CN110797300A - Filling method of metal tungsten - Google Patents
Filling method of metal tungsten Download PDFInfo
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- CN110797300A CN110797300A CN201910999534.2A CN201910999534A CN110797300A CN 110797300 A CN110797300 A CN 110797300A CN 201910999534 A CN201910999534 A CN 201910999534A CN 110797300 A CN110797300 A CN 110797300A
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- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
- H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
- H01L21/76841—Barrier, adhesion or liner layers
- H01L21/76843—Barrier, adhesion or liner layers formed in openings in a dielectric
- H01L21/76847—Barrier, adhesion or liner layers formed in openings in a dielectric the layer being positioned within the main fill metal
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- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
- H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
- H01L21/76841—Barrier, adhesion or liner layers
- H01L21/7685—Barrier, adhesion or liner layers the layer covering a conductive structure
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- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
- H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
- H01L21/76841—Barrier, adhesion or liner layers
- H01L21/76871—Layers specifically deposited to enhance or enable the nucleation of further layers, i.e. seed layers
- H01L21/76876—Layers specifically deposited to enhance or enable the nucleation of further layers, i.e. seed layers for deposition from the gas phase, e.g. CVD
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- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
- H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
- H01L21/76877—Filling of holes, grooves or trenches, e.g. vias, with conductive material
- H01L21/76882—Reflowing or applying of pressure to better fill the contact hole
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Abstract
The invention belongs to the field of semiconductor design and manufacture, and provides a filling method of metal tungsten, which comprises the following steps: forming a tungsten nitride passivation layer on the side wall of the opening; and filling metal tungsten in the opening. The invention inserts tungsten nitride passivation layer during the filling process of metal tungsten. Because the growth of the metal tungsten on the tungsten seed layer and the surface of the tungsten nitride passivation layer has obviously different deposition rates, the passivation method utilizes the passivation effect of the tungsten nitride passivation layer on the further growth of the metal tungsten to promote the subsequent deposition of the metal tungsten to generate certain delay time. According to the invention, the characteristic tungsten nitride passivation layer is inserted in the filling process of the metal tungsten, so that the difference of the hysteresis strength is generated on the inner side and the outer side of the structure, the filling effect of the metal tungsten can be obviously enhanced, the complete filling of the metal tungsten is realized, the defects of pores and the like in the structure are avoided, and the adjustability of the filling process is greatly improved.
Description
Technical Field
The invention belongs to the field of semiconductor design and manufacture, and particularly relates to a filling method of metal tungsten.
Background
With the development of the planar flash memory, the manufacturing process of the semiconductor has been greatly improved. In recent years, however, the development of planar flash memories has met with various challenges: physical limits, existing development technology limits, and storage electron density limits, among others. In this context, various three-dimensional (3D) flash memory structures, such as 3D NOR flash memory and 3D NAND flash memory, have been developed in response to the difficulties encountered with flat flash memory and the pursuit of lower production costs per unit cell.
The 3D NAND memory is based on the small volume and the large capacity, the design concept of the three-dimensional mode layer-by-layer stacking height integration of the storage units is adopted, the memory with high unit area storage density and high-efficiency storage unit performance is produced, and the mainstream process of the design and production of the emerging memory is formed.
Because of its low resistivity and high stability, metal tungsten is widely used for filling various low-level metals and hole-and-trench structures, such as contact holes (CT), the second-level metal (M0) of a metal wiring structure, and the first-level metal (M1), and has significant advantages in filling high-aspect-ratio hole-and-trench structures.
The existing various pin hole and groove structures are usually directly filled by adopting a gas phase chemical reaction mode of pure metal tungsten. By continuing the growth deposition until complete filling and it is desired to obtain a metallic tungsten structure that is as pure as possible, therefore no foreign chemical species other than tungsten are introduced during this growth.
Disclosure of Invention
In view of the above-mentioned shortcomings of the prior art, the present invention aims to provide a method for filling metal tungsten, which is used to solve the problem that voids are easily generated in the filling process of metal tungsten in the prior art.
In order to achieve the above and other related objects, the present invention provides a filling method of metal tungsten, including the steps of: forming a tungsten nitride passivation layer on the side wall of the opening; and filling metal tungsten in the opening.
Optionally, the opening is formed in a substrate, and an upper region of the opening has a curved portion recessed from the opening toward the substrate.
Optionally, a ratio of the width of the bend to the open top opening is greater than 110%.
Optionally, the angle of inclination between the side walls of the opening and the bottom of the opening is greater than 85 °.
Optionally, the aspect ratio of the opening is between 5 and 50.
Optionally, the thickness of the tungsten nitride passivation layer gradually decreases from the opening of the opening toward the inside of the opening.
Optionally, the tungsten nitride passivation layer has a thickness in a range between 5 angstroms and 150 angstroms.
Optionally, the chemical formula of the tungsten nitride passivation layer is WNx, wherein a value range of x is between 0.1 and 2.0.
Optionally, the opening includes an upper trench portion and a lower trench portion, and the tungsten nitride passivation layer is formed only on a sidewall of the upper trench portion or/and a top surface of the opening.
Optionally, before forming the tungsten nitride passivation layer, the method further includes: depositing a tungsten seed layer and a tungsten body layer covering the tungsten seed layer in the opening, wherein the tungsten body layer surrounds a hole, and the tungsten nitride passivation layer is positioned in the hole and is in contact with the tungsten body layer; or; and depositing a tungsten seed layer in the opening, wherein the tungsten seed layer surrounds a hole, and the tungsten nitride passivation layer is positioned in the hole and is in contact with the tungsten seed layer.
Optionally, a tungsten seed layer is grown by using a chemical vapor deposition process or an atomic layer deposition process, wherein a gas source of the chemical vapor deposition process or the atomic layer deposition process comprises a first gas source and tungsten hexafluoride, the first gas source comprises one or two of silane and diborane, the volume ratio of the tungsten hexafluoride to the first gas source is 0.4-3, the flow rate of the first gas source is 50-1000 sccm, the flow rate of the tungsten hexafluoride is 50-1500 sccm, the deposition temperature is 250-400 ℃, the deposition time is 0.5-500 seconds, and the thickness of the tungsten seed layer is 15-500 angstroms.
Optionally, a chemical vapor deposition process or an atomic layer deposition process is used to form the tungsten bulk layer, wherein a gas source of the chemical vapor deposition process or the atomic layer deposition process includes tungsten hexafluoride and hydrogen, a volume ratio of the tungsten hexafluoride to the hydrogen is 10-100, a flow rate of the tungsten hexafluoride is 50-1500 sccm, a flow rate of the hydrogen is 1000-50000 sccm, a deposition temperature is 250-400 ℃, a deposition time is 0-500 seconds, and a thickness of the tungsten bulk layer is 0-1500 angstroms.
Optionally, a remote plasma processing process is used to form the tungsten nitride passivation layer on the partially filled metal tungsten surface, wherein a gas source used in the remote plasma processing process includes nitrogen gas for generating active nitrogen ions and reacting with the tungsten thin layer to form the tungsten nitride passivation layer, a flow rate of the nitrogen gas is 5 seem to 100 seem, a reaction temperature is 20 ℃ to 450 ℃, a reaction time is 0.2 second to 60 seconds, and a thickness of the tungsten nitride passivation layer is 5 angm to 100 angm.
Optionally, an in-situ plasma treatment process is adopted to form the tungsten nitride passivation layer on the partially filled metal tungsten surface, wherein a gas source adopted by the in-situ plasma treatment process comprises nitrogen and argon, the nitrogen source is used for performing nitridation treatment on the surface of the tungsten seed layer to form the tungsten nitride passivation layer, the flow rate of the nitrogen is 5 sccm-100 sccm, the deposition temperature is 20 ℃ to 350 ℃, the deposition time is 0.2 second to 60 seconds, and the thickness of the tungsten nitride passivation layer is 5 angm-100 angm.
Optionally, a chemical vapor deposition process is used to form the tungsten nitride passivation layer, wherein a gas source of the chemical vapor deposition process includes ammonia gas and tungsten hexafluoride, a volume ratio of the tungsten hexafluoride to the ammonia gas is 0.2-10, a flow rate of the tungsten hexafluoride is 10 sccm-400 sccm, a flow rate of the ammonia gas is 5 sccm-300 sccm, a deposition temperature is 100-450 ℃, a deposition time is 0.5 sec-60 sec, and a thickness of the tungsten nitride passivation layer is 5 angstrom-150 angstrom.
Optionally, the tungsten nitride passivation layer is formed by an atomic layer deposition process, wherein a gas source of the atomic layer deposition process includes ammonia gas, tungsten hexafluoride and diborane, a volume ratio of the tungsten hexafluoride to the ammonia gas is 0.2-10, a flow range of the tungsten hexafluoride is 10 sccm-400 sccm, a flow range of the ammonia gas is 5 sccm-300 sccm, a flow range of the diborane is 0-300 sccm, a deposition temperature is 100-450 ℃, a deposition time is 0.5 sec-60 sec, and a thickness of the tungsten nitride passivation layer is 5 angstrom-120 angstrom.
Optionally, filling the unclosed opening with tungsten metal by using a chemical vapor deposition process, wherein a gas source of the chemical vapor deposition process comprises tungsten hexafluoride and hydrogen, a volume ratio of the tungsten hexafluoride to the hydrogen is 10-100, and a deposition temperature is 350-500 ℃.
As described above, the method for filling metal tungsten according to the present invention has the following advantageous effects:
the invention inserts tungsten nitride passivation layer during the filling process of metal tungsten. Because the growth of the metal tungsten on the tungsten seed layer and the surface of the tungsten nitride passivation layer has obviously different deposition rates, the passivation method utilizes the passivation effect of the tungsten nitride passivation layer on the further growth of the metal tungsten to promote the subsequent deposition of the metal tungsten to generate certain delay time. According to the invention, the characteristic tungsten nitride passivation layer is inserted in the filling process of the metal tungsten, so that the difference of the hysteresis strength is generated on the inner side and the outer side of the structure, the filling effect of the metal tungsten can be obviously enhanced, the complete filling of the metal tungsten is realized, the defects of pores and the like in the structure are avoided, and the adjustability of the filling process is greatly improved.
The invention can effectively avoid the defects of pores and the like caused by incomplete filling of the metal tungsten structure, and greatly reduces the risk of fluorine corrosion caused by exposed pores.
The invention can improve the reaction temperature of the metal tungsten filling, thereby increasing the deposition rate and reducing the reaction time and the gas consumption. In the traditional metal tungsten deposition process, in order to enhance the filling of the metal tungsten structure, the reaction rate needs to be reduced to improve the step coverage rate, and after the tungsten nitride passivation layer is formed by treatment, the growth of the top of the filling structure is stopped, so that higher step coverage rate can be realized at a higher deposition rate, and simultaneously, the overhang (overhung) effect of the top of the structure at a high deposition rate is avoided.
The metal tungsten structure has stronger filling effect and higher reaction temperature, and the obtained metal tungsten has higher crystallinity, can obviously reduce the on-resistance and improve the response speed of a device.
Drawings
Fig. 1 to fig. 3 are schematic structural diagrams showing steps of a method for filling metal tungsten.
Fig. 4 to 11 are schematic structural diagrams of steps of the filling method of tungsten metal of the invention, wherein fig. 11 is a schematic structural diagram of tungsten metal of the invention.
Fig. 12 shows a growth rate curve (BSL) of metal tungsten on the surface of a general tungsten seed layer and a growth rate curve (WN substrate) of metal tungsten on the surface of a tungsten nitride (WNx) passivation layer.
Fig. 13 is a graph showing different growth lag times of metal tungsten at different depths of an opening during the filling process of the metal tungsten of the present invention.
Fig. 14 is a graph showing different growth thicknesses of metal tungsten at different depths of the opening during the filling process of the metal tungsten according to the present invention.
Description of the element reference numerals
101 substrate
102 opening of the container
103 bending (bowing)
104 metallic tungsten
105 pores
201 metal pad
202 insulating substrate
203 opening
204 bending part
205 tungsten seed layer
206 tungsten body layer
207 tungsten nitride passivation layer
208 metallic tungsten
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
As in the detailed description of the embodiments of the present invention, the cross-sectional views illustrating the device structures are not partially enlarged in general scale for convenience of illustration, and the schematic views are only examples, which should not limit the scope of the present invention. In addition, the three-dimensional dimensions of length, width and depth should be included in the actual fabrication.
For convenience in description, spatial relational terms such as "below," "beneath," "below," "under," "over," "upper," and the like may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that these terms of spatial relationship are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the figures. Further, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.
In the context of this application, a structure described as having a first feature "on" a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed in between the first and second features, such that the first and second features may not be in direct contact.
It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the drawings only show the components related to the present invention rather than being drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of each component in actual implementation may be changed arbitrarily, and the layout of the components may be more complicated.
As shown in fig. 1 to 3, a method for filling metal tungsten includes the steps of: 1) etching an opening 102 in the substrate 101, as shown in fig. 1; 2) filling the opening 102 with tungsten metal 104, as shown in fig. 2; 3) a chemical mechanical polishing process is used to remove the metal tungsten from the substrate surface, as shown in fig. 3.
Due to the increased demands for device integration density and performance, more high aspect ratio structures are required for the etching process. However, the etching process itself has process weaknesses, and the bending (bending) 103 and necking (necking) become more severe as the aspect ratio is higher, and these structures with the bending (bending) 103 and necking (necking) present a great challenge to the metal filling as shown in fig. 1. For the continuous growth filling process of metal tungsten chemical vapor deposition, although the filling can be completed quickly, the filling effect is greatly limited by the depth-width ratio of the structure, the taper angle of the structure side wall and the potential bending problem of the structure appearance. For high aspect ratio structures with shallow bend locations, incomplete filling can easily result in the exposure of the voids 105 after CMP due to the significant filling challenges, posing a significant risk to subsequent processing and overall device reliability. As shown in fig. 3, tungsten metal formed by a sequential chemical vapor deposition process generally results in a large void in the middle of the structure, which leads to defect problems and a threat of fluorine leakage in subsequent processes. To reduce risk, continuous chemical vapor deposition processes often require a sacrifice in process efficiency and cost to reduce porosity.
In order to improve the filling effect and efficiency of the metal tungsten, as shown in fig. 4 to 11, the present embodiment provides a filling method of the metal tungsten, including the following steps:
as shown in fig. 4 to 5, step 1) is performed first, a substrate is provided, and an opening 203 is formed in the substrate.
The base may be, for example, a semiconductor substrate such as silicon, silicon germanium, gallium arsenide, indium phosphide, silicon carbide, or the like, an insulating substrate such as silicon dioxide, silicon nitride, silicon oxynitride, or the like, but is not limited to the above-mentioned examples. In the present embodiment, the substrate is selected as an insulating substrate 202, such as silicon dioxide, and the insulating substrate 202 is disposed on a metal pad 201.
An opening 203 is formed in the insulating substrate 202 by using a photolithography process and an etching process, the metal pad 201 is exposed at the bottom of the opening 203, the opening 203 may be a hole structure or a slot structure, and in this embodiment, the opening 203 is a hole structure. The angle of inclination a between the side wall of the opening 203 and the bottom of the opening 203 is greater than 85 °. In order to improve the integration density and performance of the device, the aspect ratio of the opening 203 is between 5 and 50. As the aspect ratio increases, the upper region of the opening 203 may have a curvature 204 that is concave from the opening 203 toward the base, with the ratio of the width of the curvature 204 to the top opening of the opening 203, D1: D2, being greater than 110%. For the opening 203 with the larger bending part 204, the defects of complete filling, pores and the like are difficult to overcome by adopting the traditional filling method, but the filling method of the metal tungsten of the embodiment has a great improvement on the filling effect of the opening 203 with the bending part 204, and particularly has a significant improvement on the filling effect of a structure with the ratio D1: D2 of the width of the bending part 204 to the width of the opening at the top of the opening 203 being more than 110%.
As shown in fig. 6 to 8, step 2) is then performed to form a tungsten nitride passivation layer 207 on the sidewall of the opening 203. The chemical formula of the tungsten nitride passivation layer 207 is WNx, wherein the value range of x is between 0.1 and 2.0, and the value of x can be adjusted through different proportions of gas sources.
In an embodiment, before forming the tungsten nitride passivation layer 207, a step of partially filling the opening with metal tungsten is further included, for example, a tungsten seed layer 205 may be first deposited in the opening 203, the tungsten seed layer 205 covers the bottom and the sidewall of the opening 203, the tungsten seed layer 205 surrounds a hole, and a subsequently formed tungsten nitride passivation layer is located in the hole and is in contact with the tungsten seed layer 205, so that the tungsten seed layer 205 can effectively increase a rate of subsequent metal tungsten filling. For example, the tungsten seed layer 205 may be formed by a chemical vapor deposition process or an atomic layer deposition process, wherein a gas source of the chemical vapor deposition process or the atomic layer deposition process includes a first gas source, tungsten hexafluoride and hydrogen, the first gas source includes one or two of silane and diborane, a volume ratio of the tungsten hexafluoride to the first gas source is 0.4 to 3, a flow rate of the first gas source is 50 to 1000sccm, a flow rate of the tungsten hexafluoride is 50 to 1500sccm, a deposition temperature is 250 to 400 ℃, a deposition time is 0.5 to 500 seconds, and a thickness of the tungsten seed layer 205 is 15 to 500 angstroms. Specifically, when the gas source is tungsten hexafluoride and silane, the volume ratio of tungsten hexafluoride to silane is between 0.5 and 3, and if the gas source is tungsten hexafluoride and diborane, the volume ratio of tungsten hexafluoride to diborane is between 0.4 and 2.5.
Before forming the tungsten nitride passivation layer 207, a step of depositing a tungsten body layer 206 in the opening 203 may be further included, the tungsten body layer 206 covers the seed layer 205, a hole is defined by the tungsten seed layer 205 and the tungsten body layer 206, a subsequently formed tungsten nitride passivation layer is located in the hole and is in contact with the tungsten body layer 206, and the tungsten body layer 206 is deposited at a lower temperature, which may effectively increase the thickness of the tungsten seed layer 205 and simultaneously avoid defects such as diffusion of metal tungsten in a subsequent high-temperature process of filling metal tungsten. For example, the tungsten bulk layer 206 may be formed by a chemical vapor deposition process, wherein a gas source of the chemical vapor deposition process includes tungsten hexafluoride and hydrogen, a volume ratio of the tungsten hexafluoride to the hydrogen is 10 to 100, a flow rate of the tungsten hexafluoride is 50sccm to 1500sccm, a flow rate of the hydrogen is 1000sccm to 10000sccm, a deposition temperature is 250 ℃ to 400 ℃, for example, the deposition temperature may be 300 ℃ or 350 ℃, a deposition time is 0 second to 500 seconds, and a thickness of the tungsten bulk layer 206 is 0 angstrom to 1500 angstrom.
In this embodiment, the opening 203 includes an upper trench portion and a lower trench portion, a height ratio of the upper trench portion to the lower trench portion may be between 1:10 and 2:1, for example, 1:1, the tungsten nitride passivation layer 207 is formed only on the sidewall of the upper trench portion or only on the sidewall of the upper trench portion and the top surface of the opening, and the tungsten nitride passivation layer 207 is not formed on the lower trench portion. This configuration can preferentially deposit in the lower hole groove portion and not in the upper hole groove portion during subsequent metal tungsten filling, and can further avoid void generation caused by early closing of the opening 203 by filling.
Preferably, in this embodiment, the thickness of the tungsten nitride passivation layer 207 is gradually reduced from the opening of the opening 203 toward the inside of the opening 203, so that in the subsequent metal tungsten filling process, the lag time generated by the growth of the corresponding metal tungsten is different, and the thickness of the tungsten nitride passivation layer 207 near the opening of the opening 203 is larger, so that the lag time of the growth of the metal tungsten at the position is longer, and the thickness of the tungsten nitride passivation layer 207 inside the opening 203 is smaller, so that the metal tungsten can preferentially grow, thereby greatly improving the filling effect of the metal tungsten. In particular, the tungsten nitride passivation layer 207 may have a thickness ranging between 5 angstroms and 150 angstroms.
In an embodiment, the tungsten nitride passivation layer 207 may be formed on the surface of the tungsten seed layer 205 by using a remote plasma processing process, wherein a gas source used in the remote plasma processing process includes nitrogen gas for generating active nitrogen ions and reacting with the tungsten seed layer 205 to form the tungsten nitride passivation layer 207, a flow rate of the nitrogen gas is 5sccm to 100sccm, a reaction temperature is 20 ℃ to 450 ℃, a reaction time is 0.2 second to 60 seconds, and a thickness of the tungsten nitride passivation layer 207 is 5 angstrom to 100 angstrom. For example, in one embodiment, the flow rate of the nitrogen gas is 50sccm, the reaction temperature is 250 ℃, the reaction time is 30 seconds, and the thickness of the tungsten nitride passivation layer 207 is about 50 angstroms.
In another embodiment, the tungsten nitride passivation layer 207 may be formed on the surface of the tungsten seed layer 205 by using a physical vapor deposition process, wherein a gas source used in the physical vapor deposition process includes nitrogen and argon, the nitrogen is used to perform a nitridation process on the surface of the tungsten seed layer 205 to form the tungsten nitride passivation layer 207, a flow rate of the nitrogen is between 5sccm and 100sccm, a deposition temperature is between 20 ℃ and 350 ℃, a deposition time is between 0.2 seconds and 60 seconds, and a thickness of the tungsten nitride passivation layer 207 is between 5 angstrom and 100 angstrom. For example, in one implementation, the nitrogen gas flow may be 50sccm, the deposition temperature may be 250 ℃, the deposition time may be 30 seconds, and the tungsten nitride passivation layer 207 may have a thickness of about 50 angstroms.
In yet another embodiment, the tungsten nitride passivation layer 207 may be formed by a chemical vapor deposition process, wherein a gas source of the chemical vapor deposition process includes ammonia gas and tungsten hexafluoride, a volume ratio of the tungsten hexafluoride to the ammonia gas is 0.2 to 10, a flow rate of the tungsten hexafluoride is 10sccm to 400sccm, a flow rate of the ammonia gas is 5sccm to 300sccm, a deposition temperature is 100 ℃ to 450 ℃, a deposition time is 0.5 seconds to 60 seconds, and a thickness of the tungsten nitride passivation layer 207 is 5 angstrom to 150 angstrom. For example, in one embodiment, the volume ratio of the tungsten hexafluoride to the ammonia gas may be 1, the tungsten hexafluoride flow rate is 200sccm, the ammonia gas flow rate is 200sccm, the deposition temperature may be 350 ℃, the deposition time may be 30 seconds, and the tungsten nitride passivation layer 207 may have a thickness of 100 angstroms.
In yet another embodiment, the tungsten nitride passivation layer 207 may be formed by an atomic layer deposition process, wherein a gas source of the atomic layer deposition process includes ammonia gas, tungsten hexafluoride and diborane, a volume ratio of the tungsten hexafluoride to the ammonia gas is 0.2 to 10, a flow rate of the tungsten hexafluoride is 10sccm to 400sccm, a flow rate of the ammonia gas is 5sccm to 300sccm, a flow rate of the diborane is 0sccm to 300sccm, a deposition temperature is 100 ℃ to 450 ℃, a deposition time is 0.5 seconds to 60 seconds, and a thickness of the tungsten nitride passivation layer 207 is 5 angstroms to 120 angstroms. For example, in a specific implementation process, the volume ratio of the tungsten hexafluoride to the ammonia gas is 2, the flow rate of the tungsten hexafluoride is 300sccm, the flow rate of the ammonia gas is 150sccm, the flow rate of the diborane is 100sccm, the deposition temperature is 350 ℃, the deposition time is 30 seconds, and the thickness of the tungsten nitride passivation layer 207 is about 80 angstroms.
As shown in fig. 9 to fig. 11, step 3) is finally performed to fill the metal tungsten 208 in the unclosed opening 203, and remove the metal tungsten on the substrate surface by a chemical mechanical polishing process, where the filling structure of the metal tungsten prepared in this embodiment is shown in fig. 11.
In the embodiment, a chemical vapor deposition process is used to fill the opening 203 with the metal tungsten 208, wherein a gas source of the chemical vapor deposition process includes tungsten hexafluoride and hydrogen, a volume ratio of the tungsten hexafluoride to the hydrogen is between 10 and 100, and a deposition temperature is between 350 ℃ and 500 ℃. For example, the deposition temperature may be 450 ℃ or higher. According to the invention, the tungsten nitride passivation layer 207 is inserted in the metal tungsten filling process, so that the growth of the top of the filling structure is stopped, a higher step coverage rate can be realized at a higher deposition rate, and an overhang (overhung) effect of the top of the structure at a high deposition rate is avoided, so that the reaction temperature of the metal tungsten filling can be increased, the deposition rate is increased, the reaction time and the gas consumption are reduced, and meanwhile, the obtained metal tungsten has higher crystallinity, the on-resistance can be obviously reduced, and the response speed of a device is improved.
Fig. 12 shows a growth rate curve (BSL) of metal tungsten on a normal tungsten seed layer 205 (tungsten layer) and a growth rate curve (WN substrate) of metal tungsten on a surface of a tungsten nitride (WNx) passivation layer in a chemical vapor deposition process of metal tungsten. Research shows that the deposition rate of the metal tungsten has a strong dependence on the morphology and the composition of the substrate, and the growth of the metal tungsten has significantly different deposition rates on the surfaces of the common tungsten seed layer 205 (tungsten layer) and the tungsten nitride (WNx) passivation layer, particularly at the initial stage of deposition. The passivation layer 207 of tungsten nitride has passivation effect on the further growth of the metal tungsten, which can lead to a certain lag (delay) time for the deposition of the metal tungsten, and the invention can optimize the filling of the chemical vapor deposition process of the metal tungsten by utilizing the growth property of the metal tungsten on the surface of the passivation layer 207 of tungsten nitride.
The tungsten nitride passivation layer 207 is formed on the surface of the grown part of the metal tungsten (such as the tungsten seed layer 205 and the tungsten body layer 206), and the tungsten nitride passivation layer 207 is gradually thinned from the opening to the inside in the opening 203 to form gradient distribution, so that the structure can have different growth lag times (delay intervals, as shown in fig. 13) at different depths in the subsequent filling process of the metal tungsten, and further, the openings 203 are formed at different depths, and the thickness of the grown metal tungsten is different after the same deposition time, as shown in fig. 10 and 14, the tungsten nitride passivation layer 207 is inserted in the filling process of the metal tungsten, the growth of the metal tungsten on the surfaces of the tungsten seed layer 205 and the tungsten nitride passivation layer 207 has significantly different deposition rates, especially at the early stage of tungsten deposition, the tungsten nitride passivation layer 207 has passivation effect on the further growth of the metal tungsten, compared with the method of inserting the tungsten nitride passivation layer 207 in the tungsten filling process, the method can enhance the filling effect of the tungsten, realize the complete filling of the tungsten, avoid the defects of pores in the structure and the like, and greatly improve the adjustability of the filling process.
As described above, the method for filling metal tungsten according to the present invention has the following advantageous effects:
the invention inserts tungsten nitride passivation layer during the filling process of metal tungsten. Because the growth of the metal tungsten on the tungsten seed layer and the surface of the tungsten nitride passivation layer has obviously different deposition rates, the passivation method utilizes the passivation effect of the tungsten nitride passivation layer on the further growth of the metal tungsten to promote the subsequent deposition of the metal tungsten to generate certain delay time. According to the invention, the characteristic tungsten nitride passivation layer is inserted in the filling process of the metal tungsten, so that the difference of the hysteresis strength is generated on the inner side and the outer side of the structure, the filling effect of the metal tungsten can be obviously enhanced, the complete filling of the metal tungsten is realized, the defects of pores and the like in the structure are avoided, and the adjustability of the filling process is greatly improved.
The invention can effectively avoid the defects of pores and the like caused by incomplete filling of the metal tungsten structure, and greatly reduces the risk of fluorine corrosion caused by exposed pores.
The invention can improve the reaction temperature of the metal tungsten filling, thereby increasing the deposition rate and reducing the reaction time and the gas consumption. In the traditional metal tungsten deposition process, in order to enhance the filling of the metal tungsten structure, the reaction rate needs to be reduced to improve the step coverage rate, and after the tungsten nitride passivation layer is formed by treatment, the growth of the top of the filling structure is stopped, so that higher step coverage rate can be realized at a higher deposition rate, and simultaneously, the overhang (overhung) effect of the top of the structure at a high deposition rate is avoided.
The metal tungsten structure has stronger filling effect and higher reaction temperature, and the obtained metal tungsten has higher crystallinity, can obviously reduce the on-resistance and improve the response speed of a device.
Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (17)
1. A filling method of metal tungsten is characterized by comprising the following steps:
forming a tungsten nitride passivation layer on the side wall of the opening;
and filling metal tungsten in the opening.
2. The method for filling metallic tungsten according to claim 1, wherein: the opening is formed in a substrate, and an upper region of the opening has a curved portion recessed from the opening toward the substrate.
3. The method for filling metallic tungsten according to claim 2, wherein: the ratio of the width of the curved portion to the width of the open top opening is greater than 110%.
4. The method for filling metallic tungsten according to claim 1, wherein: the inclination angle between the side wall of the opening and the bottom of the opening is greater than 85 degrees.
5. The method for filling metallic tungsten according to claim 1, wherein: the depth-to-width ratio of the opening is between 5 and 50.
6. The method for filling metallic tungsten according to claim 1, wherein: the thickness of the tungsten nitride passivation layer is gradually reduced from the opening of the opening to the inner part of the opening.
7. The method for filling metallic tungsten according to claim 6, wherein: the thickness range of the tungsten nitride passivation layer is between 5 and 150 angstroms.
8. The method for filling metallic tungsten according to claim 1, wherein: the chemical formula of the tungsten nitride passivation layer is WNx, wherein the value range of x is between 0.1 and 2.0.
9. The method for filling metallic tungsten according to claim 1, wherein: the opening comprises an upper hole groove part and a lower hole groove part, and the tungsten nitride passivation layer is only formed on the side wall of the upper hole groove part or/and the top surface of the opening.
10. The method for filling metallic tungsten according to claim 1, wherein: before forming the tungsten nitride passivation layer, the method further comprises:
depositing a tungsten seed layer and a tungsten body layer covering the tungsten seed layer in the opening, wherein the tungsten body layer surrounds a hole, and the tungsten nitride passivation layer is positioned in the hole and is in contact with the tungsten body layer; or;
and depositing a tungsten seed layer in the opening, wherein the tungsten seed layer surrounds a hole, and the tungsten nitride passivation layer is positioned in the hole and is in contact with the tungsten seed layer.
11. The method for filling metallic tungsten according to claim 10, wherein: the method comprises the steps of growing a tungsten seed layer by adopting a chemical vapor deposition process or an atomic layer deposition process, wherein a gas source of the chemical vapor deposition process or the atomic layer deposition process comprises a first gas source and tungsten hexafluoride, the first gas source comprises one or two of silane and diborane, the volume ratio of the tungsten hexafluoride to the first gas source is 0.4-3, the flow rate of the first gas source is 50-1000 sccm, the flow rate of the tungsten hexafluoride is 50-1500 sccm, the deposition temperature is 250-400 ℃, the deposition time is 0.5-500 seconds, and the thickness of the tungsten seed layer is 15-500 angstroms.
12. The method for filling metallic tungsten according to claim 10, wherein: the tungsten body layer is formed by adopting a chemical vapor deposition process or an atomic layer deposition process, wherein a gas source of the chemical vapor deposition process or the atomic layer deposition process comprises tungsten hexafluoride and hydrogen, the volume ratio of the tungsten hexafluoride to the hydrogen is 10-100, the flow rate of the tungsten hexafluoride is 50-1500 sccm, the flow rate of the hydrogen is 1000-50000 sccm, the deposition temperature is 250-400 ℃, the deposition time is 0-500 seconds, and the thickness of the tungsten body layer is 0-1500 angstrom.
13. The method for filling metallic tungsten according to claim 10, wherein: and forming the tungsten nitride passivation layer on the surface of the partially filled metal tungsten by adopting a remote plasma treatment process, wherein a gas source adopted by the remote plasma treatment process comprises nitrogen gas for generating active nitrogen ions and reacting with the tungsten thin layer to form the tungsten nitride passivation layer, the flow rate of the nitrogen gas is 5 sccm-100 sccm, the reaction temperature is 20-450 ℃, the reaction time is 0.2-60 seconds, and the thickness of the tungsten nitride passivation layer is 5-100 angstroms.
14. The method for filling metallic tungsten according to claim 10, wherein: and forming the tungsten nitride passivation layer on the surface of the partially filled metal tungsten by adopting an in-situ plasma treatment process, wherein a gas source adopted by the in-situ plasma treatment process comprises nitrogen and argon and is used for performing nitridation treatment on the surface of the tungsten seed layer to form the tungsten nitride passivation layer, the flow rate of the nitrogen is between 5sccm and 100sccm, the deposition temperature is between 20 ℃ and 350 ℃, the deposition time is between 0.2 second and 60 seconds, and the thickness of the tungsten nitride passivation layer is between 5 angm and 100 angm.
15. The method for filling metallic tungsten according to claim 1, wherein: and forming the tungsten nitride passivation layer by adopting a chemical vapor deposition process, wherein a gas source of the chemical vapor deposition process comprises ammonia gas and tungsten hexafluoride, the volume ratio of the tungsten hexafluoride to the ammonia gas is 0.2-10, the tungsten hexafluoride flow is 10-400 sccm, the ammonia gas flow is 5-300 sccm, the deposition temperature is 100-450 ℃, the deposition time is 0.5-60 seconds, and the tungsten nitride passivation layer is 5-150 angstroms thick.
16. The method for filling metallic tungsten according to claim 1, wherein: the tungsten nitride passivation layer is formed by adopting an atomic layer deposition process, wherein a gas source of the atomic layer deposition process comprises ammonia gas, tungsten hexafluoride and diborane, the volume ratio of the tungsten hexafluoride to the ammonia gas is 0.2-10, the flow range of the tungsten hexafluoride is 10-400 sccm, the flow range of the ammonia gas is 5-300 sccm, the flow range of the diborane is 0-300 sccm, the deposition temperature is 100-450 ℃, the deposition time is 0.5-60 seconds, and the thickness of the tungsten nitride passivation layer is 5-120 angstrom.
17. The method for filling metallic tungsten according to claim 1, wherein: filling metal tungsten in the unclosed opening by adopting a chemical vapor deposition process, wherein a gas source of the chemical vapor deposition process comprises tungsten hexafluoride and hydrogen, the volume ratio of the tungsten hexafluoride to the hydrogen is 10-100, and the deposition temperature is 350-500 ℃.
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