Etching Pretreatment for Metal Etching

Abstract

A method of processing a substrate, comprising exposing the substrate to a first plasma containing carbon, wherein the substrate includes a first layer containing a dielectric material and a second layer containing a metal, and the first plasma forms a first carbonaceous deposit on the first layer and a second carbonaceous deposit on the second layer; exposing the first carbonaceous deposit and the second carbonaceous deposit to a second plasma containing a halogen, wherein the second plasma selectively etches the second carbonaceous deposit relative to the first carbonaceous deposit to expose the surface of the second layer; and exposing the first carbonaceous deposit and the exposed surface of the second layer to the second plasma to selectively etch the second layer relative to the first carbonaceous deposit, wherein the first carbonaceous deposit protects the first layer from being etched by the second plasma.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of U.S. Non - Provisional Patent Application No. 17 / 742,445, filed on May 12, 2022, which is incorporated herein by reference.

[0002] The present invention generally relates to a method of processing a substrate, and in certain embodiments, to a pre - etching treatment for etching a metal.

Background Art

[0003] Generally, semiconductor devices such as integrated circuits (ICs) are fabricated by sequentially depositing and patterning layers of dielectric, conductive, and semiconductor materials on a substrate to form a network of monolithic - ally integrated electronic components and interconnecting elements (e.g., transistors, resistors, capacitors, metal lines, contacts, and vias). Many of the processing steps used to form the constituent structures of semiconductor devices are carried out using plasma processes.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The semiconductor industry has repeatedly shrunk the minimum feature size of semiconductor devices down to a few nanometers in order to increase the integration density of components. Accordingly, the semiconductor industry increasingly demands plasma processing technologies for providing processes that pattern features, often at atomic - scale dimensions, with accuracy, precision, and profile control. These requirements are particularly stringent for three - dimensional (3D) structures, such as fin - type field - effect transistors (FinFETs) in which a gate electrode wraps around three sides of closely - spaced, narrow and long fin - type semiconductor features formed by etching grooves in a semiconductor substrate. Addressing this challenge, along with the uniformity and reproducibility required for high - volume production of ICs, requires further innovation in plasma processing technology.

Means for Solving the Problem

[0005] According to one embodiment of the present invention, there is provided a method for processing a substrate, comprising exposing the substrate to a first plasma generated from a pretreatment gas containing carbon, wherein the substrate includes a first layer containing a dielectric material and a second layer containing a metal, the first plasma is exposed to the first layer and the second layer, the first plasma forms a first carbonaceous deposit on the first layer and a second carbonaceous deposit on the second layer, the first carbonaceous deposit has a composition different from that of the second carbonaceous deposit, exposing; exposing the first carbonaceous deposit and the second carbonaceous deposit to a second plasma generated from an etching gas containing a halogen, wherein the second plasma selectively etches the second carbonaceous deposit with respect to the first carbonaceous deposit to expose the surface of the second layer, exposing; and exposing the first carbonaceous deposit and the exposed surface of the second layer to the second plasma to selectively etch the second layer with respect to the first carbonaceous deposit, wherein the first carbonaceous deposit protects the first layer from being etched by the second plasma. The method includes etching.

[0006] According to one embodiment of the present invention, there is provided a method for processing a substrate, comprising exposing the substrate to a first halogen-containing plasma to etch a part of a first layer containing a dielectric material and expose a second layer containing a metal disposed under the first layer; exposing the remaining part of the first layer and the exposed second layer to a carbon-containing plasma to form a first carbonaceous deposit on the remaining part of the first layer and a second carbonaceous deposit on the exposed second layer; exposing the first carbonaceous deposit and the second carbonaceous deposit to a second halogen-containing plasma to selectively etch the second carbonaceous deposit with respect to the first carbonaceous deposit to expose the surface of the exposed second layer; and exposing the first carbonaceous deposit and the exposed surface of the exposed second layer to a second plasma to selectively etch the second layer with respect to the first carbonaceous deposit. The method includes etching.

[0007] According to one embodiment of the present invention, a method for processing a substrate, comprising: forming a plurality of regions on the substrate, the plurality of regions including a stack of layers and including a nitride layer, an oxide layer, and an organic dielectric layer; etching through the plurality of regions by exposing the substrate to a first halogen-containing plasma to form openings in the plurality of regions and expose a underlying metal-containing film; forming a carbonaceous deposit on the plurality of regions by exposing the substrate to a carbon-containing plasma; and selectively etching the metal-containing film with respect to a part of the carbonaceous deposit on the nitride layer, the oxide layer, and the organic dielectric layer by exposing the substrate to a second halogen-containing plasma, wherein a part of the carbonaceous deposit protects the nitride layer, the oxide layer, and the organic dielectric layer from being etched by the second halogen-containing plasma.

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

Brief Description of the Drawings

[0009]

FIG. 1A-1F

FIG. 2A-2F

FIG. 3A-3C

FIG. 4

FIG. 5

FIG. 6

FIG. 7A-7C

[0010] This application relates to a method of processing a substrate, and more particularly, to a pre-etch treatment for selectively etching a metal. The selective metal etching process described in the present disclosure includes a plasma pre-treatment step of forming a carbonaceous deposit on the substrate, followed by a plasma etching step of selectively etching a portion containing the metal. As the complexity of fabricating semiconductor devices increases, it has become more inevitable to selectively add and remove different types of dielectric materials, semiconductive materials, and conductive materials during fabrication. In some cases, it may be desirable in terms of process efficiency to etch multiple materials simultaneously with various selectivities. However, in a single-step plasma etching process, selectively and effectively removing a metal-containing film can be a challenge. For example, conventional plasma etching using halogens may be effective in removing a metal-containing film, but may not be selective with respect to dielectric materials such as silicon oxide, silicon nitride, and organic dielectrics. Embodiments of the present application disclose a method of selective metal etching using a plasma pre-treatment step, and the carbonaceous deposit formed by the plasma pre-treatment step selectively protects other materials from being etched during the metal etching step.

[0011] The method described in the present disclosure can advantageously improve complex patterning schemes involving metal-containing films in semiconductor fabrication. For example, titanium nitride (TiN), which is widely used as a gate metal and a diffusion barrier metal in complementary metal-oxide-semiconductor (CMOS) devices, can be selectively etched. The plasma pre-treatment step may require only a short period, for example, less than 30 seconds. The etching selectivity can be adjusted by the plasma pre-treatment process time. In certain embodiments, varying the plasma pre-treatment process time can also enable etching selectivity between two metal-containing films (e.g., TiN and AlO). In various embodiments, the selective metal etching process can be inserted during the dielectric etching of a layer stack. For example, the method can be used as part of a self-aligned block (SAB) process in back-end-of-line (BEOL) trench patterning.

[0012] First, the steps of a selective metal etching process according to various embodiments will be described with reference to FIGS. 1A - 1F. Next, exemplary applications of the selective metal etching process in semiconductor fabrication will be described with reference to FIGS. 2A - 2F and FIGS. 3A - 3C. The deposition and etching amounts resulting from the plasma pretreatment step and the plasma etching steps of various materials are shown in FIGS. 4 - 6. Exemplary process flow diagrams are shown in FIGS. 7A - 7C. All figures in the present disclosure are drawn for illustrative purposes only and are not to scale, including the aspect ratios of the features.

[0013] FIGS. 1A - 1F show cross - sectional views of two exemplary substrates during an exemplary selective metal etching process according to various embodiments.

[0014] FIG. 1A shows a first substrate 110 including a dielectric material, and FIG. 1B shows a second substrate 115 including a metal.

[0015] In various embodiments, the dielectric material may include silicon oxide, silicon nitride (SiN), or an organic dielectric, and the metal may include titanium (Ti) or aluminum (Al). In certain embodiments, the second substrate 115 may include a metal nitride (e.g., TiN) or a metal oxide (e.g., AlO). Thus, the second substrate 115 may include a metal - containing dielectric material.

[0016] FIGS. 1C and 1D show the first substrate 110 and the second substrate 115, respectively, after the plasma pretreatment step of the selective metal etching process under the same process conditions.

[0017] The plasma pretreatment step forms carbonaceous deposits as thin films: a first carbonaceous deposit 120 (FIG. 1C) on a first substrate 110 and a second carbonaceous deposit 125 (FIG. 1D) on a second substrate 115. The plasma pretreatment step can be carried out by exposing the substrate to a plasma generated by a pretreatment gas containing carbon as a precursor in a plasma processing chamber. The carbonaceous deposit can be formed, for example, as a polymer film. Due to the difference in composition between the two substrates, the deposition mechanism on the surface can also be different. Thus, in certain embodiments, the first carbonaceous deposit 120 and the second carbonaceous deposit 125 can have different compositions, while in other embodiments, their compositions can be the same.

[0018] In various embodiments, the pretreatment gas can contain hydrocarbons. In certain embodiments, the pretreatment gas can contain methane (CH 4 ). In one or more embodiments, the pretreatment gas can be a gas mixture containing dihydrogen (H 2 ). In certain embodiments, an inert gas (e.g., noble gas and dinitrogen) can also be added to the pretreatment gas. In one embodiment, the pretreatment gas can contain CH 4 and H 2 .

[0019] While not wishing to be limited by any theory, during the plasma pre-treatment step, conditions of a plasma rich in radicals may be desired for the formation of carbonaceous deposits. To achieve an environment rich in radicals, a sufficiently high source power may be applied. In one embodiment, a relatively low bias power may be preferred, but in other embodiments, any level of bias power may be used to control the anisotropy of the plasma pre-treatment step, as long as damage to the material not being etched is minimized. In various embodiments, the source power may be from 50 W to 1000 W, the bias power may be from 0 W to 200 W, the total gas flow rate may be from 20 to 1000 sccm, and the process pressure may be from 5 to 100 mTorr. The desired directionality (i.e., isotropic / anisotropic) of the plasma pre-treatment step may vary depending on the application. In certain embodiments, the process conditions may be selected to achieve conformal isotropic formation of carbonaceous deposits by the plasma pre-treatment step. However, in another embodiment, a specific level of anisotropic formation may be desired such that the deposits are mainly formed on the stop surface and not on the sidewalls within the recesses. Such embodiments may be advantageous, for example, in a spacer opening etching process of a multiple patterning scheme.

[0020] In various embodiments, the plasma pre-treatment process time may be controlled to achieve the desired thickness of the carbonaceous deposits. In certain embodiments, the carbonaceous deposits may be formed as a thin film having a thickness of less than 1 nm. In one or more embodiments, the plasma pre-treatment process time may be from 1 second to 60 seconds. In one embodiment, a short process time of 5 seconds to 30 seconds may advantageously be sufficient to form carbonaceous deposits that may provide selectivity in a subsequent plasma metal etching step.

[0021] Figures 1E and 1F show a first substrate 110 and a second substrate 115, respectively, after a plasma metal etching step under the same process conditions.

[0022] The plasma metal etching step can be carried out by exposing the substrate to a plasma generated from an etching gas within a plasma processing chamber. As shown in FIGS. 1E and 1F, the first carbonaceous deposit 120 formed on the first substrate 110 can function as a protective layer during the plasma metal etching step, whereby etching of the dielectric material of the first substrate 110 may not occur. Further, in certain embodiments, the plasma metal etching step may even cause the deposition of an additional layer 130 (FIG. 1E). In contrast, the second carbonaceous deposit 125 formed on the second substrate 115 may be completely removed, exposing the surface of the second substrate 115, and etching of the metal of the second substrate 115 may occur (FIG. 1F).

[0023] In various embodiments, the etching gas may include a halogen. In certain embodiments, the etching gas may include BCl 3 , Cl 2 , HBr, CF 4 , CHF 3 or NF 3 . In further embodiments, the etching gas may include a non-halogen gas such as diatomic oxygen (O 2 ). In certain embodiments, an inert gas (e.g., noble gas and dinitrogen) may also be added to the etching gas.

[0024] In the plasma metal etching step, in certain embodiments, it is important to achieve conditions for anisotropic etching, particularly when etching high aspect ratio features. For anisotropic etching conditions, a relatively high bias power compared to the plasma pretreatment step is desired. In various embodiments, the source power can be from 10 W to 1000 W, the bias power can be from 50 W to 500 W. The total gas flow rate can be from 20 to 1000 sccm. The process pressure can be from 5 to 100 mTorr. In other embodiments, the plasma conditions for the plasma metal etching step can be selected to reduce the anisotropy of the plasma metal etching step, for example, by increasing the pressure in the plasma processing chamber and / or decreasing the bias power.

[0025] In various embodiments, both the plasma pretreatment step and the plasma metal etching step can advantageously be performed in the same plasma processing chamber. In one or more embodiments, the switch from the plasma pretreatment step to the plasma metal etching step can be performed by switching the gas components flowing into the plasma processing chamber without completely turning off the source power or the bias power. In certain embodiments, the plasma pretreatment step and the plasma metal etching step can be repeated as part of a periodic plasma process. Such periodic embodiments of the selective metal etching process can be advantageous for substrates containing multiple metal-containing regions and / or multiple levels of layers (e.g., 3D structures) since each period can be adjusted according to the target layers and materials to be protected and etched.

[0026] Figures 2A - 2D illustrate cross - sectional views of an exemplary substrate 200 during a semiconductor fabrication process that includes a selective metal etching process. In the illustrated embodiments, a gate stack etching process during the fabrication of a metal - oxide semiconductor field - effect transistor (MOSFET) that includes a dielectric and a metal gate is described. However, the selective metal etching process can generally be applicable to any fabrication process that requires selective etching of a metal - containing layer. In one or more embodiments, the selective metal etching process can be part of BEOL fabrication and / or part of a process to form metal lines.

[0027] In Figure 2A, an incoming substrate 200 includes a layer stack and a patterned photoresist layer 250. In various embodiments, the substrate 200 can be part of a semiconductor device or can include a semiconductor device and can, for example, be the result of several processing steps after a conventional process. Thus, the substrate 200 can include semiconductor layers useful in various microelectronics. For example, a semiconductor structure can include a substrate 200 in which various device regions are formed.

[0028] In one or more embodiments, the substrate 200 can be a silicon wafer or a silicon - on - insulator (SOI) wafer. In certain embodiments, the substrate 200 can include a silicon - germanium wafer, a silicon - carbide wafer, a gallium - arsenide wafer, a gallium - nitride wafer, or other compound semiconductors. In other embodiments, the substrate 200 includes hetero - geneous layers such as silicon - germanium - on - silicon, gallium - nitride - on - silicon, silicon - carbon - on - silicon, and silicon - on - silicon layers or an SOI substrate. In various embodiments, the substrate 200 is patterned or embedded within other components of the semiconductor device.

[0029] In FIG. 2A, the laminate of the substrate 200 may include a dielectric layer 210, a metal gate layer 220, a polysilicon layer 230, and a hard mask layer 240. The following description of the laminate structure is merely exemplary, and other reasonable structures are possible in other embodiments. In various embodiments, the dielectric layer 210 may include silicon oxide. In certain embodiments, the dielectric layer 210 may include a high-k dielectric material such as tantalum oxide, hafnium oxide, zirconium oxide, hafnium silicate, and aluminum oxide. The dielectric layer 210 may be deposited using deposition techniques including chemical vapor deposition (CVD), physical vapor deposition (PVD), and atomic layer deposition (ALD), as well as other plasma processes such as plasma CVD (PECVD), sputtering, and other processes.

[0030] On top of the dielectric layer 210, the metal gate layer 220 may be deposited using deposition techniques similar to those described above. In various embodiments, the metal gate layer 220 may include titanium nitride (TiN). In one or more embodiments, the thickness of the metal gate layer 220 may be from about 10 nm to about 100 nm.

[0031] A polysilicon layer 230 may be formed on the metal gate layer 220. The polysilicon used in the polysilicon layer 230 may include doped polysilicon so as to have desired material properties including electrical properties. The polysilicon layer 230 may be deposited on the metal gate layer 220 using the appropriate deposition techniques described above. In one or more embodiments, the polysilicon layer 230 may have a thickness of from about 50 nm to about 500 nm.

[0032] Still referring to FIG. 2A, a hard mask layer 240 may be formed on the polysilicon layer 230. In one embodiment, the hard mask layer 240 may include silicon oxide. The silicon oxide may be prepared, for example, by plasma CVD or fluidized CVD using tetraethyl orthosilicate (TEOS) as a precursor. In various embodiments, the hard mask layer 240 may include silicon nitride, silicon carbonitride (SiCN), or silicon oxycarbide (SiOC). In one or more embodiments, the hard mask layer 240 may include other suitable organic materials such as a spin-on carbon hard mask (SOH) material. The hard mask layer 240 may be deposited using the above-described suitable deposition techniques or other processes including wet processes. In various embodiments, the hard mask layer 240 may have a thickness of about 5 nm to about 50 nm. In one or more embodiments, an additional layer such as a silicon-containing antireflective coating film (SiARC) or other ARC film may be formed on the hard mask layer 240.

[0033] The patterned photoresist layer 250 can be formed over the hard mask layer 240. In various embodiments, the patterned photoresist layer 250 provides a pattern for forming respective features in the underlying layer stack. In the illustrated example, the patterned photoresist layer 250 functions as a first etching mask when forming respective features in the hard mask layer 240 (FIG. 2B), and then the features formed in the hard mask layer 240 can function as a second etching mask during a plasma process for etching the polysilicon layer 230, the metal gate layer 220, and the dielectric layer 210 (FIGS. 2C and 2D). In certain embodiments, the patterned photoresist layer 250 can include a 248 nm resist, a 193 nm resist, a 157 nm resist, an EUV (extreme ultraviolet) resist, or an electron beam (EB) sensitive resist. In various embodiments, the photoresist can be deposited over the hard mask layer 240 using a dry process or a wet process, such as spin coating techniques. The deposited photoresist can then be patterned using an appropriate lithography process to form the patterned photoresist layer 250. In one embodiment, the patterned photoresist layer 250 has a thickness of 20 nm to 100 nm.

[0034] FIG. 2B shows a cross-sectional view of the substrate 200 after patterning the hard mask layer 240.

[0035] The hard mask layer 240 can be patterned using a plasma etching process, such as a reactive ion etching (RIE) process. The portions of the hard mask layer 240 not masked by the patterned photoresist layer 250 are removed, whereby the pattern defined by the patterned photoresist layer 250 can be transferred to the hard mask layer 240. As shown in FIG. 2B, at least a portion of the polysilicon layer 230 can be exposed. In one or more embodiments, the substrate 200 can include additional layers above and / or below the hard mask layer 240, and the additional layers can also be removed during this etching step. In one or more embodiments, although not shown in FIG. 2B, a portion of the patterned photoresist layer 250 can remain during subsequent steps, while in other embodiments it can be removed at any stage.

[0036] FIG. 2C shows a cross-sectional view of the substrate 200 during gate stack etching.

[0037] After patterning the hard mask layer 240, the polysilicon layer 230 can be etched in an etch-back step using, for example, a reactive ion etching (RIE) process. As shown in FIG. 2C, at least a portion of the metal gate layer 220 can be exposed. In various embodiments, this etch-back step can be timed such that the top surface of the metal gate layer 220 is exposed. Alternatively, in certain embodiments, the etch-back step can be stopped at an optional etch stop layer. Once a portion of the metal gate layer 220 is exposed, a selective metal etching process method can be applied to pattern the metal gate layer 220.

[0038] FIG. 2D shows a cross-sectional view of the substrate 200 after the plasma pretreatment step of the selective metal etching process.

[0039] The plasma pretreatment step can be performed as previously described in the previous embodiments. The substrate 200 is treated with a carbon-containing (e.g., in one embodiment, CH 4 / H 2Exposing the mixture to a plasma can lead to the formation of a first carbonaceous deposit 260 on the hard mask layer 240 and a second carbonaceous deposit 265 on the metal gate layer 220. In certain embodiments, the first carbonaceous deposit 260 can be formed on the sidewalls of the hard mask layer 240. In one or more embodiments, as shown in FIG. 2D, the first carbonaceous deposit 260 may extend to cover the sidewalls of the polysilicon layer 230.

[0040] FIG. 2E shows a cross-sectional view of the substrate 200 after the metal etching step of the selective metal etching process.

[0041] The plasma metal etching step of the selective metal etching process can be performed as described above in the previous embodiments. By exposing the substrate 200 to a plasma containing a halogen, the second carbonaceous deposit 265 in FIG. 2D can be removed, and the metal gate layer 220 can be exposed. At this time, the exposed portion of the metal gate layer 220 can be etched during this step, while other portions (e.g., the hard mask layer 240) can be protected from damage. In FIG. 2E, the first carbonaceous deposit 260 prevents the etching of the hard mask layer 240 and the polysilicon layer 230. In certain embodiments, the processing conditions for the plasma metal etching step of the selective metal etching process can be selected to enable anisotropic etching.

[0042] FIG. 2F shows the substrate after gate stack etching.

[0043] In various embodiments, when the dielectric layer 210 contains metal, the selective metal etching process may remove a portion of the dielectric layer 210 in addition to the metal gate layer 220, as shown in FIG. 2F. Such examples of the dielectric layer 210 may include hafnium oxide and aluminum oxide. In other embodiments, the dielectric layer 210 may include a silicon-based material such as silicon dioxide, and the selective metal etching process only removes the metal gate layer 220. In other words, depending on the composition of the metal gate layer 220 and the dielectric layer 210, the patterning of these two layers shown in FIG. 2F may be performed by simply a selective metal etching process or a series of etching processes with different process conditions.

[0044] After the patterning of the metal gate layer 220 and the dielectric layer 210 is completed, the semiconductor manufacturing process may proceed to subsequent steps, such as ion implantation for source / drain formation and / or spacer formation.

[0045] In various embodiments, the above-described manufacturing steps (FIGS. 2A-2D) including the selective metal etching process may advantageously be performed in a single plasma processing chamber equipped with one or more plasma sources such as inductively coupled plasma (ICP), capacitively coupled plasma (CCP), microwave plasma (MW). In certain embodiments, the selective metal etching process may advantageously be performed to selectively etch two or more metals relative to other materials.

[0046] FIGS. 3A-3C show cross-sectional views of an exemplary substrate 300 during a semiconductor manufacturing process including a selective metal etching process according to an alternative embodiment. FIG. 3A shows an incoming substrate including a laminate having two layers of metal-containing liners.

[0047] In FIG. 3A, the incoming substrate 300 includes a laminate. In various embodiments, the substrate 300 can be part of a semiconductor device or can include a semiconductor device. The laminate of the substrate 300 can include a dielectric layer 310, a patterned interlayer dielectric (ILD) layer 340, and a hard mask layer 350. In FIG. 3A, the laminate further includes two metal-containing liners, i.e., a first metal-containing liner 320 and a second metal-containing liner 330, which are deposited on the dielectric layer 310 and separated from each other by the patterned ILD layer 340. In various embodiments, the first metal-containing liner 320 can include a first metal, and the second metal-containing liner 330 can include a second metal. In one embodiment, the first metal-containing liner 320 can include titanium nitride (TiN), and the second metal-containing liner 330 can include aluminum oxide. In certain embodiments, the thicknesses of the two metal-containing liners can be from 1 nm to 20 nm. The dielectric layer 310, the patterned ILD layer 340, or the hard mask layer 350 can include a silicon-based material. These two liners can advantageously be removed by a selective metal etching process without damaging the patterned ILD layer 340.

[0048] FIG. 3B shows a cross-sectional view of the substrate 300 after the plasma pretreatment step of the selective metal etching process.

[0049] The plasma pretreatment step can be carried out as described above in the previous embodiments. The substrate 300 is exposed to a carbon-containing (e.g., in one embodiment, CH 4 / H 2Exposing the mixture to a plasma can lead to the formation of a first carbonaceous deposit 360 on the hard mask layer 350. In certain embodiments, the first carbonaceous deposit 360 can be formed on the sidewalls of the hard mask layer 240. In one or more embodiments, as shown in FIG. 3B, the first carbonaceous deposit 360 may extend to cover the sidewalls of the ILD layer 340. At this stage, a second carbonaceous deposit 265 and a third carbonaceous deposit 367 can be formed on the first metal-containing liner 320 and the second metal-containing liner 330, respectively. Due to the difference in composition on the surface, the deposition mechanism on the surface can also be different. Thus, in certain embodiments, the first carbonaceous deposit 360, the second carbonaceous deposit 365, and the third carbonaceous deposit 367 can have different compositions, while in other embodiments, their compositions can be the same.

[0050] FIG. 3C shows a cross-sectional view of the substrate 300 after the metal etching step of the selective metal etching process.

[0051] The plasma metal etching step of the selective metal etching process can be carried out as described above in the previous embodiments. By exposing the substrate 300 to a plasma containing a halogen, the second carbonaceous deposit 365 and the third carbonaceous deposit 367 in FIG. 3B can be removed, and the first metal-containing liner 320 and the second metal-containing liner 330 can be exposed. At this time, the exposed portions of the first metal-containing liner 320 and the second metal-containing liner 330 can be etched during this step, while other portions (e.g., the hard mask layer 350) can be protected from damage. In FIG. 3C, the first carbonaceous deposit 360 prevents the etching of the hard mask layer 350 and the ILD layer 340.

[0052] FIG. 4 shows the influence of the plasma pretreatment step on the etching amounts of various materials during the plasma etching process.

[0053] FIG. 5 represents the etching amounts of various materials after the selective metal etching process.

[0054] In FIG. 4, various materials are compared with respect to the etching amount enabled by the selective metal etching process. As an example, the plasma pretreatment step is carried out using a plasma containing CH 4 / H 2 , and the metal etching step is carried out using a plasma containing BCl 3 . The five materials investigated are silicon nitride (SiN), silicon dioxide prepared using tetraethyl orthosilicate (TEOS), an organic dielectric material (or an organic dielectric layer, ODL), aluminum oxide (AlO), and titanium nitride (TiN). When the materials are etched without a plasma pretreatment step, all five materials are etched. In particular, ODL and TiN are etched substantially more than the other three materials, indicating a lack of metal etching selectivity. In contrast, by performing plasma pretreatment as described above, the etching of SiN, TEOS, and ODL is suppressed during the metal etching step, while the effect on AlO and TiN is much smaller. For metal etching after 10 seconds of plasma pretreatment, the etching of SiN, TEOS, and ODL is substantially reduced, while the etching of AlO and TiN is only reduced by about 1 / 4. Furthermore, when the plasma pretreatment is carried out for 20 seconds, the contrast between the materials becomes greater as shown in FIGS. 4 and 5. No etching occurs on SiN, TEOS, and ODL, and rather some deposits are seen on these materials. In addition, the etching of AlO is almost completely suppressed, while the etching of TiN remains at the same level as before the 10-second treatment. These results demonstrate that selective metal etching on silicon dielectric materials and organic dielectric materials is made possible by utilizing CH 4 / H 2 plasma pretreatment. Specifically, a short process time for the plasma pretreatment step, for example 10 - 20 seconds, may be sufficient to produce a large etching selectivity. It should also be noted that the process time of the plasma pretreatment step can be utilized to adjust the etching selectivity between different metal-containing materials (e.g., TiN vs. AlO).

[0055] Figure 6 shows the amount of deposits formed on various materials during the plasma pretreatment step.

[0056] In Figure 6, five materials are characterized with respect to the amount of deposits formed during the plasma pretreatment step. During the plasma pretreatment step, carbonaceous deposits are formed in varying amounts on all five materials. Without wishing to be bound by any theory, as shown in Figures 4 and 5, during subsequent metal etching steps, the carbonaceous deposits effectively prevent SiN, TEOS, and ODL from being etched, while not preventing the formation of carbonaceous deposits on AlO and TiN. Instead, on AlO and TiN, the carbonaceous deposits are completely removed during subsequent metal etching steps, enabling selective etching of AlO and TiN.

[0057] Figures 7A - 7C show process flowcharts of methods of a selective metal etching process according to various embodiments. The process flow can follow the figures (Figures 1A - 1F) described above and thus will not be described again.

[0058] In FIG. 7A, process flow 70 begins by exposing a substrate including a dielectric layer and a metal-containing film to a first plasma generated from a pretreatment gas containing carbon to form a first carbonaceous deposit on the dielectric layer and a second carbonaceous deposit on the metal-containing film (block 710, e.g., FIGS. 1C and 1D). In certain embodiments, an optional purge step may be inserted after the plasma pretreatment step (block 715). After forming carbonaceous deposits on both layers, the substrate is exposed to a second plasma generated from a halogen-containing etching gas such that the second carbonaceous deposit on the metal-containing film is selectively etched relative to the first carbonaceous deposit on the dielectric layer, revealing the surface of the metal-containing film (block 720). Subsequently, in addition to the first carbonaceous deposit, the metal-containing film is exposed to the second plasma (block 730, e.g., FIGS. 1E and 1F). At this stage, the second plasma selectively etches the metal-containing film relative to the first carbonaceous deposit while the first carbonaceous deposit protects the dielectric layer from being etched by the second plasma. In certain embodiments, the exposure to the first plasma (block 710) and the exposure to the second plasma (blocks 720 and 730) may be repeated as part of a cyclic plasma process. Such cyclic embodiments may advantageously be beneficial when, for example, accumulating a first carbonaceous deposit on the dielectric layer if the etching selectivity is not sufficiently high. In one or more embodiments, after the exposure to the second plasma (block 720), a separate etching process may be performed to etch the first carbonaceous deposit on the dielectric layer (block 730).

[0059] In FIG. 7B, process flow 72 begins by exposing a substrate including a dielectric layer to a first halogen-containing plasma to etch a portion of the dielectric layer and expose a metal-containing film disposed under the dielectric layer (block 702, e.g., FIG. 2C). Next, the remaining portion of the dielectric layer and the exposed metal-containing film are exposed to a carbon-containing plasma to form a first carbonaceous deposit on the remaining portion of the dielectric layer and a second carbonaceous deposit on the exposed metal-containing film (block 712, e.g., FIG. 2D). After the carbonaceous deposits are formed on both layers, the carbonaceous deposits are exposed to a second halogen-containing plasma to selectively etch the second carbonaceous deposit on the metal-containing film with respect to the first carbonaceous deposit, exposing the surface of the exposed metal-containing film (block 722). Next, the surface of the exposed metal-containing film is exposed to a second halogen-containing plasma such that the metal-containing film can be selectively etched with respect to the first carbonaceous deposit (block 732, e.g., FIG. 2E).

[0060] In FIG. 7C, process flow 74 begins by forming a plurality of regions on the substrate including a stack of layers having a nitride layer, an oxide layer, and an organic dielectric layer (block 701). Next, the substrate is exposed to a first halogen-containing plasma to etch the layer stack (block 704), forming openings in the plurality of regions and exposing a metal-containing film disposed under the layer stack. Next, the substrate is exposed to a carbon-containing plasma to form carbonaceous deposits on the plurality of regions (block 714). Subsequently, the substrate is exposed to a second halogen-containing plasma to selectively etch the metal-containing film with respect to portions of the carbonaceous deposits over the nitride layer, the oxide layer, and the organic dielectric layer (block 734). At this stage, the portions of the carbonaceous deposits protect the nitride layer, the oxide layer, and the organic dielectric layer from being etched by the second halogen-containing plasma.

[0061] Here, exemplary embodiments of the present invention are summarized. Other embodiments can also be understood from the entire specification and the claims appended hereto.

[0062] Example 1. A method for processing a substrate, comprising exposing the substrate to a first plasma generated from a pretreatment gas containing carbon, wherein the substrate includes a first layer containing a dielectric material and a second layer containing a metal, the first plasma is exposed to the first layer and the second layer, the first plasma forms a first carbonaceous deposit on the first layer and a second carbonaceous deposit on the second layer, the first carbonaceous deposit has a composition different from that of the second carbonaceous deposit, exposing; exposing the first carbonaceous deposit and the second carbonaceous deposit to a second plasma generated from an etching gas containing a halogen, wherein the second plasma selectively etches the second carbonaceous deposit with respect to the first carbonaceous deposit to expose the surface of the second layer, exposing; exposing the first carbonaceous deposit and the exposed surface of the second layer to the second plasma to selectively etch the second layer with respect to the first carbonaceous deposit, wherein the first carbonaceous deposit protects the first layer from being etched by the second plasma, etching.

[0063] Example 2. The method according to Example 1, wherein the dielectric material includes silicon or an organic material, and the metal includes titanium or aluminum.

[0064] Example 3. The method according to one of Example 1 or 2, wherein the second layer includes titanium nitride or aluminum oxide.

[0065] Example 4. The method according to one of Examples 1 to 3, wherein the pretreatment gas includes methane (CH 4 ).

[0066] Example 5. The method according to one of Examples 1 to 4, wherein the pretreatment gas further includes dihydrogen (H 2 ).

[0067] Example 6. The first plasma and the second plasma are formed in the same plasma processing chamber, and the method further includes purging the plasma processing chamber with an inert gas after exposing to the first plasma and before exposing to the second plasma. The method according to one of Examples 1 to 5.

[0068] Example 7. The method according to one of Examples 1 to 6, wherein the second plasma forms an additional deposit on the first carbonaceous deposit.

[0069] Example 8. The method according to one of Examples 1 to 7, further comprising repeating exposing a substrate to a first plasma, exposing a first carbonaceous deposit and a second carbonaceous deposit to a second plasma, and exposing an exposed surface of the first carbonaceous deposit and the second layer to the second plasma.

[0070] Example 9. The method according to one of Examples 1 to 8, further comprising etching the first carbonaceous deposit after exposing an exposed surface of the first carbonaceous deposit and the second layer to the second plasma.

[0071] Example 10. The second layer includes a metal nitride, the substrate further includes a third layer including a metal oxide, the third layer is exposed to the first plasma and the second plasma, the first plasma forms a third carbonaceous deposit on the third layer, and the second plasma selectively etches the third carbonaceous deposit and the third layer with respect to the first carbonaceous deposit. The method according to one of Examples 1 to 9.

[0072] Example 11. The substrate further includes a third layer including another metal different from the metal in the second layer, the third layer is exposed to the first plasma, the first plasma forms a third carbonaceous deposit on the third layer, and the third carbonaceous deposit protects the third layer from being etched when the third layer is exposed to the second plasma. The method according to one of Examples 1 to 10.

[0073] Example 12. A method of processing a substrate, comprising exposing the substrate to a first halogen-containing plasma to etch a part of a first layer containing a dielectric material and expose a second layer containing a metal disposed under the first layer; exposing the remaining part of the first layer and the exposed second layer to a carbon-containing plasma to form a first carbonaceous deposit on the remaining part of the first layer and a second carbonaceous deposit on the exposed second layer; exposing the first carbonaceous deposit and the second carbonaceous deposit to a second halogen-containing plasma to selectively etch the second carbonaceous deposit with respect to the first carbonaceous deposit to expose the surface of the exposed second layer; and exposing the first carbonaceous deposit and the exposed surface of the exposed second layer to a second plasma to selectively etch the second layer with respect to the first carbonaceous deposit.

[0074] Example 13. The method according to claim 12, further comprising generating a first halogen-containing plasma by applying power to a source electrode and a bias electrode in a plasma processing chamber, generating a carbon-containing plasma by flowing a pre-treatment gas containing carbon into the plasma processing chamber, and feeding power to the source electrode and the bias electrode in the plasma processing chamber while the substrate is being exposed to the first halogen plasma, while the carbon-containing plasma is being generated, and while the substrate is being exposed to the carbon-containing plasma.

[0075] Example 14. The method according to one of Examples 12 or 13, wherein the first halogen-containing plasma and the second halogen-containing plasma are generated from the same etching gas.

[0076] Example 15. A method of processing a substrate, comprising: forming a plurality of regions on the substrate, the plurality of regions including a layer stack and including a nitride layer, an oxide layer, and an organic dielectric layer; etching through the plurality of regions by exposing the substrate to a first halogen-containing plasma to form openings in the plurality of regions and expose a underlying metal-containing film; forming a carbonaceous deposit on the plurality of regions by exposing the substrate to a carbon-containing plasma; and selectively etching the metal-containing film with respect to a portion of the carbonaceous deposit on the nitride layer, the oxide layer, and the organic dielectric layer by exposing the substrate to a second halogen-containing plasma, wherein a portion of the carbonaceous deposit protects the nitride layer, the oxide layer, and the organic dielectric layer from being etched by the second halogen-containing plasma.

[0077] Example 16. The method according to Example 15, wherein the carbonaceous deposit is formed on the upper surfaces of the plurality of regions and the sidewalls of the openings.

[0078] Example 17. The method according to one of Examples 15 or 16, wherein the carbon-containing plasma is generated from a gas including methane (CH 4 ) and dihydrogen (H 2 ).

[0079] Example 18. The method according to one of Examples 15 to 17, wherein the second halogen-containing plasma is generated from a gas including BCl 3 .

[0080] Example 19. The method according to one of Examples 15 to 18, wherein the composition of the carbonaceous deposit on the sidewalls of the openings is different on the oxide layer, the nitride layer, and the organic dielectric layer.

[0081] Example 20. The method according to one of Examples 15 to 19, wherein selectively etching the metal-containing film forms a metal line.

[0082] Although the present invention has been described with reference to exemplary embodiments, this specification 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 be apparent to those skilled in the art by reference to this specification. Accordingly, the appended claims are intended to cover any such modifications or embodiments.

Claims

1. A method for processing a substrate, comprising: exposing the substrate to a first plasma generated from a pretreatment gas containing carbon, wherein the substrate includes a first layer containing a dielectric material and a second layer containing a metal, the first plasma is exposed to the first layer and the second layer, the first plasma forms a first carbonaceous deposit on the first layer and a second carbonaceous deposit on the second layer, and the first carbonaceous deposit has a composition different from that of the second carbonaceous deposit; exposing the first carbonaceous deposit and the second carbonaceous deposit to a second plasma generated from an etching gas containing a halogen, wherein the second plasma selectively etches the second carbonaceous deposit with respect to the first carbonaceous deposit and exposes the surface of the second layer; exposing the exposed surface of the first carbonaceous deposit and the second layer to the second plasma to selectively etch the second layer with respect to the first carbonaceous deposit, wherein the first carbonaceous deposit protects the first layer from being etched by the second plasma; A method having the above steps.

2. The method according to claim 1, wherein the dielectric material includes silicon or an organic material, and the metal includes titanium or aluminum.

3. The method according to claim 1, wherein the second layer includes titanium nitride or aluminum oxide.

4. The pre-treatment gas contains methane (CH ４ ), and the method according to claim 1.

5. The pretreatment gas further contains dihydrogen (H ２ ), and the method according to claim 1.

6. The first plasma and the second plasma are formed in the same plasma processing chamber, and the method further includes: purging the plasma processing chamber with an inert gas after the step of exposing to the first plasma and before the step of exposing to the second plasma. The method according to claim 1 having the above step.

7. The method according to claim 1, wherein the second plasma forms an additional deposit on the first carbonaceous deposit.

8. Furthermore, the step of exposing the substrate to the first plasma; the step of exposing the first carbonaceous deposit and the second carbonaceous deposit to the second plasma; the step of exposing the exposed surface of the first carbonaceous deposit and the second layer to the second plasma; The method according to claim 1 having the step of repeating the above steps.

9. The method according to claim 1, further comprising, after the step of exposing the exposed surface of the first carbonaceous deposit and the second layer to the second plasma, etching the first carbonaceous deposit.

10. The second layer contains a metal nitride, The substrate further includes a third layer containing a metal oxide, and the third layer is exposed to the first plasma and the second plasma, The first plasma forms a third carbonaceous deposit on the third layer, The method according to claim 1, wherein the second plasma selectively etches the third carbonaceous deposit and the third layer with respect to the first carbonaceous deposit.

11. The substrate further includes a third layer containing another metal different from the metal in the second layer, and the third layer is exposed to the first plasma, The first plasma forms a third carbonaceous deposit on the third layer, The method according to claim 1, wherein the third carbonaceous deposit protects the third layer from being etched when the third layer is exposed to the second plasma.

12. A method for processing a substrate, comprising: Exposing the substrate to a first halogen-containing plasma to etch a part of a first layer containing a dielectric material and expose a second layer containing a metal disposed under the first layer; Exposing the remaining part of the first layer and the exposed second layer to a carbon-containing plasma to form a first carbonaceous deposit on the remaining part of the first layer and a second carbonaceous deposit on the exposed second layer; Exposing the first carbonaceous deposit and the second carbonaceous deposit to a second halogen-containing plasma to selectively etch the second carbonaceous deposit with respect to the first carbonaceous deposit and expose the surface of the exposed second layer; Exposing the first carbonaceous deposit and the exposed surface of the exposed second layer to the second plasma to selectively etch the second layer with respect to the first carbonaceous deposit; A method comprising:

13. Furthermore, Generating the first halogen-containing plasma by applying power to a source electrode and a bias electrode in a plasma processing chamber; Generating the carbon-containing plasma by flowing a pre-treatment gas containing carbon into the plasma treatment chamber; During the step of exposing the substrate to the first halogen-plasma, during the step of forming the carbon-containing plasma, and during the step of exposing the substrate to the carbon-containing plasma, feeding power to the source electrode and the bias electrode in the plasma treatment chamber; The method according to claim 12, comprising:

14. The method according to claim 12, wherein the first halogen-containing plasma and the second halogen-containing plasma are generated from the same etching gas.

15. A method for processing a substrate, comprising: Forming a plurality of regions on the substrate, the plurality of regions having a stack of layers and including a nitride layer, an oxide layer, and an organic dielectric layer; Performing etching through the plurality of regions by exposing the substrate to a first halogen-containing plasma, forming openings in the plurality of regions, and exposing a lower metal-containing film; Forming a carbonaceous deposit on the plurality of regions by exposing the substrate to a carbon-containing plasma; Selectively etching the metal-containing film with respect to a part of the carbonaceous deposit on the nitride layer, the oxide layer, and the organic dielectric layer by exposing the substrate to a second halogen-containing plasma, the part of the carbonaceous deposit protecting the nitride layer, the oxide layer, and the organic dielectric layer from being etched by the second halogen-containing plasma; A method, comprising:

16. The method according to claim 15, wherein the carbonaceous deposit is formed on the upper surface of the plurality of regions and the sidewalls of the openings.

17. The carbon-containing plasma is generated from a gas containing methane (CH ４ ), and dihydrogen (H ２ ), the method according to claim 15.

18. The second halogen-containing plasma is generated from a gas containing BCl ３ as described in claim 15.

19. The method according to claim 15, wherein the composition of the carbonaceous deposit on the sidewalls of the openings on the oxide layer, the nitride layer, and the organic dielectric layer is different.

20. The method according to claim 15, wherein the step of selectively etching the metal-containing film forms metal lines.

Images