A deposition process for a metal titanium layer

Abstract

The application discloses a deposition process of a metal titanium layer, comprising the following steps: placing a substrate in a reaction cavity of a semiconductor processing device, wherein the substrate has a plurality of openings defined by sidewalls and bottoms; a deposition step: introducing a titanium source precursor and a reducing gas into the reaction cavity, under the action of a radio frequency source, the titanium source precursor and the reducing gas are dissociated and chemically reacted to deposit a metal titanium layer on the sidewalls and the bottoms of the openings; an etching step: closing the radio frequency source and introducing an etching gas into the reaction cavity, the etching gas and the metal titanium layer are chemically reacted to reduce the thickness of the metal titanium layer; the deposition step and the etching step are repeated N times until the metal titanium layer reaches a set thickness and a set step coverage. Through the deposition step and the etching step repeated N times, the thickness and the step coverage of the metal titanium layer formed in a complex three-dimensional structure can meet the process requirements.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically to a deposition process for a metallic titanium layer. Background Technology

[0002] In the semiconductor manufacturing field, with the continuous advancement of technology nodes and the shrinking of device feature sizes, three-dimensional (3D) structures such as 3D NAND and 3D DRAM are gradually becoming mainstream. The realization of these structures places higher demands on metallization processes, especially in the filling capability of contact holes and interconnect holes. Among numerous metallization materials, Ti-based silicides (TiSi) are... x Titanium (where x represents the relative atomic ratio of Si) has been widely used in advanced semiconductor processes due to its advantages such as low electrical resistance, high thermal stability, self-cleaning impurities, and mature deposition technology. However, with the increasing complexity of device structures, traditional titanium (Ti) deposition processes, such as physical vapor deposition (PVD) and chemical vapor deposition (CVD), face significant challenges in three-dimensional structure filling. Among these challenges, achieving high step coverage has become an urgent problem to be solved in current titanium deposition processes.

[0003] Plasma-enhanced chemical vapor deposition (PECVD) is highly anticipated due to its advantages in principle, characteristics, and process flexibility, and has become an important direction for exploring solutions to related problems.

[0004] Existing PECVD deposition of Ti (PECVD-Ti) processes mainly consist of two stages:

[0005] Phase 1: Deposition Phase

[0006] During the deposition stage, titanium chloride (TiCl4) and hydrogen (H2) are injected into the reaction chamber simultaneously as reactant gases, along with argon (Ar) as the carrier gas. With the assistance of plasma, these gases undergo a chemical reaction to generate metallic titanium (Ti), which forms a thin film on the silicon wafer. This process involves the chemical reaction between TiCl4 and H2, as well as the participation of radicals and ions in the plasma, which jointly promote the formation of the titanium thin film.

[0007] Phase Two: Purge Phase

[0008] During the purging phase, the flow of TiCl4 and H2 reaction gases is stopped, and the plasma is shut off. Only Ar gas is flowed in to purge the wafer surface and remove residual reaction gases and byproducts.

[0009] The aforementioned conventional PECVD-Ti process can meet the film deposition requirements of semiconductor processes on planar structures, but its filling capability on three-dimensional structures is relatively limited. Furthermore, the corresponding step coverage is difficult to meet increasingly stringent industrial standards, such as... Figure 1 As shown, a titanium layer 2 covers the surface of the opening 1, and the thickness of the titanium layer 2 gradually decreases from top to bottom.

[0010] The main reasons for this problem include: chemical precursors such as TiCl4, H2 and their related free radicals and ions preferentially react in the top region of the structural pores, resulting in a thicker Ti film. However, the amount of chemical precursors reaching the bottom of the structural pores is reduced, resulting in a thinner Ti film and a lower step coverage.

[0011] To improve step coverage, the industry has attempted to address the issue of chemical precursors failing to reach the bottom of structures adequately by increasing precursor flow rate and plasma intensity. However, due to the inherent characteristics of PECVD, these adjustments have limited effectiveness in improving step coverage in PECVD-Ti processes, especially when structures become more complex (e.g., 3D NAND, 3D DRAM). Simply adjusting the chemical precursor flow rate is no longer sufficient to effectively solve the problem of low step coverage.

[0012] Therefore, there is an urgent need to develop new technologies to improve the filling capability and step coverage of PECVD-Ti processes in three-dimensional structures in order to meet the demand for high-performance metallization processes in the semiconductor manufacturing field. Summary of the Invention

[0013] The purpose of this invention is to provide an improved titanium metal layer deposition process to overcome the limitations of existing processes in filling three-dimensional structures, improve step coverage, and meet the increasingly complex semiconductor device manufacturing requirements.

[0014] To achieve the above objectives, the present invention provides a deposition process for a metallic titanium layer, comprising:

[0015] A substrate is placed in the reaction chamber of a semiconductor processing device, the substrate having several openings defined by sidewalls and bottom;

[0016] Deposition step: A titanium source precursor and a reducing gas are introduced into the reaction chamber. Under the action of a radio frequency source, the titanium source precursor and the reducing gas dissociate and undergo a chemical reaction, depositing a metallic titanium layer on the sidewall and bottom of the opening.

[0017] Etching step: Turn off the radio frequency source, introduce etching gas into the reaction chamber, and the etching gas reacts chemically with the titanium metal layer to reduce the thickness of the titanium metal layer;

[0018] The deposition and etching steps are repeated N times until the titanium layer reaches a set thickness and a set step coverage; where N is a positive integer.

[0019] Optionally, the etching step includes:

[0020] Etching process: Etching gas is introduced to perform the etching process, and

[0021] Purging action: Carrier gas is introduced to perform a purging action.

[0022] Optionally, the etching gas contains at least one of TiCl4, ClF3, NF3, WCl5, and MoCl5; the carrier gas contains at least one of Ar, He, Ne, and Kr.

[0023] Optionally, during the etching step, a carrier gas is continuously introduced to perform a purging action.

[0024] Optionally, in the etching step, etching gas is continuously introduced to perform the etching action.

[0025] Optionally, in the etching step, the etching gas is introduced in a multiple-interval manner.

[0026] Optionally, in the etching step, the etching gas is pressurized before being pumped into the reaction chamber.

[0027] Optionally, in the etching step, the flow rate and / or pressure of the etching gas are controlled by a pulse signal.

[0028] Optionally, the titanium source precursor comprises TiCl4; the reducing gas comprises a hydrogen-containing reducing gas.

[0029] Optionally, the reducing gas contains H2, and the etching gas contains TiCl4.

[0030] Optionally, a carrier gas is continuously introduced during the deposition step, the carrier gas containing at least one of Ar, He, Ne, and Kr.

[0031] Optionally, the switching of the radio frequency source can be controlled by a pulse signal.

[0032] Optionally, the deposition process temperature is 300℃~600℃.

[0033] Optionally, when the deposition process temperature is 300℃~400℃, after the titanium metal layer meets the process requirements, the substrate is further annealed to form a titanium silicide layer at the interface between the titanium metal layer and the substrate.

[0034] Optionally, the annealing temperature is 500℃~900℃.

[0035] Optionally, the substrate is a memory chip, the memory chip includes the opening, the sidewalls and bottom of the opening are made of silicon material, and the titanium metal layer reacts with the silicon material in contact with it to form a titanium silicide layer on the sidewalls and bottom of the opening.

[0036] Optionally, the substrate is a memory chip, the memory chip includes a lateral opening, the substrate of the sidewall of the lateral opening includes silicon oxide or silicon nitride, the substrate at the bottom of the lateral opening includes silicon material, and the titanium metal layer reacts with the silicon material in contact with it to form a titanium silicide layer at the bottom of the lateral opening; wherein the silicon material includes silicon or a silicon-germanium alloy.

[0037] Optionally, the substrate is a logic chip, the logic chip includes the opening, the substrate at the bottom of the opening includes silicon material, and the titanium metal layer reacts with the silicon material in contact with it to form a titanium silicide layer at the bottom of the opening.

[0038] Optionally, after the titanium metal layer reaches a set thickness and a set step coverage, nitrogen source gas is introduced into the reaction chamber to form a titanium nitride layer on the surface of the titanium metal layer.

[0039] Optionally, the nitrogen source gas includes NH3 and H2.

[0040] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0041] In the deposition step of this invention, the radio frequency (RF) source is turned on. Under the action of plasma, the titanium source precursor can react with the reducing gas at a relatively low process temperature, which can quickly form a metallic titanium layer on the surface of the opening. The thickness of the metallic titanium layer gradually decreases from the top to the bottom of the opening. In the etching step, the RF source is turned off, and the etching gas reacts chemically with the metallic titanium layer, causing the metallic titanium layer to thin. The degree of thinning gradually decreases from the top to the bottom of the opening, improving the step coverage of the metallic titanium layer. Through multiple cycles of deposition and etching steps of this invention, the thickness and step coverage of the metallic titanium layer formed in complex three-dimensional structures can meet the process requirements.

[0042] Furthermore, this invention selects TiCl4 as the titanium source precursor when the radio frequency source is turned on and as the etching gas when the radio frequency source is turned off. By controlling the switch of the radio frequency source, the deposition step and the etching step can be switched. The method is simple and does not require equipment improvement or the addition of new equipment. Moreover, no new impurities are introduced during the etching process. Attached Figure Description

[0043] Figure 1 This is a schematic cross-sectional view of a titanium metal layer deposited in an open structure using the PECVD-Ti process.

[0044] Figure 2 This is a schematic diagram of a process for depositing a metallic titanium layer according to the present invention.

[0045] Figure 3 This is a schematic cross-sectional view of the titanium layer formed during the deposition process of a titanium layer according to the present invention.

[0046] Figure 4 This is a schematic cross-sectional view of a partial structure of a 3D DRAM device with an opening structure having several lateral openings.

[0047] Figure 5 This is a schematic diagram of the process in Example 1, where a represents the deposition step and b represents the etching step.

[0048] Figure 6 This is a schematic diagram of the process in Example 2, where a represents the deposition step and b represents the etching step.

[0049] Figure 7 This is a schematic diagram of the process in Example 3.

[0050] Figure 8 This is a schematic diagram of the state of a 3D DRAM device with a lateral opening structure before and after processing according to the present invention, wherein a represents before processing, b represents after the deposition step, and c represents after the etching step. Detailed Implementation

[0051] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0053] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0054] The “active particles” mentioned in this article refer to plasma formed by dissociation from a radio frequency source, which includes particles such as free radicals, excited-state atoms, ions, or ionic groups.

[0055] The term "step coverage" as used in this article refers to the degree to which a titanium layer, deposited on a substrate with a stepped structure, covers various surfaces of the step (including the vertical sidewalls and bottom of the opening). It is an indicator used to measure whether the deposited titanium layer can completely and uniformly cover all parts of a substrate with varying elevations (similar to a step). The step coverage can be calculated as the ratio of the thickness of the titanium layer formed on the sidewalls of the opening structure to the thickness of the titanium layer formed on the surface of the substrate (the top of the opening).

[0056] As described in the background section, simply adjusting the conditions of the PECVD-Ti process itself, such as increasing the precursor flow rate or increasing the plasma intensity, cannot effectively improve the step coverage problem of three-dimensional structure filling, especially for through-hole structures with high aspect ratios.

[0057] Therefore, this invention adds a chemical etching step to the PECVD-Ti deposition process. In this chemical etching step, the etching rate gradually decreases from the top to the bottom of the opening, etching more of the thicker titanium layer deposited at the top of the opening, thereby reducing the difference in critical dimensions between the top and bottom of the opening. This process is repeated multiple times between the deposition and etching steps until the step coverage of the opening and the thickness of the formed titanium layer both meet the process objectives. The following is combined with... Figures 2-7 Please provide an explanation.

[0058] like Figure 2 As shown, the present invention provides a deposition process for a metallic titanium layer, comprising:

[0059] Step S1: A substrate is placed in the reaction chamber of a semiconductor processing device, the substrate having a plurality of openings defined by sidewalls and bottom.

[0060] The substrate can be a silicon substrate or a compound semiconductor substrate. In semiconductor manufacturing, silicon substrates are often processed with open structures. For example, when used to fabricate integrated circuits, numerous tiny openings, such as contact holes and interconnect holes, are created on the silicon wafer through processes such as photolithography and etching. These openings can be cylindrical holes perpendicular to the silicon wafer surface, with diameters as small as tens of nanometers or even smaller, mainly used for subsequent metal filling to achieve electrical connections between different device layers. Especially when forming 3D NAND or 3D DRAM devices, these openings have high aspect ratios, for example, greater than 5:1 or even greater than 20:1. Such high aspect ratio structures are particularly challenging to fill with metal; for example, achieving good step coverage is difficult. The method of the present invention is applicable to the filling of titanium metal with various aspect ratio opening structures, and has more advantages in filling high aspect ratio opening structures, but is not limited to high aspect ratio opening structures.

[0061] Step S2, Deposition Step: A titanium source precursor and a reducing gas are introduced into the reaction chamber. Under the action of a radio frequency source, the titanium source precursor and the reducing gas dissociate and undergo a chemical reaction, depositing a metallic titanium layer on the sidewall and bottom of the opening.

[0062] The reducing gas comprises a hydrogen-containing reducing gas. For example, the reducing gas contains H2, and the titanium source precursor contains TiCl4. Under the action of a radio frequency source, TiCl4 and H2 dissociate to form highly active Ti-containing plasma and H-containing plasma, respectively, and the chemical reaction barrier is lowered. Therefore, at a lower reaction temperature, the Ti-containing plasma can be reduced to form metallic Ti, which is deposited on the opening surface. Because the plasma contains a large number of free radicals and ions, these active particles can enhance the chemical reaction activity during deposition. When depositing metallic titanium on surfaces with complex three-dimensional structures, the presence of plasma allows the reactive gas to react more fully in some microscopic regions with high aspect ratios, promoting the formation of metallic titanium films and helping to improve the filling effect of metallic titanium within the three-dimensional structure.

[0063] In some embodiments, a carrier gas is continuously introduced during the deposition step. The carrier gas primarily serves to dilute process gases (e.g., reactant gases such as titanium source precursors and reducing gases), stabilize the gas flow environment in the chamber, provide physical cleaning, and protect the titanium film from oxidation. The carrier gas can be at least one of helium (He), neon (Ne), argon (Ar), or krypton (Kr). For example, argon can be selected. Argon has a larger atomic mass, resulting in greater momentum under the same flow rate and pressure conditions. This allows argon to more effectively remove residual reactant gases and byproducts from the wafer surface through its physical impact, achieving a better purging effect. Furthermore, the larger atomic mass of argon is more conducive to promoting the dissociation of titanium source precursors and reducing gases. Moreover, the diffusion rate of argon is relatively moderate; it diffuses too quickly, failing to remain on the wafer surface long enough for effective protection and cleaning, nor is it too slow, making it difficult to form a uniform and stable gas flow environment within the reaction chamber.

[0064] In some embodiments, the step coverage of the deposited titanium layer in the deposition step can be improved by adjusting the flow rate and relative ratio of the titanium source precursor, reducing gas, and carrier gas, or by adjusting the power of the radio frequency source. However, even by adjusting the flow rate of the reactants and increasing the power of the radio frequency source, for titanium filling with an opening structure having a high aspect ratio, there are still defects such as insufficient uniformity and low step coverage. Figure 3 As shown in Figure a, the thickest titanium layer 2 is formed on the field surface of opening 1, and the thickness of the titanium layer 2 gradually decreases from top to bottom on the sidewall of the opening. Therefore, the present invention modifies the morphology of the titanium layer by adding an etching step.

[0065] Step S3, etching step: turn off the radio frequency source, introduce etching gas into the reaction chamber, and the etching gas reacts chemically with the titanium metal layer to reduce the thickness of the titanium metal layer.

[0066] The etching gas can provide halogen atoms, which can undergo a redox reaction with metallic Ti to form gaseous titanium halide, thereby reducing the thickness of the metallic titanium layer.

[0067] In some embodiments, the etching gas is selected from halides, such as ClF3, NF3, etc.

[0068] In other embodiments, the etching gas may be selected from metal halides, such as at least one of TiCl4, WCl5, and MoCl5.

[0069] In the etching step, the radio frequency source is turned off, and chemical etching is performed. Chemical etching, as opposed to plasma etching, refers to etching through a chemical reaction without the participation of plasma. During chemical etching, the halogen atoms of the etching gas undergo a redox reaction with metallic titanium, forming gaseous titanium halide products, which are extracted from the reaction chamber, causing the metallic titanium layer to gradually thin. Compared to the top of the opening, gas molecules have more difficulty entering the bottom of the opening, so the thinning chemical reaction occurs more frequently at the top of the opening. Therefore, in the etching step, the thickness gradually decreases from the top to the bottom of the opening, resulting in a gradual reduction in the difference between the critical dimensions at the top and bottom of the opening, thus improving the step coverage. Figure 3 As shown in b.

[0070] To avoid introducing impurities, this invention innovatively uses TiCl4 as the etching gas. TiCl4 reacts chemically with metallic Ti, as shown in the following equation:

[0071]

[0072] During the etching stage, the radio frequency (RF) source was turned off. The titanium layer formed within the opening reacted chemically with TiCl4 to form gaseous compounds such as TiCl3 and TiCl2, which were carried away by the purge gas. This facilitated the further rightward progression of reaction I, leading to the gradual thinning of the titanium layer. Turning off the RF source during the etching step avoids the risk that the dissociation of TiCl4, TiCl3, and TiCl2 by the RF electric field would cause reaction I to proceed to the left, generating metallic Ti, which would be detrimental to etching thinning.

[0073] The etching step includes an etching action and a purging action. The etching action is performed by introducing an etching gas, and the purging action is performed by introducing a carrier gas. The carrier gas can be at least one of helium (He), neon (Ne), argon (Ar), krypton (Kr), etc.

[0074] In some embodiments, during the etching step, etching gas is continuously introduced to perform the etching action, while carrier gas is continuously introduced to perform the purging action. See [link to relevant documentation]. Figure 5 b. In other words, during the etching step, purging is performed simultaneously with etching, which can immediately remove the generated gaseous titanium halide product from the reaction chamber, thus facilitating the reversible reaction of Formula I to proceed to the right.

[0075] In some embodiments, during the etching step, the etching gas is introduced at multiple intervals while a carrier gas is continuously introduced to perform the purging action. That is, the purging action continues indefinitely, while after a period of etching, the etching gas supply is stopped, and only the purging action is performed. This facilitates the reversible reaction of Formula I proceeding to the right, resulting in thinning of the titanium layer. In some embodiments, the etching gas can be pressurized using a pressure tank. After pressurization, the etching gas is pumped into the reaction chamber at a certain pressure, allowing it to enter the open structure more quickly and in greater quantities, further promoting the rightward progression of the reaction of Formula I and facilitating etching. The etching method is atomic layer deposition (ALD) (see...). Figure 6 (b) This is achieved through a process of "pumping in etching gas → purging → pumping in etching gas → purging." During purging, the etched byproducts are rapidly removed, and then etching gas is continuously introduced to promote etching in the positive direction. The etching gas flow rate can be controlled from 1 sccm to 300 sccm, preferably 1 to 100 sccm; the pressure is 0.1 to 10 Torr, preferably 0.1 to 5 Torr; and the purging gas supply time is 0 to 5 seconds. The above flow rate, pressure, and time parameters are for illustrative purposes only and are not intended to limit the process. The requirements for these parameters will vary depending on the deposited structure. By adjusting the flow rate and pressure of the etching gas, the etching depth and / or the amount of etching at different depths can be controlled.

[0076] Step S4: The deposition and etching steps are repeated N times until the titanium metal layer reaches the set thickness and the set step coverage; where N is a positive integer.

[0077] This invention does not limit the number of cycles. In extreme cases, N can be 1, meaning that only one deposition and etching step is needed to form a titanium layer that meets the set process target. The process target requires that the thickness of the titanium layer formed in the opening reaches the required thickness (i.e., the set thickness), and that the step coverage meets the required process target (i.e., the set step coverage). For example, if the process requires a titanium layer thickness of 10 nm and a step coverage of 80% in the opening, and during the cycle, if the step coverage of the titanium layer reaches 80% but its thickness is less than 10 nm, the deposition step needs to be continued, and if necessary, the etching step can also be continued until both the thickness and step coverage meet the requirements.

[0078] Different processes have different requirements for step coverage, such as 80%, 85%, 90%, 95%, or 99%. The method of this invention can achieve this through multiple cycles of deposition and etching steps, and therefore does not limit the step coverage. The thickness of the titanium layer can be in the nanometer range, for example, 5nm to 10nm. This invention does not limit the thickness of the titanium layer formed in the opening structure. In some embodiments, the titanium layer formed using the method of this invention can completely fill the opening structure.

[0079] It should be noted that the method of the present invention is more advantageous for processes requiring higher step coverage and / or thinner titanium layers, especially for filling processes of high aspect ratio three-dimensional devices. This is because existing PECVD-Ti methods struggle to achieve step coverage exceeding 90% in high aspect ratio three-dimensional filling, particularly when the capping layer thickness is required to be thin (e.g., below the nanometer level).

[0080] The method of this invention forms a titanium layer with a gradually decreasing thickness from top to bottom at the top (field surface), sidewalls, and bottom of the opening through a deposition step. Then, it switches to an etching step, where the thickness of the titanium layer removed (thinning thickness) gradually decreases from top to bottom, starting from the top of the opening. This invention allows each etching step to achieve the step coverage required by the process target before proceeding with the deposition step. This process is repeated multiple times until both the thickness of the titanium layer and the step coverage meet the target requirements. This invention also allows each etching step to improve the step coverage only, without requiring the step coverage after each etching step to meet the process target. In the final etching step, the step coverage only needs to meet the process target requirement. Figure 3 As shown in c.

[0081] In some embodiments, TiCl4 serves not only as a titanium source precursor but also as an etching gas, with hydrogen and argon gas being introduced simultaneously. The deposition or etching step is switched by turning the RF source on or off. When the RF source is on, the deposition step is performed, and TiCl4 is reduced to metallic titanium under the action of the RF source. At this time, hydrogen gas acts as a co-reactant, providing reducing hydrogen-containing active particles. When the RF source is off, the etching step is performed, and TiCl4, as the etching gas, reacts chemically with the metallic titanium to generate gaseous TiCl3 or TiCl2, which is then purged out of the chamber. At this time, hydrogen and argon gas are used together as purge gases. This process design can be performed directly on existing deposition equipment without equipment modification, and is simple to operate without introducing impurities. Furthermore, in some embodiments, the switching of the RF source can be controlled by a pulse signal, see [link to relevant documentation]. Figure 7The sheath collapse phase during pulse shutdown allows charged particles (ions) to penetrate deep into the structure, while uncharged radicals can freely diffuse to the lateral vias of the memory chip during this time, enhancing the deposition effect. The duty cycle of the pulse signal is 10%–90%, preferably 20%–50%.

[0082] The deposition process temperature can be between 300°C and 600°C. In some embodiments, the deposition process temperature is between 500°C and 600°C, at which temperature metallic Ti can react with the Si in contact with it to form titanium silicide (TiSi). x Here, x represents the relative atomic proportion of Si (e.g., x can be 2), and high-temperature annealing is not required. The conversion of metallic Ti into titanium silicide not only improves electrical performance but also enhances the thermal and chemical stability of the device.

[0083] In some embodiments, when the deposition process temperature is 300°C to 400°C, after the formed titanium metal layer reaches a set thickness and a set step coverage, the substrate can be annealed to form a titanium silicide layer at the interface between the titanium metal layer and the substrate. The annealing temperature is 500°C to 900°C.

[0084] In some embodiments, the substrate includes a memory chip, the memory chip includes the opening, the sidewalls and bottom of the opening are made of silicon material, and the titanium layer reacts with the silicon material in contact with it to form a titanium silicide layer on the sidewalls and bottom of the opening to reduce contact resistance.

[0085] In some embodiments, the substrate includes a logic chip, the logic chip includes the opening, the sidewall substrate of the opening is silicon oxide, the substrate at the bottom of the opening includes silicon material, and the titanium layer is selectively formed at the bottom of the opening as a titanium silicide layer to reduce contact resistance.

[0086] like Figure 4The diagram shows a partial cross-sectional view of a 3D DRAM device with several lateral openings. Conductive metal needs to be filled into the openings 1 to serve as electrodes for capacitors. The sidewalls of the openings 1 are made of Si, and the bottom of the openings 1 is made of SiGe. A titanium layer 2 can be formed in the openings 1 using the method of this invention. To further reduce contact resistance, the process temperature can be set not lower than 500°C to form titanium silicide at the contact interface between the titanium layer 2 and the openings 1. Finally, conductive metal is filled into the openings 1 to lead out the capacitors. In some embodiments, when the process temperature is lower than 500°C, a high-temperature annealing step can be added after forming the titanium layer to form the titanium silicide layer. The high-temperature annealing temperature can be between 500°C and 900°C.

[0087] like Figure 8 The diagram shows the state of a 3D DRAM device with a multi-lateral opening structure before and after the deposition and etching steps of this invention are performed, depositing a titanium layer in the opening structure of the device. Figure 8 Figure 'a' is a partial cross-sectional schematic diagram of a 3D DRAM device including an opening structure. The opening structure includes several lateral openings 81. The sidewalls 811 of the lateral openings 81 are made of silicon oxide (SiO2) or silicon nitride (SiN), and the bottom 812 of the lateral openings 81 is made of Si or SiGe. A metallic titanium layer 82 is deposited on the surface of the opening structure using the method of this invention. For example, TiCl4 and H2 are introduced. Under the action of a radio frequency source, TiCl4 and H2 dissociate to form highly active Ti-containing plasma and H-containing plasma, respectively. The Ti-containing plasma can be reduced by the H-containing plasma to form metallic Ti, which is deposited on the opening surface. The process temperature is set not lower than 500°C to form a titanium silicide (TiSi) layer at the contact interface between the metallic titanium layer 82 and the bottom 812 of the lateral openings 81. X )83, since the material of the sidewall 811 of the lateral opening 81 does not easily react with the titanium layer 82 at its contact interface, that is, the titanium layer 82 formed on the surface of the sidewall 811 is retained, and the cross-sectional schematic diagram of the formed device is shown in Figure 83. Figure 8 As shown in b. Then, the etching step of the present invention is adopted, that is, the radio frequency source is turned off, and an etching gas (e.g., TiCl4) is introduced into the reaction chamber. The etching gas reacts chemically with the titanium metal layer 82 covering the sidewall 811 of the side opening 81, thereby etching away the titanium metal layer 82. Since the titanium silicide layer 83 formed on the bottom 812 of the side opening 81 is not easily reacted with the etching gas and is retained, the cross-sectional schematic diagram of the final device is shown in Figure 1. Figure 8As shown in c. In other embodiments, when the deposition process temperature is below 500°C, the titanium metal layer formed at the bottom 812 of the lateral opening 81 is difficult to react with the silicon material it contacts to form titanium silicide. Therefore, a high-temperature annealing step can be added after forming the titanium metal layer 82 to form a titanium silicide layer 83 at the bottom 812 of the lateral opening 81, before performing the etching step to form... Figure 8 The device structure shown in c. The high-temperature annealing temperature can be 500℃~900℃.

[0088] In some embodiments, after the titanium layer reaches a set thickness and a set step coverage, to prevent oxidation of the surface titanium layer, a nitrogen source gas can be introduced into the reaction chamber to form a titanium nitride layer as a protective layer on the surface of the titanium layer. The nitrogen source gas includes NH3 and H2. In subsequent processes, a conductive metal, such as tungsten or copper, can be filled into the opening.

[0089] Example 1

[0090] like Figure 5 Figure a shows a schematic diagram of the deposition steps in Example 1. Ar gas is continuously introduced into the reaction chamber containing the substrate as a carrier gas at a flow rate of 2400 sccm, and the reaction chamber temperature is 400°C. After the gas flow environment in the reaction chamber stabilizes, TiCl4 and H2 are introduced as co-reactants. Simultaneously, the radio frequency source is turned on to ignite and apply plasma to deposit a titanium layer on the open surface of the substrate. The flow rate of TiCl4 is 25 sccm, and the flow rate of H2 is 3000 sccm. After 10 seconds, the introduction of TiCl4 and H2 is stopped, and the radio frequency source is turned off.

[0091] like Figure 5 Figure b shows a schematic diagram of the etching steps in Example 1. Ar gas is continuously introduced into the reaction chamber at a flow rate of 2400 sccm. After the gas flow environment in the reaction chamber stabilizes, TiCl4 is introduced at a flow rate of 50 sccm. After 15 seconds, the TiCl4 introduction is stopped, and Ar gas purging continues.

[0092] The deposition and etching steps were repeated for 5 cycles. After thickness testing, the thickness of the formed titanium metal layer was 5 nm, and the step coverage of the titanium metal layer was 85%, which met the thickness and step coverage requirements set in the process.

[0093] Example 2

[0094] like Figure 6Figure a shows a schematic diagram of the deposition steps in Example 2. Ar gas is continuously introduced into the reaction chamber as a carrier gas at a flow rate of 2400 sccm, and the reaction chamber temperature is 600°C. After the gas flow environment in the reaction chamber stabilizes, TiCl4 and H2 are introduced as co-reactants. Simultaneously, the radio frequency source is turned on to ignite and apply plasma to deposit a titanium layer on the surface of the open structure. The flow rate of TiCl4 is 25 sccm, and the flow rate of H2 is 3000 sccm. After 30 seconds, the introduction of TiCl4 and H2 is stopped, and the radio frequency source is turned off.

[0095] like Figure 6 Figure b shows a schematic diagram of the etching steps in Example 2. Ar gas is continuously introduced into the reaction chamber at a flow rate of 2400 sccm. After the gas flow environment in the reaction chamber stabilizes, TiCl4 is introduced at a flow rate of 50 sccm. After 10 seconds, the TiCl4 introduction is stopped, and Ar gas purging is maintained. TiCl4 is introduced again, stopped after 10 seconds, and Ar gas purging is maintained. This etching and purging process is repeated 5 times.

[0096] The deposition and etching steps were repeated for three cycles. After thickness testing, the resulting titanium layer had a thickness of 10 nm and a step coverage rate of 90%, which met the thickness and step coverage requirements set in the process.

[0097] Example 3

[0098] like Figure 7 The diagram illustrates a process for deposition and etching steps controlled by a pulse signal. Ar gas is continuously introduced into the reaction chamber as a carrier gas at a flow rate of 2400 sccm, and the reaction chamber temperature is 500℃. After the gas flow environment in the reaction chamber stabilizes, TiCl4 and H2 are introduced as co-reactants. The flow rate of TiCl4 is 25 sccm, and the flow rate of H2 is 3000 sccm. The switching of the radio frequency (RF) source is controlled by a pulse signal, with a duty cycle of 50%. When the RF source is turned on, plasma is applied. TiCl4, as a titanium source precursor, and H2 dissociate to form Ti-containing plasma and H-containing plasma, respectively. The Ti-containing plasma and the H-containing plasma undergo a redox reaction, depositing a metallic titanium layer on the surface of the open structure. When the RF source is turned off, TiCl4, as an etching gas, reacts chemically with the metallic titanium layer formed in the opening to form TiCl3 and / or TiCl2, which are then discharged from the reaction chamber under Ar and H2 purging, reducing the thickness of the metallic titanium layer.

[0099] After 100 seconds, a thickness test showed that the formed titanium layer was 8 nm thick, and the step coverage of the titanium layer was 95%, which met the thickness and step coverage requirements set in the process.

[0100] In summary, this invention deposits a titanium layer in an open structure of a substrate through cyclic deposition and etching steps: In the deposition step, an RF source is turned on, and under the action of plasma, a titanium layer can be formed relatively quickly on the surface of the open structure, with the thickness of the titanium layer gradually decreasing from the top to the bottom of the open structure; In the etching step, the RF source is turned off, and the etching gas reacts chemically with the titanium layer, gradually thinning the titanium layer from the top to the bottom of the open structure, thus improving the step coverage of the titanium layer. Through multiple cycles of this invention, the thickness and step coverage of the titanium layer formed in complex three-dimensional structures can both meet the process requirements.

[0101] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A deposition process for a metallic titanium layer, characterized in that, Include: A substrate is placed in the reaction chamber of a semiconductor processing device, the substrate having several openings defined by sidewalls and bottom; Deposition step: A titanium source precursor and a reducing gas are introduced into the reaction chamber. Under the action of a radio frequency source, the titanium source precursor and the reducing gas dissociate and undergo a chemical reaction, depositing a metallic titanium layer on the sidewall and bottom of the opening. Etching step: Turn off the radio frequency source, introduce etching gas into the reaction chamber, and the etching gas reacts chemically with the titanium metal layer to reduce the thickness of the titanium metal layer; The deposition and etching steps are repeated N times until the titanium layer reaches a set thickness and a set step coverage; where N is a positive integer.

2. The deposition process of the metallic titanium layer as described in claim 1, characterized in that, The etching step includes: Etching process: Etching gas is introduced to perform the etching process, and Purging action: Carrier gas is introduced to perform a purging action.

3. The deposition process of the metallic titanium layer as described in claim 2, characterized in that, The etching gas contains at least one of TiCl4, ClF3, NF3, WCl5, and MoCl5; the carrier gas contains at least one of Ar, He, Ne, and Kr.

4. The deposition process of the metallic titanium layer as described in claim 2, characterized in that, During the etching step, carrier gas is continuously introduced to perform a purging action.

5. The deposition process of the metallic titanium layer as described in claim 4, characterized in that, In the etching step, etching gas is continuously introduced to perform the etching action.

6. The deposition process of the metallic titanium layer as described in claim 4, characterized in that, In the etching step, the etching gas is introduced in a multiple-interval manner.

7. The deposition process of the metallic titanium layer as described in claim 6, characterized in that, In the etching step, the etching gas is pressurized before being pumped into the reaction chamber.

8. The deposition process of the metallic titanium layer as described in claim 7, characterized in that, In the etching step, the flow rate and / or pressure of the etching gas are controlled by a pulse signal.

9. The deposition process of the metallic titanium layer as described in any one of claims 1-8, characterized in that, The titanium source precursor contains TiCl4; the reducing gas contains a hydrogen-containing reducing gas.

10. The deposition process of the metallic titanium layer as described in claim 9, characterized in that, The reducing gas contains H2, and the etching gas contains TiCl4.

11. The deposition process of the metallic titanium layer as described in claim 9, characterized in that, During the deposition step, a carrier gas is continuously introduced, the carrier gas containing at least one of Ar, He, Ne, and Kr.

12. The deposition process of the metallic titanium layer as described in claim 11, characterized in that, The switching of the radio frequency source is controlled by a pulse signal.

13. The deposition process of the metallic titanium layer as described in claim 1, characterized in that, The deposition process is carried out at a temperature of 300℃ to 600℃.

14. The deposition process of the metallic titanium layer as described in claim 13, characterized in that, When the deposition process temperature is 300℃~400℃, after the titanium metal layer meets the process requirements, the substrate is also annealed to form a titanium silicide layer at the interface between the titanium metal layer and the substrate.

15. The deposition process of the metallic titanium layer as described in claim 14, characterized in that, The annealing temperature is 500℃~900℃.

16. The deposition process of the metallic titanium layer according to any one of claims 13 to 15, characterized in that, The substrate is a memory chip, the memory chip includes the opening, the sidewalls and bottom of the opening are made of silicon material, the titanium metal layer reacts with the silicon material in contact with it to form a titanium silicide layer on the sidewalls and bottom of the opening.

17. The deposition process of the metallic titanium layer according to any one of claims 13 to 15, characterized in that, The substrate is a memory chip, the memory chip includes a lateral opening, the substrate of the sidewall of the lateral opening includes silicon oxide or silicon nitride, the substrate at the bottom of the lateral opening includes silicon material, the titanium metal layer reacts with the silicon material in contact with it to form a titanium silicide layer at the bottom of the lateral opening; wherein, the silicon material includes silicon or silicon-germanium alloy.

18. The deposition process of the metallic titanium layer according to any one of claims 13-15, characterized in that, The substrate is a logic chip, the logic chip includes the opening, the substrate at the bottom of the opening contains silicon material, and the titanium metal layer reacts with the silicon material in contact with it to form a titanium silicide layer at the bottom of the opening.

19. The deposition process of the metallic titanium layer as described in claim 1, characterized in that, After the titanium metal layer reaches a set thickness and a set step coverage, nitrogen source gas is introduced into the reaction chamber to form a titanium nitride layer on the surface of the titanium metal layer.

20. The deposition process of the metallic titanium layer as described in claim 19, characterized in that, The nitrogen source gas includes NH3 and H2.

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