A low resistivity high failure temperature single layer diffusion barrier for copper interconnects

Abstract

The application belongs to the field of integrated circuit manufacturing, and particularly relates to a single-layer diffusion barrier layer with low resistivity and high failure temperature for copper interconnection. The diffusion barrier layer is a copper interconnection diffusion barrier layer, which is located between copper and a silicon substrate, and contains M and N elements, wherein M is selected from one of Zr and Hf. The copper interconnection diffusion barrier layer is prepared by a magnetron sputtering process, and the nitrogen content accounts for 18% to 25% of the working gas content during the preparation of the copper interconnection diffusion barrier layer by magnetron sputtering. The single-layer nitride diffusion barrier layer prepared by magnetron sputtering has an ultra-thin thickness, a resistivity lower than 40 micro-ohm per centimeter (even lower than 10 micro-ohm per centimeter) at 600 degrees Celsius, and a failure temperature higher than 600 degrees Celsius. The application has reasonable component design, simple and controllable process, and is convenient for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of integrated circuit manufacturing, and specifically relates to a single-layer diffusion barrier layer with low resistivity and high failure temperature for copper interconnects. Background Technology

[0002] Zirconium metal has an hcp (α phase) structure, which transforms into a body-centered cubic (bcc) structure (β phase) at 1135 K. (α-Zr) has a lower work function (4.15 eV), a higher melting point (2128 K), and a lower resistivity (3.86 × 10⁻⁶ at room temperature) compared to metallic Ti. – 5 W·cm 2 Its numerous advantages have led to its frequent application in silicon-based microelectronic devices and power electronic devices. [62-64] Compared to commonly used TiN and TaN diffusion barrier layer materials, ZrN exhibits lower electrical resistance and a higher heat of formation (-87.33 kcal / mol), compared to TiN (-80.4 kcal / mol) and TaN (-60.3 kcal / mol). This higher heat of formation implies better thermal stability, and these advantages of the thin film demonstrate its significant strengths as a diffusion barrier layer material.

[65] TAKEYAMA MB's research demonstrated that 100 nm nanocrystalline ZrN (Cu / ZrN / Si) barrier layers do not undergo structural changes at 800 °C. When the ZrN barrier layer thickness is reduced to 20 nm, no solid-state reaction or significant structural changes occur at temperatures up to 600 °C or higher. Satoetal et al. demonstrated that 5 nm thick ZrN films exhibit structural changes at 1.33 × 10⁻⁶ ℃. -5ZrN films can withstand high-temperature annealing at 500℃ in vacuum without copper diffusion. Researchers such as Cheng-Shi Chen prepared two ZrN films with different preferred orientations by changing the substrate temperature. They studied the diffusion barrier properties of ZrN films in the Cu / ZrN / Si system as a function of texture coefficient and film thickness, concluding that the Cu diffusion distance depends on the orientation and thickness of the ZrN film, which can be explained by atomic structure, morphology, and total grain boundary area. They demonstrated that a ZrN film with a thickness of 120 nm and a texture coefficient of 0.27 possesses both good resistivity and a Cu diffusion barrier temperature as high as 800℃. On the other hand, a 70 nm thick ZrN film can still remain stable at 700 °C; Ying Wang et al. demonstrated that a 15 nm Zr–Ti–N barrier layer prepared by adding Ti to ZrN can still act as a barrier to prevent copper diffusion at a high temperature of 700 °C; Jian-Long Ruan et al. prepared an ultrathin ZrN (10 nm) diffusion barrier layer by DC reactive magnetron sputtering under different negative substrate bias voltages, which can remain as a diffusion barrier layer between Cu and SiO2 for 30 minutes at temperatures as high as 800 °C; Y. Menga et al. prepared a 5 nm amorphous Zr-BN film by reactive magnetron sputtering, which showed good thermal stability and barrier performance below 650 °C. With the trend of increasingly smaller feature sizes in future integrated circuits and the pursuit of ultrathin interconnect barrier layer thickness, the research on Zr-based metal barrier layers is of great significance. Researchers such as Woo-Cheol ROH deposited a 100 nm thick Hf(C,N) film on a silicon substrate using pulsed DC plasma-enhanced metal-organic chemical vapor deposition, which effectively prevented Cu diffusion into silicon at temperatures up to 600 °C; Ken-ichi YOSHIMOTO et al.

[79] Thin films prepared by sputtering, Cu / Hf(250nm) / Si, Cu / CuHf2(150nm) / Hf(100nm) / Si, and Cu / HfN(100nm) / Hf(150nm) / Si have failure temperatures below 480℃, below 480℃, and above 630℃, respectively. Keng-LiangOu prepared Cu / Hf(50nm) / Si by magnetron sputtering, which, after annealing at 600℃, formed Cu3Si in copper-diffused silicon, with Cu / HfN... 0.47 The (50 nm) / Si contact system can be annealed at 650 °C for 30 minutes without any reaction. Cu3Si compounds were observed after annealing at 700 °C due to accelerated diffusion of Cu through the crystalline Hf-N barrier layer.

[0003] However, a search revealed that there are currently few reports on technologies that can achieve a resistivity of less than 40 microohms per centimeter (or even less than 10 microohms per centimeter) at 600 degrees Celsius and a failure temperature greater than 600 degrees Celsius for ultrathin nitride diffusion barrier layers. Summary of the Invention

[0004] This invention focuses on elements from the fifth period onwards in Group 4, and for the first time uses magnetron sputtering to prepare a diffusion barrier layer with a resistivity of less than 40 microohms per centimeter at 600 degrees Celsius.

[0005] After optimization, this invention can produce a diffusion barrier layer with a resistivity of less than 10 microohms per centimeter at 600 degrees Celsius and a failure temperature greater than 600 degrees Celsius.

[0006] This invention discloses a single-layer diffusion barrier layer with low resistivity and high failure temperature for copper interconnects. The diffusion barrier layer is a copper interconnect diffusion barrier layer located between a copper and a silicon substrate. The copper interconnect diffusion barrier layer contains both M and N elements, with M selected from Zr and Hf. The copper interconnect diffusion barrier layer is prepared by magnetron sputtering. When preparing the copper interconnect diffusion barrier layer by magnetron sputtering, the nitrogen content accounts for 18% to 25% of the working gas content.

[0007] This invention discloses a single-layer diffusion barrier layer with low resistivity and high failure temperature for copper interconnects. When preparing the ZrN diffusion barrier layer by magnetron sputtering, the following is controlled:

[0008] The background vacuum level is 1~15×10⁻⁶. -4 Pa, preferably 1.8~2.5×10 -4 Pa, further preferably 2×10 -4 Pa;

[0009] The target distance is 10-20cm, preferably 14-18cm, and more preferably 16cm;

[0010] The sputtering power is 60~150W, preferably 80~120W, and more preferably 100W;

[0011] The working gas flow rate is 20-30 sccm, preferably 22-28 sccm, and more preferably 25 sccm;

[0012] The working pressure is 0.6~0.8 Pa, preferably 0.65~0.75 Pa, and more preferably 0.7 Pa;

[0013] The target material is a Zr target material with a purity of ≥99.95%;

[0014] The working gas is composed of argon and nitrogen, wherein the nitrogen content accounts for 18% to 22% of the working gas content, more preferably 20%;

[0015] The temperature of the substrate is 20~25℃.

[0016] Preferably, when preparing the ZrN diffusion barrier layer by magnetron sputtering, the volume ratio of argon to nitrogen in the working gas is 20:5, that is, the flow rate of argon is 20 sccm and the flow rate of nitrogen is 5 sccm. At this time, the sputtering power is preferably 100W.

[0017] The roughness of the obtained ZrN diffusion barrier layer is 0.98 nm;

[0018] The resistivity of the obtained ZrN diffusion barrier layer after heat treatment at 600 ℃ for 30 min was 7.31 μΩ·cm.

[0019] The resistivity of the obtained ZrN diffusion barrier layer after heat treatment at 700 ℃ for 30 min was 20.2 μΩ·cm.

[0020] This invention discloses a single-layer diffusion barrier layer with low resistivity and high failure temperature for copper interconnects. When preparing the HfN diffusion barrier layer by magnetron sputtering, the following is controlled:

[0021] The background vacuum is 1~15×10-4 Pa, preferably 1.8~6.2×10-4 Pa, and more preferably 5×10-4 Pa;

[0022] The target distance is 10-20cm, preferably 14-18cm, and more preferably 16cm;

[0023] The sputtering power is 50~120W, preferably 70-100W, and more preferably 80W;

[0024] The working gas flow rate is 18~30 sccm, preferably 19~28 sccm, and more preferably 25 sccm;

[0025] The working pressure is 0.6~0.8 Pa, preferably 0.65~0.75 Pa, and more preferably 0.7 Pa;

[0026] The target material is an Hf target material with a purity of ≥99.95%;

[0027] The working gas is composed of argon and nitrogen, wherein the nitrogen content accounts for 18% to 22% of the working gas content, more preferably 20%;

[0028] The temperature of the substrate is 20~25℃.

[0029] Preferably, when preparing the HfN diffusion barrier layer by magnetron sputtering, the volume ratio of argon to nitrogen in the working gas is 20:5, that is, the flow rate of argon is 25 sccm and the flow rate of nitrogen is 5 sccm. At this time, the sputtering power is preferably 80W.

[0030] The roughness of the obtained HfN diffusion barrier layer is 0.954 nm.

[0031] Before heat treatment, the resistivity of the HfN diffusion barrier layer was 38.2 μΩ·cm.

[0032] The resistivity of the obtained HfN diffusion barrier layer after heat treatment at 600 ℃ for 30 min was 9.9 μΩ·cm.

[0033] The resistivity of the obtained ZrN diffusion barrier layer after heat treatment at 700 ℃ for 30 min was 96 μΩ·cm.

[0034] The diffusion barrier layer obtained by this invention has a resistivity of less than 10 microohms per centimeter after heat treatment at 600 degrees Celsius, and its failure temperature can still be greater than 600 degrees Celsius.

[0035] After optimization, the resulting diffusion barrier layer has a resistivity of less than 8 microohms per centimeter after heat treatment at 600 degrees Celsius, and its failure temperature can still be greater than 650 degrees Celsius. Attached Figure Description

[0036] Figure 1 The surface morphology of the ZrN diffusion barrier layer prepared in Example 1 of this invention is shown.

[0037] Figure 2 The surface morphology of the HfN diffusion barrier layer prepared in Example 2 of this invention is shown.

[0038] Figure 3 The XRD patterns of the ZrN diffusion barrier layer prepared in Example 1 of this invention are shown in the deposited state and after annealing.

[0039] Figure 4 The images show the deposited state and XRD patterns of the HfN diffusion barrier layer prepared in Example 2 of this invention after annealing.

[0040] Figure 5 The resistivity change curves of the ZrN diffusion barrier layer prepared in Example 1 of this invention in its deposition state and after annealing are shown.

[0041] Figure 6 The resistivity change curves of the HfN diffusion barrier layer prepared in Example 2 of this invention are shown in the deposition state and after annealing.

[0042] Figure 7 The XRD patterns of the diffusion barrier layer in Comparative Example 1 are shown in the deposited state and after annealing.

[0043] Figure 8 To explore the resistivity change of the diffusion barrier layer before heat treatment obtained in Case Series 1.

[0044] Figure 9 The XRD patterns of the diffusion barrier layer in Comparative Example 2 are shown in the deposited state and after annealing.

[0045] Figure 10 To explore the resistivity change of the diffusion barrier layer before heat treatment obtained in Case Series 2. Detailed Implementation

[0046] In the embodiments and comparative examples of the present invention, ZrN layer, HfN layer barrier layer thin film and 180nm copper layer simulate Cu interconnect layer are prepared on N-type single crystal silicon (100) substrate.

[0047] The resistivity of N-type single-crystal silicon (100) substrates is 0.05-0.1 Ω·cm;

[0048] 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.

[0049] The main equipment used was the SB-5200DTD ultrasonic cleaner, the TRP-450 magnetron sputtering coating machine, and the SLG1000-60 tube furnace.

[0050] Preprocessing:

[0051] 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.

[0052] During copper deposition, control the following:

[0053] Background vacuum level 5×10 -4 The parameters are: Pa, target distance: 16 cm, sputtering power: 100 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℃.

[0054] Example 1

[0055] On a spare N-type single-crystal silicon (100) substrate, a zirconium nitride layer was deposited by magnetron sputtering, followed by a copper layer 180 nm thick, to obtain a Cu(180 nm) / ZrN(10 nm) / Si deposition sample; during the ZrN layer deposition, the following was controlled:

[0056] Background vacuum level 2×10 -4 The parameters were: Pa, target distance: 16 cm, sputtering power: 100 W, working gas flow rate: 25 sccm, and working pressure: 0.7 Pa. The target material used was Zr with a purity of ≥99.95%. The working gas consisted of argon and nitrogen, with an argon flow rate of 20 sccm and a nitrogen flow rate of 5 sccm. The substrate temperature was 25℃. Sputtering time was 30 min.

[0057] like Figure 1 The surface morphology of the deposited barrier layer is shown, and the layer is continuous, dense, and crack-free.

[0058] Failure temperature test experiment:

[0059] Annealing was performed at 500℃-700℃ under a nitrogen atmosphere (test time 30 min). The XRD patterns of the obtained products before and after annealing are shown below. Figure 3 The resistivity changes after annealing at different temperatures are shown in the figure. Figure 5 ,Depend on Figure 3 , 5 It can be seen that the Cu(180nm) / ZrN(10nm) / Si deposited sample prepared in Example 1 has a diffusion barrier aging temperature of approximately 700℃.

[0060] The obtained ZrN diffusion barrier layer has a roughness of 0.98 nm and a resistivity of 35.2 μΩ·cm.

[0061] The resistivity of the obtained ZrN diffusion barrier layer after heat treatment at 600 ℃ for 30 min was 7.31 μΩ·cm.

[0062] The resistivity of the obtained ZrN diffusion barrier layer after heat treatment at 700 ℃ for 30 min was 20.2 μΩ·cm.

[0063] Exploring Case Series 1

[0064] All other conditions are the same as in Example 1, except that:

[0065] The working gas flow rate is 25 sccm, and the nitrogen flow rate accounts for 20%, 30%, and 40% of the working gas flow rate, respectively.

[0066] The resistivity of the obtained products is 3.52 × 10⁻⁶. -5 Ω∙cm, 5.23×10-5 Ω∙cm, 14.4×10 -5 Ω∙cm, such as Figure 8 With the increase of nitrogen partial pressure, the resistivity of the thin film generally shows a gradual upward trend.

[0067] Comparative Example 1

[0068] Other conditions were the same as in Example 1, except that the working gas was argon. The XRD patterns of the resulting diffusion barrier layer deposition state and after annealing are shown below. Figure 7 .from Figure 7 It can be seen from this that the aging temperature of the diffusion barrier obtained is approximately 600℃.

[0069] Example 2

[0070] On a spare N-type single-crystal silicon (100) substrate, a hafnium nitride layer was deposited by magnetron sputtering, followed by a copper layer 180 nm thick, to obtain a Cu(180 nm) / HfN(10 nm) / Si deposition sample; during the deposition of the HfN layer, the following was controlled:

[0071] Background vacuum level 2×10 -4 The parameters were: Pa, target distance: 16 cm, sputtering power: 80 W, working gas flow rate: 25 sccm, and working pressure: 0.7 Pa. The target used was Hf target with a purity of ≥99.95%. The working gas consisted of argon and nitrogen, with an argon flow rate of 20 sccm and a nitrogen flow rate of 5 sccm. The substrate temperature was 25℃. Sputtering time was 30 min.

[0072] like Figure 2 The surface morphology of the deposited barrier layer is shown, and the layer is continuous, dense, and crack-free.

[0073] Failure temperature test experiment:

[0074] Annealing was performed at 500℃-700℃ under a nitrogen atmosphere (test time 30 min). The XRD patterns of the obtained products before and after annealing are shown below. Figure 4 The resistivity changes after annealing at different temperatures are shown in the figure. Figure 6 ,Depend on Figure 4 , 6 It can be seen that the diffusion barrier aging temperature of the Cu(180nm) / HfN(10nm) / Si deposited sample prepared in Example 2 is about 600~650℃.

[0075] The roughness of the obtained HfN diffusion barrier layer is 0.954 nm.

[0076] Before heat treatment, the resistivity of the HfN diffusion barrier layer was 38.2 μΩ·cm.

[0077] The resistivity of the obtained HfN diffusion barrier layer after heat treatment at 600 ℃ for 30 min was 9.9 μΩ·cm.

[0078] The resistivity of the obtained HfN diffusion barrier layer after heat treatment at 700 °C for 30 min was 96 μΩ·cm.

[0079] Comparative Example 2

[0080] Other conditions were the same as in Example 2, except that the working gas was argon. The XRD patterns of the resulting diffusion barrier layer in its deposited state and after annealing are shown below. Figure 9 .from Figure 9 It can be seen from this that the aging temperature of the diffusion barrier obtained is approximately 550℃.

[0081] Exploring Case Series 2

[0082] All other conditions are the same as in Example 2, except that:

[0083] The working gas flow rate is 25 sccm, and the nitrogen flow rate accounts for 20%, 30%, and 40% of the working gas flow rate, respectively.

[0084] The resistivity of the obtained product is shown in the figure. Figure 10 .

Claims

1. A single-layer diffusion barrier layer with low resistivity and high failure temperature for copper interconnects, characterized in that: On a spare N-type single-crystal silicon (100) substrate, a zirconium nitride layer was deposited by magnetron sputtering, followed by a copper layer 180 nm thick, to obtain a Cu(180 nm) / ZrN(10 nm) / Si deposition sample; during the ZrN layer deposition, the following was controlled: Background vacuum level 2×10 -4 The parameters were: Pa, target distance 16 cm, sputtering power 100 W, working gas flow rate 25 sccm, and working pressure 0.7 Pa; the target material used was a Zr target with a purity of ≥99.95%; the working gas consisted of argon and nitrogen, with an argon flow rate of 20 sccm and a nitrogen flow rate of 5 sccm; the substrate temperature was 25℃; and the sputtering time was 30 min. The obtained ZrN diffusion barrier layer has a roughness of 0.98 nm and a resistivity of 35.2 μΩ·cm. The resistivity of the obtained ZrN diffusion barrier layer after heat treatment at 600 ℃ for 30 min was 7.31 μΩ·cm. The resistivity of the obtained ZrN diffusion barrier layer after heat treatment at 700 ℃ for 30 min was 20.2 μΩ·cm.

2. A single-layer diffusion barrier layer with low resistivity and high failure temperature for copper interconnects, characterized in that: On a spare N-type single-crystal silicon (100) substrate, a hafnium nitride layer was deposited by magnetron sputtering, followed by a copper layer 180 nm thick, to obtain a Cu(180 nm) / HfN(10 nm) / Si deposition sample; during the deposition of the HfN layer, the following was controlled: Background vacuum level 2×10 -4 The parameters were: Pa, target distance 16 cm, sputtering power 80 W, working gas flow rate 25 sccm, and working pressure 0.7 Pa; the target used was an Hf target with a purity of ≥99.95%; the working gas consisted of argon and nitrogen, with an argon flow rate of 20 sccm and a nitrogen flow rate of 5 sccm; the substrate temperature was 25℃; and sputtering lasted 30 min. The roughness of the obtained HfN diffusion barrier layer is 0.954 nm; Before heat treatment, the resistivity of the HfN diffusion barrier layer was 38.2 μΩ·cm; The resistivity of the obtained HfN diffusion barrier layer after heat treatment at 600 °C for 30 min was 9.9 μΩ·cm. The resistivity of the obtained HfN diffusion barrier layer after heat treatment at 700 °C for 30 min was 96 μΩ·cm.

Images