the characteristic frequency of NPN transistors manufactured by standard bipolar process is generally lower than 1 MHz

. When high frequency and high speed performance are required, micro-machining, thin layer epitaxy and shallow junction technology are used, and the characteristic frequency of the device can reach 3 ~ 5 MHz. A typical high frequency process is shown in Figure 4.

high withstand voltage technology the linear bipolar process can usually achieve the withstand voltage performance of 5 ~ 6 volts. In order to obtain the breakdown voltage of nearly 1 volts or higher, the following measures can be taken: ① increasing the thickness of N-type epitaxial layer (such as more than 2 microns) to improve the breakdown voltage of NPN tube; (2) increasing the thickness of the oxide layer to prevent the metal interconnection line with negative potential from generating parasitic MOS tube effect when crossing the lateral PNP transistor; (3) Protect the surface of the isolation junction with a field electrode to avoid the electric field being too concentrated, which will lead to the decrease of the breakdown voltage (Figure 5).

linear CMOS technology this is a very complex universal compatible technology, which can be used to make

various bipolar devices and CMOS devices at the same time (see complementary metal-oxide-semiconductor integrated circuits). With this technology, high-performance linear circuits and high-density high-speed logic circuits can be combined on one chip. A linear CMOS process using refractory metal molybdenum as the gate material can make P-channel and N-channel MOS devices on the N-type epitaxial layer of a linear bipolar chip, and it only needs 1 photoetches, and it has two layers of interconnects of aluminum and molybdenum. P-channel and N-channel devices can use an N-region alone or * * * (Figure 6).

precision element passive element resistors usually adopt semiconductor resistors formed by diffusion layers or ion implantation layers. Better temperature stability can be obtained by fabricating alloy thin film resistors on silicon wafers. However, the resistance accuracy of both is less than 1%. High-precision resistors need to be obtained by various resistance correction techniques. Usually, a pulsed laser beam with a diameter of about 1 microns is used, and the correction methods include the method of fusing interconnection lines (Figure 7a) and the method of fusing diffusion layers (Figure 7b).

mos transistor is a metal-oxide (oxid)-semiconductor field effect transistor, or metal-insulator-semiconductor. The source and drain of MOS transistor can be switched, and they are both N-type regions formed in P-type backgate. In most cases, the two regions are the same, and even if the two ends are switched, the performance of the device will not be affected. Such devices are considered to be symmetrical.