JPS61124944A - Mask - Google Patents

Abstract

PURPOSE:To make possible normalizing and to prevent the generation of a partial temp. difference of a resist by forming a light shielding film of a mask of a good heat conductive material. CONSTITUTION:The photomask 1 is constituted by depositing the light shielding film 3 atop a glass plate 2 and depositing the resist film 4 atop the film 3. The film 3 is formed of the two-layered construction in which the 1st layer 3a consists of copper and the 2nd layer 3b consists of chromium. Since the copper having excellent heat conductivity (having heat conductivity of about 6 times the heat conductivity of chromium at an ordinary temp.) is used in combination, the generated heat can be quickly diffused over the entire part of the light shielding film even if the heat is locally generated in the light shielding film or the glass surface in the stage of exposing with an electron ray and therefore the generation of the different temp. parts in the resist film owing to the generation of the heat is effectively prevented. The generation of the partial unbalance in the exposing sensitivity occurring from the nonuniform temp. is thereby prevented. The exact exposure patterning is thus attained.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field C] The present invention relates to a mask, and relates to a technique that can be effectively applied to improve the performance of the mask.

[Background technology]

-m, photomasks are used to pattern wiring and elements on silicon wafers in the production of pellets to be mounted on semiconductor devices.

This photomask usually uses a photomask in which a light-shielding film made of chromium is deposited on a glass substrate and a resist is deposited on the film, and the resist film is exposed to electron beams or the like.
It is formed by patterning into a predetermined shape by etching, etching a chromium film, or the like.

In the future, as perelefts become more highly integrated, the pattern of the photomask will become even finer, and it is thought that long-term exposure using electron beam irradiation will become necessary.

Incidentally, drawing by electron beam irradiation is performed by exposing a resist film to secondary electrons that are reflected or scattered on a chromium film or glass under a chromium film, and at that time, a considerable amount of heat is generated on the chrome surface, etc. It accompanies it.

However, the resist film used in the mask is
It has the property that its exposure sensitivity is easily affected by temperature. This change in sensitivity due to temperature is particularly problematic when a long exposure time is required due to miniaturization of the mask pattern as described above, since the amount of heat generated increases.

That is, if the patterning width differs, the amount of heat generated by electron beam irradiation naturally differs, so the temperature of the resist film differs depending on the location, resulting in a difference in sensitivity. The inventors of the present invention have discovered that a problem arises in that accurate patterning cannot be performed.

Regarding technology related to photomasks, please refer to Japanese Patent Application Laid-open No. 5
It is described in detail in Japanese Patent No. 7-64738.

[Purpose of the invention]

An object of the present invention is to provide a technique for effectively preventing exposure sensitivity differences in a resist film even when long-time electron beam exposure is performed regarding a mask.

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

[Summary of the invention]

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

In other words, by forming the light-shielding film of the mask from a material with good thermal conductivity, heat generated locally in the light-shielding film etc. due to electron collision during electron-irradiation can be quickly transmitted to the entire light-shielding film and leveled out. This makes it possible to prevent the occurrence of local temperature differences in the resist, thereby achieving the above object.

Furthermore, by filling the resist film with a heat-transferable filler, the resist film itself has a function of equalizing temperature differences, thereby achieving the above-mentioned object.

Note that the term "mask" here naturally includes a mask used in forming a so-called reticle, which is used as a mask during reduction exposure.

[Example 1] FIG. 1 shows a photomask according to Example 1 of the present invention.
This is a cross-sectional view taken along a plane cut approximately at the center.

The photomask l of Example 1 is formed by depositing a light shielding film 3 on the upper surface of a glass plate 2, and a resist 1II4 deposited on the upper surface of the light shielding film 3.
It is formed with a two-layer structure in which the layer 3a is made of copper and the second Ftab is made of chromium.

In this way, since copper, which has excellent thermal conductivity (approximately 6 times the thermal conductivity of chromium at room temperature) is used, heat is generated locally on the light-shielding film or glass surface during electron beam exposure. Even if heat generation occurs, the heat generation can be quickly diffused throughout the light-shielding film, so it is possible to effectively prevent the generation of areas with different temperatures in the resist film due to the heat generation. Moreover, it is therefore possible to prevent a partial imbalance in exposure sensitivity from occurring in the resist film due to non-uniform temperature, and as a result, accurate exposure patterning can be achieved.

In the photomask of Example 1, the second layer, which is the upper layer of the light-shielding film 3, is made of chromium, which is a normal light-shielding film material, so that the exposure technology applied to normal photomasks can be applied as is. It is.

Further, the two-layer light-shielding film can be easily formed by two-step vapor deposition or sputtering.

[Embodiment 2] FIG. 2 is a partial sectional view showing the features of a photomask according to Embodiment 2 of the present invention.

The photomask 1 of the second embodiment is the same as the first embodiment except that the first layer 3a of the light shielding film 3 is made of chromium and the second layer 3b is made of copper.

In this way, by making the light shielding film 3 have a two-layer structure opposite to that of Example 1, it utilizes the adhesion properties of chromium to glass, which is commonly used, and imparts heat transfer properties. When used as a light shielding film, it is possible to suppress reflection of light on the surface of the light shielding film.

[Embodiment 3] FIG. 3 is a partial cross-sectional view of a mask 1 according to Embodiment 3 of the present invention.

The mask 1 of the third embodiment is characterized in that the light shielding film 3 is made of copper or an alloy containing copper as a main component, and the rest is the same as that of the first embodiment.

In this way, by using copper or an alloy mainly composed of copper as the material for the light shielding film 3, it is possible to form a light shielding film 3 with extremely excellent thermal conductivity, resulting in a mask with extremely reliable sensitivity. can be provided. Furthermore, it is possible to provide a material with low surface reflectance.

The alloy referred to in Example 3 is made by incorporating one or more slightly saturated metals such as manganese or chromium into copper, thereby maintaining the thermal conductivity of the copper and improving other physical properties such as strength. is adapted to meet the requirements of the light shielding film 3.

[Example 4] The mask of Example 4 according to the present invention has almost the same structure as Example 3, and is characterized in that the light shielding film 3 is formed of aluminum or a material containing aluminum as a main component. It is something.

In this way, by replacing copper in Example 3 with aluminum, a mask provided with a light-shielding film 3 having good thermal conductivity can be provided at a low cost.

(Example 5) The mask l, which is Example 5 according to the present invention, is
Although it has a single-layer light shielding film 3 similarly to the above, it is different in that the material thereof is an alloy consisting of an arbitrary ratio of chromium and copper.

In this way, by using an alloy of chromium and copper in any proportion, it is possible to form a mask l having a light shielding film 3 that has the advantages of both metals.

[Embodiment 6] FIG. 4 is a partial cross-sectional view of a mask 1 according to a sixth embodiment of the present invention, taken along a plane cut approximately at the center thereof.

The mask 1 of Example 6 has a light shielding film 3 on the top surface of a glass plate 2.
The resist film 4 is deposited on the upper surface of the light shielding film 3, which is the same as that shown in Examples 1 to 5 above, but the resist film 4 itself has thermal conductivity. Its characteristics lie in the fact that it has been given gender.

In other words, by filling the resist@4 with fine carbon powder, which is a thermally conductive filler, it is possible to create a structure that itself has thermal conductivity, which prevents the occurrence of temperature unevenness in the resist film. It is preventable.

The resist M4 can be easily formed by a normal resist film forming method by simply preparing a raw material mixed with fine carbon powder in advance.

Note that by applying the technique shown in Example 6 to the light shielding film 3 shown in Examples 1 to 5, a mask with even better performance can be provided.

〔effect〕

(1) By forming the light-shielding film of the mask with a material with good thermal conductivity, the heat generated when electrons collide with the light-shielding film during electron beam irradiation is quickly transmitted to the entire light-shielding layer, and the temperature Therefore, even if the generated heat occurs locally due to different patterning widths, it is possible to prevent local temperature differences from occurring in the resist film.

(2) According to (1) above, it is possible to prevent the resist film from having areas with partially different exposure sensitivities, so it is possible to perform accurate patterning even if there are large differences during exposure with the electron beam. can.

(3) According to (1) and (2) above, accurate patterning can be achieved even when long exposure is required, such as with a mask having a resist film with low exposure sensitivity such as a positive resist.

(4) The light shielding film has a two-layer structure consisting of copper on the top surface of the transparent substrate and chromium coated on top of it, which has the characteristics of commonly used chromium and has excellent heat conductivity. A mask having a film can be formed.

(5) By making the light-shielding film a two-layer structure consisting of chrome on the top surface of the transparent substrate and copper on top, it has the adhesion characteristics of chromium normally used on transparent plates, and also A mask including a light shielding film with excellent conductivity can be formed.

(6) In (5) above, since the upper layer is made of copper, it is possible to reduce the light reflectance when used as a mask, so it is possible to prevent the image from becoming unclear due to reflected light. .

(7) By forming the light-shielding film from copper or an alloy containing copper as a main component, it is possible to provide a mask having a light-shielding film with extremely excellent thermal conductivity.

(8) In (7) above, by incorporating one or more trace amounts of different elements, an alloy having physical properties such as strength suitable for a light shielding film can be formed.

(9) By forming the light-shielding film from aluminum or an alloy containing aluminum as a main component, a mask having substantially the same characteristics as in (7) above can be provided at a low cost.

(10) In the above (9), by mixing one or more trace amounts of different elements, an alloy having the same physical properties as in the above (8) can be formed.

(11) By filling the resist film with a thermally conductive filler, it is possible to give the resist film itself the ability to equalize temperature differences, so it is possible to create a mask with the same performance as described in (2) above. Can be provided.

(12) By using fine carbon powder as a thermally conductive filler, the mask described in (11) above with excellent reliability can be provided at a low cost.

(13) By depositing the resist film described in (11) or (12) above on the top surface of the light-shielding film described in (1), a mask provided with a resist film with more uniform exposure sensitivity is provided. can.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, although an example has been described in which glass is used as the transparent substrate, any material may be used as long as it is made of a material that can be used for the same purpose.

Furthermore, it goes without saying that the material and structure of the light shielding film are not limited to those of the above embodiments.

Furthermore, in Example 6, only the filler and carbon fine powder to be filled into the resist were explained, but the invention is not limited to these (for example, by adjusting the exposure conditions, even metal fine powder can be used). It is possible.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view showing a photomask substrate according to a first embodiment of the present invention, FIG. 2 is a partial cross-sectional view showing a photomask substrate according to a second embodiment according to the present invention, and FIG. 3 is a partial cross-sectional view showing a photomask substrate according to a second embodiment according to the present invention. FIG. 4 is a partial cross-sectional view showing a mask according to Example 3 of the present invention. FIG. 4 is a partial cross-sectional view showing a mask according to Example 6 of the present invention. DESCRIPTION OF SYMBOLS 1... Photomask, 2... Glass plate, 3... Light shielding film, 3a... First layer, 3b... Second layer, 4... Resist film.

Claims (1)

[Scope of Claims] 1. A mask comprising a transparent substrate, at least a part of which is made of a light-shielding film made of a material with good thermal conductivity, and a resist film on the light-shielding film. 2. The mask according to claim 1, wherein the light shielding film is made of copper or an alloy containing copper as a main component. 3. The mask according to claim 1, wherein the light shielding film is made of aluminum or an alloy containing aluminum as a main component. 4. The mask according to claim 1, wherein the light shielding film is formed of two layers: copper on the substrate and chromium thereon. 5. The mask according to claim 1, wherein the light shielding film is formed of two layers: chromium on the substrate and copper on top of the chromium. 6. The mask according to claim 1, wherein the light shielding film is an alloy of chromium and copper. 7. A mask in which a light-shielding film is deposited on a transparent substrate, and a resist film filled with a thermally conductive filler is deposited on the light-shielding film. 8. The mask according to claim 7, wherein the filler is carbon powder. 9. The mask according to claim 7, wherein the filler is a metal powder.