KR20090025689A - Stripping of high dose ion-implanted photoresist using cosolvent and additive in supercritical carbon dioxide - Google Patents

Abstract

A method for removing photoresist is provided to remove the photoresist injected with high ion from a substrate in supercritical carbon dioxide by using co-solvent and additives without an oxygen plasma ashing process. A method for removing photoresist injected with high ion from a substrate in supercritical carbon dioxide by using co-solvent and additives comprises the steps of (i) mounting a wafer having photoresist injected with high ion on a reaction container; (ii) after adding carbon dioxide, co-solvent and additives which have the temperature of 30-150 °C and the pressure of 2000-5000 psi to the reaction container, and removing the photoresist injected with high ion by contacting the materials with a wafer; (iii) separating carbon dioxide, co-solvent and additive from the reaction container; (iv) rinsing the top of wafer by using pure supercritical carbon dioxide; and (v) removing the pure supercritical carbon dioxide from the reaction container of high pressure and separating the wafer from which the photoresist injected with high ion is removed.

Description

Removal of high dose ion-implanted photoresist using cosolvent and additive in supercritical carbon dioxide

The present invention relates to a method of removing high ion implanted photoresist from a substrate using cosolvents and additives in supercritical carbon dioxide.

In the semiconductor device manufacturing process, deposition, photolithography, and etching processes are repeatedly performed, and photoresist is used to form various microstructures of a circuit pattern through a photolithography process.

Such photoresist must be removed after the formation of the microstructure and before the next process. If the photoresist is not completely removed, the photoresist remains as an impurity, which causes deterioration and failure of the final product.

Photoresist is a polymeric material comprising a photosensitive agent that is a photoactive compound and is used to shape a pattern image onto a substrate. In the process of implanting ions to change the electrical characteristics of the device, photoresists are used as masks to prevent the implantation of ions into unwanted areas. At this time, atoms such as hydrogen present in the photoresist are released on the surface of the photoresist to form a carbonized layer. In general, the carbonized layer formed on the upper and side surfaces of the photoresist is changed to a non-porous structure, which makes it impossible to penetrate the solvent, which is difficult to remove by a general wet method.

Conventional methods for removing the photoresist having such a carbonized layer are removed through a wet scrubbing step using chemicals or diluted acids to remove residual residues after oxygen plasma ashing. The temperature rises to a high temperature so that solvents or low molecular weight volatiles present in the photoresist are not easily escaped by the carbonized layer of the photoresist and cause swelling or rupture in the photoresist, causing damage to the micropattern.

The resulting burst residue particles can also accumulate in process equipment and be resorbed to other substrates. In order to remove this, a large number of cleaning processes are required, and a large amount of chemicals and diluted acids are used, which incurs another cost for treating them.

Recently, in order to solve the problems described above, Korean Patent No. 0597656 and Patent No. 0559017 describe a general method of removing photoresist and fortresist residues. It is difficult to remove the photoresist of the substrate having the surface carbide layer.

Accordingly, Korean Patent 0525855 proposes a technique for removing photoresist injected with high ions in supercritical carbon dioxide after oxygen plasma ashing.

The patent removes high ion implanted photoresist residues using carbon dioxide after ashing with oxygen plasma, but the residues such as cosolvents and photoresist residues remaining on the wafer are not completely removed even after this process. And water are used to separate rinse steps.

This process imposes another rinsing process to treat the problems generated in the oxygen plasma ashing process and the residues not removed even in the carbon dioxide treatment, which may lower the production efficiency and cause additional costs and other environmental problems.

The present invention is to solve the above problems, an object of the present invention is to completely remove the high ion implanted photoresist from the substrate in a short time using a co-solvent and additives in supercritical carbon dioxide without oxygen plasma ashing process The purpose.

Since supercritical carbon dioxide has fast material transfer characteristics and low surface tension, it is possible to rapidly penetrate into the surface carbide layer of the photoresist injected with high ion together with cosolvents and additives, resulting in photoresist rupture due to high heat generated during plasma ashing. This does not occur.

In addition, cosolvents and additives used in conjunction with supercritical carbon dioxide serve to dissolve the photoresist components appropriately and remove them from the substrate, thereby quickly removing the high ion implanted photoresist from the substrate.

The present invention for achieving the above technical problem is to provide a method for removing a high ion implanted photoresist from a substrate using a co-solvent and an additive in supercritical carbon dioxide.

Supercritical carbon dioxide diffuses rapidly like gas, has a very low surface tension, and therefore relatively easily penetrates into the carbonized layer of the ion implanted photoresist and simultaneously flows as a liquid wet medium.

However, since the non-polar supercritical carbon dioxide does not effectively dissolve the photoresist components containing the polar material, it is possible to overcome the above disadvantages by using a cosolvent and an additive properly for efficient removal.

The reason for adding the cosolvent and the additive in the supercritical carbon dioxide of the present invention is to increase the solubility of the photoresist implanted with high ions from the substrate to improve the removal efficiency.

The cosolvent may be used alone or in combination of alcohols including methanol, ethanol, isopropanol, benzoyl alcohol, monoethanolamine, diethanolamine, triethanolamine, carbon tetrachloride, acetone, methyl ethyl ketone and tetrahydrofuran. It is used as a mixture above.

The additive is used alone or in a mixture of two or more of tetraalkylammonium hydroxide, formalin, formic acid, acetic acid, phosphoric acid and sulfuric acid.

The substrate may be a semiconductor wafer, an aluminum-aluminum oxide substrate, a gallium arsenide substrate, a ceramic substrate, a copper substrate, or the like.

In a preferred embodiment, the supercritical carbon dioxide content used is in the range of 60 to 95% by weight, the content of the cosolvent is 4 to 30% by weight, and the content of the additive is in the range of 1 to 10% by weight.

The material to be removed by cosolvents and additives in supercritical carbon dioxide is a high ion implanted photoresist.

In the photoresist, various photoresists such as I-line photoresist, KrF excimer laser photoresist, and ArF excimer laser photoresist are ion-implanted with 1 × 10 ¹⁵ atoms / cm 2 dose or more.

The wafer may be rotated at 100 to 10000 RPM to increase the contact effect with supercritical carbon dioxide in order to effectively remove the photoresist implanted with high ions in carbon dioxide.

In an embodiment of the present invention, the photoresist is a photoresist for KrF excimer laser, a photoresist ion-implanted with 1 × 10 ¹⁵ atoms / cm 2 dose or more, and the substrate is a semiconductor wafer.

Removal efficiency of photoresist using cosolvent and additive in supercritical carbon dioxide can be improved by changing cosolvent type and concentration, type of additive and concentration condition. It can be improved according to the change of temperature, pressure and contact time in the contacting step of the photoresist to be made.

The components and concentrations of the cosolvents and additives of the present invention were optimized and complete removal was achieved with small amounts of use. In addition, after the step of removing the contact with the photoresist, there is no residue of photoresist residue, cosolvent and additives on the wafer, so that no rinse treatment or drying process using a separate solvent is required.

As shown in FIG. 1, an apparatus for removing a high ion implanted photoresist from a wafer having a high ion implanted photoresist according to the present invention is characterized in that the carbon dioxide is initially supplied from the carbon dioxide source 11 to the high pressure reaction vessel 16. It is connected through a supply pipe 12 for supplying and supplying carbon dioxide during rinsing. A high pressure pump 14 for injecting the carbon dioxide in a high pressure state, the supply pipe 12 is connected to the co-solvent and additive supply source 15, the high pressure reaction vessel is a heater for controlling a predetermined reaction temperature (17), a circulating pump 18 for circulating the heated fluid outside the reactor, a circulation tube 19, a photoresist component and supercritical carbon dioxide, co-solvent and additives attached to and removed from the high pressure reaction vessel 16; Is removed through the discharge pipe (20).

A preferred method of removing a high ion implanted photoresist using a cosolvent and an additive of the present invention comprises the steps of: (1) mounting a wafer having a high ion implanted photoresist in a reaction vessel; (2) adding carbon dioxide, a co-solvent, and an additive at a temperature of 30 to 150 ° C. and a pressure of 2000 to 5000 psi to the reaction container to remove the high ion implanted photoresist; (3) separating carbon dioxide and cosolvent and additives from the reaction vessel; (4) rinsing the top of the wafer using pure supercritical carbon dioxide; (5) removing the pure supercritical carbon dioxide from the high pressure reaction vessel, and separating the wafer from which the high ion implanted photoresist has been removed; The high ion implanted photoresist is removed from the wafer through this series of processes.

The present invention enables the rapid penetration of the surface carbonized layer of the photoresist implanted with a high ion with a cosolvent and an additive using supercritical carbon dioxide having fast material transfer characteristics and low surface tension, resulting in high heat generated during plasma ashing. There is no rupture of the resist, and the cosolvent and additives used with supercritical carbon dioxide dissolve the photoresist component properly and completely remove it from the substrate in a short time, thereby significantly reducing the process and generating waste. There is an effect of reducing the productivity in the semiconductor manufacturing process.

Hereinafter, preferred comparative examples and examples for illustrating the present invention are described.

Comparative Examples 1 to 4

The removal efficiency of the photoresist was investigated by changing the type of cosolvent and the concentration of additive. The wafer used here was spin-coated with a photoresist for KrF excimer laser, the main component of which is chemically amplified polyhydroxystyrene, to form a thickness of 1.6 μm, and nitrogen and arsenic ions were accelerated to 30 KeV and 1 × 10 ^15. It produced by injecting in atom / cm <2> concentration. As shown in FIG. 2A, a carbide layer of 0.3 μm was formed on the photoresist. THF (tetrahydrofuran) / monoethanolamine (1: 1 mixed solution) was used as a cosolvent and was added at a concentration of 15% in carbon dioxide. The results of removing the photoresist contacted for 120 seconds using supercritical carbon dioxide at a pressure of 3000 psi and a temperature of 40 to 70 ° C. are shown in Table 1, and the removal efficiency was improved as the temperature was increased.

TABLE 1 Photoresist Removal Experiments by Temperature

Examples 1-4

A wafer manufactured in the same manner as the wafer used in Comparative Example 1 was used, and an additive formic acid / acetic acid mixed solution was used as a cosolvent in a THF / acetone / monoethanolamine mixed solution. Table 2 shows the results of the removal of photoresist for 120 seconds using supercritical carbon dioxide at 3000 psi pressure and 70 ° C. As the amount of polar solvent in the cosolvent increases, the amount of additive increases It was found that the removal efficiency was improved.

<Table 2> Photoresist removal experiment according to the amount of cosolvent and additive

Examples 5-7

A wafer manufactured in the same manner as the wafer used in Comparative Example 1 was used, and 15 wt% of a mixed solution of THF / acetone / monoethanolamine (2: 2: 1) and additive formic acid / acetic acid (1: 1) were used as cosolvents. 2 wt% of the mixed solution was used. The removal efficiency according to the change of contact time using supercritical carbon dioxide at 3000 psi pressure and temperature 70 ℃ is shown in Table 3. The photoresist was removed 95% in 30 seconds and 100% in 60 seconds or more. there was.

Chemically amplified polyhydroxystyrene was spin-coated with a photoresist for KrF excimer laser, the main component of which was formed to a thickness of 1.6㎛, and prepared by injecting nitrogen and arsenic ions at an acceleration of 30 KeV and a concentration of 1 × 10 ¹⁵ atoms / ㎠ Scanning electron micrograph (FIG. 3A) and surface element analysis of the silicon wafer itself using a scanning electron microscope (FIG. 3A) and an element of the wafer surface as an EDS analysis result (FIG. 3B) as a substrate. As can be seen from the difference in the result (Fig. 4b), the result of Example 5 (Fig. 5) is a form in which some photoresist remains, and the result of Example 6 (Fig. 6) shows that the photoresist is completely removed. there was.

<Table 3> Photoresist removal experiment according to reaction time

Examples 8-9

A photoresist for KrF excimer laser, the main component of which is chemically amplified polyhydroxystyrene, was spin-coated to form a thickness of 1.6 μm. Nitrogen and arsenic ions were injected at an acceleration of 30 KeV and a concentration of 1 × 10 ¹⁵ atoms / cm 2. It was produced by. Another thickness of resist was formed to a thickness of 2.1 mu m. Nitrogen and arsenic ions were implanted at an acceleration of 30 KeV at a concentration of 1 x 10 ¹⁶ atoms / cm 2 to form a 0.3 mu m carbide layer on top of the photoresist. (Figure 2a)

As an experiment on the removal efficiency of the photoresist according to the pressure change, it was contacted for 120 seconds using supercritical carbon dioxide at 3000 psi pressure and a temperature of 70 ℃. Using THF / acetone / monoethanolamine (2: 2: 1) mixed solution as cosolvent and formic acid / acetic acid (1: 1) mixed solution as additives, the removal efficiency according to pressure change is shown in Table 4. As the pressure increases, the removal efficiency increases.

<Table 4> Experiment of Photoresist Removal with Pressure Change

Examples 10-12

Using the wafer used in Example 9 was tested the removal efficiency of the photoresist according to the change in the wafer rotation speed. The results are shown in Table 5, and as the rotational speed of the wafer increases, the contact efficiency between the supercritical fluid composition and the photoresist layer on the top of the wafer is increased, and the removal efficiency is increased.

<Table 5> Photoresist removal experiment according to rotation speed

1 is a schematic diagram of a process of removing a photoresist implanted with a high ion from a substrate using a cosolvent and an additive in supercritical carbon dioxide.

2A and 2B are cross-sectional SEM photographs of a photoresist in which a carbonized layer is formed by high ion implantation.

3A and 3B show surface SEM and EDS analysis results of a high ion implanted photoresist.

4A and 4B show surface SEM and EDS analysis results of a photoresist-free wafer.

5A and 5B show SEM and EDS analysis results of residual photoresist after treatment.

6A and 6B show SEM and EDS analysis results of a substrate surface from which photoresist is completely removed after treatment.

Claims (7)

CLAIMS 1. A method for removing a high ion implanted photoresist from a substrate using a cosolvent and an additive in supercritical carbon dioxide, comprising the steps of: (1) mounting a wafer having a high ion implanted photoresist in a reaction vessel; (2) adding carbon dioxide, a co-solvent, and an additive at a temperature of 30 to 150 ° C. and a pressure of 2000 to 5000 psi to the reaction container to remove the high ion implanted photoresist; (3) separating carbon dioxide and cosolvent and additives from the reaction vessel; (4) rinsing the top of the wafer using pure supercritical carbon dioxide; (5) removing the pure supercritical carbon dioxide from the high pressure reaction vessel and separating the wafer from which the high ion implanted photoresist has been removed; The method of claim 1, wherein the cosolvent is selected from substances such as methanol, ethanol, isopropanol, benzoyl alcohol, monoethanolamine, diethanolamine, triethanolamine, carbon tetrachloride, acetone, methyl ethyl ketone, tetrahydrofuran and the like. A removal method characterized by being used alone or in a mixture of two or more. The method according to claim 1, wherein the additive is used alone or in a mixture of two or more kinds of substances such as tetraalkylammonium hydroxide, formalin, formic acid, acetic acid, phosphoric acid and sulfuric acid. The method of claim 1, wherein the substrate comprises a semiconductor wafer, an aluminum-aluminum oxide substrate, a gallium arsenide substrate, a ceramic substrate, and a copper substrate. The method of claim 1, wherein the supercritical carbon dioxide content used is 60 to 95% by weight, the content of the cosolvent is 4 to 30% by weight, and the content of the additive is in the range of 1 to 10% by weight. 2. The method of claim 1, wherein the wafer is rotated at 100 to 10000 RPM to increase the contact effect with supercritical carbon dioxide. The method of claim 1, wherein the removal efficiency of the photoresist using the cosolvent and the additive in the supercritical carbon dioxide can be improved according to the change of the type and concentration of the cosolvent and the additive, the temperature, the pressure, and the contact time. Removal method.

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