New PCT application

BASF Aktiengesellschaft, 67056 Ludwigshafen (Deutschland)

CLEANING COMPOSITION FOR REMOVING POST-DRY-ETCH

RESIDUES

Background of the Invention Field of the Invention

The present invention relates to a composition of a photoresist stripping solution provided for a lithographic process of a thin film transistor-liquid crystal display (TFT-LCD), and in particular to a cleaning solution for removing post-dry-etch residues.

Description of the Prior Art

An etching process can be considered as one of the most important steps during a lithographic process throughout the semiconductor and liquid crystal thin film display industries. In general, an element pattern on a mask is firstly transferred onto a photoresist by a lithographic process. Then, the ultimate goal for transferring the whole pattern onto a thin film is achieved by a etching process. The thin film after lithography and etching will be a part of semiconductor elements. Talcing the process of the metal-oxide-semiconductor (MOS) or complementary-metal-oxide- semiconductor (CMOS) as an example, this thin film may be silica (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), poly-silicon (Poly-Si), aluminum alloy (Al alloy), copper, or phosphosilicate glass (PSG), and so on. That is to say, most of the main materials for making up the semiconductor elements must be subject to such three procedures as thin film deposition, lithography and etching, so as to fabricate the element layer by layer.

For example, in the common process for forming a conductor pattern, firstly, a silica layer and a conductor layer (poly-silicon or other metal materials, such as

aluminum or copper) are typically formed to a substrate sequentially, followed by forming a patterned photoresist layer on this conductor layer. Next, the photoresist layer is used as the etching mask, and the exposed conductor layer is etched by dry etching, so as to form a conductor pattern. Afterward, the photoresist layer is removed.

However, in the process for forming the conductor pattern, since the gas for etching the conductor layer contains carbon, chlorine or oxygen, which can chemically react with the photoresist layer and the conductor layer, to yield the polymer residues, which will causes poor performances of the conductor layer in addition to the influence on the subsequent processes, on sidewalls of the photoresist layer and conductor layer, after removing the patterned photoresist layer, typically, a cleaning process is performed to remove the post-dry-etch polymer residues adhered on the surface of the conductor pattern .

For example, in the Array process of the liquid crystal thin film displays, a substrate is provided firstly, which at least has a copper metal wire layer and a dielectric layer on the copper metal wire layer thereon. Next, the substrate is etched by a mask defining etching pattern, to provide an opening to expose a part of the copper metal wire.

At this time, a polymer and copper oxide-polymer compounds are produced as residues on the exposed surface of the dielectric layer, while copper oxide is produced on the exposed surface of copper metal.

Generally, in order to remove the residues, it is necessary to perform a cleaning step by a cleaning solution. The conventional methods for removing the polymer residues can be classified into the organic amines method and the hydrofluoric acids method according to the components of the solution. In the organic amines method, ethanolamine is mainly used, in conjunction with the combinations of different organic solvents, for example, the composition as disclosed in U.S. Patent Application Publication No. 2001/0034313. A step for cleaning the organic solvent is desired to be added in producing process of the products after removing the photoresist, in order to prevent the corrosion effect on the metal layer (aluminum or copper) in subsequent

water-washing procedure. For the hydrofluoric acids method, hydrofluoric acid is the key component, in conjunction with the organic solvents and corrosion resistant hydroxyl-containing aromatic compounds, for example, the composition as disclosed in U.S. Patent Publication No.5,905,063. However, in the applications to copper processes, the removal ability of copper oxide is yet to be enhanced for the cleaning solution disclosed in the above patents.

Summary of the Invention

The present invention provides a cleaning composition for removing a post-dry- etch residue, which may effectively remove a post-dry-etch polymer residue on a pattern surface and copper oxide on a copper metal surface.

The present invention further provides a method for cleaning post-dry-etch residues, including contacting a substrate etched by a lithographic process with a photoresist ashed by a plasma process, with the cleaning composition of the present invention, so as to remove the post-dry-etch residue from the substrate.

Brief description of the drawings

The purposes, features and advantages of the present invention can be understood by the following drawings and illustration, in which:

FIG. 1 is a flow chart of a method for cleaning a patterned glass substrate according to a preferred embodiment of the present invention.

FIG. 2 shows a photoresist pattern post-dry-etched by a plasma process, where the material below the photoresist is silicon nitride.

FIG. 3 shows a photoresist cleaned by Embodiment 1, in which a favorable photoresist removal ability is clearly shown.

FIG. 4 shows a photoresist cleaned by Comparative Example 1, in which a photoresist with post-dry-etch residue not completely removed is shown.

Detailed Description

A cleaning composition of the present invention for removing a post-dry-etch

residue contains 1 to 30 wt% of at least a water-soluble amine compound selected from the group consisting of hydrazine, hydrazine hydrate, and a mixture thereof, 30 to 90 wt% of at least a water soluble organic solvent, and 1 to 20 wt% of water, based on the total weight of the composition.

Hydrazine is preferred for the water-soluble amines used in the present invention.

The content of the water-soluble amines used in the present invention is from 1 to 30 wt%, preferably from 1 to 15 wt%, based on the total weight of the composition.

The water-soluble organic solvent used in the present invention is preferably selected from the group consisting of dimethyl sulfoxide (DMSO), glycol compounds, N-methyl pyrrolidone (NMP), N,N-dimethyl acetamide (DMAC), N,N-dimethyl formamide (DMF), and mixtures thereof.

The glycol compounds useful in the present invention as the water-soluble organic solvents are preferably carbitol and the derivatives thereof, for example, but not limited to, diethylene glycol monobutyl ether (BDG), diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, or diethylene glycol acetate monobutyl ether. In the cleaning composition of the present invention, a glycol compound can be used alone, or more than two glycol compounds can be incorporated to be used.

The content of the water-soluble organic solvent used in the present invention is from 30 to 90 wt%, preferably from 60 to 90 wt%, based on the total weight of the composition.

The water used in the present invention is preferably deionized water with a content from 1 to 20 wt%, preferably from 1 to 10 wt%, based on the total weight of the composition.

The cleaning composition of the present invention may optionally further contain additional components well known by those ordinarily skilled in the art, for example, a corrosion inhibitor, particularly one having a metal chelating effect, for example, but not limited to, catechol, 1,2,3-benzotriazole.

The cleaning composition of the present invention can effectively remove the

post-dry-etch polymer residues adhered to the pattern sidewall of the dielectric layer. Moreover, while the organic and inorganic residues are effectively removed, the metal surface is prevented from being corroded, and the removal of the oxide layer on the post-dry-etch copper surface is improved to a great extent.

Accordingly, the present invention further provides a method for cleaning the post-dry-etch residues, which includes contacting a substrate etched by a lithographic process with a photoresist ashed by a plasma process, with the cleaning composition of the present invention, so as to remove the post-dry-etch residue from the substrate.

Referring to FIGl, it shows a flow chart of a method for cleaning a patterned glass substrate according to a preferred embodiment of the present invention.

Firstly, the patterned glass substrate is provided (Step A), which is a glass substrate etched by a lithographic process with a photoresist ashed by a plasma process.

Thereafter, the glass substrate is cleaned by the cleaning composition of the present invention for removing the post-dry-etch residues (Step B).

Next, the glass substrate is cleaned by water (Step C), to wash off the cleaning composition remaining on the glass substrate. And then, the glass substrate is dried (Step D), to complete cleaning the photoresist on the glass substrate.

In addition, in the cleaning method, after drying the glass substrate (Step D), the glass substrate surface can be observed by a scanning electron microscope (SEM) , to confirm whether the residues are still on the glass substrate surface.

To verify the feasibility of the present invention, a plurality of tests are performed by using the cleaning composition of the present invention, and test results are compared with that of the conventional cleaning composition. The following embodiments are intended to illustrate the tests carried out for the cleaning composition of the present invention and the conventional cleaning composition, but not to limit the scope of the present invention merely, and any modifications and alterations that can be easily achieved by those ordinarily skilled in the art are encompassed within the scope of the present invention.

Embodiments

(1) Removal test of ashed photoresist and post-dry-etch residues

Firstly, a glass substrate was provided, and then patterned. Next, the glass substrate was immersed in the cleaning composition, taken out after a defined time and rinsed with water before drying. Thereafter, a SEM was used to observe whether the residues were present on the glass substrate.

(2) Copper layer corrosion test

In this test of the present invention, several metals commonly used in the process were tested. Firstly, a sheet of metal was provided, and then immersed in the cleaning composition. After a defined time, the metal sheet was taken out. The thickness was measured, and then the etching rate of the cleaning composition on the metal was calculated.

(3) Test of removal ability of copper oxide

Firstly, a sheet of copper was provided, and copper oxide with uniform thickness was formed on the surface thereof. Next, the copper sheet was immersed in the cleaning composition, and taken out after a defined time. The remained thickness of the copper sheet was measured, then the rate of copper oxide removed by the cleaning composition (the removal rate of the copper oxide) was calculated.

(4) Preparation of the test solution

The post-dry-etch cleaning compositions of Embodiments 1 to 3 and Comparative Examples 1 to 2 were respectively prepared by the following ingredients in Table 1.

The ashed photoresist and post-dry-etch residues removal test (1) , copper layer corrosion test (2), and the test of removal ability of copper oxide (3) were carried out in the cleaning composition prepared according to this table. The results are shown in Table 2, 3, and 4 respectively.

Table 1: the composition of the cleaning composition for removing the post-dry- etch residues

DMSO: dimethyl sulfoxide MEA: monoethanolamine HF: Hydrofluoric acid

Test 1 : the ashed photoresist and post-dry-etch residues removal test The ashed photoresist and post-dry-etch residues removal test was carried out with the cleaning compositions shown in table 1. The results were shown in Table 2. Table 2:

o: represents the complete removal of the ashed photoresist and post-dry-etch residue on the glass substrate .

: represents the removal of most of the ashed photoresist and post-dry-etch residue on the glass substrate, but a little remained.

In addition, FIGs. 2-4 are scanning electron microscope photos, which compare the cleaning compositions of Embodiment 1 and Comparative Example 1 for the individual ability for removing the post-dry-etch residue. FIGs. 2-4 show the test results of the removal ability of the post-dry-etch residue.

FIG. 2 shows a photoresist pattern post-dry-etched by a plasma process. The pattern has a structure including a layer of silicon nitride (SiN), and the post-dry-etch

residues of the photoresist above silicon nitride.

FIG. 3 shows a photoresist cleaned by Embodiment I ₅ in which a favorable photoresist removal ability is clearly shown.

FIG. 4 shows a photoresist cleaned by Comparative Example I ₅ in which a photoresist with post-dry-etch residue not completely removed is shown.

Test 2: copper layer corrosion test

The copper layer corrosion test was performed by the cleaning compositions shown in Table 1. It can be seen from the results shown in Table 3 that the post-dry- etch cleaning composition of the present invention hardly has corrosion action on copper. Therefore, the cleaning composition of the present invention can effectively remove the post-dry-etch residue without damaging the metal surface.

Table 3:

o: represents no corrosion on the copper surface. : represents slight corrosion on the copper surface.

X: represents severe corrosion on the copper surface.

Test 3: test of removal ability of copper oxide

The test of removal ability of copper oxide was performed by immersing three copper sheets with copper oxide formed on the surface thereof respectively in the three cleaning compositions of Embodiment I ₅ Comparative Example 1 and Comparative Example 2 shown in table 1 for 20 minutes. The results are shown in Table 4, where a horizontal axis represents the category of the cleaning compositions, a vertical axis represents the removal rate of copper oxide, ♦ represents the results obtained by the cleaning composition of Embodiment 1, ■ represents the results

obtained by the cleaning composition of Compaiative Example 1, and ▲ represents the results obtained by the cleaning composition of Comparative Example 2. Table 4.

It can be known from Table 4 that copper oxide on the copper sheets can be completely removed by immersing into the cleaning composition of Embodiment 1 of the present invention for about 20 minutes. However, if the cleaning composition of Comparative Example 1 is used, copper oxide will not be removed at all, while if the cleaning composition of Comparative Example 2 is used, copper oxide on the copper sheet is removed by 25% in thickness. Therefore, it can be known from the results that, the cleaning compositions of the present invention has significant effect in removing copper oxide over the conventional cleaning compositions. Accordingly, the cleaning composition of the present invention has an excellent removal ability of metal oxide.

Although the present invention is disclosed as above with a preferable embodiment, it is not intended to limit the present invention. It will be apparent to any one skilled in the art that some variations and modifications can be made without departing from the scope or spirit of the invention. In view of the foregoing, the scope of the right protected by the present invention should be defined by the appended claims.