GB2299711A - Method for making a semiconductor and apparatus for the same - Google Patents

Abstract

A method for making a semiconductor using corona discharge comprises; supplying 15 a first gas to at least one electrode 14a, 14b capable of generating corona discharge above a substrate 12 with an RF power source 13; irradiating ions or radicals resulting from the decomposition of said first gas by corona discharge to said substrate; and allowing said ions or radicals to chemically react with or diffuse into said substrate at atmospheric pressure. The apparatus includes a supply 20 for a second gas, such as nitrogen, to the exterior of the substrate to prevent breakdown of the first gas and to protect the substrate from contamination by external air. An exhaust system 21 is provided around the electrodes and substrate support 11.

Description

METHOD FOR MAXING A SEMICONDUCTOR AND APPARATUS FOR THE SAME BACKGROUND OF THE INVENTION The present invention relates in general to a method for fabricating a semiconductor and an apparatus for the same, and more particularly to a method for making a semiconductor, capable of performing various processes using various gases by use of an inexpensive equipment utilizing corona discharge under the atmosphere, along with the apparatus.

Hereinafter, conventional fabrication methods and apparatus are to be described with reference to a few drawings for better understanding of the background of the invention.

FIG. I shows schematically a conventional hydrogen plasma treatment apparatus. As shown in this figure, the conventional apparatus comprises a vacuum chamber 1 in which an external power source 2 enables a pair of cathodes 3 to generate radio frequency ,and an anode that consists of a substrate 4 supported by a supporter 5 are provided.

In the apparatus, a gas supply system 6 which supply hydrogen (H2) gas to the space between the pair of cathodes of the vacuum chamber 1 is set at the exterior of the chamber to control the quantity of hydrogen whereas an exhaust system 7 which appropriately maintains the pressure of the vacuum chamber 1 in working is set at one side of the chamber.

Description for the processings with the above-mentioned hydrogen plasma treating apparatus will be given next.

Hydrogen (H2) gas is supplied in the quantity of approximately 10 to 500 sccm into the vacuum chamber 1 in proportional to the size of the substrate 4 or the vacuum chamber 1. While the temperature of the substrate is maintained in a range of approximately 250 to 350 OC, reaction pressure is kept in a degree of vacuum of approximately 0.1 to 1 torr by controlling the exhaust system 7.

Under such conditions, the power which is supplied to the vacuum chamber in the quantity of approximately 0.05 to 1 W/cm) from the RF power source 2 forces the hydrogen (H2) to be separated into plasma which is then, diffused into semiconductor film on the substrate 4, resulting in the hydrogenation of the semiconductor film. At this time, the control of the apparatus is determined by the concentration of hydrogen radical (separated into plasma) on the surface of the substrate 4 and the hydrogen diffusion rate which is dependent on the substrate temperature.

Turning now to FIG. 2, there is shown another conventional apparatus for semiconductor hydrogenation treatment, which employs light for the hydrogenation. As shown in this figure, this apparatus comprises of a chamber 1 in which a substrate 4 supported by a substrate supporter 5 is provided in a lower portion, a gas supply system supplying gas such as H2 or Hg in a constant quantity, an exhaust system 7 keeping the degree of vacuum within the chamber 1 constant, dependent on the working of a vacuum pump, a quartz perspective window 8 mounted on the upper portion of the chamber, and a low pressure mercury lamp 9 illuminating the chamber through the quartz perspective window 8.

In such apparatus, hydrogen (H2) and mercury (Hg) gases are, at same time, supplied from the gas supply system 6 into the vacuum chamber 1 in constant flow rates, respectively.

Illumination of the ultraviolet rays with wavelengths of 184.9 and 254 nm causes Hg to become an excited state (Hgt) which, in turn, decomposes H2 gas into radicals. The hydrogen radicals diffuses into a semiconductor film to hydrogenate it.

The apparatus is controlled by the concentration of hydrogen radical on the surface of the substrate and the hydrogen diffusion rate which is dependent on the substrate temperature. The H2 concentration is determined by the partial pressures of s2 and Hg within the vacuum chamber 1.

The conventional apparatuses for the treatment of semiconductor hydrogenation and methods according to the same show problems as follows: first, since the hydrogenation processes are carried out within the vacuum chamber 1, an exhaust system must be required; second, accordingly, the high cost of equipment is needed due to the high priced chamber and the exhaust system; third, the time for treating the substrate is lengthened because processes are carried out in a vacuum state; fourth, if the apparatus shown in FIG. 1 is used in a step of process which is mainly performed under atmosphere, the vacuum formation within the vacuum chamber becomes a factor that lowers the productivity; fifth, since the apparatus described with reference to FIG. 2 use mercury (Hg), there occur pollution problems; sixth, in case that a large substrate is made, it is required to scale make large the quartz perspective window 9 passing the light irradiated from the low pressure mercury lamp 9; finally, since the low pressure mercury lamp is unable to uniformly illuminate large area, it is difficult to make a semiconductor with a good quality.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the aforementioned problems encountered in the prior arts and to provide a method for making a semiconductor, capable of consistently producing semiconductors in mass and improving the productivity, along with an apparatus for the method.

According to an aspect of the present invention, this object can be accomplished by providing a method for making a semiconductor which comprises the steps of: supplying a reactive gas to, at least, one electrode capable of generating corona discharge above a substrate with an RF power source under the atmosphere; irradiating ions or radicals resulted from the decomposition of said reactive gas by said corona discharge to said substrate; allowing said ions or radicals to be chemically reacted with said substrate or be diffused in said substrate.

According to another aspect of the present invention, this object cab be accomplished by providing an apparatus which comprised of: at least, one electrode installed above a substrate supporter, said electrode being generating corona discharge with an RF power source; a gas supply system supplying a reactive gas to said electrode; an exhaust system installed around said substrate support and said electrode, said exhaust system preventing a substrate from being contaminated by external air.

The above and other objects and advantages of the present invention will become more apparent as the following description proceeds.

The following description and the annexed drawing set forth in detail a certain illustrative embodiment of the invention, this being indicative, however, of but one of the various ways in which the principles of the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS In the annexed drawing: FIG. 1 is a schematic sectional view illustrating a conventional apparatus for hydrogenating semiconductor; FIG. 2 is a schematic sectional view illustrating another conventional apparatus for hydrogenating semiconductor; FIGS. 3a and 3b are schematic views explaining a semiconductor treatment apparatus in accordance with one eiiodirnent of the present invention: : FIG. 4 is a graph of 3 relation between the inter electrode distance and the c scharge initiation voltage in accordance with an sixdiment of the present invention; FIG. 5 is an analysis graph of a hydrogen distribution in a silicon wafer formed with an amorphous silicon film and hydrogenated in accordance with an embodiment of the present invention; and FIGS. 6a and 6b are a sectional view and a crosssectional view illustrating a semiconductor treatment apparatus in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, preferred embodiments of the present invention will be described in detail with reference to several irawincs vherein like reference numerals designate like parts. FIG. 3 schematically shows semiconductor treatment apparatus emboding the present invention.As shown in the figure, the apparatus comprises of a substrate supporter 11 supporting a substrate 12 thereon and heating at a constant temperature, a power source 13 applying RF electric power so as to generate corona c.scharge, at least an electrode 14 connected with the power source and a gas supply system li. For treating the substrate, above the substrate supporter 11 supporting the substrate 12 thereon are provided a pair of electrode 14 which are connected with the RF power source 13 and the earth, respectively, as snown in FIG. 3A. Alternatively, only an electrode 14 is provided which is connected with the RF power source 13, while the substrate supporter 11 supporting the substrate 12 is earthed, as shown in FIG. 3B.In any cases, application of the RF power source generates corona discharge between a pair of electrodes 14, or the electrode 14 and the substrate support 11.

In the state that the corona discharge occurs, reactive gas selected from the group consisting of H2, O2,SiH4, SiF4, Si2H6, GeH4, Ge2H,He, Ar, O, CF4, SF6, CiF2, NF3, CC12F2, C12, CCl4, WF6, 2MoCl5, Cr(C6H5CH(CH3)2]2, Al(C4F)3 is supplied from the gas supply system into the upper region of the electrode 14. The electrons which are exited between a pair of the electrodes 14 make the molecules of the reactive gas become ions and radicals with high energies. The ions and radicals with high energies which are generated by the corona discharge causes chemical reaction or diffuses on the surface of semiconductor.

Such processes are performed under the atmosphere pressure. While the processes proceed, it is preferred to supply nitrogen (N^) to the surrounds of the electrode 14 n order to prevent the substrate from being contaminated with other gases (the air) besides the reactive gas.

The electrode used includes a high melting metal such as W, Ta and the like and is subjected to surface treatment by use of :go or Sino.

The power source used employs a high frequency power of above 100 KHz in order to prevent arc discharge and to constantly generate corona discharge.

An field which is generated by the power source and determined by the distance dl between the electrodes 14 or the distance d2 between the electrode 14 and the substrate 12 is preferably above 1 KV/mm (for example, d., d2-5, Sky).

Referring now to FIG. 4, there is shown dependency of initialization voltage of charge (Vi) on the distance d2 between electrodes of FIG. 3B. From the curves for different diameter cases, that is, ,-i mm, #2=2 mm, a.-4 mm, it is found that Vi is in proportional to log d. Tn addition, as the diameter of the electrode is small, the Vi becomes reduced.

For example, using a high frequency power source with 80 KHz, discharge is initialized at 6 KV in the apparatus of FIG.

3A under such a condition that the electrode is made of 3 tungsten line enveloped with melted Sing, the distance dl S 2 mm and hydrogen is supplied in the quantity of 200 sccm.

Turning now to FIG. 5, there is shown a profile illustrating the distribution state of hydrogen within an amorphous silicon film which is formed on a silicon wafer (substrate) in a t;-ickness of 3,000 A by low pressure chemical vapor deposition (LPCVD), heated to 350 OC, and then, treated at 8 KV for 30 minutes in accordance with an embodiment of the present invention From the profile, t is apparent that the H2 concentration within the surface is at least octuple as much as the initiai concentration. n addition, since the concentration of hydrogen according to the depth of the amorphous silicon is profiled as an error function, the substrate is hydrogenated by the hydrogen diffusion dependent on the substrate temperature.

A preferred embodiment is to be described with reference to FIGS. 6a and 6b. In accordance with this embodiment a semiconductor thin film formed on a large sized insulating film is capable or being treated in sequence under the atmosphere. An electrode which causes corona discharge is comprised of a first electrode l4a and a second electrode 14b.

The first electrode 14a which is made of a metal selected from the group consisting of W, Nb, Ta and ;lo is coated with a metal oxide film selected from the group consisting of Ta2Oc, Nb2O51 SiO2 and flgO, and the surface of the second electrode is treated with a metal oxide film, as well. The second electrode 14b is formed in the outside of the first electrode 14a in such a way to provide, at least, a discharge chamber 16 which has a tube shape and extends in an X direction. The first electrode lEa shapes into a line or a bar and has a diameter of at least 1 mm. A reactIve gas is supplied into the space between the first electrode 14a and the second electrode 14b, that is, the discharge chamber 16 by a gas supply system ~~ which also controls the flow rates so as to supply the gas in a constant quantity.

A diffuser IT is provided at an upper portion of the discharge chamber 16, which plays a role in supplying the reactive gas more uniformly.

An RF power source 13 used in the apparatus employs AC voltage that has the maximum level of 20KV at 80KHz. The RF power source 13 is connected between the first electrode 14a and the second electrode 14b.

Ions and radicals with high energies which results from the decomposition of the reactive gas are passed through a nozzle which has a taper slit shape.

A substrate 12 is laid on a timing belt 18 disposed above a substrate supporter 11 and fed to the substrate supporter 11, followed by heating of the substrate 12 into a predetermined temperature. The processing degree is controlled by the flow rate of reactive gas, a discharge voltage, a feed speed, the heating temperature of the substrate temperature. Nitrogen (N2) gas is supplied to the exterior of substrate 12 in order to prevent the reactive gas from being leaked and protect the apparatus from being contaminated with the air. The nitrogen gas is supplied from a nitrogen supply system 20 via a nitrogen inlet 19, so that the leakage of the reactive gas and the contamination of the substrate can be prevented. Exhaust systems 21 which exhaust the reactive gas is piaced above the timing belt 18 and at the outside thereof.Unreacted gas may pollute the air and thus, is not exhausted until it is oxidized with oxygen.

The dependence of production process on the kind of the reactive gas will be further described with reference to specific examples.

EXAMPLE 1 Process for Dopping Impurities in Wafer.

Instead of hydrogen gas used in the described ernbodiment, phosphine (PH3), diborane (B2HS) and arsine (AsH,) gas containing 3 or S valence elements which are gases for dopping semiconductor impurity were supplied to the discharge chamber 16 via the gas supply system 15 and the diffuser 17, decomposed by means of corona discharge, and diffused in the semiconductor thin film on the surface of the substrate 12 to give an n type or p type semiconductor.

As compared with a conventional semiconductor dopping method whereby ions are diffused at a high temperature to be implanted, the method embodying the present invention whereby 3 or 5 valence elements to be decomposed with a high energy are irradiated to the substrate under the atmosphere allows large-sized substrate including a semiconductor thin film to be treated with impurities in a large scale.

EXAMPLE 2 Process for Washing Surface and Removing Polymer Film.

Instead of hydrogen (H2) gas used in described aodimcnt, oxygen (02) gas was decomposed to irradiate oxygen ions and radicals with high energies to the surface of the substrate 12.

The oxygen ions and radicals with high energies react with the organic materials remaining on the surface of the substrate 12 so as to oxidize and remove them.

Such process applicable to an ashing process which is for removing a photo resist film is capable of being carried out in a large scale by using high energy oxygen ions and radicals under the atmosphere, as compared with a conventional dry etch or UV ashing process.

EXAMPLE. 3 Process for Forming Semiconductor Film.

Instead of hydrogen (H2) gas used in the described eSxdIment, silane gases (SiS4, Si2H6, SiF4) was decomposed by means of corona discharge to irradiate the silane ions and radicals with high energies to the surface of the substrate 12. As a resuit, an amorphous silicon film or a polysilicon film was formed.

While t.e conventional apparatus for forming a semiconductor film is comprised of a high priced vacuum installations, the present apparatus is capable of being carried out to forming a semiconductor film in sequence under the atmosphere.

EXAMPLE 3 Process for Forming Insulating Film.

Instead of hydrogen (H2) gas used in the described embodiment , silane gases (SiS4, Si2H6, SiF4) were used in admixture with oxidative gases (021 N20) or a gas for nitride film (NHj)w to form a silicon oxide film and a silicon nitride film.

Instead of the silane gases, a reactive gas containing various metals such as WF6, 2MoC15, Cr!C6H5CH(CH2)2J2 and Al(C4F)3 was admixed with an oxidative gas or a gas for nitride film to form a metal oxidative gas or metal nitride film.

EXAMPLE 3 Dry Etch Process.

Instead of hydrogen (H2) gas used in the described sixdiment a gas for dry etch, such as CF4, NF3, CH2F21 SF6, CC12F2 was decomposed by means of corona discharge to irradiate the gas ions and radicals with high energies to the surface of the substrate 12. As a result, the present process allows a dry etch process to be applied to a metal film, semiconductor film and insulating film.

As described hereinbefore, gases selected for desirable purposes can be decomposed by means of corona discharge to irradiate the ions and radicals of the gas to a substrate surface, resulting in chemical reactions or diffusion of the ions and radicals under the atmosphere.

Accordingly, a large-sized substrate can be treated in more improved efficiency.

In addition, the apparatus can be used in the process that is carried out under the atmosphere, thereby enabling a total production process to proceed in sequence and bringing about such an effect that semiconductors are consistently produced in mass.

Claims (20)

1. An apparatus for making a semiconductor, comprising:

at least one electrode installed above a supporter for supporting a substrate and adapted to receive an RY voltage to perform corona discharge; a gas supply system supplying a reactive gas to said electrode; an exhaust system installed around said substrate supporter and said electrode and adapted to prevent said substrate from being contaminated by external air.

2. An apparatus according to Claim 1, wherein said electrode comprises a first electrode and a second electrode, said first electrode and the second electrode defining a discharge chamber therebetween.

3. An apparatus according to Claim 2, wherein said first electrode is made of a metal selected from the group consisting of W, Nb, Ta, and Mo.

4. An apparatus according to Claim 2, wherein said second electrode is provided at its surface with a metal oxide film.

5. An apparatus according to Claim 2 or 3, wherein said first electrode is coated at its surface with one selected from the group consisting of Ta2051 Nb205, r Sio2 and MgO.

6. An apparatus according to Claim 2, wherein said first and second electrodes are arranged such that the second electrode surrounds the first electrode to define a space therebetween, said space constituting said discharge chamber.

7. An apparatus according to Claim 6, wherein said gas supply system has a diffuser for uniformly distributing said reactive gas in an upper portion of said discharge chamber.

8. An apparatus according to Claim 1, further comprising a timing belt disposed above said substrate supporter and adapted to continuously feed substrates.

9. An apparatus for making a sanicooductor substatialiy as herein described with reference to Figures 3a-6b of the accapanyihg drawings.

10. A method for making a semiconductor using corona discharge, which comprises the steps of: supplying a reactive gas to, at least, one electrode capable of generating corona discharge above a substrate with an RY power source under the atmosphere; irradiating ions or radicals resulted from the iecomposition of said reactive gas by said corona discharge to said substrate; allowing said ions or radicals to be chemically reacted with said substrate or be diffused in said substrate.

11. A method according to Claim 10, which further comprising the step of supplying nitrogen (N2) gas into the outside of said reactive gas supplied into said electrode in order to preventing the leakage of said reactive gas and the contamination caused by the air.

12. A method according to Claim 10, wherein said reactive gas is hydrogen (R,), said hydrogen gas being decomposed by said corona discharge into hydrogen ions or radicals which are irradiated to said substrate to diffuse in said semiconductor film.

13. A method according to Claim 10, wherein said reactive gas is oxygen (02) gas, said oxygen gas being decomposed by said corona discharge into hydrogen ions or radicals which are irradiated to said substrate to form an oxide film by reacting or oxidize materials on the surface of said substrate, whereby an oxide film can be formed on said substrate or said material can be oxidized to be removed in gaseous state.

14. A method according to Claim 10, wherein said reactive gas is a silane type gas selected from the group consisting of SiS4, SiF4 and Si2H5, said silane type gas being decomposed by corona discharge into ions or radical including silicon which are irradiated to said substrate to form an amorphous silicon or polysilicon on said substrate.

15. A method according to Claim lO,wherein said reactive gas is a germanium type gas selected from the group consisting of Get4, GeF4 and Ge2Ei, said silane type gas being decomposed by corona discharge into ions or radical which are irradiated to said substrate to form an amorphous germanium or polygermanium on said substrate.

16. A method according to Claim I0,wherein said reactive gas is an inert gas selected from Be and Ar, said inert gas reacting with a so lane type gas supplied to the around of said substrate whereby an amorphous silicon or polysilicon film is formed on the surface of said substrate.

17. A method according to Claim 10, wherein said reactive gas is a gas containing oxygen (0) or nitrogen (N), said gas being decomposed by corona discharge into ions or radical including silicon which are irradiated to said substrate to form a silicon oxide film or a silicon nitride film.

18. A method according to Claim 10, wherein said reactive gas is selected from the group consisting of CF4, SF6, CUFF2, NF3, CC12F2, C12 and CC14, said gas being decomposed by corona discharge into ions or radical which are irradiated to said substrate to etch materials on the surface of said substrate.

19. A method according to ClaimlO, wherein said reactive gas is a germanium type gas selected from the group consisting of WF6, 2MoCl5, Cr(C6H5CH(CH3)2]2 and Al(C4H9)3, said gas being decomposed by corona discharge into ions or radical which are irradiated to said substrate to deposit a metal selected from the group consisting of W, Mo, Cr, and Al.

20. A method for making a semiconductor substantially as herein described with reference to Figures 3a-6b of the accoenying draings.