Method for manufacturing thin film capacitor with anodic oxidation film as dielectric layer

[0056] Example one:

[0057] On a sapphire substrate 1 with a thickness of 0.254 mm, a Ta film is deposited as a metal film 2 by magnetron sputtering. The thickness of the Ta film is about 300 nm, such as figure 1 Shown.

[0058] The metal thin film 2 is patterned by a photolithography etching process to form a lower electrode 202 and a first lower electrode lead line 201, such as figure 2 Shown. Among them, Ta etchant uses HF buffer.

[0059] A photoresist is spin-coated on the lower electrode 202 and the first lower electrode lead-out line 201, and an anodic oxidation mask is formed through a photolithography process. The thickness of the patterned anodic oxidation mask 3 is 8 microns. The anodizing mask 3 completely covers the first lower electrode lead-out line 201 to prevent the first lower electrode lead-out line 201 from being oxidized during anodization. The opening area of ​​the anodizing mask 3 is larger than that of the lower electrode 202, so that the side surface of the lower electrode 202 is also exposed. The positive pole of the DC stabilized current power supply is connected to the bottom electrode 202 as the anode through the first bottom electrode lead wire 201, and the negative pole of the power supply is connected to the steel plate as the cathode, soaked in the electrolyte. The composition of the electrolyte is oxalic acid: water: ethylene glycol = 1: 2:3 (weight ratio), temperature 25°C. Anodizing is carried out by using constant current first and then constant voltage. Set the current according to the area of ​​anodization, that is, the area of ​​the lower electrode 202, so that the current density is 1mA/mm 2 , The oxidation voltage is set to 180V. After being energized, the portion of the bottom electrode 202 in contact with the electrolyte undergoes an oxidation reaction to generate metal oxide Ta 2 O 5 At the beginning of the electrolysis reaction, the lower electrode 202 has better conductivity and lower access resistance, so the voltage is lower. As the electrolysis reaction time increases, an oxide film grows on the surface of the lower electrode 202, and the resistance gradually increases, so the voltage also gradually increases. When the voltage increases to the set voltage of 180V, the oxidation reaction continues, the access resistance continues to increase, and the current gradually decreases, when the current density decreases to 2μA/mm 2 Stop anodizing at the time. A dielectric layer 4 is formed on the surface (including the side surface) of the lower electrode 202. The thickness of the dielectric layer 4 is about 320nm (1.78*180=320.4), and the thickness of the consumed Ta film is 128nm (0.4*320.4=128.2). The dielectric layer 4 The thickness of the unoxidized Ta film below is about 171.8nm (300-128.2=171.8), such as image 3 Shown.

[0060] Remove the anodic oxidation mask 3, and deposit TiW-Au multilayer metal film as the electrode layer 5 by magnetron sputtering on the substrate 1 that already contains the circuit pattern. TiW is used as an adhesion layer to increase the Au layer and the substrate. The adhesion between the sheets 1, the thickness of the TiW layer is about 50nm, and the thickness of the Au layer is about 200nm, such as Figure 4 Shown.

[0061] The electrode layer 5 is patterned by a photolithography etching process to form a second lower electrode lead-out line 501, an upper electrode 503, and an upper electrode lead-out line 502, such as Figure 5 Shown. Among them, the TiW layer is etched with hydrogen peroxide, and the Au layer is etched with iodine and potassium iodide solutions.