Stress sensor for detecting mechanical stress in semiconductor chip, has four resistors that are integrated in active surface of semiconductor chip, to form Wheatstone bridge

[0001] The invention concerns a stress sensor for the collection of mechanical stresses in a semiconductor chip and a stress-compensated resounding sensor. Resounding sensors are magnetic field sensors, which are based on the hall effect and supply an electrical output signal, which is proportional to a pre-determined component of the magnetic field. A resounding sensor covers a Hallelement or a cluster of Hallelementen and an electronic circuit for the enterprise of the Hallelemente and the evaluation of the output signals of the Hallelemente. The resounding sensor is manufactured as integrated circuits, which is embedded into a semiconductor chip. The semiconductor chip is packed into a housing. Hallelemente exhibit an offset, which is due to prozessund geometry-conditioned deviations. The offset can by the parallel connection of several Hallelementen (cluster) and/or the enterprise with the well-known Spinning Current method to be effectively reduced. This is admits from a multiplicity of patent documents, e.g. WHERE 0,118,556, EP 548,391, DE 4,302,342. The semiconductor chip packed in the housing is exposed to mechanical stresses, which depend on environmental influences such as temperature and humidity, etc. The changing mechanical stresses cause on the one hand changes of the off set of the Hallelemente and because of the Piezo HalI effect also changes of the sensitivity of the Hallelemente. Changes of the off set are effectively suppressed by the measures described above. In order to compensate the changes of sensitivity, it is well-known, for example from DE 10,154,495, DE 10,154,498, DE 10 2004 003,853, DE 10 2008 051,949 to use a stress sensor to use which seizes the mechanical stresses, and whose output signal, in order to compensate the change of the sensitivity of the Hallelemente caused by the Piezo HalI effect. The invention are the basis the tasks to compensate in as simple a way as possible the change of the sensitivity of a Hallelementes caused by the Piezo HalI effect and to develop a to a large extent stress-compensated resounding sensor. The tasks mentioned solved according to invention by the characteristics of the requirements 1 to 3. The invention is more near described in the following on the basis of remark examples and on the basis the design. Fig. 1 Fig. 2 Fig. 3A-C Fig. 4 Fig. Fig. 6 Fig. 7 Fig. 8. to the electrical diagram of a according to invention, by resistances of formed stress sensor, shows illustrates the internal structure in principle of the resistances, shows remark examples of the resistances, points a sensor cell, which covers a Hallelement, a p-type resistance and a n-type resistance, shows two sensor cells, which form a stress sensor according to invention and a resounding sensor, shows a circuit to the enterprise of a Hallelementes, shows in supervision a sensor cell, which covers a Hallelement, two n-type of resistances and two p-type of resistances, and shows a further stress sensor according to invention. The Fig. 1 shows the electrical diagram of a stress sensor according to invention 1. the stress sensor 1 consists of a Wheatstone bridge formed by four of resistances g 1, R2, R3 and R4, which are integrated into a semiconductor chip 2. In the following designate x, y and z the axles of a cartesian coordinate system, whereby the Z-axis runs perpendicularly to the active surface 3 of the semiconductor chip and the x axis and the y axis parallel to those edges of the semiconductor chip, which encloses the active surface 3. The resistances the g 1 and R2 are switched into row, the resistances the R3 and R4 are switched in row and parallel to the resistances g 1 and R2. The resistances R and R3 have a common knot 4 and the resistances the R2 and R4 to have a common knot 5, which is connectable to a supply terminal or a power source. The resistances the g 1 and R2 have a common knot 6 and the resistances the R3 and R4 to have a common knot 7, over which the output signal of the Wheatstone bridge is measured as differenzielles tension signal and supplied to a Verstärkerschaltung 8. The resistances R R2, R3 and R4 exhibit the following characteristics: 1. The resistances R and R4 are p-type of resistances, i.e. in the semiconductor chip resistances with one pTyp doping integrated 2. 2, 3, 4, 5, 6, the resistances the R2 and R3 is n-type of resistances, i.e. in the semiconductor chip resistances with one nTyp doping integrated 2. For the resistances g 1, R2, R3 and R4 used dopings are preferably for the production of the contacts used highly endowed N+ and/or P+ the dopings. Everyone of the resistances g 1, R2, R3 and R4 is compound from oblong resistance sections, which directly or by electrical conductor are connected and which forms resistance, whereby each of the resistance sections exhibits an XY-even pre-determined orientation in the active surface the 3 of the semiconductor chip defined, whereby a sum of the resistance values of all resistance sections, which exhibit a first orientation and to the same resistances R R2, R3 and/or R4 belong, and a sum of the resistance values of all resistance sections, which exhibit likewise second, for first orientation turned around 90° and to this the same resistances R R2, R3 and/or R4 belong, which has same nominal value. The nominal values of the four resistances R R2, R3 and R4 are, apart from process-conditioned tolerances, equally large, i.e. g 1 = R2 = R3 = R4. This reached by the layer resistance the p-type doping and/or n-type doping appropriate relationship from length to width of the resistance strips. In the resistance cut flowing rivers flow into substantially parallel to the active surface 3 of the semiconductor chip 2. the resistances R off R2, R3 and R4 can therefore as lateral of resistances be designated. The principle Iässt indicated in characteristic 4 most simply realizes itself by a pair of oblong resistance strips, whereby the two resistance strips of the pair are switched in the XY-even of the semiconductor chip 2 around 90° turned to each other arranged and in row. I.e. the two resistance strips of a pair form together a L-shaped resistance. For standard (100) silicon with a <110> orientation of the Fiat is approximately given by the following equations the dependence of the resistance values on the stress: BRn/Rn = -24%/GPa* (Txx +Tyy) + 53%/GPa*Tzz ARp/Rp = 2.7%/G Pa* (Txx +Tyy) - 1.1%/G Pa*Tzz (1) (2), whereby Txx, Tyy and Tzz toward the x axis and/or y axis and/or Z-axis arranged standard voltage components of the mechanical stress tensor designate the three. The indicated percentages (24%, 53%, 2,7% and 1,1%) are to be understood as approximate values with low doping and with (100) silicon independently of the turning situation of S iliziumswafers. Because Tzz is mostly many smaller in practice than Txx and Tyy, been approximating ARn/Rn = -24%/G Pa* (Txx +Tyy) is valid for ARp/Rp = 2.7%/GPa* (Txx +Tyy) (3) (4). The change of the resistance values the n-type of resistances is on the one hand around approximately an order of magnitude (here approximately by the factor 9), caused by mechanical loads, more largely than the change of the resistance values the p-type of resistances. This is a condition that by the resistances the g 1 to R4, formed Wheatstone bridge supplies at all an output signal. The output signal of the Wheatstone bridge is proportional to the sum Txx + Tyy. On the other hand have the n-type of resistances R and R4 similar temperature coefficients as the p-type of resistances R2 and R3, with the consequence that the output signal of the Wheatstone bridge is affected by changes of temperature only few. The temperature coefficients of the highly endowed N÷ and/or P÷ of resistances are smaller with the used CMOS process around for instance the factor 2,5 than the temperature coefficients of the fewer strongly endowed n-tubs and/or p-tubs. This is the reason, why for the resistances prefers the highly endowed N+ and/or P+ the dopings are used. The differenzielle output signal of the Wheatstone bridge is supplied to the Verstärkerschaltung 8, where it is converted for example by means of a first operation amplifier 9 into a difference signal and offset-compensated by means of a second operation amplifier 10 by subtraction of a constant value V and then as output signal Vs of the stress sensor 1 is available. The Fig. 2 the internal structure in principle of the resistances R R2, R3 and R4 illustrates that it per at least two oblong resistance strips 11 and 12 exhibits, which exhibit the same nominal resistance value, to each other over 90° twistedly and into row are switched. In the example the four resistance strips 11 are parallel to the x axis and the four resistance strips 12 parallel to the y axis aligned. The resistance strips 11 and 12 can be turned however within the level stretched by xund the y axis at any angle, importantly are only that its, relative turning situation referred one on the other remains, i.e. that they lie in the XY-even and include an angle of 90°. With in the Fig. 2 remark example shown is connected the resistance strips 11 and 12 everyone of the resistances g 1, R2, R3 and R4 two individual, from each other separated resistance strips, those by an electrical conductor is and so together the appropriate resistance g 1, RZ, R3 and/or. R “result in. The Fig. 3A shows a remark example one of the resistances g 1, RZ, R3 and R4 in supervision to the active surface 3 of the semiconductor chip 2. The resistance is compound up from several oblong resistance sections 13,1 to 13,4, whereby in each case two resistance sections 13, by which a resistance section 13 is turned around 90° regarding the other resistance section the 13 in the XY-even, which same nominal resistance value has and a pair to form. Here there are two pairs: The resistance sections form the first pair 13,1 and 13,3, the second pair form the resistance sections 13,2 and 13.4. The resistance section 13,2 is turned in relation to the resistance section 13,1 at the angle 45°. The resistance section 13,4 is turned in relation to the resistance section 13,1 at the angle 45°. The resistance sections 13,1 to 13,4 can with one another be as represented by electrical conductor into row switched. In this case the resistance sections at arbitrary and different places on the semiconductor chip 2 can be. In addition, the resistance sections 13,1 to 13,4 can as in the Fig. 3B represented directly connected its and a only one connected resistance strip form. The Fig. 3C shows a further remark example one of the resistances g 1, R2, R3 and R4. The resistance is compound up from five oblong resistance sections 13,1 to 13,5. The resistance sections 13,2, 13,3 and 13,4 have the same nominal resistance value, R. the resistance sections 13,1 and 13,5 have the half resistance value R/2, them are therefore as a common resistance section with the nominal resistance value R to be regarded, which is split up into two parts geometrically. The sum of the resistance values of the resistance sections 13,1, 13,3 and 13,5, which a same, first orientation have, amount to 2*R and are equal the sum of the resistance values of the resistance sections 13,2 and 13,4, which a same, second orientation to have, whereby first and second orientation in by the active surface 3 of the semiconductor chip 2 defined XY-even are turned around 90° to each other. The relationship from length to width of the resistance sections, which are to be assigned to the same pair, is in such a way limited in the principle that a mechanical load causes just as large change of the resistance formed by the resistance sections by the standard voltage component Txx as a mechanical load by the standard voltage component Tyy. The stress sensor according to invention is suitable for example, in order to compensate with a magnetic field sensor which is based on the hall effect the change of sensitivity caused by Piezo resounding effect. The Fig. a sensor cell 14 in supervision, which covers a Hallelement 15, a n-type resistance 16 and a p-type resistance 17, shows 4. The Hallelement 15 is with this example a square n-tub (or a p-tub) and the four contacts 18 for the supply of resounding Rome and the pick-up of the resounding tension are arranged in the corners of the square. The n-type resistance 16 is formed by four straight n-type resistance courses 19, which are connected parallel to the four sides of the square n-tub aligned and by electrical conductive strips. Two each of the four n-type resistance courses 19 run thus parallel to the x axis and to the y axis. The p-type resistance 17 is formed by four straight p-type resistance courses 20, which are connected parallel to the sides of the square aligned and by electrical conductive strips. Two each of the four p-type resistance courses 20 run thus parallel to the x axis and to the y axis. The layout of the individual elements of the sensor cell 14 is implemented with as high a symmetry as possible, so that mechanical loads distribute themselves as evenly as possible over the Sensorielle 14. The Fig. 5 shows in supervision two sensor cells 14 in the Fig. 4 of type shown. Both the n-type of resistances 16 and both the p-type of resistances 17 of the two sensor cells 14 are in accordance with in the Fig. 1 electrical diagram shown as Wheatstone bridge wired and form a stress sensor according to invention. For the representation of the wiring for reasons of the graphic clarity different lines, i.e. taken off, painted and dotted lines are used. The two Hallelemente 15 form a resounding sensor together with the electronic circuit necessary for their enterprise. The differenzielle output signal of the Wheatstone bridge is supplied to a Verstärkerschaltung 8, for example in the Fig. described 1 Verstärkerschaltung 8, where it is strengthened and the offset of the Wheatstone bridge is eliminated so far as possible, so that the output signal Vs of the stress sensor is available as offset-compensated output signal. The Fig. a preferential remark example shows 6, like the output signal Vs in the Fig. 5 of stress sensor shown is used, in order to compensate the change of the magnetic field-referred sensitivity of the two Hallelemente 15 caused by Piezo resounding effect. The change of the sensitivity of the two Hallelemente 15 caused by the Piezo hall effect is proportional in first approximation to the sum Txx + Tyy of the mechanical loads working in the x-direction and the y-direction. The two Hallelemente 15 are offset-compensated with advantage in well-known way by parallel connection and enterprise with the Spinning Current method (e.g. see to EP 548,391). The two Hallelemente 15 are operated thereby separately from each other with the Spinning Current method, whereby everyone of its own regulated current source is fed, and then adds its output signals. The Fig. therefore only the electrical gear change of the electronic circuit for a Hallelement 15 shows 6. The electronic circuit in this example four power sources 21 to 24, their rivers to be added enclosure and/or subtracted and to the Hallelement 15 as river I by way of a Spinning Current multiplexer be supplied. The resounding tension resting against the exit of the multiplexer is an alternating voltage, which can be processed and evaluated in well-known way. The first power source 21 is a PTAT regulated current source (PTAT = proportionally ton absolute temperature) and supplies a river I to the absolute temperature is proportional. The second power source 22 is a CTAT regulated current source (CTAT = complementary ton absolute temperature) and supplies a river 12, which decreases with increasing temperature. The third power source 23 is steered by an temperature-independent resistance RQ and supplies a river 13 independent of the temperature. The fourth power source 24 is steered by the output signal Vs of the stress sensor 1 and supplies a river 14, which is proportional to the sum (Txx + Tyy). I1 = Ip* [1 + a* (TTo)] 12 = Ic* [1 - b * (TTo)] 13 = IR 14=C*Vs whereby ton a selected fixed temperature is. The four power sources 21 to 24 are co-ordinated so that the rivers are given to I to 14 within a certain temperature range through: I = OE * I1 + * 12,-13 + 7 * L4 = IO * [1 + 6 * (TTo) + X * Vs] the coefficients o y, 6 and; L are constants, IO designates at the temperature the tons and with absence of mechanical loads of the power sources 21 to 24 supplied river. The temperature range, in which the Hallelement 15 is to be used, is typically into several, e.g. three, temperature ranges subdivided, in which the coefficients OE are so selected, ¥ and tons that in each individual temperature range by the river I on the one hand the linear dependence of the currentreferred sensitivity of the Hallelementes and the linear dependence of the output signal Vs of the stress sensor on the temperature and on the other hand the dependence of the currentreferred sensitivity of the Hallelementes of mechanical loads are compensated, and that over all temperature ranges also the square dependence of the currentreferred sensitivity of the Hallelementes and the square dependence of the output signal Vs of the stress sensor on the temperature are compensated, so that the resounding tension supplied by the Hallelement 15 UH of the temperature T and of mechanical loads Txx and Tyy is to a large extent independent. For (100) silicon with <110> Flat results the river I = Io* [1 + 8 " (T25 °C) + s* (T25 °C) 2 +; L* Vs] whereby the constants of 5, s and X in an experimental example had the following values: 6 = 300 ppm/°C =5 ppm/°C2; L = 2.2N it is favourable for reasons of the offset compensation well-known masses to operate two or more Hallelemente parallel and besides with the Spinning Current method and to add their resounding tensions with correct sign. The two Hallelemente 15 in the Fig. 5 of HalI sensor shown is together surrounded by two n-type resistance 16 and two p-type resistance 17, which forms together the Wheatstone bridge of the stress sensor 1. If the resounding sensor covers four Hallelemente 15, then it is favourably, the resounding sensor and the stress sensor 1 further from sensor cells 14 in the Fig. to form 4 of type shown. Since the Wheatstone needs bridge of the stress sensor 1 of only four resistances, she can be for example formed, as two each n-type of resistances 16 and two p-type of resistances 17 that are selected altogether eight resistances and other four resistances are not used. Alternatively can be used all eight resistances of the four sensor cells 14, as per two resistances of the same type into row or and from it the Wheatstone bridge of the stress sensor 1 is parallel switched are formed. Another possibility is to plan two types of sensor cells whereby the first type covers a Hallelement and the Hallelement surrounding n-type resistance and the second type a Hallelement and the Hallelement surrounding p-type resistance. The Fig. a sensor cell 14 in supervision, which covers a Hallelement 15, two n-type of resistances 16,1 and 16,2 and two p-type of resistances 17,1 and 17,2, shows 7. The n-type of resistances 16,1 and 16,2 are by ever two straight, over 90° to each other rotate arranged n-type resistance courses 19 in an educated manner, which are connected parallel to the sides of the square tub of the Hallelementes 15 aligned and by electrical conductive strips. The p-type of resistances 17,1 and 17,2 are by ever two straight, over 90° to each other rotate arranged p-type resistance courses in an educated manner, which are connected parallel to the sides of the square tub of the Hallelementes 15 aligned and by electrical conductive strips. This sensor cell 14 contains thus two n-type and two p-type of resistances, which exhibit all characteristics necessary for the education of a stress sensor according to invention 1, and a Hallelement and represents thus the simplest example, around one for example in accordance with in the Fig. 6 gear change shown temperaturund stress-compensated magnetic field sensor to a large extent to form. The Fig. 8 to 10 shows further resounding sensors, which cover a Hallelement 15 (or a cluster from Hallelementen) and a stress sensor according to invention 26. The stress sensor 26 consists again of a Wheatstone bridge formed by four of resistances g 1, R2, R3 and R4, which are integrated into a semiconductor chip 2. The resistances the g 1 and R2 are switched into row, the resistances the R3 and R4 are switched in row and parallel to the resistances g 1 and R2. The resistances R and R3 have a common knot 4 and the resistances the R2 and R4 to have a common knot 5, which is connectable to a supply terminal or a power source. The resistances R and R2 have a common knot 6 and the resistances the R3 and R4 to have a common knot 7, over which the output signal of the Wheatstone bridge is measured as differenzielles tension signal and supplied to a Verstärkerschaltung. The resistances R and R4 are p-type of resistances, the resistances the R2 and R3 are n-type of resistances. If one on the basis of in the Fig. 2 structure in principle shown of the resistances R R2, R3 and R4 a multiplicity of pairs of short resistance touches 11 and 12 lines up, receives one a treppenförmigen resistance and if one makes the resistance strips 11 and 12 in the Limes infinitely short, one receives one concerning the x axis around 45° or -45° turned, oblong resistance. Into the Fig. 8 to 10 resistances shown g 1, R2, R3 and R4 of the stress sensor 26 are such resistances. The stress sensor 26 and the Hallelement 15 (and/or a cluster from Hallelementen) can be combined with use of (100) silicon with <110> Fiat to a stress-compensated resounding sensor, if the following conditions are fulfilled: - The resistances R; R2, R3 and R4 are oblong of resistances, which are turned around 45° or -45° concerning the <110> crystal orientation of the silicon (the x axis shown in the figures runs parallel to the <110> crystal orientation). - The Hallelement 15 (and/or the Hallelemente of a cluster) exhibits at least four contacts, which are so aligned that in admission of two of these four contacts with a river the river under an angle of 45° or -45° flows diagonally to the <110> crystal orientation by the Hallelement 15. The output signal of the Wheatstone bridge steers a power source, whose river is supplied to the Hallelement 15 as with the preceding examples, in order to reduce the influence from mechanical loads to. In the Fig. has 10 Hallelement shown 15 a octogonalen outlined with eight equal long sides and eight contacts 18, whereby turned in each operating phase of the Spinning Current method in each case two of each other diametrically facing contacts as current contacts and two further in addition around 90°, each other diametrically facing contacts than tension contacts, arranged, to serve. Here the river flows in each case in the individual operating phases under an angle from 0°, 45°, -45° or 90° to the <110> crystal orientation.