Source: http://www.google.de/patents/US5569953?hl=de
Timestamp: 2013-05-24 05:49:27
Document Index: 551983080

Matched Legal Cases: ['art 13', 'art 13', 'arts 13', 'arts 13', 'art 13', 'art 13', 'art 13', 'art 13', 'art 13']

Patent US5569953 - Semiconductor device having an isolation region enriched in oxygen - Google PatenteSuche Bilder Maps Play YouTube News Gmail Drive Mehr » Erweiterte Patentsuche | Webprotokoll | Anmelden Erweiterte Patentsuche PatenteA method for growing an epitaxial layer of a group III-V compound semiconductor material that contains oxygen comprises the steps of supplying molecules of an organic compound that contains a group V element and oxygen in the molecule, and decomposing the molecules of the organic compound to release...http://www.google.de/patents/US5569953?utm_source=gb-gplus-sharePatent US5569953 - Semiconductor device having an isolation region enriched in oxygen Ver�ffentlichungsnummerUS5569953 APublikationstypErteilung Anmeldenummer08/449,113 Ver�ffentlichungsdatum29. Okt. 1996Eingetragen24. Mai 1995 Priorit�tsdatum19. Febr. 1991Auch ver�ffentlicht unterEP0526646A1EP0526646B1US5480833WO1992015113A1 ErfinderToshihide KikkawaTatsuya OhoriUrspr�nglich Bevollm�chtigterFujitsu Limited US-Klassifikation257/607257/609257/610257/E27.12257/E21.111257/E21.542257/E21.126257/612257/E27.13257/E21.697Internationale KlassifikationH01L29/778H01L21/338H01L29/812H01L21/20H01L21/76C30B25/02H01L27/06H01L21/205H01L21/8252 UnternehmensklassifikationH01L21/0262H01L21/02505H01L21/02395H01L21/02463H01L21/02507H01L21/02546H01L21/02573C30B25/02H01L27/0611H01L27/0605C30B29/40H01L21/7605H01L21/8252 Europ�ische KlassifikationH01L21/02K4B5L3H01L21/02K4E3CH01L21/02K4A1B3H01L21/02K4B1B3H01L21/02K4C1B3H01L21/02K4C3CH01L21/02K4B5L3AH01L21/8252H01L21/76PH01L27/06DH01L27/06CC30B25/02C30B29/40ReferenzenPatentzitate (9)Nichtpatentzitate (10) Referenziert von (8)Externe LinksUSPTO USPTO-Zuordnung EspacenetSemiconductor device having an isolation region enriched in oxygenUS 5569953 A Zusammenfassung A method for growing an epitaxial layer of a group III-V compound semiconductor material that contains oxygen comprises the steps of supplying molecules of an organic compound that contains a group V element and oxygen in the molecule, and decomposing the molecules of the organic compound to release the group V element and oxygen.
We claim: 1. A semiconductor integrated circuit, comprising: a substrate having upper and lower major surfaces; a buffer layer of AlGaAs provided on said upper major surface of the substrate, said buffer layer having upper and lower major surfaces and containing oxygen with a concentration level substantially exceeding 10.sup.19 ions cm.sup.-3, said buffer layer interrupting a flow of carriers therethrough and interrupting a passage of an electric flux line; a device layer provided on the upper major surface of the buffer layer, said device layer having upper and lower major surfaces and formed therein with a plurality of active devices; and a device isolation region provided between adjacent active devices for isolating the active devices from each other, said device isolation region extending from the upper major surface of the active layer toward the substrate.
2. A semiconductor integrated circuit as claimed in claim 1 in which said buffer layer contains oxygen with a concentration level substantially exceeding 4
3. A semiconductor integrated circuit as claimed in claim 1 in which said buffer layer contains oxygen with a concentration level of about 10.sup.20 ions cm.sup.-3.
TECHNICAL FIELD The present invention generally relates to semiconductor devices and more particularly to the fabrication of a compound semiconductor device that includes a layer of group III-V compound semiconductor material.
BACKGROUND ART FIG. 1 shows an example of the conventional device that employs such a device isolation.
DISCLOSURE OF THE INVENTION Accordingly, it is a general object of the present invention to provide a novel and useful process for fabricating a semiconductor device, wherein the foregoing problems are eliminated.
Another object of the present invention is to provide a compound semiconductor device that has a buffer layer of a group III-V compound semiconductor material that is doped with oxygen ions to a concentration level of oxygen exceeding 1 present invention, the penetration of the electric field of one device into the region of another device is effectively interrupted by the oxygen ions in the buffer layer, as the electric charge of the oxygen ions intercepts the electric flux line associated with the electric field. Further, oxygen ions form a deep impurity level in the group III-V compound semiconductor material and the buffer layer thus formed shows a large resistivity. Therefore, the buffer layer acts as an effective barrier for the penetration of both the electric field and the carriers, and an excellent device isolation can be achieved.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing the structure of a conventional HEMT integrated circuit that uses a conventional buffer layer and a device isolation structure;
In the first embodiment, an epitaxial layer of oxygen-containing AlGaAs is grown by an MOCVD process that employs organic gases for the source of the group III and group V elements. As usual in the MOCVD process, organic source materials such as TMG (trimethyl gallium) and TMA (trimethyl aluminum) are introduced into a reaction vessel in which a substrate of a compound semiconductor material such as GaAs is supported, together with arsine (AsH.sub.3) that acts as a source of As. As a result of the pyrolysis of the organic molecules, the elements such as Al and Ga are released and deposited on the suitable site of the GaAs crystal that forms the substrate together with As that is released by the pyrolysis of arsine.
In order to form the AlGaAs layer to have a high resistivity and high concentration of oxygen ions, the present invention employs tertiary buthoxy arsine (tBOAs; C.sub.4 H.sub.9 OAsH.sub.2) as another organic source of As. As will be described detail in later, the tertiary buthoxy arsine is usually used concurrently with arsine, although tBOAs may be used alone.
FIG. 3 shows the FTNMR (Fourier transform nuclear magnetic resonance) spectrum of the tBOAs molecule that is used in the present embodiment. The material of tBOAs is produced from AsCl.sub.3 and is available from FURUKAWA Co. Ltd, Tokyo as "tertiary buthyl arsine." From the FTNMR spectrum of FIG. 3 that was obtained based upon the optical resonance for the group containing H, this material was found to be a mixture of usual tertiary buthyl arsine (tBA; (CH.sub.3).sub.3 CAsH.sub.2) and tBOAs.
More specifically, FIG. 3 shows a number of peaks attributed to the CH.sub.3 group, CH.sub.2 group and the AsH.sub.2 group that are pertinent to tBA. In addition, one can observe a slope represented by the broken line at the base part of the peak of the CH.sub.3 group. Such a shift occurs in correspondence to the existence of O that is combined with the CH.sub.3 group. In other words, the result of FIG. 3 clearly indicates the existence of the buthoxy group (C.sub.4 H.sub.9 O) in the molecule of the material. About the identification of the FTNMR spectrum, see for example A. YAMAZAKI, "Kakujiki-kyoumei-bunnkouhou" (Nuclear Magnetic Resonance Spectroscopy), Kyoritsu Publishing KK, Tokyo, 1984 (in Japanese), which is incorporated herein as reference.
Referring to FIG. 4(A), the epitaxial growth is made on a GaAs substrate 11 that is held in a reaction vessel (not shown) under the ordinary pressure condition at a temperature of 630 grown on the substrate 11 while flowing arsine alone for the source of As. More specifically, an arsine gas diluted to 18% by a H.sub.2 carrier is supplied with a flowrate of 100 cc/minute. Simultaneously, TMG is supplied by bubbling a TMG liquid held at a temperature of -4 pressure of 59 Torr by a H.sub.2 carrier gas with the flowrate of 34.1 cc/min. Thereby, the GaAs layer 12 is grown with a suitable thickness such as 2000 Å.
After the GaAs layer 12 is thus formed, the growth of an AlGaAs layer 13 on the GaAs layer 12 is started. In this process, the flow rate of arsine is increased to 260 cc/min and the supply of tBOAs is started simultaneously. The source of tBOAs is a liquid and is held at a temperature of 10 C. and a pressure of 96 Torr. The supply of tBOAs is achieved by bubbling the foregoing liquid source by a hydrogen carrier with the flowrate of 200 cc/min. As already noted, tBOAs contains oxygen in the molecule.
Simultaneously to the supply of arsine and tBOAs, TMG and TMA (trimethyl aluminum) are supplied respectively as the source of Ga and Al. There, the source liquids of TMG and TMA are held at 3 18 of TMA are supplied respectively to the reaction vessel with the flowrates of 16 cc/minute and 12.8 cc/minute by the bubbling the liquid sources by H.sub.2. This procedure is continued for about 10 minutes and a first part 13a of the layer 13 is formed with a thickness of about 2000 Å. As will be described later with reference to FIG. 5, the layer part 13a thus formed contains substantial amount of oxygen.
Referring to FIG. 5, it will be seen that the concentration level of Ga is substantially constant throughout the structure, while the concentration level of Al increases steeply in correspondence to the AlGaAs layer 13. Further, the concentration level of O changes in correspondence to the layer parts 13A, 13B and 13C such that the concentration level exceeds far above 10.sup.19 cm.sup.-3 in the layer parts 13A or 13C. In fact, the concentration level of O exceeds 4 part 13C, while the concentration level reaches almost 10.sup.20 cm.sup.-3 in the layer part 13A. Thereby, the layers 13A and 13C show a high resistivity associated with the existence of the deep impurity level of oxygen. Oxygen thus observed is believed to be incorporated into the crystal structure of AlGaAs and exist in the form of oxygen ions.
In FIG. 5, it should be noted that the concentration level of oxygen in the layer part 13B remains well below 10.sup.19 cm.sup.-3. More specifically, the oxygen concentration level of the part 13B is about 3 cm.sup.-3 that is about one tenth of the oxygen concentration level in the layer part 13C. Further, it should be noted that the concentration level of oxygen in the GaAs layer 14 that is grown on the oxygen-containing AlGaAs layer 13c is substantially the same as the oxygen concentration level of the GaAs layer 12 which was formed prior to the growth of the layer 13.
FIG. 8 shows the shift of the threshold voltage V.sub.TH of the D-mode HEMT of FIG. 7 in response to the application of a side gate voltage to another D-mode HEMT in the adjacent device region. In FIG. 8, the result for the device of FIG. 7 is represented by the open circles. In this measurement, the gates of the devices were separated from each other by a distance of 3 μm (L.sub.sg =3 μm) across the device isolation region 42, and no voltage was applied to the gates of the E-mode HEMTs. For the sake of comparison, the result of similar measurement for the HEMT integrated circuit that has an identical structure except for the buffer layer 33 is represented by the solid circles.
As can be seen clearly from FIG. 8, the device of the present embodiment can suppress the side gate effect even when a side gate voltage as large as -8 volts is applied to the adjacent device. On the other hand, the conventional device shows a conspicuous side gate effect even when the side gate voltage of -1 volt is applied. The device thus constructed showed the K factor of 293 mA/V/mm.sup.2 and the transconductance g.sub.m of 241 mS/mm.
FIG. 10 shows the thermal cycling process that is conducted in a single reaction vessel for the growth of the epitaxial layers 52-57. Referring to FIG. 10, the substrate 51 includes therein the silicon substrate 51a and the strained superlattice layer 51b, and is baked at a high temperature T.sub.1 such as 1000 to remove any oxide film or contamination from the surface of the layer 51b. Next, the temperature is lowered to a temperature T.sub.4 such as 300 about 600 the first level are grown consecutively. Next, the temperature is lowered to T.sub.4 and raised again to T.sub.2, and the growth of the layers 52a and 52b for the second level is achieved. Further, the temperature is lowered to T.sub.4 and raised again to T.sub.2 and the growth of the layers 52a and 52b for the third level is achieved. It should be noted that the foregoing thermal cycling is achieved in the same reaction vessel, without taking the substrate therefrom.
In this experiment, a buffer layer corresponding to the layer 52 was formed on a semi-insulating GaAs substrate corresponding to the substrate 51 of FIG. 7 by an alternate repetition of a high purity GaAs layer and an oxygen-containing AlGaAs layer with the total thickness of the GaAs layer of 20 nm and the total thickness of the AlGaAs layer of about 30 nm. The deposition of the GaAs and AlGaAs buffer layers was repeated three times, five times or eight times, wherein the deposition of the oxygen-containing AlGaAs layer was made under the condition similar to the first embodiment. On the buffer layer thus formed, another buffer layer of undoped GaAs was grown with a thickness of 20 nm, and a channel layer of undoped InGaAs having a composition of In.sub.0.2 Ga.sub.0.8 As was grown thereon in correspondence to the channel layer 53 of FIG. 9.
Referring to FIG. 12(A) first, an epitaxial layer 72 of undoped AlGaAs is grown epitaxially on a GaAs substrate 71, and a SiON layer 73 is deposited on the AlGaAs layer 72. Further, the layer 73 is patterned to form windows 73a that expose the upper major surface of the AlGaAs layer 72 in correspondence to where a selective epitaxial growth of a III-V material is to be made. For example, the windows 73a may expose a strip-like region extending in the &lt;010&gt; direction of AlGaAs layer 72.
In the step of FIG. 12(B), the AlGaAs layer 72 is subjected to an RIE process while using the SiON layer 73 as a mask, and a plurality of grooves 72a are formed in correspondence to the device region such that the grooves 72a extend in the &lt;010&gt; direction.
Referring to FIG. 13(A), an undoped AlGaAs layer 82 is grown on a semi-insulating GaAs substrate 81 and a mask layer 83 of SiON is grown on the layer 82. The mask layer 83 is patterned subsequently to form a number of strip-like patterns extending parallel with each other on the surface of the AlGaAs layer 82 in the &lt;010&gt; direction.
In the foregoing description, the growth of the oxygen-containing AlGaAs layer has been achieved by using tBOAs for the source of O and As. However, the source of O and As that can be used in the process of the present invention is not limited to tBOAs but other organic sources of As can also be used. These organic sources include: monoethoxy arsine (C.sub.2 H.sub.5 OAsH.sub.2); monophenoxy arsine (C.sub.6 H.sub.5 OAsH.sub.2); monomethoxy arsine (CH.sub.3 OAsH.sub.2); ditertiary buthoxy arsine ((C.sub.4 H.sub.9 O).sub.2 AsH); diethoxy arsine ((C.sub.2 H.sub.5 O).sub.2 AsH); diphenoxy arsine ((C.sub.6 H.sub.5 O).sub.2 AsH); dimethoxy arsine ((CH.sub.3 O).sub.2 AsH); tritertiary buthoxy arsine ((C.sub.4 H.sub.9 O).sub.3 As); triethoxy arsine ((C.sub.2 H.sub.5 O).sub.3 As); triphenoxy arsine ((C.sub.6 H.sub.5 O).sub.3 As); and trimethoxy arsine ((CH.sub.3 O).sub.3 As).
INDUSTRIAL APPLICABILITY According to the present invention, one can introduce oxygen into a reaction vessel without causing a contamination. As oxygen is supplied in the form of organic molecules of the source gas of the group V element and as the source gas of the group V element is supplied with much larger amount as compared with the source gas of the group III element, a large amount of oxygen ions can be incorporated into the reaction vessel and hence into the epitaxial layer. By using such an epitaxial layer that contains large amount of oxygen ions as the impurity for the buffer layer, one can achieve an effective device isolation.
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