Al wire forming method

Abstract

The invention discloses an Al line forming method, and relates to the technical field of semiconductor devices, and the method comprises the steps: providing a wafer, forming a semiconductor device on the wafer, covering the semiconductor device with an ILD layer, and forming a groove in the ILD layer; depositing a barrier layer on the ILD layer and the surface of the groove; depositing a wetting layer on the barrier layer; cooling the wetting layer; depositing an Al layer on the wetting layer, wherein the groove is filled with the Al layer; and carrying out planarization treatment to remove the barrier layer, the wetting layer and the Al layer outside the groove. The wetting layer is deposited after the barrier layer is deposited, so that the step coverage rate of the barrier layer is improved; through cooling treatment on the wetting layer, the problem that in the follow-up Al deposition process, due to high temperature, grains are too large, and heating treatment cannot be conducted is solved, the problem that in the related technology, when shape-preserving filling is conducted, and the filling effect is not good, an Al wire may form a narrow or broken part is solved, and the yield of the Al wire is improved. And the high-quality Al line filling effect is realized while the process compatibility is maintained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor devices, and in particular to an Al line forming method. BACKGROUND

[0002] Currently, in the process of 90nm and below, the aluminum (Al) line mainly adopts a redistribution layer (RDL) deposition as a pad. This method has a great influence on the reliability and stability of electrical connection, especially for products with high reliability requirements. The Al line needs to be conformally filled. When the filling effect is not good, the Al line may form a narrow or disconnected part, i.e., pinch off, which affects the reliability of the Al line.

[0003] The Al line deposited by the redistribution layer deposition method usually uses a sputtering method to form a thin film in a physical vapor deposition (PVD) process. However, the step coverage of the Al line obtained by this method is poor. For some small size structures, direct sputtering cannot meet the filling requirements. Therefore, for high-power products, a reflow process can be introduced. Through hot air circulation or infrared heating, the aluminum layer is locally softened, and the surface tension drives the metal to flow to the recessed area. However, the integrated circuit (IC) product has strict control on the heat budget during heat treatment, so the Al filling cannot be completely performed by increasing the temperature. SUMMARY

[0004] The present application provides an Al line forming method, which can solve the problem that the Al line may form a narrow or disconnected part when conformal filling and the filling effect is not good in the related art.

[0005] In one aspect, an Al line forming method is provided, including: providing a wafer, a semiconductor device is formed on the wafer, an ILD layer is covered on the semiconductor device, and a recess is formed in the ILD layer; depositing a barrier layer on the surface of the ILD layer and the recess; depositing a wetting layer on the barrier layer; cooling the wetting layer; depositing an Al layer on the wetting layer, the Al layer filling the recess; performing a planarization process to remove the barrier layer, the wetting layer, and the Al layer outside the recess.

[0006] In some embodiments, the barrier layer includes a TaN layer.

[0007] In some embodiments, the thickness of the barrier layer is 200 angstroms to 500 angstroms.

[0008] In some embodiments, the wetting layer comprises a Ti layer.

[0009] In some embodiments, the thickness of the wetting layer is 25 angstroms to 100 angstroms.

[0010] In some embodiments, the deposition temperature of the wetting layer is 100 to 200 degrees Celsius.

[0011] In some embodiments, the cooling treatment of the wetting layer comprises: cooling the wetting layer with nitrogen in a cooling chamber.

[0012] In some embodiments, the time of the cooling treatment process is 30 seconds to 60 seconds.

[0013] In some embodiments, the depositing an Al layer on the wetting layer comprises: depositing an Al layer on the wetting layer by a PVD process.

[0014] In some embodiments, the temperature of the Al deposition process is 300 degrees Celsius to 350 degrees Celsius.

[0015] In some embodiments, the thickness of the Al layer is 8000 microns to 40000 microns.

[0016] In some embodiments, a reflow process is used in the process of depositing an Al layer on the wetting layer by a PVD process.

[0017] The technical scheme of the present application at least has the following advantages: By depositing a wetting layer after depositing a barrier layer, the step coverage of the barrier layer is improved; by cooling treatment of the wetting layer, the problem of too large crystal grains caused by high temperature in the subsequent Al deposition process is avoided, so that the temperature can be increased in the reflow process for Al filling, solving the problem of narrow or disconnected Al lines in the related art when the conformal filling effect is not good, and achieving the effect of high-quality Al line filling while maintaining process compatibility. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the description of the specific embodiments or the prior art. Obviously, the drawings described below are some embodiments of the present application, and those skilled in the art can obtain other drawings without creative labor on the basis of these drawings.

[0019] Figure 1 is a flow chart of an Al line forming method provided by an exemplary embodiment of the present application; Figure 2 is a structure sectional view after deposition of a barrier layer provided by an exemplary embodiment of the present application; Figure 3 is a structure sectional view after deposition of a wetting layer provided by an exemplary embodiment of the present application; Figure 4 is a structure sectional view after Al layer forming provided by an exemplary embodiment of the present application; Figure 5 is a structure sectional view after pad forming provided by an exemplary embodiment of the present application; Figure 6 is an SEM image of an Al line formed by PVD sputtering in the related art; Figure 7 is an SEM image of an Al line provided by an exemplary embodiment of the present application. DETAILED DESCRIPTION

[0020] The technical solutions in the present application will be described clearly and completely below with reference to the drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0021] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application. In addition, the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0022] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements, or it can be wireless connection, or it can be wired connection. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0023] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0024] Reference Figure 1 which shows a flow chart of an Al line forming method provided by an exemplary embodiment of the present application, as shown in Figure 1 which includes the following steps: Step S101, providing a wafer, the wafer is formed with a semiconductor device, the semiconductor device is covered with an ILD layer, and the ILD layer is formed with a recess; Reference Figure 2 which shows a structure cross-sectional view after deposition of a barrier layer provided by an exemplary embodiment of the present application, as shown in Figure 2 which includes the following steps: Exemplarily, a wafer 201 is selected as a substrate, the surface of the wafer 201 is cleaned to remove impurities and oxides, and an inter-layer dielectric (ILD) layer 202 is deposited on the wafer 201. Through the foregoing process, the wafer 201 is formed with a semiconductor device (not shown in the figure), the semiconductor device is covered with the inter-layer dielectric (ILD) layer 202, the ILD layer 202 further has a Cu metal interconnection structure (not shown in the figure), the ILD layer 202 is formed with a recess, and the Cu metal layer at the bottom of the recess is exposed (not shown in the figure). Figure 2 Figure 2 Figure 2

[0025] Step S102, depositing a barrier layer on the surface of the ILD layer and the recess.

[0026] Optionally, the barrier layer includes a TaN layer.

[0027] The thickness of the TaN layer is 200 angstroms to 500 angstroms.

[0028] As shown in Figure 2 exemplarily, the deposition of the barrier layer 203 is performed on the surface of the ILD layer 202 and the recess, the barrier layer 203 includes a tantalum nitride (TaN) layer, and the use of TaN as the material of the barrier layer can effectively inhibit the diffusion of Cu metal; the thickness of the barrier layer 203 is 400 angstroms.

[0029] Exemplarily, the barrier layer 203 can further include a titanium nitride (TiN) layer; the use of TiN as the material of the barrier layer 203 can effectively inhibit the diffusion of Cu metal.

[0030] Step S103, depositing a wetting layer on the barrier layer.

[0031] Optionally, the wetting layer includes a Ti layer.​​​

[0032] The thickness of the wetting layer is 25 angstroms to 100 angstroms.

[0033] The deposition temperature of the wetting layer is 100 to 200 degrees Celsius.

[0034] Reference Figure 3 which shows a structure cross-sectional view of the wetting layer after deposition provided by an exemplary embodiment of the present application, as shown in Figure 3 including: Exemplarily, a thermal deposition process is performed on the barrier layer 203 at a temperature of 150 degrees Celsius to form the wetting layer 204 after deposition; the wetting layer 204 includes a Ti layer; the thickness of the wetting layer 204 after deposition is 50 angstroms; and the deposition of the wetting layer 204 at a high temperature of 150 degrees Celsius can improve the step coverage of the barrier layer 203 and the wetting layer 204, and ensure good conductivity and anti-diffusion ability of the generated Al wire.

[0035] Step S104, cooling treatment of the wetting layer.

[0036] Optionally, the cooling treatment of the wetting layer includes: cooling treatment of the wetting layer by nitrogen in a cooling chamber.

[0037] The cooling treatment process lasts for 30 seconds (s) to 60 s.

[0038] Exemplarily, after the high-temperature deposition of the wetting layer 204, the wetting layer 204 is subjected to cooling treatment, which includes but is not limited to: cooling the wetting layer 204 by nitrogen in a cooling chamber, and the temperature of the wetting layer 204 is reduced to 25 degrees Celsius after cooling for 60 s. The cooling of the wetting layer 204 is conducive to the subsequent combination of Ti and Al.

[0039] Step S105, depositing an Al layer on the wetting layer, the Al layer filling the groove.

[0040] Optionally, the deposition of the Al layer on the wetting layer includes: depositing the Al layer on the wetting layer by a PVD process.

[0041] Optionally, the temperature for depositing the Al layer is 300 degrees Celsius to 350 degrees Celsius.

[0042] Optionally, the thickness of the Al layer is 8000 microns to 40000 microns.

[0043] In the process of depositing the Al layer on the wetting layer by the PVD process, a reflow process is used.

[0044] Reference Figure 4 which shows a structure cross-sectional view of the Al layer after formation provided by an exemplary embodiment of the present application, as shown in Figure 4As shown, including: Exemplarily, the Al layer 205 is deposited on the wetting layer 204 at a temperature of 320 degrees Celsius, the Al of the Al layer 205 combines with the Ti of the wetting layer 204, and due to the cooling treatment of the wetting layer 204, the Al combines with the Ti to form an inner lining of titanium aluminide (TiAl3) alloy. Due to the imperfect atomic arrangement at the grain boundary of the TiAl3 alloy, the TiAl3 alloy has a large grain boundary energy, and the TiAl3 alloy grain with a large grain boundary energy is small. In the Al deposition process, the Al layer 205 is treated by a reflow process to locally soften the Al layer 205, the surface tension drives the Al metal to flow to the recessed area, fills the pattern gap, eliminates internal stress and improves the surface morphology, thereby achieving the effect of conformal filling. The thickness of the deposited Al layer 205 is 20000 microns.

[0045] In step S106, a planarization treatment is performed to remove the barrier layer, the wetting layer and the Al layer outside the recess.

[0046] Reference Figure 5 As shown, a structure cross-sectional view after the pad is formed is shown; as Figure 6 As shown, including: Exemplarily, the Al layer 205 is planarized to remove the barrier layer 203, the wetting layer 204 and the Al layer 205 outside the recess, and the barrier layer 203, the wetting layer 204 and the Al layer 205 in the recess constitute an Al pad. After the pad is formed, a passivation layer can be subsequently covered on the pad, and a passivation layer opening is formed by etching as a bonding point.

[0047] Reference Figure 6 As shown, an SEM image of an Al line formed after PVD sputtering in the related art is shown; as Figure 5 As shown, in the process of 90nm and below, the Al line needs to be conformally filled. When the filling effect is not good, the Al line may form a narrow or disconnected part.

[0048] Reference Figure 7 As shown, an SEM image of an Al line provided by an exemplary embodiment of the present application is shown; as Figure 7 As shown, the Al line made by the method of the present application improves the step coverage of the barrier layer by depositing the wetting layer after depositing the barrier layer. Through the cooling treatment of the wetting layer, the problem of excessively large grains caused by high temperature in the subsequent Al deposition process is avoided, so that the Al filling in the reflow process can be performed by increasing the temperature, thereby solving the problem that when the conformal filling effect is not good, the Al line may form a narrow or disconnected part, while maintaining process compatibility and achieving the effect of high-quality Al line filling.

[0049] Obviously, the above embodiments are merely example for clearly illustrating but not limitation to the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments are not required to be enumerated and it is impossible to enumerate all the embodiments. The changes or variations derived from the above are still within the protection scope of the present application.

Claims

1. A method for forming an Al wire, characterized in that: include: Providing a wafer, wherein a semiconductor device is formed on the wafer, the semiconductor device is covered with an ILD layer, and a groove is formed in the ILD layer; Depositing a barrier layer on the ILD layer and the surface of the groove; depositing a wetting layer on the barrier layer; Cooling the wetted layer; depositing an Al layer on the wetting layer, wherein the Al layer fills the groove; A planarization process is performed to remove the barrier layer, the wetting layer and the Al layer outside the groove.

2. The method according to claim 1, wherein The barrier layer includes a TaN layer.

3. The method according to claim 2, wherein The barrier layer has a thickness of 200 angstroms to 500 angstroms.

4. The method according to claim 1, wherein The wetting layer includes a Ti layer.

5. The method according to claim 4, wherein The thickness of the wetting layer is 25 angstroms to 100 angstroms.

6. The method according to claim 4, wherein The deposition temperature of the wetting layer is 100 to 200 degrees Celsius.

7. The method according to claim 1, wherein The cooling process of the wetting layer comprises: The wet layer is cooled using nitrogen in a cooling chamber.

8. The method according to claim 7, wherein The cooling process takes 30 to 60 seconds.

9. The method according to claim 1, wherein The step of depositing an Al layer on the wetting layer comprises: An Al layer is deposited on the wetting layer by a PVD process.

10. The method according to claim 9, wherein The temperature for depositing the Al layer is 300 degrees Celsius to 350 degrees Celsius.

11. The method according to claim 9, wherein The thickness of the Al layer is 8000 micrometers to 40000 micrometers.

12. The method according to claim 9, wherein During the deposition of the Al layer on the wetting layer by the PVD process, a reflow process is used.

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