Silicon-based Al2O3 film chip capacitor and making method thereof

Abstract

The invention discloses a silicon-based Al2O3 film chip capacitor which can be used for bypass and filtration in microwave and radio-frequency circuits. The chip capacitor comprises a low-resistance (resistivity is not greater than 1*10<-3>omega.cm) silicon substrate, an amorphous Al2O3 insulating film, an upper electrode and a lower electrode. A radio-frequency magnetic control sputtering methodis adopted and comprises the following steps of: growing an amorphous Al2O3 insulating film on a single-crystal Si substrate by using high-purity Al2O3 ceramic as a target material, and then sputtering and growing a Ti or TiW layer and an Au layer; after electroplating Au for thickening, making an upper electrode figure with a photoetching and corroding method; and thinning the back surface of a Si chip according to the requirement on the thickness of the chip capacitor, sputtering the Ti or TiW layer and the Au layer on the back as the lower electrode, and making the chip capacitor after scribing. The capacitor has the advantages of high Q value, low loss, simple structure and process, low cost, small size and the like.

Description

technical field [0001] The invention belongs to the field of film ceramic capacitors, in particular to a microchip capacitor and a manufacturing method. Background technique [0002] Microchip capacitors are a very important electronic device in microwave integrated circuits and multi-chip component packages. They function as bypasses and filters to stabilize the power supply voltage of ICs operating in the microwave frequency band. It is required to be small in size, high in Q value, wide in capacitance value range, and low in cost. [0003] Usually chip capacitors are made by sintering dielectric green sheets and conductor sheets, which have problems such as easy deformation, fragile green porcelain, and special processing for bonding strength. [0004] Another way to make chip capacitors is to use semiconductor technology, which is formed by sequentially forming a lower plate, a dielectric film, and an upper plate on a silicon substrate. This method is suitable for the ...

AI Technical Summary

Problems solved by technology

However, there are the following problems: 1. The thickness of the silicon wafer is fixed, and the height of the chip capacitance cannot be flexibly changed according to the actual packaging needs; 2. The relative dielectric constant of silicon dioxide is only 3.9, and the dielectric constant k is small, while Al 2 o 3 The relative dielectric constant of ceramics is 9 to 10.5, which is SiO 2 2.5 times that of the same dielectric thickness and capacitance, SiO 2 Film Capacitance Ratio Al 2 o 3 The area of ​​the film capacitor is doubled, and the SiO 2 Breakdown field strength ratio Al 2 o 3 Ceramics are low and have poor withstand voltage characteristics; 3. Using ordinary silicon wafers, the metal back electrode contact will introduce contact resistance, and the silicon wafer itself has a certain resistivity, which will also introduce series parasitic resistance, causing the Q value to drop; 4. Up Electrode, SiO 2 The thin film and Si substrate form a MOS structure. If the doping concentration of the Si substrate is not high enough, no matter it is N-type or P-type, there will be obvious variation characteristics of the capacitance C value with the voltage V. The test C-V curve reflects the obvious electron ( or holes) accumulation and inversion changes, the value of capacitance C changes under positive bias and negative bias conditions, which cannot well meet the needs and applications in actual circuits

Images