US20110120648A1 - Apparatus and a method for controlling the depth of etching during alternating plasma etching of semiconductor substrates - Google Patents
Apparatus and a method for controlling the depth of etching during alternating plasma etching of semiconductor substrates Download PDFInfo
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- US20110120648A1 US20110120648A1 US13/019,351 US201113019351A US2011120648A1 US 20110120648 A1 US20110120648 A1 US 20110120648A1 US 201113019351 A US201113019351 A US 201113019351A US 2011120648 A1 US2011120648 A1 US 2011120648A1
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- 238000005530 etching Methods 0.000 title claims abstract description 86
- 239000000758 substrate Substances 0.000 title claims abstract description 54
- 238000000034 method Methods 0.000 title claims abstract description 51
- 238000001020 plasma etching Methods 0.000 title claims abstract description 10
- 239000004065 semiconductor Substances 0.000 title abstract description 11
- 238000002161 passivation Methods 0.000 claims description 14
- 230000008021 deposition Effects 0.000 claims description 4
- CPBQJMYROZQQJC-UHFFFAOYSA-N helium neon Chemical compound [He].[Ne] CPBQJMYROZQQJC-UHFFFAOYSA-N 0.000 claims description 3
- 230000009466 transformation Effects 0.000 abstract description 3
- 239000007789 gas Substances 0.000 description 17
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 16
- 229910052710 silicon Inorganic materials 0.000 description 16
- 239000010703 silicon Substances 0.000 description 16
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 13
- 239000010410 layer Substances 0.000 description 12
- 229910052681 coesite Inorganic materials 0.000 description 6
- 229910052906 cristobalite Inorganic materials 0.000 description 6
- 239000000377 silicon dioxide Substances 0.000 description 6
- 229910052682 stishovite Inorganic materials 0.000 description 6
- 229910052905 tridymite Inorganic materials 0.000 description 6
- 235000012431 wafers Nutrition 0.000 description 5
- 238000009434 installation Methods 0.000 description 4
- 238000005459 micromachining Methods 0.000 description 4
- 229910018503 SF6 Inorganic materials 0.000 description 3
- 229910004014 SiF4 Inorganic materials 0.000 description 3
- 230000003287 optical effect Effects 0.000 description 3
- ABTOQLMXBSRXSM-UHFFFAOYSA-N silicon tetrafluoride Chemical compound F[Si](F)(F)F ABTOQLMXBSRXSM-UHFFFAOYSA-N 0.000 description 3
- SFZCNBIFKDRMGX-UHFFFAOYSA-N sulfur hexafluoride Chemical compound FS(F)(F)(F)(F)F SFZCNBIFKDRMGX-UHFFFAOYSA-N 0.000 description 3
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 2
- 238000000708 deep reactive-ion etching Methods 0.000 description 2
- 229910052731 fluorine Inorganic materials 0.000 description 2
- 239000011737 fluorine Substances 0.000 description 2
- NBVXSUQYWXRMNV-UHFFFAOYSA-N fluoromethane Chemical compound FC NBVXSUQYWXRMNV-UHFFFAOYSA-N 0.000 description 2
- 238000003754 machining Methods 0.000 description 2
- 239000013307 optical fiber Substances 0.000 description 2
- 229920006254 polymer film Polymers 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 238000002310 reflectometry Methods 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- XPDWGBQVDMORPB-UHFFFAOYSA-N Fluoroform Chemical compound FC(F)F XPDWGBQVDMORPB-UHFFFAOYSA-N 0.000 description 1
- 229910004074 SiF6 Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000007717 exclusion Effects 0.000 description 1
- 238000005305 interferometry Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000004556 laser interferometry Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 229960000909 sulfur hexafluoride Drugs 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
Images
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/32—Gas-filled discharge tubes
- H01J37/32917—Plasma diagnostics
- H01J37/32935—Monitoring and controlling tubes by information coming from the object and/or discharge
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
- H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
- H01L21/3065—Plasma etching; Reactive-ion etching
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
- H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
- H01L21/3065—Plasma etching; Reactive-ion etching
- H01L21/30655—Plasma etching; Reactive-ion etching comprising alternated and repeated etching and passivation steps, e.g. Bosch process
Definitions
- the present invention relates to the field of micromachining semiconductor substrates to make components for microelectromechanical systems (MEMS) or for microoptical electromechanical systems (MOEMS).
- MEMS microelectromechanical systems
- MOEMS microoptical electromechanical systems
- the invention relates more particularly to controlling the depth of etching during micromachining of silicon by plasma using the alternating etching technique, and in particular the invention relates to the apparatus and to the method used.
- Integrated circuits are made in the bulk of semiconductor material wafers. Lines are reproduced on the surface of the wafer in a grid pattern so that the individual integrated circuits, known as “chips”, can easily be separated from one another. Once treatment of the wafer has been finished, it is cut up along the lines in order to separate the chips.
- One method consists in sending a light beam of uniform frequency, preferably a laser beam, onto a substrate for etching that comprises two distinct layers having different indices of refraction.
- the beam is reflected therefrom and picked up by a detector.
- a sudden change in the detected light intensity, due to the change in the index of refraction on passing from one layer to another marks the end of etching.
- Proposals have thus been made to use a method based on laser interferometry.
- a monochromatic beam generated by a laser is directed substantially perpendicularly onto a semitransparent layer for etching.
- the partially-reflected beam is picked up by a suitable photodetector.
- the beams coming from reflection on the interface between said layer and the substrate interfere so as to give a characteristic sinusoidal curve.
- the flattening in the curve indicates that the semitransparent layer has been consumed in full, and thus marks the end of the etching operation.
- the treatment chamber has two windows coupled to a spectrometer for observing the plasma.
- Each spectrometer delivers a signal based on the wavelength of a selected species in the radiation of the light-emitting discharge.
- the first window observing in a plane parallel to the surface of the substrate, provides a signal relating to variation in intensity during etching at a selected wavelength.
- the second window observing in a plane normal to the surface of the substrate, gives a signal containing information relating to the variation in the intensity of the selected wavelength and to the variation in the reflectivity of the layer of SiO2 which is redeposited in continuous manner during the treatment.
- a signal is obtained relating to the variation over time in the intensity of the surface reflectivity of the wafer, and thus relating to the thickness of the SiO 2 layer which depends thereon directly.
- Means enable the depth of the etching and the thickness of the SiO 2 layer to be deduced therefrom.
- Micromachining silicon using a plasma also known as deep reactive ion etching (DRIE) commonly makes use of an alternating etching technique which is characterized by alternating steps of removal and of deposition which follow one another very quickly. That method is described in particular in document U.S. Pat. No. 5,501, 893.
- the technique consists in hiding the silicon substrate in part by means of a mask, and in subjecting the hidden substrate to an alternating succession of etching steps using an etching gas plasma and of passivation steps using a passivation gas plasma.
- the etching gas plasma such as sulfur hexafluoride SF 6 makes cavities in those zones of the substrate that are not hidden by the mask.
- the passivation gas plasma such as a fluorocarbon gas, e.g. C 4 F 8 , deposits a protecting polymer film on the wall of the cavity.
- a fluorocarbon gas e.g. C 4 F 8
- the passivation gas plasma deposits a protecting polymer film on the wall of the cavity.
- the etching of the silicon that is obtained is, in fact, practically anisotropic, fast, and selective.
- the problem posed by the present invention is to improve the apparatus and the method for alternating etching of silicon by a succession of etching steps and of passivation steps in such a manner as to provide improved control over the depth to which a semiconductor substrate is etched.
- An object of the invention is to provide apparatus for controlling the end of a plasma etching operation on a substrate once the desired depth has been reached.
- Another object of the invention is to provide a method that makes it possible in certain and accurate manner to determine the end of the etching operation.
- the present invention provides apparatus for controlling the operation of plasma etching a semiconductor substrate by an alternating etching method, the apparatus comprising:
- the emitter means comprise a helium-neon laser generating a monochromatic signal having a wavelength of 632.8 nanometers (nm).
- the emitter means preferably also comprise a semireflecting mirror. The mirror enables the beam emitted by the laser towards the substrate to be reflected and allows the beam reflected by the substrate towards the detector to pass through.
- the second detector means comprise an interferometer.
- the first detector means comprise an emission spectrometer.
- the plane of the second window is substantially perpendicular to the plane of the first window.
- the invention also provides a method of controlling the operation of plasma etching the surface of a semiconductor substrate by the alternating etching method using the above apparatus, the method comprising the following steps:
- the substrate is of silicon and the species whose presence is detected during the material-removal step is a species of the SiF x type, such as SiF 4 , for example.
- the substrate is of silicon and the species whose presence is detected during the material-removal step is a species of the CF x type, such as CF 2 , for example.
- the present invention has the advantage of making it possible to obtain a signal which corresponds solely to those periods during which etching is actually taking place, and which consequently provides information that is directly usable.
- FIG. 1 is a diagram of etching apparatus in which the method of the present invention is implemented.
- FIG. 2 is a graph plotting the reconstituted signal as a function of time.
- the installation for micromachining semiconductor substrates comprises a sealed enclosure 1 shaped to receive and contain a semiconductor substrate 2 for etching.
- the substrate 2 e.g. a silicon wafer
- Vacuum generator means 5 connected to the process chamber 1 and comprising for example a primary pump and a secondary pump, serve to create and maintain a suitable vacuum inside the enclosure 1 .
- the substrate 2 is oriented in the chamber 1 in such a manner as to cause its surface 2 a for working to be visible. Facing the surface 2 a for machining, there are means for generating a plasma that is directed towards the surface 2 a for machining
- the installation includes means for selectively injecting gases into the chamber 1 , in particular etching gases and passivation gases.
- the plasma 6 contains electrically neutral active atoms such as atoms of fluorine, which propagate in all directions, and ions such as SF 5 + which are attracted to the negatively biased substrate 2 and which attack the silicon.
- a fluorocarbon gas such as CHF 3 , C 2 F 6 , C 2 F 4 , or C 4 F 8 is injected which causes a protective polymer film to be formed over the entire etched surface.
- the enclosure 1 includes a first quartz window 7 placed over a first wall 8 facing the surface to be etched 2 a so as to observe the surface to be etched 2 a along an axis 9 which is substantially perpendicular thereto, and a second window 10 disposed in a second wall 11 , in this case perpendicular to the wall 8 , in such a manner as to observe the plasma 6 along an axis 12 , in this case substantially parallel to the axis to be etched 2 a.
- the installation further comprises means 13 for generating a monochromatic optical signal, in particular a laser diode or preferably a helium-neon laser, for example.
- the light signal 14 emitted by the laser 13 is directed by means of a semireflecting mirror 15 towards the surface 2 a of the substrate 2 through the window 7 .
- the incident signal 14 a is reflected on the surface 2 a that is being etched, and the reflected signal 14 b which is practically totally reflected returns substantially along the same path in the opposite direction.
- the reflected signal 14 b is directed to detector means 16 such as an interferometer by means of an optical fiber, for example.
- the laser signal is emitted and detected throughout the entire duration of the operation of treating the substrate with alternating etching.
- the installation also includes means for observing the plasma 6 .
- the light signal 17 coming from observation of the plasma 6 through the window 10 is directed by means of an optical fiber, for example, to an emission spectrometer 18 which analyses the signal 17 in order to identify the presence of species coming from the reaction of the etching gas with the substrate 2 , and in particular the presence of SiF 4 in the event of SiF 6 being reacted with silicon.
- Signal transformation means 19 such as a computer, extract from the signal received by the detector 16 periods during which the spectrometer 18 detects the presence of species coming from the reaction of the etching gas with the substrate 2 , and in particular SiF 4 . This produces a reconstituted laser interferometer signal 20 as shown in FIG. 2 and which corresponds solely to the periods during which the substrate is being etched, to the exclusion of passivation periods 21 and possibly also depassivation periods.
- the reconstituted signal 20 is plotted as variation as a function in time in the ratio I 0 /I r where I 0 is the intensity of the signal 12 emitted by the laser, and I r is the intensity of the reflected signal 14 b received by the detector 16 .
- the computer 19 analyzes the signal 20 to determine the end of the etching operation.
- the substrate includes a layer of silicon Si placed over a fine buried layer of SiO 2
- the etching operation consists in totally etching the surface layer of silicon Si and stopping at the surface of the SiO 2 layer, then the signal 20 will flatten when the Si/SiO 2 interface is reached.
- the silicon substrate is uniform and if the etching operation consists in etching the silicon to a determined depth, it is then possible from the signal 20 to estimate the depth that has been etched and thus the almost instantaneous speed of etching V, by measuring the time t that elapses between two extrema, in application of the relationship:
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Plasma & Fusion (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Manufacturing & Machinery (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
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Abstract
The present invention provides apparatus for controlling the operation of plasma etching a semiconductor substrate by an alternating etching method, the apparatus comprising:
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- a process chamber (1) in which said substrate (2) is processed,
- means for generating a plasma (6);
- at least one first window (7) formed in a first wall (8) of said chamber (1) facing the surface (2 a) to be etched of said substrate (2);
- at least one second window (10) formed in a second wall (11) of said chamber (1) lying in a plane different from said first wall (8);
- first means (18) coupled to said second window (10) to detect a light signal (17) relating to a selected wavelength emitted by said plasma (6);
- means (13, 15) for emitting a monochromatic light signal (14) through said first window (7) towards said surface (2 a) in a direction (9) substantially perpendicular to said surface (2 a) in such a manner that said incident signal (14 a) is reflected on said surface (2 a);
- second means (16) for detecting said reflected signal (14 b); and
- transformation means (19) coupled to said first means (18) and to said second means (16) to transform the signal detected by said second means (16) as a function of the signal detected by said first means (18).
Description
- This is a Divisional Application of U.S. patent application Ser. No. 11/319,506, filed Dec. 29, 2005, entitled “APPARATUS AND A METHOD FOR CONTROLLING THE DEPTH OF ETCHING DURING ALTERNATING PLASMA ETCHING OF SEMICONDUCTOR SUBSTRATES” (Attorney Docket No. TEGL-01255US0) and which claims priority to French Patent No. FR 0453276 filed Dec. 31, 2004. All of the aforementioned patent and patent applications are incorporated herein by reference in their entireties.
- The present invention relates to the field of micromachining semiconductor substrates to make components for microelectromechanical systems (MEMS) or for microoptical electromechanical systems (MOEMS). The invention relates more particularly to controlling the depth of etching during micromachining of silicon by plasma using the alternating etching technique, and in particular the invention relates to the apparatus and to the method used.
- Integrated circuits are made in the bulk of semiconductor material wafers. Lines are reproduced on the surface of the wafer in a grid pattern so that the individual integrated circuits, known as “chips”, can easily be separated from one another. Once treatment of the wafer has been finished, it is cut up along the lines in order to separate the chips.
- Most applications using components etched on silicon substrates require the etched pattern to be of very great precision, in particular in terms of depth. It is therefore necessary to control depth very precisely in order to determine without ambiguity when the etching operation has come to an end. The most widespread method for detecting the end of the etching operation are methods that rely on optical techniques.
- One method consists in sending a light beam of uniform frequency, preferably a laser beam, onto a substrate for etching that comprises two distinct layers having different indices of refraction. The beam is reflected therefrom and picked up by a detector. A sudden change in the detected light intensity, due to the change in the index of refraction on passing from one layer to another marks the end of etching.
- Proposals have thus been made to use a method based on laser interferometry. In that method, a monochromatic beam generated by a laser is directed substantially perpendicularly onto a semitransparent layer for etching. The partially-reflected beam is picked up by a suitable photodetector. The beams coming from reflection on the interface between said layer and the substrate interfere so as to give a characteristic sinusoidal curve. The interference phenomenon is controlled by the relationship d=λ/2n, where d is the thickness of the layer to be etched, is the wavelength of the beam, and n is the index of refraction in the propagation medium (n=1 in a vacuum). The flattening in the curve indicates that the semitransparent layer has been consumed in full, and thus marks the end of the etching operation.
- Another document describes a device for controlling the operation of plasma etching a semiconductor substrate. The treatment chamber has two windows coupled to a spectrometer for observing the plasma. Each spectrometer delivers a signal based on the wavelength of a selected species in the radiation of the light-emitting discharge. The first window, observing in a plane parallel to the surface of the substrate, provides a signal relating to variation in intensity during etching at a selected wavelength. The second window, observing in a plane normal to the surface of the substrate, gives a signal containing information relating to the variation in the intensity of the selected wavelength and to the variation in the reflectivity of the layer of SiO2 which is redeposited in continuous manner during the treatment. By interferometry, a signal is obtained relating to the variation over time in the intensity of the surface reflectivity of the wafer, and thus relating to the thickness of the SiO2 layer which depends thereon directly. Means enable the depth of the etching and the thickness of the SiO2 layer to be deduced therefrom.
- Micromachining silicon using a plasma, also known as deep reactive ion etching (DRIE), commonly makes use of an alternating etching technique which is characterized by alternating steps of removal and of deposition which follow one another very quickly. That method is described in particular in document U.S. Pat. No. 5,501, 893. The technique consists in hiding the silicon substrate in part by means of a mask, and in subjecting the hidden substrate to an alternating succession of etching steps using an etching gas plasma and of passivation steps using a passivation gas plasma. During each etching step, the etching gas plasma such as sulfur hexafluoride SF6 makes cavities in those zones of the substrate that are not hidden by the mask. During each passivation step, the passivation gas plasma, such as a fluorocarbon gas, e.g. C4F8, deposits a protecting polymer film on the wall of the cavity. Each of the etching and passivation steps has a duration that is very short, a few seconds, and the passivation prevents the etching gas plasma from etching the side wall of the cavity during the subsequent etching step. As a result, etching takes place selectively in the bottom of the cavity after the etching gas plasma has removed the film of protective polymer at the bottom of the cavity. Thus, in spite of the isotropic nature of the way in which silicon is etched by a plasma of an etching gas, such as a fluorine containing gas, the etching of the silicon that is obtained is, in fact, practically anisotropic, fast, and selective.
- The methods of using optical techniques to detect the end of the etching operation in prior art methods are not suitable for use with the alternating etching method since the information provided is disturbed by the alternation, and is therefore unusable.
- The problem posed by the present invention is to improve the apparatus and the method for alternating etching of silicon by a succession of etching steps and of passivation steps in such a manner as to provide improved control over the depth to which a semiconductor substrate is etched.
- An object of the invention is to provide apparatus for controlling the end of a plasma etching operation on a substrate once the desired depth has been reached.
- Another object of the invention is to provide a method that makes it possible in certain and accurate manner to determine the end of the etching operation.
- The present invention provides apparatus for controlling the operation of plasma etching a semiconductor substrate by an alternating etching method, the apparatus comprising:
-
- a process chamber in which said substrate is processed;
- means for generating a plasma;
- at least one first window formed in a first wall of said chamber facing the surface to be etched of said substrate;
- at least one second window formed in a second wall of said chamber lying in a plane different from said first wall;
- first means coupled to said second window to detect a light signal relating to a selected wavelength emitted by said plasma;
- means for emitting a monochromatic light signal through said first window towards said surface in a direction substantially perpendicular to said surface in such a manner that said incident signal is reflected on said surface;
- second means for detecting said reflected signal; and
- transformation means coupled to said first means and to said second means to transform the signal detected by said second means as a function of the signal detected by said first means.
- In a first embodiment of the invention, the emitter means comprise a helium-neon laser generating a monochromatic signal having a wavelength of 632.8 nanometers (nm). The emitter means preferably also comprise a semireflecting mirror. The mirror enables the beam emitted by the laser towards the substrate to be reflected and allows the beam reflected by the substrate towards the detector to pass through.
- In a second embodiment, the second detector means comprise an interferometer.
- In a third embodiment, the first detector means comprise an emission spectrometer.
- In a fourth embodiment, the plane of the second window is substantially perpendicular to the plane of the first window.
- The invention also provides a method of controlling the operation of plasma etching the surface of a semiconductor substrate by the alternating etching method using the above apparatus, the method comprising the following steps:
-
- generating a monochromatic signal;
- sending said signal to the substrate in a direction substantially perpendicular to the surface to be etched;
- detecting said signal reflected on said substrate;
- detecting a signal associated with the presence in the plasma of a species stemming from the reaction of the etching gas with said substrate; and
- extracting from said reflected signal those portions of the signal that corresponds to the presence of said species in order to obtain a curve representative of etching steps alone.
- In an implementation of the invention, the substrate is of silicon and the species whose presence is detected during the material-removal step is a species of the SiFx type, such as SiF4, for example.
- In another implementation of the invention, the substrate is of silicon and the species whose presence is detected during the material-removal step is a species of the CFx type, such as CF2, for example.
- The present invention has the advantage of making it possible to obtain a signal which corresponds solely to those periods during which etching is actually taking place, and which consequently provides information that is directly usable.
- Other characteristics and advantages of the present invention appear on reading the following description of an embodiment that is naturally given by way of non-limiting illustration, and from the accompanying drawing, in which:
-
FIG. 1 is a diagram of etching apparatus in which the method of the present invention is implemented; and -
FIG. 2 is a graph plotting the reconstituted signal as a function of time. - In the embodiment shown in
FIG. 1 , the installation for micromachining semiconductor substrates comprises a sealedenclosure 1 shaped to receive and contain a semiconductor substrate 2 for etching. - In conventional manner, the substrate 2, e.g. a silicon wafer, is secured on a support that is electrically biased by bias means 4 to a potential that is negative relative to ground. Vacuum generator means 5, connected to the
process chamber 1 and comprising for example a primary pump and a secondary pump, serve to create and maintain a suitable vacuum inside theenclosure 1. The substrate 2 is oriented in thechamber 1 in such a manner as to cause itssurface 2 a for working to be visible. Facing thesurface 2 a for machining, there are means for generating a plasma that is directed towards thesurface 2 a for machining The installation includes means for selectively injecting gases into thechamber 1, in particular etching gases and passivation gases. During the etching step, SF6 is introduced as the etching gas, for example, theplasma 6 contains electrically neutral active atoms such as atoms of fluorine, which propagate in all directions, and ions such as SF5 + which are attracted to the negatively biased substrate 2 and which attack the silicon. During the passivation steps, a fluorocarbon gas such as CHF3, C2F6, C2F4, or C4F8 is injected which causes a protective polymer film to be formed over the entire etched surface. - In the present invention, the
enclosure 1 includes afirst quartz window 7 placed over afirst wall 8 facing the surface to be etched 2 a so as to observe the surface to be etched 2 a along anaxis 9 which is substantially perpendicular thereto, and asecond window 10 disposed in asecond wall 11, in this case perpendicular to thewall 8, in such a manner as to observe theplasma 6 along anaxis 12, in this case substantially parallel to the axis to be etched 2 a. - According to the invention, the installation further comprises means 13 for generating a monochromatic optical signal, in particular a laser diode or preferably a helium-neon laser, for example. The
light signal 14 emitted by thelaser 13 is directed by means of asemireflecting mirror 15 towards thesurface 2 a of the substrate 2 through thewindow 7. The incident signal 14 a is reflected on thesurface 2 a that is being etched, and the reflectedsignal 14 b which is practically totally reflected returns substantially along the same path in the opposite direction. After passing through thewindow 7, and then through thesemireflecting mirror 15, the reflectedsignal 14 b is directed to detector means 16 such as an interferometer by means of an optical fiber, for example. The laser signal is emitted and detected throughout the entire duration of the operation of treating the substrate with alternating etching. - According to the invention, the installation also includes means for observing the
plasma 6. Thelight signal 17 coming from observation of theplasma 6 through thewindow 10 is directed by means of an optical fiber, for example, to anemission spectrometer 18 which analyses thesignal 17 in order to identify the presence of species coming from the reaction of the etching gas with the substrate 2, and in particular the presence of SiF4 in the event of SiF6 being reacted with silicon. - Signal transformation means 19, such as a computer, extract from the signal received by the
detector 16 periods during which thespectrometer 18 detects the presence of species coming from the reaction of the etching gas with the substrate 2, and in particular SiF4. This produces a reconstitutedlaser interferometer signal 20 as shown inFIG. 2 and which corresponds solely to the periods during which the substrate is being etched, to the exclusion ofpassivation periods 21 and possibly also depassivation periods. - In
FIG. 2 , thereconstituted signal 20 is plotted as variation as a function in time in the ratio I0/Ir where I0 is the intensity of thesignal 12 emitted by the laser, and Ir is the intensity of the reflectedsignal 14 b received by thedetector 16. The distance d is a function of the wavelength λ of the laser and of the index of refraction n of the propagation medium (in this case a vacuum, so n=1), where d=λ/2n and represents the thickness of the laser to be etched. Thecomputer 19 analyzes thesignal 20 to determine the end of the etching operation. - For example, if the substrate includes a layer of silicon Si placed over a fine buried layer of SiO2, and if the etching operation consists in totally etching the surface layer of silicon Si and stopping at the surface of the SiO2 layer, then the
signal 20 will flatten when the Si/SiO2 interface is reached. - If the silicon substrate is uniform and if the etching operation consists in etching the silicon to a determined depth, it is then possible from the
signal 20 to estimate the depth that has been etched and thus the almost instantaneous speed of etching V, by measuring the time t that elapses between two extrema, in application of the relationship: -
V i =d/t=λ/2nt - The present invention is not restricted to the embodiments described explicitly above, but naturally including any variants and generalizations that are within the competence of the person skilled in the art.
Claims (20)
1. A plasma etching reactor for etching a substrate by an alternating etching process, which comprises an etching portion and a deposition portion, the reactor comprising:
a process chamber;
a plasma source to form a plasma in the process chamber;
a first detector for receiving a reflected signal reflected from the substrate which is representative of the alternating etching process;
a second detector for detecting an etch signal indicative of the etching portion of the alternating etching process; and
a controller coupled to the first and second detectors, the controller receiving simultaneously the reflected signal and the etch signal and using the etch signal to transform the reflected signal as a function of the etch signal.
2. A reactor as in claim 1 further comprising a light source for emitting a light signal towards the substrate surface in a direction substantially perpendicular to the surface, wherein the light signal is reflected from the substrate surface to be detected by the first detector.
3. A reactor as in claim 1 , wherein the second detector detects at least one of a light signal relating to a selected wavelength emitted by the plasma, and a signal associated with the presence in the plasma of a species stemming from the reaction of an etching gas with said substrate.
4. A reactor as in claim 1 , wherein the controller transforms the reflected signal, which is representative of the alternating etching process, in order to obtain a curve representative of etching steps alone.
5. A reactor as in claim 1 , wherein the transformed reflected signal provides information regarding at least one of an etch rate and an end of the alternating etching process.
6. A plasma etching reactor for etching a substrate by an alternating etching process, which comprises an etching portion and a deposition portion, the reactor comprising:
a process chamber;
a plasma source to form a plasma in the process chamber;
a monochromatic laser for sending a photon beam to the substrate in such a manner that the photon beam is reflected on the substrate surface;
a first detector for detecting the reflected signal which is representative of the alternating etching process;
a second detector for detecting an emission signal associated with the presence in the plasma of a species stemming from the reaction of an etching gas with the substrate; and
a controller coupled to the first and second detectors, the controller receiving simultaneously the reflected signal and the emission signal and using the emission signal to extract from the reflected signal a signal representative of the etching portion within the alternating etching process.
7. A reactor as in claim 6 , wherein the second detector detects plasma species of the type SiFx or CFx.
8. A reactor as in claim 6 , wherein the controller extracting from said reflected signal those portions of the signal that correspond to the presence of said species in order to obtain a curve representative of etching steps alone.
9. A reactor as in claim 6 , wherein extracting a signal comprises retrieving a portion of the signal associated with the time that the second signal shows the etching process.
10. A reactor as in claim 6 , wherein the extracted signal provides information regarding at least one of an etch rate and an end of the etching process.
11. A plasma etching reactor for etching a substrate by an alternating etching process, which comprises an etching portion using an etching gas and a deposition portion, the reactor comprising:
a process chamber;
a plasma source to form a plasma in the process chamber;
an interferometer for sending and receiving an interferometer signal reflected from the substrate which is representative of the alternating etching process;
an emission spectrometer for receiving an emission signal associated with the presence in the plasma of a species stemming from the reaction of the etching gas with the substrate; and
a controller coupled to the interferometer and the emission spectrometer, the controller receiving simultaneously the interferometer signal and the emission signal and using the emission signal to extract from the interferometer signal a signal representative of the etching portion within the alternating etching process,
wherein extracting a signal comprises retrieving a portion of the interferometer signal associated with the time that the interferometer signal shows the etching process.
12. A reactor as in claim 11 wherein the process chamber comprises a first window formed in a first wall of the chamber facing the substrate surface to be etched, and wherein the interferometer is coupled to the first window to send and receive the interferometer signal.
13. A reactor as in claim 12 wherein the process chamber comprises a second window formed in a second wall of the chamber lying in a plane different from the first wall, and wherein the emission spectrometer is coupled to the second window to detect the emission signal.
14. A reactor as in claim 13 wherein the plane of the second window is substantially perpendicular to the plane of the first window.
15. A reactor as in claim 11 wherein the interferometer comprises at least one of a monochromatic laser, a helium-neon laser, a laser diode, and a semireflecting mirror.
16. A reactor as in claim 11 wherein the emission spectrometer detects at least one of a light signal relating to a selected wavelength emitted by the plasma, and a signal associated with the presence in the plasma of a species stemming from the reaction of the etching gas with the substrate.
17. A reactor as in claim 11 wherein the emission spectrometer detects plasma species of the type SiFx or CFx.
18. A reactor as in claim 11 further comprising
an etching gas source, and means for controlling the etching flow rate to govern the introduction of etching gas into the plasma source;
a passivation gas source, and means for controlling the passivation flow rate for governing the introduction of passivation gas into the plasma source; and
a control device adapted to cause the etching gas flow rate control means and the passivation gas flow rate control means to operate in alternation.
19. A reactor as in claim 11 wherein the controller extracting from the reflected signal those portions of the emission signal in order to obtain a curve representative of etching steps alone.
20. A reactor as in claim 11 wherein the extracted signal provides information regarding at least one of an etch rate and an end of the etching process.
Priority Applications (1)
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US13/019,351 US20110120648A1 (en) | 2004-12-31 | 2011-02-02 | Apparatus and a method for controlling the depth of etching during alternating plasma etching of semiconductor substrates |
Applications Claiming Priority (4)
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FR0453276 | 2004-12-31 | ||
FR0453276A FR2880470B1 (en) | 2004-12-31 | 2004-12-31 | DEVICE AND METHOD FOR CONTROLLING THE ETCH DEPTH DURING PLASMA ALTERNATE ETCHING OF SEMICONDUCTOR SUBSTRATES |
US11/319,506 US7892980B2 (en) | 2004-12-31 | 2005-12-29 | Apparatus and a method for controlling the depth of etching during alternating plasma etching of semiconductor substrates |
US13/019,351 US20110120648A1 (en) | 2004-12-31 | 2011-02-02 | Apparatus and a method for controlling the depth of etching during alternating plasma etching of semiconductor substrates |
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US11/319,506 Division US7892980B2 (en) | 2004-12-31 | 2005-12-29 | Apparatus and a method for controlling the depth of etching during alternating plasma etching of semiconductor substrates |
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US20110120648A1 true US20110120648A1 (en) | 2011-05-26 |
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US13/019,351 Abandoned US20110120648A1 (en) | 2004-12-31 | 2011-02-02 | Apparatus and a method for controlling the depth of etching during alternating plasma etching of semiconductor substrates |
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EP (1) | EP1677338B1 (en) |
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US9658106B2 (en) * | 2014-05-05 | 2017-05-23 | Tokyo Electron Limited | Plasma processing apparatus and measurement method |
US9640371B2 (en) | 2014-10-20 | 2017-05-02 | Lam Research Corporation | System and method for detecting a process point in multi-mode pulse processes |
JP6603586B2 (en) * | 2016-01-19 | 2019-11-06 | 東京エレクトロン株式会社 | Plasma processing method and plasma processing apparatus |
US10300551B2 (en) * | 2016-11-14 | 2019-05-28 | Matthew Fagan | Metal analyzing plasma CNC cutting machine and associated methods |
RU2686579C1 (en) * | 2018-08-16 | 2019-04-29 | Федеральное государственное бюджетное учреждение науки Институт радиотехники и электроники им. В.А. Котельникова Российской академии наук | Method of determining plasma etching parameters |
CN112388155B (en) * | 2020-12-01 | 2022-03-29 | 强一半导体(苏州)有限公司 | MEMS probe laser etching device |
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US6406924B1 (en) * | 1998-04-17 | 2002-06-18 | Applied Materials, Inc. | Endpoint detection in the fabrication of electronic devices |
US6720268B1 (en) * | 1999-04-30 | 2004-04-13 | Robert Bosch Gmbh | Method for anisotropic plasma etching of semiconductors |
US20040238489A1 (en) * | 2003-05-09 | 2004-12-02 | David Johnson | Envelope follower end point detection in time division multiplexed processes |
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US4927485A (en) * | 1988-07-28 | 1990-05-22 | Applied Materials, Inc. | Laser interferometer system for monitoring and controlling IC processing |
DE19730644C1 (en) * | 1997-07-17 | 1998-11-19 | Bosch Gmbh Robert | Detecting material transition in semiconductor structure |
US6390019B1 (en) * | 1998-06-11 | 2002-05-21 | Applied Materials, Inc. | Chamber having improved process monitoring window |
US6526355B1 (en) | 2000-03-30 | 2003-02-25 | Lam Research Corporation | Integrated full wavelength spectrometer for wafer processing |
US6977184B1 (en) * | 2001-10-31 | 2005-12-20 | Lam Research Corporation | Method and apparatus for nitride spacer etch process implementing in situ interferometry endpoint detection and non-interferometry endpoint monitoring |
US20040097077A1 (en) * | 2002-11-15 | 2004-05-20 | Applied Materials, Inc. | Method and apparatus for etching a deep trench |
US20040200574A1 (en) * | 2003-04-11 | 2004-10-14 | Applied Materials, Inc. | Method for controlling a process for fabricating integrated devices |
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2004
- 2004-12-31 FR FR0453276A patent/FR2880470B1/en not_active Expired - Fee Related
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2005
- 2005-11-25 EP EP05111324.9A patent/EP1677338B1/en not_active Not-in-force
- 2005-11-30 WO PCT/FR2005/051011 patent/WO2006072717A1/en not_active Application Discontinuation
- 2005-12-29 US US11/319,506 patent/US7892980B2/en active Active
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2011
- 2011-02-02 US US13/019,351 patent/US20110120648A1/en not_active Abandoned
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
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US6406924B1 (en) * | 1998-04-17 | 2002-06-18 | Applied Materials, Inc. | Endpoint detection in the fabrication of electronic devices |
US6720268B1 (en) * | 1999-04-30 | 2004-04-13 | Robert Bosch Gmbh | Method for anisotropic plasma etching of semiconductors |
US20040238489A1 (en) * | 2003-05-09 | 2004-12-02 | David Johnson | Envelope follower end point detection in time division multiplexed processes |
Also Published As
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FR2880470B1 (en) | 2007-04-20 |
US7892980B2 (en) | 2011-02-22 |
FR2880470A1 (en) | 2006-07-07 |
EP1677338A1 (en) | 2006-07-05 |
US20060175010A1 (en) | 2006-08-10 |
EP1677338B1 (en) | 2016-07-27 |
WO2006072717A1 (en) | 2006-07-13 |
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