JP2010080477A - Method for cleaning fine pattern base - Google Patents

Abstract

It is possible to remove dust and foreign matters on the surface of a base material without damaging a fine pattern base material.
The method includes a step of coating a surface of a fine pattern of a fine pattern substrate 1 having a fine pattern with a cleaning protective film 3, a step of cleaning the cleaning protective film, and a step of removing the cleaning protective film. ing.
[Selection] Figure 4

Description

  The present invention relates to a fine pattern base material that removes dust and foreign matter adhering to the surface of a fine pattern base material, such as a stamper for optical disk manufacturing, a stamper for manufacturing a patterned magnetic recording medium, and various semiconductor wafers having a fine circuit pattern. This relates to the cleaning method.

  Conventionally, cleaning of a fine pattern base material for removing dust and foreign matters adhering to the surface of a fine pattern base material, such as a stamper for optical disk manufacturing, a stamper for manufacturing a patterned magnetic recording medium, and various semiconductor wafers having a fine circuit pattern A method is known (see, for example, Patent Document 1). In this method, after cleaning the substrate by ultrasonic cleaning, steam cleaning is performed as a final cleaning method.

Patent Document 2 discloses a technique for suppressing damage to a substrate due to cleaning. In this method, ozone is supplied into an ammonium hydroxide solution to suppress etching damage to the silicon wafer.
JP-A-4-205737 JP-A-57-204132

  However, ultrasonic cleaning does not have a sufficient foreign matter removing ability because of a cleaning method based on the effect of bubbles (cavitation) generated by ultrasonic waves. In addition, there is a problem that the standing wave of the ultrasonic wave existing in the cleaning tank hits the surface of the base material and causes damage.

  In addition, in the method by adding a damage inhibitor to chemical cleaning, since there is a cleaning agent that damages the base material itself, even if the damage can be reduced by the inhibitor, it is not possible to completely eliminate the damage. Can not.

  The present invention has been made in consideration of the above circumstances, and provides a fine pattern substrate cleaning method capable of removing dust and foreign matter on the substrate surface without damaging the fine pattern substrate. Aim to do.

  The method for cleaning a fine pattern substrate according to an aspect of the present invention includes a step of coating a surface of the fine pattern of a fine pattern substrate having a fine pattern with a cleaning protective film, a step of cleaning the cleaning protective film, And a step of removing the cleaning protective film.

  According to the present invention, dust and foreign matter on the substrate surface can be removed without damaging the fine pattern substrate.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
A fine pattern substrate cleaning method according to a first embodiment of the present invention will be described with reference to FIGS. The cleaning method of this embodiment will be described by taking a nanoimprint stamper for a patterned magnetic recording medium as an example of a fine pattern substrate.

  FIG. 1 shows a cross section of the stamper 1 before performing the cleaning method of the present embodiment. The stamper 1 is a Ni stamper produced by electroforming based on a silicon master on which a fine pattern is drawn by an electron beam drawing method. When the stamper 1 is peeled off from the silicon master, dust and foreign matter are attached to the surface. Prior to the cleaning method of the present embodiment, a pre-cleaning process at a level that does not damage the substrate surface such as pure water rinsing and dry nitrogen blowing may be performed, but foreign matters cannot be completely removed. . FIG. 2 shows a photograph of the appearance of the Ni stamper surface after performing a 2 minute pure water rinse as a pre-cleaning. FIG. 2 is a photograph taken using a micro defect VMX-3100 manufactured by Vision Cytec. It can be seen that foreign matter is adhered between the servo pattern patterns. FIG. 1 shows a state in which the foreign matter 2 is attached. The fine pattern of the stamper 1 had an uneven height of 55 nm, a recording track land width of 65 nm, a groove width of 55 nm, and a pitch of 120 nm. No foreign matter having a diameter of 60 nm or less was found.

  As described above, the cleaning method according to the present embodiment is applied to the stamper 1 to which foreign substances have adhered after pre-cleaning. 3 to 6 show the first to third steps of the cleaning method according to the present embodiment.

First, as shown in FIG. 3, a cleaning protective film 3 is formed which covers a fine pattern of the stamper 1 to which foreign matter has adhered and covers even the foreign matter. This cleaning protective film 3 only needs to have chemical resistance when the cleaning process performed in the next process is only cleaning of chemicals such as acid and alkali. However, if it is assumed that a physical cleaning method having excellent cleaning performance such as scrub cleaning and polishing tape burnishing as in the present embodiment is assumed, the cleaning protective film 3 is a material having excellent hardness and wear resistance. Is desirable. In the third step, a material that can be easily selectively removed from the base material is preferable. Examples of materials that satisfy these conditions include Ta, Ti, W, Mo, and Cr as simple metals, two or more metal compounds, and nitrogen compounds thereof. These metals have sufficient hardness and wear resistance, particularly in nitrides, and can easily form a film by reactive DC sputtering. Further, Cr can be easily removed by a Cl-based gas material, and other metals can be easily removed by fluorine-based gas material dry etching. Al ₂ O ₃ , SiO ₂ , and SiN are also desirable materials. These oxides and nitrides are sufficiently hard and have good coatability, and films can be formed by high frequency sputtering. It can be easily removed with a fluorine-based gas material.

  However, in the cleaning method of this embodiment, a desirable material for the cleaning protective film 3 is carbon. Carbon is used in hard carbon films such as amorphous carbon called diamond-like carbon (DLC film or aCH film) and tetrahedral amorphous carbon (ta-C film), and has extremely excellent properties in hardness and wear resistance. . Moreover, it is possible to increase the hardness by including any one or more of hydrogen, nitrogen, fluorine, and boron in these hard carbon films, and to provide lubricity so that cleaning can be performed more smoothly. In addition, when forming these hard carbon films, a fine pattern is generally used because a formation method having excellent coating performance, such as sputtering, plasma CVD, arc vapor deposition, and PVD (physical vapor deposition), is generally used. It becomes possible to wear enough. Also, carbon can easily react with oxygen and be removed. In this embodiment, reactive DC sputtering is performed in an atmosphere in which a nitrogen flow rate is added 5% to 15% with respect to Ar by using a rotating magnetron DC sputtering apparatus C-3010 manufactured by Canon Anelva, and nitriding is excellent in wear resistance and lubricity. Amorphous carbon (aCN) was formed.

  In addition, when the thickness of the deposited cleaning protective film is insufficient, the cleaning damage cannot be completely blocked because it does not have sufficient protection capability, causing phenomena such as scratches, scratches, and fine pattern breakage. If the film thickness is thicker than necessary, it will function as a protective film against dust and foreign matters that should be removed, and the cleaning ability will not function. Further, the film thickness to be removed increases, which is disadvantageous in view of cost and labor. In the cleaning method used in the present embodiment, a fine protective film functions as a protective film that blocks cleaning damage, and a foreign matter adhesion portion is detached together with foreign matter in the cleaning process. The film thickness is desirably 1 nm to 20 nm. When a hard amorphous carbon film is used as the cleaning protective film, the film strength and abrasion resistance are more excellent, so that a thickness of about 1 nm to 10 nm is more desirable. The film thickness of the nitrided amorphous carbon film formed in this embodiment is 5 nm.

Next, when the first step is completed, the second step is performed. In this second step, as shown in FIG. 4, the stamper 1 is installed on a rotary stage (spindle), and a polishing tape burnishing process is performed in a rotated state. Here, as the polishing tape 5, AWA 15000 manufactured by MIPOX, which is a ceramic abrasive polishing tape (count # 15000, abrasive diameter 0.3 μm, tape width 1/2 inch) is used. The polishing tape 5 is pressed with a load of 150 gf using a pressing pad 4 made of urethane sponge having a pressing area of 50 mm ² and a hardness of 25 degrees. The spindle speed is controlled so that the linear velocity is constant at 6 m / sec with respect to the polishing tape 5, and the stamper 1 is moved from the outer peripheral end of the stamper 1 to the inner peripheral end and again to the outer peripheral end at a speed of 0.1 mm / sec. Vanish the entire surface.

  By this tape burnishing process, the foreign matter 2 such as dust firmly attached to the surface of the stamper 1 is polished and cleaned together with the cleaning protective film 3 and attached to and removed from the polishing tape 5 side. What is not removed by the polishing tape 5 is blown off into the atmosphere or gently reattached onto the stamper 1. The amount of re-adhesion can be optimized in the material of the stamper 1 and the cleaning protective film 3. The polishing material is diamond abrasive grains or alumina abrasive grains, the count is # 4000 to 20000, the pressing load is 5 gf to 250 gf, Moreover, the seek speed of the polishing tape 5 in the radial direction of the stamper 1 is suppressed by optimizing the linear speed between the polishing tape 5 and the stamper 1 within 0.5 m / sec to 30 m / sec. Is possible. Only a small amount of redeposition was observed under the conditions of this embodiment. In addition, the stamper 1 itself is not scratched or scratched in spite of a strong cleaning process in which foreign matter is scraped off.

  If the foreign matter 2 is reattached to the stamper 1 regardless of the burnishing conditions, scrub cleaning may be further performed after the tape burnishing process. Scrub cleaning is typically performed by placing a stamper on a rotating stage, pressing the Bergrin brush 6 while supplying ultrapure water and a surface active agent while rotating the stamper 1 at about 500 rpm, and scrubbing. After applying for about 3 minutes and then washing with megasonic nozzle running water for about 2 minutes, spin drying may be performed at 2500 rpm for about 2 minutes (see FIG. 5). As a result, dust and foreign matters that have reattached to the stamper are washed away, and a clean stamper surface is obtained. In this embodiment, slight reattachment due to the vanish cleaning was removed by scrub cleaning, and a clean stamper surface was obtained. In the portion where the foreign matter has been removed, a concave defect is newly generated by the thickness of the cleaning protective film 2 formed.

  In this embodiment, the tape burnishing process is performed as the cleaning process. However, scrub cleaning may be performed instead of the tape burnishing process. Further, tape burnishing may be performed.

Next, a third step of removing the cleaning protective film 2 is performed. In this third step, the stamper 1 is placed in a high vacuum of 5 × 10 ⁻³ Pa or less, pure oxygen is adjusted and supplied to 0.1 Pa, RF plasma is generated and exposed for 30 seconds. By doing so, the hard carbon film which is the cleaning protective film 3 is completely removed (see FIG. 6). Thereby, a new concave defect generated by removing the foreign matter 2 in the second step is removed, and the surface of the stamper 1 having a completely clean fine pattern is obtained. This removal step only needs to be able to supply a reactant capable of removing the cleaning protective film 3 such as oxygen ion treatment in addition to the oxygen RIE treatment. In particular, techniques such as ozone treatment by UV (ultraviolet) irradiation in the atmosphere or oxygen atmosphere, or heat treatment (annealing) in the oxygen atmosphere may be selected as a simpler technique than removing carbon. However, these processes need to be performed in a clean environment so that new dust and foreign substances do not adhere. Further, the step of removing the cleaning protective film may be performed using any of plasma treatment, UV treatment, and annealing treatment in an atmosphere of oxygen gas, fluorine-based gas, or a mixed gas thereof. .

  FIG. 7 shows the number of foreign matters on the surface of the stamper 1 before and after the cleaning method of this embodiment is applied to the five stampers. The confirmation of the foreign matter is performed by a micro defect visualization inspection apparatus Micromax VMX-3100 manufactured by Vision Cytec. Micromax can easily visualize foreign matters and defects of 20 nm or more. The number of foreign matters was measured over the entire surface of a nanoimprint stamper for a hard disk substrate having a diameter of 48 mm. As can be seen from FIG. 7, by performing the cleaning method of the present embodiment, dust and foreign matter on the surface of the substrate 1 can be removed without damaging the stamper (fine pattern substrate) 1.

  FIG. 8 shows a photograph of foreign matter observed with Micromax of the stamper 1 subjected to the third step according to the cleaning method of the present embodiment. In the photograph of FIG. 2 before cleaning, a large number of foreign matters and dust are observed as white spots, but it can be seen that the foreign matters are completely removed by using the cleaning method of this embodiment. Further, FIG. 9 shows a micromax photograph of the stamper surface after performing only the cleaning process without providing the cleaning protective film in order to evaluate the damage blocking ability of the cleaning protective film 3. It can be seen that scratches due to the polishing tape are intensely generated on the entire surface of the stamper, and the pattern itself has disappeared.

  As described above, according to the present embodiment, dust and foreign matters on the surface of the substrate can be removed without damaging the fine pattern substrate.

(Second Embodiment)
Next, a cleaning method according to the second embodiment of the present invention will be described. The cleaning method of this embodiment uses a Si master for producing this stamper instead of the stamper described in the first embodiment as a fine pattern substrate in the cleaning method of the first embodiment. .

  Even if the fine pattern base material is a Si master, dust and foreign matters on the surface of the base material can be removed without damaging the fine pattern base material as in the first embodiment.

  As described above, the cleaning method according to each embodiment of the present invention includes the first step of forming a cleaning protective film for blocking damage caused by cleaning on the surface of the fine pattern substrate to be cleaned, and the fine pattern substrate itself. Has a second step of applying a cleaning method capable of damaging but having a sufficient foreign matter removing ability, and a third step of removing the cleaning protective film.

  In the above-described cleaning method, the cleaning protective film formed in the first step is formed so as to completely cover the fine uneven pattern on the surface of the fine pattern substrate and to cover part or all of the foreign matter. In the second step, scrub cleaning that can sufficiently remove dust, foreign matter, and the like and scrubbing with an abrasive are performed to completely remove the foreign matter. At this time, the cleaning damage to the fine pattern base material itself is blocked by the cleaning protective film, so that no scratches or disappearance of the fine pattern occurs. The portion from which the foreign matter has been removed also has the cleaning protective film detached at the same time, and new irregularities are generated between the portion where the protective film remains. However, when the cleaning protective film is removed by the third step, the unevenness disappears, and only the fine pattern inherent to the substrate remains.

  As described above, according to each embodiment of the present invention, it is possible to remove deposits such as dust and foreign matters without damaging the surface of the fine pattern substrate.

Sectional drawing of the stamper before performing the washing | cleaning method by 1st Embodiment of this invention. The photograph which shows the foreign material observation result of the stamper before performing the washing | cleaning method of 1st Embodiment. Sectional drawing explaining the 1st process of 1st Embodiment. Sectional drawing explaining the 2nd process of 1st Embodiment. Sectional drawing explaining the 2nd process of 1st Embodiment. Sectional drawing of the stamper after giving the 3rd process of 1st Embodiment. The figure which shows the dust on the stamper before and behind performing the cleaning method of 1st Embodiment, and the number of foreign materials. The photograph which shows the foreign material observation result of the stamper after performing the washing | cleaning method of 1st Embodiment. The photograph which shows the observation result of the foreign material and damage | wound of a stamper after wash | cleaning without using a washing | cleaning protective film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stamper 2 Foreign material 3 Cleaning protective film 4 Pressing pad 5 Polishing tape 6 Berglin brush

Claims (5)

Coating the surface of the fine pattern of the fine pattern substrate having a fine pattern with a cleaning protective film;
Cleaning the cleaning protective film;
Removing the cleaning protective film;
A method for cleaning a fine pattern substrate, comprising:   2. The fine pattern substrate cleaning method according to claim 1, wherein the cleaning step includes at least one cleaning process of scrub cleaning or polishing cleaning with an abrasive.   As the cleaning protective film, one or more of Ta, Ti, W, Mo, Cr, Al, Si, and C elements or compounds, and at least one of nitrogen, hydrogen, boron, and fluorine are included. The method for producing a fine pattern base material according to claim 1 or 2, wherein any one of the compounds to which is added is used.   The step of coating the cleaning protective film is performed by sputtering, vapor deposition, PVD method (physical vapor deposition method), or CVD method (chemical vapor deposition method). It is 1 nm-20 nm, The manufacturing method of the fine pattern base material of Claim 3 characterized by the above-mentioned.   2. The step of removing the cleaning protective film uses any one of plasma, UV treatment, and annealing treatment in an atmosphere of oxygen gas, fluorine-based gas, or a mixed gas thereof. 5. The method for cleaning a fine pattern substrate according to any one of 4 to 4.