JP2013239899A - Oscillator manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make gaps between a diaphragm and electrodes be uniform and promptly form the gap regions between the diaphragm and the electrodes when a vibrator including the diaphragm and the electrodes arranged around the diaphragm on a substrate by a MEMS method.SOLUTION: An oscillator manufacturing method comprises: etching a second polysilicon film 42 after forming the second polysilicon film 42 on a first sacrifice film 61 to form a diaphragm 10; and subsequently stacking a third sacrifice film 63 and a third polysilicon film 43 from the bottom in this order so as to cover the diaphragm 10. At this time, by depositing the third sacrifice film 63 by using an ALD method, a film thickness t of the third sacrifice film 63 becomes extremely uniform and the film promptly dissolves in an aqueous solution of hydrofluoric.

Description

  The present invention relates to a method of forming a vibrator having a diaphragm and electrodes arranged around the diaphragm on a substrate by using a MEMS technique in which a film formation process and an etching process are combined.

  There is known a method of forming a vibrator made of polysilicon (Si) on a silicon substrate by using a MEMS (Micro Electro Mechanical System) technique in which a film forming process and an etching process are combined. The vibrator includes, for example, a disk-shaped diaphragm, and a pair of input electrodes and a pair of output electrodes arranged around the diaphragm. When an electric signal is input to the input electrode, the input electrode The diaphragm vibrates due to electrostatic coupling with the diaphragm, and an output signal corresponding to the vibration is similarly taken out through electrostatic coupling with the output electrode. Therefore, an extremely narrow gap region having a gap dimension of, for example, 100 nm or less is interposed between these electrodes and the diaphragm.

A method for forming such a vibrator will be briefly described. First, for example, an insulating film, a conductive film, a sacrificial film, and a polysilicon film are stacked in this order on the surface of a silicon substrate in this order. The diaphragm is formed by dry etching the film. Next, a sacrificial film made of, for example, a silicon oxide film (SiO ₂ film) or the like is formed so as to cover the diaphragm by a film thickness corresponding to the gap dimension, and another polycrystal is formed on the sacrificial film. A silicon film is formed. Subsequently, dry etching is performed on the upper polysilicon film so that the electrode is disposed around the diaphragm. Thereafter, the sacrificial film is removed (dissolved) by wet etching using, for example, hydrofluoric acid (HF), so that the diaphragm is lifted from the silicon substrate, and a gap region is formed between the electrode and the diaphragm. Is done. A large number of such vibrators are formed vertically and horizontally on a silicon substrate, and are separated into pieces by, for example, dicing after the wet etching process described above is finished. The diaphragm and the electrodes are actually supported by the conductive film while being insulated from each other, but the description thereof is omitted here.

  At this time, the above-described sacrificial film is formed by supplying a film formation gas to the heated substrate by, for example, a low pressure chemical vapor deposition (CVD) method or a plasma CVD method. However, in such a film formation method, since the heating temperature and gas flow rate (concentration) of the substrate vary in the furnace, the thickness of the sacrificial film can be obtained with a uniformity of about ± 4% within the surface of the substrate. Absent. Therefore, the gap dimension between the electrode and the diaphragm becomes non-uniform according to the variation in the thickness of the sacrificial film, and the characteristics of the vibrators vary. Also, for one of the many vibrators formed on the substrate, for example, the gap between the diaphragm and the input electrode and the gap between the diaphragm and the output electrode vary. It may occur. Further, productivity is reduced by the time spent for wet etching of the sacrificial film.

  Patent Document 1 describes a technique for forming an aluminum oxide layer as a sacrificial layer by an ALD method when a semiconductor support structure substrate is formed using aluminum. Patent Document 2 describes a technique using hafnium aluminate or zirconium aluminate as the High-k film 5. However, these patent documents 1 and 2 do not discuss the above-described problems.

Special table 2008-538810 (paragraphs 0049-0051) JP 2006-60155

  This invention is made | formed in view of such a situation, The objective was equipped with the electrode arrange | positioned around the diaphragm and this diaphragm using the MEMS method which combined the film-forming process and the etching process. In forming a vibrator on a substrate, it is an object to provide a technique capable of uniforming the gap dimension between the diaphragm and the electrode and quickly forming the gap region between the diaphragm and the electrode.

The method of manufacturing the vibrator of the present invention includes
In a method of forming a vibrator on a base substrate including a diaphragm and an electrode disposed around the diaphragm to vibrate the diaphragm,
A first conductive film is formed on the base substrate and patterned on the first conductive film, and a diaphragm base for supporting a side surface of the diaphragm from the lower side and the electrode on the lower side Forming each of the electrode bases to support from,
Laminating a lower-layer sacrificial film and a second conductive film in this order from the lower side so as to cover the first conductive film;
Patterning the second conductive film to form the diaphragm and a support beam extending from the diaphragm toward the upper side of the diaphragm base;
Next, a step of forming an upper sacrificial film containing aluminum and oxygen so as to cover the second conductive film;
In order to expose the electrode base while leaving the upper-layer-side sacrificial film on the peripheral surface of the diaphragm, and to expose the diaphragm base through a through-hole penetrating the support beam vertically, Etching the lower sacrificial film and the upper sacrificial film,
Subsequently, a third conductive film is formed so as to cover the upper-layer sacrificial film, and the third conductive film is patterned to form the electrode, and through the through-hole, the electrode is formed. Forming a support column for connecting the diaphragm base and the support beam to each other;
Thereafter, by etching the upper sacrificial film using hydrogen fluoride, the diaphragm and the electrode are separated from each other by the film thickness of the upper sacrificial film,
The step of forming the upper-layer sacrificial film is a step of sequentially supplying a first gas and a second gas that react with each other to the base substrate.

The method for manufacturing the vibrator may be specifically configured as follows.
The thickness of the upper sacrificial film is 10 nm to 100 nm.
A configuration in which, after the step of forming the support pillar, the step of floating the diaphragm from the base substrate is performed by etching the lower-layer sacrificial film.
A large number of the vibrators are formed vertically and horizontally on the base substrate.
The base substrate and the lower layer side sacrificial film are a silicon substrate and a silicon oxide film, respectively.
Each of the first conductive film, the second conductive film, and the third conductive film is a polysilicon film.

  The present invention provides a sacrificial film containing aluminum and oxygen between a diaphragm and an electrode when a vibrator including the diaphragm and an electrode arranged around the diaphragm is formed on a base substrate. A film is being formed. At this time, since the sacrificial film is formed by the ALD method, the sacrificial film has a uniform thickness over the surface and is easily dissolved in hydrogen fluoride. For this reason, after the vibrator is formed, the sacrificial film is removed by wet etching, whereby variation in the gap dimension between the diaphragm and the electrode can be suppressed. Therefore, even when a large number of vibrators are formed vertically and horizontally on the base substrate, the characteristics of the vibrators can be made uniform. In addition, for example, the rate of dissolution of the sacrificial film with respect to hydrogen fluoride is faster than that of a silicon oxide film, so that the time required for the wet etching process of the sacrificial film can be suppressed, and thus the vibrator can be manufactured quickly.

It is a perspective view which shows an example of the disc vibrator of this invention. It is a top view which shows the said disk vibrator. It is a longitudinal cross-sectional view which shows the said disk vibrator. FIG. 5 is a partially enlarged perspective view showing a support beam that supports the disk vibrator. It is a perspective view which shows the manufacturing method of the said disk vibrator. It is a perspective view which shows the manufacturing method of the said disk vibrator. It is a perspective view which shows the manufacturing method of the said disk vibrator. It is a longitudinal cross-sectional view which shows the manufacturing method of the said disk vibrator. It is a longitudinal cross-sectional view which shows the manufacturing method of the said disk vibrator. It is a longitudinal cross-sectional view which shows the manufacturing method of the said disk vibrator. It is explanatory drawing which shows the manufacturing method of the said disk vibrator. It is explanatory drawing which shows the manufacturing method of the said disk vibrator. It is explanatory drawing which shows the manufacturing method of the said disk vibrator. It is a longitudinal cross-sectional view which shows the manufacturing method of the said disk vibrator. It is a longitudinal cross-sectional view which shows the manufacturing method of the said disk vibrator. It is a longitudinal cross-sectional view which shows the manufacturing method of the said disk vibrator. It is explanatory drawing which shows the manufacturing method of the said disk vibrator. It is explanatory drawing which shows the manufacturing method of the said disk vibrator. It is explanatory drawing which shows the manufacturing method of the said disk vibrator. It is explanatory drawing which shows the manufacturing method of the said disk vibrator. It is explanatory drawing which shows the manufacturing method of the said disk vibrator. It is explanatory drawing which shows the manufacturing method of the said disk vibrator. It is explanatory drawing which shows the manufacturing method of the said disk vibrator. It is explanatory drawing which shows the manufacturing method of the said disk vibrator. It is a top view which shows the manufacturing method of the said disk vibrator. It is a characteristic view showing the result of experiment about the disk vibrator. It is a longitudinal cross-sectional view which shows an example of the apparatus which forms the sacrificial film of the said disk vibrator.

  An example of an embodiment of a method for manufacturing a vibrator according to the present invention will be described with reference to FIGS. Before describing the manufacturing method in detail, the structure of the vibrator will be briefly described first. As shown in FIGS. 1 to 4, the vibrator is a disk (disk) -like vibration made of, for example, polysilicon. A plate 10 and a plurality of, for example, four electrodes 20 each of which is arranged around the vibration plate 10 and made of polysilicon are provided, and formed on a base substrate 1 such as silicon. With these electrodes 20, the diaphragm 10 is configured to resonate (vibrate) in a wine glass mode. As will be described later, the vibrator is configured such that the gap dimension h between the diaphragm 10 and the electrode 20 when viewed in a plane is aligned over the plane. Subsequently, a specific configuration of the vibrator will be described. FIG. 3 shows a state in which the vibrator is cut along the line AA in FIG.

  A support portion 30 is provided on the outer peripheral side of the vibration plate 10 to support the vibration plate 10 in a state of floating from the base substrate 1 (specifically, a first polysilicon film 41 described later). The portions 30 are arranged at equal intervals at a plurality of locations, for example, four locations along the circumferential direction of the diaphragm 10. Accordingly, the electrode 20 is sandwiched from the front-rear direction (X direction in FIG. 2) and the left-right direction (Y direction in FIG. 2) so as to be positioned between the support portions 30 adjacent to each other. Is arranged. A silicon oxide (Si—O) film 3 and a silicon nitride (Si—N) film 4 are laminated in this order from below on the base substrate 1 below the diaphragm 10 and the electrode 20. .

  On the upper side of the silicon nitride film 4, the conductive film 5 patterned so as to correspond to the shapes of the diaphragm 10, the support portion 30, and the electrode 20 is formed, and each of the support portions 30 corresponds to the support portion 30. Is supported by the conductive film 5 on the lower side. That is, as shown in FIG. 3, each of the support portions 30 includes a support beam 31 that extends horizontally from the side peripheral surface of the diaphragm 10 toward the outer peripheral side, and a front end portion of the support beam 31 in the vertical direction. A support column 33 is provided so as to fit in the through-hole 32 that penetrates. Then, by connecting the lower ends of the respective support pillars 33 and the conductive film 5 to each other, the support unit 30 supports the diaphragm 10 from the outer peripheral side, and supports the diaphragm 10 and the conductive film 5. The parts 30 are electrically connected to each other via the part 30. The conductive film 5 and the support part 30 are also made of polysilicon. In the conductive film 5, the part connected to the lower end of the support pillar 33 forms a diaphragm base.

  As shown in FIGS. 1 and 2, the side wall surface of the conductive film 5 on the lower side of the support portion 30 is directed from the conductive film 5 toward the outer peripheral side through a region between the electrodes 20, 20 adjacent to each other. One end side of the extending electrode 6 is connected. As will be described later, the extraction electrode 6 forms a port for applying a DC bias voltage to the diaphragm 10 when the diaphragm 10 is vibrated.

  Around the diaphragm 10, approximately box-shaped electrodes 20 are arranged at four positions so as to be spaced apart from each other at equal intervals in the circumferential direction of the diaphragm 10. On the other hand, they are formed so as to face each other through the gap region S (so as not to contact the diaphragm 10). A dimension h of the gap region S (a distance dimension between the diaphragm 10 and the electrode 20 when viewed in a plane) is, for example, 10 nm to 100 nm. Each electrode 20 is supported by the conductive film 5 on the lower side of the electrode 20 while being insulated from the diaphragm 10 and the support portion 30. The conductive films 5 on the lower side of the electrodes 20 each form an electrode base.

  These four electrodes 20 face each other through the diaphragm 10 in the front-rear direction when the two electrodes 20, 20 are viewed in a plane, and the remaining two electrodes 20, 20 pass through the diaphragm 10 in the left-right direction. Are arranged so as to face each other. Among the electrodes 20 and 20 facing each other, the electrodes 20 and 20 arranged in the left-right direction are respectively referred to as first electrodes 21 and 21, and the electrodes 20 and 20 arranged in the front-rear direction are respectively second electrodes. 22 and 22, the first electrodes 21 and 21 are, as shown in FIG. 2, by a beam portion 10 a formed so as to be spaced upward from the diaphragm 10 in the upper region of the diaphragm 10. Are connected to each other. Further, as shown in FIG. 2, the first electrodes 21 and 21 are connected to the first electrodes 21 and 21 by conductive paths 23 such as wires connected to the upper surfaces of the first electrodes 21 and 21, respectively. An input port 24 for inputting an input signal to 21 is connected.

  The second electrodes 22 and 22 are respectively formed such that the upper end portion on the diaphragm 10 side extends upward and the upper end portion extends horizontally toward the center side of the diaphragm 10. Yes. One end side of a conductive path 23 such as a wire is connected to, for example, the upper surface side of the second electrodes 22 and 22, and the other end side of the conductive path 23 detects (takes out) vibration of the diaphragm 10. Output port 25 is connected. Accordingly, the first electrodes 21 and 21 each serve as an input electrode, and the second electrodes 22 and 22 each serve as an output electrode.

  In the disk vibrator configured as described above, when an input signal is input to the first electrodes 21, 21 while applying a DC bias voltage to the diaphragm 10, the first electrodes 21, 21, the diaphragm 10, The diaphragm 10 vibrates in the wine glass mode due to the electrostatic coupling between the two. Specifically, the diaphragm 10 repeats an operation that expands in the front-rear direction and contracts in the left-right direction and an operation that contracts in the front-rear direction and expands in the left-right direction at a predetermined frequency. This vibration is taken out as an output signal by the second electrode 22, 22 by electrostatic coupling between the diaphragm 10 and the second electrode 22, 22.

  An example of a method for manufacturing the disk vibrator described above by the MEMS method will be described with reference to FIGS. As shown in FIGS. 5 and 8, first, the silicon oxide film 3 and the silicon nitride film 4 are stacked on the base substrate 1 in this order from the lower side by using, for example, a CVD method. As shown in FIG. 25, which will be described later, a large number of disk vibrators are formed vertically and horizontally on the base substrate 1. A single vibrator will be described below. In addition, in FIG. 5 to FIG. 25, part of the drawing is simplified.

  Next, after a first polysilicon film (first conductive film) 41 made of polycrystalline silicon is formed on the silicon nitride film 4 by the CVD method, phosphorus is diffused into the first polysilicon film 41. Then, a resist film (not shown) patterned so as to correspond to the diaphragm 10, the support portion 30, the electrode 20, and the extraction electrode 6 is formed on the first polysilicon film 41, as shown in FIGS. Thus, the first polysilicon film 41 is dry-etched through this resist film. Thereafter, the conductive film 5 made of the first polysilicon film 41 is exposed by removing the resist film.

  Subsequently, as shown in FIGS. 7 and 10, on the upper layer side of the first polysilicon film 41, for example, a first sacrificial film (lower sacrificial film) 61 made of silicon oxide and a first sacrificial film made of polycrystalline silicon. A polysilicon film (specifically, a film doped with phosphorus after forming a polycrystalline silicon film) 42 and a second sacrificial film 62 made of, for example, silicon oxide, are laminated in this order, for example, by CVD. To do. Then, a resist film (not shown) patterned so as to correspond to the shape of the support beam 31 provided with the through-hole 32 and the vibration plate 10 is laminated on the upper layer side of the second sacrificial film 62, and FIGS. As shown in FIG. 13, the second sacrificial film 62 and the second polysilicon film 42 are dry-etched through this resist film. Thereafter, the resist film is peeled off. The second polysilicon film 42 forms a second conductive film. Note that the thickness of the first sacrificial film 61 and the second sacrificial film 62 is about several hundred nm.

  Next, a third layer made of silicon oxide is used by an ALD (Atomic Layer Deposition) method so as to cover the structure made up of the second sacrificial film 62 and the second polysilicon film 42 formed in the above steps. A sacrificial film (upper layer sacrificial film) 63 is formed as a gap oxide film. Specifically, as shown in FIG. 14, in a vacuum atmosphere of about 20 Pa, a first gas containing aluminum, such as TMA (for example, TMA) is applied to the base substrate 1 heated to 50 ° C. to 400 ° C. in this example, 250 ° C. (Trimethylaluminum) gas is supplied. The first gas extends over the surface of the base substrate 1 (specifically, the exposed surfaces of the first sacrificial film 61, the second polysilicon film 42, and the second sacrificial film 62). The adsorption layer 71 is formed by adsorbing one or more layers.

Subsequently, when the first gas is exhausted from the atmosphere in which the base substrate 1 is placed and then a second gas, for example, H ₂ O (water) gas is supplied to the base substrate 1, as shown in FIG. 1 is oxidized to form an oxide layer 72 made of alumina (Al ₂ O ₃ : aluminum oxide). Thus, when the oxide layer 72 is stacked many times while alternately switching the first gas and the second gas, the third sacrificial film 63 having a film thickness t of 10 nm to 100 nm is formed as shown in FIG. It is formed. When the third sacrificial film 63 is thus formed by the ALD method, the horizontal plane (the surface of the first sacrificial film 61 and the surface of the second sacrificial film 62) and the vertical plane (on the side of the second polysilicon film 42). An extremely smooth third sacrificial film 63 having a film thickness uniformity of about ± 1% is obtained over the peripheral surface and the side peripheral surface of the second sacrificial film 62. Therefore, the third sacrificial film 63 has a uniform thickness over the entire surface. Note that a conventional apparatus is used as a film forming apparatus for forming the third sacrificial film 63 by the ALD method, and will be described later.

  Next, as shown in FIGS. 17 to 19, the sacrificial films 61 to 63 are dry-etched through a resist film (not shown), and the conductive film 5 (first film) on the lower side of each of the through hole 32 and the electrode 20. The polysilicon film 41) is exposed. At this time, with respect to the second sacrificial film 62 and the third sacrificial film 63 around the through-hole 32 on the upper surface side of the second polysilicon film 42, the above-described support pillar 33 and the support beam 31 are brought into contact with each other. In order to achieve this, etching is performed so that the opening is slightly larger than the opening size of the through-hole 32 (so that the second polysilicon film 42 is exposed around the through-hole 32). Thereafter, the resist film is removed.

  20 to 21, a third polysilicon film 43 made of polycrystalline silicon is formed on the base substrate 1, and the third polysilicon film 43 is doped with phosphorus. The third polysilicon film 43 is formed along the exposed surface such as the inner region of the through hole 32 described above. Therefore, the third polysilicon film 43, the conductive film 5 below the through-hole 32, and the conductive film 5 below the electrode 20 are in contact (conducting) with each other. Further, since the above-described third sacrificial film 63 is interposed between the third polysilicon film 43 and the diaphragm 10, the third polysilicon film 43 and the diaphragm 10 are The third sacrificial film 63 is separated from each other by the film thickness dimension t. Thereafter, a resist film (not shown) having an opening other than the electrode 20, the support pillar 33, and the beam portion 10a is formed, and the third polysilicon film 43 is dry-etched as shown in FIGS.

Subsequently, when the structure formed on the base substrate 1 is immersed together with the base substrate 1 in an etching solution such as an aqueous hydrogen fluoride solution, the etching solution is placed below the third polysilicon film 43 or on the support beam. It goes around 31. At this time, the third sacrificial film 63 is usually made of alumina which is a ceramic that does not dissolve in the etching solution (for example, when formed by the CVD method), but is formed by the ALD method. Therefore, it dissolves very easily and quickly in this etching solution. Therefore, the sacrificial films 61 to 63 are removed by this wet etching as shown in FIGS. Thus, the electrode 20 and the diaphragm 10 are separated from each other by the film thickness dimension t of the third sacrificial film 63, and the diaphragm 10 is in a state of floating from the first polysilicon film 41. Supported through. Further, the beam portion 10 a is in a state of floating from the diaphragm 10 by the thickness of the second sacrificial film 62 and the third sacrificial film 63. Here, since the film thickness dimension of the third sacrificial film 63 is extremely thin as described above, it is difficult for the etching solution to enter the region between the electrode 20 and the diaphragm 10. However, since the third sacrificial film 63 is formed of an ALD film that is easily etched, the third sacrificial film 63 is quickly etched, and a reduction in throughput is suppressed.
Thereafter, as shown in FIG. 25, each vibrator is separated into pieces by cutting the base substrate 1 along dicing lines 73 that divide each vibrator.

  According to the above-described embodiment, when the disk vibrator is formed on the base substrate 1, the alumina film formed by the ALD method is used as the third sacrificial film 63 formed between the diaphragm 10 and the electrode 20. Is used. Therefore, the third sacrificial film 63 has a very uniform film thickness dimension t in the plane of the base substrate 1 and dissolves quickly in the hydrogen fluoride aqueous solution. Therefore, in a certain vibrator, the variation in the gap dimension h between the diaphragm 10 and the electrode 20 is suppressed to be extremely small, and the gap dimension h is uniform between the vibrators. That is, as described above, the vibrator is capable of vibrating the diaphragm 10 (input signal input) and extracting the vibration (output signal output) by electrostatic coupling between the diaphragm 10 and the electrode 20 as described above. Done. Therefore, for a certain vibrator, if the gap dimension h between the diaphragm 10 and the first electrodes 21 and 21 and the gap dimension h between the diaphragm 10 and the second electrodes 22 and 22 are different, for example, an input signal An output signal having a level corresponding to the above cannot be obtained. Further, when the gap dimension h varies between the vibrators, for example, the output level of the obtained output signal varies between the vibrators. However, by forming the third sacrificial film 63 by the ALD method, even when a large number of vibrators are formed, the characteristics of the vibrators can be set to values as set.

At this time, when the film is formed by applying the ALD method, the film thickness dimension t is 100 nm or less, not the first sacrificial film 61 and the second sacrificial film 62 which are as thick as several hundred nm. Since the third sacrificial film 63 that is extremely thin and requires high uniformity with respect to the film thickness dimension t is targeted, it is possible to suppress a decrease in productivity and an increase in cost (an increase in the amount of gas used). Further, since the third sacrificial film 63 is formed by the ALD method, the thin film can be satisfactorily embedded even in an extremely narrow region such as the inside of the through hole 32.
Further, for example, the dissolution rate of the third sacrificial film 63 in the aqueous hydrogen fluoride solution is faster than that of the silicon oxide film, so that the time required for wet etching of the third sacrificial film 63 can be shortened, and therefore vibrations are generated. The child can be manufactured quickly. In other words, by using an alumina film formed by the ALD method as the third sacrificial film 63, productivity can be improved as compared with the case where a silicon oxide film is used as the third sacrificial film 63.

Here, the results of comparing the etching rates of the respective films with respect to the hydrogen fluoride aqueous solution are shown in FIG. In FIG. 26, a silicon nitride (Si—N) film, a thermal oxide film (a film obtained by thermally oxidizing a silicon layer), and a TEOS film (tetraethyl orthosilicate: Si (OC ₂ H ₅ ) ₄ are applied on a substrate. 5% hydrogen fluoride aqueous solution for each of the above-described third sacrificial film 63 and the HTO film (for example, a film obtained by the low pressure CVD method at a high temperature of about 800 ° C.). The etching rate when immersed in the film is shown. As a result, the third sacrificial film 63 has an etching rate that is three times faster than other silicon oxide films.

  Hereinafter, an example of an apparatus for forming the above-described third sacrificial film 63 using the ALD method will be briefly described with reference to FIG. In FIG. 27, reference numeral 81 denotes a mounting table for mounting the base substrate 1, and 82 denotes a vacuum container for storing the mounting table 81 and performing a film forming process. A gas supply unit 83 is provided above the mounting table 81 so as to face the mounting table 81, and the first gas and the second gas described above are provided inside the gas supply unit 83. A gas flow path (not shown) is formed so that the gas can be discharged to the mounting table 81 without being mixed with each other. A purge gas supply path 86 for supplying nitrogen gas to the first supply path 84 and the second supply path 85 for supplying the first gas and the second gas to the gas supply section 83, respectively. When the first gas and the second gas are switched, nitrogen gas is supplied as a purge gas into the vacuum vessel 82 and the atmosphere in the vacuum vessel 82 can be replaced. In FIG. 27, reference numeral 87 denotes a transport port, and 88 denotes a vacuum pump. The mounting table 81 is provided with a heater (not shown), but the drawing is omitted here.

  When the above-described third sacrificial film 63 is formed in such an apparatus, after the base substrate 1 is placed on the placing table 81, the inside of the vacuum vessel 82 is evacuated and is suitable for the film forming process. Set to processing pressure. Next, after supplying the first gas to the base substrate 1 and forming the aforementioned adsorption layer 71, nitrogen gas is supplied into the vacuum vessel 82 to replace the atmosphere in the vacuum vessel 82. Subsequently, the second gas is supplied to the base substrate 1 to form the oxide layer 72, and the atmosphere in the vacuum vessel 82 is similarly replaced with nitrogen gas. Thus, the third sacrificial film 63 is formed by sequentially switching the gas over many times.

  As described above, in order to form the third sacrificial film 63 having a uniform film thickness t and soluble in an aqueous hydrogen fluoride solution by the ALD method, the film formation temperature (the heating temperature of the base substrate 1) is used. May be set to 50 ° C. to 400 ° C. and the processing pressure during film formation may be set to 1 Pa to 100 Pa, respectively. As the first gas and the second gas, dimethylethylamine lane or dimethylaluminum hydrate ( Dimethyl hydride) or ozone may be used.

  The third sacrificial film 63 has been described as an alumina film containing aluminum and oxygen formed by the ALD method. However, in addition to these aluminum and oxygen, other elements such as C (carbon) and H can be used at the impurity level. (Hydrogen) may be contained, or the other element may be mixed up to about 3%, for example. That is, at this level of impurities, a good wet etching rate can be obtained for the hydrogen fluoride aqueous solution as described above. Further, if the film thickness dimension t of the third sacrificial film 63 is too thin, it is difficult to secure the gap dimension h between the diaphragm 10 and the electrode 20, while if it is too thick, the third sacrificial film 63 has a thickness t. The film formation takes a long time and productivity is lowered, and electrostatic coupling between the vibration plate 10 and the electrode 20 is difficult to obtain, so that the thickness is 10 nm to 100 nm, preferably 30 nm to 80 nm. Furthermore, although the first sacrificial film 61 and the second sacrificial film 62 are each composed of a silicon oxide film, an alumina film formed by the ALD method may be used similarly to the third sacrificial film 63.

  Further, although the circular diaphragm 10 has been described, the diaphragm 10 may be an ellipse, a quadrangle, a triangle, or the like. Further, as the base substrate 1, a nitride film or a polyimide film may be used instead of silicon, and as the polysilicon films 41 to 43, other conductive films such as a metal film such as aluminum or copper, or SiGe (silicon A germanium compound) may be used. Furthermore, as an etchant used when removing the sacrificial films 61 to 63, vapor (gas) of hydrogen fluoride may be used instead of the hydrogen fluoride aqueous solution.

DESCRIPTION OF SYMBOLS 1 Base substrate 10 Diaphragm 20-22 Electrode 30 Support part 31 Support beam 33 Support pillar 41-43 Polysilicon film 61-63 Sacrificial film

Claims (5)

In a method of forming a vibrator on a base substrate including a diaphragm and an electrode disposed around the diaphragm to vibrate the diaphragm,
A first conductive film is formed on the base substrate and patterned on the first conductive film, and a diaphragm base for supporting a side surface of the diaphragm from the lower side and the electrode on the lower side Forming each of the electrode bases to support from,
Laminating a lower-layer sacrificial film and a second conductive film in this order from the lower side so as to cover the first conductive film;
Patterning the second conductive film to form the diaphragm and a support beam extending from the diaphragm toward the upper side of the diaphragm base;
Next, a step of forming an upper sacrificial film containing aluminum and oxygen so as to cover the second conductive film;
In order to expose the electrode base while leaving the upper-layer-side sacrificial film on the peripheral surface of the diaphragm, and to expose the diaphragm base through a through-hole penetrating the support beam vertically, Etching the lower sacrificial film and the upper sacrificial film,
Subsequently, a third conductive film is formed so as to cover the upper-layer sacrificial film, and the third conductive film is patterned to form the electrode, and through the through-hole, the electrode is formed. Forming a support column for connecting the diaphragm base and the support beam to each other;
Thereafter, by etching the upper sacrificial film using hydrogen fluoride, the diaphragm and the electrode are separated from each other by the film thickness of the upper sacrificial film,
The step of forming the upper-layer sacrificial film is a step of supplying a first gas and a second gas that react with each other in order to the base substrate.   The method for manufacturing a vibrator according to claim 1, wherein a film thickness dimension of the upper-layer sacrificial film is 10 nm to 100 nm.   3. The vibrator manufacturing method according to claim 1, wherein after the step of forming the support pillar, a step of floating the diaphragm from the base substrate is performed by etching the lower-layer sacrificial film. Method.   4. The method of manufacturing a vibrator according to claim 1, wherein a large number of the vibrators are formed vertically and horizontally on the base substrate. 5. The base substrate and the lower layer side sacrificial film are a silicon substrate and a silicon oxide film, respectively.
5. The vibrator manufacturing method according to claim 1, wherein each of the first conductive film, the second conductive film, and the third conductive film is a polysilicon film. 6. Method.

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