Source: http://www.google.com/patents/US7981700?dq=7,403,220
Timestamp: 2017-07-28 01:15:14
Document Index: 475407817

Matched Legal Cases: ['Application No. 2003', 'art 150', 'art 152', 'art 150', 'art 152', 'application No. 06714039', 'application No. 10']

Patent US7981700 - Semiconductor oxidation apparatus and method of producing semiconductor element - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA semiconductor oxidation apparatus is provided with a sealable oxidation chamber defined by walls, a base provided within the oxidation chamber and configured to support a semiconductor sample, a supply part configured to supply water vapor into the oxidation chamber to oxidize a specific portion of...http://www.google.com/patents/US7981700?utm_source=gb-gplus-sharePatent US7981700 - Semiconductor oxidation apparatus and method of producing semiconductor elementAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS7981700 B2Publication typeGrantApplication numberUS 10/592,213PCT numberPCT/JP2006/302898Publication dateJul 19, 2011Filing dateFeb 13, 2006Priority dateFeb 15, 2005Fee statusPaidAlso published asUS20080233017Publication number10592213, 592213, PCT/2006/302898, PCT/JP/2006/302898, PCT/JP/6/302898, PCT/JP2006/302898, PCT/JP2006302898, PCT/JP6/302898, PCT/JP6302898, US 7981700 B2, US 7981700B2, US-B2-7981700, US7981700 B2, US7981700B2InventorsShunichi Sato, Naoto Jikutani, Akihiro Itoh, Shinya Umemoto, Yoshiaki Zenno, Takatoshi YamamotoOriginal AssigneeRicoh Company, Ltd.Export CitationBiBTeX, EndNote, RefManPatent Citations (10), Non-Patent Citations (5), Referenced by (9), Classifications (22), Legal Events (2) External Links: USPTO, USPTO Assignment, EspacenetSemiconductor oxidation apparatus and method of producing semiconductor element
US 7981700 B2Abstract
1. A method for producing a semiconductor element, comprising:
placing within a water vapor atmosphere a semiconductor sample that includes a mesa having a semiconductor layer including Al and As;
forming a current constricting part and a current injecting part that is surrounded by the current constricting part in the semiconductor layer by oxidizing the semiconductor layer from a peripheral end of the semiconductor layer appearing at an outer peripheral side surface of the mesa towards an inner radial direction so as to leave a central portion of the semiconductor layer non-oxidized;
interrupting an oxidation process at least once during oxidation of the semiconductor layer; and
monitoring an oxidation rate of the semiconductor layer while the oxidation process is interrupted; and
exhausting an atmosphere gas within the oxidation chamber by vacuum while the oxidation process is interrupted,
moving the semiconductor sample within an oxidation chamber to a position where the mesa is adjacent to a monitoring part provided outside the oxidation chamber via a monitoring window of the oxidation chamber while the oxidation process is interrupted; and
obtaining the oxidation rate based on a size of the current constricting part or the current injecting part that is monitored by the monitoring part.
obtaining an amount of additional oxidation that is to be made based on the oxidation rate; and
additionally oxidizing the semiconductor layer by the amount of additional oxidation.
3. A method for producing a semiconductor element, comprising:
interrupting an oxidation process at least once during oxidation of the semiconductor layer;
spraying or blasting an inert gas onto the semiconductor sample within the oxidation chamber while the oxidation process is interrupted,
utilizing the semiconductor element to form a vertical-cavity surface-emitting laser (VCSEL).
5. A method for producing a semiconductor element, comprising:
supplying an inert gas at a low temperature onto the semiconductor sample while the semiconductor sample is within an oxidation chamber while the oxidation process is interrupted, to replace the water vapor atmosphere within the oxidation chamber with the inert gas and to cool the semiconductor sample.
determining said predetermined timing by subtracting a predetermined amount from a total required oxidation time. Description
A semiconductor oxidation apparatus satisfying such needs is proposed in Zenno et al., “Development of New Oxidation Apparatus For Manufacturing Surface-Emitting Lasers”, Optical Alliance, pp. 42-46, April 2004. FIG. 1 shows a general structure of this proposed semiconductor oxidation apparatus. A semiconductor oxidation apparatus 1010 shown in FIG. 1 has a sealable container (or oxidation chamber) 1012, and a heating stage 1016 that has a built-in heater is provided in a chamber interior 1014 of this oxidation chamber 1012. A substrate holder 1018 is provided on the heating stage 1016, and a semiconductor sample (or semiconductor substrate) 1020 is placed on the substrate holder 1018. The oxidation chamber 1012 is also provided with an inlet pipe 1022 for supplying an oxidizing atmosphere including vapor into the chamber interior 1014, and an exhaust pipe 1024 for exhausting the oxidizing atmosphere within the chamber interior 1014 after an oxidation process ends. According to the semiconductor oxidation apparatus 1010 having such a structure, it is possible to uniformly oxidize the semiconductor sample 1020 with a relatively good reproducibility. However, the amount of oxidation of the semiconductor sample 1020 is affected by inconsistencies among the lots, such as the composition and the film thickness after the crystal growth in a semiconductor film forming apparatus. Particularly in the case of a semiconductor layer including Al and As, the film thickness and the AlAs composition are extremely sensitive to the oxidation temperature and the like as described in Choquette et al., “Advances in Selective Wet Oxidation of AlGaAs Alloys”, IEEE Journal of Selected Topics in Quantum Electronics, Vol. 3, No. 3, pp. 916-926, June 1997, and are also affected by the thickness of a natural oxidation layer that is formed on a side surface of a non-oxidized layer of the semiconductor sample immediately prior to the oxidation process. As a result, the size of the current constricting part causes the inconsistency in the oscillation characteristic such as the optical output, and the yield deteriorates. Particularly in the case of a single-mode element in which the absolute value of the area of the current constricting part is small compared to that of a multi-mode element, the effects of the inconsistency in the amount of oxidation on the inconsistency of the element characteristics are extremely large, and if the area of the current constricting part becomes large the element that should originally behave as a single-mode element may behave like a multi-mode element.
In order to solve the problems described above, methods of monitoring the amount of oxidation during the oxidation process have been proposed in Feld et al., “In Situ Optical Monitoring of AlAs Wet Oxidation Using a Novel Low-Temperature Low-Pressure Steam Furnace Design”, IEEE Photonics Technology Letters, Vol. 10, No. 2, pp. 197-199, February 1998 and a Japanese Laid-Open Patent Application No. 2003-179309. According to the proposed methods, a semiconductor sample 1020 during the oxidation process is monitored by a microscope 1028 via a monitoring window 1026 as shown in FIG. 2. The oxidation distance or the area of the non-oxidized region (oxidation rate) is estimated from the contrast between the oxidized region and the non-oxidized region that are monitored by the microscope 1028, and the amount of oxidation is thereafter controlled based on the estimated oxidation distance or the area of the oxidation rate. But normally, the mesa diameter of the VCSEL is approximately 10 μm to approximately 50 μm, and the magnification of the microscope 1028 must be set to approximately 1000 times in order to strictly control the diameter of the current constricting part. In addition, in order to match the focal point of the microscope 1028 on the mesa, a distance L1 between the semiconductor sample 1020 and the monitoring window 1026 and a distance L2 between the monitoring window 1026 and the microscope 1028 must be set short as possible. However, if the distance L1 between the semiconductor sample 1020 and the monitoring window 1026 during the oxidation process is set short, local inconsistencies are generated in the vapor density distribution on the semiconductor sample 1020 and the temperature distribution on the semiconductor sample 1020, to thereby generate an in-plane distribution of the amount of oxidation and cause a deterioration in the yield. On the other hand, if the distance L2 between the monitoring window 1026 and the microscope 1028 is set short, the index of refraction of the monitoring window 1026 may change due to the heat generated from the heater, and the optical elements such as a lens assembled in the microscope 1028 may undergo a thermal deformation and generate a shift in the focal point, to thereby deteriorate the measuring accuracy.
As shown in FIGS. 5B and 8, the non-oxidized region 142 having the predetermined size and the oxidized region 140 surrounding the periphery of the non-oxidized region 142 are formed on the mesa 126 after the secondary oxidation process #30 ends. The non-oxidized region 142 and the oxidized region 140 respectively become a current injecting part 150 and a current constricting part 152. The semiconductor sample 20 that is formed with the current injecting part 150 and the current constricting part 152 is thereafter subjected to the necessary thin-film forming process, to form a VCSEL 160 shown in FIG. 9. This VCSEL 160 includes an insulator layer 154 made of SiO2 or the like, an insulator layer 156 made of a polyimide or the like, and a p-electrode 158.
In order to carry out an origin restoring step, it is preferable to use for the motor 32 that rotates the base 16 a servo motor having an encoder provided with an origin position (Z-phase). More particularly, a description will be given of the origin restoring step using the Z-phase of the servo motor. Suppose that the focal point of the microscope 44 (that is, the camera) exists at a position (r, θ) moved by a predetermined distance (x0, y0) in the X and Y directions from a center (origin of the XY coordinate system) of the driving shaft 30 as shown in FIG. 11, that the evaluation target mesa 126 is located at this camera focal point, and that the servo motor is stopped in a state where a predetermined number of pulses have been output from the Z-phase output at a time when the primary oxidation process or the secondary oxidation process starts. In order to simplify matters for the sake of convenience, it is assumed that the predetermined number of pulses is zero. Under these conditions, suppose that the evaluation target mesa 126 has stopped at a coordinate (r, θ+θ′) moved by an angle θ′ from the camera focal point at the time when the primary or secondary oxidation process ends. In this case, the control apparatus 102 stores a number Nθ of pulses from a time when the Z-phase of the servo motor is output to a time when the rotation thereof stops. The number Nθ of pulses corresponds to the moved angle θ″. Accordingly, in the origin restoring step, the control apparatus 102 calculates the moved angle θ′ from the number Nθ of pulses output from the servo motor, and calculates an angle (360°-θ′) required to rotate and restore the rotary shaft of the servo motor to the angular position at the time prior to the oxidation process and a number N(360°-θ) of pulses corresponding to the angle (360°-θ′). In addition, the control apparatus 102 rotates the rotary shaft of the servo motor until the number N(360°-θ) of pulses is output from the servo motor, so as to move the evaluation target mesa 126 to within a camera field (or field of view) 134. Therefore, the amount of oxidation after the primary oxidation process and the secondary oxidation process can be evaluated with respect to the same mesa 126.
FIG. 13 is a cross sectional view showing a structure of a VCSEL produced by the first embodiment. A VCSEL 200 shown in FIG. 13 outputs a laser oscillation having a wavelength of 1.3 μm, and has an n-GaAs substrate 202 having a <100> face orientation of 3-inch size. An n-AlxGa1-xAs (x=0.9) layer and an n-GaAs layer are alternately stacked for 35.5 periods on the substrate 202, to form a periodic structure having a thickness that is ¼ the oscillation wavelength within the medium and forming an n-semiconductor distributed Bragg reflection mirror (hereinafter referred to as a lower semiconductor DBR mirror or simply lower DBR mirror) 204. A multi-quantum well active region 212, including an undoped lower GaAs spacer layer 206 and an undoped upper GaAs spacer layer 214, is formed on the lower DBR mirror 204. The multi-quantum well active region 212 further includes GaInNAs well layers 208 and GaAs barrier layers 210 that are alternately stacked between the undoped upper and lower GaAs spacer layers 214 and 206. There are 3 GaInNAs well layers 208 and 2 GaAs barrier layers 210 in the multi-quantum well active region 212.
A p-semiconductor distributed Bragg reflection mirror (hereinafter referred to as an upper semiconductor distributed DBR or simply upper DBR mirror) 216 is formed on the spacer layer 214. A C-doped p-AlxGa1-xAs (x=0.9) layer and a p-GaAs layer are alternately stacked for 25 periods, for example, to form a periodic structure having a thickness that is ¼ the oscillation wavelength within the medium and forming the upper DBR mirror 216. A selectively oxidizing layer 218 made of AlAs and having a thickness of 30 nm, for example, is formed at a lower part within the upper DBR mirror 216. A GaAs contact layer 220 at an uppermost part of the upper DBR mirror 216 also functions as a contact layer for making contact with the electrode. The In composition x is 33% and the nitrogen composition is 1.0% for the well layer 208 within the active region 212. The well layer 208 has a thickness of 7 nm, and has a compression distortion (high distortion) of approximately 2.1% with respect to the substrate 202.
MOCVD is used for the thin-film forming method. H2 is used for a carrier gas, and trimethylgallium (TMG), trimethylindium (TMI) and arsine (AsH3) are used as raw materials for the GaInNAs well layer 208. Dimethylhydrazine (DMHy) is used as a raw material for the nitrogen. Since DMHy dissolves at a low temperatures, it is suited for lower-temperature growth at temperature of 600° C. or lower, and is particularly suited for growing the well layer of the multi-quantum well active region having a large distortion that requires the low-temperature growth. In a case where the distortion of the well layer of the multi-quantum well active region in the GaInNAs VCSEL is large, it is preferable to use the low-temperature growth that becomes unbalanced. In this embodiment, the GaInNAs well layer 208 is grown at 540° C.
A mesa 222 is formed by wet etching or a dry etching such as RIE, RIBE and ICP, in a state where at least the side surface of the p-AlAs selectively oxidizing layer 218 is exposed. The mesa 222, when viewed from the top towards the bottom in FIG. 13 has a square shape. Thereafter, the oxidation apparatus 10 described above is used to form an AlxOy current constricting part by oxidizing the AlAs selectively oxidizing layer 218 from exposed side surface by use of water vapor. In this state, the wafer (sample) is placed on the sample table (substrate holder), the base is moved to the oxidizing position, and predetermined water vapor is supplied. Since the monitoring window is separated from the wafer, the oxidation is made uniformly. The wafer is then raised to a predetermined oxidation temperature of approximately 400° C., and the primary oxidation is started. The oxidation is interrupted before reaching an anticipated time when the desired amount of oxidation will be reached. Thereafter, the heating table having the wafer placed thereon is moved to the monitoring position that is close to the monitoring window, and the oxidizing distance, oxidizing area, the vertical horizontal lengths of the non-oxidized region, and the area of the non-oxidized region are monitored by the microscope. Based on the information obtained by the monitoring of the microscope, the oxidation speed of the primary oxidation and the oxidizing distance required for the secondary oxidation (additional oxidation) are calculated, and the additional oxidation time is obtained. The wafer is returned to the oxidizing position, and the secondary oxidation (additional oxidation) is carried out. When the oxidation time of the secondary oxidation elapses, the supply of water vapor is stopped and low-temperature nitrogen is sprayed or blasted onto the wafer, and the oxidation is ended by stopping the heater.
FIG. 15 is a cross sectional view showing a structure of a VCSEL produced by a second embodiment of the present invention. A VCSEL 300 shown in FIG. 15 outputs a laser oscillation having a wavelength of 780 nm, and has an n-(100)GaAs substrate 302 having an inclination angle of 2° in a direction of the <100> face orientation. An n-Al0.9Ga0.1As layer and an n-Al0.3Ga0.7As layer are alternately stacked for 35.5 periods on the substrate 302, to form a periodic structure having a thickness that is ¼ the oscillation wavelength within the medium and forming an n-semiconductor distributed Bragg reflection mirror (hereinafter referred to as a first reflection mirror or simply n-DBR mirror) 304. Between two mutually adjacent n-Al0.9Ga0.1As and n-Al0.3Ga0.7As layers, there is inserted a composition inclined layer (not shown) having a thickness of 20 nm and in which the Al composition gradually changes from the Al composition of the n-Al0.9Ga0.1As layer to the Al composition of the n-Al0.3Ga0.7As layer. The composition inclined layer is also sometimes referred to as a composition modulated layer or a composition gradation layer. The thickness of the periodic structure, including the composition inclined layers, is set to ¼ the oscillation wavelength within the medium. Due to this structure, when a current is applied to the n-DBR mirror 304, it is possible to smoothen the band discontinuity between the n-Al0.9Ga0.1As layer and the n-Al0.3Ga0.7As layer and suppress the resistance from becoming high. A quantum well active region 308, including an Al0.5Ga05As lower spacer (cladding) layer 306 and an Al0.5Ga0.5As upper spacer (cladding) layer 310, is formed on the n-DBR mirror 304. The quantum well active region 308 which makes the wavelength 780 nm further includes AlGaAs well layers and Al0.3Ga0.7As barrier layers that are alternately stacked between the upper and lower spacer layers 310 and 306, and there are 3 AlGaAs well layers and 2 Al0.3Ga0.7As barrier layers. On the spacer layer 310, p-AlxGa1-xAs (x=0.9) and p-AlxGa1-xAs (x=0.3) layers are alternately stacked for 25 periods, for example, to form a periodic structure that forming an n-semiconductor distributed Bragg reflection mirror (hereinafter referred to as a second reflection mirror or simply p-DBR mirror) 312. Between two mutually adjacent p-AlxGa1-xAs (x=0.9) and p-AlxGa1-xAs (x=0.3) layers, there is inserted a composition inclined layer (not shown), similarly to the n-DBR mirror 304. A p-GaAs contact layer 314 is formed on the top for making contact with the electrode. Between the n-DBR mirror 304 and the p-DBR mirror 312, the length amounts to 1 oscillation wavelength (that is, the so-called random cavity is employed).
FIG. 20 is a plan view on an enlarged scale showing the light source 706 for exposure in the image forming apparatus 700 shown in FIG. 19. As shown in FIG. 20(A), the VCSEL array 706 has VCSELs 712 that have the oscillation wavelength of 780 nm arranged two-dimensionally. More particularly, 16 VCSELs 712 are arranged in a 4×4 arrangement, with 4 VCSELs 712 arranged at a predetermined pitch (40 μm) in a horizontal direction in FIG. 20(A) (main scanning direction or an axial direction of the photoconductive body 702) and 4 VCSELs 712 arranged at a predetermined pitch (40 μm) in a vertical direction (sub scanning direction or a rotating direction of the photoconductive body 702). Between two mutually adjacent columns extending in the vertical direction, the positions of the VCSELs 712 in one column is shifted by 10 μm in the vertical direction with respect to the corresponding VCSELs 712 in the adjacent column. Accordingly, as shown in FIG. 20(B), 16 spots 714 are formed on the photoconductive body 702 at intervals of essentially 10 μm in the sub scanning direction.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS5493577Dec 21, 1994Feb 20, 1996Sandia CorporationEfficient semiconductor light-emitting device and methodUS6495381Jan 2, 2001Dec 17, 2002Samsung Electronics Co., Ltd.Apparatus and method for forming aperture of vertical cavity surface emitting laser by selective oxidationJP2001332813A Title not availableJP2002343792A Title not availableJP2003179309A Title not availableJP2004022686A Title not availableJP2004289169A Title not availableJPH08227881A Title not availableKR20010105786A Title not availableKR20020095832A Title not availableNon-Patent CitationsReference1Choquette, et al., "Advances in Selective Wet Oxidation of AlGaAs Alloys", IEEE Journal of Selected Topics in Quantum Electronics, vol. 3, No. 3, Jun. 1997, pp. 916-925.2Feld, et al., "In Situ Optical Monitoring of AlAs Wet Oxidation Using a Novel Low-Temperature Low-Pressure Steam Furnace Design", IEEE Photonics Technology Letters, vol. 10, No. 2, Feb. 1998, pp. 197-198.3Oct. 18, 2010 European search report in connection with counterpart European patent application No. 06714039.4Oct. 31, 2007 Korean official action (and English translation thereof) in connection with corresponding Korean application No. 10-2006-7021340.5Zenno, et al. "Development of New Oxidation Apparatus for Manufacturing Surface-Emitting Lasers", Optical Alliance, pp. 42-46, Apr. 2004 (including partial English translation of Development of Improved Proto Apparatus).Referenced byCiting PatentFiling datePublication dateApplicantTitleUS8609447Mar 15, 2010Dec 17, 2013Ricoh Company, Ltd.Method of manufacturing surface emitting laser, and surface emitting laser, surface emitting laser array, optical scanning device and image forming apparatusUS8624950Sep 14, 2010Jan 7, 2014Ricoh Company, Ltd.Surface-emitting laser comprising emission region having peripheral portion with anisotropy in two perpendicular directions, and surface-emitting laser array, optical scanning apparatus and image forming apparatus including the sameUS8774242May 8, 2012Jul 8, 2014Ricoh Company, Ltd.Surface emitting laser diode, optical scanning apparatus and image forming apparatusUS8803936Dec 15, 2010Aug 12, 2014Ricoh Company, Ltd.Optical device capable of minimizing output variation due to feedback light, optical scanning apparatus, and image forming apparatusUS8809089Jul 12, 2013Aug 19, 2014Ricoh Company, Ltd.Method of manufacturing surface emitting laser, and surface emitting laser, surface emitting laser array, optical scanning device and image forming apparatusUS8971372Jul 15, 2013Mar 3, 2015Ricoh Company, Ltd.Surface emitting laser device and atomic oscillatorUS9252567Mar 14, 2012Feb 2, 2016Ricoh Company, Ltd.Surface-emitting laser element, atomic oscillator, and surface-emitting laser element testing methodUS9287682Nov 1, 2013Mar 15, 2016Ricoh Company, Ltd.Surface emitting laser device and atomic oscillatorUS9496686Nov 29, 2012Nov 15, 2016Ricoh Company, Ltd.Surface-emitting laser element, method for manufacturing a surface-emitting laser element, and atomic oscillatorClassifications U.S. Classification438/5, 438/17, 438/432, 438/7, 438/16, 438/11, 438/12, 438/8, 438/6, 438/14, 438/400, 438/13, 438/18, 438/10, 438/9International ClassificationH01L21/76, G01R31/26, H01L21/00Cooperative ClassificationH01S5/2215, H01S5/18313, H01S5/18358European ClassificationH01S5/183PLegal EventsDateCodeEventDescriptionSep 7, 2006ASAssignmentOwner name: RICOH COMPANY, LTD., JAPANFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:SATO, SHUNICHI;JIKUTANI, NAOTO;ITOH, AKIHIRO;AND OTHERS;SIGNING DATES FROM 20060809 TO 20060825;REEL/FRAME:018315/0908Jan 15, 2015FPAYFee paymentYear of fee payment: 4RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services