Method for forming metallic gap fills - Patents.com

Abstract

The present disclosure generally relates to methods for processing substrates, and more particularly, to methods for forming a metal gap fill. In one embodiment, the method includes forming a metal gap fill in an opening using a multi-step process. The multi-step process includes forming a first portion of the metal gap fill, performing a sputtering process to form one or more layers on one or more sidewalls, and growing a second portion of the metal gap fill to fill the opening with the metal gap fill. The metal gap fill formed by the multi-step process is seamless, and the one or more layers formed on the one or more sidewalls seal any gaps or defects between the metal gap fill and the sidewalls. As a result, liquids utilized in subsequent processes do not diffuse through the metal gap fill.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate generally to processing substrates and, more particularly, to methods for forming metallic gap fills. [Background technology]

[0002] In semiconductor processing, devices are produced with ever-decreasing feature dimensions. As device dimensions continue to shrink and the two-dimensional limitations of Moore's Law become insurmountable, manufacturers are turning to three-dimensional structures to drive future growth. Devices such as fin field effect transistors (FinFETs) and three-dimensional memory devices such as dynamic random access memory (DRAM) devices typically feature layers of different materials in a stack. Many devices or cells can be stacked one on top of the other, and several devices are typically formed on one substrate. The layers are often different materials, so that one structure can include alternating layers of insulating layers, semiconductor layers, and metal layers, such as SiO2, SiN, a-Si, and poly-Si. Typically, a stack is composed of 32, or 64, or even 128 of these alternating layers.

[0003] Certain metals, such as tungsten, have been used at the contact level for logic applications for about 20 years. In recent advanced complementary metal oxide semiconductor (CMOS) devices, new technologies such as metal gates and FinFETs have emerged, which have led to new applications of these metals as metal gate fills for both p-type metal oxide semiconductor (PMOS) and n-type metal oxide semiconductor (NMOS) devices. In 3D NAND devices, such metals are also used for metal gate fills. The requirement for gap fills, for example using tungsten, is becoming increasingly challenging for several reasons. For example, at contacts, overhangs are becoming more difficult as the contact dimensions are shrinking and tungsten conformal fills generally leave seams. Furthermore, the seams are exposed to slurry during chemical mechanical polishing (CMP), which creates integration issues. In addition, in metal gate trenches for both advanced CMOS and 3D NAND, traditional tungsten conformal growth inevitably leaves a seam in the middle.

[0004] Therefore, improved methods of forming metal gap fill are needed for both the contacts and metal gate fill of advanced logic and memory devices. Summary of the Invention

[0005] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate generally to methods for processing of substrates, and more particularly to a method for forming a metal gap fill. In one embodiment, a method of forming a metal gap fill includes forming a first portion of a metal gap fill over a surface of a first layer in an opening formed in a second layer, performing a sputtering process on the first portion, and forming a second portion of the metal gap fill to fill the opening with the metal gap fill.

[0006] In another embodiment, a method for forming a metal gap fill includes forming a first portion of the metal gap fill over a surface of a first layer in an opening formed in a second layer, forming one or more layers on one or more sidewalls of the second layer, and forming a second portion of the metal gap fill to fill the opening with the metal gap fill.

[0007] In another embodiment, a processing system includes a transfer chamber, a plurality of process chambers coupled to the transfer chamber, and a controller configured to cause the processing system to perform a process including forming a first portion of a metal gap fill over a surface of a first layer in an opening formed in a second layer, performing a sputtering process on the first portion, and forming a second portion of the metal gap fill to fill the opening with the metal gap fill.

[0008] So that the above-recited features of the present disclosure can be understood in detail, a more particular description of the present disclosure, briefly summarized above, can be made by reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings depict only exemplary embodiments, and therefore should not be considered as limiting the scope of the embodiments, as other equally effective embodiments may be recognized. [Brief description of the drawings]

[0009] [Figure 1] 1 is a flow diagram of a method for forming a metal gap fill, according to one embodiment. [Fig. 2A-2F] 2A-2D are various views of a substrate during different stages of the method of FIG. 1 according to one embodiment. [Diagram 3] 2 is a schematic top view of an exemplary multi-chamber processing system suitable for performing the method of FIG. 1, according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] For ease of understanding, the same reference numbers have been used, where possible, to designate identical elements that are common to the figures. It is intended that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0011] The present disclosure generally relates to methods for processing a substrate, and more particularly, to a method for forming a metal gap fill. In one embodiment, which may include or be combined with one or more embodiments described herein, the method includes forming a metal gap fill in an opening using a multi-step process. The multi-step process includes growing a first portion of the metal gap fill by a selective deposition process, performing a sputtering process to form one or more layers on one or more sidewalls, and growing a second portion of the metal gap fill by a selective deposition process to fill the opening with the metal gap fill. The metal gap fill formed by the selective deposition process is seamless, and the one or more layers formed on the one or more sidewalls seal any gaps or defects between the metal gap fill and the sidewalls. As a result, liquids utilized in subsequent processes do not diffuse through the metal gap fill to interact with layers disposed below the metal gap fill.

[0012] FIG. 1 is a flow diagram of a method 100 for forming a metal gap fill. FIGS. 2A-2F show various views of a substrate 200 during different stages of the method 100 of FIG. 1. It should be noted that the method 100 may be utilized to form other semiconductor structures not presented herein. Those skilled in the art should appreciate that the complete process for forming semiconductor devices and related structures is not shown in the drawings or described herein. Although various operations are shown in the drawings and described herein, no limitation as to the order of such steps or the presence or absence of steps is implied. Operations shown or described as a sequence are done solely for purposes of illustration, unless expressly indicated otherwise, and do not exclude the possibility that the respective steps are in fact performed at least partially, if not completely, simultaneously or overlapping.

[0013] The method 100 begins in operation 102 by performing a pre-cleaning process on a substrate 200 in a process chamber. In one example, the process chamber is an etch chamber. As shown in FIG. 2A, the substrate 200 includes a first layer 202, at least one opening 204 formed in the first layer 202, and a second layer 206 disposed in the opening 204. The first layer 202 can be a dielectric layer made of SiO2, SiN, SiCN, Al2O3, AlN, or other suitable dielectric material. Alternatively, the first layer 202 can be a carbon layer for hard mask applications. The opening 204 can be a via or a trench, and the opening 204 is defined by a surface 210 of the second layer 206 and one or more sidewalls 212 of the first layer 202. The opening 204 has a height H1. The second layer 206 may be made from a conductive material, such as a metal, a semiconductor, a conductive ceramic, or other suitable conductive material. In one example, the second layer 206 is made from cobalt, titanium nitride, or silicon.

[0014] A pre-cleaning process is performed on the surface 210 of the second layer 206. The pre-cleaning process is performed to remove contaminants on the surface 210 of the second layer 206, such as metal oxides, fluorides, carbon, polymers, or other post-etch process residues. The pre-cleaning process can be any suitable cleaning method, such as chemical cleaning or plasma cleaning. Chemical cleaning utilizes cleaning agents, such as hydrogen radicals, or reactive gases, such as H2, CO, C2H5OH, WF6, WCl5, or other suitable reactive gases. Some cleaning agents, such as hydrogen radicals, H2, or CO, reduce metal oxide contaminants back to metal. Some cleaning agents, such as WF6 or WCl5, etch the contaminants by volatilizing them into a gas. In one example, the pre-cleaning process utilizes hydrogen radicals to remove CoO x , CuO x , and / or reduce metal oxides such as WO. Hydrogen radicals may be formed in a remote plasma source and then flowed along with hydrogen or argon gas to the substrate 200. The substrate 200 may be maintained at a temperature ranging from about 200 degrees Celsius to about 400 degrees Celsius. In another example, the pre-cleaning process utilizes a H thermal soak to reduce CoO x , CuO x , and / or reduce metal oxides such as WO3. The thermal soak process includes flowing hydrogen and argon gases into the process chamber, the chamber pressure is in the range of about 30 Torr to about 300 Torr, and the substrate 200 is maintained at a temperature in the range of about 300 degrees Celsius to about 600 degrees Celsius. In another example, the pre-clean process utilizes an ethanol soak to reduce metal oxides, and the substrate 200 is maintained at a temperature in the range of about 200 degrees Celsius to about 400 degrees Celsius. In another example, the pre-clean process utilizes a WF6 or WCl5 soak to react with metal oxides at high temperature and low pressure, turning the metal oxides into gas / liquid phase metal compounds (e.g., WOF4, CuCl2, CoCl2), and the substrate 200 is maintained at a temperature in the range of about 200 degrees Celsius to about 500 degrees Celsius.

[0015] The pre-cleaning process can be a plasma cleaning process. The plasma cleaning process utilizes an Ar / He plasma or an H2 plasma. Some plasma cleaning processes physically sputter off contaminants while other plasma cleaning processes enhance the reaction to clean the surface 210. In one example, the pre-cleaning process utilizes an argon plasma where the argon ions physically sputter off the contaminants on the surface 210 of the second layer 206. The argon plasma can be capacitively coupled, inductively coupled, or a combination thereof. The plasma frequency ranges from about 350 kHz to about 40 MHz, the plasma power ranges from about 0 W to about 1000 W, and the chamber pressure ranges from about 10 mTorr to about 100 Torr. In another example, the pre-cleaning process utilizes a hydrogen plasma where the hydrogen ions react with the contaminants on the surface 210 of the second layer 206 to form metal and water. The hydrogen plasma cleaning process has a similar chemistry to the hydrogen heat soak, but less thermal energy is utilized in the hydrogen plasma cleaning process.

[0016] In one example, the pre-clean process is performed in a process chamber using a remote plasma source. One exemplary process chamber suitable for performing the pre-clean process is an AKTIV Pre-Clean™ chamber or a SICONI® cleaning chamber available from Applied Materials, Inc., Santa Clara, Calif. Alternatively, the pre-clean process is performed in an etch chamber, such as an etch chamber using an inductively coupled plasma (ICP) source. One exemplary etch chamber can be a modified Displaced Plasma Nitridation (DPN) chamber available from Applied Materials Inc., Santa Clara, Calif. However, it is contemplated that other appropriately configured chambers from other manufacturers may also be implemented to perform the pre-clean process.

[0017] In operation 104, a nucleation process is performed on the cleaned surface 210 of the second layer 206. The nucleation process removes the incubation period of metal gap-fill to be formed on the surface 210 and the opening 204, which also removes the lattice mismatch due to the very different metal growth incubation of different metals. The nucleation process can include forming a metal seed layer 214 on the surface 210 of the second layer 206, as shown in FIG. 2B, which can be made of tungsten, cobalt, ruthenium, or other suitable metals. The metal seed layer 214 is formed by a selective process, such that the metal seed layer 214 is not formed on one or more sidewalls 212. In one example, the metal seed layer 214 is formed by a chemical soak process utilizing one or more gases, such as B2H6, SiH4, Si2H6, WF6, WCl5, TiCl4, or other suitable gases. In another example, the metal seed layer 214 is formed by a selective metal atomic layer deposition (ALD) process. The one or more precursors utilized in the selective metal ALD process include B2H6, WF6, H2, SiH4, WCl5, W(CO)6, or other suitable precursors. In some implementations, one or more gases containing a metal other than tungsten are utilized. For example, a cobalt or ruthenium-containing gas may be utilized to form the metal seed layer 214. In some implementations, the nucleation process is omitted and the metal seed layer 214 is not present.

[0018] Next, in operation 106, a first portion 216 of a metal gap fill is formed on the metal seed layer 214, as shown in FIG. 2C. In some embodiments, the first portion 216 of the metal gap fill is formed on the surface 210 of the second layer 206. The first portion 216 of the metal gap fill is fabricated from a metal, such as tungsten, cobalt, ruthenium, or other suitable metal. The first portion 216 is formed by a selective process and grows from the bottom up. In other words, the first portion 216 is selectively formed or grown on the surface 210 of the metal seed layer 214 or the second layer 206, and not on one or more sidewalls 212. The first portion 216 contacts a portion of the one or more sidewalls 212, as shown in FIG. 2C, but the first portion 216 does not grow from the one or more sidewalls 212. The first portion 216 has a height H2, and the height H2 is between about 10 percent and about 50 percent of the height H1 of the opening 204.

[0019] The selective process for forming the first portion 216 can be a chemical vapor deposition (CVD) process, and the selectivity is based on the chamber pressure and the ratio of precursor gases. In one example, the selective process includes flowing a metal-containing gas and a second gas into a process chamber. The metal-containing gas can be any suitable metal-containing gas, such as WF6. The second gas can be hydrogen gas. The ratio of the second gas to the metal-containing gas ranges from about 6:1 to about 8000:1. The chamber pressure ranges from about 1 Torr to about 300 Torr, and the substrate is maintained at a temperature range from about 200 degrees Celsius to about 500 degrees Celsius. The chamber pressure and the ratio of gases can affect the selectivity. In one example, at a relatively high temperature, such as greater than about 400 degrees Celsius, the selectivity is maintained when the ratio of the second gas to the metal-containing gas is high and the chamber pressure is low.

[0020] Next, in operation 108, as shown in FIG. 2D, a sputtering process is performed to remove a portion of the first portion 216 of the metal gap-fill and to form one or more layers 218 on the one or more sidewalls 212. The sputtering process can have the same processing conditions as the pre-cleaning process utilizing argon plasma. The sputtering process sputters a portion of the first portion 216 of the metal gap-fill onto the one or more sidewalls 212. As a result, a layer 218 is formed on each sidewall 212. The layer 218 is made of the same material as the first portion 216 of the metal gap-fill.

[0021] Next, in operation 110, as shown in FIG. 2E, a second portion 220 of the metal gap fill is formed on the first portion 216 of the metal gap fill. The second portion 220 can be formed in the same process as the first portion 216 of the metal gap fill. The second portion 220 is fabricated from the same material as the first portion 216. The metal gap fill formed in the opening 204 includes the first portion 216, the one or more layers 218, and the second portion 220. The multi-step process for forming the metal gap fill is seamless, and no gaps or defects exist between the metal gap fill and the sidewalls 212. As a result, liquids utilized in subsequent processes do not diffuse through the metal gap fill to interact with the second layer 206.

[0022] Next, in operation 112, a chemical mechanical polishing (CMP) process is performed on the substrate 200 to form a planar surface 222, as shown in Figure 2F. During the CMP process, slurry does not diffuse through the metal gap fill having the first portion 216, the layer 218, and the second portion 220 because the sidewalls 212 are sealed with the layer 218. Therefore, the second layer 206 is protected from the slurry during the CMP process.

[0023] Referring back to FIG. 1 , operations 106, 108, and 110 are performed to form a seamless metal gap fill, with no gaps or defects between the metal gap fill and the sidewalls. In some implementations, operations 106, 108, and 110 are replaced by a single operation, which forms a single-phase crystalline metal gap fill from bottom up. A single-phase crystalline metal gap fill does not have grain boundaries formed therein, and the resistance of the metal gap fill is independent of the size of the opening 204. Thus, the single-phase crystalline metal gap fill is seamless and has reduced electrical resistance. The single-phase crystalline metal gap fill can be formed in a CVD process in which the substrate 200 is maintained at a temperature of 450 degrees Celsius or greater.

[0024] Examples of processing systems that may be suitably modified according to the teachings provided herein include the ENDURA®, PRODUCER®, or CENTURA® integrated processing systems available from Applied Materials, Inc., Santa Clara, Calif., or other suitable processing systems. It is contemplated that other processing systems (including those from other manufacturers) may be configured to benefit from aspects described herein. FIG. 3 shows a schematic top view of an exemplary multi-chamber processing system 300 that may be used to perform the method 100 shown in FIG. 1, according to an embodiment of the present disclosure. As shown in FIG. 3, a plurality of process chambers 302 are coupled to a first transfer chamber 304. The first transfer chamber 304 is also coupled to a first pair of pass-through chambers 306. The first transfer chamber 304 has a centrally located transfer robot (not shown) for transferring substrates between the pass-through chambers 306 and the process chambers 302. The pass-through chamber 306 is coupled to a second transfer chamber 310, which is coupled to a process chamber 314 configured to perform a pre-clean process, such as operation 102, and a process chamber 316 configured to perform a nucleation processing operation, such as operation 106. The second transfer chamber 310 has a set of load lock chambers 312 and a centrally located transfer robot (not shown) for transferring substrates between the process chambers 314 or 316. A factory interface 320 is connected to the second transfer chamber 310 by the load lock chambers 312. The factory interface 320 is coupled to one or more pods 330 on the opposite side of the load lock chambers 312. The pods 330 are typically front-opening unified pods (FOUPs) accessible from a cleaning room.

[0025] In operation, the substrate is first transferred to process chamber 314 where a pre-clean process, such as operation 102, is performed to remove contaminants, such as metal oxide contaminants, from the bottom of the opening. The substrate is then transferred to process chamber 316 where operation 106 is performed. The substrate is then transferred to one or more process chambers 302 where operations 106, 108, and 110 are performed. Because operations 102, 104, 106, 108, 110 are all performed within the same processing system 300, vacuum is not broken when the substrate is transferred to the various chambers, thereby reducing the opportunity for contamination and improving the quality of the metal gap fill.

[0026] A system controller 380 is coupled to the processing system 300 to control the processing system 300 or its components. For example, the system controller 380 can control the operation of the processing system 300 using direct control of the chambers 302, 304, 306, 310, 312, 314, 316 of the processing system 300 or by controlling the controllers 360 associated with the chambers 302, 304, 306, 310, 312, 314, 316. During operation, the system controller 380 enables data collection and feedback from each chamber to regulate the performance of the processing system 300.

[0027] The system controller 380 generally includes a central processing unit (CPU) 382, ​​a memory 384, and support circuits 386. The CPU 382 may be one of any form of general-purpose processor that may be used in an industrial environment. The memory 384, a non-transitory computer-readable medium, or machine-readable storage device, is accessible by the CPU 382 and may be one or more of local or remote memory, such as a random access memory (RAM), a read-only memory (ROM), a floppy disk, a hard disk, or any other form of digital storage. The support circuits 386 are coupled to the CPU 382 and may include cache, clock circuits, input / output subsystems, power supplies, and the like. The system controller 380 is configured to execute the method 100 stored in the memory 384. The various embodiments disclosed in the present disclosure may generally be implemented by executing computer instruction codes stored in the memory 384 (or in the memory of a particular process chamber) under the control of the CPU 382, ​​for example, as a computer program product or software routine. That is, the computer program product is tangibly embodied in memory 384 (or a non-transitory computer-readable medium or machine-readable storage device). When the computer instruction codes are executed by the CPU 382, ​​the CPU 382 controls the chamber to perform operations according to various embodiments.

[0028] In summary, embodiments of the present disclosure enable the formation of a seamless metal gap fill that prevents liquids from diffusing therethrough. The seamless metal gap fill is formed by a multi-step process that includes growing a first portion of the metal gap fill by a selective deposition process, performing a sputter process to form one or more layers on one or more sidewalls, and growing a second portion of the metal gap fill by a selective deposition process to fill the opening with the metal gap fill. The metal gap fill formed by the selective deposition process is seamless, and the one or more layers formed on the one or more sidewalls seal any gaps or defects between the metal gap fill and the sidewalls. As a result, liquids utilized in subsequent processes do not diffuse through the metal gap fill.

[0029] While the forgoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, the scope of which is determined by the following claims.

Claims

1. 1. A method for forming a metallic gap fill, the method comprising: forming a second layer between sidewalls of an opening formed in the first layer; selectively forming a first portion of the metal gap fill on a first surface of the second layer, the first surface being between the sidewalls of the opening, the first portion comprising a material that includes a first metal; sputtering the first metal from the first portion onto the sidewall of the opening to form a layer in direct contact with the sidewall of the opening and the first portion; forming a second portion of the metal gap fill to fill the opening with the metal gap fill; wherein the second portion is the same material as the first portion, and the first metal comprises cobalt, tungsten, or ruthenium.

2. The method of claim 1 , wherein the first portion of the metallic gap fill and the second portion of the metallic gap fill are fabricated from cobalt, tungsten, or ruthenium.

3. the first layer comprises a metal; The method of claim 1 , wherein the second layer comprises a dielectric layer.

4. The method of claim 1 , further comprising performing a pre-cleaning process on a surface of the first layer prior to forming the first portion of the metallic gap fill.

5. The method of claim 4 , further comprising forming a metal seed layer on the surface of the first layer, the first portion of the metal gap fill being formed on the metal seed layer.

6. The method of claim 1 , wherein the sputtering process utilizes an argon plasma.

7. 1. A method for forming a metallic gap fill, the method comprising: forming a second layer between sidewalls of an opening formed in the first layer; selectively forming a first portion of the metal gap fill on a first surface of the second layer, the first surface being between the sidewalls of the opening, the first portion comprising a material that includes a first metal; forming a layer comprising the first metal in direct contact with the sidewall and the first portion of the opening; forming a second portion of the metal gap fill to fill the opening with the metal gap fill; wherein the second portion is the same material as the first portion, and the first metal comprises cobalt, tungsten, or ruthenium.

8. The method of claim 7 , wherein the first portion of the metallic gap fill, the layer, and the second portion of the metallic gap fill are fabricated from cobalt, tungsten, or ruthenium.

9. the first layer comprises a metal; The method of claim 7 , wherein the second layer comprises a dielectric layer.

10. performing a pre-cleaning process on a surface of the first layer prior to forming the first portion of the metallic gap fill; forming a metal seed layer on the surface of the first layer, the first portion of the metal gap fill being formed on the metal seed layer; Further comprising: The method according to claim 7.

11. The method of claim 7 , wherein the layer is formed by a sputtering process utilizing an argon plasma.

12. 1. A processing system comprising: A transfer chamber; a plurality of process chambers coupled to the transfer chamber; a controller configured to cause the processing system to execute a process, the process comprising: forming a second layer between sidewalls of an opening formed in the first layer; selectively forming a first portion of a metallic gap fill on a first surface of the second layer, the first surface being between the sidewalls of the opening, the first portion comprising a first material including a first metal; performing a sputtering process on the first portion to partially remove the first portion of the metal gap fill and to form a layer in direct contact with the sidewall of the opening and the first portion; forming a second portion of the metal gap fill to fill the opening with the metal gap fill; A controller including: wherein the second portion is the same material as the first portion, and the first metal is selected from cobalt, tungsten, or ruthenium.

13. 13. The processing system of claim 12, wherein said first portion of said metallic gap fill and said second portion of said metallic gap fill are fabricated from cobalt, tungsten, or ruthenium.

14. the first layer comprises a metal; The processing system of claim 12 , wherein the second layer comprises a dielectric layer.

15. performing a pre-cleaning process on a surface of the first layer prior to forming the first portion of the metallic gap fill; forming a metal seed layer on the surface of the first layer, the first portion of the metal gap fill being formed on the metal seed layer; The processing system of claim 12 further comprising:

Images