JP2544478B2 - Wet etching method - Google Patents

Description

The present invention relates to a wet etching method, particularly a wet etching method which is advantageous when forming a fine pattern in the manufacture of a semiconductor device and a mask. Process for forming a resist film having an opening for etching on the film to be etched for the purpose of providing an etching method that does not cause deterioration of the pattern quality due to peeling, film peeling, etc., the resist film including the inner surface of the opening A step of coating and forming an antistatic agent film on the surface of, a step of drying the antistatic agent film, the resist film having the antistatic film as a mask, the etching target film under the opening,
It is configured to have a step of selectively dissolving and removing with an etching solution.

[Industrial applications]

The present invention relates to a wet etching method, and more particularly to a wet etching method which is advantageous when forming a fine pattern in manufacturing a semiconductor device and a mask.

As the integration of semiconductor ICs progresses from LSI to VLSI, the patterns that make up these ICs are becoming finer, and even the photomasks and reticles used to manufacture these ICs are on the order of submicron order. It is necessary to form a fine pattern with high accuracy.

A high-quality pattern with high accuracy is usually formed by anisotropic dry etching using a resist as a mask, but a resist with high resolution that can form a submicron-order fine pattern with high accuracy is generally anisotropic. There is a problem that the etching resistance in the dry etching is low, and therefore the shape of the mask is deformed during the etching, and sufficient processing accuracy cannot be obtained in the fine pattern. Therefore, it is necessary to make it possible to process a fine pattern with high accuracy by using a wet etching means that does not damage the high resolution resist.

[Conventional technology]

Conventionally, dry etching having anisotropy such as reactive ion etching has been considered as an effective means for processing a fine pattern on a mask and a reticle.

However, electron beam (EB) resists with a sufficiently high resolution for submicron patterns,
For example, in EBR-9 (acrylic radiation-decomposable resist manufactured by Toray Industries, Inc.) or PBS (olefin-based resist containing sulfone group manufactured by Mead), etc., resistance to normal anisotropic dry etching is used. Sufficient exposure accuracy because the etching property is about 1/5 to 1/7 compared with the conventional photoresist, that is, it is only about 1/2 to 1/4 with respect to the light-shielding film such as chromium that is the film to be etched. 1-2 μm
In order to fully perform the mask function with a certain film thickness,
It is necessary to increase the etching resistance of the resist by making the etching close to isotropic. However, even in this case, the etching property of the resist is considerably high, and therefore, the pattern accuracy is lowered due to the loss of the resist, and at the same time, the side etching caused by the etching becoming close to isotropic is also added. There is a problem that accuracy cannot be obtained.

Therefore, in order to improve the etching resistance of the resist and prevent the deterioration of the mask accuracy due to the loss of the resist, a method of dissolving and removing the film to be etched by a wet etching means has been conventionally used.

In this conventional method of forming a mask by wet etching, for example, the positive high-resolution EB resist film is formed on a blank substrate in which a light-shielding film is formed on a mask substrate, as shown in the process diagram of FIG. Thereafter, the resist film is exposed 51 with a predetermined fine opening pattern by EB exposure or the like, the exposed region is removed by development 52 to form a fine etching opening pattern in the resist film, and the post bake 53 is performed. After that, the development residue of the resist at the bottom of the etching opening pattern is removed by ultraviolet light (UV) irradiation 54, and then the light shielding film exposed at the bottom of the etching opening is wetted with a predetermined etching solution. etching
It was a method of dissolving and removing by 57.

[Problems to be Solved by the Invention]

However, according to the conventional wet etching method described above, the resist film having a high insulation property and the etching solution having a high resistance are both negatively (-) charged during etching, and as a result, they repel each other and thus, as shown in FIG. ), A phenomenon in which the etching solution 6 becomes spherical and adheres to the resist film 3 is generated, particularly when the etching openings 4 become submicron. The etching liquid 6 does not completely penetrate to the bottom of the etching hole 4 due to the above repulsion phenomenon, so that FIG.
As shown in the schematic process sectional view of FIG. 3, the light-shielding film such as a chromium (Cr) film 2 exposed at the bottom of the etching opening 4 is not uniformly etched, and an etching residue 2p is easily generated. (1 is a mask substrate) Therefore, in the conventional method, the etching residue 2p
In order to reduce the generation rate of Cr, over etching of about 1.5 to 2 times is applied. Therefore, in addition to the above etching residue, as shown in the schematic process plan view of FIG.
A region 2q in which the thickness of the Cr film 2 is reduced due to the permeation of the etching solution, a chip 2r due to peeling of the Cr film 2 and the like are generated around the opening pattern 7 of the film 2, resulting in a decrease in the pattern accuracy and a consequent manufacturing yield. There was a problem of causing a decrease.

Therefore, an object of the present invention is to provide a wet etching method which does not cause deterioration of pattern quality due to etching residue, etching solution seepage, film peeling, etc. when forming a fine pattern.

[Means for solving the problem]

The above problems include a step of forming a resist film having an opening for etching on a film to be etched, a step of coating and forming an antistatic agent film on the surface of the resist film including the inner surface of the opening, and the antistatic agent. A wet etching method according to the present invention includes a step of drying a film, and a step of selectively dissolving and removing the film to be etched under the opening with a resist film having the antistatic film as a mask by an etching solution. It

[Work]

That is, the present invention reduces the contact resistance between the resist mask and the etching solution by forming an antistatic agent film on the surface including the inner surface of the etching opening of the resist mask formed on the film to be etched. It is possible to prevent a phenomenon in which the surface including the inner surface of the opening and the etching liquid surface in contact with the surface are charged negatively (-) and repel each other. As a result, the etching solution easily penetrates to the bottom of the sub-micron opening for fine etching formed in the resist mask and comes into uniform contact with the surface to be etched.

Therefore, the film to be etched in the etching hole is completely dissolved and removed without leaving an etching residue by adding a slight overetching time for compensating the in-plane distribution of etching to the specified etching time. Therefore, it is possible to prevent the deterioration of the pattern accuracy and the manufacturing yield due to the permeation of the etching solution and the peeling of the film caused by the over-etching.

〔Example〕

 Hereinafter, the present invention will be specifically described with reference to illustrated embodiments.

FIG. 1 is a process diagram showing a configuration example of the present invention, and FIG. 2 (a).
(F) is process sectional drawing of one Example of the method of this invention.

As shown in FIG. 1, the wet etching method according to the present invention includes, for example, a step of exposing 51 a predetermined fine pattern to a resist film formed on a film to be etched, and removing (remaining) this exposed area to remove Step of developing 52 for forming an opening pattern for etching on the resist film, step of post-baking 53 for solidifying the resist film, UV for removing the development residue of the resist on the bottom surface of the opening for etching
The step of forming a resist mask including the step of irradiation 54 and the like, the step of forming an antistatic agent film 55 of applying an antistatic agent to the surface including the inner surface of the etching opening of the resist film, and the antistatic agent applied and formed as described above. Step 56 of drying the antistatic agent film to completely solidify the agent layer, and wet etching for selectively removing the film to be etched under the etching opening of the resist film with a predetermined etching solution using the resist film as a mask The feature of the method of the present invention which is mainly constituted by 57 steps and is different from the conventional method is that prior to the wet etching 57 step, an antistatic agent film is formed on the surface of the resist mask including the inner surface of the etching opening by coating. This is the point including the step 55 of performing and the step 56 of drying the antistatic agent film.

Hereinafter, the method of the present invention will be specifically described with reference to the drawings with respect to an embodiment for producing a chromium (Cr) mask having a fine pattern for a photo process.

2 (a) That is, when forming a Cr mask by the method of the present invention, a Cr film 2 having a thickness of, for example, about 600 Å (antireflection on the Cr film) is formed on a mask substrate 1 made of quartz or the like as in the conventional case. For thickness 3
A positive type EB resist film having a high resolution of, for example, EBR-9 described above and having a high resolution of about 5000Å is formed on a blank substrate formed with a not-illustrated chromium oxide film of about 00Å) 3 is applied and formed on the resist film 3 by ordinary EB exposure, for example, 0.5 μm □
Expose a pattern (3L is the exposure area).

Next, referring to FIG. 2B, the resist film 3 is formed, for example, with methyl isobutyl ketone (MiBK): isopropyl alcohol (iPA) = 80:
The exposed area 3L is removed by developing with a developing solution composed of a mixed solution of 20 (volume ratio), and an opening 4 for etching of about 0.5 μm □ is formed in this portion.

At this time, a resist development residue 3s called scum remains on the bottom of the opening 4.

See FIG. 2C. Then, after the resist film 3 is post-baked at a temperature of 90 to 150 ° C., 100 to 200 W is applied on the resist film 3.
60 with ultraviolet light (UV) from a mercury lamp with a moderate output
Irradiation is performed for about 300 seconds to ash the resist film 3 for about 200 Å to remove the development residue 3s of the resist.

See FIG. 2 (d). Then, the surface of the resist film 3 including the inner surface of the etching opening 4 is sprayed or dropped / spun (250 rpm).
Then, the antistatic agent film 5 having a thickness of about 50 to 100 Å is formed by the method.

The following antistatic agents are used, for example.

Antistatic agent "Zero Charge" Surface specific resistance 2.0 x 10 ⁸ Ω (manufactured by Sanyo Chemical Industry Co., Ltd.) Antistatic agent "Sunstat 2012A" Surface specific resistance 1.5 x 10 ⁹ Ω (manufactured by Sanyo Chemical Industry Co., Ltd.) 1500 at room temperature or below 50 ℃
The antistatic agent film 5 is dried by spin drying or standing drying at a rotation speed of about rpm. If this drying is not performed, the antistatic agent film 5 will dissolve in the etching liquid in the subsequent wet etching process and the etching opening 4 will be formed.
The Cr film 2 stays inside and functions as an etching inhibitor, so that the Cr film 2 in the etching opening 4 cannot be completely removed.

Next, as shown in FIG. 2E, the Cr film 2 below the etching opening 4 of the resist film 3 is selectively etched by the paddle method of dropping the etching solution while rotating the substrate or the dipping method (6).
Is an etching solution). As the etching liquid 6, an aqueous solution of perchloric acid, cerium ammonium nitrate or the like having a pH value of about 1 or less is conventionally used.

During this wet etching, the antistatic agent film 5
Due to the effect, the phenomenon that both the resist film 3 and the etching solution 6 are negatively charged and repel each other does not occur, and the surface of the resist film 3 has the etching solution 6 as shown in the figure.
Get wet evenly. Therefore, the etching liquid 6 is evenly filled inside the etching openings 4, and evenly contacts the Cr film 2 on the bottom surface of the etching openings 4 through the antistatic agent film 5. Here, since the antistatic agent film 5 has water permeability, the etching solution 6 penetrates through the film and uniformly penetrates into the entire surface of the Cr film 2 below the antistatic agent film 5, so that the etching residue is partially removed. The entire surface of the Cr film 2 is uniformly melted without leaving. The antistatic agent film 5 on the Cr film 2 is lifted off at the beginning of etching, and then the etching solution is brought into direct contact with the Cr film 2 to perform etching.

See FIG. 2 (f). Then, a plurality of etching holes 4 on the entire surface of the mask substrate.
When the Cr film 2 on the bottom surface is completely removed and the mask substrate 1 is completely exposed on the bottom surfaces of the openings 4, immediately rinsing with pure water is performed to stop etching, and after drying, ash by oxygen plasma is removed. The antistatic agent film 6 and the resist film 3 are removed by a chemical treatment to complete the Cr mask 8 having the highly accurate fine hole pattern 7 according to the present invention.

As shown in the above examples, according to the wet etching method of the present invention, since the repulsive action due to charging does not occur between the resist film and the etching solution, the opening of a fine resist film of submicron size is possible. The etching solution can be filled evenly inside, and the entire surface to be etched exposed on the bottom surface of the opening can be uniformly contacted with the etching solution, so that the etching film exposed inside the opening is partially etched. The residue is uniformly etched and removed in a uniform time without being generated, and a defect such as a pattern drop (a pattern is not formed) or the like caused by the residue is prevented. Further, since the etching is made uniform as described above, it is necessary to perform excessive over-etching on the film to be etched exposed in the fine openings of the numerous resist films dispersedly arranged on the entire surface of the substrate to be processed. Since it is possible to uniformly remove the etching solution, it is possible to prevent the deterioration of the pattern accuracy and the manufacturing yield due to the permeation of the etching solution and the peeling of the film, which are caused by the over-etching.

The method of the present invention is, of course, for manufacturing a mask and a reticle having a light-shielding film other than the Cr film shown in the embodiment, an insulating film on a semiconductor substrate in manufacturing a semiconductor device,
It is also applied when patterning a semiconductor film, a metal film or the like.

〔The invention's effect〕

As described above, according to the present invention, a submicron-sized fine pattern can be formed without causing pattern loss or deterioration in pattern accuracy. Therefore, it is possible to improve the reliability and manufacturing yield of masks, reticles, semiconductor devices, and the like. There is a big contribution.

[Brief description of drawings]

FIG. 1 is a process drawing showing a configuration example of the present invention, FIGS. 2 (a) to (f) are process sectional views of an embodiment of the method of the present invention, FIG. 3 is a process drawing of a conventional method, and FIG. FIGS. 5A and 5B are process sectional views of the conventional method. FIG. 5 is a plan view of the conventional method. In the figure, 1 is a mask substrate, 2 is a Cr film, 2p is a Cr film etching residue, 2q is a Cr film thickness reduction region, 2r is a Cr film chip, 3 is a positive type EB resist film, and 3L is an exposure region. 4 is an etching hole, 5 is an antistatic agent film, 6 is an etching solution, 7 is a Cr film opening pattern, 8 is a Cr mask, 51 is exposure, 52 is development, 53 is post-baking, and 54 is UV irradiation. 55 indicates antistatic agent film formation, 56 indicates drying, and 57 indicates wet etching.

Claims (1)

(57) [Claims] 1. A step of forming a resist film having an opening for etching on a film to be etched, a step of coating and forming an antistatic agent film on the surface of the resist film including the inner surface of the opening, the antistatic A wet etching method comprising a step of drying the agent film, and a step of selectively dissolving and removing the film to be etched under the opening with an etching solution using a resist film having the antistatic film as a mask. .