JP3337951B2 - Projection exposure apparatus and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus and method for illuminating a circuit pattern on an original with illumination light having a predetermined wavelength and projecting and exposing the circuit pattern on a substrate via a projection optical system.
More particularly, the present invention relates to a projection exposure apparatus in which a main body of the projection exposure apparatus is mounted on an anti-vibration apparatus and a projection exposure method using the same.

[0002] The present invention relates to an exposure method for projecting and exposing an electronic circuit pattern on a reticle surface to a wafer surface in a step-and-repeat manner via a projection optical system when manufacturing a semiconductor device such as an IC or LSI. In an exposure system (a so-called scanner), and similarly, an exposure system (a so-called scanner) that projects and exposes an electronic circuit pattern on the reticle surface by step-and-scan on the wafer surface through a projection optical system in the same way, for vibration reduction of the main body When the air spring is used, even if the main body structure is deformed due to the pressure fluctuation, the alignment error and the shot positioning error due to it are calculated and corrected in real time, and the main body structure is hardly influenced by the main body structural deformation due to the pressure fluctuation. It is particularly suitably embodied as an exposure apparatus for manufacturing semiconductors.

[0003]

2. Description of the Related Art In recent years, as patterns of semiconductor integrated circuits such as ICs and LSIs have become finer, projection exposure apparatuses have
There is a demand for further improvements in image performance, overlay accuracy, and throughput. The overlay accuracy can be roughly classified into a global component of the shot arrangement in the wafer and a component in the shot. The former is generally a wafer shift,
It can be subdivided into components such as wafer magnification, wafer rotation, and orthogonality. The latter can generally be subdivided into components such as shot (chip) magnification, shot (chip) distortion, and shot (chip) rotation. Among these series of errors, in recent years, due to improvement in device performance, error components caused by deformation of the main body structure have gradually become apparent.

An error component caused by a structural deformation is mainly a global component of a shot arrangement in a wafer.
Static components are reproduced each time the wafer stage or reticle stage moves, and dynamic components that are difficult to reproduce due to heat, reaction force or vibration caused by the wafer stage or reticle stage step.

[0005] In particular, as a countermeasure against mechanical disturbances such as vibration and reaction force, conventionally, high rigidity of the main body structure has been measured. That is, the structure does not deform even when a slight external force is applied to the structure, or the structure does not follow the disturbance vibration by increasing the natural frequency. However, as the rigidity of the main body is increased, the weight of the main body is also increased, and it has become difficult to design to satisfy both the weight reduction and the rigidity increase at the same time. If the product is manufactured with only the rigidity of the main unit taken into consideration, the weight of the main unit will increase extremely, making the product extremely difficult to handle in terms of unloading, loading, and installing the device. It is easily expected that this will happen.

[0006]

The main causes of deformation of the main body are, besides the direct deformation caused by the stage step reaction force,
It has recently been clarified that deformation due to body vibration caused by the stage step reaction force occupies a large component. In other words, the fluctuation of the supporting force of the vibration isolator synchronized with the vibration of the main body causes the main body structure to be deformed, which has a non-negligible effect on alignment measurement data, burning data, and the like.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and has been made in a projection exposure apparatus mounted on a vibration isolator without impairing the function of the vibration isolator.
It is an object to improve the exposure accuracy of the projection exposure apparatus.

[0008]

According to the present invention, there is provided a projection optical system, a substrate stage having a substrate mounted thereon and movable in a direction perpendicular to an optical axis of the projection optical system. In a projection exposure apparatus including a main body structure that supports the projection optical system and the substrate stage, and a vibration isolator for supporting the main body structure and isolating vibration from the floor, upon actual exposure, When positioning the substrate stage to sequentially move the substrate mounted on the substrate stage to a plurality of predetermined shot positions, a force acting on the main body structure from the vibration isolation device is measured, and based on the measurement result, To correct the alignment error of the substrate and / or the positioning of the stage. Then, after positioning the substrate stage at each shot position of the substrate, the circuit pattern on the original is illuminated with illumination light having a predetermined wavelength, and the substrate on the substrate stage is projected and exposed through the projection optical system.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment of the present invention, the target of the deformation of the main body exerted by the vibration isolator is focused without impairing the function of the vibration isolator, and even if the structure is deformed, the deformation is measured. , Thereby achieving high overlay accuracy without being affected by fluctuations in the supporting force of the vibration isolation device.

That is, in this embodiment, the deformation of the main body exerted by the vibration isolator is focused on, a sensor capable of measuring the force applied to the structure by the vibration isolator is attached, and the acting force is measured. By constantly monitoring the acting force and grasping in advance the relationship between the acting force change, the alignment error, and the stage lattice error through experiments and numerical simulations, the alignment measurement sensor and the stage position are always determined based on the relational expression. It is characterized in that the measurement value of the measurement sensor is corrected. When the vibration isolator uses an air spring as an actuator, the sensor capable of measuring the force is a pressure gauge or a load cell.

[0011]

By using the above means, it is possible to measure the force applied to the main body structure by the vibration isolator and to predict the alignment error and the stage lattice error exerted by the vibration isolator. It is possible to maintain a high-accuracy overlay that is not affected by structural deformation without impairing the function. Further, as the moving speed of the stage increases, the force applied to the main body by the vibration isolator also increases. However, in this embodiment, since this force can be constantly monitored and an error component can be predicted, the throughput can be reduced while maintaining the overlay accuracy. It can also be improved. Further, by using this means, the performance required for the structure is more focused on the viewpoint of good reproducibility than on the viewpoint of high rigidity, and it is possible to prevent unnecessary weight increase. Become like

[0012]

【Example】

(First Embodiment) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. First, a main part of a projection exposure apparatus (stepper) to which an embodiment of the present invention is applied is shown in FIG.
This will be described with reference to FIG. In the figure, 1 is an illumination system,
The reticle 2 on which a circuit pattern on which Cr is deposited is formed is illuminated. The illumination system 1 includes an unshown ultra-high pressure mercury lamp or an excimer laser, a shutter, an illumination optical system, and the like. Reference numeral 3 denotes a base on which a reticle stage (not shown) is mounted. The reticle 2 is positioned by a reticle stage drive mechanism with reference to a mark provided on the reticle stage base 3. Then, the measured position value is stored in the console unit 16 which controls the entire apparatus.

Reference numeral 6 denotes a projection lens for projecting the circuit pattern image of the reticle by the illumination system 1 onto the wafer 18, and reference numeral 7 denotes a well-known lens drive unit for correcting a change in the imaging performance due to the atmospheric pressure of the projection lens 6 and exposure. is there. Reference numeral 8 denotes a part of a main body structure on which main units such as a projection lens 6, an alignment measurement system, a reticle stage, and a wafer stage are mounted.
Are supported by a vibration isolator (not shown). Numeral 4 is a mirror for bending probe light for wafer alignment measurement by TTL (Through The Lens) method in off-axis mode, and numeral 5 is a measurement system for the same. The alignment light emitted from the measurement system 5 is bent by 90 ° by the mirror 4 and is incident on the projection lens 6 to illuminate the alignment mark on the wafer 18, and the reflected light passes through the opposite optical path, and the alignment measurement is performed again. Alignment measurement is performed by re-entering the system 5 and measuring a relative displacement with respect to a reference mark (not shown).

The light projector 10 and the light receiver 11 constitute a well-known focus and wafer tilt detector. The light beam is emitted from the light projector 10 to the surface of the wafer 18 at a low angle, and the reflected light is photoelectrically detected by the light receiver 11. Thereby, the focus position of the projection lens 6 and the inclination of the wafer 18 are detected.
Then, using this detector, the wafer is aligned in the z direction for each shot or for each wafer by using a later-described wafer stage focus and tilt drive function.

Numeral 12 is a wafer chuck for vacuum chucking the wafer 18, 13 is a tilt, a θz tilt stage capable of coarse and fine movement in the θz direction, and 15 is an xy stage capable of coarse and fine movement in the x and y directions. It comprises a tilt stage 13 and an xy stage 15. The position is determined by the laser interferometer bar mirror 17 and the laser interferometer 14 attached to the tilt stage.
Is constantly monitored by The console unit 16 controls the entire exposure apparatus including these main units. The above is the outline of the projection exposure apparatus to which the embodiment of the present invention is applied.

Next, the first embodiment of the present invention will be specifically described. FIG. 2 shows a state in which the main body structure is deformed by the step of the wafer stage. In this figure, the illumination system, reticle stage, alignment measurement system, and the like are not shown in order to emphasize main units and members involved in the deformation of the structure of the stepper.

In the figure, 6 is a projection lens, 20 is a member for joining the projection lens 6 and the main body structure 8, 14 is a laser interferometer mounted on a column, 18 is a wafer, 12 is a wafer chuck, and 17 is a bar mirror. , 13 is a θz tilt stage, 15 is an xy stage, 25 is a stage surface plate,
21 and 22 are vibration damping devices for vibration damping from the floor (
Hereinafter, this is referred to as mount). Although only two mounts are shown in the figure, usually four or three mounts support the main body. The mount according to the present embodiment realizes a vibration isolation function by performing feedback control of the internal pressure of the air spring actuator using the compressed air as an energy source and the acceleration of the main body. Reference numeral 23 denotes a main body support plate on which the main body is mounted via the mounts 21 and 22.

The mechanism by which the main body structure 8 is deformed when the wafer stage steps will be described with reference to FIG. When the wafer stage steps in the x direction, a reaction force of acceleration and deceleration is applied to the main body structure 8, and the main body is deformed and vibrates. Then, the main body structure 8 is pulled, compressed, or bent in the horizontal direction, and static and dynamic deformation occurs in the main body structure 8 as shown in FIG.

As described above, when the structure is deformed due to the fluctuation of the mounting pressure, the performance of the apparatus is greatly affected. That is, since the projection lens and the laser interferometer are directly attached to the structure, when the main body structure 8 is deformed as shown in FIG. 2, the relative distance between the optical axis of the projection lens 6 and the optical axis of the interferometer 14 becomes larger. Change. On the other hand, since the position servo is applied to the wafer stage, it is always positioned at the target position. Therefore, although the measurement itself of the laser interferometer is correct, the relative error between the projection lens optical axis and the interferometer optical axis changes, or the relative distance between the projection lens optical axis and the alignment measurement meter changes, resulting in a positional error. In such a state, alignment measurement and exposure are performed. A problem caused by a change in the relative distance between the optical axis of the projection lens and the optical axis of the interferometer is a lattice pattern formed by the wafer stage according to the interferometer measurement values, that is, a fluctuation of the stage lattice. For example, there is a case where the stage grating at the time of global alignment is different from the stage grating at the time of subsequent step and repeat, or a case where the stage grating is different for each layer. In such a case, the shot is burned at a position different from the shot arrangement burned in the previous layer,
The overlay accuracy as a device is reduced.

Therefore, in the present embodiment, the acting force applied to the main body structure by the mount and the acting force (in this embodiment, pressure) in the stage step are measured in real time, and an experiment is performed in advance based on the measured value. By comprehending the relationship between the pressure-stage position error and the pressure-alignment measurement error through numerical simulations or the like, errors in the stage lattice and alignment accuracy are corrected in real time.

In the present embodiment, first, at the stage of the first layer exposure, a shot arrangement which is not affected by the mount pressure fluctuation can be obtained by the error estimating method according to the present invention. Next, in the exposure operation of the second and subsequent layers, at the time of global alignment measurement, the alignment measurement value is corrected by the same error estimation method. Then, normal statistical processing is performed from the correction value, and the target coordinates of each shot are calculated. Next, movement to each shot is performed based on these coordinates, but by measuring the force acting on the main body also at the time of positioning, the correction amount of each shot position is always calculated by this error estimation method, Correct it. As described above, each shot positioning step of the first layer, 2n
the stage of global alignment measurement after the d layer,
At the stage of positioning each shot, by always correcting the error caused by the fluctuation of the force acting on the main body, it is possible to improve the alignment accuracy of the wafer stage and maintain a good overlay accuracy.

Further, as an application of this embodiment, it is conceivable to increase the speed of the wafer stage for the purpose of improving the throughput. When the acceleration / deceleration of the wafer stage increases,
As a matter of course, the reaction force acting on the main body by the stage also increases, and the force applied by the mount to the main body to dampen the main body also increases, so that deformation of the main body structure is expected. In such a case, in this embodiment, as described above, at each stage of processing the wafer, that is, at each shot positioning stage, at the stage of alignment measurement, the fluctuation of the mount pressure which fluctuates greatly is measured, and the error component due to this is measured. Can be predicted. As a result, it is possible to greatly improve the throughput while maintaining the overlay accuracy of the apparatus.

According to the above embodiment, the relationship between the mounting pressure, the alignment error, and the stage position error that causes the deformation of the main body structure is grasped in advance, so that the mounting pressure can be reduced during the actual exposure sequence. Monitors, corrects measurement errors due to structural deformations that occur during global alignment, and corrects stage positioning errors due to structural deformations that occur during step-and-repeat. A projection exposure apparatus having high accuracy can be provided.

[0024]

[Embodiment of Device Production Method] Next, an embodiment of a device production method using the above-described exposure apparatus or exposure method will be described. FIG. 3 shows a micro device (a semiconductor chip such as an IC or an LSI, a liquid crystal panel, a CCD, a thin film magnetic head,
2 shows a flow of manufacturing a micromachine or the like. Step 1
In (Circuit Design), a device pattern is designed. Step 2 is a process for making a mask on the basis of the designed pattern. Step 3 (wafer manufacturing)
Then, a wafer is manufactured using a material such as silicon or glass. Step 4 (wafer process) is called a pre-process,
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 of forming a semiconductor chip using the wafer produced in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). 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).

FIG. 4 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. Step 15
In (resist processing), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the exposure apparatus to print and expose the circuit pattern of the mask onto the wafer. Step 17 (development)
Then, 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 this embodiment,
A highly integrated device, which was conventionally difficult to manufacture, can be manufactured at low cost.

[0026]

According to the present invention, there is no need to focus on increasing the rigidity of the structure, and an increase in the weight of the structure can be suppressed. Implementation of the present invention does not require drastic design changes, and can be dealt with only by mounting sensors and improving measurement control software, so implementation is relatively simple.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing main units of a semiconductor exposure apparatus to which an embodiment of the present invention is applied.

FIG. 2 is a view showing a state in which a main body structure is deformed by a stage step.

FIG. 3 is a diagram showing a flow of manufacturing a micro device.

FIG. 4 is a diagram showing a detailed flow of a wafer process in FIG. 3;

[Explanation of symbols]

1: illumination system, 2: reticle, 5: alignment scope, 6: projection lens, 7: imaging performance correction unit, 8:
Main body structure 10, 11: Focus, tilt measuring instrument,
12: wafer chuck, 13: tilt stage, 14:
Laser interferometer, 15: xy stage, 16: console unit, 17: bar mirror, 18: wafer, 21 and 22
2: Mount.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-8-124845 (JP, A) JP-A-5-121294 (JP, A) JP-A-9-4677 (JP, A) JP-A 8- 264430 (JP, A) JP-A-8-88167 (JP, A) JP-A-7-307279 (JP, A) JP-A-11-8189 (JP, A) JP-A-5-335205 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/027 G03F 9/00 G12B 5/00

Claims (7)

(57) [Claims] 1. A projection optical system, a substrate stage mounted with a substrate and movable in a direction perpendicular to an optical axis of the projection optical system,
A main body structure supporting the projection optical system and the substrate stage, a vibration isolator for supporting the main body structure and isolating vibrations from the floor, and a plurality of substrates mounted on the substrate stage. The substrate stage is positioned to sequentially move to the shot positions, and after positioning at each shot position, the circuit pattern on the original is illuminated with illumination light of a predetermined wavelength, and the projection optical system is placed on the substrate on the substrate stage. A projection exposure apparatus having control means for projecting and exposing through a device, wherein: a means for measuring a force acting on the main body structure from the vibration isolation device; and correcting the positioning of the stage based on a measurement result of the measurement means. A projection exposure apparatus, comprising: 2. The correction means constantly monitors a force acting on the main body structure during an actual exposure, and based on a relational expression between the acting force and the stage accuracy, which is derived in advance by an experiment or a numerical simulation. 2. The projection exposure apparatus according to claim 1, wherein the positioning of the substrate stage is corrected. 3. The correction means constantly monitors a force acting on the main body structure during an actual exposure, and calculates the acting force, the alignment error of the substrate, and the stage accuracy, which are preliminarily obtained by experiments or numerical simulations. 2. The projection exposure apparatus according to claim 1, wherein the alignment measurement of the substrate and the positioning of the substrate stage are corrected based on the relational expression. 4. The method according to claim 1, wherein after positioning at each of the shot positions, projection exposure is performed by synchronously scanning the original and the substrate with respect to the projection optical system under the illumination light. 4. The projection exposure apparatus according to any one of 3. 5. The projection exposure apparatus according to claim 1, wherein the vibration isolation device uses an air spring as an actuator, and the measurement unit uses a pressure gauge. 6. A projection optical system, a substrate stage mounted with a substrate and movable in a direction perpendicular to an optical axis of the projection optical system,
A main body structure that supports the projection optical system and the substrate stage; and a vibration damping device that supports the main body structure, damps vibration of the main body structure, and damps vibration from the floor. Using a projection exposure apparatus, the substrate stage is positioned so as to sequentially move the substrate mounted on the substrate stage to a plurality of predetermined shot positions, and after positioning at each shot position, the circuit pattern on the original plate has a predetermined wavelength. In a projection exposure method of illuminating with illumination light and projecting and exposing the substrate on the substrate stage via the projection optical system, a force acting on the main body structure from the vibration isolation device is measured, and And correcting the positioning of the stage based on the projection exposure method. 7. A semiconductor device manufactured by using the projection exposure apparatus according to claim 1 or the projection exposure method according to claim 6.