JP2006171472A - Resist pattern forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resist pattern forming method by which the density of pits formed in an optical disk substrate can be increased in a simple way suitable for mass production. <P>SOLUTION: In a positive resist pattern forming method, a baking temperature and a baking time are set in a baking step so that a decomposition reaction takes place in an area smaller than an area in which an acid is generated. In a negative resist pattern forming method, a baking temperature and a baking time are set in a baking step so that a crosslinking reaction takes place in an area smaller than an area in which an acid is generated. In particular, a baking temperature and a baking time are preferably set so that the decomposition reaction or crosslinking reaction takes place in the presence of not less than the amount of an acid generated under exposure energy corresponding to 40-80% of the maximum exposure energy. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a resist pattern forming method, and more particularly, to a resist pattern forming method applied to a stamper used to mold an optical disk substrate.

Conventionally, an optical disk substrate is manufactured by injection molding using a stamper.
The process of manufacturing this stamper is called mastering.
This mastering process is divided into a glass master production process for forming a fine pattern on a photoresist on a glass substrate and a metal master production process for transferring the resist pattern to a metal master.
By the way, fine depressions called pits are spirally formed on the optical disk substrate, and the pit rows correspond to recording signals.
At the time of signal reproduction, a pit row is scanned by a laser, and a signal is read by receiving reflected light modulated by the pit.

For example, in a CD having a capacity of 640 MB, the interval between pit rows, that is, the track pitch is 1.6 μm, and the shortest pit length is about 0.8 μm.
In a DVD having a capacity 7 times larger than that of a CD, the track pitch is 0.74 μm and the shortest pit length is 0.4 μm.
The resist pattern for forming the pits is formed by exposing a photoresist coated on a glass substrate with a laser focused to a submicron diameter with a recording lens, and then developing.

Usually, a positive type photoresist is used, but in this case, the exposed portion becomes soluble in a developer such as alkali, and holes are formed after development (see, for example, Patent Document 1).
On the other hand, in the case of a negative type photoresist, the unexposed part becomes soluble in a developer such as alkali, and protrusions are formed after development.

Here, FIG. 9 shows a three-dimensional graph of a general exposure amount distribution when pits are formed.
As shown in the figure, the shape of the exposure distribution is vertically long in accordance with the pit shape which is an oval depression.
This exposure amount distribution is formed by scanning the laser in the pit longitudinal direction.

FIG. 10 shows a cross-sectional graph along the pit width direction.
In addition, below the graph, the shape of holes formed after the exposure is shown.
The hole 101 a is formed in the photoresist layer 101 on the substrate 100.
This photoresist layer 101 is a positive photoresist because the exposed portion becomes a hole.
It should be noted that the exposure dose distribution shown in this figure is a distribution that approximates a Gaussian distribution (normal distribution).
E0 on the vertical axis shown in the figure indicates an exposure amount at which the photoresist layer 101 starts to be dissolved by development, and E1 is an exposure that can dissolve the applied photoresist layer 101 over the entire thickness direction. Indicates the amount.

The intersection of the exposure amount graph and the exposure amount = E0 corresponds to the edge position of the upper periphery around the hole 101a of the photoresist layer 101, and the intersection point of the exposure amount graph and the exposure amount = E1 is the bottom of the hole 101a. It corresponds to the outer peripheral position.
The hole 101a is formed by etching after exposure.
When a negative type chemically amplified resist is used, the hole 101a remains as a protrusion and the other part is removed.
The protrusions and holes formed by the etching described above are for forming pits on the optical disk substrate by injection molding. In order to reduce the pits and increase the density of recorded data, The side surface is preferably formed along the etching direction.

The width of the protrusion or hole formed as described above corresponds to the spot size of the narrowed laser.
In general, in order to obtain a smaller spot, it is necessary to shorten the wavelength of the laser or increase the numerical aperture of the recording lens.
The capacity of the optical disk depends not only on the pit size but also on the modulation method.

However, as capacity increases, smaller pits must be formed accordingly.
In the case of CD, a signal is recorded by a laser of g-line class having a wavelength of 458 nm or the like, but in the case of DVD, an ultraviolet laser of 400 nm or less is used.
A recording lens having a numerical aperture of NA of 0.9 is almost used.
JP 2003-6947 A

At present, various standards having a larger capacity than DVD have been proposed.
In a next-generation DVD whose capacity is about five times that of DVD, for example, the track pitch is 0.32 μm and the shortest pit length is 0.16 μm.
To form small pits, the laser needs to be squeezed smaller.
However, it is difficult to stably form pits of the above size at the factory level even with a Deep UV laser having a wavelength of 266 nm or the like.
For this purpose, an SIL (Solid Immersion Lens) method in which the NA value is 1 or more and exposure by an electron beam are being studied.
However, none of them are stable at present and are not mature to mass production level.
Also, electron beam exposure has drawbacks such as expensive equipment.

The present invention has been made on the basis of such background technology, and has been made to overcome the above-described problems of the background technology.
That is, an object of the present invention is to provide a resist pattern forming method capable of increasing the density of pits formed on an optical disk substrate by a simple method with high productivity.

  Thus, as a result of earnest research on the background of such problems, the present inventor has found that the cross-linking reaction or decomposition reaction occurs in a region smaller than the region where the acid is generated by exposing the chemically amplified resist layer with a laser. As will occur, the inventors have found that the above problems can be solved by setting the baking temperature and baking time in the baking process, and the present invention has been completed based on this finding.

  That is, the present invention relates to (1) a chemically amplified resist layer containing a photoacid generator and a dissolution inhibitor in the base resin, or containing a photoacid generator in the base resin into which a dissolution inhibitor group has been introduced. A laser exposure step in which an acid is generated by a chemical reaction of a photoacid generator in the chemically amplified resist layer, and the exposed portion of the laser is chemically treated using the acid generated in the laser exposure step as a catalyst. A positive baking process, and a positive etching process that removes the exposed part decomposed in the baking process while increasing the difference in dissolution rate between the exposed part and the unexposed part by the action of a dissolution inhibitor. A method for forming a resist pattern of a mold, wherein a baking temperature and baking are performed in the baking step so that a decomposition reaction occurs in a region smaller than the region where the acid is generated. Resides in method of forming a resist pattern for setting a grayed time.

  (2) The exposure amount distribution of the laser is a Gaussian distribution or a distribution approximate to a Gaussian distribution, and is greater than or equal to the amount of acid generated by an exposure amount that is an intermediate value (a value smaller than the maximum exposure amount) of the exposure amount distribution. In the method for forming a resist pattern according to the above (1), the baking temperature and baking time are set so that the decomposition reaction of the chemically amplified resist layer occurs.

  In addition, (3) a chemically amplified resist layer containing a photoacid generator and a crosslinking agent in the base resin or containing a photoacid generator in the base resin into which a crosslinking group has been introduced is exposed with a laser. A laser exposure step for generating an acid in the chemically amplified resist layer by a chemical reaction of a photoacid generator, and using the acid generated in the laser exposure step as a catalyst, the exposed portion of the laser is chemically treated by the crosslinking agent. A negative resist pattern forming method comprising: a baking step of crosslinking by the step of: and an etching step of forming protrusions by removing portions other than the exposed portion crosslinked in the baking step, wherein the method is smaller than the acid-generated region. In a resist pattern forming method, a baking temperature and a baking time are set in the baking step so that a crosslinking reaction occurs in a region. To.

  (4) The amount of acid generated by the exposure amount distribution of the laser, which is a Gaussian distribution or a distribution approximate to a Gaussian distribution, and an intermediate exposure value (a value smaller than the maximum exposure amount) of the exposure amount distribution. The resist pattern forming method according to (3) above, wherein the baking temperature and the baking time are set so that the cross-linking reaction of the chemically amplified resist layer occurs.

  And (5), the said intermediate value exists in the formation method of the resist pattern as described in said (2) or (4) which is the value of 40 to 80% of the maximum exposure amount.

  In addition, as long as the objective of this invention is met, the structure which combined the said claim suitably is also employable.

According to the present invention, since the cross-linking reaction or the decomposition reaction occurs in a region smaller than the region where the acid is generated by exposing the chemically amplified resist layer with a laser, the resist molding having fine protrusions or holes is performed. Can be done.
Therefore, it is possible to perform exposure with a laser in a stable state as compared with the conventional method in which the exposure amount is reduced and miniaturized.
In addition, the pit can be miniaturized without using an electron beam, and it is possible to use the current laser oscillator to support the next generation DVD.

Furthermore, the exposure dose distribution of the laser is a Gaussian distribution or a distribution approximating a Gaussian distribution, and the chemical amplification resist layer has a value that is greater than or equal to the amount of acid generated by the exposure dose that is an intermediate value of the exposure dose distribution (a value smaller than the maximum exposure dose). If the baking temperature and baking time are set in consideration of the exposure amount of the laser so that the decomposition reaction or the crosslinking reaction occurs, the pits can naturally be made finer.
Note that the slope of the graph is maximized at the half value of the laser exposure dose distribution, so if the intermediate value is half value, the slope of the formed protrusions and holes will be closest to the vertical, and if it exceeds this value, it will be somewhat Although the inclination becomes gentle, it does not affect the narrowing of the track pitch width.
Further, the reason why the distribution approximated to the Gaussian distribution is included is that, after the laser passes through the recording lens, a side rope is generated because the lens is opened at the lens aperture, and the Gaussian distribution is not correct.
In addition, although baking is described, baking after exposure is generally called post-exposure baking (PEB).

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.
FIG. 1 shows a laser irradiation system used in the resist pattern forming method of the present invention.
This laser irradiation system has a laser oscillator 1.
The laser emitted from the laser oscillator 1 is subjected to output control by the power control unit 2 and then subjected to on / off modulation corresponding to a signal to be recorded by the optical modulator 3.
Thereafter, the beam expander 4 widens the beam diameter and enters the recording lens 5.
The beam focused by the recording lens 5 exposes a glass substrate 6 coated with a resist provided near the focal position.

The diameter Φ of the beam waist when a gaussian beam that is not lost is narrowed by a lens is expressed by the following formula at a relative intensity ratio of 1 / e2.
Φ (1 / e2) = 0.64λ / NA
Here, λ is the laser wavelength, and NA is the lens numerical aperture.

Since the actual lens has an aperture limit, the periphery of the beam is set.
When the radius of the lens aperture is a and the radius of 1 / e2 of the incident beam is wa, m = a / wa is referred to as a Truncation factor.
If r is the distance from the optical axis, and the amplitude distribution on the image plane of the lens is u (r, m), the intensity distribution on the focal plane normalized by the center intensity is expressed by the following equation.
I (r, m) / I (0, m) = | u (r, m) | 2 / | u (0, m) | 2
I (r, m) represents the intensity distribution, and I (0, m) represents the intensity at the center.

FIG. 2 shows the intensity distribution of the laser when m = 1.
This intensity distribution is the energy distribution of the laser, and is also the distribution of the exposure amount when exposed for a certain period of time.
The vertical axis is the beam intensity, and the horizontal axis is the distance from the optical axis.
This figure shows the laser intensity distribution in the case of an optical system for DVD, more specifically, the laser intensity distribution when the laser wavelength is 351 nm and the lens NA is 0.9.
The full width at half maximum is about 0.2 μm.
The full width at half maximum is the beam diameter when the laser intensity is 0.5.

FIG. 3 shows an exposure amount when the laser shown in FIG. 2 exposes the substrate 6.
A substrate 6 is shown below the graph.
A chemically amplified resist layer 7 is formed on the substrate 6.
As described in the background art, E0 on the vertical axis shown in the figure indicates an exposure amount at which the conventional photoresist starts to be dissolved by development, and E1 indicates the entire thickness direction of the applied conventional photoresist. The exposure amount that can be dissolved over the range is shown.
The hole 7a formed in the chemically amplified resist layer 7 is indicated by a solid line, and the hole 101a in the case of using a conventional photoresist is indicated by a dotted line.

  As shown in the figure, when the chemically amplified resist layer 7 is used, the intersection of the exposure amount graph and the exposure amount = E0 corresponds to the edge position of the upper edge around the hole 7a of the chemically amplified resist layer 7. The intersection of the exposure amount graph and the exposure amount = E1 does not correspond to the outer peripheral position of the bottom of the hole 7a.

Here, if the value of E1 is determined to be, for example, half (half value) of the exposure amount when the distance from the optical axis is 0, the intersection of the exposure amount graph and the exposure amount = E1 of the hole 101a indicated by a dotted line. Since it corresponds to the outer peripheral position of the bottom, the full width at half maximum of the exposure amount distribution corresponds to the width of the bottom of the hole 101a.
Since the exposure amount distribution is a Gaussian distribution or a distribution approximated to a Gaussian distribution, the slope of the graph is maximum at the full width at half maximum, and the side surface of the hole 101a is closest to the vertical.

However, even if the value is more than half the value, the slope becomes somewhat gentle, but it does not affect the narrowing of the track pitch width.
Including that, E1 is preferably set to a value (intermediate value) of 40% to 80% of the maximum exposure amount.
The reason why the value is 40% or more is that if it is less than 40%, the inclination of the side surface of the hole 7a becomes too gentle as can be seen from the shape of the graph of FIG.
Further, the reason why it is set to 80% or less is that, up to 80%, as can be seen from the shape of the graph of FIG.

Hereinafter, the chemically amplified resist will be described.
The chemically amplified resist used in the present invention is obtained by blending a photoacid generator in a base resin.
In the case of a positive chemically amplified resist, a dissolution inhibitor is added to this chemically amplified resist, or a dissolution inhibitor group is introduced into the base resin.
On the other hand, in the case of a negative chemically amplified resist, a crosslinking agent is added or a crosslinking group is introduced into the base resin.
This chemically amplified resist is usually prepared as a varnish by dissolving the above components in an organic solvent and filtering.

In the chemically amplified resist, when a dissolution inhibitor is added or when a dissolution inhibiting group is introduced into the base resin, the elimination of the dissolution inhibiting group occurs in a chain reaction in post-exposure baking (PEB), The difference in dissolution rate between the exposed area and the unexposed area is increased.
Moreover, when a crosslinking agent is added or a crosslinking group is introduced into the base resin, the crosslinking reaction occurs in a chain reaction by subsequent baking.
Therefore, in the chemically amplified resist, even if the amount of the photoacid generator added is reduced, elimination of the dissolution inhibiting group and a crosslinking reaction occur in a chain and high sensitivity can be easily obtained.
In addition, in a positive chemically amplified resist, if a small amount of a crosslinking agent is added or introduced into the base resin, the effect of improving the resolution can be obtained (see JP 2004-4669 A, paragraphs 0005 and 0010). .

Hereinafter, each component of the chemically amplified resist will be described.
First, the base resin will be described.
As the material of the base resin, a material that is insoluble or hardly soluble in alkali by itself, but undergoes a chemical change by the action of an acid and becomes alkali-soluble is used.
Examples of such a base resin include resins having a phenol skeleton such as polyvinylphenol and novolac resin, and resins having a (meth) acrylic acid skeleton such as polymethacrylate and polyacrylate.

Next, the photoacid generator will be described.
The photoacid generator generates an acid when exposed to light.
When a crosslinking agent is added or when a crosslinking group is introduced into the base resin, the acid is used as a catalyst to crosslink the base resin in the baking step.
When a dissolution inhibitor is added or when a dissolution inhibitor group is introduced into the base resin, the dissolution inhibitor group is eliminated in a chain reaction, resulting in a large difference in dissolution rate between the exposed and unexposed areas. The solubility of the base resin during development is accelerated.

As the photoacid generator, for example, arylonium salts, naphthoquinonediazide compounds, diazonium salts, sulfonate compounds, sulfonium compounds, sulfamide compounds, iodonium compounds, sulfonyldiazomethane compounds, and the like can be used.
In particular, conjugated polycyclic aromatic compounds such as arylonium salts having a naphthalene skeleton or a dibenzothiophene skeleton, sulfonate compounds, sulfonyl compounds, and sulfamide compounds are advantageous in terms of transparency to short wavelength light and heat resistance.

A preferable blending amount of the photoacid generator is 0.001 to 50% by weight, more preferably 0.01%, based on the entire other solid content, as described in paragraph 0072 of JP 2000-330287 A. Within the range of ˜40% by weight.
If it is less than 0.001% by weight, it is difficult to form a resist pattern with high sensitivity. If it exceeds 50% by weight, the mechanical strength and the like may be impaired when a resist film is formed.
That is, it is sufficient that the photoacid generator is contained in a slight amount, and it can hardly be assumed that products containing 50% by weight are actually on the market.

Next, a dissolution inhibitor used for a positive resist will be described.
In addition, the description of this dissolution inhibitor quoted a part of Unexamined-Japanese-Patent No. 2003-6947.
In the base resin according to the present invention, the alkali-insoluble resin is decomposed by the acid generated by irradiating the compounded photoacid generator with light, and becomes alkali-soluble.
Therefore, in order to increase the difference in the dissolution rate between the exposed part and the unexposed part, it is preferable to introduce a dissolution inhibiting group into the base resin or add a dissolution inhibiting agent.

As the dissolution inhibiting group compound in which a dissolution inhibiting group is introduced into the base resin, for example, among the compounds described in U.S. Pat. Nos. 4,491,628 and 4,603,101, JP-A-63-27829, etc. Any cyclic aromatic ring can be used.
Alternatively, any compound in which part or all of the hydroxy terminal of a compound having a carboxylic acid or a phenolic hydroxyl group is substituted on a condensed polycyclic aromatic ring skeleton with a protecting group decomposable with an acid can be used.

On the other hand, the dissolution inhibitor is preferably a conjugated polycyclic aromatic compound having excellent transparency to short wavelength light.
That is, in these compounds, the light absorption band is shifted to a low wavelength region due to the conjugated stabilization of π electrons, and in the present invention, particularly by using a conjugated polycyclic aromatic compound as a dissolution inhibitor, A resist having excellent transparency to light and sufficient heat resistance can be obtained.

The addition amount of the dissolution inhibitor to the resist composition is desirably 3% by weight or more and less than 40% by weight with respect to the polymer as described in paragraph 0078 of JP-A No. 2000-330287.
The reason is that if the amount added to the resist composition is less than 3% by weight, the effect cannot be obtained or the resolution is lowered, and conversely if it is 40% by weight or more, the coating film performance or the dissolution rate is remarkably increased. It is because it falls.
Usually between 10 and 30% by weight is more desirable.

Next, the crosslinking agent used mainly for negative resists will be described.
As the crosslinking agent, those that cause a crosslinking reaction by the action of an acid are used.
Examples of the crosslinking agent include melamine-based, benzoguanamine-based, and urea resin-based compounds, as well as alkoxyalkylated amino resins such as alkoxyalkylated melamine resins and alkoxyalkylated urea resins.

These crosslinking agents can be used alone or in admixture of two or more.
As described in paragraph 0035 of JP-A-10-186661, the content of the crosslinking agent is preferably 3 to 70% by weight based on the entire other solid content.
This is because when the crosslinking agent is less than 3% by weight, the formation of the resist pattern is poor, and when it exceeds 70% by weight, the developability is lowered.

Next, steps for actually forming a resist pattern will be described with reference to FIG.
First, in step S1, a substrate 6 on which a chemically amplified resist layer 7 as shown in FIG. 3 is prepared is prepared and placed at a position where a laser can be exposed as shown in FIG. 1 [substrate preparation step].

Next, in step S2, the substrate 6 is exposed to a laser [laser exposure step].
Specifically, when a positive chemically amplified resist is used, a photoacid generator and a dissolution inhibitor are contained in the base resin, or a photoacid is generated in the base resin into which a dissolution inhibitor group has been introduced. A chemically amplified resist layer containing an agent is exposed with a laser, and an acid is generated in the chemically amplified resist layer by a chemical reaction of a photoacid generator.
When a negative chemically amplified resist is used, a chemically amplified resist containing a photoacid generator and a crosslinking agent in the base resin or containing a photoacid generator in the base resin into which a crosslinking group has been introduced The layer is exposed with a laser, and an acid is generated in the chemically amplified resist layer by a chemical reaction of a photoacid generator.

Next, in step S3, the substrate 6 is baked [baking step].
When a positive chemically amplified resist is used, the exposed portion of the laser is chemically decomposed using the acid generated in the laser exposure step as a catalyst.
At this time, the baking temperature and baking time are set so that the decomposition reaction occurs in a region smaller than the region where the acid is generated.
When a negative chemically amplified resist is used, the exposed portion of the laser is chemically cross-linked by the action of a cross-linking agent using the acid generated in the laser exposure step as a catalyst.
At this time, the baking temperature and baking time are set so that the crosslinking reaction occurs in a region smaller than the region where the acid is generated.

As can be seen from the experiment described later, when the baking time is constant, the chemically amplified resist is not easily dissolved in an alkaline solution below a certain baking temperature, and no protrusions or holes are formed.
In addition, this restriction of a certain temperature or less correlates with a change in exposure intensity by the laser.
Therefore, if this property is utilized, the hole width can be freely changed by adjusting the baking temperature and baking time.
In other words, the pits can be miniaturized by reducing the width of the holes.

Next, in step S4, the substrate 6 is etched [etching step].
When a positive chemically amplified resist is used, a hole is formed by removing the exposed portion decomposed in the baking step while increasing the difference in dissolution rate between the exposed portion and the unexposed portion by the action of a dissolution inhibitor.
When a negative type chemically amplified resist is used, protrusions are formed by removing portions other than the exposed portion crosslinked in the baking process.
In this way, a resist pattern is formed on the substrate 6.

This resist pattern is then transferred to a metal disk by electroforming to produce a stamper.
Note that pure nickel is mainly used as the material of the metal plate.

  Although the present invention has been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that other various modifications are possible without departing from the essence thereof.

(Experimental result)
Hereinafter, experimental results in the case where protrusions are formed using a negative chemically amplified resist will be described.
FIG. 5 shows the relationship between the baking temperature and the protrusion width.
The vertical axis represents the protrusion width, and the horizontal axis represents the baking temperature.
The spot diameter of the laser used in this experiment was about 0.42 μm at 1 / e 2 of the Gaussian distribution and about 0.24 μm at the half value.
The laser output was 30%, 40%, and 50% of the full power output of the power control unit 2 in FIG.
The baking time was 120 seconds.

When the laser output was 50%, when the baking temperature was shaken in increments of 5 ° C. from 100 ° C. to 115 ° C., the protrusion width changed linearly in the range of 170 nm to 450 nm.
When the laser output was 40%, when the baking temperature was shaken in increments of 5 ° C. from 105 ° C. to 115 ° C., the protrusion width changed linearly in the range of 230 nm to 430 nm.
Furthermore, when the laser output was 30%, when the baking temperature was shaken in increments of 5 ° C. from 105 ° C. to 115 ° C., the protrusion width changed linearly in the range of 160 nm to 380 nm.
Here, when the laser output is 30% and 40%, there is no data when the baking temperature is set to 100 ° C. because no projection is formed at 100 ° C.
That is, it is considered that the crosslinking reaction was not performed because the amount of acid generated by the laser output was small and the baking temperature was low.
Further, it was found that when the laser output is the same, that is, when the baking temperature is changed even if the amount of acid generated is the same, the protrusion width also changes.

FIG. 6 shows the relationship between baking time and protrusion width.
The vertical axis represents the protrusion width, and the horizontal axis represents the baking time.
The baking temperature was 110 ° C.
The laser spot diameter used in this experiment is the same as in the case of the relationship between the baking temperature and the protrusion width in FIG. 5, and the laser output is also 30%, 40% with respect to the full power output of the power control unit. The output was 50%.

When the laser output was 50%, when the baking temperature was shaken in increments of 30 seconds from 60 seconds to 240 seconds, the protrusion width monotonically increased as a whole in the range of 240 nm to 470 nm.
Further, when the laser output was 40%, the protrusion width monotonously increased as a whole in the range of 180 nm to 420 nm.
Furthermore, when the laser output was 30%, the protrusion width monotonously increased as a whole in the range of 120 nm to 380 nm.
Further, it was found that when the laser output is the same, that is, the acid generation amount is the same, the protrusion width also changes when the baking time is changed.

FIG. 7 shows the relationship between the exposure amount and the formed holes.
Here, a positive chemically amplified resist is used.
The laser output was 50%.
E0a and E1a shown in the figure indicate data when the baking temperature is 105 ° C., and E0b and E1b indicate data when the baking temperature is 100 ° C.
E0a and E0b represent threshold exposure amounts at which decomposition starts at the respective temperatures, and E1a and E1b represent exposure amounts capable of decomposing the chemically amplified resist layer 7 having a thickness applied at the respective temperatures.
That is, E0a and E0b represent exposure amounts at which crosslinking or decomposition reaction of the chemically amplified resist layer 7 starts at the respective baking temperatures, and serve as criteria for determining the exposure amount necessary for pattern formation.

A substrate 6 is shown below the graph, and holes formed in the chemically amplified resist layer 7 on the substrate 6 are indicated by a solid line and a dotted line.
A hole 7b indicated by a solid line indicates a case where the baking temperature is 100 ° C., and a hole 7c indicated by a dotted line indicates a case where the baking temperature is 105 ° C.
The hole 7b indicated by the solid line has a width of about 170 nm at a half depth, and a bottom width of 140 nm.
Further, the hole 7c indicated by the dotted line has a width of about 270 nm at a half depth, and a bottom width of 240 nm.

In FIG. 7, E1a substantially corresponds to half the exposure amount, and the full width at half maximum is about 240 nm.
This means that baking at 105 ° C. forms a hole having a size almost the same as the hole 101a formed by the conventional photoresist shown in FIG.
In the case of a normal resist which is not a chemically amplified resist, the half width of a hole to be formed is 270 nm with respect to an exposure amount distribution having a full width at half maximum of 240 nm. However, in the chemically amplified resist layer 7, the baking temperature is set to 100 ° C. As a result, the half width of the hole formed for the exposure amount distribution having the same full width at half maximum of 240 nm is about 170 nm.
This is because the baking temperature and baking time are intentionally set so that crosslinking or decomposition occurs in a region smaller than the region where the acid generated by exposure is present.

As a result, the full width at half maximum (distribution width at the half height position, here the distribution width at E1a) of the exposure amount distribution is larger than the full width at half maximum (projection width at the half depth position) of the hole 7b. Yes. Simply put, this means that holes smaller than the spot diameter of the laser to be recorded are formed.
The relationship between the laser spot diameter, the baking conditions, and the formed holes can be found by accumulating experimental data.

Next, FIG. 8 shows a comparison between hole formation of the present invention using a chemically amplified resist and hole formation by a conventional method.
The graph in FIG. 8 shows the exposure amount similar to that in FIG.
The exposure amount distribution A is the same as the distribution in FIG. 7, and E1b also indicates the exposure amount necessary to dissolve the coating film thickness, as in FIG.
As described above, in the exposure distribution A, the hole 7b was formed in the resist layer, and the bottom width was 140 nm.

Here, E1c represents an exposure amount necessary for dissolving the coating film thickness in the conventional resist.
This threshold is unique to the resist and is uniquely determined by the conditions of the coating process.
Therefore, in order to obtain the same bottom width as that of the hole 7b by the conventional method, the exposure amount must be lowered to form the exposure amount distribution B.
The exposure dose distribution B is approximately half the intensity of the exposure dose distribution A.

In general, the laser intensity control in the power control unit 2 of FIG. 1 becomes unstable when the intensity is small.
For this reason, conventionally, a laser output of a sufficient size has been provided at the power control unit 2 and then the strength is reduced by a filter.
However, this is not necessary in the present invention.

Further, comparing the slope at the intersection of the exposure dose distribution A and the threshold value E1b with the slope at the intersection of the exposure dose distribution B and the threshold value E1c, the exposure dose distribution A is clearly steeper.
This means that in the exposure amount distribution A, the variation in the bottom width value of the hole 7b is smaller than the variation in the intensity distribution or the variation in the threshold value of the resist.
As described above, in the present invention, control of the laser intensity is more stable than in the conventional method for forming holes having the same width.
In addition, fluctuations in the formed hole width are reduced with respect to fluctuations in the laser intensity and variations in resist sensitivity that occur during the process.

FIG. 1 is an explanatory view showing a laser irradiation system used in the resist pattern forming method of the present invention. FIG. 2 is an explanatory diagram showing the intensity distribution of the laser. FIG. 3 is an explanatory diagram showing the distribution of the exposure amount when the laser exposes the substrate. A substrate is also shown. FIG. 4 is an explanatory diagram showing the flow of steps when forming a resist pattern. FIG. 5 is an explanatory diagram showing the relationship between the baking temperature and the protrusion width. FIG. 6 is an explanatory diagram showing the relationship between baking time and protrusion width. FIG. 7 is an explanatory diagram showing the relationship between the exposure amount and the formed holes. FIG. 8 is an explanatory view showing a comparison between hole formation of the present invention using a chemically amplified resist and hole formation by a conventional method. FIG. 9 is an explanatory diagram showing a three-dimensional graph of a general exposure amount distribution when pits are formed. FIG. 10 is an explanatory view showing the relationship between the conventional exposure dose distribution and the holes formed in the substrate.

Explanation of symbols

1 Laser oscillator
2 Power control unit
3 Optical modulator
4 Beam expander
5 Recording lens
6 Substrate
7 Chemically amplified resist layer
7a, 7b, 7c holes
A, B Exposure dose distribution

Claims (5)

A chemically amplified resist layer containing a photoacid generator and a dissolution inhibitor in a base resin or containing a photoacid generator in a base resin into which a dissolution inhibitor group has been introduced is exposed with a laser, and the chemical amplification type A laser exposure process for generating an acid by a chemical reaction of a photoacid generator in the resist layer;
A baking step of chemically decomposing the exposed portion of the laser using the acid generated in the laser exposure step as a catalyst;
An etching step of removing the exposed portion decomposed in the baking step to form a hole while increasing the difference in dissolution rate between the exposed portion and the unexposed portion by the action of the dissolution inhibitor;
A method for forming a positive resist pattern having
A resist pattern forming method, wherein a baking temperature and a baking time are set in the baking step so that a decomposition reaction occurs in a region smaller than the region where the acid is generated. The exposure dose distribution of the laser is a Gaussian distribution or a distribution approximating a Gaussian distribution,
Baking temperature and baking time are set so that decomposition reaction of the chemically amplified resist layer occurs at an amount of acid generated by an exposure amount of an intermediate value (a value smaller than the maximum exposure amount) of the exposure amount distribution. The method for forming a resist pattern according to claim 1. A chemically amplified resist layer containing a photoacid generator and a crosslinking agent in a base resin, or a chemically amplified resist layer containing a photoacid generator in a base resin into which a crosslinking group has been introduced is exposed with a laser, and the chemically amplified resist layer A laser exposure process for generating an acid by a chemical reaction of a photoacid generator,
A baking step of chemically crosslinking the exposed portion of the laser by the action of the crosslinking agent using the acid generated in the laser exposure step as a catalyst;
Etching process to remove protrusions other than the exposed part crosslinked in the baking process, and to form protrusions;
A negative resist pattern forming method comprising:
A method for forming a resist pattern, wherein a baking temperature and a baking time are set in the baking step so that a crosslinking reaction occurs in a region smaller than the region where the acid is generated. The exposure dose distribution of the laser is a Gaussian distribution or a distribution approximating a Gaussian distribution,
Baking temperature and baking time are set so that a cross-linking reaction of the chemically amplified resist layer occurs at an amount of acid generated by an exposure amount that is an intermediate value (a value smaller than the maximum exposure amount) of the exposure amount distribution. The method for forming a resist pattern according to claim 3. 5. The method for forming a resist pattern according to claim 2, wherein the intermediate value is a value that is not less than 40% and not more than 80% of a maximum exposure amount.

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