KR100408530B1 - A method for fabricating a microgyroscope - Google Patents

Abstract

PURPOSE: A micro gyroscope manufacturing method is provided to prevent torsion, equalize vibrating states of two suspended vibrating structures, and improve the non-linearity of angular velocity sensing output by removing internal stress of all structures comprising the micro gyroscope by two heat-treatment processes. CONSTITUTION: A micro gyroscope manufacturing method is composed of steps for successively forming an insulating layer, a nitride layer, and a doped poly silicon layer on a substrate; forming an electrode by patterning the poly silicon layer; depositing a sacrificial layer for covering the electrode on the nitride layer; patterning the sacrificial layer to expose a portion of the electrode; forming suspended structure layers(201,201') by depositing poly silicon on the patterned sacrificial layer; primarily heat-treating the resultant material with a heat treating mechanism including a gas reacting tube, a heater, a gas inlet, a gas outlet, a gas feeding unit, and a temperature control unit; forming an etching cut-off film on the suspended structure layer; forming an etching cut-off pattern by patterning the etching cut-off film; etching the suspended structure layer by using the etching cut-off pattern; secondarily heat-treating the resultant material with the heat treating mechanism; and removing the etching cut-off pattern and the sacrificial layer.

Description

A method for fabricating a microgyroscope

The present invention relates to a method for manufacturing a microgyroscope, and more particularly, to solve the internal stress of the suspension structure, to improve the frequency characteristics of the suspension structure, and to increase the linearity of the angular velocity output response. It relates to a manufacturing method.

The angular velocity sensor for detecting the angular velocity of an inertial body has long been widely used for military purposes as a key component for navigation devices such as missiles, ships, aircrafts, etc. Recently, acceleration sensors or angular velocity sensors such as automobile navigation systems and high magnification video cameras have been used. Its core parts are gradually being used for civilian purposes. However, the angular velocity sensing gyroscope, which was used for military or aircraft, has been difficult to be applied to general industrial or consumer electronics because it is expensive to manufacture and bulky. However, in order to improve the disadvantages of the gyroscopes as described above, researches to develop ultra-small and ultra-low cost micro gyroscopes have been actively conducted in recent years by using micro machining technology.

In general, the principle of the angular velocity sensor, that is, the gyroscope, is that when the inertial body which vibrates or rotates in the first axis direction constantly receives the input of the angular velocity by the rotational force about the second axis perpendicular to the first axis direction, The magnitude of the rotational angular velocity is detected by detecting a Coriolis force occurring in the direction of the third axis orthogonal to the three axes. At this time, if the force applied to the inertia is balanced, the accuracy of the angular velocity detection is increased. In particular, in order to increase the linearity and bandwidth of the angular velocity detection signal, a structure using force balance is desirable.

FIG. 1 is a schematic perspective view of a comb motor type microgyroscope using ultra-precision machining technology, ie, a tuning fork mode developed using surface machining technology. It is published in Patent 5,349,855. By applying an alternating voltage to the excitation plate 101, the electrostatic force is generated in the comb structure 102. Since the electrostatic force exists only in the attraction force, the two suspension vibration structures 103 and 103 'are excited in opposite directions in the x-axis direction. At this time, if the inertial body receives the rotational force about the y axis with the angular velocity (Ω), the Coriolis force is generated in the z axis direction so that the two suspension vibration structures 103 and 103 'vibrate in opposite directions in the z axis direction. . The vibration in the z-axis direction due to the Coriolis force of the suspension vibration structures 103 and 103 'is controlled by the sensing plates 105 and 105' disposed under the two suspension vibration structures 103 and 103 ', respectively. It is detected in the form. That is, a change in capacitance depending on a distance difference between the suspension vibration structures 103 and 103 'and the sensing plates 105 and 105' is detected in the form of a voltage signal. The Coriolis force can be measured from the sensed voltage signal, and the angular velocity (Ω) due to the rotational force can be obtained from the Coriolis force.

Here, the two suspension vibration structures 103 and 103 'cancel each other's change in the sensed output caused by line acceleration, angular acceleration, temperature change, etc. or noise generated in the two suspension vibration structures 103 and 103'. To double the sense output. For this reason, it is essential for a microgyroscope to have two suspended vibration structures.

In addition, to achieve good performance as a gyroscope, both suspension vibration structures must resonate at the resonant frequency. If the resonant frequencies of the two suspension vibration structures are different from each other in a gyroscope having two suspension vibration structures, the signal processing circuit may be deteriorated or the vibration processing force must be sensed after having each vibration structure at two different frequencies. It becomes very complicated and it is difficult to obtain the component corresponding to the angular velocity in the sense output.

The suspension vibration structures 103 and 103 ', the spring 104, the support beam 106 and the comb teeth 102 and 107 are formed of the same kind of semiconductor film, which have internal stresses during manufacture, FIG. And as shown in FIG. 3, are prone to torsion. FIG. 2 illustrates a case in which the horizontal twist occurs and the spring 104 and the support beam 106 are twisted due to stress, and FIG. 3 illustrates a case in which the two suspension structures 103 and 103 'and the spring are vertically twisted. The case where 104 is totally curved is shown. Such horizontal and vertical twists may occur simultaneously. This torsion makes the vibration of the suspension vibration structures 103 and 103 'nonlinear, thereby not only deviating the resonance frequency of the suspension vibration structures 103 and 103' from the original design value, but also the suspension vibration structure 103 , 103 ') is varied. In addition, since the torsion mode may change again depending on the surrounding environment such as humidity or temperature, stable characteristics cannot be expected, and the canceling effect intended by the tuning structure is difficult to expect.

In order to reduce the internal stress of the structures, heat treatment is conventionally performed only immediately after the formation of the semiconductor film for forming the structure. However, this does not take into account the internal stresses of the structures that may occur in the next continuous process and ultimately it was very difficult to eliminate the torsion caused by internal stresses.

The present invention has been made to improve the above problems, a micro gyroscope that can remove the horizontal or vertical distortion of the structure caused by the internal stress caused by the heat applied during the deposition of the semiconductor film for forming all structures Its purpose is to provide a process for the preparation.

1 is a schematic perspective view of a conventional tuning fork mode comb-driven microgyroscope,

2 is a view for explaining a horizontal twist caused by the internal stress appearing in the manufacture of the micro-gyroscope of FIG.

3 is a view for explaining the vertical twist due to the internal stress appearing during the manufacture of the micro-gyroscope of FIG.

Figure 4 is a schematic cross-sectional view of the heat treatment mechanism used in the manufacturing method of the tuning fork micro gyroscope according to the present invention,

5 is a schematic plan view of a tuning fork-type microgyroscope manufactured according to the method of manufacturing a tuning fork-type microgyroscope according to the present invention;

6 to 17 are cross-sectional views after the step-by-step process of manufacturing the tuning fork-type microgyroscope according to the present invention.

<Description of the symbols for the main parts of the drawings>

101. Comb structure

103, 103 '. Suspension vibration structure 104. spring

105, 105 '. Sensing plate 106. Support beam

102, 107. Comb 201, 201 '. Suspension vibration structure

202, 202 '. Anchor 203, 203 '. Support beam

204, 204 '. With plate 205, 205 '. Comb

206, 206 '. Comb teeth of suspension vibration structures207. spring

208, 208 '. Detection plate

301. Gas Reaction Tubes. Burner

303. Gas Inlet 304. Gas outlet

305. Gas supply 306. Temperature control unit

In order to achieve the above object, a method of manufacturing a microgyroscope according to the present invention is to reduce the internal stress generated during the film formation immediately after the conductive semiconductor film is formed and to reduce the mechanical defects present in the film, A first heat treatment step of readjusting the impurity distribution to have uniform conductivity; And a second heat treatment step of restoring physical defects on the film generated in the etching of the relatively thick film immediately after etching the conductive semiconductor film, improving the intrinsic physical constant, and at the same time, improving the internal stress. .

Hereinafter, a method of manufacturing a microgyroscope according to the present invention will be described in detail with reference to the accompanying drawings.

By improving the torsion of all structures due to the internal stress as described above, it is possible to prevent microstructures from deviating from their original positions, and to restore the physical characteristic constants of each structure, thus making it possible to manufacture a microgyroscope with linear vibration characteristics. . Almost all structures of the micro gyroscope are composed of a conductive silicon film. As a means of minimizing the internal coagulation of the microgyroscope, a low pressure chemical vapor deposition (LPCVD) method is used to obtain a dense and uniform film. During vapor deposition, heat treatment after film formation is necessary to consider film formation conditions. In addition, the heat treatment process may have a number of variables such as the process sequence, the heat treatment temperature, time, frequency.

4 is a schematic cross-sectional view of a heat treatment apparatus used in the method of manufacturing a microgyroscope according to the present invention. As shown, the heat treatment apparatus used in the manufacturing process of the present invention is a gas reaction tube 301, heater 302, gas inlet 303, gas outlet 304, gas supply unit 305 and temperature control unit 306 ).

In the heat treatment method according to the present invention using such a heat treatment mechanism, as shown in FIGS. 6 to 17, the heat treatment is performed twice in total to effectively remove stress generated in each process. The first heat treatment is performed immediately after the conductive silicon film is formed to reduce internal stresses generated during the film formation and to reduce mechanical defects present in the film. Further, by adjusting the impurity distribution inside the conductive film, a conductive silicon film having uniform conductivity is formed.

Next, a second heat treatment is performed immediately after etching the conductive silicon film to form all the structures of the microgyroscope, thereby restoring the physical defects on the film resulting from the etching of the relatively thick film and intrinsic physical constants. At the same time improve internal stress.

Referring to Figures 6 to 17, the manufacturing method of the tuning fork-type microgyroscope accompanying the heat treatment process as described above is as follows.

First, as shown in FIG. 6, SiO 2 is grown on the substrate 1 to form the insulating layer 2. Next, as shown in FIG. 7, Si 3 N 4 is deposited on the SiO 2 insulating layer 2 to form a nitride layer 3. Next, as shown in FIG. 8, a polysilicon layer 4a is formed on the Si3N4 nitride layer 3. Next, as shown in FIG. 9, the polysilicon layer 4a is doped with phosphorus (P) to improve conductivity. Next, as shown in Fig. 10, patterning is performed to form a polycrystalline silicon electrode pattern 4b. Next, as shown in Fig. 11, PSG (phosphorus silicated glass) is completely covered to cover the electrode pattern 4b. E) is deposited to form the sacrificial layer 5a. Next, as shown in FIG. 12, the PSG sacrificial layer 5a is etched to form the PSG sacrificial pattern 5b for anchor formation. Next, as shown in FIG. 13, polysilicon is deposited by low pressure chemical vapor deposition (LPCVD) on the PSG sacrificial pattern 5b to form a polysilicon suspension structure layer 6a. PSG is deposited on the polysilicon structure layer 6a to form an etch stop layer 7a.

The first heat treatment process as described above is carried out. Next, as shown in FIG. 14, the PSG etch stop layer 7a is etched to form a PSG etch stop pattern 7b as shown in FIG. 15. Next, the polysilicon structure layer 6a is etched using the PSG blocking pattern 7b to form the polysilicon structure 6b, as shown in FIG. Next, a second heat treatment process as described above is performed. Next, the PSG etch blocking pattern 7b and the PSG sacrificial pattern 5b are completely etched and removed, so that the secondary heat treated polysilicon structure 6b has a suspended structure, as shown in FIG. 17. Complete Here, the polysilicon structure 6b corresponds to a comb-type suspended inertial mass.

A tuning fork microgyroscope manufactured by the above manufacturing method is shown in FIG. 5. This figure is a schematic plan view of a tuning fork microgyroscope. As shown, the suspension vibration structures 201 and 201 'are supported in a floating state (suspended structure) on the substrate at equal intervals through the anchors 202 and 202' and the support beams 203 and 203 '. Combs 205 and 205 'of the excitation plates 204 and 204' fixed to the substrate and combs 206 and 206 'of the suspension vibration structures 201 and 201' are arranged at regular intervals without being spaced apart. They float to the same height and are aligned. The support beams 203, 203 ′ and the spring 207 float on the substrate without twisting and sagging.

Through the above results, the excitation of the suspension vibration structures 201 and 201 'is applied to the comb teeth 205 and 205 by applying an AC voltage having the same frequency as the resonance frequency of the vibration mode to the excitation plates 204 and 204' fixed to the substrate. ', 206, 206') generate an electrostatic force. The generated electrostatic force vibrates the two suspension vibration structures 201 and 201 'linearly in opposite directions in the x-axis direction, respectively. At this time, both vibration structures 201 and 201 'vibrate at the resonant frequency. When the angular velocity (Ω) is input from the outside, the Coriolis force is generated so that the two suspension vibration structures 201 and 201 'vibrate linearly in opposite directions in the z-axis direction. Vibrate. At this time, the distance between the suspension vibration structure and the sensing plate caused by the z-axis vibration of the two suspension vibration structures between the two suspension vibration structures 201 and 201 'and the two sensing plates 208 and 208' respectively positioned at the bottom thereof. By measuring the change in capacitance in the form of voltage and measuring the Coriolis force, the input angular velocity can be obtained.

As described above, the manufacturing method of the tuning fork-type microgyroscope according to the present invention uses two heat treatment processes to remove internal stresses of all structures constituting the microgyroscope, thereby preventing the occurrence of torsion and thereby causing two suspensions. The vibration aspect of the vibration structure is made the same to improve the nonlinearity of the angular velocity detection output. In addition, it is possible to improve the performance of the micro gyroscope, to improve the stability, and to effectively cancel the influence of the sensing output change or noise generated in the environment changes by precise tuning of the two suspension vibration structure.

Claims (2)

Firstly forming an insulating layer, a nitride layer and a doped polysilicon layer on the substrate; A second step of forming an electrode by patterning the polysilicon layer; Depositing a sacrificial layer covering the electrode on the nitride layer; Patterning the sacrificial layer to partially expose the electrode; Depositing polysilicon on the patterned sacrificial layer to form a suspension structure layer; A sixth step of subjecting the resultant product of the fifth step to a heat treatment apparatus including a gas reaction tube, a heater, a gas inlet, a gas outlet, a gas supply part, and a temperature control part; A seventh step of forming an etch barrier layer on the suspension structure layer; An eighth step of patterning the etch stop layer to form an etch stop pattern; A ninth step of etching the suspension structure layer using the etch stop pattern; A tenth step of subjecting the resultant product of the ninth step to the second heat treatment device; And And an eleventh step of removing the etch stop pattern and the sacrificial layer. The method of claim 1, And the suspending structure layer of the fifth step is formed by a low pressure chemical vapor deposition method.