CN1560905A - Method for preparing stabilizing rare-earth oxide grate dielectric film - Google Patents

Abstract

The invention introduces the aluminum oxide protection layer to produce stable rare earth oxide grating dielectric film, it deposits the rare earth oxide film on the semi-conductor substrate material to be used as high dielectric grating media material, then carries in situ aluminum oxide protection layer deposition, the rare earth oxide film material: Y2O3, La2O3, and other oxide of the lanthanum series such as Pr2O3, CeO2, Gd2O3, and Er2O3.

Description

The method for preparing stable rare earth oxide grid dielectric film

One, technical field

The invention belongs to the technology of semiconductor integrated circuit, relate to a kind of method, especially introduce the method that protective layer of alumina prepares stable rare earth oxide grid dielectric film the protection of rare earth oxide grid dielectric film.

Two, background technology

Metal-oxide-semicondutor field effect transistor (MOSFETs) is the elementary cell that constitutes memory cell, microprocessor and logical circuit in the silicon-based semiconductor integrated circuit, and its volume is directly connected to the integrated level of very lagre scale integrated circuit (VLSIC).According to famous Moore's Law, to double every the integrated level of 18 months integrated circuits.After the size of transistor device narrows down to submicron order (below 0.1 micron), this traditional gate medium device material of silicon dioxide has reached its basic physical limit.Tunnel effect is with big leakage current between the grid that cause and the silicon chip, and interfacial structure, boron infiltration and reliability aspect also a series of problems will occur.In order to address these problems, must use material to replace existing SiO with high dielectric constant (high-k) and low-leakage current ₂, this has become the bottleneck that restricts MOSFETs integrated level raising in following 10 years.

In the high-k candidate material of research, rare earth oxide mainly comprises Y ₂O ₃La with group of the lanthanides ₂O ₃, Pr ₂O ₃, CeO ₂, Gd ₂O ₃, Er ₂O ₃,, and become one of most promising election contest material of grid medium with high dielectric of future generation because it has suitably big dielectric constant, bigger energy gap and the good thermodynamic stability that contacts with Si.Yet its weak point is that rare earth oxide easily absorbs airborne steam and carbon dioxide in common environment, cause the deterioration of electrical properties and device performance.How to prevent the generation of this situation, become a key issue that must solve in the application of rare earth oxide grid dielectric material.

Three, summary of the invention

It is 9 that aluminium oxide has medium dielectric constant, except dielectric constant is not high enough, the standard that meets all high dielectric materials, having the thermal stability of very large energy gap 8.7eV, high temperature and the chemical stability of environment, also is the grid dielectric material that can satisfy a kind of replacement of silicon dioxide of short-term requirement in the semi-conductor industry.

The objective of the invention is: introduce the method that protective layer of alumina prepares stable rare earth oxide grid dielectric film.

The object of the present invention is achieved like this: introduce the method that protective layer of alumina prepares stable rare earth oxide grid dielectric film; deposition of rare-earth sull 4 is as the grid medium with high dielectric material on semiconductor substrate materials, and the in-situ deposition protective layer of alumina 2 then.

Rare earth oxide thin-film material: yittrium oxide (Y ₂O ₃), lanthana (La ₂O ₃) and other oxides such as the Pr of group of the lanthanides ₂O ₃, CeO ₂, Gd ₂O ₃, Er ₂O ₃Film thickness is in the 1-1000 nanometer.Y ₂O ₃, La ₂O ₃, Pr ₂O ₃, CeO ₂, Gd ₂O ₃, Er ₂O ₃Adopt chemical vapour deposition technique (CVD) Deng film, or physical vaporous deposition (PVD) is as growths such as pulsed laser deposition method, magnetron sputtering method, electron beam evaporations.

Protective layer: aluminium oxide; Film thickness is in the 0.5-100 nanometer; fine and close protective layer of alumina; adopt and rare earth oxide growth phase in-situ deposition technology together, chemical vapour deposition technique (CVD), or physical vaporous deposition (PVD) is as growths such as pulsed laser deposition method, magnetron sputtering method, electron beam evaporations.

Core of the present invention has been to adopt a kind of simple and feasible method; introduce the protective layer of alumina of skim densification by the back original position that finishes at deposited lanthanide oxide; blocked the absorption of rare earth oxide effectively to water in air vapour and carbon dioxide; improved electric property significantly; thereby improved the reliability of device, can satisfy the requirement of MOSFET technology braiding.

Backing material: commercial monocrystalline silicon piece, N or P type, orientation (100) or (111), resistivity 0.01-20 Ω cm.

Electrode material: vacuum moulding machine back electrode aluminium, magnetron sputtering top electrode platinum or vacuum-deposited gold

Membrane deposition method: chemical vapour deposition technique (CVD), or physical vaporous deposition (PVD) is as pulsed laser deposition method, magnetron sputtering method, electron beam evaporation etc.

Depositing operation: in-situ deposition and growth, the substrate that standard semiconductor technology clean is crossed are put into reaction chamber substrate and are warmed up to temperature required, the rare earth oxide film of in-situ deposition desired thickness, the protective layer of alumina of in-situ deposition desired thickness.

Invention effect: the protective layer of alumina of introducing the skim densification by the back original position that finishes at deposited lanthanide oxide; blocked the absorption of rare earth oxide effectively to water in air vapour and carbon dioxide; improve electric property significantly, improved the reliability and the applicability of device.

Four, description of drawings

Fig. 1 is a rare earth oxide grid dielectric structure schematic diagram of the present invention:

Fig. 2 is capacitance-voltage (C-V) curve of sample D, B.Measuring frequency is that 500kHz and 1MHz. can calculate the C-V curve with frequency-independent thus,

Fig. 3 is exposing the infrared spectrogram that air recorded after 10 hours for the two kinds of films of Fig. 2 among the present invention.Platinum or goldentop electrode 1, protective layer of alumina 2, aluminum back electrode 3, rare earth oxide film 4, substrate 5.

Five, embodiment

Adopt Metalorganic Chemical Vapor Deposition (MOCVD), on the monocrystalline substrate of N type 2-10 Ω cm (100), use the beta diketone salt (La (dpm) of lanthanum respectively ₃) and the acetylacetonate (Al (acac) of aluminium ₃) as the MO source, preparation lanthana (La ₂O ₃) grid dielectric film and aluminium oxide (Al ₂O ₃) protective layer, concrete growthing process parameter is: La (dpm) ₃Serviceability temperature be 185～190 ℃, Al (acac) ₃Serviceability temperature be 90～95 ℃, transporting carrier gas is high-purity N ₂, the reative cell deposition pressure is 2～4Torr, and depositing temperature is 650 ℃, and deposition atmosphere is an oxygen.The lanthana growth for Thin Film time is 5-30 minute.The growth time of aluminum oxide film is 0-3 minute.With lanthana grid dielectric film is example, adopts chemical vapour deposition technique (CVD), or physical vaporous deposition (PVD), and the growing method for preparing other rare earth oxide is similar, and the performance of material also roughly the same.

A kind of growth protective layer of alumina sample is A; A kind of sample of the protective layer of alumina of not growing is B.We measure electrical properties and the infrared spectrum that has compared two kinds of films.

Fig. 2 A, B have showed capacitance-voltage (C-V) curve of sample A, B respectively.Here the lanthana growth time is 5 minutes, and the sedimentation time of protective layer of alumina is 1 minute; Measuring frequency is that 500kHz and 1MHz. can calculate the C-V curve with frequency-independent thus, obtains equivalent oxide thickness t by following formula again _Eq(EOT, equivalent oxide thickness) promptly refers to the thickness of thin layer equivalence of any dielectric material is the thickness of silicon dioxide, by $\mathrm{EOT}={\mathrm{<figure-callout\; id="2"\; label="t\; SiO"\; filenames="A20041001406700062.png"\; state="\{\{state\}\}">t</figure-callout>}}_{\mathrm{SiO}}+t_{\mathrm{highkoxide}}\&CenterDot;\frac{{\mathrm{\&epsiv;}}_{\mathrm{<figure-callout\; id="2"\; label="Si\; O"\; filenames="A20041001406700062.png"\; state="\{\{state\}\}">Si</figure-callout>}{O}_{}{}_2}}{{\mathrm{\&epsiv;}}_{\mathrm{highkoxide}}}$ Here t _SiO2And t _{High k oxide}Corresponding to SiO ₂With the thickness of high dielectric oxide, ε _SiO2And ε _{High k oxide}Corresponding to SiO ₂ $({\mathrm{\&epsiv;}}_{{\mathrm{<figure-callout\; id="2"\; label="SiO"\; filenames="A20041001406700062.png"\; state="\{\{state\}\}">SiO</figure-callout>}}_2}=3.9)$ Dielectric constant with high dielectric oxide.As seen, under much the same sedimentary condition, sample A has less EOT (1.8nm) and smaller flat band variation (0.7V), and sample B has the EOT of obvious increase, reach 8.6nm, in the C-V curve, also occurred double step in addition, mean to have between film and the substrate to concentrate and divide other interfacial state.

Fig. 3 has shown that two kinds of films are exposing the infrared spectrum that air recorded after 10 hours.Here the lanthana sedimentation time is 30 minutes, and the alumina deposit time is 3 minutes.Usually sample B is in exposing air after 10 minutes, seen tangible hydroxyl peak and carbonate peak in the infrared spectrum, along with the prolongation of open-assembly time, the intensity at peak also can increase, until saturated, mean that lanthana is transformed into the compound of lanthanum hydroxide or basic carbonate lanthanum fully.And after sample A had protective layer of alumina, then exposing air after 10 hours, and still not having hydroxyl peak to occur, even in environment, placed 10 days, the INFRARED SPECTRUM of film still changes very little.Such stability can satisfy the requirement of MOSFET technology braiding.

Claims (4)

1, introduces the method that protective layer of alumina prepares stable rare earth oxide grid dielectric film, it is characterized in that on semiconductor substrate materials deposition of rare-earth sull (4) as the grid medium with high dielectric material, then in-situ deposition protective layer of alumina (2).

2, prepare the method for stable rare earth oxide grid dielectric film by the described introducing protective layer of alumina of claim 1, it is characterized in that the rare earth oxide thin-film material: yittrium oxide (Y ₂O ₃), lanthana (La ₂O ₃) and other oxides such as the Pr of group of the lanthanides ₂O ₃, CeO ₂, Gd ₂O ₃, Er ₂O ₃

3, the method that is prepared stable rare earth oxide grid dielectric film by the described introducing protective layer of alumina of claim 1 is characterized in that film thickness is in the 1-1000 nanometer.

4, the method that is prepared stable rare earth oxide grid dielectric film by the described introducing protective layer of alumina of claim 1 is characterized in that protective layer aluminum oxide film film thickness is in the 0.5-100 nanometer.

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