Self-aligned top via formation at the online end

Abstract

A method of forming a self-aligned via (2302, 2402) at an online end, comprising: patterning even / odd metal lines (202, 302), including using a first / second hard mask (102, 104); cutting the hard mask (102, 104) and a selected metal line (202, 302), even or odd, using a cut mask (402, 1102) having a window (404) that exposes the hard mask (102, 104) over a cut region of the selected metal line (202, 302); enlarging the window (404) to expose the hard mask (102, 104) on either side of the cut region; selectively etching the hard mask (102, 104) using the enlarged window (1104) to form a T-shaped cavity (902, 1502) within the cut region; filling the T-shaped cavity (902, 1502) with a gap fill dielectric (2002); removing the hard mask (102, 104); and recessing the metal line (202, 302) with the gap fill dielectric (2002) overhanging a portion of the selected metal line (202, 302) through the recess forming the self-aligned via (2302, 2402) at an end of the metal line (202, 302). A structure is also provided.

Description

Technical Field

[0001] This invention relates to top via formation, and more particularly to a technique for forming self-aligned top vias at online ends. Background Technology

[0002] In semiconductor device metallization processes, vias are often formed above metal lines. However, this top-via approach can lead to alignment problems, especially when the via is formed above the end of the metal line.

[0003] One challenge in top-via solutions is forming vias at the line tip without any change in the critical dimension (CD) of the via. However, controlling the via CD is difficult if alignment with the metal line is achieved using photolithography. Specifically, a limited overlay offset can cause the via to move away from the line tip or be cut off, resulting in a reduced via CD. Overlap offset can also occur due to pattern-to-pattern misalignment during the photolithography process.

[0004] Therefore, an improved technique for forming top vias is desired. Summary of the Invention

[0005] This invention provides a technique for forming self-aligned top vias at the ends of wires. In one aspect of the invention, a method for forming self-aligned vias at the ends of wires is provided. The method includes: patterning a metal line comprising alternating even and odd numbers of metal lines using a hard mask, the hard mask including a first hard mask for patterning the even numbers of metal lines and a second hard mask for patterning the odd numbers of metal lines; cutting the hard mask and selected metal lines (even or odd) using a cutting mask, the cutting mask having a window exposing the hard mask above a cut area of ​​the selected metal lines; enlarging the window in the cutting mask to expose the hard mask on either side of the cut area of ​​the selected metal lines; selectively etching the hard mask using the enlarged window in the cutting mask to form a T-shaped cavity in the cut area of ​​the selected metal lines; filling the T-shaped cavity with a gap-filling dielectric; removing the hard mask; and selectively recessing the metal lines relative to the gap-filling dielectric, wherein the gap-filling dielectric hangs over the selected metal lines through the recess at the end of the metal lines forming the self-aligned via.

[0006] In another aspect of the invention, another method for forming a self-aligned via at the end of a line is provided. The method includes: patterning a metal line comprising alternating even and odd numbers of metal lines using a hard mask, the hard mask including a first hard mask for patterning the even-numbered metal lines and a second hard mask for patterning the odd-numbered metal lines; cutting a selected one of the first hard mask and the even-numbered metal lines using a first cutting mask, the first cutting mask having a window exposing the first hard mask over a cut area of ​​the selected even-numbered metal line; enlarging the window in the first cutting mask to expose the first hard mask on either side of the cut area of ​​the selected even-numbered metal line; selectively etching the first hard mask using the enlarged window in the first cutting mask to form a first T-shaped cavity within the cut area of ​​the selected even-numbered metal line; and cutting the second hard mask and the odd-numbered metal lines using a second cutting mask. In one of the following steps, the second cutting mask has a window that exposes the second hard mask over the cutting area of ​​the selected odd-numbered metal lines; the window in the second cutting mask is enlarged to expose the second hard mask on either side of the cutting area of ​​the selected odd-numbered metal lines; the second hard mask is selectively etched using the enlarged window in the second cutting mask to form a second T-shaped cavity in the cutting area of ​​the selected odd-numbered metal lines; the first T-shaped cavity and the second T-shaped cavity are filled with a gap-filling dielectric; the first hard mask and the second hard mask are removed; and the metal lines are selectively recessed relative to the gap-filling dielectric, wherein the gap-filling dielectric hangs over the selected even-numbered metal lines and the selected odd-numbered metal lines through the recessed portion forming the self-aligned via at the end of the metal lines.

[0007] In another aspect of the invention, a further method for forming a self-aligned via at a line end is provided. The method includes: patterning a metal line comprising alternating even and odd number metal lines using a hard mask, the hard mask including a first hard mask for patterning the even number metal lines and a second hard mask for patterning the odd number metal lines; cutting a selected one of the first hard mask and the even number metal lines using a first cutting mask, the first cutting mask having a window exposing the first hard mask over a cut area of ​​the selected even number metal line; and enlarging the window in the first cutting mask to expose the first hard mask on either side of the cut area of ​​the selected even number metal line. The process involves: selectively etching the first hard mask using an enlarged window in the first cutting mask to form a first T-shaped cavity within the cutting region of the selected even-numbered metal lines; using a second cutting mask to cut a selected one of the second hard mask and the odd-numbered metal lines, the second cutting mask having a window that exposes the second hard mask over the cutting region of the selected odd-numbered metal lines; enlarging the window in the second cutting mask to expose the second hard mask on either side of the cutting region of the selected odd-numbered metal lines; and selectively etching the first hard mask using the enlarged window in the second cutting mask. The second hard mask is selectively etched to form a second T-shaped cavity within the cut area of ​​the selected odd-numbered metal lines; the first hard mask is cut using a mask having a window exposing the first hard mask above the non-wire end of one of the even-numbered metal lines to form a gap in the first hard mask; the second hard mask is cut using another mask having a window exposing the second hard mask above the non-wire end of one of the odd-numbered metal lines to form a gap in the second hard mask; the first T-shaped cavity, the second T-shaped cavity, and the first hard mask are filled with a gap-filling dielectric. The gap in the mold and the gap in the second hard mask; removing the first hard mask and the second hard mask; and selectively recessing the metal line relative to the gap-filling dielectric, wherein the gap-filling dielectric hangs over the even-numbered metal lines through the recess to form the self-aligned via at the ends of the even-numbered and odd-numbered metal lines, and wherein selectively recessing the metal line relative to the gap-filling dielectric in the gap in the first hard mask and the gap-filling dielectric in the gap in the second hard mask to form a non-line-end via.

[0008] In another aspect of the invention, a structure is provided. The structure includes: a metal wire; a cut in a selected one of the metal wires; a via aligned with an end of the selected metal wire on either side of the cut; and a dielectric filling the gap between the ends of the wires.

[0009] A more complete understanding of the invention, as well as its further features and advantages, will be obtained by referring to the following detailed description and accompanying drawings. Attached Figure Description

[0010] Figure 1 This is a top-down diagram illustrating a first hard mask for patterning even-numbered metal lines and a second hard mask for patterning odd-numbered metal lines according to an embodiment of the present invention, as well as dielectric material deposited on / around the (even / odd) metal lines and the first and second hard masks.

[0011] Figure 2 This is a cross-sectional view (AA′) of a first hard mask over one of an even number of metal lines according to an embodiment of the present invention;

[0012] Figure 3 This is a cross-sectional view (BB′) of a second hard mask located on one of the odd-numbered metal lines according to an embodiment of the present invention;

[0013] Figure 4 This is a top view showing a (first) cutting mask formed on a first hard mask and a second hard mask according to an embodiment of the present invention, the first hard mask and the second hard mask having windows of the first hard mask on a cutting area exposing a selected one of the even number of metal lines to be cut;

[0014] Figure 5 The image is a cross-sectional view (AA′) showing that a first cutting mask according to an embodiment of the invention has been used to pattern / cut a first hard mask over a selected even number of metal lines;

[0015] Figure 6 This is a cross-sectional view (BB′) illustrating an embodiment of the present invention, in which even if a window in the first cutting mask intrudes into an adjacent odd-numbered metal line, the cutting of the odd-numbered metal line will not occur due to the use of different first hard masks and second hard masks.

[0016] Figure 7 It is a cross-sectional view (AA′) according to an embodiment of the present invention, which shows the pattern from a first hard mask that has been transferred to the selected even-numbered metal lines, thereby cutting the even-numbered metal lines;

[0017] Figure 8 This is a top view showing a lateral etching of a first cutting mask that has been performed to enlarge a window according to an embodiment of the present invention;

[0018] Figure 9A cross-sectional view (AA′) of an embodiment of the invention shows a first cutting mask after a window has been enlarged / widened by lateral etching, and the first cutting mask has been used to selectively etch portions of the first hard mask over selected (even) metal lines on either side of the cutting area exposed by the enlarged / widened window to form a (first) "T-shaped" cavity;

[0019] Figure 10 The cross-sectional view (BB′) according to an embodiment of the present invention shows that even if the now enlarged window of the first cutting mask intrudes into the second hard mask above the adjacent odd-numbered metal lines, the use of different first / second hard mask materials and selective etching prevents any etching of the second hard mask from occurring;

[0020] Figure 11 This is a top view showing a (second) cutting mask formed on a first hard mask and a second hard mask according to an embodiment of the present invention, the first hard mask and the second hard mask having windows of the second hard mask on a cutting area exposing a selected one of the odd number of metal lines to be cut;

[0021] Figure 12 This is a cross-sectional view (AA′) showing an embodiment of the invention, in which even if a window in the second cutting mask intrudes into an adjacent even-numbered metal line, no cutting of the even-numbered metal line due to the use of different first and second hard masks occurs.

[0022] Figure 13 This is a cross-sectional view (BB′) according to an embodiment of the present invention, which shows that a second hard mask has been patterned / cut on a selected odd number of metal lines using a second cutting mask, and the pattern from the second hard mask has been transferred to the selected odd number of metal lines, which are then cut.

[0023] Figure 14 The cross-sectional view (AA′) according to an embodiment of the present invention shows that after the lateral etching of the first cutting mask has been performed to enlarge the window, even though the now enlarged window of the second cutting mask encroaches on the first hard mask above the adjacent even number of metal lines, different first / second hard mask materials and selective etching prevent any etching of the first hard mask from occurring.

[0024] Figure 15 This is a cross-sectional view (BB′) according to an embodiment of the invention, showing a second cutting mask after the window has been enlarged / widened by lateral etching, and the second cutting mask has been used to selectively etch portions of the second hard mask above selected (odd) metal lines on either side of the cutting area exposed by the enlarged / widened window to form a (second) "T-shaped" cavity;

[0025] Figure 16 This is a top view showing a (third) cut mask formed on top of first and second hard masks according to an embodiment of the present invention, the first and second hard masks having windows of the first hard mask exposing one of an even number of metal lines, and the first hard mask being patterned on the selected even number of metal lines using the third cut mask, thereby forming gaps in the first hard mask;

[0026] Figure 17 This is a cross-sectional view (AA′) according to an embodiment of the present invention, showing a (third) cutting mask filling a first T-shaped cavity in a cutting region of a selected even number of metal wires;

[0027] Figure 18 This is a top view showing a (fourth) cut mask formed on a first hard mask and a second hard mask according to an embodiment of the present invention. The first hard mask and the second hard mask have windows of the second hard mask that expose one of the odd number of metal lines, and the fourth cut mask has been used to pattern the second hard mask on the selected odd number of metal lines, thereby forming a gap in the first hard mask.

[0028] Figure 19 This is a cross-sectional view (AA′) of a second T-shaped cavity in a cutting region of a selected odd number of metal wires, as illustrated in the fourth embodiment of the present invention.

[0029] Figure 20 This is a top view showing the gap-filling dielectric in the first / second T-shaped cavity of the cut region of the selected even / odd number of metal wires according to an embodiment of the present invention, and the (non-wire end) gap in the first / second hard mask;

[0030] Figure 21 This is a cross-sectional view (AA′) according to an embodiment of the present invention, showing a gap-filling dielectric filling a first T-shaped cavity in a cut region of a selected even number of metal wires;

[0031] Figure 22 This is a cross-sectional view (BB′) according to an embodiment of the present invention, showing a gap-filling dielectric filling a second T-shaped cavity in a cut region of a selected odd number of metal wires;

[0032] Figure 23 The diagram is a cross-sectional view (AA′) according to an embodiment of the invention, showing that the first hard mask has been removed and the even-numbered metal lines have been selectively recessed relative to the gap-filling dielectric, such that the portion of the even-numbered metal lines covered by the gap-filling dielectric at the line ends is not recessed, and a via is formed that is self-aligned with the (even-numbered) line ends.

[0033] Figure 24This is a cross-sectional view (BB′) according to an embodiment of the invention, showing that the second hard mask has been removed and the odd-numbered metal lines have been selectively recessed relative to the gap-fill dielectric, whereby the portion of the odd-numbered metal lines covered by the gap-fill dielectric at the line ends is not recessed, and vias self-aligned with the (odd-numbered) line ends are formed; and

[0034] Figure 25 This is a cross-sectional view (AA′) of a gap-filling dielectric according to an embodiment of the invention, which has been polished to expose the top of the via at the even-numbered line ends. Detailed Implementation

[0035] This paper provides a technique for forming self-aligned top vias at the wire ends, which first uses dicing lithography to define a wire cut, then widens the mask opening in the cut area and transfers the pattern to the underlying metal wire hard mask layer. Subsequently, the enlarged opening is filled with a dielectric to form a mask for the self-aligned top via at the wire end. As will be described in detail below, this technique places the via on both sides of the wire-cut area (i.e., at the wire end). Advantageously, there is no via critical size (CD) variation, which would otherwise occur due to photolithographic alignment of the via to the previously formed wire cut. Moreover, with this process, the via CD at the wire end is controlled by the amount of lateral etching of the hard mask.

[0036] See now Figure 1-25 An exemplary method for forming a self-aligned via at the end of a line is described. For example... Figure 1 As shown in the top view, the process begins with patterning even-numbered metal lines using a first hard mask 102 and patterning odd-numbered metal lines using a second hard mask 104. The terms "even-numbered" and "odd-numbered" are used herein to refer to alternating metal lines. The designation of which metal lines are even-numbered and which are odd-numbered is arbitrary. However, if a given metal line is even-numbered, the next adjacent metal line is odd-numbered, and vice versa. The terms "first" and "second" may also be used herein to refer to even-numbered and odd-numbered metal lines, respectively.

[0037] It is worth noting that the following description illustrates the formation of self-aligned vias at even / odd metal wire ends, and the formation of non-wire end vias above even / odd metal wire ends. However, it should be understood that this technique can be implemented to form any of these wire end and / or non-wire end vias for even / odd metal wires, individually or in combination, and in any order. For example, this technique can be implemented to simply form wire end vias above even and / or odd metal wire ends, and / or form non-wire end vias for even and / or odd metal wires.

[0038] This method requires different hard masks (formed from different materials) for even and odd number of metal lines. As will become apparent from the following description, this dual hard mask configuration allows for selective cutting of even-numbered to odd-numbered metal lines, and vice versa. According to an exemplary embodiment, the first hard mask 102 is formed of materials such as titanium (Ti), tantalum (Ta), titanium oxide (TiOx), titanium nitride (TiN), and / or tantalum nitride (TaN), and the second hard mask 104 is formed of materials such as silicon nitride (SiN), silicon carbonitride (SiCN), hydrogen-containing silicon carbonitride (SiCNH), and / or silicon carbide (SiC). The first hard mask 102 and the second hard mask 104 can be patterned using a patterning technique such as photolithography, followed by an etching process. Suitable etching processes include, but are not limited to, directional (anisotropic) etching processes such as reactive ion etching (RIE). Alternatively, the first hard mask 102 and the second hard mask 104 may be formed by any other suitable technique, including but not limited to sidewall image transfer (SIT), self-aligned double patterning (SADP), self-aligned quadruple patterning (SAQP), and other self-aligned multiple patterning (SAMP).

[0039] Even-numbered and odd-numbered metal lines can be formed using directional (anisotropic) etching processes such as RIE, employing a first hard mask 102 and a second hard mask 104 respectively. That is, the first hard mask 102 and the second hard mask 104 are formed on a metal layer (not shown), which is then patterned into separate even-numbered and odd-numbered metal lines. Suitable metals for the metal layer / metal lines include, but are not limited to, tungsten (W), cobalt (Co), and / or ruthenium (Ru).

[0040] Then, a dielectric material 106 is deposited on / around the (even / odd) metal lines and the first and second hard masks 102 and 104, followed by a polishing process such as chemical mechanical polishing (CMP) to remove excess dielectric. Suitable dielectric materials 106 include, but are not limited to, oxide materials such as silicon oxide (SiOx) and / or organosilicon glass (SiCOH) and / or ultra-low κ interlayer dielectric (ULK-ILD) materials, for example, having a dielectric constant κ of less than 2.7. By comparison, silicon dioxide (SiO2) has a dielectric constant κ value of 3.9. Suitable ultra-low κ dielectric materials include, but are not limited to, porous organosilicon glass (pSiCOH).

[0041] Figure 2 This shows a cross-sectional view of the first hard mask 102 above the even-numbered metal lines 202 (along line AA′ - see below). Figure 1 ). Figure 3 This shows a cross-sectional view of the second hard mask 104 above the odd-numbered metal lines 302 (along line BB′ - see below). Figure 1 ).

[0042] Then, uniform metal wire 202 cutting is performed. For this purpose, a (first) cutting mask 402 is formed over the first hard mask 102 and the second hard mask 104. See also Figure 4 (Top view). Window 404 (exposing the cutting area) exists in the cutting mask 402 above one of the first hard masks 102 (above a selected one of the even-numbered metal lines 202 to be cut). According to an exemplary embodiment, the cutting mask 402 is formed of a multilayer photolithographic stack, which includes, but is not limited to, a photoresist disposed on an anti-reflective coating (ARC) and an organic planarization layer (OPL). Ideally, window 404 only opens the first hard mask 102 above the selected even-numbered metal lines 202 to be cut (i.e., the desired cutting area). However, as Figure 6 As shown and described below, using different hard masks for even and odd metal lines expands the process window because different / secondary hard masks 104 exist on adjacent odd metal lines and protect adjacent odd metal lines.

[0043] Figure 5 This is a cross-sectional view (along line AA′) showing the cutting mask 402 that has been used to pattern / cut the first hard mask 102 on the selected even-numbered metal lines 202 to be cut. Figure 6 As shown (cross-sectional view (along line BB′)), even though window 404 encroaches on the adjacent odd-numbered metal line 302, the odd-numbered metal line 302 is protected by the second hard mask 104 (i.e., a different hard mask material, see above). Therefore, no cutting of the odd-numbered metal line 302 occurs. By way of example only, a plasma etching process using chlorine-containing plasma can be used to selectively etch the hard mask 102.

[0044] Figure 7 The image (along line AA′) is a cross-sectional view showing that the pattern from the first hard mask 102 has been transferred to selected even-numbered metal lines 202, which are then cut. For wire cutting, a directional (anisotropic) etching process such as RIE can be used.

[0045] like Figure 8As shown in the top view, a lateral etching of the cut mask 402 is then performed (see arrow 802) to enlarge the window 404. This enlargement / widening of the window 404 defines the width of the via, and based on the lateral etching, the via is now positioned on both sides of the wire-cut region (i.e., at the ends of the selected even-numbered metal lines 202 that have already been cut). According to the exemplary embodiment, oxygen plasma etching is used to perform this lateral etching of the cut mask 402. It must be noted that the widened / enlarged window 404 is sufficient to expose a portion of the first hard mask 102 over the selected (even-numbered) metal lines on either side of the cut region, without widening the window 404 too much to expose the first hard mask 102 over another different even-numbered metal line 202.

[0046] Figure 9 This is a cross-sectional view (along line AA′) of the cutting mask 402 after the window 404 has been enlarged / widened by lateral etching. As described above, the enlarged window 404 exposes a portion of the first hard mask 102 above selected (even-numbered) metal lines on either side of the cutting area. Next, as... Figure 9 As shown, the cutting mask 402 is used to selectively etch those portions of the first hard mask 102 located above selected (even) metal lines on either side of the cutting area exposed by the enlarged / widened window 404. As described above, a plasma etching process using chlorine-containing plasma can be used to selectively etch the hard mask 102. Figure 9 As shown, the first hard mask 102 etched over the cut area of ​​the selected even number of metal lines forms a (first) "T-shaped" cavity 902.

[0047] like Figure 10 As shown in the cross-sectional view (along line BB′), even though the now enlarged window 404 encroaches on the adjacent second hard mask 104 / odd-number metal line 302, the use of different first / second hard mask materials and selective etching prevents any etching of the second hard mask 104. After the first hard mask 102 above the selected (even-number) metal line on either side of the cut area has been etched through the enlarged window 404, the cut mask 402 is removed.

[0048] Then, the same general process is used to cut one of the odd-numbered metal wires 302. That is, as... Figure 11As shown in the top view, a (second) dicing mask 1102 is formed on a first hard mask 102 and a second hard mask 104. A window 1104 (exposing the dicing area) exists in the dicing mask 1102 above one of the second hard masks 104 (above a selected one of the odd-numbered metal lines 302 to be diced). According to an exemplary embodiment, the dicing mask 1102 is formed from a multilayer photolithographic stack such as a photoresist / ARC / OPL stack. Ideally, the window 1104 only opens the second hard mask 104 above the selected odd-numbered metal lines 302 to be diced (i.e., the desired dicing area). However, using different hard masks for even-numbered and odd-numbered metal lines expands the process window because different / first hard masks 102 exist above and protect adjacent even-numbered metal lines. That is, as Figure 12 As shown in the cross-sectional view (along line AA′), even if window 1104 encroaches on an adjacent even-numbered metal line 202, this even-numbered metal line 202 is protected by the first hard mask 102 (i.e., a different hard mask material, see above). Therefore, no cutting of the even-numbered metal line 202 occurs. By way of example only, a plasma etching process using fluorocarbon plasma can be used to selectively etch the hard mask 104. Furthermore, as... Figure 12 As shown, the cutting mask 1102 fills the T-shaped cavity 902 in the cutting area of ​​the selected even number of metal wires.

[0049] Figure 13 This is a cross-sectional view (along line BB′) showing that a cutting mask 1102 has been used to pattern / cut a second hard mask 104 over selected odd-numbered metal lines 203, and the pattern from the second hard mask 104 has been transferred to the selected odd-numbered metal lines 302, which are then cut. For wire cutting, a directional (anisotropic) etching process such as RIE can be used. Although in Figure 13 Combining Chinese and Western elements, but in the above... Figure 5 and Figure 7 The separate hard mask and metal line patterning steps are described (in the case of patterning a selected even number of metal lines).

[0050] Then, a lateral etching of the cutting mask 1102 is performed to widen the second hard mask 104 and the window 1104 above the selected odd-numbered metal lines 302. As... Figure 14 As shown in the cross-sectional view (along line AA′), even though the now enlarged window 1104 (see arrow 1402) encroaches on the adjacent first hard mask 102 / even-number metal line 202, different first / second hard mask materials and selective etching prevent any etching of the first hard mask 102 from occurring.

[0051] As described above, the widening of window 1104 defines the width of the via, and based on lateral etching, the via is now positioned on both sides of the wire-cut region (i.e., at the ends of the selected odd-numbered metal lines 302 that have already been cut). According to an exemplary embodiment, this lateral etching of the cut mask 1102 is performed using oxygen plasma etching. It must be noted that the widened / enlarged window 1104 is sufficient to expose a portion of the second hard mask 104 over the selected (odd-numbered) metal lines on either side of the cut region, without widening window 1104 too much to expose a second hard mask 104 over another different odd-numbered metal line 302.

[0052] Figure 15 This is a cross-sectional view (along line BB′) of the cut mask 1102 after window 1104 has been enlarged / widened by lateral etching. As described above, the enlarged window 404 exposes a portion of the second hard mask 104 above selected (odd number) metal lines on either side of the cut area. Next, as... Figure 15 As shown, the cutting mask 1102 is used to selectively etch those portions of the second hard mask 104 located above selected (odd number) metal lines on either side of the cutting area exposed by the enlarged / widened window 1104. As described above, a plasma etching process using fluorocarbon plasma can be used to selectively etch the hard mask 104. Figure 15 As shown, a second hard mask 104 etched over the cut area of ​​a selected odd number of metal lines forms a (second) "T-shaped" cavity 1502. After the second hard mask 104 over the selected (odd number) metal lines on either side of the cut area has been etched through the enlarged window 1104, the cut mask 1102 is removed.

[0053] Non-wire-end vias (i.e., top vias not above the ends of metal lines) can also be patterned in the corresponding first / second hard masks 102 / 104 on the even / odd number of metal lines 202 / 302, respectively. For example, as Figure 16 As shown in the top view, a (third) via mask 1602 is formed over a first hard mask 102 and a second hard mask 104. A window 1604 (defining the via region) exists in the via mask 1602, which is located above one of the first hard masks 102, above a selected one of the even-numbered metal lines 202. According to an exemplary embodiment, the via mask 1602 is formed from a multilayer photolithographic stack, such as a photoresist / ARC / OPL stack. Figure 17 As shown, (along line AA′) a cross-sectional view of the via mask 1602 fills a T-shaped cavity 902 in the cut region of a selected even-numbered metal wire. In the same manner, the via mask 1602 fills a T-shaped cavity 1502 in the cut region of a selected odd-numbered metal wire (although not explicitly shown in the figures).

[0054] Return to reference Figure 16 The via mask 1602 is then used to pattern a first hard mask 102 over a selected even number of metal lines 202, thereby forming gaps 1606 in the first hard mask 102. As described above, a plasma etching process using chlorine-containing plasma can be used to selectively etch the hard mask 102. After the non-line-end vias have been etched in the first hard mask 102 over the selected (even number) metal lines, the via mask 1602 is removed.

[0055] The same process applies to forming non-line-end vias in a second hard mask 104 above a selected odd number of metal lines. For example, as... Figure 18 As shown in the top view, a (fourth) via mask 1802 is formed over the first hard mask 102 and the second hard mask 104. A window 1804 (defining the via region) exists in the via mask 1802, which is above the second hard mask 104 above a selected one of the odd-numbered metal lines 302. According to an exemplary embodiment, the via mask 1802 is formed from a multilayer photolithographic stack such as a photoresist / ARC / OPL stack. Figure 19 As shown in the cross-sectional view (along line BB′), the via mask 1802 fills the T-shaped cavity 1502 in the cut region of the selected odd-numbered metal lines. In the same manner, the via mask 1802 fills the T-shaped cavity 902 in the via region of the selected even-numbered metal lines (although not explicitly shown in the figures).

[0056] Return to reference Figure 18 The via mask 1802 is then used to pattern a second hard mask 104 over a selected odd number of metal lines 302, thereby forming gaps 1806 in the second hard mask 104. As described above, a plasma etching process using fluorocarbon plasma can be used to selectively etch the hard mask 104. After the non-line-end vias have been etched in the second hard mask 104 over the selected (odd number) metal lines, the via mask 1802 is removed.

[0057] Then, a gap-filling dielectric is deposited into and fills the (line-end) T-shaped cavities 902 / 1502 in the diced regions of the selected even / odd metal lines, and the gap-filling dielectric is deposited into and fills the (non-line-end) gaps 1606 / 1806 in the first / second hard masks 102 / 104, followed by a polishing process such as CMP to remove excess dielectric. Suitable gap-filling dielectric materials include, but are not limited to, silicon oxide (SiOx) and / or spin-coated glass (SoG). That is, as... Figure 20As shown in the top view, the gap-filling dielectric 2002 now fills the T-shaped cavities 902 / 1502 in the cut regions of the selected even / odd metal wires and the (non-wire end) gaps 1606 / 1806 in the first / second hard masks 102 / 104.

[0058] Figure 21 It is a cross-sectional view (along line AA′) showing the gap-filling dielectric 2002 of the T-shaped cavity 902 in the cut region filled with the selected even number of metal wires. Figure 22 This is a cross-sectional view (along line BB′) of the gap-filling dielectric 2002 filling the T-shaped cavity 1502 in the cut region of the selected odd-numbered metal wires. Optionally, an additional mask (not shown) may be used to remove one side overhang of the T-shaped gap-filling dielectric 2002 to avoid forming vias on both sides of the cut in both odd and even-numbered lines. This allows for the formation of self-aligned vias only on one side of the cut.

[0059] Then, the first / second hard masks 102 / 104 are removed using a hard mask and selective metal line etching of the gap-filling dielectric 2002. That is, Figure 23 The diagram shows a cross-sectional view (along line AA′) illustrating that the first hard mask 102 has been removed and the even-numbered metal lines 202 have been selectively recessed into the gap-filling dielectric 2002. Due to the configuration of the T-shaped cavity 902, the gap-filling dielectric 2002 hangs over / covers a portion of the even-numbered metal lines 202 at their ends. As a result, the covered portion of the even-numbered metal lines 202 at their ends is not recessed, and a via 2302 self-aligned with the (even-numbered) line ends is formed. This process also forms non-line-end vias (not shown). As described above, a plasma etching process using chlorine-containing plasma can be used to selectively etch the hard mask 102. Metal-selective RIE can be employed to selectively recess the even-numbered metal lines 202 into the gap-filling dielectric 2002.

[0060] Figure 24 This is a cross-sectional view (along line BB′) showing that the second hard mask 104 has been removed and the odd-numbered metal lines 302 have been selectively recessed against the gap-filling dielectric 2002. Due to the T-shaped cavity 1502, the gap-filling dielectric 2002 hangs over / covers a portion of the odd-numbered metal lines 302 at their ends. As a result, this covered portion of the odd-numbered metal lines 302 at their ends is not recessed, and a via 2402 self-aligned with the (odd-numbered) line ends is formed. The process also forms non-line-end vias (not shown). As described above, a plasma etching process using fluorocarbon plasma can be used to selectively etch the hard mask 104. Metal-selective RIE can be used to selectively recess the odd-numbered metal lines 302 against the gap-filling dielectric 2002.

[0061] All of the above-described processes can damage the dielectric material 106. Therefore, according to an exemplary embodiment, the damaged dielectric material 106 is removed and replaced with a new dielectric material (now given reference numeral 106'). In this case, the dielectric material 106' not only fills the space between the lines, but also fills the space between all the top vias (line-end vias 2302, 2402 and other non-line-end vias) along the lines.

[0062] Finally, a process such as CMP is used to polish the 106′ capping layer and polish the gap-filling dielectric 2002 down to the vias 2302 / 2402, thereby exposing the tops of the vias 2302 / 2402 at the even / odd line ends. For example, Figure 25 This is a cross-sectional view (along line AA′) showing that the gap-filling dielectric 2002 has been polished down to the via 2302, thus exposing the top of the via 2302 at the even-numbered line ends. The same configuration exists for the via 2402 at the odd-numbered line ends.

[0063] For example, such as Figure 25 As shown, the resulting structure includes cuts in at least one selected metal wire (i.e., an even number and / or an odd number of metal wires). Vias (e.g., Figure 25 The via 2302 in the cut is perfectly aligned with the end of the selected metal wire on either side of the cut. For example, as Figure 25 As shown, the sidewall of each via 2302 is coplanar with the end of the selected metal wire. A gap 2002 is filled between the wire ends.

[0064] While illustrative embodiments of the invention have been described herein, it should be understood that the invention is not limited to those precise embodiments, and various other changes and modifications can be made by those skilled in the art without departing from the scope of the invention.

Claims

1. A method for forming a self-aligned via at an online end, the method comprising the following steps: A hard mask is used to pattern metal lines comprising alternating even and odd numbers of metal lines, the hard mask comprising a first hard mask for patterning the even numbers of metal lines and a second hard mask for patterning the odd numbers of metal lines. The hard mask and selected even-numbered or odd-numbered metal lines are cut using a cutting mask, the cutting mask having a window that exposes the hard mask above the cutting area of ​​the selected metal lines; Enlarge the window in the cutting mask to expose the hard mask on either side of the cutting area of ​​the selected metal wire; The hard mask is selectively etched using an enlarged window in the cutting mask to form a T-shaped cavity within the cutting area of ​​the selected metal wire; The T-shaped cavity is filled with a gap-filling dielectric. Remove the hard mask; as well as Selectively recess a selected metal wire relative to the gap-filling dielectric, wherein the gap-filling dielectric hangs over the selected metal wire through the recess to form a portion of the self-aligned via at the end of the selected metal wire. The first hard mask and the second hard mask are made of different materials.

2. The method according to claim 1, wherein, The first hard mask comprises a material selected from the group consisting of titanium (Ti), tantalum (Ta), titanium oxide (TiOx), titanium nitride (TiN), tantalum nitride (TaN), and combinations thereof.

3. The method according to claim 1, wherein, The second hard mask comprises a material selected from the group consisting of silicon nitride (SiN), silicon carbonitride (SiCN), hydrogen-containing silicon carbonitride (SiCNH), silicon carbide (SiC), and combinations thereof.

4. The method according to claim 1, wherein, The even-numbered metal wires and the odd-numbered metal wires include metals selected from the group consisting of tungsten (W), cobalt (Co), ruthenium (Ru), and combinations thereof.

5. The method according to claim 1, further comprising the following steps: A dielectric is deposited on the even-numbered metal lines, the odd-numbered metal lines, and the hard mask.

6. The method of claim 1, further comprising the following steps: The cutting mask is used to pattern the hard mask over the selected metal line; as well as The pattern is transferred from the hard mask to the selected metal line to cut the selected metal line.

7. The method according to claim 1, wherein, The window in the cut mask is enlarged using lateral etching.

8. The method of claim 1, further comprising the following steps: After the recess is polished, the gap is filled with a dielectric.

9. The method of claim 1, further comprising the following steps: The hard mask is cut using a mask with a window that exposes the hard mask above the non-wire end of one of the metal lines to form a gap in the hard mask; as well as The gap in the hard mask is filled with the gap-filling dielectric, thereby selectively recessing one of the metal lines relative to the gap to form a non-line-end via.

10. The method of claim 1, further comprising the following steps: Remove the overhang of the gap-filling dielectric, so that a self-aligned via is formed only at one end of the selected metal wire through the recess.

11. The method according to claim 1, comprising: A first cutting mask is used to cut a selected one of the first hard mask and the even number of metal lines, the first cutting mask having a window that exposes the first hard mask above the cutting area of ​​the selected even number of metal lines; Enlarge the window in the first cutting mask to expose the first hard mask on either side of the cutting area of ​​the selected even-numbered metal wires; The first hard mask is selectively etched using an enlarged window in the first cutting mask to form a first T-shaped cavity within the cutting area of ​​the selected even-numbered metal wires; A second cutting mask is used to cut a selected one of the second hard mask and the odd number of metal lines. The second cutting mask has a window that exposes the second hard mask over the cutting area of ​​the selected odd number of metal lines. Enlarge the window in the second cutting mask to expose the second hard mask on either side of the cutting area of ​​the selected odd number of metal wires; The second hard mask is selectively etched using an enlarged window in the second cutting mask to form a second T-shaped cavity within the cutting area of ​​the selected odd number of metal lines; The first T-shaped cavity and the second T-shaped cavity are filled with a gap-filling dielectric. Remove the first hard mask and the second hard mask; as well as The metal wire is selectively recessed relative to the gap-filling dielectric, wherein the gap-filling dielectric hangs over the selected even-numbered metal wire and the selected odd-numbered metal wire, and the portion of the self-aligned via is formed at the end of the metal wire through the recess.

12. The method according to claim 11, wherein, The first hard mask and the second hard mask are made of different materials.

13. The method of claim 11, further comprising the following steps: After the recess is polished, the gap is filled with a dielectric.

14. The method of claim 11, further comprising the following steps: The first hard mask is cut using a mask having a window exposing the first hard mask above the non-wire end of one of the even-numbered metal lines to form a gap in the first hard mask; and The gap in the first hard mask is filled with the gap-filling dielectric, thereby selectively recessing the metal line relative to the gap in the first hard mask to form a non-wire-end via.

15. The method of claim 14, further comprising the following steps: The second hard mask is cut using another mask, the other mask having a window exposing the second hard mask above the non-wire end of one of the odd-numbered metal lines to form a gap in the second hard mask; and The gap in the second hard mask is filled with the gap-filling dielectric, thereby selectively recessing the metal line relative to the gap in the second hard mask to form another non-wire-end via.

16. The method of claim 11, comprising: A second cutting mask is used to cut one of the second hard mask and the odd number of metal lines, the second cutting mask having a window that exposes the second hard mask over the cutting area of ​​the selected odd number of metal lines; Enlarge the window in the second cutting mask to expose the second hard mask on either side of the cutting area of ​​the selected odd number of metal wires; The second hard mask is selectively etched using an enlarged window in the second cutting mask to form a second T-shaped cavity within the cutting area of ​​the selected odd number of metal lines; The first hard mask is cut using a mask, the mask having a window that exposes the first hard mask above the non-wire end of one of the even number of metal wires to form a gap in the first hard mask; The second hard mask is cut using another mask, the other mask having a window that exposes the second hard mask above the non-wire end of one of the odd number of metal wires to form a gap in the second hard mask; The gaps in the first T-shaped cavity, the second T-shaped cavity, the first hard mask, and the second hard mask are filled with a gap-filling dielectric. Remove the first hard mask and the second hard mask; as well as The metal lines are selectively recessed relative to the gap-filling dielectric, wherein the gap-filling dielectric hangs over the even-numbered metal lines through the recess to form portions of the self-aligned vias at the ends of the even-numbered and odd-numbered metal lines, and wherein the metal lines are selectively recessed relative to the gap-filling dielectric in the gaps of the first hard mask and the gap-filling dielectric in the gaps of the second hard mask to form non-line-end vias.

17. The method according to claim 12 or 14, wherein, The first hard mask comprises a material selected from the group consisting of Ti, Ta, TiOx, TiN, TaN and combinations thereof.

18. The method according to claim 12 or 14, wherein, The second hard mask comprises a material selected from the group consisting of SiN, SiCN, SiCNH, SiC, and combinations thereof.

19. A structure comprising a metal wire, comprising: Metal wire; A cut in one of the selected metal wires; A via, which is aligned with the end of a selected metal wire on either side of the cut; as well as The gap between the wire ends is filled with a dielectric material, which contacts the via.

20. The structure according to claim 19, wherein, The sidewall of each via is coplanar with the end of the selected metal wire.

21. The structure according to claim 19, wherein, The metal wire comprises metals selected from the group consisting of W, Co, Ru, and combinations thereof.

Images