This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2009-014558, filed Jan. 26, 2009, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a pattern generation method and pattern formation method using imprint lithography and, more particularly, to a pattern generation method of generating a pattern of an imprint lithography template to be used in the development and fabrication of a device, a computer-readable recording medium configured to store program instructions to be applied to the pattern generation method, and a pattern formation method using imprint lithography.
2. Description of the Related Art
As a technique capable of forming micropatterns and increasing the productivity at the same time in the semiconductor element fabrication process, imprint lithography that transfers a pattern formed at a template onto a transfer target substrate is attracting attention.
Imprint lithography is a method by which a template having a pattern to be transferred is pressed against a photocurable organic material layer applied on a substrate, and the pattern is transferred onto the organic material layer by curing it by irradiating it with light (see, e.g. Jpn. Pat. Appln. KOKAI Publication No. 2001-068411, Jpn. Pat. Appln. KOKAI Publication No. 2000-194142).
In imprint lithography, to eliminate defects caused by incomplete filling of the organic material in the pattern formed on the template, it is necessary to prolong the time after the template is brought into contact with the organic material and before the light is radiated, thereby completely filling the organic material in the pattern of the template. However, if the time after the template is brought into contact with the organic material and before the light is radiated is prolonged more than necessary, problems such as the decrease in throughput arise.
According to a first aspect of the present invention, there is provided a pattern generation method of generating a three-dimensional pattern to be formed at a template for use in a method of forming a pattern by filling a resist material in the three-dimensional pattern of the template comprising: performing at least one of adjustment of a depth of the three-dimensional pattern and division of the three-dimensional pattern, based on a relationship between a filling time of the resist material and a dimension or shape of the three-dimensional pattern.
According to a second aspect of the present invention, there is provided a computer-readable recording medium configured to store a program instruction to be applied to a method of generating a three-dimensional pattern to be formed at a template for use in a method of forming a pattern by filling a resist material in the three-dimensional pattern of the template, the program instruction causing a computer to execute at least one of adjustment of a depth of the three-dimensional pattern, and division of the three-dimensional pattern, based on a relationship between a filling time of the resist material and a dimension or shape of the three-dimensional pattern.
Embodiments of the present invention will be explained below with reference to the accompanying drawing.
As shown in
A three-dimensional transfer pattern is formed at the template 1. The template 1 is held on the template stage 2 such that the transfer pattern faces the transfer target substrate 3. The template 1 is made of a material such as quartz or fluorite that transmits ultraviolet light (UV light).
The template stage 2 includes a correction driving means for finely adjusting the position of the template 1. A good pattern can be formed because the template stage 2 controls the posture of the template 1 when transferring the pattern. Note that a pressurizing unit for pressing the template 1 against the transfer target substrate 3 is a mechanism separated from the template stage 2, but is not shown in
The chuck 4 is fixed to the sample stage 5, and holds the transfer target substrate 3. The sample stage 5 is preferably drivable along the X-axis, Y-axis, and Z-axis and around these three axes, i.e., a total of six axes. The reference mark table 6 is fixed on the sample stage 5, and serves as the reference position of the imprinting apparatus. The calibration of the alignment sensors 7 and the posture control and adjustment of the template 1 are performed by using a reference mark placed on the reference mark table 6.
The alignment sensors 7 are fixed on the alignment stage 8. When aligning the template 1 and transfer target substrate 3, the alignment sensors 7 sense an alignment mark (not shown) formed as an alignment reference on the transfer target substrate 3, and a template alignment mark (not shown) formed on the template 1 so as to face the alignment mark on the substrate. Note that
A measurement method using the alignment sensors 7 is as follows. First, the sample stage 5 is moved to a position where it is possible to simultaneously sense the alignment marks (e.g., diffraction gratings) formed on the template 1 and transfer target substrate 3. Then, light is emitted to each alignment mark, and a relative positional difference is measured from the center of gravity of light having returned to the alignment sensor 7 after being diffracted and reflected. The correction driving means controls the posture of the template 1 by using the sensed relative positions of the alignment marks on the template 1 and transfer target substrate 3. This makes it possible to perform high-accuracy pattern transfer.
The UV light source 10 is fixed to a main platen (not shown). The UV light source 10 exposes a photosensitive resin (not shown) applied on a transfer position on the transfer target substrate 3 to ultraviolet light through the template 1. Note that the UV light source 10 is installed immediately above the temperature 1 in
The misalignment testing mechanism 12 is installed on the base 9 of the imprinting apparatus. The misalignment testing mechanism 12 measures the difference between the relative positions of the pattern formed on the transfer target substrate 3 and the transfer pattern of the template 1, which is patterned on the photosensitive resin applied on the transfer target substrate 3.
First, a resist coating recipe taking account of the density of a pattern formed at a template is formed. The volatilization amount of an imprinting resist material during the process (e.g., the volatilization amount of the resist produced after the resist is applied on the substrate and before the three-dimensional pattern of the template is transferred) is compensated with respect to the recipe, thereby calculating an optimum resist distribution amount (S1).
Then, a transfer target substrate is coated with a necessary amount of the resist controlled in step S1 in accordance with the recipe (S2). A general imprint lithography process uses a resist coating method by which a necessary amount of a resist is dropped at a predetermined interval by using an inkjet nozzle for each shot. The local optimization of the resist amount is controlled by the distribution of the resist amount to be dropped.
After the transfer target substrate is coated with the proper amount of the resist in step S2, the template is brought into contact with the resist and held in this state, thereby filling the liquid-like resist in recesses of the template pattern. Note that the time required to fill the resist in the template pattern is generally short for fine patterns, and long for large patterns such as a dummy pattern and mark. After the resist is sufficiently filled in the template pattern, the resin of the resist is cured by emitting UV light from above the template for a desired time, and the template is removed from the resist. The pattern is formed by this imprinting process (S3).
Subsequently, the transfer target substrate on which the pattern is formed in step S3 is loaded into a defect testing apparatus, and a pattern defect test is conducted. In this step, the defect testing apparatus is used to perform a die-to-die or cell-array pattern defect test, thereby detecting a defect caused by imprinting (S4). Although a defect such as particle dust caused by a factor other than the imprinting process factor is naturally detected as well, the test is conducted to mainly detect and extract a non-filling defect called non-fill unique to imprinting. The non-filling defect often occurs as a common defect in a place where the resist material is locally insufficient, or when the filling time is insufficient. Since, however, a wafer has the unevenness of an undercoat or the like, the non-filling defect sometimes occurs owing to the wafer surface trend. In either case, the non-filling defect becomes a large-scale defect or large-size defect in many cases, and can easily be classified. Therefore, the non-filling defect may also be classified by SEM-Review. Note that the detection of a defect unique to imprinting performed using the optical defect testing apparatus has been explained as an example. However, this embodiment is not limited to this test, and a similar test can be conducted by using an EB defect testing apparatus or the like.
The defect information detected in step S4 is fed back to the resist coating amount distribution, thereby correcting it (S5). Of detected defects, information of only defects unique to imprinting, particularly, information of only the non-filling defect is often used. The information to be used contains the position coordinates of the defect and the defect size. Based on these pieces of information, a locally deficient resist coating amount is calculated, and the drop amount is adjusted and controlled, thereby forming a drop recipe having a new resist coating amount distribution. The drop amount can be adjusted and controlled by increasing or decreasing the drop amount per drop, or increasing or decreasing the density and interval of drop.
Then, a necessary amount of the resist is applied in accordance with the drop recipe formed in step S5. After that, an imprinting operation similar to that in step S3 is performed (S6). In this step, the resist coating process can be executed on the transfer target substrate after the resist pattern already formed on it is removed, or on a transfer target substrate different from the substrate on which the resist pattern is formed.
A further optimized resist coating recipe can be formed by continuing steps S1 to S6 described above until there is no more non-filling defect. This makes it possible to apply imprint lithography to an actual process, and form a defect-free, high-accuracy pattern.
First, as shown in
Then, as shown in
After that, as shown in
Consequently, as shown in
In imprint lithography, the time required to completely fill the organic material in the grooves of the template is related to the pattern size and the recess depth of the pattern.
As described above, the organic material for imprinting is filled in the micropattern of the template by the capillary phenomenon. Therefore, the time required to fill the organic material in the pattern recesses prolongs as the pattern dimension increases or the pattern recesses deepen, and a non-filling defect occurs if the waiting time before light irradiation is short. To prevent this non-filling defect, it is only necessary to well prolong the waiting time. In this case, however, the throughput decreases.
Accordingly, an embodiment of the present invention proposes a pattern formation method using a template in which the recess depth is adjusted by taking account of the pattern dimension or the like.
Pattern formation method example 1 will be explained below with reference to
As shown in
More specifically, let a, b, and c be the intersections of threshold X and the straight lines of depths A, B, and C. Assume that the recess depth of a pattern dimension smaller than a is less than or equal to depth A, the recess depth of a pattern dimension greater than or equal to a and less than b is less than or equal to depth B, and the recess depth of a pattern dimension greater than or equal to b and less than or equal to c is depth C (
As described above, when the surface of the template 23 has both a small pattern and large pattern as shown in
Note that in this example, when the larger pattern of the template is shallowed by taking account of the filling time, the small pattern of the template need not be shallowed unlike the large pattern. When etching the residual film of the resist pattern after the pattern is transferred by imprinting, the film thickness of the resist pattern must be greater than or equal to a predetermined value in order to ensure the etching resistance of the resist pattern. For this purpose, the depth of the small pattern of the template is preferably greater than or equal to that of the large pattern.
On the other hand, when the film thickness of the resist pattern corresponding to the large pattern of the template decreases, the edges of the resist pattern are etched in the etching step and the pattern dimension varies in some cases. However, no large problem arises because the ratio of the dimensional variation in the whole pattern is low. Also, the large pattern is used to form, e.g., a dummy pattern or alignment mark. Since the larger pattern is not required to have high dimensional accuracy in many cases, no large problem arises.
Pattern formation method example 2 will be explained below with reference to
As shown in
Therefore, letting A be the depth of a line shape template and B be the depth of a hole shape template, the hole shape is made shallower than the line shape. Examples of the hole shape and line shape are a pad, dummy pattern, alignment mark, and fringe (extracting pad).
Note that in the hole shape examples shown in
In pattern formation method example 2, the filling times of the hole shape and line shape are different not only because the recess volumes are different.
Also, the hole shape is preferably made shallower than the line shape for the same pattern size.
In pattern formation method example 2 as described above, as shown in
Pattern formation method example 3 will be explained below with reference to
As shown in
As described above, pattern formation method example 3 determines whether the recess depth of the template adjusted by above-mentioned pattern formation method example 1 or 2 can secure the film thickness required to process the organic material. If the film thickness required to process the organic material is not secured, the pattern is divided. This makes it possible to give the processing resistance to the organic film thickness after the pattern is formed.
Note that it is also possible to combine pattern formation method examples 1 and 2, and apply the combination to pattern formation method example 3.
Note also that in pattern formation method example 3, whether the film thickness required to process the organic material is ensured is determined based on the recess depth of the template adjusted by pattern formation method example 1 or 2. However, the present invention is not limited to this. That is, it is also possible to divide the pattern by determining whether the film thickness required to process the organic material is assured, based on the recess depth of the template not adjusted by pattern formation method example 1 or 2.
First, as shown in
Then, 2D pattern information and throughput information are input to the rules, and the recess depth of the template is calculated for each pattern size or shape (S14 or S24). More specifically, the recess depth of the template is defined in accordance with pattern formation method example 1 or 2 described previously.
Subsequently, whether the calculated depth can secure the film thickness required for processing is determined in the same manner as in above-mentioned pattern formation method example 3 (S15 or S25). Note that determination step S15 or S25 may also be executed by omitting depth calculation step S14 or S24.
If the film thickness can be assured, the file of mask write data is divided based on the recess depth calculated in step S14 or S24 (S16 or S26), and the process advances to the template manufacturing process.
On the other hand, if the film thickness cannot be ensured, whether the pattern can be divided based on the device characteristic is checked (S17 or S27). That is, whether the pattern is a dividable pattern such as a dummy pattern is checked. If pattern division is possible for the device, the pattern is divided (S18 or S28), and the depth is recalculated in accordance with the rules (S14 or S24). The pattern is kept divided until the depth can secure the film thickness. On the other hand, if pattern division is impossible for the device, the throughput is changed (S19 or S29), and the depth is recalculated in accordance with the changed rules.
Note that when omitting the rule formation step (S13 or S25) and the like, the pattern division and the calculation of the filling time are repeated until the result of the filling time in step S12 or S22 satisfies the desired throughput. To satisfy the desired throughput, the pattern depth is appropriately decreased. When the pattern depth is decreased, whether a sufficient film thickness can be secured is verified so that the dimensional variation when etching the resist pattern falls within the allowable range.
Note that the above-described pattern data generation method can also be applied, as a program executable by a computer, to various apparatuses by writing the program to a recording medium such as a magnetic disk, optical disk, or semiconductor memory, or by transmitting the program by a communication medium. A computer that implements this apparatus reads the programs recorded on the recording medium, and executes the aforementioned processing while the operation of the computer is controlled by the programs.
To manufacture a template having patterns different in depth, etching must be performed a plurality of number of times, so the file of write data must be divided. Therefore, the manufacture of a template having a pattern a in which the recess depth is depth A and a pattern b in which the recess depth is depth B (depth; A>B) will be explained below.
As shown in
First, as shown in
As described above, in the write data file of division method example 1, the first-layer data (resist 32) has the shape of only pattern a, and the second-layer data (resist 36) has the shape of only pattern b (see
As shown in
First, as shown in
As described above, in the write data file of division method example 2, the first-layer data (resist 33) has the shapes of both patterns a and b, and the second-layer data (resist 36) has the shape having the opening in the region of pattern a (see
According to an embodiment of the present invention, the recess depth of a pattern is adjusted in accordance with the pattern dimension or pattern shape in imprint lithography. More specifically, the recess depth of a template is decreased as the pattern dimension increases, and the recess depth of a template having a hole shape is made smaller than that of a template having a line shape. Since this makes it possible to control the time required to fill the organic material in the recesses of the template, it is possible to reduce non-filling defects of a pattern while suppressing the decrease in throughput.
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
Number | Date | Country | Kind |
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2009-014558 | Jan 2009 | JP | national |