TWI247102B - Semiconductor pressure sensor and method of making the same - Google Patents

Abstract

This invention describes a semiconductor pressure sensor which includes a Si wafer and the Si wafer comprise an effective surface and a bottom surface opposited to the effective surface. A film forms by etching the bottom surface of the Si wafer. A silicon oxide grows onto the film and a metal grows onto the said silicon oxide. This invention also introduces a method of making the semiconductor pressure sensor. Thus this semiconductor pressure sensor can be sensitive to the signal, so it can reach precision that semiconductor technology needs.

Description

1247102 V. INSTRUCTION DESCRIPTION OF THE INVENTION (1) Technical Field The present invention relates to a sensor and a method of manufacturing the same, and more particularly to a semiconductor pressure sensor that measures pressure by changing a resistance value and a method of manufacturing the same. [Prior Art] According to the components manufactured by microfabrication technology, pressure sensors are widely used, and pressure sensors have been widely used in automobiles, medical, industrial measurement, automatic control, and various electronic products.

At present, the most commonly used method for the enamel pressure sensing element used in semiconductors is to form a p_n junction in a single crystal germanium lattice by a diffusion method or an ion cloth value method, and the ρ - η junction is a piezoresistive The component, when the p_n type piezoresistive element is subjected to external force application, its own resistance changes, and the changed resistance value ΔR/R can be used to measure the change of pressure.

Referring to the first figure, it is a conventional internal structure view of a semiconductor pressure sensing element load gauge (Load cel 1 ) made of a ρ-n type piezoelectric material 2, when a force F is applied thereto. Change the resistance value, causing a change in the voltage or current of the v-turn. This is the result of the change of the physical properties of the piezoresistive material by external force. We can use this characteristic to measure the change of pressure. ® However, when the ρ-η piezoresistive element of the conventional semiconductor pressure sensor is subjected to external force application, the piezoresistive change AR/R is extremely small, so the signal response is not obvious. The sensitivity is not precise enough for the current semiconductor. High-precision technology such as packaging is no longer applicable. Therefore, it is necessary to design a new semiconductor pressure sensor to adapt to today's high

Page 5 1247102 V. DESCRIPTION OF THE INVENTION (2) Precise stress sensing needs [Summary of the Invention] The object of the present invention is to improve the measurement precision. To achieve the foregoing semiconductor substrate, the opposite side of the surface, a thin film is formed on the board, thereby forming a semiconductor t The change of the resistance is used to measure the mechanical stress of the conductor pressure sensor and the prior art substrate without breaking, and the deformation size is used. The P1 precision used in the measurement technology [Embodiment] Please refer to the second % pressure sensor S1 Fer ) 1 0, the opposite side of the thiol group 1 2, the crystal plane of the direction. Load 21, metal pad 22 position to develop. It is to provide a semiconductor sensor with a significant density. The semiconductor pressure sensor of the present invention comprises a semiconductor substrate having an effective surface and a concave portion formed on the back surface of the active surface to form a gold layer on the oxide layer and the oxide layer on the semiconductor substrate and the oxide film. , I force sensing element, sensing component i pressure according to semiconductor pressure. At the same time, the invention also relates to a method of manufacturing the above-described half. Compared with the ultra-thin crucible of the semiconductor pressure sensor of the present invention, it has better elasticity, can withstand large deformation, and its leakage current is significantly increased and decreased with mechanical stress, and its sensitivity is much higher. The traditional pressure-sensing n-type piezoelectric material can be adapted to the high development needs of semiconductor packaging. As shown in the second and fifth figures, the semiconductor of the present invention comprises a semiconductor germanium substrate made of tantalum (the Si Wa-plate 10 has an active surface 11 and the active surface u and the active surface 11 and the back surface) 12 has -<u〇> heavy gauge 1, that is, resistors Ri, &, r3 and ^, and metal wiring on the discharge surface 11, metal wiring 21 and metal pad 22

Page 6 1247102 V. Description of invention (3)

It is electrically connected to the wiring diffusion region 15 for electrically connecting the wiring diffusion region and the resistors A, A, R3, and & Referring to Fig. 5, the back surface 丨 2 of the ruthenium substrate 1 is subjected to an isotropic etching to form the concave portion 13 by a semi-conductive method, and by forming the concave portion 13, the ruthenium substrate 1 is thinned to form a thin film 14. A ruthenium dioxide layer 16 is formed on the film 14 of the ruthenium substrate 1 and a metal aluminum layer 丨7 is formed on the ruthenium oxide layer 16. Thus, the resistor cores, R2, R3 and 匕 are formed. It can be seen that the resistors &, & 'heart and RJP load gauge 1 are made of M0S (Metal 〇xide Semic〇nduct〇〇 structure. As shown in the second and third figures, resistance & The &, & and 仏 are connected to the film 14 formed on the 矽 base plate 10 by means of a Wheatstone bridge 4. Referring to the third figure, the aforementioned metal wiring and metal pad 22 is electrically connected to the wiring diffusion region 15, electrically connecting the wiring diffusion regions together to form two terminals 1a and 11}, and applying a DC constant voltage Vin between the two terminals, from a bridge circuit formed on the substrate 1 The potential difference Vout between the first potential pa and the second potential Pb is picked up. The bridge circuit is connected to the external circuit through a bonding wire (not shown) connected to the metal pad 22. When the pressure F to be detected is applied to the film On the upper side of the fourth side, the resistance phases of the resistors &, &, 仏 and 仏 are changed by the strain generated on the film 14, and the potential difference Vout is outputted in association with the resistance change. The potential difference v〇 is passed through the metal pad 22. Ut is output to the H^% path. The external circuit pairs the potential Processing, providing the final output signal for detecting pressure. Referring to the third and fourth figures, the resistors &, ^, the heart and the 匕 are connected in series to form a closed circuit. The resistors Rl, R2, R3 and仏 basically along the substrate with which it is located! 有效 有效 有效 丨 & & 晶 晶 晶 晶

1247102 V. INSTRUCTIONS (4) Stretching, because the piezoresistive coefficient of the crystal axis of the crystal axis along the direction of the crystal axis of the <110> direction is large/resistance, the pressure is measured and the resistance is Tian / want to be just! The pressure acts to detect the pressure according to the change of the resistance, in which the electricity; ": 2 changes, the strain is easy to occur ‘that is, for the force to be measured, it is more sensitive than y and W is more resistant to changes in R2 and R3. And if the third force and the core are less than the electrical stress caused by the strain, the resistance R and the electrical σ :: the first force sensor resistance R 盥 resistance R 笙 笙 ^ κ 2 between the brother a potential Pa and resistance R^, : The second potential pb between M4 is on the opposite side

When one of Pb increases, another one drops. Therefore, the first potential p/Watada second 1⁄2 Pb:, the potential difference v〇ut changes corresponding to the applied pressure. - Master continues to refer to the third figure, the *s relationship satisfies the following formula: H jin Ding a bridge 4 resistance and electricity V 〇 Ut == (Ri R4 'R2R3 > Vi n / change produces AR if Ratio #2二RfR4.r, when the pressure sensor changes slightly due to pressure, the formula (1) can be simplified as follows: V〇ut-(R + RAR_R) Vin/(2R+AR)2R ^ ARVin/4R (2) It can be seen from equation (2) that when the piezoresistive change AR/R is larger, the amount of change is greater, and the precision of the measurement is higher. It is shown that the semiconductor pressure sensing element load gauge 1 of the present invention replaces the conventional semiconductor made of the p-n type piezoelectric material 2 by using a structure of M eta 1 Ο X ide S emic ο nductor The sensing component load gauge of the pressure sensor. The first step of fabricating the M〇S structure is to fabricate an ultrathin germanium substrate as a substrate by using a semiconductor process, and form a thin film 14 on the ultrathin germanium substrate 10, The ultra-thin germanium substrate 1 is compared when mechanical stress is applied

1247102

=I This document has a large deformation without breaking; the second step is on the film 14 of the upper ll# ^ super-substrate 1G to form a thickness of about 14 conductors of the second layer of the galenium layer; After the step, a semi-private method is used to re-evaporate the above-mentioned ceria layer 16 - the metal aluminum layer 17 is used for signal detection.

4, as shown in the fifth figure, when the pressure sensing element load gauge 1 of the m〇s (Metal Oxide Semiconductor) structure of the present invention is applied with a force F, the MOS structure is deformed by mechanical stress, The bond angle of the oxidized stone layer 16 and the ultra-thin ruthenium substrate is reversed, and the band gap (B andgap) of the oxidized second layer is reduced, and the probability of electron passing through the energy barrier is greatly increased. , so that the leakage current is increased by hundreds or even several times. According to the electrical characteristic R = V / I, the resistance change Δ R / R of the M 〇 s structure of the present invention changes significantly as the leakage current increases, so that the formed semi-conductive body pressure sensor 玎 reaches a high level. measurement accuracy. _ In summary, the invention has indeed met the requirements of the invention patent, and i has not filed a patent application according to law. However, the above description is only a preferred embodiment of the present invention, and the scope of the present invention is not limited thereto. Equivalent modifications made by those skilled in the art in the spirit of the present invention are still within the scope of the appended claims. $

Page 9 1247102 Schematic description of the first diagram The second diagram of a conventional sensor is in accordance with the nature of the third view of the plane and the second equivalent of the fourth figure is located on the effective surface of the fifth system The internal structure view of the semiconductor pressure sensing element load gauge made of the p-n type piezoelectric material of the internal junction of the present invention. A schematic diagram of a semiconductor pressure sensor of an embodiment of the invention. The Wheatstone bridge road map in the semiconductor pressure sensor shown in the figure. A view of the crystal axis included on the Si Wafer shown in the second figure. A sensing element load profile view of a semiconductor pressure sensor.

[Description of component symbols] Semiconductor pressure sensor S1 Load gauge 1 Wheatstone bridge 4 矽 Substrate 10 Effective surface 11 Back surface 12 Recessed portion 13 Film 14 Wiring diffusion area 15 Dioxide layer 16 Metal aluminum layer 17 Metal wiring 21 Metal pad 22 Resistor R1, R2 R3, R4 1 ii· iiil 1 I 1 ϋ 119 I , page 10

Claims (1)

1247102 1 · A semiconductor pressure sensor' includes a semiconductor substrate having an effective surface and a back surface opposite to the effective surface, and a recessed portion is formed on the semiconductor substrate A metal pressure layer is formed on the oxide film and the oxide layer, and a semiconductor pressure sensing element is formed, and the pressure is measured according to the resistance change of the semiconductor pressure sensing element. 2. The semiconductor pressure sensor according to claim 1, wherein the pressure sensing element is a load gauge, which is a MOS (Metal Oxide Semiconductor) structure. The semiconductor pressure sensor of claim 1, wherein the oxide layer is a hafnium oxide layer. 4. The semiconductor pressure sensor of claim 1, wherein the thickness of the oxide layer is about 15 angstroms to 20 angstroms. 5. The semiconductor pressure sensor of claim 1, wherein the metal layer is deposited on the oxide layer. 6. The semiconductor pressure sensor of claim 1, wherein the metal layer is aluminum. 7. The semiconductor pressure sensor of claim 1, wherein more than three semiconductor pressure sensing elements are formed on the film, and all four semiconductor pressure sensing elements are used to form a Wheatstone bridge. . 8 . A method for manufacturing a semiconductor pressure sensor according to claim 1, wherein the first step is to fabricate a substrate as a substrate by using a semiconductor process, and form a thin film on the germanium substrate; The step of oxidizing the film on the substrate of the germanium to form a dioxin b layer; Page 11 1247102 Page 12