JPH11111583A - Projection optical system distortion measuring method, projection exposure apparatus using the same, and device manufacturing method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distortion measuring method for a projection optical system capable of repeatedly projecting a pattern on a mask surface onto a substrate surface with high overlay accuracy, a projection exposure apparatus using the same, and a projection exposure apparatus using the same. Obtain a device manufacturing method. SOLUTION: A distortion reticle having a pattern formed on a substrate with a single light-shielding layer is projected on the substrate by a projection optical system, and coordinate information of the pattern formed on the substrate is obtained. Measurement of distortion of the projection optical system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring distortion of a projection optical system, a projection exposure apparatus using the same, and a method for manufacturing a device using the same, for example, a semiconductor device such as an IC or LSI, or an imaging device such as a CCD. And a projection exposure apparatus for manufacturing a device such as a display device such as a liquid crystal panel. In the projection exposure apparatus, a distortion on a projection optical system in the projection exposure apparatus is correctly measured, and a pattern on a first object plane is adjusted by adjusting the projection optical system. Can be repeatedly projected and exposed on the second object plane with high precision.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for higher integration of semiconductor devices such as ICs and LSIs. A reduction type projection exposure apparatus (stepper) for forming a circuit pattern of a mask (reticle) on a photosensitive substrate (wafer) by a projection optical system and exposing the photosensitive substrate in a step-and-repeat manner;
Alternatively, in a reduced projection exposure apparatus (scanner) that exposes a circuit pattern of a mask (reticle) and a photosensitive substrate by a scanning method, in order to cope with high integration, it is necessary to improve the resolution of a pattern image and perform repeated projection exposure. The overlay accuracy of each pattern has been improved.

[0003] When a projection pattern is repeatedly projected by a projection exposure apparatus, the overlay accuracy of each pattern is made up of many factors such as stage accuracy and alignment accuracy. One of the important factors related to the overlay accuracy is the distortion of the projection optical system.
There is.

[0004] If the distortion of the projection optical system differs greatly between apparatuses, when a circuit pattern of a mask (reticle) is projected and exposed on a photosensitive substrate by a projection optical system and superimposed on each apparatus, a projection pattern image is formed. Will not overlap exactly. As a result, there arises a problem that required device characteristics cannot be obtained. Therefore, for example, in a 64MDRAM class device, the distortion of the projection optical system is reduced to, for example, 50 nm.
It is required that:

[0005] The distortion of the projection optical system is several tens of nm.
In order to set it to the degree, high-precision distortion measurement and high-precision machining / assembly adjustment technology are required.

Conventionally, as a method of measuring distortion of a projection optical system, a reticle having a pattern for distortion measurement (hereinafter referred to as a distortion reticle) is used, and a projection optical system is used to project and expose a photosensitive substrate (wafer). The coordinate position of the pattern formed by development is measured using a coordinate measuring instrument (for example, LMS2020 manufactured by Leica, Inc.).
A measurement method using a Nikon's Rampass 3i) is often used. At this time, the coordinate position of the pattern on the distortion reticle is separately measured by a coordinate measuring instrument, and this is regarded as the manufacturing error (coordinate error) of the distortion reticle, and the coordinate position of the pattern formed on the photosensitive substrate is determined. In general, the distortion of the projection optical system is extracted by subtracting it from the measurement result.

Conventionally, as a mask (reticle) on which a circuit pattern used in a projection exposure apparatus is drawn, a so-called double-layer chrome reticle composed of a chromium layer and a chromium oxide layer on a glass substrate, and a glass substrate On top of that, a so-called three-layer chrome reticle composed of a chromium oxide layer, a chromium layer, and a chromium oxide layer is generally used. The purpose of arranging these chromium oxide layers on one side or both sides of the chromium layer is to suppress the occurrence of unnecessary flare and ghost by functioning as an antireflection film that lowers the reflectance of the chromium layer. Things. Similarly, a distortion reticle for measuring the distortion of the projection optical system generally uses a two-layer chrome reticle or a three-layer chrome reticle.

[0008]

When a two-layer chrome reticle or a three-layer chrome reticle is used as a distortion reticle for measuring the distortion of a projection optical system, a pattern (distortion reticle of a distortion reticle) formed on a photosensitive substrate is used. There is a problem that the coordinate position of the pattern on the distortion reticle, which is measured to extract the distortion of the projection optical system from the coordinate position measurement result of the pattern, cannot be correctly measured. As a result, an error occurs in the measurement of the distortion of the projection optical system, and there has been a problem that it is not possible to achieve highly accurate distortion performance of the projection optical system.

At this time, one of the reasons why the coordinate position of the pattern on the distortion reticle cannot be measured correctly is the pattern edge structure of the two-layer chrome reticle or the three-layer chrome reticle.

That is, if there is a manufacturing error of an asymmetric shape at a pattern edge, a distortion occurs in a detection signal obtained therefrom, which causes a problem that a measurement error occurs.

According to the present invention, a distortion of a projection optical system for projecting and exposing an electronic circuit pattern on a first object plane (mask, reticle) onto a second object plane (wafer) can be measured with high accuracy. A projection optical system distortion measurement method capable of achieving a more accurate projection optical system distortion performance and easily manufacturing a highly integrated device, a projection exposure apparatus using the same, and a device manufacturing using the same The purpose is to provide a method.

[0012]

According to the present invention, there is provided a method for measuring distortion of a projection optical system, comprising the steps of: (1-1) projecting a distortion reticle having a pattern formed on a substrate with a single light-shielding layer onto the substrate by a projection optical system. Obtaining coordinate information of the pattern formed on the substrate,
By utilizing this, the distortion of the projection optical system is measured.

In particular, (1-1-1) the single light-shielding layer is formed of chromium.

In the projection exposure apparatus of the present invention, (2-1) the distortion of the projection optical system is adjusted using the data obtained by using the distortion measuring method for the projection optical system having the configuration (1-1). It is characterized by that.

The method of manufacturing a device according to the present invention is characterized in that it includes a step of (3-1) printing a pattern on a mask surface on a substrate surface using the projection exposure apparatus having the configuration (2-1). .

The distortion reticle of the present invention is characterized in that (4-1) a pattern is formed on a substrate with a single light-shielding layer made of chromium, and the distortion of the projection optical system is measured.

The distortion measuring method for a projection optical system according to the present invention is characterized in that (5-1) the distortion of the projection optical system is measured using the distortion reticle having the configuration (4-1).

According to the projection exposure apparatus of the present invention, (6-1) the distortion of the projection optical system is adjusted using the data obtained by using the distortion measuring method of the projection optical system having the configuration (5-1). It is characterized by that.

The method of manufacturing a device according to the present invention is characterized in that it includes the step of (4-1) printing a pattern on a mask surface on a substrate surface using the projection exposure apparatus having the configuration (6-1). .

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of a main part of a projection exposure apparatus according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes light source means, which is composed of, for example, a high-pressure mercury lamp or an excimer laser. Reference numeral 2 denotes an illumination optical system (illumination system) that uniformly illuminates a reticle (first object) R surface as a surface to be illuminated mounted on the reticle stage 3 with a light beam from the light source means 1.

Reference numeral 8 denotes an illumination stop, which comprises a plurality of stops having different aperture shapes or a stop having a variable aperture shape. The illumination condition of a surface to be irradiated (reticle R) is changed in various ways to switch a plurality of illumination modes. Is available.

Reference numeral 4 denotes a projection optical system (projection lens) for reducing and projecting a circuit pattern on the reticle R surface onto the wafer W placed on the wafer stage 5.

The wafer stage 5 performs XYZ drive, θ drive, tilt drive, and the like. Reference numeral 7 denotes a mirror (interference mirror) which is mounted on the wafer stage 5, monitors the position of the wafer stage 5 with a laser length measuring device 6, and drives using a signal obtained by the laser length measuring device 6. The wafer stage 5 is driven by means (not shown) to position the wafer W at a predetermined position.

Reference numeral 9 denotes a light projecting means, which is an optical axis La of the wafer W.
In order to detect the surface position in the direction, the surface of the wafer W is irradiated obliquely with a light beam that does not expose the photoresist applied to the wafer W. 10 is a detecting means (gap sensor)
That is, the reflected light from the surface of the wafer W is detected, and the distance in the optical axis direction between the projection lens 4 and the wafer W is measured without passing through the projection lens 4.

FIG. 2A is a cross-sectional view of a distortion reticle having a pattern formed of a single light-shielding layer made of chromium according to the present invention, and FIG. 2B is a transmission light intensity distribution of the reticle, and FIG. C) shows the reflected light intensity distribution of this reticle.

FIG. 3A is a sectional view of a conventional distortion reticle having a pattern formed of two-layer chromium.
FIG. 3B is a conceptual diagram of a transmitted light intensity distribution of the distortion reticle, and FIG. 3C is a conceptual diagram of a reflected light intensity distribution of the distortion reticle. FIG. 4 is an explanatory diagram showing an example of a distortion reticle on which a pattern for distortion measurement is arranged, and FIG. 5 is a flowchart showing an example of a method for measuring distortion of a projection optical system.

As shown in FIG. 5, in the method of measuring the distortion of the projection optical system, (a1) the coordinate position of the pattern on the distortion reticle is measured by a coordinate measuring device. Reticle coordinate error:
Dreticle (a2) A pattern on the distortion reticle is projected and exposed on a photosensitive substrate by a projection optical system.

(A3) The photosensitive substrate is developed, and the coordinate position of the formed pattern is measured by a coordinate measuring device. Wafer coordinate error: Dwafer (a4) Calculation of distortion Dlens of the projection optical system.

Dlens = Dwafer-Dretic
The order of le / m (m is the magnification of the projection optical system) is good.

Conventionally, as a distortion reticle, a two-layer chrome reticle or a three-layer chrome reticle (not shown) as shown in FIG.

However, when a two-layer chrome reticle or a three-layer chrome reticle is used as a distortion reticle for measuring the distortion of the projection optical system, an asymmetrical shape as shown in FIG. If there is a manufacturing error, distortion occurs in the detection waveform of the detection signal based on the manufacturing error. As a result, an error occurs in the coordinate position measurement of the pattern, and there has been a problem that correct measurement cannot be performed.

Particularly, in actual projection exposure, FIG.
While image formation is performed based on the light intensity distribution of the transmitted light of the distortion reticle as shown in FIG. 3B, measurement of the coordinate position of the distortion reticle generally involves distortion as shown in FIG. In many cases, coordinate position measurement is performed based on the light intensity distribution of the reflected light of the reticle. In this case, in particular, the interference condition of the anti-reflection film is different between the transmitted light and the reflected light, the difference between the wavelengths of the light sources used in the projection exposure and the coordinate position measurement, and the projection exposure optical system and the coordinate position measurement optical system. The interference condition of the anti-reflection film varies with the NA (numerical aperture), which causes measurement errors.

Therefore, in the present invention, as shown in FIG. 2A, a distortion reticle having a pattern formed of a single light-shielding layer made of chromium on a glass substrate is used.
According to this, since the problem of the asymmetric manufacturing error as shown in FIG. 3A does not occur at the pattern edge, the coordinate position measurement error occurs due to the problem of the pattern edge due to the difference in the interference condition of the antireflection film. In other words, the coordinate position of the pattern on the distortion reticle can be measured more correctly by using a coordinate position measuring device as conventionally used.

As a result, the distortion of the projection optical system is more correctly extracted, thereby achieving a highly accurate distortion performance of the projection optical system.

The result of the distortion of the projection optical system, which is more correctly separated and extracted, is used for assembling the projection optical system,
By reflecting the distortion in the adjustment of the distortion, the distortion performance of the projection optical system is maintained in a well-balanced manner. As a result, a projection exposure apparatus with improved pattern image overlay performance is achieved.

Further, by using the projection exposure apparatus of the present embodiment, various highly integrated devices such as IC, LSI, CCD, image pickup device, liquid crystal panel, and magnetic head can be easily manufactured.
It can be manufactured efficiently and accurately.

FIG. 6 shows a flow of manufacturing a device (a semiconductor chip such as an IC or an LSI, or a liquid crystal panel or a CCD) according to the present invention.

In step 1 (circuit design), a circuit of a semiconductor device is designed. Step 2 is a process for making a mask on the basis of the circuit pattern design.

On the other hand, in step 3 (wafer manufacturing), a wafer is manufactured using a material such as silicon. Step 4
The (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 of forming a semiconductor chip using the wafer prepared in step 4, and includes an assembly process (dicing and bonding) and a packaging process (chip encapsulation). And the like.

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. 7 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.

In step 13 (electrode formation), electrodes are formed 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 above-described exposure apparatus to print and expose the circuit pattern of the mask onto the wafer.

In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist are removed. In step 19 (resist stripping), the resist that has become unnecessary after the etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the manufacturing method of this embodiment, it is possible to easily manufacture a highly integrated device which has conventionally been difficult to manufacture.

[0046]

According to the present invention, a projection optical system for projecting and exposing an electronic circuit pattern on a first object plane (mask, reticle) onto a second object plane (wafer) by employing the above method. And a distortion measuring method for a projection optical system capable of easily achieving a high-precision distortion performance of a projection optical system and easily manufacturing a highly integrated device. It is possible to achieve a projection exposure apparatus and a device manufacturing method using the same.

In particular, according to the present invention, by using a distortion reticle composed of a single light-shielding layer made of chromium to measure the distortion of the projection optical system, the coordinate position of the pattern on the distortion reticle can be more accurately measured. As a result, the distortion of the projection optical system can be more correctly separated and extracted.

The result of the distortion of the projection optical system, which has been correctly separated and extracted, is used for assembling the projection optical system,
By reflecting the result in the adjustment of distortion, highly accurate distortion performance of the projection optical system can be achieved. As a result, it is possible to achieve a projection exposure apparatus in which the superposition performance of a pattern image repeatedly projected is improved.

When the projection exposure apparatus of the present invention is used,
Various highly integrated devices such as C, LSI, CCD, imaging device, liquid crystal panel, and magnetic head can be easily, efficiently, and accurately manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic view of a main part of a projection exposure apparatus according to the present invention.

FIG. 2 is a sectional view of a distortion reticle according to the present invention.

FIG. 3 is a cross-sectional view of a conventional distortion reticle having a pattern formed of a two-layer chromium structure.

FIG. 4 is an overall view of a distortion reticle on which a pattern for distortion measurement is arranged.

FIG. 5 is a flowchart illustrating an example of a method for measuring distortion of a projection optical system.

FIG. 6 is a flowchart of a device manufacturing method according to the present invention.

FIG. 7 is a flowchart of a device manufacturing method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source means 2 Illumination optical system 3 Reticle stage 4 Projection optical system 5 Wafer stage 6 Laser length measuring device 7 Mirror 8 Illumination stop 9 Light emitting means 10 Light receiving means W Wafer R Reticle

Claims (8)

[Claims] 1. A distortion reticle having a pattern formed on a substrate with a single light-shielding layer is projected onto the substrate by a projection optical system, and coordinate information of the pattern formed on the substrate is obtained. A distortion measuring method for a projection optical system, wherein the distortion of the projection optical system is measured. 2. The distortion measuring method for a projection optical system according to claim 1, wherein said single light shielding layer is formed of chromium. 3. A projection exposure apparatus, wherein the distortion of the projection optical system is adjusted using data obtained by using the distortion measurement method for the projection optical system according to claim 1. 4. A method of manufacturing a device, comprising printing a pattern on a mask surface on a substrate surface using the projection exposure apparatus of claim 2. 5. A distortion reticle, wherein a pattern is formed on a substrate with a single light-shielding layer made of chromium, and distortion of a projection optical system is measured. 6. A distortion measuring method for a projection optical system, comprising: measuring a distortion of a projection optical system using the distortion reticle according to claim 5. 7. A projection exposure apparatus, wherein the distortion of a projection optical system is adjusted using data obtained by using the distortion measurement method for a projection optical system according to claim 6. 8. A method for manufacturing a device, comprising printing a pattern on a mask surface on a substrate surface using the projection exposure apparatus according to claim 7.