JP3808780B2 - Resist pattern manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to formation of a photoresist fine pattern, and more particularly to a method for forming a fine pattern using the heat flow of a resist.
[0002]
[Prior art]
In general, a conventional resist fine pattern forming technique is obtained by exposing and developing a resist film through light having a wavelength at which the resist is exposed to a mask on which a fine pattern is drawn. Further, by giving a temperature at which the resist causes a heat flow to the pattern obtained by development, for example, the hole pattern can be reduced, and the size and shape of other patterns can be changed (FIG. 10A). ). In addition, as in the case of a general positive resist, a resist that releases light from a protective group and improves the heat resistance of the resist film by using light irradiation as a trigger, further irradiates light at an arbitrary place after pattern development. It is possible to control the heat flow at the location irradiated with light (FIG. 10B).
[0003]
First, a conventional heat flow process will be described with reference to FIG.
[0004]
FIG. 10 shows a conventional heat flow process.
(A) A resist 11 is applied on the wafer 10.
(B) A mask 12 is positioned on the resist 11 and exposed.
Next, the region 15 of the resist 11 corresponding to the opening of the mask pattern is exposed by the exposure.
(C) When the resist 11 is developed, the exposed area 15 is removed, and a resist 11 having an opening 18 defined by the exposed area 15 is formed.
(D) Next, when baked, the resist portion 16 shielded by the light-shielding portion of the mask 12 is unexposed and the protective group R remains, so that the heat resistance is lowered, causing heat dripping, and The diameter is reduced, that is, the opening 19 has a reduced diameter.
[0005]
Next, FIG. 10B shows a heat flow process to which a conventional double exposure is applied.
The process up to the exposure using the mask A is the same as the process of FIG. Next, half of the resist is exposed using a mask B that is approximately half the size of mask A. Next, when baking (heat flow) is performed, the exposed resist portion opening 18 does not shrink, and the resist portion shielded by the mask B causes shrinking, and the opening 18 becomes an opening 19 having a reduced diameter. .
[0006]
The resist will be described using, for example, a general positive resist shown in FIG.
[0007]
FIG. 11 is a diagram showing a structural formula of a polymer containing a conventional polyhydroxystyrene structural unit.
[0008]
Polyhydroxystyrene has —OR in place of hydroxyl group —OH in a state before exposure. R is a protecting group for —OH.
[0009]
The “protecting group” means the following “”. “In the reaction of an organic compound containing two or more functional groups, the reaction often occurs at the functional group. When you want to react only with a certain functional group of such a compound, other functionalities that are more reactive. It is necessary to convert the group so that it does not react during the reaction but can be easily restored after the reaction, which is called protection, which is used to temporarily protect the reactive characteristic group. The atomic group is called a protective group. "
When the resist having -OR is exposed to light, a photoacid generator present in the resist reacts to generate an acid. Thereafter, when heat is applied, the above-OR changes to a hydroxyl group-OH using the acid as a catalyst.
[0010]
In the course of this change, the heat resistance of the resist in which -OR is changed to -OH by exposure is higher than that of a resist having -OR before exposure. As a result, the resist including the hydroxyl group —OH after exposure can suppress the deformation of the resist film due to heating as compared with the resist including —OR.
[0011]
[Problems to be solved by the invention]
However, the above-described forming method (process) requires two exposure processes, and there is a problem that it takes time for new equipment investment, two masks, and final pattern formation. There is also a problem that it is necessary to manage the environment and the time from development to twice exposure.
[0012]
An object of the present invention is to use an exposure mask and an exposure mask, which use a mask having a plurality of regions having different transmittances, and easily cause a heat flow effect on the resist by a single exposure process. It is to provide a method for producing a resist pattern.
[0013]
[Means for Solving the Problems]
The present invention employs the following solutions in order to achieve the above object.
(1) In the resist pattern manufacturing method, the method includes a step of applying a resist to a substrate, an exposure step of exposing a plurality of regions of the resist with different strengths, and a step of baking the resist after exposure, The photomask used in the exposure process has three regions having different light transmittances from each other, and is configured such that the light transmittance increases sequentially from the first region to the third region, The third region surrounded by the region is provided more densely than the third region surrounded by the second region.
(2) In the resist pattern manufacturing method according to (1), in order to provide a hole pattern in the resist, a mask region facing a pattern having a wide pitch between holes is a semi-transparent region, and a pitch between holes is narrow. The mask region facing the pattern is a light-shielding region, and the transmittance of the semi-transparent mask is determined according to the degree of contraction of the resist size that can be recognized by the hole pitch.
(3) In the resist pattern manufacturing method according to the above (1), a mask region corresponding to a region in which the film thickness of the resist is 0.1 μm and the hole pitch of the resist is 0.8 μm or more is reduced in resist dimensions. The semi-translucent region to be suppressed is used.
(4) In the resist pattern manufacturing method according to the above (2), the hole pattern is a repetitive pattern of holes, and the mask region corresponding to the outermost peripheral pattern of the hole pattern is a semi-transparent region. To do.
(5) In the resist pattern manufacturing method according to any one of (1) to (4), when n is an arbitrary number in the range of 0 <n <100, the size of the hole pattern is the transmittance. In the case of the pre-shrink dimension in a range larger than the pre-shrink dimension corresponding to the intersection of both characteristic curves representing the change of the post-shrink dimension with respect to the pre-shrink dimension in the case of 0% and the transmittance n%, the transmittance of the mask is set to the n %.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the drawings.
[0015]
(First embodiment of the present invention)
FIG. 1 is a process flow of the first embodiment of the present invention.
[0016]
FIG. 2 is a block diagram of a mask used in the first embodiment of the present invention.
[0017]
The light-shielding portion in FIG. 2 is a portion that does not transmit light, and the semi-transmissive portion is also a portion that has x% (where 0 <x <100) where the light transmittance is arbitrarily set on the resist.
[0018]
First, the process of the first embodiment will be described with reference to FIG.
(A) A resist 11 is applied on the wafer 10.
(B) The mask 12 of the present invention is positioned on the resist 11 and exposed.
As illustrated in FIG. 2, the mask 12 is divided into two as a whole, the light shielding region 24 including the light shielding portion 13 having the light transmitting portion 20 formed in the center on the left side, and the light transmitting portion 21 in the center on the right side. A semi-transparent region 25 including the semi-transmissive portion 14 having the light transmittance x% is provided. The setting of the transmittance x% and the patterning made up of the light transmission part 21 and the semi-transmission part 14 are appropriately set as necessary.
[0019]
The mask basically needs to be a mask in which at least a semi-transmissive part and a light-shielding part having different transmittances are integrally provided.
Next, the region 15 of the resist 11 corresponding to the opening of the mask pattern is exposed by the exposure.
(C) When the resist 11 is developed, the exposed area 15 is removed, and a resist 11 having an opening 18 defined by the exposed area 15 is formed.
[0020]
(D) Next, when baked, the resist portion 16 shielded by the light-shielding portion 13 of the mask 12 is left unexposed and the protective group R remains, so that the heat resistance is lowered, causing heat dripping, and the opening 18 That is, the diameter of the opening 19 is reduced. On the other hand, the resist portion 17 that has been semi-transmitted by the semi-transmissive portion 14 of the mask 12 has a predetermined transmittance. Therefore, the resist portion 17 remains reduced to the number of protecting groups R corresponding to the transmittance, and the number of the protecting groups R thus reduced. Accordingly, the heat resistance is increased, and heat dripping is less likely to occur. Therefore, the diameter of the opening 18 is formed with almost no reduction.
[0021]
FIG. 3 is a diagram showing the light transmission amount in each region of the mask of FIG.
[0022]
FIG. 3 shows the transmission amount of the transmission part with respect to the exposure amount that varies linearly.
[0023]
When the exposure amount is small, the exposure amount of the light-shielding portion, that is, 0 mJ, determines 0 level, and when the exposure amount is large, the maximum exposure amount AmJ / cm ² of the transmission portion is defined as 100%. The range of use is that the lower limit is the exposure amount of the semi-transmissive portion where the resist does not generate heat flow at an exposure amount below this, and the upper limit is the exposure amount of the semi-transmissive portion where the resist is developed at an exposure amount greater than this. The value in between is defined as the exposure amount of the semi-transmissive portion≈BmJ / cm ² .
[0024]
As shown in FIG. 3, the resist transmittance x% is AmJ / cm ² , which is the target exposure amount that has passed through the transmissive part, and the exposure amount that changes the heat flow characteristics in double exposure, while the resist is not exposed or patterned. / Cm ² , x = (B / A) × 100.
[0025]
In the present invention, the first region a region of the exposure amount 0 mJ / cm ^2, the second region a region of the exposure amount BMJ / cm ^2, the area of the exposure amount AMJ / cm ² of the third region.
[0026]
When a mask as shown in FIG. 2 is used at the time of exposure, the resist Am exposed through the light transmitting portion 20 of the light shielding region 24 of the mask 12 has a large exposure amount AmJ / cm ² sufficient to pattern the resist. As a result, the light-shielded resist portion 16 of the resist in contact with the light shielding portion 13 around the light transmitting portion 20 in the light shielding region 24 of the mask 12 is not exposed.
[0027]
On the other hand, the resist exposed through the light transmitting portion 21 in the semi-transmissive region 25 of the mask 12 can obtain an exposure amount of AmJ / cm ² , but the resist exposed through the semi-transmissive portion 14 in the semi-transmissive region 25 is transparent. Depending on the rate, in this example, it is exposed to such an extent that it is not patterned (BmJ / cm ² ). In the baking of FIG. 1, the pattern formed in the light shielding region 24 generates heat flow, but the semi-transparent region 25 suppresses heat flow.
[0028]
(Effects of the first embodiment)
As described above, according to the first embodiment of the present invention, since the light shielding region and the semi-transparent region are provided on one mask, the semi-transmission part is an arbitrary x% of the transmission part (where 0 <x <100) It is exposed. Thereby, although depending on the transmittance x%, the heat resistance of the resist is temporarily improved and the heat flow is suppressed.
[0029]
FIG. 4 shows, for example, a dimensional behavior due to heat flow when a hole pattern is formed with an acetal-based chemically amplified photoresist using a mask with a transmittance of 6%, and similarly a mask with a transmittance of 0% is used. It is the figure which compared the dimensional behavior in the case. If a mask in which these two transmittances are mixed is used, it is possible to control the amount of shrinkage with a single mask in the shrink technique using the heat flow of the hole pattern. Shrinking means that the diameter of the hole pattern is reduced by baking. This will be described in detail below.
[0030]
FIG. 4A shows the size of the hole pattern when the resist is exposed using a mask with a transmittance of 6% and then baked at 90 ° C. and when baked at 136 ° C. FIG. FIG. 4B shows the size of the hole pattern when the resist is exposed using a mask having a transmittance of 0% and then baked at 90 ° C. and when baked at 136 ° C. FIG. In the case of baking for shrinking the hole pattern, the resist is baked at 136 ° C., so the size of the hole pattern when baking at 90 ° C. is substantially the size of the hole pattern before baking. It corresponds to. Also, the larger the hole pattern, the greater the amount of light required to sensitize the resist, so the larger the hole pattern, the greater the exposure.
[0031]
As can be seen from FIG. 4A and FIG. 4B, when the size of the hole pattern before baking is larger than about 0.25 μm, it is better to expose using a mask with a transmittance of 6%. The hole pattern after baking becomes large. That is, shrinkage of the hole pattern can be suppressed. From FIG. 4A and FIG. 4B, holes before and after baking when exposed using a mask with a transmittance of 6% and when exposed using a mask with a transmittance of 0%. FIG. 4C is a graph showing the change in pattern size.
[0032]
(Second embodiment of the present invention)
In the second embodiment of the present invention, a plurality of semi-transparent regions are provided in place of the mask of the first embodiment, and the transmittance x% (however, 0 <x <100) of these regions is continuously different. x1, x2, x3... are set.
[0033]
FIG. 5 is a block diagram of the mask of the second embodiment of the present invention.
[0034]
FIG. 6 is a view showing the exposure amount in each region of the mask of the second embodiment of the present invention.
[0035]
The mask of FIG. 5 is based on the configuration of the mask of FIG. 2, and has a configuration in which four regions having different transmittances are continuously developed from the left side to the right side.
[0036]
The left region of the mask in FIG. 5 is the same as the light shielding region 24 shown in FIG. 2, and the light shielding region 24 is composed of a rectangular light shielding portion 13 having a light transmitting portion 20 in the center.
[0037]
3 are basically the same as the semi-transparent region of the mask of FIG. 2 in terms of configuration, and are a rectangular semi-transparent portion provided with a light transmission portion 21 in the center. 14, 14 ′, 14 ″. The setting of the transmittance value x% is arbitrarily set in relation to a region requiring heat flow.
[0038]
In the mask of this embodiment, four regions whose transmittances are continuously changed are arranged in a straight line. However, the present invention is not limited to this, and the shape of the mask and each region can be arbitrarily determined in relation to the region requiring heat flow. Can be set.
[0039]
(Transmittance setting)
The setting of the transmittance x% of the mask in FIG. 5 will be described based on the drawing showing the exposure amount in each region of the mask in FIG.
[0040]
FIG. 6 shows the transmission amount of the transmission part with respect to the exposure amount that varies linearly.
[0041]
When the exposure amount is small, the exposure amount of the light-shielding portion, that is, 0 mJ, determines 0 level, and when the exposure amount is large, the maximum exposure amount AmJ / cm ² of the transmission portion is defined as 100%. The range of use is that the lower limit is the exposure amount of the semi-transmissive portion where the resist does not generate heat flow at an exposure amount below this, and the upper limit is the exposure amount of the semi-transmissive portion where the resist is developed at an exposure amount greater than this. A continuous discrete value between them is set as the exposure amount of the semi-transmissive portion, B1 mJ / cm ² (x1%), B2 mJ / cm ² (x2%), and B3 mJ / cm ² (x3%). The exposure amount is set according to the shrink amount of each region.
[0042]
The transmittance x% of the resist is expressed as x = (B / A) × 100, as in the first embodiment.
[0043]
In the exposure process of FIG. 1, the resist is exposed with exposure amounts corresponding to the four types of transmittance of the mask. The rest is the same as the first embodiment.
[0044]
(Effect of the second embodiment)
As described above, by performing exposure with a mask having a plurality of transmittances in the semi-transparent region, the shrinkage amount can be controlled at a plurality of levels at a time with one mask. For example, when x1%>x2%> x3%, the shrinkage can be most suppressed in a region having a transmittance of x1%, followed by x2% and x3% in this order.
[0045]
(Third embodiment of the present invention)
In the third embodiment of the present invention, in the resist hole (opening) pattern, the semi-transparent region of the mask is applied to a pattern having a wide pitch between holes, and the light shielding region is applied to a pattern having a narrow pitch between holes. It is an example. The reason for this will be described with reference to FIG.
[0046]
FIG. 8 is a characteristic diagram of hole pattern pitch vs. dimension using a normal mask having a transmittance of 0%.
[0047]
FIG. 8 shows the characteristics before and after shrinking for each pitch when the resist hole pattern is heat-flowed at 136 ° C. with a constant exposure amount. In other words, the line representing the characteristics without heat flow is almost constant regardless of the hole pitch, whereas the line representing the characteristics with heat flow shows a degree of thermal sag in the narrow hole pitch range. Since it is relatively small, the degree of shrinkage of the resist dimension is small, and in the range where the hole pitch is wide, the degree of thermal sagging is relatively large, and thus the degree of shrinkage of the resist dimension becomes large.
[0048]
From this characteristic, when baking the hole pattern of the resist, in order to obtain a constant resist size, in the range where the hole pitch is narrow, the characteristic curve of FIG. In the range where the hole pitch is wide, it is necessary to control so that the characteristic curve of FIG. 8 becomes parallel, that is, not to shrink too much, and therefore the resist becomes semi-transparent. Is recognized.
[0049]
In addition, since the degree of shrinkage of the resist size can be determined by the hole pitch, it is necessary to set the transmittance of the semi-transparent mask to a desired value in advance.
[0050]
For example, when a resist having a film pressure of 0.1 μm as shown in FIG. 8 is required, a semi-translucent region is applied to a mask region having a resist hole pitch of 0.8 μm or more to suppress shrinkage of the resist size. .
[0051]
(Shrink amount)
As shown in FIG. 4C, when exposed, the semi-transparent region is less likely to heat flow, and in the case of holes, the hole diameter is large even with the same mask size as the light shielding region. The dimensions increase. In the resist of FIG. 8, when the pitch portion of 0.8 μm or more is made a semi-transparent region, the shrinkage amount suppressing effect of 0 to 30 nm (or more depending on the exposure amount) is obtained as shown in FIG. As a result, if the hole pitch is less than 0.8 μm, the shrinkage amount suppressing effect does not occur.
[0052]
(Effect of the third embodiment)
As described above, according to the third embodiment, the pitch dependency of the shrink amount is absorbed by providing the semi-transparent region in the pitch portion where the hole interval is wide. If the example of FIG. It is possible to suppress the dimensional difference of .about.0.07 .mu.m to 0.15 .mu.m in the range of 6 .mu.m or more and 0.08 .mu.m in the range to 0.1 .mu.m to 0.15 .mu.m and 0.05 .mu.m in the range.
[0053]
(Fourth embodiment of the present invention)
The fourth embodiment of the present invention is an example in which a mask of the outermost peripheral part pattern is a semi-transparent region in a repetitive pattern of holes.
[0054]
FIG. 9 is a diagram showing the dimensional behavior of a 0.8 μm pitch repetitive hole pattern and the outer peripheral heat flow using a normal mask with a transmittance of 0%.
[0055]
FIG. 9 shows the dimensions in the vicinity of the repetitive ends particularly when a resist having an initial dimension of 0.26 μm before heat flow is shrunk by heat flow. In the numbers 1 to 6 in FIG. 9, 1 is the end, 2 is the second, 3 is the third,. When the end portion is reduced in size, for example, in FIG. 9, the outermost end portion and the second end portion are defined as the final outside, the hole pattern in the outermost peripheral portion is formed by setting the mask of this portion as a semi-translucent region. An increase in the amount of shrinkage that occurs can be suppressed.
[0056]
(Effect of the fourth embodiment)
As described above, according to the fourth embodiment, by using a mask having the outermost peripheral portion of the repetitive pattern as a semi-transparent region, the variation of the dimension range of the repetitive hole pattern can be changed for the same reason as in the third embodiment. It becomes possible to suppress.
[0057]
(Other embodiments)
In the above embodiments, the hole pattern was described, but the present invention can be applied to all resist patterns whose shapes are changed by heat. Although the figure of the mask to be used is described as a region where the semi-transparent region absorbs light, it can also be applied as a region containing a dummy pattern where the resist is not resolved but the resist is exposed. Is possible.
[0058]
FIG. 7 is a block diagram of the mask on which the dummy pattern is formed.
[0059]
The light shielding region 24 on the left side of the mask in the figure is the same as already described. In the semi-transparent region 25 on the right side of the figure, the remaining rectangular region excluding the central light transmitting portion 21 is a perforated portion 26 in which a hole 22 of the same ground color as that of the light shielding portion 13 is opened. The substantial transmittance changes depending on the degree of opening of the hole 22.
[0060]
In addition, the present invention can be applied to all positive resists that are sensitive to the exposure wavelength and have improved heat resistance. Further, the semi-transparent region 25 may be made of materials having different transmittances.
[0061]
【The invention's effect】
According to the present invention, a region where shrinkage occurs due to subsequent baking and a region where shrinkage does not occur can be formed at a time by one exposure, and thus the process can be easily configured.
[0062]
In addition, a mask that can form a region where shrinkage is caused by subsequent baking and a region where no shrinkage occurs at a time by one exposure can be simplified.
[Brief description of the drawings]
FIG. 1 is a process flow of a first embodiment of the present invention.
FIG. 2 is a configuration diagram of a mask used in the first embodiment of the present invention.
FIG. 3 is a diagram showing light transmission amounts in each region of the mask of FIG. 2;
FIG. 4 is a diagram showing hole pattern heat flow behavior when using a mask with a transmittance of 6% and 0%.
FIG. 5 is a block diagram of a mask according to a second embodiment of the present invention.
FIG. 6 is a view showing an exposure amount in each region of a mask according to a second embodiment of the present invention.
FIG. 7 is a configuration diagram of a mask on which a dummy pattern of the present invention is formed.
FIG. 8 is a characteristic diagram of hole pattern pitch vs. dimension using a normal mask with a transmittance of 0%.
FIG. 9 is a diagram showing a dimensional behavior of a 0.8 μm pitch repetitive hole pattern using a normal mask with a transmittance of 0% and the outer peripheral heat flow.
FIG. 10 is a conventional heat flow process.
FIG. 11 is a diagram showing a structural formula of a polymer containing a conventional polyhydroxystyrene structural unit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Wafer 11 Resist 12 Mask 13 Light-shielding part 14 Semi-transmission part 15 Exposure area 16 Light-shielded resist part 17 Semi-transmission resist part 18 Opening 19 Reduced-diameter opening 20, 21 Light transmission part 22 Hole 24 Light-shielding area 25 Semi-translucent area 26 Hole opening

Claims (5)

A photomask used in the exposure step includes a step of applying a resist to a substrate, an exposure step of exposing a plurality of regions of the resist with different strengths, and a step of baking the resist after exposure. The three regions having different light transmittances are configured such that the light transmittance increases sequentially from the first region to the third region, and the third region surrounded by the first region A method for producing a resist pattern, wherein the region is provided more densely than the third region surrounded by the second region. In order to provide a hole pattern in the resist, a mask region facing a pattern having a wide pitch between holes is a semi-transparent region, and a mask region facing a pattern having a narrow pitch between holes is a light-shielding region. 2. The method of manufacturing a resist pattern according to claim 1, wherein the transmittance of the mask having the property corresponds to the degree of shrinkage of the resist size which can be recognized by the hole pitch. A mask region corresponding to a region in which the resist film thickness is 0.1 μm and the hole pitch of the resist is 0.8 μm or more is the semi-transparent region that suppresses shrinkage of resist dimensions. Item 2. A method for producing a resist pattern according to Item 1. 3. The method of manufacturing a resist pattern according to claim 2, wherein the hole pattern is a repetitive pattern of holes, and a mask region corresponding to the outermost peripheral pattern of the hole pattern is a semi-translucent region. Both characteristic curves representing the change in the dimension after shrinking with respect to the dimension before shrinking when the hole pattern size is 0% transmittance and transmittance n% when n is an arbitrary number in the range of 0 <n <100 5. The method of manufacturing a resist pattern according to claim 1, wherein, in the case of the pre-shrink dimension in a range larger than the pre-shrink dimension corresponding to the intersection point, the transmittance of the mask is set to the n%. .

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