JPS6180820A - Projection exposure equipment - Google Patents

Abstract

PURPOSE:To contrive reducing the reflected light from a pattern or on a wafer by forming a low reflection film at the position which includes the pattern of a reticule and by carrying out low reflection treatment against the photo resist of a semiconductor wafer. CONSTITUTION:A reticule 12 is based upon a transparent quartz glass substrate 10 on the surface of which the pattern 11 of a metal film such as chromium is formed in a required shape. In this case, a low reflection film 13 is formed on the surface of the pattern 11. On the other hand, a patterned or etched film is formed on the surface of a semiconductor wafer 40 and a photo resist film 41 is formed on the patterned or etched film. If the above-mentioned reticule or wafer is each set in a projection exposure equipment 9 and the pattern of a reticule 3A is copied on a wafer 5A, the reflected light on the surface or on the back of the reticule 3A or the wafer 5A is reduced.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to a reticle and an optical system for projection exposure.

The present invention relates to a projection exposure apparatus designed to prevent defective pattern transfer due to reflected light generated on a semiconductor wafer or the like.

[Background technology]

As the element patterns of semiconductor devices such as ICs and LSIs become finer, the reduction magnification of reticle patterns transferred onto half-quad wafers also increases, and along with this, transfer defects caused by reflected light are increasing. The occurrence is becoming more noticeable. For example, a recent reduction type projection exposure apparatus is published by Press Journal Co., Ltd. "Sem1conductor World".
J (1984, 7 p. 58-pH 4), as schematically shown in FIG. configured to form an image. And, with this device, the same figure ■～■
As shown, between the condenser lens 2 and the reticle 30,
The front and back sides of the reticle 3, between the reticle 3 and the optical system 4,
Light reflection occurs between the optical system 4 and the wafer 5, on the photoresist 6 on the wafer 5, on the surface of the wafer 5, and the like. In particular, since the reticle 3 has a pattern 8 formed of a gold PA (chromium) film on the glass substrate 7, the reflection in this pattern 8 is also large. When such light reflection occurs, each reflected light reaches the wafer 5 as it is or while repeating multiple reflections, resulting in so-called ghosts and flares that expose the wafer surface other than the regular pattern and cause transfer defects. become.

In order to analyze the phenomena and causes of problems caused by multiple reflections, for example, W.
trust 5tudies in High-Per
formansProjection 0ptics”
IEεE Trans, Ele-ctron De
vice・Vo I-ED-30: Nov, p,
1474 (1983), but no solution is provided.

[Purpose of the invention]

An object of the present invention is to provide a projection exposure apparatus that suppresses or prevents multiple reflections in an illumination optical system, a reticle, and a reduction optical system, thereby improving pattern transfer defects.

Further, the object of the present invention is to provide an illumination optical system, a reticle, a reduction
An object of the present invention is to provide a semiconductor device which can further improve transfer by suppressing and preventing reflections on a semiconductor wafer in addition to a small optical system.

The above and other objects and novel features of the present invention include:
It will become clear from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

In other words, by forming a low-reflection film on areas of the reticle that contain small patterns (including patterns), we aim to reduce the amount of light reflected from the patterns, which is particularly noticeable.

It is possible to reduce the amount of reflected light between each reduction optical system, prevent ghosts and flares, and improve transfer defects.

Further, by applying low-reflection treatment to the photoresist of the semiconductor wafer, it is possible to reduce reflected light on the wafer, thereby further improving the effect of preventing ghost and flare.

〔Example〕

FIG. 1 shows an embodiment in which the present invention is applied to a reticle, and FIG. 4 to r) show different modifications.

Here, each reticle is basically formed by forming a pattern 11 of a metal film such as chromium, which does not transmit light, in a desired shape on the surface (lower surface in the figure) of a transparent quartz glass substrate 10.

In FIG. 1, a low reflection film 13 is formed on the surface of a pattern 110. As the low reflection film 13, for example, when the pattern 11 is formed of a chromium film, a chromium oxide film is used. This chromium oxide film has a pattern thickness of 20 to 200
The thickness ranges from 5 to 200 nm.

The reticle can be manufactured by forming a chromium film and a chromium oxide film on the glass substrate 10, and then selectively etching (patterning) both films at the same time using photolithography or the like.

In this reticle 12 structure, a light beam (gljl=436 nm, hil=4 O
5 nm, i-line = 365 nm) can be controlled to an arbitrary value by suppressing the reflectance to a range of 1 to 30% and adjusting the film thickness, etc.

FIG. 1 (I31 is a reticle 16 in which low reflection films 14 and 15 are formed on the front surface 2 and back surface of the pattern 11.

The membrane material and thickness are the same as the metal. In this example, pattern 1
Reflection on the back surface of 1 can also be prevented.

Including the +CI pattern shown in FIG. 1, low reflection films 18 and 19 are formed on the entire surface and back surface of the reticle 170, and especially on the surface, the film 18 is formed so as to cover the pattern 11. The material for the low reflection film 18°]9 is M
gFt , S r xoy + Achi03°CaF2
, MgO,PrawnlIn2O31ZrQ,
tT+xOy.

An inorganic film of ZnS is effective, and the thickness is 5 to 20
0 nm is preferred. In this case, the low reflection film 18.19
It is also possible to improve the antireflection effect by forming one to three layers with stepwise different refractive indexes. In addition, organic film binding, photoresist materials with added dyes (for example, dyes added to Tokyo Ohka Co., Ltd.'s 0NPR-830, 0DUR-1010), antireflection films with good coating properties (for example, Br
e-wer 5science company! ARC), nitrocellulose, polymethyl methacrylate, polyvinyl alcohol, novolak resin, polyvinyl carbazole, etc. are used.

In FIG. 1 [)l, a thick low-reflection film 20 is formed on the surface side of the pattern 11, and this film absorbs the light diffracted at the edge of the pattern among the light passing through the reticle 21 at an almost vertical angle. Absorb at 20. The thickness of the film 20 is preferably 100 nm or more, and is optimally 0.5 to 10 times the pattern width (space width in the case of a positive resist process). However, the thickness may be greater than 1, for example 10:
When there is a space of 10 .mu.m in the reticle for reduction projection 1, a thickness of 5 to 100 .mu.m is optimal, and a sufficient effect can be obtained even if the reticle is thinner or thicker than this.

The material for the film 20 may be the same as in the previous example, but when forming a thick film, it is more effective to use a photosensitive organic material. That is, when forming the reticle 21, the low reflection film 22 and the chromium film 11 are formed on the glass substrate 10, and then patterned by the process described above to form the pattern 11, and then the photosensitive organic material or the like is formed. By forming a thick film and irradiating light from the back side of the reticle 21, the organic material is exposed in a self-line manner by the pattern 11, and if this is subsequently developed, the film 20 can be completed only on the pattern 11. Note that when an inorganic material is used, it can be formed by a normal photolithography technique (also in this case, exposure can be performed in a cell 7 aligned manner using a previously formed pattern).

According to this example, not only can the diffracted light at the edge portion of the pattern 11 be absorbed, but also the focal plane (focal plane position of the reticle pattern) can be arbitrarily selected. In other words, by making the thickness of the vacuum-adsorbed area of the reticle different from the thickness of the pattern in the exposed area, and freely changing the thickness of the former, it is possible to set an arbitrary focal plane and facilitate focus adjustment. can be achieved.

Figure 1) is a low reflection film 23.2 on the surface of the glass substrate 10.
A chromium film pattern 11 is formed together with 4, while a pattern II is formed on the back side of the substrate 10 together with a low reflection film 25 and 26.
A and constitutes a °C reticle 27. ℃, the patterns 11A and the like on the back side are formed so that the pattern dimensions are about 1 to 30% smaller than those on the front side.

This configuration is a measure against the fact that the incident angle of illumination light has a slight spread with respect to the vertical plane of the reticle, and by making the pattern dimensions on the front and back surfaces different, it is possible to prevent the transmission of inclined light rays. When the thickness of the glass substrate 10 is 22 mm, the difference in pattern dimensions between the front and back surfaces (one-sided dimension difference with respect to the center) is preferably 0 to 5 μm.

FIG. 1 (Fl is a known pesocles film (for example, LR0°865-28 manufactured by ASP) provided to cover the pattern 11 to prevent foreign matter from adhering to the surface of the reticle 28.
A low reflection film 30 is formed (coated) on 29 and heated to 29°C.

Since the pesocles film 29 usually has a thickness of 1 μm or less and has low mechanical strength, it is coated with the above-mentioned inorganic material on the front and back surfaces in a 1-3 layer structure with a thickness of 5-2 (1 nm). It is desirable that the low reflection film 30 has a low refractive index toward the surface side.

On the other hand, as shown in FIG. 2, the semiconductor wafer to which the pattern is transferred has a structure in which the pattern up to the previous process and the film to be etched are formed on the surface of the semiconductor wafer 40, and a photoresist film is formed thereon. Basically, there is again.

In the second arrangement, the photoresist film 41 contains a dye having absorption characteristics for G-line, H-line, or I-line.

For example, dyes such as orange yellow, Sudan orange, etc. are added to 0.5 to 1
By mixing 0 wt %, applying this to a thickness of 1 μm, and soft baking, the light transmittance of the resist can be reduced from zero to 30% or less, and this value can be set arbitrarily. The light interference inside the resist film 41 does not have a constant value because the reflection efficiency differs depending on the substance forming the lower layer of the resist, but it depends on the dye concentration.

Optimal conditions can be found by controlling the resist thickness.

In this example, since most of the exposed light is absorbed by the resist, an effect equivalent to low reflection can be obtained.

In FIG. 2 [F], a film 42 having sufficient absorbency for G-line, H-line or 1liK is formed in advance on the surface of a wafer 40, and a photoresist film 43 is formed thereon.

The film 42 is a low reflection Si thin film (3 to 200 nm thick)
, ARCL2 (1
A thickness of 0 to 500 nm) is effective.

FIG. 2 1cI shows a photoresist film 44 on a wafer 40.
One to three thin films 45 having a refractive index of 1.3 to 28 are formed thereon, and the refractive index of each layer is made smaller on the surface side. The materials described in FIG. 1 can be used as the materials for the thin film 45, and the optimum thickness can be obtained between 5 nm and 500 nm. The photoresist film 44 may be constructed using a two-layer or three-layer resist method. That is, in the case of the two-layer resist method, polymethacrylate containing a dye is coated on the wafer 40, and a resist film 7 is applied thereon.
144, then 1 to 3 thin films 45 of the present invention
form a layer. In the three-layer resist method, a positive resist containing a dye (for example, Tokyo Ohka G.

NPR-830) is coated, and then a Sin film (for example, 0CD manufactured by Tokyo Ohka Co., Ltd.) is coated and baked, and then a photoresist film 44 and a thin film 45 of the present invention are formed by polishing for one to three times.

If the reticle formed as described above is set in the projection exposure apparatus 9 shown in Ranihara's FIG. 3, and the pattern of the reticle 3A is transferred onto the wafer 5A, the pattern of the reticle 3-?
Reflected light on the front and back surfaces of the wafer 5A is reduced,
Therefore, it is possible to suppress or prevent the abnormal reflected light shown in the figures (1) to (2), and it is possible to prevent ghosts and flares and perform accurate pattern transfer.

〔effect〕

(1) Since the reticle is small (both have a low-reflection film formed on the pattern area, it is possible to suppress reflected light from the pattern surface with many scenes, and prevent ghosts, flares, etc. caused by this reflected light, Pattern transfer can be suitably performed.

(Since a low-reflection film is formed on the front and back surfaces of the 21 patterns, reflection on the front and back surfaces of the pattern is suppressed, and the overall amount of reflected light is reduced, making the pattern transfer even better.

(Since a thick low-reflection film is formed on the 31°C surface,
It is possible to prevent diffracted light from passing through the pattern edge portions.

(4) Patterns are formed on the front and back surfaces of the reticle glass substrate, and the pattern on the back side is formed to be slightly smaller than the pattern on the front side, so that transmission of light at an angle oblique to the reticle can be prevented.

(51) Since the photoresist film formed on the semiconductor wafer contains a material with light absorption properties, it prevents abnormal reflection of light irradiated onto the photoresist and enables accurate pattern transfer.

(Since a low reflection film is formed on the upper or lower surface of the photoresist film on the 61 wafer, reflected light on the upper or lower surface of the photoresist film can be reduced.

Although the invention made by the present inventor has been specifically explained based on Examples above, the present invention is not limited to the above Examples, and may be modified in various ways without departing from the gist thereof. Needless to say, for example, the above-mentioned reticles described individually can be combined with each other, and various configurations other than those shown in the drawings can be obtained.Of course, the configurations of the illumination optical system and the projection optical system can also be varied. can be adopted.

[Application field]

In the above explanation, the invention made by the present inventor has mainly been explained in the case where it is applied to a projection exposure apparatus for manufacturing semiconductor devices, which is the background field of application, but it is not limited to this, and in particular, Reticle improvements can be applied to photolithography techniques in general.

[Brief explanation of the drawing]

Figures 1-r) are cross-sectional views of different embodiments of the reticle, Figures 2-(0) are cross-sectional views of different embodiments of the semiconductor wafer, and Figure 3 is a schematic structure and abnormalities of a projection exposure apparatus. It is a diagram showing a reflection state. 1... Light!, 2... Condenser lens, 3, 3A...
... Reticle, 4... Projection optical system, Death... Wafer,
6... Photoresist, 9... Projection exposure device, 10
...Glass substrate, 11,11A...Pattern (chrome film), 12.16,17,21,27.28...Reticle, 13.14,15,18,19,20,22゜23. 24, 25, 26.30...Low reflection film, 29.
... Pesocle, 40 ... Wafer, 41, 43, 44
...Photoresist, 42.45...Low reflection film. Agent Patent Attorney Akira Takahashi Arrival Figure 1 (A), / ;Z (,), 4. ! ′ \
ゝ, ' , '=/ ''' Figure 1 and Fノ,,,7.

Claims (1)

[Scope of Claims] 1. In a projection exposure apparatus comprising an illumination optical system that illuminates a reticle on which a desired pattern is formed and a projection optical system that projects the pattern of the reticle, at least a pattern portion of the reticle is provided with low reflection. A projection exposure apparatus characterized by forming a film. 2. The projection exposure apparatus according to claim 1, wherein a low reflection film is formed on the front and back surfaces of the pattern. 3. The projection exposure apparatus according to claim 1, wherein a thick low-reflection film is formed on the surface of the pattern. 4. The projection exposure apparatus according to claim 1, wherein a back pattern that is minutely smaller than the pattern is formed on the back surface of the reticle, and a low reflection film is formed on each of the pattern and the back pattern. 5. The projection exposure apparatus according to claim 1, further comprising a pescule film covering the pattern, and a low reflection film formed on the pescule film. 6. In a projection exposure apparatus equipped with an illumination optical system that illuminates a reticle on which a desired pattern has been formed and a projection optical system that projects the pattern of this reticle onto the surface of a semiconductor wafer, the wafer surface is subjected to a low reflection treatment. A projection exposure apparatus characterized by forming a photoresist film. 7. The projection exposure apparatus according to claim 6, wherein the photoresist film contains a low reflection substance. 8. The projection exposure apparatus according to claim 6, wherein a low reflection film is formed on the lower surface of the photoresist film. 9. The projection exposure apparatus according to claim 6, wherein one or more films having a lower refractive index than the photoresist film are formed on the upper surface of the photoresist film.