Advanced self-aligned patterning process with sit spacer as a final dielectric etch hardmask

A method of forming a metallization layer by ASAP is provided. Embodiments include forming an ULK layer; forming a SAC SiN layer over the ULK layer; forming mandrels directly on the SAC SiN layer; cutting the mandrels; selectively etching the SAC SiN layer across the cut mandrels, forming first trenches; filling the first trenches with a metal oxide; forming a conformal metal oxide layer over the cut mandrels, the metal oxide, and the SAC SiN layer; removing horizontal portions of the conformal metal oxide layer over the cut mandrels and the SAC SiN layer; removing the cut mandrels; removing exposed portions of the SAC SiN layer and etching the underlying ULK layer, forming second trenches; and stripping a remainder of the metal oxide, conformal metal oxide layer, and SAC SiN layer.

TECHNICAL FIELD

The present disclosure relates to the manufacture of semiconductor devices, such as integrated circuits (ICs). The present disclosure is particularly applicable to formation of a metallization layer in the fabrication of a semiconductor device, particularly for the 7 nanometer (nm) technology node and beyond.

BACKGROUND

As semiconductor devices continue to get smaller and technology nodes shrink into the lower nanometer range, device scaling needs to continue to provide both lower cost and improved performance. An advanced self-aligned patterning (ASAP) is one of the methods for extending the capabilities of photolithographic techniques.FIG. 1illustrates a conventional ASAP film stack. InFIG. 1, an ultra low-K (ULK) layer103is formed over an Nblock (©Applied Materials) layer101, and a self-aligned contact (SAC) silicon nitride (SiN) layer105is formed over the ULK layer103. Next, a TiN layer107and a SiN layer109are consecutively formed over the SAC SiN layer105as a hardmask (HM) and memorization layer, respectively. Then, an amorphous silicon (aSi) layer111, a spin-on hardmask (SOH) layer113, a silicon oxynitride (SiON) layer115, a bottom antireflective coating (BARC) layer117, and a photoresist119are consecutively formed over the SiN layer109. Next, the photoresist119is patterned, and mandrels are formed by reactive ion etching (RIE) the aSi layer111through the patterned photoresist. Then, another SOH layer, SiON layer, BARC layer, and photoresist are formed over the mandrels, the photoresist is patterned, and the mandrels are cut by RIE through the patterned photoresist. The layers are repeated once more, and the SiN layer is cut by RIE through the patterned photoresist. Then, spacers are formed around the cut mandrels, and the mandrels are removed. Next, the TiN HM is removed, the underlying ULK layer103is etched by RIE through the spacers, and metal is deposited in the etched ULK layer. However, extra materials and deposition process steps are needed to form the SiN and TiN layers.

A need therefore exists for methodology enabling an ASAP process with fewer layers and reduced process steps.

SUMMARY

An aspect of the present disclosure is a method of forming a metallization layer including forming mandrels directly on the SAC SiN layer.

Another aspect of the present disclosure is a method of forming a metallization layer including forming a conformal metal oxide as sidewall image transfer (SIT) spacers for final dielectric etch hardmask.

According to the present disclosure, some technical effects may be achieved in part by a method including: forming a ULK layer; forming a SAC SiN layer over the ULK layer; forming mandrels directly on the SAC SiN layer; cutting the mandrels; selectively etching the SAC SiN layer across the cut mandrels, forming first trenches; filling the first trenches with a metal oxide; forming a conformal metal oxide layer over the cut mandrels, the metal oxide, and the SAC SiN layer; removing horizontal portions of the conformal metal oxide layer over the cut mandrels and the SAC SiN layer; removing the cut mandrels; removing exposed portions of the SAC SiN layer and etching the underlying ULK layer, forming second trenches; and stripping a remainder of the metal oxide, conformal metal oxide layer, and SAC SiN layer.

Another aspect includes cutting the mandrels by: forming a SOH layer over the mandrels; forming a SiON layer over the SOH layer; forming a BARC layer over the SiON layer; forming and patterning a photoresist over the BARC layer; etching the BARC layer, the SiON layer, the SOH layer and the mandrels through the patterned photoresist by RIE; and removing the photoresist and a remainder the BARC layer, the SiON layer and the SOH layer. Further aspects include selectively etching the SAC SiN layer by a dry etch stopping on the ULK layer or a timed etch stopping part way through the SAC SiN layer. Other aspects include forming the conformal metal oxide layer by atomic layer deposition (ALD). Additional aspects include conformal metal oxide layer including titanium oxide (TiOx). Another aspect includes removing horizontal portions of the conformal metal oxide layer by dry etch. Further aspects include removing exposed portions of the SAC SiN layer and etching the underlying ULK layer by RIE. Other aspects include forming the mandrels of aSi or amorphous carbon (aC). Additional aspects include filling the second trenches with metal. Another aspect includes forming the SAC SiN layer to a thickness of 5 nm to 20 nm.

A further aspect of the present disclosure is a method including: forming an ULK layer; forming a SAC SiN layer to a thickness of 5 nm to 20 nm over the ULK layer; forming a mandrel layer over the SAC SiN layer; etching the mandrel layer, forming mandrels; forming a SOH layer over the mandrels; forming a SiON layer over the SOH layer; forming a BARC layer over the SiON layer; forming and patterning a photoresist over the BARC layer; cutting the mandrels by etching the BARC layer, the SiON layer, the SOH layer and the mandrels through the patterned photoresist by RIE; removing the photoresist, the BARC layer, the SiON layer and the SOH layer; selectively etching the SAC SiN layer by dry etch stopping on the ULK or by a timed etch stopping part way through the SAC SiN layer, forming first trenches; filling the first trenches with metal oxide; forming a conformal metal oxide layer over the cut mandrels, the metal oxide, and the SAC SiN layer; removing horizontal portions of the conformal metal oxide layer over the cut mandrels and the SAC SiN layer; removing the cut mandrels; removing exposed portions of the SAC SiN layer and etching the underlying ULK layer, forming second trenches; and stripping a remainder of the metal oxide, conformal metal oxide layer, and SAC SiN layer.

Aspects include selectively etching the SAC SiN layer perpendicular to and crossing the cut mandrels. Other aspects include forming the conformal metal oxide layer by ALD. A further aspect includes the conformal metal oxide layer including TiOx. Another aspect includes removing horizontal portions of the conformal metal oxide layer by dry etch. Other aspects include removing exposed portions of the SAC SiN layer and etching the underlying ULK layer by RIE. A further aspect includes forming the mandrels of aSi or aC. Another aspect includes filling the second trenches with metal.

Another aspect of the present disclosure is a method including: forming an ULK layer; forming a SAC SiN layer to a thickness of 5 nm to 20 nm over the ULK layer; forming aSi or aC mandrels over the SAC SiN layer; forming a SOH layer over the mandrels; forming a SiON layer over the SOH layer; forming a BARC layer over the SiON layer; forming and patterning a photoresist over the BARC layer; cutting the mandrels by etching the BARC layer, the SiON layer, the SOH layer and the mandrels through the patterned photoresist by RIE; removing the photoresist, the BARC layer, the SiON layer and the SOH layer; selectively etching the SAC SiN layer perpendicular to and crossing the cut mandrels by dry etch stopping on the ULK or by a timed etch stopping part way through the SAC SiN layer, forming first trenches; filling the first trenches with TiOx; depositing a conformal TiOxlayer by ALD over the cut mandrels, the TiOx, and the SAC SiN layer; removing horizontal portions of the conformal TiOxlayer over the cut mandrels and the SAC SiN layer by dry etch; removing the cut mandrels; removing exposed portions of the SAC SiN layer and etching the underlying ULK layer by RIE, forming second trenches; and stripping a remainder of the TiOx, conformal TiOxlayer, and SAC SiN layer. Another aspect includes filling the second trenches with metal.

DETAILED DESCRIPTION

The present disclosure addresses and solves the current problem of extra layers and corresponding process steps of layer formation attendant upon performing a conventional ASAP process. In accordance with embodiments of the present disclosure, mandrels are formed directly on an SAC SiN layer and a conformal metal oxide layer is used as a final dielectrics etch HM, thereby eliminating the need for a TiN HM and a SiN memorization layer.

Methodology in accordance with embodiments of the present disclosure includes forming an ULK layer and a SAC SiN layer over the ULK layer. Then, mandrels are formed directly on the SAC SiN layer. Next, the mandrels are cut. Then, the SAC SiN layer is selectively etched across the cut mandrels. Next, first trenches are formed and are filled with a metal oxide. Subsequently, a conformal metal oxide layer is formed over the cut mandrels, the metal oxide, and the SAC SiN layer. Then, horizontal portions of the conformal metal oxide layer over the cut mandrels and the SAC SiN layer are removed. Next, the cut mandrels are removed. After that, the exposed portions of the SAC SiN layer are removed, and the underlying ULK layer is etched, thereby forming second trenches. Then, a remainder of the metal oxide, conformal metal oxide layer, and SAC SiN layer are stripped.

FIGS. 2A through 2Ischematically illustrate sequential steps of a ASAP method, in accordance with an exemplary embodiment. Adverting toFIG. 2A, an ULK layer203is formed, for example to a thickness of 30 nm to 60 nm, over an Nblock layer201having a thickness of 10 nm to 20 nm. A SAC SiN layer205is formed, e.g. to a thickness of 5 nm to 20 nm over the ULK layer203. Subsequently, mandrels207are formed directly on the SAC SiN layer205. The mandrels are formed by depositing, for example, aSi or aC by plasma enhanced chemical vapor deposition (PECVD) to a thickness of 40 nm to 80 nm, patterning a lithographic mask over the aSi or aC, and performing RIE. The mandrels207are formed of aSi or aC.

Adverting toFIG. 2B, a SOH layer209is formed, e.g. to a thickness of 60 nm to 100 nm, a SiON layer211is formed, e.g. to a thickness of 15 nm to 30 nm, and a BARC layer213is formed, e.g. to a thickness of 15 nm to 30 nm, sequentially over the mandrels207. Then, a photoresist215is formed, for example to a thickness of 60 nm to 100 nm, over the BARC layer213and is patterned, forming a cut mask for the mandrels.

The BARC layer213, the SiON layer211, the SOH layer209and the mandrels207are etched through the patterned photoresist215by RIE (not shown for illustrative convenience), stopping on the SAC SiN layer205. Then, the patterned photoresist215is removed. Next, the remainder of the BARC layer213, the SiON layer211and the SOH layer209are removed. Accordingly, cut mandrels217are formed over the SAC SiN layer205.FIG. 2Cis a top view of the cut mandrels217over the SAC SiN layer205.

InFIG. 2D, trenches219are formed by selectively etching the SAC SiN layer205across the cut mandrels217. The SAC SiN layer205is selectively etched by a dry etch, stopping on the ULK layer203, or by a timed etch, stopping part way through the SAC SiN layer205. The width of the trenches219is design rule dependent, but must be less than double the thickness of the subsequently formed spacers225(shown inFIG. 2F).

Adverting toFIG. 2E, the trenches219are filled with metal oxide221. Then, a conformal metal oxide layer223is formed over the cut mandrels217, the metal oxide221, and the SAC SiN layer205by atomic layer deposition (ALD). The conformal metal oxide layer223may for example be formed of TiOx. The thickness of the conformal metal oxide layer223may be approximately 20 nm, but is design rule dependent.

InFIG. 2F, the horizontal portions of the conformal metal oxide layer223over the cut mandrels217and the SAC SiN layer205are removed by dry etch revealing the cut mandrels217. Then, the cut mandrels217are removed by a dry etch. As a result, vertical portions of the conformal metal oxide layer225, or spacers225, remain over the SAC SiN layer205and the metal oxide221.

Adverting toFIG. 2G, the exposed portions of the SAC SiN layer205are removed by RIE using the metal oxide spacers225as a mask. Then, the underlying ULK layer203is etched forming trenches229.

InFIG. 2H, the metal oxide221and the remainder of the spacers225are stripped. Then, inFIG. 2I, the remainder SAC SiN layer205is stripped. Thereafter, the trenches229are filled with metal forming a metallization layer.

The embodiments of the present disclosure can achieve several technical effects, such as reducing the number of layers and the process steps of layer formation during an ASAP process. Devices formed in accordance with embodiments of the present disclosure enjoy utility in various industrial applications, e.g., microprocessors, smart phones, mobile phones, cellular handsets, set-top boxes, DVD recorders and players, automotive navigation, printers and peripherals, networking and telecom equipment, gaming systems, and digital cameras. The present disclosure therefore enjoys industrial applicability in any of various types of highly integrated semiconductor devices, particularly for the 7 nm technology node and beyond.