JPH11111585A - Projection aligner for manufacturing semiconductor, and semiconductor device manufacturing process using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection aligner for manufacturing a semiconductor, wherein contamination with a projection optical system is prevented when a chemical amplification resist is used for precision pattern transfer with stability for extended period of time. SOLUTION: In a projection aligner for manufacturing a semiconductor wherein a semiconductor substrate 10 is exposed with an exposure light from a projection optical system 6, an optical system contamination preventive shielding member 14 comprising an opening for the exposure light to pass is provided, while the pressure at an optical system side space S1 formed by separating with the shielding member is set higher than that in a substrate side space S2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a semiconductor manufacturing exposure apparatus used in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art In recent years, high integration of semiconductor integrated circuits has been progressing toward the gigabit DRAM generation. With this high integration, the performance required for the exposure apparatus, especially for the projection optical system, has also become higher.

Here, the resolution of the exposure apparatus can be increased by increasing the numerical aperture (NA) of the projection optical system, but the depth of focus is reduced by increasing the NA. Therefore, the NA cannot be increased to a certain degree or more, and it is required to shorten the exposure wavelength in order to increase the resolution.

For these reasons, KrF excimer lasers and ArF excimer lasers are promising as light sources for use in exposure equipment of the gigabit DRAM generation.
As the wavelength of the light source becomes shorter, the resist shifts to a chemically amplified resist having a higher resolution. Chemically amplified resist is Kr
Generating an acid by exposure using a light source such as F;
The positive type causes a protective group elimination reaction and the negative type causes a cross-linking reaction by using an acid as a catalyst during the pake treatment after exposure, thereby changing the dissolution rate with respect to an alkaline developer to increase the aspect ratio after development. Can be obtained.

FIG. 6 shows the outline of the reaction of a positive chemically amplified resist. (A), (B), (C),
The reaction proceeds in the order of (D). The resist is composed of a base resin 61 having a protective group 62 and a photoacid generator 63 (A). When exposed to light from a KrF or ArF light source, the photoacid generator 63 reacts to generate an acid 64 (B). The acid 64 acts as a catalyst to remove the protecting group 62 to form a reaction product 65 (C). The reaction product 65 is vaporized,
Since the resist goes out of the resist film, the thickness of the resist decreases (D).

The phenomena (C) and (D) in the figure mainly occur during the heat treatment after exposure. However, the chemically amplified resist actually used during the exposure or during the period from exposure to baking. Also get up. This is a result of improving the sensitivity of the resist to increase the throughput of the exposure apparatus,
This is because the protecting group elimination reaction occurs sensitively to the presence of an acid, and the reaction proceeds at room temperature without baking at a high temperature. FIG. 7 shows the change in the resist film thickness after the actual exposure. As can be seen from this figure, the reaction speed differs depending on the exposure amount, and the speed of decreasing the film thickness differs.

[0007]

As described above, the reaction product is vaporized from exposure to heat treatment to produce a gas. This gas reacts with the exposure light to produce an organic substance, and the projection lens system There is a problem that is contaminated.

That is, as shown in FIG. 8, when light from a light source passes through an illumination optical system, a reticle, and a projection optical system 86 to a substrate 90 to be exposed, the resist on the substrate 90 reacts and gas 88 Occurs. The generated gas 88 reacts with the light from the light source to generate an organic substance 87, which adheres to the surface of the final lens 89 of the projection optical system 86.

For example, the elimination reaction of 1-ethoxyethoxy group, which is a typical protecting group, is more sensitive to acid acting as a catalyst than to temperature, and the reaction proceeds in a state before baking. Acetaldehyde and ethanol generated in this elimination reaction (Chem. 1) have high volatility, and volatilize together with the residual solvent present in the resist and additives such as acids, acid generators and surfactants.

[0010]

Embedded image

The organic substance released outside the film together with the reaction product gas adheres and solidifies on the surface of the projection lens and the like through a complicated reaction process including decomposition and recombination by light irradiation. And when the projection lens is contaminated in this way,
There is a problem in that the resolution performance of the exposure apparatus is reduced, and the line width within the angle of view is varied due to uneven illuminance, and the yield of manufactured semiconductor devices is reduced.

To solve such a problem, Japanese Patent Laid-Open No. 6-14 / 1994
No. 0304, the exposure apparatus shown in FIG. 9 of the present application uses the lens 99 of the projection optical system 96 and the substrate 100 to be exposed.
A film 101 is provided in between to prevent the gas 98 generated from the resist from adhering to the lens surface.

However, in such an exposure apparatus,
There is a problem that there is no film material having a sufficient transmittance corresponding to a shorter wavelength of exposure light. Exposure light may damage the film and change its transmittance, or substances adhered to the film surface may cause a bias in the transmittance within the film surface, degrading the resolution performance and changing the illuminance. There is also the problem of doing.

In the exposure apparatus proposed in Japanese Patent Application Laid-Open No. Hei 6-260385 and shown in FIG. 10 of the present application, a nozzle 113 is provided around a substrate 110 to be exposed, and a projection optical system 106 is provided.
By supplying the inert gas 112 between the lens 109 and the substrate 110 to be exposed, exposure in the inert gas can be performed without lowering the throughput.

However, in such an exposure apparatus,
Although the generated gas 108 from the resist hardly adheres to the projection optical system, there is a problem that the refractive index in the exposure atmosphere fluctuates due to the flow of the inert gas, thereby causing uneven exposure of the substrate to be exposed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an exposure apparatus for manufacturing a semiconductor which can stably and accurately transfer a pattern for a long period of time while preventing contamination of a projection optical system when a chemically amplified resist is used. I have.

[0017]

To achieve the above object, the present invention provides a semiconductor manufacturing exposure apparatus for exposing a semiconductor substrate with exposure light from a projection optical system. A shielding member for preventing contamination of an optical system having an opening for allowing exposure light to pass therethrough, and furthermore, a pressure in a space (optical system side space) between the projection optical system and the shielding member is applied between the substrate and the shielding member. Pressure setting means for making the pressure higher than the pressure in the space (substrate side space). For example, when exposing an 8-inch substrate with a sequential moving type reduction projection exposure apparatus (stepper), the time required to process one substrate is 6 hours.
It is about 0 seconds. During this time, degassing occurs from the resist in the exposed area, causing contamination of the projection optical system. The distance between the final surface of the photographing lens and the substrate to be exposed is close to about 30 mm, and there is nothing between them in the conventional exposure apparatus, so that the structure easily comes into contact with the gas generated from the resist. However, the space that allows the projection optical system and the substrate to be exposed to pass should be a minimum area that does not hinder the exposure optical path, and by providing a shielding member having an opening that can secure such an area, gas generated from the resist can be obtained. Is extremely low in contact with the projection optical system (in particular, the final surface of the projection lens).

Further, the pressure in the optical system side space is made higher than the pressure in the substrate side space by introducing an inert gas into the optical system side space by pressure setting means, so that the optical system side space is opened through the opening of the shielding member. Gas can be prevented from flowing into the space, and a high optical system contamination prevention effect can be obtained. The pressure in the optical system side space is 1.001 to 1.2 atm when the pressure in the substrate side space is 1.000 atm.
Preferably, the pressure is set to 1.001 to 1.01 atm.

Further, if the opening area of the shielding member can be changed in accordance with the numerical aperture of the projection optical system, the opening area of the shielding member at the time of exposure can be made the minimum area which does not always hinder the optical path. The effect of preventing optical system contamination can be enhanced.

Further, by coating the surface of the shielding member with a substance that adsorbs an organic gas, the gas can be adsorbed more effectively, and the effect of preventing contamination of the optical system may be further enhanced.

Examples of the coating material include starches such as polyvinyl alcohol, polyvinyl pyrrolidine and cellulose; polyethylene glycol, gelatin, polyacrylic acid, polymethacrylic acid, polymaleic acid, polyacrylamide, and water-soluble materials such as these dielectrics. And organic soluble polymers such as methacrylates, acrylates, polyetheretherketones, polycarbonates, polyesters, and dielectrics thereof. The coating material may contain a substance that chemically adsorbs an organic gas, for example, calcium, strontium, barium, titanium, zirconium, hafnium, vanadium, tantalum, chromium, molybdenum, tungsten, iron, or the like.

The shielding member is made of a transparent material, and the surface of the shielding member (substrate side surface) is coated with titanium oxide. It is desirable to be decomposed and removed by the effect of the photocatalytic reaction. This clean action of titanium oxide eliminates the need for frequent replacement of the shielding member, and can avoid the inconvenience of frequently stopping the production line. The term “transparent” used herein means cleaning light (exposure light, etc.).
At least 30% or more, preferably 8
0% or more.

As a result, it is possible to improve the resolution performance and the long-term stability of the illuminance of the exposure apparatus and to stably obtain a good resist pattern.

The shielding member may have a slit-like opening which is always open, but may have a shutter-like shape that opens during exposure and closes during non-exposure. As described above, when exposing an 8-inch substrate with a stepper, the time required to process one substrate is about 60 seconds. However, the pure exposure time excluding the time required for moving the non-exposed substrate or the like from this time is several seconds. Therefore, if the exposure opening is opened only during the pure exposure time and the exposure opening is closed during other times, contamination of the projection optical system due to gas generated from the resist is effectively prevented. It becomes possible.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 shows a configuration of an exposure section of a KrF successively moving reduction projection exposure apparatus (stepper) according to a first embodiment of the present invention. In this figure, 6 is a projection optical system, and 9 is a final stage projection lens. Reference numeral 10 denotes a substrate to be exposed, and a shutter (shielding member) 14 is provided between the substrate 10 and the projection lens 9.

The shutter 14 opens an opening through which exposure light passes during exposure, and closes the opening during non-exposure.
The shutter 14 has a structure in which the opening area can be changed according to the numerical aperture (NA) of the projection optical system 6 so that the opening area of the shutter 14 does not obstruct the optical path of the exposure light.
That is, when the NA is large, the opening area of the shutter 14 is set large, and when the NA is small, the opening area of the shutter 14 is set small.

Further, in this embodiment, the shutter 14
A space (optical-system-side space) S1 on the projection optical system 6 side and a space (substrate-side space) S2 on the substrate 10 side are formed with a gas inlet (pressure setting means) in the optical-system-side space S1. 16
Through which an inert gas is introduced. Thereby, the pressure in the optical system side space S1 becomes slightly higher than the pressure in the substrate side space S2. In the present embodiment, when the pressure in the substrate side space S2 is 1.000 atmosphere, the pressure in the optical system side space S1 is set to 1.005 atmosphere.

In the stepper configured as described above, as shown in FIG. 1 (A), the exposure light 15 from the KrF light source (not shown) is emitted while the shutter 14 is opened.
Projection optical system 6 on which a reticle (not shown) is set
The exposure is performed by irradiating the substrate to be exposed 10 through the light emitting device.

After the completion of the exposure, as shown in FIG.
The opening of the shutter 14 is immediately closed to prevent the gas 8 generated from the resist on the substrate 10 from moving to the projection optical system 6 side. Thus, the projection lens 9 immediately after the exposure (before the substrate 10 to be exposed moves to the next shot position).
Of the gas 8 is prevented.

Subsequently, as shown in FIG. 1C, the substrate 10 to be exposed moves to the next shot position and the opening of the shutter 14 is opened. At this time, the gas 8 is generated from the resist already exposed. The area where the shutter is
4 moves from directly below the opening, and furthermore, the optical system side space S1
Since the pressure in the inside is slightly higher than the pressure in the substrate side space S2, the gas 8 does not move to the projection optical system 6 side through the opening of the shutter 14. Thereby, the projection lens 9 after the exposure target substrate 10 has moved to the next shot position
The contamination by the gas 8 is also prevented.

When the projection lens 9 was inspected after such a stepper was used for 6 months in a normal operation, the amount of deposits on the projection lens 9 was extremely small and was within an acceptable range.

(Second Embodiment) FIG. 2 shows a second embodiment of the present invention.
1 illustrates a configuration of an exposure unit of a KrF scanning type reduction projection exposure apparatus (scanner) according to an embodiment. Note that, in the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals as in the first embodiment, and description thereof will be omitted.

The present embodiment differs from the first embodiment in that a slit plate 24 having a slit-like opening that is always open is provided between the substrate 10 to be exposed and the projection lens 9. The slit plate 24 has a structure in which the opening area (length of the long side of the slit) can be changed in accordance with the numerical aperture (NA) of the projection optical system 6 in order to minimize the area that does not obstruct the optical path of the exposure light. It has become. That is, when the NA is large, the opening area of the slit plate 34 is set large,
Is small, the opening area of the slit plate 34 is set small.

The substrate-side surface of the slit plate 34 is coated with a 500-nm-thick polymethyl methacrylate film containing 5 parts of calcium.

Further, in this embodiment, as in the first embodiment, an inert gas is introduced into the optical system side space S1 through the gas introduction port 16. Thereby, the pressure in the optical system side space S1 becomes slightly higher than the pressure in the substrate side space S2. In the present embodiment, when the pressure in the substrate side space S2 is 1.000 atmosphere, the pressure in the optical system side space S1 is set to 1.005 atmosphere.

In the scanner configured as described above, as shown in FIG. 2A, the exposure light from the KrF light source (not shown) is used to project the projection light on which a reticle (not shown) is set. The exposure is performed by irradiating the exposure target substrate 10 through the opening of the system 6 and the slit plate 24.

After the exposure is completed, as shown in FIG.
Immediately, the substrate 10 moves to the next shot position. At this time, the region already exposed and generating the gas 8 from the resist also moves from directly below the opening of the slit plate 24. Moreover, in the case of the scanner, the slit size in the scanning direction is smaller than the opening size of the stepper, and the pressure in the optical system side space S1 is slightly higher than the pressure in the substrate side space S2. Since the substrate-side surface of the substrate 34 is coated with a substance capable of chemically adsorbing an organic gas, the gas 8 does not move toward the projection optical system 6 through the opening of the slit plate 24. For this reason, contamination of the surface of the projection lens 9 by the gas 8 can be more effectively prevented than in the first embodiment.

After using such a scanner for six months in a regular operation, the projection lens 9 was inspected. As a result, it was found that the amount of deposits on the projection lens 9 was extremely small and within an acceptable range.

In the first and second embodiments,
The case where the substrate side surfaces of the shielding members 14 and 24 are coated with polymethyl methacrylate has been described.
The shielding member of the present invention may be coated with another adsorbing material.

(Third Embodiment) FIG. 3 shows a third embodiment of the present invention.
1 illustrates a configuration of an exposure unit of a KrF scanning type reduction projection exposure apparatus (scanner) according to an embodiment. Note that, in the present embodiment, the same components as those in the second embodiment are denoted by the same reference numerals as in the second embodiment, and description thereof will be omitted.

Also in this embodiment, a slit plate 34 is provided between the substrate 10 to be exposed and the projection lens 9, and this slit plate 34 is made of quartz, and its surface on the substrate side is made of titanium oxide. Are coated with a thickness of 100 nm.

Also in this embodiment, as in the second embodiment, an inert gas is introduced into the optical system side space through the gas inlet 16. Thereby, the pressure in the optical system side space becomes slightly higher than the pressure in the substrate side space. In the present embodiment, when the pressure in the substrate side space is set to 1.000 atmosphere, the pressure in the optical system side space is set to 1.005 atmosphere.

In the scanner configured as described above, similarly to the second embodiment, the contamination of the surface of the projection lens 9 by gas is prevented by the slit plate 34 and the pressure difference between the optical system side space and the substrate side space. be able to. In addition,
In the present embodiment, as shown in FIG. 3, the titanium oxide (that is, the slit plate 34) is periodically (1 in normal operation).
The cleaning light 19 from a KrF light source (not shown) is irradiated through the projection optical system 6 at a rate of about once a week. The irradiation of the cleaning light 19 causes the titanium oxide to act as a photocatalyst, and organic substances attached to the surface of the slit plate 34 on the substrate side are decomposed and removed. For this reason, the slit plate 34
Frequent replacement is unnecessary.

In this embodiment, the case where the slit plate is made of quartz has been described, but a transparent material other than quartz may be used. Further, the shutter of the stepper shown in the first embodiment may be made of a transparent material such as quartz and coated with titanium oxide.

In the first to third embodiments, K
Although a stepper and a scanner using a light source such as rF have been described, the present invention can be applied to an exposure apparatus using a light source or a method other than these.

(Fourth Embodiment) FIGS. 4 and 5 show a manufacturing process of a semiconductor device using the stepper or scanner described in each of the above embodiments. This manufacturing process is used for manufacturing semiconductor chips such as ICs and LSIs, liquid crystal panels, CCDs, thin-film magnetic heads, micro machines, micro optics, and the like.

FIG. 4 shows a flow from circuit design to shipment. First, when a circuit design of a semiconductor device is performed in step 1, a mask (FIG. 4) on which the designed circuit pattern is formed is formed in step 2. A reticle) structure is created. On the other hand, in step 3, a wafer is manufactured using a material such as silicon.

Next, in step 4, a preprocess, that is, a process of forming an actual circuit on the wafer by photolithography using the mask structure and the wafer is performed. Then, in step 5, a post-process, that is, a process of forming a wafer on which circuits are formed into semiconductor chips is performed. The post-process includes an assembly process (dicing and bonding process) and a packaging process.

The semiconductor device manufactured in this manner is subjected to various checks such as operation confirmation and durability in step 6, and shipped in step 7.

FIG. 5 shows a detailed flow of the above pre-process. First, in step 11, the surface of the wafer is oxidized, and in step 12, an insulating film is formed on the wafer surface by CVD. Next, in step 13, electrodes are formed on the wafer by vapor deposition, and in step 14, ions are implanted into the wafer.

Subsequently, in step 15, a photosensitive agent is applied to the wafer, and in step 16, the circuit pattern of the mask is printed on the wafer and exposed. In this step 16, the use of the stepper or the like of each of the above-described embodiments makes it possible to manufacture a highly integrated semiconductor device, which has been conventionally difficult. Before the execution of step 16, an inert gas is introduced into the optical system side space through the gas inlet 16 to increase the pressure in the optical system side space (step 1).
6 '). When the scanner according to the third embodiment is used, the cleaning light is periodically irradiated to the shutter 24 before the execution of Step 16 (Step 16 ″).

After the exposure, the circuit pattern on the wafer is developed in step 17, portions other than the pattern image developed by etching are scraped in step 18, and in step 19 the unnecessary resist after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

[0053]

As described above, according to the present invention,
An optical system contamination prevention shielding member having an opening for allowing exposure light to pass therethrough is provided between the projection optical system and the substrate to be exposed, and a pressure in an optical system side space formed by being partitioned by the shielding member. Is set higher than the pressure in the space on the substrate side, so that the gas generated from the resist can be prevented from flowing into the space on the optical system side without hindering the exposure of the substrate, thereby preventing high optical system contamination. The effect can be obtained.
As a result, the resolution performance and long-term stability of the illuminance of the exposure apparatus can be improved, and a good resist pattern can be stably obtained.

If the shielding member is made of a transparent material and the surface of the shielding member (substrate side surface) is coated with titanium oxide, the organic substances adhering to the surface of the shielding member are decomposed by the photocatalytic reaction of the titanium oxide. -Since it can be removed, frequent replacement of the shielding member is not required, and problems such as frequent stoppage of the production line can be avoided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a stepper according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a configuration of a scanner according to a second embodiment of the invention.

FIG. 3 is a schematic diagram illustrating a configuration of a scanner according to a third embodiment of the invention.

FIG. 4 is a flowchart showing a manufacturing process of a semiconductor device using the stepper and the scanner.

FIG. 5 is a flowchart of a pre-process in the manufacturing process.

FIG. 6 is a diagram illustrating the reaction of a positive chemically amplified resist.

FIG. 7 is a graph showing a change in resist film thickness after exposure.

FIG. 8 is an explanatory view showing a structure of contamination of a projection lens by a gas generated from a resist.

FIG. 9 is a schematic view of an exposure apparatus provided with a conventional lens contamination prevention film.

FIG. 10 is a schematic view of an exposure apparatus provided with a conventional lens contamination prevention nozzle.

[Explanation of symbols]

 6,86,96,106 Projection optical system 8,88,98,108 Gas 9,89,99,109 Projection lens 10,90,100,110 Substrate to be exposed 14 Shutter 15 Exposure light 16 Gas inlet 19 Cleaning light 24 , 34 slit plate 61 base resin 62 protecting group 63 photoacid generator 64 acid 65 reaction product 101 film 113 nozzle 112 inert gas

Claims (11)

[Claims] 1. An exposure apparatus for manufacturing a semiconductor, which exposes a semiconductor substrate with exposure light from a projection optical system, wherein the exposure apparatus is provided between the projection optical system and the substrate, and has an opening through which the exposure light passes. Semiconductor manufacturing, comprising: a shielding member; and pressure setting means for setting a pressure in a space between the projection optical system and the shielding member higher than a pressure in a space between the substrate and the shielding member. Exposure equipment. 2. The apparatus according to claim 1, wherein the pressure setting unit introduces an inert gas into a space between the projection optical system and the shielding member. 3. The exposure apparatus according to claim 1, wherein the shielding member has a shutter shape that opens the opening during exposure and closes the opening during non-exposure. 4. The exposure apparatus according to claim 1, wherein the shielding member has a slit-shaped opening. 5. The exposure apparatus according to claim 1, wherein the size of the opening is changeable according to the number of numerical apertures of the projection optical system. 6. The exposure apparatus according to claim 1, wherein the surface of the shielding member is coated with a substance that adsorbs an organic gas. 7. The semiconductor manufacturing device according to claim 1, wherein the shielding member is made of a transparent material, and the surface of the shielding member is coated with titanium oxide. Exposure equipment. 8. The semiconductor manufacturing exposure apparatus according to claim 7, wherein the shielding member is irradiated with cleaning light from the projection optical system. 9. A semiconductor device manufacturing process using the semiconductor manufacturing exposure apparatus according to claim 1. Description: 10. The method according to claim 1, further comprising the step of: making the pressure in the space between the projection optical system and the shielding member higher than the pressure in the space between the substrate and the shielding member by the pressure setting means. The semiconductor device manufacturing process according to claim 9. 11. The semiconductor device manufacturing process according to claim 9, further comprising a step of irradiating the shielding member with cleaning light using the semiconductor manufacturing exposure apparatus according to claim 7.