Method of manufacturing a semiconductor structure

Abstract

The embodiment of the present disclosure provides a preparation method of a semiconductor structure, the semiconductor structure comprising a titanium nitride layer and a metal layer arranged on the surface of the titanium nitride layer, the preparation method comprising: before forming the metal layer on the surface of the titanium nitride layer, performing first pretreatment on the titanium nitride layer by using a nitrogen and hydrogen containing gas. In the first pretreatment step, the nitrogen and hydrogen containing gas reacts with residual chlorine ion impurities in the titanium nitride layer, so that the chlorine ion impurities are removed, the resistivity of the titanium nitride layer is reduced, and the conductivity of the semiconductor structure is improved. Meanwhile, the nitrogen and hydrogen containing gas can also form a nitrogen-rich layer at the bottom of the titanium nitride layer, thereby further improving the threshold voltage of a transistor formed by using the semiconductor structure.

Description

Technical Field

[0001] The present disclosure relates to the field of integrated circuits, and in particular to a method for preparing a semiconductor structure. Background Art

[0002] Dynamic Random Access Memory (DRAM) is a semiconductor device commonly used in electronic devices such as computers. It consists of multiple memory cells, each of which typically includes a transistor and a capacitor. The gate electrode of the transistor is electrically connected to a word line, the source electrode is electrically connected to a bit line, and the drain electrode is electrically connected to the capacitor. The word line voltage on the word line can control the on and off of the transistor, thereby allowing data stored in the capacitor to be read or written through the bit line.

[0003] In DRAM processes, the gate of a buried word line (BWL) typically consists of an oxide / titanium nitride (TiN) / metal layer. Titanium nitride, with its unique optical properties, has a wide range of applications in optics and optoelectronics. For example, during the metal filling process, a titanium nitride layer is used as an adhesion layer for the metal layer. However, the performance of the titanium nitride layer does not meet the requirements. Summary of the Invention

[0004] The embodiments of the present disclosure provide a method for preparing a semiconductor structure, which can reduce the resistivity of a titanium nitride layer and improve the conductive performance of the semiconductor structure.

[0005] In one embodiment, the semiconductor structure includes a titanium nitride layer and a metal layer disposed on the surface of the titanium nitride layer. The preparation method includes: before forming the metal layer on the surface of the titanium nitride layer, performing a first pretreatment on the titanium nitride layer using nitrogen and hydrogen-containing gases.

[0006] In one embodiment, the method of performing a first pretreatment on the titanium nitride layer with nitrogen and hydrogen-containing gases includes: introducing the nitrogen and hydrogen-containing gases at a set flow rate and maintaining the gas at a first temperature for a set time; and cooling the gas to a second temperature within the set time.

[0007] In one embodiment, the set flow rate is 1 to 10 slm.

[0008] In one embodiment, the first temperature is 500-800 degrees Celsius.

[0009] In one embodiment, the second temperature is 200-500 degrees Celsius.

[0010] In one embodiment, the first temperature is higher than the second temperature.

[0011] In one embodiment, a changing trend of the set flow rate is opposite to a changing trend of the first temperature.

[0012] In one embodiment, a changing trend of the set flow rate is opposite to a changing trend of the second temperature.

[0013] In one embodiment, the changing trend of the first temperature is the same as the changing trend of the second temperature.

[0014] In one embodiment, a changing trend of the set flow rate is opposite to a changing trend of the first temperature and the second temperature, and a changing trend of the first temperature is the same as a changing trend of the second temperature.

[0015] In one embodiment, the nitrogen and hydrogen-containing gas is ammonia.

[0016] In one embodiment, the metal layer is a tungsten metal layer.

[0017] In one embodiment, the method for forming the tungsten metal layer includes: after a step of pre-treating the titanium nitride layer for the first time at a preset temperature using nitrogen and hydrogen-containing gases, pre-treating the titanium nitride layer for the second time using borane and tungsten-containing gas to form a tungsten nucleation layer on the titanium nitride surface; and forming a tungsten layer on the tungsten nucleation layer using tungsten-containing gas and reducing gas as reaction gases.

[0018] In one embodiment, after the step of forming a tungsten layer on the tungsten nucleation layer, the method further includes: etching back the tungsten layer to form the semiconductor structure.

[0019] In one embodiment, the titanium nitride layer contains chloride ions, and during the first pretreatment process, the nitrogen and hydrogen-containing gas can remove the chloride ions.

[0020] In the preparation method provided by the embodiment of the present disclosure, in the first pretreatment step, the nitrogen and hydrogen-containing gas reacts with the residual chloride ion impurities in the titanium nitride layer, thereby removing the chloride ion impurities, reducing the resistivity of the titanium nitride layer, and improving the conductivity of the semiconductor structure; at the same time, the nitrogen and hydrogen-containing gas can also form a nitrogen-rich layer at the bottom of the titanium nitride layer, further improving the threshold voltage of the transistor formed using the semiconductor structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the steps of the preparation method provided by one embodiment of the present disclosure;

[0022] Figures 2A to 2E is a schematic flow chart of a preparation method provided in one embodiment of the present disclosure;

[0023] Figure 3 is a schematic diagram of a method for forming a metal layer provided by an embodiment of the present disclosure;

[0024] Figure 4A This is a graph showing the relationship between the flow rate of nitrogen and hydrogen gases and the thickness of the tungsten metal layer;

[0025] Figure 4B is a graph showing the relationship between the first temperature and the thickness of the tungsten metal layer;

[0026] Figure 4C is a graph showing the relationship between the second temperature and the thickness of the tungsten metal layer. DETAILED DESCRIPTION

[0027] The following describes in detail the specific embodiment of the method for preparing the semiconductor structure provided by the present disclosure in conjunction with the accompanying drawings. The semiconductor structure described in this specific embodiment can be, but is not limited to, a gate structure of a DRAM.

[0028] An embodiment of the present disclosure provides a method for preparing a semiconductor structure, wherein the semiconductor structure includes a titanium nitride layer and a metal layer arranged on the surface of the titanium nitride layer. The preparation method includes: before forming the metal layer on the surface of the titanium nitride layer, using nitrogen and hydrogen-containing gases to perform a first pretreatment on the titanium nitride layer.

[0029] In some embodiments, the titanium nitride layer contains chloride ions, meaning that a significant amount of chloride ion impurities remain within the titanium nitride layer. During the first pretreatment step, the nitrogen- and hydrogen-containing gas reacts with the chloride ion impurities, removing or reducing the chloride ion impurities, thereby lowering the resistivity of the titanium nitride layer and improving the conductivity of the semiconductor structure. Furthermore, the nitrogen- and hydrogen-containing gas may form a nitrogen-rich layer at the bottom of the titanium nitride layer, further improving the threshold voltage of transistors formed using the semiconductor structure.

[0030] In some embodiments, the nitrogen- and hydrogen-containing gas includes, but is not limited to, ammonia (NH3), a mixture of ammonia (NH3) and an inert gas, or an organic compound containing an amino group. The inert gas includes, but is not limited to, nitrogen, argon, and the like. The organic compound containing an amino group includes, but is not limited to, methylamine, dimethylamine, and trimethylamine. The ammonia or amino group can react with chloride ions to form hydrogen chloride, thereby removing residual chloride ion impurities in the titanium nitride layer.

[0031] As an example, an embodiment of the present disclosure provides a method for preparing the semiconductor structure.

[0032] Figure 1 This is a schematic diagram of the steps of the preparation method provided by an embodiment of the present disclosure, please refer to Figure 1 The preparation method includes the following steps: step S10, providing a substrate, a titanium nitride layer is provided on the surface of the substrate; step S11, using nitrogen and hydrogen-containing gases to perform a first pretreatment on the titanium nitride layer; step S12, forming a metal layer on the surface of the titanium nitride layer.

[0033] Figures 2A to 2E It is a schematic flow chart of a preparation method provided in one embodiment of the present disclosure.

[0034] See also Figure 1 and Figure 2A In step S10, a substrate 200 is provided, and a titanium nitride layer 210 is disposed on the surface of the substrate 200. The titanium nitride layer 210 can effectively prevent ions in the precursor, such as boron ions (B), from diffusing downward into the substrate 200 during the subsequent process of forming a metal layer, and improves the adhesion of the subsequently formed metal layer.

[0035] In some embodiments, the base 200 includes 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 .

[0036] The substrate 201 includes, but is not limited to, a silicon substrate, a germanium (Ge) substrate, a silicon germanium (SiGe) substrate, an SOI substrate, or a GOI (Germanium-on-Insulator) substrate; the substrate 201 may also be a substrate comprising other elemental semiconductors or compound semiconductors, such as gallium arsenide, indium phosphide, or silicon carbide; the substrate 201 may also be a stacked structure, such as a silicon / silicon germanium stack; in addition, the substrate 201 may be an ion-doped substrate, which 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, which may also include other device structures, such as transistor structures, metal wiring structures, etc., but they are not shown because they are not related to this application.

[0037] The insulating layer 202 includes, but is not limited to, an oxide layer or an oxynitride layer, such as a silicon oxide layer or a silicon oxynitride layer. 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 is a single-layer structure. In other embodiments, the insulating layer 202 may also be a multi-layer composite structure.

[0038] In this embodiment, a shallow trench 203 is formed in the substrate 201, the insulating layer 202 covers the sidewalls of the shallow trench 203, the titanium nitride layer 210 covers the surface of the insulating layer 202, and the titanium nitride layer 210 does not completely fill the shallow trench 230. 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 formed directly on the upper surface of the substrate 201, and the titanium nitride layer 210 covers the surface of the insulating layer 202.

[0039] As an example, an embodiment of the present disclosure provides a method for forming a titanium nitride layer 210 on the surface of the substrate 200. An atomic layer deposition (ALD) process is typically used to deposit the titanium nitride layer 210 on the insulating layer 202. Specifically, assuming that the titanium nitride layer 210 thin film initially starts with -NH2, that is, the surface of the substrate 200 has -NH2 groups, TiCl4 is introduced into the reaction chamber. Based on the following chemical reaction, the -H in the -NH2 groups on the surface of the substrate 200 is replaced by -TiCl3:

[0040] TiCl4+-NH2→-TiNCl2+2HCl.

[0041] The reaction chamber is purged with an inert gas, such as nitrogen or argon, to carry out the by-product HCl and the unreacted TiCl 4 from the reaction chamber.

[0042] After purging with inert gas, NH3 is introduced into the reaction chamber. Based on the following chemical reaction, -Cl on the film surface is replaced by -NH2:

[0043] NH3+-TiCl x →-TiNH 3-x +xHCl, where x is less than or equal to 3.

[0044] The reaction chamber is purged with an inert gas, such as nitrogen or argon, to carry out the by-product HCl and the unreacted NH3 from the reaction chamber.

[0045] In the above reaction process, HCl is produced as a by-product; HCl, as a corrosive gas, reacts with -NH2 on the surface of the titanium nitride film to generate NH3, and -Cl, as a substitute, is always present during the growth process of the titanium nitride film, resulting in a high chloride ion impurity content in the formed titanium nitride layer 210, which affects the resistivity of the titanium nitride layer 210.

[0046] After forming the titanium nitride layer 210 , a planarization process is further performed, such as chemical mechanical polishing, to form the titanium nitride layer 210 with a flat surface, thereby providing a good process plane for the subsequent formation of the metal layer 220 .

[0047] See also Figure 1 and Figure 2B In step S11, before forming the metal layer 220, the titanium nitride layer 210 is subjected to a first pretreatment using a nitrogen and hydrogen-containing gas. For example, in some embodiments, the titanium nitride layer 210 is subjected to the first pretreatment using ammonia (NH3). The ammonia (NH3) reacts with residual chloride ions (Cl) in the titanium nitride layer 210 to remove at least a portion of the chloride ions (Cl) in the titanium nitride layer 210, thereby increasing the resistivity of the titanium nitride layer 210.

[0048] In some embodiments, the first pretreatment of the titanium nitride layer 210 using nitrogen and hydrogen-containing gas includes the following steps:

[0049] The nitrogen- and hydrogen-containing gases are introduced at a set flow rate and maintained at a first temperature for a set time. In some embodiments, the nitrogen- and hydrogen-containing gases may be the same reactant gases used in forming the titanium nitride layer. In other embodiments, the nitrogen- and hydrogen-containing gases may be different from the reactant gases used in forming the titanium nitride layer.

[0050] The temperature is lowered to a second temperature within a set time. The first temperature is higher than the second temperature. In this step, the flow of nitrogen and hydrogen gases is stopped, and only the temperature is lowered to remove residual nitrogen and hydrogen gases, thereby preventing them from affecting the subsequent formation of the metal layer.

[0051] See also Figure 1 and Figure 2C In step S12, after the titanium nitride layer 210 is pretreated for the first time with nitrogen and hydrogen-containing gases, 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 downward into the substrate 200, and improves the adhesion of the formed metal layer.

[0052] Since the titanium nitride layer 210 is treated with nitrogen and hydrogen-containing gases before forming the metal layer, the chloride ion impurities in the titanium nitride layer 210 are removed or reduced, thereby reducing the resistivity of the titanium nitride layer 210. In addition, the first pretreatment includes a step of cooling to a second temperature within a set time, which can reduce or remove the nitrogen and hydrogen-containing gases remaining on the surface of the titanium nitride layer 210, thereby avoiding the influence of the residual nitrogen and hydrogen-containing gases on the electrical properties of the metal layer.

[0053] In some embodiments, the metal layer 220 includes but is not limited to a tungsten metal layer.

[0054] As an example, an embodiment of the present disclosure provides a method for forming the metal layer 220, wherein the metal layer 220 is a tungsten metal layer. The method includes the following steps:

[0055] See also Figure 3 The titanium nitride layer 210 is pretreated for the second time using borane (B2H6) and a tungsten-containing gas to form a tungsten nucleation layer 221 on the surface of the titanium nitride layer 210. The tungsten nucleation layer 221 serves as a growth point for the tungsten layer 222. This step is the nucleation stage of metallic tungsten.

[0056] The tungsten-containing gas includes but is not limited to at least one of tungsten hexachloride (WCl6), tungsten hexafluoride (WF6) and tungsten hydroxyl. The tungsten-containing gas is the main reaction gas for tungsten chemical vapor deposition, and the borane is an auxiliary gas.

[0057] In this embodiment, borane (B2H6) reduces tungsten hexafluoride (WF6) to form a thin tungsten nucleation layer 221 on the surface of the titanium nitride layer 210. In subsequent processes, the tungsten nucleation layer 221 serves as a growth point for the tungsten layer 222. Specifically, see Figure 3 In step (a), borane (B2H6) is first introduced into the reaction chamber to fully wet the surface of the titanium nitride layer 210, and borane (B2H6) is decomposed into boron (B + ), adsorbed on the surface of the titanium nitride layer 210; see Figure 3 In (b), tungsten hexafluoride (WF6) is introduced, and tungsten (W) is displaced and adsorbed on the surface of the titanium nitride layer 210 to form a tungsten nucleation layer 221.

[0058] See also Figure 3 As shown in (c), (d), and (e), a tungsten-containing gas and a reducing gas are used as reaction gases to form a tungsten layer 222 on the tungsten nucleation layer 221. In this step, the reaction gases use the tungsten nucleation layer 221 as a growth point to form the tungsten layer 222. The tungsten nucleation layer 221 and the tungsten layer 222 together serve as the metal layer 220.

[0059] The tungsten-containing gas includes, but is not limited to, at least one of tungsten hexachloride (WCl6), tungsten hexafluoride (WF6), and tungsten hydroxyl. This tungsten-containing gas is the primary reaction gas for tungsten chemical vapor deposition. The reducing gas includes, but is not limited to, at least one of borane (B2H6), silane (SiH4), and hydrogen (H2). In this embodiment, the tungsten-containing gas is tungsten hexafluoride (WF6), and the reducing gas is silane (SiH4).

[0060] This step is the bulk growth stage of metallic tungsten. The process parameters of chemical vapor deposition (such as pressure, gas flow rate, etc.) in the bulk growth stage are different from those in the nucleation stage. Compared with the nucleation stage, the deposition rate, deposition time, and deposition amount of the bulk growth stage are higher. The tungsten deposited in the bulk growth stage accounts for approximately 90% of the total tungsten deposition amount in the same chemical vapor deposition process. The deposition temperature used in the chemical vapor deposition should avoid affecting the structures already formed on the semiconductor structure. In some embodiments of the present disclosure, the process temperature used in the bulk growth stage is set at, for example, 350°C to 550°C.

[0061] After the step of forming a tungsten layer on the tungsten nucleation layer, the method includes etching back the tungsten layer to form the semiconductor structure.

[0062] In some embodiments, the tungsten layer 222 covers the surface of the titanium nitride layer 210 and fills the shallow trench 203. In other embodiments, the tungsten layer 222 only covers the surface of the titanium nitride layer 210 and does not fill the shallow trench 203, that is, the tungsten layer 222 only fills the lower part of the shallow trench 203. In this embodiment, the tungsten layer 222 covers the surface of the titanium nitride layer 210 and fills the shallow trench 203. Figure 2C In this embodiment, the tungsten layer also covers the upper surface of the insulating layer 202 .

[0063] 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 also included. Figure 2D The tungsten layer 222 is etched back to retain only the tungsten layer 222 located below the shallow trench 203, thereby forming the semiconductor structure. The etch-back process includes but is not limited to a wet etching process.

[0064] In this embodiment, before performing the etch-back process, a chemical mechanical polishing process is further used 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 the etch-back process.

[0065] In this embodiment, the tungsten nucleation layer 221 is also removed during the etch-back process. After the etch-back process, 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 etch-back process. After the etch-back process, the top surface of the titanium nitride layer 210 is flush with the top surface of the tungsten layer 222.

[0066] See also Figure 2EA filling layer 230 is formed to cover the surface of the tungsten layer 222, forming 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 damage during subsequent semiconductor processes.

[0067] The inventors discovered that in the semiconductor structure provided by the embodiments of the present disclosure, the resistance of the metal layer 220 formed on the titanium nitride layer 210 is relatively large and cannot meet the device requirements. After further in-depth research by the inventors, the reason for this phenomenon is that after the titanium nitride layer 210 is first pretreated with nitrogen and hydrogen gases, nitrogen and hydrogen gases still remain on the surface of the titanium nitride layer 210. The residual nitrogen and hydrogen gases react with borane, causing the borane to be unable to completely decompose, resulting in smaller particles in the formed tungsten nucleation layer 221, and thus smaller particles in the formed tungsten layer 222, and increased resistance. For example, when the titanium nitride layer 210 is first pretreated with ammonia (NH3), ammonia (NH3) remains on the surface of the titanium nitride layer 210. The residual ammonia (NH3) reacts with borane (B2H6) to form B3H6N3. B3H6N3 affects the action of borane (B2H6), resulting in smaller particles in the tungsten nucleation layer 221.

[0068] In view of this, in one embodiment of the present disclosure, during the first pretreatment process, the set flow rate, first temperature and second temperature of the nitrogen- and hydrogen-containing gases are adjusted to reduce the residual nitrogen- and hydrogen-containing gases on the surface of the titanium nitride layer 210, thereby preventing the residual nitrogen- and hydrogen-containing gases from affecting the effect of borane. At the same time, there is no need to add other additional process steps, and the method is simple and easy to implement.

[0069] The inventors found that in the first pretreatment, the smaller the flow rate of the nitrogen and hydrogen-containing gas, the larger the particles of the tungsten layer 222. Therefore, in some embodiments of the present disclosure, in the first pretreatment, the set flow rate of the nitrogen and hydrogen-containing gas is set to 1 to 10 slm. On the one hand, it can remove chloride ion impurities in the titanium nitride layer 210, and on the other hand, it can also reduce the amount of nitrogen and hydrogen-containing gas remaining on the surface of the titanium nitride layer 210.

[0070] The inventors also found that in the first pretreatment, the higher the first temperature, the larger the particles in the tungsten layer 222. Therefore, in some embodiments of the present disclosure, in the first pretreatment, the first temperature is set to 500-800 degrees Celsius. On the one hand, it can remove chloride ion impurities in the titanium nitride layer 210, and on the other hand, it uses high temperature to volatilize the residual nitrogen and hydrogen gases to reduce the amount of nitrogen and hydrogen gases remaining on the surface of the titanium nitride layer 210, and also avoid the temperature being too high to affect other structures in the semiconductor structure.

[0071] The inventors also found that in the first pretreatment, the higher the second temperature, the larger the particles of the tungsten layer 222. Therefore, in some embodiments of the present disclosure, in the first pretreatment, the second temperature is set to 200-500 degrees Celsius. On the one hand, high temperature is used to volatilize the residual nitrogen and hydrogen gases to reduce the amount of nitrogen and hydrogen gases remaining on the surface of the titanium nitride layer 210. On the other hand, it also avoids the temperature being too high and affecting other structures in the semiconductor structure, and also prepares for the subsequent formation of the metal layer 220.

[0072] When setting the set flow rate, first temperature, and second temperature of the nitrogen-containing and hydrogen-containing gases, follow the following principles:

[0073] In some embodiments, the changing trend of the set flow rate is opposite to the changing trend of the first temperature. That is, in order to simultaneously remove chloride ion impurities in the titanium nitride layer 210 and reduce the amount of nitrogen- and hydrogen-containing gases remaining on the surface of the titanium nitride layer 210, the set flow rates of the nitrogen- and hydrogen-containing gases cannot be increased and the first temperature cannot be lowered, or the set flow rates of the nitrogen- and hydrogen-containing gases cannot be lowered and the first temperature cannot be raised at the same time. For example, in some embodiments, the set flow rates of the nitrogen- and hydrogen-containing gases can be increased and the first temperature can be lowered; or the set flow rates of the nitrogen- and hydrogen-containing gases can be lowered and the first temperature can be raised, so as to simultaneously remove chloride ion impurities in the titanium nitride layer 210 and reduce the amount of nitrogen- and hydrogen-containing gases remaining on the surface of the titanium nitride layer 210.

[0074] In some embodiments, the changing trend of the set flow rate is opposite to the changing trend of the second temperature. That is, in order to simultaneously remove chloride ion impurities in the titanium nitride layer 210 and reduce the amount of nitrogen and hydrogen-containing gases remaining on the surface of the titanium nitride layer 210, the set flow rates of the nitrogen and hydrogen-containing gases cannot be increased and the second temperature cannot be lowered, or the set flow rates of the nitrogen and hydrogen-containing gases cannot be lowered and the second temperature cannot be raised at the same time. For example, in some embodiments, the set flow rates of the nitrogen and hydrogen-containing gases can be increased and the second temperature can be lowered, or the set flow rates of the nitrogen and hydrogen-containing gases can be lowered and the second temperature can be raised, so as to simultaneously remove chloride ion impurities in the titanium nitride layer 210 and reduce the amount of nitrogen and hydrogen-containing gases remaining on the surface of the titanium nitride layer 210.

[0075] In some embodiments, the changing trend of the first temperature is the same as the changing trend of the second temperature. That is, in order to minimize the amount of nitrogen-containing and hydrogen-containing gases remaining on the surface of the titanium nitride layer 210, the first temperature and the second temperature may be increased simultaneously, or the first temperature may be maintained constant and the second temperature increased, or the second temperature may be maintained constant and the first temperature increased. For example, in some embodiments, while the set flow rates of the nitrogen-containing and hydrogen-containing gases remain unchanged, the first temperature or the second temperature may be increased, or the first temperature and the second temperature may be increased simultaneously to minimize the amount of nitrogen-containing and hydrogen-containing gases remaining on the surface of the titanium nitride layer 210.

[0076] In some embodiments, the changing trend of the set flow rate is opposite to the changing trend of the first temperature and the second temperature, and the changing trend of the first temperature is the same as the changing trend of the second temperature. That is, in order to take into account both the removal of chloride ion impurities in the titanium nitride layer 210 and the reduction of the amount of nitrogen-containing and hydrogen-containing gases 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 gases and reduce the first temperature and the second temperature, or simultaneously reduce the set flow rate of the nitrogen-containing and hydrogen-containing gases and increase the first temperature and the second temperature. For example, in some embodiments, the set flow rate of the nitrogen-containing and hydrogen-containing gases can be increased and the first temperature and the second temperature can be reduced; or the set flow rate of the nitrogen-containing and hydrogen-containing gases can be reduced and the first temperature and the second temperature can be increased; so as to take into account both the removal of chloride ion impurities in the titanium nitride layer 210 and the reduction of the amount of nitrogen-containing and hydrogen-containing gases remaining on the surface of the titanium nitride layer 210.

[0077] In some embodiments, the holding time at the first temperature and the set time for cooling to the second temperature can be controlled. For example, the holding time at the first temperature can be reduced to reduce the residual amount of nitrogen- and hydrogen-containing gases, and the set time for cooling to the second temperature can be increased to increase the volatilization amount of nitrogen- and hydrogen-containing gases, thereby reducing the residual nitrogen- and hydrogen-containing gases on the surface of the titanium nitride layer 210. In the embodiment of the present disclosure, since the titanium nitride layer 210 is pretreated for the first time with nitrogen- and hydrogen-containing gases, and the flow rate of the nitrogen- and hydrogen-containing gases and the treatment temperature (first temperature and second temperature) are controlled, the particles of the formed tungsten layer 222 are larger, which greatly reduces the resistivity of the tungsten layer 222.

[0078] The inventors also discovered that using nitrogen and hydrogen-containing gases to perform a first pretreatment on the titanium nitride layer 210 and controlling the flow rate and treatment temperature (first temperature and second temperature) of the nitrogen and hydrogen-containing gases can affect the rate of chemical mechanical polishing in the step of removing part of the tungsten nucleation layer 221 and the tungsten layer 222.

[0079] For example, Figure 4A As shown, in Figure 4AThe horizontal axis is the flow rate of nitrogen and hydrogen gas, and the vertical axis is the thickness of the remaining tungsten metal layer after the tungsten metal layer of set thickness is grown and then thinned for a fixed time. Figure 4A It can be seen that under the conditions of the same growth thickness and the same polishing time, as the flow rate of the nitrogen and hydrogen-containing gases decreases, the thickness of the remaining tungsten metal layer increases, that is, as the flow rate of the nitrogen and hydrogen-containing gases decreases, the chemical mechanical polishing rate of the tungsten layer 222 becomes smaller and the polishing becomes more difficult. This indicates that as the flow rate of the nitrogen and hydrogen-containing gases decreases, the density of the tungsten layer 222 increases and the particles of the tungsten layer 222 become larger. This further proves that as the flow rate of the nitrogen and hydrogen-containing gases decreases, less nitrogen and hydrogen-containing gases remain on the surface of the titanium nitride layer 210.

[0080] For example, Figure 4B As shown, in Figure 4B The horizontal axis is the first temperature, and the vertical axis is the thickness of the remaining tungsten metal layer after the tungsten metal layer of the set thickness is grown and then thinned by grinding for a fixed time. The flow rate of the nitrogen and hydrogen gas is set to 5slm. Figure 4B It can be seen that under the conditions of the same growth thickness and the same grinding time, as the first temperature increases, the thickness of the remaining tungsten metal layer increases, that is, as the first temperature increases, the chemical mechanical grinding rate of the tungsten layer 222 decreases and the grinding becomes more difficult. This indicates that as the first temperature increases, the density of the tungsten layer 222 increases and the particles of the tungsten layer 222 become larger. This further proves that as the first temperature increases, the amount of nitrogen and hydrogen gases remaining on the surface of the titanium nitride layer 210 decreases.

[0081] For example, Figure 4C As shown, in Figure 4C The horizontal axis is the second temperature, and the vertical axis is the thickness of the remaining tungsten metal layer after the tungsten metal layer of the set thickness is grown and then thinned for a fixed time. Figure 4C It can be seen that under the conditions of the same growth thickness and the same grinding time, as the second temperature increases, the thickness of the remaining tungsten metal layer increases, that is, as the second temperature increases, the chemical mechanical grinding rate of the tungsten layer 222 decreases and the grinding becomes more difficult. This indicates that as the second temperature increases, the density of the tungsten layer 222 increases and the particles of the tungsten layer 222 become larger. This further proves that as the second temperature increases, the nitrogen and hydrogen gases remaining on the surface of the titanium nitride layer 210 decrease.

[0082] The above description is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a semiconductor structure, characterized in that: The semiconductor structure includes a titanium nitride layer and a metal layer disposed on the surface of the titanium nitride layer. The preparation method includes: before forming the metal layer on the surface of the titanium nitride layer, performing a first pretreatment on the titanium nitride layer using a nitrogen and hydrogen-containing gas; The method of performing a first pretreatment on the titanium nitride layer using nitrogen and hydrogen-containing gas includes: introducing the nitrogen and hydrogen-containing gases at a set flow rate and maintaining the temperature at a first temperature for a set time; Cool down to the second temperature within the set time; The change trend of the set flow rate is opposite to the change trend of the first temperature.

2. The method for preparing a semiconductor structure according to claim 1, wherein: The set flow rate is 1 to 10 slm.

3. The method for preparing a semiconductor structure according to claim 1, wherein: The first temperature is 500-800 degrees Celsius.

4. The method for preparing a semiconductor structure according to claim 1, wherein: The second temperature is 200-500 degrees Celsius.

5. The method for preparing a semiconductor structure according to claim 1, wherein: The first temperature is higher than the second temperature.

6. The method for preparing a semiconductor structure according to claim 1, wherein: The change trend of the set flow rate is opposite to the change trend of the second temperature.

7. The method for preparing a semiconductor structure according to claim 1, wherein: The changing trend of the first temperature is the same as the changing trend of the second temperature.

8. The method for preparing a semiconductor structure according to claim 1, wherein: The change trend of the set flow rate is opposite to the change trends of the first temperature and the second temperature, and the change trend of the first temperature is the same as the change trend of the second temperature.

9. The method for preparing a semiconductor structure according to claim 1, wherein: The nitrogen and hydrogen-containing gas is ammonia.

10. The method for preparing a semiconductor structure according to claim 1, wherein: The metal layer is a tungsten metal layer.

11. The method for preparing a semiconductor structure according to claim 10, wherein: The method of forming the tungsten metal layer includes: After the titanium nitride layer is pretreated for the first time using nitrogen and hydrogen-containing gases at a preset temperature, the titanium nitride layer is pretreated for the second time using borane and tungsten-containing gases to form a tungsten nucleation layer on the titanium nitride surface; A tungsten layer is formed on the tungsten nucleation layer by using a tungsten-containing gas and a reducing gas as reaction gases.

12. The method for preparing a semiconductor structure according to claim 11, wherein: After the step of forming a tungsten layer on the tungsten nucleation layer, the method includes etching back the tungsten layer to form the semiconductor structure.

13. The method for preparing a semiconductor structure according to claim 1, wherein: The titanium nitride layer contains chloride ion impurities, and during the first pretreatment process, the nitrogen and hydrogen-containing gas can remove the chloride ion impurities.

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