Method for filling contact hole in integrated circuit process

Abstract

The invention belongs to the field of integrated circuit process, and relates to a method for filling a contact hole in the integrated circuit process, which comprises the following steps of: sequentially preparing a first TiN layer, a second TiN layer and a Ti layer in the contact hole by adopting ionized metal plasma deposition; depositing Al on the surface of the Ti layer by adopting a physical vapor deposition method, and completely filling the contact hole; the stoichiometric ratio of the titanium element to the nitrogen element in the second TiN layer is uniformly increased in a gradient manner from the bottom of the second TiN layer along the deposition direction from 1: 1 until the top of the second TiN layer is a pure titanium layer. Compared with the prior art, the method has the advantages that fewer cavity types are used, the equipment cost is lower, and complete filling of the contact hole with the small radius and the large depth-to-width ratio is achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of integrated circuit process, and relates to a filling method of a contact hole in an integrated circuit process. BACKGROUND

[0002] The integrated circuit process enters a high-speed development stage, and the preparation method of the interconnection layer also changes accordingly. In order to provide a larger area of interconnection, the industry introduces a more flexible multi-layer metallization process. The most difficult problem in the multi-layer metallization is to ensure the electrical continuity at the contact hole and the via hole. For example, the step coverage of sputtered aluminum is sharply reduced with the increase of the aspect ratio of the hole. In the submicron design rule, the step coverage of the contact hole and the via hole cannot be lower than 20%, and the connection between the layers of metal relies on the vertical interconnection-via plug. And the connection between the poles and the metal relies on the vertical contact hole plug. At present, the submicron standard process adopted by the industry is Al Plug, W Plug and CuECP technology, which has reliability and practicability. With the increase of the aspect ratio, how to improve the step coverage of the film layer is crucial to improve the stability and yield of the device.

[0003] In order to connect the different metal wire layers above and below, the multi-layer wiring process adopts a metal filling plug technology to form a metal interconnection structure. The metal filling plug process includes a contact hole filling plug and a via hole filling plug. The former is specifically used to connect the device electrode and the first layer of metal layer, and the latter is used to connect the different metal wire layers above and below. It is worth noting that in the via hole connecting the upper and lower metal layers, although aluminum has good conductivity, when the aluminum filling plug is formed by sputtering method, there will be a problem of poor step coverage. SUMMARY

[0004] In order to solve the technical problems existing in the prior art, the present application provides a filling method of a contact hole in an integrated circuit process. Compared with the prior art, the method uses fewer cavity types, lower equipment cost, and realizes complete filling of a small radius and large aspect ratio contact hole.

[0005] In order to achieve the above technical effects, the present application adopts the following technical solutions:

[0006] The present application provides a filling method of a contact hole in an integrated circuit process, which comprises:

[0007] A first TiN layer, a second TiN layer and a Ti layer are prepared in the contact hole in sequence by using ionized metal plasma deposition;

[0008] Al is deposited on the surface of the Ti layer by using physical vapor deposition method, and the contact hole is completely filled;

[0009] The stoichiometric ratio of titanium element and nitrogen element in the second TiN layer starts from 1:1, increases uniformly in a gradient from the bottom of the second TiN layer to the top of the second TiN layer along the deposition direction, and is a pure titanium layer at the top of the second TiN layer.

[0010] As a preferred technical solution of the present application, the diameter of the contact hole is less than 0.18 μm, and the aspect ratio is 3-5:1.

[0011] As a preferred technical solution of the present application, the thickness of the first TiN layer is less than 200 angstroms.

[0012] As a preferred technical solution of the present application, the second TiN layer is on average substoichiometric TiN.

[0013] As a preferred technical solution of the present application, the thickness of the second TiN layer is 200-800 angstroms.

[0014] As a preferred technical solution of the present application, the thickness of the Ti layer is 150-250 angstroms.

[0015] As a preferred technical solution of the present application, the physical vapor deposition method is performed in a standard process reaction cavity.

[0016] As a preferred technical solution of the present application, the physical vapor deposition method includes cold deposition and hot deposition performed in sequence.

[0017] As a preferred technical solution of the present application, the temperature of the cold deposition is less than 100 ℃, and the thickness of the deposited Al is less than 2000 angstroms.

[0018] As a preferred technical solution of the present application, the temperature of the hot deposition is 350-450 ℃.

[0019] Compared with the prior art, the present application has at least the following beneficial effects:

[0020] (1) The present application provides a filling method for a contact hole in an integrated circuit process, which realizes the preparation of a Ti adhesion layer and a TiN wetting layer in a single IMP cavity by setting a more reasonable deposition mode, reduces the use of a CVD cavity, and shortens the overall process time to one third of the original process.

[0021] (2) The present application provides a filling method for a contact hole in an integrated circuit process, which uses an IMP cavity to deposit TiN instead of a conventional CVD cavity to deposit TiN, optimizes the submicron hole step coverage, enables Al filling to achieve a smaller CD and a larger aspect ratio, reduces the Al puncture phenomenon, and reduces the Al filling temperature.

[0022] (3) The application provides a filling method for a contact hole in an integrated circuit process. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The filling effect SEM&FIB diagram of the filling method for the contact hole in the integrated circuit process provided by the application.

[0024] The application will be further described below. However, the following examples are only simple examples of the application and do not represent or limit the protection scope of the application, and the protection scope of the application is subject to the claims. DETAILED DESCRIPTION

[0025] The technical scheme of the application will be further described below through a specific embodiment.

[0026] The application provides a filling method for a contact hole in an integrated circuit process, and the method comprises the following steps:

[0027] A first TiN layer, a second TiN layer and a Ti layer are sequentially prepared in the contact hole by using ionized metal plasma deposition;

[0028] Al is deposited on the surface of the Ti layer by using physical vapor deposition, and the contact hole is completely filled;

[0029] The stoichiometric ratio of titanium elements and nitrogen elements in the second TiN layer is started from 1:1, uniformly increases in the deposition direction from the bottom of the second TiN layer, and is a pure titanium layer at the top of the second TiN layer.

[0030] In the application, the IMP (ionized metal plasma) cavity is used to prepare the TiN layer, instead of the CVD cavity in the prior art, so that the film quality of the TiN layer is improved, the resistivity and mechanical properties of the TiN layer prepared by the IMP cavity are better than those of the TiN layer prepared by the CVD cavity, and the gradient transformation of the stoichiometric ratio of titanium elements and nitrogen elements in the second TiN layer can be realized. The pure TiN film layer is a columnar structure, and the TiN gradient distribution structure improves the TiN-based diffusion barrier. The TiN gradient distribution barrier can relieve the mutual diffusion in the columnar TiN barrier through a rapid diffusion path, because the thin substoichiometric TiN intermediate layer will cause the destruction or displacement of the TiN columnar grains, and create a bonding point for Al, and the Ti at the top can be more conducive to the diffusion of Al, so that a better filling effect is achieved.

[0031] In one embodiment of the present application, the diameter of the contact hole is less than 0.18 μm, and the aspect ratio is 3-5:1. The diameter of the contact hole can be 0.05 μm, 0.08 μm, 0.10 μm, 0.12 μm, 0.15 μm, or 0.18 μm, and the aspect ratio can be 3:1, 3.2:1, 3.5:1, 3.8:1, 4:1, 4.2:1, 4.5:1, 4.8:1, or 5:1, but is not limited to the listed values, and other values not listed in the above ranges are also applicable.

[0032] In one embodiment of the present application, the size of the contact hole is not limited to the above defined size, and other contact holes with a larger diameter and a lower aspect ratio are also applicable to the present method.

[0033] In one embodiment of the present application, the thickness of the first TiN layer is less than 200 angstroms, such as 50 angstroms, 80 angstroms, 120 angstroms, 150 angstroms, 180 angstroms, or 200 angstroms, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0034] In one embodiment of the present application, the conditions for ionized metal plasma deposition of the first TiN layer can be: a radio frequency power of 2-4 kW, a substrate bias of 1505-250 V, a cavity pressure of 10-15 mtorr, a substrate temperature of 200-250°C, a flow ratio of N2 and Ti of 1:4-1:5, and a total flow of 20-50 sccm.

[0035] In one embodiment of the present application, the second TiN layer is on average substoichiometric TiN. Substoichiometric TiN refers to a titanium nitride (TiN) in which the content of nitrogen (N) is lower than the standard stoichiometric ratio (TiN 1.0 ), and the substoichiometric TiN can adjust the conductivity and mechanical properties of the thin film. In particular, it performs outstandingly in terms of wear resistance, crack resistance, and interfacial bonding force, with a hardness of 30-40% higher than that of standard stoichiometric TiN, an elastic modulus of 20-25% higher, a scratch test of 40% higher, and a tensile peel strength of 40% higher.

[0036] In one embodiment of the present application, the thickness of the second TiN layer is 200-800 angstroms, such as 200 angstroms, 300 angstroms, 400 angstroms, 500 angstroms, 600 angstroms, 700 angstroms, or 800 angstroms, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0037] In one embodiment of the present application, the method for ionized metal plasma deposition of the second TiN layer is to set the process parameters in the process recipe, let it stand for 10 s after the deposition of the first layer of TiN, change N2:Ar=1:6, and then deposit the required thin film in sequence.

[0038] In one embodiment of the present application, the Ti layer has a thickness of 150-250 angstroms, such as 150 angstroms, 160 angstroms, 170 angstroms, 180 angstroms, 190 angstroms, 200 angstroms, 210 angstroms, 220 angstroms, 230 angstroms, 240 angstroms, or 250 angstroms, but is not limited to the listed values, and other values within the range are also applicable.

[0039] In one embodiment of the present application, the conditions for depositing the Ti layer by ionized metal plasma can be: a radio frequency power of 1-8 kW, a direct current bias of 50-500 V, a chamber pressure of 0.5-5 mtorr, a substrate temperature of room temperature-400°C, and an argon flow rate of 20-100 sccm.

[0040] In one embodiment of the present application, the physical vapor deposition is performed in a standard process chamber.

[0041] In one embodiment of the present application, the physical vapor deposition includes cold deposition and thermal deposition performed in sequence.

[0042] In one embodiment of the present application, the cold deposition is performed at a temperature of less than 100°C, and the deposited Al has a thickness of less than 2000 angstroms. The temperature for cold deposition can be 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, or 90°C, but is not limited to the listed values, and other values within the range are also applicable.

[0043] In one embodiment of the present application, the thermal deposition is performed at a temperature of 350-450°C, such as 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, 410°C, 420°C, 430°C, 440°C, or 450°C, but is not limited to the listed values, and other values within the range are also applicable.

[0044] In one embodiment of the present application, the thermal deposition is performed in a standard process chamber to physically vapor deposit Al to completely fill the contact hole, and the deposited Al has a thickness of greater than 4000 angstroms.

[0045] In one embodiment of the present application, in addition to the deposition temperature, the other conditions for physically vapor depositing Al by cold deposition and thermal deposition can be: a sputtering power of 10-15 kW, a sputtering pressure of 0.5-2 mtorr, an argon flow rate of 10-15 sccm, and a sputtering time of 6-8 s.

[0046] In one embodiment of the present application, the substrate is pretreated before deposition.

[0047] In one embodiment of the present invention, the pretreatment method includes sequentially performing cleaning, degassing, and surface activation. Cleaning may include ultrasonic cleaning with deionized water and drying. Degassing may involve removing water vapor and residues from previous etching processes, such as by releasing unstable nuclides through high-temperature heating (thermal desorption) and ionizing them for subsequent removal. Surface activation may involve etching with argon plasma at a power of 250-300 W for 10-30 seconds to remove surface oxides.

[0048] In a specific embodiment of the present invention, the purity of the titanium target, aluminum target and nitrogen used for deposition are conventional in the art and are not further limited herein.

[0049] In a specific embodiment of the present invention, the contact hole filling method in the integrated circuit process is applicable to all commonly used substrates in the integrated circuit field, and the model and material of the substrate are not further limited herein.

[0050] To better illustrate the present invention and facilitate understanding of the technical solutions of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0051] Example 1

[0052] This embodiment provides a method for filling a contact hole in an integrated circuit process, the method comprising:

[0053] The pretreated substrate was placed in the IMP chamber for ionized metal plasma deposition to deposit the first TiN layer in the contact hole with a thickness of 150 Å. The deposition conditions were: DC power of 2.1 kW, RF power of 2.25 kW, substrate bias of 200 V, chamber pressure of 11 mtorr, substrate temperature of 200°C, flow ratio of N2 and Ar of 1:4.5, and total flow of 30 sccm.

[0054] A second TiN layer was deposited on the surface of the first TiN layer. The thickness of the second TiN layer was 300 angstroms. The deposition conditions were as follows: DC power of 2.1 kW, RF power of 2.25 kW, substrate bias of 200 V, chamber pressure of 11 mtorr, substrate temperature of 200°C, flow ratio of N2 and Ar of 1:6, total flow rate of 30 sccm, and the stoichiometric ratio of titanium and nitrogen at the bottom of the second TiN layer was 1:1. The stoichiometric ratio of titanium and nitrogen increased gradually along the deposition direction, and the top was pure Ti.

[0055] A Ti layer with a thickness of 200 angstroms was deposited on the surface of the second TiN layer. The deposition conditions were: DC power of 1.8 kW, RF of 2.75 kW, DC bias of 150 V, chamber pressure of 6 mtorr, substrate temperature of 200°C, and argon flow rate of 25 sccm.

[0056] The substrate is placed in a standard process chamber for physical vapor deposition of Al, with a sputtering power of 12 kW, a chamber pressure of 1 mtorr, and argon as the sputtering carrier gas at a flow rate of 12 seem. A cold process is used initially, with a deposition temperature of 50°C, and after a 1500 A thick Al layer is deposited, the deposition temperature is raised to 430°C, and a hot deposition process is used until the desired film thickness is reached.

[0057] Example 2

[0058] The present example provides a method for filling a contact hole in an integrated circuit process, the method comprising:

[0059] The pretreated substrate is placed in an IMP chamber for ionized metal plasma deposition, and a first TiN layer is deposited in the contact hole, with a thickness of 100 A and the same deposition conditions as in Example 1.

[0060] A second TiN layer is deposited on the surface of the first TiN layer, with a thickness of 200 A and the following deposition conditions: a DC power of 2.1 kW, an RF power of 2.25 kW, a substrate bias of 200 V, a chamber pressure of 11 mtorr, a substrate temperature of 200°C, a flow rate ratio of N2 to Ar of 1:6, and a total flow rate of 30 seem. The stoichiometric ratio of titanium to nitrogen at the bottom of the second TiN layer is 1:1, and the stoichiometric ratio of titanium to nitrogen increases along the deposition direction, with pure Ti at the top.

[0061] A Ti layer is deposited on the surface of the second TiN layer, with a thickness of 150 A and the same deposition conditions as in Example 1.

[0062] The substrate is placed in a standard process chamber for physical vapor deposition of Al, with a sputtering power of 0.8 kW, a chamber pressure of 1 mtorr, and argon as the sputtering carrier gas at a flow rate of 12 seem. A cold process is used initially, with a deposition temperature of 30°C, and after a 1000 A thick Al layer is deposited, the deposition temperature is raised to 450°C, and a hot deposition process is used until the desired film thickness is reached.

[0063] Example 3

[0064] The present example provides a method for filling a contact hole in an integrated circuit process, the method comprising:

[0065] The pretreated substrate is placed in an IMP chamber for ionized metal plasma deposition, and a first TiN layer is deposited in the contact hole, with a thickness of 180 A and the same deposition conditions as in Example 1.

[0066] A second TiN layer was deposited on the surface of the first TiN layer, with a thickness of 800 angstroms, and the deposition conditions were as follows: DC power of 2.1 kW, RF power of 2.25 kW, substrate bias of 200 V, cavity pressure of 11 mtorr, substrate temperature of 200°C, flow ratio of N2 and Ar of 1:6, total flow of 30 sccm, stoichiometric ratio of titanium element and nitrogen element at the bottom of the second TiN layer of 1:1, and the stoichiometric ratio of titanium element and nitrogen element gradually increased along the deposition direction, with pure Ti at the top.

[0067] A Ti layer was deposited on the surface of the second TiN layer, with a thickness of 250 angstroms, and the deposition conditions were the same as in Example 1.

[0068] The substrate was placed in a standard process reaction chamber for physical vapor deposition of Al, with a sputtering power of 12 kW, cavity pressure of 1 mtorr, and argon as the sputtering carrier gas at a flow rate of 12 sccm. A cold process was initially used for deposition, with a deposition temperature of 80°C, and after obtaining an aluminum layer with a thickness of 1800 A, the deposition temperature was raised to 350°C, and a hot deposition process was used until the process time ended, achieving the desired film thickness.

[0069] The diameter of the contact hole in Examples 1-3 was 0.15 μm, and the aspect ratio was 4:1.

[0070] Example 4

[0071] This example was the same as Example 1, except that the diameter of the contact hole was 0.12 μm, and the aspect ratio was 3:1.

[0072] Example 5

[0073] This example was the same as Example 1, except that the diameter of the contact hole was 0.18 μm, and the aspect ratio was 5:1.

[0074] Comparative Example 1

[0075] This comparative example was the same as Example 1, except that the stoichiometric ratio of titanium element and nitrogen element in the second TiN layer did not have a gradient change, and the overall stoichiometric ratio of titanium element and nitrogen element was 1:1.

[0076] Comparative Example 2

[0077] This comparative example was the same as Example 1, except that the stoichiometric ratio of titanium element and nitrogen element in the second TiN layer did not have a gradient change, and the overall stoichiometric ratio of titanium element and nitrogen element was 2:1.

[0078] Comparative Example 3

[0079] The substrate is placed on the hot plate in the CVD cavity, and the TiN layer is deposited for 35 min under the conditions of chamber pressure 1.3 torr, radio frequency power 750 W, hot plate temperature 400 ℃, TDMAT (tetra-dimethylamino titanium) 225 sccm, N2 flow rate 200 sccm, and H2 flow rate 300 sccm, and the stoichiometric ratio of titanium element and nitrogen element in the TiN layer is 1:1; the substrate with the deposited TiN layer is placed in the IMP cavity, and the Ti layer is deposited by ionized metal plasma, and the Al physical vapor deposition is performed in the standard process reaction cavity. The deposition conditions of the Ti layer and the Al are the same as those in Example 1.

[0080] Comparative Example 4

[0081] The comparative example is the same as Example 1 except that only the hot deposition process is used until the contact hole is completely filled with Al, and the cold deposition process is not used.

[0082] Comparative Example 5

[0083] The comparative example is the same as Example 1 except that the stoichiometric ratio of titanium element and nitrogen element in the TiN layer is 1:1, and the TiN layer is prepared in the CVD cavity (the preparation conditions are the same as those in Comparative Example 3); the hot deposition process is used until the contact hole is completely filled with Al, and the cold deposition process is not used.

[0084] The filling rate of the contact hole after the deposition of Examples 1-5 and Comparative Examples 1-5 is tested by atomic force microscopy (AFM), and the results are shown in Table 1.

[0085] Table 1

[0086]

[0087] The present application is described in detail by the above examples to illustrate the detailed structural features of the present application, but the present application is not limited to the above detailed structural features, i.e. it does not mean that the present application must rely on the above detailed structural features to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of the components selected by the present application, addition of auxiliary components, selection of specific modes, etc. all fall within the protection scope and disclosure scope of the present application.

[0088] The preferred embodiments of the present application are described in detail above, but the present application is not limited to the specific details in the above embodiments, and within the technical concept scope of the present application, the technical solutions of the present application can be subjected to various simple modifications, and these simple modifications all belong to the protection scope of the present application.

[0089] It should be further noted that the various technical features described in the above detailed description can be combined in any suitable manner without departing from the scope of the application. To avoid not necessary repetition regarding various combinations, no further combinations will be described.

[0090] Furthermore, the various embodiments of the application can also be combined with each other, as long as it does not violate the idea of the application, it should also be considered as disclosed by the present application.

Claims

1. A method of filling a contact hole in an integrated circuit process, characterized by, The method comprises: sequentially preparing a first TiN layer, a second TiN layer and a Ti layer in the contact hole by using ionized metal plasma deposition; depositing Al on the surface of the Ti layer by using physical vapor deposition method, and completely filling the contact hole; the stoichiometric ratio of titanium element and nitrogen element in the second TiN layer is started from 1:1, uniformly gradiently increases from the bottom of the second TiN layer along the deposition direction, and is a pure titanium layer at the top of the second TiN layer.

2. The method of claim 1, wherein the contact hole is filled by the integrated circuit process. The diameter of the contact hole is less than 0.18 μm, and the aspect ratio is 3-5:

1.

3. The method of claim 1, wherein the contact hole is filled by the integrated circuit process. The thickness of the first TiN layer is less than 200 angstroms.

4. The method of claim 1, wherein the contact hole is filled by the integrated circuit process. The second TiN layer is substoichiometric TiN on average.

5. The method of claim 1, wherein the contact hole is filled by the integrated circuit process. The thickness of the second TiN layer is 200-800 angstroms.

6. The method of claim 1, wherein the contact hole is filled in an integrated circuit process. The thickness of the Ti layer is 150-250 angstroms.

7. The method of claim 1, wherein the contact hole is filled in an integrated circuit process. The physical vapor deposition method is carried out in a standard process reaction cavity.

8. The method of claim 7, wherein the contact hole is filled by the integrated circuit process. The physical vapor deposition method comprises cold deposition and hot deposition carried out in sequence.

9. The method of claim 8, wherein the contact hole is filled by the integrated circuit process. The temperature of the cold deposition is less than 100 ℃, and the deposited Al thickness is less than 2000 angstroms.

10. The method of claim 8, wherein the contact hole is filled by the integrated circuit process. The temperature of the hot deposition is 350-450 ℃.

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