# Patent

## Title
Diethylsilane as a silicon source in the deposition of metal silicate films

## Abstract

A method for forming a metal silicate as a high k dielectric in an electronic device, comprising the steps of: providing diethylsilane to a reaction zone; concurrently providing a source of oxygen to the reaction zone; concurrently providing a metal precursor to the reaction zone; reacting the diethylsilane, source of oxygen and metal precursor by chemical vapor deposition to form a metal silicate on a substrate comprising the electronic device. The metal is preferably hafnium, zirconium or mixtures thereof. The dielectric constant of the metal silicate film can be tuned based upon the relative atomic concentration of metal, silicon, and oxygen in the film.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/809,255 filed May 30, 2006.


BACKGROUND OF THE INVENTION
The electronics fabrication industry uses metal silicate films of zirconium or hafnium in the fabrication of electronic devices, such as used for high dielectric constant materials and gate dielectric films.
Metal silicates for electronic materials have been studied by those skilled in the art. For instance, Wilk, et. al., Hafnium and Zirconium silicates for advanced gate dielectrics, Journal of Applied Physics, Vol. 87, No. 1, 2000, pp. 484-492 describe the use of metal silicates as gate dielectric films with varying metal contents. Depositions were by sputtering and e-beam evaporation. Separate films were deposited at specific temperatures chosen over the range of 25° C. to 600° C.
U.S. Pat. No. 6,841,439 identifies metal silicates as desirable gate dielectric films and describes various synthesis routes.
US Pat. Appl. Pub. No. US 2005/0139937 A1 Pub. Date: Jun. 30, 2005, describes the growth of hafnium silicate films by atomic layer deposition, a process whereby the hafnium, silicon, and oxygen sources are alternately fed to and purged from the deposition chamber. The growth rates of the atomic layer deposition process are very low.
The present invention overcomes this deficiency by co-feeding the metal, silicon, and oxygen sources simultaneously to the deposition chamber in a chemical vapor deposition.
BRIEF SUMMARY OF THE INVENTION
One embodiment of the present invention is a method for forming a metal silicate as a high k dielectric in an electronic device, comprising the steps of: providing diethylsilane to a reaction zone; concurrently providing a source of oxygen to the reaction zone; concurrently providing a metal precursor to the reaction zone; reacting the diethylsilane, source of oxygen and metal precursor by chemical vapor deposition to form a metal silicate on a substrate.
Another embodiment of the present invention is a method for forming hafnium silicate as a high k dielectric in an electronic device, comprising the steps of:

    
    
        providing diethylsilane to a reaction zone;
        concurrently providing a source of oxygen to the reaction zone;
        concurrently providing tetrakis(diethylamino)hafnium to the reaction zone;
        reacting the diethylsilane, source of oxygen and tetrakis(diethylamino)hafnium by chemical vapor deposition to form hafnium silicate on a substrate comprising the electronic device.
    
    


Another embodiment of the present invention is a method for forming zirconium silicate as a high k dielectric in an electronic device, comprising the steps of:

    
    
        providing diethylsilane to a reaction zone;
        concurrently providing a source of oxygen to the reaction zone;
        concurrently providing tetrakis(diethylamino)zirconium to the reaction zone;
        reacting the diethylsilane, source of oxygen and tetrakis(diethylamino)zirconium by chemical vapor deposition to form zirconium silicate on a substrate comprising the electronic device.
    
    


The present invention also shows that the metal silicate film dielectric constant can be tuned based upon the relative atomic concentration of metal, silicon, and oxygen in the film.



BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 shows the absorbance as a function of Wavenumbers (cm−1) for films deposited from: a zirconium oxide film from Zr(N(CH2CH3)2)4 alone—V1519; a silicon oxide film from Diethylsilane alone—V1522; and a zirconium silicate film from Zr(N(CH2CH3)2)4 and Diethylsilane—V1525; in accordance with Table III.
FIG. 2 shows the index of refraction of Hf—Si—O films as a function of the flow rate (sccm) of SiH2(CH2CH3)2; in accordance with Table V.



DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to the formation of metal silicates as high k dielectrical for an electronic device. The metal, silicon, and oxygen sources are simultaneously fed to the deposition chamber in a chemical vapor deposition. Among the silicon sources, diethylsilane has been selected in the deposition of metal silicate films in the present invention. The growth rate of the metal silicate is faster than that achieved by atomic layer deposition. Lower carbon contamination in metal silicate films are found as compared with our previously reported and demonstrated process, U.S. Pat. No. 6,537,613 (which is hereby specifically incorporated by reference in their entirety herein), that uses silicon amides as the silicon source. Lower carbon contamination results in higher dielectric constants. Another benefit is that silicon incorporation into these films can be achieved at lower process temperatures as compared with a process that uses silicon amides as the silicon source; the thermal process budget is reduced (and, thus, process cost is reduced). And most importantly, the present invention also shows that the dielectric constant of the metal silicate film can be tuned based upon the atomic concentration of metal, silicon, and oxygen in the film.
A Chemical Vapor Deposition (CVD) system is configured to simultaneously receive metal precursor feed by Direct Liquid Injection (DLI) (converted to vapor before the reaction zone), silicon precursor vapor feed by Vapor Draw, and oxygen reactant gas feed into the reaction zone above the heated substrate. The temperature and pressure of the reaction zone are established; and the precursor vapor and reactant gas flows are established prior to introduction into the reaction zone. A substrate is introduced into the reaction zone and allowed to equilibrate to the temperature and pressure of the reaction zone. The precursor vapor and reactant gas flows are introduced into the reaction zone and are allowed to flow for a time sufficient to grow a metal silicate film.
The operating conditions are: pressure ranging from 0.5 to 2 Torr; substrate temperature ranging from 250° C.-450° C.; DLI vaporizer temperature ranging from 85° C.-95° C.; metal precursor flow rate ranging from 0.05 to 0.1 ml/min; helium carrier gas flow ranging from 100 to 150 sccm (Standard Cubic Centimeters per Minute); silicon precursor flow rate ranging from 5 to 100 sccm; helium dilution gas flow rate ranging from 0 to 50 sccm, residence time ranging from 0.05 to 2 seconds.
WORKING EXAMPLES
The present invention is illustrated in the following examples.
Example 1 
Zr—Si—O Thin Film 
Reactants used in the Zr—Si—O thin film deposition were:
1) Tetrakis(DiEthylAmino)Zirconium(IV)—TDEAZ, Zr(N(CH2CH3)2)4;
2) diethylsilane—DES (LTO-410), SiH2(CH2CH3)2; and
3) oxygen, O2.
Liquid Tetrakis(DiEthylAmino)Zirconium(IV) was delivered at 0.1 mL per minute to a direct liquid injection system with subsequent a vaporization at a temperature of 90° C. using a helium sweep gas flow of 100 sccm into a manifold that feeds a precursor delivery ring situated below the gas showerhead in a single wafer, cold wall LPCVD reactor. Diethylsilane vapor was simultaneously delivered at 6.3 sccm through a 100 sccm nitrogen Mass Flow Controller (MFC) (equivalent to 18 sccm full scale flow of diethylsilane) into the aforementioned manifold. Flows of oxygen varied between 100 sccm and 150 ccm, were delivered to the showerhead of this reactor. These three flows were simultaneously directed onto a silicon wafer that was maintained at temperatures between 250° C. and 450° C. on a resistively heated wafer pedestal. The reactor chamber pressure was varied between 1 Torr and 1.5 Torr.
Table I shows the process parameters required to deposit a ZrO2 film from Zr(N(CH2CH3)2)4 and O2; “TDEAZ Only”.
Table II shows the process parameters required to deposit a SiO2 film from SiH2(CH2CH3)2 and O2; “DES Only”.
Table III shows the process parameters required to deposit a Zr—Si—O film by simultaneously delivering Zr(N(CH2CH3)2)4, SiH2(CH2CH3)2 and O2 to the reaction chamber; “TDEAZ and DES”.
As shown in Table I, a high deposition rate and high index of refraction were obtained for ZrO2 film.
As shown in Table II, a relatively lower index of refraction was obtained from SiO2 film. The deposition rate varied.
Table III indicates a relatively lower deposition rate of the zirconium silicate film. The index of refraction of Zr—Si—O film is much higher than the index of refraction of SiO2 film, and thus the high dielectric constant k of Zr—Si—O film.







TABLE I







TDEAZ Only


















Wafer





Run
Index

Dep



Temp
Press
DLI
He Swp
DES
O2
time
of Ref.
Thickness
Rate


Run
(° C.)
(mTorr)
(ml/min)
(sccm)
(sccm)
(sccm)
(min)
n
(Å)
(Å/min)




















V1519
296
1000
0.1
100
0
100
2.5
2.146
2618
1047


V1520
316
1000
0.1
100
0
100
1.2
2.143
1857
1592


V1521
277
1000
0.1
100
0
100
3.5
2.092
2412
689
















TABLE II







DES Only


















Wafer





Run
Index

Dep



Temp
Press
DLI
He Swp
DES
O2
time
of Ref.
Thickness
Rate


Run
(° C.)
(mTorr)
(ml/min)
(sccm)
(sccm)
(sccm)
(min)
n
(Å)
(Å/min)





V1522
400
variable
0
0
variable
100
na
1.444
variable
variable
















TABLE III







TDEAZ and DES

























Index





Wafer





Run
of

Dep



Temp
Press
DLI
He Swp
DES
O2
time
Ref.
Thickness
Rate


Run
(° C.)
(mTorr)
(ml/min)
(sccm)
(sccm)
(sccm)
(min)
n
(Å)
(Å/min)










DES injected through ring

















V1525
405
1500
0.1
100
6.3
100
1.5
1.942
923
615


V1526
405
1500
0.1
150
6.3
100
1.5
1.882
931
621


V1527
405
1500
0.1
100
6.3
150
2
1.711
606
303









FIG. 1 shows the individual FTIR spectra of the ZrO2, SiO2, and the Zr—Si—O films superimposed on each other. Run V1519 is the spectrum of the ZrO2 film. The absorbance at 1545 wavenumbers is the indication of a Zr—O—Zr stretch. Run V1522 is the spectrum of the SiO2 film. The absorbance at 1074 wavenumbers is the characteristic of the Si—O—Si stretch. Run V1525 is the spectrum of the Zr—Si—O film; it exhibits the characteristic peaks of both the individual oxides, and thus indicates the characteristics of a Zr—Si—O film.
Example 2 
Hf—Si—O Thin Film 
Similar experiments as shown in Example 1 have been performed for Hf—Si—O thin film. Note that, chemical properties of Hafnium and Zirconium are very similar since they belong to the same group in the periodic table.
Reactants used in the Hf—Si—O thin film deposition were:
1) Tetrakis(DiEthylAmino)Hafnium(IV)—TDEAH, Hf(N(CH2CH3)2)4;
2) diethylsilane—DES (LTO-410), SiH2(CH2CH3)2; and
3) oxygen, O2.
Liquid Tetrakis(DiEthylAmino)Hafnium(IV) was delivered at 0.1 mL per minute to a direct liquid injection system with subsequent a vaporization at a temperature of 90° C. using a helium sweep gas flow of 100 sccm into a manifold that feeds a precursor delivery ring situated below the gas showerhead in a single wafer, cold wall LPCVD reactor. Diethylsilane vapor was simultaneously delivered at 6.3 to 45 sccm through a 500 sccm nitrogen MFC (equivalent to 90 sccm full scale flow of diethylsilane) into the aforementioned manifold. Flows of oxygen varied between 75 sccm and 100 sccm, were delivered to the showerhead of this reactor. These three flows were simultaneously directed onto a silicon wafer that was maintained by heater set point, which was at 650° C. and 700° C., on a resistively heated wafer pedestal. The reactor chamber pressure was varied between 0.5 Torr and 1.5 Torr.
Table IV shows the process parameters required to deposit an HfO2 film from Hf(N(CH2CH3)2)4 and O2; “TDEAH Only”.







TABLE IV







TDEAH Only
























Index






Wafer


He

Run
of


FTIR



Temp
Press
DLI
Swp
O2
time
Ref.
Thickness
Dep Rate
Peak


Run
(° C.)
(mTorr)
(ml/min)
(sccm)
(sccm)
(min)
n
(Å)
(Å/min)
(cm−1)




















V1541
255
1000
0.1
100
100
5
1.954
784
156.8
1582.6









1.957
810
162.0
1583









2.177
891
178.2
2210


V1542
253
1000
0.1
100
100
5
1.959
737
147.4
1574









1.968
850
170.0
2210









1.972
918
183.6









Table V shows the process parameters required to deposit a Hf—Si—O film by simultaneously delivering Hf(N(CH2CH3)2)4, SiH2(CH2CH3)2 and O2 to the reaction chamber; “TDEAH and DES”.
Again, as for the Zi—Si—O films, Table IV indicates that the index of refraction of Hf—Si—O film is much higher than the index of refraction of SiO2 film, and thus the high dielectric constant k of Hf—Si—O film.
Most importantly, Table V also indicates that the index of refraction of Hf—Si—O films vary with the relative concentration (represented by the flow rates) of hafnium, silicon, and oxygen used in the CVD process.
As an example, FIG. 2 shows the index of refraction of Hf—Si—O films as a function of the flow rate (sccm) of SiH2(CH2CH3)2, in accordance with Table V. The silicon precursor flow rate varied from 6.3 sccm to 25 sccm; while the other conditions were kept unchanged. The pressure was at 1.5 Torr; the wafer temperature was at 492° C.; metal (Hafnium) precursor flow rate was at 0.1 ml/min; helium carrier gas flow was at 100 sccm; helium dilution gas flow rate was at 0 sccm; and oxygen flow rate was at 100 sccm.







TABLE V







TDEAH and DES



























Index



Wafer




He
Dep
Dep
Thick-
of



Temp
Press
DLI
DES
O2
dilute
Time
Rate
ness
Ref.


Run
(° C.)
(Torr)
(ml/min)
(sccm)
(sccm)
(sccm)
(min)
(Å/min)
(Å)
n




















1443-47-1
492
1.5
0.1
6.3
100
—
1.5
898
1347
1.9201


1443-47-2
492
1.5
0.1
6.3
100
—
1.5
1068
1602
1.9246


1443-48-1
492
1.5
0.1
10.3
100
—
1.5
1031
1546
1.8983


1443-48-2
492
1.5
0.1
14.3
100
—
1.5
999
1499
1.8459


1443-48-3
492
1.5
0.1
14.3
100
—
1.6
1093
1748
1.8451


1443-48-4
492
1.5
0.1
25
100
—
1.5
1477
2216
1.7599


1443-48-5
492
1.5
0.1
25
100
—
1
1417
1417
1.7870


1443-49-1
523
1.5
0.1
25
100
30
1
879
879
1.7881


1443-49-2
523
1.5
0.1
25
100
15
1
1366
1366
1.7558


1443-49-3
523
1.5
0.1
25
75
15
1
831
831
1.7095


1443-49-4
523
1.5
0.1
25
75
30
2.5
1408
3519
1.8332


1443-50-1
523
1.5
0.1
25
75
30
1
570
570
1.6874


1443-50-2
523
1.5
0.1
25
75
30
2.5
578
1444
1.7707


1443-50-3
523
1.5
0.1
25
75
0
1
164
164
1.3200


1443-50-4
511
1
0.1
25
100
0
1
1357
1357
1.8047


1443-50-5
493
0.5
0.1
25
100
0
1
1061
1061
1.8920


1443-50-6
493
0.5
0.1
25
100
5
1
1049
1049
1.9014


1443-51-1
493
0.5
0.05
25
100
5
1
792
792
2.0525


1443-51-2
511
1
0.1
45
100
15
1
1084
1084
1.7652


1443-51-3
511
1
0.1
45
100
10
1
1321
1321
1.7887









The salient feature shown in FIG. 2 is the index of refraction of the Hf—Si—O films (thus the dielectric constant of the Hf—Si—O film) decreases approximately linearly as the flow rate of the silicon precursor (thus the relative atomic concentration of silicon) increases. Therefore, FIG. 2 clearly indicates that the dielectric constant of hafnium silicate films can be tuned based upon the atomic concentration of hafnium, silicon, and oxygen in the film.
The embodiments of the present invention listed above, including the working examples, are exemplary of numerous embodiments that may be made of the present invention. It is contemplated that numerous other configurations of the process may be used, and the materials used in the process may be selected from numerous materials other than those specifically disclosed. In short, the present invention has been set forth with regard to particular embodiments, but the full scope of the present invention should be ascertained from the claims as follow.

## Claims

1. A method for forming a metal silicate as a high k dielectric in an electronic device, comprising the steps of:
providing diethylsilane at a flow rate of 5 to 100 standard cubic centimeters per minute to a reaction zone;
concurrently providing a source of oxygen to the reaction zone;
concurrently providing a metal precursor at a flow rate of 0.05 to 0.1 milliliters per minute to the reaction zone;
reacting the diethylsilane, source of oxygen and metal precursor by chemical vapor deposition to form a metal silicate on a substrate comprising the electronic device.

2. The method of claim 1 wherein the source of oxygen is selected from the group consisting of oxygen gas, air, ozone and mixtures thereof.

3. The method of claim 1 wherein the residence time of the diethylsilane, source of oxygen and metal precursor in the reaction is in the range of 0.05 to 2 seconds.

4. The method of claim 1 wherein the high k of metal silicate is changed by varying relative atomic concentration of metal precursor, diethylsilane, and oxygen in the reaction zone.

5. The method of claim 1 wherein the metal precursor is selected from the group consisting of metal amide, metal alkoxide and mixtures thereof.

6. The method of claim 5 wherein the metal is selected from the group consisting of hafnium, zirconium, and mixtures thereof.

7. The method of claim 1 wherein the diethylsilane, source of oxygen and metal precursor are reacted under chemical vapor deposition conditions.

8. The method of claim 7 wherein the chemical vapor deposition conditions comprise a pressure in the range of 0.5 to 2 Torr, and a temperature in the range of 250° C. to 450° C.

9. The method of claim 8 wherein a sweep gas is in the range of 100 to 150 standard cubic centimeters per minute.

10. The method of claim 9 wherein the sweep gas is selected from the group consisting of helium, argon, nitrogen and mixtures thereof.

11. A method for forming hafnium silicate as a high k dielectric in an electronic device, comprising the steps of:
providing diethylsilane at a flow rate of 5 to 100 standard cubic centimeters per minute to a reaction zone;
concurrently providing a source of oxygen to the reaction zone;
concurrently providing tetrakis(diethylamino)hafnium at a flow rate of 0.05 to 0.1 milliliters per minute to the reaction zone;
reacting the diethylsilane, source of oxygen and tetrakis(diethylamino)hafnium by chemical vapor deposition to form hafnium silicate on a substrate comprising the electronic device.

12. The method of claim 11 wherein the high k of hafnium silicate is changed by varying relative atomic concentration of tetrakis(diethylamino)hafnium, diethylsilane, and oxygen in the reaction zone.

13. The method of claim 11 wherein the chemical vapor deposition conditions comprise a pressure in the range of 0.5 to 2 Torr, and a temperature in the range of 250° C. to 450° C.

14. A method for forming zirconium silicate as a high k dielectric in an electronic device, comprising the steps of:
providing diethylsilane at a flow rate of 5 to 100 standard cubic centimeters per minute to a reaction zone;
concurrently providing a source of oxygen to the reaction zone;
concurrently providing tetrakis(diethylamino)zirconium at a flow rate of 0.05 to 0.1 milliliters per minute to the reaction zone;
reacting the diethylsilane, source of oxygen and tetrakis(diethylamino)zirconium by chemical vapor deposition to form zirconium silicate on a substrate comprising the electronic device.

15. The method of claim 14 wherein the high k of zirconium silicate is changed by varying relative atomic concentration of tetrakis(diethylamino)zirconium, diethylsilane, and oxygen in the reaction zone.

16. The method of claim 14 wherein the chemical vapor deposition conditions comprise a pressure in the range of 0.5 to 2 Torr, and a temperature in the range of 250° C. to 450° C.