Variable hardness amorphous carbon mask

Abstract

A method of fabricating an amorphous carbon layer (ACL) mask includes forming an 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 further includes forming a patterned layer over the ACL and forming an ACL mask by etching through both the soft ACL portion and the hard ACL portion of the ACL using the patterned layer as an etch mask to expose the underlying layer. Forming the ACL may include depositing one or both of the soft ACL portion and the hard ACL portion. Processing conditions may also be varied during formation of the ACL to create a hardness gradient transitioning from the soft ACL to the hard ACL.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This disclosure claims the benefit of U.S. Non-provisional Patent Application No. 17 / 660,111, filed April 21, 2022, which is incorporated by reference in its entirety.

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

[0003] The formation of microelectronic devices can involve a series of manufacturing techniques involving the formation, patterning, and removal of multiple layers of materials on a substrate. An etch mask may be formed (e.g., deposited) to protect areas of the substrate and enable pattern transfer by etching. Obtaining high aspect ratios during etching is important for various semiconductor processes, such as high aspect ratio contact (HARC) formation, NAND formation (e.g., 3D-NAND), NOR formation, memory formation, and others.

[0004] Distortion may occur when transferring a pattern to an underlying layer. For example, features transferred to an underlying layer may have various undesirable defects, such as widening or narrowing, size or position mismatch, and non-vertical sidewalls. Distortion is one particular problem involving deviation from a desired vertical profile that causes lateral drift of features. As the thickness of the underlying layer increases, distortion may become more and more pronounced. Therefore, it may be desirable to have an etch mask with improved profile control while maintaining a desired mask thickness and throughput. Summary of the Invention

[0005] According to one embodiment of the present invention, a method of fabricating an amorphous carbon layer (ACL) mask includes forming an 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 further includes forming a patterned layer over the ACL and forming the ACL mask by etching through both the soft ACL portion and the hard ACL portion of the ACL using the patterned layer as an etch mask to expose the underlying layer.

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

[0007] According to yet 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 the soft ACL layer and the hard ACL layer. The soft ACL layer is at least 0.5 μm thick and has a first hardness. The hard ACL layer is at least 0.5 μm thick and has a second hardness greater than the first hardness. [Brief description of the drawings]

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

[0009] [Figure 1A] 1 illustrates a cross-sectional view of an exemplary mask layer according to an embodiment of the present invention, showing the mask layer having vertical features. [Figure 1B] 2 illustrates a cross-sectional view of an exemplary mask layer according to an embodiment of the present invention, showing the mask layer having distorted features. [Diagram 2] 1 illustrates a cross-sectional view of an example of an exemplary amorphous carbon layer (ACL) mask including a soft ACL portion and a hard ACL portion, in accordance with an embodiment of the present invention. [Diagram 3] 1 illustrates a cross-sectional view of an exemplary ACL mask including an intermediate ACL layer, in accordance with an embodiment of the present invention. [Figure 4] 1 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. [Diagram 5] 1 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. [Figure 6A] 1 illustrates a cross-sectional view of an exemplary workpiece during an underlayer etching process using an ACL mask according to an embodiment of the present invention, illustrating the formation of a soft ACL layer. [Figure 6B] 1 illustrates a cross-sectional view of an exemplary workpiece during an underlayer etching process using an ACL mask according to an embodiment of the present invention, showing the formation of a hard ACL layer. [Figure 6C] 1 illustrates a cross-sectional view of an exemplary workpiece during an underlying layer etching process using an ACL mask according to an embodiment of the present invention, illustrating the formation of a patterned layer. [Figure 6D] 1A-1C show cross-sectional views of an exemplary workpiece during an underlying layer etching process using an ACL mask according to an embodiment of the present invention, illustrating the formation of the ACL mask. [Figure 6E] 1A-1C show cross-sectional views of an exemplary workpiece during an underlying layer etching process using an ACL mask according to an embodiment of the present invention, illustrating etching of the underlying layer. [Figure 6F] 1 illustrates a cross-sectional view of an exemplary workpiece during an underlying layer etching process using an ACL mask according to an embodiment of the present invention, showing a pattern transferred to the underlying layer. [Figure 7A]1 illustrates a cross-sectional view of an exemplary workpiece during another etching process of an underlying layer using an ACL mask according to an embodiment of the present invention, illustrating the formation of a soft ACL portion of the ACL. [Figure 7B] 1 illustrates a cross-sectional view of an exemplary workpiece during another etching process of an underlying layer using an ACL mask according to an embodiment of the present invention, illustrating the formation of a hard ACL portion of the ACL. [Figure 7C] 4A-4C show cross-sectional views of an exemplary workpiece during another etching process of an underlying layer using an ACL mask according to an embodiment of the present invention, illustrating the formation of the ACL mask. [Figure 8] 1 illustrates a flow chart of an exemplary method for manufacturing an ACL mask, according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Corresponding numerals and symbols in different drawings generally refer to corresponding parts unless otherwise indicated. The drawings are drawn to clearly show relevant aspects of the embodiments and are not necessarily drawn to scale. The ends of features drawn in the drawings do not necessarily indicate the end of the scope of the feature.

[0011] Detailed descriptions of the making and use of various embodiments are provided below. It should be understood, however, that the various embodiments described herein are applicable in a wide variety of specific contexts. The specific embodiments described are merely illustrative of specific ways to make and use the various embodiments and should not be construed as limiting in scope.

[0012] Amorphous carbon masks are useful for etching underlying layers of a workpiece, such as during the formation of microelectronic devices. In particular, hard amorphous carbon layer (ACL) masks may be used for high aspect ratio processes, such as in HARC processes. For example, high aspect ratio processes may be used during memory fabrication, including dynamic random access memory (DRAM), NAND flash, NOR flash, and the like. During the etching process, the pattern of the hard ACL mask may be transferred to the underlying layers (e.g., one or more dielectric layers including oxide, nitride, and the like). Etching contact holes is one specific application of such high aspect ratio etching of ACL hard masks.

[0013] A few micrometers of amorphous carbon are often used as a hard mask for dielectric (e.g., oxide, nitride, ONO) opening during device fabrication (e.g., 3D-NAND devices) due to its good etch selectivity to dielectrics. Opening thick ACL layers can be time consuming due to their high aspect ratio. Etching may be performed in a plasma processing chamber, such as, for example, an inductively coupled plasma (ICP) chamber.

[0014] Amorphous carbon with high hardness (i.e., hard ACLs) may be used for etching processes, such as for etching dielectrics, due to better etch selectivity than amorphous carbon with low hardness (i.e., soft ACLs). Hardness may be increased during hard ACL formation by increasing the temperature. For this reason, hard ACLs are sometimes referred to as high temperature ACLs (although high temperature is not the only factor that determines the hardness of an ACL). One example of a high temperature ACL is the APF® family of thin films available from Applied Materials. Because temperature affects the hardness of the ACL, temperature and other variables may be controlled to form ACLs with different properties. For example, a low temperature ACL (e.g., formed at 450° C.) may result in a soft ACL.

[0015] However, although hard ACLs are more etch resistant than soft ACLs, they are also much more difficult to open and can result in profile distortion at high aspect ratios. For example, when etching hard ACLs, twisting (which can also refer to bending of features from the desired vertical etch profile) can begin at a relatively shallow depth of 1.5 μm or even before that depth. This correlates with what may be considered a medium aspect ratio. Additionally, the increased etch depth combines with the effects of twisting, making profile distortion in hard ACLs even more pronounced in high aspect ratio processes. In many cases, hard ACL masks must be much thicker than 1.5 μm to ensure that the ACL is not completely consumed during etching.

[0016] Simply continuing to increase the hardness of the ACL could further improve selectivity so that thinner masks could be used. However, increased hardness would also increase the time to open, causing distortion to occur more quickly, making such a solution impractical. Additionally, for a variety of reasons, it may be undesirable to vary the thickness of the mask. Also, there may be practical constraints (e.g., difficulty, cost, diminishing profit margins) to increasing the hardness of the ACL beyond a certain point.

[0017] In contrast, soft ACLs may be easier to open and obtain better profiles while having reduced etch resistance (e.g., during dielectric opening) compared to harder ACLs. Distortions such as kinking in soft ACLs may occur at much deeper depths, such as 2.5 μm or more. Therefore, soft ACLs do not start to experience even mild profile distortions until they are in the high aspect ratio range. However, soft ACLs, by themselves, need to be made very thick for high aspect ratio etching due to their low selectivity.

[0018] In various embodiments, the ACL mask includes a soft ACL portion and a hard ACL portion. The hard ACL portion is located at an upper portion of the ACL mask and has a higher hardness than the soft ACL portion. The pattern for transfer to the underlayer extends through the hard ACL portion and the soft ACL portion of the ACL mask. The ACL mask may be fabricated by forming a patterned layer that is located above the ACL mask and etching through both the soft ACL portion and the hard ACL portion using the patterned layer as an etch mask.

[0019] The ACL mask of the embodiments described herein advantageously combines the benefits of both soft and hard ACLs to improve profile distortion and throughput while maintaining high etch selectivity. It is desirable to both control the etch profile and maintain high etch selectivity. The proposed approach utilizes at least two ACL sections of different hardness in a single ACL mask, where the hard ACL section sits above the soft ACL section. By replacing the uniform ACL with an ACL of variable hardness, the low to medium aspect ratio section of the aspect ratio etch advantageously utilizes the hard ACL while the medium to high aspect ratio section utilizes the soft ACL. In this way, the ACL is easier to etch (i.e., faster and less distorted) when transitioning to high aspect ratio.

[0020] Another potential advantage of an embodiment of the ACL mask is that the thickness of the ACL mask can be advantageously controlled. In particular, the use of a hard ACL portion located above a soft ACL portion may advantageously allow the thickness of the ACL mask to remain the same while achieving improved profile control and throughput. The variable hardness of an embodiment of the ACL mask may facilitate optimization of mask thickness, throughput, and profile distortion. Even if the soft ACL portion is at the bottom of the ACL mask, there may be a sufficient amount of ACL remaining after etching so that the etching performance is not degraded. Despite careful design and optimization, this remaining ACL may advantageously be primarily soft ACL. That is, the hard ACL portion may act as a protection against etching at the beginning of the etching, and the soft ACL portion may act as an etching protection at the end of the etching.

[0021] The embodiments presented below describe various etching processes and structures, particularly those involving variable hardness amorphous carbon masks. Several embodiments are described in the following description. Figures 1A and 1B are used to describe an example of profile distortion. An embodiment of an ACL mask is described with reference to Figure 2. Three further ACL mask embodiments are described with reference to Figures 3-5. An embodiment of an etching process is described with reference to Figures 6A-6F. Another embodiment of an etching process is described with reference to Figures 7A-7C. An embodiment of a method for manufacturing an ACL mask is described with reference to Figure 8.

[0022] 1A and 1B show cross-sectional views of an exemplary mask layer according to an embodiment of the present invention, with FIG. 1A showing a mask layer having vertical features and FIG. 1B showing a mask layer having distorted features.

[0023] 1, the workpiece 100 includes an underlayer 20 supported by a substrate 10. In some cases, the underlayer 20 may be a substrate, and of course other additional layers may be included. A mask layer 102 (e.g., a hard mask layer) is disposed on the underlayer 20. The mask layer 102 is shown here as having vertical features 103. That is, features of the patterned layer 30 disposed above the mask layer 102 are accurately transferred to the mask layer 102 as vertical features.

[0024] In contrast, workpiece 105 includes mask layer 106 that is subject to distortion (e.g., twisting as shown) during transfer of features from patterned layer 30 to mask layer 106. The result is distorted features 107 that do not accurately reflect the desired locations of the features in patterned layer 30. This undesirable distortion can result from a number of reasons, such as increased mask thickness or increased mask hardness, as discussed above.

[0025] In particular, distortion may be more likely at higher aspect ratios. Etch depths less than 1.5 μm may be considered low aspect ratios, while etch depths greater than 1.5 μm may be considered medium to high aspect ratios. In embodiments of hard amorphous carbon masks (e.g., used in high aspect ratio dielectric etches), undesirable levels of distortion may occur at medium to high aspect ratios (e.g., 1.5 μm or greater). Since etch depths greater than 1.5 μm are frequently required, strategies to mitigate distortion at high aspect ratio etches may be desirable. The following description details various techniques that allow features transferred from a patterned layer to a mask layer to approximate ideal vertical features 103 of the mask layer 102, rather than distorted features 107 of the mask layer 106.

[0026] 2 illustrates a cross-sectional view of one example of an exemplary ACL mask including a soft ACL portion and a hard ACL portion, according to an embodiment of the present invention. Similar labeled elements may be similar to those previously described.

[0027] 2, the ACL mask 212 includes an ACL 214 that includes a soft ACL portion 216 and a hard ACL portion 218. The hard ACL portion 218 is harder than the soft ACL portion 216 and is located above the soft ACL portion 216. For example, the soft ACL portion 216 has a hardness of H s while the hard ACL portion 218 may have H s Hardness H higher than h The high aspect ratio pattern 213 extends through both the hard ACL portion 218 and the soft ACL portion 216.

[0028] The soft ACL portion 216 also has a thickness d s and the hard ACL portion 218 has a thickness d h In one embodiment, d s d h In another embodiment, d s d h For example, to improve throughput and reduce profile distortion, the thickness d of the rigid ACL portion 218 may be h However, in some cases, for example, it may be advantageous to reduce the overall thickness d t (i.e. d s +d h ), so that the opposite may be true if higher selectivity is desired to reduce the overall thickness of the ACL mask 212.

[0029] In some embodiments, d s is at least 0.5 μm, and in various embodiments, d s is at least 1 μm. In one embodiment, d s is less than about 3 μm. Similarly, in some embodiments, d h is at least 0.5 μm, and in various embodiments, d h is at least 1 μm. In one embodiment, d h is less than about 2 μm, and in another embodiment, less than 1.5 μm. In various embodiments, d tis at least 1 μm, and in one embodiment at least 2 μm. t is less than about 4 μm. However, these ranges are merely examples reflecting various potential considerations. The concepts described herein also apply to other thicknesses, depending on the specifics of a given application.

[0030] Either or both of the soft ACL portion 216 and the hard ACL portion 218 may be implemented as layers (e.g., a lower layer and an upper layer, respectively). In particular, as shown, the soft ACL portion 216 has a thickness d s The ACL 214 has a substantially uniform hardness throughout, with a definable boundary separating the soft ACL portion 216 and the hard ACL portion 218. For example, the ACL 214 may be a multi-layer ACL laminate (i.e., at least two layers) with the hardest ACL layer 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 may incorporate a gradient hardness transition, as described in more detail below.

[0031] The ACL may be formed using any suitable process, such as, by way of example, plasma enhanced chemical vapor deposition (PECVD), however, other methods are possible including electron cyclotron resonance (ECR), reactive sputtering, electron cyclotron wave resonance (ECWR), plasma beam source (PBS), filtered cathodic vacuum arc (FCVA), etc.

[0032] The properties of the ACL, such as hardness, may be controlled during the ACL formation process. The temperature during ACL formation is one way to distinguish between soft and hard ACLs. For example, a soft ACL (low temperature ACL) may be formed at a lower temperature than a hard ACL (high temperature ACL), such as 450° C. However, temperature is not the only variable that affects the hardness of the ACL. Therefore, by changing other process conditions, it may be possible to form a hard ACL at a “low temperature” and a soft ACL at a “high temperature”.

[0033] Hard ACLs may have certain physical characteristics that distinguish them from soft ACLs. These distinguishing characteristics include sp 3 These may include the atomic percentage of bonded carbon, the atomic percentage of hydrogen, density, and (obviously) hardness. For example, a hard ACL may have less than about 40% sp 3 Bonded carbon, with about 20% to 40% hydrogen, about 1.6 to 2.2 g / cm 3 The resulting hardness H h The hardness may be higher than 10 GPa, and in one embodiment, ranges from about 10 GPa to 20 GPa. In one embodiment, the hard ACL is a tetrahedral amorphous carbon layer (ta-C:H), which has even higher hardness (up to 50 GPa H). h ) is observed.

[0034] In contrast, soft ACLs contain at least 60% sp 3 Contains bound carbon (e.g. up to 70%), about 40%-50% hydrogen, and about 1.2-1.6 g / cm 3 The soft ACL may have a density in the range of 0.1 to 0.5 mm. s is H h For example, the hardness Hs of a soft ACL may be less than about 10 GPa.

[0035] 3 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 FIG. 3 may be a specific implementation of other ACL masks described herein, such as, for example, the ACL mask of FIG. 2. Similarly labeled elements may be similar to those described above.

[0036] 3, ACL mask 312 includes ACL 314 including soft ACL portion 316 and hard ACL portion 318 implemented as soft and hard ACL layers. Note that here and below, conventions are adopted for brevity and clarity, where elements following the pattern [x12] may be relevant implementations of ACL masks in various embodiments. For example, ACL mask 312 may be similar to ACL mask 212 unless otherwise stated. Similar conventions are adopted for other elements, as will become apparent from the use of similar terminology in combination with the aforementioned three-digit numbering system.

[0037] The ACL mask 312 is a specific embodiment that includes an intermediate ACL layer 317 between a hard ACL portion 318 and a soft ACL portion 316. The high aspect ratio pattern 313 extends through the hard ACL portion 318, the intermediate ACL layer 317, and the soft ACL portion 316. The intermediate ACL layer 317 is s Higher than H h Hardness H is less than i The intermediate ACL layer 317 also has a thickness d i The thickness d of the intermediate ACL layer 317 i may be any suitable thickness and may depend on the specifics of a given application. In various embodiments, the total thickness d t is maintained within the aforementioned range, while d s , d i , and d h (as well as the hardness of each layer) are selected to suit the desired parameters.

[0038] 4 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 FIG. 4 may be a specific implementation of other ACL masks described herein, such as, for example, the ACL mask of FIG. 2. Similarly labeled elements may be similar to those described above.

[0039] 4, the ACL mask 412 includes an ACL 414 that includes a soft ACL portion 416 and a hard ACL portion 418 (implemented as a soft ACL layer and a hard ACL layer, as shown). The ACL mask 412 includes an intermediate ACL layer 417 as well as an intermediate ACL layer 417, each of which includes a H s ~H h The high aspect ratio pattern 413 extends through the hard ACL portion 418, all of the included intermediate ACL layers 417, and the soft ACL portion 416. As previously mentioned, the total thickness d of the ACL mask 412 is d 1 . t may be maintained within the aforementioned ranges while selecting the thickness of the ACL layer as desired.

[0040] 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. The ACL mask of FIG. 5 may be a specific implementation of other ACL masks described herein, such as, for example, the ACL mask of FIG. 2. Similarly labeled elements may be similar to those described above.

[0041] 5, ACL mask 512 includes an ACL 514 that includes a soft ACL portion 516 and a hard ACL portion 518. Conceptually, ACL mask 512 is a further generalization of ACL mask 412, which is implemented without definable layers. Rather, 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 d of ACL mask 512 is 100 nm. t may be in the ranges discussed above. Various properties of the ACL mask 512 may be advantageously controlled by selecting an appropriate hardness transition profile (e.g., linear or otherwise).

[0042] 6A-6F show cross-sectional views of an exemplary workpiece during an etching process of an underlayer using an ACL mask according to an embodiment of the present invention, where 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 underlayer, and FIG. 6F shows the pattern transferred to the underlayer. The etching process of FIG. 6A-6F may be performed using the systems and apparatus described herein in combination with other methods. For example, the etching process of FIG. 6A-6F may be combined with any of the embodiments of FIG. 1A-5, FIG. 7A-7C, and FIG. 8. Similarly labeled elements may be similar to those described above.

[0043] 6A, the workpiece 600 includes an underlayer 20 that may be supported by a substrate 10. In some cases, the underlayer 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 underlayer 20 may be any layer that exhibits sufficient etch selectivity for a given process to amorphous carbon.

[0044] In various embodiments, the underlayer 20 comprises a dielectric. In one embodiment, the underlayer 20 comprises an oxide. In one embodiment, the underlayer 20 comprises a nitride. For example, the underlayer 20 may be an oxide, a nitride, and an oxynitride, or various combinations thereof, among other possibilities. In one specific example, the underlayer 20 is an oxide-nitride-oxide stack (ONO), which may have any suitable number of layers. In another embodiment, the underlayer 20 comprises polysilicon.

[0045] A soft ACL layer 616 is formed on the underlayer 20, as shown in Figure 6A. The soft ACL layer 616 may be formed using any suitable process, and in one embodiment is deposited using PECVD. The hardness H of the soft ACL layer 616 is smay be controlled by selecting specific values ​​for various parameters such as temperature, hydrogen content, bias voltage, and pressure, among others. In one embodiment, H s The thickness d of the soft ACL layer 616 is less than 10 GPa. s may be at least 0.5 μm.

[0046] The hard ACL layer 618 is formed overlying the soft ACL layer 616, as shown in FIG. 6B. The combination of the soft ACL layer 616 and the hard ACL layer 618 is a multi-layer ACL laminate 614 that is disposed on the foundation layer 20. The hardness H of the hard ACL layer 618 is h is similarly controlled during the formation of H s In one embodiment, H h is less than 10 GPa.

[0047] Also, an additional intermediate layer of intermediate hardness Hi may be formed in some embodiments prior to forming the hard ACL layer 618. That is, forming the multi-layer ACL laminate 614 may further include depositing an intermediate ACL layer on the lower layer (the soft ACL layer 616) prior to depositing the hard ACL layer 618. The intermediate ACL layer may have a hardness of H s Higher than H h Hardness H less than i may have the following structure:

[0048] A patterned layer 30 (which may include resist, multiple layers may also be used to define features, e.g., PR / SiARC / ODL / SiON, PR: 15-60 nm, SiARC: 20-40 nm, ODL: 200-400 nm, SiON: 135-340 nm) is formed on a hard ACL layer 618 of a multi-layer ACL stack 614, as shown in FIG. 6C. The pattern of the patterned layer 30 is transferred to the multi-layer ACL stack 614 using an etching process (e.g., a high aspect ratio process) to form an ACL mask 612 with high aspect ratio features 613 (FIG. 6D). The ACL plasma etch chemistry may include oxygen-containing gases (such as O2) and / or sulfur-containing gases (such as SO2 or COS). The patterned layer 30 is then removed.

[0049] The ACL mask 612 is used as an etch mask to transfer the high aspect ratio features 613 to the underlying layer 20, as shown in FIG. 6E. The hard ACL layer 618 is slowly consumed during etching of the underlying layer 20. In some embodiments, a portion of the hard ACL layer 618 may remain after the underlying layer 20 is opened, as an example. However, in other embodiments, the soft ACL layer 616 (and any other potential intervening layers) may also be partially consumed during etching of the underlying layer 20. In particular, a portion (or portions for gradient embodiments) of the soft ACL layer 616 remains after etching, such that the integrity of the underlying layer 20 is advantageously maintained.

[0050] Advantageously, the ACL layers (including soft ACL layer 616, hard ACL layer 618, and any other ACL layers of ACL mask 612) are removable after etching of underlying layer 20. For example, ACL mask 612 may be ashed to facilitate its removal. The end result, shown in FIG. 6F, is a transferred pattern 40 that reflects the desired location and profile of patterned layer 30 by advantageously reducing distortion in ACL mask 612.

[0051] 7A-7C show cross-sectional views of an exemplary workpiece during another etching process of an underlying layer using an ACL mask according to an embodiment of the present invention, where FIG. 7A shows the formation of a soft ACL portion of an ACL, FIG. 7B shows the formation of a hard ACL portion of an ACL, and FIG. 7C shows the formation of an ACL mask. The etching process of FIGS. 7A-7C may be performed using the systems and apparatus described herein in combination with other methods. For example, the etching process of FIGS. 7A-7C may be combined with any of the embodiments of FIGS. 1A-6F and 8. Similar labeled elements may be similar to those described above. Similar labeled elements may be similar to those described above.

[0052] 7A-7C, a workpiece 700 includes an underlayer 20, which may be supported by a substrate 10. An ACL 714, which includes a soft ACL portion 716 and a hard ACL portion 718, is formed on the underlayer 20. The etching process of FIGS. 7A-7C is similar to the etching process of FIGS. 6A-6F, except that a gradient hardness transition is formed by varying process conditions during the formation of the ACL 714.

[0053] For example, the temperature may be controllably varied (e.g., increased) during the deposition process to gradually (e.g., linearly) increase the hardness of ACL 714 as it is formed. Also, other parameters such as hydrogen concentration (e.g., via precursor composition), bias voltage, and pressure may be controllably altered during deposition.

[0054] In various embodiments, forming the ACL 714 may involve modifying process conditions during deposition of the ACL 714 to reduce the H of the underlayer 20. s From the top surface of ACL714 h In one embodiment, altering the process conditions while depositing ACL714 includes increasing the temperature while depositing the ACL. In one embodiment, altering the process conditions while depositing ACL714 includes increasing the bias voltage while depositing ACL714.

[0055] Similar to Figures 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 and form an ACL mask 712 (Figure 7C) having high aspect ratio features 713.

[0056] FIG. 8 illustrates a flow chart of an exemplary method of manufacturing an ACL mask, according to an embodiment of the present invention. The method of FIG. 8 may be performed using the systems and apparatus described herein in combination with other methods. For example, the method of FIG. 8 may be combined with any of the embodiments of FIG. 1-7C. The arrangement and numbering of the steps of FIG. 8 is illustrated in a logical order, but is not intended to be limiting. The method steps of FIG. 8 may be performed in any suitable order or concurrently with one another, as would be apparent to one of ordinary skill in the art.

[0057] Referring to FIG. 8, a method 800 of manufacturing an ACL mask includes step 801 of forming an ACL on an underlayer. The ACL includes a soft ACL portion having a first hardness located under a hard ACL portion having a second hardness higher than the first hardness. Step 801 may be accomplished in various ways. In step 802, the soft ACL portion may be deposited on the underlayer as an underlayer of the ACL. The hard ACL portion may be deposited on the soft ACL portion as an overlayer of the ACL, as shown in step 803. Optionally, in step 806, at least one intermediate ACL layer may be deposited on the underlayer. The at least one intermediate ACL layer may have a third hardness higher than the first hardness and lower than the second hardness.

[0058] Additionally or alternatively, forming the ACL 801 may be accomplished using step 807 of modifying process conditions during deposition of the ACL to create a hardness gradient going from a first hardness at the underlayer to a second hardness at the top surface of the ACL. For example, as shown in Figure 7C, this may be the only way to form the ACL. However, as shown with the dashed arrow, layers and gradients may also be combined in any suitable configuration depending on the specific details of a given application.

[0059] After the ACL is formed in step 801, a patterned layer is formed on the ACL in step 804. Step 805 then forms an ACL mask by etching through both the soft and hard ACL portions of the ACL using the patterned layer as an etch mask to expose the underlying layer. The ACL mask may be used as an etch mask for the underlying layer as described herein.

[0060]

[0023] Exemplary embodiments of the present invention are summarized herein. Other embodiments can be seen throughout the specification and claims appended hereto.

[0061] Working Example

[0062] Example 1. A method of fabricating an amorphous carbon layer (ACL) mask, the method including forming an ACL on an underlying layer, the ACL including a soft ACL portion having a first hardness underlying a hard ACL portion having a second hardness greater than the first hardness; forming a patterned layer over the ACL; and forming the ACL mask by etching through both the soft ACL portion and the hard ACL portion of the ACL using the patterned layer as an etch mask to expose the underlying layer.

[0063] Example 2. The method of example 1, wherein forming the ACL includes depositing a soft ACL portion onto the underlayer as a lower layer of the ACL, and depositing a hard ACL portion onto the soft ACL portion as a upper layer of the ACL.

[0064] Example 3. The method of example 2, wherein forming the ACL further comprises depositing an intermediate ACL layer on the underlayer before depositing the hard ACL portion, the intermediate ACL layer having a third hardness greater than the first hardness and less than the second hardness.

[0065] Example 4. The method of any one of Examples 1-3, wherein forming the ACL includes varying process conditions during deposition of the ACL to create a hardness gradient transitioning from a first hardness of a soft ACL portion at the underlayer to a second hardness of a hard ACL portion at the top surface of the ACL.

[0066] Example 5. The method of example 4, wherein altering the process conditions during deposition of the ACL includes increasing the temperature during deposition of the ACL.

[0067] Example 6. The method of example 4 or 5, wherein altering the process conditions during deposition of the ACL comprises increasing the bias voltage during deposition of the ACL.

[0068] Example 7. The method of any one of Examples 1-6, wherein forming the ACL mask includes performing a high aspect ratio carbon etch to etch through both the soft and hard ACL portions.

[0069] Example 8. The method according to any one of Examples 1 to 7, wherein the first hardness is less than 10 GPa and the second hardness is 10 GPa or more.

[0070] Example 9. The soft ACL portion is made of sp 3 The hard ACL portion includes bonded carbon and has an atomic percentage of sp 3 The method according to any one of Examples 1 to 8, comprising a bonded carbon.

[0071] Example 10. A method of manufacturing an amorphous carbon layer (ACL) mask, the method including: depositing a soft ACL layer of a multi-layer ACL laminate on an underlayer, the soft ACL layer having a first hardness of less than 10 GPa and a first thickness of at least 0.5 μm; depositing a hard ACL layer of a multi-layer ACL laminate on the soft ACL layer, the hard ACL layer having a second hardness of 10 GPa or greater; forming a patterned layer on the multi-layer ACL laminate; and forming the ACL mask by etching through the multi-layer ACL stack using the patterned layer as an etch mask to expose the underlayer.

[0072] Example 11. The method of example 10, further comprising depositing an intermediate ACL layer on the soft ACL layer prior to depositing the hard ACL layer, the intermediate ACL layer having a third hardness greater than the first hardness and less than the second hardness.

[0073] Example 12. The method of example 10 or 11, wherein forming the ACL mask includes performing a high aspect ratio carbon etch to etch through the multi-layer ACL stack.

[0074] Example 13. The soft ACL layer is made of sp 2 with an atomic percentage of 60% or more. 3 The hard ACL layer comprises bonded carbon and has an atomic percentage of sp 3 The method according to any one of Examples 10 to 12, comprising a bonded carbon.

[0075] Example 14. The method of any one of Examples 10-13, wherein the first thickness is at least 1 μm and the hard ACL layer has a second thickness less than or equal to the first thickness.

[0076] Example 15. An amorphous carbon layer (ACL) mask comprising: a soft ACL layer at least 0.5 μm thick having 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 both the soft ACL layer and the hard ACL layer.

[0077] Example 16. The ACL mask of example 15, further comprising an intermediate ACL layer disposed on the soft ACL layer and underlying the hard ACL layer, the intermediate ACL layer having a third hardness greater than the first hardness and less than the second hardness.

[0078] Example 17. The ACL mask of example 15 or 16, wherein the first hardness is less than 10 GPa and the second hardness is equal to or greater than 10 GPa.

[0079] Example 18. The soft ACL layer is made of sp 2 with an atomic percentage of 60% or more. 3 The hard ACL layer comprises bonded carbon and has an atomic percentage of sp 3 The ACL mask of any one of Examples 15-17, comprising bonded carbon.

[0080] Example 19. The ACL mask of any one of Examples 15-18, wherein the soft ACL layer has a thickness of at least 1 μm and the hard ACL layer has a thickness of 1 μm or less.

[0081] Example 20. The ACL mask of example 19, wherein the ACL mask has a thickness greater than 2 μm.

[0082] While 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 invention, will become apparent to those skilled in the art upon reading the above description. It is therefore intended that the appended claims cover any such modifications or embodiments.

Claims

1. A method for producing an amorphous carbon layer (ACL) mask, wherein the method is: The ACL is formed on a sublayer, and the ACL includes a soft ACL having a first hardness of less than 10 GPa, located beneath a hard ACL having a second hardness of 10 GPa or more. Forming a patterned layer on the ACL, A method comprising using the patterned layer as an etching mask to form an ACL mask by etching that penetrates both the soft ACL portion and the hard ACL portion of the ACL, thereby exposing the underlying layer.

2. Forming the ACL means The soft ACL portion is deposited on the underlying layer as the lower layer of the ACL, The method according to claim 1, comprising depositing the hard ACL portion on top of the soft ACL portion as an upper layer of the ACL.

3. Forming the ACL means The method according to claim 2, further comprising depositing an intermediate ACL layer on the lower layer before depositing the hard ACL portion, wherein the intermediate ACL layer has a third hardness that is higher than the first hardness and lower than the second hardness.

4. Forming the ACL means The process involves continuously depositing ACL starting from the soft ACL portion in the aforementioned subsoil layer, The method according to claim 1, further comprising changing the processing conditions while continuously depositing the ACL to create a hardness gradient that transitions from the first hardness to the second hardness of the hard ACL portion on the upper surface of the ACL.

5. The method according to claim 4, wherein changing the processing conditions while continuously depositing the ACL includes increasing the temperature while depositing the ACL.

6. The method according to claim 4, wherein changing the processing conditions while continuously depositing the ACL includes increasing the bias voltage while depositing the ACL.

7. The method according to claim 1, wherein forming the ACL mask involves performing high-aspect-ratio carbon etching to etch through both the soft ACL portion and the hard ACL portion.

8. The method according to claim 1, wherein the soft ACL portion contains sp3 bonded carbon atoms in an atomic proportion of 60% or more, and the hard ACL portion contains sp3 bonded carbon atoms in an atomic proportion of more than about 20% but less than 40%.

9. A method for producing an amorphous carbon layer (ACL) mask, wherein the method is: The method involves depositing a soft ACL layer of a multilayer ACL laminate onto a substrate, wherein 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 of the multilayer ACL laminate is deposited on top of the soft ACL layer, wherein the hard ACL layer has a second hardness of 10 GPa or more. Forming a patterned layer on the multilayer ACL laminate, A method comprising using the patterned layer as an etching mask to form an ACL mask by etching through the multilayer ACL laminate, thereby exposing the underlying layer.

10. The method according to claim 9, further comprising depositing an intermediate ACL layer on the soft ACL layer before depositing the hard ACL layer, wherein the intermediate ACL layer has a third hardness that is higher than the first hardness and lower than the second hardness.

11. The method according to claim 9, wherein forming the ACL mask comprises performing high aspect ratio carbon etching to etch through the multilayer ACL laminate.

12. The aforementioned soft ACL layer has an atomic ratio of 60% or more sp ３ The hard ACL layer contains bonded carbon, and the atomic ratio of sp is greater than about 20% but less than 40%. ３ The method according to claim 9, comprising a bonded carbon.

13. The method according to claim 9, wherein the first thickness is at least 1 μm, and the hard ACL layer has a second thickness less than or equal to the first thickness.

14. A method for producing an amorphous carbon layer (ACL) mask, wherein the method is: The ACL is formed on a sublayer, wherein the ACL includes a soft ACL portion having a first hardness, located below a hard ACL portion having a second hardness higher than a first hardness, and the formation of the ACL is The process involves continuously depositing ACL starting from the soft ACL portion in the aforementioned subsoil layer, This includes changing the processing conditions while continuously depositing the ACL to create a hardness gradient that transitions from the first hardness to the second hardness of the hard ACL portion on the upper surface of the ACL, Forming a patterned layer on the ACL, A method comprising using the patterned layer as an etching mask to form an ACL mask by etching that penetrates both the soft ACL portion and the hard ACL portion of the ACL, thereby exposing the underlying layer.

15. The method according to claim 14, wherein changing the processing conditions while continuously depositing the ACL includes increasing the temperature while depositing the ACL.

16. The method according to claim 14, wherein changing the processing conditions while continuously depositing the ACL includes increasing the bias voltage while depositing the ACL.

17. Changing the processing conditions while continuously depositing the ACL includes increasing the temperature while depositing the ACL, or increasing the bias voltage while depositing the ACL, The method according to claim 14, wherein the first hardness is less than 10 GPa and the second hardness is 10 GPa or more.

18. The method according to claim 14, wherein forming the ACL mask comprises performing high aspect ratio carbon etching to etch through both the soft ACL portion and the hard ACL portion.

19. The method according to claim 14, wherein the soft ACL portion contains sp3 bonded carbon in an atomic proportion of 60% or more, and the hard ACL portion contains sp3 bonded carbon in an atomic proportion greater than about 20% but less than 40%.

20. The method according to claim 14, wherein the total thickness of the ACL is greater than approximately 1.5 μm.

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