JP2006203035A - Plasma etching method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an etching method whereby a groove is formed with a high accuracy in a silicon substrate and a quick processing is made possible while giving shapes having roundness to the shoulders of this groove. <P>SOLUTION: In a first plasma processing, the gas containing such a hydrofluorocarbon as CHF<SB>3</SB>, CH<SB>2</SB>F<SB>2</SB>, CH<SB>3</SB>F is used to form deposition substances D at least on the side walls of a groove 110. Subsequently, in a second plasma processing, a silicon substrate 101 is subjected to a plasma etching by using an etching gas to form a trench 120. Since the deposition substances D formed by the first plasma processing function as protective films and the etching rates of the silicon substrate 101 are lowered near the side walls of the groove 110, shoulders 120a of the formed trench 120 are formed into curved-surface shapes having roundness. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a plasma etching method, and more particularly to a plasma etching method applicable to, for example, trench formation in shallow trench isolation (STI), which is an element isolation technique in the process of manufacturing a semiconductor device.

STI is known as a technique for electrically isolating elements formed on a silicon substrate. In STI, silicon is etched using a silicon nitride film or the like as a mask to form a trench, an insulating film such as SiO ₂ is embedded therein, and then a mask (silicon nitride) is formed by chemical mechanical polishing (CMP) processing. A step of flattening is performed using the film) as a stopper.

  Incidentally, in recent years, design rules for semiconductor elements constituting an LSI are becoming increasingly finer due to demands for higher integration and higher speed of LSIs, and there are also increasing demands for power saving. When a fine trench is formed in STI, the shape of the shoulder (the upper corner of the trench sidewall) of the trench formed by etching tends to be acute. As a result, there is a problem in that the leakage current between the gate electrode and the active region increases via the shoulder portion, which becomes a factor for increasing power consumption.

Therefore, a first step of performing plasma processing for forming a roundness at the upper end of the side wall of the groove using a mixed gas containing HBr and N ₂ as a processing gas, and a plasma processing for forming a groove in the silicon of the silicon substrate are performed. There has been proposed an etching method in which a second step and a third step of performing a plasma treatment for introducing a mixed gas containing HBr and Cl ₂ as a processing gas to form a round portion at the bottom of the groove (for example, Patent Document 1).
JP 2003-218093 A

  In the etching method described in Patent Document 1, it is possible to form a round shape (top rounding) in the shoulder portion of the trench by performing the first step, thereby reducing leakage current. It is an excellent technology. However, since the method of Patent Document 1 is a multi-stage plasma etching method in which the silicon substrate is plasma etched in the first step to form a shallow groove, and then the second step and the third step are performed. As the total etching time becomes longer, the shoulder of the mask may drop, leaving room for improvement in improving the precision of microfabrication. Further, in the method of Patent Document 1, since the substrate temperature (lower electrode temperature) is changed in the first step and the second step in order to give the shoulder a round shape with high accuracy, this temperature adjustment takes time. The time required for continuous processing tended to be long. For this reason, provision of the process which can improve a throughput further was calculated | required.

  Accordingly, an object of the present invention is to provide an etching method capable of forming a groove in a silicon substrate with high accuracy and capable of rapid processing while giving a round shape to the shoulder of the groove.

In order to solve the above problems, according to a first aspect of the present invention,
Etching is performed on an object to be processed having at least a layer to be etched and a patterned mask layer formed on the layer to be etched, and a recess corresponding to the pattern of the mask layer is formed in the layer to be etched. A plasma etching method,
A first plasma treatment step of forming a deposit on at least the layer to be etched in the vicinity of the boundary between the layer to be etched and the mask layer in the openings constituting the pattern in the mask layer;
After the first plasma treatment step, a second plasma treatment step of forming the recess by etching the etched layer;
Including
In the second plasma processing step, a plasma etching method is provided, wherein a corner of the upper end of the side wall constituting the concave portion is formed in a curved shape.

In the plasma etching method of the first aspect, the processing gas in the first plasma processing step is preferably a gas containing hydrofluorocarbon, and a gas containing CHF ₃ , CH ₂ F _2, or CH ₃ F. It is more preferable.
The processing gas in the second plasma processing step is preferably a halogen-containing gas, and the halogen-containing gas is preferably a gas containing HBr or Cl ₂ or both.
The treatment time in the first plasma treatment step is preferably 3 seconds or more and 60 seconds or less.
The curvature radius of the upper corner of the side wall constituting the recess is adjusted according to the processing time in the first plasma processing step, and the side wall constituting the recess is controlled by the processing temperature in the second plasma processing step. It is preferable to adjust the angle.
Moreover, it is preferable to adjust the radius of curvature of the upper corner of the side wall constituting the recess by mixing a gas having an etching action with the processing gas in the first plasma processing step.
The plasma etching method of the first aspect as described above is preferably applied to trench etching in shallow trench isolation.

According to the second aspect of the present invention, at least a silicon substrate, a silicon oxide film formed on the silicon substrate, and a silicon nitride film formed on the silicon oxide film are included. Plasma for forming a trench corresponding to the pattern of the mask layer on the silicon substrate by etching the object to be processed in which the silicon oxide film and the silicon nitride film are patterned as a mask layer to form an opening An etching method comprising:
Deposits are deposited on the silicon substrate at least in the vicinity of the boundary between the silicon substrate and the mask layer in the mask layer by the plasma of the first processing gas containing C, F, and H as constituent elements. A first plasma treatment step to be formed;
A second plasma processing step of forming the trench by etching the silicon substrate with a plasma of a second processing gas after the first plasma processing step;
Including
In the second plasma processing step, a plasma etching method is provided, wherein a corner portion of an upper end of a side wall constituting the trench is formed in a curved shape.

According to a third aspect of the present invention, a plasma supply source for generating plasma;
A processing container for partitioning a processing chamber for performing an etching process on an object to be processed by the plasma;
A support for placing the object to be processed in the processing container;
An exhaust means for decompressing the inside of the processing vessel;
Gas supply means for supplying gas into the processing vessel;
A control unit for controlling the plasma etching method of the first aspect or the second aspect to be performed;
A plasma etching apparatus is provided.

  According to a fourth aspect of the present invention, the plasma processing apparatus operates on a computer and controls the plasma processing apparatus so that the plasma etching method according to the first aspect or the second aspect is performed at the time of execution. A control program is provided.

According to a fifth aspect of the present invention, there is provided a computer storage medium storing a control program that operates on a computer,
A computer storage medium is provided, wherein the control program controls a plasma processing apparatus so that the plasma etching method of the first aspect or the second aspect is performed at the time of execution. .

  According to the present invention, the deposit formed by the first plasma treatment suppresses the progress of etching of the etching target layer such as the silicon substrate near the side wall of the opening (near the boundary with the mask layer), and the shoulder of the recess. The part can be rounded. Moreover, the roundness (radius of curvature) can be easily controlled by the time of the first plasma treatment. Therefore, in forming a trench such as STI, it is possible to form a recess having a rounded shoulder with high accuracy and high throughput. In a semiconductor device in which an element isolation region is formed using a recess formed by this etching method, for example, a leakage current between a gate electrode and an active region is suppressed, and it is possible to meet a demand for power saving. .

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 schematically shows an enlarged main portion of a longitudinal section of a semiconductor wafer (hereinafter simply referred to as “wafer”) W in a silicon trench etching process such as STI, for example, in order to explain an embodiment of the present invention. It is shown. As shown in FIG. 1A, a silicon oxide film 102 such as SiO ₂ is formed on a silicon substrate 101 constituting the wafer W, and a silicon nitride film such as Si ₃ N ₄ is further formed thereon. 103 is formed. This silicon nitride film 103 functions as a hard mask.

  The silicon nitride film 103 and the silicon oxide film 102 are patterned into a predetermined shape to form a mask layer. FIG. 1A shows a groove 110 as an opening constituting the pattern. Note that the patterning of the silicon nitride film 103 and the silicon oxide film 102 can be performed by performing etching using a resist pattern formed by, for example, a photolithography technique as a mask in a process not shown here.

The pattern of the first plasma treatment is shown in FIG. In this first plasma treatment, the silicon substrate 101 and the mask layer (in this example, the silicon nitride film 103 and the silicon oxide film 102), which are the etched layers, are formed on at least the etching target layer near the side wall of the groove 110. A deposit D is formed on the exposed surface of the silicon substrate 101 in the vicinity of the boundary.
As the processing gas in the first plasma processing, any gas species that can form the deposit D may be used. For example, a processing gas containing at least C, F, and H as constituent elements can be used. As an example of such a gas, for example, a gas containing a hydrofluorocarbon such as CHF ₃ , CH ₂ F ₂ , and CH ₃ F is preferable. Since the hydrofluorocarbon generates a polymer by the first plasma treatment, a deposit D is formed on the wafer W. At this time, in the first plasma treatment, for example, an ion component in the plasma is generated by applying a high frequency power to the lower electrode and generating a bias voltage using an upper and lower power application type plasma etching apparatus (see FIG. 3). Is preferably incident on the wafer W. Thus, a thick deposit D is formed near the boundary between the silicon substrate 101 and the mask layer on the bottom surface of the groove 110 where the silicon substrate 101 is exposed, and a small amount of deposit D is formed near the center of the bottom surface of the groove 110. Not.

As a processing gas in the first plasma processing, for example, a mixed gas containing hydrofluorocarbon and an inert gas such as a rare gas or N ₂ can be used. Examples of the rare gas include Ar, He, Xe, Kr, and the like.
In addition, a gas having an etching action, for example, CF ₄ , O ₂ , SF ₆ , NF _3, or the like can be mixed in the processing gas in the first plasma processing. The deposition rate of the deposit D can be controlled by providing a gas having an etching action in the processing gas at a predetermined ratio to remove the deposit D that is formed. That is, by mixing a gas having an etching action, the deposition rate can be easily controlled as compared with a case where a gas having a strong deposition property such as hydrofluorocarbon is used alone.

Next, as shown in FIG. 1C, etching for forming the trench 120 in the silicon substrate 101 is performed by the second plasma treatment using the silicon oxide film 102 and the silicon nitride film 103 as a mask.
That is, the silicon substrate 101 made of single crystal silicon is plasma-etched using an etching gas, and trenches 120 are formed in the silicon substrate 101 as shown in FIG. At this time, due to the presence of the deposit D formed by the first plasma treatment, the etching is slower in the vicinity of the side wall of the groove 110 than at the bottom center of the groove 110. That is, the deposit D functions as a protective film, and the etching rate of the silicon substrate 101 decreases near the side wall of the groove 110. As a result, the shoulder of the formed trench 120 [indicated by reference numeral 120a in FIG. 1C] is formed in a rounded curved shape.

The second plasma treatment can be performed, for example, under the same conditions as trench etching in normal STI. The processing gas in the second plasma processing step may be any gas having an etching action, but for example, a halogen-containing gas is preferably used. Examples of the halogen-containing gas include a gas containing HBr, Cl ₂ or the like, or a mixed gas thereof. The processing gas in the second plasma processing step can be mixed with a gas such as O ₂ , He, or Ar as necessary.

  FIG. 2 shows an enlarged cross-sectional structure of the main part of the wafer W after the second plasma processing step. In the trench 120 formed by the second plasma treatment step, the shape of the portion (shoulder portion 120a) surrounded by a circular broken line in FIG. 2 has a curved surface. If the deposit D formed by the first plasma treatment shown in FIG. 1B increases, the silicon near the corner of the bottom of the groove 110 (near the boundary between the silicon substrate 101 to be etched and the mask layer) Since the etching of the substrate 101 is further suppressed, the roundness of the shoulder 120a of the trench 120 is also formed large.

  The amount of deposit D increases in proportion to the processing time in the first plasma processing step under the same conditions. Therefore, the roundness (curvature radius) of the shoulder 120a can be controlled by controlling the processing time of the first plasma processing step. The radius of curvature of the shoulder 120a is preferably adjusted to about 5 to 30 nm, for example. From such a viewpoint, the processing time in the first plasma processing step is not particularly limited, but can be selected from a range of 3 seconds to 60 seconds, for example, 5 seconds to 30 seconds. preferable.

  Further, as described above, the amount of the deposit D can be controlled by mixing the composition of the processing gas in the first plasma processing, for example, a gas having an etching action in the processing gas. Therefore, the size (curvature radius) of the shoulder can be controlled also by selecting the composition of the processing gas.

In the second plasma treatment, by controlling conditions such as temperature, the angle θ of the side wall of the trench 120 is changed to be tapered, or the corner portion 120b at the bottom of the trench 120 is rounded. You can also. The angle θ of the sidewall of the trench 120 is preferably 82 ° to 88 °, for example.
Further, by providing the corner portion 120b with roundness, the stress after the insulator is embedded can be relieved, the leakage current can be reduced, and the reliability of the semiconductor device can be improved.

  FIG. 3 schematically shows a configuration example of a plasma etching apparatus that can be suitably used for carrying out the method of the present invention. The plasma etching apparatus 1 is configured as a capacitively coupled parallel plate etching apparatus in which electrode plates are opposed in parallel in the vertical direction, and a high frequency power source is connected to both.

  The plasma etching apparatus 1 has a chamber 2 formed into a cylindrical shape made of aluminum, for example, whose surface is anodized (anodized), and the chamber 2 is grounded. In the chamber 2, a wafer W made of, for example, silicon and having a predetermined film formed thereon as a target object is placed horizontally, and a susceptor 5 functioning as a lower electrode is supported by the susceptor support 4. It is provided in the state. A high pass filter (HPF) 6 is connected to the susceptor 5.

  A temperature control medium chamber 7 is provided inside the susceptor support 4, and the temperature control medium is introduced into the temperature control medium chamber 7 through the introduction pipe 8 and circulated so that the susceptor 5 can be controlled to a desired temperature. It is like that.

  The upper center portion of the susceptor 5 is formed into a convex disk shape, and an electrostatic chuck 11 having substantially the same shape as the wafer W is provided thereon. The electrostatic chuck 11 has a configuration in which an electrode 12 is interposed between insulating materials. When a DC voltage of, for example, 1.5 kV is applied from a DC power source 13 connected to the electrode 12, the electrostatic chuck 11 is subjected to Coulomb force. The wafer W is electrostatically adsorbed.

  The insulating plate 3, the susceptor support 4, the susceptor 5, and the electrostatic chuck 11 are heated to a predetermined pressure (back pressure) with a heat transfer medium, for example, He gas, on the back surface of the wafer W that is the object to be processed. A gas passage 14 is formed for supply, and heat transfer is performed between the susceptor 5 and the wafer W via the heat transfer medium so that the wafer W is maintained at a predetermined temperature. .

  An annular focus ring 15 is disposed at the upper peripheral edge of the susceptor 5 so as to surround the wafer W placed on the electrostatic chuck 11. The focus ring 15 is made of an insulating material such as ceramics or quartz, and acts to improve etching uniformity.

  An upper electrode 21 is provided above the susceptor 5 so as to face the susceptor 5 in parallel. The upper electrode 21 is supported on the upper portion of the chamber 2 via an insulating material 22, constitutes a surface facing the susceptor 5, and has a large number of discharge holes 23, for example, an electrode plate 24 made of quartz, A conductive material that supports the electrode 24, for example, an electrode support 25 made of aluminum having an anodized aluminum surface is used. The interval between the susceptor 5 and the upper electrode 21 can be adjusted.

A gas introduction port 26 is provided at the center of the electrode support 25 in the upper electrode 21, and a gas supply pipe 27 is connected to the gas introduction port 26. Further, a valve is connected to the gas supply pipe 27. 28 and a mass flow controller 29 are connected to a processing gas supply source 30, and an etching gas for plasma etching is supplied from the processing gas supply source 30. In FIG. 3, only one processing gas supply source 30 is representatively illustrated, but a plurality of processing gas supply sources 30 are provided, for example, CHF ₃ , Ar, Cl ₂ , HBr, O _2. The gas is configured to be supplied into the chamber 2 by independently controlling the flow rate of each gas.

  An exhaust pipe 31 is connected to the bottom of the chamber 2, and an exhaust device 35 is connected to the exhaust pipe 31. The exhaust device 35 includes a vacuum pump such as a turbo molecular pump, and is configured so that the inside of the chamber 2 can be evacuated to a predetermined reduced pressure atmosphere, for example, a predetermined pressure of 1 Pa or less. Further, a gate valve 32 is provided on the side wall of the chamber 2 so that the wafer W is transferred to and from an adjacent load lock chamber (not shown) with the gate valve 32 opened. It has become.

  A first high frequency power supply 40 is connected to the upper electrode 21, and a matching unit 41 is provided on the feeder line. Further, a low pass filter (LPF) 42 is connected to the upper electrode 21. The first high-frequency power supply 40 has a frequency in the range of 50 to 150 MHz, and forms a high-density plasma in a preferable dissociated state in the chamber 2 by applying such a high frequency. And plasma processing under low-pressure conditions is possible. The frequency of the first high-frequency power supply 40 is preferably 50 to 80 MHz, and typically a condition of 60 MHz or its vicinity is adopted as shown in FIG.

  A second high frequency power supply 50 is connected to the susceptor 5 as the lower electrode, and a matching unit 51 is provided on the power supply line. The second high-frequency power supply 50 has a frequency in the range of several hundreds kHz to several tens of MHz. By applying power having a frequency in such a range, the wafer W is not damaged. Appropriate ion action can be provided. As the frequency of the second high frequency power supply 50, for example, a condition such as 13.56 MHz or 800 KHz is adopted as shown in FIG.

  Each component of the plasma etching apparatus 1 is connected to and controlled by a process controller 60 having a CPU. The process controller 60 includes a user interface 61 including a keyboard that allows a process manager to input commands to manage the plasma etching apparatus 1, a display that visualizes and displays the operating status of the plasma etching apparatus 1, and the like. It is connected.

  The process controller 60 stores a recipe in which a control program (software) for realizing various processes executed by the plasma etching apparatus 1 under the control of the process controller 60 and processing condition data are recorded. A storage unit 62 is connected.

  Then, if desired, an arbitrary recipe is called from the storage unit 62 by an instruction from the user interface 61 and is executed by the process controller 60, so that a desired process in the plasma processing apparatus 1 is performed under the control of the process controller 60. Is performed. In addition, recipes such as the control program and processing condition data may be stored in a computer-readable storage medium such as a CD-ROM, a hard disk, a flexible disk, a non-volatile memory, or the like. For example, it is possible to transmit the data from time to time via a dedicated line and use it online.

  Next, a process of forming the trench 120 as shown in FIG. 2 by etching the wafer W made of a silicon single crystal by the plasma etching apparatus 1 configured as described above will be described.

  First, the wafer W on which the silicon oxide film 102 and the silicon nitride film 103 are formed is loaded into the chamber 2 from a load lock chamber (not shown) with the gate valve 32 opened, and placed on the electrostatic chuck 11. The wafer W is electrostatically adsorbed on the electrostatic chuck 11 by applying a DC voltage from the DC power source 13.

Next, the gate valve 32 is closed, and the inside of the chamber 2 is evacuated to a predetermined vacuum level by the exhaust device 35. Thereafter, the valve 28 is opened, and, for example, CHF ₃ is supplied from the processing gas supply source 30 as a processing gas for the first plasma processing by the mass flow controller 29 at a predetermined flow rate, for example, 50 to 300 mL / min, preferably 150 to 250 mL / min. 3 is introduced into the hollow portion of the processing gas supply pipe 27, the gas introduction port 26, and the upper electrode 21, and the wafer W is applied to the wafer W through the discharge holes 23 of the electrode plate 24 as indicated by arrows in FIG. Dispense evenly.

  In the first plasma treatment, the pressure in the chamber 2 is maintained at a predetermined pressure, for example, about 1.3 to 13.3 Pa (10 to 100 mTorr), preferably 3.3 to 10 Pa (25 to 75 mTorr). The first high-frequency power source 40 to the upper electrode 21 is 100 to 700 W, preferably 200 to 400 W, and the second high-frequency power source 50 to the susceptor 5 as the lower electrode is 100 to 700 W, preferably 200 to 400 W. , And the processing gas is turned into plasma to deposit the deposit D in the groove 110 of the pattern formed on the wafer W. Although processing time is not specifically limited, For example, it can be 5-30 seconds suitably. As other conditions, for example, the temperature in the chamber may be 60 to 90 ° C. for the upper electrode 21, 50 to 70 ° C. for the side wall, and 20 to 80 ° C. for the susceptor 5 (wafer W).

Next, in the second plasma treatment, a trench 120 is formed in the silicon substrate 101. That is, the valve 28 is opened, as a gas for etching from the processing gas supply source 30, for example, a gas containing C1 ₂ and / or HBr, while adjusting to a predetermined flow ratio by a mass flow controller 29, the processing gas supply pipe 27, the gas introduction port 26 and the upper electrode 21 are introduced into the hollow portion, and are uniformly ejected onto the wafer W through the ejection holes 23 of the electrode plate 24 as indicated by arrows in FIG. Conditions such as processing pressure, high-frequency power, and processing temperature in the second plasma processing can be performed under the same conditions as in normal silicon trench etching.

  After the second plasma treatment is completed, element isolation is performed by performing a normal STI process, that is, embedding an oxide film and planarization by CMP.

Next, experimental results for confirming the effects of the present invention will be described.
First, a test sample was prepared as follows.
An SiO ₂ film (silicon oxide film 101) having a thickness of 5.5 nm is formed on the silicon substrate 101 by thermal oxidation, and Si film having a thickness of 60 nm is formed thereon by LPCVD (low pressure chemical vapor deposition). _{A 3} N ₄ film (silicon nitride film) was formed. An antireflection film (BARC) having a thickness of 60 nm was formed thereon, and a photoresist layer having a thickness of 166 nm was formed thereon. The photoresist layer was patterned by a photolithography technique, and the opening 110 was formed by etching the Si ₃ N ₄ film and the SiO ₂ film until the silicon substrate 101 was exposed using the photoresist layer as a mask. Next, after ashing the photoresist layer and the antireflection film with oxygen gas plasma, the natural oxide film formed on the exposed surface of the silicon substrate 101 in the groove 110 is removed by plasma treatment with HBr gas to form a bottom surface of the groove 110. A test sample in which the silicon substrate 101 was exposed was used.

  The first plasma treatment and the second plasma treatment were continuously performed on this test sample using the plasma etching apparatus 1 of FIG. 3 under the following conditions. Here, the influence on the roundness (curvature radius) of the shoulder of the trench 120 and the angle (taper angle) of the trench wall was examined by changing the time of the first plasma treatment and the treatment temperature. The results are shown in Table 1.

<First plasma processing condition>
Process gas: CHF _3, flow rate 200 mL / min (sccm)
Chamber pressure: 6.7 Pa (50 mTorr)
High frequency power: upper electrode 300W, lower electrode 300W
Gap between electrodes: 150mm
Processing time: 5 seconds, 7.5 seconds, or 10 seconds Back pressure: Center portion / edge portion of wafer W = 1333/1333 Pa (10/10 Torr)
Chamber temperature: upper electrode 80 ° C., sidewall 60 ° C., wafer W 40 ° C., 50 ° C. or 60 ° C.

<Second plasma processing condition>
As process gas, a gas containing C1 ₂ and / or HBr, was performed in accordance with a conventional etching conditions in STI. The chamber temperature was set to 80 ° C. for the upper electrode, 60 ° C. for the sidewall, and 40 ° C., 50 ° C. or 60 ° C. for the wafer W, as in the first plasma treatment.

  From Table 1, it can be seen that the roundness (curvature radius) of the shoulder 120a of the trench 120 formed in the silicon substrate 101 is highly dependent on temperature and processing time and can be controlled mainly by these conditions. It was also shown that the taper angle θ of the trench 120 can be controlled mainly by temperature.

  From the above results, it is understood that it is particularly advantageous to adjust the roundness of the shoulder 120a of the trench 120 according to the processing time of the first plasma processing step, and to adjust the taper angle θ of the trench 120 according to the temperature. In the first plasma processing, if the round shape size (curvature radius) is controlled by temperature, the control range of the taper angle θ is naturally limited when performing the second plasma processing at the same temperature. When the second plasma processing is performed at different temperatures, it is necessary to adjust the temperature of the lower electrode 5 before the second plasma processing, and time for that is required. On the other hand, if the roundness of the shoulder 120a of the trench 120 is adjusted by the processing time of the first plasma processing step and the taper angle θ of the trench 120 is adjusted by the temperature, the throughput is improved at a constant temperature. The degree of freedom in adjusting the taper angle θ can be increased. Thus, according to the present invention, the roundness of the shoulder 120a and the taper angle of the trench 120 can be simultaneously controlled while maintaining the temperature constant in the first and second plasma treatments.

As mentioned above, although embodiment of this invention was described, this invention is not restrict | limited to the said embodiment, A various deformation | transformation is possible.
For example, in the above embodiment, the capacitively coupled parallel plate type plasma etching apparatus that applies high frequency power to the upper electrode 21 and the susceptor 5 as the lower electrode, respectively, is used. For example, plasma etching that applies high frequency power only to the lower electrode An apparatus may be used.
In the above embodiment, the trench formation in the STI has been described as an example. However, the present invention is not limited to the STI as long as the purpose is to form a round shape on the upper end (shoulder) of the side wall of the recess by etching. It is.

BRIEF DESCRIPTION OF THE DRAWINGS Drawing which shows typically the structure of a wafer cross section in order to demonstrate the process example of one Embodiment of this invention. The figure which shows typically the structure of the wafer cross section in which the trench was formed. BRIEF DESCRIPTION OF THE DRAWINGS Drawing which shows the outline | summary of the plasma etching apparatus used for implementation of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Plasma etching apparatus 2; Chamber 60; Process controller 61; User interface 62; Memory | storage part 101; Silicon substrate 102; Silicon oxide film 103; Silicon nitride film 110; Groove part 120; Trench 120a; Shoulder part 120b;

Claims (13)

Etching is performed on an object to be processed having at least a layer to be etched and a patterned mask layer formed on the layer to be etched, and a recess corresponding to the pattern of the mask layer is formed in the layer to be etched. A plasma etching method,
A first plasma treatment step of forming a deposit on at least the layer to be etched in the vicinity of the boundary between the layer to be etched and the mask layer in the openings constituting the pattern in the mask layer;
After the first plasma treatment step, a second plasma treatment step of forming the recess by etching the etched layer;
Including
In the second plasma processing step, the corner portion at the upper end of the side wall constituting the concave portion is formed in a curved shape.   The plasma etching method according to claim 1, wherein the processing gas in the first plasma processing step is a gas containing hydrofluorocarbon. _2. The plasma etching method according to claim 1, wherein the processing gas in the first plasma processing step is a gas containing CHF ₃ , CH ₂ F _2, or CH ₃ F. ₃ .   The plasma etching method according to any one of claims 1 to 3, wherein a processing gas in the second plasma processing step is a halogen-containing gas. The plasma etching method according to claim 4, wherein the halogen-containing gas is a gas containing HBr, Cl ₂ , or both.   The plasma etching method according to any one of claims 1 to 5, wherein a processing time in the first plasma processing step is 3 seconds or more and 60 seconds or less.   The curvature radius of the corner of the upper end of the side wall that constitutes the recess is adjusted according to the processing time in the first plasma processing step, and the angle of the side wall that constitutes the recess depends on the processing temperature in the second plasma processing step. The plasma etching method according to claim 6, wherein the method is adjusted.   7. The curvature radius of the corner of the upper end of the side wall constituting the recess is adjusted by mixing a gas having an etching action with the processing gas in the first plasma processing step. 8. The plasma etching method according to 7.   The plasma etching method according to claim 6, wherein the plasma etching method is applied to trench etching in shallow trench isolation. At least a silicon substrate, a silicon oxide film formed on the silicon substrate, and a silicon nitride film formed on the silicon oxide film, the silicon oxide film and the silicon nitride film being a mask layer A plasma etching method for forming a trench corresponding to a pattern of the mask layer on the silicon substrate by performing etching on an object to be processed that has been patterned to form an opening,
Deposits are deposited on the silicon substrate at least in the vicinity of the boundary between the silicon substrate and the mask layer in the mask layer by the plasma of the first processing gas containing C, F, and H as constituent elements. A first plasma treatment step to be formed;
A second plasma processing step of forming the trench by etching the silicon substrate with a plasma of a second processing gas after the first plasma processing step;
Including
In the second plasma processing step, a corner portion at an upper end of a side wall constituting the trench is formed in a curved shape. A plasma source for generating plasma;
A processing container for partitioning a processing chamber for performing an etching process on an object to be processed by the plasma;
A support for placing the object to be processed in the processing container;
An exhaust means for decompressing the inside of the processing vessel;
Gas supply means for supplying gas into the processing vessel;
A controller that controls the plasma etching method according to any one of claims 1 to 10 to be performed;
A plasma etching apparatus comprising:   A control program which operates on a computer and controls the plasma processing apparatus so that the plasma etching method according to any one of claims 1 to 10 is performed at the time of execution. A computer storage medium storing a control program that runs on a computer,
The computer program is characterized in that, when executed, the control program controls the plasma processing apparatus so that the plasma etching method according to any one of claims 1 to 10 is performed. Medium.

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