JP3107958B2 - Exposure equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus used in a lithography step in a semiconductor manufacturing process, and more particularly to an exposure apparatus capable of automatically correcting lens aberration of an optical system.

[0002]

2. Description of the Related Art A lithography process (pattern transfer by an exposure apparatus) used many times in a semiconductor manufacturing process.
Therefore, it is important to eliminate errors between processes. When an error occurs, a pattern shift may occur and a product may not be produced.

In the semiconductor process, there are roughly two types of pattern transfer methods. One is a method in which a pattern originally formed on a mask or a reticle is transferred onto a wafer through an optical system. The other is a direct drawing type in which a pattern is directly drawn by EB (electron beam) or laser light.

[0004] In the former case, the throughput is fast because the transferred pattern is already drawn, and the current mainstream is confined. However, since errors between apparatuses are included, as the number of superpositions increases, the error from the pattern first exposed increases. Also, depending on the type of semiconductor, there is room for improvement because many reticles or masks are required. The latter has a drawback that the throughput is extremely slow since the drawing is performed directly for each wafer.

A conventional exposure apparatus for transferring a pattern formed on a mask or a reticle has the following disadvantages.

(1) It is not easy to perform matching between exposure apparatuses.

(2) A large number of reticles or masks are required for the number of steps.

(3) There is a temporal change of the optical system.

On the other hand, by using a transmissive flat panel display as the mask, it is not necessary to prepare a large number of masks for each exposure step, and the entire exposure step for one wafer can be performed without exchanging masks. An exposure apparatus that can be implemented by a single apparatus has been proposed in Japanese Patent Application Laid-Open No. 1-155347.

However, the exposure apparatus disclosed in Japanese Patent Application Laid-Open No. 1-155347 does not solve the problems of the aging of the optical system and the matching between the exposure apparatuses.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and has as its object to provide an exposure apparatus capable of automatically correcting lens aberration of an optical system.

[0012]

In order to achieve the above object, an exposure apparatus according to the present invention comprises a reticle or mask capable of erasing and writing a pattern, and a reticle or mask on a reticle or mask based on given pattern data. Pattern writing means for drawing a pattern, an optical system for illuminating the reticle or mask, and projecting a transfer image of the pattern drawn on the reticle or mask to a position to be exposed, and an optical system for projecting the pattern A sensor for detecting a transferred image, drawing a reference grating on the reticle or mask, causing the sensor to detect a transferred image of the reference grating, and correcting the aberration of the optical system based on the detected transferred image of the reference grating. When detecting and drawing an exposure pattern on the reticle or mask, an exposure pattern is used to cancel the aberration based on the aberration detection result. Ndeta corrected to a characterized by comprising a control means for providing the pattern writing means.

In one embodiment of the present invention, a transmissive flat display is used as the reticle or mask.

In another embodiment of the present invention, the reticle or the mask comprises a chargeable film and a plurality of stripe-shaped transparent electrodes arranged in parallel with each other. And two sets of electrodes whose directions are orthogonal to each other.
Data of a reference grid pattern and an exposure pattern to be drawn on the reticle or mask are stored as digital data as orthogonal coordinates indicating each intersection of the striped transparent electrodes constituting the two sets of electrodes. The writing means draws a pattern by charging a portion of the chargeable film indicated by the pattern data provided from the control means and selectively applying a magnetic fluid to the charged portion.

[0015]

According to the exposure apparatus of the present invention, the reticle or the mask can draw a pattern on the reticle or the mask by an electric on / off signal (digital information) or the like. A reference grating is drawn and captured by a sensor on the transfer stage or at a position where the transfer image light can be received as transfer image light after transmission through the optical system.Based on the transfer signal received by this sensor, the amount of deviation from the reference grating CPU and other calculations to calculate the error from the ideal transfer image, create new pattern data by applying error correction to the exposure pattern data required for semiconductor fabrication, etc., and place it on the reticle or mask. It draws after clearing the previous data.

As described above, after the exposure pattern is subjected to error correction, by drawing on a reticle or a mask, it is possible to obtain pattern data in which optical system aberrations are taken into consideration.

[0017] Matching between devices becomes easier.

It is not necessary to have many reticles or masks, and only data such as MT may be used.

A new pattern can be created by data input for pattern change (peripheral exposure, numbering on a wafer, etc. can also be input as information to this pattern data).

It is possible to correct the aging of the optical system.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of an exposure apparatus according to one embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a transmission type reticle (or mask), for example, a transmission type liquid crystal display can be used. 2 is a light source for illuminating the reticle 1,
Reference numeral 3 denotes an optical system for projecting a pattern image of the reticle 1, and reference numeral 4 denotes a movable stage on which a semiconductor wafer 5 is mounted. On the stage 4, a CCD sensor 6 is provided. A control device 10 controls the operation of the entire exposure apparatus.
11, a memory 12, and various interfaces 15 for connecting the reticle 1, the light source 2, the shutter device (not shown), the optical system 3, the stage 4, the sensor 6, and the like to the control device 10 and the like.

Next, the operation of the apparatus of FIG. 1 will be described with reference to the flowchart of FIG. The reference grid pattern and the data of the pattern used in the semiconductor integrated circuit to be manufactured are stored in advance in an external memory device such as a magnetic tape device together with a program for operating the CPU 11, and the data of the reference grid pattern is It is assumed that the memory 12 has been read when the program of the exposure apparatus is loaded. The data of the reticle pattern to be used in the exposure processing is transferred from the external memory device to the memory 12 when the reticle pattern to be used in the exposure processing is specified by a keyboard or the like.
Further, it is assumed that a predetermined area such as a register for the calculated amount of distortion in the memory 12 has been subjected to necessary initialization.

When an operation start is instructed by an input from a set of semiconductor wafers or a keyboard or the like, the CPU 1
1. First, the data of the reference lattice pattern is read from the memory 12 and sent to the reticle 1 (step 10).
1). As a result, a reference grating pattern is formed on the reticle 1. Further, the stage 4 is driven to move the sensor 6 into the field of view of the optical system 3, and the reticle 1 is irradiated with light from the light source 2 to project a reference grid pattern transferred image by the optical system 3 onto the sensor (step). 102). Next, the data of the reference grid pattern transfer image from the sensor 6 is fetched,
By calculating this, it is determined whether or not the transferred image has distortion (step 103). If there is no distortion, the process proceeds to step 121 described later.

On the other hand, if there is distortion, the amount of distortion at each coordinate is calculated (step 111), the reference grid pattern on the reticle is erased (step 112), and the reference grid is corrected with the calculated distortion amount. Is drawn on the reticle 1 (step 113) and projected on the sensor 6 (step 114). Then, it is determined whether or not the distortion of the reference lattice image has been removed based on the sensor output at that time (step 1).
15). If the distortion is removed, the process proceeds to step 1 described later.
Move to 21. On the other hand, if the distortion has not been removed, the distortion amount of each coordinate is recalculated based on the previous distortion amount calculation value and the current sensor output (step 111), and then the processes of steps 112 to 115 are repeated.

In step 121, the reticle pattern is erased. Subsequently, a pattern of the semiconductor integrated circuit to be manufactured is drawn on the reticle 1 in a state where the pattern is corrected by the distortion amount calculated in step 111 (step 122), and the wafer is mounted on the stage 4 and the stage 4 is moved. Then, the wafer is exposed.

In the above description, an example in which the aberration determination processing is performed for each type of pattern has been described. However, such processing may be performed for each lot of wafers, or may be performed for a predetermined period, for example, periodically. It may be performed every inspection period. When all patterns of one type of semiconductor integrated circuit are exposed by the same exposure apparatus, the exposure may be performed for each predetermined number of semiconductor integrated circuits or for each lot.

Further, the above-described reticle is disclosed in
A liquid crystal display which draws a pattern with a laser as shown in Japanese Patent No. 55347 may be used.

[0029]

FIG. 3 shows an exposure apparatus according to a second embodiment of the present invention. The apparatus shown in the figure is obtained by applying the electrostatic copying technique to the reticle (or mask) 1 in the apparatus shown in FIG. That is, according to the present embodiment, the mask or the reticle is covered with the ferroelectric film or the like, and the magnetic fluid or the like can be drawn as a mask / reticle image in the portion where the potential is applied. Electrode groups for applying a potential in a desired pattern shape are arranged on both surfaces of the ferroelectric film. Each of these electrode groups is composed of a number of stripe-shaped transparent electrodes arranged in parallel, and the directions of the stripes are orthogonal to each other on both surfaces.

In FIG. 3, reference numeral 31 denotes an external memory device such as a magnetic tape device, a pattern information input circuit including a keyboard and a mouse, and 32 denotes a CPU and the like.
A pattern information correction circuit for controlling the processing as shown in FIG.
Reference numeral 3 denotes an input signal circuit, and reference numeral 34 denotes a timing drive circuit 35 which generates a drive signal necessary for driving the reticle 1 based on an output of the pattern information correction circuit sent via the input signal circuit 33, and is formed by a timing drive circuit 35. A control circuit for supplying the drive signal according to the timing; a timing drive circuit for generating a timing signal for driving the reticle 1 at the timing; and a timing drive circuit for applying the drive signal to the reticle 1 at that timing; An electric signal line for connecting the circuit 35 and the stripe-shaped transparent electrode of the reticle 1, and 37 is a connector.

In the exposure apparatus shown in FIG. 3, similarly to the exposure apparatus shown in FIG. 1, a reference grating is first drawn, and a transferred image after passing through the optical system is received by a sensor 6 such as a CCD or the like. The shift amount is recognized and corrected by CPU processing calculation. Therefore, errors such as aberrations of the projection optical system 3 can be corrected so as not to be present on the reticle or mask, and errors in the transferred image on the wafer can be eliminated.

When the pattern is changed, the potential application section is provided with a reverse potential, the magnetic fluid or the like drawn on the mask or reticle is collected, and the potential accompanying new data is applied again to draw the pattern again. Possible,
The structure does not need to have many reticles or masks. The reference grid pattern and the pattern for manufacturing a semiconductor integrated circuit are patterned by turning on / off an electric signal.
The pattern operates on information from the CPU.

The reticle portion shown in FIGS. 1 and 3 may have the structure shown in FIG. In FIG. 4, 1 is a reticle, 1a
Is a transparent conductive film, 36 is an electric signal line, and 37 is a connector. As a medium for forming a pattern on a reticle, a medium such as a magnetic fluid can be used. An orthogonal electrode is formed of a transparent conductive film, and this electrode is connected to a circuit including a timing drive circuit, a control circuit, an input signal circuit, a pattern information correction circuit, and a pattern information input circuit shown in FIG. Data is given in the form of electric charge on rectangular coordinates. As a result, the reticle is maintained in a state having a partial positive or negative charge. Here, the magnetic fluid is displaced to the charged portion 62 on the reticle by scanning the roller 61 with the magnetic fluid on the reticle. In this state, exposure is performed on the wafer.

After the exposure is completed, there is a need for initialization, and a charge opposite to the charge initially applied is applied to the reticle.
By scanning the roller side, the reticle can be returned to a completely initial state.

FIG. 5 shows an example using a reflection type reticle (or mask). The reticle (or mask) in FIG. 5 includes a high-reflection substrate portion 1b and a ferroelectric portion 1c. The ferroelectric portion 1c has the configuration shown in FIG. 4, and can be provided with a magnetic fluid or the like as shown in FIG. It is to be noted that the use of a metal as the base (highly reflective substrate portion 1b) makes it easy to return the electric charge. In FIG. 6, 61
Is a roller with a magnetic fluid. This roller may be a magnetic brush as used in electrostatic copying machines.

It is to be noted that the method of using the reticle / mask as in the present invention can be used also as a stop (aperture) in an optical system or as a mask portion for deformed illumination. It becomes easy to parameterize.

[0037]

As described above, according to the present invention, a reference grating on a reticle or a mask is projected on a sensor,
Data correction for the aberration of the optical system can be performed by calculating the sensor output by the CPU processing. For this reason, matching between the exposure apparatuses becomes easy, and it is also possible to cancel a temporal change of the main optical system. Also, it is possible to simplify the adjustment of each dimension of the optical system.

Further, since the reticle or the mask can be written / erased, there is no need to have a large number of reticles or masks, so that the cost can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the apparatus of FIG. 1;

FIG. 3 is a configuration diagram of an exposure apparatus according to another embodiment of the present invention.

FIG. 4 is a perspective view showing a specific example of the reticle in FIGS. 1 and 3;

FIG. 5 is a configuration diagram of an exposure apparatus according to still another embodiment of the present invention.

FIG. 6 is a perspective view showing a specific example of the reticle in FIGS. 3 and 5;

[Explanation of symbols]

1: reticle (or mask), 1a: transparent conductive film, 1
b: high reflection substrate part, 1c: ferroelectric part, 2: light source, 3:
Projection optical system, 4: Stage, 5: Wafer, 6: CCD sensor, 10: Control device, 11: CPU, 12: Memory,
15: Interface, 31: Pattern information input circuit, 32: Pattern information correction circuit, 33: Input signal circuit, 34: Control circuit, 35: Timing drive circuit, 3
6: electric signal line, 37: connector, 61: roller, 6
2: Charged portion on the reticle.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/027 G03F 7/20 521

Claims (5)

(57) [Claims] 1. A reticle or mask capable of erasing and writing a pattern, pattern writing means for drawing a pattern on the reticle or mask based on given pattern data, and illuminating the reticle or mask. And an optical system for projecting a transfer image of a pattern drawn on the reticle or mask to a position to be exposed, a sensor for detecting a transfer image projected by the optical system, and a reference grating on the reticle or mask. When drawing, the sensor detects a transfer image of the reference grating, detects aberration of the optical system based on the detected transfer image of the reference grating, and draws a pattern for exposure on the reticle or mask. A control means for correcting exposure pattern data to cancel the aberration based on the aberration detection result and providing the corrected pattern data to the pattern writing means. Exposure apparatus characterized by comprising and. 2. The exposure apparatus according to claim 1, wherein the reticle or the mask comprises a transmission type flat display. 3. The reticle or the mask has a chargeable film, and the writing means charges the chargeable film in a shape indicated by given pattern data, and selectively applies a magnetic fluid to the charged portion. 2. The exposure apparatus according to claim 1, wherein the pattern is drawn by coating. 4. An exposure apparatus according to claim 1, wherein said control means includes storage means for storing digital data of a reference lattice pattern to be drawn on said reticle or mask and an exposure pattern. 5. The reticle or the mask includes a plurality of stripe-shaped transparent electrodes which are arranged in parallel with each other, and includes two sets of electrodes which face each other with the chargeable film interposed therebetween and in which the directions of the stripes are orthogonal to each other. 4. An exposure apparatus according to claim 3, wherein said storage means stores the pattern data as orthogonal coordinates indicating respective intersections of the striped transparent electrodes constituting the two electrode groups.