ANALYSIS OF PATTERN FEATURES
The embodiments disclose a method for an electron curing reverse-tone process, including depositing an etch-resistant layer onto a patterned imprinted resist layer fabricated onto a hard mask layer deposited onto a substrate, curing the etch-resistant layer using an electron beam dose during etching processes of imprinted pattern features into the hard mask and into the substrate and using analytical processes to quantify reduced pattern feature placement drift errors and to quantify increased pattern feature size uniformity of imprinted pattern features etched.
This application is based on U.S. Provisional Patent Application Ser. No. 61/672,271 filed: Jul. 16, 2012, entitled “Electron Curing Reverse-Tone Process”, by Zhaoning Yu.
BACKGROUNDImprint resists are mainly designed to optimize their feature filling and release properties; they usually do not provide sufficient mechanical stability and etch resistance.
In a following description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration a specific example in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention.
General Overview:It should be noted that the descriptions that follow, for example, in terms of an electron curing a reverse-tone process is described for illustrative purposes and the underlying system may apply to any number and multiple types of reverse-tone processes.
In an embodiment the fabrication of BPM pattern at various densities including 250 Gb/in2, 450 Gb/in2, 500 Gb/in2, 1 Tb/in2, 1.5 Tb/in2 and 2 Tb/int to 5 Tb/in2 uses a “reverse-tone” process including a wet reverse-tone process, in which a silicon-rich, etch-resistant material (such as HSQ) is deposited including spin-coated on a resist pattern and then etched back through multi-step reactive ion etching (RIE) to form a negative tone replica of the original.
In some embodiments increasing areal density may cause narrowing of the process window feature mechanical instability during etch-back may increase dot placement error (the “shifting dots” problem), insufficient etch resistance, and non-homogeneity of resist material at this scale degrades the dot size uniformity.
The etch-resistant layer covers and fills the pattern features of the imprinted resist pattern. A controlled electron beam dose is used for curing the etch-resistant layer using a controlled electron beam dose 110 that structurally transforms the etch-resistant layer material. The curing may be done alternatively before or after the spin on glass (SOG) etch-back, the two alternatives lead to different characteristics in the results, but both increase the pattern quality. The electron beam curing structural transformation is creating mechanical stability and reducing drift of etch area and pattern feature position when etching the hard mask material 120. Etching the hard mask material is achieved using a 2-step reverse-tone etching process 130. A first predefined etch performs an etch-back of the electron beam cured etch-resistant layer to expose the imprinted resist pattern.
A second predefined etch is used for removing the imprinted resist and etching a pattern into the hard mask layer down to the substrate 140. The second predefined etch removes the imprinted resist pattern and forms a negative tone replica of the original pattern. The remaining electron beam cured etch-resistant layer can be removed creating a hard mask patterned template used for replicating semiconductors and stacks including high density bit patterned media (BPM) 150. The removal of the electron beam cured etch-resistant layer includes using a wet-chemical process such as sodium hydroxide (NaOH). Alternatively the remaining HSQ itself is used as part of the mask for the etching of the underlying stack or semiconductor. Replicating stacks including high density bit patterned media (BPM) includes using the mask for etching of magnetic layers of stacks by ion beam etching.
DETAILED DESCRIPTION Controlled Electron Beam Curing ProcessAn apparatus is used to cure the etch-resistant layer using electron beam dose 250 which is controlled to create mechanical stability 252 in the etch-resistant layer. The mechanical stability will reduce drift of etch area and pattern feature position 256. The electron beam curing dose is controlled to a predetermined voltage and dose 270 to achieve electron beam curing 260 of the etch-resistant layer material. The predetermined voltage 303 of
The controlled electron beam dose uses a predetermined voltage 303 for an acceleration voltage. The electron beam irradiation 300 is used to structurally transform etch-resistant layer material 310 which reduces volume 312, increases refractive index N 314 and increases densification 316.
In one embodiment curing the etch-resistant layer 320 is performed on the etch-resistant layer 350. The electron beam irradiation step is added before a reverse-tone process including a 2-step etch-back and etching. The curing may increase the mechanical stability of the HSQ features during the 2-step reverse-tone processing, thus greatly alleviating the “shifting dots” problem. When the e-beam treatment is performed before the HSQ etch-back, the process tends to produce features with bigger size.
After curing the etch-resistant layer 320 a 2-step reverse-tone etching process 330 is used to etch the hard mask material. A first predefined etch 340 including reactive ion etching (RIE) 342 using tetrafluoromethane (CF4) 346 is used to etch-back cured etch-resistant layer 360. This embodiment continues as described in
In another embodiment before the electron beam curing process the first predefined etch 340 is used to etch-back the uncured etch-resistant layer 355.
The electron beam curing 260 of
The second predefined etch 410 performs an etch of a hard mask layer 430 and removes the imprinted resist layer 435. This process is etching a pattern down to the substrate 440. The electron beam cured and etched back etch-resistant layer reduces pattern feature placement drift errors 442 and increases pattern feature size uniformity 446. The remaining HSQ itself can be used as part of the mask for the etching of the underlying stack or semiconductor. The second predefined etch 410 can alternatively be followed by a stripping process to remove the etched back etch-resistant layer 450 and forming a negative tone replica of the original pattern.
The etched hard mask including a carbon hard mask layer and alternatively including the etched back electron beam cured etch-resistant layer create a hard mask patterned template 460. In one embodiment subsequent processes include a substrate ion milled using patterned hard mask 465 for patterning of the substrate including a BPM magnetic stack. The resulting hard mask patterned template 460 may be used for subsequent replication of high-density (>1 Tb/in2) patterned media. BPM replicated using the hard mask patterned template produced by the electron curing reverse-tone process 100 may have 1.5 Tb/in2 density, corresponding to a minimum dot-to-dot distance of 22.1 nm. The electron curing reverse-tone process 100 increases the quality of the replicated BPM pattern at >1 Tb/in2 density, producing arrays with markedly increased dot size at a minimum dot-to-dot distance of 22.1 nm. The hard mask patterned template 460 with reduced pattern feature placement drift errors and increased pattern feature size uniformity is used for replicating semiconductors 470 and used for replicating stacks 480 including high density bit patterned media (BPM) 490. The electron curing reverse-tone process 100 creates the advantages of placement accuracy and size uniformity thereby increasing the replicated quality of semiconductors and stacks.
Spin Coating an Etch-Resistant LayerA descum process 534 is used to descum the imprinted resist layer 532. The descum process 534 removes excess resist material from each pattern feature 538 and exposes portions of the hard mask layer 510. An etch-resistant material is deposited onto the resist pattern 540. An etch-resistant layer material 545 including hydrogen silsesquioxane (HSQ) 235 of
The 2-step reverse-tone etching process 330 of
The second predefined etch 410 of
Alternatively the etched etch-resistant material 590 removal process is not included where by the remaining etch-resistant material 590 for example HSQ is used as part of the mask as well. A subsequent process including using a RIE process is used to transfer the pattern into an underlying Si substrate followed by a process to remove the HSQ/carbon mask stack. The patterned hard mask layer 595 on the substrate 500 creates a hard mask patterned template 598. The hard mask patterned template 598 is used for used for replicating semiconductors and stacks including high density bit patterned media (BPM).
Resist Layer Imprinted PatternIn this embodiment the 2-step reverse-tone etching process 330 of
The controlled electron beam dose 555 is used for electron beam curing of etched back etch-resistant material 630. The electron beam curing process results in etched back cured etch-resistant material 575. The etched back cured etch-resistant material 575 has structurally transformed molecules with increased mechanical stability. Descriptions of subsequent processes are shown in
Following the reactive ion etching using O2 585, an alternative stripping process is used to remove the etched etch-resistant material 587 including a NaOH solution wet-chemical etch 588 removes the etched etch-resistant material 590. In the alternate the remaining HSQ itself is used as part of the mask for the etching of the underlying stack or semiconductor. The patterned hard mask layer 595 on the substrate 500 creates the hard mask patterned template 598 used for replicating semiconductors 470 of
A controlled electron beam emitting apparatus 710 is used to produce for example flooding electron beams 720 into the etch-resistant layer 230. The flooding electron beams 720 diffuse as they penetrate the etch-resistant material. The controlled electron beam emitting apparatus 710 regulates the strength of the emitted electron beams using a predetermined voltage and dose. The predetermined voltage is controlled to enable the flooding electron beams 720 to saturate the volume and depth of the etch-resistant layer 230 thus curing the etch-resistant materials to structurally transform the molecules of the etch-resistant layer 230.
The etch-resistant layer 230 using HSQ is structurally transformed at a curing dose including ˜1000 μC/cm2 to 50,000 μC/cm2. The process affected by the changes in HSQ properties includes the toppling and shifting in HSQ pillars and the strength and adhesion may help the pillars stand including stress vs. strength, and material failure. The molecular structural transformation reduces volume 312 of
Each cured structurally transformed etch-resistant layer material molecule 820 has a cross-linked “network” structure caused by an atomic redistribution reaction. The etch-resistant layer 545 using for example HSQ is structurally transformed at a curing dose of for an example in ranges from 1,000 μC/cm2 to 50,000 μC/cm2. The electron beam curing structural transformation shrinks the molecule's volume and increases its density resulting in increased etch resistance. The electron beam curing increased etch resistance creates mechanical stability preventing pattern feature shifts in position and size degradations during etching. This advantage of electron beam curing produces replications of pattern feature arrays with markedly increased placement accuracy and size uniformity increasing the quality of replications for example semiconductors and stacks including BPM patterned at >1 Tb/in2 density.
Coercivity and Signal Amplitude Vs. Magnetic DiameterThe electron beam curing dose is controlled to a predetermined voltage and dose 270 of
A statistical size and placement distribution quality analysis 1014 is performed for each statistical analysis reference group 1016. The statistical analysis reference group 1016 includes targeted pattern features and density 1018, hard mask and substrate layer materials used 1020 and electron beam voltage and dose settings 1022. The quality of the size of the pattern features and placement of the patterned features are analyzed. Patterned features size and placement errors from reverse tone process can be separated 1024. The statistical size and placement distribution analysis 1014 is programmed to evaluate the size and placement decoupled 1026. One evaluation is a reverse tone feature size analysis 1030 which is described further in
The data collected in the histogram 1110 is an analysis of the brightness of all the pixels in the original SEM image of the features for example dots. The histogram 1110 distribution (horizontal axis) is from 0 to 255 to correspond to a gray scale for example a 256-level brightness. The histogram 1110 distribution (horizontal axis) is used to set the brightness “threshold” to turn the original gray-scale (0-255) image into a binary image (0 and 1) that is used to determine a size (brightness) threshold 1120. The threshold 1120 is used as a filter to create binary 1130 feature size data from the SEM 1105. The binary 1130 is used to create MB 1140 a binary representation of the SEM 1105. The MB 1140 is a filtered and “smoothened” version of the binary 1130 through several image processing operations to make the size calculation more stable. In binary 1130 there are smaller dots near the large dots, these small dots may be interpreted by computer as individual dots, that's why filtering is applied to “smoothen” the binary 1130 image. The MB 1140 data is shown as a size distribution 1150 which is compared to a targeted size quality 1160 as a basis for a size evaluation of one embodiment.
Feature Placement EvaluationThe foregoing has described the principles, embodiments and modes of operation of the present invention. However, the invention should not be construed as being limited to the particular embodiments discussed. The above described embodiments should be regarded as illustrative rather than restrictive, and it should be appreciated that variations may be made in those embodiments by workers skilled in the art without departing from the scope of the present invention as defined by the following claims.
Claims
1. A method for an electron curing reverse-tone process, comprising:
- depositing an etch-resistant layer onto a patterned imprinted resist layer fabricated onto a hard mask layer deposited onto a substrate;
- curing the etch-resistant layer using an electron beam dose during etching processes of imprinted pattern features into the hard mask and into the substrate; and
- using analytical processes to quantify reduced pattern feature placement drift errors and to quantify increased pattern feature size uniformity of imprinted pattern features etched.
2. The method of claim 1, wherein the depositing of an etch-resistant layer includes hydrogen silsesquioxane (HSQ) and is configured to include deposition processes including spin coating.
3. The method of claim 1, wherein the electron beam curing is configured to increase mechanical stability by molecularly transforming etch-resistant layer materials including hydrogen silsesquioxane (HSQ) including material densification and a reduction in its volume and an increase in its refractive index n to reduce pattern feature placement drift errors and increase pattern feature size uniformity.
4. The method of claim 1, wherein curing includes using irradiation including thermal, ion beam, electron beam, x-ray, photon, UV, DUV, VUV, plasma, microwave, or other types of irradiation controlled to a predetermined energy and dose determined using analytical processes to analyze size and placement distribution.
5. The method of claim 1, wherein the hard mask layer is patterned using an etch process including reactive ion etching (RIE) including using oxygen gas (O2).
6. The method of claim 1, wherein etching a pattern down to the substrate using a 2-step reverse-tone etching process includes a reactive ion etching (RIE) including using Tetrafluoromethane (CF4) and a reactive ion etching (RIE) including using oxygen gas (O2).
7. The method of claim 1, wherein an etch-back of the cured etch-resistant layer and imprinted resist layer includes using a reactive ion etching (RIE) including using Tetrafluoromethane (CF4).
8. The method of claim 1, wherein the electron curing electron beam dose is performed before a first reactive ion etching (RIE) and alternatively performed after a first reactive ion etching (RIE) and before a second reactive ion etching (RIE).
9. The method of claim 1, wherein the electron curing reverse-tone process can reduce pattern feature placement drift errors and increase pattern feature size uniformity in processes replicating semiconductors and stacks including bit patterned media.
10. An apparatus, comprising:
- means for curing an etch-resistant layer deposited onto a pattern imprinted resist layer deposited onto a substrate with a hard mask layer deposited thereon;
- means for etching the cured pattern imprinted resist layer features into the hard mask layer and substrate; and
- means for analyzing distributions of placement drift errors and pattern feature size uniformity of the etched, cured, imprinted, resist layer pattern features.
11. The apparatus of 10, further comprising means for controlling the electron beam dose curing using a predetermined voltage and dose of irradiation including thermal, ion beam, electron beam, x-ray, photon, UV, DUV, VUV, plasma, microwave, or other types of irradiation determined using a statistical size and placement distribution quality analysis.
12. The apparatus of 10, further comprising means for structurally changing the properties and transforming etch-resistant layer materials including hydrogen silsesquioxane (HSQ) including material densification, a reduction in its volume and an increase in its refractive index n.
13. The apparatus of 10, further comprising means for etching the hard mask and substrate using the 2-step reverse-tone etching process including using a reactive ion etching (RIE) including a first reactive ion etching (RIE) using Tetrafluoromethane (CF4) and a second reactive ion etching (RIE) using oxygen gas (O2).
14. The apparatus of 10, further comprising means for using an electron beam dose to cure an etch-resistant layer includes changing the etch-resistant layer material on a molecular level including causing an atomic redistribution reaction to create a cross-linked “network” structure.
15. An electron beam curing process, comprising:
- using doses of electron beams to cure etch-resistant materials deposited onto an pattern imprinted resist layer to create mechanical stability;
- employing a reverse-tone etching process including using etching processes to etch the electron beam cured mechanically stabilized imprinted resist layer patterned features into a hard mask layer and into a substrate; and
- using analytical processes to predetermine the electron beam curing doses.
16. The electron beam curing process of claim 15, wherein the electron beam curing is controlled to regulate voltage and dose based on the type and thicknesses of imprinted resist materials, etch-resistant materials, hard mask layer and substrate and analytical processes results.
17. The electron beam curing process of claim 15, wherein the curing includes irradiation including thermal, ion beam, electron beam, x-ray, photon, UV, DUV, VUV, plasma, microwave, or other types of irradiation used at a predetermined energy and dose determined using a statistical size and placement distribution quality analysis.
18. The electron beam curing process of claim 15, wherein the hard mask patterned template using a 2-step reverse-tone etching process includes using a first etch including a reactive ion etching (RIE) using Tetrafluoromethane (CF4) and using a second etch including reactive ion etching (RIE) using oxygen gas (O2).
19. The electron beam curing process of claim 15, wherein the electron beam curing of the etch-resistant materials creates mechanical stability to reduce pattern feature placement drift errors and increase pattern feature size uniformity.
20. The electron beam curing process of claim 15, wherein the electron beam curing is configured to structurally change the properties and transform materials used for the etch-resistant layer including hydrogen silsesquioxane (HSQ) including material densification, a reduction in its volume and an increase in its refractive index n.
Type: Application
Filed: Mar 13, 2013
Publication Date: Jan 16, 2014
Inventors: Zhaoning Yu (Palo Alto, CA), Nobuo Kurataka (Compbell, CA), Gennady Gauzner (San Jose, CA)
Application Number: 13/798,130
International Classification: B05C 21/00 (20060101);