KR20100049333A - Overcoating composition for photoresist and forming method of photoresist pattern using the same - Google Patents

Abstract

The present invention relates to an overcoating composition for photoresist and a pattern forming method for reducing the line-width of a photoresist pattern using the same, and more particularly, a thermal acid generator on the entire surface of a photoresist pattern formed by a general lithography process. The method of forming a pattern for reducing the line width of the photoresist pattern by applying an overcoating composition containing, and heat treatment to diffuse the acid into the photoresist pattern, and then etching the acid-diffused first photoresist pattern region with an alkaline solution. It is about.

Description

Overcoating Composition for Photoresist and Forming Method of Photoresist Pattern Using the Same}

The present invention relates to an overcoating composition for photoresist and a method of forming a photoresist pattern using the same, and more particularly, to an overcoating composition for photoresist for implementing an ultrafine pattern of 30 nm or less that can overcome the resolution limit of exposure equipment. And it relates to a photoresist pattern forming method using the same.

Today's electronic and electrical technologies are rapidly evolving to build a simpler information network, while storing more capacity, processing and transmitting information faster, and keeping pace with the 21st century's high-telecommunications society. have.

In particular, as the application area of the semiconductor device is expanded, various technologies have been developed to manufacture the semiconductor device with high reliability and at the same time realize the component elements as small as possible without deteriorating the electrical characteristics.

In order to satisfy the component sizes required for high-density semiconductor devices and next-generation devices, it is necessary to implement patterns having a fine line width of at least 40 nm.

ArF immersion lithography process, the latest exposure technology among semiconductor device manufacturing techniques, is known as a technique for controlling the critical dimension of the pattern line width.

However, the ArF immersion lithography process has a disadvantage in that process margin is vulnerable due to lack of resolution in the process of manufacturing 40 nm DRAM and flash devices currently under development, and thus, it is difficult to apply the device mass production process. For example, there is a disadvantage in that a pattern collapses while forming a line & space (L / S) pattern having a 1: 1 pitch of 42 nm or less (see FIG. 1).

Furthermore, in the case of the 3X class device, which is a subsequent device, direct patterning itself is not possible with only a single exposure process of the immersion lithography process. Therefore, in order to form a 40nm pattern, a double patterning process or the like should be further applied.

The double exposure technique is a method of forming first patterns having a pitch twice as large as a desired pattern pitch, and then forming a second pattern having the same double pitch between the first patterns. Since the double exposure technique mainly uses the L / S pattern structure of the first 1: 3 pitch, the resolution margin is more favorable than the L / S pattern of the 1: 1 pitch, and it is estimated that 30 nm-class pattern formation is possible.

However, the double exposure technique is not only complicated in the process, but also the pattern collapses during the second patterning process (see FIG. 2), or the overlay accuracy in the mask process for forming the first pattern and the second pattern. Mis-alignment of the) leads to low pattern reliability.

As such, the current semiconductor device manufacturing technology has many limitations in manufacturing next-generation devices. Accordingly, those skilled in the art are continuing to make efforts to improve the limitations of the exposure process technology by using the exposure process technology using a high index fluid material and an EUV light source.

For example, Korean Patent Application No. 10-2004-0117172 proposes a trimming or slimming technique for reducing the pattern line width by applying heat relax or SAFIER to the upper part of the first pattern formed, and then heat-treating it. In Korea Application No. 10-2003-41167, an overcoating composition comprising a water-soluble polymer, an acid compound such as organic sulfonic acid, and a solvent is applied onto a pattern, followed by a baking process for acid diffusion. A method of reducing line width has been disclosed.

However, in the case of the conventional method, there is a disadvantage that does not improve the effect of the pattern pitch or layout. For example, when the pattern line width is reduced by applying a well-known overcoating composition to 500 mm thick, the 80 nm L / S pattern of the cell region having a 1: 1 pitch is reduced to about 62 nm size (about 22%), Since isolated-patterns formed in the peripheral circuit region have a high acid content relative to the pattern area, the pattern line width is greatly reduced to 30 nm or less or mostly collapses compared to the cell region pattern. For this reason, it is difficult to form the pattern reduced to a uniform magnitude | size on the whole surface of a board | substrate.

It is an object of the present invention to provide an overcoating composition containing a thermal acid generator in order to form a pattern reduced in a uniform width in the cell region and the peripheral circuit region of the substrate. In addition, in the present invention, the overcoating composition is applied to the entire surface of the photoresist pattern formed by a general lithography process and then heated to independently reduce the line width of the photoresist pattern regardless of the cell region and the peripheral circuit region. It is another object to provide a formation method.

Hereinafter, the present invention will be described in detail.

The present invention provides a photoresist overcoating composition comprising a thermal acid generator, a water-soluble polymer, and a residual amount of an organic solvent, which can be dissolved in an alkaline developer.

The thermal acid generator is not particularly limited so long as it is a compound containing an alkali soluble group and / or sulfonic acid group as a functional group, and for example, any one compound selected from the group consisting of the following Chemical Formulas 1 to 3 may be mentioned. have.

[Formula 1]

[Formula 2]

(3)

The thermal acid generator is included in an amount of 0.002 to 0.2 parts by weight, preferably 0.02 parts by weight, based on 100 parts by weight of the total overcoating composition. In this case, when the thermal acid generator content is less than 0.002 parts by weight, the effect of reducing the pattern line width is low, and when the amount exceeds 0.2 parts by weight, the effect of reducing the pattern line width is so large that the pattern collapses.

In addition, the water-soluble polymer of the present invention is not particularly limited, but is preferably represented by the following formula (4).

[Formula 4]

Wherein R1, R2, R3 are each hydrogen or methyl group, X is linear or branched alkyl or NH- (R4) ₂ , substituted with hydroxy group (OH), wherein R4 is 1-3 Is alkyl, and a, b and c each represent a mole fraction of each polymerization repeating unit, and represent 0.05 to 0.9, respectively. In this case, in the compound of Formula 4, R1 to R3 are each hydrogen or a methyl group, and X is hydroxypropyl, hydroxyethyl or N-isopropylamide (-NH- (CH ₃ ) ₂ ).

The water-soluble polymer is included in 0.2 to 10 parts by weight, preferably 2 parts by weight based on 100 parts by weight of the total overcoating composition. If the content of the water-soluble polymer is less than 0.2 parts by weight, the thickness of the overcoat is too low to perform the subsequent process formed, and if the content of the water-soluble polymer is more than 10 parts by weight, the overcoat film is formed too thick, the pattern It is difficult to control the CD reduction amount of the line width.

In addition, the organic solvent is not particularly limited, and 4-methyl-2-pentanol or heptaol may be mentioned.

A general overcoating composition is applied on top of the photoresist film prior to forming the photoresist pattern, i.e., with the photoresist film applied, so as to leach and swell the photoresist pattern during the subsequent ArF immersion lithography process. defects) and protects the photoresist from distilled water, which is the medium of the immersion lithography process. However, after forming the photoresist pattern, the overcoating composition of the present invention is applied to the entire surface of the formed pattern serves to reduce the line width of the pattern. That is, the overcoating composition of the present invention is overcoated on the already formed photoresist pattern. Furthermore, in the case of the overcoating composition including the conventional photoacid generator, since the amount of acid generated in the isolated line region after exposure is higher than the dense region of the pattern density, In the non-dense area, the reduced pattern CD difference is large. In contrast, in the case of the overcoating composition containing the thermal acid generator of the present invention, since acid is generated only by heat regardless of the exposure conditions or the pattern pitch, the concentration is controlled to form a uniformly reduced pattern on the entire surface of the wafer. can do.

Such a method of forming a photoresist pattern using the overcoating composition of the present invention will be described in detail with reference to FIG. 4.

That is, the method of forming a photoresist pattern of the present invention includes the following steps:

Forming a first photoresist pattern 100 by a lithography process on the substrate having the etched layer;

Applying the overcoating composition (102) of the present invention to the entire surface of the first photoresist pattern (100);

Baking the applied overcoating composition; And

Removing the overcoating composition with an alkaline developer to form a second photoresist pattern 106 having a reduced line width.

In this case, the photolithography process includes a conventional method of forming a photoresist pattern by forming a photoresist film on a substrate, followed by immersion exposure and development. In this case, the first photoresist pattern includes an L / S pattern and an island pattern of 1: 1 or 1: 3 pitch.

In addition, in order to obtain the effect of reducing the pattern line width that is most suitable in the method of the present invention, when the photoresist pattern height is 100, the overcoating composition is applied at about 20 to 110%, specifically 50% of the height. It is preferable. For example, when the photoresist pattern height is about 1000 GPa, it is applied by a spin-coating method at a thickness of about 200 to 1100 GPa, preferably 500 GPa.

The bake process step is an acid diffusion bake step of diffusing acid into the photoresist pattern from the thermal acid generator included in the overcoating composition, which is higher than about 90 ° C. to 100 ° C., which is a heating temperature of a conventional overcoating composition. It is a method of increasing the acid generation effect of a thermal acid generator to perform about 30 to 2 minutes at 110-170 degreeC high temperature.

As described above, when the acid generated from the overcoating layer during the baking process is diffused into the photoresist pattern, and the acid 104 is increased on the surface of the photoresist pattern, the acid is removed together with the overcoating composition during the subsequent alkali developing process. Increase the etched portion of the photoresist pattern. In addition, the line width of the pattern may be adjusted to a desired size by using a principle in which the acid diffusion distance is increased as the temperature of the acid diffusion bake, the heat treatment time, or the thickness of the overcoating layer is thick. Specifically, the heat treatment process is performed until the second photoresist pattern line width is reduced by about 20 to 45% compared to the first photoresist pattern line width. For example, when the line width of the first photoresist pattern is 45 nm, the line width of the second photoresist pattern may be about 30 to 35 nm reduced by about 10 to 15 nm.

The alkaline developer may be used in addition to a commonly used aqueous TMAH solution, or a KOH aqueous solution or an NaOH aqueous solution. At this time, the line width of the pattern is reduced in proportion to the alkali treatment time, so that the target line width can be obtained by adjusting the treatment time, and increasing the concentration of the alkaline solution increases the etching speed of the resist, thereby improving the treatment speed. 2.38 It is preferable to process for 30 to 60 second with the TMAH aqueous solution by weight.

The method may further include applying a negative photoresist film to the entire surface including the second photoresist pattern after the forming of the second photoresist pattern; Performing a lithography process on the negative photoresist film to form a third photoresist pattern having the same pitch as the first photoresist pattern in a space between the second photoresist pattern and the pattern; And repeating the method of applying the composition for overcoating of the present invention to the developing step to perform a double patterning process of forming a fourth photoresist pattern having the same line width and pitch as the second photoresist pattern.

The method may further include etching the etched layer by using the second photoresist pattern as an etching mask after the second photoresist pattern; Repeating the first photoresist pattern forming method or the overcoating composition developing step of the present invention on the entire surface including the etched layer to form a third photoresist pattern having the same line width and pitch size as the etched layer pattern between the etched layer patterns. Another double patterning process may be carried out to form a.

As described above, the method of the present invention can not only form a photoresist pattern having a resolution that cannot be obtained under current exposure equipment and exposure conditions and photoresist conditions, but also includes a 1: 1 pitch L / S pattern. A fine pattern of 30 nm or less reduced to the same size may be implemented in a DRAM region or a cell region and a peripheral circuit region of a flash device including a 1: 3 pitch L / S pattern. In particular, the overcoating composition including the thermal acid generator of the present invention has excellent matching property with the photoresist film, and can be performed using existing equipment in an in-line track, With no additional cost, a simple method can eliminate pattern line widths that shrink in non-exposed areas or in areas with large acid diffusion, with the same thickness. Therefore, the cost reduction effect of semiconductor device manufacturing can be expected.

As described above, the process of the present invention can form a fine pattern reduced to a uniform thickness in the cell region and the peripheral circuit region by a simple overcoating composition coating process and heat treatment process without the investment of new equipment, etc., The cost savings are great, and ultimately, the transistor line width can be reduced to improve the operation speed of the semiconductor device.

Hereinafter, the present invention will be described in detail with reference to examples. However, the examples are only to illustrate the most preferred invention of the present invention, the present invention is not limited by the following examples.

I. Preparation of Overcoating Composition

Example 1

When 1 g of photoresist resin (X = hydroxypropyl in the compound of Formula 4) and 0.02 g of thermal acid generator (compound of Formula 1) are added to 50 g of 4-methyl-2-pentanol and stabilized After stirring to, filtered through a 0.2㎛ filter to prepare the overcoating composition of the present invention.

Example 2

1 g of photoresist resin (X = N-isopropylamide in the compound of Formula 4) and 0.02 g of a thermal acid generator (compound of Formula 2) are added to 50 g of 4-methyl-2-pentanol and stabilized After stirring until it was filtered through a 0.2㎛ filter to prepare the overcoating composition of the present invention.

Example 3

When 1 g of photoresist resin (X = hydroxyethyl in the compound of Formula 4) and 0.02 g of thermal acid generator (compound of Formula 3) are added to 50 g of 4-methyl-2-pentanol and stabilized After stirring to, filtered through a 0.2㎛ filter to prepare the overcoating composition of the present invention.

II. Pattern Formation Method

Example 4

(A) A photoresist film (ARX1221J, manufactured by JSR Co., Ltd.) was formed on the entire surface of the wafer to a thickness of 1000 Å, followed by an ArF immersion lithography process to form a 1: 1 pitch L / S pattern in the cell region, and the peripheral circuit region. An island-like photoresist pattern was formed on the substrate. At this time, the pattern CD measurement result shows that the L / S pattern is 81.1 nm and the island pattern is 107 nm (see FIG. 5).

(B) The overcoating composition prepared in Example 1 was applied to the entire surface of the wafer including the two types of photoresist patterns at a thickness of 500 mm 3. Subsequently, after heat treatment of the overcoating composition at 150 ° C. for 60 seconds, a portion of the overcoating composition and the photoresist pattern was removed using a 2.38% TMAH developer. As a result, an L / S pattern of 62.6 nm was formed in the cell region, and an island pattern of 84.9 nm was formed in the peripheral circuit region (see FIG. 6). That is, it can be seen that the reduction amount of the pattern CD is reduced by 22% for the L / S pattern, and the 20% is reduced for the island pattern, so that the CD reduction amount is almost similar regardless of the pattern pitch.

Example 5

(A) A photoresist film (ARX1221J, manufactured by JSR Co., Ltd.) was formed on the entire surface of the wafer to a thickness of 1000 Å, followed by an ArF immersion lithography process to form a 1: 1 pitch L / S pattern in the cell region, and the peripheral circuit region. An island-like photoresist pattern was formed on the substrate. At this time, the pattern CD measurement result shows that the L / S pattern is 80 nm and the island pattern is 107.5 nm (see FIG. 7).

(B) The overcoating composition prepared in Example 2 was applied to the entire surface of the wafer including the two types of photoresist patterns at a thickness of 500 mm 3. Subsequently, after heat treatment of the overcoating composition at 150 ° C. for 60 seconds, the overcoating composition and a portion of the first photoresist pattern were removed using a 2.38% TMAH developer. As a result, an L / S pattern of 62.3 nm was formed in the cell region, and an island pattern of 84.4 nm was formed in the peripheral circuit region (see FIG. 8). That is, it can be seen that the reduction amount of the pattern CD is reduced by 22% in the L / S pattern and the 21% is reduced in the island pattern, so that the CD reduction is almost similar regardless of the pattern pitch.

Example 6

(A) A photoresist film (ARX1221J, manufactured by JSR Co., Ltd.) was formed on the entire surface of the wafer to a thickness of 2000 microseconds, and then an ArF immersion lithography process was performed to form a 1: 1 pitch L / S pattern in the cell region and to the peripheral circuit region. An island-like photoresist pattern was formed. At this time, as a result of CD measurement, the L / S was 84.2 nm and the island type was 107 nm (see FIG. 9).

(B) The overcoating composition prepared in Example 3 was applied to the entire surface including the two types of photoresist patterns at a thickness of 500 mm 3. Subsequently, after heat treatment of the overcoating composition at 150 ° C. for 60 seconds, the overcoating composition and a portion of the first photoresist pattern were removed using a 2.38% TMAH developer. As a result, an L / S pattern of 52.9 nm was formed in the cell region, and an island pattern of 87.3 nm was formed in the peripheral circuit region (see FIG. 10). That is, it can be seen that the reduction amount of the pattern CD is reduced by 22% in the L / S pattern and the 21% is reduced in the island pattern, so that the CD reduction is almost similar regardless of the pattern pitch.

Example 7

The overcoating composition prepared in Example 1 was coated on the entire surface of the L / S photoresist pattern obtained by the method of Example 4 to a thickness of 30 nm (300 kPa) and 90 nm (900 kPa), and then baked at 150 ° C. for 60 seconds. After development using a 2.38 wt% TMAH solution, the reduced value of the photoresist pattern line width obtained according to each thickness is shown in Table 1 below. In this case, the initial L / S pattern line width is for comparing the reduction degree values, and the line width values are not the same. Meanwhile, FIG. 10 shows a pattern reduction result according to the 30 nm coating thickness, and FIG. 11 shows a pattern reduction result according to the 90 nm coating thickness.

 TABLE 1

Composition thickness for overcoating Initial L / S Line Width Line width after TARC treatment Output (%) 30 nm 88.2 nm 75.4 nm 12.8nm (14.5%) 90 nm 89.7 nm 67.5 nm 22.2 nm (24.7%)

That is, as shown in Table 1, it was found that the reduced line width of the photoresist pattern can be controlled according to the coating thickness of the overcoating composition. For example, as the coating thickness of the overcoating composition increases, the degree of pattern line width reduction is large.

1 is an electron micrograph of a 1: 1 pitch L / S (line & space) pattern formed by a conventional method.

Figure 2 is an electron micrograph of the L / S pattern of 1: 3 pitch formed by the method of applying the conventional double exposure technique.

3 is a view showing a pattern forming method according to the present invention.

4 and 5 is a pattern photograph according to the fourth embodiment.

6 and 7 are pattern pictures according to the fifth embodiment.

8 and 9 is a pattern photograph according to the sixth embodiment.

10 and 11 are pattern photographs according to the seventh embodiment.

<Description of Brief Symbols for Major Parts of Drawings>

100, 106 photoresist pattern 102: overcoating layer

104: acid diffusion region

Claims (15)

An overcoating composition for a photoresist, comprising a thermal acid generator, a water-soluble polymer, and a residual organic solvent. The method according to claim 1, The thermal acid generator is any one selected from the group consisting of the following formula 1 to 3 overcoating composition for a photoresist: [Formula 1]

[Formula 2]

(3)

. The method according to claim 1, The thermal acid generator is an over-coating composition for a photoresist, characterized in that contained in 0.002 to 0.2 parts by weight based on 100 parts by weight of the total overcoating composition. The method according to claim 1, The water-soluble polymer is an over-coating composition for a photoresist, characterized in that represented by the formula [Formula 4]

Wherein R1, R2 and R3 are each hydrogen or methyl group, X is linear or branched alkyl or -NH- (R4) ₂ , which is substituted with hydroxy group (OH), wherein R4 is 1 to Alkyl of 3, and a, b and c each represent a molar fraction of each polymerization repeating unit, and represent 0.05 to 0.9, respectively. The method according to claim 4, In the compound of Formula 4, R1 to R3 are each hydrogen or a methyl group, and X is hydroxypropyl, hydroxyethyl or N-isopropylamide (-NH- (CH ₃ ) ₂ ). Coating composition. The method according to claim 1, The water-soluble polymer is an over-coating composition for a photoresist, characterized in that contained in 0.2 to 10 parts by weight based on 100 parts by weight of the overcoating composition. The method according to claim 1, The organic solvent is an over-coating composition for a photoresist, characterized in that 4-methyl-2-pentanol or heptanol. Forming a first photoresist pattern on a substrate having an etched layer by a lithography process; Applying the overcoating composition of claim 1 to the entire surface of the first photoresist pattern; Baking the applied overcoating composition; And Developing the overcoating composition with an alkaline developer to form a second photoresist pattern having a reduced line width. The method according to claim 8, The photoresist pattern includes a L / S pattern and an island pattern of 1: 1 or 1: 3 pitch. The method according to claim 8, The overcoating composition is a pattern forming method characterized in that the coating is applied in a thickness of 20 to 110% to the height of the photoresist pattern when the total photoresist pattern height to 100. The method according to claim 8, The baking process for the overcoating composition is a pattern forming method, characterized in that carried out at a high temperature of 110 ~ 170 ℃. The method according to claim 8, And the second photoresist pattern width is reduced by 20 to 45% compared to the first photoresist pattern width. The method according to claim 8, The alkaline developer is a TMAH solution, KOH aqueous solution or NaOH aqueous solution pattern formation method characterized in that. The method according to claim 8, The method after forming the second photoresist pattern, Applying a negative photoresist film to the entire surface including the second photoresist pattern; Performing a lithography process on the negative photoresist film to form a third photoresist pattern having the same pitch as the first photoresist pattern in a space between the second photoresist pattern and the pattern; And And repeating the application of the overcoating composition to the developing step to form a fourth photoresist pattern having the same line width and pitch as the second photoresist pattern. The method according to claim 8, The method after forming the second photoresist pattern, Etching the etched layer using the second photoresist pattern as an etching mask; Repeating the first photoresist pattern forming step and the overcoating composition developing step on the entire surface including the etched layer to form a third photoresist pattern having the same line width and pitch size as the etched layer pattern between the etched layer patterns. Pattern forming method further comprising the step of.

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