Variable hardness amorphous carbon mask

Abstract

A method for manufacturing an amorphous carbon layer (ACL) mask includes forming an ACL on an underlying substrate. This ACL includes a soft ACL portion having a first hardness and a hard ACL portion having a second hardness. The soft ACL portion is located beneath the hard ACL portion. The second hardness is greater than the first hardness. The method also includes forming a patterned layer on the ACL and using the patterned layer as an etching mask to form the ACL mask by etching through both the soft and hard ACL portions of the ACL to expose the underlying substrate. The steps of forming the ACL may include depositing one or both of the soft and hard ACL portions. Process conditions may also be varied during ACL formation to create a hardness gradient transitioning from the softer to the harder regions.

Description

Technical Field

[0001] This application claims priority to and the benefit of U.S. non-provisional application No. 17 / 660,111, filed April 21, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present invention generally relates to etching processes and, in particular embodiments, to variable hardness amorphous carbon masks and methods thereof. Prior Art

[0003] Microelectronic device formation can involve a range of manufacturing techniques, including the formation, patterning, and removal of multiple material layers on a substrate. Etch masks can be formed (e.g., deposited) to protect areas of the substrate and allow for pattern transfer via etching. Achieving a high aspect ratio during etching is crucial for various semiconductor processes, such as high-aspect-ratio contact (HARC) formation, NAND formation (e.g., 3D-NAND), NOR formation, and memory formation.

[0004] Distortion can occur when transferring a pattern to the underlying layer. For example, features transferred to the underlying layer may exhibit any number of undesirable defects, such as widening or narrowing, inconsistent size or position, and non-vertical sidewalls. Distortion is a particular problem, involving deviations from the desired vertical profile, causing features to drift laterally. Distortion can become increasingly pronounced as the thickness of the underlying layer increases. Therefore, it may be desirable to have etch masks with improved profile control while maintaining the desired mask thickness and yield. Summary of the Invention

[0005] According to an embodiment of the present invention, a method for manufacturing an amorphous carbon layer (ACL) mask includes forming the ACL on an underlying layer. The ACL includes a soft ACL portion having a first hardness and a hard ACL portion having a second hardness. The soft ACL portion is located below the hard ACL portion. The second hardness is greater than the first hardness. The method also includes forming a patterned layer on the ACL and using the patterned layer as an etching mask to form the ACL mask by etching through both the soft ACL portion and the hard ACL portion of the ACL to expose the underlying layer.

[0006] According to another embodiment of the present invention, a method for manufacturing an ACL mask includes depositing a soft ACL layer of a multi-layer ACL stack on a bottom layer, and depositing a hard ACL layer of a multi-layer ACL stack on the soft ACL layer. The soft ACL layer has a first hardness of less than 10 GPa and a first thickness of at least 0.5 µm. The hard ACL layer has a second hardness greater than or equal to 10 GPa. The method also includes forming a patterned layer on the multi-layer ACL stack, and using the patterned layer as an etch mask to form the ACL mask by etching through the multi-layer ACL stack to expose the bottom layer.

[0007] According to another embodiment of the present invention, an ACL mask includes a soft ACL layer, a hard ACL layer disposed on the soft ACL layer, and a high-aspect ratio pattern extending through both the soft ACL layer and the hard ACL layer. The soft ACL layer has a thickness of at least 0.5 μm and a first hardness. The hard ACL layer has a thickness of at least 0.5 μm and a second hardness greater than the first hardness. Simple diagram description

[0008] For a more complete understanding of the present invention and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:

[0009] 1A and 1B illustrate cross-sectional views of exemplary mask layers according to embodiments of the present invention, wherein FIG. 1A illustrates a mask layer having vertical features, and FIG. 1B illustrates a mask layer having deformed features;

[0010] Figure 2 illustrates a cross-sectional view of an exemplary amorphous carbon layer (ACL) mask including a soft ACL portion and a hard ACL portion according to an embodiment of the present invention;

[0011] Figure 3 shows a cross-sectional view of an exemplary ACL mask including an intermediate ACL layer according to an embodiment of the present invention;

[0012] Figure 4 shows a cross-sectional view of an exemplary ACL mask including at least one intermediate ACL layer according to an embodiment of the present invention;

[0013] Figure 5 illustrates a cross-sectional view of an exemplary ACL mask including a gradient transition from a soft ACL portion to a hard ACL portion according to an embodiment of the present invention;

[0014] 6A-6F illustrate cross-sectional views of an exemplary workpiece during an etching process of a bottom layer using an ACL mask according to an embodiment of the present invention, wherein FIG. 6A shows the formation of a soft ACL layer, FIG. 6B shows the formation of a hard ACL layer, FIG. 6C shows the formation of a patterned layer, FIG. 6D shows the formation of an ACL mask, FIG. 6E shows the etching of the bottom layer, and FIG. 6F shows the pattern transferred to the bottom layer.

[0015] 7A-7C illustrate cross-sectional views of an exemplary workpiece during another etching process of a bottom layer using an ACL mask according to an embodiment of the present invention, wherein FIG. 7A shows the formation of a soft ACL portion of the ACL, FIG. 7B shows the formation of a hard ACL portion of the ACL, and FIG. 7C shows the formation of the ACL mask; and

[0016] FIG. 8 is a flow chart illustrating an exemplary method for manufacturing an ACL mask according to an embodiment of the present invention.

[0017] Unless otherwise indicated, corresponding numbers and symbols in the different figures generally refer to corresponding parts. The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale. The edges of features drawn in the figures do not necessarily indicate the ends of the features. Implementation Method

[0018] The making and using of various embodiments are discussed in detail below. However, it should be understood that the various embodiments described herein can be used in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the various embodiments and should not be construed as limiting the scope.

[0019] Amorphous carbon masks can be used to etch underlying layers of a workpiece, such as during the formation of microelectronic devices. Specifically, hard amorphous carbon layer (ACL) masks can be used in high-aspect ratio processes, such as the HARC process. For example, high-aspect ratio processes can be used during the manufacture of memory devices, including dynamic random access memory (DRAM), NAND flash memory, and NOR flash memory. During the etching process, the pattern of the hard ACL mask can be transferred to the underlying layer (e.g., a dielectric layer or a layer including oxide, nitride, etc.). Etching contact holes is a specific application of high-aspect ratio etching using ACL hard masks.

[0020] Amorphous carbon, several microns thick, is often used as a hard mask for dielectric (e.g., oxide, nitride, ONO) openings during device formation (e.g., 3D-NAND devices) due to its good etch selectivity to dielectrics. Opening thick ACL layers can take a long time due to their high aspect ratio. Etching can occur in a plasma processing chamber, such as an inductively coupled plasma (ICP) chamber.

[0021] Amorphous carbon with higher hardness (i.e., hard ACL) can be used in etching processes, such as for etching dielectrics, because it exhibits better etch selectivity compared to amorphous carbon with lower hardness (i.e., soft ACL). During the formation of hard ACL, the hardness can be increased by increasing the temperature. Therefore, hard ACL is also referred to as high-temperature ACL (although high temperature is not the sole factor determining ACL hardness). An example of high-temperature ACL is the APF® series of films sold by Applied Materials. Because temperature affects ACL hardness, temperature and other variables can be manipulated to form ACLs with varying properties. For example, low-temperature ACL (e.g., formed at 450°C) may result in a soft ACL.

[0022] However, while hard ACL is more etch-resistant than soft ACL, it is also more difficult to open and can suffer from profile distortion at high aspect ratios. For example, when etching hard ACL, distortion (possibly meaning features bend from the desired vertical etch profile) can begin at or even before a relatively shallow depth of 1.5 µm. This is relevant for what can be considered a medium aspect ratio. Furthermore, as etch depth increases, the effects of the distortion compound make profile distortion in hard ACL more pronounced for high-aspect ratio processes. In many cases, the hard ACL mask must be significantly thicker than 1.5 µm to ensure that the ACL is not completely consumed during the etch process.

[0023] Simply increasing the stiffness of the ACL could further improve selectivity, allowing for the use of thinner masks. However, increased stiffness would also increase opening time and lead to more rapid deformation, making this solution unfeasible. Furthermore, varying the thickness of the mask may be undesirable for a variety of reasons. Increasing the stiffness of the ACL beyond a certain point may also have practical limitations (e.g., difficulty, cost, diminishing returns).

[0024] Relatively speaking, soft ACLs can be opened more easily and achieve better profiles than stiffer ACLs, while exhibiting reduced etch resistance (e.g., during dielectric opening). The onset of deformation, such as distortion, in soft ACLs may occur at much deeper depths, such as 2.5 µm or greater. Therefore, even slight profile deformation may not begin to occur until well into the high-aspect ratio range. However, due to its lower selectivity, soft ACLs inherently require significantly thicker thicknesses for high-aspect ratio etching.

[0025] In various embodiments, the ACL mask includes a soft ACL portion and a hard ACL portion. The hard ACL portion is located on top of the ACL mask and has a higher hardness than the soft ACL portion. The pattern to be transferred to the underlying layer extends through both the hard and soft ACL portions of the ACL mask. The ACL mask can be manufactured by forming a patterned layer covering the ACL mask and etching through both the soft and hard ACL portions using the patterned layer as an etching mask.

[0026] The ACL mask of the embodiments described herein advantageously combines the advantages of both soft and hard ACL to improve profile deformation and productivity while maintaining high etch selectivity. It is ideal to both control the etch profile and maintain high etch selectivity. The proposed method utilizes at least two ACL sections of varying hardness within a single ACL mask, with the harder ACL section positioned above the softer ACL section. By replacing a uniform ACL with a variable hardness ACL, the low- to medium-aspect ratio portions of a high-aspect ratio etch can advantageously utilize the harder ACL, while the medium- to high-aspect ratio portions utilize the softer ACL. In this way, etching the ACL becomes easier (i.e., faster and with less deformation) when transitioning to high aspect ratios.

[0027] Another potential advantage of the ACL mask of embodiments is that it advantageously allows the thickness of the ACL mask to be controlled. Specifically, using a hard ACL portion positioned above a soft ACL portion can advantageously allow the thickness of the ACL mask to remain the same while achieving improved profile control and yield. The variable hardness of the ACL mask of embodiments can facilitate optimization of mask thickness, yield, and profile deformation. Even with a soft ACL portion at the lower portion of the ACL mask, etching performance is not degraded because a sufficient amount of ACL can remain after etching. Through careful design and optimization, this remaining ACL can advantageously be primarily soft ACL. That is, the hard ACL portion can serve as etching protection at the beginning of etching, while the soft ACL portion can serve as etching protection at the end of etching.

[0028] The following examples describe various etching processes and structures, particularly etching processes and structures including variable hardness amorphous carbon masks. The following description describes the embodiments. Figures 1A and 1B illustrate an example of profile deformation. Figure 2 describes an ACL mask according to an embodiment. Figures 3 through 5 describe three additional ACL masks according to embodiments. Figures 6A through 6F describe an etching process according to an embodiment. Figures 7A through 7C describe another etching process according to an embodiment. Figure 8 describes a method for manufacturing an ACL mask according to an embodiment.

[0029] 1A and 1B illustrate cross-sectional views of exemplary mask layers according to embodiments of the present invention, wherein FIG. 1A illustrates a mask layer having vertical features, and FIG. 1B illustrates a mask layer having deformed features.

[0030] 1 , a workpiece 100 includes a bottom layer 20 supported by a substrate 10. In some cases, the bottom layer 20 may be a substrate and may include other additional layers. A mask layer 102 (e.g., a hard mask layer) is disposed on the bottom layer 20. Mask layer 102 is shown as having vertical features 103. That is, the features of the patterned layer 30 disposed on the mask layer 102 are accurately transferred to the mask layer 102 as vertical features.

[0031] In contrast, workpiece 105 includes mask layer 106, which undergoes deformation (e.g., twisting as shown) during the transfer of features from patterned layer 30 to mask layer 106. The result is deformed features 107 that do not accurately reflect the desired positioning of features of patterned layer 30. This undesirable deformation can occur for a variety of reasons, such as, for example, increased mask thickness or increased mask hardness, as described above.

[0032] Specifically, deformation is more likely to occur at higher aspect ratios. Etch depths less than 1.5 µm can be considered low aspect ratios, while etch depths greater than 1.5 µm can be considered medium to high aspect ratios. In the specific example of a hard amorphous carbon mask (e.g., used for high-aspect ratio dielectric etches), undesirable levels of deformation can occur at medium to high aspect ratios (e.g., greater than or equal to 1.5 µm). Because etch depths greater than 1.5 µm are often required, strategies to mitigate deformation in high-aspect ratio etches may be needed. The following description details various techniques for transferring features from a patterned layer to a mask layer that approximate the ideal vertical features 103 of the mask layer 102 rather than the deformed features 107 of the mask layer 106.

[0033] 2 illustrates a cross-sectional view of an exemplary ACL mask including a soft ACL portion and a hard ACL portion according to an embodiment of the present invention. Like numbered elements may be as previously described.

[0034] 2 , ACL mask 212 includes ACL 214, which includes a soft ACL portion 216 and a hard ACL portion 218. Hard ACL portion 218 is harder than soft ACL portion 216 and covers soft ACL portion 216. For example, soft ACL portion 216 may have a hardness Hs, while hard ACL portion 218 may have a hardness Hh greater than Hs. High aspect ratio pattern 213 extends through both hard ACL portion 218 and soft ACL portion 216.

[0035] The soft ACL portion 216 also has a thickness ds, and the hard ACL portion 218 has a thickness dh. In one embodiment, ds is approximately equal to dh. In another embodiment, ds is greater than dh. For example, it may be advantageous to reduce the thickness dh of the hard ACL portion 218 to increase productivity and reduce contour deformation. However, in some cases, the opposite may be true if, for example, greater selectivity is desired, the total thickness dt of the ACL 214 (i.e., ds + dh) is reduced, thereby reducing the overall thickness of the ACL mask 212.

[0036] In some embodiments, ds is at least 0.5 µm, and in various embodiments, ds is at least 1 µm. In one embodiment, ds is less than approximately 3 µm. Similarly, in some embodiments, dh is at least 0.5 µm, and in various embodiments, dh is at least 1 µm. In one embodiment, dh is less than approximately 2 µm, and in another embodiment, less than 1.5 µm. In various embodiments, dt is at least 1 µm, and in one embodiment, at least 2 µm. In one embodiment, dt is less than approximately 4 µm. However, these ranges are merely examples reflecting various potential considerations. Depending on the specifics of a given application, the concepts described herein may also be applicable to other thicknesses.

[0037] One or both of the soft ACL portion 216 and the hard ACL portion 218 can be implemented as layers (e.g., a lower layer and an upper layer, respectively). Specifically, as shown, the soft ACL portion 216 can have a substantially uniform hardness throughout the thickness ds and have a definable boundary separating it from the hard ACL portion 218. For example, the ACL 214 can be a multi-layer ACL stack (i.e., at least two layers), with the stiffest ACL layer positioned on top of the ACL mask 212. However, uniformity is not a requirement. For example, in some embodiments, some or all of the ACL 214 can incorporate a gradient hardness transition, as described in more detail below.

[0038] As an example, the ACL can be formed using any suitable process, such as plasma-enhanced chemical vapor deposition (PECVD). However, other methods are also possible, including electron cyclotron resonance (ECR), reactive sputtering, electron cyclotron wave resonance (ECWR), plasma light source (PBS), filtered cathodic vacuum arc (FCVA), etc.

[0039] ACL properties, such as hardness, can be controlled during the ACL formation process. The temperature during ACL formation is one way to differentiate between soft and hard ACLs. For example, soft ACLs (low-temperature ACLs) can be formed at lower temperatures (e.g., 450°C) than hard ACLs (high-temperature ACLs). However, temperature is not the only variable that influences ACL hardness. Therefore, by varying other process conditions, it is possible to form hard ACLs at low temperatures and soft ACLs at high temperatures.

[0040] Hard ACL can have specific physical properties that distinguish it from soft ACL. These distinguishing properties may include the atomic percentage of sp3-bonded carbon, the atomic percentage of hydrogen, density, and (of course) hardness. For example, hard ACL can have less than approximately 40% sp3-bonded carbon, approximately 20%–40% hydrogen, and a density in the range of approximately 1.6–2.2 g / cm3. In one embodiment, the resulting hardness, Hh, can be greater than 10 GPa and in the range of approximately 10 GPa–20 GPa. In one embodiment, hard ACL is a tetrahedral amorphous carbon layer (ta-C:H) and exhibits even higher hardness (up to 50 GPa Hh).

[0041] In contrast, soft ACL can include at least 60% sp3-bonded carbon (e.g., up to 70%), approximately 40%-50% hydrogen, and have a density in the range of approximately 1.2-1.6 g / cm3. The hardness Hs of soft ACL is correspondingly lower than Hh. For example, the hardness Hs of soft ACL can be less than approximately 10 GPa.

[0042] FIG3 illustrates a cross-sectional view of an exemplary ACL mask including an intermediate ACL layer according to an embodiment of the present invention. The ACL mask of FIG3 may be, for example, an embodiment of other ACL masks described herein, such as the ACL mask of FIG2 . Like numbered elements may be as previously described.

[0043] 3 , ACL mask 312 includes ACL 314, which includes a soft ACL portion 316 and a hard ACL portion 318 implemented as soft and hard ACL layers. It should be noted that for the sake of brevity and clarity, a convention has been adopted here and below, where elements according to type [x12] may be related implementations of the ACL mask in various embodiments. For example, unless otherwise noted, ACL mask 312 may be similar to ACL mask 212. Similar conventions are adopted for other elements, which can be clarified by using similar terminology and the aforementioned three-digit numbering system.

[0044] ACL mask 312 is a specific embodiment in which an intermediate ACL layer 317 is contained between a hard ACL portion 318 and a soft ACL portion 316. A high-aspect ratio pattern 313 extends through hard ACL portion 318, intermediate ACL layer 317, and soft ACL portion 316. Intermediate ACL layer 317 has a hardness H i greater than H s and less than H h . Intermediate ACL layer 317 also has a thickness di . The thickness di of intermediate ACL layer 317 can be any suitable thickness and can depend on the specifics of a given application. In various embodiments, the total thickness dt of ACL mask 312 remains within the previously described ranges, while ds , di , and dh (as well as the hardness of each layer) are selected to suit the desired parameters.

[0045] FIG4 illustrates a cross-sectional view of an exemplary ACL mask including at least one intermediate ACL layer according to an embodiment of the present invention. The ACL mask of FIG4 may be, for example, an embodiment of other ACL masks described herein, such as the ACL mask of FIG2 . Like numbered elements may be as previously described.

[0046] Referring to Figure 4, ACL mask 412 includes ACL 414, which includes a soft ACL portion 416 and a hard ACL portion 418 (implemented as soft and hard ACL layers, as shown). ACL mask 412 is a generalized version of ACL mask 312, where, in addition to intermediate ACL layer 417, any suitable number of additional intermediate ACL layers may be included, each having a suitable hardness between Hs and Hh. A high-aspect ratio pattern 413 extends through hard ACL portion 418, all included intermediate ACL layers 417, and soft ACL portion 416. As previously described, the total thickness dt of ACL mask 412 can be maintained within the previously described ranges, while the thickness of the ACL layers can be selected as desired.

[0047] FIG5 illustrates a cross-sectional view of an exemplary ACL mask including a gradient transition from a soft ACL portion to a hard ACL portion, according to an embodiment of the present invention. The ACL mask of FIG5 may be, for example, an embodiment of other ACL masks described herein, such as the ACL mask of FIG2 . Like numbered elements may be as previously described.

[0048] Referring to FIG. 5 , ACL mask 512 includes ACL 514, which includes a soft ACL portion 516 and a hard ACL portion 518. ACL mask 512 is a conceptually more generalized version of ACL mask 412, implemented without defined layers. More specifically, ACL mask 512 includes a gradient hardness transition from soft ACL portion 516 to hard ACL portion 518. High-aspect ratio pattern 513 extends through hard ACL portion 518 and the gradient to soft ACL portion 516. The total thickness dt of ACL mask 512 can be within the ranges previously described. Various properties of ACL mask 512 can be advantageously controlled by selecting an appropriate hardness transition curve (e.g., linear).

[0049] Figures 6A-6F illustrate cross-sectional views of an exemplary workpiece during an etching process of a bottom layer using an ACL mask according to an embodiment of the present invention, wherein Figure 6A shows the formation of a soft ACL layer, Figure 6B shows the formation of a hard ACL layer, Figure 6C shows the formation of a patterned layer, Figure 6D shows the formation of an ACL mask, Figure 6E shows the etching of the bottom layer, and Figure 6F shows the pattern transferred to the bottom layer. The etching process of Figures 6A-6F can be combined with other methods and performed using the systems and apparatus described herein. For example, the etching process of Figures 6A-6F can be combined with any of the embodiments of Figures 1A-5, Figures 7A-7C, and Figure 8. Like-numbered elements can be as previously described.

[0050] 6A , a workpiece 600 includes a bottom layer 20 that may be supported by a substrate 10. In some cases, the bottom layer 20 may be the substrate 10 rather than a separately defined layer. The substrate 10 may be any suitable substrate, such as a semiconductor substrate, a metal substrate, an insulating substrate, etc. The bottom layer 20 may be any layer that exhibits sufficient etch selectivity relative to amorphous carbon for a given process.

[0051] In various embodiments, the bottom layer 20 comprises a dielectric. In one embodiment, the bottom layer 20 comprises an oxide. In one embodiment, the bottom layer 20 comprises a nitride. For example, the bottom layer 20 may be an oxide, a nitride, an oxynitride, or various combinations thereof. In one specific example, the bottom layer 20 is an oxide-nitride-oxide stack (ONO), which may have any suitable number of layers. In another embodiment, the bottom layer 20 comprises polysilicon.

[0052] As shown in FIG6 , a soft ACL layer 616 is formed on the bottom layer 20. In one embodiment, the soft ACL layer 616 can be formed using any suitable process and deposited using PECVD. The hardness Hs of the soft ACL layer 616 can be controlled by selecting specific values ​​for various parameters such as temperature, hydrogen content, bias voltage, and pressure. In one embodiment, Hs is less than 10 GPa. The thickness ds of the soft ACL layer 616 can be at least 0.5 µm.

[0053] As shown in FIG6B , a hard ACL layer 618 is formed overlying the soft ACL layer 616. The combination of the soft ACL layer 616 and the hard ACL layer 618 is a multi-layer ACL stack 614 disposed on the base layer 20. The hardness H h of the hard ACL layer 618 is similarly controlled during formation and is greater than H s. In one embodiment, H h is greater than 10 GPa.

[0054] In some embodiments, an additional intermediate layer having an intermediate hardness H i may be formed before forming hard ACL layer 618. That is, forming multi-layer ACL stack 614 may further include depositing an intermediate ACL layer on the underlying layer (soft ACL layer 616) before depositing hard ACL layer 618. The intermediate ACL layer may have a hardness H i greater than H s and less than H h.

[0055] As shown in FIG6C , a patterned layer 30 (which may include a resist and may also use multiple layers to define features, such as PR / SiARC / ODL / SiON, with PR: 15-60 nm, SiARC: 20-40 nm, ODL: 200-400 nm, and SiON: 135-340 nm) is formed on a hard ACL layer 618 of a multi-layer ACL stack 614. An etching process (e.g., a high-aspect ratio process) is used to transfer the pattern of patterned layer 30 to the multi-layer ACL stack 614 to form an ACL mask 612 having high-aspect ratio features 613 ( FIG6D ). The ACL plasma etch chemistry may include oxygen-containing (e.g., O2) and / or sulfur-containing (e.g., SO2 or COS) gases. The patterned layer 30 is then removed.

[0056] As shown in FIG6E , ACL mask 612 serves as an etch mask to transfer high-aspect ratio features 613 to bottom layer 20. Hard ACL layer 618 is slowly consumed during the etching of bottom layer 20. In some embodiments, as depicted, some of hard ACL layer 618 may remain after bottom layer 20 is opened. However, in other embodiments, soft ACL layer 616 (and any potential intervening layers) may also be partially consumed during the etching of bottom layer 20. Notably, some of soft ACL layer 616 (or portions in gradient embodiments) remains after etching, advantageously preserving the integrity of bottom layer 20.

[0057] The ACL layers (including soft ACL layer 616, hard ACL layer 618, and any other ACL layers of ACL mask 612) can be advantageously removed after etching bottom layer 20. For example, ACL mask 612 may be ashed to facilitate its removal. The end result, shown in FIG6F , is a transferred pattern 40 that reflects the desired position and contours of patterned layer 30 by advantageously reducing distortion in ACL mask 612.

[0058] Figures 7A-7C illustrate cross-sectional views of an exemplary workpiece during another etching process of a bottom layer using an ACL mask according to an embodiment of the present invention, wherein Figure 7A shows the formation of the soft ACL portion of the ACL, Figure 7B shows the formation of the hard ACL portion of the ACL, and Figure 7C shows the formation of the ACL mask. The etching process of Figures 7A-7C can be combined with other methods and performed using the systems and apparatus described herein. For example, the etching process of Figures 7A-7C can be combined with any of the embodiments of Figures 1A-6F and Figure 8. Like-numbered elements can be as previously described. Like-numbered elements can be as previously described.

[0059] 7A-7C , a workpiece 700 includes a bottom layer 20 that may be supported by a substrate 10. An ACL 714, including a soft ACL portion 716 and a hard ACL portion 718, is formed on the bottom layer 20. The etching process of FIG. 7A-7C is similar to the etching process of FIG. 6A-6F , except that the gradient hardness transition is formed by changing the process conditions during the formation of the ACL 714.

[0060] For example, the temperature can be controllably varied (e.g., increased) during the deposition process to gradually (e.g., linearly) increase the hardness of the ACL 714 as it forms. Other parameters can also be controllably varied during deposition, such as hydrogen concentration (e.g., via precursor composition), bias, and pressure.

[0061] In various embodiments, forming ACL 714 includes modifying process conditions during deposition of ACL 714 to produce a hardness gradient transitioning from Hs at bottom layer 20 to Hh at the upper surface of ACL 714. In one embodiment, modifying process conditions during deposition of ACL 714 includes increasing the temperature during deposition of ACL. In one embodiment, modifying process conditions during deposition of ACL 714 includes increasing the bias voltage during deposition of ACL 714.

[0062] 6C and 6D , a patterned layer 30 is then formed on the ACL 714, and the ACL 714 is etched to transfer the pattern of the patterned layer 30 to the ACL 714, thereby forming an ACL mask 712 having high aspect ratio features 713 ( FIG. 7C ).

[0063] FIG8 illustrates a flow chart of an exemplary method for manufacturing an ACL mask according to an embodiment of the present invention. The method of FIG8 can be combined with other methods and performed using the systems and apparatus described herein. For example, the method of FIG8 can be combined with any of the embodiments of FIG1 through FIG7C . While shown in a reasonable order, the arrangement and numbering of the steps in FIG8 are not intended to be limiting. The method steps of FIG8 can be performed in any suitable order or concurrently with one another, as would be apparent to one of ordinary skill in the art.

[0064] Referring to Figure 8 , method 800 for manufacturing an ACL mask includes step 801 of forming an ACL on a base layer. The ACL includes a soft ACL portion having a first hardness, which is positioned below a hard ACL portion having a second hardness greater than the first hardness. Step 801 can be performed in a variety of ways. In step 802, the soft ACL portion can be deposited on the base layer as a lower layer of the ACL. The hard ACL portion can be deposited on the soft ACL portion as an upper layer of the ACL, as shown in step 803. Optionally, in step 806, at least one intermediate ACL layer can be deposited on the lower layer. The at least one intermediate ACL layer can have a third hardness greater than the first hardness and less than the second hardness.

[0065] Additionally or alternatively, step 801 of forming the ACL can be completed using step 807, which involves modifying process conditions during deposition of the ACL to produce a hardness gradient that transitions from a first hardness at the underlying layer to a second hardness at the upper surface of the ACL. As shown in FIG7C , for example, this may be the only method for forming the ACL. However, as indicated by the dashed arrows, layers and gradients can be combined in any suitable configuration depending on the specifics of a given application.

[0066] After forming the ACL in step 801, a patterned layer is formed on the ACL in step 804. Then, in step 805, the patterned layer is used as an etch mask to etch through the soft and hard ACL portions of the ACL to expose the underlying layer, thereby forming an ACL mask. The ACL mask can then be used as an etch mask for the underlying layer, as described herein.

[0067] While exemplary embodiments of the present invention are summarized herein, other embodiments can be understood from the entire specification and claims filed herein.

[0068] Example 1. A method for manufacturing an amorphous carbon layer (ACL) mask, the method comprising: forming an ACL on an underlying layer, the ACL comprising a soft ACL portion having a first hardness, the soft ACL portion being located below a hard ACL portion having a second hardness greater than the first hardness; forming a patterned layer on the ACL; and using the patterned layer as an etch mask to form an ACL mask by etching through both the soft ACL portion and the hard ACL portion of the ACL to expose the underlying layer.

[0069] Example 2. The method of Example 1, wherein the step of forming the ACL includes: depositing the soft ACL portion on the bottom layer as a lower layer of the ACL, and depositing the hard ACL portion on the soft ACL portion as an upper layer of the ACL.

[0070] Example 3. The method of Example 2, wherein the step of forming the ACL further comprises: before depositing the hard ACL portion, depositing an intermediate ACL layer on the lower layer, the intermediate ACL layer having a third hardness greater than the first hardness and less than the second hardness.

[0071] Example 4. The method of any one of Examples 1 to 3, wherein the step of forming the ACL includes: changing process conditions when depositing the ACL to produce a hardness gradient transitioning from the first hardness of the soft ACL portion at the bottom layer to the second hardness of the hard ACL portion at the upper surface of the ACL.

[0072] Example 5. The method of Example 4, wherein the step of changing the process conditions while depositing the ACL includes increasing the temperature while depositing the ACL.

[0073] Example 6. The method of one of Examples 4 and 5, wherein the step of changing the process conditions while depositing the ACL includes increasing a bias voltage while depositing the ACL.

[0074] Example 7. The method of any of Examples 1 to 6, wherein forming the ACL mask comprises performing a high aspect ratio carbon etch to etch through both the soft ACL portion and the hard ACL portion.

[0075] Example 8. The method of any one of Examples 1 to 7, wherein the first hardness is less than 10 GPa, and wherein the second hardness is greater than or equal to 10 GPa.

[0076] Example 9. The method of any one of Examples 1 to 8, wherein the soft ACL portion comprises greater than or equal to 60 atomic percent sp3 bonded carbon, and wherein the hard ACL portion comprises greater than about 20 atomic percent and less than 40 atomic percent sp3 bonded carbon.

[0077] Example 10. A method for manufacturing an amorphous carbon layer (ACL) mask, the method comprising: depositing a soft ACL layer of a multi-layer ACL stack on a bottom layer, the soft ACL layer having a first hardness less than 10 GPa and a first thickness of at least 0.5 μm; depositing a hard ACL layer of the multi-layer ACL stack on the soft ACL layer, the hard ACL layer having a second hardness greater than or equal to 10 GPa; forming a patterned layer on the multi-layer ACL stack; and etching through the multi-layer ACL stack to expose the bottom layer using the patterned layer as an etch mask to form an ACL mask.

[0078] Example 11. The method of Example 10 further includes: before depositing the hard ACL layer, depositing an intermediate ACL layer on the soft ACL layer, the intermediate ACL layer having a third hardness greater than the first hardness and less than the second hardness.

[0079] Example 12. The method of one of Examples 10 and 11, wherein forming the ACL mask comprises performing a high aspect ratio carbon etch to etch through the multi-layer ACL stack.

[0080] Example 13. The method of any one of Examples 10 to 12, wherein the soft ACL layer comprises greater than or equal to 60 atomic percent sp3 bonded carbon, and wherein the hard ACL layer comprises greater than about 20 atomic percent and less than 40 atomic percent sp3 bonded carbon.

[0081] Example 14. The method of any one of Examples 10 to 13, wherein the first thickness is at least 1 μm, and wherein the hard ACL layer has a second thickness less than or equal to the first thickness.

[0082] Example 15. An amorphous carbon layer (ACL) mask comprises: a soft ACL layer having a thickness of at least 0.5 µm and a first hardness; a hard ACL layer disposed on the soft ACL layer, the hard ACL layer having a thickness of at least 0.5 µm and a second hardness greater than the first hardness; and a high aspect ratio pattern extending through the soft ACL layer and the hard ACL layer.

[0083] Example 16. The ACL mask of Example 15 further includes: an intermediate ACL layer disposed on the soft ACL layer and below the hard ACL layer, the intermediate ACL layer including a third hardness greater than the first hardness and less than the second hardness.

[0084] Example 17. The ACL mask of one of Examples 15 and 16, wherein the first hardness is less than 10 GPa, and wherein the second hardness is greater than or equal to 10 GPa.

[0085] Example 18. The ACL mask of any of Examples 15 to 17, wherein the soft ACL layer comprises greater than or equal to 60 atomic percent sp3 bonded carbon, and wherein the hard ACL layer comprises greater than about 20 atomic percent and less than 40 atomic percent sp3 bonded carbon.

[0086] Example 19. The ACL mask of any one of Examples 15 to 18, wherein the thickness of the soft ACL layer is at least 1 μm, and wherein the thickness of the hard ACL layer is less than or equal to 1 μm.

[0087] Example 20. The ACL mask of Example 19, wherein the thickness of the ACL mask is greater than 2 µm.

[0088] Although the present invention has been described with reference to exemplary embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the exemplary embodiments, as well as other embodiments of the present disclosure, will be apparent to those skilled in the art upon reference to the description. Accordingly, the appended claims are intended to cover any such modifications or embodiments.

[0089] 10:Substrate 20: Bottom 30: Patterned layer 40: Transfer pattern 100:Workpiece 102: Mask layer 103: vertical feature 105: Workpiece 106: Mask layer 107: Deformation feature 212:ACL mask 213: High aspect ratio pattern 214:ACL 216:Soft ACL part 218:Hard ACL 312:ACL mask 313: High aspect ratio pattern 314:ACL 316:Soft ACL part 317: Intermediate ACL layer 318:Hard ACL 412:ACL mask 413: High aspect ratio pattern 414:ACL 416: Soft ACL part 417: Intermediate ACL layer 418:Hard ACL part 512:ACL mask 513: High aspect ratio pattern 514:ACL 516:Soft ACL part 518:Hard ACL part 600: Workpiece 612:ACL mask 613: High aspect ratio feature 614: Multi-layer ACL stacking 616:Soft ACL layer 618: Hard ACL layer 700:Workpiece 712:ACL mask 713: High aspect ratio feature 714:ACL 716: Soft ACL 718:Hard ACL part dh: thickness di: thickness ds: thickness dt: thickness

Claims

1. A method for manufacturing an amorphous carbon layer (ACL) mask, the method comprising: An ACL is formed on a base layer, the ACL including a soft ACL portion having a first hardness of less than 10 GPa, the soft ACL portion being located below a hard ACL portion having a second hardness of greater than or equal to 10 GPa; a patterned layer is formed on the ACL; and the patterned layer is used as an etch mask to form an ACL mask by etching through both the soft ACL portion and the hard ACL portion of the ACL to expose the base layer.

2. The method for manufacturing the amorphous carbon layer mask as claimed in claim 1, wherein the step of forming the ACL includes: The soft ACL portion is deposited on the underlying layer as the lower layer of the ACL, and the hard ACL portion is deposited on the soft ACL portion as the upper layer of the ACL.

3. The method for manufacturing the amorphous carbon layer mask as described in claim 2, wherein the step of forming the ACL further includes: Before depositing the hard ACL portion, an intermediate ACL layer is deposited on the lower layer, the intermediate ACL layer having a third hardness greater than the first hardness and less than the second hardness.

4. The method for manufacturing the amorphous carbon layer mask as claimed in claim 1, wherein the step of forming the ACL includes: The ACL is continuously deposited starting from the soft ACL portion at the bottom layer; And changing process conditions when continuously depositing the ACL to generate a hardness gradient from the first hardness to the second hardness of the hard ACL portion at the upper surface of the ACL.

5. The method for manufacturing an amorphous carbon layer mask as claimed in claim 4, wherein the step of changing the process conditions during continuous deposition of the ACL includes increasing the temperature during deposition of the ACL.

6. The method for manufacturing an amorphous carbon layer mask as claimed in claim 4, wherein the step of changing the process conditions during continuous deposition of the ACL includes increasing the bias voltage during deposition of the ACL.

7. A method for manufacturing an amorphous carbon layer mask as claimed in claim 1, wherein the step of forming the ACL mask includes performing high aspect ratio carbon etching to etch through both the soft ACL portion and the hard ACL portion.

8. A method for manufacturing an amorphous carbon layer mask as claimed in claim 1, wherein the soft ACL portion comprises an atomic percentage of sp3-bonded carbon greater than or equal to 60%, and wherein the hard ACL portion comprises an atomic percentage of sp3-bonded carbon greater than about 20% and less than 40%.

9. A method for manufacturing an amorphous carbon layer (ACL) mask, the method comprising: A soft ACL layer of a multi-layer ACL stack is deposited on a base layer, the soft ACL layer having a first hardness of less than 10 GPa and a first thickness of at least 0.5 μm; a hard ACL layer of the multi-layer ACL stack is deposited on the soft ACL layer, the hard ACL layer having a second hardness of greater than or equal to 10 GPa; a patterned layer is formed on the multi-layer ACL stack; and the patterned layer is used as an etch mask, an ACL mask is formed by etching through the multi-layer ACL stack to expose the base layer.

10. The method for manufacturing the amorphous carbon layer mask as described in claim 9 further includes: Before depositing the hard ACL layer, an intermediate ACL layer is deposited on the soft ACL layer, the intermediate ACL layer having a third hardness greater than the first hardness and less than the second hardness.

11. A method for manufacturing an amorphous carbon layer mask as claimed in claim 9, wherein the step of forming the ACL mask includes performing a high aspect ratio carbon etching to etch through the multilayer ACL stack.

12. The method of manufacturing an amorphous carbon layer mask as claimed in claim 9, wherein the soft ACL layer comprises an atomic percentage of sp3-bonded carbon greater than or equal to 60%, and wherein the hard ACL layer comprises an atomic percentage of sp3-bonded carbon greater than about 20% and less than 40%.

13. The method of manufacturing an amorphous carbon layer mask as claimed in claim 9, wherein the first thickness is at least 1µm, and wherein the hard ACL layer has a second thickness less than or equal to the first thickness.

14. A method for manufacturing an amorphous carbon layer (ACL) mask, the method comprising: An ACL is formed on a substrate, the ACL including a soft ACL portion having a first hardness, the soft ACL portion being located beneath a hard ACL portion having a second hardness greater than the first hardness, wherein forming the ACL includes: continuously depositing the ACL starting from the soft ACL portion at the substrate; and changing process conditions while continuously depositing the ACL to create a hardness gradient from the first hardness to the second hardness of the hard ACL portion at the upper surface of the ACL; forming a patterned layer on the ACL; and using the patterned layer as an etch mask to form an ACL mask by etching through both the soft ACL portion and the hard ACL portion of the ACL to expose the substrate.

15. The method for manufacturing an amorphous carbon layer mask as claimed in claim 14, wherein the step of changing the process conditions during continuous deposition of the ACL includes increasing the temperature during deposition of the ACL.

16. The method of manufacturing an amorphous carbon layer mask as claimed in claim 14, wherein the step of changing the process conditions during continuous deposition of the ACL includes increasing the bias voltage during deposition of the ACL.

17. A method for manufacturing an amorphous carbon layer mask as claimed in claim 14, wherein, The steps of changing the process conditions during continuous deposition of the ACL include increasing the temperature or increasing the bias voltage during deposition of the ACL; and wherein the first hardness is less than 10 GPa, and wherein the second hardness is greater than or equal to 10 GPa.

18. A method for manufacturing an amorphous carbon layer mask as claimed in claim 14, wherein the step of forming the ACL mask includes performing high aspect ratio carbon etching to etch through both the soft ACL portion and the hard ACL portion.

19. The method of manufacturing an amorphous carbon layer mask as claimed in claim 14, wherein the soft ACL portion comprises an atomic percentage of sp3-bonded carbon greater than or equal to 60%, and wherein the hard ACL portion comprises an atomic percentage of sp3-bonded carbon greater than about 20% and less than 40%.

20. The method for manufacturing an amorphous carbon layer mask as claimed in claim 14, wherein the overall thickness of the ACL is greater than about 1.5 μm.

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