Elm Exhibit 2147
`Samsung, Micron, SK hynix v. Elm
`IPR2016-00703
`
`

`
`U.S. Patent
`
`Jul. 28, 1998
`
`Sheet 1 of 2
`
`5,786,278
`
`
`HIGH PRESSURE
`ANNEALI NG
`
`CHAMBER
`
`
`
`INTEGRATED
`CIRCUIT
`WAFER
`
`INTEGRATED
`CIRCUIT WAFER
`WITH SiO2 FILM
`
`F/G_/
`
`PROCESSED
`INTEGRATED
`CIRCUIT WAFER
`
`STRESS
`CONVERSION
`POINT
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`TEMPERATURE
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`
`Elm Exhibit 2147, Page 2
`
`

`
`U.S. Patent
`
`Jul. 28, 1998
`
`Sheet 2 of 2
`
`5,786,278
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`TEMPERATURE
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`Elm Exhibit 2147, Page 3
`
`

`
`5 ,786.278
`
`1
`METHOD OF STRESS-RELIEVING SILICON
`OXIDE FILMS
`
`BRIEF SUMMARY OF THE INVENTION
`
`This invention relates generally to a method of stress
`relieving APCVD silicon oxide based films. and more par-
`ticularly to a method of converting tensile stress to com-
`pressive stress in such films by processing at high pressure
`and low temperature.
`BACKGROUND OF THE INVENTION
`
`Tetracthoxysilane (TEOS) has been used extensively as
`the source material for atmospheric pressure chemical vapor
`deposition (APCVD) or subatmospheric pressure CVD
`(SACVD) of silicon oxide films on semiconductor wafers.
`APCVD deposition of silicon dioxide (SiO2) films at low
`temperatures using an alkoxysilane such as TEOS and ozone
`is described in U.S. Pat. No. 4.845.054. Other precursors
`have also been used extensively to deposit silicon oxide
`films. such and silane and oxygen. as well as dopants of
`boron and/or phosphorous to create doped oxide films such
`as borophosphosilicate (BPSG) glass. The oxide films are
`used to fill gaps between adjacent metal lines in integrated
`circuits and for interlayer dielectric isolation.
`A drawback of prior art APCVD TEOS/ozone films is that
`they are under tensile stress. The tensile stress can lead to
`cracking of the film. Further. the films are unstable and
`provide dielectric isolation over limited periods.
`It is known that by increasing the pressure at which
`borophosphosilicate glass films are deposited the flow tem-
`perature of the film is reduced. This is important in that
`lower processing temperatures cause less thermal damage to
`the underlying integrated circuits. It is also known that at
`atmospheric pressure. the tensile stress of APCVD films will
`convert from tensile to compressive stress at about 750° C.
`However. conversion at these temperatures is likely to cause
`thermal damage to the underlying integrated circuit.
`Accordingly. it is desirable to provide a process for con-
`verting tensile stress in oxide films to compressive stress at
`temperatures that doe not damage the underlying integrated
`circuit.
`
`OBJECFS AND SUMMARY OF THE
`INVENTION
`
`It is an object of this invention to provide a method for
`converting tensilely stressed deposited oxide films to com-
`pressively stressed films.
`It is another object of the invention to provide a method
`for low-temperature conversion of tensile stress in an
`APCVD TEOS/ozone film to compressive stress.
`In accordance with the invention. tensile stress is con-
`verted to compressive stress in an APCVD oxide film by
`subjecting the film to pressures above atmospheric pressure
`and to temperatures below the conversion temperature at
`atmospheric pressure.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The foregoing and other objects of the invention will be
`more fully understood from the following description when
`read in connection with the accompanying drawings.
`wherein:
`FIG. 1 is a schematic representation of an APCVD
`apparatus and an annealing apparatus.
`FIG. 2 shows stress in an APCVD oxide film as a function
`of temperature at one atmosphere of pressure.
`
`2
`FIG. 3 shows stress in an APCVD oxide film as a function
`of temperature at various pressures in accordance with the
`present invention.
`FIG. 4 shows stress in an APCVD oxide filrn doped with
`phosphorous as a function of temperature at various pres-
`sures in accordance with the present invention.
`
`DESCRIPTION OF PREFERRED
`ENIBODINEENTS
`
`The apparatus shown in FIG. 1 is suitable for carrying out
`the invention. In an exemplary embodiment. an APCVD
`module 11 is used to deposit the SiO2 film by the decom-
`position of TEOS in the presence of ozone. Other suitable
`chemical precursors may be used to deposit the oxide film.
`and deposition of SiO2 films is well-known and is described.
`for example. in U.S. Pat. Nos. 3.934.060 and 4.845.054.
`among others. The wafer with deposited dielectric film is
`placed in an annealing chamber 12 where it is subjected to
`elevated temperature and pressure. During annealing. tensile
`stress is converted to compressive stress at an elevated
`temperature which is dependent on pressure. In the prior art.
`the wafer was subjected to temperatures above 750° C. at
`atmospheric pressure for a period of minutes. FIG. 2 shows
`how the tensile stress increases as the temperature increases.
`and then decreases to zero at 750° C. and is converted to
`compressive stress as the temperature decreases. Annealing
`at these elevated temperatures thermally sl:resses the inte-
`grated circuits. for instance by causing dopants in the
`integrated circuit to redistribute. Furthermore. other material
`degradation occurs. such as the melting of aluminum inter-
`connect lines.
`
`In accordance with the present invention. the annealing
`chamber 12 is capable of sustaining high pressures. The
`wafer with the deposited dielecnic film is placed in the
`chamber and the pressure in the chamber is increased to a
`predetermined pressure. The temperature is increased and
`maintained for a predetermined period of time. The stress is
`converted from tensile to compressive at lower tempera-
`tures.
`
`Referring to FIG. 3. the stress conversion temperature
`decreases with increasing pressure. Stress conversion per-
`mits the dielectric laym‘ to smooth out and to better fill gaps.
`This. in turn. will permit the use of oxide films in high
`density integrated circuits while minimizing damage to the
`underlying integrated circuits.
`Doped silicon oxide (glass) films are lmown to flow at
`lower temperatures for topography smoothing applications
`and planarization processes when boron and/or phosphorous
`is added. Of particular advantage. the addition of phospho-
`rous or boron to deposited oxide films will further reduce the
`stress conversion temperature. This aspect of the invention
`is illustrated in FIG. 4.
`
`Currently. with conventional methods. the thickness of the
`deposited film is limited. Thick films tend to crack and are
`not useful for integrated circuit applications. However. if
`thin films are processed in accordance with the teaching of
`the present invention. they can be subjected to repeated
`deposition and annealing steps. This is schematically illus-
`trated by the dotted arrow 13 in FIG. 1. which illust:rates the
`return of a wafer processed in accordance with the invention
`to the deposition module 11.
`Thus. there has been provided a method of processing
`TEOS/ozone silicon oxide films at low temperatures. mak-
`ing such films useful
`in high density integrated circuit
`applications.
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`Elm Exhibit 2147, Page 4
`
`

`
`5786.278
`
`3
`
`What is claimed:
`1. A method of converting tensile stress to compressive
`stress in an APCVD oxide film which comprises the step of:
`after depositing said oxide film. subjecting the oxide film to
`pressures above atmospheric pressure and temperatures
`below the atmospheric pressure conversion temperature.
`said atmospheric pressure conversion temperature being
`where the tensile stress in said oxide film converts to
`compressive stress at atmospheric pressure.
`2. The method as in claim 1 wherein the APCVD oxide
`film is formed by reacting an alkoxysilane and ozone.
`3. The method of claim 1 wherein the APCVD oxide film
`is formed by reacting TEOS and ozone.
`4. The method of claim 1 wherein the APCVD oxide film
`is doped with boron.
`S. The method of claim 1 wherein the APCVD oxide film
`is doped with phosphorus.
`6. The method of claim 1 wherein the APCVD oxide film
`is doped with boron and phosphorus.
`7. The method of claim 1 wherein said pressures are in the
`range of approximately 2 atmospheres to 500 aunospheres.
`8. The method of claim 1 wherein said temperatures are
`in the range of approximately 740° C. to 200° C.
`9. The method of claim 1 wherein said temperatures are
`in the range of equal to or less than approximately 400° C.
`10. A method of converting tensile stress to compressive
`stress in an APCVD oxide fi]_m which comprises the step of:
`after depositing said oxide film. subjecting the oxide film to
`pressures in the range of equal to or less than approximately
`500 atmosphaes. and temperatures in the range of equal to
`or less than approximately 400° C.
`11. The method as in claim 10 wherein the APCVD oxide
`film is formed by reacting an alkoxysilane and ozone.
`12. The method of claim 10 wherein the APCVD oxide
`film is formed by reacting TEOS and ozone.
`
`4
`13. The method of claim 10 wherein the APCVD oxide
`film is doped with boron.
`14. The method of claim 10 wherein the APCVD oxide
`film is doped with phosphorus.
`15. The method of claim 10 wherein the APCVD oxide
`film is doped with boron and phosphorus.
`16. The method of claim 10 wherein said APCVD oxide
`film contains phosphorus in the range of approximately 2 to
`4 percent phosphorus by concentration.
`17. A method of forming a silicon oxide film having
`compressive stress. on a substrate by CVD. comprising the
`steps of:
`
`reacting a silicon precursor and an oxygen precursor in an
`CVD chamber. whereby said precursors interact proxi-
`mate the surface of said substrate to form a silicon
`oxide film on said surface;
`
`removing said substrate from said CVD chamber;
`placing said substrate in an annealing chamber; and
`subjecting said substrate to pressures above atmospheric
`pressure and temperatures below the atmospheric pres-
`sure conversion temperature said atmospheric pressure
`temperature being where the tensile stress in said oxide
`film converts to compressive stress at atmospheric
`pressure. thereby converting the oxide film on said
`substrate from tensile stress to compressive stress.
`18. The method of claim 17 further comprising repeating
`each of said reacting and subjecting steps to form additional
`silicon oxide films on the surface of said substrate.
`19. The method of claim 17 wherein said reacting step
`further comprises reacting a dopant precursor to form a
`doped silicon oxide mm on the surface of said substrate.
`*
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`Elm Exhibit 2147, Page 5