JPS5821739A - Manufacture of photomask - Google Patents

Abstract

PURPOSE:To obtain a photomask having a fine and accurate mask pattern faithful to a resist pattern by treating a mask substrate with an inorg. alkali soln. prior to an etching stage so as to enable uniform etching independently of a resist scum layer remaining on the mask substrate. CONSTITUTION:A mask substrate is coated with an electron beam resist polymer contg. halogen represented by the general formula such as polytrifluoroethyl alpha-chloroacrylate, and the coated substrate is pattern wise exposed to electron beams and developed. The mask substrate is then treated with an aqueous soln. of inorg. metallic salt prior to chemical etching. Thus, defects during chemical etching due to a resist scum layer remaining on the substrate after development can be eliminated thoroughly, and the resulting photomask has a small pattern conversion difference and is faithful to the resist pattern, fine and accurate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for manufacturing molds such as 7 O) w star J manufacturing method KIIL, and further details L(t!, resist pattern KlIA 夷, mold Ill
Rishima accuracy is 1! 7 Otostar O manufacturing method with star pattern tube In particular, photomask manufacturing technology using electron beam lithography is being actively studied because it can easily and quickly form fine masks and full turns. There is.

Conventionally, the following method has been adopted as a method for manufacturing a photomask using an electron beam. That is, first, electron beam resis) I! ! Cover. Then, Fl+ of the Lenost membrane
One electron beam is drawn in a t-' turn shape. Furthermore, the solvent rc was added to the electron beam irradiated area and unirradiated area of the resist film.
A soluble O lead tube is used to perform a current treatment, and only one area is removed by 't-development to form a Lennost pattern tube.

Then, the obtained resist/temple turn is set as SaSa,
The exposed shielding film layer is etched with an etching solution to form a desired mask pattern.

In the above method, various organic polymer materials are used as materials for electron beam resist theory, for example,
I dilid fv methyl memetarylate and negative! 104
Ridarisigil Meta! A typical example is the Silate group. In recent years, various resist materials have been proposed that improve the characteristics of these resist materials, particularly sensitivity, resolution, and dry etching resistance. For example, special M@6
B-18638 discloses a cloudy resist material with significantly improved sensitivity of polymethyl methacrylate.
α-halon substituted acrylic acid fluorinated X J f k
Examples of O homopolymers and copolymers with other vinyl polymers are disclosed.

Regisji Materials Co., Ltd., after energizing and dissolving it under appropriate conditions, it can be made into a TM cloth solution by, for example, the spin cord method.
It is coated on the substrate to a thickness of α2 to 21 nsO. Then,
Heat treatment (7"9 bake) is performed for the purpose of removing the solvent and improving adhesion to the substrate. After this process,
In the resist pattern formed by electron beam pattern brass-1** ring release, the resist film to be dissolved and removed is formed into an extremely thin organic film (hereinafter referred to as resist scum) on the exposed surface area of the mask base material. There is a tendency for the name to remain as a layer. Therefore, when wet etching/dying the mask base material with an acidic etching solution using the resist pattern as a protective film, etching is almost impossible due to the presence of the resist scum layer, or etching is difficult. Even when the process progresses, there are drawbacks such as uneven no-f turns and edge roughness.

In particular, the resist material containing a halogen element as disclosed in the above-mentioned Japanese Patent Laid-Open No. 55-18638 is extremely hydrophobic and has good acid resistance. Therefore, in an etching process using an acidic etching liquid such as Wk cerium ammonium nitric acid, compared to a resist film made of something like polymethyl methacrylate,
The remaining resist scum layer, which is composed of illimer containing the element Heron, has a high degree of interference with etching, and may not only result in non-uniform etching but also cause mask defects. . For this reason, it is often possible to reduce the hydrophobic effect by adding a surfactant to the etching solution. The disadvantage is that it is difficult to obtain an af turn with an accuracy of 1.

In order to avoid such an influence on the five layers of the resin layer, prior to the etching process, plasma ashing using an oxygen gas atmosphere is performed.
A method of removing the μ cam layer has been adopted.

Although this method is extremely effective, the rate of plasma conversion of the resist scum layer at the mother turn opening (exposed part of the mask layer) varies depending on the resist material used. For materials with relatively high oxygen plasma resistance, such as membranes, it is necessary to set severe plasma conditions such as increasing the height of the output tube and subjecting the material to a long period of exposure. However, under these conditions, the resist layer is significantly damaged at the fine resist/f-turn edge, and the deviation from the predetermined dimension (9-turn conversion difference) becomes large. There is a drawback that it is difficult to obtain a mask/mother turn with high accuracy.

In addition, as another method to avoid the influence of the resist scum layer, there is a method of directly dry etching the mask substrate tube using a 41$ tube of Xiyang Hwatroch (J-El@etroch@m
.

11oc,, 126.1749. (197G)) has been adopted. However, this method has disadvantages in that the equipment is expensive, and it is not always easy to process a large number of mask substrates in a short period of time (and it lacks simplicity in practical production.

The present invention has been successfully developed as a solution to overlaying a nine-fault tube, and its purpose is to enable uniform etching without being affected by the resist scum layer remaining on the mask substrate, and to improve the resist pattern. To provide a method for manufacturing a photomask having a fine and highly accurate mask pattern that is faithful to the above.
As a result of extensive research, we discovered that the objective could be achieved by treating the i-sufficient substrate tube with an inorganic alkaline aqueous solution prior to Etching S, and completed this book. The photomaster O manufacturing method of the invention includes a first step of coating an electron beam resist dreamer containing a halogen element on a mask substrate, and drawing a desired portion of the resist layer in a 79-turn shape with a tube electron beam. Step I2: Step 3 of applying Asahi salt to the pattern layer, and mask substrate I exposed using the obtained resist pattern as a protective film.
! A method for manufacturing a photomask comprising a fourth step of performing a one-sided tube chemical etching treatment, characterized by including a step of treating the mask substrate with an inorganic alkali metal wave between the third and fourth steps. It is something.

In the following, the invention will be explained in more detail.

The treatment with the inorganic alkali metal solution of the present invention is carried out, for example, by immersing the entire substrate in the solution, or by spraying the inorganic alkali solution I onto the substrate. The escape time varies depending on the type of inorganic alkali solution and the type of inorganic alkali solution, and can be selected as appropriate.

The inorganic alkaline solution used in the present invention includes alkali metal hydroxides, carbonates, phosphates, phosphorus hydroxides,
and metasilicates], an aqueous solution of one or more selected compounds is suitable. Examples of such compounds include sodium hydroxide, potassium hydroxide, sodium legate, sodium phosphate, potassium potassium phosphate, sodium hydrogen phosphate, and sodium metasilicate.

The inorganic alkaline solution of the present invention has a pH of 8 to 140, preferably a pH of 10-13.

Furthermore, depending on the inorganic alkaline flNiR lamp of the present invention and the membership fee, a buffer bath solution may be added. Such buffer stations include, for example, sodium tetraborate/hydrochloric acid system, sodium phosphorus hydroxide/sodium hydroxide system, sodium tetraborate/sodium carbonate system, or sodium carbonate/*Ii sodium hydrogen system. Various types can be selected and used depending on the purpose.

The substrates treated with these inorganic alkali #1IEK and J) #a processes are preferably subsequently washed with water in order to suppress deterioration of the acidic etching solution.

Note that the method of the present invention is based on the resist scum layer rC of the mask substrate.
On the other hand, is the ashing process caused by the pyrolytic f-zuma? It may be applied after the application. It is not necessary to carry out the fdsma ashing treatment until all of the resist scum layer is removed.The electron beam renost polymer used in the present invention has the following general formula (wherein, X is a methyl group or fluorine, (represents chlorine or odor), and R represents an alkyl group or alkoxyalkyl group Tt having a vertical number of 1 to 10, in which at least 41 or more hydrogen atoms have been replaced with a halodane atom. It is preferable to have the following. Such polymers include, for example, trifluoroethyl α-chloroacrylate, trichloromethyl methacrylate, zochlorderovir methacrylate, tritalol isoderovir methacrylate, trichlortyl methacrylate,
Trik. luisoderovir α-chloro acrylate, tetrafluoromychlor acrylate, trifluorogutyl α-thalol acrylate, trifluorisozolohyl α-fluoroacrylate, octafluoropentyl α
Examples include homopolymers or copolymers such as -1g more acrylate, or copolymers of these, vinyl monomers, and O. Examples of the vinyl monomer include methyl methacrylate, methyl methacrylate, α-cyanoacrylate, interene, and the like.

If the method of the present invention is used, the chemical etching caused by the resist scum layer that remains after development 4611 can be avoided.
It is possible to eliminate the drawbacks of the following in one meal. Furthermore, the obtained photomask has a small p4 turn conversion difference, is faithful to the resist I pattern, and is moldy and highly accurate.

Although it is not clear why the method of the present invention makes it possible to manufacture a uniform and highly accurate photomask when using the above-mentioned halogen element-containing resist)/remer, the following can be considered. I can do it.

That is, in order for etching to proceed uniformly, it is necessary that the four-turn opening be wetted with the etching solution. If the wetting is uniform, the etching solution will evenly contact the pattern openings! The chromium layer, which is a foam layer, is oxidized and etching progresses. Resist polymers containing halogen elements have extremely poor wettability with water, which inherently makes uniform etching difficult to proceed.

Such polymers have rc (critical surface tension), which is a measure of wettability, in the range of 20 to 30 dyn@/am! lK
On the other hand, the surface tension of acidic etching solution is 50-7
It is in the range of 0 dyn*z-. Therefore, if the rennos scum layer remains, wettability becomes extremely poor.
As a result, etching is not uniform. On the other hand, when the surface of the resist scum layer made of a halogen element-containing polymer is treated with an inorganic alkaline solution after development, the 27Je reamer on top is easily hydrolyzed by the inorganic alkaline solution. , a nuclear I remer surface rMKII4 aqueous group will be added, and rc will change drastically to 70-80 dy
ne/cm. It is thought that this is accompanied by a significant improvement in the wettability of the polymer surface, making it possible to uniformly and highly etching the mask. It is considered that the treatment with an inorganic alkaline solution according to the method of the present invention has an extremely effective effect on making the polymer surface hydrophilic.

In the following, the present invention will be explained in more detail by way of example.

Example 1 On a mask substrate consisting of two layers of chromium and chromium oxide,
r trifluoroethyl α-chloroacrylate spin code method, approx. 5. After setting it to the thickness of GOOA,
We held a Gribeke meeting for 1 hour at 180C. A dose of SsC is applied to a desired portion of this resist film using an electron beam device.
/d, 9 turns were drawn at an accelerating voltage of 2°KV, and a mixture of methyl isolyl methyl ketone, isozoro, and ethanol was used. Mask group I [
[, Sodium metasilicate-sodium hydrogen phosphate water f
The mask was immersed in PI (13) for 60 seconds at 1IVr, and after thorough washing with water, it was etched for 50 seconds with an etching solution containing cerium ammonium nitrate as the main component to form a mask mother turn. The photomask had no incomplete etching or etching roughness, and had a very small pattern conversion difference.

For comparison with the present example, etch 4. Upon observation of the photomask obtained by applying the NDA J6 field, it was found that there were many spots where etching had not progressed at all.

Implementation Ga 2 A mask substrate with a resist mask prepared in the same manner as in Example 1 was treated with captive oxygen plasma for 1 minute, ■ treated with JilP plasma for 5 minutes, and C) After being exposed to H1tf plasma for 1 minute, each sample was treated for 30 seconds in a sodium hydrogen phosphate-sodium metasilicate aqueous solution (pH 13). When these tubes were subjected to etching of the mask layer under the same conditions as in Example 1, the photomask with the circular ring was formed.
Many areas where the etching was incomplete were introduced. Also, (B
) The line and etching progressed almost uniformly on the photomask that had undergone the above process (one spot was completely etched), but the pattern dimensions were far from the predetermined value. On the other hand, photomasks processed according to the present invention are etched uniformly, and the difference in arm turn conversion is almost #1, making it possible to obtain mask patterns with extremely high precision. Ta.

As is clear from the above, according to the VC1 method of the present invention, it is possible to perform etching without being affected by the resist scum layer after the current etching process. It is faithful, minute, and highly accurate. Also, is the conversion difference small and high resolution? Because of this, when used in the manufacture of semiconductor integrated circuits, etc.

It is extremely useful.

Claims (3)

[Claims] (1) Electron beam resist poly! containing /-arn element is placed on the mask substrate. The first step is to coat the resist layer with a pattern of VC- using an electron beam.
The second step is to image, and the third step is to apply development I6 process to the nucleated film F layer.
The process and the obtained resist cutter are preserved, and the surface of the mask substrate to be printed is chemically etched! A
A method for manufacturing a photomask comprising a fourth step of treating the mask substrate with an inorganic alkaline solution between the third and fourth steps. (2) - The alkali solution contains one or more selected alkali metal hydroxides, carbonates, phosphates, hydrogen phosphates, and metasilicates. The compound water is 11M. A method for manufacturing a photomask according to claim 1. (3) The method for producing 7 otomask OIt according to claim 1, wherein the inorganic alkali number is in the pH range of 8 to 140. (41 electron beam resist mesimer has the general formula (wherein,
X is a methyl group, fluorine, chlorine, or bromine; 7 Otomaster OII manufacturing method according to claim 1, which has the structure 1 represented by O).