Formation method of semiconductor structure

Abstract

The invention provides a method for forming a semiconductor structure, which comprises the following steps of: providing a substrate with a copper layer, and placing the substrate in a reaction cavity; controlling the flow of the silicon source gas at a first preset value; and introducing the silicon source gas with the flow rate of the first preset value and the nitrogen source gas with the flow rate of the second preset value into the reaction cavity so as to form a silicon nitride layer covering the copper layer through a plasma enhanced chemical vapor deposition process.

Description

Technical Field

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

[0002] As the integration level increases, the line width and spacing of metal interconnects in semiconductor structures continue to decrease, and the resistance and parasitic capacitance of metal interconnects increase accordingly, which will have a negative impact on the performance of semiconductor structures. Therefore, low dielectric constant materials are needed as materials for metal interconnects to reduce parasitic effects and increase the signal transmission rate of metal interconnects. In this demand context, copper with low dielectric constant and resistivity has become the preferred material for metal interconnects. However, copper easily diffuses in dielectric materials and causes leakage, so how to improve the reliability of copper wires has become an urgent problem to be solved. Summary of the invention

[0003] In view of this, an embodiment of the present disclosure provides a method for forming a semiconductor structure to solve at least one problem existing in the prior art.

[0004] To achieve the above objectives, the technical solution of the embodiment of the present disclosure is implemented as follows:

[0005] The present disclosure provides a method for forming a semiconductor structure, comprising:

[0006] Providing a substrate having a copper layer, and placing the substrate in a reaction chamber;

[0007] Controlling the flow rate of the silicon source gas to a first preset value;

[0008] The silicon source gas having a flow rate of the first preset value and the nitrogen source gas having a flow rate of the second preset value are introduced into the reaction chamber to form a silicon nitride layer covering the copper layer through a plasma enhanced chemical vapor deposition process.

[0009] In an optional implementation, controlling the flow rate of the silicon source gas to a first preset value includes:

[0010] Closing a first gas valve between a silicon source gas inlet and the reaction chamber, and opening a second gas valve between the silicon source gas inlet and an exhaust chamber to pass the silicon source gas to the exhaust chamber, until a first flow meter located between the silicon source gas inlet and the reaction chamber shows that the flow rate of the silicon source gas reaches the first preset value and is maintained for 5 to 10 seconds;

[0011] The step of introducing the silicon source gas having a flow rate of the first preset value into the reaction chamber comprises:

[0012] The second gas valve is closed, and the first gas valve is opened to allow the silicon source gas with a flow rate of the first preset value to flow into the reaction chamber.

[0013] In an optional embodiment, a second flow meter is included between the first flow meter and the reaction chamber; and the step of introducing the silicon source gas into the reaction chamber comprises:

[0014] The flow rate of the silicon source gas is monitored by the second flow meter.

[0015] In an optional embodiment, the first preset value ranges from 250 sccm to 300 sccm;

[0016] In an optional embodiment, before the nitrogen source gas having a flow rate of a second preset value is introduced into the reaction chamber, the silicon source gas is in contact with the copper layer for a time ranging from 2 seconds to 4 seconds.

[0017] In an optional implementation, the second preset value is 125 sccm.

[0018] In an optional embodiment, before forming the silicon nitride layer covering the copper layer, the resistance of the copper layer is greater than 0.76 ohms; after forming the silicon nitride layer covering the copper layer, the resistance of the copper layer is less than 0.76 ohms.

[0019] In an optional embodiment, when the silicon nitride layer covering the copper layer is formed by a plasma enhanced chemical vapor deposition process, the dissociation energy of the silicon source gas is in a range of 55 watts to 65 watts, and the dissociation time is in a range of 3 seconds to 4 seconds.

[0020] In an optional implementation, the method for forming the semiconductor structure further includes:

[0021] Before the silicon source gas having a flow rate of the first preset value is introduced into the reaction chamber, the nitrogen source gas is introduced into the reaction chamber and a radio frequency power source is turned on to pretreat the copper layer.

[0022] In an optional implementation, the method for forming the semiconductor structure further includes:

[0023] A barrier layer is formed on the silicon nitride layer; the material of the barrier layer includes silicon carbonitride.

[0024] In the technical solution provided in the present disclosure, when a silicon nitride layer covering a copper layer is formed by a plasma enhanced chemical vapor deposition (PECVD) process, the flow rate of a silicon source gas is first precisely controlled at a first preset value, and the contact time between the silicon source gas and the copper layer is controlled so that the copper layer and the silicon source gas are fully in contact and a greater bonding force is generated between the formed silicon nitride layer and the copper layer, while avoiding excessive resistance of the copper layer due to excessive silicon source gas and fluctuation of resistance of the copper layer due to unstable flow rate of the silicon source gas, thereby reducing the loss of signal transmission rate in the copper layer and improving the yield of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of a process for forming a semiconductor structure provided by an embodiment of the present disclosure;

[0026] Figure 2 A process flow chart of forming a silicon nitride layer covering a copper layer provided in an embodiment of the present disclosure;

[0027] Figure 3 A schematic diagram of the structure of a PECVD machine provided in an embodiment of the present disclosure;

[0028] Figure 4 Schematic diagram of the flow direction of silicon source gas in the PECVD machine provided in the embodiment of the present disclosure Figure 1 ;

[0029] Figure 5 Schematic diagram of the flow direction of silicon source gas in the PECVD machine provided in the embodiment of the present disclosure Figure 2 ;

[0030] Figure 6 A schematic diagram showing how the resistance of the copper layer changes with the flow rate of silane provided in an embodiment of the present disclosure;

[0031] Figure 7 A schematic diagram of bonding conditions at the interface between a copper layer and a silicon nitride layer provided in an embodiment of the present disclosure;

[0032] Figure 8 A schematic diagram of the structure of a semiconductor structure provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0033] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the specific embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0034] In the following description, a large number of specific details are given to provide a more thorough understanding of the present disclosure. However, it is obvious to those skilled in the art that the present disclosure can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present disclosure, some technical features known in the art are not described; that is, all features of actual embodiments are not described here, and well-known functions and structures are not described in detail.

[0035] In the drawings, like reference numerals refer to like elements throughout.

[0036] It should be understood that spatial relationship terms such as "under", "below", "below", "under", "above", "above", etc., may be used here for convenience of description to describe the relationship between an element or feature shown in the figure and other elements or features. It should be understood that in addition to the orientation shown in the figure, the spatial relationship terms are intended to also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is turned over, then the elements or features described as "under other elements" or "under it" or "under it" will be oriented as "on" other elements or features. Therefore, the exemplary terms "under" and "under" may include both upper and lower orientations. The device can be oriented otherwise (rotated 90 degrees or other orientations) and the spatial description terms used herein are interpreted accordingly.

[0037] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be a limitation of the present disclosure. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0038] In order to further improve the integration of integrated circuits, the size of semiconductor structures continues to shrink, and the line width of metal interconnects and the spacing between metal interconnects in semiconductor structures continue to decrease. The resistance and parasitic capacitance of metal interconnects increase accordingly, which will have a negative impact on the performance of semiconductor structures. Therefore, low dielectric constant materials are needed as materials for metal interconnects to reduce the parasitic effects of metal interconnects and increase the signal transmission rate of metal interconnects. In this demand context, copper with low dielectric constant and resistivity has become the preferred material for metal interconnects.

[0039] In practical applications, copper is easy to diffuse in the dielectric layer and cause leakage, so it is necessary to form a barrier layer on the surface of the copper wire to prevent the diffusion of copper. In some embodiments, in order to increase the bonding force between the copper wire and the barrier layer, it is necessary to form a silicon nitride layer between the copper wire and the barrier layer as a bonding layer. However, during the formation of the bonding layer, defects are easily generated at the interface between the bonding layer and the copper wire, resulting in an increase in the resistance of the copper wire or instability, and as the width of the copper wire is further reduced, the defects on the interface will be amplified, resulting in a decrease in the signal transmission rate in the copper wire, and ultimately resulting in a decrease in the yield of the product.

[0040] Therefore, it is necessary to further improve the formation process of the bonding layer to reduce defects on the interface between the bonding layer and the copper wire and improve the performance of the copper wire. In this regard, the present disclosure proposes the following implementation methods.

[0041] The present invention provides a method for forming a semiconductor structure. Figure 1 is a schematic diagram of a method for forming a semiconductor structure, such as Figure 1 As shown, the method for forming a semiconductor structure includes the following steps:

[0042] S10: providing a substrate having a copper layer, and placing the substrate in a reaction chamber;

[0043] S20: controlling the flow rate of the silicon source gas to a first preset value;

[0044] S30: introducing the silicon source gas having a flow rate of the first preset value and the nitrogen source gas having a flow rate of the second preset value into the reaction chamber to form a silicon nitride layer covering the copper layer through a plasma enhanced chemical vapor deposition process.

[0045] In the embodiment of the present disclosure, a silicon nitride layer covering a copper layer is formed by PECVD, the flow rate of the silicon source gas is first controlled to a first preset value, and then the silicon source gas is introduced into the reaction chamber to contact the substrate in the reaction chamber, thereby controlling the interface properties of the copper layer.

[0046] In some embodiments, Figure 2 A process flow chart of forming a silicon nitride layer covering a copper layer provided in an embodiment of the present disclosure, Figure 3 A partial structural schematic diagram of a PECVD machine provided in an embodiment of the present disclosure, Figure 4 and Figure 5 The following is a schematic diagram of the flow of silicon source gas in the PECVD machine. Figures 1 to 5 The method for forming the semiconductor structure provided by the embodiment of the present disclosure is described in detail.

[0047] First, step S10 is performed to place the substrate having the copper layer 101 in the reaction chamber 201 .

[0048] In some embodiments, the base may include a substrate, a device layer, and a wiring layer sequentially stacked in a thickness direction of the copper layer 101 .

[0049] In some specific examples, the substrate can be a single semiconductor material substrate (for example, a silicon substrate, a germanium substrate, etc.), a compound semiconductor material substrate (for example, a germanium silicon substrate, etc.), or a silicon on insulator (SOI) substrate, a germanium on insulator (GeOI) substrate, etc.

[0050] In some specific examples, the device layer can include a memory array and / or peripheral circuits.

[0051] In some specific examples, the wiring layer may include multiple metal layers and conductive vias connecting the metal layers, and dielectric layers between the metal layers. The copper layer 101 in the embodiment of the present disclosure may be any metal layer or other conductive structure in the wiring layer.

[0052] It should be noted that the present disclosure does not limit the specific position of the copper layer 101 in the substrate. Figure 2 Other structures in the substrate are omitted.

[0053] In some embodiments, reference Figure 3 The PECVD machine includes a reaction chamber 201 and a gas pipeline for conveying silicon source gas. A first gas valve 205 is arranged between the silicon source gas inlet 202 and the reaction chamber 201, and a second gas valve 206 is arranged between the silicon source gas inlet 202 and the exhaust chamber 207. The specific process of executing step S20 may be: closing the first gas valve 205, and opening the second gas valve 206 to pass the silicon source gas to the exhaust chamber 207, until the first flowmeter 203 located between the silicon source gas inlet 202 and the reaction chamber 201 shows that the flow rate of the silicon source gas reaches a first preset value.

[0054] In the embodiment of the present disclosure, before the silicon source gas is introduced into the reaction chamber 201, the flow rate of the silicon source gas needs to be stabilized at a first preset value. Figure 4 As indicated by the arrows in FIG. 2 , at this stage, the silicon source gas enters the gas pipeline from the silicon source gas inlet 202 , flows through the first flow meter 203 and the second gas valve 206 , and is transported to the exhaust chamber 207 by the gas pump.

[0055] It is understandable that in the initial stage of passing the silicon source gas into the gas pipeline from the silicon source gas inlet 202, the fluctuation degree of the silicon source gas flow rate may be relatively large. Therefore, in this stage, the silicon source gas needs to be first introduced into the exhaust chamber 207 so that the silicon source gas flow rate reaches the first preset value and is maintained at the first preset value.

[0056] In some specific examples, when the first flow meter 203 indicates that the flow rate of the silicon source gas reaches the first preset value, it needs to be maintained for 5 to 10 seconds before the subsequent steps can be executed.

[0057] In some embodiments, in conjunction with reference Figure 2 Figure (b) and Figure 5 After the flow rate of the silicon source gas is stabilized at the first preset value, step S30 is performed, and the specific process may include: closing the second gas valve 206 and opening the first gas valve 205 to pass the silicon source gas with the flow rate of the first preset value into the reaction chamber 201. Figure 5 As indicated by the arrow in , at this stage, the silicon source gas enters the gas pipeline from the silicon source inlet 202, flows through the first flowmeter 203, the first gas valve 205, the second flowmeter 204, and then enters the reaction chamber 201 and contacts the copper layer 101 located in the reaction chamber 201.

[0058] In the embodiment of the present disclosure, the gas pipeline between the first flowmeter 203 and the reaction chamber 201 is long and includes a corner, which may cause a deviation between the actual flow rate of the silicon source gas entering the reaction chamber 201 and the flow rate displayed by the first flowmeter 203. Therefore, in order to accurately control the flow rate of the silicon source gas, a second flowmeter 204 is arranged between the first flowmeter 203 and the reaction chamber 201. The second flowmeter 204 is closer to the reaction chamber 201 than the first flowmeter 203. By monitoring the flow rate of the silicon source gas through the second flowmeter 204, the actual flow rate of the silicon source gas entering the reaction chamber 201 can be more accurately reflected.

[0059] In some specific examples, the first flow meter 203 and the second flow meter 204 can be mass flow controllers (MFCs), which can control the gas flow rate while displaying the gas flow rate, thereby further ensuring that the flow rate of the silicon source gas entering the reaction chamber 201 is stable at a first preset value.

[0060] In some specific examples, the second flow meter 204 can also be connected to a defect detection and classification system (FDC) to monitor the flow of the silicon source gas online in real time, and when the flow of the silicon source gas deviates from the first preset value, an early warning can be issued in time to improve the reliability of the process.

[0061] In the embodiment of the present disclosure, the silicon source gas is first passed to the exhaust chamber 207 to stabilize the flow rate of the silicon source gas at a first preset value before the silicon source gas is passed into the reaction chamber 201. The flow rate of the silicon source gas entering the reaction chamber 201 is monitored by a second flow meter 204 that is closer to the reaction chamber 201 to further improve the stability of the silicon source gas flow rate.

[0062] In some specific examples, the flow rate of the silicon source gas, ie, the first preset value, ranges from 250 sccm to 300 sccm.

[0063] It should be noted that in the embodiment of the present disclosure, the range of the first preset value is 250sccm to 300sccm, which does not mean that the flow rate of the silicon source gas can fluctuate within this range, but that the flow rate of the silicon source gas should be selected as a fixed flow value in the range, that is, the first preset value, and in the process of executing PECVD, the flow rate of the silicon source gas is stabilized at the first preset value. It can be understood that in the deposition reaction, improving the stability of the reaction gas flow rate is helpful to improve the uniformity of the film layer formed by the deposition reaction and the stability of the interface properties between the film layers.

[0064] In some specific examples, before the nitrogen source gas with a flow rate of the second preset value is introduced into the reaction chamber 201, the silicon source gas is in contact with the copper layer 101 for a time range of 2 seconds to 4 seconds. During this process, the silicon source gas can form a gas adsorption layer on the surface of the copper layer 101.

[0065] In the embodiment of the present disclosure, in addition to the need to control the flow rate of the silicon source gas, it is also necessary to control the contact time between the silicon source gas and the copper layer 101. The contact time between the silicon source gas and the copper layer 101 cannot be too short, otherwise the silicon source gas cannot form a saturated gas adsorption layer on the surface of the copper layer 101, which may result in the subsequent formation of the silicon nitride layer in some areas of the surface of the copper layer 101 due to insufficient silicon source gas and the inability to form a silicon nitride layer; and the contact time between the silicon source gas and the copper layer 101 cannot be too long, otherwise it will cause the silicon source gas on the surface of the copper layer 101 to be oversaturated, and the silicon source gas will form multiple adsorption layers on the surface of the copper layer 101, and the adsorption layer far away from the surface of the copper layer 101 has a weak adsorption force with the copper layer 101, which makes it difficult for the gas molecules to be evenly arranged, which may result in a larger thickness or uneven thickness of the silicon nitride layer formed subsequently. Both of the above situations may have a negative impact on the interface properties of the copper layer and the silicon nitride layer. Therefore, it is necessary to control the contact time between the silicon source gas and the copper layer 101 within a certain range so that a single layer of saturated gas adsorption layer is formed on the surface of the copper layer 101, which is helpful for the subsequent formation of a smaller and uniform silicon nitride layer.

[0066] In some embodiments, reference Figure 2 In Figure (c), while introducing a nitrogen source gas with a flow rate of a second preset value, the RF power supply is turned on to ionize the silicon source gas and the nitrogen source gas to generate plasma. The silicon-containing plasma and the nitrogen-containing plasma undergo a plasma chemical reaction on the surface of the copper layer 101 to generate silicon nitride, thereby forming a silicon nitride layer 102 covering the copper layer 101.

[0067] In a specific example, the flow rate of the nitrogen source gas, ie, the second preset value, is 125 sccm.

[0068] In the embodiment of the present disclosure, the silicon nitride layer 102 covering the copper layer 101 is formed by PECVD. Specifically, the substrate including the copper layer 101 is placed on the cathode plate in the reaction chamber 201, and then silicon source gas and nitrogen source gas are introduced as reaction gases, and the radio frequency power supply is turned on to generate glow discharge, and the reaction gas near the surface of the copper layer 101 is ionized, and the reaction gas is activated. At the same time, cathode sputtering occurs on the surface of the copper layer 101, thereby improving the surface activity. There are not only thermochemical reactions on the surface of the copper layer 101, but also complex plasma chemical reactions. The silicon nitride layer 102 is formed under the combined action of these two chemical reactions. Since in the semiconductor structure, the copper layer 101 as a metal interconnect is usually formed in the back-end process, that is, before the copper layer 101 is formed, most of the devices in the semiconductor structure have been formed, and the deposition temperature required for PECVD is relatively low, so the impact on other structures in the substrate can be reduced.

[0069] In some embodiments, during the process of silicon source gas and nitrogen source gas reacting to generate silicon nitride 102, hydrogen gas is generated as a byproduct. The hydrogen gas can be pumped from the reaction chamber 201 through the exhaust gas pipe between the gas pump and the reaction chamber 201 to the exhaust gas chamber 207 by an air pump to prevent the hydrogen gas from affecting the structure in the substrate.

[0070] In some embodiments, in order to further improve the reliability of the process, the flow rate of the nitrogen source gas can be controlled by a method similar to that of controlling the flow rate of the silicon source gas. Specifically, the nitrogen source gas can be first passed to the exhaust chamber 207 so that the flow rate of the nitrogen source gas reaches a second preset value and is maintained for a period of time, and then the nitrogen source gas is passed into the reaction chamber 201. In addition, a flow meter can be added to the gas pipeline of the nitrogen source gas at a position close to the reaction chamber 201, and the flow rate of the nitrogen source gas can be monitored by the flow meter to further improve the stability of the flow rate of the nitrogen source gas.

[0071] In some embodiments, refer back to Figure 2 In Figure (a), before the silicon source gas is introduced into the reaction chamber 101, the nitrogen source gas can be introduced into the reaction chamber 101 and the radio frequency power supply can be turned on to pre-treat the copper layer 101. Specifically, the nitrogen-containing plasma can react with the natural oxide film located on the surface of the copper layer 101, the main component of which is copper oxide, and remove the natural oxide film on the surface of the copper layer 101, so that the silicon atoms can be more easily bonded with the copper atoms in the subsequent deposition reaction.

[0072] In some specific examples, the silicon source gas may be one of tetramethylsilane, ethyl orthosilicate and silane; and the nitrogen source gas may be ammonia or nitrogen.

[0073] In the embodiment of the present disclosure, the silicon source gas is silane SiH4 and the nitrogen source gas is ammonia NH3 as an example.

[0074] Figure 6 In order to fix the flow rate of ammonia when forming silicon nitride covering the copper layer by PECVD, the change in the resistance of the copper layer is obtained by changing the flow rate of silane gas. Here, the flow rate of ammonia is fixed at 125sccm. The thickness of the silicon nitride layer formed under different silane gas flow rates is the same, which is 3nm. Before the formation of the silicon nitride layer, the resistance of the copper layer is 0.81 ohms. Figure 7 After the silicon nitride layer covering the copper layer is formed, three bonding situations are observed at the interface between the copper layer and the silicon nitride layer.

[0075] Combined with reference Figure 6 and Figure 7 As the silane gas flow rate increases, the bonding conditions at the interface between the copper layer and the silicon nitride layer change, and the resistance of the copper layer also increases. This shows that the flow rate of the silicon source gas does affect the interface properties of the copper layer. Specifically, when the silane gas flow rate is less than 250 sccm, the bonding conditions at the interface between the copper layer and the silicon nitride layer are as follows: Figure 7 As shown in Figure (d), when the silane gas is insufficient, the silicon atoms on the interface are also insufficient, resulting in some copper atoms not bonding with silicon atoms and some copper atoms bonding with nitrogen atoms. In this case, the bonding force between the copper layer and the silicon nitride layer is weak, which may cause the barrier layer to fall off after the barrier layer is formed. When the flow rate of the silane gas exceeds 300 sccm, the bonding situation on the interface between the copper layer and the silicon nitride layer is as follows: Figure 7 As shown in Figure (f), due to the excess of silane gas, the silicon atoms on the interface are also excessive, causing the silicon atoms to enter the interior of the copper layer and increase the resistance of the copper layer.

[0076] In the embodiment of the present disclosure, when the silicon nitride layer 102 covering the copper layer 101 is formed by PECVD, the flow rate of the silane gas is controlled to be a first preset value, and the range of the first preset value is 250 sccm to 300 sccm. In this case, the bonding condition at the interface between the copper layer 101 and the silicon nitride layer 102 is as follows: Figure 7 As shown in Figure (e), each copper atom on the interface is bonded to a silicon atom, the silicon atoms on the interface are arranged neatly, and the silicon atoms do not enter the interior of the copper layer 101. This not only allows a greater bonding force to be generated between the copper layer 101 and the silicon nitride layer 102, but also allows the resistance of the copper layer 101 to be controlled below 0.76 ohms, thereby avoiding a reduction in signal transmission rate due to excessive resistance of the copper layer 101.

[0077] In some embodiments, when a silicon nitride layer covering a copper layer is formed by PECVD, the dissociation energy of the silicon source gas is in a range of 55 W to 65 W, and the dissociation time is in a range of 3 seconds to 4 seconds. Here, the dissociation energy of the silicon source gas is the energy of the radio frequency power source when the silicon source gas is ionized to generate silicon-containing plasma.

[0078] In the embodiment of the present disclosure, in addition to accurately controlling the flow rate of the silicon source gas, the dissociation energy and dissociation time of the silicon source gas can also be controlled. Specifically, under the condition that the silicon source gas can be fully dissociated, the dissociation energy of the silicon source gas is small and the dissociation time is short, which can weaken the thermal effect of the plasma and reduce the protrusion defects on the surface of the copper layer caused by the compression of the copper grains by the plasma.

[0079] In some embodiments, reference Figure 8 The method for forming a semiconductor structure further includes: forming a barrier layer 103 on the silicon nitride layer 102 .

[0080] In some specific examples, the barrier layer 103 can be formed by PECVD. In this case, the barrier layer 103 covering the silicon nitride layer 102 can be formed in the same reaction chamber 201 without transferring the substrate to another reaction chamber, thereby effectively improving the process efficiency. Specifically, after the silicon nitride layer 102 covering the copper layer 101 is formed, the excess reaction gas and reaction byproducts in the reaction chamber 201 can be removed by purging with an inert gas, and then the reaction gas required to form the barrier layer 103 is introduced into the reaction chamber 201 to form the barrier layer 103 by PECVD.

[0081] In a specific example, the material of the barrier layer 103 includes silicon carbonitride. When the barrier layer 103 is formed by PECVD, the reaction gases are tetramethylsilane and ammonia.

[0082] The disclosed embodiment provides a method for forming a semiconductor structure. When a silicon nitride layer covering a copper layer is formed by PECVD, the flow rate of a silicon source gas is precisely controlled at a first preset value, the range of the first preset value is 250sccm to 300sccm, and the flow rate control method of the silicon source gas is to first pass the silicon source gas into the exhaust chamber, and after the flow rate of the silicon source gas reaches the first preset value and is maintained for a period of time, the silicon source gas is then passed into the reaction chamber, and the flow rate of the silicon source gas is monitored by a second flow meter closer to the reaction chamber to further improve the stability of the flow rate of the silicon source gas. In addition, when a silicon nitride layer covering a copper layer is formed by PECVD, the contact time between the silicon source gas and the copper layer is also controlled. The method for forming a semiconductor structure can ensure that the copper layer and the silicon source gas are in full contact, and a large bonding force is generated between the formed silicon nitride layer and the copper layer, while avoiding excessive resistance of the copper layer due to excessive silicon source gas or fluctuation of resistance of the copper layer due to unstable silicon source gas flow. Therefore, after the barrier layer is formed, a large bonding force can be generated between the barrier layer and the copper layer through the silicon nitride layer, and while the silicon nitride layer and the barrier layer are formed to prevent copper diffusion, the signal transmission rate in the copper layer will not be sacrificed, thereby further improving the yield of the product.

[0083] Based on the concept similar to the method for forming the semiconductor structure in the aforementioned embodiment, the present disclosure also provides a semiconductor structure, such as Figure 8 As shown, the semiconductor structure includes a copper layer 101 located in a substrate, a silicon nitride layer 102 covering the copper layer 101 , and a barrier layer 103 covering the silicon nitride layer 102 .

[0084] In a specific example, the resistance of the copper layer 101 is lower than 0.76 ohms.

[0085] In some specific examples, the material of the barrier layer 103 includes, but is not limited to, silicon carbonitride.

[0086] In the embodiments of the present disclosure, the semiconductor structure can be formed by the method for forming the semiconductor structure in any of the aforementioned embodiments. Since the flow rate of the silicon source gas is precisely controlled in the process of forming the silicon nitride layer 102 covering the copper layer 101 by PECVD, the defects on the interface between the copper layer 101 and the silicon nitride layer 102 in the formed semiconductor structure are relatively few, the resistance of the copper layer 101 is relatively small, the signal transmission rate in the copper layer 101 is relatively high, and there is a relatively large bonding force between the copper layer 101 and the silicon nitride layer 102. The silicon nitride layer 102 acts as a bonding layer to prevent the barrier layer 103 from falling off. Therefore, the semiconductor structure has relatively high reliability.

[0087] In some specific embodiments, the semiconductor structure in any of the foregoing embodiments may be located in a chip, and the chip may be a logic chip, a memory chip, or a power management chip (Power Management Integrated Circuit, PMIC). The types of logic chips include, but are not limited to, a central processing unit (CPU) chip, a graphics processing unit (GPU) chip, an image processor (ISP) chip, an application processor (AP) chip, an embedded neural network processing unit (NPU) chip, and a video processing unit (VPU) chip. Types of memory chips include, but are not limited to, dynamic random access memory (DRAM) chips, static random access memory (SRAM) chips, phase change random access memory (PRAM) chips, magnetoresistive random access memory (MRAM) chips, ferroelectric random access memory (FeRAM) chips, resistive random access memory (RRAM) chips and flash memory chips.

[0088] The methods disclosed in several method embodiments provided in the present disclosure can be arbitrarily combined without conflict to obtain new method embodiments.

[0089] The above is only a specific embodiment of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A method for forming a semiconductor structure, characterized in that: include: Providing a substrate having a copper layer, and placing the substrate in a reaction chamber; Controlling the flow rate of the silicon source gas to a first preset value; The silicon source gas having a flow rate of the first preset value and the nitrogen source gas having a flow rate of the second preset value are introduced into the reaction chamber to form a silicon nitride layer covering the copper layer through a plasma enhanced chemical vapor deposition process.

2. The method for forming a semiconductor structure according to claim 1, wherein: The step of controlling the flow rate of the silicon source gas to a first preset value comprises: Closing a first gas valve between a silicon source gas inlet and the reaction chamber, and opening a second gas valve between the silicon source gas inlet and an exhaust chamber to pass the silicon source gas to the exhaust chamber, until a first flow meter located between the silicon source gas inlet and the reaction chamber shows that the flow rate of the silicon source gas reaches the first preset value and is maintained for 5 to 10 seconds; The step of introducing the silicon source gas having a flow rate of the first preset value into the reaction chamber comprises: The second gas valve is closed, and the first gas valve is opened to allow the silicon source gas with a flow rate of the first preset value to flow into the reaction chamber.

3. The method for forming a semiconductor structure according to claim 2, wherein: A second flow meter is included between the first flow meter and the reaction chamber; and the step of introducing the silicon source gas into the reaction chamber comprises: The flow rate of the silicon source gas is monitored by the second flow meter.

4. The method for forming a semiconductor structure according to claim 1, wherein: The first preset value ranges from 250 sccm to 300 sccm.

5. The method for forming a semiconductor structure according to claim 1, wherein: Before the nitrogen source gas having a flow rate of the second preset value is introduced into the reaction chamber, the silicon source gas is in contact with the copper layer for a time ranging from 2 seconds to 4 seconds.

6. The method for forming a semiconductor structure according to claim 1, wherein: The second preset value is 125 sccm.

7. The method for forming a semiconductor structure according to claim 1, wherein: Before forming the silicon nitride layer covering the copper layer, the resistance of the copper layer is greater than 0.76 ohms; after forming the silicon nitride layer covering the copper layer, the resistance of the copper layer is less than 0.76 ohms.

8. The method for forming a semiconductor structure according to claim 1, wherein: When a silicon nitride layer covering the copper layer is formed by a plasma enhanced chemical vapor deposition process, the dissociation energy of the silicon source gas is in a range of 55 watts to 65 watts, and the dissociation time is in a range of 3 seconds to 4 seconds.

9. The method for forming a semiconductor structure according to claim 1, wherein: The method for forming the semiconductor structure further comprises: Before the silicon source gas having a flow rate of the first preset value is introduced into the reaction chamber, the nitrogen source gas is introduced into the reaction chamber and a radio frequency power source is turned on to pretreat the copper layer.

10. The method for forming a semiconductor structure according to claim 1, wherein: The method for forming the semiconductor structure further comprises: A barrier layer is formed on the silicon nitride layer; the material of the barrier layer includes silicon carbonitride.

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