CN1156005C - Force-sensitive operational amplifier for integrated MOS pressure sensor - Google Patents

Abstract

The present invention relates to a force-sensitive operational amplifier for an integrated MOS force-sensitive operational amplifying pressure sensor, which is characterized in that the present invention comprises a concave silicon cup which is made on an N-shaped silicon film (100) and is composed of a pair of operational amplifiers which are fully symmetrical but channels are mutually vertical to replace PMOS differential input tubes M1, M2 of the pair of operational amplifiers on the input end of a force-sensitive operational amplifying circuit, and the rest part of the force-sensitive operational amplifying circuit made on a thick body silicon and connected with the tubes M1, M2. The present invention has the advantages of simple structure, high pressure response sensitivity, good linearity, low system temperature shift and power consumption, few elements, no resistance making process, high yield and low production cost; the present invention only needs regulating zero once, and the input end is conveniently regulated to zero.

Description

The stress-sensitive operational amplifier device that integrated MOS force-sensitive operational pressure sensor is used

Technical field

The stress-sensitive operational amplifier device that a kind of integrated MOS force-sensitive operational pressure sensor is used belongs to the stress-sensitive operational amplifier device and makes the field.

Background technology

Making general monocrystalline silicon piezoresistance formula pressure sensor is to adopt diffusion or ion implantation to form the force sensing resistance bar that four resistances equate in the suitable crystal orientation of (100) crystal face selection, and they are connected into a Wheatstone bridge; Be processed into spill overleaf and form flexible sheet, be commonly called as silicon cup.In the ideal case, when not having impressed pressure to affact on the silicon diaphragm, electric bridge is in poised state, and output voltage is zero.When impressed pressure, electric bridge disequilibrium and produce pressure-dependent output voltage, thus draw force value.In fact because processes such as plate-making, photoetching, diffusion or injection have caused deviation.Under normal conditions, the force sensing resistance resistance in the different chips departs from nominal value up to 10-25%.Even on same wafer, for the wide resistance of 10 μ m, variable quantity is between 1-3%.In addition, electric bridge also exists imbalance at zero point and zero temperature drift problem.Compensation technique commonly used comprises the laser correction of film resistor network, the ingenious combination of outer meeting resistance, diode compensation method and various material behaviors etc.But they are all different because of transducer, need relate to the multiple tracks manufacture craft again, can increase the manufacturing cycle and the cost of transducer undoubtedly.More be pointed out that:the differential output voltage of semiconductor pressure sensor Wheatstone bridge is generally tens mV, utilizes the output voltage of the micro-pressure sensor of surface micromachined making to have only tens-hundreds of μ v.Thereby, present integrated pressure sensor mainly is made up of force sensing element (Wheatstone bridge) and a plurality of operational amplifier, power consumption is big, not only force sensing element has null offset, temperature to float problem, operational amplifier has these problems too, thereby all must zeroing, thereby it be complicated to make null offset and temperature float problem.A main developing direction of moment sensor is that to make senser and signal processing circuit integrated be that monolithic is integrated, even intelligent.Promptly, make senser both play a part detectable signal, play corresponding circuit function again the part of senser as treatment circuit.Having a kind of is the senser in the monolithic integrated circuit to be taken out be placed directly on the stressed object with the acceleration of ergometry. utilize in the quick difference amplifier of power of MOSFET piezoresistive effect and the application ＂ on three axis accelerometer (the Stress-sensitivedifferential amplifies using piezoresistive effects of MOSFETs and their applicationto three-axial accelerometers) literary composition thereof such as ＂ by name among " sensor and performer " (Sensors and Actuators A65 (1998) 61-68) and propose: can be four jiaos that are placed on as 4 PMOS pipes in the quick CMOS difference amplifier of two power of force sensing element on the acceleration beam; The centre adds a bearing block, connects the acceleration analysis circuit again and just can be used for acceleration measurement behind the quick CMOS difference amplifier of above-mentioned power. Wherein see on the whole that as the quick CMOS differential amplifier of the power of force sensing element not being integrated into a device in fact plays sensing and amplification simultaneously, and as transducer also need add one with the discrete measurement by magnification circuit of its force sensing element.

Summary of the invention

What the object of the present invention is to provide that an integrated MOS force-sensitive operational pressure sensor uses can be integrated in a stress-sensitive operational amplifier device on the substrate to quick sensing element of power and operational amplifier.

The invention is characterized in that it contains: the upper surface be SiO ₂The substrate of layer, open on the substrate bottom surface and the spill silicon cup of band flexible sheet, be made in that this silicon chip is concentrated on N type (100) silicon diaphragm by complete symmetry side stress but raceway groove orthogonal in order to the quick difference input of the PMOS power that replaces a pair of differential pair tube of stress-sensitive operational amplifier circuit input end to pipe (M1, M2), be made in that thick body silicon low stress area links to each other with the drain electrode of above-mentioned M1, M2 pipe respectively but the remainder of taking the stress-sensitive operational amplifier circuit behind a pair of differential pair tube of above-mentioned input away that links to each other with its source electrode simultaneously.Described silicon cup is a C type structure.Described stress-sensitive operational amplifier circuit can be to form with NMOS, PMOS and/or bipolar transistor.(M1, channel direction M2) are respectively edge [011] and [0 11] directions to pipe in described difference input.

Experimental results show that: it has reached intended purposes.

Description of drawings:

Fig. 1: the quick differential pair tube circuit theory diagrams of PMOS power.

Fig. 2: force-sensitive operational device schematic top plan view.

A-A ' the profile of Fig. 3: Fig. 2.

Fig. 4: the circuit theory schematic diagram of stress-sensitive operational amplifier device.

Fig. 5: E/EPMOS operation amplifier circuit figure.

Fig. 6: the structural representation of stress-sensitive operational amplifier device.

Fig. 7: the manufacture craft flow chart of stress-sensitive operational amplifier device.

Fig. 8: the pressure-responsive figure of the integrated MOS force-sensitive operational pressure sensor that makes.

Embodiment:

Ask for an interview Fig. 1.The difference input is symmetrical fully to pipe M1 and M2, and both channel directions are vertical mutually, short circuit and ground connection between its grid,

Grid voltage V then _G1=V _G2=V _G=0

Leakage current I ₀=I _D1+ I _D2

The metal-oxide-semiconductor channel mobility equates μ when at the silicon diaphragm upward pressure being zero ₁=μ ₂=μ then ${\mathrm{<figure-callout\; id="1"\; label="I\; D"\; filenames="C0113433700072.png"\; state="\{\{state\}\}">I</figure-callout>}}_D={\mathrm{<figure-callout\; id="2"\; label="I\; D"\; filenames="C0113433700072.png,C0113433700081.png"\; state="\{\{state\}\}">I</figure-callout>}}_D=\frac{\mathrm{\&mu;}{C}_{\mathrm{OX}}W}{2L}{(V_{\mathrm{GS}}-V_T)}^2$

Wherein, C _OxBe unit are gate oxide electric capacity, W is a channel width, V _TBe cut-in voltage, L is a channel length.Vertical mutually owing to this channel direction to the PMOS pipe when applying certain pressure on silicon diaphragm, they are subjected to the effect of horizontal and vertical stress respectively, and variation round about will take place channel mobility simultaneously,

Be μ ₁=μ+Δ μ ₁, μ ₂=μ-Δ μ ₂, Δ μ ₁＞0, Δ μ ₂＞0, thereby ${\mathrm{\&Delta;I}}_D=I_{D1}-{\mathrm{<figure-callout\; id="2"\; label="I\; D"\; filenames="C0113433700072.png,C0113433700081.png"\; state="\{\{state\}\}">I</figure-callout>}}_D=\frac{({\mathrm{\&Delta;\&mu;}}_1+{\mathrm{\&Delta;\&mu;}}_2)}{2\mathrm{\&mu;}}{\mathrm{<figure-callout\; id="0"\; label="I"\; filenames="C0113433700102.png"\; state="\{\{state\}\}">I</figure-callout>}}_0.$

Therefore, Δ μ ₁+ Δ μ ₂Effect and the input difference voltage V of common differential pair tube _IDEffect identical, can be considered the input signal of the quick differential pair tube of PMOS power.If after the drain electrode of M1 pipe and M2 pipe connects the metal-oxide-semiconductor active load of not affected by force respectively, promptly constitute the quick differential amplifier of power.It is converted to voltage output with electric current output, thereby just can obtain force value by measuring output voltage.But the MOS differential amplifier generally exists voltage gain low, and output impedance is big, drives a little less than the load capacity, and shortcoming such as zero output can only be made the input stage of integrated MOS force-sensitive operational pressure sensor and use in the time of can not realizing zero input.

Goodbye Fig. 2-Fig. 6.Fig. 2 is placed on the region of high stress on the silicon diaphragm to the quick difference input pipe of a pair of PMOS power, and other elements in the operation amplifier circuit are placed on the schematic diagram of the low stress area on the thick body silicon, thereby constitutes the force-sensitive operational device.Wherein, the 1st, operation amplifier circuit, the 2nd, do not contain input difference all the other elements after to pipe in the operation amplifier circuit, these elements can be NMOS, PMOS and/or bipolar transistor.Fig. 3 is the A-A ' cut-away view of Fig. 2, the 3rd, and the aluminum metal connecting line.Its concrete circuit connecting mode is seen Fig. 4, and whole amplifier adopts open loop or closed loop mode, and multiplication factor is tens～several thousand times.For the ease of making, what we adopted is a kind of common E/E PMOS discharge circuit shown in Figure 5, and it is made up of 26 metal-oxide-semiconductors and a feedback capacity.Through the Pspice software simulation, the open-loop gain of the operational amplifier that designs and produces is 60.8db, and quiescent dissipation is 4.91mW.At hypothesis PMOS input difference the channel mobility of pipe is increased respectively and reduces under 6% the condition, with Pspice software the stress-sensitive operational amplifier device is simulated, the result shows that output voltage is 2.14V.

In Fig. 6, silicon cup 4 adopts C type structure of silicon cup, and chip size is 5mm * 5mm, and diaphragm size is 2mm * 2mm * 20 μ m.The input of the quick difference of PMOS power is concentrated the maximum stress district that is arranged on N type (100) silicon diaphragm to pipe M1, M2, and the channel direction that makes them is respectively along [011] and [0 11] direction; Other elements of discharge circuit are all concentrated the thick silicon body region that is arranged on beyond diaphragm 200 μ m, and its stress can be ignored.Press welding block 5 is inputs of force-sensitive operational device, connects zeroing circuit at this, the 6th, and substrate.Integrated with the monolithic of MOS or BiMOS technology realizable force photosensitive elements and amplifying circuit when making, promptly adopt plane P MOS technology such as 5 μ m Si-gates to produce circuit earlier in chip front side, it is protected processing after, form silicon cup 4 with KOH solution corrosion chip back.

Fig. 7 is its manufacture craft flow chart.Fig. 7 a is illustrated on N type (100) silicon chip and makes the stress-sensitive operational amplifier device, be with the channel direction of PMOS difference input pipe M1 and M2 respectively along [011] and [0 11] direction of silicon chip.Fig. 7 b is at two-sided deposit etch resistant layer 7.Fig. 7 c is photoetching overleaf and etches corrosion window.Fig. 7 d goes out silicon cup 4 with the KOH solution corrosion overleaf.Fig. 7 e is two-sided removal etch resistant layer 7.Thereby make the force-sensitive operational device.

Between the grid of the quick differential pair tube M1 of power, M2, promptly the input of stress-sensitive operational amplifier device as shown in Figure 6, inserts zeroing circuit at press welding block 5 places and promptly constitutes MOS force-sensitive operational pressure sensor, its pressure-responsiveization in the stress-sensitive operational amplifier device.Zeroing circuit is used voltage V in the present embodiment _ZeroingReplace.This shows, the integrated MOS force-sensitive operational pressure sensor that the stress-sensitive operational amplifier device that the present invention proposes is made has following advantage: the monolithic of having realized force sensing element and signal processing circuit with simple structure is integrated, has very high pressure-responsive sensitivity and good linearty; Only need return to zero at its input and once to get final product flexible and convenient operation; It can obviously reduce system's temperature floats and power consumption, with low cost, is suitable for producing in batches; Minimum and the non-resistance manufacture craft of the number of elements that it comprises can obviously improve rate of finished products and reduces production costs.

Claims (4)

1, the stress-sensitive operational amplifier device used of a kind of integrated MOS force-sensitive operational pressure sensor contains the substrate of stress-sensitive operational amplifier circuit and band silicon cup, and it is characterized in that it contains: SiO has been in the upper surface ₂The substrate of layer, open on the substrate bottom surface and the spill silicon cup of band flexible sheet, be made on N type (100) silicon diaphragm that this silicon cup concentrates side stress by complete symmetry but raceway groove orthogonal in order to the quick difference input of the PMOS power that replaces a pair of differential pair tube of stress-sensitive operational amplifier circuit input end to pipe (M1, M2), be made in that thick body silicon low stress area links to each other to the drain electrode of pipe with the input of the quick difference of above-mentioned power respectively but the while links to each other with its source electrode takes the remainder of the stress-sensitive operational amplifier circuit behind a pair of differential pair tube of above-mentioned input away.

2, the stress-sensitive operational amplifier device used of integrated MOS force-sensitive operational pressure sensor according to claim 1, it is characterized in that: described silicon cup is a C type structure.

3, the stress-sensitive operational amplifier device used of integrated MOS force-sensitive operational pressure sensor according to claim 1 is characterized in that: described stress-sensitive operational amplifier circuit can be to form with NMOS, PMOS and/or bipolar transistor.

4, the stress-sensitive operational amplifier device used of integrated MOS force-sensitive operational pressure sensor according to claim 1, it is characterized in that: (M1, channel direction M2) are respectively edge [011] and [0 11] directions to pipe in described difference input.

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