Method for forming a metal gap filler

Abstract

The present disclosure relates generally to methods for processing substrates, and more particularly to methods for forming metal gap fillers. In one embodiment, the method includes forming a metal gap filler in an opening using a multi-step process. The multi-step process includes: forming a first portion of the metal gap filler, performing a sputtering process to form one or more layers on one or more sidewalls, and growing a second portion of the metal gap filler to fill the opening with the metal gap filler. The metal gap filler 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 filler and the sidewalls. Thus, fluids utilized in subsequent processing do not diffuse through the metal gap filler.

Description

[0001] background

[0002] field

[0003] Various embodiments of the present disclosure relate generally to processing of substrates, and more particularly to methods for forming metal gap fillers.

[0004] Related technical notes

[0005] In semiconductor processing, devices are being fabricated with ever-decreasing feature sizes. As device dimensions continue to shrink, and the two-dimensional size limitations of Moore's Law cannot be overcome, 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. Multiple devices or cells can be stacked one on top of another, and several devices are typically formed on a single substrate. These layers are often different materials, so a structure may contain alternating layers of insulating, semiconducting, and metallic layers, such as SiO 2 , SiN, a-Si and polymeric Si. Typically, this stack consists of 32 or 64 or even 128 layers of these alternating layers.

[0006] Certain metals, such as tungsten, have been used in logic applications at the contact level for about twenty years. In recent advanced complementary metal oxide semiconductor (CMOS) devices, new technologies such as metal gates and FinFETs have emerged, leading to new applications of these metals as metal gate fillers for both p-type metal oxide semiconductor (PMOS) and n-type metal oxide semiconductor (NMOS) devices. In 3D NAND devices, these metals are also used for metal gate fillers. The requirements for gap fillers (such as using tungsten) are becoming more and more challenging for several reasons. For example, for contacts, overhang becomes more challenging as the size of the contacts becomes smaller and because conformal fillers of tungsten usually leave a seam. In addition, the seam will be exposed to the slurry during chemical mechanical polishing (CMP), which will cause integration problems. In addition, for metal gate trenches in both advanced CMOS and 3D NAND, traditional tungsten conformal growth inevitably leaves a seam in the middle.

[0007] Therefore, there is a need for an improved method of forming metal gap fill for both contacts and metal gate fill in advanced logic and memory devices. Summary of the invention

[0008] Various embodiments of the present disclosure are generally directed to methods for processing substrates, and more particularly to methods for forming metal gap fillers. In one embodiment, a method for forming a metal gap filler includes: forming a first portion of the metal gap filler above 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 filler to fill the opening with the metal gap filler.

[0009] In another embodiment, a method for forming a metal gap filler includes: forming a first portion of the metal gap filler above 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 filler to fill the opening with the metal gap filler.

[0010] In another embodiment, a processing system includes: a transfer chamber; a plurality of processing chambers coupled to the transfer chamber; and a controller configured to initiate a process to be performed in the processing system, the process including: forming a first portion of a metal gap filler above 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 filler to fill the opening with the metal gap filler. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to understand the above features of the present disclosure in detail, a more specific description of the present disclosure briefly summarized above can be obtained by referring to multiple embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the accompanying drawings only illustrate multiple exemplary embodiments of the present disclosure and are not intended to be used as limitations on the scope of the present disclosure, and the present disclosure may allow for other multiple equivalent embodiments.

[0012] Figure 1 is a flow chart of a method for forming a metal gap filler according to one embodiment.

[0013] Figure 2A-2F According to one embodiment, Figure 1 Various views of the substrate during different stages of the method.

[0014] Figure 3 According to one embodiment, a method for implementing Figure 1 Schematic top view of an exemplary multi-chamber processing system for the method of FIG.

[0015] To facilitate understanding, identical reference numerals have been used, where possible, to identify identical elements that are common to the figures. It will be appreciated that various elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. DETAILED DESCRIPTION

[0016] The present disclosure relates generally to methods for processing substrates, and more particularly to methods for forming metal gap fillers. In one embodiment that can include or be combined with one or more embodiments described herein, the method includes forming a metal gap filler in an opening using a multi-step process. The multi-step process includes: growing a first portion of the metal gap filler 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 filler by a selective deposition process to fill the opening with the metal gap filler. The metal gap filler 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 filler and the sidewalls. Thus, fluids utilized in subsequent processing do not diffuse through the metal gap filler and interact with layers disposed below the metal gap filler.

[0017] Figure 1 is a flow chart of a method 100 for forming a metal gap filler. Figure 2A-2F Draw on Figure 1 Various views of a substrate 200 during different stages of the method 100 of FIG. 1 are shown. It should be noted that the method 100 may be utilized to form any other semiconductor structure not presented herein. One skilled in the art will recognize that the complete process for forming semiconductor devices and associated structures is not depicted in these figures or described herein. Although various operations are depicted in these figures and described herein, no limitation is implied as to the order of these steps or the presence or absence of steps. Unless expressly stated, the operations depicted or described in sequence are done only for the purpose of explanation and do not exclude the possibility that the various steps are actually performed in a concurrent or overlapping manner (if not entirely, then at least partially).

[0018] The method 100 begins at operation 102 by performing a pre-cleaning process on a substrate 200 in a processing chamber. In one example, the processing chamber is an etching chamber. Figure 2A As shown in FIG. 1 , 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 may be a dielectric layer made of SiO 2 、SiN、SiCN、Al 2 O 3, AlN or other suitable dielectric materials. Alternatively, in a hard mask application, the first layer 202 may be a carbon layer. The opening 204 may 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 H 1 The second layer 206 may be made of a conductive material, such as a metal, a semiconductor, a conductive ceramic or other suitable conductive materials. In one example, the second layer 206 is made of cobalt, titanium nitride or silicon.

[0019] The 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-etching residues. The pre-cleaning process can be any suitable cleaning method, such as chemical cleaning or plasma cleaning. Chemical cleaning uses a cleaning agent or a reactive gas, such as a hydrogen radical, and a reactive gas such as H 2 ,CO,C 2 H 5 OH, WF 6 、WCl 5 or other suitable reactive gases. Certain cleaning agents, such as hydrogen radicals, H 2 or CO, reducing metal oxide contaminants to metals. Certain cleaning agents, such as WF 6 or WCl 5 , corroding contaminants by volatilizing them into gases. In one example, the pre-cleaning process utilizes hydrogen radicals to reduce carbon dioxide such as CoO x , CuO x and / or WO 3 Such metal oxides. Hydrogen radicals can be formed in a remote plasma source and then flowed to the substrate 200 along with hydrogen or argon gas. The substrate 200 can be maintained at a temperature ranging from about 200 degrees Celsius to about 400 degrees Celsius. In another example, the pre-cleaning process utilizes H 2 Hot dip to reduce CoO x , CuO x and / or WO 3 The hot dip treatment includes flowing hydrogen and argon into the processing chamber, the chamber pressure ranges from about 30 Torr to about 300 Torr, and the substrate 200 is maintained at a temperature ranging from about 300 degrees Celsius to about 600 degrees Celsius. In another example, the pre-cleaning treatment utilizes ethanol soaking to reduce the metal oxide, and the substrate 200 is maintained at a temperature ranging from about 200 degrees Celsius to about 400 degrees Celsius. In another example, the pre-cleaning treatment utilizes WF 6 or WCl 5The metal oxide is immersed in the water to react with the metal oxide and convert the metal oxide into a gas / liquid phase metal compound (e.g., WOF) at high temperature and low pressure. 4 , CuCl 2 、CoCl 2 ), and the substrate 200 is maintained at a temperature ranging from about 200 degrees Celsius to about 500 degrees Celsius.

[0020] The pre-cleaning process may be a plasma cleaning process. The plasma cleaning process utilizes Ar / He plasma or H 2 Plasma. Some plasma cleaning processes physically sputter contaminants away, while other plasma cleaning processes enhance the reaction to clean the surface 210. In one example, the pre-cleaning process utilizes an argon plasma, and the argon ions physically sputter contaminants on the surface 210 of the second layer 206. The argon plasma may be capacitively coupled, inductively coupled, or a combination of capacitive and inductive coupling. 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, and the hydrogen ions react with contaminants on the surface 210 of the second layer 206 to form metal and water. The hydrogen plasma cleaning process has a chemistry similar to a hydrogen hot dip, but less thermal energy is utilized in the hydrogen plasma cleaning process.

[0021] In one example, a pre-clean process is performed in a processing chamber using a remote plasma source. An example processing chamber suitable for performing the pre-clean process is the AKTIV Pre-Clean RT-PCR System available from Applied Materials, Inc., Santa Clara, California, USA. TM Chamber or Alternatively, the pre-clean process is performed in an etch chamber, such as an etch chamber using an inductively coupled plasma (ICP) source. An example etch chamber may be a modified decoupled plasma nitridation (DPN) chamber available from Applied Materials, Inc., Santa Clara, California, USA. However, it is contemplated that other appropriately configured chambers from other manufacturers may also be implemented to perform the pre-clean process.

[0022] At operation 104, a nucleation treatment is performed on the cleaned surface 210 of the second layer 206. The nucleation treatment eliminates the incubation period to form a metal gap filler on the surface 210 and in the opening 204, and also eliminates lattice mismatch because it is very difficult to grow a certain metal on a different metal. Figure 2BAs shown in FIG. 1 , the nucleation treatment may include forming a metal seed layer 214 on the surface 210 of the second layer 206. The metal seed layer 214 may be made of tungsten, cobalt, ruthenium, or other suitable metals. The metal seed layer 214 is formed by a selective process so 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 using, for example, B 2 H 6 、SiH 4 、Si 2 H 6 、WF 6 、WCl 5 、TiCl 4 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 used in the selective metal ALD process include B 2 H 6 、WF 6 , H 2 、SiH 4 、WCl 5 、W(CO) 6 Or other suitable precursors. In some embodiments, one or more gases containing metals other than tungsten are used. For example, a gas containing cobalt or ruthenium may be used to form the metal seed layer 214. In some embodiments, the nucleation treatment is omitted and the metal seed layer 214 is not present.

[0023] Next, at operation 106, if Figure 2C As shown in , a first portion 216 of a metal gap filler is formed on the metal seed layer 214. In some embodiments, the first portion 216 of the metal gap filler is formed on the surface 210 of the second layer 206. The first portion 216 of the metal gap filler is made of a metal, such as tungsten, cobalt, ruthenium, or other suitable metal. The first portion 216 is formed by selective processing and grows from the bottom to the top. In other words, the first portion 216 is selectively formed on the metal seed layer 214 or the surface 210 of the second layer 206, or grows from the metal seed layer 214 or the surface 210 of the second layer 206, and is not formed on one or more sidewalls 212. As shown in FIG. Figure 2C As shown in FIG. 1 , the first portion 216 contacts a portion of the one or more sidewalls 212, but the first portion 216 does not grow from the one or more sidewalls 212. The first portion 216 has a height H 2 , and the height H 2 is the height H of the opening 204 1 About ten percent to about fifty percent.

[0024] The selective process used to form 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 the precursor gases. In one example, the selective process includes flowing a metal-containing gas and a second gas into the process chamber. The metal-containing gas can be any suitable metal-containing gas, such as WF 6 . The second gas can be hydrogen. The ratio of the second gas to the metal-containing gas ranges from about six to one to about eight thousand to one. The chamber pressure ranges from about 1 Torr to about 300 Torr, and the substrate is maintained at a temperature ranging from about 200 degrees Celsius to about 500 degrees Celsius. The chamber pressure and the ratio of the gases can affect selectivity. In one example, at relatively high temperatures, such as greater than about 400 degrees Celsius, selectivity is maintained when the ratio of the second gas to the metal-containing gas is high and the chamber pressure is low.

[0025] Next, at operation 108, if Figure 2D As shown in , a sputtering process is performed to remove some of the first portion 216 of the metal gap filler and form one or more layers 218 on one or more sidewalls 212. The sputtering process may have the same process conditions as the pre-cleaning process using argon plasma. The sputtering process sputters some of the first portion 216 of the metal gap filler onto one or more sidewalls 212. Thus, 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 filler.

[0026] Next, at operation 110, Figure 2E As shown in , a second portion 220 of the metal gap filler is formed on the first portion 216 of the metal gap filler. The second portion 220 may be formed by the same process as the process for the first portion 216 of the metal gap filler. The second portion 220 is made of the same material as the first portion 216. The metal gap filler formed in the opening 204 includes the first portion 216, one or more layers 218, and the second portion 220. The multiple steps for forming the metal gap filler are seamless, and there are no gaps or defects between the metal gap filler and the sidewalls 212. As a result, fluids utilized in subsequent processing will not diffuse through the metal gap filler and interact with the second layer 206.

[0027] Next, at operation 112, if Figure 2F As shown in FIG. 2 , a chemical mechanical polishing (CMP) process is performed on substrate 200 to form a planar surface 222. During the CMP process, the slurry does not diffuse through the metal gap filler having the first portion 216, the layer 218, and the second portion 220 because the sidewall 212 is sealed by the layer 218. Thus, the second layer 206 is protected from the slurry during the CMP process.

[0028] Reference Figure 1 , operations 106, 108, and 110 are performed to form a seamless metal gap filler without gaps or defects between the metal gap filler and the sidewalls. In some embodiments, operations 106, 108, and 110 are replaced with a single operation to form a single phase crystal metal gap filler from the bottom up. The single phase crystal metal gap filler does not have any grain boundaries formed in the metal gap filler, and the resistivity of the metal gap filler is independent of the size of the opening 204. Therefore, the single phase crystal metal gap filler is seamless and has reduced resistance. The single phase crystal metal gap filler can be formed by a CVD process, wherein the substrate 200 is maintained at a temperature greater than or equal to 450 degrees Celsius.

[0029] Examples of processing systems that may be suitably modified in accordance with the teachings provided herein include the EMBODIMENTS®, commercially available from Applied Materials, Inc., located in Santa Clara, California, USA. or Integrated processing system, or other suitable processing system. It is contemplated that other processing systems (including processing systems from other manufacturers) may be employed to benefit from the aspects described herein. Figure 3 A schematic top view of an example multi-chamber processing system 300 is shown, according to various embodiments of the present disclosure, which can be used to complete Figure 1 The method 100 shown in FIG. Figure 3 As shown in FIG. 1 , 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 disposed transfer robot (not shown) for transferring substrates between the pass-through chamber 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-cleaning process such as operation 102, and a process chamber 316 configured to perform a nucleation treatment operation such as operation 106. The second transfer chamber 310 has a centrally disposed transfer robot (not shown) for transferring substrates between a set of load lock chambers 312 and the process chambers 314 or the process chambers 316. A factory interface 320 is connected to the second transfer chamber 310 through the load lock chamber 312. The factory interface 320 is coupled to one or more bays 330 on the opposite side from the load lock chamber 312. The bays 330 are typically front opening unification bays (FOUPs) that are accessible from a clean room.

[0030] During operation, the substrate is first transferred to the processing chamber 314, where a pre-cleaning 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 the processing chamber 316, where operation 106 is performed. The substrate is then transferred to one or more processing chambers 302, where operations 106, 108, and 110 are performed. Because all operations 102, 104, 106, 108, and 110 are performed in the same processing system 300, the vacuum is not broken as the substrate is transferred to each chamber, which reduces the chance of contamination and improves the quality of the metal gap fill.

[0031] The system controller 380 is coupled to the processing system 300 for controlling the processing system 300 or controlling components of the processing system 300. For example, the system controller 380 may 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. In operation, the system controller 380 enables data collection and feedback from the various chambers to coordinate the performance of the processing system 300.

[0032] 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 can 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 memories, such as random access memory (RAM), read only memory (ROM), a floppy disk, a hard disk, or any other form of digital storage, whether local or remote. The support circuits 386 are coupled to the CPU 382 and may include cache memory, clock circuits, input / output subsystems, power supplies, and the like. The system controller 380 is configured to implement the method 100 stored in the memory 384. The various embodiments disclosed in the present disclosure may generally be implemented by executing computer instruction code (e.g., a computer program product or software program) stored in the memory 384 (or in the memory of a particular processing chamber) under the control of the CPU 382. That is, the computer program product is tangibly installed on the memory 384 (or a non-transitory computer-readable medium or a machine-readable storage device). When the computer instruction code is executed by the CPU 382, ​​the CPU 382 controls the chamber to carry out operations according to various embodiments.

[0033] In summary, various embodiments of the present disclosure enable the formation of a seamless metal gap filler that prevents any fluid from diffusing therethrough. The seamless metal gap filler is formed by a multi-step process that includes: growing a first portion of the metal gap filler 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 filler by a selective deposition process to fill the opening with the metal gap filler. The metal gap filler 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 filler and the sidewalls. Thus, fluids utilized in subsequent processing do not diffuse through the metal gap filler.

[0034] 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 thereof, the scope of which is to be determined by the claims that follow.

Claims

1. A method for forming a metal gap filler, the method comprising the following steps: forming a second layer between side walls of the opening formed in the first layer; selectively forming a first portion of the metal gap filler on a first surface of the second layer, the first surface being between the sidewalls of the opening, the first portion comprising a material comprising a first metal; sputtering the first metal from the first portion to the sidewalls of the opening to form a layer in direct contact with the sidewalls of the opening and the first portion; and forming a second portion of the metal gap filler to fill the opening with the metal gap filler, wherein the second portion is the same material as the first portion, wherein The first metal comprises cobalt, tungsten or ruthenium.

2. The method of claim 1, wherein The first layer comprises a metal, and The second layer includes a dielectric layer.

3. The method of claim 1, further comprising the step of performing a pre-cleaning process on the surface of the first layer before forming the first portion of the metal gap filler.

4. The method of claim 3, further comprising the step of forming a metal seed layer on the surface of the first layer, wherein the first portion of the metal gap filler is formed on the metal seed layer. The method of claim 1 , wherein the sputtering process utilizes an argon plasma.

6. A method for forming a metal gap filler, the method comprising the following steps: forming a second layer between side walls of the opening formed in the first layer; selectively forming a first portion of the metal gap filler on a first surface of the second layer, the first surface between the sidewalls of the opening, and the first portion comprising a material comprising a first metal; forming a layer directly contacting the sidewalls of the opening and the first portion, the layer comprising the first metal; and forming a second portion of the metal gap filler to fill the opening with the metal gap filler, wherein the second portion is the same material as the first portion, The first metal comprises cobalt, tungsten or ruthenium.

7. The method of claim 6, wherein The first layer comprises a metal, and The second layer includes a dielectric layer.

8. The method of claim 6, further comprising the steps of: performing a pre-cleaning process on the surface of the first layer before forming the first portion of the metal gap filler; and A metal seed layer is formed on the surface of the first layer, wherein the first portion of the metal gap filler is formed on the metal seed layer.

9. The method of claim 6, wherein the one or more layers are formed by a sputtering process using an argon plasma.

10. A processing system comprising: transfer chamber; a plurality of processing chambers coupled to the transfer chamber; and A controller configured to cause a process to be performed on the processing system, the process comprising: forming a second layer between side walls of the opening formed in the first layer; selectively forming a first portion of a metal gap filler 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 comprising a first metal; performing a sputtering process on the first portion to partially remove the first portion of the metal gap filler and form a layer directly contacting the sidewall of the opening and the first portion; and forming a second portion of the metal gap filler to fill the opening with the metal gap filler, wherein the second portion is the same material as the first portion, The first metal is selected from cobalt, tungsten or ruthenium.

11. The processing system of claim 10, wherein The first layer comprises a metal, and The second layer includes a dielectric layer.

12. The processing system of claim 10, further comprising performing a pre-cleaning process on the surface of the first layer before forming the first portion of the metal gap filler, and A metal seed layer is formed on the surface of the first layer, wherein the first portion of the metal gap filler is formed on the metal seed layer.

Images