CN1264020C - Micrograving acceleration-grade capacitor-type acceleration sensor - Google Patents

Abstract

The invention discloses a micro-gravity acceleration-level capacitive acceleration sensor for microelectronic machinery, which is composed of a supporting edge, a capacitor and a quality block composed of a capacitive dynamic plate and a capacitive fixed plate, and the supporting edge and the capacitor are both Set in the anchor area, the anchor area set on the edge of the support is connected to the anchor area set on the capacitor through the cantilever beam. There is a movable plate anchor area between the heavily boron-doped movable lower electrode and the polysilicon movable upper electrode, and the capacitor fixed plate is fixed and supported on the edge and is located on the dense boron heavily doped movable lower electrode and the polysilicon movable upper electrode. Between the electrodes, the mass block is a polysilicon mass block and is arranged on a movable electrode heavily doped with concentrated boron. The invention reduces the mass of the mass block, but does not change the size of the sensitive capacitance, adopts a simple processing technology, and the rigidity of the polysilicon fixed electrode can meet the requirements of the closed-loop control of the sensor.

Description

Microgravity acceleration level capacitive acceleration sensor

1. Technical field

The invention belongs to the technical field of micro-electro-mechanical systems (MEMS), in particular to a microgravity acceleration (μg) level capacitive acceleration sensor.

2. Background technology

The resolution of the fully surface-processed capacitive acceleration sensor is about several hundred microgravity accelerations (μg). In order to integrate high-resolution capacitive acceleration sensors with a microgravity acceleration (μg) level, bulk silicon processing is generally required. technology. In 1997, Yazdi et al. used bulk silicon processing technology to integrate a capacitive acceleration sensor with a resolution of microgravity acceleration (μg) level. In this method, the upper and lower polysilicon fixed electrodes need to be designed in a "T" shape, and the entire middle The mass block acts as a movable electrode, which requires multiple double-sided photolithography. In addition, double-sided leads are required. The processing technology is complicated, and the sensor is not easy to integrate with the interface circuit on the same silicon chip. In 1999, Yazdi et al. improved this structure (N. Yazdi, et. al, "A high sensitivity capacitive microaccelerometer with a folded-electrode structure" Iht. Micro Electro Mechanical Systems Conf., pp.600-605, Jan 1999, Twelfth), but because it is impossible to reduce the quality of the mass block without changing the size of the sensitive capacitor, the polysilicon fixed electrode still needs to be designed in a "T" shape, which is difficult to process and low yield.

3. Contents of the invention

The invention provides a microgravity acceleration-level capacitive acceleration sensor which is beneficial to improve measurement accuracy and measurement range and is easy to process. The invention can be manufactured by surface processing and partial body processing post-processing technology.

The present invention adopts following technical scheme:

A microgravity acceleration-level capacitive acceleration sensor for microelectronic machinery, consisting of a supporting edge 1, a capacitor composed of a capacitive moving plate and a capacitive fixed plate 2, and a mass block 3, both on the supporting edge 1 and the capacitor Set in the anchor areas 4 and 5, the anchor area 4 set on the supporting edge 1 is connected with the anchor area 5 set on the capacitor through the cantilever beam 6, and the feature is that the moving plate of the capacitor is made of dense boron heavily doped movable lower electrode 7 and polysilicon movable upper electrode 8, a movable plate anchor area 9 is set between the concentrated boron heavily doped movable lower electrode 7 and the polysilicon movable upper electrode 8, and the capacitor fixed plate 2 is fixed and supported by the edge 1 and located between the boron heavily doped movable lower electrode 7 and the polysilicon movable upper electrode 8 , the mass 3 is a polysilicon mass and is arranged on the boron heavily doped movable lower electrode 7 .

The present invention can also adopt following technical measures to further improve its performance:

(1) Damping holes are respectively provided on the movable lower electrode heavily doped with concentrated boron and the movable upper electrode of polysilicon;

(2) The cantilever beam is a folded beam, and part of the folded beam is connected to the movable upper electrode of polysilicon, and part of the folded beam is connected to the movable lower electrode of concentrated boron and heavy doping;

(3) In the present invention, at least one cantilever beam is electrically connected to the polysilicon movable upper electrode, and the rest of the cantilever beams are electrically connected to the concentrated boron heavily doped movable lower electrode through the anchor region.

Compared with the prior art, the present invention has the following technical effects:

① The present invention reduces the quality of the mass block, but does not change the size of the sensitive capacitor. Using a simple processing technology, the rigidity of the polysilicon fixed electrode can meet the needs of the closed-loop control of the sensor; damping holes can be etched on the three-layer electrodes, Reduce the damping, thereby reducing the noise of the sensor; the sensor structure and the measurement circuit can be integrated on the same silicon chip to achieve monolithic integration, which can greatly improve the measurement accuracy and measurement range. However, the invention adopts the electrode structure of polysilicon-polysilicon-concentrated boron heavily doped self-stop layer, so that it can be realized by surface processing and some simple bulk processing techniques, thereby reducing the processing difficulty.

② The present invention provides damping holes on the capacitor plates, and these damping holes can reduce the air damping when the electrode plates move, which is more beneficial to the improvement of resolution.

③The adoption of the folded beam makes the present invention have the advantage of being less affected by residual stress. Part of the folded beam is connected to the movable upper electrode of polysilicon, and part of the folded beam is connected to the lower electrode plate doped with concentrated boron, so that the present invention has the advantages of simple and convenient electrode extraction.

4. Description of drawings

Figure 1 is a three-dimensional simplified view of the structure of the present invention.

Fig. 2 is a three-dimensional view of the proof mass in Fig. 1 .

Fig. 3 is a side view of the structure of the present invention.

Figure 4 is a top view of the structure of the present invention.

Fig. 5 is a brief process flow diagram of the structure of the present invention.

5. Specific implementation plan

A microgravity acceleration-level capacitive acceleration sensor for microelectronic machinery, consisting of a supporting edge 1, a capacitor composed of a capacitive moving plate and a capacitive fixed plate 2, and a mass block 3, both on the supporting edge 1 and the capacitor Set in the anchor areas 4 and 5, the anchor area 4 set on the supporting edge 1 is connected with the anchor area 5 set on the capacitor through the cantilever beam 6, and the feature is that the moving plate of the capacitor is made of heavy boron doped movable lower electrode 7 and polysilicon movable upper electrode 8, a movable plate anchor area 9 is set between the concentrated boron heavily doped movable lower electrode 7 and the polysilicon movable upper electrode 8, and the capacitor fixed plate 2 is fixed and supported by the edge 1 and located between the boron-heavy doped movable lower electrode 7 and the polysilicon movable upper electrode 8, the mass block 3 is a polysilicon mass block and is arranged on the boron-concentrated heavily doped movable lower electrode 7, and the boron-doped heavily doped Holes 10 and 11 are respectively provided on the movable lower electrode 7 and the movable upper electrode 8 of polysilicon. The cantilever beam 6 is a folded beam and at least one cantilever beam is electrically connected to the movable upper electrode 8 of polysilicon. The rest of the cantilever beams pass through the anchor area. 5 is electrically connected to the movable lower electrode 7 which is heavily doped with concentrated boron.

Below in conjunction with Fig. 5, the brief process step of the structure of the present invention is provided, at first will be processed into the silicon chip surface region of high fraction capacitive acceleration sensor mass block concentrated boron diffusion heavy doping is about 4.5 microns as the back anisotropy The self-stopping layer of the corrosion, the damping hole area of the self-stopping layer is not heavily doped with boron (Figure 5: a, b, c); the back of the silicon substrate is etched to a depth of 1 micron for overload protection of the sensor (Figure 5 : d); then integrate other structures of the sensor (Figure 5: e, f, g, h, i, j, k, l, m, n, o); and then use EPW to perform anisotropic etching on the back of the silicon wafer, Obtain a quality block with a properly reduced mass (Figure 5: p); in addition, there is a process of engraving grooves on the sacrificial layer PSG between f and g and between l and n in the flow chart to prevent the structure from being released when the sacrificial layer is released. Adhesion occurs; POLY1 and POLY2 are etched at the same time to engrave damping holes; between p and q there are metal lead hole etching, aluminum steaming, back-etching aluminum to form metal pads (leads) and other process steps; finally use The photoresist is used as a mask to release the sacrificial layer.

Claims (4)

1. microgravity AL Acceleration Level capacitance acceleration transducer that is used for microelectron-mechanical, by bearing edge (1), form by capacitor and mass (3) that electric capacity movable plate electrode and capacitor fixed plate (2) constitute, on bearing edge (1) and capacitor, be equipped with anchor district (4 and 5), the anchor district (4) that is located on the bearing edge (1) links to each other with anchor district (5) on being located at capacitor by semi-girder (6), it is characterized in that the electric capacity movable plate electrode is made up of movable bottom electrode of dense boron heavy doping (7) and the movable top electrode of polysilicon (8), at the movable bottom electrode of dense boron heavy doping (7) and the movable top electrode of polysilicon (8) but between be provided with the anchor district (9) of movable plate electrode, capacitor fixed plate (2) is fixed on the bearing edge (1) and is positioned between movable bottom electrode of dense boron heavy doping (7) and the movable top electrode of polysilicon (8), and mass (3) is the polysilicon mass and is located on the movable bottom electrode of dense boron heavy doping (7).

2. microgravity AL Acceleration Level capacitance acceleration transducer according to claim 1 is characterized in that being respectively equipped with damping hole (10 and 11) on movable bottom electrode of dense boron heavy doping (7) and the movable top electrode of polysilicon (8).

3. microgravity AL Acceleration Level capacitance acceleration transducer according to claim 1 and 2, it is characterized in that semi-girder (6) links to each other for folded beam and by the movable top electrode of partially folded beam and polysilicon (8), partially folded beam links to each other with the movable bottom electrode of dense boron heavy doping (7).

4. microgravity AL Acceleration Level capacitance acceleration transducer according to claim 1, it is characterized in that having at least a semi-girder to be electrically connected with the movable top electrode of polysilicon (8), all the other semi-girders are electrically connected with the movable bottom electrode of dense boron heavy doping (7) by anchor district (5).

Images