JP4534311B2 - Dry etching method and manufacturing method of semiconductor dynamic quantity sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dry etching how, is suitable in particular used in semiconductor dynamic quantity sensor, such as a semiconductor acceleration sensor or a semiconductor angular velocity sensor.
[0002]
[Prior art]
In recent years, an SOI substrate is increasingly used for manufacturing a semiconductor sensor. This is because the buried oxide film (insulating film) of the SOI substrate can be used as a sacrificial layer for etching removal in the process of making a fine structure (sensing part) composed of a movable electrode, a fixed electrode, and the like.
[0003]
Conventionally, wet etching using hydrofluoric acid or the like has been mainly used for removing an oxide film from an SOI substrate. However, wet etching causes so-called sticking (adhesion) that structures adhere to each other due to the surface tension of a liquid. ) The phenomenon is easy to occur.
[0004]
In order to avoid the occurrence of this sticking phenomenon, dry etching using plasma has recently been used to remove the oxide film of the SOI substrate. In this dry etching, an apparatus having a processing chamber provided with parallel plate electrodes is prepared, an SOI substrate is disposed on one of the plate electrodes, an etching gas is introduced into the processing chamber, and high frequency power is applied to the parallel electrodes. This is applied to generate plasma and remove the oxide film.
[0005]
[Problems to be solved by the invention]
However, when the oxide film is removed from the SOI substrate by dry etching, there arises a problem that the etching rate becomes nonuniform within the surface of the SOI substrate.
[0006]
When such an etching rate non-uniformity occurs, even if a sufficient etching selection ratio between silicon and oxide film is taken, silicon is etched, so that the structure is partially over-etched, and the movable electrode and the fixed electrode And the capacitance determined by the distance between the movable electrode and the fixed electrode changes from the design position.
[0007]
The present invention has been made in view of the above points, and an object of the present invention is to improve the uniformity of the etching rate in the substrate surface when the insulating film of the substrate is removed by dry etching.
[0008]
[Means for Solving the Problems]
The present inventors considered that the charge accumulated on the wafer is involved as a factor for making the etching rate non-uniform, and examined the charge accumulated during dry etching. FIG. 4 shows a schematic diagram of a dry etching apparatus. Hereinafter, the dry etching method will be described with reference to FIG.
[0009]
First, an SOI substrate 100 to be dry-etched, that is, an active layer 100a is selectively etched to form a structure including a movable electrode and a fixed electrode, and a support layer 100b is selectively etched to form an oxide film 100c. An SOI substrate 100 in which an opening 100d reaching up to 100 mm is formed is prepared.
[0010]
This SOI substrate 100 is placed in a counterbore formed on the quartz plate 101. At this time, the support layer 100b side faces the upper electrode 102 side. Then, an etching gas is introduced into the apparatus, and high-frequency power is applied to the lower electrode 103 from a high-frequency power source (RF power source) 104 to generate plasma 105. Thereby, the etching gas is decomposed into ions and radicals (active species), and the oxide film 100c is dry-etched.
[0011]
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 charges accumulated in the SOI substrate 100 are difficult to escape. Easy to charge up.
[0012]
Further, in a fine structure such as an acceleration sensor or an angular velocity sensor, since the insulating separation is performed by the trench 100e in order to form a capacitor by insulating the movable electrode and the fixed electrode, an island-shaped minute region is formed by the trench 100e. Insulated.
[0013]
Therefore, the equivalent circuit of the dry etching apparatus of FIG. 4 is shown by the circuit configuration of FIG. That is, a circuit configuration in which the plasma 105 corresponds to the resistor R1, the so-called sheath 106 that serves as a boundary between the plasma 105 and the SOI substrate 100 is 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. It becomes.
[0014]
Due to such a circuit configuration, when the capacitance by the trench 100e (capacitor C3 equivalent to the trench 100e) is charged up, the in-plane of the SOI substrate 100 is caused by the bias of positive charge and negative charge generated by plasma. It is considered that the distribution of charge-up (charge charging) occurs, the incident amount of ions decomposed by the plasma 105 varies in the plane of the SOI substrate 100, and the etch rate uniformity deteriorates.
[0015]
Therefore, according to the first aspect of the present invention, an insulating film is formed on one electrode (3) of the pair of electrodes in the processing chamber (2) provided with the pair of electrodes (3, 4) arranged to face each other. (20c) An active layer (20a) is disposed on one side and an SOI substrate (20) having a support layer (20b) is disposed on the other side, and an etching gas is introduced into the processing chamber. by applying high-frequency power to the pair of electrodes, conductive dry etching process for removing the insulating film, and controls the high frequency power is introduced an etching gas into the processing chamber, an insulating film and a step of dry etching, the SOI substrate by contacting the sexual member (13), and a charge eliminating step for releasing the charged charges on the SOI substrate, by repeating alternately the discharging process and dry etching, the insulating It is characterized by removing the.
[0016]
In this manner, by performing the discharging process, since it is possible SOI substrate during dry etching releases the charge on the SOI substrate by be charged up charge eliminating step, eliminating the charge-up distribution in the SOI substrate plane be able to. Thereby, there is no variation in the amount of incident ions within the SOI substrate surface, and the uniformity of the etching rate can be improved.
[0017]
Specifically, as in the invention described in claim 2, between the first and second electrodes in the processing chamber (2) provided with the first and second electrodes (3, 4) arranged to face each other. Among them, on the first electrode (3), an SOI substrate in which an active layer (20a) is disposed on one surface side of the insulating film (20c) and a support layer (20b) is disposed on the other surface side ( 20), in the dry etching method for removing the insulating film by introducing an etching gas into the processing chamber and applying high-frequency power to the first and second electrodes, the first electrode with respect to the first electrode A hole (3b) penetrating in the thickness direction of the electrode is formed, the active layer side of the SOI substrate is directed to the first electrode side, the SOI substrate is disposed on the first electrode, and an etching gas is introduced into the processing chamber. Introducing and controlling the high frequency power and dry etching the insulating film , By contacting the conductive member (13) on the active layer side of the SOI substrate through the holes, viewed it contains a charge eliminating step for releasing the charged charges in the SOI substrate, subjected to discharging process after the dry etching process Then, it is preferable to perform the dry etching process after performing the static elimination process .
[0019]
In the first and second aspects of the invention, as in the third aspect of the invention, it is preferable that the conductive member is in contact with a region of the SOI substrate where a large amount of charge is charged during dry etching. .
[0020]
Further, in the dry etching method described in claims 1 to 3 , as shown in claim 4 , after preparing the SOI substrate (20), the active layer is selectively etched to form the trench (20e). A step of forming a structure having a movable electrode and a fixed electrode for measuring a mechanical quantity, a step of selectively etching the support layer to form an opening (20d) reaching the insulating film, In the method of manufacturing a semiconductor dynamic quantity sensor comprising the steps of dry etching the insulating film and releasing the structure, it is preferable to apply the method when dry etching the insulating film.
[0021]
In the invention of claim 4, as in the invention of claim 5 , it is preferable that the step of dry etching the insulating film is performed from the support layer side of the SOI substrate through the opening.
[0022]
In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments shown in the drawings will be described below. FIG. 1 shows a cross-sectional configuration of an etching apparatus 1 used for carrying out the dry etching method. FIG. 2 shows a cross-sectional configuration of the SOI substrate 20 on which dry etching is performed.
[0024]
The SOI substrate 20 shown in FIG. 2 is in the process of manufacturing a semiconductor dynamic quantity sensor (for example, a semiconductor acceleration sensor or a semiconductor angular velocity sensor). That is, the SOI substrate 20 includes a step of forming a structure including a movable electrode and a fixed electrode on the active layer 20a (made of silicon) and a support layer 20b (made of silicon) of the manufacturing process of the semiconductor dynamic quantity sensor. ), And a step of forming an opening 20d reaching the oxide film (insulating film) 20c.
[0025]
For example, the structure is formed by selectively etching the active layer 20a and forming the trench 20e reaching the oxide film 20c, and by selectively etching the support layer 20b with a KOH aqueous solution or the like, the oxide film 20c is reached. A reaching opening 20d 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.
[0026]
As shown in FIG. 1, the etching apparatus 1 includes a processing chamber 2. Dry etching of the SOI substrate 20 is performed in the processing chamber 2. In the processing chamber, a pair of electrodes 3 and 4 are arranged, and the pair of electrodes 3 and 4 is a lower electrode on which an SOI substrate 20 to be dry-etched is arranged (the first electrode or one of the claims). Electrode) 3 and an upper electrode (second electrode in the claims) 4 arranged so as to face the lower electrode 3.
[0027]
The lower electrode 3 is provided with an insulating plate 3a made of quartz or the like on the upper electrode 4 side. This insulating plate 3 a serves as a susceptor for fixing the SOI substrate 20. The lower electrode 3 is formed with a hole 3b penetrating in the thickness direction. The hole 3 b is formed in a portion facing the SOI substrate 20, and the size of the hole 3 b is smaller than that of the SOI substrate 20. In the processing chamber 2, a movable conductive member 13 that can be fitted into the hole 3 b is provided. As this electroconductive member 13, what consists of stainless steel, for example can be used. The conductive member 13 includes a plate-like portion that is brought into contact with the SOI substrate 20 and a rod-like portion for moving the plate-like portion up and down. The conductive member 13 is not shown, but is assumed to be grounded.
[0028]
For example, a high frequency power (RF power) of 13.56 MHz can be applied to the lower electrode 3 from a high frequency power source 5. 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-like manner. These lower electrode 3 and upper electrode 4 can be cooled by cooling water (not shown).
[0029]
The etching apparatus 1 is provided with a gas inlet 6 for supplying various gases. The gas introduction port 6 is disposed above the upper electrode 4, and various gases supplied from the gas introduction port 6 are supplied into the processing chamber 2 through the gas supply holes 4 a of the upper electrode 4.
[0030]
A gas introduction pipe 7 having a valve 7 a is connected to the gas introduction port 6. The gas introduction pipe 7 is connected with a plurality (three in this embodiment) of gas introduction pipes 8 a, 9 a, 10 a connected to various gas supply sources 8, 9, 10. In the present embodiment, CHF ₃ gas, CF ₄ gas, and Ar gas are supplied from the gas introduction pipes 8a, 9a, and 10a, respectively. The gas introduction pipes 8a, 9a, and 10a have valves 8b, 9b, and 10b for opening and closing the gas introduction pipes 8a, 9a, and 10a, and mass flow controllers 8c, 9c, and 10c for adjusting the gas flow rate. Is provided.
[0031]
On the other hand, an exhaust pipe 11 is connected to the lower part of the processing chamber 2. Through this exhaust pipe 11, the inside of the processing chamber 2 can be depressurized by a vacuuming means 12 such as a vacuum pump. With such a configuration, the inside of the processing chamber 2 can be maintained at a degree of vacuum of, for example, about 1.33 Pa to 133 Pa (10 mTorr to 1 Torr) while supplying gas from the gas supply sources 8, 9, and 10. .
[0032]
Using the dry etching apparatus 1 configured as described above, dry etching is performed as follows. First, the one surface side (active layer 20a side) of the SOI substrate 20 is directed to the lower electrode 3 side, and the hole 3b formed in the lower electrode 3 and the insulating plate 3a is positioned substantially at the center of the SOI substrate 20. The SOI substrate 20 is disposed on the lower electrode 3. As a result, the outer edge portion of the SOI substrate 20 is held. Then, the following steps are performed.
[0033]
[Etching process]
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 flow rate of each gas is controlled by the mass flow controllers 8c to 10c. Further, the gas pressure in the processing chamber 2 is set to a predetermined value by the vacuuming means 12.
[0034]
Then, the upper electrode 4 is set to the ground potential, and high frequency power of 13.56 MHz, for example, is applied from the high frequency power source 5 to the lower electrode 3 so that the RF power becomes 2.5 kW, for example. As a result, the gas in the processing chamber 2 generates a glow discharge, and plasma is generated between the upper electrode 4 and the lower electrode 3. Various gases are decomposed into charged ions, radicals, and electrons by the plasma, and the SOI substrate 20 The oxide film 20c is dry-etched from the other surface side (support layer 20b side) of the SOI substrate 20.
[0035]
This dry etching is performed by accelerating the charged ions by 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. In some cases, the radicals that are extremely active are drawn into the surface of the oxide film 20c and react with the oxide film 20c.
[0036]
As such dry etching proceeds, the SOI substrate 20 is partially charged relatively to the surroundings due to the arrival of charged ions. As a result, the charged ions cannot reach the oxide film 20c due to the electric repulsive force, and the etching rate becomes slow. In addition, the uniformity of the etching rate is reduced due to the distribution of charge in the SOI substrate 20.
[0037]
Therefore, the etching is stopped within a time (for example, about several minutes) in which the uniformity of etching does not deteriorate, and the following static elimination process is performed. The [etching step] is performed in a state where the conductive member is not in contact with the SOI substrate 20.
[0038]
[Static elimination process]
The etching is stopped, that is, the application of high frequency power is stopped. Thereafter, the conductive member 13 is brought into contact with the one surface side of the SOI substrate 20 through the hole 3b formed in the lower electrode 3 and the insulating plate 3a. Thereby, the electric charge charged in the SOI substrate 20 is released through the conductive member 13.
[0039]
Then, after the [etching step] is performed within a time period in which the SOI substrate 20 is charged with electric charges and etching uniformity is not deteriorated, the [static elimination step] is performed to release the charged charges. Thereafter, the [etching step] and the [static elimination step] are alternately repeated as appropriate, and dry etching is performed until the oxide film 20c is removed. Thereby, the structure which consists of the movable electrode and fixed electrode formed in the active layer 20a is released, and a semiconductor dynamic quantity sensor is manufactured.
[0040]
As described above, by alternately repeating the [etching step] and the [static elimination step], it is possible to improve the uniformity of the etching rate within the surface of the SOI substrate 20 and perform dry etching with a small variation in the etching rate. . For this reason, the distance between the movable electrode and the fixed electrode is uniform, and a semiconductor dynamic quantity sensor having good characteristics can be manufactured.
[0041]
By the way, if the conductive member is always kept in contact with the SOI substrate, it becomes difficult to control the potential of the SOI substrate to the optimum potential at the time of plasma generation. This control is more difficult when the conductive member is grounded as in this embodiment. As a result, the etching selectivity between the oxide film and silicon is deteriorated, and the distribution of the etching rate in the SOI substrate surface is deteriorated.
[0042]
However, in the present embodiment, since the conductive member 13 is intermittently brought into contact with the SOI substrate 20, the electric charge charged on the SOI substrate 20 is controlled while suitably controlling the potential of the SOI substrate 20. Can be released.
[0043]
In this embodiment, the [etching step] and the [static elimination step] are repeatedly performed. If possible, the [etching step] is performed after the [etching step] and the [static elimination step]. Just do it.
[0044]
(Second Embodiment)
In 1st Embodiment, although the malfunction of making a conductive member contact always was described, this embodiment eliminates the malfunction. FIG. 3 shows a cross-sectional configuration of an etching apparatus used for carrying out the dry etching method of the present embodiment. In the following, differences from the first embodiment will be mainly described, and the same portions are denoted by the same reference numerals in the drawings, and description thereof will be omitted.
[0045]
As shown in FIG. 3, the lower electrode 3 as a conductive member is a flat plate and also serves as a susceptor for fixing the SOI substrate 20. As the material of the lower electrode 3, for example, stainless steel can be used. The gas introduction pipe 7 is connected with four gas introduction pipes 31 a, 32 a, 33 a, 34 a connected to the four types of gas supply sources 31, 32, 33, 34. In the present embodiment, C ₄ F ₈ gas, CHF ₃ gas, O ₂ gas, and Ar gas are supplied through the gas introduction pipes 31a to 34a, respectively. The gas introduction pipes 31a to 34a are provided with valves 31b, 32b, 33b and 34b for opening and closing the gas introduction pipes 31a to 34a and mass flow controllers 31c, 32c, 33c and 34c for adjusting the gas flow rate. It has been.
[0046]
Then, dry etching is performed as follows. First, on the lower electrode 3, the entire surface of the SOI substrate 20 (all of the island-shaped active layer 20 a in FIG. 2) is arranged in contact with the lower electrode 3. Then, with the SOI substrate 20 in contact with the lower electrode 3, the oxide film 20 c of the SOI substrate 20 is dry etched from one surface side of the SOI substrate 20. When dry etching is performed in such a state, the charge charged on the SOI substrate 20 is released through the lower electrode 3 (conductive member), so that the charge on the SOI substrate 20 is charged by the charged ions as described above. Can be prevented. However, since the SOI substrate 20 is always in contact with the conductive member, the etching selectivity is lowered and the in-plane distribution of the etching rate is deteriorated as described above.
[0047]
Therefore, the etching conditions with the etching selectivity increased to compensate for the decrease in the etching selectivity, that is, the etching selection to such an extent that the in-plane distribution of the etching rate caused by bringing the conductive member into contact with the SOI substrate 20 can be ignored. The oxide film 20c is etched under the condition where the ratio is increased.
[0048]
Such conditions, for example, the C ₄ F ₈ gas and CHF ₃ gas and O ₂ gas 3 to 15: 10 to 50: 1 and a ratio, and 60-80% Ar gas flow rate is the total gas flow rate It is preferable to control the flow rate of each gas so as to obtain a mixed gas. For the dry etching method under the condition that the etching selectivity between the oxide film and silicon is high, the technique described in Japanese Patent Application No. 11-193322 filed earlier by the present inventors can be referred to. In the present embodiment, the SOI substrate 20 is always neutralized via the lower electrode 3 during dry etching.
[0049]
As described above, the uniformity of the etching rate in the SOI substrate 20 can be improved by bringing the SOI substrate 20 into contact with the conductive member and performing etching under conditions with a high etching selectivity.
[0050]
Note that the etching gas described above is an example, and any etching gas may be used as long as a desired etching selectivity can be ensured. Moreover, although the example in which the lower electrode 3 also serves as a susceptor has been shown, a susceptor made of a conductive member made of a material different from that of the lower electrode is disposed on the lower electrode, and the SOI substrate is brought into contact with the susceptor. It may be arranged.
[0051]
(Other embodiments)
In the first and second embodiments, an example in which almost the entire surface on one surface side of the SOI substrate 20 is brought into contact with the conductive member has been described. For example, the same effect as in the first and second embodiments can be exhibited by bringing a conductive member into contact with a region of an SOI substrate where a large amount of charge is charged during dry etching.
[0052]
In this case, in the dry etching method in which the charge removal process is performed as in the first embodiment, the plate-like portion of the conductive member may be reduced. Further, in the dry etching method in which the SOI substrate 20 is always in contact with the conductive member as in the second embodiment, the conductive susceptor is a portion of the SOI substrate that faces a region charged with a large amount of charge during dry etching. Or a portion of the susceptor that faces this region protrudes toward the SOI substrate. Further, a desired region of the susceptor may be made into a conductive member and brought into contact with a desired region of the SOI substrate.
[Brief description of the drawings]
FIG. 1 is a diagram showing a cross-sectional configuration of an etching apparatus used for dry etching according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a cross-sectional configuration of an SOI substrate subjected to dry etching.
FIG. 3 is a diagram showing a cross-sectional configuration of an etching apparatus used for dry etching according to a second embodiment of the present invention.
FIG. 4 is a diagram showing an outline of conventional dry etching.
FIG. 5 is a diagram showing an equivalent circuit when the dry etching shown in FIG. 4 is performed.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Etching apparatus, 2 ... Processing chamber, 3 ... Lower electrode, 3a ... Insulating plate,
3b ... hole, 4 ... upper electrode, 5 ... high frequency power supply, 6 ... gas inlet, 7 ... gas inlet tube,
7a ... Valve, 8-10, 31-34 ... Gas supply source,
8a-10a, 31a-34a ... gas introduction pipe,
8b-10b, 31b-34b ... valve,
8c-10c, 31c-34c ... mass flow controller,
DESCRIPTION OF SYMBOLS 11 ... Exhaust pipe, 12 ... Vacuum evacuation means, 13 ... Conductive member, 20 ... SOI substrate,
20a ... active layer, 20b ... support layer, 20c ... oxide film, 20d ... opening,
20e ... trench.

Claims (5)

Of the pair of electrodes in the processing chamber (2) provided with a pair of electrodes (3, 4) arranged to face each other, an active layer is formed on one surface of the insulating film (20c) on one electrode (3). (20a) is disposed, and an SOI substrate (20) having a support layer (20b) disposed on the other side is disposed , an etching gas is introduced into the processing chamber, and high-frequency power is applied to the pair of electrodes. In the dry etching method for removing the insulating film by applying,
Introducing an etching gas into the processing chamber and controlling the high-frequency power to dry-etch the insulating film;
By contacting the conductive member to the SOI substrate (13), and a charge eliminating step of releasing said charged to a SOI substrate charge,
A dry etching method, wherein the insulating film is removed by alternately and repeatedly performing the dry etching and the charge removal step. Among the first and second electrodes in the processing chamber (2) provided with the first and second electrodes (3, 4) arranged to face each other, on the first electrode (3), An SOI substrate (20) having an active layer (20a) disposed on one side of the insulating film (20c) and a support layer (20b) disposed on the other side is disposed, and an etching gas is introduced into the processing chamber. In the dry etching method of removing the insulating film by introducing and applying high frequency power to the first and second electrodes,
A hole (3b) penetrating in the thickness direction of the first electrode is formed in the first electrode, the active layer side of the SOI substrate is directed to the first electrode side, and the SOI substrate is Disposed on the first electrode;
Introducing an etching gas into the processing chamber and controlling the high-frequency power to dry-etch the insulating film;
Through said hole, said by contacting the conductive member (13) on the active layer side of the SOI substrate, seen including a neutralization step of releasing said charged to a SOI substrate charge,
A dry etching method comprising: performing the static elimination process after performing the dry etching process; and performing the dry etching process after performing the static elimination process . 3. The dry etching method according to claim 1, wherein the conductive member is brought into contact with a region of the SOI substrate where a large amount of charge is charged during the dry etching. After preparing the SOI substrate (20), said active layer is selectively formed a trench (20e) by etching a constitute a structure having a movable electrode and the fixed electrode for mechanical quantity measurement 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. In the manufacturing method of the semiconductor dynamic quantity sensor consisting of:
Wherein an insulating film during dry etching, a method of manufacturing a semiconductor dynamic quantity sensor, characterized by applying the dry etching method according to any one of claims 1 to 3. The method of manufacturing a semiconductor dynamic quantity sensor according to claim 4, wherein the step of dry etching the insulating film is performed from the support layer side of the SOI substrate through the opening .

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