Diffusion barrier containing a group 6 nitride in copper interconnects for integrated circuits

Abstract

This invention relates to diffusion barrier layers containing Group 6 subnitrides in copper interconnects of integrated circuits, belonging to the field of chip manufacturing. The diffusion barrier layers include Cr-containing diffusion barrier layers, molybdenum nitride-containing diffusion barrier layers, and tungsten nitride-containing diffusion barrier layers; the Cr-containing diffusion barrier layers contain Cr and N, preferably composed of Cr and N. The Cr-containing diffusion barrier layers with a thickness of 16 nm or less designed and prepared according to this invention do not lose their diffusion barrier performance after annealing at 800°C. The molybdenum nitride-containing diffusion barrier layers with a thickness of 16 nm or less designed and prepared according to this invention do not lose their diffusion barrier performance after annealing at 700°C. The tungsten nitride-containing diffusion barrier layers with a thickness of 16 nm or less designed and prepared according to this invention do not lose their diffusion barrier performance after annealing at 600°C. The coating composition design of this invention is reasonable, the preparation process is simple and controllable, the obtained product has excellent performance, and it is easy to apply industrially.

Description

Technical Field

[0001] This invention relates to a diffusion barrier layer containing group 6 subnitrides in copper interconnects of integrated circuits, and belongs to the field of chip manufacturing. Background Technology

[0002] Chip manufacturing involves multiple process steps, among which the diffusion barrier layer is a crucial one. Diffusion barrier layers are typically applied using materials such as silicon nitride, aluminum nitride, refractory metals, binary compounds, ternary compounds, and high-entropy alloys. Their purpose is to form an oxide or nitride layer that restricts the diffusion of impurities within the chip, preventing them from damaging the chip's basic structure.

[0003] As research progressed, it was discovered that elemental layers lost their integrity at temperatures exceeding 450°C, and their barrier function rapidly diminished. To further improve the barrier performance of these layers at high temperatures, researchers explored various compositions, including TaN, Ti / TaN, W–Ti–N, Zr–B–N, and AlCrTaTiZrMoN. 0.2 The development of diffusion barrier layers is underway. For example, YM Zhou et al. studied and compared sputtered TaN and Ti / TaN bilayers as diffusion barrier layers. The results showed that the sheet resistance of Cu / Ti / TaN / SiO2 / Si was lower than that of the Cu / TaN / SiO2 / Si system. The Ti / TaN bilayer structure exhibited superior diffusion isolation performance for copper, with no Cu3Si formation before annealing to 800℃. The failure mechanism of the Ti / TaN bilayer was similar to that of a single-layer TaN barrier layer. After annealing at 800℃, Cu atoms diffused through the grain boundaries of the Ti / TaN bilayer, and voids and bulges appeared on the surface. Wang et al. prepared W–Ti–N diffusion barriers by reactive magnetron sputtering. They characterized the surface morphology, structure, and sheet resistance of Cu- / W–Ti–N / Si samples annealed at different temperatures and discussed the failure mechanism. The results showed that the crystallization temperature of the W–Ti–N amorphous film was above 800 °C, and the film mainly consisted of TiN and W. The prepared W–Ti–N film still exhibited good stability at 700 °C. Meng et al. investigated the thermal stability and barrier properties of Zr–B–N films deposited by reactive DC magnetron sputtering. The results showed that the deposited Zr–B–N film was amorphous, mainly composed of ZrO2, BN, and a small amount of ZrN. The amorphous Zr–B–N film exhibited good thermal stability and barrier properties; a 5 nm Zr–B–N barrier layer could effectively block the diffusion of Cu and Si below 650 °C. Significant recrystallization of the Zr–B–N film occurred at approximately 650 °C, leading to barrier failure. Summary of the Invention

[0004] This invention attempts to further improve the performance of integrated circuits by using a simple, single-layer, ultrathin (less than or equal to 16 nm) diffusion barrier layer with simple components and a simple structure.

[0005] The present invention relates to a diffusion barrier layer containing Group 6 subnitrides in the copper interconnect of an integrated circuit, wherein the diffusion barrier layer includes a Cr-containing diffusion barrier layer, a molybdenum nitride-containing diffusion barrier layer, and a tungsten nitride-containing diffusion barrier layer.

[0006] The Cr-containing diffusion barrier layer contains Cr and N.

[0007] The present invention relates to a Cr-containing diffusion barrier layer in the copper interconnect of integrated circuits, which is composed of Cr and N.

[0008] The present invention provides a diffusion barrier layer containing a group 6 subnitride in the copper interconnect of the integrated circuit, wherein the thickness of the diffusion barrier layer is less than or equal to 155 nm, preferably less than or equal to 16 nm.

[0009] The diffusion barrier layer was prepared by magnetron sputtering.

[0010] When preparing the Cr-containing diffusion barrier layer by magnetron sputtering, the following is controlled:

[0011] The background vacuum level is 1~10×10 -4 Pa, preferably 4~6×10 -4 Pa, further preferably 5×10 -4 Pa.

[0012] The target distance is 10-20cm, preferably 14-18cm, and more preferably 16cm.

[0013] The sputtering power is 20-60W, preferably 35-45W, and more preferably 38-42W, which naturally includes 40W. In this invention, the sputtering power is crucial to product quality. Too low a sputtering power results in a low film deposition rate, while too high a power leads to target poisoning. Target poisoning significantly impacts the deposition process, causing extreme instability, severe film damage, increased internal defects, and even target surface damage, greatly shortening the target's lifespan.

[0014] The working gas flow rate is 18~22 sccm, preferably 19~21 sccm, and more preferably 20 sccm.

[0015] The working pressure is 0.4~1.0 Pa, preferably 0.5~0.8 Pa, and more preferably 0.6~0.7 Pa.

[0016] The target material is a Cr target material with a purity of ≥99.95%.

[0017] The working gas consists of argon and nitrogen.

[0018] As a further preferred option, the volume ratio of argon to nitrogen in the working gas is 19:1.

[0019] As a further preferred option, the temperature of the substrate is 20~25℃.

[0020] The diffusion barrier layer containing Cr in the copper interconnect of the integrated circuit of the present invention can be directly attached to the copper or attached to a pad layer, with the pad layer attached to the copper.

[0021] In this invention, a thickness of 16 nm or less exhibits excellent diffusion blocking performance. The Cr-containing diffusion blocking layer (with a thickness of approximately 15 nm) developed and prepared in this invention maintains good diffusion blocking performance even after annealing at 800 °C.

[0022] When preparing the molybdenum nitride-containing diffusion barrier layer by magnetron sputtering, the following is controlled:

[0023] The background vacuum level is 1~10×10 -4 Pa, preferably 4~6×10 -4 Pa, further preferably 5×10 -4 Pa.

[0024] The target distance is 10-20cm, preferably 14-18cm, and more preferably 16cm.

[0025] The sputtering power is 20~40W, preferably 20~25W, and even more preferably 20~22W, which of course includes 40W.

[0026] The working gas flow rate is 18~22 sccm, preferably 19~21 sccm, and more preferably 20 sccm.

[0027] The working pressure is 0.5~1.0 Pa, preferably 0.5~0.8 Pa, and more preferably 0.6~0.7 Pa.

[0028] The target material is a Mo target material with a purity of ≥99.95%.

[0029] The working gas consists of argon and nitrogen.

[0030] As a further preferred embodiment, the volume ratio of argon to nitrogen in the working gas is 18:2, and as a further preferred embodiment, the flow rate of argon in the working gas is 18 sccm and the flow rate of nitrogen is 2 sccm.

[0031] As a further preferred option, the temperature of the substrate is 20~25℃.

[0032] The diffusion barrier layer containing molybdenum nitride in the copper interconnect of the integrated circuit of the present invention can be directly attached to the copper or attached to a pad layer, with the pad layer attached to the copper.

[0033] In this invention, when the thickness of the molybdenum nitride-containing diffusion barrier layer is about 15 nm, it exhibits extremely excellent diffusion barrier performance.

[0034] The molybdenum nitride-containing diffusion barrier layer (with a thickness of about 15 nm) developed and prepared in this invention can still maintain good diffusion barrier performance after annealing at 700 °C.

[0035] When preparing the tungsten nitride-containing diffusion barrier layer by magnetron sputtering, the following is controlled:

[0036] The background vacuum level is 1~10×10 -4 Pa, preferably 4~6×10 -4 Pa, further preferably 5×10 -4 Pa.

[0037] The target distance is 10-20cm, preferably 14-18cm, and more preferably 16cm.

[0038] The sputtering power is 20~40W, preferably 20~25W, and even more preferably 20~22W, which of course includes 40W.

[0039] The working gas flow rate is 18~22 sccm, preferably 19~21 sccm, and more preferably 20 sccm.

[0040] The working pressure is 0.5~1.0 Pa, preferably 0.5~0.8 Pa, and more preferably 0.6~0.7 Pa.

[0041] The target material is a W target material with a purity of ≥99.95%.

[0042] The working gas consists of argon and nitrogen.

[0043] As a further preferred embodiment, the volume ratio of argon to nitrogen in the working gas is 19:1, and as a further preferred embodiment, the flow rate of argon in the working gas is 19 sccm and the flow rate of nitrogen is 1 sccm.

[0044] As a further preferred option, the temperature of the substrate is 20~25℃.

[0045] The tungsten nitride diffusion barrier layer in the copper interconnect of the integrated circuit of the present invention can be directly attached to the copper or attached to a pad layer, with the pad layer attached to the copper.

[0046] In this invention, when the thickness of the tungsten nitride-containing diffusion barrier layer is about 15 nm, it exhibits extremely excellent diffusion barrier performance.

[0047] The tungsten nitride diffusion barrier layer (with a thickness of about 15 nm) developed and prepared in this invention can still maintain good diffusion barrier performance after annealing at 600°C.

[0048] When the diffusion barrier layer developed and prepared in this invention has a structure of Cu / CrN / MN / Si, and M is Mo and / or W, even if the thickness is 15 nm, the aging temperature of the product is greater than 800 °C.

[0049] Principles and advantages

[0050] The present invention provides a (CrN, MoN, WN) thin film with a thickness of approximately 15 nm prepared by DC (reactive) magnetron sputtering under optimized process conditions. The resulting film has a smooth surface and excellent continuity. After optimization, the failure temperatures of the (CrN, MoN, WN) barrier layer film are increased to 800℃, 750℃, and 700℃ and above, respectively. Attached Figure Description

[0051] Figure 1 The graph shows the change in resistivity of the product obtained in Example 1 after annealing at 400℃-800℃.

[0052] Figure 2 The image shows the GIXRD pattern of the product obtained in Example 1 after annealing at 400℃-800℃.

[0053] Figure 3 The image shows a cross-sectional SEM image of the product obtained in Example 1 after annealing at 400℃-800℃.

[0054] Figure 4 The graph shows the resistivity variation of CrN thin films under different N2 flow rates.

[0055] Figure 5 The graph shows the change in resistivity of the product obtained in Example 1 after annealing at 400℃-800℃.

[0056] Figure 6 The image shows the GIXRD pattern of the product obtained in Example 1 after annealing at 400℃-800℃.

[0057] Figure 7 The image shows a cross-sectional SEM image of the product obtained in Example 1 after annealing at 400℃-800℃.

[0058] Figure 8 The graph shows the resistivity variation of MoN thin films under different N2 flow rates.

[0059] Figure 9The graph shows the change in resistivity of the product obtained in Example 1 after annealing at 400℃-800℃.

[0060] Figure 10 The image shows the GIXRD pattern of the product obtained in Example 1 after annealing at 400℃-800℃.

[0061] Figure 11 The image shows a cross-sectional SEM image of the product obtained in Example 1 after annealing at 400℃-800℃.

[0062] Figure 12 The graph shows the resistivity variation of the WN thin film under different N2 flow rates.

[0063] Figure 13 The image shows the GIXRD pattern of the product obtained in Comparative Example 1 after annealing at 400℃-800℃.

[0064] Figure 14 The image shows the GIXRD pattern of the product obtained in Comparative Example 2 after annealing at 400℃-800℃.

[0065] Figure 15 The image shows the GIXRD pattern of the product obtained in Comparative Example 3 after annealing at 400℃-800℃. Detailed Implementation

[0066] In the embodiments and comparative examples of the present invention, Cr layer, CrN layer, Mo layer, MoN layer, W layer, WN barrier layer thin film with a thickness of about 15 nm and a simulated Cu interconnect layer with a thickness of about 150 nm are prepared on an N-type single crystal silicon (100) substrate.

[0067] The resistivity of N-type single-crystal silicon (100) substrates is 0.05-0.1 Ω·cm;

[0068] The purity of the target material used is greater than 99.95%, and the purity of the argon and nitrogen gas used is 5N grade or above.

[0069] The main equipment used was the SB-5200DTD ultrasonic cleaner, the TRP-450 magnetron sputtering coating machine, and the SLG1000-60 tube furnace.

[0070] Preprocessing:

[0071] First, the silicon wafer is ultrasonically cleaned in acetone solution for 10 minutes to remove organic contaminants from the surface. After removal, it is rinsed with deionized water and dried with nitrogen. Next, the silicon wafer is ultrasonically cleaned in anhydrous ethanol for 5 minutes to remove grease from the substrate surface, ensuring better adhesion of the film to the silicon substrate. Again, it is rinsed with deionized water and dried with nitrogen. Then, the silicon wafer is immersed in 5% HF solution for 2 minutes to remove the surface oxide layer. The silicon oxide (SiO2) layer on the silicon surface can hinder film deposition and lead to poor uniformity. After removal, it is rinsed with deionized water and dried with nitrogen. Finally, it is ultrasonically cleaned in anhydrous ethanol for 5 minutes, removed, and dried with nitrogen for later use.

[0072] Example 1

[0073] On a spare N-type single-crystal silicon (100) substrate, a chromium nitride layer was deposited by magnetron sputtering, followed by a copper layer of 150 nm, to obtain a Cu(150 nm) / CrN(15 nm) / Si deposited sample; the resistivity of the CrN film was 78 μΩ·cm.

[0074] When depositing chromium nitride layers, control the following:

[0075] Background vacuum level 5×10 -4 The parameters are: Pa, target distance: 16 cm, sputtering power: 40 W, working gas flow rate: 20 sccm, and working pressure: 0.6 Pa. The target material used is a Cr target material with a purity of ≥99.95%; the working gas used consists of argon and nitrogen, with an argon flow rate of 19 sccm and a nitrogen flow rate of 1 sccm.

[0076] The temperature of the substrate is 25℃.

[0077] When depositing copper layers, control the following:

[0078] Background vacuum level 5×10 -4 The parameters are: Pa, target distance: 16 cm, sputtering power: 60 W, working gas flow rate: 20 sccm, and working pressure: 0.7 Pa. The target material used is a Cu target with a purity of ≥99.95%; the working gas used is argon with a flow rate of 20 sccm; and the substrate temperature is 25℃.

[0079] Then, annealing tests were conducted at 400℃-800℃ under a nitrogen atmosphere. The resistivity change of the resulting product is shown in the figure. Figure 1 GIXRD patterns after annealing at different temperatures are shown below. Figure 2 SEM cross-sectional images of annealed at different temperatures are shown below. Figure 3 ;Depend on Figure 2It can be seen that the diffusion barrier aging temperature of the Cu(150nm) / CrN(15nm) / Si deposited sample prepared in Example 1 is about 800℃.

[0080] Example 2

[0081] The other conditions are the same as in Example 1, except that the flow rate of argon is 18 sccm and the flow rate of nitrogen is 2 sccm, and the resistivity of the resulting CrN film is about 105 μΩ·cm.

[0082] Example 3

[0083] The other conditions are the same as in Example 1, except that the flow rate of argon is 16 sccm and the flow rate of nitrogen is 4 sccm, and the resistivity of the resulting CrN film is about 140 μΩ·cm.

[0084] Based on Examples 1, 2, and 3, some further explorations were conducted, and the results are shown below. Figure 4 To reduce the resistivity of the CrN thin film, the present invention optimizes the argon flow rate to 19 sccm and the nitrogen flow rate to 1 sccm.

[0085] Example 4

[0086] On a spare N-type single-crystal silicon (100) substrate, a molybdenum nitride layer was deposited by magnetron sputtering, followed by a copper layer of 150 nm, to obtain a Cu(150 nm) / MoN(15 nm) / Si deposited sample; the resistivity of the MoN film was 51.2 μΩ·cm.

[0087] During the deposition of the molybdenum nitride layer, the following should be controlled:

[0088] Background vacuum level 5×10 -4 The parameters are: Pa, target distance: 16 cm, sputtering power: 20 W, working gas flow rate: 20 sccm, and working pressure: 0.7 Pa. The target material used is a Mo target with a purity of ≥99.95%; the working gas consists of argon and nitrogen, with an argon flow rate of 18 sccm and a nitrogen flow rate of 2 sccm.

[0089] The temperature of the substrate is 25℃.

[0090] When depositing copper layers, control the following:

[0091] Background vacuum level 5×10 -4The parameters are: Pa, target distance: 16 cm, sputtering power: 60 W, working gas flow rate: 20 sccm, and working pressure: 0.7 Pa. The target material used is a Cu target with a purity of ≥99.95%; the working gas used is argon with a flow rate of 20 sccm; and the substrate temperature is 25℃.

[0092] Then, annealing tests were conducted at 400℃-800℃ under a nitrogen atmosphere. The resistivity change of the resulting product is shown in the figure. Figure 5 GIXRD patterns after annealing at different temperatures are shown below. Figure 6 SEM cross-sectional images of annealed at different temperatures are shown below. Figure 7 ;Depend on Figure 6 It can be seen that the diffusion barrier aging temperature of the Cu(150nm) / MoN(15nm) / Si deposited sample prepared in Example 4 is about 750℃.

[0093] Example 5

[0094] The other conditions are the same as in Example 4, except that the flow rate of argon is 19 sccm and the flow rate of nitrogen is 1 sccm, and the resistivity of the resulting MoN film is about 75 μΩ·cm.

[0095] Example 6

[0096] The other conditions are the same as in Example 4, except that the flow rate of argon is 16 sccm and the flow rate of nitrogen is 4 sccm, and the resistivity of the resulting MoN film is about 190 μΩ·cm.

[0097] Based on Examples 4, 5, and 6, some further explorations were conducted, and the results are shown below. Figure 8 To reduce the resistivity of the MoN thin film, the present invention optimizes the argon flow rate to 18 sccm and the nitrogen flow rate to 2 sccm.

[0098] Example 7

[0099] On a spare N-type single-crystal silicon (100) substrate, a tungsten nitride layer was deposited by magnetron sputtering, followed by a copper layer of 150 nm, to obtain a Cu(150 nm) / WN(15 nm) / Si deposition sample; wherein the resistivity of the WN thin film is 25 μΩ·cm.

[0100] When depositing tungsten nitride layers, control the following:

[0101] Background vacuum level 5×10 -4The parameters are: Pa, target distance: 16 cm, sputtering power: 20 W, working gas flow rate: 20 sccm, and working pressure: 0.7 Pa. The target material used is W target material with a purity of ≥99.95%; the working gas used consists of argon and nitrogen, with an argon flow rate of 19 sccm and a nitrogen flow rate of 1 sccm.

[0102] The temperature of the substrate is 25℃.

[0103] When depositing copper layers, control the following:

[0104] Background vacuum level 5×10 -4 The parameters are: Pa, target distance: 16 cm, sputtering power: 60 W, working gas flow rate: 20 sccm, and working pressure: 0.7 Pa. The target material used is a Cu target with a purity of ≥99.95%; the working gas used is argon with a flow rate of 20 sccm; and the substrate temperature is 25℃.

[0105] Then, annealing tests were conducted at 400℃-800℃ under a nitrogen atmosphere. The resistivity change of the resulting product is shown in the figure. Figure 9 GIXRD patterns after annealing at different temperatures are shown below. Figure 10 SEM cross-sectional images of annealed at different temperatures are shown below. Figure 11 ;Depend on Figure 10 It can be seen that the diffusion barrier aging temperature of the Cu(150nm) / WN(15nm) / Si deposited sample prepared in Example 7 is about 750℃.

[0106] Example 8

[0107] The other conditions are the same as in Example 7, except that the flow rate of argon is 18 sccm and the flow rate of nitrogen is 2 sccm, and the resistivity of the resulting MoN film is about 45 μΩ·cm.

[0108] Example 9

[0109] The other conditions are the same as in Example 7, except that the flow rate of argon is 16 sccm and the flow rate of nitrogen is 4 sccm, and the resistivity of the resulting CrN film is about 235 μΩ·cm.

[0110] Based on Examples 7, 8, and 9, some further explorations were conducted, and the results are shown below. Figure 12 To reduce the resistivity of the MoN thin film, the present invention optimizes the argon flow rate to 19 sccm and the nitrogen flow rate to 1 sccm.

[0111] Comparative Example 1

[0112] Other conditions were the same as in Example 1, except that the working gas was only argon. The resulting product was Cu(150nm) / Cr(15nm) / Si; the GIXRD patterns of the product obtained in this comparative example after annealing at different temperatures are shown below. Figure 13 ;from Figure 13 As can be seen above, the diffusion barrier layer has failed at 750℃.

[0113] Comparative Example 2

[0114] Other conditions were the same as in Example 4, except that the working gas was only argon. The resulting product was Cu(150nm) / Mo(15nm) / Si; the GIXRD patterns of the product obtained in this comparative example after annealing at different temperatures are shown below. Figure 14 ;from Figure 14 As can be seen above, the diffusion barrier layer has failed at 600℃.

[0115] Comparative Example 3

[0116] Other conditions were the same as in Example 7, except that the working gas was only argon. The resulting product was Cu(150nm) / W(15nm) / Si; the GIXRD patterns of the product obtained in this comparative example after annealing at different temperatures are shown below. Figure 15 ;from Figure 15 As can be seen above, the diffusion barrier layer has failed at 600℃.

Claims

1. A diffusion barrier layer containing a group 6 subnitride in the copper interconnect of an integrated circuit, characterized in that: The diffusion barrier layer is a Cr-containing diffusion barrier layer; The Cr-containing diffusion barrier layer is composed of Cr and N; The diffusion barrier layer is prepared by magnetron sputtering; the thickness of the diffusion barrier layer is less than or equal to 16 nm. When preparing the Cr-containing diffusion barrier layer by magnetron sputtering, the following is controlled: The background vacuum degree is 1~10×10 -4 Pa; The target distance is 14~18cm; The sputtering power is 35~45W; The working gas flow rate is 18~22 sccm; The working pressure is 0.4~1.0 Pa; The target material is a Cr target material with a purity of ≥99.95%; The working gas consists of argon and nitrogen; The temperature of the substrate is 20~25℃ The volume ratio of argon to nitrogen in the working gas is 19:

1.

2. The diffusion barrier layer containing group 6 subnitrides in the copper interconnect of the integrated circuit according to claim 1, characterized in that: When preparing the Cr-containing diffusion barrier layer by magnetron sputtering, the following is controlled: The background vacuum degree is 4~6×10 -4 Pa; The target distance is 16cm; The sputtering power is 38~42W; The working gas flow rate is 19~21 sccm; The working pressure is 0.5~0.8Pa.

3. The diffusion barrier layer containing a nitride of the sixth transition group in an integrated circuit copper interconnect according to claim 2, characterized in that: When preparing the Cr-containing diffusion barrier layer by magnetron sputtering, the following is controlled: The background vacuum degree is 5 x 10 -4 Pa; The working gas flow rate is 20 sccm; The working pressure is 0.6~0.7 Pa.

4. The diffusion barrier layer containing a nitride of the sixth transition group in an integrated circuit copper interconnect according to claim 1, characterized in that: The diffusion barrier properties of Cr-containing diffusion barrier layers with a thickness of 16 nm or less did not fail after annealing at 800 °C.

Images