CN115863257A - Preparation method of semiconductor structure - Google Patents
Preparation method of semiconductor structure Download PDFInfo
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- CN115863257A CN115863257A CN202310025239.3A CN202310025239A CN115863257A CN 115863257 A CN115863257 A CN 115863257A CN 202310025239 A CN202310025239 A CN 202310025239A CN 115863257 A CN115863257 A CN 115863257A
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Abstract
The embodiment of the present disclosure provides a preparation method of a semiconductor structure, where the semiconductor structure includes a titanium nitride layer and a metal layer disposed on the surface of the titanium nitride layer, and the preparation method includes: and before the metal layer is formed on the surface of the titanium nitride layer, performing primary pretreatment on the titanium nitride layer by adopting nitrogen and hydrogen gas. In the preparation method provided by the embodiment of the disclosure, in the first pretreatment step, nitrogen and hydrogen containing gas reacts with residual chloride ion impurities in the titanium nitride layer, so that the chloride ion impurities can be removed, the resistivity of the titanium nitride layer is reduced, and the conductivity of the semiconductor structure is improved; meanwhile, a nitrogen-rich layer can be formed at the bottom of the titanium nitride layer by the nitrogen and hydrogen containing gas, so that the threshold voltage of a transistor formed by the semiconductor structure is further improved.
Description
Technical Field
The present disclosure relates to the field of integrated circuits, and more particularly, to a method for fabricating a semiconductor structure.
Background
Dynamic Random Access Memory (DRAM) is a semiconductor device commonly used in electronic devices such as computers, and is composed of a plurality of Memory cells, each of which typically includes a transistor and a capacitor. The transistor has a gate electrode electrically connected to a word line, a source electrode electrically connected to a bit line, and a drain electrode electrically connected to a capacitor, and a word line voltage on the word line can control the transistor to be turned on and off, so that data information stored in the capacitor can be read or written through the bit line.
In the DRAM process, the gate of the embedded Word Line (Buried Word Line) is usually composed of Oxide (Oxide)/titanium nitride (TiN)/metal layer, and titanium nitride has a wide application in the optical and optoelectronic fields due to its unique optical properties. For example, in a filling process of a metal layer, a titanium nitride layer is used as an adhesion layer of the metal layer, and the like. However, the properties of the titanium nitride layer are not satisfactory.
Disclosure of Invention
The embodiment of the disclosure provides a preparation method of a semiconductor structure, which can reduce the resistivity of a titanium nitride layer and improve the conductivity of the semiconductor structure.
In one embodiment, the semiconductor structure comprises a titanium nitride layer and a metal layer disposed on a surface of the titanium nitride layer, and the preparation method comprises: and before the metal layer is formed on the surface of the titanium nitride layer, performing primary pretreatment on the titanium nitride layer by adopting nitrogen and hydrogen gas.
In one embodiment, the method for performing a first pretreatment on the titanium nitride layer with a gas containing nitrogen and hydrogen comprises: introducing the nitrogen-containing and hydrogen-containing gas at a set flow rate, and keeping the gas at a first temperature for a set time; and reducing the temperature to a second temperature within a set time.
In one embodiment, the set flow rate is 1 to 10slm.
In one embodiment, the first temperature is 500 to 800 ℃.
In one embodiment, the second temperature is 200 to 500 degrees celsius.
In an embodiment, the first temperature is higher than the second temperature.
In one embodiment, the set flow rate has a trend opposite to a trend of the first temperature.
In one embodiment, the set flow rate has a trend opposite to the trend of the second temperature.
In one embodiment, the trend of change of the first temperature is the same as the trend of change of the second temperature.
In one embodiment, the set flow rate has a trend opposite to the first temperature and the second temperature, and the trend of the first temperature is the same as the trend of the second temperature.
In one embodiment, the nitrogen and hydrogen containing gas is ammonia gas.
In one embodiment, the metal layer is a tungsten metal layer.
In one embodiment, the method of forming the tungsten metal layer includes: after the step of carrying out primary pretreatment on the titanium nitride layer at a preset temperature by adopting nitrogen and hydrogen containing gas, carrying out secondary pretreatment on the titanium nitride layer by adopting borane and tungsten containing gas, and forming a tungsten nucleation layer on the surface of the titanium nitride; and forming a tungsten layer on the tungsten nucleation layer by using tungsten-containing gas and reducing gas as reaction gases.
In one embodiment, the step of forming a tungsten layer on the tungsten nucleation layer is followed by: and etching back the tungsten layer to form the semiconductor structure.
In one embodiment, the titanium nitride layer contains chloride ions, which can be removed by the nitrogen and hydrogen containing gas during the first pretreatment.
In the preparation method provided by the embodiment of the disclosure, in the first pretreatment step, nitrogen and hydrogen containing gas reacts with residual chloride ion impurities in the titanium nitride layer, so that the chloride ion impurities can be removed, the resistivity of the titanium nitride layer is reduced, and the conductivity of the semiconductor structure is improved; meanwhile, a nitrogen-rich layer can be formed at the bottom of the titanium nitride layer by the nitrogen and hydrogen containing gas, so that the threshold voltage of a transistor formed by the semiconductor structure is further improved.
Drawings
FIG. 1 is a schematic illustration of steps of a method of preparation provided by an embodiment of the present disclosure;
fig. 2A to fig. 2E are schematic flow charts of a preparation method provided in an embodiment of the present disclosure;
fig. 3 is a schematic diagram of a method of forming a metal layer according to an embodiment of the disclosure;
FIG. 4A is a graph showing the relationship between the flow rate of a nitrogen-and-hydrogen-containing gas and the thickness of a tungsten layer;
FIG. 4B is a graph of a first temperature versus tungsten layer thickness;
fig. 4C is a graph of the second temperature versus the tungsten layer thickness.
Detailed Description
The following describes in detail a specific embodiment of a method for fabricating a semiconductor structure provided in the present disclosure with reference to the accompanying drawings. The semiconductor structure described in this embodiment may be, but is not limited to, a gate structure of a DRAM.
The embodiment of the present disclosure provides a method for manufacturing a semiconductor structure, where the semiconductor structure includes a titanium nitride layer and a metal layer disposed on a surface of the titanium nitride layer, and the method includes: and before the metal layer is formed on the surface of the titanium nitride layer, performing primary pretreatment on the titanium nitride layer by adopting nitrogen and hydrogen gas.
In some embodiments, the titanium nitride layer contains chloride ions, i.e., a large amount of chloride ion impurities remain in the titanium nitride layer, and in the first pretreatment step, the nitrogen and hydrogen-containing gas reacts with the chloride ion impurities to remove or reduce the chloride ion impurities, thereby reducing the resistivity of the titanium nitride layer and improving the conductivity of the semiconductor structure. Meanwhile, a nitrogen-rich layer can be formed at the bottom of the titanium nitride layer by the nitrogen and hydrogen containing gas, so that the threshold voltage of a transistor formed by the semiconductor structure is further improved.
In some embodiments, the nitrogen and hydrogen containing gas includes, but is not limited to, ammonia (NH) 3 ) Ammonia (NH) 3 ) A mixture with an inert gas including but not limited to nitrogen, argon, etc., or an amino group-containing organic substance including but not limited to methylamine, dimethylamine, trimethylamine. The ammonia gas or the amino can react with chloride ions to form hydrogen chloride, and then residual chloride ion impurities in the titanium nitride layer are removed.
As an example, an embodiment of the present disclosure provides a method of fabricating the semiconductor structure.
Fig. 1 is a schematic diagram illustrating steps of a preparation method according to an embodiment of the present disclosure, referring to fig. 1, the preparation method includes the following steps: step S10, providing a substrate, wherein a titanium nitride layer is arranged on the surface of the substrate; s11, adopting nitrogen-containing and hydrogen-containing gas to carry out primary pretreatment on the titanium nitride layer; and S12, forming a metal layer on the surface of the titanium nitride layer.
Fig. 2A to 2E are schematic flow diagrams of a preparation method provided in an embodiment of the disclosure.
Referring to fig. 1 and fig. 2A, in step S10, a substrate 200 is provided, and a titanium nitride layer 210 is disposed on a surface of the substrate 200. The titanium nitride layer 210 can effectively block ions, such as boron ions (B), from diffusing down into the substrate 200 in a precursor of a subsequent metal layer forming process, and increase the adhesion of the subsequently formed metal layer.
In some embodiments, the base 200 comprises a substrate 201 and an insulating layer 202 disposed on a surface of the substrate 201, and the titanium nitride layer 210 is formed on a surface of the insulating layer 202.
The substrate 201 includes, but is not limited to, a silicon substrate, a Germanium (Ge) substrate, a silicon Germanium (SiGe) substrate, an SOI substrate, a GOI (Germanium-on-Insulator) substrate, or the like; the substrate 201 may also be a substrate including other element semiconductors or compound semiconductors, such as gallium arsenide, indium phosphide, or silicon carbide, and the like, and the substrate 201 may also be a stacked structure, such as a silicon/germanium-silicon stack; in addition, the substrate 201 may be a substrate after ion doping, and may be P-type doped or N-type doped; a plurality of peripheral devices, such as field effect transistors, capacitors, inductors, and/or diodes, may also be formed in the substrate 201. In this embodiment, the substrate 201 is a silicon substrate, and may further include other device structures therein, such as a transistor structure, a metal wiring structure, and the like, but is not shown since it is not relevant to the present application.
The insulating layer 202 includes, but is not limited to, an oxide layer, an oxynitride layer, such as a silicon oxide layer, a silicon oxynitride layer, and the insulating layer 202 serves as an insulating isolation layer between the titanium nitride layer 210 and the substrate 201. In some embodiments, the insulating layer 202 has a single-layer structure, and in other embodiments, the insulating layer 202 may also have a multi-layer composite structure.
In the present embodiment, a shallow trench 203 is formed in the substrate 201, the insulating layer 202 covers a sidewall of the shallow trench 203, the titanium nitride layer 210 covers a surface of the insulating layer 202, and the titanium nitride layer 210 does not fill the shallow trench 230, and the titanium nitride layer 210 and the shallow trench 203 have the same profile. In other embodiments, the shallow trench 203 is not formed in the substrate 201, the insulating layer 202 is directly formed on the upper surface of the substrate 201, and the titanium nitride layer 210 covers the surface of the insulating layer 202.
As an example, an embodiment of the present disclosure provides a method for forming a titanium nitride layer 210 on a surface of the substrate 200. An Atomic Layer Deposition (ALD) process is typically selected to deposit a titanium nitride layer 210 on the insulating layer 202. Specifically, suppose titanium nitride layer 210 is initially formed with-NH 2 Starting, i.e. with-NH at the surface of the substrate 200 2 Radical, introducing TiCl into the reaction chamber 4 Based on the following chemical reaction, the surface of the substrate 200-NH 2 In which radical-H is-TiCl 3 Instead of this:
TiCl 4 +-NH 2 →-TiNCl 2 +2HCl。
purging the reaction chamber with an inert gas, such as nitrogen, argon, etc., to remove HCl and unreacted TiCl as by-products of the chamber 4 Carried out of the reaction chamber.
Blowing NH into the reaction chamber after inert gas purging 3 the-Cl-NH-is formed on the surface of the film by the following chemical reaction 2 Instead of this:
NH 3 +-TiCl x →-TiNH 3-x + xHCl, wherein x is less than or equal to 3.
Purging the reaction chamber with an inert gas, such as nitrogen, argon, etc., to remove HCl and unreacted NH as by-products of the chamber 3 Carried out of the reaction chamber.
A byproduct HCl is generated in the reaction process; HCl is used as corrosive gas to react with-NH on the surface of the titanium nitride film 2 Reaction to form NH 3 and-Cl, as a substitute, is always present during the growth of the titanium nitride film, resulting in a high content of chloride ion impurities in the titanium nitride layer 210, affecting the resistivity of the titanium nitride layer 210.
After the titanium nitride layer 210 is formed, a planarization process, such as chemical mechanical polishing, is further included to form the titanium nitride layer 210 with a flat surface, so as to provide a good process plane for the formation of the subsequent metal layer 220.
Referring to fig. 1 and 2B, in step S11, before forming the metal layer 220, a first pretreatment is performed on the titanium nitride layer 210 by using nitrogen and hydrogen gas. For example, in some embodiments, ammonia (NH) is employed 3 ) The titanium nitride layer 210 is pretreated for the first time by the ammonia gas (NH) 3 ) Reacting with the residual chloride ions (Cl) in the titanium nitride layer 210 can remove at least some of the chloride ions (Cl) in the titanium nitride layer 210, increasing the resistivity of the titanium nitride layer 210.
In some embodiments, the first pretreatment of the titanium nitride layer 210 with nitrogen and hydrogen containing gas comprises the following steps:
and introducing the nitrogen-containing and hydrogen-containing gas at a set flow rate, and keeping the gas at the first temperature for a set time. In some embodiments, the nitrogen and hydrogen containing gas may be the same as the reaction gas used in forming the titanium nitride layer, and in other embodiments, the nitrogen and hydrogen containing gas may be different from the reaction gas used in forming the titanium nitride layer.
And reducing the temperature to a second temperature within a set time. Wherein the first temperature is higher than the second temperature. In the step, the introduction of the nitrogen-containing gas and the hydrogen gas is stopped, and only the temperature is reduced to remove the residual nitrogen-containing gas and the residual hydrogen gas, so that the influence of the residual nitrogen-containing gas and the residual hydrogen gas on the formation of the subsequent metal layer is avoided.
Referring to fig. 1 and fig. 2C, in step S12, after performing a first pretreatment on the titanium nitride layer 210 by using nitrogen and hydrogen containing gas, a metal layer 220 is formed on the surface of the titanium nitride layer 210, and the metal layer 220 is in contact with the titanium nitride layer 210. In this step, the titanium nitride layer 210 can effectively block ions in the precursor, such as boron ions (B), from diffusing down into the substrate 200, and increase the adhesion of the formed metal layer.
Because the titanium nitride layer 210 is treated by adopting the nitrogen-containing and hydrogen-containing gas before the metal layer is formed, the chloride ion impurities in the titanium nitride layer 210 are removed or reduced, the resistivity of the titanium nitride layer 210 is reduced, and the first pretreatment comprises the step of cooling to the second temperature within the set time, the nitrogen-containing and hydrogen-containing gas remaining on the surface of the titanium nitride layer 210 can be reduced or removed, and the influence of the remaining nitrogen-containing and hydrogen-containing gas on the electrical property of the metal layer is avoided.
In some embodiments, the metal layer 220 includes, but is not limited to, a tungsten metal layer.
As an example, an embodiment of the present disclosure provides a method for forming the metal layer 220, where the metal layer 220 is a tungsten metal layer. The method comprises the following steps:
referring to FIG. 3, borane (B) is used 2 H 6 ) And carrying out second pretreatment on the titanium nitride layer 210 by using tungsten-containing gas, forming a tungsten nucleation layer 221 on the surface of the titanium nitride layer 210, wherein the tungsten nucleation layer 221 is used as a growth point of a tungsten layer 222, and the step is a nucleation stage of metal tungsten.
The tungsten-containing gas includes, but is not limited to, tungsten hexachloride (WCl) 6 ) Tungsten hexafluoride (WF) 6 ) And hydroxyl tungsten, wherein the tungsten-containing gas is a main reaction gas for tungsten chemical vapor deposition, and the borane is an auxiliary gas.
In this example, borane (B) 2 H 6 ) Reduction of tungsten hexafluoride (WF) 6 ) A thin tungsten nucleation layer 221 is formed on the surface of the titanium nitride layer 210, and in the subsequent process, the tungsten nucleation layer 221 serves as a growth point of the tungsten layer 222. Specifically, referring to FIG. 3 (a), first, borane (B) is introduced into the reaction chamber 2 H 6 ) The surface of the titanium nitride layer 210 is fully wetted with borane (B) 2 H 6 ) Decomposition into boron (B) + ) Adsorbed on the surface of the titanium nitride layer 210; referring to FIG. 3 (b), tungsten hexafluoride (WF) is introduced 6 ) Tungsten (W) is replacement adsorbed on the nitrideA tungsten nucleation layer 221 is formed on the surface of titanium layer 210.
Referring to (c), (d) and (e) of fig. 3, a tungsten layer 222 is formed on the tungsten nucleation layer 221 using a tungsten-containing gas and a reducing gas as reaction gases. In this step, the reaction gas takes the tungsten nucleation layer 221 as a growth point to form a tungsten layer 222. The tungsten nucleation layer 221 and the tungsten layer 222 together serve as the metal layer 220.
The tungsten-containing gas includes, but is not limited to, tungsten hexachloride (WCl) 6 ) Tungsten hexafluoride (WF) 6 ) And hydroxyl tungsten, the gas containing tungsten is the main reaction gas of tungsten chemical vapor deposition; the reducing gas includes, but is not limited to, borane (B) 2 H 6 ) Silane (SiH) 4 ) Hydrogen (H) 2 ) At least one of (1). In this embodiment, the tungsten-containing gas is tungsten hexafluoride (WF) 6 ) The reducing gas is Silane (SiH) 4 )。
The step is a bulk growth stage of metal tungsten, the chemical vapor deposition in the bulk growth stage has different process parameters (such as pressure, gas flow and the like) from the nucleation stage, and compared with the nucleation stage, the deposition rate in the bulk growth stage is higher, the deposition time is longer, the deposition amount is larger, and the tungsten deposited in the bulk growth stage is about 90% of the total tungsten deposition amount in the same chemical vapor deposition process. The chemical vapor deposition is carried out at a deposition temperature that avoids affecting the structures formed on the semiconductor structure. In some embodiments of the present disclosure, the process temperature used during the bulk growth phase is set, for example, at 350 ℃ to 550 ℃.
The step of forming a tungsten layer on the tungsten nucleation layer is followed by: and etching back the tungsten layer to form the semiconductor structure.
In some embodiments, the tungsten layer 222 covers the surface of the titanium nitride layer 210 and fills the shallow trenches 203; in other embodiments, the tungsten layer 222 covers only the surface of the titanium nitride layer 210 and does not fill the shallow trench 203, i.e., the tungsten layer 222 only fills the lower portion of the shallow trench 203. In the present embodiment, the tungsten layer 222 covers the surface of the titanium nitride layer 210 and fills the shallow trench 203, please refer to fig. 2C. In this embodiment, the tungsten layer also covers the upper surface of the insulating layer 202.
In some embodiments, after forming the tungsten layer 222, a step of removing a portion of the tungsten layer 222 to form a semiconductor structure is further included. Specifically, referring to fig. 2D, the tungsten layer 222 is etched back, and only the tungsten layer 222 located at the lower portion of the shallow trench 203 is remained, so as to form the semiconductor structure. The etch-back process includes, but is not limited to, a wet etch process.
In this embodiment, before performing the etch-back process, a chemical mechanical polishing process is further performed to thin the tungsten layer 222 on the upper surface of the insulating layer 202 until the insulating layer 202 stops. After the chemical mechanical polishing process, the tungsten layer 222 is further removed by an etch-back process.
In the present embodiment, the tungsten nucleation layer 221 is also removed during the etch-back process, and after the etch-back process is performed, the tungsten nucleation layer 221 is flush with the top surface of the tungsten layer 222. In this embodiment, the titanium nitride layer 210 is also partially removed during the performing of the etch-back process, and after the performing of the etch-back process, the top surface of the titanium nitride layer 210 is flush with the top surface of the tungsten layer 222.
Referring to fig. 2E, a filling layer 230 is formed to cover the surface of the tungsten layer 222, so as to form a buried word line structure. The filling layer 230 includes, but is not limited to, a silicon nitride layer. The filling layer 230 can protect the metal layer 220 from being damaged in other semiconductor processes.
The inventors found that, in the semiconductor structure provided by the embodiment of the present disclosure, the resistance of the metal layer 220 formed on the titanium nitride layer 210 is large, and thus the device requirements cannot be met. After further intensive research, the reason for this phenomenon is that after the titanium nitride layer 210 is pretreated with nitrogen-containing and hydrogen-containing gas for the first time, nitrogen-containing and hydrogen-containing gas remains on the surface of the titanium nitride layer 210, and the remaining nitrogen-containing and hydrogen-containing gas reacts with borane, so that the borane cannot be completely decomposed, and the formed tungsten nucleation layer 221 has smaller particles, and further the formed tungsten layer 222 has smaller particles and increased resistance. For example, in the presence of ammonia (NH) 3 ) To pairWhen the titanium nitride layer 210 is subjected to the first pretreatment, ammonia (NH) remains on the surface of the titanium nitride layer 210 3 ) Residual ammonia (NH) 3 ) Will react with borane (B) 2 H 6 ) Reaction to form B 3 H 6 N 3 ，B 3 H 6 N 3 Can affect borane (B) 2 H 6 ) Thereby causing the particles of the tungsten nucleation layer 221 to be smaller.
In view of this, in an embodiment of the disclosure, in the first pretreatment process, the set flow rate, the first temperature and the second temperature of the nitrogen-containing and hydrogen-containing gas are adjusted to reduce the residue of the nitrogen-containing and hydrogen-containing gas on the surface of the titanium nitride layer 210, thereby preventing the residual nitrogen-containing and hydrogen-containing gas from affecting the function of the borane, and at the same time, no additional process steps are required, so that the method is simple and easy.
The inventors have found that the smaller the flow rate of the nitrogen-and-hydrogen-containing gas in the first pretreatment, the larger the particles of the tungsten layer 222, and therefore, in some embodiments of the present disclosure, the set flow rate of the nitrogen-and-hydrogen-containing gas is set to 1 to 10slm in the first pretreatment, which enables removal of the chlorine ion impurities in the titanium nitride layer 210 and also enables reduction of the amount of the nitrogen-and-hydrogen-containing gas remaining on the surface of the titanium nitride layer 210.
The inventors have further found that the particles of the tungsten layer 222 are larger as the first temperature is higher in the first pretreatment, and thus, in some embodiments of the present disclosure, the first temperature is set to 500 to 800 degrees celsius in the first pretreatment, so that on one hand, the chlorine ion impurities in the titanium nitride layer 210 can be removed, and on the other hand, the residual nitrogen and hydrogen containing gas is volatilized by using a high temperature, so as to reduce the amount of the nitrogen and hydrogen containing gas remaining on the surface of the titanium nitride layer 210, and also avoid the influence of the high temperature on other structures in the semiconductor structure.
The inventors have further found that the particles of the tungsten layer 222 are larger as the second temperature is higher in the first pretreatment, and thus, in some embodiments of the present disclosure, the second temperature is set to 200 to 500 degrees celsius in the first pretreatment, so that on one hand, the residual nitrogen and hydrogen containing gas is volatilized by using a high temperature to reduce the amount of the residual nitrogen and hydrogen containing gas on the surface of the titanium nitride layer 210, and on the other hand, the temperature is prevented from being too high to affect other structures in the semiconductor structure, and at the same time, preparation is made for forming the metal layer 220 subsequently.
When the set flow, the first temperature and the second temperature of the nitrogen and hydrogen containing gas are set, the following principles are followed:
in some embodiments, the trend of the set flow rate is opposite to the trend of the first temperature, i.e. in order to achieve both removal of the chloride ion impurities in the titanium nitride layer 210 and reduction of the amount of the nitrogen-containing and hydrogen-containing gas remaining on the surface of the titanium nitride layer 210, it is not possible to simultaneously increase the set flow rate of the nitrogen-containing and hydrogen-containing gas and lower the first temperature, or simultaneously decrease the set flow rate of the nitrogen-containing and hydrogen-containing gas and raise the first temperature. For example, in some embodiments, the set flow rate of the nitrogen and hydrogen-containing gas may be increased, and the first temperature may be decreased; or the set flow rate of the nitrogen and hydrogen containing gas is reduced, and the first temperature is increased, so that the chlorine ion impurities in the titanium nitride layer 210 can be removed, and the amount of the nitrogen and hydrogen containing gas remaining on the surface of the titanium nitride layer 210 can be reduced.
In some embodiments, the trend of the set flow rate is opposite to the trend of the second temperature, i.e. in order to achieve both removal of the chloride ion impurities in the titanium nitride layer 210 and reduction of the amount of the residual nitrogen-containing and hydrogen-containing gas on the surface of the titanium nitride layer 210, it is not possible to simultaneously increase the set flow rate of the nitrogen-containing and hydrogen-containing gas and lower the second temperature, or simultaneously decrease the set flow rate of the nitrogen-containing and hydrogen-containing gas and raise the second temperature. For example, in some embodiments, the set flow rate of the nitrogen and hydrogen-containing gas may be increased, and the second temperature may be decreased; or reducing the set flow rate of the nitrogen-containing and hydrogen-containing gas and increasing the second temperature; so as to remove the chloride ion impurities in the titanium nitride layer 210 and reduce the amount of the nitrogen and hydrogen gas remaining on the surface of the titanium nitride layer 210.
In some embodiments, the trend of the first temperature is the same as the trend of the second temperature, i.e. in order to minimize the amount of residual nitrogen and hydrogen containing gas on the surface of titanium nitride layer 210, the first temperature and the second temperature may be simultaneously increased, or the first temperature may be maintained and the second temperature may be increased, or the second temperature may be maintained and the first temperature may be increased. For example, in some embodiments, the first temperature or the second temperature, or both, may be increased without changing the set flow rate of the nitrogen and hydrogen containing gas, so as to minimize the amount of residual nitrogen and hydrogen containing gas on the surface of the titanium nitride layer 210.
In some embodiments, the trend of the set flow rate is opposite to the trend of the first temperature and the trend of the second temperature, and the trend of the first temperature is the same as the trend of the second temperature, i.e. in order to remove the chloride ion impurities in the titanium nitride layer 210 and reduce the amount of the nitrogen-containing and hydrogen-containing gas remaining on the surface of the titanium nitride layer 210, the set flow rate of the nitrogen-containing and hydrogen-containing gas cannot be increased and the first temperature and the second temperature cannot be decreased simultaneously, or the set flow rate of the nitrogen-containing and hydrogen-containing gas cannot be decreased and the first temperature and the second temperature cannot be increased simultaneously. For example, in some embodiments, the set flow rate of the nitrogen and hydrogen-containing gas may be increased, and the first and second temperatures may be decreased; or reducing the set flow rate of the nitrogen-containing and hydrogen-containing gas and increasing the first temperature and the second temperature; so as to remove the chlorine ion impurities in the titanium nitride layer 210 and reduce the amount of the nitrogen and hydrogen gas remaining on the surface of the titanium nitride layer 210.
In some embodiments, the remaining amount of the nitrogen and hydrogen gas can be reduced by adjusting the holding time of the first temperature and the setting time of the temperature reduction to the second temperature, for example, decreasing the holding time of the first temperature, and increasing the setting time of the temperature reduction to the second temperature to increase the volatilization amount of the nitrogen and hydrogen gas, thereby decreasing the remaining amount of the nitrogen and hydrogen gas on the surface of the titanium nitride layer 210. In the embodiment of the present disclosure, the titanium nitride layer 210 is pretreated with nitrogen and hydrogen containing gas for the first time, and the flow rate and the treatment temperature (the first temperature and the second temperature) of the nitrogen and hydrogen containing gas are controlled, so that the particles of the formed tungsten layer 222 are larger, and the resistivity of the tungsten layer 222 is greatly reduced.
The inventors have also found that a first pretreatment of the titanium nitride layer 210 with a nitrogen and hydrogen containing gas, and controlling the flow rate and the treatment temperature (first and second temperatures) of the nitrogen and hydrogen containing gas can affect the cmp rate in the step of removing portions of the tungsten nucleation layer 221 and the tungsten layer 222.
For example, as shown in fig. 4A, the abscissa in fig. 4A represents the flow rate of the nitrogen-and hydrogen-containing gas, and the ordinate represents the thickness of the tungsten metal layer remaining after the polishing for a fixed time after the growth of the tungsten metal layer of a predetermined thickness and the polishing for the same time, and as can be seen from fig. 4A, the thickness of the remaining tungsten metal layer increases with a decrease in the flow rate of the nitrogen-and hydrogen-containing gas, that is, the chemical mechanical polishing rate of the tungsten layer 222 decreases with a decrease in the flow rate of the nitrogen-and hydrogen-containing gas, and the tungsten layer is more difficult to polish, which indicates that the particles of the tungsten layer 222 increase with an increase in the density of the tungsten layer 222 with a decrease in the flow rate of the nitrogen-and hydrogen-containing gas, and that the nitrogen-and hydrogen-containing gas remaining on the surface of the titanium nitride layer 210 decreases with a decrease in the flow rate of the nitrogen-and hydrogen-containing gas.
For another example, as shown in fig. 4B, the abscissa in fig. 4B is the first temperature, and the ordinate is the thickness of the tungsten metal layer remaining after the tungsten metal layer of a set thickness is grown and is polished for a fixed time, wherein the flow rate of the nitrogen-and-hydrogen-containing gas is set to 5slm, and as can be seen from fig. 4B, in the case of the same growth thickness and the same polishing time, the thickness of the remaining tungsten metal layer increases with the increase of the first temperature, that is, the chemical mechanical polishing rate of the tungsten layer 222 decreases with the increase of the first temperature, and the polishing becomes more difficult, which means that the density of the tungsten layer 222 increases with the increase of the first temperature, the particles of the tungsten layer 222 increase, and it is further proved that the nitrogen-and-hydrogen-containing gas remaining on the surface of the titanium nitride layer 210 decreases with the increase of the first temperature.
For another example, as shown in fig. 4C, the abscissa in fig. 4C is the second temperature, and the ordinate is the thickness of the tungsten metal layer remaining after the tungsten metal layer of the set thickness is grown and is polished for a fixed time, and it can be seen from fig. 4C that, in the case of the same growth thickness and the same polishing time, the thickness of the remaining tungsten metal layer increases with the increase of the second temperature, that is, the chemical mechanical polishing rate of the tungsten layer 222 decreases with the increase of the second temperature, and the tungsten layer 222 is more difficult to polish, which means that the density of the tungsten layer 222 increases, the particles of the tungsten layer 222 increase, and it is further proved that the nitrogen and hydrogen containing gas remaining on the surface of the titanium nitride layer 210 decrease with the increase of the second temperature.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, many modifications and adaptations can be made without departing from the principle of the present invention, and such modifications and adaptations should also be considered as the scope of the present invention.
Claims (15)
1. A preparation method of a semiconductor structure, wherein the semiconductor structure comprises a titanium nitride layer and a metal layer arranged on the surface of the titanium nitride layer, and the preparation method comprises the following steps: and before the metal layer is formed on the surface of the titanium nitride layer, performing primary pretreatment on the titanium nitride layer by adopting nitrogen and hydrogen gas.
2. The method of claim 1, wherein the step of pretreating the titanium nitride layer with nitrogen and hydrogen comprises:
introducing the nitrogen-containing and hydrogen-containing gas at a set flow rate, and keeping the gas at a first temperature for a set time;
and reducing the temperature to a second temperature within a set time.
3. The method of claim 2, wherein the set flow rate is 1 to 10slm.
4. The method of claim 2, wherein the first temperature is 500-800 degrees Celsius.
5. The method of claim 2, wherein the second temperature is 200-500 degrees Celsius.
6. The method of claim 2, wherein the first temperature is higher than the second temperature.
7. The method according to claim 2, wherein the set flow rate has a trend opposite to that of the first temperature.
8. The method according to claim 2, wherein the set flow rate has a trend opposite to that of the second temperature.
9. The method according to claim 2, wherein the trend of the first temperature is the same as the trend of the second temperature.
10. The method according to claim 2, wherein the set flow rate has a trend opposite to that of the first temperature and the second temperature, and the trend of the first temperature is the same as that of the second temperature.
11. The method of claim 1, wherein the nitrogen and hydrogen containing gas is ammonia.
12. The method of claim 1, wherein the metal layer is a tungsten metal layer.
13. The method of claim 12, wherein the step of forming the tungsten metal layer comprises:
after the step of carrying out primary pretreatment on the titanium nitride layer at a preset temperature by adopting nitrogen and hydrogen containing gas, carrying out secondary pretreatment on the titanium nitride layer by adopting borane and tungsten containing gas, and forming a tungsten nucleation layer on the surface of the titanium nitride;
and forming a tungsten layer on the tungsten nucleation layer by using tungsten-containing gas and reducing gas as reaction gases.
14. The method of claim 13, wherein the step of forming a tungsten layer on the tungsten nucleation layer is followed by: and etching back the tungsten layer to form the semiconductor structure.
15. The method of claim 1, wherein the titanium nitride layer contains chloride ion impurities, and the nitrogen and hydrogen containing gas is capable of removing the chloride ion impurities during the first pretreatment.
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