High-Voltage CMOS

QUESTION What is high-volt CMOS technology?

ten Have The ELMOS high-volt CMOS technology makes it possible to integrate medium-complex digital and memory cells, high-precision analogous functions and driver transistors on only one chip. Our challenge was to develop a process capable of creating all these circuit blocks with their various requirements. This means: high switching speed and packing density in the digital area with supply voltages of three to five volts, various components to create complex analogous functions for a voltage range of three to 16 volts, as well as voltage and space optimized driver transistors for voltages of up to 120 volts.

QUESTION Which elements can be used with this technology?

Rolfes-Gehrmann The possibilities of CMOS technology are numerous. The spectrum ranges from standard CMOS transistors, various resistors, PN and Zener diodes, voltage independent condensers through to DMOS driver structures. All these components exist for voltage ranges of between 16 and 120 volts. Beyond this aligning elements in the form of zapping diodes are available.

ten Have Moreover, we offer memory elements like EEPROMs and flashes. Additionally, high precision bipolar transistors make it possible to use voltage references and low-noise amplifiers for analogous circuits.

QUESTION Are there any limitations using the ELMOS-HV CMOS technology?

ten Have There aren’t actually any limitations but the field of application can be fenced off by the technical possibilities. The ELMOS high-volt CMOS technology is suitable for a high frequency usage of up to two GHz, can drive currents of up to ten Ampère and can deal with voltages of up to 120 volts. This applies not only at room temperature but at a temperature range of – 40°C to + 150°C, and in special applications even up to + 175°C. The digital complexity which can be achieved isn’t comparable to the high-end processes of Intel or AMD but is the cost optimum for our target market.

QUESTION Why is the high-volt CMOS technology especially suitable for applications in vehicles?

ten HaveThis is due to automobile requirements. Take for example the window lifter: a typical window lifter consists of a relay driver, analogous components and a micro-controller. This can be created without any problems. However in a car, the requirements are higher. This is mainly because of the voltage of the onboard power supply. This is designed for twelve volts, but nevertheless interfering pulses of up to 120 volts are reached. The microcontroller must withstand these voltages. The electronics in a vehicle must also be able to withstand harsh environmental factors, for example when the door freezes up in winter or when the sun shines on the car door for several hours in summer. Individual chips, for example in the throttle flap, must withstand temperatures of up to + 160°C when there is heat accumulation.
Rolfes-Gehrmann Moreover, we must ensure that the mechanic in the garage will not destroy the chips through electrostatic charge. Therefore, the CMOS technology offers ESD strengths of up to 4 kV and if required, of 8 kV also. Thus, the automotive peripherals are characterized by various other special requirements which are pushing the original functional solution to the background.

QUESTION How complex is the semiconductor production process using high-volt CMOS technology?

Rolfes-Gehrmann Compared to other technologies, the process is not as complex. We use fewer mask steps and the development effort is not as high since the high-volt CMOS process is built up modularly. This means less effort, lower production costs and lower prices for the product. The challenge is to reach this high functionality using very few mask steps. As a comparison: at ELMOS the mask complexity varies between 12 and 22 masks. Nowadays purely digital processes which nonetheless have a much higher packing density already need 26 and more mask steps.

QUESTION What benefits does this modular construction have for the customer?

ten Have We offer the customer a variety of process options from which he can assemble his own cost-optimal ASIC process according to his needs. He can choose the high-volt abi-lity as an option for example, if his product is to be exposed to higher-voltages. What is more, we work out with the customer whether or not further components are necessary. This could be: a capacitor module, EEPROM and various flash modules, double-poly-condensers and various metal options of up to four metal layers and power-metal options. These power-metal options are characterised by particularly thick metallization and are therefore of special interest in high current drivers.

QUESTION
How closely involved is the customer with the development of a semiconductor?

ten Have The customer has traditionally always been closely involved at ELMOS in the creation of his chip. Usually the customers come to us with abstract ideas. Together with them we coordinate their wishes with the abilities of the semiconductor. He is not involved at the primary stage of technology development as this is our job. The processes are derived from their wishes and requirements which have been previously developed. We work very closely with our customers, targeting their needs to find the best possible solution in terms of costs and time.

QUESTION Which steps are planned for the future of high-volt CMOS technology?

ten Have We would like to make further improvements in the digital packing density. We are currently deveolping, for example, a 0.35 µm process. Moreover we are improving the flash ability for up to 16-bit controller applications, without changing the high-volt ability.