective lens chamber at the top layer, and the length direction of the air duct is perpendicular to the horizontal plane.
Preferably, a plurality of vent holes are symmetrically distributed on each objective lens chamber, the corresponding vent holes on two adjacent objective lens chambers are connected through a vent pipe, and gas in the objective lens chambers flows into the adjacent objective lens chambers through the vent pipes.
Preferably, the length direction of the vent pipe between the objective lens chamber of the top layer and the adjacent objective lens chamber forms an included angle of 45 degrees with the horizontal plane, and the rest vent pipes are all perpendicular to the horizontal plane.
Preferably, the objective chamber is composed of an optic and a mount coaxial with the optic.
Preferably, the vent hole is provided in the lens holder.
Preferably, the lenses of two adjacent objective chambers are connected by a lens holder assembly.
Preferably, the gas outlet is located at the bottom of the objective lens chamber of the bottom layer.
The invention also provides a photoetching system which sequentially comprises the following components from top to bottom
An illumination system for providing illumination light;
the mask table is used for placing a mask;
a projection objective as described above for adjusting the illumination light;
a silicon chip platform for placing a silicon chip to be photoetched;
the projection lens system further comprises a supporting frame, and the illumination system, the projection objective and the wafer stage are all fixed on the supporting frame.
Compared with the prior art, the invention has the beneficial effects that: the invention provides a projection objective lens for exposure and a photoetching system using the projection objective lens, wherein a gas flow guide device is arranged at the top of the projection objective lens, so that external gas enters an objective lens chamber of the projection objective lens from the gas flow guide device, the flowing direction of the gas is changed, the pressure applied when the gas flows is changed, the generation of flowing dead angles is avoided, and the probability of polluting a projection objective lens can be reduced.
Drawings
FIG. 1 is a schematic diagram of a prior art lithography machine;
FIGS. 2 and 3 are schematic views of a projection objective in the prior art;
FIG. 4 is a prior art vector diagram of a flow field within a projection objective;
FIG. 5 is a cross-sectional view of a projection objective provided by the present invention;
FIG. 6 is a schematic structural diagram of a device for testing the air flow in an objective chamber according to the present invention;
fig. 7 is a comparison diagram of the structure streamline of the projection objective lens provided by the prior art and the present invention.
In FIGS. 1-3: 1-supporting frame, 2-lighting system, 3-mask stage, 4-projection objective, 401-404-objective chamber, 41-outer ring lens seat, 42-inner ring lens, 430-vent, 44-through hole, 45-vent pipe, 5-silicon chip, 6-silicon chip stage,
In fig. 4-5: 4001-first objective chamber, 4002-second objective chamber, 4003-third objective chamber, 4004-fourth objective chamber, 4100-lens, 4200-lens holder, 4310-vent, 4610-pneumatic control box, 4620, 4640-pressure sensor, 4630, 4650-flow sensor, 4670-dissolved oxygen sensor.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
Example one
When the projection objective works, in order to prevent oxidation pollution caused by a lens group due to heat influence generated by exposure or photoresist pollution caused by retention of introduced gas, an overpressure environment for flowing is required to be maintained in the objective, a flow field in the objective is expected to flow uniformly as much as possible, the technology of the aspect is mainly influenced by the structure of an objective chamber and is theoretically embodied as the effect of reducing the pressure difference resistance of the objective chamber as much as possible, the resistance is caused by tangential stress and pressure difference caused by fluid flowing around an object and is divided into friction resistance and pressure difference resistance, the friction resistance is the result of direct action of viscosity, the pressure difference resistance is the projection sum of the pressure acting on the surface of the object in the incoming flow direction and is the result of indirect action of viscosity, and the projection sum is formed by generating wake vortexes in the tail area of the object due to the separation of a. The invention mainly reduces the shape resistance of the objective chamber through structural improvement. The drag coefficient of an object is determined by:
FDthe frictional resistance of the wall surface caused by viscous force, A is the sectional area of the object in the direction perpendicular to the moving direction or the incoming flow direction, rho is the gas density, and v is the flow velocity.
In order to reduce the flow resistance of the objective lens chamber, the invention adopts a mechanical similarity principle to solve the problem of dead angles caused by the flow resistance in the objective lens chamber, the mechanical similarity principle is that all dimensionless coefficients are correspondingly equal in the similar object flow and the model flow, and for the motion differential equation of the model flow which accords with the incompressible fluid, the projection in the X direction is as follows:
where P is the pressure, t is the local time, uxIs the velocity component in the X direction, ▽2Is the laplacian operator.
Then, each physical quantity in the physical model similar to mechanics has a certain proportional relationship with each physical quantity in the model flow, so the equation of motion of the physical flow can be expressed as:
all terms in the N-S equation have the dimension LT-2 of acceleration, so the scales preceding each term of the above equation are scales of acceleration, which should be equal, i.e.:
this deltag、
The four terms have definite physical meanings and respectively represent the ratio of mass force, pressure force, viscous force and inertia force acting on the unit mass fluid in the real flow and the model flow.
For the gas, neglecting the ratio of the first term mass force, the fourth term is removed by the second and third terms in the above formula, and the ratio of the gauge pressure to the inertia force is obtained respectively:
called the euler number:
and ratio of inertial force to viscous force:
called Reynolds number:
the similarity criterion is not only a criterion for distinguishing similarity but also a criterion for designing a model, because satisfying the similarity criterion essentially means that the following two constraints are kept between similarity ratios:
however, the method satisfies such constraint relationship to achieve complete mechanical similarity, is difficult to design, and has a large or small model, but the scale delta of the fluid kinematic viscosity2 νTo be associated with deltalIt is not easy to keep a constant value. For single gas under a specific environment, the viscosity is a fixed value, and the pressure resistance and the viscous resistance can be reduced only by continuously adjusting the size of the flow model, so that the similar mechanics is achieved as much as possible.
In order to achieve the above object, referring to fig. 5, the present invention provides a projection objective lens for exposure based on the above principle, which includes a plurality of objective lens chambers in sequence from top to bottom, in which the number of objective lens chambers is four, and the objective lens chambers include a first objective lens chamber 4001, a second objective lens chamber 4002, a third objective lens chamber 4003, and a fourth objective lens chamber 4004 from top to bottom, respectively, a gas guiding device is disposed on the top of the first objective lens chamber 4001, and a gas outlet hole (not shown) is disposed in the fourth objective lens chamber 4004, so that gas flows into the four objective lens chambers from top to bottom in sequence from the gas guiding device and flows out from the gas outlet hole.
The gas guiding device provided by the invention is the vent hole 4310 arranged at the top of the first objective lens cavity 4001, and the length direction of the vent hole 4310 is parallel to the vertical direction, namely perpendicular to the horizontal plane, so that gas enters the first objective lens cavity 4001 from the vent hole 4310 at the top to form a gas circulation mode from top to bottom, the pressure can be gradually reduced from top to bottom, the circulation is smooth, the existence of a flow field dead zone in the first objective lens cavity 4001 is avoided, and the pressure and the flow rate of the first objective lens cavity 4001 are uniformly distributed.
The four objective lens chambers are all composed of lens 4100 and lens holder 4200 coaxial with the lens 4100, two adjacent lens 4100 are connected through lens holder components, the bottom of the four objective lens chambers are all provided with a plurality of through holes uniformly distributed, the corresponding through holes between every two adjacent objective lens chambers are connected in pairs by using vent pipes, so that the gas in one objective lens chamber flows out from the through hole of the other objective lens chamber through the through holes and the vent pipes and flows uniformly in the objective lens chamber.
Referring to fig. 5, each layer is provided with a plurality of uniformly distributed vent pipes, the inclination angles and the distribution positions of the vent pipes of two adjacent layers are different, the vent pipes between the first objective chamber 4001 and the second objective chamber 4002 are placed in a length direction to form an included angle of 45 degrees with the horizontal plane, the vent pipes between the second objective chamber 4002 and the third objective chamber 4003, and the vent pipes between the third objective chamber 4003 and the fourth objective chamber 4004 are all in a vertical direction, i.e., perpendicular to the horizontal plane, and the vent pipes of the two layers are staggered.
In order to detect whether the unobstructed degree of the air flow inside the projection objective lens provided by the invention is increased, the magnitudes of the pressure resistance and the viscous resistance which are applied to the air flowing in the projection objective lens provided by the prior art and the projection objective lens provided by the invention are verified through simulation, and the sum of the pressure resistance and the viscous resistance which are respectively applied to the air in the three directions of XYZ is calculated and listed as the following table:
as can be seen from the table, the difference between the sum of the pressure resistance and the viscous resistance of the gas in the Y direction is significant, that is, the resistance in the Y direction is significantly reduced when the gas is used to flow in the projection objective provided by the present invention. From simulation experiments, it can be calculated that the flow field distribution of the lens area in the projection objective is uniform, the pressure distribution range is 100.43-100.00 Pa, the flow field speed is uniform, the distribution range is about 0-0.05m/s, and the fluctuation ranges of the pressure and the flow speed are within the expected values.
In order to detect whether the contamination of the projection objective lens provided by the present invention to the lens is significantly reduced, please refer to fig. 6, which provides a testing apparatus for air flow in the objective lens chamber, to test the projection objective lens structure in the prior art and the projection objective lens structure provided by the present invention, the testing apparatus provides a gas control box 4610, the gas provided by the gas control box 4610 passes through the flow sensor 4630 and the pressure sensor 4620, and then enters the two projection objective lenses through the vent 4310 and the vent 430, and is tested, the gas flows in the two projection objective lenses, and then flows out of the whole projection objective lens from the gas outlet, passes through the pressure sensor 4640 and the flow sensor 4650, and then passes through the dissolved oxygen sensor 4670 for detection, and then is recovered to the gas control box 4610. When the gas control box 4610 supplies gas to the air vents 430 and 4310, the overpressure of the objective chamber is expected to be 100 Pa, and the flow rate of the air vents 430 and 4310 is expected to be 12L/min, and by using the projection objective structure provided by the invention, the pressure of the objective chamber is expected to be kept at 100 +/-1 Pa and the content of oxygen in the dissolved oxygen sensor 4670 is detected, and the expected value is 0 only after 20 minutes of pressure stabilization. When the projection objective structure provided in the prior art is used for testing, the test results are as follows: when the dissolved oxygen sensor 4670 is used to detect that the oxygen concentration content is zero, the time required to be consumed is more than 1 hour, that is, the time for the gas molecules inside the objective lens to diffuse is more than 1 hour, and a large amount of time is consumed for the objective lens to stabilize the overpressure state, thereby reducing the yield to some extent.
The invention researches the flow velocity updating condition of the objective chamber region, referring to fig. 7, which is a streamline comparison diagram of the existing projection objective and the projection objective structure provided by the invention, under the working condition that other technical parameters are consistent, the invention obviously influences the circulation state of the objective chamber flow field region by improving the structure of the vent 4310, and the streamline comparison of the structures provided by the existing technology and the invention shows that: the more the streamline distribution, the more uniform the flow distribution of the flow field, the prior art structure shows that the gas only rotates around the ring wall close to the lens seat, but no streamline is in the central area close to the lens, the flow field has no differential pressure flow but only shear flow, so that the gas can only exchange through molecular diffusion, and the distribution rate of the introduced gas flow field is low. In addition, the improved design provided by the invention can keep the utilization rate of the through holes to be more than 80%, namely, the internal structure of the objective lens chamber is fully optimized, so that the upper lens surface and the lower lens surface of the objective lens chamber are prevented from being easily polluted due to gas retention or exposure reaction.
The present invention has been described in the above embodiments, but the present invention is not limited to the above embodiments. It will be apparent to those skilled in the art that various changes and modifications may be made in the invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (7)
1. A projection objective for exposure sequentially comprises a plurality of objective chambers from top to bottom, and is characterized in that a gas flow guide device is arranged at the top of the objective chamber at the top layer, gas outlets are arranged in the objective chamber at the bottom layer, and gas flows into all the objective chambers from top to bottom and flows out from the gas outlets in sequence from the gas flow guide device; the gas guiding device is a gas guide tube communicated with the objective lens cavity at the top layer, and the length direction of the gas guide tube is vertical to the horizontal plane; and a plurality of vent holes are symmetrically distributed on each objective lens cavity, the corresponding vent holes on two adjacent objective lens cavities are connected through vent pipes, and gas in the objective lens cavities flows into the adjacent objective lens cavities through the vent pipes.
2. The projection objective for exposure according to claim 1, wherein the length direction of the vent tube between the objective chamber of the top layer and the adjacent objective chamber forms an angle of 45 ° with the horizontal plane, and the remaining vent tubes are all perpendicular to the horizontal plane.
3. Projection objective for exposure according to claim 1, characterized in that the objective chamber consists of a lens and a lens holder coaxial with the lens.
4. Projection objective for exposure according to claim 3, characterized in that the vent is arranged on the lens holder.
5. Projection objective for exposure according to claim 3, characterized in that the lenses of two adjacent objective chambers are connected by a lens holder assembly.
6. Projection objective for exposure according to claim 1, characterized in that the gas outlet opening is located at the bottom of the objective chamber of the bottom layer.
7. A lithography system is characterized by comprising a substrate, a mask and a mask layer from top to bottom in sequence
An illumination system for providing illumination light;
the mask table is used for placing a mask;
an exposure projection objective according to any one of claims 1 to 6 for adjusting illumination light;
a silicon chip platform for placing a silicon chip to be photoetched;
the projection lens system further comprises a supporting frame, and the illumination system, the projection objective lens for exposure and the wafer stage are all fixed on the supporting frame.
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| CN201710060955.XA CN108345079B (en) | 2017-01-25 | 2017-01-25 | Projection objective for exposure and photoetching system |
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| CN201710060955.XA CN108345079B (en) | 2017-01-25 | 2017-01-25 | Projection objective for exposure and photoetching system |
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| CN108345079A CN108345079A (en) | 2018-07-31 |
| CN108345079B true CN108345079B (en) | 2020-05-01 |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1440512A (en) * | 2000-03-31 | 2003-09-03 | 株式会社尼康 | Method and device for holding optical member, optical device, exposure apparatus and device manufacturing method |
| CN101031847A (en) * | 2004-09-30 | 2007-09-05 | 先进微装置公司 | Method and system for contamination detection and monitoring a lithographic exposure tool and operating method for the same under controlled atmospheric conditions |
| CN102937777A (en) * | 2012-11-12 | 2013-02-20 | 浙江大学 | Gas-sealing and gas-liquid isolating device for immersed type photoetching machine |
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- 2017-01-25 CN CN201710060955.XA patent/CN108345079B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1440512A (en) * | 2000-03-31 | 2003-09-03 | 株式会社尼康 | Method and device for holding optical member, optical device, exposure apparatus and device manufacturing method |
| CN101031847A (en) * | 2004-09-30 | 2007-09-05 | 先进微装置公司 | Method and system for contamination detection and monitoring a lithographic exposure tool and operating method for the same under controlled atmospheric conditions |
| CN102937777A (en) * | 2012-11-12 | 2013-02-20 | 浙江大学 | Gas-sealing and gas-liquid isolating device for immersed type photoetching machine |
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