JP2006320807A - Method for forming coating film on substrate having difference in level - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a coating film having a high conformal property on a substrate having a difference in level. <P>SOLUTION: The method for forming a coating film having high conformal property on the substrate having a difference in level comprises: a first step of forming the coating film of a composition for forming the coating film on the substrate having the difference in level by a spin coat method; a second step of heating the substrate having the coating film to harden a lower layer portion of the coating film; and a third step of removing an upper layer portion of the coating film by using a solvent. The substrate having the difference in level is a semiconductor substrate having the difference of 0.1-1 height/width value in level. The spin coat method at the first step is carried out for 30-300 seconds at 500-5,000 (revolutions per minute) revolving speed. The heating at the second step is carried out for 10-300 seconds at 50-150°C. At the third step, the solvent is applied onto the coating film and after 1-300 seconds have passed, the upper layer portion of the coating film is removed by rotating the substrate for 30-300 seconds at 500-5,000 (revolutions per minute) revolving speed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for forming a coating film on a substrate having a step used in the manufacture of a semiconductor device, a display, an image sensor, and the like. Specifically, the present invention relates to a method for forming a highly conformal coating film on a substrate having a step by spin coating using a thermosetting coating film forming composition.

  Conventionally, a film forming method by spin coating has been performed in the manufacture of various electronic devices. Spin coating uses a centrifugal force by applying a solution of a film-forming material onto a semiconductor substrate such as a silicon wafer, a transparent electrode, a substrate after pattern formation, and a flat display substrate, and rotating the substrate at high speed. Thus, a film forming method for forming a coating film. In addition, since a highly uniform film can be formed at a low cost in a short time, it is a widely used film forming method.

  In addition, a resist for semiconductor, an antireflection film for lithography, a liquid crystal, a liquid crystal alignment film, an EL film, an antireflection film for display, a photosensitive film, an insulating film, and a conductive film are formed on the substrate by spin coating. Can do. When a material having heat curing characteristics is used for the film formation, the substrate is heated by a hot plate or the like after the spin coating, so that a thermosetting coating having solvent resistance is formed on the substrate. It is known that a covering film can be formed.

  However, with spin coating, it is possible to form a film with high uniformity (thickness uniformity) on a substrate with a flat surface. However, with a substrate with steps, the solution of the film forming material There is a problem in that a film having the same film thickness (uniformity of film thickness) cannot be formed by flowing into the recess from the step protrusion by flow.

  On the other hand, a film forming method using a vapor deposition method called CVD (chemical vapor deposition) or PVD (physical vapor deposition) can form a film having a uniform thickness on a substrate having a step. It is known (see, for example, Patent Document 1). However, the film formation by the vapor deposition method has a problem of low throughput and high cost.

  In recent years, film thickness control has become an important factor in creating electronic devices. In addition, when a film having a uniform film thickness, that is, a film having a high conformal property cannot be formed, there is a material in which a target physical property of the film is lowered (for example, see Patent Document 2). Therefore, it is desired that a highly conformal film can be formed even on a stepped substrate. In particular, it is desired that a highly conformal film can be formed on a substrate having a step by spin coating which is superior in cost and handling properties as compared with vapor deposition.

For example, when spin coating is used, by changing the material composition such as the viscosity and shrinkage rate of the chemical solution, the flow is suppressed, or the bias between the convex and concave portions is reduced to improve the uniformity of the film thickness on the substrate. A method has been proposed (see, for example, Patent Documents 3 to 6). However, changing the material composition to improve the uniformity of the film thickness on the substrate has a problem that other physical properties must be changed at the same time. For this reason, a new film forming method by spin coating has been desired.
JP-A-8-64492 (Claims) Japanese Patent Laid-Open No. 11-8248 (Claims) Japanese Patent Application No. 4-162093 (Claims) JP 10-228113 A (Claims) Japanese Patent Laid-Open No. 7-230164 (Claims) JP-T 2003-531252 (Claims)

  An object of the present invention is to provide a method for forming a highly conformal film on a substrate having a step by spin coating using a composition for forming a coating film.

As a first aspect, the present invention provides a first step of forming a coating film of a composition for forming a coating film on a substrate having a step by spin coating, and heating the substrate having the coating film to thereby apply the coating A method of forming a highly conformal coating film on a substrate having a step including a second step of curing the lower layer portion of the film and a third step of removing the upper layer portion of the coating film with a solvent;
As a second aspect, the method for forming a coating film according to the first aspect, wherein the stepped substrate is a semiconductor substrate having a height / width value of 0.1 to 1,
As a third aspect, the method for forming a coating film according to the first aspect or the second aspect, wherein the spin coating of the first aspect is performed at a rotational speed of 500 to 5000 (times / minute) and a rotational time of 30 to 300 seconds. ,
As a fourth aspect, the method of forming a coating film according to any one of the first aspect to the third aspect, wherein the heating in the second step is performed at a temperature of 50 to 150 ° C. for a time of 10 to 300 seconds,
As a fifth aspect, in the third step, a solvent is applied onto the coating film, and after 1 to 300 seconds have elapsed, the substrate is rotated at a rotational speed of 500 to 5000 (times / minute) and at a rotational time of 30 to 300 seconds. A method for forming a coating film according to any one of the first to fourth aspects,
As a sixth aspect, the coating film forming composition is an antireflective film forming composition for forming an antireflective film used in a lithography process for manufacturing a semiconductor device. A method for forming a coating film according to any one of the above,
As a seventh aspect, the method for forming a coating film according to the sixth aspect, wherein the antireflection film-forming composition is a composition containing at least a polymer, a crosslinkable compound, and a crosslinking catalyst,
As an eighth aspect, the method for forming a coating film according to any one of the first aspect to the seventh aspect, further including a fourth step of heating the substrate after the third step, and a ninth aspect The method for forming a coating film according to the eighth aspect, wherein the heating in the fourth step is performed at a temperature of 100 to 350 ° C. for a time of 10 to 300 seconds.

  In the present invention, any coating film forming composition can be used as long as it is a resin composition that is cured by thermal crosslinking. By applying the coating film-forming composition on a substrate having a step (ie, unevenness) and heating the substrate, heat curing proceeds from the portion near the substrate along the substrate that is heated through the substrate, and the whole is cured. Before heating, stop heating and then contact the substrate with the coating film-forming composition in contact with the solvent, so that the uncured part is removed by the solvent, so apply with a uniform film thickness along the step. It is thought that a film is formed.

  Such a substrate coated with a coating film with a uniform film thickness can be applied to various applications by selecting the coating film forming composition. For example, the coating film forming composition is a semiconductor. A resist composition for manufacturing, an antireflection film for lithography for semiconductor manufacturing, a liquid crystal, a liquid crystal alignment film, an EL film, an antireflection film for display, a photosensitive film, an insulating film, a conductive film, and the like can be formed. .

  A substrate having a highly conformal film obtained with a uniform film thickness can minimize the reflectance at the interface between the film and the substrate, and has excellent optical characteristics.

  The present invention provides a first step of applying a coating film forming composition by spin coating on a stepped substrate to form a coating film, and heating the substrate having the coating film to form a lower layer of the coating film. This is a method for forming a highly conformal coating film, including a second step of curing the portion and a third step of removing the upper layer portion of the coating film with a solvent.

  In FIG. 1, (a) is a substrate, (b) is the height of the step, and (c) is a coating film. (D) is the film thickness of the minimum portion of the coating film concave portion, (e) is the film thickness of the vertex portion of the coating film convex portion, (f) the width of the step convex portion, and (g) the step concave portion. Width.

  And the conformality is calculated | required by following Formula.

Conformal property (%) = [1− (film thickness of minimum portion of concave portion (d) −film thickness of top portion of convex portion (e)) / height of step (b)] × 100
Here, the highly conformal coating film means that there is no difference in film thickness between the convex part and the concave part of the step when the film is coated on the substrate having the step (see FIG. 1). ). That is, a highly conformal coating film obtained from the conformal formula has a conformal property of 50% or more, preferably 70% or more, more preferably 90% or more.

  Hereinafter, the method for forming a coating film of the present invention will be described in detail.

  The substrate used in the first step in the method for forming a coating film of the present invention is not particularly limited as long as it has a step. For example, a semiconductor substrate for manufacturing a semiconductor device such as a silicon wafer, a display substrate such as a glass substrate or an ITO electrode, and the like can be given. Further, the level difference depends on the use application of each substrate, and is not particularly limited as long as it can be used for the application. As the step, for example, in FIG. 1, the height (b) / width (g) value is 0.1 to 1.0, or 0.2 to 0.8, or 0.3 to 0.5. is there.

  Such a substrate is installed in a device used for spin coating, for example, a spin coater for manufacturing a semiconductor device, a coater developer for manufacturing a semiconductor device, a high-speed spin coater for a thin film, a bench top type spin coater, and the like. And the composition for coating film formation is dripped on a board | substrate.

  The dropping can be performed while the substrate is stationary. It is also possible to carry out the process while the substrate is rotating at a speed of 10 to 3000 revolutions per minute, for example. Although there is no restriction | limiting in particular as dropping time, As time from dripping start to completion | finish, it is 0.5 to 30 second, for example.

  The composition for forming a coating film to be used is not particularly limited as long as it is a composition that can be cured by heat to form a coating film. The composition to be used is appropriately selected depending on the application of the substrate to be used. For example, a composition for forming a coating film such as an antireflection film, a photoresist film, a low dielectric material film, a hard mask film, and a gap fill film used in a lithography process for manufacturing a semiconductor device can be given. Moreover, for example, a composition for forming a coating film such as a liquid crystal alignment film, an antistatic film, an antireflection film, a polarizing film, and a pixel separation insulating film for a liquid crystal display device can be given.

  The dripping amount of the composition for forming a coating film depends on the size and use of the substrate to be used, the required film thickness of the coating film, etc. There is no particular limitation as long as the step protrusion can be sufficiently covered. For example, a composition (antireflection film forming composition) for forming an antireflection film used in a lithography process as a coating film forming composition is dropped on a substrate having a diameter of 200 mm used for manufacturing a semiconductor device. In this case, the dripping amount is, for example, 0.5 ml to 10 ml.

  After completion of the dropping, a coating film of the composition for forming a coating film is formed on the substrate by spin coating. The spin coating can be appropriately selected from the range of a rotation speed of 500 to 5000 (times / minute) and a rotation time of 30 to 300 seconds in consideration of the use of the substrate and the coating film. By carrying out under such conditions, the dropped coating film forming composition spreads on the substrate by centrifugal force, and a coating film is formed. Further, during this time, the excessive coating film forming composition, the solvent in the coating film forming composition, and the like are removed from the substrate.

  As a film thickness of the coating film formed, it is 0.01-10 micrometers, for example, Preferably it is 0.1-1 micrometer. The film thickness is appropriately selected depending on the application. The film thickness of the coating film can be adjusted by changing the type of the coating film forming composition, the dropping amount, and the spin coating conditions.

  In the second step, the substrate having the coating film on the surface obtained by the above step is heated. Heating can be performed using a hot plate apparatus such as an electrothermal hot plate or an IR hot plate. By using these apparatuses, the substrate is heated from the lower part (opposite the surface having the coating film).

  Since the coating film on the surface of the substrate has a property of being cured by heat, it is cured by heating and hardly soluble in the solvent. And since the heating is performed from the lower part of a board | substrate, it is thought that hardening of a coating film starts from the lower part (side near the board | substrate surface). Further, the curing of the coating film proceeds in accordance with the distance from the substrate surface, and it is considered that the same degree of curing occurs in a portion where the distance from the substrate surface is equal. That is, it is considered that the coating film is cured along the surface of the substrate having a step with the same thickness from the substrate surface as the substrate is heated.

  Then, the heating of the substrate is selected under conditions that allow the lower layer portion of the coating film to be cured, that is, a condition that causes the coating film not to be completely cured by heat and an uncured portion remains in the upper layer portion. Done. The degree of curing of the lower layer portion of the coating film is such that curing occurs at a portion of 5% or more with respect to the thickness of the coating film in the thickness direction from the portion in contact with the substrate. %, Preferably 10-80%, more preferably 30-70%, most preferably 50-60%.

Such heating conditions largely depend on the type of coating film forming composition used. Therefore, the heating conditions are individually determined depending on the type of the composition for forming a coating film to be used, and are suitably selected from, for example, a heating temperature of 50 to 150 ° C. and a time of 10 to 300 seconds.
In the third step, the uncured upper layer portion of the coating film is removed with a solvent. As described above, in the second step, the lower layer portion of the coating film on the substrate is thermally cured, but since the upper layer portion is uncured, the uncured upper layer portion is removed by the solvent. And since thermosetting occurs in the lower layer portion of the coating film at the same distance from the substrate surface, the uncured upper layer portion is removed, so that the thickness of the film is almost the same along the substrate surface. A thermally cured film (lower layer part of the coating film) remains. That is, a highly uniform coating film is formed on a substrate having a step.

  The solvent used is not particularly limited as long as the uncured coating film upper layer portion can be removed. The organic solvent used for the composition for forming a coating film can be used. Examples of the solvent include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, methyl cellosolve acetate, ethyl cellosolve acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol propyl. Ether acetate, toluene, xylene, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethyl 2-hydroxypropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methylbutanoate , Methyl 3-methoxypropionate, 3 Methoxy ethyl propionate, ethyl 3-ethoxypropionate, methyl 3-ethoxypropionate, methyl pyruvate, ethyl pyruvate, ethyl acetate, butyl acetate, ethyl lactate, and can be exemplified butyl lactate and the like. These solvents can be used alone or in combination of two or more.

  The removal of the uncured upper layer portion with a solvent can be performed by various methods. For example, it can be performed by immersing the substrate having the coating film in a solvent.

  After removing the upper layer portion with the solvent, the substrate having the coating film can be dried by an appropriate method.

  The removal of the uncured upper layer portion with a solvent can be performed using a spin coater. The substrate after the second step is set on a spin coater, and a solvent is dropped so as to cover the coating film. The amount of the solvent may be an amount that can cover the entire coating film. For example, after leaving in this state for 1 to 300 seconds, removal can be performed by rotating at a rotation speed of 500 to 5000 (times / minute) for a rotation time of 30 to 300 seconds. The dripping and rotation of the solvent can be repeated as necessary. Moreover, it can also serve as drying by selecting a rotation speed and rotation time suitably. It can also be carried out by dropping the solvent on the substrate placed on the spin coater while rotating the substrate at a speed of 10 to 500 revolutions per minute.

  In the method of the present invention, if necessary, a fourth step of heating the substrate having the coating film can be added after the third step. Heating can be performed under conditions appropriately selected from the range of a temperature of 100 to 350 ° C. and a time of 10 to 300 seconds. By this heating step, the substrate having the coating film can be dried. In addition, the coating film can be further cured by heat.

  The coating film forming method of the present invention is suitable for forming an antireflection film used in a lithography process for manufacturing a semiconductor device with high conformality on a semiconductor substrate having a step.

  There is no restriction | limiting in particular in the anti-reflective film forming composition used for forming an anti-reflective film. An existing heat-curable composition for forming an antireflection film can be used.

As the antireflection film-forming composition, a composition containing at least a polymer, a crosslinkable compound, a crosslinking catalyst, and a solvent is preferably used. This composition contains a crosslinkable compound and is a curable composition by heat.
The polymer is a resin having a crosslinking site such as a hydroxyl group, and examples thereof include acrylic resins, novolac resins, phenol resins, polyester resins, natural polymer resins, melamine resins, and silicon resins. Specifically, a polymer having a site that absorbs light used for exposure of a photoresist is used. For example, the polymer which has aromatic hydrocarbon rings, such as a benzene ring, a naphthalene ring, and an anthracene ring, as a site | part which absorbs light is mentioned. Examples of the site that absorbs light include polymers having a hetero ring such as a quinoline ring, a thiophene ring, a triazine trione ring, a pyrimidine trione ring, a furan ring, and a pyridine ring. As the polymer, polymers having these ring structures in the main chain can be used, and polymers having these ring structures in the side chains can be used. Examples of the polymer include structures having an aromatic hydrocarbon ring such as phenyl methacrylate, benzyl acrylate, benzyl methacrylate, styrene, 1-vinylnaltalene, 1-naphthyl methacrylate, 9-anthryl methacrylate, and 9-anthrylmethyl methacrylate. Is a polymer having a repeating unit structure.

Examples of the crosslinkable compound include one to six, or two to two nitrogen atoms substituted with an alkoxymethyl group such as a methylol group or a methoxymethyl group, an ethoxymethyl group, a butoxymethyl group, and a hexyloxymethyl group. The nitrogen-containing compound which has four is mentioned. Specifically, hexamethoxymethyl melamine, tetramethoxymethyl benzoguanamine, 1,3,4,6-tetrakis (methoxymethyl) glycoluril, 1,3,4,6-tetrakis (butoxymethyl) glycoluril, 1,3 , 4,6-tetrakis (hydroxymethyl) glycoluril, 1,3-bis (hydroxymethyl) urea, 1,1,3,3-tetrakis (butoxymethyl) urea, 1,1,3,3-tetrakis (methoxy) Nitrogen-containing compounds such as methyl) urea, 1,3-bis (hydroxymethyl) -4,5-dihydroxy-2-imidazolinone, and 1,3-bis (methoxymethyl) -4,5-dimethoxy-2-imidazolinone Compounds. The crosslinkable compound can be used at a ratio of 0.1 to 40 parts by weight with respect to 100 parts by weight of the polymer.
Examples of the crosslinking catalyst include acid compounds such as p-toluenesulfonic acid, trifluoromethanesulfonic acid, pyridinium-p-toluenesulfonic acid, salicylic acid, camphorsulfonic acid, sulfosalicylic acid, 4-chlorobenzenesulfonic acid, 4-hydroxybenzene. Mention of sulfonic acid compounds such as benzenesulfonic acid, benzenedisulfonic acid, 1-naphthalenesulfonic acid and pyridinium-1-naphthalenesulfonic acid, and carboxylic acid compounds such as salicylic acid, sulfosalicylic acid, citric acid, benzoic acid and hydroxybenzoic acid Can do. The acid can be used at a ratio of 0.01 to 10 parts by weight with respect to 100 parts by weight of the polymer.

And in an anti-reflective film forming composition, it can have 1 to 40 weight% as solid content.
And the crosslinking start temperature, ie, the temperature at which thermosetting starts, can be easily adjusted by changing the kind and amount of the crosslinkable compound and the crosslinking catalyst.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited by this.

Example 1
A silicon wafer substrate having a diameter of 8 inches and having a step height of 200 nm, a width of the recess of 600 nm, and a step where the protrusion and the recess exist at a ratio of 1: 1 was placed on a spin coater. Then, with the substrate stationary, an antireflection film-forming composition (acrylic resin as a polymer, tetramethoxymethylmelamine as a crosslinkable compound, paratoluenesulfonic acid and pyridinium-paratoluenesulfonic acid as a crosslinking catalyst, and ethyl lactate as a solvent. And 100 parts by weight of acrylic resin, 20 parts by weight of tetramethoxymethylmelamine, 2 parts by weight of paratoluenesulfonic acid and pyridinium-paratoluenesulfonic acid, and the solid content is 5% by weight.) About 1 ml Was dripped. After the dropping, spin coating (rotation speed 2500 (times / min), rotation time 60 seconds) was performed to form a coating film on the substrate. Next, the substrate having the coating film was heated on a hot plate at 80 ° C. for 60 seconds to form a coating film. About 10 ml of ethyl lactate as a solvent was dropped after the coating was formed and left for 60 seconds, followed by spin coating (rotation speed 3500 (times / minute), rotation time 30 seconds), and ethyl lactate was spin-dried. Further, the substrate having the coating film was heated on a hot plate at 205 ° C. for 60 seconds to form a coating film.

The cross-sectional shape of the substrate coated with the obtained coating film was observed with a scanning electron beam microscope (SEM), and the conformality of the coating film was evaluated.
The film thickness of the minimum part of the concave part was 85 nm, the film thickness of the apex part of the convex part was 74 nm, and the height of the step was 200 nm.
From the above formula, the conformal property was 95.3%.

Comparative Example 1
A silicon wafer substrate having a diameter of 8 inches and having a step height of 200 nm, a width of the recess of 600 nm, and a step where the protrusion and the recess exist at a ratio of 1: 1 was placed on a spin coater. Then, with the substrate still, about 1 ml of the same antireflection film-forming composition used in Example 1 was dropped in about 1 second. After the dropping, spin coating (rotation speed 2500 (times / min), rotation time 60 seconds) was performed to form a coating film on the substrate. The substrate was heated on a hot plate at 205 ° C. for 60 seconds.

The cross-sectional shape of the substrate coated with the obtained coating film was observed with a scanning electron beam microscope (SEM), and the conformality of the coating film was evaluated.
The film thickness of the minimum portion of the concave portion was 203 nm, the film thickness of the top portion of the convex portion was 112 nm, and the height of the step was 200 nm.
From the above formula, the conformality was 44.1%.

  By spin coating, it has high conformal properties such as semiconductor resist, antireflection film for lithography, liquid crystal, liquid crystal alignment film, EL film, antireflection film for display, photosensitive film, insulating film and conductive film on the substrate. A film can be formed.

Stepped substrate with conformal coating SEM photograph of Example 1 (magnification is 50000 times) SEM photograph of Comparative Example 1 (magnification is 50000 times)

Explanation of symbols

a) Substrate b) Height of step c) Coating film d) Film thickness of minimum part of coating film concave part e) Film thickness of apex part of coating film convex part f) Width of coating film convex part g) Covering film recess width

Claims (9)

  A first step of forming a coating film of the composition for forming a coating film on a substrate having a step by spin coating; a second step of curing a lower layer portion of the coating film by heating the substrate having the coating film; A method for forming a highly conformal coating film on a substrate having a step including a step and a third step of removing an upper layer portion of the coating film with a solvent.   The method for forming a coating film according to claim 1, wherein the substrate having a step is a semiconductor substrate having a step having a height / width value of 0.1 to 1. 5.   The method for forming a coating film according to claim 1 or 2, wherein the spin coating in the first step is performed at a rotation speed of 500 to 5000 (times / minute) and a rotation time of 30 to 300 seconds.   The method of forming a coating film according to any one of claims 1 to 3, wherein the heating in the second step is performed at a temperature of 50 to 150 ° C for a time of 10 to 300 seconds.   The third step is performed by applying a solvent on the coating film and rotating the substrate at a rotation speed of 500 to 5000 (times / minute) and a rotation time of 30 to 300 seconds after 1 to 300 seconds. The method for forming a coating film according to any one of claims 1 to 4.   The antireflection film forming composition for forming an antireflection film used in a lithography process for manufacturing a semiconductor device, wherein the coating film forming composition is any one of claims 1 to 5. A method for forming the coating film according to the description.   The method for forming a coating film according to claim 6, wherein the antireflection film-forming composition is a composition containing at least a polymer, a crosslinkable compound, and a crosslinking catalyst.   The method of forming a coating film according to any one of claims 1 to 7, further comprising a fourth step of heating the substrate after the third step.   The method for forming a coating film according to claim 8, wherein the heating in the fourth step is performed at a temperature of 100 to 350 ° C for a time of 10 to 300 seconds.