FORMATION OF CARBON FILMS AS THE SUBGATE DIELECTRIC OF GaAs MICROCIRCUITS

The progress in the development of integrated circuits/ large scale integrated circuits (ICs/LSICs) technologies on GaAs was characterized by significantly less success than provided previously [1–3]. In particular, this is due to the problems of obtaining reproducible, less-defective initial materials and structures on Schottky field and complementary metal-oxide-semiconductor (CMOS) transistors of submicron sizes with a small dispersion of the output parameters over the substrate plane. Carbon films due to a large number of stable and metastable modifications and high activation barriers between them are promising as a subgate dielectric for GaAs-CMOS LSIСs. The use of carbon films as a subgate dielectric enables to form CMOS transistors on GaAs epitaxial layers (thereafter, epilayers) with symmetric threshold voltages, which is very actual and opens a new direction for the development of the sub-micron technology of LSIСs.


Introduction
The progress in the development of integrated circuits/ large scale integrated circuits (ICs/LSICs) technologies on GaAs was characterized by significantly less success than provided previously [1][2][3].In particular, this is due to the problems of obtaining reproducible, less-defective initial materials and structures on Schottky field and complementary metal-oxide-semiconductor (CMOS) transistors of submicron sizes with a small dispersion of the output parameters over the substrate plane.
Carbon films due to a large number of stable and metastable modifications and high activation barriers between them are promising as a subgate dielectric for GaAs-CMOS LSIСs.The use of carbon films as a subgate dielectric enables to form CMOS transistors on GaAs epitaxial layers (thereafter, epilayers) with symmetric threshold voltages, which is very actual and opens a new direction for the development of the sub-micron technology of LSIСs.

Literature review and problem statement
Silicon has always played a decisive role in the technology of ICs as the main semiconductor material.In recent years, as an alternative, semiconductor compounds such as AI II B V (for example, gallium arsenide) have been used.Since 2010, the volume of commercial products of microelectronics based on gallium arsenide has increased several times [4].This growth trend persists until now.One of the applications of GaAs electronic devices is microwave electronics.Typical values of the diameters of the grown ingots are 100-150 mm.The commercial crystals of 200 mm in diameter have also appeared [5], but they are quite expensive.

V . M a n d z y u k
PhD* Е-mail: mandzyuk_vova@ukr.net*Department of computer engineering and electronics Vasyl Stefanyk Precarpathian National University Shevchenko ave., 57, Ivano-Frankivsk, Ukraine, 76018 The decrease of geometric sizes of transistors results in a reduction of the crystal area, parasitic capacitances, LSICs energy consumption and increase of speed.In recent years, the gate length of the MOS-transistor has decreased to less than 60 nm [6].Today, special attention is focused on the architecture of structures for the LSI of submicron range [7,8].It is the architecture that qualitatively expresses the issue of technology: the growth of epistructures, the formation of functional layers and circuitry [9,10].
Due to the significant influence of technological factors of obtaining on electrical properties, it is difficult to achieve stable results on large-diameter substrates.Therefore, indepth studies of the technological aspects of carbon films obtaining from the point of view of their use as a subgate dielectric for GaAs chips on Si-substrates of large diameter remain relevant.

The aim and objectives of the study
The aim of the work is to develop a technology for the formation of CMOS transistor structures for LSICs on GaAs epilayers grown on silicon substrates of large diameter (>150 mm).
To achieve this aim, the following objectives were accomplished: -to develop a technology for the formation of carbon films by deposition from a carbon target; -to develop the technology of low-temperature epitaxy of GaAs layers on silicon substrates using excimer lasers, where germanium film acts as a buffer layer between Si and GaAs; -to form CMOS-transistors on GaAs epilayers with symmetric threshold voltages using carbon films as a subgate dielectric.

Methods of ion-plasma deposition of carbon films as insulating layers of a subgate dielectric
The α-C:H films were formed by depositing from the directional ion-plasma streams of particles of the "Radical" type and by magnetron sputtering of the carbon film (graphite target) in different environments with the supply of an additional potential to the substrate holder.The main parameters of the deposition processes for the directed flow technology are: the energy of particles 0.5-6 keV, ion current density 0.5-1.7 mA/cm 2 , the power emitted on the Si-substrate 100-800 W.These parameters for magnetron sputtering are equal, respectively, to: 0.1-0.5 keV, 0.1-10 mA/cm 2 , 1-100 W.
If during the deposition from directed ion-plasma streams, the interaction of particles in the stream can be neglected, then during magnetron deposition it is necessary to take into account the collective interaction of particles, which is comparable to the distance of the source-substrate of the device [15].
The measurement of the film density, the study of the atomic and electronic structure of the films were carried out by auger spectroscopy [17][18][19].The estimation of the size of graphite clusters was carried out by comparing the position of the maximum of the π-subzone with the data of photoelectron spectroscopy and π-states of carbon molecules, which consist of different numbers of C and H atoms.
The choice of initial environments was also due to the hybridization of bonds in molecular carbon: sp 3  According to research results, carbon films obtained from cyclohexane C 6 H 12 and toluene C 7 H 8 contain diamond and graphite phases in the ratio of 7 and 90 %, respectively, and in the carbon films obtained from acetylene C 2 H 2 , the carbon phase is less than 55 %.The maximum content of the diamond phase is achieved at an accelerating voltage of 2.9-3.1 kV.
The study of the kinetics of the carbon film formation showed that the deposition rate of the films obtained by depositing from the selected compounds is substantially nonmonotonic.Maximum growth rates, density and specific resistance of carbon films are given in Table 1.The dependence of the conductivity of amorphous carbon α-C:H films on the magnitude of the accelerating voltage showed a fundamental difference in the effect of low-energy streams on the electrical conductivity of the films obtained from the compounds of cyclohexane (C 6 H 12 ), toluene (C 7 H 8 ), and acetylene (C 2 H 2 ).An increase in the accelerating voltage for particles forming a carbon film up to 2.5 kV or a decrease to 0.3 kV lead to an increase in the proportion of graphite dielectric properties, and, conversely, contributes to the growth of specific resistance.This fact suggests that the electrical conductivity of carbon films is determined by the contribution of the graphite component (based on sp 3 -bonding), the degree of cluster disorder and the size of the clusters themselves.The lower the energy of the maximum of the density of states in the π-zone, the larger the size of the π-cluster, i. e. fragmentation of the structure based on sp 3 -hybridization takes place.
For films made in C 6 H 12 vapors, the reduction of the accelerating voltage U acc affects the position of the maximum of the π-zone (Fig. 2): E(π max )=9 eV for U acc =3 kV, E(π max )=9.5 eV for U acc =8 kV.Thus, the reduction of the graphite cluster size leads to a significant increase in the specific resistance to 10 11 Ω•cm and activation energy from 0.4 to 1 eV.The studies have shown that α-C:H carbon films obtained from carbohydrates are amorphous and heterophasic.The properties of such carbon films depend not only on the predominant type of short-range ordering, but also on the structure of the graphite component.This structure determines the electronic states in the slit of mobility (localized states) and electrophysical properties in conditions of hopping conductivity.
The particle energy and ion current density, as well as the type of the resulting carbon compound, affect the dominant type of short-range ordering and the structure of the graphite component.
The effect of the particle energy change from 0.3 to 0.5 kV and ion current density from 0.5 to 1.7 mA/cm 2 on the type of short-range ordering, formation kinetics and composition of the films were considered in [17][18][19].In this case, α-C:H carbon films were obtained from directed sources of particles of the "Radical" type, formed from carbohydrate layers using ion current.The change in the ion energy and the ion current density are determined by the magnitude of the accelerating voltage and the discharge current.
Relevant data on the π-electronic system of films from C 6 H 12 , which allow determining the size of graphite clusters by the presence and characteristics of CH-bonds, are given in Table 2.

Table 2
The effect of formation modes on the size of clusters of α-C:Н films There is a decrease in the size of graphite clusters, an increase in the H 2 content and the activation energy of conductivity, when the accelerating voltage decreases.Under such conditions, the removal of hydrogen from the molecule is less effective.At the same time, the growth rate and density of the films decrease to 0.005 nm/s and 1.8 g/cm 3 respectively, while the specific resistance increases.
The values of the electrical conductivity of α-C:H films obtained by deposition from directed ion-plasma streams formed from C 6 H 12 vapors are given in Table 3.
The use of a magnetron discharge for obtaining amorphous α-C:H films gives a wider ability to control the process of carbon films forming.This can significantly increase the process efficiency by increasing the ion stream density and improve the uniformity of the films in thickness on the large diameters of the substrates (>150 mm).The use of different gas environments for the same target makes it possible to form carbon films with a specific resistance of up to 10 9 Ω•cm.
Films, formed with the use of argon as a working gas, exhibit metal conductivity.Their specific resistance is less than 1 Ω•cm and is practically constant in the temperature range -180÷+200 °С.In the case of cyclohexane use, carbon α-C:H films have a thermally activated mechanism, and the specific resistance value is up to 2•10 9 Ω•cm.
The electronic structure of α-C:H films indicates graphite phase composition (up to 90 %).The difference in the nature and magnitude of the conductivity of the films, depending on the formation conditions, is very well correlated with the size of graphite clusters.The shift of the π-subband maximum is about 8 eV for the films obtained by sputtering of the graphite target in Ar and 9 eV for the ones formed in Ar+ C 6 H 12 (1:3), indicating a decrease in the size of the graphite clusters.
Thus, the application of the magnetron sputtering of the graphite target (puriss.spec.) in С 6 Н 12 will significantly increase the deposition rate at the size of graphite clusters and film properties that are characteristic for deposition from directed ion-plasma flows.This makes it possible to significantly reduce the power emitted on the substrate, which is especially important for a large-diameter substrate (≥150 mm).
The research, the results of which were recorded using the test electrophysical diagnostics (Fig. 3), showed that the deposition of amorphous α-C: H film led to an increase in the capacity of test structures (TS) over the whole voltage range (curves 1 and 2, respectively).Such results are related to the expansion of the TS area in the presence of a deposited film, which is essentially semi-insulating one.The calculated change in the voltage of flat bands (U FT ) of the MOS-structure after the deposition of the protective α-C: H film was 0.3 V, which is a very good indicator when comparing these films with protective coatings for the Si-technology, such as Si 3 N 4 , Al 2 O 3 , Ta 2 O 5 .The estimation of the protective properties of carbon films was also carried out on the basis of the analysis of the change in the capacitance C inv of TS, depending on the time of exposure by a constant voltage, which exceeds the inversion voltage.These changes relate to the redistribution of charge on the surface due to their boundary migration.Accumulation of charge on the surface of the upper metal electrode of the MOS-structure can lead to the expansion of the area of the inversion region, and, accordingly, to an increase in the capacity of the structure.
Thus, the rate of change of C inv upon exposure of the MOS-structure under the bias will characterize the protective and stabilizing properties of the carbon α-C:H films de-posited on the gallium arsenide surface.The studies have shown that C inv(t) significantly depends on the mode of carbon film obtaining.C inv(t) dependence was constant and didn't change with prolonged exposure in the conditions of high humidity (90 %) and high temperature (125 °C) for optimal regimes using the deposition method from C 6 H 12 with the simultaneous introduction of electrons into the ion-plasma stream.This behaviour characterizes the carbon films as an excellent protective coating, in contrast to films such as phosphorus silicate glass (PSG), Al 2 O 3 , SiO 2 , Ta 2 O 5 , which in these test regimes gave a significant increase in C inv in the range of 70-80 %.Thus, the change in the hybridization type of the initial state by changing the C:H ratio in the gas molecule and the effect on the film properties showed that the carbon films formed from the vapors of compounds with sp 3 -hybridization of the bond (C 6 H 12 ) provide the maximum deposition rate of the mass of the substance with the highest value of specific resistance (10 9 Ом•cm).
The change in particle energy during the carbon film formation affects in a different way the electronic structure and properties of α-C:H films obtained from compounds with different types of bond hybridization in the initial material.Thus, the reduction of particle energy from 2.5-0.3 keV for films deposited from C 6 H 12 results in a sharp increase of the graphite component (from 35 to 92 %) and an increase in specific resistance from 10 5 to 10 11 Ω•cm in the case of cluster size reduction.The reduction of particle energy during deposition of α-C:H films from C 7 H 8 leads to an increase in specific resistance from 10 5 to 10 8 Ω•cm; the contents of the graphite component and the size of the clusters do not change.For α-C:H films deposited from C 2 H 2 , when the particle energy was reduced, no change in specific resistance was practically observed.
The use of magnetron sputtering of the graphite target (puriss.spec.) in the C 6 H 12 atmosphere can significantly increase the deposition rate of carbon film at the size of graphite clusters and the properties of amorphous films characteristic for deposition from directed ion-plasma streams at low particle energies, but with a significant reduction in the power allocated on the substrate (silicon or arsenide gallium).
The estimation of the protective and stabilizing properties of carbon α-C:H films by changing the capacitance of test structures of MOS-transistors as electrophysical diagnostics showed that these properties of carbon films formed by magnetron deposition considerably exceed the protective and stabilizing properties of coatings such as Si 3 N 4 , SiO x N y , SiO 2 , Al 2 O 3 , PSG, Ta 2 O 5 .Such films can be used as a subgate dielectric for arsenide-gallium CMOS structures of LSICs formed on large-diameter substrates, which makes arsenide technology competitive with silicon one.

Carbon films as a subgate dielectric when forming submicron structures on GaAs epilayers
The methods of formation and properties of carbon films with high hardness, chemical inertness and high thermoand radiation resistance were considered above.Such films can be used as wear-resistant, masking, passivating coatings in the technology of ICs manufacturing both on Si and GaAs substrates.Today, the possibility of carbon films using as a subgate dielectric in promising super high-speed MOS-devices based on A III V V semiconductors, as well as the main material in multilayered structures with quantum wells in resonance tunneling diodes and a subgate insulator for GaAs-transistors, is intensively investigated.
α-C:H films, as discussed above, were obtained by depositing from directed ion-plasma streams of hydrocarbon vapors (cyclohexane, toluene, acetylene) and magnetron deposition in plasma of hydrocarbons.The particle energy during α-C:H films formation was 0.1-0.6 keV, the thickness of the films varied in the range of 30-300 nm.Also, pre-treatment of substrates with argon ions with an energy of 1-2 keV for 10-30 s was carried out.
The deposition of α-C:H films was carried out on silicon substrates (SHB-80 (100)) and n-GaAs substrates of 0.3-0.5 mm in thickness.The ohmic contact to the substrates was performed by burning of In-electrode, and to α-C:H films -by thermal spraying of Ni or Al layers in a vacuum.In addition, α-C:H carbon films were deposited directly on glass substrates, where low-ohmic tin oxide layer (SnO 2 ) was as an electrode.
The study of the carbon films stability was carried out using the method of charge deep level transient spectroscopy Q-DLTS [17].The automated measuring system allowed the formation of Q-DLTS spectra when using both the temperature-free scan and scan in a time window, as well as measuring the kinetics of photodetection in a mode close to idle.In other words, spectra were viewed which made it possible to estimate both the temperature and time drift of the charge state of the interphase boundary, which is important for the formation of the threshold voltage.
The kinetics of photo-emf for the heterostructure (HS) α-C:H-GaAs with |V ph |≈|φ s | is shown in Fig. 4. The intensity of the pulsed illumination was ≥10 22 quanta/cm•s, which was sufficient for the saturation of the photo-emf.The analysis of V ph (t) dependence for this and other heterostructures (AlGaAs -α-C:H) shows the formation of the convergence of the zone bends in semiconductor materials of HS at the boundary with the α-C:H layer regardless of the type of substrate and the mode of application of the carbon film layer.This is due to the presence of traps for the main carriers of bend on the heterointerface in all investigated samples.The spectrum of the HS (inset in Fig. 4) was obtained at room temperature using a scan in the time window Δt=2t, where t is the time from the beginning of the discharge (relaxation) to the charge after switching the sample from the source of the bias voltage U bias in the measured circuit.Q-DLTS spectra were obtained for all voltages U bias used at various temperatures, amplitudes and duration of enrichment pulses.Data analysis showed that the traps, located at the heterointerface and in the volume of the carbon layer, give the predominant contribution to the spectra.There are two peaks A and B in all the spectra (Fig. 5), associated with an increase in the density of traps with ionization energy E t =0.30 eV and a capture cross section σ n =3•10 -18 cm 2 .These peaks are in Q-DLTS spectra for all HS on semiconductor Si and GaAs substrates and may be due to traps located in the α-C: H carbon layer near the heterointerface at a distance no more than 50 nm.The change in the thickness of α-C:H layer from 30 to 300 nm has a rather weak effect on Q-DLTS spectra.Peak A was not detected in the spectra of semiconductor substrates based on Si and GaAs (without α-C:H layer).There was no peak A in the spectra of structures obtained by depositing one or several (with different energy of optical activation of conductivity) α-C:H layers on glass substrates (optical glass KO-8 of the photomask) with the SnO 2 layer as an electrode.At the same time, the integral density of recharging traps in TS was the same as in HS on semiconductor substrates and essentially depended on the modes of carbon film formation.The research of dependence of the density of traps of the HS test samples, which are responsible for the accumulation of ions A and B in the spectrum (Fig. 5), on the time t of treatment of Si or GaAs substrates by argon ions was performed.An increase in time t (10-60 s) leads to a decrease in the density of traps from 10 12 to 10 11 cm -2 in the region of peak A (by an order of magnitude) and approximately the same magnitude in the mode of the investigated spectral region (from 0.2 to 1 eV).Peak B is smaller, and the peak A decreases by an order of magnitude and more.
Annealing of the HS in a vacuum (10 -6 mm Hg) at T=450 K decreases also the order of the density of traps on the interphase boundary.The values of the density of traps N a with ionization energy corresponding to peak A in Q-DLTS spectra before and after annealing for TS on p-Si, n-GaAs, and n-Al-GaAs substrates are given in Table 4.

Table 4
Effect of annealing on the density of traps A on the interphase boundary on p-Si, n-GaAs, n-AlGaAs substrates The conditions and method of α-C:H carbon films forming determine the significant effect on the density of traps on the interphase boundary.For example, a decrease in the density of traps, which have an activation energy of 0.36 eV corresponding to peak A to (1-5)•10 10 cm -2 is possible.This indicates that the search for the technology and modes of formation of α-C:H carbon films was carried out.In particular, we have found technological regimes for the formation of HS that allow us to change the density of traps in a wide range of energy and to obtain structures with a relatively small trap density.This is essentially a necessary and sufficient condition for using of α-C:H carbon films as a subgate dielectric in sub-micron CMOS LSICs on gallium arsenide.The technology allows the formation of super-fast LSICs on silicon substrates, on which the epitaxial arsenide-gallium layers are grown.

Results discussion and practical realization of sub-micron technologies of CMOS LSICs on GаAs
To reduce the cost of LSICs structures, a technology for the formation of GaAs-structures on silicon substrates with a diameter >150 mm was developed.This technology allows using the whole set of special technology equipment of silicon technology [20].Here, instead of GaAs-substrates, epitaxial layers are used which significantly reduce the cost of gallium [21], which in nature is only ≤10-4 %.In addition, gallium arsenide has a thermal conductivity of almost an order of magnitude smaller than monosilicon, which limits the power of sub-micron structures on GaAs.
Therefore, the basis of this technology is atomic layer epitaxy (ALE) on GaAs using an excimer laser KrF, which provides the deposition of only one monolayer during one growth cycle at a temperature T=500±25 °C.In addition, the epitaxial growth of layers on GaAs (AlGaAs) completely excludes the presence of isoconcentric impurities of oxygen and carbon from the films, which negatively affects the charge state of the interphase boundary.This process is also unique in this regard, which allows forming a buffer layer with one to two germanium monolayers between a silicon substrate and an epitaxial GaAs-layer to equalize a constant silicon lattice to gallium arsenide.ALE of gallium arsenide using an excimer laser makes the process low-temperature due to the efficient decomposition of reagents by photochemical reactions.
Monolayers of semiconductor compounds can be grown by the method of plasma-photochemical deposition from the layers of organometallic compounds at temperatures >650 °C.The ALE method, in which the deposition stimulated by radiation by an excimer (KrF) laser greatly increases the epitaxial growth with decreasing temperature.Theoretically, it is believed that there are two mechanisms for influencing on ALE in photo-radiation by a laser: the first one is to increase the decomposition of the Ga-and Ge-containing absorbents due to the transition of photo-carriers to the surface of the substrate; the second one is a significant increase in the decomposition of reagents due to the absorption of photons by absorbent.The effect of photo irradiation on the epitaxial growth increases significantly with a decrease in wavelength (up to 248 nm).In both cases, it is necessary to eliminate or reduce the phenomenon of photolysis of initial materials in the gas phase.
The low-temperature method of epitaxial growth of GaAs-layers on silicon substrates is developed.The equipment for such layers growth is shown in Fig. 6.
Trimethygallium (TMG), trimethylaluminium (TMAl), AsH 3 (10 % in H 2 ) are used as gaseous sources and H 2 as a carrier gas with a dew point of not higher than -72 °C.The reactor is a vertical stainless steel pipe, which is designed to suppress the convection of the gas stream.The carbon resistive heater provides the thermal mode of the substrate (Si or GaAs).Mono-Si substrates (SHB-80 (100)) were treated in peroxide-ammonia and peroxide-salt mixtures.Then, the epitaxy of germanium from GeH 4 (20 % in H 2 ) to form a buffer monolayer for equalizing the lattice constants of mono-Si and GaAs was carried out on these substrates at T=480-520 °C.Here organometallic compounds Ga(CH 3 ) 3 , Ga(C 2 H 5 ) 3 , Al(CH 3 ) 3 , As(CH 3 ) 3 are used.
Si-substrates were heated at T=600±20 °C in the hydrogen stream before the start of the epitaxial growth.TMG and AsH3 were alternately fed to the GaAs growth surface.Such gas streams were interrupted by hydrogen to prevent the movement of gases in the gas stream.
TMG and AsH 3 were alternately delivered to the GaAs growth surface.Such gas streams were interrupted by hydrogen to prevent the movement of gases in the gas stream.
One technological cycle consists of a sequence of four gas pulses when growing GaAs, i. e. AsH 3 , H 2 , TMG, H 2 .The duration of each pulse was seconds (3-10 s), the flow rate of AsH 3 -25 cm 3 /min.A fifth gas cycle is also possible, when it is necessary to dope the film by a donor or acceptor impurity.For example, the n-type donor impurity from monosilane (SiH 4 in H 2 , 10 %), where gas compounds Si, S, Se are the donor impurities, and Be, Cd, Tе -acceptor ones.All these impurities should be represented as compounds with hydrogen with a dew point of -72 °C and a purity of 10 -4 %.
After etching of SiO 2 -mask, the height of the step was measured on the Si-substrate using the MII-11 interferometer (angle measurement error was <1 %).
Epitaxial films usually didn't deposit on SiO 2 .In addition, the developed epitaxial process removes all oxides and increases the purity of epilayers by an order of magnitude.One should pay attention to the second unique feature of ALE, which is that the simple replacement of an excimer KrF laser (248 nm) with ArF one (193 nm) allows increasing the power of such an equipment almost 1.5-2 times and reducing the temperature of growth to 470 °С.
Six growth cycles were realised in the experiment of the atomic layer epitaxial process of deposition of mono-GaAs-layers.The rate of growth per cycle was determined by dividing the height of the step by the number of cycles.It was found that monoatomic growth was achieved in a rather narrow temperature range close to 500 °C.This fact suggests that Ga-containing absorbents give stable Ga-As-bonds during the growth deposition of GaAs at higher temperatures.
When researching the dependence of the growth rate on the TMG flow rate for the thermal process, it was found that TMG is absorbed and decomposed intensively on arsenic atoms.This is the novelty of the epitaxial process using an excimer laser.Fig. 7 shows the change in the growth rate of epilayer per cycle as a function of the deposition temperature at laser irradiation.The growth rate of TMG was 1.85 cm 3 /min, and AsH 3 -25.5 cm 3 /min.
Monolayer growth is achieved in a wider temperature range (470÷530 °C) compared to thermal growth during irradiation by KrF laser (Fig. 7, curve 3).The effect of laser irradiation on the expansion of the temperature range can be explained by the following processes: 1 -increase in temperature; 2 -collision of such reactive particles as gallium atoms during TMG photolysis in the gas phase; 3 -decomposition of Ga-containing absorbents in photochemical reactions.
If the laser irradiation causes an increase in the temperature of the Si-substrate, then the start of the decrease in the growth rate should occur at a temperature below 500 °C.The temperature range of the monolayer formation expands not only in the region of lower temperatures, but also in the region of higher temperatures under the action of laser excimer radiation.This fact indicates the effect of laser irradiation on the growth of the substrate temperature.The cross section of the absorption spectrum of TMG on the length of the excimer laser KrF (248 nm) or ArF (193 nm) is approximately 1•10 -18 cm or 1•10 -16 cm, respectively.Although these quantities are rather small, there is a probability that the photolysis of TMG in the gas phase increases with the expansion of the temperature range of the monolayer growth.This reaction is amplified with a decrease in the wavelength of the excimer laser to λ=193 nm, i. e. monolayer growth is already achieved at T=500 °C during laser irradiation of the gas stream.This result indicates that monolayer growth is also achieved at T<500 °C during irradiation by an excimer laser.This result shows that reactive particles in the gas phase are not created by laser irradiation.Accordingly, the observed effect of laser irradiation is due to a significant increase of decomposition of Ga-containing absorbents on the surface with arsenic atoms.It turned out that such a photochemical process is similar to the process that provides the activation of implanted impurities, so-called photoannealing.
Thus, the original complete self-limiting monolayer growth of GaAs-films was obtained by the ALE method.The temperature range of monolayer growth is formed in the temperature range of 470-530 °C (or 450-550 °C) when irradiated with an excimer laser KrF (or ArF).Therefore, the effect of laser irradiation is due to the significant increase in decomposition of Ga-containing absorbents due to active photochemical reactions and effective heating of Si-substrates.As a result, there are no isoconcentric impurities of oxygen and carbon in the GaAs epitaxial film.The latter fact creates the basis for a significant decrease in the charge state at the interphase boundary.
Consider the aspects of the formation of a complementary structure on MOS-GaAs transistors with induced channels, which have a self-aligned structure.Such structure is formed on a weakly alloyed Si-substrate (1) of p-type (KHB-80) (Fig. 8).
As shown above, a buffer germanium monolayer is formed between the Si-substrate and GaAs-epilayer to equalize lat-in the plasma of cyclohexane and argon while rotating the magnetic field in a magnetron and cooling of the magnetron by deionized water.
2. The experimental equipment of low-temperature gas-phase laser epitaxy based on the UNES-2PKV device was designed, which allows forming doped and non-doped layers of gallium arsenide and a buffer layer of germanium to equalize the lattice constants of germanium and gallium arsenide.The low temperature of the epitaxy (470-530 °C) provides the formation of the highly stable charge state of the interphase boundary due to the absence of isoconcentric impurities of oxygen and carbon.This is confirmed by complex investigations of epitaxial layers formed by atomic layer epitaxy with excimer (KrF or ArF) laser using charge deep level transient spectroscopy Q-DLTS.
3. The technology of multicharge ion implantation and photon annealing was developed for the formation of retrograde drain-source regions with a small contact resistance of local and lateral isolation using multicharge implantation of boron (B ++ ) or oxygen (O ++ ) with the provision of high insulating properties of the formed layers.The unique property of multicharge implantation in the formation of n-and p-pockets for the formation of CMOS-transistors on gallium arsenide was researched and the small doses of multicharge implantation for the fine fitting of threshold voltages of n-and p-channel transistors to their symmetry and level U Тр (U Тn )=0.5±0.05V are determined.

Fig. 2 .
Fig. 2. Electron structure of amorphous α-C:Н films of 100 Å in thickness formed from С 6 Н 12 at U acc =3 kV (a) and U acc =8 kV (b) α-C:H carbon films, obtained by C 7 H 8 decomposition in the ionic source and containing mainly the graphite phase change their conductivity to a lesser degree at the change of the accelerating voltage.At the same time, the maximum of the π-subband within ±0.4 eV does not change its position

Fig. 5 .
Fig. 5. Q-DLTS spectrum of the α-С:Н-Si heterostructure (peak A is related to the recharging of traps with the ionization energy of 0.35 eV; peak B -with the ionization energy of 0.5 eV)

Fig. 7 .
Fig. 7.The deposition rate of GaAs-epilayers at ALE using photoactivation by an excimer laser as a function of temperature (1 -monolayer, 2 -growth during irradiation, 3 -growth without irradiation)

Table 3
The effect of formation modes of ion-plasma streams and magnetron sputtering on the electrical conductivity of α-C:Н films