KR20060077748A - Illumination in lithography - Google Patents

Abstract

The present invention relates to an illumination system of an exposure apparatus, wherein the aperture of the exposure apparatus is composed of a hybrid aperture in which two or more apertures are mixed so that it can be used in High-NA while maintaining the advantages of the incident light illumination system, and the exposure source is polarized. In addition, I / D (iosolation / dense) bias and proximal effect are reduced, so it is equipped with a compound aperture useful for emulsion lithography technology that improves idle margin and convenience of optical process correction (OPC). It relates to an illumination system of an exposure apparatus.

Exposure system, illumination system, polarization, hybrid, aperture

Description

Illumination in lithography

1 is a view showing an illumination system of an exposure apparatus according to the prior art,

Figure 2a is a view showing the illumination using the conventional aperture,

Figure 2b is a view showing the illumination using the annular aperture,

2c shows illumination using a dipole X aperture,

2d is a diagram showing illumination using a dipole Y aperture,

Figure 2e is a view showing the illumination using a quadrupole aperture,

Figure 2f is a view showing the illumination using the cross pole aperture,

FIG. 3A illustrates a hybrid aperture in which an aperture is mixed with a conventional aperture; FIG.

FIG. 3B illustrates a hybrid aperture in which a quadrupole aperture and a conventional aperture are mixed; FIG.

3c illustrates a hybrid aperture in which a crosspole aperture and a conventional aperture are mixed;

4 is a graph showing the relationship between Exposure Latitude and DOF,

5 shows polarization directions in respective illumination systems.

* Description of the symbols for the main parts of the drawings *

11: aperture 12. condenser lens

13: Projection Lens 14. Mask

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an illumination device of a stepper and a scanner, and more particularly to an illumination system of an exposure device having a polarization exposure source and a composite aperture.

Recently, photolithography (photolithograph) technologies for forming finer patterns have been developed according to the trend of higher integration and higher density of semiconductor devices. In particular, high-resolution and high depth-of-focus (DOF) are required to manufacture ultra-high-density devices (ULSI) of 256M DRAM or higher, such as the off-axis method using aperture. The utilization of the lighting method is actively performed.

1 is a view showing an illumination system of an exposure apparatus in the prior art. As shown in FIG. 1, the aperture 11, which is a light limiting means for limiting the exposure source incident on the condenser lens 12 from the light source, and the condenser lens 12 which condenses the exposure source passing through the aperture 11. ) Is installed. A projection lens 13 is installed below the condenser lens 12, and a mask 14 for forming a pattern on the wafer 10 between the condenser lens 12 and the projection lens 13. Is inserted and mounted.

In the conventional illumination system configured as described above, after the exposure source is filtered through the aperture 11 and the condenser lens 12 and collected and passed through the mask 14, the photoresist is applied through the projection lens 13. In addition to being exposed to the wafer 10, a pattern formed on the mask 14 is formed on the wafer 10.

In such exposure, the light passing through the condenser lens 12 and the mask 14 is derived by +1, -1, 0 order by the diffraction component, by Pupil filtering. -1st order light is removed, and only + 1st order light and 0th order light are imaged on the wafer 20.

That is, in the photolithography of the semiconductor device, the illumination system device used in the manufacturing process has a high resolution and a depth of focus (DOF) while having a light amount sufficient to expose the photoresist film since the light intensity is determined when the light source is determined. Ideally).

However, when the general illumination system is further enlarged, the disadvantage is that the amount of light decreases and the uniformity of the amount of light deteriorates. In order to overcome these disadvantages and to be able to use it, an increase in manufacturing cost is required. In addition, there is a problem that can not be expanded to some extent due to the limitations in manufacturing equipment.

Accordingly, as the integration of semiconductor devices is advanced, there is a need for an illumination system device having higher resolution and deeper DOF. In other words, as the semiconductor device is highly integrated, the device density per unit area is increasing, and thus, the pitch between patterns formed on the wafer is narrower than before. In order to form such a pattern, the resolution of the illumination system device exposing the photosensitive film should be higher than that of the conventional illumination system device, and the DOF must be deeper. For this purpose, a deformation illuminator is a device that exhibits high resolution and deep DOF by modifying the aperture of the illumination system, and by applying an off-axis illumination (OAI: Off Axis Illumination), other process margins ( For example, DOF or Dose margin can be increased.

The deformed illumination system is a device inserted between an illumination source and a condenser lens of an exposure apparatus so as to use the 0th light and the 1st light of the exposure source to inject light, and various shapes according to a desired pattern. It can have Such deformed illumination systems include annular apertures, quadrupole apertures, dipole apertures, and cross pole apertures. It's going on.

FIG. 2A is an illumination using a conventional aperture, FIG. 2B is an illumination using an annular aperture, FIG. 2C is an illumination using a dipole X aperture, FIG. 2D is an illumination using a dipole Y aperture, and FIG. 2F Is the illumination using the quadrupole aperture, and FIG. 2G shows the illumination using the crosspole aperture.

Such a modified illumination system is designed to use one light difference and zero order light of ± 1 order light by intentionally tilting the exposure axis. The use of one +1 or -1 order light and 0 order light causes loss of light, but can form a desired pattern.

On the other hand, the focal plane of the mask exists in any part of the exposure apparatus, and the diffraction image of the light diffracted through the mask forms a surface, which is called an entrance pupil or an entrance pupil surface, and forms an image in the entrance pupil. The contrast of the pattern formed on the wafer is determined by the shape and extent of the diffraction image to be formed. In general, a method of increasing the process margin by increasing the amount of diffracted primary light incident on the entrance pupil through incidence illumination is used.

In particular, recently, immersion technology has been introduced, and accordingly, numerical aperture (NA) has become more extreme. As NA increases, the need for a polarized light source of light sources is emerging. The light source itself is polarized in the direction of TM (transverse magnetic) or TE (Transverse electric).

However, the above-mentioned incident lights can increase the process margin, that is, DOF, etc., beyond the limits of the general illumination system, and have the advantage of realizing a smaller pattern, but I / D (iosolation) due to the nature of the incident light / dense) The application was limited because it was influenced by the bias difference and the proximity effect. That is, there is a problem that makes the photo process difficult as the device is reduced.

The present invention has been made to solve the problems of the prior art as described above, the I / D (iosolation / dense) bias and the proximal effect is reduced so that it can be used in High-NA while maintaining the advantages of the incident light system It is an object of the present invention to provide an exposure apparatus having a compound aperture useful for emulsion lithography technology that improves idle margin and convenience of optical process correction (OPC).

The illumination system of the exposure apparatus according to the present invention for achieving the above object includes a projection lens, a mask formed with a pattern to be transferred to the exposure object, a condenser lens, a light shielding area for blocking light incident on the condenser lens; An exposure apparatus having an aperture and an exposure source having a transmissive region for transmitting light, wherein the aperture is a hybrid aperture in which two or more apertures are mixed, and the aperture is a conventional aperture ( and two selected from a conventioal aperture, an annular aperture, a dipole aperture, a quadrupole aperture, and a cross pole aperture. One of the features is that it is a conventional aperture.

 The exposure source is characterized in that the polarization.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

2A to 2F are views showing illumination using a conventional aperture, an aperture aperture, a dipole X aperture, a dipole Y aperture, a quadrupole aperture, and a cross pole aperture, and FIG. 3A is an aperture aperture. FIG. 3B illustrates a hybrid aperture in which a hybrid aperture and a conventional aperture are mixed. FIG. 3B illustrates a hybrid aperture in which a quadrupole aperture and a conventional aperture are mixed. FIG. 3C illustrates a crosspole aperture and a convention. It is a figure which shows the hybrid aperture which mixed the national aperture. 4 is a graph showing the relationship between the exposure latitude and the DOF, and FIG. 5 is a diagram showing the polarization direction in each illumination system.

The illumination system of the exposure apparatus of the present invention also has a projection lens over the exposure object, a mask having a pattern to be transferred to the exposure object, a condenser lens, a light shielding area for blocking light incident on the condenser lens, and a light transmitting area for transmitting light. The use of an exposure apparatus provided with an aperture and an exposure source is the same as in the prior art, and in providing the aperture, two or more apertures are mixed and used.

It is equipped with a pupil shape optic (not shown) in the exposure system of a typical scanner, which forms an illumination shape, which can be used to polarize the exposure source through the filtering or polarization lens of the device. 2A to 2F, the conventional aperture, the annular aperture, the dipole aperture, the quadrupole aperture crosspole aperture, and the like. Use a combination of two apertures selected from the cross pole apertures.

An example of the mixed spreader is shown in FIGS. 3A-3C. That is, FIG. 3A is a view illustrating a hybrid aperture in which an annular aperture and a conventional aperture are mixed, and FIG. 3B is a view of a hybrid aperture in which a quadrupole aperture and a conventional aperture are mixed. 3C is a diagram illustrating a hybrid aperture in which a crosspole aperture and a conventional aperture are mixed.

By irradiating polarized illumination through the filter shape or polarization lens of the pupil shape optics to the mixed type aperture as described above, the conventional illumination and the annular illumination are mixed with the polarized illumination. When exposed in a hybrid manner, it is possible to reduce the disadvantages while maintaining the advantages of incidence illumination.

In other words, by investigating the conventional lighting in the incident lighting system, it is possible to reduce the difference of I / D (iosolation / dense) bias, which is a disadvantage of the employees, and also to reduce the impact due to the effect of proximity. And convenience of optical process correction (OPC) is improved.

FIG. 4 is a graph illustrating the relationship between exposure latitude and DOF. When comparing the polarization exposure source and the non-polarization exposure source, it can be seen that the exposure source polarized in the HIGH-NA has increased energy latitude and DOF, and thus polarization is used. In this case, an improvement in process margin can also be expected.

That is, FIG. 5 illustrates the polarization direction in each illumination system, and thus the process margin may be maximized by specifying the polarization direction.

Although the technical spirit of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above embodiment is for the purpose of description and not of limitation. In addition, it will be understood by those skilled in the art that various implementations are possible within the scope of the technical idea of the present invention.

The present invention described above, while maintaining the advantages of the incorporating illumination system, the difference in I / D (iosolation / dense) bias is reduced, and the effect of the proxyity is reduced, thereby improving process margin and convenience of optical process correction (OPC). This has the effect of being improved.

In addition, the device development period is shortened by reducing the number of mask changes due to the reduction of I / D bias.

Claims (4)

A projection lens, a mask having a pattern to be transferred to the exposure object, a condenser lens, an aperture having a light blocking area for blocking light incident on the condenser lens, and a light transmitting area for transmitting light, and an exposure source. In the exposure apparatus, The aperture is an illumination system of an exposure apparatus, characterized in that the hybrid aperture is a mixture of two or more apertures. The method of claim 1, wherein the aperture comprises a conventional aperture, an annular aperture, a dipole aperture, a quadrupole aperture, and a crosspole aperture. An illumination system of an exposure apparatus, characterized in that two selected from the pole aperture. 3. An illumination system according to claim 2, wherein one of the selected apertures is a conventional aperture.  The illumination system of claim 1, wherein the exposure source is polarized light.

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