JP4738561B2 - Exposure apparatus and device manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to, for example, an exposure apparatus that projects a pattern such as a mask (also referred to as a reticle) on a substrate by reduction projection in a lithography process for manufacturing a semiconductor element, a liquid crystal substrate, and the like, and a device manufacturing method using the same About.
[0002]
[Prior art]
Conventionally, a reduction projection exposure apparatus is used in a manufacturing process of a semiconductor element formed from an ultrafine pattern such as an LSI or a VLSI. In such a reduction type projection exposure apparatus, as the mounting density of semiconductor elements is improved, further miniaturization of the pattern is required, and it has been required to cope with the miniaturization of the exposure apparatus simultaneously with the development of the resist process.
[0003]
As means for improving the resolution of the exposure apparatus, there are a method of changing the exposure wavelength to a shorter wavelength and a method of increasing the numerical aperture (NA) of the projection optical system. In general, it is known that the resolution is inversely proportional to the exposure wavelength and proportional to the numerical aperture. In addition, efforts have been made to ensure the depth of focus of the projection optical system while improving the resolution. In general, since the depth of focus is proportional to the exposure wavelength and inversely proportional to the square of NA, it is known that the improvement in resolution and the securing of the depth of focus are contradictory.
[0004]
With regard to exposure light, KrF excimer lasers having a center wavelength near 248 nm have become mainstream from i-line having a center wavelength near 365 nm, and more recently ArF having a center wavelength near 193 nm. Excimer laser is used. Further, the wavelength of exposure light is further shortened.
[0005]
On the other hand, in the conventional exposure apparatus using a mercury lamp for emitting g-line or i-line light or a KrF excimer laser having a central wavelength of 248 nm as the light source, the emission spectral lines of these light sources do not overlap with the oxygen absorption spectrum region. In addition, there was no inconvenience caused by the decrease in light utilization efficiency due to the absorption of oxygen and the generation of ozone due to the absorption of oxygen. Therefore, these exposure apparatuses can be exposed in the air atmosphere.
[0006]
However, in an exposure apparatus that uses i-line (wavelength 365 nm) as exposure light, or an exposure apparatus that uses light having a shorter wavelength than i-line as exposure light, impurities and oxygen in the air are photochemically exposed by these short-wavelength exposure light. It is known that a reaction occurs, the product adheres to the optical element, and an opaque “cloudy substance” is generated in the optical element (glass member). Here, “cloudy substance” means, for example, ammonium sulfate (NH ₄ ) ₂ SO ₄ produced by reacting with ammonia NH ₃ in the air when sulfurous acid SO ₂ gas absorbs light energy and becomes excited. It is. This ammonium sulfate is white and, when attached to the surface of an optical element such as a lens, causes the “cloudy” state. The exposure light is scattered and absorbed by ammonium sulfate, resulting in a decrease in the exposure light transmittance.
[0007]
If a “cloudy substance” such as ammonium sulfate adheres to a plurality of lenses, mirrors, or other optical elements arranged in the illumination optical system or projection optical system, the optical elements are fixed in a held state. Therefore, it is necessary to disassemble, and workability is extremely bad.
[0008]
Conventionally, as a means for preventing deterioration of the optical element due to the “cloudiness”, the entire optical path is filled with high-purity air or inert gas.
[0009]
In addition, in the light source such as the ArF excimer laser, the emission spectrum line overlaps with the absorption spectrum region of oxygen, and thus inconvenience due to the generation of ozone due to the absorption of oxygen described above occurs. For example, assuming that the transmittance of ArF excimer laser light in vacuum or in an inert gas atmosphere such as nitrogen or helium is 100%, the ArF excimer laser in the spontaneous emission state has a spectral width of 90%, and oxygen Even in the case of using an ArF laser that avoids this absorption band, the transmittance is lowered to 98%.
[0010]
Such a decrease in transmittance is considered to be due to the absorption of light by oxygen and the influence of ozone generated thereby. The generation of ozone not only lowers the transmittance, but also causes degradation of device performance due to reaction with the optical material surface and other parts, and environmental pollution.
[0011]
Thus, in an exposure apparatus having a light source such as an ArF excimer laser, filling the entire optical path with an inert gas such as nitrogen is a necessary means for avoiding the above-described decrease in light transmittance and generation of ozone. It is well known that it is one.
[0012]
In general, an exposure apparatus includes an illumination optical system for uniformly illuminating a mask with light from a light source, a projection optical system for forming an image of a circuit pattern formed on the mask on a wafer, a wafer supporting and It has stage means for appropriately moving and positioning.
[0013]
[Problems to be solved by the invention]
In the exposure apparatus configured as described above, purge control using an inert gas or the like is required. That is, compared with a KrF excimer laser having a central wavelength near 248 nm, an ArF excimer laser having a central wavelength near 193 nm has a higher ozone generation rate, and thus not only causes environmental pollution, but also various products adhere to the optical element. It is known that the optical characteristics are deteriorated.
In addition, since the optical index (refractive index) varies depending on the gas component, various optical aberrations occur when the purge gas component becomes unstable, which significantly affects the imaging characteristics.
[0014]
However, according to the above prior art, since the container for storing the optical system is not highly sealed, an inert gas is supplied every time exposure is started, and the oxygen concentration in the container is lowered to a predetermined value. It is necessary to make the exposure apparatus stand by or to continue supplying the inert gas even if the exposure apparatus is inoperative. In the former case, the standby time of the exposure apparatus becomes long, which causes a reduction in throughput. In the latter case, a large amount of inert gas is consumed in order to constantly supply the inert gas.
[0015]
At this time, the supply line for supplying the inert gas to the container for storing the optical system includes an opening / closing valve provided in the supply line, a gas flow path switching unit, and driving start and stop of the light source of the optical system, respectively. Control means for opening and closing the on-off valve in synchronization and driving the flow path switching means based on a predetermined program after the on-off valve is opened. Alternatively, after the driving of the light source is started, the oxygen in the container is monitored by a sensor, and the flow path switching means is activated after the oxygen concentration is reduced below a predetermined value.
[0016]
When any malfunction occurs during the operation of these control systems, the inert gas is excessively supplied into the container, the inert gas pressure in the container is increased, and the lens position and posture are affected. This not only harms good optical properties, but also has a risk of damaging the container and the optical component.
[0017]
Further, further improvement in throughput is required from the viewpoint of manufacturing cost of semiconductor elements.
[0018]
In the present invention, it is possible to suppress the gas pressure on the optical path of the exposure apparatus from exceeding a desired value, improve the throughput of the exposure apparatus itself, internal damage to the optical system container and the optical elements disposed in the container, and the like. The purpose is to prevent the reduction of the rate or the deterioration of the optical characteristics, and to reduce the apparatus down time by maintenance.
[0019]
[Means for Solving the Problems]
The present invention has been made to solve the above problems, and a first exposure apparatus according to the present invention has an optical system for projecting a pattern drawn on a mask onto a substrate using light from a light source. , A supply line for supplying an inert gas , a first discharge line and a second discharge line for discharging an inert gas, and an optical element of the optical system are accommodated and connected to the supply line and the first discharge line It is, comprises a container whose inner portion space becomes different atmospheres from the outside by an inert gas supplied from the supply line, and a pressure adjusting mechanism for adjusting the pressure of the inner space of the container, the pressure adjusting mechanism, the supply line of the course or the first branch line which is branched from the middle of the discharge line, and are connected to the second discharge line, internal space of the container through the branch line And availability moving member that moves under pressure, and a restraining means having a restraining force to restrain the front Symbol movable member, when the pressure in the inner space of the container does not exceed a predetermined pressure, the movable member the constraining When the pressure in the inner space of the container exceeds the predetermined pressure, the movable member moves against the restraining force of the restraining means and is blocked by the means and shuts off the branch line and the second discharge line. And the second discharge line communicate with each other, and the internal space of the container is decompressed.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram schematically showing a configuration of an exposure apparatus according to the first embodiment. The illustrated apparatus includes a light source 1 that emits short-wavelength laser light such as an ArF excimer laser. The light beam emitted from the light source 1 is reflected by the reflecting mirrors 2, 3, and 4, and is uniformly irradiated onto the mask 5 through an appropriate illumination optical element (not shown). In the path from the light source 1 to the mask 5, the illumination optical system 6 is roughly shielded from the outside air by a container 7, and this container contains an inert gas supply source (purge means) 8 to a valve 9 and an oxygen sensor 10. Through this, nitrogen gas is supplied as an inert gas.
[0031]
The light transmitted through the mask 5 reaches the surface of the wafer 13 placed on the wafer stage 12 via various optical elements (not shown) constituting the projection optical system 11, and forms an image of the pattern drawn on the mask. To do. Here, the projection optical system 11 is also shielded from outside air by the container 14, and nitrogen gas is supplied to the container from the inert gas supply source 8 through the valve 15 and the oxygen sensor 16.
[0032]
Further, since the mask 5 is opened to the outside air when it is exchanged, it is in a container 17 that shields the ventilation with the outside air independent of the illumination optical system 6 and the projection optical system 11. Or it can also be set as the structure which can supply to the container 17 with the nitrogen gas supply to the container 7, In that case, when the container 17 is opened, the shielding means which shields the container 7 and the container 17 spatially is provided. . In any case, the container 17 is supplied with an inert gas such as nitrogen gas from the inert gas supply source 18 via the valve 19 and the oxygen sensor 20.
[0033]
As shown in FIG. 1, the pressure adjusting mechanism 21 according to the present invention is disposed, for example, at a position immediately before supplying nitrogen gas to the illumination optical system 6, and the inert gas in the container 7 containing the illumination optical system 6 is When the pressure exceeds the desired pressure and reaches a preset pressure, the pressure adjusting mechanism 21 automatically discharges the inert gas to the outside of the container 7 and is inert if the inert gas drops to the desired pressure value. The discharge of the gas is terminated, and the pressure of the inert gas in the container 7 is maintained at a desired value.
[0034]
Similarly, the pressure adjusting means 22 and 23 are also arranged, for example, immediately before supplying the nitrogen gas to the projection optical system 11 and the mask space 5, respectively, and the inert gas in the containers 14 and 17 storing these respectively has a desired pressure. When the pressure value exceeds a preset pressure value, the pressure adjusting means 22 and 23 automatically discharge the inert gas to the outside of the container, and if the inert gas drops to a desired pressure value, the inert gas The discharge is terminated and the inert gas in the container is maintained at a desired pressure value.
[0035]
FIG. 2 is a diagram schematically showing a configuration of an exposure apparatus according to another embodiment of the present invention.
As shown in FIG. 2, the pressure adjusting mechanism 21 according to the present invention is disposed on, for example, a nitrogen gas discharge line of the illumination optical system 6, and the inert gas in the container 7 exceeds a desired pressure value and is set in advance. When the specified pressure value is reached, the inert gas is automatically discharged from a line different from the discharge line, and when the inert gas drops to the desired pressure value, the discharge of the inert gas is terminated, and the container The pressure value of the inert gas is maintained at a desired pressure value.
[0036]
Similarly, the pressure adjusting means 22 and 23 are also disposed, for example, on the nitrogen gas discharge line of the projection optical system 11 and the mask space 5, respectively, and the inert gas in the containers 14 and 17 exceeds a desired pressure value. When the pre-set pressure value is reached, the inert gas is automatically discharged from a line different from the discharge line, and when the inert gas drops to the desired pressure value, the discharge of the inert gas is terminated. The inert gas in the container is maintained at a desired pressure value.
[0037]
FIG. 3 shows another embodiment of the projection optical system 11 according to the present invention, which is an example in which the optical elements of the projection optical system are partially cut off from the outside air.
The optical elements 31 and 32 are disposed in the container 33, and the optical elements 34, 35, and 36 are disposed in the container 37, respectively, so as to substantially shield the ventilation with the outside air. In this example, the ventilation with the outside air of the containers 33 and 37 is performed. Is roughly shielded by the large container 38. The container 38 includes windows 39 and 40 so that light can pass through the optical elements 31, 32 and 34 to 36.
The containers 33 and 37 are connected by flexible pipes 41, 42, and 43 so as to be equivalent in pressure. The inert gas flows in the direction of arrows III to IV.
[0038]
When the pressure adjusting mechanisms 44 and 45 according to the present invention are disposed in, for example, the containers 38 and 37, respectively, and the inert gas in the containers 38 and 37 exceeds a desired pressure value and reaches a preset pressure value. The inert gas is automatically discharged from a line different from the discharge line, and when the inert gas drops to a desired pressure value, the discharge of the inert gas is terminated, and the pressure value of the inert gas in the container is set to the desired value. Hold at pressure value. These pressure adjustment mechanisms 44 and 45 may operate independently of each other.
[0039]
In addition, as indicated by a dotted line in FIG. 3, a means for discharging excess inert gas directly from the container 38 via the pipe 46 may be added to the pressure adjusting mechanism 45 according to the present invention.
[0040]
In the embodiment of FIG. 3, the projection optical system has been described. However, an exposure apparatus characterized by adopting the above-described structure in at least a part or all of the illumination optical system and the mask space may be used.
[0041]
FIG. 4 shows schematic cross-sectional views of several forms of the pressure adjustment mechanism according to the present invention. The pressure receiving movable element 51 in (a) is fixed to the internal space of the pressure adjusting mechanism by a spring 52. When the internal pressure of the container 7 or the like containing the illumination optical system exceeds a desired pressure value and reaches a preset pressure value, when the gas I flows into the pressure adjustment mechanism, the pressure is received and the pressure The gas II is discharged when the receiving movable element 51 moves upward and is separated from the seal 53. This gas II becomes the gas amount that can be adjusted.
[0042]
As a means for restraining the pressure receiving movable element 51 in the pressure adjusting mechanism internal space, a weight 55 of (b) or a lever 56 of (c) may be used instead of the spring 52 of FIG. By changing the strength and weight of the mover restraining means, the pressure value to be set in advance can be adjusted in advance.
[0043]
Instead of the pressure receiving movable element 51, the pressure adjusting mechanism may be a mechanism that includes a sensor that detects pressure, and adjusts the pressure by an exhaust valve or the like according to the sensor.
In this case, as shown in FIG. 5, when the indicated value of the pressure gauge 57 is read by a control system (not shown) and a preset pressure is exceeded according to the indicated value from the pressure gauge, the command to the exhaust valve 58 is given. The inert gas is discharged and the desired pressure value is maintained.
[0044]
Thus, the gas flow in the pressure adjusting mechanism according to the present invention is limited to, for example, one direction I → II in FIG. This prevents ventilation from outside air into the container.
[0045]
In the above embodiment, nitrogen has been described as an example of the inert gas. However, an inert gas having no oxygen absorption spectrum in the exposure wavelength region, for example, a gas such as helium may be used.
[0046]
Furthermore, in the above-described embodiment, an exposure apparatus using ArF excimer laser and exposing light having a wavelength region of 200 nm or less as exposure light has been described as an example. However, without departing from the scope of the present invention, an oxygen atmosphere is generated during exposure. It is clear that the present invention can be effectively applied to masks of dislike type regardless of the exposure wavelength.
[0047]
Next, an embodiment of a device manufacturing method using the above-described exposure apparatus will be described. FIG. 6 shows a manufacturing flow of a microdevice (a semiconductor chip such as an IC or LSI, a liquid crystal panel, a CCD, a thin film magnetic head, a micromachine, etc.). In step 1 (circuit design), a device pattern is designed. In step 2 (mask production), a mask on which the designed pattern is formed is produced. On the other hand, in step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon or glass. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer. The next step 5 (assembly) is called a post-process, and is a process for forming a semiconductor chip using the wafer produced in step 4, and is a process such as an assembly process (dicing, bonding), a packaging process (chip encapsulation), or the like. including. In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).
[0048]
FIG. 7 shows a detailed flow of the wafer process (step 4). In step 11 (oxidation), the wafer surface is oxidized. In step 12 (CVD), an insulating film is formed on the wafer surface. In step 13 (electrode formation), an electrode is formed on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. In step 15 (resist process), a resist is applied to the wafer. In step 16 (exposure), the mask circuit pattern is arranged in a plurality of shot areas on the wafer and printed by the exposure apparatus of the present invention described above. In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), unnecessary resist after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.
By using the production method of the present invention, it is possible to manufacture a large-sized device that has been difficult to manufacture at low cost.
[0049]
【The invention's effect】
The exposure apparatus of the present invention suppresses the gas pressure on the optical path from exceeding a desired value, improves the throughput of the exposure apparatus itself, and includes an optical system container and an optical element disposed in the container. It is possible to prevent a reduction in internal damage rate and optical characteristics, and to reduce the apparatus stop time due to maintenance.
[Brief description of the drawings]
FIG. 1 is a schematic view of an exposure apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic view of an exposure apparatus according to another embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view in which an optical element of the projection optical system is partially cut off from ventilation with outside air.
FIG. 4 is a schematic cross-sectional view of several forms of a pressure adjustment mechanism.
FIG. 5 is a schematic view of an exposure apparatus according to still another embodiment of the present invention.
FIG. 6 is a manufacturing flow of a microdevice.
FIG. 7 is a detailed flow of a wafer process (Step 4).
[Explanation of symbols]
1: Light source, 2, 3, 4: Mirror, 5: Mask (reticle), 6: Illumination optical system, 11: Projection optical system, 12: Wafer stage, 13: Wafer (photosensitive substrate), 7: Illumination from light source 1 A container for substantially sealing the optical system 6, 14: a container for substantially sealing the projection optical system 11, 17: a container for substantially sealing the mask space, 21: pressure adjusting mechanism (light source to illumination optical system), 22: pressure adjusting mechanism ( (Projection optical system), 23: pressure adjustment mechanism (mask space), 10: oxygen sensor (light source to illumination optical system), 16: oxygen sensor (projection optical system), 20: oxygen sensor (mask space), 8: inert Gas supply source (light source to illumination optical system, projection optical system), 18: inert gas supply source (mask space), V: exhaust unit, 31, 32, 34, 35, 36: optical elements constituting the projection optical system 33: Optical elements 31 and 3 of the projection optical system 37: A container that roughly shields the ventilation with the outside air, 37: A container that roughly shields the optical elements 34, 35, and 36 of the projection optical system from the ventilation with the outside air, 38: A schematic outline of a part of the projection optical system with the ventilation of the outside air Shielding containers, 39, 40: windows, 41, 42, 43, 46: piping for supplying inert gas to the containers 38, 33, 37, 44: pressure adjusting mechanism arranged in the container 38, 45: arranged in the container 37 Pressure adjustment mechanism, III: inert gas supply direction, IV: inert gas exhaust direction, I: flow direction of exhaust gas from the exposure apparatus supplied to the pressure adjustment mechanism, II: discharge discharged from the pressure adjustment mechanism Gas flow direction, 51: pressure receiving mover, 52: spring, 53, 54: seal, 55: weight, 56: lever, 57: pressure gauge, 58: exhaust valve.

Claims (5)

In an exposure apparatus having an optical system for projecting a pattern drawn on a mask onto a substrate using light from a light source,
A supply line for supplying an inert gas ;
A first discharge line and a second discharge line for discharging inert gas ;
Housing the optical element of the optical system, said being connected to the supply line and the first discharge line, a container whose inner portion space becomes different atmospheres from the outside by an inert gas supplied from the supply line ,
A pressure adjusting mechanism for adjusting the pressure of the internal space of the container ,
The pressure adjusting mechanism is connected to a branch line branched from the middle of the supply line or the middle of the first discharge line and a second discharge line, and the internal space of the container is connected via the branch line . and a restraining means having a variable dynamic member that moves under pressure, the restraining force for restraining the front Symbol movable member,
When the pressure in the internal space of the container does not exceed a predetermined pressure, the movable member is constrained by the restraining means to block the branch line and the second discharge line, and the pressure in the internal space of the container is the predetermined pressure. When the pressure is exceeded, the movable member moves against the restraining force of the restraining means, communicates the branch line and the second discharge line, and depressurizes the internal space of the container .   The optical system is at least one of an illumination optical system for guiding light from a light source to the mask and a projection optical system for projecting an image of the pattern of the mask formed by the light of the light source onto the substrate. The exposure apparatus according to claim 1, wherein: The restraining means, an exposure apparatus according to claim 1 or 2, characterized in that it comprises a spring. The said pressure adjustment means is connected to the said branch line branched from the middle of the said 1st discharge line , and the said 2nd discharge line, The Claim 1 characterized by the above-mentioned. Exposure device. A device manufacturing method comprising:
An exposure step of exposing the substrate with the exposure apparatus according to any one of claims 1 to 4,
And a developing step for developing the exposed substrate.

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