1. Field of the Invention
The present invention relates to a structure with an integrated circuit (IC) and a silicon condenser microphone mounted on a substrate and a method for manufacturing the structure, and more particularly, relates to a structure with an integrated circuit (IC) and a silicon condenser microphone mounted on a same substrate and a method for manufacturing the structure under low temperature.
2. Description of Related Art
Microphone is a transducer for changing sound signals into electronic signals. The traditional silicon condenser microphone typically includes a diaphragm acting as one electrode of a variable capacitance and a back plate acting as the other electrode of the capacitance. With sound signals entering the microphone, the diaphragm is deformed under influence of the sound pressures of the sound signals, which changes the capacitance between the diaphragm and the back plate. As a result, the change of the capacitance is transformed into the electronic signals by the following processing circuits.
The silicon condenser microphone has been in a research and development stage for more than 20 years. Because of its potential advantages in miniaturization, performance, reliability, environmental endurance, low cost, and mass production capability, the silicon condenser microphone is widely recognized as the next generation product to replace the conventional electrets condenser microphone (ECM) that has been widely used in communication, multimedia, consumer electronics, hearing aids, and so on. The ECM has stored charge either in its back plate or diaphragm. However, such stored charge is easily leaked under high temperatures up to 260 degrees during automotive assembly.
Unlike the ECM, the silicon condenser microphone depends on the external bias voltage to pump the required charge into its variable capacitor. As a result, the silicon condenser microphone can't worry about the leaking of the stored charge. The silicon condenser microphone can endure high temperatures during surface mountable installation so that it can be automatically assembled on the corresponding PCB instead of hand installation.
Nowadays, there are two general types of integration methods for fabricating a MEMS component and an IC. One method is called multiple substrate integration among which the MEMS component and the IC are individually fabricated on different substrates by different companies. Thereafter, the MEMS component and the IC are packaged into a functional unit. The advantages of this method are that the design and manufacture of MEMS component can be solely optimized with low cost. The other method is called single substrate integration among which the MEMS component and the IC are fabricated on the same substrate. Such method is normally used for manufacturing high output impedance sensor or capacitive sensor in order to improve their integral performance and decrease influence of the outside noise interference.
There are three kinds of methods of single substrate integration. The first method is to fabricate the MEMS component first and then finish the fabrication of the IC on a same single substrate. The second method is interlaced fabricate the MEMS component and the IC are on the same single substrate. The third method is to fabricate the IC through standard semiconductor processing and then to fabricated the MEMS component on the same substrate. However, the IC manufactured by the first and the second methods is easily polluted by the prior MEMS component. Regarding to the third method, after the IC is fabricated on the substrate, high temperature must be avoided in the following steps for fabricating the MEMS component because the metal electrodes of the IC cannot endure high temperatures over 400 degrees.
Hence, it is desired to have an improved structure with an integrated circuit (IC) and a silicon condenser microphone mounted on a single substrate and a method for manufacturing the structure with low temperature solving the problems above.