RU2528278C1 - Method of obtaining silicon dioxide layer - Google Patents

Method of obtaining silicon dioxide layer Download PDF

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RU2528278C1
RU2528278C1 RU2013118790/28A RU2013118790A RU2528278C1 RU 2528278 C1 RU2528278 C1 RU 2528278C1 RU 2013118790/28 A RU2013118790/28 A RU 2013118790/28A RU 2013118790 A RU2013118790 A RU 2013118790A RU 2528278 C1 RU2528278 C1 RU 2528278C1
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reactor
silicon dioxide
deposition
range
substrate
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RU2013118790/28A
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Владислав Юрьевич Васильев
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Общество с ограниченной ответственностью "СибИС" (ООО "СибИС")
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Abstract

FIELD: chemistry.
SUBSTANCE: in a method of obtaining a silicon dioxide layer, which includes loading of a semiconductor substrate into a reactor, heating the semiconductor substrate to a required temperature in the range of 300-500°C, supply of vapours of alcoxysilane, preferably tetraethoxysilane, and an oxidiser in the form of a mixture of oxygen and ozone, with concentration of the latter in the former in the range of 0-16 wt %, support of working pressure in the reactor in the range of 0.5-760 mm Hg, the process of precipitation is performed in cycles, consisting of successive impulses of alcoxysilane and the oxidiser, separated by an impulse of blow-off inert gas, with the duration of impulses constituting 0.1-20 seconds, and a number of cycles being calculated from the required layer thickness and a rate of precipitation of the silicon dioxide layer during one cycle.
EFFECT: invention makes it possible to provide a uniform growth of the silicon dioxide layers under conditions of the process realisation, excluding the interaction of initial reagents or their residues that have not reacted in the reactor, and provides the interaction of the reagents on the heated surface of the substrate in an adsorption layer.
7 dwg, 1 tbl

Description

The present invention relates to the field of microelectronics technology, namely, chemical vapor deposition (CVD) of thin dielectric layers (hereinafter referred to as layers) from the initial silicon compounds, and can be used in the production of submicron ultra-large integrated circuits (hereinafter referred to as VLSI).

The deposition of layers by means of CVD on substrates, used as the basis for the production of VLSI, is carried out in flow-type chemical reactors (hereinafter referred to as reactors), which provide the necessary temperature for heating the substrates and its uniformity within the substrates. The build-up of a thin layer on the heated surface of the substrates during the course of CVDF is the final result of irreversible reactions of continuously supplied to the reactors the initial gaseous (vaporous) substances - components of the reaction, the unreacted part of which, together with the by-product gaseous reaction products, is removed from the reactors. Gas deposition processes are usually described as multi-route and multi-stage, including parallel or sequential course of individual routes and stages of formation of intermediate and final reaction products in the gas phase of reactors and on the surface of heated substrates.

The designs of the actual reactors for CVHF differ, for example: a) they can be designed for one substrate, or for a group of several tens or hundreds of substrates; b) may have cold walls and an internal heater for heating only substrates or hot walls that simultaneously heat a group of substrates; c) can function at atmospheric or reduced pressure with activation of the gas phase by plasma discharge, etc.

When applying CVD to create layers of dielectric materials based on silicon dioxide for VLSI technology with submicron design and technological standards, the following problems were discovered [1]:

- there are limitations of the CVD processes on the temperature of the maximum possible substrate heating <~ 550 ° C, due to the presence on the surface of the VLSI structures of metal conductors degrading at high temperatures. As a result, the limitations of the applicability of the deposition processes at temperature significantly narrow the range of possible starting chemical reagents (silicon compounds and oxidizing agents), primarily because of their reactivity at low temperatures;

- the deposition of thin layers with the highest possible deposition rate is necessary to ensure the productivity of the processes and with a very low, within 1-3%, heterogeneity of the thickness, structure and properties of the deposited coatings both on one substrate and on all substrates processed simultaneously (in the case of the use of group-type reactors with the processing of tens or hundreds of substrates simultaneously);

- it is necessary to control and minimize the imperfection introduced by the processes of HOGF in the form of microparticles. For example, for VLSI with design and technological standards less than 0.25 μm, the permissible number of microparticles with sizes from 0.2 μm per 1 cm 2 of the substrate surface should not exceed 0.1 pcs / cm 2 . The possibility of the formation of microparticles as by-products of the reaction is a characteristic feature of CVDF and is determined by the combination of components used, types of reactors, selected conditions for the implementation of CVDF processes, the purity of the initial substrates, etc .;

- it is necessary to ensure the maximum possible conformity of the coating of the stepped microrelief of the VLSI structures by the layers deposited during the CVDF. The problem of conformity of the deposition of layers during CVD is illustrated in Fig. 1. On the substrate 1 there are rectangular structures 2 with a height of 11 and a gap G between them, onto which the CVD of a thin layer 3 is realized. Under the conformity of deposition is meant the difference in layer thicknesses in different parts of the VLSI stepped reliefs, in mostly reduced thickness on the lower and side surfaces of the VLSI relief steps. Quantitatively, the conformity of the deposition is expressed as d 2 / d 1 ,% (Fig. 1), and for the vast majority of the studied processes of the CVD layers of silicon dioxide, it is significantly less than 100%. In this case, the determining factor for conformity is the complexity of the structures on the surface of which thin-layer coatings are grown. The complexity of structures is characterized by the “aspect ratio” (AR = H / G or “structure complexity” (SC = H / G 2 ) parameters, Fig. 1. However, in addition to the complexity of the original structure, the problem of conformity in is largely determined by a sharp complication of the structure parameters in the course of layer growth, which is illustrated in Fig. 2 by the dependence of the LR and SC values for the case of perfectly conformal deposition of the layer on structures with vertical walls and an initial gap value of 0.1 μm, which shows that before closing the fronts growing towards b postglacial walls of the structures there is a sharp increase in the greatness of the AR and SC;

- when CVD is the formation of voids 4 (figure 1) in the narrow gaps of the relief VLSI, which is a consequence of non-conformal deposition of layers. Moreover, the complexity of the structures of promising VLSIs has a pronounced tendency to increase [2], which leads to an increase in the problem of the formation of voids with each subsequent generation of microelectronic devices.

Known low-temperature high-speed methods for producing a layer of silicon dioxide using the oxidation reaction of monosilane with oxygen [3], as well as low-temperature processes with plasma activation of mixtures of monosilane with nitrous oxide [4] and tetraethoxysilane (TEOS) and oxygen [5]. Common disadvantages of the indicated high-speed low-temperature CVDF processes are the strong nonconformity of the layer growth on the steps of the VLSI relief and, accordingly, the problems with filling voids in the gaps of submicron VLSI [3]. The reason for the non-conformity of the deposited layers during high-speed multi-stage CVD processes is explained by the fact that such processes occur with the participation of free radicals or ions. In this case, the limiting stages of the CVDF processes are chemical reactions that occur in the gas phase of the reactors, and not on the surface of the substrates. The quantity of the effective rate constant of the chemical process (k eff ) is used as a quantitative characteristic of the rate of the course of the CVD process [2]. The experimentally obtained dependence of growth conformity on k eff for various methods for producing thin layers of silicon dioxide is shown in Fig. 3 [2] and shows a decrease in conformity to 40–20% for high-speed CVD processes. Such values of conformance of layers are unacceptable for VLSI technology with submicron design and technological standards.

A known low-temperature method for producing silicon dioxide layers [6], in which the processes of deposition of silicon dioxide from monosilane and oxygen with gas additives (slowing down chemical reactions in the gas phase by "quenching" of free radicals), and directional lateral sputtering of the deposited material by argon ions are combined. The method provides a significant improvement in the filling of gaps in the VLSI structures, however, the disadvantages of the method are the formation of specific "comb-like" layer deposition profiles on the upper surfaces of the VLSI structures, requiring additional operations for their planarization (alignment), as well as the possibility of negatively affecting the integrated circuits with high plasma density.

In addition, a low-temperature method is known for producing a silicon dioxide layer by the reaction of a reagent from the group of alkoxysilanes and a mixture of ozone with oxygen [7], which includes loading the semiconductor substrate into the reactor, heating the semiconductor substrate to the required temperature in the range of 300-500 ° C, supplying vapor to the reactor a reagent from the group of alkoxysilanes (mainly tetraethoxysilane) and an oxidizing agent in the form of a mixture of oxygen and ozone with a concentration of the latter in the range of 0-10 wt.% and maintaining the working pressure in the range of 0.5-760 mm Hg before deposition of the silicon dioxide layer on the semiconductor substrate to the required thickness by maintaining continuous flows of vapors of alkoxysilane and oxidizing agent.

Various options for implementing this method and the results obtained are described in the literature [8-12]. The method allows deposition of layers at low deposition temperatures with good conformity of deposition on VLSI structures with design and technological standards of 0.25 μm or less. An increase in ozone concentration within the specified limits causes the following effects: a significant increase in the deposition rate of silicon dioxide layers at an ozone concentration of 0-2 wt.%, The appearance of the so-called “Surface sensitivity effect”, that is, significant differences in the deposition rates and properties of coatings on the surfaces of different materials at an ozone concentration of> 2 wt.%, As well as the formation of “coherent” coating profiles on the vertical steps of the relief of semiconductor devices.

The disadvantages of the method is the dependence of the conformity of the deposition on the concentration of ozone and deposition conditions, which was associated with the occurrence of intensive chemical processes in the gas phase of the reactor [11, 13]. The data of FIG. 3 indicate that in order to achieve maximum conformity of deposition, it is necessary to realize the processes of CVD of thin layers at a low speed, that is, in the mode of small values of the effective rate constant of the chemical process (k eff ). This corresponds to the regime of limiting the contribution of chemical reactions occurring in the gas phase and the implementation of the CVD process under conditions when the process is limited by surface reactions.

The technical problem to which the invention is directed is to exclude the interaction of the reagent and the oxidizing agent in the gas phase and to localize the chemical reaction of the growth of the silicon dioxide layer during the interaction of TEOS and ozone on the surface of the heated substrate.

This object is achieved in that the preparation of the silicon dioxide layer involves loading the semiconductor substrate into the reactor, heating the semiconductor substrate to the required temperature in the range of 300-500 ° C, feeding alkoxysilane and oxidizer vapor into the reactor in the form of a mixture of oxygen and ozone with the concentration of the latter in the first the range 0-16 wt.%, maintaining the working pressure in the reactor in the range of 0.5-760 mm Hg, characterized in that in order to exclude the chemical reaction of alkoxysilane and the oxidizing agent in the gas phase of the reactor and localization the process of forming a layer of silicon dioxide on the surface of a heated substrate, the deposition process is carried out in cycles consisting of successive pulses of vapors of alkoxysilane and an oxidizing agent, separated by pulses of a purge inert gas, the pulse duration being 0.1-20 s, and the number of cycles calculated from the required layer thickness and layer deposition rate silicon dioxide in one cycle.

The successive pulses of alkoxysilane, inert gas purge, oxidizing agent and inert gas purge comprise one deposition cycle shown in FIG. 4.

The method is as follows. A single-crystal silicon wafer with a diameter of 200 mm, which underwent standard chemical processing of microelectronic production, followed by washing in deionized water and drying in a centrifuge, was loaded into an individual mud reactor (on one substrate) of a DCVD Centura D × Z deposition apparatus manufactured by Applied Materials (USA) ) A simplified installation diagram is shown in figure 5 and displays the following: 5 - input components; 6 - release of reaction products; 7 - heater; 8 - substrate; 9 - stifled (perforated) gas distribution system; 10 - operating pressure regulator (throttle to regulate and maintain the pressure in the deposition chamber); 11 - pressure meter, the electrical output of which is associated with throttle control; the term “clearance” refers to the distance from the shower gas distribution system to the heated substrate holder.

Next, the reactor was sealed, vacuum pumped to the maximum residual pressure of the mechanical pump, inert gas was supplied to the reactor in the dynamic forvacuum mode until the selected substrate temperature in the reactor was stabilized at 498 ° C, the inert gas was turned off, and the reactor was disconnected from the vacuum pump by closing the vacuum shutter upon reaching maximum pressure in the reactor, checking the reactor for leaks by recording the rate of increase in pressure, opening the vacuum shutter, stabilization the position of the pressure regulator in the reactor during the inlet of a constant flow of purge gas by a value of 540 mm Hg Further performance of the deposition process for a predetermined time was controlled by the number of deposition cycles and was carried out according to the parameters given in Table 1 during a sequentially pulsed supply of vapor from a group of alkoxysilanes (mainly tetraethoxysilane) and an oxidizing agent into the reactor.

The pulse durations were: tetraethoxysilane pulse - 10 s; purge gas pulse - 20 s; mixtures of ozone - oxygen - 10 s; purge gas pulse - 20 s. The total cycle time was thus 1 min. The inert purge gas flow used was many times greater than that necessary for the complete removal of residual reactants from the reactor and the gas supply lines, thus eliminating the possibility of their interaction in the gas phase of the reactor. After the deposition process was completed, the reactor was purged with inert gas, the substrate was unloaded from the reactor and the setup intermediate chamber, the substrate was moved from the intermediate chamber to the storage chamber of the installation, and the next substrate was loaded. In the case of deposition on one substrate after purging the reactor, the reactor was filled with inert gas to atmospheric pressure.

Table 1 The parameters of the pulsed deposition process of silicon dioxide Parameter Value Substrate Temperature (° C) 498 Working pressure (mmHg) 540 TEOS consumption (mg / min) 1000 O 2 / O 3 flow rate (cm 3 / min) 5000 The concentration of ozone (wt.%) 16 Oxygen consumption (cm / min) 4000 Helium purge gas flow rate (cm 3 / min) * 6000-15000 Total gas flow (cm 3 / min) 15,000 The gap between the substrate and the shower (mm) 8.9 The duration of the feed pulse of the gel oxides and TEOS (s) 10 Number of cycles 23 Note. * The minimum flow rate of helium was used to compensate for gas flow rates to a total flow rate of 15,000 cm 3 / min; the maximum flow rate of helium was used to purge the reactor.

In the modes of the pulse process indicated in Table 1, the deposition rates of silicon dioxide layers on a silicon substrate with natural oxide 0.5-0.9 nm thick were 0.08 nm / cycle. In other examples, when changing the process parameters in table 1 at intervals: temperature 488-508 ° C, pressure 200-540 mm Hg, gap 6-12 mm, total gas flow 7500-15000 cm 3 / min, speed deposition was in the range 0.06-0.1 nm / cycle. The values of the growth rate of silicon dioxide layers obtained in order in the indicated modes of deposition processes indicate the localization of the chemical reaction of the growth of a silicon dioxide layer during the interaction of TEOS and ozone on the surface of a heated substrate. The data of FIG. 6 indicates an approximately twofold difference in the deposition rates on silicon and silicon dioxide, i.e. on the presence of the effect of "surface sensitivity" in the localization of the chemical reaction of the growth of a layer of silicon dioxide on the surface of a heated substrate. The data of Fig. 7 show the dependence of the deposition rate on ozone concentration, recalculated from the data given in Table 1, into the dimension of ozone molecules per pulse. The obtained result indicates a strong effect of ozone concentration on the deposition rate, as well as the saturation of the deposition rate at 0.06 nm / cycle at ozone concentrations above 1.5 × 10 20 molecules. In this case, the amount of ozone supplied per cycle is approximately two orders of magnitude, and the TEOS is more than an order of magnitude greater than the potential amount of adsorbed molecules on a substrate surface with a diameter of 200 mm.

Thus, the pulsed mode of supply of the reaction components with the separation of the inert purge gas stream eliminates the interaction of alkoxysilane and oxidizer vapors in the gas phase and allows localizing the chemical reaction on the heated surface of the substrate.

Information sources

1. Vasiliev B.Yu. Application of methods of chemical deposition of thin layers from the gas phase for microcircuits with technological standards of 0.35-0.18 microns. Part 1. The main trends in the development of methods - Electronic technology. Ser. 2. Semiconductor Devices, 2010, no. 1 (224), p. 67-82.

2. Vasiliev B.Yu. Application of methods for chemical deposition of thin layers from the gas phase for microcircuits with technological standards of 0.35-0.18 microns. Part 5. Growth patterns and correlation of the patterns of deposition and the properties of thin layers - Electronic Technology. Ser. 2. Semiconductor Devices, 2012, Issue 2 (229), pp. 54-69.

3. US patent No. 3481781, issued 02.12.1969.

4. US patent No. 3757733, issued September 11, 1973.

5. US patent No. 5362526, issued 08.11.1994.

6. US patent No. 6583069, issued 24.06.2003.

7. US patent No. 4845054, issued 04.07.1989.

8. Fujino K., Nishimoto Y., Tokumasu N., Maeda K. Silicon Dioxide Deposition by Atmospheric Pressure and Low-Temperature CVD Using TEOS and Ozone - J. Electrochem. Soc., 1990, 137, N9, p. P. 2883-2887.

9. Fujino K., Nishimoto Y., Tokumasu N., Maeda K. Dependence of Deposition Characteristics on Base Materials in TEOS and Ozone CVD at Atmospheric Pressure - J. Electrochem. Soc., 1991, 138, N2, p. P. 550-554.

10. Fujino K., Nishimoto Y., Tokumasu N., Maeda K. Surface Modification of Base Materials for TEOS / O 3 Atmospheric Pressure Chemical Vapor Deposition - J. Electrochem. Soc., 1992, 139, N6, pp1690-1692.

11. Huang J., K.wok K., Witt D., Donohoe K. Dependence of Film Properties of Subatmospheric Pressure Chemical Vapor Deposited Oxide on Ozone-to-Tetraethylorthosilicatc Ratio - J. Electrochem. Soc., 1993, 140, N6, p. P. 1682-1686.

12. Xia L.Q., Nemani S., Galiano M., Pichai S., Changan S., Yieh E., Cote D., Conti R., Restano D., Tobben D. High Temperature Subatmospheric Chemical Vapor Deposited Unclopecl Silicate Glass. L. Solution for Next Generation Shallow Trench Isolation - J. Electrochem. Soc., 1999, 146, N3, p. P. 1181-1185.

13. Dobkin DM, Makhtari S., Schmidt M., Pant A., Robinson L. Mechanisms of Deposition of SiO 2 from TEOS and Related Organosilicon Compounds and Ozone - J. Electrochem. Soc., 1995, 142, N7, pp2332-2340.

Claims (1)

  1. A method of producing a silicon dioxide layer, including loading a semiconductor substrate into a reactor, heating the semiconductor substrate to a desired temperature in the range of 300-500 ° C, feeding alkoxysilane and oxidizing agent vapor into the reactor in the form of a mixture of oxygen and ozone with a concentration of the latter in the range 0-16 wt.%, maintaining the working pressure in the reactor in the range of 0.5-760 mm Hg, characterized in that in order to eliminate the chemical reaction of alkoxysilane and the oxidizing agent in the gas phase of the reactor and localize the process of formation of the diode layer silicon oxide on the surface of the heated substrate, the deposition process is carried out in cycles consisting of successive pulses of vapors of alkoxysilane and an oxidizing agent, separated by pulses of a purge inert gas, the pulse duration being 0.1-20 s, and the number of cycles calculated from the required layer thickness and deposition rate of the silicon dioxide layer one cycle.
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4845054A (en) * 1985-06-14 1989-07-04 Focus Semiconductor Systems, Inc. Low temperature chemical vapor deposition of silicon dioxide films
RU2077751C1 (en) * 1993-06-24 1997-04-20 Институт физики полупроводников СО РАН Process of manufacture of modified layers of silicon dioxide (variants)
US7125815B2 (en) * 2003-07-07 2006-10-24 Micron Technology, Inc. Methods of forming a phosphorous doped silicon dioxide comprising layer
US7294583B1 (en) * 2004-12-23 2007-11-13 Novellus Systems, Inc. Methods for the use of alkoxysilanol precursors for vapor deposition of SiO2 films

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4845054A (en) * 1985-06-14 1989-07-04 Focus Semiconductor Systems, Inc. Low temperature chemical vapor deposition of silicon dioxide films
RU2077751C1 (en) * 1993-06-24 1997-04-20 Институт физики полупроводников СО РАН Process of manufacture of modified layers of silicon dioxide (variants)
US7125815B2 (en) * 2003-07-07 2006-10-24 Micron Technology, Inc. Methods of forming a phosphorous doped silicon dioxide comprising layer
US7294583B1 (en) * 2004-12-23 2007-11-13 Novellus Systems, Inc. Methods for the use of alkoxysilanol precursors for vapor deposition of SiO2 films

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