A low cost evaluation method for damascene copper electroplating formulations and processes

Abstract

The present application belongs to the field of integrated circuit manufacturing, and specifically provides a low-cost evaluation method for damascene copper electroplating formula and process, to solve the problems of high threshold and high cost in the process of damascene copper electroplating formula research and development and electroplating parameter verification. The present application proposes to use a porous anodic aluminum oxide (AAO) template to simulate the blind hole structure of the dielectric layer in the damascene copper electroplating technology, and to realize the metallization of the AAO surface by matching the barrier layer and the seed layer manufacturing process. The metallized AAO substrate can be used for electroplating experiments alone, or can be embedded in a large cathode to simulate larger size wafer electroplating. The electroplating solution formula and many parameters of the electroplating process can be freely adjusted. After electroplating, the electroplating effect evaluation can be realized by observing the surface and cross section of the plated part. In summary, the present application uses a cheap and easily available porous anodic aluminum oxide template to replace expensive patterned silicon wafers, significantly reducing the cost, and has the advantages of being fast and efficient.

Description

Technical Field

[0001] This invention belongs to the field of integrated circuit manufacturing and relates to damascus copper plating technology. Specifically, it provides a low-cost evaluation method for damascus copper plating formulations and processes. Background Technology

[0002] As integrated circuit manufacturing processes continue to advance, transistor sizes are becoming increasingly smaller, making interconnection more challenging. In the early days of the semiconductor industry, aluminum was used as the interconnect material. Later, to reduce interconnect resistance and avoid electromigration effects, damascene technology, also known as damascus copper plating, was proposed and widely applied in integrated circuit manufacturing. Damascus copper plating involves first etching blind vias and trenches into the dielectric layer, then depositing a barrier layer and a seed layer within them, followed by electroplating to fill the blind vias and trenches, and finally removing excess copper using chemical mechanical polishing to obtain an electronic interconnect with embedded copper lines. Acidic copper sulfate system is currently the most widely used copper plating system, suitable for PCB, packaging substrate, integrated circuit and other fields. This copper plating system consists of a base plating solution (VMS, Virgin Make-up Solution) and trace organic additives. VMS mainly includes three inorganic components: copper sulfate, sulfuric acid and chloride ions. The organic additives can be classified according to their functions into inhibitors (such as polyethylene oxide), accelerators (such as sodium polydithiopropane sulfonate), and leveling agents (such as Janus Green). The interaction of the three can achieve defect-free blind via superfilling.

[0003] Currently, the size of blind vias and trenches in damascus copper plating is getting smaller and smaller, while the wafer size is getting larger and larger, resulting in a higher and higher cost for manufacturing copper interconnect layers within the wafer. Furthermore, the blind via and trench structures in the dielectric layer need to be prepared through complex processes such as photoresist coating, exposure, and etching. Without expensive specialized equipment such as photolithography machines and ion etching machines, it is difficult to use conventional methods to screen additive components and formulations. Therefore, the process of developing damascus copper plating formulations and verifying plating parameters has extremely high barriers to entry and is extremely costly. Summary of the Invention

[0004] The purpose of this invention is to provide a low-cost evaluation method for damascus copper electroplating formulations and processes, addressing the high barriers to entry and high costs associated with damascus copper electroplating formulation development and electroplating parameter verification. This invention proposes using porous anodic aluminum oxide (AAO) templates to simulate the blind-hole structure of the dielectric layer in damascus copper electroplating technology. Porous anodic aluminum oxide is a common and inexpensive hard template material, such as… Figure 1As shown, the substrate mainly consists of an aluminum substrate and a surface-structured alumina layer. The surface alumina layer has a regular pore array structure, and ordered nanoporous structures of various pore sizes and depths can be obtained by adjusting the solution composition, anode voltage, and oxidation time. Based on this, an AAO template is used to simulate nanoscale pore structures, with blind pore diameters ranging from 15 to 500 nm and pore depths approximately 2 to 3 times the pore diameter. This can be combined with barrier layer and seed layer fabrication processes, or various mainstream physical and chemical methods can be used directly to achieve AAO surface metallization. The metallized AAO substrate can be used for electroplating experiments independently, or embedded in a large cathode to simulate larger-scale wafer electroplating. The electrolytic cell can be adapted to rack plating tanks or fountain-type electroplating tanks with rotating cathodes. Many parameters of the electroplating solution and electroplating conditions can be freely adjusted. After electroplating, the surface and cross-section of the plated part can be observed to evaluate the electroplating effect. This invention can evaluate the formulation and process parameters of damascus copper electroplating, as well as the electroplating and electroless plating effects of cobalt, ruthenium, and other integrated circuits.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A low-cost evaluation method for a Damascus copper electroplating formulation and process, characterized by comprising the following steps:

[0007] Step 1. Use a porous anodized aluminum template, clean it and set it aside;

[0008] Step 2. A dense and uniform conductive seed layer is applied to the front side of the porous anodic aluminum oxide template using a seed layer preparation process to form a conductive porous anodic aluminum oxide template;

[0009] Step 3. Fix a single conductive porous anodic aluminum oxide template onto the conductive copper surface of the electrochemical deposition support. After the front side is connected, a cathode for electroplating copper is formed.

[0010] Alternatively, multiple conductive porous anodic aluminum oxide templates can be fixed on a single-sided copper-clad laminate, and their front sides can be made to be connected to the single-sided copper-clad laminate to form a large cathode for electroplating copper.

[0011] Step 4. Transfer the cathode into the electrolytic cell, which contains an electroplating solution prepared according to the Damascus copper plating formula to be evaluated. Then, complete the electroplating according to the Damascus copper plating process to be evaluated to obtain the copper-plated part.

[0012] Step 5. Rinse and dry the copper-plated parts, and use focused ion beam technology and scanning electron microscopy to test the surface morphology and cross-sectional morphology of the copper-plated parts, so as to evaluate the Damascus copper plating formula and process.

[0013] Furthermore, in step 1, the porous anodic aluminum oxide template has a pore size of 20–500 nm and a pore depth of 60–1000 nm; the size of the porous anodic aluminum oxide template is 1–5 cm.

[0014] Furthermore, in step 2, the conductive seed layer is made of platinum, gold, tungsten, or copper, and the thickness of the conductive seed layer is 5–20 nm.

[0015] Furthermore, in step 5, the composition of the damascus copper plating formulation to be evaluated is as follows:

[0016] Copper sulfate pentahydrate at 20–160 g / L, sulfuric acid at 10–120 g / L, chloride ions at 40–70 ppm, inhibitors at 100–800 ppm, accelerators at 2–20 ppm, and leveling agents at 2–20 ppm.

[0017] Furthermore, in step 5, the damascus copper plating process to be evaluated has a current density of 0.5–10 A / dm³. 2 The plating solution circulation flow rate is 0.2–2.0 m³ / h. 3 / h, temperature is 25℃, electrodeposition time is 30s~10min.

[0018] Based on the above technical solution, the beneficial effects of the present invention are as follows:

[0019] 1) This invention uses inexpensive and readily available porous anodic aluminum oxide templates to replace expensive patterned silicon wafers. The porous structure of the AAO template simulates the hole / groove structure inside the wafer, which avoids complex photolithography processes and saves raw material costs.

[0020] 2) This invention can replace expensive wafer copper electrodeposition equipment with a simple circulating electrolytic cell, saving equipment costs;

[0021] 3) This invention enables the evaluation of damascus copper electroplating formulations and processes with low cost advantages, which is conducive to the rapid development of electroplating solutions for wafer-level copper interconnect technology. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the porous anodic aluminum oxide template in this invention, wherein 2-1 is an aluminum substrate and 2-2 is an aluminum oxide surface layer with a pore array structure.

[0023] Figure 2 This is a scanning electron microscope (SEM) image of the porous anodic aluminum oxide template used in Embodiment 1 of the present invention.

[0024] Figure 3 This is a cross-sectional scanning electron microscope image of the porous anodic aluminum oxide template after electroplating and filling in Embodiment 1 of the present invention.

[0025] Figure 4This is a schematic diagram of the structure of the large cathode with an embedded AAO template in Embodiment 2 of the present invention, wherein 1 is a single-sided copper-clad plate and 2 is an AAO template. Detailed Implementation

[0026] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0027] Example 1

[0028] This embodiment provides a low-cost evaluation method for damascus copper electroplating formulations and processes, including the following steps:

[0029] Step 1. Select a square porous anodic aluminum oxide template with a pore size of 100nm and a pore depth of 300nm. The template size is 1.5cm×1.5cm. Place the porous anodic aluminum oxide template into a 100mL beaker, add 20mL of acetone and 20mL of ethanol in sequence, and ultrasonically clean for 10min each. Then dry it for later use.

[0030] Step 2. Place the cleaned porous anodized aluminum template into a magnetron sputtering instrument, with gold as the sputtering target; a 10nm thick gold conductive seed layer is generated on the front side of the porous anodized aluminum;

[0031] Step 3. Attach the conductive porous anodic aluminum oxide template from Step 2 to the conductive copper surface of the electrochemical deposition support using conductive copper tape, ensuring a secure installation. This serves as the cathode for copper electroplating. The back of the conductive porous anodic aluminum oxide template is tightly attached to the conductive copper surface, ensuring that the copper plating solution only contacts the front of the template, preventing the solution from seeping into the back of the template.

[0032] Step 4. Place the cathode, after removing air bubbles from the holes, into the electroplating solution. The electroplating solution consists of: 160 g / L sulfuric acid pentahydrate, 75 g / L sulfuric acid, 60 mg / L sodium chloride, 500 mg / L polyethylene glycol 8000, 2 mg / L SPS sodium dithiodipropane sulfonate, and 4 mg / L imidazole epoxy polymer; use a current density of 0.5 A / dm³. 2 Circulation flow rate 0.5m 3 Electroplating at 25℃ for 3 minutes per hour achieves electrodeposited copper filling with a 100nm aperture and 300nm depth, resulting in a copper-plated part.

[0033] Step 5. Rinse and dry the copper-plated parts from Step 4, and then test the surface and cross-sectional morphology of the copper plating using focused ion beam (FIB) technology and scanning electron microscopy. Evaluate the damascus copper plating formula and process based on the morphology.

[0034] In this embodiment, the porous anodized aluminum template is as follows: Figure 1As shown, it mainly consists of an aluminum substrate 2-1 and a surface-structured alumina surface layer 2-2, with the alumina surface layer having a regular pore array structure; the surface scanning electron microscope image of the porous anodic alumina template is shown below. Figure 2 As shown, the cross-sectional scanning electron microscope image of the porous anodic aluminum oxide template after electroplating and hole filling is as follows. Figure 3 As shown; by Figure 2 and Figure 3 As can be seen, copper plating can completely fill the blind holes in the porous anodized aluminum template. The copper plating formula and process parameters provided in this embodiment can be applied to damascus plating, and the evaluation cost is low, fast and efficient.

[0035] Example 2

[0036] This embodiment provides a low-cost evaluation method for damascus copper electroplating formulations and processes, including the following steps:

[0037] Step 1. Select a square porous anodic aluminum oxide template with a pore size of 50nm and a pore depth of 150nm. The template size is 1.5cm×1.5cm. Place the porous anodic aluminum oxide template in a 100mL beaker, add 20mL of acetone and 20mL of ethanol in sequence, and ultrasonically clean for 10min each. Then dry it for later use.

[0038] Step 2. Place the cleaned porous anodic aluminum template into a magnetron sputtering instrument, with platinum (Pt) as the sputtering target; a 7nm thick Pt conductive seed layer is generated on the front side of the porous anodic aluminum.

[0039] Step 3. Attach multiple conductive porous anodized aluminum templates from Step 2 to a 12-inch single-sided copper-clad laminate using conductive copper tape to form a large cathode for copper plating. The multiple conductive porous anodized aluminum templates are arranged from the inside to the outside along the radius of the single-sided copper-clad laminate. The back of the conductive porous anodized aluminum template is tightly attached to the single-sided copper-clad laminate to ensure that the copper plating solution only contacts the front of the porous anodized aluminum template, preventing the plating solution from seeping into the back of the porous anodized aluminum template.

[0040] Step 4. Place the cathode, now free of air bubbles, into the electroplating solution. The electroplating solution consists of: 120 g / L sulfuric acid pentahydrate, 10 g / L sulfuric acid, 60 mg / L sodium chloride, 500 mg / L polyethylene glycol 8000, 12 mg / L SPS sodium dithiodipropane sulfonate, and 10 mg / L imidazole epoxy polymer; use a current density of 1.2 A / dm³. 2 Circulation flow rate 0.4m 3 Electroplating at 25℃ for 1 minute at a time of 1 hour achieves electrodeposition of copper with a pore diameter of 50nm and a pore depth of 150nm, resulting in a copper-plated part.

[0041] Step 5. Rinse and dry the copper-plated parts from Step 4, and then test the surface and cross-sectional morphology of the copper plating using Focused Ion Beam (FIB) technology and Scanning Electron Microscopy (SEM). Evaluate the Damascus copper plating formula and process based on the morphology. Furthermore, the edge effect of the large cathode can be evaluated by the filling effect of the AAO template at the center and edge.

[0042] In this embodiment, the large cathode is as follows: Figure 4 As shown, three conductive porous anodized aluminum templates 2 are arranged sequentially from the center outwards along the radius of the single-sided copper-clad plate 1.

[0043] It should be noted that in Examples 1 and 2 above, the conductive seed layer may not be generated by magnetron sputtering, but may be generated by surface metallization techniques such as PVD, CVD, or chemical plating and chemical deposition; in step 5, the electroplating solution may also be other copper plating solution systems, such as acidic fluoroborate copper plating systems, acidic methanesulfonate copper plating systems, alkaline pyrophosphate copper plating systems, etc.; and the electroplating process can be adapted to a rack plating tank or a fountain-type electroplating tank with a rotating cathode. In addition, this invention can evaluate the formulation and process parameters of damascus copper plating, and can also evaluate the electroplating and chemical plating effects of cobalt, ruthenium, and other integrated circuits.

[0044] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A low-cost evaluation method for a damascus copper electroplating formulation and process, characterized in that, Includes the following steps: Step 1. Use a porous anodized aluminum template, clean it, and set it aside; Step 2. A dense and uniform conductive seed layer is applied to the front side of the porous anodic aluminum oxide template using a seed layer preparation process to form a conductive porous anodic aluminum oxide template; Step 3. Fix a single conductive porous anodic aluminum oxide template onto the conductive copper surface of the electrochemical deposition support, and form a cathode for electroplating copper after the front side is conductive; Alternatively, multiple conductive porous anodic aluminum oxide templates can be fixed on a single-sided copper-clad laminate, and their front sides can be made conductive to the single-sided copper-clad laminate to form a large cathode for copper electroplating. Step 4. Transfer the cathode into the electrolytic cell, which contains an electroplating solution prepared according to the Damascus copper plating formula to be evaluated. Then, complete the electroplating according to the Damascus copper plating process to be evaluated to obtain the copper-plated part. Step 5. Rinse and dry the copper-plated parts, and use focused ion beam technology and scanning electron microscopy to test the surface morphology and cross-sectional morphology of the copper-plated parts, so as to evaluate the Damascus copper electroplating formula and process.

2. A low-cost evaluation method for the damascus copper electroplating formulation and process according to claim 1, characterized in that, In step 1, the porous anodic aluminum oxide template has a pore size of 15~500nm and a pore depth of 60~1000nm.

3. A low-cost evaluation method for the damascus copper electroplating formulation and process according to claim 1, characterized in that, In step 2, the conductive seed layer is made of platinum, gold, tungsten or copper, and the thickness of the conductive seed layer is 5~20nm.

4. A low-cost evaluation method for the damascus copper electroplating formulation and process according to claim 1, characterized in that, In step 4, the composition of the damascus copper plating formulation to be evaluated is as follows: Copper sulfate pentahydrate at 20-160 g / L, sulfuric acid at 10-120 g / L, chloride ions at 40-70 ppm, inhibitors at 100-800 ppm, accelerators at 2-20 ppm, and leveling agents at 2-20 ppm.

5. A low-cost evaluation method for the damascus copper electroplating formulation and process according to claim 1, characterized in that, In step 4, the damascus copper plating process to be evaluated has a current density of 0.5~10 A / dm³. 2 The plating solution circulation flow rate is 0.2~2.0 m³ / h. 3 / h, temperature is 25℃, electrodeposition time is 30s~10min.

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