A METHOD AND AN APPARATUS FOR DISPOSING EPITAXIAL SILICON AND SILICIDES

Abstract: A method of disposing epitaxial layers of silicon and silicides, on to a substrate or wafer, comprising the following steps: the wafer is transported into a first vacuum area, such as to dispose one or more epitaxial layers at low temperature, on to said wafer, the substrate is transported from that first vacuum area through a second vaccum area to a third vacuum area after said disposition and a layer of silicide is disposed in said third vacuum area.

Description: A method and an apparatus for disposing epitaxial silicon and suicides. BACKGROUND OF THE INVENTION The development of denser and threedimensional circuit integration requires materials that show low bulk and contact resistance, while they should be compatible with other processing techniques. For this purpose suicides are under investigation. In this respect the following prior art is known: - S.P. Murarka en D.B. Fraser: "Silicide formation in thin cosputtered (titanium+silicon) films on polychrystailline silicon and Siθ2"; - T. Makino, N. Sato, M. Takeda, Y. Furumura, and K. Imaoka: "a stacked-source-drain mosfet using selective epitaxy"; - T.P.H.F. Wendling, C. Wieczorek, K. Hieber: "selective CVD of aSi2". Further to the applicant the following patent applications are known in the field of processing apparatus for semi-conductor purposes: - EP patent application No. 0070751; - EP patent application No. 0157052; - EP patent application No. 0133121; - EP patent application No. 0230652; SUMMARY OF THE INVENTION The present invention provides a novel method for disposing a suicides layer on to a substrate provided with an epitaxial silicon layer, comprising the following steps: the wafer is transported into a first vacuum area, such as to dispose one or more epitaxial layers at low temperature, the substrate is transported from the first vacuum area through a second vacuum area to a third vacuum area and a layer of silicide is disposed in said third vacuum area. Further the present invention provides an apparatus for — Z ~ such a method, comprising: a first vacuum area for disposing one or more epitaxial layers, a second vacuum area for loading and transporting said wafer and a third vacuum area for disposing a layer of suicides on to such wafer, wherein said first, second and third vacuum areas are connected by means of vacuum channels. Although the present invention should not be limited by theory, the silicide layers will be grown epitaxially on to said epitaxial silicon layer, as it is preventend that the epitaxial silicon layer is oxidized. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION. Through a gate or lock 1 (figure) wafers are transported in one batch or one by one into a first or main vacuum area 2. Thereafter they can be transported by means of a not shown transport mechanism one by one or in batches into a second vacuum area or reactor 3. In this reactor 3 one or more epi- taxial silicon layers can be applied in a way known as such. Thereafter the wafers can be transported e.g. by means of so called frogarms (not shown) to be arranged in vacuum area 2, into a third vacuum area or silicide reactor 4 for applying the suicides. First, second and third vacuum areas constitute one va¬ cuum system, comprising channels between those vacuum areas. Preferably this first vacuum area 2 is connected to a cleaning area 5, also connected to the vacuum system, for cleaning the wafers, either before or after the applying of the layers, or in between. Specifications for the second vacuum area or epitaxial reactor 3 for disposing one or more epitaxial silicon layer are as follows: maximum temperatur 1050°C temperature range 650°C - 1050°C pressure range 0.05 - 50 Torr temperature uniformity for the wafers: + 5°C in-situ plasma and/or NF3 cleaning optional backgroundpressure 800°C: 10 ~6 Torr 1000°C: 10 -3 Tθrr The maximum gas leakage at 25°C should be 5 x 10 6 mbar I/sec Preferably as gasses are used: HCl (max. mass flow 2slm), SiH2Cl2 (500 seem) , H2/N2(5slm), SiH 4 (500 seem) , as well as dopants and/or H2- A reactor or processor 3 according to the above spe¬ cification can conventionally be built or sought. As third vacuum area or suicides reactor 4, preferably a low pressure chemical vapor deposition reactor is used or a Rapid Thermal Processing (RTP) reactor for single wafer use, while a source for metal precursor such as Tungsten ( ) or kobalt. The temperature should be controllable between 150°C and 900°C and a maximum temperature should be 100°C. Preferably wafers can be cleaned in-situ inside the reactor. Also preferably lines for metal precursors are heatible. Also preferably lines for non-corrosive gasses, such as SiH , N2Ar or other are included. A suicides reactor according to the above specifica- tions can be built conventionally or bought. The above described process and apparatus are usuable both in the field of MOS circuits and bipolar circuits, more specifically to the SAC(Self Aligned Contact)-technique for disposing an emitter contact of suicides, while the emitter consists of epitaxial silicon, or suicides contacts on sour¬ ce and drain areas disposed epitaxially. Hot-carrier effects and short-channel effects can be prevented at shallow and gredible junctions near a drain, such as occur in Lightly Doped Drain (LDD)-MOS-FET-tech- nique. Especially in Stacked Source Drain (SSD) MOS-FET-tech- nique hot-carrier effects can be surpressed, such that down¬ sizing to submicron dimensions becomes possible. In SSD- technique fosfor (P) and arsenicum (As) can be combined. Generally speaking advantages of the present invention comprised the following: - threedimensional integration is facilitated; - thermical mismatch is obviated; - - - processing temperature is lowered, such that in gene¬ ral downsizing of the mention of integrated circuits becomes possible; and - selective growth is also facilitated.

Claims: CLAIMS 1. A method of disposing epitaxial layers of silicon and suicides, on to a substrate or wafer, comprising the following steps: - the wafer is transported into a first vacuum area, such as to dispose one or more epitaxial layers at low tem¬ perature, on to said wafer; - the substrate is transported from that first vacuum area through a second vacuum area to a third vacuum area af¬ ter said disposition; and - a layer of silicide is disposed in said third vacuum area. 2. A method according to claim 1, wherein said low tem- perature is about 1000° C. 3. An apparatus for disposing layers of epitaxial sili¬ con and silicide on to a substrate or wafer, comprising: - a first vacuum area for disposing one or more epi¬ taxial layers; - a second vacuum area for loading and transporting sa¬ id wafer; and - a third vacuum area for disposing a layer of sui¬ cides on to such wafer, wherein said first, second and third vacuum areas are connected by means of vacuum channels. 4. An apparatus according to claim 1, wherein said third vacuum area is comprised by a low pressure chemical vapor deposition apparatus. For an apparatus according to claim 2 or 3 wherein a fourth vacuum area for cleaning said substrate is connected through said second vacuum area through a vacuum channel.

Inventors: MAEX KAREN IRMA JOZEF, NIJS JOHAN FRANCIS ALBERT, MAEX, KAREN, IRMA, JOZEF, NIJS, JOHAN, FRANCIS, ALBERT
Applicants: IMEC INTER UNI MICRO ELECTR, INTERUNIVERSITAIR MICRO-ELEKTRONICA CENTRUM VZW
Application year: 1990
Main classification: C30B29
IPC codes: C23C16, C30B25, C30B29