METHOD AND DEVICE FOR COMPENSATING DRIFT IN A SEMICONDUCTOR ELEMENT

Abstract: A method and device for compensating drift wherein a feedback voltage is applied to a region of semiconductor material adjoining the insulating region.

Description: METHOD AND DEVICE FOR COMPENSATING DRIFT IN A SEMICONDUCTOR ELEMENT Semiconductor elements, particularly SOI circuits (Sili¬ con on Insulator) , are very useful for applications in envi¬ ronments wherein a determined radiation dose can fall on the semiconductor element. SOI elements in particular are inεenεi- tive to short radiation pulses and transient photocurrentε because of the small amount of silicon. A film of silicon oxide is usually kept as thin as possible so that when it is radiated as little charge carrier as possible is created in the oxide. Semiconductor elements are usually provided with a feedback voltage in order to obtain a suitable operating or threshold voltage of the semiconductor element even in the case of induced charge carriers. CMOS-SOI technology in particular is being applied more and more for manufacture of circuits wherein high speed is important, such as in oscillators and the like. With respect to the so-called SIMOX technique wherein oxygen is implanted in silicon, a silicon layer of for in¬ stance 100 nm thickness can be obtained. The present invention relates to a method and device as according to claims 1, 2 and 3. By making the feedback dependent on the sensed amount of radiation a threshold voltage remains relatively constant at a radiation value of 50-100 krad, which is highly advantageous for instance in space travel. The sub-claims relate to preferred embodiments for em¬ bodying the concept of the invention in elegant manner. Further advantages, features and details will become apparent with reference to the drawings, wherein: fig. 1 shows a block diagram of a first preferred embodi- ent according to the present invention; fig. 2 is a block diagram of a second preferred embodi¬ ment according to the present invention; and fig. 3 is a circuit diagram of the preferred embodiment of fig. 2. In fig. 1 a voltage emanating from a sensor 1 is compared in a differential amplifier 2 to a reference voltage V f and a voltage V , is subsequently fed back to the part of the semiconductor element for which drift has to be compensated. A block diagram in fig. 2 makes use as radiation-sensi¬ tive element onto which radiation R falls of an invertor 3 in SOI (preferably SIMOX) technology, the output of which is compared in a differential amplifier 2' to a reference voltage Vref_ whereafter the feedback is fed back to the backgate of an SOI transistor via a voltage source U of for example minus 10 volts. Fig. 3 shows a circuit diagram as preferred embodiment of the block diagram of fig. 2, wherein the sensor 1 is formed by an N- and P-channel FET and the differential amplifier 2' is likewise formed by a number of P- and N-channel FETs. Via a buffer circuit 4 also consisting of P- and N-channel FETs and the voltage source U the voltage V f , is fed back to the backgate as indicated schematically with the arrow A. The semiconductor element according to the present inven¬ tion can be integrated in simple manner during manufacture of a CMOS circuit; it is however also possible to employ a sepa¬ rate circuit for the feedback. Simulations using a computer have shown that the thres¬ hold voltage V. of a SOI transistor with both a P-channel and an N-channel FET is stabilized to a considerable extent. *****

Claims: CLAIMS 1. Method for compensating drift occurring in a semicon¬ ductor element in the threshold voltage in a region of semi¬ conductor material, wherein the semiconductor element com¬ prises a region of insulating material and wherein the voltage value of a feedback voltage is transmitted to a region of semiconductor material adjoining the insulating region depend¬ ing on an amount of detected radiation. 2. Device for performing the method as claimed in claim 1. 3. Semiconductor element comprising an SOI circuit and a backgate, provided with a sensor for sensing the amount of radiation falling on the semiconductor element and means for feeding back a voltage to the backgate, wherein the voltage value is dependent on the amount of radiation sensed by the sensor. 4. Semiconductor element as claimed in claim 3, wherein the sensor is embodied integrated with the semiconductor element. 5. Semiconductor element as claimed in claim 2, 3 or 4 in SIMOX technology, wherein the sensor comprises an invertor. 6. Semiconductor element as claimed in claim 5, provided with a CMOS invertor and an integrated operational amplifier, the output whereof is coupled to the backgate. *****

Inventors: COLINGE JEAN PIERRE, COLINGE, JEAN, PIERRE
Applicants: IMEC INTER UNI MICRO ELECTR, INTERUNIVERSITAIR MICRO-ELEKTRONICA CENTRUM VZW
Application year: 1990
Main classification: G05F3
IPC codes: G05F3, H01L21, H01L27