KR100589207B1 - Modified aperture in exposure equipment for semiconductor device fabrication - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor manufacturing technology, and more particularly, to an illumination system of exposure equipment for manufacturing semiconductor devices, and more particularly, to a deformation aperture of exposure equipment for manufacturing semiconductor devices. SUMMARY OF THE INVENTION An object of the present invention is to provide a deformation aperture of exposure equipment for manufacturing a semiconductor device capable of realizing a pattern pitch below the limit resolution of an exposure source. According to an aspect of the present invention, the first and second openings of a fan-shaped arc shape ('()' shape) symmetrically disposed at the anode in the X-axis direction, and symmetrically disposed at the anode in the Y-axis direction. And the third and fourth openings having a circular arc shape ('()' shape), wherein the opening angles of the first and second openings are 35 to 45 °, and the opening angles of the third and fourth openings are There is provided a deformation aperture of exposure equipment for manufacturing a semiconductor device, which is 5 to 25 degrees.

Lithography, Illumination System, Strain Aperture, Opening Angle, Diffraction Beam

Description

Deformation aperture of exposure equipment for semiconductor device manufacturing {MODIFIED APERTURE IN EXPOSURE EQUIPMENT FOR SEMICONDUCTOR DEVICE FABRICATION}             

1 is a view showing the configuration of an illumination system of the exposure equipment.

2A is a view showing a layout of a general aperture.

2B illustrates the layout of various strain apertures.

3 shows the principle of general illumination and modified illumination;

4 is a view showing the layout of the deformation aperture according to an embodiment of the present invention.

5 is a view showing a layout of a deformation aperture according to another embodiment of the present invention.

6 is a view showing an aerial image obtained using an illumination system to which the present invention is applied.

7 to 9 are electron micrographs of actual patterns obtained using the illumination system to which the present invention is applied, respectively.

* Explanation of symbols for the main parts of the drawings

θ1: Opening angle (X axis direction)

θ2: Opening angle (Y axis direction)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor manufacturing technology, and more particularly, to an illumination system of exposure equipment for manufacturing semiconductor devices, and more particularly, to a deformation aperture of exposure equipment for manufacturing semiconductor devices.

Since mass production of semiconductor products based on DRAM (Dynamic Random Access Memory) has begun, development of lithography technology has been rapidly made. Lithography is a key process for determining the density of semiconductor products.

The density of DRAM has increased almost fourfold every three years, and the design rule (minimum pattern size) of the product has also been reduced from 0.8 µm for 4Mb DRAM to 0.18 µm for 1Gb DRAM, and is now non-optical lithography. (non optical lithography) technology is in the stage of preparation.

The resolution in optical lithography is inversely proportional to the wavelength of the exposure light source. The wavelength of the light source used in the initial stepper employing the "step and repeat" exposure method is 436 nm ( It is mainly used as a stepper or scanner type exposure equipment that uses a DUV with a wavelength of 248 nm (KrF excimer laser) through 365 nm (i-line) to g-line).

Optical lithography has been used to develop photoresist materials such as chemically amplified resist (CAR) type resists as well as the development of exposure systems such as lenses and apertures of high apertures (NA) of 0.6 or more. In terms of the development and process aspects, such as Tri Layer Resist (TLR), Top Surface Imaging (TSI), Anti Reflective Coating (ARC), and Phase Shift Mask (PSM) and Optical Proximity Correction (OPC) in terms of masks. Many technological developments have been made. KrF excimer lasers with a wavelength of 248 nm initially had many problems such as process time delay and substrate dependence, but were able to implement a 0.18 μm design rule. However, in order to implement the design rules below, technology development for next-generation light sources such as ArF excimer laser (193 nm) and F2 (157 nm) must be continued.

Typically, Kohler illumination is applied to an illumination system of an exposure apparatus.

1 is a diagram illustrating a configuration of an illumination system of an exposure apparatus.

Referring to FIG. 1, an illumination method in which light starting from an effective light source forms an image in an entrance pupil of a projection lens may be obtained to obtain uniform illuminance on a surface on which a mask is placed. Wherever the effective light source is located, an aperture is placed to select the optimum exposure condition.

FIG. 2A illustrates a layout of a conventional aperture, and FIG. 2B illustrates a layout of various deformation apertures.

Referring to FIGS. 2A and 2B, a general aperture is a shape having a circular opening, and all of the apertures except this may be referred to as deformation apertures.

Currently used deformation apertures include an annular aperture (a) having an opening in the form of a round band as shown in FIG. 2b, and a quadrupole upper having four small circular openings arranged in a square. (B), a crosspole aperture (c) having four small circular openings arranged crosswise, a dipole aperture (d) having two elliptical openings, and the like.

FIG. 3 shows the principle of conventional illumination and off-axis illumination.

Referring to FIG. 3, in the case of general illumination, the zero-order diffracted light contributes to the pattern formation and increases only the DC component on the spatial image of the pattern, resulting in a decrease in the spatial image MTF (Modulation Transfer Function) value. In addition, when the pattern size is small, there is a disadvantage in that the first diffracted light does not pass through the projection lens and thus the pattern cannot be formed (see dotted arrow).

On the other hand, in the case of modified illumination, the zero-order diffracted light of the DC component is incident off the optical axis. As a result, the incident light splits into zero order light that is straight without diffraction in the pattern on the reticle, ± 1 order light that is diffracted by the pattern, and higher order light. Among them, the pattern on the mask is formed on the wafer by using two luminous fluxes, 0th order light and + 1th order light. Accordingly, the DC component is removed from the spatial image to increase the MTF value, resulting in an improvement in resolution and an increase in depth of focus (DOF) margin.

In the case of using KrF excimer laser, which is currently being applied in mass production, as an exposure source, the product that can be implemented even with the aforementioned deformation aperture is limited to a product having a half pitch of the pattern of 100 nm or more. If the half pitch of the pattern is reduced to 100 nm or less, the diffraction angle of the incident light becomes large due to the reduced pattern size on the mask, thereby making it difficult to pattern due to insufficient contrast.

Table 1 below shows the amount of diffraction beams per aperture / design when the KrF excimer laser is used as the exposure source, and Table 2 shows the aperture of the dipole aperture when the KrF excimer laser is used as the exposure source. It shows the amount of diffraction beam for each design.

Annular Quadrupole 25 Dipole 90 100nm half pitch 18.3% 6.7% 73.2% 90nm half pitch 7.6% 0.0% 30.2%

50 55 60 65 70 80 90 190nm half pitch 97.6% 94.8% 90.8% 85.4% 79.3% 69.4% 61.7% 180 nm half pitch 68.3% 62.4% 57.2% 52.0% 49.1% 42.9% 38.2%

Referring to Table 1, when performing exposure using a KrF excimer laser light source with a lens of 0.80 NA (internal sigma 0.65, external sigma 0.89) (Reiley process factor k1 = 0.322), for example, dipole aperture (opening angle) 90), when applying a mask for forming a 100-nm half pitch line-space pattern, the rate at which the first diffracted beam reaches incident pupil is 73.2%, and a 90-nm half pitch line-space pattern is formed. If you apply the mask for the ratio drops to about 30.2%. Typically, to achieve a stable pattern, the arrival rate of the first diffraction beam should be 70% or more.

Table 2 shows the KrF excimer laser light source using the lens with the aperture sigma 0.70 and the outer sigma 0.90, even if the same type of aperture is used, depending on the design (half pitch) and the opening angle. It can be seen that the arrival rate of the diffraction beam is different.

On the other hand, in order to realize a pattern below 100 nm half pitch, an exposure source having a shorter wavelength than that of a KrF excimer laser may be used. However, this method is not only expensive, but also requires development and verification of resists. There is a problem that must be preceded.

The present invention has been proposed to solve the above problems of the prior art, and an object thereof is to provide a deformation aperture of exposure equipment for manufacturing a semiconductor device capable of realizing a pattern pitch of less than the limit resolution of an exposure source.

According to an aspect of the present invention for achieving the above technical problem, the first and second openings of the fan-shaped arc ('()' shape) arranged symmetrically to the anode in the X-axis direction, and the Y-axis direction The third and fourth openings having a fan-shaped arc ('()' shape) symmetrically disposed at an anode of the opening, and the opening angles of the first and second openings are 35 to 45 °, and the third And a deformation aperture of the exposure apparatus for manufacturing a semiconductor element, wherein the opening angle of the fourth opening is 5 to 25 degrees.

Preferably, the X-axis direction corresponds to the pitch direction of the line pattern disposed relatively densely in the device.

According to another aspect of the present invention, in the exposure system including the deformation aperture, a KrF excimer laser is used as the exposure source, and 0.80NA (internal sigma 0.70, external sigma 0.90) is applied. An exposure system is provided.

The present invention proposes a deformation aperture capable of obtaining an optimized diffraction beam. Since most semiconductor devices including DRAM have a line structure densely arranged in a specific direction, the deformation aperture is designed to obtain more diffraction beams in that direction. The pattern was also considered.

Hereinafter, preferred embodiments of the present invention will be introduced in order to enable those skilled in the art to more easily carry out the present invention.

4 is a view showing the layout of the deformation aperture according to an embodiment of the present invention.

Referring to FIG. 4, the deformation aperture according to the present embodiment has a fan-shaped symmetrical opening in the anode in the X-axis direction and the anode in the Y-axis direction, respectively. This is as if the opening of the annular aperture is limited to the opening area of the cruciform aperture, and it will be easy to understand that the openings facing each other form a '()' shape.

On the other hand, the opening angle θ1 of the opening arranged in the X-axis direction is 40 °, and the opening angle θ2 of the opening arranged in the Y-axis direction is preferably 10 °.

5 is a view showing the layout of the deformation aperture according to another embodiment of the present invention.

Referring to FIG. 5, the deformation aperture according to the present embodiment has a fan-shaped symmetrical opening in the anode in the X-axis direction and the anode in the Y-axis direction, respectively. Compared with the deformation aperture of the above-described embodiment, it can be said to be the same except that the opening angle in the Y-axis direction is changed.

Here, the opening angle θ1 of the opening disposed in the X-axis direction is 40 °, and the opening angle θ2 of the opening disposed in the Y-axis direction is preferably 20 °.

In summary, the opening angle θ1 of the opening arranged in the X-axis direction can be determined in a range of 35 to 45 °, and the opening angle θ2 of the opening arranged in the Y-axis direction is 5 to 25 °. You can decide in the range.

When the above-described deformation aperture is introduced into the illumination system and the KrF excimer laser is used as the exposure source, the amount of the first diffraction beam can be increased to maintain the maximum contrast in the X-axis direction (the pitch direction of the gate cell pattern). In addition, an appropriate amount of the first diffraction beam can be ensured even in the Y-axis direction.

6 is a view showing an aerial image obtained using an illumination system to which the present invention is applied, and FIGS. 7 to 9 are electron micrographs of actual patterns obtained using the illumination system to which the present invention is applied.

6 to 9 are results obtained by using the deformation apertures (θ1 = 40 ° and θ2 = 10 °) shown in FIG. 4 under the conditions of internal σ 0.70 and external σ 0.90 in the KrF 0.80NA system, respectively, as an exposure source. .

First, in FIG. 6, (a) is an aerial image of the device isolation layer pattern, (b) is an aerial image of the landing plug contact pattern, and (c) is an aerial image of the storage node contact pattern.

7 is an electron micrograph of a substrate on which an actual device isolation layer is formed, FIG. 8 is an electron micrograph of a substrate on which a landing plug contact is formed, and FIG. 9 is an electron micrograph of a substrate on which a storage node contact is formed.

The above results show that the gate cell pitch of 90-100 nm can be realized and stable in all directions even when the KrF excimer laser is used as the exposure source by applying the deformation aperture proposed in the present invention and performing appropriate OPC. Prove that you can get a profile. In addition, within a tolerance range of ± 10% of the target CD, the cell had a DOF of 0.3 µm or more and an exposure latitude of 9% or more.

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-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

For example, in the above-described embodiment, the case where the KrF excimer laser is used as an exposure source has been described as an example, but the deformation aperture according to the present invention has a shorter wavelength than the KrF excimer laser, such as an ArF excimer laser and an F2 laser. It can also be applied to an exposure system.

The above-described present invention can implement a pattern pitch of less than the limit resolution of the exposure source, thereby suppressing the cost increase due to the introduction of the next generation exposure system.

Claims (3)

delete First and second openings in a fan shape ('()' shape) symmetrically disposed at an anode in the X-axis direction, The third and fourth openings of a fan-shaped arc ('()' shape) symmetrically disposed on the anode in the Y-axis direction, The opening angles of the first and second openings are 35 to 45 °, the opening angles of the third and fourth openings are 5 to 25 °, and the X-axis direction is relatively densely arranged in the device. The deformation aperture of the exposure apparatus for manufacturing a semiconductor element, corresponding to the pitch direction of the. An exposure system comprising the deformation aperture of claim 2, An exposure system using a KrF excimer laser as an exposure source and applying 0.80NA (internal sigma 0.70, external sigma 0.90) conditions.

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