TW531888B - Silicon piezo-resistance type pressure sensing device and its manufacturing method - Google Patents

Abstract

The present invention is related to a semiconductor sensing device and its manufacturing method, in which temperature compensation circuit is not required and three strips of piezo resistors are required for each side. The doping concentration of piezo resistor is about 10<19>-10<20> cm<-3> to reduce the temperature effect. The conduction wire between the pressure resistors (called inner connection wire) is formed through the manufacture of highly doped connecting wire (about 10<21> cm<-3>) in the direction that has the smallest stress. The piezo resistors are connected to the connection circuit part (called the external connection circuit) of the external Wheatstone bridge. One end close to the diaphragm is also manufactured in the direction having the smallest stress, and the conduction wire close to one end of the diaphragm edge is guided to the external circuit by using a straight conduction wire perpendicular to the diaphragm. Therefore, four resistors of the Wheatstone bridge can be balanced and symmetrical such that zero offset caused by low voltage difference of bridge can be decreased and signal processing circuit can be simplified.

Description

531888

V. Description of the invention (1) [Scope of the invention] The present invention relates to a semiconductor sensing element and a method for fabricating the same. The element has a low temperature drift, crushing resistance and connecting wires; the direction of the layout on the suspended sheet H makes it get the biggest pressure sensing signal and meets the needs of the simplicity of balanced Wyeth bridge circuit. [Background of the Invention] The principle of a 'Shi Xi piezoresistive pressure sensing element in a semiconductor pressure sensing element is to sense the pressure of the external environment through Shi Xi's piezoresistive effect. In 1954, "Smith in the United States first discovered the piezoresistive effect of semiconductors (see reference [1])", that is, when the silicon material lattice is formed, the material deforms slightly, causing the resistance value of the material to go there. Small and change.

In the past, the manufacture of pressure gauges often uses a thin metal wire as a strain gage 'to sense the strain caused by external pressure. Because semiconductor materials have a gage factor that is 100 times greater than traditional strain gauges, today a thin plate is made using silicon as the substrate, and the silicon piezoresistance is placed on the edge surface of the thin plate. Suspend the maximum stress caused by the external environmental pressure, so as to obtain more information = silicon piezoresistive pressure sensing element has become the mainstream of the current pressure gauge production. In a semiconductor pressure sensing device manufactured by micro-electro-mechanical technology, a piezoresistance is usually fabricated on a diaphragm of monocrystalline silicon through a semiconductor process, and the connection is made into a Wheatstone bridge. Since the silicon piezoresistance is in different lattice directions, its piezoresistance coefficient will be different, so the silicon piezoresistance position and direction on the Wyeth bridge will affect the components.

531888 V. Description of Invention (2) ------ Effectiveness. The imbalance of the Hui-type bridge circuit will also cause the phenomenon of zero drift (ζα〇 of f set). The doping concentration of silicon piezoresistance affects the output signal and the temperature. All the above factors will increase the complexity of the compensation circuit. At present, the piezoresistive pressure sensing element produced by micro-electromechanical technology mainly etches a silicon substrate in a form of micro-fabrication (bu 1 kmi cromach ini ng) to etch a suspended thin plate. Deformation and stress cause changes in the resistance value of the silicon piezoresistance on the surface of the floating sheet, and then amplify its output voltage by Wyeth bridge induction. Among them, as shown in the above and the first figure (please refer to reference [2]), the piezoresistance coefficient will change and implicitly change with the lattice direction, so the piezoresistance position and direction of Shi Xi on the Wyeth bridge will affect the component. Performance. In addition, due to the different thermal expansion coefficients of the metal aluminum layer and the silicon nitride insulating layer, stress residues will be generated in the process, which will cause the floating sheet to be affected, which will affect the linearity of pressure sensing. Therefore, the connection wires in the thin plate area are mainly silicon wires with high concentration and low resistance. As shown in Fig. 1, on a silicon (100) substrate, the piezoresistance coefficient of the silicon piezoresistor made in the [11 0] direction family is the largest, and the piezoresistance coefficient in the [100] direction family is the smallest. In the present invention, according to this relationship, the high-resistance piezoresistance on the silicon suspension sheet is made in the [1 1 0] direction family to obtain the maximum resistance change; the piezoresistive low-resistance wire is connected to the sheet to make In the [100] direction family that is least affected by stress changes, to reduce the influence of stress factors on the connecting wires. The resistance on the Whitney bridge is mainly contributed by the piezoresistance in the [110] direction family, thereby increasing the linearity of the pressure sensing element. Four resistor balances on the Wyeth bridge-one of the important considerations as the mismatch of resistance values will result in zero output voltage

Page 5 531888 5. Description of the invention (3) Point drift. In addition, the piezoresistive doping concentration is designed to be about 10l 102G cm-3, which can reduce the influence of temperature. Based on the above design principles, the linearity of signal output can be improved and the degree of temperature influence can be reduced. &lt; Description of prior art &gt; Piezoresistive pressure-sensing elements have been previously proposed by some manufacturing methods, briefly described as follows: 1) · US Patent No. 4,672, 4 1 1, Shimizu et al. in the n-type A pair of low-doped port-type lamination resistors were made along the &lt; 11〇 &gt; direction on a suspension sheet of silicon (100), where the pair of piezoresistors were grouped in the [1〇〇] direction and Highly doped P + type layer wires are used for connection. In addition, at the other two ends of the pair of piezoresistors, a p-type layer conductor made of ytterbium doped in the direction of the center [1 0 0] is also used to connect it to the metal wires outside the sheet. Please refer to Figure 2 and reference materials for the situation. .2) · It also studies the pressure sensing element published by κ 1 m and others in the journal: designed on a type 0 Shixi square suspended thin plate, and each of the two opposite sides is made up of a straight bar piezoresistance 32 0, and two U-chuck resistors are made on the other opposite sides, and the four groups of resistors are connected using a metal wire 33〇 = Please = Figure 3 and reference material ⑷. Its production is due to Chengping T's crimes near the edge of the sheet 310, and the mentality he received was' early! Has a higher signal output. However, in the pressing part of the vertical thin plate, the longer the ® resistance, the smaller the average stress will be: to obtain a higher resistance value and signal output. Straight bar, another,:, the piezoresistive effect of the above ’, where the piezoresistive coefficient has the following relationship, (please see the reference [5])

531888 V. Description of the invention (4) π (Ν, Τ) = P (Ν? Τ) π (3 0 0Κ) ττ (Ν, Τ): piezoresistance coefficient P (N, T): piezoresistance Piezoresistance factor tt (3 0 0K): piezoresistance coefficient at room temperature (T = 3 0 0K) In reference [5], the relationship of piezoresistance factor to temperature and doping concentration is as follows Figure 4 shows. From this figure, it is known that if the piezoresistance concentration is selected to be greater than 1019 cm-3 in an environment with a high temperature difference, it has the advantage that the piezoresistance temperature is low. In addition, due to the consideration of reducing the manufacturing cost of the component, the size of the pressure sensing element is developing toward miniaturization, so that the size of the piezoresistive element becomes longer than the size of the sensing element, which affects the linearity of the component and the size of the signal output. Reduce the length of the piezoresistance; in order to achieve the low temperature effect of the piezoresistance (which can simplify the temperature compensation circuit), using a high doping concentration results in a relatively small piezoresistance value. So in a nutshell, when the piezoresistive length and the resistance of the piezoresistive chip become smaller, more straight piezoresistives must be used to maintain the total resistance value, and then meet the electrical specifications and applications. . The present invention π central betrays the piezoresistive pressure-sensing point. In the case of purlin piezoresistance, the reel age t ^ a ^% system, soil-you 2 k out-a novel piezoresistive pressure sensor. . When the clothes have two low-doped piezoresistances (approximately 10110 gas to make your personal life with the least stress) U} ^ β π 1 Inch, about 1019 —102 line, the same on the -end of the inner side of the thin plate Production:

531888 V. Description of the invention (5), and the wire on the edge of the sheet to the external circuit. In this way, the linearity of the lead of the vertical thin plate can be derived with good linearity, so the four resistors can be balanced and a circuit design can be obtained for subsequent signal processing. The zero point drift and simplification of the element "1" Therefore, the purpose of the present invention is to describe the characteristics of ψ _, and at the same time each side needs to have a 佟 m with a small influence of the fork temperature

The I p Λ resistor is made of a low-doped P-type resistor and placed in the direction where the party stress has the greatest influence on the A-board, and is placed in a violent position. It is derived from the square, which is the least affected by the stress on the substrate, and thin; the true u = 1 design is located at the edge of the floating sheet. The connection to the external metal is: the direction of the vertical sheet (⑴〇 ] Orientation, connection, / External connection wires on the inside of the board are [010] Orientation =: Manufactured to take into account the simplicity of balancing the Wyeth Bridge circuit. The detailed structure of your invention and its manufacturing method are attached hereby. The following detailed description according to the drawings can be fully understood. [Detailed description of the specific embodiment of the car] π. Needle tracing of the pressure sensing element of the preferred embodiment of the present invention to make the two =% For example, a silicon substrate is used as the material of the structure. With the consideration of low temperature drift and high linear output accuracy based on the semiconductor manufacturing desire, the piezoresistance and connection wires are made on the second board in the most appropriate direction and position. A larger signal output is transmitted. The production of the components of Yuben! M does not have to completely conform to the described process, and the second one: when various changes and modifications can be made without departing from the actual spirit and scope of the present invention. E.g. Of the manufacturing process, can only

531888 V. Description of the invention (6) Change its piezoresistance and the process sequence of the internal and external connecting wires to make a similar structure 'to achieve the same function, which is specified first. [Example 1] Figure 5 is a schematic diagram of the design of the pressure sensing element proposed in the present invention, 2 is the dashed line inside, which shows the n-type single-crystal silicon (100) cymbal plate area produced by the body microfabrication process, and Figure 6 is Figure 5 is a partially enlarged schematic diagram showing the dopant concentration and directivity. First, on the front surface of a p-type substrate having an η-type epitaxial layer, a piezoresistance 3 is defined along the &lt; 110〉 direction, and &lt; 1〇〇 &gt; and &010; The piezoresistance 3 Β of the connecting wire overlapping &lt; 11〇 &gt; or &lt; ^ 〇 &gt; and the piezoresistance 3 C overlapping the other external connecting wire, etc., this part is made of low-doped p-type ion implantation In this way, each of them can form a continuous high resistance piezoresistive area. , Μ. Βπ, connecting the inner and outer leads. First of all, the conductor 4 is fixed in the directions of &lt; 1〇〇 &gt; and &lt; 010 &gt; (overlapping with piezoresistance at 3A), and along with <〇1〇 &gt; overlapping with piezoresistance, along the direction of the vertical sheet. Continuously: J5A (overlapping with piezoresistance at 3β), and defines the outer expansion along the direction of the vertical thin plate. ^ 部 ί 'This internal and external connecting wire part is implanted by ion implantation or only by the moon method to make highly doped P-type silicon. Wires so that the basin can be connected to the wire area of A. &amp; Then, as a low-resistance type, the external connection wire 5A is connected to the Ming metal wire to form a Kui-type envelope bridge, as shown in FIG. 7. By carefully matching the four life limits of Chenghui Bridge 佶. ^, The layout is used to balance the Wyeth zero drift; the total resistance of the bridge is Μ to eliminate the final opening on the back of the substrate Etch window stopped by electrochemical etch

531888 5. Description of the invention (7) (electrochemical etch-stop) technology, using potassium hydroxide (KOH) as an etching solution, etches the p-type substrate from the back, leaving the n-type epitaxial layer stone suspension sheet in area 2 to Changes in induced pressure. [Reference] [1] C.S. Smith, 丨 ’Piezoresistance effect in germanium and silicon”, Physical Review, 94, 42-49 (1954) · [2] 0. N. Tufte and E. L. Stelzer,

Piezoresistive properties of silicon diffused layers'1, J. Appl. Phys. 34. 3 1 3- 1 8 (1 96 3).

[3] I. Shimizu and J. Hoy a,, f Pressure sensor ”, United States Patent, Patent Number: 4,672,411 (1 9 8 7).

[4] S. -C. Kim and K. D. Wise, M Temperature sensitivity in silicon piezoresistive pressure transducers ", IEEE Transactions on Electron Devices, Vol. ED-30, No. 7, pp.802-810, 1983.

[5] Y. Kanda, &quot; A Graphical Representation of the Piezoresistance Coefficients in Silicon1 丨, IEEE Transactions on Electron Devices, Vol. ED-29,

No. 1, pp. 64-70, 1982.

Page 10 531888 Brief Description of Drawings Figure 1 shows the relationship between the lattice direction of a silicon (100) wafer and the piezoresistance coefficient. Fig. 2 shows the structure of the pressure sensing element proposed by Isa 0 S h i m i z u. Fig. 3 shows the composition of the pressure sensing element proposed by Sea-C h u n g Kim. Fig. 4 shows the relationship between the piezoresistive factor P (N, T) of p-Si and the impurity concentration (N) and temperature (T). FIG. 5 shows a pressure sensing element according to the present invention. The interior of the dotted line indicates the suspended sheet portion. Fig. 6 shows a partially enlarged view of the pressure sensing element proposed by the present invention, and shows its doping concentration and directivity. Fig. 7 shows the bridge resistances of the Wyeth bridge corresponding to Fig. 5. Comparison of symbols and component names in the diagram] 1: Silicon substrate 1 0 0: Relation between the crystal lattice direction of the silicon (100) wafer and the piezoresistance coefficient Figure 2: η-type single crystal silicon (100) suspending sheet 3 : Low-doped p-type resistance layer (main piezoresistive wire) 3Α: Low-doped p-type resistance layer and 4 overlapping regions 3B: Low-doped p-type resistance layer and 5 overlapping regions 3C: Low-doped p-type resistance layer and 5Α overlap area 320 330 310 Straight piezoresistive metal wire sheet edge

Page 11 531888

Page 12

Claims (1)

531888 ^ Application scope 1 ♦ A method for manufacturing a semiconductor pressure sensing element 5 is a kind of semi-pressure sensing element connected to three piezoresistive connecting wires, and the method includes the following steps: · Provide a silicon substrate, which includes an 11-type upper surface area; than in the area of the square suspended thin plate on the upper surface of the silicon substrate, each side contains three piezoresistive piezoresistive elements, &lt; An internal connecting wire is formed on the upper surface of the silicon substrate, so that the three piezoresistors can be connected to each other through the internal connecting wire; d. An external connecting wire is formed on the upper surface of the silicon substrate, so that the three piezoresistance The external connecting wire leads the signal to a metal wire. 2. The manufacturing method of the pressure sensing element as described in the first item of the patent application scope, wherein the directivity of the silicon substrate is a silicon wafer with a (丨 〇〇) plane. 3. The method of manufacturing a pressure sensing element as described in item 1 of the Patent Scope, wherein the two piezoresistances are three piezoresistances parallel to each other along <丨 10> or its direction family. ^ Normal 4 .If applying for The manufacturer of the pressure sensing element of the range item 丨 wherein the inner connecting wire is a continuous conductor along the intersection of &lt; 100 &gt; and &lt; 010 &gt; 5. If the application of the pressure sensing element of the range 1; Method, wherein the outer connecting wire is divided into three piezo-resistances connected by a / square connecting wire: jins 17 77 ', u 疋 from the inner side of the inner human path Ap to the outside of the square suspended sheet to the outer outer connecting wire portion The lead wire is: <10 ° 2 = Qiao, the lead wire is connected outside the lead. 6 · As the manufacturer of the pressure sensing element of the $ 100 baguole project in Jiaming Guide, the sixth, apply for a patent Range = Line: Among them, the other one is the outer connecting wire through the inner connecting wire;: Shape; the end point is exported to the external metal direction and the piezoresistive signal is led out = guide ^, the table is the vertical method along the edge of the sheet , JL: Two: "", surrounding the high-resistance area of the pressure sensing element of item 1; inside and outside direct entry method or ion diffusion method to form a P-type to form a ρ-type low-resistance area. Implantation method or ion diffusion method for conducting 8-line type ^: pressure sensor It is a piezoresistive combination of three piezoresistive substrates including an upper surface area of η type; an edge containing two ^ upper plates on the surface of a square suspended thin plate; a piezoresistive combination containing two piezoresistances per transmission; C • The internal connection leads formed on the upper surface of the Shizuki substrate, so that the three piezoresistances can be guided to each other through the internal connection wire ^ Internal connection ^ Wire piezoresistance ^ The outer connection wire formed on the upper surface of the dream substrate 'Let the three W f ^ external connection wires lead the signal to the metal wire. Sha Qigu: The pressure sensing element of item 8 of the Lee range, in which the silicon substrate has a directivity of (100) plane silicon wafer. -佟 1 ^ As described in item 8 of the pressure sensing element of Maru's patent application, where the piezoresistance is three independent parallels along &lt; 11〇 &gt; or its direction family 531888 VI. Scope of patent application 1 2 · For the pressure sensing element of the scope of patent application item 8, the external connection ‘Sen is divided into two parts. One of them is derived from the end points of three piezoresistive elements close to the inside of the square suspended sheet connected by the inner connecting wires to the outer connecting wire portion of the outer metal wire. The wire is along &lt; 1 0 0 &gt; or &lt; 0 1 〇 &gt; The direction leads the piezoresistive signal out of the connecting wire. I3 · As for the pressure sensing element in the scope of application for patent No. 12, the == line in the basin, the other one is a three-bar shape connected by an inner connecting wire, and the ends of the edges are led to the outer connecting wire portion of the outer metal wire For example, this wire is a connection wire other than the thin lead. &amp; ▲ the vertical direction of the piezoresistive signal 1 4 · As the scope of the patent application, the piezoresistive method is the ion implantation method or the ion diffusion method 2 test element _ # 'Where it is. The internal and external connection wires are P-type low resistance area . P 31 冋 Resistance value area ’