Copper-tungsten electrical connection structure and method for forming the same

Abstract

A copper-tungsten electrical connection structure and a method for forming the same, the method comprising: forming a first barrier layer on the surface of a copper layer; forming a buffer layer on the surface of the first barrier layer; forming a second barrier layer on the surface of the buffer layer; wherein, a tungsten layer is formed on the surface of the second barrier layer. The present invention can meet various requirements such as preventing metal diffusion, improving device stability, and reducing production costs.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing technology, and particularly to a copper-tungsten electrical connection structure and a method for forming the same. Background Art

[0002] With the improvement of the integration degree of semiconductor technology, the size of transistors continues to shrink, and the complexity of internal device wiring is further increased. Considering that the relative area available on the wafer surface decreases as the size shrinks, higher requirements are imposed on the density and integration degree of metal internal wiring.

[0003] Taking the current multi-metal internal wiring process as an example, the process combination of vias and metal plugs is widely used due to its high integration degree and good step coverage. Specifically, as the integration degree of the bonded wafers increases, the size of the through-silicon vias needs to be reduced accordingly, and the aspect ratio of the vias needs to be increased accordingly. Metal plugs can be used to connect upper and lower metal layers to achieve the function of metal interconnection.

[0004] It should be noted that the metal filled in the vias is likely to diffuse into the upper metal layer or the lower metal layer, affecting the electrical conductivity. In the prior art, a barrier layer can be formed to prevent metal diffusion. However, the existing barrier layers often have problems of poor stability with adjacent materials or high production costs.

[0005] There is an urgent need for a method for forming a copper-tungsten electrical connection structure to meet various requirements such as preventing metal diffusion, improving device stability, and reducing production costs. Summary of the Invention

[0006] The technical problem solved by the present invention is to provide a copper-tungsten electrical connection structure and a method for forming the same, which can meet various requirements such as preventing metal diffusion, improving device stability, and reducing production costs.

[0007] To solve the above technical problem, an embodiment of the present invention provides a method for forming a copper-tungsten electrical connection structure, including: forming a first barrier layer on the surface of a copper layer; forming a buffer layer on the surface of the first barrier layer; forming a second barrier layer on the surface of the buffer layer; wherein, a tungsten layer is formed on the surface of the second barrier layer.

[0008] Optionally, one or more of the following are satisfied: the material of the first barrier layer is selected from tantalum nitride and tantalum silicon nitride; the material of the buffer layer is tantalum; the material of the second barrier layer is selected from tantalum nitride and tantalum silicon nitride.

[0009] Optionally, one or more of the following are satisfied: the material of the first barrier layer is selected from titanium nitride and titanium silicon nitride; the material of the buffer layer is titanium; the material of the second barrier layer is selected from titanium nitride and titanium silicon nitride.

[0010] Optionally, one or more of the following are satisfied: the material of the first barrier layer is selected from: tungsten nitride; the material of the buffer layer is titanium and / or tantalum; the material of the second barrier layer is selected from: tungsten nitride.

[0011] Optionally, before forming the first barrier layer on the surface of the copper layer, the method for forming the copper-tungsten electrical connection structure further includes: cleaning the surface of the copper layer by a reactive plasma cleaning process.

[0012] Optionally, the process parameters of the reactive plasma cleaning process are selected from one or more of the following: the process temperature is 30 - 200 °C; the gas pressure in the process chamber is 20 - 60 mTorr; the control power is 400 - 1200 W; the gas in the process chamber includes argon, helium, and hydrogen-containing gas.

[0013] Optionally, the copper-tungsten electrical connection structure is used to form a plug structure, and one end of the plug structure is connected to the surface of the copper layer; wherein, the first barrier layer is further formed on the inner sidewall surface of the plug structure.

[0014] Optionally, the process for forming the second barrier layer on the surface of the buffer layer is selected from: when the aspect ratio of the through hole for filling the plug structure is less than a preset threshold, forming the second barrier layer by physical vapor deposition; when the aspect ratio of the through hole for filling the plug structure is greater than or equal to the preset threshold, forming the second barrier layer by chemical vapor deposition or atomic layer deposition.

[0015] Optionally, before forming the first barrier layer on the surface of the copper layer, the method for forming the copper-tungsten electrical connection structure further includes: providing a semiconductor substrate; forming a front dielectric layer, a copper layer, and a back dielectric layer, wherein the front dielectric layer is located on the first surface of the semiconductor substrate, and the back dielectric layer is located on the second surface of the semiconductor substrate; forming a through hole penetrating the front dielectric layer, the semiconductor substrate, and a part of the back dielectric layer, and the bottom surface of the through hole exposes the surface of the copper layer; forming a sidewall dielectric layer on the inner sidewall surface of the through hole; wherein, the first barrier layer is further formed on the surface of the sidewall dielectric layer.

[0016] To solve the above technical problems, an embodiment of the present invention provides a copper-tungsten electrical connection structure, including: a first barrier layer located on the surface of a copper layer; a buffer layer located on the surface of the first barrier layer; a second barrier layer located on the surface of the buffer layer; wherein, a tungsten layer is formed on the surface of the second barrier layer.

[0017] Optionally, one or more of the following are satisfied: the material of the first barrier layer is selected from: tantalum nitride and tantalum silicon nitride; the material of the buffer layer is tantalum; the material of the second barrier layer is selected from: tantalum nitride and tantalum silicon nitride.

[0018] Optionally, one or more of the following are satisfied: the material of the first barrier layer is selected from titanium nitride and titanium silicon nitride; the material of the buffer layer is titanium; the material of the second barrier layer is selected from titanium nitride and titanium silicon nitride.

[0019] Optionally, one or more of the following are satisfied: the material of the first barrier layer is selected from tungsten nitride; the material of the buffer layer is titanium and / or tantalum; the material of the second barrier layer is selected from tungsten nitride.

[0020] Optionally, the copper-tungsten electrical connection structure is used to form a plug structure, and one end of the plug structure is connected to the surface of the copper layer; wherein, the first barrier layer is located on the inner sidewall surface of the plug structure.

[0021] Optionally, the formation process of the second barrier layer is selected from: when the aspect ratio of the through hole for filling the plug structure is less than a preset threshold, the formation process of the second barrier layer is a physical vapor deposition process; when the aspect ratio of the through hole for filling the plug structure is greater than or equal to the preset threshold, the formation process of the second barrier layer is a chemical vapor deposition process or an atomic layer deposition process.

[0022] Optionally, the copper-tungsten electrical connection structure further includes: a semiconductor substrate; a front dielectric layer, a copper layer, and a back dielectric layer, wherein the front dielectric layer is located on the first surface of the semiconductor substrate, and the back dielectric layer is located on the second surface of the semiconductor substrate; a through hole that penetrates the front dielectric layer, the semiconductor substrate, and a part of the back dielectric layer, and the bottom surface of the through hole exposes the surface of the copper layer; a sidewall dielectric layer located on the inner sidewall surface of the through hole; wherein, the first barrier layer is further formed on the surface of the sidewall dielectric layer.

[0023] Compared with the prior art, the technical solution of the embodiment of the present invention has the following beneficial effects:

[0024] In the embodiment of the present invention, by sequentially arranging the first barrier layer, the buffer layer, and the second barrier layer as the electrical connection structure between copper and tungsten, the first barrier layer and the second barrier layer can be used to prevent metal diffusion, and the buffer layer can be used to provide a good contact surface for the first barrier layer and the second barrier layer, improving the stability and reliability of the entire structure, and meeting various requirements such as preventing metal diffusion, improving device stability, and reducing production costs.

[0025] Further, in the embodiments of the present invention, the material of the first barrier layer is selected from tantalum nitride and tantalum silicon nitride (TaSiN); the material of the buffer layer is tantalum; the material of the second barrier layer is selected from tantalum nitride and tantalum silicon nitride. Since tantalum nitride and tantalum silicon nitride have good barrier properties against copper diffusion and good adhesion to copper itself, they can reduce the contact resistance while achieving good contact with metallic copper. Compared with the prior art where an additional adhesion material is used to form an adhesion layer between the barrier layer and the metal layer, the technical solution of the embodiments of the present invention can prevent the diffusion of metallic copper and reduce the production cost. Using tantalum as the buffer layer can balance the stress of the upper and lower layer materials, absorb stress, and provide a good contact surface for the second barrier layer, which helps to improve the stability and reliability of the entire structure. Since tantalum nitride and tantalum silicon nitride also have good barrier properties against tungsten diffusion and low contact resistance with tungsten, they can prevent the diffusion of metallic tungsten. And tantalum nitride has a low temperature coefficient of resistance, and the resistance change caused by temperature change is small. In addition, the deposition of metallic tungsten on tantalum nitride is not affected by its surface roughness, and the thickness uniformity of metallic tungsten is better.

[0026] Further, in the embodiments of the present invention, the material of the first barrier layer is selected from titanium nitride and titanium silicon nitride; the material of the buffer layer is titanium; the material of the second barrier layer is selected from titanium nitride and titanium silicon nitride. Titanium nitride and titanium silicon nitride both have good barrier properties against copper diffusion and tungsten diffusion, and titanium nitride has a smaller resistance. For example, in the case of the same thickness, its resistance is smaller than that of tantalum nitride, which helps to improve the electrical performance of the device. Compared with the prior art where a single layer of titanium nitride is used to block copper diffusion and tungsten diffusion, problems such as peeling and fracture may occur due to stress. By adopting the solution of the embodiments of the present invention, adding a buffer layer between the titanium nitrides can balance the stress of the upper and lower layer materials, absorb stress, and improve the stability and reliability of the entire structure.

[0027] Further, in the embodiments of the present invention, the material of the first barrier layer is selected from tungsten nitride; the material of the buffer layer is titanium and / or tantalum; the material of the second barrier layer is selected from tungsten nitride. Tungsten nitride has good barrier properties against both copper diffusion and tungsten diffusion. When its thickness is small, its barrier ability is even greater than that of tantalum nitride and titanium nitride. When the copper-tungsten electrical connection structure is used to form a plug structure, if the size of the through hole for filling the plug structure is small (for example, less than 600 nm), due to the presence of the barrier layer and the buffer layer, the actual through hole size will be significantly reduced, affecting the through hole resistance. At this time, by using atomic layer deposition technology to form a thin tungsten nitride layer, it helps to meet both the through hole size and the barrier requirements. And adding a buffer layer between the tungsten nitrides can balance the stress of the upper and lower layer materials, absorb stress, and improve the stability and reliability of the entire structure.

[0028] Further, the process for forming the second barrier layer on the surface of the buffer layer is selected from: when the aspect ratio of the through-hole for filling the plug structure is less than a preset threshold (for example, the aspect ratio of the filling hole is less than 1:3), the second barrier layer is formed by physical vapor deposition. Physical vapor deposition is preferably selected for the second barrier layer. In this case, the entire process flow is simpler. The entire process of tantalum nitride, tantalum, and tantalum nitride can be completed in one reaction chamber, and problems such as increased contact resistance and reliability caused by metal surface oxidation due to breaking vacuum can be avoided. When the aspect ratio of the through-hole for filling the plug structure is greater than or equal to the preset threshold (for example, the aspect ratio of the filling hole is greater than or equal to 1:3), the second barrier layer is formed by chemical vapor deposition or atomic layer deposition. These two methods have better step coverage. Atomic layer deposition can deposit a relatively thin thickness, which can effectively reduce the contact resistance.

[0029] Further, a through-hole penetrating the crystal plane dielectric layer, the semiconductor substrate, and a part of the crystal back dielectric layer can be formed. The bottom surface of the through-hole exposes the surface of the copper layer. A sidewall dielectric layer is formed on the inner sidewall surface of the through-hole. The first barrier layer is formed not only on the surface of the copper layer but also on the surface of the sidewall dielectric layer, so that the copper-tungsten electrical connection structure forms a plug structure filled in the through-silicon via, improving the electrical performance of the plug structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a flowchart of a method for forming a copper-tungsten electrical connection structure according to an embodiment of the present invention;

[0031] Figure 2 is a schematic cross-sectional structure diagram of a copper-tungsten electrical connection structure according to an embodiment of the present invention;

[0032] Figures 3 to 5 is a schematic diagram of the device cross-sectional structure corresponding to each step in a method for forming a copper-tungsten electrical connection structure according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] As described above, the metal filled in the through-hole is likely to diffuse into the upper metal layer or the lower metal layer, affecting the conductivity.

[0034] The inventors of the present invention have found through research that in the prior art, a barrier layer can be formed to prevent metal diffusion. However, the existing barrier layers often have problems of poor stability with adjacent materials (such as the metal filled in the through-hole, the upper metal layer, or the lower metal layer). For example, using a single-layer barrier layer results in excessive stress. There may also be problems of relatively high production costs. For example, using an additional adhesion material to form an adhesion layer between the barrier layer and the metal layer increases the production cost.

[0035] In the embodiments of the present invention, by sequentially providing a first barrier layer, a buffer layer, and a second barrier layer as the electrical connection structure between copper and tungsten, the first barrier layer and the second barrier layer can be utilized to prevent metal diffusion, and the buffer layer can be utilized to provide a good contact surface for the first barrier layer and the second barrier layer, improving the stability and reliability of the entire structure and meeting various requirements such as preventing metal diffusion, improving device stability, and reducing production costs.

[0036] To make the above objects, features, and beneficial effects of the present invention more obvious and understandable, the following specifically describes the embodiments of the present invention in conjunction with the accompanying drawings.

[0037] Refer to Figure 1 , Figure 1 which is a flowchart of a method for forming a copper-tungsten electrical connection structure in an embodiment of the present invention. The method for forming the copper-tungsten electrical connection structure may include steps S11 to S13:

[0038] Step S11: Form a first barrier layer on the surface of the copper layer;

[0039] Step S12: Form a buffer layer on the surface of the first barrier layer;

[0040] Step S13: Form a second barrier layer on the surface of the buffer layer, wherein a tungsten layer is formed on the surface of the second barrier layer.

[0041] The following Figure 2 describes each of the above steps.

[0042] Refer to Figure 2 , Figure 2 which is a schematic cross-sectional structure diagram of a copper-tungsten electrical connection structure in an embodiment of the present invention.

[0043] Specifically, the copper-tungsten electrical connection structure may include a first barrier layer 102, a buffer layer 103, and a second barrier layer 105.

[0044] Among them, the first barrier layer 102 may be formed on the surface of the copper layer 101, and a buffer layer 103 is formed on the surface of the first barrier layer 102, a second barrier layer 104 is formed on the surface of the buffer layer 103, and a tungsten layer 105 is formed on the surface of the second barrier layer 104.

[0045] Further, the first barrier layer 102 has the ability to block copper diffusion, thereby realizing the function of blocking copper diffusion.

[0046] Further, the adhesion force between the first barrier layer 102 and copper is greater than or equal to a first preset adhesion force threshold.

[0047] In the embodiment of the present invention, by setting that there is good adhesion between the first barrier layer 102 and copper, good contact with metallic copper can be achieved. Compared with the prior art in which an additional adhesion material is used to form an adhesion layer between the barrier layer and the metal layer, the technical solution of the embodiment of the present invention can prevent the diffusion of metallic copper and reduce the production cost.

[0048] Further, the stress of the buffer layer 103 can be less than a preset stress range.

[0049] In the embodiment of the present invention, by setting that the stress of the buffer layer 103 is less than a preset stress range, the stress of the upper and lower layer materials can be balanced and the stress can be absorbed. In addition, a good contact surface can be provided for the second barrier layer 104, which helps to improve the stability and reliability of the whole structure.

[0050] Further, the second barrier layer 104 has the ability to block the diffusion of tungsten, so as to realize the function of blocking the diffusion of tungsten.

[0051] Further, the adhesion force between the second barrier layer 104 and tungsten is greater than or equal to a second preset adhesion force threshold.

[0052] In the embodiment of the present invention, by setting that there is good adhesion between the second barrier layer 104 and tungsten, good contact with metallic tungsten can be achieved. Compared with the prior art in which an additional adhesion material is used to form an adhesion layer between the barrier layer and the metal layer, the technical solution of the embodiment of the present invention can prevent the diffusion of metallic tungsten and reduce the production cost.

[0053] In the first specific embodiment of the embodiment of the present invention, the material of the first barrier layer 102 can be selected from tantalum nitride and tantalum silicon nitride; the material of the buffer layer 103 is tantalum; the material of the second barrier layer 104 can be selected from tantalum nitride and tantalum silicon nitride.

[0054] In the embodiments of the present invention, since tantalum nitride and tantalum silicon nitride (TaSiN) have good barrier properties against copper diffusion and good adhesion to copper itself, while achieving good contact with metallic copper, the contact resistance can be reduced. Compared with the prior art where an additional adhesion material is used to form an adhesion layer between the barrier layer and the metal layer, the technical solution of the embodiments of the present invention can prevent the diffusion of metallic copper and reduce production costs. Using tantalum as the buffer layer 103 can balance the stress of the upper and lower layer materials, absorb stress, and also provide a good contact surface for the second barrier layer, which helps to improve the stability and reliability of the entire structure. Since tantalum nitride and tantalum silicon nitride also have good barrier properties against tungsten diffusion and have a low contact resistance with tungsten, they can prevent the diffusion of metallic tungsten. Moreover, tantalum nitride has a low resistance temperature coefficient, and the resistance change caused by temperature variation is small. In addition, the deposition of metallic tungsten on tantalum nitride is not affected by its surface roughness, and the thickness uniformity of metallic tungsten is good.

[0055] In the second specific embodiment of the embodiments of the present invention, the material of the first barrier layer 102 can be selected from: titanium nitride and titanium silicon nitride; the material of the buffer layer 103 is titanium; the material of the second barrier layer 104 can be selected from: titanium nitride and titanium silicon nitride.

[0056] In the embodiments of the present invention, the material of the first barrier layer 102 can be selected from: titanium nitride and titanium silicon nitride; the material of the buffer layer is titanium; the material of the second barrier layer 104 can be selected from: titanium nitride and titanium silicon nitride. Titanium nitride and titanium silicon nitride both have good barrier properties against copper diffusion and tungsten diffusion, and titanium nitride has a small resistance. For example, in the case of the same thickness, its resistance is smaller than that of tantalum nitride, which helps to improve the electrical performance of the device. Compared with the prior art where a single layer of titanium nitride is used to block copper diffusion and tungsten diffusion, problems such as peeling and fracture may occur due to stress (for example, when the thickness of a single layer of titanium nitride exceeds 300 Å). By adopting the solution of the embodiments of the present invention and adding the buffer layer 103 between the titanium nitrides, it can balance the stress of the upper and lower layer materials, absorb stress, and also improve the stability and reliability of the entire structure.

[0057] In the third specific embodiment of the embodiments of the present invention, the material of the first barrier layer 102 can be selected from: tungsten nitride; the material of the buffer layer 103 is titanium and / or tantalum; the material of the second barrier layer 104 can be selected from: tungsten nitride.

[0058] In an embodiment of the present invention, the material of the first barrier layer 102 is selected from tungsten nitride; the material of the buffer layer is titanium and / or tantalum; the material of the second barrier layer 104 is selected from tungsten nitride. Tungsten nitride has good barrier properties against both copper diffusion and tungsten diffusion. When the thickness is small, its barrier ability is even greater than that of tantalum nitride and titanium nitride. When the copper-tungsten electrical connection structure is used to form a plug structure, if the size of the through hole for filling the plug structure is small (for example, less than 600 nm), due to the provision of the barrier layer and the buffer layer 103, the actual through hole size will be significantly reduced, affecting the through hole resistance value. At this time, by using atomic layer deposition technology to form a thin tungsten nitride layer, it helps to meet the through hole size and barrier requirements simultaneously (for example, a thin tungsten nitride layer with a thickness of 40 - 100 Å has the opportunity to meet the requirements of semiconductor devices). And adding the buffer layer 103 between tungsten nitrides can play a role in balancing the stress of the upper and lower layer materials, absorbing stress, and improving the stability and reliability of the entire structure.

[0059] Further, before forming the first barrier layer on the surface of the copper layer, the method for forming the copper-tungsten electrical connection structure may further include: cleaning the surface of the copper layer by using a reactive plasma cleaning process.

[0060] Further, the process parameters of the reactive plasma cleaning process may be selected from one or more of the following: the process temperature is 30 - 200 °C; the gas pressure in the process chamber is 20 - 60 mTorr; the control power is 400 - 1200 W; the gas in the process chamber includes argon, helium, and hydrogen-containing gas.

[0061] Specifically, a large amount of inert gas (for example, including argon and helium) can be introduced into the reaction chamber to raise the temperature of the wafer surface to around 30 - 200 °C. At this time, a mixed gas of inert gas (for example, including argon and helium) and hydrogen-containing gas is continuously introduced, the chamber pressure is maintained at around 20 - 60 mTorr, and the control power is approximately 400 - 1200 W.

[0062] In an embodiment of the present invention, the reactive plasma cleaning process can be used to clean the surface of the copper layer, remove metal oxides, reduce contact resistance, increase the density of the insulating film, and provide a good contact surface for the buffer layer and the second barrier layer.

[0063] In an embodiment of the present invention, by sequentially providing the first barrier layer 102, the buffer layer 103, and the second barrier layer 104 as the electrical connection structure between copper and tungsten, the first barrier layer 102 and the second barrier layer 104 can be used to prevent metal diffusion, and the buffer layer can be used to provide a good contact surface for the first barrier layer 102 and the second barrier layer 104, improving the stability and reliability of the entire structure, and meeting various requirements such as preventing metal diffusion, improving device stability, and reducing production costs.

[0064] In another copper-tungsten electrical connection structure according to an embodiment of the present invention, the copper-tungsten electrical connection structure can be used to form a plug structure.

[0065] Referring to Figures 3 to 5 , Figures 3 to 5 is a schematic cross-sectional structure diagram of devices corresponding to each step in a method for forming a copper-tungsten electrical connection structure according to an embodiment of the present invention.

[0066] Referring to Figure 3 , a semiconductor substrate 200 is provided, and a crystal plane dielectric layer 212, a copper layer 220, and a crystal back dielectric layer 211 are formed. Among them, the crystal plane dielectric layer 212 is located on the first surface of the semiconductor substrate 200, and the crystal back dielectric layer 211 is located on the second surface of the semiconductor substrate 200. Among them, a carrier wafer 201 can be bonded to the surface of the crystal back dielectric layer 211.

[0067] Specifically, the semiconductor substrate 200 can be a silicon substrate, or the material of the semiconductor substrate 200 can also be an appropriate material for an image sensor such as germanium, silicon germanide, silicon carbide, gallium arsenide, or indium gallium arsenide. The semiconductor substrate 200 can also be a silicon substrate on an insulator surface or a germanium substrate on an insulator surface, or a substrate with an epitaxy layer grown thereon. A through hole penetrating the crystal plane dielectric layer 212, the semiconductor substrate 200, and a part of the crystal back dielectric layer 211 is formed, and the bottom surface of the through hole exposes the surface of the copper layer 220.

[0068] Further, before forming the through hole penetrating the crystal plane dielectric layer 212, the semiconductor substrate 200, and a part of the crystal back dielectric layer 211, it may further include: providing a carrier wafer, bonding the front surface of the carrier wafer to the front surface of the semiconductor substrate 200 (including the crystal back dielectric layer 211 and the copper layer 220), then flipping the bonded device, and performing a thinning process from the back surface of the semiconductor substrate 200.

[0069] It should be noted that the step of forming the through hole penetrating the crystal plane dielectric layer 212, the semiconductor substrate 200, and a part of the crystal back dielectric layer 211 is also performed from the back surface of the semiconductor substrate 200. As Figure 3 shown, the crystal plane dielectric layer 212 is located on the back surface of the semiconductor substrate 200.

[0070] It can be understood that, in a specific implementation manner of the embodiments of the present invention, forming the crystal plane dielectric layer 212, the copper layer 220, and the crystal back dielectric layer 211 may be to first form the crystal back dielectric layer 211, then form the copper layer 220 within the crystal back dielectric layer 211, then bond the carrier wafer to the semiconductor substrate 200, and after flipping, form the crystal plane dielectric layer 212. However, in the embodiments of the present invention, other process sequences may also be used to form the crystal plane dielectric layer 212, the copper layer 220, and the crystal back dielectric layer 211, and no limitations are imposed on the specific process parameters.

[0071] The steps of forming a through hole that penetrates the crystal plane dielectric layer 212, the semiconductor substrate 200, and a part of the crystal back dielectric layer 211, and forming a sidewall dielectric layer 230 on the inner sidewall surface of the through hole may include: using an etching process to form an initial through hole (not shown in the figure) that penetrates the crystal plane dielectric layer 212, the semiconductor substrate 200, and a part of the crystal back dielectric layer 211, with a preset distance between the bottom surface of the initial through hole and the surface of the copper layer 220; forming a protective dielectric layer (not shown in the figure) on the back surface of the semiconductor substrate 200 and on the bottom and sidewall surfaces of the initial through hole, where the protective dielectric layer is used to protect the sidewall surface of the initial through hole; etching the initial through hole to obtain the through hole.

[0072] Among them, the bottom surface of the through hole exposes the surface of the copper layer 220, and the remaining protective dielectric layer after etching is the sidewall dielectric layer 230 formed on the inner sidewall surface of the through hole. Among them, the materials of the crystal plane dielectric layer 212 and the crystal back dielectric layer 211 may be selected from silicon oxide and silicon nitride, and the crystal plane dielectric layer 212 and the crystal back dielectric layer 211 may also be a stack of silicon oxide and silicon nitride to reduce device stress.

[0073] In the embodiments of the present invention, a through hole that penetrates the crystal plane dielectric layer 212, the semiconductor substrate 200, and a part of the crystal back dielectric layer 211 may be formed, the bottom surface of the through hole exposes the surface of the copper layer 220, a sidewall dielectric layer 230 is formed on the inner sidewall surface of the through hole, and the first barrier layer 240 is formed not only on the surface of the copper layer 220 but also on the surface of the sidewall dielectric layer 230, so that the copper-tungsten electrical connection structure forms a plug structure filled in the through-silicon via, improving the electrical performance of the plug structure.

[0074] Refer to Figure 4 , a sidewall dielectric layer 230 is formed on the inner sidewall surface of the through hole, a first barrier layer 240 is formed on the surface of the sidewall dielectric layer 230, a buffer layer 250 is formed on the surface of the first barrier layer 240, and a second barrier layer 260 is formed on the surface of the buffer layer 250.

[0075] It is understandable that the first barrier layer 240 is formed not only on the surface of the sidewall dielectric layer 230, but also on the surface of the copper layer 220.

[0076] In Figures 3 to 5 In the shown copper-tungsten electrical connection structure, the first barrier layer 240, the buffer layer 250, and the second barrier layer 260 are used to form a plug structure. One end of the plug structure is connected to the surface of the copper layer 220, and the other end is connected to the surface of the tungsten layer 270.

[0077] Wherein, the plug structure may further include a sidewall dielectric layer 230, and the first barrier layer 240 is also formed on the inner sidewall surface of the plug structure, that is, on the surface of the sidewall dielectric layer 230.

[0078] Further, the process of forming the second barrier layer 260 on the surface of the buffer layer 250 may be selected from: when the aspect ratio of the through hole for filling the plug structure is less than a preset threshold, a physical vapor deposition process is used to form the second barrier layer; when the aspect ratio of the through hole for filling the plug structure is greater than or equal to the preset threshold, a chemical vapor deposition process or an atomic layer deposition process is used to form the second barrier layer.

[0079] In the embodiment of the present invention, the process of forming the second barrier layer 260 on the surface of the buffer layer is selected from: when the aspect ratio of the through hole for filling the plug structure is less than a preset threshold (for example, the aspect ratio of the filling hole is less than 1:3), a physical vapor deposition process may be used to form the second barrier layer. The second barrier layer preferably selects physical vapor deposition. In this case, the entire process flow is simpler. The entire process of tantalum nitride, tantalum, and tantalum nitride can be completed in one reaction chamber, and problems such as an increase in contact resistance and reliability caused by metal surface oxidation due to breaking vacuum will not occur.

[0080] In a specific application of the embodiment of the present invention, the film thickness of the second barrier layer 260 in this case may be greater than 100 Å - 300 Å.

[0081] In the embodiment of the present invention, when the aspect ratio of the through hole for filling the plug structure is greater than or equal to the preset threshold (for example, the aspect ratio of the filling hole is greater than or equal to 1:3), a chemical vapor deposition process or an atomic layer deposition process is used to form the second barrier layer. These two methods have better step coverage. Atomic layer deposition can deposit a relatively thin thickness, which can effectively reduce the contact resistance.

[0082] In a specific application of the embodiment of the present invention, the thickness of the second barrier layer 260 in this case may be 10 Å - 150 Å.

[0083] For more information about the first barrier layer 240, the buffer layer 250, and the second barrier layer 260, please refer to the foregoing and Figures 1 to 2 the relevant description, which will not be elaborated here.

[0084] Refer to Figure 5 , a tungsten layer 270 is formed on the surface of the second barrier layer 260 to utilize the second barrier layer 260 to prevent the diffusion of tungsten metal.

[0085] In an embodiment of the present invention, a copper-tungsten electrical connection structure is also disclosed. Refer to Figure 5 , the copper-tungsten electrical connection structure may include: a first barrier layer 240 located on the surface of the copper layer 220; a buffer layer 250 located on the surface of the first barrier layer 240; a second barrier layer 240 located on the surface of the buffer layer 250; wherein, a tungsten layer 270 is formed on the surface of the second barrier layer 240.

[0086] Further, one or more of the following may be satisfied: the material of the first barrier layer 240 is selected from tantalum nitride and tantalum silicon nitride; the material of the buffer layer 250 is tantalum; the material of the second barrier layer 260 is selected from tantalum nitride and tantalum silicon nitride.

[0087] Further, one or more of the following may be satisfied: the material of the first barrier layer 240 is selected from titanium nitride and titanium silicon nitride; the material of the buffer layer 250 is titanium; the material of the second barrier layer 260 is selected from titanium nitride and titanium silicon nitride.

[0088] Further, one or more of the following may be satisfied: the material of the first barrier layer 240 is selected from tungsten nitride; the material of the buffer layer 250 is titanium and / or tantalum; the material of the second barrier layer 260 is selected from tungsten nitride.

[0089] Further, the copper-tungsten electrical connection structure is used to form a plug structure, and one end of the plug structure is connected to the surface of the copper layer 220; wherein, the first barrier layer 240 is located on the inner sidewall surface of the plug structure.

[0090] Further, the formation process of the second barrier layer 260 is selected from: when the aspect ratio of the through hole for filling the plug structure is less than a preset threshold, the formation process of the second barrier layer 260 is a physical vapor deposition process; when the aspect ratio of the through hole for filling the plug structure is greater than or equal to the preset threshold, the formation process of the second barrier layer 260 is a chemical vapor deposition process or an atomic layer deposition process.

[0091] Furthermore, the copper-tungsten electrical connection structure further includes: a semiconductor substrate 200; a crystal plane dielectric layer 212, a copper layer 220, and a crystal back dielectric layer 211, wherein the crystal plane dielectric layer 212 is located on the first surface of the semiconductor substrate 200, and the crystal back dielectric layer 211 is located on the second surface of the semiconductor substrate 200; a through hole that penetrates the crystal plane dielectric layer 212, the semiconductor substrate, and a part of the crystal back dielectric layer 211, and the bottom surface of the through hole exposes the surface of the copper layer 220; a sidewall dielectric layer 230 located on the inner sidewall surface of the through hole; wherein the first barrier layer 240 is further formed on the surface of the sidewall dielectric layer 230.

[0092] In the embodiment of the present invention, by sequentially providing the first barrier layer 240, the buffer layer 250, and the second barrier layer 260 as the electrical connection structure between copper and tungsten, the first barrier layer 240 and the second barrier layer 260 can be used to prevent metal diffusion, and the buffer layer can be used to provide a good contact surface for the first barrier layer 240 and the second barrier layer 260, improving the stability and reliability of the entire structure, and meeting various requirements such as preventing metal diffusion, improving device stability, and reducing production costs.

[0093] For the principle, specific implementation, and beneficial effects of this copper-tungsten electrical connection structure, please refer to the relevant descriptions of the formation method of the copper-tungsten electrical connection structure described above, and will not be elaborated here.

[0094] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.

Claims

1. A method for forming a copper-tungsten electrical connection structure, characterized in that, comprising: forming a first barrier layer on the surface of the copper layer; forming a buffer layer on the surface of the first barrier layer; forming a second barrier layer on the surface of the buffer layer; wherein, a tungsten layer is formed on the surface of the second barrier layer; wherein, the stress of the buffer layer is less than a preset stress range to play a role in balancing the stress of the upper and lower layer materials and absorbing stress.

2. The method for forming a copper-tungsten electrical connection structure according to claim 1, characterized in that, meeting one or more of the following: the material of the first barrier layer is selected from: tantalum nitride and tantalum silicon nitride; the material of the buffer layer is tantalum; the material of the second barrier layer is selected from: tantalum nitride and tantalum silicon nitride.

3. The method for forming a copper-tungsten electrical connection structure according to claim 1, characterized in that, meeting one or more of the following: the material of the first barrier layer is selected from: titanium nitride and titanium silicon nitride; the material of the buffer layer is titanium; the material of the second barrier layer is selected from: titanium nitride and titanium silicon nitride.

4. The method for forming a copper-tungsten electrical connection structure according to claim 1, characterized in that, meeting one or more of the following: the material of the first barrier layer is selected from: tungsten nitride; the material of the buffer layer is titanium and / or tantalum; the material of the second barrier layer is selected from: tungsten nitride.

5. The method for forming a copper-tungsten electrical connection structure according to claim 1, characterized in that, before forming the first barrier layer on the surface of the copper layer, further comprising: cleaning the surface of the copper layer by a reactive plasma cleaning process.

6. The method for forming a copper-tungsten electrical connection structure according to claim 5, characterized in that, the process parameters of the reactive plasma cleaning process are selected from one or more of the following: the process temperature is 30 - 200 °C; the gas pressure in the process chamber is 20 - 60 mTorr; the control power is 400 - 1200 W; the gas in the process chamber includes argon, helium and hydrogen-containing gas.

7. The method for forming a copper-tungsten electrical connection structure according to claim 1, characterized in that, the copper-tungsten electrical connection structure is used to form a plug structure, and one end of the plug structure is connected to the surface of the copper layer; wherein, the first barrier layer is also formed on the inner sidewall surface of the plug structure.

8. The method for forming a copper-tungsten electrical connection structure according to claim 7, characterized in that, the process for forming the second barrier layer on the surface of the buffer layer is selected from: when the aspect ratio of the through hole for filling the plug structure is less than a preset threshold, forming the second barrier layer by physical vapor deposition; when the aspect ratio of the through hole for filling the plug structure is greater than or equal to the preset threshold, forming the second barrier layer by chemical vapor deposition or atomic layer deposition.

9. The method for forming a copper-tungsten electrical connection structure according to claim 1, characterized in that, before forming the first barrier layer on the surface of the copper layer, the method further comprises: providing a semiconductor substrate; A crystal plane dielectric layer, a copper layer, and a crystal back dielectric layer are formed. Among them, the crystal plane dielectric layer is located on the first surface of the semiconductor substrate, and the crystal back dielectric layer is located on the second surface of the semiconductor substrate; A through hole penetrating the crystal plane dielectric layer, the semiconductor substrate, and a part of the crystal back dielectric layer is formed, and the bottom surface of the through hole exposes the surface of the copper layer; A sidewall dielectric layer is formed on the inner sidewall surface of the through hole; Among them, the first barrier layer is also formed on the surface of the sidewall dielectric layer.

10. A copper-tungsten electrical connection structure, Characterized in that, It includes: A first barrier layer located on the surface of the copper layer; A buffer layer located on the surface of the first barrier layer; A second barrier layer located on the surface of the buffer layer; Among them, a tungsten layer is formed on the surface of the second barrier layer; Among them, the stress of the buffer layer is less than a preset stress range to play a role in balancing the stress of the upper and lower layer materials and absorbing stress.

11. The copper-tungsten electrical connection structure according to claim 10, Characterized in that, Meet one or more of the following: The material of the first barrier layer is selected from tantalum nitride and tantalum silicon nitride; The material of the buffer layer is tantalum; The material of the second barrier layer is selected from tantalum nitride and tantalum silicon nitride.

12. The copper-tungsten electrical connection structure according to claim 10, Characterized in that, Meet one or more of the following: The material of the first barrier layer is selected from titanium nitride and titanium silicon nitride; The material of the buffer layer is titanium; The material of the second barrier layer is selected from titanium nitride and titanium silicon nitride.

13. The copper-tungsten electrical connection structure according to claim 10, Characterized in that, Meet one or more of the following: The material of the first barrier layer is selected from tungsten nitride; The material of the buffer layer is titanium and / or tantalum; The material of the second barrier layer is selected from tungsten nitride.

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