Technological method for prolonging service life of CVD (chemical vapor deposition) tungsten machine

Abstract

The invention discloses a technological method for prolonging the service life of a CVD tungsten machine table. The technological method comprises the step that a Ti layer is formed on the surface of a bottom layer structure. N2 plasma treatment is carried out to nitride the surface of the Ti layer to form a TiN layer without C and O, and the Ti layer and the TiN layer are stacked to form an adhesion barrier layer. Tungsten chemical vapor deposition is carried out in a CVD tungsten machine table to form a tungsten seed crystal layer on the surface of the TiN layer, a tungsten-containing precursor of tungsten chemical vapor deposition comprises WF6, and in tungsten chemical vapor deposition forming the tungsten seed crystal layer, the WF6 and the TiN layer are subjected to a self-limiting reaction and form titanium fluoride, so that the tungsten seed crystal layer is formed. And by utilizing the characteristic that the TiN layer does not contain C and O, the thickness of a defective film formed by condensing titanium fluoride onto the gas spraying head of the CVD tungsten machine table is reduced or disappears, so that the service life of the gas spraying head is prolonged. The service life of the gas spraying head of the CVD tungsten machine table can be prolonged, and the size of the tungsten main body layer can be further increased, so that the contact resistance is reduced.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a semiconductor integrated circuit, and more particularly to a process for improving the lifetime of a CVD tungsten machine. Background Art

[0002] In the middle-stage chip manufacturing process, a combination of Ti + TiN is generally used as a barrier layer, i.e., an adhesion barrier layer, for chemical vapor deposition (CVD) tungsten (W) vias.

[0003] However, in actual applications, it is found that the lifetime of the showerhead of the W nucleation (nuc), i.e., the seed crystal, machine is much shorter than that of other parts. When replacing the showerhead, a wipeable white film is found, and defect particles with components of C, O, and Ti are found in the defect scan of the product.

[0004] As Figure 1 shown, it is a schematic diagram of the cavity structure of an existing CVD tungsten machine; the cavity has a cavity wall 101, and at the bottom of the cavity, there is a heater 102 passing through the bottom surface of the cavity wall 101. The top surface of the heater 102 serves as the support surface for the wafer 103.

[0005] A lid 104 is provided at the top of the cavity. A blocker plate 105 and a showerhead 106 are provided at the bottom of the lid 104.

[0006] A gas mixer 107 is provided at the top of the lid 104.

[0007] The gas mixer 107 and the lid 104 are provided with air holes for the process gas to flow in; a plurality of small air holes are respectively provided on the blocker plate 105 and the showerhead 106 for uniformly distributing the process gas into the cavity.

[0008] In the existing via formation process, the tungsten seed layer needs to be grown in the cavity of the CVD tungsten machine as Figure 1 shown, but a defect film is likely to form on the surface of the showerhead 106. The defect film not only easily blocks the small air holes, thus affecting the gas inflow, but also easily falls onto the surface of the wafer 103, thus affecting the yield of the product. Therefore, when the defect film appears or accumulates to a certain amount, the showerhead 106 cannot be used continuously and needs to be cleaned or directly replaced. Therefore, the lifetime of the showerhead 106 is reduced, and the lifetime of the CVD tungsten machine is also reduced, thus affecting the production. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a process method for improving the service life of a CVD tungsten machine tool, which can improve the service life of the gas spray head of the CVD tungsten machine tool, and can also increase the volume of the tungsten main body layer and thus reduce the contact resistance.

[0010] To solve the above technical problems, the process method for improving the service life of a CVD tungsten machine tool provided by the present invention includes the following steps:

[0011] Provide a bottom layer structure, and form a Ti layer on the surface of the bottom layer structure.

[0012] Perform N2 plasma treatment to nitride the surface of the Ti layer to form a TiN layer without C and O, and form an adhesion barrier layer by superimposing the Ti layer and the TiN layer.

[0013] Perform tungsten chemical vapor deposition in the CVD tungsten machine tool to form a tungsten seed layer on the surface of the TiN layer. The tungsten-containing precursor for the tungsten chemical vapor deposition includes WF 6 , in the tungsten chemical vapor deposition for forming the tungsten seed layer, WF 6 and the TiN layer will undergo a self-limiting reaction to form titanium fluoride, and use the characteristics of the TiN layer without C and O to reduce or eliminate the thickness of the defective film formed by condensing the titanium fluoride onto the gas spray head of the CVD tungsten machine tool, thereby improving the service life of the gas spray head.

[0014] A further improvement is that it further includes the step of:

[0015] Form a tungsten main body layer on the surface of the tungsten seed layer.

[0016] A further improvement is that the tungsten main body layer is a part of the through hole.

[0017] Before forming the Ti layer, it further includes:

[0018] Perform patterning etching to form an opening of the through hole in a selected area of the bottom layer structure.

[0019] After the tungsten main body layer is formed, the opening of the through hole is completely filled.

[0020] A further improvement is that the Ti layer is formed by PVD process, and the Ti layer is formed on the bottom surface, side surface and outer surface of the opening of the through hole.

[0021] A further improvement is that after the tungsten main body layer is formed, it further includes:

[0022] Perform a chemical mechanical polishing process to remove the tungsten main body layer, the tungsten seed layer, the TiN layer and the Ti layer outside the opening of the through hole.

[0023] A further improvement is that heating is also included in the N2 plasma treatment. By heating, the thickness of the TiN layer is further reduced, and then the thickness of the adhesion barrier layer is reduced, so that the volume of the tungsten main layer filled in the opening of the through hole increases.

[0024] A further improvement is that the thickness of the defective film is adjusted by adjusting the time of the N2 plasma treatment.

[0025] A further improvement is that the underlying structure includes an interlayer film.

[0026] The opening of the through hole passes through the interlayer film.

[0027] In the present invention, a special setting is made for the formation process of the TiN layer before the tungsten chemical vapor deposition of the tungsten seed layer. The TiN layer is no longer obtained by thermal decomposition, such as by the thermal decomposition of titanium tetrakis(dimethylamino), but by subjecting the Ti layer to N2 plasma treatment. The N2 plasma will not introduce by-products of other elements. For example, it will not introduce C and O impurities, so that the TiN layer does not contain C and O. In this way, when tungsten chemical vapor deposition is used to form the tungsten seed layer, even if WF 6 and the TiN layer undergo a self-limiting reaction and form titanium fluoride (TiF x ), since there are no organic by-products such as C and O, the single titanium fluoride is not easily condensed on the gas spray head of the CVD tungsten machine tool and form a defective film after volatilization. Therefore, the present invention can reduce or eliminate the thickness of the defective film on the gas spray head, thereby improving the service life of the gas spray head, that is, the gas spray head can be used for a longer time before being replaced or cleaned.

[0028] At the same time, since the thickness of the defective film on the gas spray head is reduced or eliminated, the amount of the defective film falling on the product surface during the tungsten chemical vapor deposition process will also be reduced or eliminated, so the yield of the product can be improved.

[0029] In addition, compared with the TiN layer formed by thermal decomposition, the TiN layer obtained by N2 plasma treatment in the present invention has a lower thickness. The thickness of the adhesion barrier layer formed by stacking the Ti layer and the TiN layer can be well reduced. In the through hole process, the reduction of the thickness of the adhesion barrier layer can increase the volume of the tungsten main layer, reduce the contact resistance, and also reduce the filling difficulty of the tungsten main layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further described in detail below with reference to the drawings and specific embodiments:

[0031] Figure 1 is a schematic diagram of the cavity structure of an existing CVD tungsten machine tool;

[0032] Figure 2Schematic diagram of the formation of a defective film on the surface of a gas showerhead during the process of forming a tungsten seed layer by existing tungsten chemical vapor deposition;

[0033] Figure 3 Flow chart of the process method for improving the life of a CVD tungsten machine in an embodiment of the present invention. Detailed implementation manners

[0034] Before introducing the method of the embodiment of the present invention, the reasons for the formation of a defective film on the surface of the gas showerhead during the process of forming a tungsten seed layer by existing tungsten chemical vapor deposition are described as follows:

[0035] As Figure 2 shown, it is a schematic diagram of the formation of a defective film on the surface of the gas showerhead during the process of forming a tungsten seed layer by existing tungsten chemical vapor deposition; the steps of existing tungsten chemical vapor deposition for forming a tungsten seed layer include:

[0036] On the bottom layer structure (not shown), a Ti layer 201 is formed on the surface of the bottom layer structure.

[0037] A TiN layer 202 is formed on the surface of the Ti layer 201. In the existing method, the TiN layer 202 is obtained by thermal decomposition of tetrakis(dimethylamino)titanium, and there will be a by-product C in the obtained TiN thin film, that is, the TiN layer 202. The reaction equation is:

[0038] Ti[N(CH 3 ) 2 4 →TiN(C)+HN(CH 3 ) 2 +H 2 NCH 3 +HN(CH 2 ) 2 +Other Hydrocarbon (1);

[0039] Other Hydrocarbon represents other hydrocarbons.

[0040] In the tungsten chemical vapor deposition process of forming a tungsten seed layer, the tungsten precursor usually uses WF 6 , WF 6 and the TiN layer will undergo a self-limiting reaction to form titanium fluoride. The reaction equation is:

[0041] TiN+WF 6 àTiF x +WN x (2);

[0042] TiF x represents titanium fluoride, and x represents the number of F atoms in titanium fluoride. ​

[0043] By-products TiFx and organic by-products such as C and O in the TiN layer 202 volatilize together and condense onto the showerhead 106 (HX: 25°C) to form a defective thin film 205. Figure 2 In, the arrow line 203 indicates WF 6 flows onto the surface of the TiN layer 202; the arrow line 204 indicates that by-products TiFx and organic by-products such as C and O in the TiN layer 202 volatilize together.

[0044] As Figure 3 shown, it is a flowchart of the process method for improving the life of the CVD tungsten machine in the embodiment of the present invention; the process method for improving the life of the CVD tungsten machine in the embodiment of the present invention includes the following steps:

[0045] Step S101, provide a bottom layer structure and form a Ti layer on the surface of the bottom layer structure.

[0046] In the embodiment of the present invention, the bottom layer structure includes an interlayer film. The bottom layer structure further includes a semiconductor substrate, and semiconductor devices are formed in the semiconductor substrate; the interlayer film is formed on the semiconductor substrate.

[0047] In the embodiment of the present invention, the subsequent tungsten main layer is a part of the through hole.

[0048] Before forming the Ti layer, it further includes:

[0049] Perform patterning etching to form an opening of the through hole in a selected area of the bottom layer structure. The patterning etching includes the following sub-steps:

[0050] Perform a photolithography process to define a formation area of the opening of the through hole.

[0051] Perform etching to remove the interlayer film in the formation area of the opening of the through hole and form the opening of the through hole. The formed opening of the through hole penetrates the interlayer film.

[0052] In the embodiment of the present invention, the Ti layer is formed by a PVD process, and the Ti layer is formed on the bottom surface, side surface and outer surface of the opening of the through hole.

[0053] Step S102, perform N2 plasma treatment to nitride the surface of the Ti layer to form a TiN layer without C and O, and form an adhesion barrier layer by superimposing the Ti layer and the TiN layer.

[0054] Step S103, perform tungsten chemical vapor deposition in the CVD tungsten machine to form a tungsten seed layer on the surface of the TiN layer. The tungsten-containing precursor for the tungsten chemical vapor deposition includes WF 6 , in the tungsten chemical vapor deposition for forming the tungsten seed layer, WF6 The TiN layer will undergo a self-limiting reaction with the WF6 and TiN layers to form titanium fluoride. By utilizing the characteristics that the TiN layer does not contain C and O, the thickness of the defective film formed by condensing the titanium fluoride onto the gas showerhead of the CVD tungsten machine is reduced or eliminated, thereby increasing the lifespan of the gas showerhead.

[0055] In an embodiment of the present invention, heating is further included in the N2 plasma treatment. By heating, the thickness of the TiN layer is further reduced, and thus the thickness of the adhesion barrier layer is reduced, increasing the volume of the tungsten main body layer filled in the opening of the through hole.

[0056] The thickness of the defective film is adjusted by adjusting the time of the N2 plasma treatment.

[0057] It further includes the steps of:

[0058] A tungsten main body layer is formed on the surface of the tungsten seed layer. In some embodiments, the tungsten main body layer is formed by an electroplating process. In other embodiments, it can also be that the tungsten main body layer is formed by a PVD process or a CVD process.

[0059] After the tungsten main body layer is formed, the opening of the through hole is completely filled.

[0060] After the tungsten main body layer is formed, it further includes:

[0061] A chemical mechanical polishing process is performed to remove the tungsten main body layer, the tungsten seed layer, the TiN layer, and the Ti layer outside the opening of the through hole.

[0062] In the embodiment of the present invention, a special setting is made for the formation process of the TiN layer before the tungsten chemical vapor deposition of the tungsten seed layer. The TiN layer is no longer obtained by thermal decomposition, such as by the thermal decomposition of tetrakis(dimethylamino)titanium, but is obtained by subjecting the Ti layer to N2 plasma treatment. The N2 plasma does not introduce by-products of other elements. For example, it does not introduce C and O impurities, so that the TiN layer does not contain C and O. In this way, when forming the tungsten seed layer by tungsten chemical vapor deposition, even if WF6 6 and the TiN layer undergo a self-limiting reaction to form titanium fluoride, since there are no organic by-products such as C and O, the individual titanium fluoride is not easily condensed on the gas showerhead of the CVD tungsten machine to form a defective film after volatilization. Therefore, the present invention can reduce or eliminate the thickness of the defective film on the gas showerhead, thereby increasing the lifespan of the gas showerhead, that is, the gas showerhead can be used for a longer time before being replaced or cleaned.

[0063] At the same time, since the thickness of the defective film on the gas showerhead is reduced or eliminated, the amount of the defective film falling on the product surface during the tungsten chemical vapor deposition process is also reduced or eliminated, so the yield of the product can be increased.

[0064] In addition, compared with the TiN layer formed by thermal decomposition, the TiN layer obtained by N2 plasma treatment in the embodiments of the present invention has a lower thickness. The thickness of the adhesion barrier layer formed by stacking the Ti layer and the TiN layer can be well reduced. In the via process, the reduction of the thickness of the adhesion barrier layer can increase the volume of the tungsten bulk layer, reduce the contact resistance, and also reduce the filling difficulty of the tungsten bulk layer.

[0065] In the embodiments of the present invention, after depositing the Ti thin film, the surface of Ti is nitrided into a TiN thin film by using N2 plasma treatment to replace the previous method of depositing TiN by thermal decomposition, so that there is no source of organic substances such as C / O in the previous layer, thereby avoiding the deposition of C / O by-products on the W nuc machine and improving the lifetime of the machine. In addition, since the thickness of the barrier layer, that is, the adhesion barrier layer, can be reduced at the same time, the volume of the bulk W, that is, the tungsten bulk layer, can be expanded to reduce the contact resistance.

[0066] In the embodiments of the present invention, a heater can be used to achieve a Ti / TiN thin film with a lower thickness; different N2 treatments, that is, different treatment times of N2 plasma, can be selected to achieve different removal effects of defective thin films.

[0067] The present invention has been described in detail through specific embodiments, but these do not constitute a limitation to the present invention. Without departing from the principle of the present invention, those skilled in the art can also make many modifications and improvements, which should also be regarded as the protection scope of the present invention.

Claims

1. A process for increasing the life of a CVD tungsten machine, characterized in that: The steps include: Providing an underlying structure, and forming a Ti layer on a surface of the underlying structure; Performing N2 plasma treatment to nitride the surface of the Ti layer to form a TiN layer free of C and O, and forming an adhesion barrier layer by stacking the Ti layer and the TiN layer; Tungsten chemical vapor deposition is performed in the CVD tungsten machine to form a tungsten seed layer on the surface of the TiN layer. The tungsten-containing precursor of the tungsten chemical vapor deposition includes WF6. In the tungsten chemical vapor deposition of forming the tungsten seed layer, WF6 and the TiN layer undergo a self-limiting reaction to form titanium fluoride. The characteristic that the TiN layer does not contain C and O is utilized to reduce or eliminate the thickness of the defective film formed by the condensation of titanium fluoride onto the gas spray head of the CVD tungsten machine, thereby increasing the life of the gas spray head.

2. The process for improving the life of a CVD tungsten machine according to claim 1, characterized in that: Also includes the steps: A tungsten bulk layer is formed on the surface of the tungsten seed layer.

3. The process for improving the life of a CVD tungsten machine according to claim 2, characterized in that: The tungsten bulk layer serves as a component of the through hole; Before forming the Ti layer, the method further comprises: Performing patterned etching to form openings of the through holes in selected areas of the underlying structure; After the tungsten main layer is formed, the opening of the through hole is completely filled.

4. The process for improving the service life of a CVD tungsten machine according to claim 3, characterized in that: The Ti layer is formed by a PVD process, and is formed on the bottom surface, the side surface and the outer surface of the opening of the through hole.

5. The process for improving the service life of a CVD tungsten machine according to claim 4, characterized in that: After the tungsten main layer is formed, the method further comprises: A chemical mechanical polishing process is performed to remove the tungsten main layer, the tungsten seed crystal layer, the TiN layer and the Ti layer outside the opening of the through hole.

6. The process for increasing the service life of a CVD tungsten machine according to claim 4, characterized in that: The N2 plasma treatment also includes heating to further reduce the thickness of the TiN layer and further reduce the thickness of the adhesion barrier layer, so that the volume of the tungsten main layer filled in the opening of the through hole increases.

7. The process for improving the life of a CVD tungsten machine according to claim 4, characterized in that: The thickness of the defect film can be adjusted by adjusting the time of the N2 plasma treatment.

8. The process for improving the life of a CVD tungsten machine according to claim 4, characterized in that: The underlying structure includes an interlayer film; An opening of the through hole passes through the interlayer film.

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