JP2001351880A - Method of dry etching and dry etching apparatus used therein - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the uniformity of an etch rate in a plane of a substrate when removing an oxide film from the substrate by dry etching. SOLUTION: An insulation film is removed by repeating the following two processes: (1) a process wherein an SOI substrate 20 is disposed on a lower electrode 3 in a processing chamber 2, and then an etching gas is supplied into the processing chamber 2, and at the same time, high frequency power is applied to the lower electrode 3 to dry-etch the insulation film; (2) an electrification uniforming process wherein electrons are supplied into the processing chamber by means of an electron irradiation apparatus 13 installed in the etching apparatus 1 to uniform the distribution of electric charges stored in the SOI substrate during dry etching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method and a dry etching apparatus used in the method, and is particularly suitable for use in semiconductor dynamic quantity sensors such as a semiconductor acceleration sensor and a semiconductor angular velocity sensor.

[0002]

2. Description of the Related Art In recent years, an SOI substrate is increasingly used for manufacturing a semiconductor sensor. This is because a buried oxide film (insulating film) of the SOI substrate can be used as a sacrificial layer for etching removal in the process of forming a fine structure (sensing portion) including a movable electrode, a fixed electrode, and the like.

Conventionally, wet etching using hydrofluoric acid or the like has been mainly used for removing an oxide film from an SOI substrate. However, according to wet etching, a so-called structure in which structures adhere to each other due to surface tension of a liquid. The sticking (sticking) phenomenon is likely to occur.

In order to avoid occurrence of the sticking phenomenon, dry etching using plasma has recently been used for removing an oxide film on an SOI substrate. In this dry etching, an apparatus having a processing chamber provided with parallel plate electrodes is prepared, an SOI substrate is arranged on one of the flat electrodes, an etching gas is introduced into the processing chamber, and high-frequency power is applied to the parallel electrodes. The plasma is generated by applying the voltage, and the oxide film is removed.

[0005]

However, when the oxide film on the SOI substrate is removed by dry etching,
There is a problem that the etching rate becomes non-uniform in the SOI substrate surface.

When such an uneven etching rate occurs, the silicon is etched even if the etching selectivity between the silicon and the oxide film is sufficiently set, so that the structure is partially over-etched and the movable electrode is over-etched. The distance between the movable electrode and the fixed electrode varies, and the capacitance determined by the distance between the movable electrode and the fixed electrode changes from the design position.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and an object of the present invention is to improve the uniformity of an etching rate in a substrate surface when removing an insulating film from a substrate by dry etching.

[0008]

The present inventors considered that the charge accumulated in the wafer was involved in making the etching rate non-uniform, and examined the charge accumulated during dry etching. . FIG. 5 shows a schematic diagram of a dry etching apparatus. Hereinafter, the dry etching method will be described with reference to FIG.

First, the SOI substrate 100 on which dry etching is performed, that is, the active layer 100a is selectively etched to form a structure including a movable electrode and a fixed electrode, and the support layer 100b is selectively etched. An SOI substrate 100 having an opening 100d reaching the oxide film 100c is prepared.

The SOI substrate 100 is placed in a counterbore formed on a quartz plate 101. At this time, the support layer 100b
The side faces the upper electrode 102 side. Then, an etching gas is introduced into the apparatus, and the lower electrode 103 is formed.
A high frequency power is applied from a high frequency power supply (RF power supply) 104 to generate a plasma 105. Thereby, the etching gas is decomposed into ions and radicals (active species), and the oxide film 100c is dry-etched. And FIG.
As shown in (1), a constant amount of etching gas is continuously supplied, and dry etching is continued.

Although dry etching is performed by such a method, when the SOI substrate 100 is etched, since the active layer 100a and the support layer 100b are insulated by the oxide film 100c, the charge accumulated on the SOI substrate 100 is reduced. Is difficult to escape, and is easy to charge up.

Further, in a fine structure such as an acceleration sensor or an angular velocity sensor, insulation is separated by a trench 100e in order to form a capacitor by insulating a movable electrode and a fixed electrode from each other. Is insulated in the minute area.

For this reason, an equivalent circuit of the dry etching apparatus of FIG. 5 is shown by the circuit configuration of FIG. That is, the plasma 105 is composed of the resistor R1, the plasma 105 and the SOI substrate 1.
The so-called sheath 106, which is a boundary portion between 00 and 00, has a circuit configuration in which a parallel circuit of the capacitor C1 and the diode D1, the oxide film 100c corresponds to the capacitor C2, and the trench 100e corresponds to the capacitor C3.

With such a circuit configuration, when the capacitance of the trench 100e (capacitor C3 equivalent to the trench 100e) is charged up, the SOI substrate 100 is deflected by the bias of positive and negative charges generated by plasma. Distribution occurs in the charge-up (charge of charge) in the plane, and the incident amount of ions decomposed by the plasma 105 becomes SO
It is considered that the variation in the plane of the I-substrate 100 causes the etch rate uniformity to deteriorate.

Therefore, according to the first aspect of the present invention, one of the pair of electrodes (3) in the processing chamber (2) provided with the pair of electrodes (3, 4) arranged opposite to each other is provided.
In a dry etching method for removing an insulating film by disposing a substrate (20) provided with an insulating film (20c) thereon, introducing an etching gas into a processing chamber and applying high-frequency power to a pair of electrodes, Introducing an etching gas into the processing chamber and controlling the high-frequency power to dry-etch the insulating film, and irradiating the processing chamber with electrons to uniformize the distribution of the charges on the substrate during dry etching. The method is characterized in that the insulating film is removed by alternately and repeatedly performing the dry etching and the charging uniformizing step.

As described above, by irradiating the processing chamber with electrons, electrons are supplied to a portion of the substrate which is relatively positively charged by dry etching, and the charge-up distribution in the substrate surface is reduced. can do.
As a result, the variation in the amount of ions incident on the substrate surface is reduced, and the uniformity of the etching rate can be improved.

In this case, specifically, as in the second aspect of the present invention, the electric charge charged to the substrate at the time of dry etching is a negative electric charge. Negative charges can be supplied by electrons to a portion having a small amount, so that the charge on the substrate can be made uniform.

Further, in the dry etching method according to claim 1 or 2, the insulating film (20
c) preparing an SOI substrate (20) having an active layer (20a) disposed on one side and a support layer (20b) disposed on the other side, and then selectively etching the active layer; Forming a trench having a movable electrode and a fixed electrode for measuring a physical quantity, and selectively etching a support layer to form an opening reaching an insulating film. In a method for manufacturing a semiconductor physical quantity sensor, which includes the step of forming the step 20d) and the step of dry-etching the insulating film and releasing the structure, it is preferable to apply the method when dry-etching the insulating film.

According to a fourth aspect of the present invention, there is provided a pair of electrodes (3, 4) arranged opposite to each other and a processing chamber (2) provided with the pair of electrodes, and one of the pair of electrodes is provided. (3)
A substrate (20) provided with an insulating film (20c) is disposed thereon, and the insulating film is removed by introducing an etching gas into the processing chamber and applying high-frequency power to a pair of electrodes. Electron irradiation device (1) that can irradiate the processing chamber with electrons
3) is provided. If this dry etching apparatus is used, the dry etching method of claim 1 or 2 can be suitably performed.

Note that the reference numerals in parentheses of the above means indicate the correspondence with specific means described in the embodiments described later.

[0021]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 1 shows a sectional configuration of an etching apparatus 1 used for performing a dry etching method. Also,
FIG. 2 shows a cross-sectional configuration of the electron irradiation device 13 in FIG. FIG. 3 shows an SOI to be subjected to dry etching.
2 shows a cross-sectional configuration of a substrate 20.

The SOI substrate 20 shown in FIG. 3 is in the course of manufacturing a semiconductor dynamic quantity sensor (for example, a semiconductor acceleration sensor or a semiconductor angular velocity sensor). That is, this S
The OI substrate 20 includes a step of forming a structure including a movable electrode and a fixed electrode in the active layer 20a, and an opening reaching the oxide film (insulating film) 20c in the support layer 20b. 20d is formed.

For example, a structure is formed by selectively etching the active layer 20a and forming a trench 20e reaching the oxide film 20c.
By selectively etching with an H aqueous solution or the like, an opening 20d reaching the oxide film 20c is formed. The oxide film 20c of the SOI substrate 20 having such a structure is dry-etched by the etching apparatus 1 shown in FIG.

As shown in FIG. 1, this etching apparatus 1
Is provided with a processing chamber 2. In the processing chamber 2, SO
Dry etching of the I substrate 20 is performed. A pair of electrodes 3 and 4 are arranged in the processing chamber, and have a positional relationship such that they are substantially parallel to each other. This pair of electrodes 3, 4
Is a lower electrode (one electrode in claims) 3 on which the SOI substrate 20 to be subjected to dry etching is arranged, and an upper electrode (opposite electrode) arranged to face the lower electrode 3
4

The lower electrode 3 is provided with a quartz plate 3a, and a counterbore 3b formed on the quartz plate 3a has an SOI
The substrate 20 is arranged. The lower electrode 3 has a high frequency power supply 5
For example, 13.56 MHz high frequency power (RF power)
Can be applied. The upper electrode 4 has a plurality of gas supply holes 4a arranged at equal intervals on the side facing the lower electrode 3, and is configured to allow the etching gas to flow in a shower shape. These lower electrode 3 and upper electrode 4 can be cooled by cooling water (not shown).

The etching apparatus 1 is provided with a gas inlet 6 for supplying various gases. The gas inlet 6 is disposed above the upper electrode 4, and various gases supplied from the gas inlet 6 are supplied to the gas supply holes 4 of the upper electrode 4.
a into the processing chamber 2.

The gas inlet 6 is connected to a gas inlet pipe 7 provided with a valve 7a. In the gas introduction pipe 7,
A plurality (three in this embodiment) of gas introduction pipes 8a, 9a, 10a connected to supply sources 8, 9, 10 of various gases are connected. In the present embodiment, each gas introduction pipe 8a,
CHF ₃ gas, CF ₄ gas, and Ar gas are supplied from 9a and 10a, respectively. Each of the gas introduction pipes 8a, 9a, and 10a has a gas introduction pipe 8a.
Valves 8b, 9b, 10 for opening and closing a, 9a, 10a
b, and mass flow controllers 8c, 9c, 10c for adjusting the gas flow rate.

On the other hand, an exhaust pipe 11 is connected to a lower portion of the processing chamber 2. Through the exhaust pipe 11, the inside of the processing chamber 2 can be depressurized by evacuation means 12 such as a vacuum pump. With such a configuration, in a state where the gas is supplied from the gas supply sources 8, 9, and 10, the inside of the processing chamber 2 is, for example, 1.33 Pa to 133 Pa (10 mTorr to 1 mPa).
Torr).

An electron irradiator 13 is arranged in the vicinity of the wall of the processing chamber 2 between the lower electrode 3 and the upper electrode 4. The electron irradiation device 13 is for irradiating the processing chamber 2 with electrons according to the electrical environment of the SOI substrate 20 and its surroundings. In addition, the electron irradiation device 13
It is preferable that the SOI substrate 20 can generate electrons of low energy enough not to be damaged. Hereinafter, an example of the electron irradiation device 13 will be described in detail with reference to FIG.

As shown in FIG. 2, the electron irradiation device 13 is an arc chamber 1 in which a filament 14 is disposed.
Five. A gas supply source 16 is connected to the arc chamber 15 via a gas introduction pipe 16a, and the gas introduction pipe 16a is provided with a valve 16b for opening and closing the gas introduction pipe 16a. Also, arc chamber 1
5 is provided with an extraction hole 15a, which is an exit for electrons. Then, a portion of the arc chamber 15 where the extraction hole 15 a is formed is disposed inside the processing chamber 2.

Using the dry etching apparatus 1 configured as described above, dry etching is performed as follows. First, the SOI substrate 20 is arranged on the lower electrode 3.
Then, the following steps are performed. FIG. 4 shows a timing chart of the dry etching, and the details of the dry etching will be described with reference to FIG.

[Etching Step] All the valves 8 b to 10 b are opened, and a mixed gas of CHF ₃ / CF ₄ / Ar is introduced into the processing chamber 2. At this time, the mass flow controller 8c
The flow rate of each gas is controlled according to 10 to 10c. Further, the gas pressure in the processing chamber 2 is set to a predetermined value by the evacuation unit 12.

Then, the upper electrode 4 is set to the ground potential, and a high frequency power of 13.56 MHz, for example, is applied to the lower electrode 3 from the high frequency power supply 5 so that the RF power becomes 2.5 kW, for example. As a result, the gas in the processing chamber 2 causes a glow discharge to generate plasma between the upper electrode 4 and the lower electrode 3, and the plasma decomposes various gases into ions, radicals, and electrons, and oxidizes the SOI substrate 20. Membrane 20
c is dry-etched.

The dry etching is performed by accelerating the ions due to the potential difference between the upper electrode 4 and the lower electrode 3 and colliding with the surface of the oxide film 20c to physically remove the oxide film 20c. Chemically extremely active radicals are drawn into the surface of the oxide film 20c, and the oxide film 2
By reacting with Oc.

As such dry etching proceeds, charges are charged on the upper electrode 4 side of the SOI substrate 20, and the charge is distributed over time. Specifically, the amount of negative charge is large around the SOI substrate 20, and the amount of negative charge is small near the center. That is, the vicinity of the center of the SOI substrate 20 is relatively charged up to +. Thus, the SOI substrate 20
Is generated, the uniformity of the etching rate is reduced. Therefore, the etching is stopped at a stage (for example, about several minutes) at which the SOI substrate 20 starts charging and the etching rate starts to decrease,
The following charging uniformization step is performed.

[Electrification Equalization Step] First, the introduction of the etching gas into the processing chamber 2 and the application of the high-frequency power are stopped. Then, electrons are introduced from the electron irradiation device 13 into the processing chamber 2. The electrons are preferably low energy electrons as described above. Hereinafter, with reference to FIG.
The mechanism for emitting electrons from 3 will be described. First, the filament power supply 17 is operated, and a current is caused to flow through the filament 14 to reduce the temperature of the filament 14 to 200 degrees.
The temperature is increased to 0 ° C. or higher to emit thermoelectrons. At this time, valve 1
6b is opened to supply, for example, Ar gas from the gas supply source 16, and the arc power source 18 is operated to start the filament 1
An arc voltage of several tens of volts is applied between 4 and the wall of the arc chamber 15.

As a result, the thermoelectrons are accelerated by the arc voltage and collide with gas atoms to ionize the gas atoms and generate new electrons. By this electron multiplying action, a plasma 19 is generated between the filament (cathode) 14 and the arc chamber (anode) 15.
Then, in a state where the arc is stably formed, the electrons 2 are introduced into the processing chamber 2 from the extraction hole 15 a of the arc chamber 15.
Release 1. At this time, the drawer power supply 22
When the potential of the arc chamber 15 is lowered by several volts from the ground potential, the amount of electrons supplied into the processing chamber 2 increases.

As a result, the electrons 21 introduced into the portion where the amount of negative charge is small on the side of the upper electrode 4 of the SOI substrate 20 and relatively charged up to +.
Provides a negative charge. Thereby, charging on the SOI substrate 20 becomes uniform.

Thereafter, the introduction of the electrons 21 is stopped, and the [etching step] is performed again. Hereinafter, as shown in FIG.
[Etching Step], [Electrification Equalizing Step] and [Etching Step] are repeated a desired number of times, and dry etching is performed until the oxide film 20c is removed. Thus, the structure including the movable electrode and the fixed electrode formed on the active layer 20a is released, and the semiconductor physical quantity sensor is manufactured.

As described above, by performing the [charging uniformization step] during the [etching step], it is possible to eliminate the variation in the charge-up distribution in the SOI substrate 20 which occurs with the lapse of the etching time. it can. As a result, the uniformity of the etching rate in the plane of the SOI substrate 20 can be improved, and dry etching with a small variation in the etching rate can be performed. Therefore, the distance between the movable electrode and the fixed electrode becomes uniform, and a semiconductor dynamic quantity sensor having good characteristics can be manufactured.

The above-described electron irradiation device 13 is an example, and any other mechanism may be used as long as electrons can be supplied to the SOI substrate 20 by the electrons to make the charge distribution uniform. . Further, it is preferable that the potential of the processing chamber 2 and the lower electrode 3 is adjusted so that the electrons 21 excessively introduced in the [charging uniformization step] are absorbed by the processing chamber 2 and the lower electrode 3.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross-sectional configuration of an etching apparatus used for performing dry etching according to an embodiment of the present invention.

FIG. 2 is a diagram showing a cross-sectional configuration of the electron irradiation device in FIG.

FIG. 3 is a diagram showing a cross-sectional configuration of an SOI substrate on which dry etching is performed;

FIG. 4 is a diagram showing a timing chart of dry etching.

FIG. 5 is a diagram schematically showing conventional dry etching.

FIG. 6 is a diagram showing a timing chart of a conventional dry etching.

FIG. 7 is a diagram showing a state when the dry etching shown in FIG. 5 is performed by an equivalent circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Etching apparatus, 2 ... Processing chamber, 3 ... Lower electrode, 4 ...
Upper electrode, 5 ... High frequency power supply, 6 ... Gas inlet, 7 ... Gas inlet pipe, 7a ... Valve, 8-10 ... Gas supply source, 8A
-10a ... gas introduction pipe, 8b-10b ... valve, 8c ~
10c: mass flow controller, 11: exhaust pipe, 12
... Vacuum evacuation means, 13 ... Electron irradiation device, 20 ... SOI substrate, 20a ... Active layer, 20b ... Support layer, 20c ... Oxide film, 20d ... Opening, 20E ... Trench, 21 ... Electron.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shingo Inoue 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation (72) Inventor Shoji 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Denso Corporation (72) Inventor Koji Muto 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation (72) Inventor Hiroki Noguchi 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation (72) Inventor Takeshi Fukada 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside DENSO Corporation (72) Inventor Kazushi Asami 14 Iwatani, Shimoba-Kakucho, Nishio-shi, Aichi F-term in Japan Automotive Parts Research Institute Co., Ltd. 4M112 AA02 BA07 CA21 DA03 EA02 EA06 5F004 AA01 BA04 BB13 BB25 BB28 CA09 DA01 DA16 DA23 DB03 EB08 FA08

Claims (4)

[Claims] An insulating film (20c) is provided on one electrode (3) of a pair of electrodes in a processing chamber (2) provided with a pair of electrodes (3, 4) arranged to face each other. A dry etching method for removing the insulating film by disposing the substrate (20) provided, introducing an etching gas into the processing chamber, and applying high-frequency power to the pair of electrodes; Controlling the high-frequency power and dry-etching the insulating film; and irradiating the processing chamber with electrons to uniform the distribution of the charges charged on the substrate during the dry-etching. A dry process, wherein the insulating film is removed by alternately and repeatedly performing the dry etching and the charge uniformizing process. Etching method. 2. The method according to claim 1, wherein the charge charged on the substrate during the dry etching is a negative charge, and in the charge uniforming step, a portion of the substrate having a small amount of the negative charge is negatively charged by the electrons. 2. The dry etching method according to claim 1, wherein a charge is supplied to make the charge on the substrate uniform. 3. An active layer (2) is formed on one side of the insulating film (20c).
0a) is arranged, and the support layer (20
After preparing the SOI substrate (20) on which the component (b) is disposed, the active layer is selectively etched to form a trench (20e), which has a movable electrode and a fixed electrode for measuring a physical quantity. A step of forming a structure; a step of selectively etching the support layer to form an opening (20d) reaching the insulating film; and a step of dry-etching the insulating film to release the structure. A method of manufacturing a semiconductor physical quantity sensor comprising: a step of dry-etching the insulating film, wherein the dry etching method according to claim 1 or 2 is applied. Production method. 4. A pair of electrodes (3, 4) arranged opposite to each other.
And a processing chamber (2) in which the pair of electrodes are provided. A substrate (20) provided with an insulating film (20c) is disposed on one of the electrodes (3) of the pair of electrodes. In a dry etching apparatus adapted to remove the insulating film by introducing an etching gas into the processing chamber and applying high-frequency power to the pair of electrodes, the processing chamber may be irradiated with electrons. A dry etching apparatus, comprising an electron irradiation device (13) capable of being used.