Method for manufacturing an interconnect structure of a semiconductor device

Abstract

In general, embodiments described herein relate to methods for fabricating interconnect structures of semiconductor devices, such as a double subtractive etching process. One embodiment is a method for semiconductor processing. A titanium nitride layer is formed over a substrate. A hard mask layer is formed over the titanium nitride layer. The hard mask layer is patterned into a pattern. The pattern is transferred to the titanium nitride layer, wherein the transferring step includes etching the titanium nitride layer. After the pattern is transferred to the titanium nitride layer, the hard mask layer is removed, wherein the removing step includes performing an oxygen-containing ashing process.

Description

Technical Field

[0001] Embodiments described herein generally relate to methods for forming semiconductor devices. More specifically, some embodiments described herein generally relate to methods for fabricating interconnect structures of semiconductor devices using, for example, a dual subtractive etch process. Background Art

[0002] Reliably producing nanometer and smaller features is one of the key technical challenges for very large scale integration (VLSI) and ultra large-scale integration (ULSI) of next generation semiconductor devices. As the limits of circuit technology are pushed, the reduced size of VLSI and ULSI interconnect technologies places additional demands on processing capabilities. As the size of integrated circuit components decreases (e.g., to nanometer dimensions), the materials and processes used to manufacture the components must be carefully selected to obtain satisfactory electrical performance levels. Summary of the invention

[0003] One embodiment is a method for semiconductor processing. A first titanium nitride layer is formed over a substrate. A hard mask layer is formed over the first titanium nitride layer. The hard mask layer is patterned into a first pattern. The first pattern is transferred to the first titanium nitride layer, wherein the transferring step includes etching the first titanium nitride layer. After transferring the first pattern to the first titanium nitride layer, the hard mask layer is removed, wherein the removing step includes performing an oxygen-containing ashing process.

[0004] One embodiment is a method for semiconductor processing. A first ruthenium layer is deposited over a substrate, and the first ruthenium layer is etched. The step of etching the first ruthenium layer includes the following steps: at a first time, starting to flow a gas mixture to a chamber in which the first ruthenium layer is disposed; at a second time, using emission spectroscopy to determine an endpoint; after the second time, continuing to flow the gas mixture for an over-etching period; and terminating the flow of the gas mixture at the end of the over-etching period. The gas mixture includes oxygen and chlorine. The endpoint is determined based on a decrease in a detected light signal. The over-etching period is 10% to 100% of the duration from the first time to the second time.

[0005] Yet another embodiment is a method for semiconductor processing. A first ruthenium layer is formed over a substrate. A first etch stop layer is formed over the first ruthenium layer. A second ruthenium layer is formed over the first etch stop layer. A second etch stop layer is formed over the second ruthenium layer. A mask layer is formed over the second etch stop layer. A hard mask layer is formed over the mask layer. The hard mask layer and the mask layer are patterned into a line pattern. The line pattern is transferred to the second etch stop layer. After the line pattern is transferred to the second etch stop layer, the hard mask layer is removed using an oxygen-containing ashing process. After the hard mask layer is removed, the line pattern is transferred to the second ruthenium layer. The transfer step includes etching the second ruthenium layer using a gas mixture including oxygen and chlorine. In the gas mixture, the ratio of (i) the flow rate of oxygen to (ii) the flow rate of oxygen plus the flow rate of chlorine ranges from 82% to 95%. At the same time, the second etch stop layer is patterned into a via pattern and the line pattern is transferred to the first etch stop layer. At the same time, the via pattern is transferred to the second ruthenium layer to form vias, and the line pattern is transferred to the first ruthenium layer to form lines. A dielectric is formed on the vias and lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Therefore, the above-mentioned features of the present disclosure can be understood in detail with reference to various embodiments (some of which are shown in the accompanying drawings), as well as the more specific description of the present disclosure briefly summarized above. However, it should be noted that the accompanying drawings only illustrate typical embodiments of the present disclosure and are therefore not to be considered as limiting the scope of the present disclosure, as the present disclosure may admit of other equally effective embodiments.

[0007] Figures 1 to 13 A perspective view depicting a process of forming a metal interconnect using a double subtractive etching process according to some embodiments of the present disclosure.

[0008] Fig.14 According to some embodiments of the present disclosure, oxygen (O 2 ) is a graph of the etching rate of ruthenium as a function of ruthenium concentration.

[0009] Fig.15 According to some embodiments of the present disclosure, oxygen (O 2 ) concentration as a function of ruthenium etch selectivity relative to titanium nitride and oxide.

[0010] Fig.16 is a flow chart of a method for an etching process according to some embodiments of the present disclosure.

[0011] Fig.17 is a graph of signals detected using optical emission spectroscopy (OES) during etching of ruthenium on a patterned wafer according to some embodiments of the present disclosure.

[0012] Fig.18 Layouts of example via patterns and line patterns according to some embodiments of the present disclosure.

[0013] Fig.19 and Fig. 20 are cross-sectional views illustrating aspects of an etching process according to some embodiments of the present disclosure.

[0014] Fig.21 and Fig. 22 are cross-sectional views illustrating aspects of another etching process according to some embodiments of the present disclosure.

[0015] Fig.23 is a simplified schematic diagram of an example etch processing chamber according to some embodiments of the present disclosure.

[0016] Fig.24 is a schematic top view of an example multi-chamber processing system according to some embodiments of the present disclosure.

[0017] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. DETAILED DESCRIPTION

[0018] In general, embodiments described herein relate to methods for manufacturing interconnect structures of semiconductor devices. The methods described herein are described in the context of a double subtractive etching process. Various examples implement a film stack, the film stack comprising a first metal layer, a first etch stop layer above the first metal layer, a second metal layer above the first etch stop layer, and a second etch stop layer above the second metal layer. In some examples, the first metal layer and the second metal layer are ruthenium layers, and the first etch stop layer and the second etch stop layer are titanium nitride layers. In addition, a mask layer (e.g., an oxide layer) is formed on the second etch stop layer. The film stack is patterned using a three-layer mask, each of which may include a hard mask layer.

[0019] In some examples, the second etch stop layer (e.g., titanium nitride layer) is patterned before removing the hard mask layer of the corresponding tri-layer mask used to pattern the second etch stop layer. By patterning this second etch stop layer before removing the hard mask layer, oxidation of the second etch stop layer can be avoided. Oxidation of the second etch stop layer may prevent proper patterning of the second etch stop layer.

[0020] In some examples, a gas mixture including oxygen and chlorine is used to etch the first metal layer (e.g., ruthenium layer). The ratio of the flow rate of oxygen in the mixture to the flow rate of oxygen plus the flow rate of chlorine is in a range of about 82% to about 95%, such as about 94%. By using such a ratio of oxygen to chlorine when etching the first metal layer, a high etch selectivity of the first metal layer relative to the first etch stop layer (e.g., titanium nitride layer) and a high etch selectivity of the first metal layer relative to the mask layer (e.g., oxide layer) can be achieved by the etching process.

[0021] In some examples, based on the endpoint determination, the first metal layer (e.g., ruthenium layer) is etched for a duration. The endpoint may be determined after the gas used to etch the first metal layer begins to flow, and the etching process may be continued for an over-etching period after the endpoint is determined. The over-etching period may be some percentage of the time from when the gas begins to flow to when the endpoint is determined. In some examples, the over-etching period is 10% to 100% (e.g., from greater than 20% to less than or equal to 60%) of the duration from when the gas begins to flow to when the endpoint is determined. By using such an over-etching period, oxidation of the underlying first etch stop layer (e.g., titanium nitride layer) may be minimized or reduced while obtaining the desired profile of the etched first metal layer.

[0022] Various aspects of different examples are described below. Although multiple aspects of different examples may be described together in a process flow, each of the multiple aspects may be implemented separately or individually and / or in different process flows. In addition, various process flows are described as being performed in a sequence; however, other examples may implement the process flow in a different sequence and / or with more or fewer operations.

[0023] Figures 1 to 13 A perspective view depicting a process of forming a metal interconnect using a double subtractive etching process according to some embodiments of the present disclosure. Figure 1 Layers are shown formed on a substrate 20. The substrate 20 may include a semiconductor substrate, such as a bulk silicon wafer, a semiconductor-on-insulator (SOI) wafer, or the like. Various devices, such as fin field effect transistors (FinFETs) or the like, may be formed in and / or on the semiconductor substrate. The substrate 20 may include any number of layers and / or components on the semiconductor substrate. For example, any number of interlayer dielectrics (ILDs) and / or intermetallization dielectrics (IMDs) may be formed on the semiconductor substrate.

[0024] A first etch stop layer 22 is deposited on the substrate 20. The etch stop layer generally provides etch selectivity between adjacent layers and materials, such as by being or including a material different from the adjacent layers and materials. In some examples, the first etch stop layer 22 is titanium nitride (TiN) or another nitride material. A first metal layer 24 is deposited on the first etch stop layer 22. In some examples, the first metal layer 24 is or includes ruthenium (Ru) or another metal. A second etch stop layer 26 is deposited on the first metal layer 24. In some examples, the second etch stop layer 26 is titanium nitride (TiN) or another nitride material. A second metal layer 28 is deposited on the second etch stop layer 26. In some examples, the second metal layer 28 is or includes ruthenium (Ru) or another metal. A third etch stop layer 30 is deposited on the second metal layer 28. In some examples, the second etch stop layer 26 is titanium nitride (TiN) or another nitride material. A mask layer 32 is deposited on the third etch stop layer 30. In some examples, mask layer 32 is or includes an oxide, such as silicon oxide formed using tetraethoxysilane (TEOS), or another metal. First etch stop layer 22, first metal layer 24, second etch stop layer 26, second metal layer 28, third etch stop layer 30, and mask layer 32 may be deposited by any acceptable deposition process, such as chemical vapor deposition (CVD), physical vapor deposition (PVD), or the like.

[0025] A first three-layer mask is formed over the mask layer 32. The first three-layer mask includes a first hard mask layer 34, a first anti-reflection coating (ARC) 36, and a first photoresist 38. The first hard mask layer 34 is deposited on the mask layer 32. In some examples, the first hard mask layer 34 is a carbon-containing material, such as spin-on carbon (SOC) or the like. The first ARC 36 is deposited on the first hard mask layer 34. In some examples, the first ARC 36 is a silicon-containing ARC or another material. The first photoresist 38 is deposited on the first ARC 36. The first hard mask layer 34, the first ARC 36, and the first photoresist 38 can be deposited by any acceptable deposition process, such as spin coating techniques, CVD, or the like.

[0026] Figure 2The first photoresist 38 is patterned into line pattern 38a, line pattern 38b, line pattern 38c, and line pattern 38d. The first photoresist 38 can be patterned using any acceptable lithography technique. It will be apparent that line pattern 38a to line pattern 38d correspond to metal lines to be formed in the first metal layer 24.

[0027] Figure 3 The diagram shows that the patterns of line pattern 38a, line pattern 38b, line pattern 38c and line pattern 38d are transferred to the first hard mask layer 34 (to form line pattern 34a, line pattern 34b, line pattern 34c and line pattern 34d, respectively) and the mask layer 32 (to form line pattern 32a, line pattern 32b, line pattern 32c and line pattern 32d, respectively). Using line pattern 38a to line pattern 38d of the first photoresist 38 as a mask, the first ARC 36 is etched. The etching process for etching the first ARC 36 can be dry plasma etching, such as by inductively coupled plasma (ICP) reactive ion etching (RIE) or another etching process. Example tools for performing the etching process are described below. In some instances using ICP-RIE, a process including trifluoromethane (CHF 3 ), carbon tetrafluoride (CF 4 ) and oxygen (O 2 ) gas mixture to etch the first ARC 36. In these examples, trifluoromethane (CHF 3 ) may have a flow rate in the range of about 75 standard cubic centimeters per minute (sccm) to about 150 sccm, such as about 100 sccm; carbon tetrafluoride (CF 4 ) may have a flow rate range of about 100 sccm to about 200 sccm, such as about 150 sccm; and oxygen (O 2 ) may range from about 5 sccm to about 25 sccm, such as about 10 sccm. The pressure during the etching process may range from about 2 mTorr to about 8 mTorr, such as about 4 mTorr. The power range of the power supply of the antenna of ICP-RIE may range from about 300 W to about 700 W, such as about 500 W. The power range of the substrate bias of ICP-RIE may range from about 60 W to about 100 W, such as about 80 W.

[0028] The first hard mask layer 34 is then etched to form line pattern 34a, line pattern 34b, line pattern 34c, and line pattern 34d that correspond to line pattern 38a, line pattern 38b, line pattern 38c, and line pattern 38d of the first photoresist 38, respectively. Similar to etching the first ARC 36, the etching process for etching the first hard mask layer 34 may be a dry plasma etch, such as by ICP-RIE (where an example tool is described below) or another etching process. In some examples using ICP-RIE, a gas including chlorine (Cl 2 ), hydrogen bromide (HBr), oxygen (O 2 ) and nitrogen (N 2 ) gas mixture to etch the first hard mask layer 34. In these examples, chlorine (Cl 2 ) may have a flow rate ranging from about 15 sccm to about 35 sccm, such as about 23 sccm; a flow rate ranging from about 200 sccm to about 600 sccm, such as about 400 sccm; and an oxygen (O 2 ) may have a flow rate range of about 30 sccm to about 70 sccm, such as about 50 sccm; and nitrogen (N 2 ) may range from about 100 sccm to about 200 sccm, such as about 150 sccm. The pressure during the etching process may range from about 5 mTorr to about 15 mTorr, such as about 10 mTorr. The power of the power supply of the antenna of ICP-RIE may range from about 600 W to about 1000 W, such as about 800 W. The power of the substrate bias of ICP-RIE may range from about 100 W to about 150 W, such as about 125 W.

[0029] The mask layer 32 is then etched to form line pattern 32a, line pattern 32b, line pattern 32c, and line pattern 32d that correspond to line pattern 38a, line pattern 38b, line pattern 38c, and line pattern 38d of the first photoresist 38, respectively. Similar to etching the first ARC 36, the etching process for etching the mask layer 32 may be a dry plasma etch, such as by ICP-RIE (where an example tool is described below) or another etching process. In some examples using ICP-RIE, a process including trifluoromethane (CHF 3 ) and carbon tetrafluoride (CF 4 ) gas mixture to etch the mask layer 32. In these examples, trifluoromethane (CHF 3 ) may have a flow rate in the range of about 75 sccm to about 125 sccm, such as about 100 sccm, and carbon tetrafluoride (CF 4) may range from about 75 sccm to about 125 sccm, such as about 100 sccm. The pressure during the etching process may range from about 4 mTorr to about 8 mTorr, such as about 6 mTorr. The power range of the power supply of the antenna of ICP-RIE may range from about 400 W to about 600 W, such as about 500 W. The power range of the substrate bias of ICP-RIE may range from about 60 W to about 100 W, such as about 80 W.

[0030] During etching of the first ARC 36 , the first hard mask layer 34 , and / or the mask layer 32 , the first photoresist 38 (eg, the line patterns 38 a to 38 d ), and the first ARC 36 may be consumed.

[0031] Figure 4 The pattern of line pattern 32a, line pattern 32b, line pattern 32c, and line pattern 32d is transferred to the third etch stop layer 30 (to form line pattern 30a, line pattern 30b, line pattern 30c, and line pattern 30d, respectively). The third etch stop layer 30 is etched to form line pattern 30a, line pattern 30b, line pattern 30c, and line pattern 30d that correspond to line pattern 38a, line pattern 38b, line pattern 38c, and line pattern 38d of the first photoresist 38, respectively. Similar to etching the first ARC 36, the etching process for etching the third etch stop layer 30 can be a dry plasma etch, such as by ICP-RIE (where an example tool is described below) or another etching process. In some examples using ICP-RIE, a gas including chlorine (Cl 2 ), methane (CH 4 ) and argon (Ar) gas mixture to etch the third etching stop layer 30. In these examples, chlorine (Cl 2 ) may range from about 50 sccm to about 150 sccm, such as about 50 sccm; methane (CH 4 ) may range from about 10 sccm to about 30 sccm, such as about 15 sccm; and the flow rate of argon (Ar) may range from about 10 sccm to about 200 sccm, such as about 100 sccm. The pressure during the etching process may range from about 4 mTorr to about 10 mTorr, such as about 8 mTorr. The power range of the power supply of the antenna of ICP-RIE may range from about 400 W to about 800 W, such as about 600 W. The power range of the substrate bias of ICP-RIE may range from about 30 W to about 60 W, such as about 45 W.

[0032] Figure 5 The line patterns 34a to 34d of the first hard mask layer 34 are removed. The line patterns 34a to 34d are removed by an ashing process, such as using oxygen plasma. Figure 5As shown, in the etching Figure 4 After the third etch stop layer 30 is formed, an ashing process is performed. In some examples, the ashing process may use a molten metal including oxygen (O 2 ) and nitrogen (N 2 ) gas mixture. In these examples, oxygen (O 2 ) may have a flow rate range of about 50 sccm to about 150 sccm, such as about 100 sccm, and nitrogen (N 2 ) may range from about 10 sccm to about 40 sccm, such as about 20 sccm. The pressure during the ashing process may range from about 8 mTorr to about 12 mTorr, such as about 10 mTorr. The power of the power supply of the antenna for the ashing process may range from about 800 W to about 1200 W, such as about 1000 W. The power of the substrate bias for ICP-RIE may be less than about 40 W, such as non-biased.

[0033] In some embodiments, performing an oxygen ashing process after etching the third etch stop layer 30 may cause the patterns of line pattern 32a, line pattern 32b, line pattern 32c, and line pattern 32d to be properly transferred to the third etch stop layer 30. Some examples consider that the third etch stop layer 30 is titanium nitride (TiN). The upper portion of the titanium nitride may be exposed to a fluorine-containing substance (e.g., trifluoromethane (CHF)) during the etching process of the patterned mask layer 32. 3 ) and / or carbon tetrafluoride (CF 4 )). By exposure to a fluorine-containing substance, the upper portion of the titanium nitride can react with fluorine and form titanium fluoride (TiF) on the upper portion. x If an oxygen ashing process is performed before etching the third etch stop layer 30, titanium fluoride may react with oxygen radicals of the ashing process to form titanium oxyfluoride (TiOF) at the upper surface of the third etch stop layer 30. If titanium oxyfluoride (TiOF) is on the upper surface of the third etch stop layer 30, the etching process for etching the third etch stop layer 30 (which is implemented by chlorine (Cl 2 ), methane (CH 4 ) and argon (Ar) gas mixture) may not react properly with titanium oxyfluoride (TiOF), and thus, the third etch stop layer 30 may not be properly etched. On the other hand, if the third etch stop layer 30 is etched before the oxygen ashing process, titanium oxyfluoride (TiOF) is not formed on the upper surface of the third etch stop layer 30 as a result of the oxygen ashing process before etching the third etch stop layer 30, and thus, the third etch stop layer 30 may be properly etched. Other examples may implement other materials and / or etching chemistries, such as so that other sequences of processing may be implemented (e.g., performing an ashing process before etching the third etch stop layer 30).

[0034] Figure 6The pattern of line pattern 32a, line pattern 32b, line pattern 32c, and line pattern 32d is transferred to second metal layer 28 (to form line pattern 28a, line pattern 28b, line pattern 28c, and line pattern 28d, respectively). Second metal layer 28 is etched to form line pattern 28a, line pattern 28b, line pattern 28c, and line pattern 28d corresponding to line pattern 38a, line pattern 38b, line pattern 38c, and line pattern 38d of first photoresist 38, respectively. Similar to etching first ARC 36, the etching process for etching second metal layer 28 can be dry plasma etching, such as by ICP-RIE (where an example tool is described below) or another etching process. In some examples using ICP-RIE, a gas including oxygen (O 2 ) and chlorine (Cl 2 ) gas mixture to etch the second metal layer 28. In these examples, oxygen (O 2 ) may have a flow rate range of about 300 sccm to about 500 sccm, such as about 400 sccm, and the chlorine gas (Cl 2 ) may range from about 10 sccm to about 50 sccm, such as about 25 sccm. The pressure during the etching process may range from about 20 mTorr to about 40 mTorr, such as about 30 mTorr. The power of the power supply of the antenna of ICP-RIE may range from about 800 W to about 1200 W, such as about 1000 W. The power of the substrate bias of ICP-RIE may range from about 40 W to about 70 W, such as about 50 W.

[0035] Some examples consider that the mask layer 32 is an oxide, the second metal layer 28 is ruthenium (Ru), and the second etch stop layer 26 is titanium nitride (TiN). In these examples, ICP-RIE is performed to etch the second metal layer 28, and the ICP-RIE uses a gas including oxygen (O 2 ) and chlorine (Cl 2 ) gas mixture. Fig.14 The diagram shows oxygen (O 2 ) and chlorine (Cl 2 ) in a gas mixture containing oxygen (O 2 )'s concentration function 102. Fig.15 As oxygen (O 2 ) and chlorine (Cl 2 ) in a gas mixture containing oxygen (O 2 ) is a graph of the etching selectivity as a function of the concentration of . Fig.15Data points 104a, 104b, and 104c are shown, which show the etch selectivity of ruthenium relative to titanium nitride at different oxygen concentrations, and data points 106a, 106b, and 106c are shown, which show the etch selectivity of ruthenium relative to oxide at different oxygen concentrations. Fig.14 and Fig.15 Further shown is a first regime 110 and a second regime 112. In the first regime 110, the main etching byproduct is RuO x Cl, where x ranges from 2 to 3. In the second range 112, the main etching byproduct is RuO 4 , and the ion bombardment is mainly performed at a processing temperature below 150°C.

[0036] like Fig.14 As shown, near the boundary between the first range 110 and the second range 112 (eg, at about 94% oxygen), the etching rate 102 has a peak value of about 200 angstroms / minute. Fig.15 As shown in the data points 104a and 106a, at the boundary of the first range 110 and the second range 112 (e.g., at about 94% oxygen), the etching selectivity of ruthenium relative to titanium nitride and ruthenium relative to oxide are both high, as shown by data point 104b and data point 106b. At the boundary, as shown by data point 104b, the etching selectivity of ruthenium relative to titanium nitride is greater than 50, and as shown by data point 106b, the etching selectivity of ruthenium relative to oxide is greater than 30. Data points 104a and 106a show the etching selectivity of ruthenium relative to titanium nitride and ruthenium relative to oxide at 80% oxygen, and data points 104c and 106c show the etching selectivity of ruthenium relative to titanium nitride and ruthenium relative to oxide at 100% oxygen.

[0037] Therefore, in some examples, in the etching process for etching the second metal layer 28 of ruthenium, oxygen (O 2 ) and chlorine (Cl 2 ) in a gas mixture containing oxygen (O 2 ) concentration range is about 82% to about 95%. In this range, a high etch rate of ruthenium can be achieved, as well as a high etch selectivity of ruthenium relative to titanium nitride and ruthenium relative to oxide.

[0038] In some examples, an endpoint of the etching process is detected and the etching process continues for an over-etching period. Fig.16 The etching process is shown in FIG. 1 . In operation 120, a process gas for the etching process is started to flow. The etching process may be performed as described above with oxygen (O 2 ) and chlorine (Cl 2) mixture. In operation 122, an endpoint is determined. In some instances, optical emission spectroscopy (OES) is used to determine the endpoint. OES can be used to determine the presence of a given material on substrate 20. For example, light can be reflected by a material on substrate 20 and / or by a gas in a chamber where an etching process is performed. In some instances, a relatively high amount of reflected light can indicate the presence of a material, while a relatively low amount of reflected light can indicate the absence of a material. Generally, an endpoint is detected when a signal detected using an OES (e.g., the amount of reflected light detected) decreases by a predetermined amount. Fig.17 1 is a diagram of signals detected using an OES during etching of ruthenium on a patterned wafer according to an example. This figure shows the detected signals as a function of the magnitude of relative time. The first detected signal 132 is the magnitude of light detected with a wavelength of 656nm. The second detected signal 134 is the magnitude of light detected with a wavelength of 415nm. The third detected signal 136 is the magnitude of light detected with a wavelength of 365nm. The endpoint 140 is determined from the detected signal 132, the detected signal 134, and the detected signal 136. In some examples, the endpoint 140 is when any of the detected signal 132, the detected signal 134, and the detected signal 136 decreases by at least 1% for 5 consecutive sampling steps from the previous sampling step, wherein the frequency of the sampling step is 60Hz. In other examples, the endpoint 140 can be determined by any reduction of any or all of the detected signals, such as by any change in magnitude over time, a percentage reduction with any number of sampling steps, or the like.

[0039] Replay Fig.16 , in operation 124, the flow of the process gas for the etching process is continued for an over-etching period. In some examples, the over-etching period is a predetermined duration, i.e., a percentage (which may exceed 100%) of the duration from the time when the process gas flow is started in operation 120 to the time when the end point is determined in operation 122. At the end of the over-etching period, in operation 126, the flow of the process gas for the etching process is terminated. After the flow of the process gas for the etching process is terminated, the chamber may be purged with an inert gas.

[0040] In some examples, the etching process continues for an over-etching period that does not exceed 100% (such as not more than 60%) of the duration of the etching process until the endpoint. If the etching process continues for more than 100% of the duration of the etching process until the endpoint, the underlying titanium nitride second etch stop layer 26 may be oxidized by oxygen of the etching process. If the titanium nitride is oxidized, the subsequent etching for etching through the second etch stop layer 26 may not properly etch the second etch stop layer 26 to transfer the pattern. However, if the over-etching period does not exceed 100% (such as not more than 60%) of the duration of the etching process until the endpoint, the oxidation of the titanium nitride of the second etch stop layer 26 may be minimized or still not enough to adversely affect the etching of the second etch stop layer 26.

[0041] Furthermore, in some examples, the etching process continues for an over-etching period that is at least 10% (such as at least 20%) of the duration of the etching process until the endpoint. The duration of the over-etching period can be tuned to achieve the profiles of line pattern 28a, line pattern 28b, line pattern 28c, and line pattern 28d. If the over-etching period is less than 10% of the duration of the etching process until the endpoint, the sidewalls of line pattern 28a to line pattern 28d may be tilted (for example, line pattern 28a to line pattern 28d may have a tapered profile). Combined with a subsequent etching process of etching the first metal layer 24 (which further etches the pattern of the second metal layer 28 to form a more vertical sidewall), this can produce a shoulder that is formed on the subsequently etched second etch stop layer 26. If the over-etching period is at least 10% (such as at least 20%) of the duration of the etching process until the endpoint, the sidewalls of line patterns 28a to 28d can be substantially vertical (e.g., within 5° of the vertical plane, or more specifically within 3° of the vertical plane). This can result in more aligned sidewalls of the subsequent etched layers. Figures 19 to 22 Additional details on these aspects are described.

[0042] Figure 7The formation of a second tri-layer mask over line patterns 32a-d, line patterns 30a-d, line patterns 28a-d, and second etch stop layer 26 is shown. The second tri-layer mask includes a second hard mask layer 44, a second ARC 46, and a second photoresist 48. The second hard mask layer 44 is deposited on the line patterns 32a-d, line patterns 30a-d, line patterns 28a-d, and second etch stop layer 26. In some examples, the second hard mask layer 44 is a carbon-containing material, such as SOC or the like. The second ARC 46 is deposited on the second hard mask layer 44. In some examples, the second ARC 46 is a silicon-containing ARC or another material. The second photoresist 48 is deposited on the second ARC 46. The second hard mask layer 44, the second ARC 46, and the second photoresist 48 can be deposited by any acceptable deposition process, such as spin coating technology, CVD, or the like.

[0043] Figure 8 The second photoresist 48 is patterned into via pattern 48e, via pattern 48f, via pattern 48g, via pattern 48h, via pattern 48i and via pattern 48j. The second photoresist 48 can be patterned using any acceptable photolithography technique. It is obvious that via pattern 48e to via pattern 48j correspond to vias to be formed in the second metal layer 28. Each of via pattern 48e to via pattern 48j is vertically above at least a corresponding portion of line pattern 28a-d, line pattern 30a-d, and line pattern 32a-d. In addition, each of via pattern 48e-j extends laterally beyond line pattern 28a-d, line pattern 30a-d, and line pattern 32a-d. Fig.18 An example layout of these features is shown. Fig.18 As shown, via pattern 48h and via pattern 48g extend laterally beyond the sidewalls of line pattern 32c, line pattern 30c, line pattern 28c by dimension D. By aligning via patterns 48e-j in this manner, subsequently formed vias may be self-aligned to subsequently formed metal lines.

[0044] Fig. 9 The pattern of via pattern 48e, via pattern 48f, via pattern 48g, via pattern 48h, via pattern 48i and via pattern 48j is transferred to the second hard mask layer 44 (to form via pattern 44e, via pattern 44f, via pattern 44g, via pattern 44h, via pattern 44i and via pattern 44j, respectively) and line pattern 32a-d (to form via pattern 32e, via pattern 32f, via pattern 32g, via pattern 32h, via pattern 32i and via pattern 32j, respectively). Using via pattern 48e to via pattern 48j of second photoresist 48 as a mask, second ARC 46 is etched. The etching process for etching second ARC 46 may be the same as that of Figure 3 The etching process used to etch the first ARC 36 is the same or similar.

[0045] The second hard mask layer 44 is then etched to form via pattern 44e, via pattern 44f, via pattern 44g, via pattern 44h, via pattern 44i, and via pattern 44j corresponding to via pattern 48e, via pattern 48f, via pattern 48g, via pattern 48h, via pattern 48i, and via pattern 48j of the second photoresist 48, respectively. The etching process for etching the second hard mask layer 44 may be the same as that of the second photoresist 48. Figure 3 The etching process used to etch the first hard mask layer 34 is the same or similar.

[0046] The line patterns 32a-d of the mask layer 32 are then etched to form via patterns 32e, 32f, 32g, 32h, 32i, and 32j corresponding to the via patterns 48e, 48f, 48g, 48h, 48i, and 48j of the second photoresist 48, respectively. Figure 3 The mask layer 32 is etched using the same or similar process as previously described for etching the mask layer 32. Fig. 9 As shown, and as Fig.18 As a result of the alignment shown, via patterns 44e-j may extend laterally from and along sidewalls of via patterns 32e-j and line patterns 30a-d and line patterns 28a-d.

[0047] During etching of the second ARC 46 , the second hard mask layer 44 , and / or the mask layer 32 , the second photoresist 48 (eg, the via patterns 48 a to 48 j ), and the second ARC 46 may be consumed.

[0048] Fig.10 The via patterns 44e-j of the second hard mask layer 44 are removed. The via patterns 44e to 44j are removed by an ashing process, such as using oxygen plasma. The ashing process may be the same as described above with reference to Figure 5 The ashing process described is the same or similar.

[0049] Fig.11The diagram illustrates that the patterns of via pattern 32e, via pattern 32f, via pattern 32g, via pattern 32h, via pattern 32i and via pattern 32j are transferred to line pattern 30a-d of third etch stop layer 30 (to form via pattern 30e, via pattern 30f, via pattern 30g, via pattern 30h, via pattern 30i and via pattern 30j, respectively) and the patterns of line pattern 28a, line pattern 28b, line pattern 28c and line pattern 28d are transferred to second etch stop layer 26 (to form line pattern 26a, line pattern 26b, line pattern 26c and line pattern 26d, respectively). The line patterns 30a-d of the third etch stop layer 30 are etched to form via patterns 30e, 30f, 30g, 30h, 30i, and 30j corresponding to the via patterns 48e, 48f, 48g, 48h, 48i, and 48j of the second photoresist 48, respectively. The second etch stop layer 26 is etched to form line patterns 26a, 26b, 26c, and 26d corresponding to the line patterns 38a, 38b, 38c, and 38d of the first photoresist 38, respectively. The third etch stop layer 30 and the second etch stop layer 26 are etched simultaneously to form via patterns 30e-j and line patterns 26a-d. The etching process for etching the third etch stop layer 30 and the second etch stop layer 26 may be the same as that described above with reference to FIG. Figure 4 The etching process described for etching the third etch stop layer 30 is the same or similar.

[0050] Fig.12The diagram shows that the patterns of via pattern 32e, via pattern 32f, via pattern 32g, via pattern 32h, via pattern 32i and via pattern 32j are transferred to line pattern 28a-d of second metal layer 28 (to form via 28e, via 28f, via 28g, via 28h, via 28i and via 28j, respectively) and the patterns of line pattern 28a, line pattern 28b, line pattern 28c and line pattern 28d are transferred to first metal layer 24 (to form metal wire 24a, metal wire 24b, metal wire 24c and metal wire 24d, respectively). The line patterns 28a-d of the second metal layer 28 are etched to form vias 28e, 28f, 28g, 28h, 28i, and 28j corresponding to the via patterns 48e, 48f, 48g, 48h, 48i, and 48j of the second photoresist 48, respectively. The first metal layer 24 is etched to form metal lines 24a, 24b, 24c, and 24d corresponding to the line patterns 38a, 38b, 38c, and 38d of the first photoresist 38, respectively. The line patterns 28a-d of the second metal layer 28 and the first metal layer 24 are etched simultaneously to form vias 28e-j and metal lines 24a-d. The etching process for etching the second metal layer 28 and the first metal layer 24 may be the same as that described above with reference to FIG. Figure 6 The etching process described for etching the second metal layer 28 is the same or similar.

[0051] Figures 19 to 22 The figures illustrate different results of etching processes according to some examples. For ease of reference to the various processing steps, these figures refer to Figures 1 to 12 Describe and illustrate the features. Figures 19 to 22 The etching process described may or may not be Figures 1 to 12 is implemented in the processing. Fig.19 and Fig.21 The diagram corresponds to the above Figure 6 A cross-sectional view of the process described, and Fig. 20 and Fig. 22 The diagram corresponds to the above Fig.12 The cross-sectional view corresponds to the process described by Figure 6 and Fig.12 The XYZ axis indicates the XZ plane.

[0052] As reference Figure 6 and reference Fig.19As described, the etching process of etching the second metal layer 28 is continued for an over-etching period to form the line pattern 28a', and the over-etching period is less than 10% of the duration of the etching process until the end point. The resulting line pattern 28a' has a sloped sidewall, which results in a tapered profile of the line pattern 28a'. When the pattern of the line pattern 28a' is subsequently transferred to the second etch stop layer 26 (e.g., at Fig.11 When the line pattern 28a' is formed, the bottom of the line pattern 28a' defines the side of the line pattern 26a' of the second etch stop layer 26. The line pattern 26a' is transferred to the first metal layer 24 to form the subsequent etching process of the metal line 24a' (for example, Fig.12 The line pattern 28a' is also etched to form a via 28e'. The portion of the line pattern 28a' that remains as the via 28e' is further etched so that the sidewalls of the via 28e' become more vertical. The line pattern 26a' is not significantly etched, which results in the formation of a shoulder 150, such as Fig. 20 shown.

[0053] As reference Figure 6 and reference Fig.21 As described, the etching process of etching the second metal layer 28 is continued for an over-etching period to form the line pattern 28a", and the over-etching period exceeds 10% (e.g., exceeds 20%) but is less than 100% (e.g., less than or equal to 60%) of the duration of the etching process to the endpoint. For example, the over-etching period may be 50% of the duration of the etching process to the endpoint to form the line pattern 28a". The resulting line pattern 28a" has a vertical sidewall. When the pattern of the line pattern 28a" is subsequently transferred to the second etch stop layer 26 (e.g., in Fig.11 When the line pattern 28a' is formed, the bottom of the line pattern 28a' defines the side of the line pattern 26a' of the second etch stop layer 26. The line pattern 26a' is transferred to the first metal layer 24 to form a subsequent etching process (e.g., Fig.12 (2) Also, the line pattern 28a" is etched to form a via 28e". Because the sidewalls of the line pattern 28a" are vertical, the portion of the line pattern 28a" that is retained as the via 28e" may not be etched to make the sidewalls of the via 28e" more vertical (although undercutting may occur). This allows the sidewalls of the metal line 24a", the line pattern 26a", and the via 28e" to be vertically aligned, as shown in FIG. Fig. 22 Medium picture.

[0054] Fig.13The etching of the first etch stop layer 22 and the formation of the dielectric layer 50 are shown. The etching process for etching the first etch stop layer 22 may be a dry plasma etch, such as by ICP-RIE or another etching process. The dielectric layer 50 may be or include silicon oxide (e.g., doped or undoped), a low dielectric constant dielectric, silicon oxycarbide, the like, or a combination thereof. The dielectric layer 50 may be deposited by CVD (e.g., plasma enhanced CVD (PECVD), flowable CVD (FCVD) or the like), spin coating, or any other deposition process. After deposition, the dielectric layer 50 may be planarized, such as by chemical mechanical planarization (CMP), which may also remove the via patterns 32e-j and 30e-j.

[0055] Fig.23 2 is a simplified schematic diagram of an example etch processing chamber 200 for use in the above-described etching process. The etch processing chamber 200 is suitable for etching one or more layers on the substrate 20. An example of a processing chamber that can be used to benefit from the present disclosure is the AdvantEdge Mesa etch processing chamber, which is available from Applied Materials, Inc. in Santa Clara, California. It is contemplated that other processing chambers, including those from other manufacturers, may be suitable for practicing various embodiments of the present disclosure.

[0056] The etch process chamber 200 includes a chamber body 202 defining a chamber volume 204 therein. The chamber body 202 has sidewalls 206 and a bottom 208 coupled to a ground node 210. The sidewalls 206 have a protective lining 212 to extend the time between maintenance cycles of the etch process chamber 200. The size of the chamber body 202 and related components of the etch process chamber 200 is not limited and is generally proportionally larger than the size of the substrate (e.g., substrate 20) to be processed therein. Examples of substrate sizes include 200 mm diameter, 350 mm diameter, 400 mm diameter, 450 mm diameter, etc.

[0057] The chamber body 202 supports a chamber lid assembly 214 to enclose the chamber volume 204. The chamber body 202 may be made of aluminum or other suitable materials. A substrate access port 216 is formed through the sidewall 206 of the chamber body 202 to facilitate the transfer of substrates into and out of the etch processing chamber 200. The substrate access port 216 may be coupled to a multi-chamber processing system (an example of which is shown in FIG. Fig.24 ) of the transfer chamber and / or other chambers.

[0058] A pumping port 230 is formed through the sidewall 206 of the chamber body 202 and is connected to the chamber volume 204. A pumping device (not shown) is coupled to the chamber volume 204 via the pumping port 230 to evacuate and control the pressure therein. The pumping device may include one or more pumps and throttle valves.

[0059] The gas panel 240 is coupled to the chamber body 202 via gas lines 242 to supply process gases to the chamber volume 204. The gas panel 240 may include one or more process gas sources 244, 246, 248, 250 and may additionally include inert gases, non-reactive gases, and reactive gases. Examples of process gases that may be provided by the gas panel 240 include, but are not limited to, trifluoromethane (CHF 3 ), carbon tetrafluoride (CF 4 ), oxygen (O 2 ), chlorine (Cl 2 ), hydrogen bromide (HBr), nitrogen (N 2 ), argon (Ar) and methane (CH 4 ). The process gas may include other gases, such as an inert gas or a carrier gas.

[0060] The valve 252 controls the flow of process gases from the process gas sources 244, 246, 248, and 250 of the gas panel 240 and is managed by the controller 254. The gas flow supplied from the gas panel 240 to the chamber body 202 may include a combination of gases.

[0061] The chamber lid assembly 214 may include a nozzle 256. The nozzle 256 has one or more ports for introducing process gases from the process gas sources 244, 246, 248, 250 of the gas panel 240 into the chamber volume 204. After the process gases are introduced into the etch processing chamber 200, the gases are excited to form a plasma. An antenna 260, such as one or more inductive coils, may be provided near the etch processing chamber 200. An antenna power supply 262 may power the antenna 260 via a matching circuit 264 to inductively couple energy, such as radio frequency (RF) energy, to the process gas to maintain a plasma formed from the process gas in the chamber volume 204 of the etch processing chamber 200. Alternatively, or in addition to the antenna power supply 262, a process electrode below the substrate 20 and / or above the substrate 20 may be used to capacitively couple RF power to the process gas to maintain a plasma within the chamber volume 204. The operation of the antenna power supply 262 may be controlled by a controller, such as the controller 254 , which also controls the operation of other components in the etch processing chamber 200 .

[0062] The chamber cover assembly 214 further includes a window 266, which may be a transparent dielectric material, such as quartz. An OES measurement device 268 is located at the window 266. The OES measurement device 268 includes an emitter and a sensor. The emitter may emit light of one or more wavelengths into the etching process chamber 200 via the window 266. The light from the emitter may be reflected away from the gas and / or substrate 20 in the etching process chamber 200. The reflected light may be transmitted through the window 266 and received by the sensor of the OES measurement device 268. The reflected light detected by the sensor may be used to determine the endpoint of the etching process according to a given method. For example, the OES measurement device 268 is communicatively coupled to the controller 254 to transmit the detected reflected light to the controller 254 so that the controller 254 can determine the endpoint.

[0063] A substrate support pedestal 270 is disposed in the chamber volume 204 to support the substrate 20 during processing. The substrate support pedestal 270 may include an electrostatic chuck (ESC) 272 for holding the substrate 20 during processing. The ESC 272 uses electrostatic attraction to hold the substrate 20 to the substrate support pedestal 270. The ESC 272 includes an electrode 274 powered by a power supply 276. The electrode 274 is embedded in the ESC 272 within a dielectric body. The power supply 276 may also include a system controller for controlling the operation of the electrode 274 by directing a DC current to the electrode 274 to adsorb and desorb the substrate 20.

[0064] In addition, the electrode 274 can be further coupled to an RF power supply 280 integrated with a matching circuit 282. The RF power supply 280 can provide an RF bias (e.g., about 200 volts to about 2000 volts) to the electrode 274. In addition, the RF power supply 280 provides a bias that attracts plasma ions (formed by the process gas in the chamber volume 204) to the ESC 272 and the substrate 20 disposed thereon. The RF power supply 280 can be cycled on and off, or pulsed on and off, during processing of the substrate 20. The ESC 272 has an isolator 284 to make the sidewalls of the ESC 272 less attractive to plasma to extend the maintenance life cycle of the ESC 272. In addition, the substrate support pedestal 270 can have a cathode liner 286 to protect the sidewalls of the substrate support pedestal 270 from the plasma gas and extend the time between maintenance of the etch processing chamber 200.

[0065] The ESC 272 may include a heater disposed therein and connected to a power source (not shown) for heating the substrate, while a cooling base 288 supporting the ESC 272 may include conduits for circulating a heat transfer fluid to maintain the temperature of the ESC 272 and the substrate 20 disposed thereon. The ESC 272 is configured to perform within a temperature range required by the thermal budget of the device fabricated on the substrate 20. For example, for some embodiments, the ESC 272 may be configured to maintain the substrate 20 at a temperature of about minus 35 degrees Celsius to about 500 degrees Celsius.

[0066] A cooling base 288 is provided to help control the temperature of the substrate 20. To mitigate process drift over time, the temperature of the substrate 20 may be maintained substantially constant in the etching processing chamber 200 throughout the process of etching the substrate 20 by cooling the base 288. In one embodiment, the temperature of the substrate 20 is maintained at about 70 degrees Celsius to about 90 degrees Celsius throughout the etching process.

[0067] A cover ring 290 is disposed on the ESC 272 and along the periphery of the substrate support pedestal 270. The cover ring 290 is configured to confine the etching gas to a desired portion of the exposed top surface of the substrate 20 while protecting the top surface of the substrate support pedestal 270 from the plasma environment within the etching process chamber 200. Lift pins (not shown) selectively move through the substrate support pedestal 270 to lift the substrate 20 above the substrate support pedestal 270 to facilitate a transfer robot (not shown) or other suitable transfer mechanism to reach the substrate 20.

[0068] The controller 254 may be used to control the process sequence, thereby adjusting the gas flow from the gas panel 240 into the etch processing chamber 200, and controlling other process parameters. The software program, when executed by the CPU, switches the CPU to a dedicated computer (controller) that controls the etch processing chamber 200 to perform the process. The software program may also be stored and / or executed by a second controller (not shown) that is co-located with the etch processing chamber 200.

[0069] Various layers are disposed on the substrate 20, which may include various metal layers, etching stop layers, and mask layers, such as those described in the above examples. For different compositions of each of the other film layers disposed on the substrate 20, the various layers may require unique etching methods. These methods may be performed in a single etching process chamber or in several etching process chambers. Each etching process chamber may be configured to etch using one or more etching methods. In an embodiment, the etching process chamber 200 is configured to etch at least the metal layer to form an interconnect structure, such as the above-mentioned double subtractive etching structure. For the processing parameters provided herein, the etching process chamber 200 is configured to process a 200 mm diameter substrate (e.g., having a diameter of approximately 0.0707 mm). 2 The process parameters such as flow rate and power can be generally scaled proportionally with changes in chamber volume or substrate plan area.

[0070] Fig.24 Schematic top view of an example multi-chamber processing system 300 having an etch processing chamber 200 coupled thereto, which may be suitable for performing the processes described herein. The system 300 may include one or more load lock chambers 302, 304 for transferring substrates into and out of the system 300. Typically, because the system 300 is in a vacuum, the load lock chambers 302, 304 may "evacuate" substrates introduced into the system 300. A first robot 310 may transfer substrates between the load lock chambers 302, 304 and a first set of one or more substrate processing chambers 312, 314, 316, 200 (four shown). Each of the substrate processing chambers 312, 314, 316, and 200 is configured to perform substrate processing operations, such as etching processes, cyclical layer deposition (CLD), atomic layer deposition (ALD), CVD, PVD, degassing, pre-cleaning, orientation, and other substrate processing. The position of the etching processing chamber 200 for performing the etching process relative to the other substrate processing chambers 312, 314, and 316 is shown in the figure, and the position of the etching processing chamber 200 can be selectively switched with any one of the substrate processing chambers 312, 314, and 316.

[0071] The first robot 310 may also transfer substrates to and from one or more transfer chambers 320, 322. The transfer chambers 320, 322 may be used to maintain ultra-high vacuum conditions while allowing substrates to be transferred within the system 300. The second robot 330 may transfer substrates between the transfer chambers 320, 322 and a second set of one or more substrate processing chambers 332, 334, 336, 338. Similar to the substrate processing chambers 312, 314, 316, 200, the substrate processing chambers 332, 334, 336, 338 may be equipped to perform various substrate processing operations, including the dry etching processes described herein, and any other suitable processes including, for example, deposition, pre-cleaning, degassing, and orientation. For example, any of the substrate processing chambers 312, 314, 316, 200, 332, 334, 336, and 338 may be removed from the system 300 if not necessary for a particular process performed by the system 300.

[0072] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope of the disclosure, and the scope of the disclosure is determined by the claims that follow.

Claims

1. A method for semiconductor processing, the method The following steps are involved: forming a first ruthenium layer over the substrate; forming a second titanium nitride layer over the first ruthenium layer; forming a second ruthenium layer over the second titanium nitride layer; depositing a first titanium nitride layer on the second ruthenium layer; forming a hard mask layer over the first titanium nitride layer; patterning the hard mask layer into a first pattern; Transferring the first pattern to the first titanium nitride layer, the step of transferring the first pattern to the first titanium nitride layer comprising etching the first titanium nitride layer; and After transferring the first pattern to the first titanium nitride layer, the hard mask layer is removed, and the step of removing the hard mask layer includes performing an oxygen-containing ashing process.

2. The method of claim 1, further comprising: The following steps are involved: After removing the hard mask layer, transferring the first pattern to the first ruthenium layer includes etching the first ruthenium layer.

3. The method of claim 2, wherein the step of etching the first ruthenium layer The following steps are involved: A gas mixture including oxygen and chlorine is provided to the first ruthenium layer, and a ratio of (i) a flow rate of the oxygen gas to (ii) a flow rate of the oxygen gas plus a flow rate of the chlorine gas ranges from 82% to 95%.

4. The method of claim 2, further comprising: The following steps are involved: forming the second titanium nitride layer above the substrate, wherein the first ruthenium layer is formed above the second titanium nitride layer; forming an oxide layer on the first titanium nitride layer, wherein the hard mask layer is formed on the oxide layer; and transferring the first pattern to the oxide layer; and The step of etching the first ruthenium layer includes the following steps: using an etching process having an etching selectivity of ruthenium to titanium nitride of 50 or more and an etching selectivity of ruthenium to oxide of 30 or more.

5. The method of claim 2, wherein the step of etching the first ruthenium layer The following steps are involved: Starting the flow of an etching process gas provided to the first ruthenium layer at a first time; determining an endpoint at a second time using emission spectroscopy, the endpoint being determined based on a decrease in the detected light signal; continuing to flow the etching process gas for an over-etching period after the second time, the over-etching period ranging from 10% to 100% of the duration from the first time to the second time; and The flow of the etch process gas is terminated at the end of the over-etch period.

6. The method of claim 2, wherein the step of transferring the first pattern to the first ruthenium layer forms a ruthenium pattern having a profile with vertical sidewalls.

7. The method of claim 1, further comprising: The following steps are involved: After removing the hard mask layer, transferring the line pattern to the second ruthenium layer; simultaneously patterning the first titanium nitride layer into a via pattern and transferring the line pattern to the second titanium nitride layer; simultaneously transferring the via pattern to the second ruthenium layer to form vias and transferring the line pattern to the first ruthenium layer to form lines; and A dielectric layer is formed on the line and the via.

8. The method of claim 1, further comprising: include: After removing the hard mask layer, a layer is deposited over the first titanium nitride layer.

9. A method for semiconductor processing, the method The following steps are involved: depositing a first ruthenium layer over the substrate; depositing a second ruthenium layer over the substrate; depositing a first titanium nitride layer over the second ruthenium layer, wherein the first ruthenium layer is deposited over the first titanium nitride layer; depositing a second titanium nitride layer over the first ruthenium layer; Etching the first ruthenium layer, the step of etching the first ruthenium layer comprising the following steps: At a first time, starting to flow a gas mixture to a chamber in which the first ruthenium layer is disposed, the gas mixture comprising oxygen and chlorine; determining an endpoint at a second time using emission spectroscopy, the endpoint being determined based on a decrease in the detected light signal; continuing to flow the gas mixture for an over-etch period after the second time, the over-etch period ranging from 10% to 100% of the duration from the first time to the second time; and The flow of the gas mixture is terminated at the end of the over-etch period. 10 . The method of claim 9 , wherein the over-etching period ranges from greater than 20% to less than or equal to 100% of the duration from the first time to the second time.

11. The method of claim 9, wherein the step of flowing the gas mixture The following steps are involved: flowing the oxygen gas at a rate ranging from 300 standard cubic centimeters per minute (sccm) to 500 sccm; and The chlorine gas was flowed at a rate ranging from 10 sccm to 50 sccm.

12. The method of claim 9, further comprising: The following steps are involved: A titanium nitride layer is deposited on the substrate; the first ruthenium layer is deposited on the titanium nitride layer; depositing an oxide layer over the first ruthenium layer; and The gas mixture has an etching selectivity of ruthenium to titanium nitride of 50 or more and an etching selectivity of ruthenium to oxide of 30 or more.

13. The method of claim 9, wherein the step of etching the first ruthenium layer forms a ruthenium pattern having a profile with vertical sidewalls.

14. The method of claim 9, further comprising: The following steps are involved: forming a third titanium nitride layer over the first ruthenium layer; forming a hard mask layer over the third titanium nitride layer; patterning the hard mask layer into a pattern; transferring the pattern to the third titanium nitride layer; and After transferring the pattern to the third titanium nitride layer, removing the hard mask layer includes performing an oxygen-containing ashing process, wherein the first ruthenium layer is etched after removing the hard mask layer, and the step of etching the first ruthenium layer includes transferring the pattern to the first ruthenium layer.

15. The method of claim 9, further comprising: The following steps are involved: etching the second titanium nitride layer to form a line pattern, wherein the step of etching the first ruthenium layer transfers the line pattern to the first ruthenium layer; simultaneously etching the second titanium nitride layer to form a via pattern and etching the first titanium nitride layer to transfer the line pattern to the first titanium nitride layer; simultaneously etching the first ruthenium layer to transfer the via pattern to the first ruthenium layer and etching the second ruthenium layer to transfer the line pattern to the second ruthenium layer, wherein vias are formed in the first ruthenium layer and lines are formed in the second ruthenium layer; and A dielectric layer is deposited over the lines and the vias.

16. A method for semiconductor processing, the method The following steps are involved: forming a first ruthenium layer over the substrate; forming a first etch stop layer over the first ruthenium layer; forming a second ruthenium layer over the first etch stop layer; forming a second etch stop layer over the second ruthenium layer; forming a mask layer over the second etch stop layer; forming a hard mask layer over the mask layer; patterning the hard mask layer and the mask layer into a line pattern; transferring the line pattern to the second etch stop layer; removing the hard mask layer using an oxygen-containing ashing process after transferring the line pattern to the second etch stop layer; After removing the hard mask layer, transferring the line pattern to the second ruthenium layer comprises: etching the second ruthenium layer using a gas mixture comprising oxygen and chlorine, wherein in the gas mixture, a ratio of (i) a flow rate of oxygen to (ii) a flow rate of oxygen plus a flow rate of chlorine ranges from 82% to 95%; Simultaneously, patterning the second etch stop layer into a via pattern and transferring the line pattern to the first etch stop layer; Simultaneously, transferring the via pattern to the second ruthenium layer to form vias, and transferring the line pattern to the first ruthenium layer to form lines; and A dielectric is formed on the via and the line.

17. The method of claim 16, wherein the step of etching the second ruthenium layer The following steps are involved: Initiating flow of the gas mixture provided to the second ruthenium layer at a first time; determining an endpoint at a second time using emission spectroscopy, the endpoint being determined based on a decrease in the detected light signal; continuing to flow the gas mixture for an over-etch period after the second time, the over-etch period ranging from 10% to 100% of the duration from the first time to the second time; and The flow of the gas mixture is terminated at the end of the over-etch period. The method of claim 16 , wherein the line and the via have aligned sidewalls.

19. The method of claim 16, wherein each of the first etch stop layer and the second etch stop layer is a titanium nitride layer.

20. The method of claim 19, in: The mask layer is an oxide layer; and The gas mixture has an etch selectivity of ruthenium to titanium nitride of 50 or more and an etch selectivity of ruthenium to oxide of 30 or more.

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