JP2005223290A - Patterning method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a fine rectangular resist pattern having satisfactory resistance to dry etching with reproducibility. <P>SOLUTION: The patterning method comprises a step for baking a first organic material film 10 formed on an underlying film 2 in a semiconductor device fabrication process, a step for baking a second organic material film 11 formed on the first organic material film 10, a step for baking the second organic material film 11, by exposing it with a single wavelength through a photomask, a step for forming a second organic material film pattern, by developing the second organic material film 11, and a step for forming a desired pattern by etching the underlying film, using the second organic material film pattern as a mask, wherein an acid additive is introduced into the first organic material film. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pattern forming method that has sufficient dry etching resistance to a base film and can form a fine resist pattern in a rectangular shape with good reproducibility.

  In general, in order to form a fine pattern in a lithography process which is a key technology in semiconductor device manufacturing, the following three methods have been mainly used in addition to a special technique called a super-resolution technique.

(1) Shortening of exposure wavelength (2) Higher NA of exposure apparatus (3) Improvement of photosensitive organic film (photoresist) material and process

  In particular, the shortening of the exposure wavelength in the above (1) is effective, and until now, the wavelengths have changed to 365 nm, 248 nm, 193 nm, and 157 nm. However, when the wavelength is shortened, the resist materials that have been used so far cannot be used due to transparency problems, and the 365 nm wavelength is a novolak resin, the 248 nm wavelength is a polyhydroxystyrene resin, the 193 nm wavelength is an acrylic resin, and the 157 nm wavelength is fluorine. Photoresists based on containing resins have been applied to each light source. That is, when the resist material that has been used so far is applied, the exposure light cannot sufficiently reach the lower portion of the resist film when the base film is exposed with a film thickness sufficient for dry etching processing, and FIG. As shown in FIG. 2, the bottomed pattern is formed, and thus there is a problem that a desired base film pattern cannot be obtained. In particular, the acrylic resin used at a wavelength of 193 nm and the fluorine-containing resin used at a wavelength of 157 nm lack the dry etching resistance for processing a base film due to its structure and composition, and thus the above problem becomes remarkable. .

  On the other hand, in a resist process for forming a pattern, a standing wave due to multiple interference is generated inside the photoresist coated on the base film due to reflection from the base film to be dry etched, resulting in uneven exposure in the resist film thickness direction. There is a problem of producing. This unevenness of exposure causes deterioration of the pattern shape after exposure and development, thereby reducing the pattern resolution. In addition, the multiple interference inside the film causes a problem of pattern dimension fluctuation accompanying the film thickness fluctuation. Accordingly, a process for suppressing reflection of exposure light from the base film is essential. In KrF lithography using an excimer laser with a wavelength of 248 nm and ArF lithography with a wavelength of 193 nm, which are currently applied in the mass production of semiconductor devices, a method of suppressing reflection by forming an organic material under a photoresist (Bottom Anti Reflective Coating, (Hereinafter referred to as BARC method) is often used (see Patent Document 1).

Next, the BARC method will be described.
FIG. 4 is a process cross-sectional view in a pattern forming process flow using the conventional BARK method. In FIG. 4A, first, an antireflection film 43 made of an organic material for preventing reflection is applied on the base film 42 to be processed on the silicon substrate 41, and a photoresist 44 is applied on the antireflection film 43. To do.
Next, in FIG. 4B, exposure is performed through a photomask 45 on which a desired pattern is drawn.
Thereafter, as shown in FIG. 4C, a desired photoresist pattern 46 is formed by development.
Then, as shown in FIG. 4D, the antireflection film pattern 47 is formed by etching the antireflection film 43 with a desired photoresist pattern 46.
Thereafter, as shown in FIG. 4E, the base film pattern 48 is formed by further etching the base film 42 with the desired photoresist pattern 46.
Finally, as shown in FIG. 4F, the photoresist pattern 46 and the antireflection film pattern 47 can be removed by oxygen plasma to obtain a desired base film pattern 48.

Japanese Patent Laid-Open No. 10-301268

  In the F2 lithography with a wavelength of 157 nm, which is expected as the next generation technology of ArF lithography, the conventional I-line (wavelength 365 nm), XrF (wavelength 248 nm), and ArF (wavelength 193 nm) with resist materials and resist film thickness However, the light does not reach the bottom of the resist sufficiently because it is not transparent, and it cannot be patterned into a rectangular shape. Therefore, due to the problem of dry etching resistance, there is a problem that the photoresist as a mask is etched and disappeared before the antireflection film and the base substrate are dry etched.

  The present invention has been made in response to the above-mentioned conventional problems, and is a process of applying the BARC method to F2 lithography, and is used in conventional materials such as i-line, KrF, and ArF lithography for a photoresist and an antireflection film. The resist pattern that is mainly caused by low transparency is improved even when the resist film thickness is sufficient to dry-etch the underlying film to be processed. A pattern forming method capable of forming a rectangular shape is provided.

  The present invention is a process of applying the F2 lithography BARC method, and the resist film thickness of the resist and the antireflection film should be processed by using the conventional resist material used in i-line, KrF, and ArF lithography. An antireflection film material having acidity enough to improve the tailing of the resist pattern, which is mainly caused by low transparency, even when the film thickness is sufficient to dry-etch the base film, and to make it rectangular. It is applied.

  Specifically, as shown in claim 1 of the above-mentioned claims, the first organic material film is formed on the base film to be processed and then baked, and the first baking step is performed. A second baking step of forming a second organic material film on the organic material film and then baking; and a third baking in which the second organic material film is exposed at a single wavelength through a photomask and then baked. A step of forming a pattern of the second organic material film by developing the second organic material film, and etching the first organic material film using the pattern of the second organic material film as a mask. And a step of etching the base film using the pattern of the second organic material film as a mask to form a desired pattern, wherein the first organic material film is acid-added Agent introduced A pattern forming method characterized by that.

  According to a second aspect of the present invention, the first organic material film is formed on the base film to be processed and then baked, and the second organic material is formed on the first organic material film. A second baking step of forming a material film and then baking; a second baking step of exposing the second organic material film through a photomask at a single wavelength; and then baking; Forming a pattern of a second organic material film by developing the organic material film, etching the first organic material film using the pattern of the second organic material film as a mask, and the second organic And etching the base film using the material film pattern as a mask to form a desired pattern. In the pattern forming method, an acid additive is introduced into the first organic material film, and the second organic material film is formed. Organic material film A pattern forming method characterized in that it has etching resistance and thickness enough to etch the serial base film.

An inorganic material film may be formed between the base film and the first organic material film, and the acidity of the first organic material film into which the acidic additive is introduced is It is desirable that the tailing of the organic material film pattern due to the low transparency of the organic material film can be improved to a rectangular shape.
The first organic material film is low in transparency at a single wavelength of the first organic material film to such an extent that the upper surface reflection of the first organic material film is reduced. It is desirable that the organic film be lower in etching resistance than the organic material film.

  Further, the second organic material film is a photoresist used for exposure at a wavelength of 365 nm, and a single wavelength in the exposure is preferably shorter than 365 nm, specifically, When the second organic material film is a photoresist used for exposure at a wavelength of 365 nm, the single wavelength in the exposure is preferably 248 nm, 193 nm, or 157 nm, and the second organic material film As the material film, an organic material containing a novolac resin can be given.

  In addition, when the second organic material film is a photoresist used for exposure at a wavelength of 248 nm, it is desirable that the single wavelength in the exposure is shorter than 248 nm. In the case where the second organic material film is a photoresist used for exposure at a wavelength of 248 nm, it is desirable that a single wavelength in the exposure is 193 nm or 157 nm, Examples of the organic material film include an organic material containing polyhydroxystyrene resin or acetal resin.

  Furthermore, when the second organic material film is a photoresist used for exposure at a wavelength of 193 nm, the single wavelength in the exposure is preferably shorter than 193 nm. In the case where the second organic material film is a photoresist used for exposure at a wavelength of 193 nm, it is desirable that a single wavelength in the exposure is 157 nm, and the second organic material film An example of the material film is an acrylic resin.

  Furthermore, when the second organic material film is a photoresist used for exposure at a wavelength of 157 nm, the single wavelength in the exposure is preferably shorter than 157 nm, specifically, In the case where the second organic material film is a photoresist used for exposure at a wavelength of 157 nm, the single wavelength in the exposure is preferably 13 nm, and the second organic material As the film, an organic material containing fluorine can be given.

(Function)
By using the present invention, even in F2 lithography, without applying a fluorine-containing resist, it has a film thickness sufficient for dry etching of a base film, and a rectangular fine resist pattern has good reterminability. It becomes possible to form.

  In the present invention, in the process of applying the BARC method to F2 lithography, a resist material used in conventional i-line, KrF, and ArF lithography is used for the photoresist and the antireflection film, and the resist film thickness is processed. Anti-reflective coating material with sufficient acidity to improve the tailing of the resist pattern, mainly due to low transparency, even when the film thickness is sufficient for dry etching of the underlying film to be formed By applying the above, it is possible to form a rectangular fine resist pattern with high reproducibility, having a film thickness sufficient for dry etching of the base film without applying a fluorine-containing resist even in F2 lithography. Can do.

Next, an embodiment of the present invention will be described.
(Embodiment 1)
Embodiment 1 of the present invention will be described with reference to the drawings.
FIG. 1 shows a cross-sectional structure of a pattern forming process in this embodiment.

  In FIG. 1A, a reflection made of an organic material for preventing reflection, such as a novolac resin, on a base film to be processed, for example, a 50 nm tungsten metal film 9 used as a gate electrode of a 65 nm generation transistor. The prevention film 10 is applied with a film thickness of 20 nm and baked at 205 ° C. for 60 seconds. About 5% of the resin weight is added to the antireflection film 10 with an acidic additive containing a sulfonyl group (unit volume dissolved solution equivalent pH is about 2.0).

  Acidic additives that can be used in the present embodiment include organic sulfonic acids, particularly nonafluorobutanesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, dodecylbenzenesulfonic acid, p-toluenesulfonic acid, or triphenyl. Examples include acid generators represented by sulfonic acid and triphenyliodonium salt.

  Further, a polyhydroxystyrene type photoresist 11 for KrF lithography is applied to the antireflection film 10 with a film thickness of 120 nm and baked at 130 ° C. for 60 seconds.

  In FIG. 1B, exposure is performed using a F2 exposure apparatus having a wavelength of 15 nm through a photomask 5 necessary for processing a desired gate pattern, and baking is performed at 130 ° C. for 90 seconds.

  In FIG. 1C, the photoresist region exposed through the photomask 5 is dissolved with a 2.38% concentration tetramethylammonium hydroxide (TMAH) developer, and used as a mask for processing the gate electrode. A photoresist pattern 12 is formed. Since the KrF resist film thickness is 120 nm, the transparency is insufficient, and the photoresist pattern 12 originally has a trailing shape. However, the acid additive added to the antireflection film 10 causes a shortage of acid. The acid is supplied at the pattern skirting portion, and the photoresist pattern 12 has a rectangular shape.

  In this case, as a result of exposure with an exposure apparatus having a wavelength of 157 nm using a Levenson-type phase shift mask, which is one of the super-resolution techniques for improving the resolution, the numerical aperture is 0.85, the stop is 0.3. A 55 nm line and space pattern could be formed in a rectangular shape with a thickness of 120 nm and no film reduction. Although the acidic additive added to the antireflection film 10 used in this example contained a sulfonyl group, other acidic groups having a pH of 3.5 or less such as a hydroxyl group, a nitro group, or a carboxy group were added. However, the same effect can be obtained. However, it is necessary to adjust the acid group and the amount added depending on the degree of tailing.

In FIG. 1D, the antireflection film 10 is dry-etched using an N ₂ / O ₂ -based gas with the photoresist pattern 12 as a mask. After etching, the film thickness of the photoresist pattern 12 was reduced to 100 nm.

In FIG. 1E, a tungsten metal film pattern 13 is formed by etching the tungsten metal film 9 which is a base film using SF ₆ / N ₂ -based gas using the photoresist pattern 12 as a mask. In this case, the resist film thickness after etching was reduced to 20 nm, but a 55 nm line and space tungsten metal film pattern 13 having a rectangular shape could be formed.

  In FIG. 1G, the remaining photoresist 11 and antireflection film 10 are removed by oxygen plasma, and a desired gate electrode 14 can be obtained.

  As described above, even in exposure at a wavelength of 157 nm, a resist material conventionally used in KrF lithography is used without applying a fluorine-containing resist as a photoresist, and it is sufficient to dry-etch a base film to be processed. Even if the film thickness is set to a small thickness, it is possible to improve the reproducibility by applying an anti-reflective coating material containing an acidic additive that improves the bottoming of the resist pattern, which is mainly caused by low transparency, and makes it rectangular. A fine rectangular gate electrode pattern can be formed.

  In this embodiment, the resist material used in the KrF lithography is used, but the same effect as that obtained when the KrF resist is used can be obtained by using an ArF resist or an i-line resist. In this case, the ArF resist includes a resist based on an acrylic polymer, and the i-line resist includes a resist based on a novolac polymer.

  Next, the tailing degree in the case of the combination of the F2 wavelength and the KrF resist and the combination of the ArF wavelength and the KrF resist in the above-described embodiment will be described. As shown in the above example, the transmittance at the F2 wavelength in the KrF resist having a thickness of 200 nm is about 5%, whereas the transmittance at the ArF wavelength is almost a value of 0%. Because of the difference in transmittance, even if the same KrF resist is used, the tailing degree of the resist pattern differs depending on the wavelength, and the tailing becomes larger as the transmittance is lower. The embodiment of the present invention is characterized in that the acidity of the antireflection film under the resist is adjusted in accordance with the degree of each skirting in order to improve the skirting into a rectangular shape. In each combination, the specific pH of the antireflection film has an acidity of about PH1-5.

(Embodiment 2)
Next, Embodiment 2 of the present invention will be described.
The fine pattern forming method in this embodiment is shown in FIG.

  In FIG. 2A, an inorganic material film 15 such as a silicon nitride film for processing a tungsten metal film is formed on a base substrate to be processed, for example, a 50 nm tungsten metal film 9 used as a gate electrode of a 65 nm generation transistor. Is deposited with a thickness of 70 nm by a chemical vapor deposition (CVD) method. An antireflection film 10 that is an organic material for preventing reflection is applied to the silicon nitride film 15 to a thickness of 20 nm and baked at 205 ° C. for 60 seconds. The organic material for preventing reflection is made of, for example, polyhydroxystyrene resin, and a crosslinking agent and an acidic additive are added to the antireflection film 10 by about 5% with respect to the resin weight. A photoresist 11 for KrF lithography is applied to the antireflection film 10 to a thickness of 12 nm and baked at 130 ° C. for 60 seconds.

In FIG. 2B, exposure is performed using an F ₂ exposure apparatus through a photomask 5 necessary for processing a desired gate pattern, and baking is performed at 130 ° C. for 90 seconds.

In FIG. 2C, the photoresist region exposed through the photomask 5 is dissolved with a 2.38% concentration tetramethylammonium hydroxide (TMAH) developer, and used as a mask for processing the gate electrode. A photoresist pattern 12 is formed. Since the KrF resist film thickness is 120 nm, the transparency is insufficient, and the photoresist pattern 12 originally has a trailing shape, but it has a rectangular shape due to the effect of the acidic additive added to the antireflection film. .
In this case, as a result of exposure with an exposure apparatus having a wavelength of 157 nm using a Levenson type phase shift mask, which is one of the super-resolution techniques for improving the resolution, the numerical aperture is 0.85, the stop is 0.3. With 100, a 55 nm line and space pattern could be formed in a rectangular shape without reducing the film thickness.

In FIG. 2D, the antireflection film 10 is dry-etched using N ₂ / O ₂ -based gas using the photoresist pattern 12 as a mask. After etching, the film thickness of the photoresist pattern 12 was reduced to 100 nm.

In FIG. 2E, the silicon nitride film 15 having a thickness of 70 nm is dry-etched using CF ₄ / O ₂ / CH ₂ F ₂ -based gas using the photoresist pattern 12 as a mask to form a silicon nitride film pattern 16. To do.

In FIG. 2F, the tungsten metal film pattern 13 is formed by etching the tungsten metal film 9 which is a base film to be processed using the silicon nitride film pattern 16 as a mask by using SF ₆ / N ₂ -based gas. . In this case, the resist film thickness after etching was reduced to 40 nm, but a 55 nm line and space tungsten metal film pattern 13 having a rectangular shape could be formed.

  In FIG. 2G, the desired photoresist and antireflection film can be removed by oxygen plasma to obtain a desired gate electrode 14.

As described above, low transparency is mainly used even when a material that has been conventionally used in KrF lithography is used without applying a fluorine-containing resist as a photoresist and the underlying film is sufficiently thick to be dry-etched. By applying an antireflective film material having an acidity that can improve the tailing of the resist pattern and making it into a rectangular shape, a fine gate electrode pattern with a rectangular shape can be formed with good reproducibility. .
In the above case, the antireflection film 10 and the silicon nitride film 15 are etched under different conditions. However, by etching using a CF ₄ / O ₂ gas, the photoresist pattern 12 is used as a mask. The antireflection film 10 and the silicon nitride film 15 can be continuously etched.
Various combinations of the wavelength and the resist are conceivable as in the first embodiment.

Process sectional drawing in the pattern formation process for demonstrating Embodiment 1 of this invention. Process sectional drawing in the pattern formation process for demonstrating Embodiment 2 of this invention. Shows a pattern shape of the application of the conventional KrF lithography for thick resist the F ₂ lithography. Sectional drawing in the pattern formation process using the conventional BARC method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Base substrate 3 Antireflection film in conventional technology 4 Photoresist in conventional technology 5 Photomask 6 Photoresist pattern in conventional technology 7 Antireflection film pattern in conventional technology 8 Base film pattern in conventional technology 9 Tungsten metal film 10 Antireflective film 11 in the invention Resist 12 for KrF lithography 12 Photoresist pattern 13 formed of resist for KrF lithography 13 Tungsten metal film pattern 14 formed of tungsten metal film 15 Gate electrode 15 formed of tungsten metal film Silicon nitride film 16 Silicon nitride Silicon nitride film pattern formed by film

Claims (17)

  A first baking step in which a first organic material film is formed on a base film to be processed and then baked; and a second organic material film is formed on the first organic material film and then baked. A second baking process, a third baking process in which the second organic material film is exposed to light at a single wavelength through a photomask and then baked, and the second organic material film is developed by developing a second organic film. A step of forming a pattern of the material film, a step of etching the second organic material film using the pattern of the second organic material film as a mask, and the base film using the pattern of the second organic material film as a mask A pattern forming method comprising a step of etching the substrate to form a desired pattern, wherein an acidic additive is introduced into the first organic material film.   A first baking step in which a first organic material film is formed on a base film to be processed and then baked; and a second organic material film is formed on the first organic material film and then baked. A second baking process, a third baking process in which the second organic material film is exposed at a single wavelength through a photomask and then baked, and then the second organic material film is developed by second development. Forming the pattern of the organic material film, etching the first organic material film using the pattern of the second organic material film as a mask, and using the pattern of the second organic material film as a mask And a step of etching the base film to form a desired pattern. An acidic additive is introduced into the first organic material film, and the second organic material film is formed of the base film. Can be etched Pattern forming method characterized in that it has etching resistance and thickness of degrees.   3. The pattern forming method according to claim 1, wherein an inorganic material film is formed between the base film and the first organic material film.   The acidity of the first organic material film into which the acidic additive has been introduced is such that the tailing of the organic material film pattern due to the low transparency of the second organic material film can be improved to a rectangular shape. The pattern forming method according to claim 1, wherein the pattern forming method is provided.   The first organic material film is low in transparency at a single wavelength of the first organic material film to such an extent that the upper surface reflection of the first organic material film is reduced, and the second organic material The pattern forming method according to claim 1, wherein the pattern forming method is an organic film having lower etching resistance than the film.   The second organic material film is a photoresist used for exposure at a wavelength of 365 nm, and a single wavelength in the exposure is shorter than 365 nm. 6. A pattern forming method as described above.   The second organic material film is a photoresist used for exposure at a wavelength of 365 nm, and a single wavelength in the exposure is 248 nm, 193 nm, or 157 nm. Pattern forming method.   The pattern forming method according to claim 6, wherein the second organic material film contains a novolac resin. The second organic material film is a photoresist used for exposure at a wavelength of 248 nm, and a single wavelength in the exposure is shorter than 248 nm. The pattern formation method as described.   The pattern formation according to claim 9, wherein the second organic material film is a photoresist used for exposure at a wavelength of 248 nm, and the single wavelength in the exposure is 19 nm or 157 nm. Method.   The pattern forming method according to claim 9, wherein the second organic material film contains a polyhydroxystyrene resin or an acetal resin.   6. The photoresist according to claim 1, wherein the second organic material film is a photoresist used for exposure at a wavelength of 193 nm, and the single wavelength in the exposure is shorter than 193 nm. The pattern formation method as described.   13. The pattern forming method according to claim 12, wherein the second organic material film is a photoresist used for exposure at a wavelength of 193 nm, and a single wavelength at the exposure is 157 nm.   The pattern forming method according to claim 12, wherein the second organic material film is made of an acrylic resin.   6. The second organic material film is a photoresist used for exposure at a wavelength of 157 nm, and a single wavelength in the exposure is shorter than 157 nm. The pattern formation method as described.   The pattern forming method according to claim 15, wherein the second organic material film is a photoresist used for exposure at a wavelength of 157 nm, and a single wavelength at the exposure is 13 nm. The pattern forming method according to claim 16, wherein the second organic material film contains fluorine.

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