JPH1010703A - Semiconductor exposure device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to obtain sufficiently high resolving power in spite of use of projecting optical system in which coma aberrations exist by setting the height of the chromium patterns of a reticle to be used at integer times of the half number of a central frequency. SOLUTION: The reticle 3 is formed with chromium layers 5 of a prescribed height H in the prescribed positions of a quartz glass substrate 4. The prescribed height H is set at a nearby value satisfying the conditions of H=N.λ/2 with respect to the central frequency λ for the purpose of exposure. N denotes a positive integer. The relation between the difference Idef between the intensity of the scattered light SL1 to 3 scattered on the left side of the chromium layers 5 on a wafer and the intensity of the scattered light SL4 to 6 scattered on the light side and the height H of the chromium layers 5 is such that the amplitude of the intensity difference Idef changes sign functionally of λ in the period in proportion to the coma aberrations. The height H of the chromium layers 5 at which the intensity difference Idef attains zero satisfies the relation H=N.λ/2 without depending on the coma aberrations.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a semiconductor exposure apparatus using photolithography for transferring a fine electronic circuit pattern such as an IC, LSI, or VLSI formed on a reticle surface onto a wafer.

[0002]

2. Description of the Related Art Conventionally, a projection exposure apparatus for manufacturing a semiconductor has been required to be capable of projecting and exposing a circuit pattern on a reticle surface onto a wafer with a high resolving power in accordance with an increase in the density of integrated circuits. As a method for improving the projection resolution of a circuit pattern, for example, a method in which the wavelength of exposure light is fixed and the numerical aperture of a lens of a projection optical system is increased, or the exposure light is, for example, i-line rather than g-line, and excimer laser than i-line A method of shortening the wavelength such as the oscillation wavelength is employed.

[0003]

However, in the above-described conventional semiconductor exposure apparatus, in order to perform photographing exposure with a higher resolution, the amount of aberration of the projection optical system when projecting a reticle pattern onto a wafer is required. Needs to be reduced. When the so-called coma, which is an asymmetric aberration, is large, the asymmetry of the coma and the asymmetry of the projection optical system reinforce each other and the image performance is rapidly deteriorated. Therefore, high uniformity is required for the projection optical system. In addition, in order to increase the numerical aperture of the lens of the projection optical system, it is necessary to further reduce the residual aberration in terms of design values and manufacturing errors.

[0004] For this reason, the projection optical system has a problem that the number of lenses is increased and the system becomes complicated and large, and a long time is required for manufacturing in order to reduce a manufacturing error, thereby increasing the cost.

An object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide a semiconductor exposure apparatus capable of obtaining a sufficiently high resolution even when a projection optical system having a coma aberration is used.

[0006]

According to a first aspect of the present invention, there is provided a semiconductor exposure apparatus using photolithography for transferring a reticle pattern onto a wafer via a projection optical system at a center wavelength λ. In, the height of the chrome pattern of the reticle to be used is N · λ / 2
(N is a positive integer).

According to a second aspect of the present invention, there is provided a semiconductor exposure apparatus using optical lithography for transferring a reticle pattern onto a wafer via a projection optical system using a plurality of different exposure wavelengths λ ₁ , λ ₂ ,. The height of the chrome pattern of the reticle to be used is set at the different wavelengths λ ₁ and λ
_2, an integer multiple of half of the _{··· (N1 · λ 1/2} , N2 · λ 2 /
2,... (N1, N2,... Are positive integers).

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the illustrated embodiment. FIG. 1 is a side view of the exposure apparatus. A wafer W is mounted on a stage base 1, a projection optical system 2 is disposed above the wafer W, and a reticle 3 is provided above the projection optical system 2. FIG. 2 is a side view of the reticle of the first embodiment. The reticle 3 has a chrome layer 5 having a predetermined height H at a predetermined position on a quartz glass substrate 4.

Here, the predetermined height H is a value near the center wavelength λ for exposure that satisfies the following condition. H = N · λ / 2 (N is a positive integer)

The height H of the chrome layer 5 depends on the center exposure wavelength, and the center exposure wavelength is an i-line stepper (365 nm);
KrF stepper (248 nm), ArF stepper (19
Table 1 shows the height of the chromium layer 5 at N = 1 and 2 when the thickness is 3 nm).

[0011]

In FIG. 2, SL1 is the scattered light at the lower left part of the chromium layer 5, SL2 is the scattered light at the upper left part of the chromium layer 5 in the left direction, and SL3 is the right scattered light at the upper left part of the chromium layer 5. , SL4 is scattered light to the left at the upper right of the chrome layer 5, SL5 is scattered light to the right at the upper right of the chrome layer 5, and SL6 is scattered light at the lower right of the chrome layer 5. Is shown.

The pattern on the reticle 3 is exposed on the surface of the wafer W by the projection optical system 2. Scattered light SL1, SL2, SL3 scattered at the edge of the chrome layer 5 by the projection optical system 2
, SL4, SL5, and SL6 form an image on the wafer W,
Let's find the light intensity at that time. Here, based on the scattered light SL1, the scattered lights SL2, SL3,
SL4 and SL5 are delayed in phase by the height H of the chrome layer 5,
Further, considering the coma aberration remaining in the projection optical system 2, if the scattered lights SL3, SL5, and SL6 directed to the right are delayed in phase by the amount of the coma aberration, the scattered lights SL1, SL2, SL3, and SL
4, the phases of SL5 and SL6 can be expressed as follows. Phase P1 of SL1: EXP (jωt) Phase P2 of SL2: EXP (j (ωt + H)) Phase P3 of SL3: EXP (j (ωt + H + C)) Phase P4 of SL4: EXP (j (ωt + H)) Phase P5 of SL5: EXP (j (ωt + H + C)) Phase P6 of SL6: EXP (j (ωt + C))

Next, when the imaging performance due to the influence of the coma aberration of the projection optical system 2 is expressed using the phases P1 to P6, first, when the influence of the coma aberration of the projection optical system 2 is considered, Light SL1, SL scattered on the left side of the chrome layer 5 at
2, the intensity IL of SL3 and the scattered light SL4, SL5 scattered on the right side
And the difference Idef from the intensity IR of SL6.

The intensities IL and IR can be expressed by the following equations obtained by time-integrating the squares of the phases PL and PR.

[0016]

(Equation 1)

Where PL = P1 + P2 + P3 PR = P4 + P5 + P6

Therefore, since the intensity difference Idef is a difference between the intensities IL and IR, Idef = IL-IR. The real parts of the phases PL and PR are as follows. Re (PL) = cos (ωt) + cos (ωt + H) + cos (ωt + H + C) Re (PR) = cos (ωt + H) + cos (ωt + H + C) + cos (ωt + C)

Using these equations, numerical integration of only the real part of the intensity difference Idef is performed, and the relationship between the intensity difference Idef and the height H of the chromium layer 5 is obtained. become. In this graph, the vertical axis is the intensity difference Idef, the horizontal axis is the height H of the chrome layer 5, and the amount of coma of the projection optical system 2 is λ / 1.
A graph C1 calculated as 0 and a graph C2 calculated as λ / 20. In these graphs C1 and C2, since the height H of the chromium layer 5 on the horizontal axis is represented by being normalized by the center exposure wavelength λ, there is no need to limit the center exposure wavelength λ.

Therefore, from these two curves, the intensity difference Id
It can be seen that the amplitude of ef is proportional to the coma aberration and the period changes like a sine function of λ. Further, it can be seen that the height H of the chromium layer 5 where the intensity difference Idef becomes 0 is λ / 2, λ, 3λ / 2,... H = N · λ / 2 (N is a positive integer)

In actual optical lithography, the allowable value of the intensity difference Idef is not 0 but a finite value, so that the height H of the chromium layer 5 may be a height close to satisfying the above equation. . Here, the calculation is performed using the real parts of IL and IR. However, in the case of the imaginary part, since the cos of the above two equations may be set to sin, the result of numerical integration is exactly the same.

Further, the calculation was made on the assumption that the intensity of the scattered light at the upper part and the lower part of the chromium layer 5 was equal. However, when the intensity was different, it was calculated that the intensity of the scattered light at the upper part was half the intensity of the scattered light at the lower part. , And the left and right phases PL2 and PR2 are expressed by the following equations using P1 to P6. PL2 = P1 + P2 / 2 + P3 / 2 PR2 = P4 / 2 + P5 / 2 + P6

Accordingly, as a result of the numerical integration of the intensity difference Idef at this time, as shown in FIG. 4, the amplitudes are graphs C3 and C4 having the same characteristics as those of FIG.

Also, a plurality of different exposure wavelengths λ ₁ , λ ₂ ,
Are used for the same exposure apparatus or different exposure apparatuses, and are used when a reticle pattern is transferred onto the wafer W via the projection optical system 2 using these different wavelengths λ ₁ , λ ₂ ,. Height H of chrome layer 5 of reticle 3
Are set to near integer multiples of half the values of the different wavelengths λ ₁ , λ ₂ ,..., It becomes possible to achieve an exposure method that achieves a higher resolution.

FIG. 5 shows a side view of the two-layer chrome reticle of the second embodiment, in which a chromium layer 5 and a chromium oxide layer 10 are laminated on a quartz glass substrate 4, and the thickness of the chromium layer 5 is The chrome layer height H. The amount of the chrome layer height H with respect to the center exposure wavelength is the same as in Table 1.

FIG. 6 shows a side view of a three-layer chrome reticle according to the third embodiment.
1, a chromium layer 5 and a chromium oxide layer 10 are laminated,
Since reflected light and scattered light are generated at two boundary surfaces having a large difference in refractive index, the thickness of the chromium layer 5 becomes the chrome layer height H in the present embodiment. The amount of the chrome layer height H with respect to the center exposure wavelength is the same as in Table 1.

FIG. 7 is a side view of a halftone reticle according to a fourth embodiment.
A light-shielding band 12 made of a member shifted by 80 ° is used, and its height becomes the height H. The amount of the height H with respect to the center exposure wavelength is the same as in Table 1.

[0028]

As described above, the semiconductor exposure apparatus according to the first aspect of the present invention uses the reticle pattern having the center wavelength λ to set the height of the chromium pattern near N · λ / 2, thereby reducing the projection optical system. Without affecting the residual amount of coma of the system, it is possible to obtain the same good resolution performance as when there is no coma, and it is possible to reduce the required performance of coma of the projection optical system. Light weight, small size, simplification and cost reduction are possible.

The semiconductor exposure apparatus according to the second invention uses reticle patterns corresponding to a plurality of different exposure wavelengths λ ₁ , λ ₂ ,..., And adjusts the chrome pattern height of each reticle pattern to the reticle pattern. Exposure wavelength λ ₁ ,
λ ₂ ,... an integral multiple of half (N1 · λ / 2, N2 · λ /
2,...), It is possible to obtain the same good resolution performance as in the case where there is no coma aberration, without being affected by the residual amount of coma aberration of the projection optical system. Since the required performance of the system for coma can be reduced, it is possible to reduce the weight, size, simplification and cost.

[Brief description of the drawings]

FIG. 1 is a side view of a semiconductor exposure apparatus.

FIG. 2 is a side view of the reticle of the first embodiment.

FIG. 3 is a graph showing a relationship between a difference in intensity and a chromium layer height.

FIG. 4 is a graph showing the relationship between the intensity difference and the chromium layer height.

FIG. 5 is a side view of a two-layer chrome reticle of a second embodiment.

FIG. 6 is a side view of a three-layer chrome reticle of a third embodiment.

FIG. 7 is a side view of a halftone reticle according to a fourth embodiment.

[Explanation of symbols]

 Reference Signs List 2 shooting optical system 3 reticle 4 quartz glass substrate 5 chrome layer 10, 11 chromium oxide layer 12 light-shielding band

Claims (6)

[Claims] In a semiconductor exposure apparatus using photolithography for transferring a reticle pattern onto a wafer via a projection optical system using a center wavelength λ, the height of a chrome pattern of a reticle to be used is set to N · λ / 2 (N is a positive value). Semiconductor exposure apparatus. 2. A plurality of different exposure wavelengths λ ₁ , λ ₂ ,.
In a semiconductor exposure apparatus using photolithography that transfers a reticle pattern onto a wafer via a projection optical system, the height of a chrome pattern of a reticle to be used is an integer of a half of the different wavelengths λ ₁ , λ ₂ ,. Times (N1 / λ
_{1/2, N2 · λ 2} /2, ···) (N1, N2, ··· semiconductor exposure apparatus is characterized in that the vicinity of a positive integer). 3. The semiconductor exposure apparatus according to claim ₂ , wherein the different wavelengths λ ₁ , λ ₂ ,... Are used in the same exposure apparatus. 4. The semiconductor exposure apparatus according to claim ₂ , wherein the different wavelengths λ ₁ , λ ₂ ,... Are used in different exposure apparatuses. 5. The semiconductor exposure apparatus according to claim 1, wherein the chromium pattern has a light transmission characteristic. 6. The semiconductor exposure apparatus according to claim 1, wherein the chromium pattern is laminated together with a chromium oxide layer.