Patent Application
20130075875
The present invention relates to a silicon nitride film used in a semiconductor element, and a method and an apparatus for producing a silicon nitride film.
Plasma CVD methods and plasma CVD apparatuses have been known as methods and apparatuses for manufacturing a silicon nitride film used in a semiconductor element.
Silicon nitride films (hereinafter, referred to as SiN films) have been used as the lenses of CCD (Charge-Coupled Device) and CMOS (Complementary Metal-Oxide Semiconductor) image sensors for their high refractive indexes and high transmittances, and also used as the final protective films of wirings for their barrier properties. Currently, due to the miniaturization of semiconductor elements, there have been increasing demands for embedding a SiN film in high-aspect-ratio minute holes (holes with a hole diameter: of below 1 μm and an aspect ratio of 1 or above).
To embed a SiN film in high-aspect-ratio minute holes, it is necessary to perform that film formation by applying bias power. In Patent Document 1, the inventor of the present invention and others have proposed a technique in which a SiN film is formed by applying bias power with use of an appropriate process condition. However, since a SiN film formed by applying bias power contains Si—H bonds therein, the hydrogen escapes therefrom when the SiN film is subjected to annealing (400° C.) which is performed in a semiconductor manufacturing process. Here, the escaping hydrogen is required to be appropriately controlled depending upon the type of semiconductor element. For example, in a case of ferroelectric memories, there is a problem of deterioration by hydrogen reduction, and it is therefore necessary to block the diffusion of the escaping hydrogen. Moreover, in a case of CCD/CMOS image sensors and the like, there is a problem of dark current originating from terminals of dangling bonds, and it is therefore required to supply the escaping hydrogen and effectively utilize this hydrogen.
Meanwhile, Patent Document 2 describes a technique in which a protective insulating film for preventing the diffusion of hydrogen is formed by a plasma CVD method involving no bias application on top of an interlayer insulating film formed by an HDPCVD method involving bias application. However, both of these insulating films are SiO films, and there is no description at all regarding a film structure which uses only a SiN film to appropriately control escaping hydrogen.
The present invention has been made in view of the above problem, and an object thereof is to provide a silicon nitride film of a semiconductor element and a method and an apparatus for producing a silicon nitride film which allow appropriate control on hydrogen escaping from a silicon nitride film formed by applying bias power.
A silicon nitride film of a semiconductor element according to a first aspect of the invention for solving the above problem is a silicon nitride film formed on a substrate by plasma processing and to be used in a semiconductor element, wherein
in a case where the silicon nitride film is in contact with a film desired to be blocked from being supplied with hydrogen,
A silicon nitride film of a semiconductor element according to a second aspect of the invention for solving the above problem is a silicon nitride film formed on a substrate by plasma processing and to be used in a semiconductor element, wherein
in a case where the silicon nitride film is in contact with a film desired to be supplied with hydrogen,
A method for producing a silicon nitride film according to a third aspect of the invention for solving the above problem is a method for producing a silicon nitride film to be used in a semiconductor element by performing plasma processing to form the silicon nitride film on a substrate, wherein
in a case where the silicon nitride film is to be in contact with a film desired to be blocked from being supplied with hydrogen,
A method for producing a silicon nitride film according to a fourth aspect of the invention for solving the above problem is a method for producing a silicon nitride film to be used in a semiconductor element by performing plasma processing to form the silicon nitride film on a substrate, wherein
in a case where the silicon nitride film is to be in contact with a film desired to be supplied with hydrogen,
An apparatus for producing a silicon nitride film according to a fifth aspect of the invention for solving the above problem is an apparatus for producing a silicon nitride film to be used in a semiconductor element by performing plasma processing to form the silicon nitride film on a substrate, comprising bias supplying means for applying bias to the substrate, wherein
in a case where the silicon nitride film is to be in contact with a film desired to be blocked from being supplied with hydrogen, a first silicon nitride film and a second silicon nitride film are formed as the silicon nitride film and the second silicon nitride film is formed on a side which is in contact with the film,
An apparatus for producing a silicon nitride film according to a sixth aspect of the invention for solving the above problem is an apparatus for producing a silicon nitride film to be used in a semiconductor element by performing plasma processing to form the silicon nitride film on a substrate, comprising bias supplying means for applying bias to the substrate, wherein
in a case where the silicon nitride film is to be in contact with a film desired to be supplied with hydrogen, a first silicon nitride film and a second silicon nitride film are formed as the silicon nitride film and the first silicon nitride film is formed on a side which is in contact with the film,
According to the first, third, and fifth aspects of the invention, the second silicon nitride film formed without applying any bias is disposed on the side which is in contact with the film desired to be blocked from being supplied with hydrogen. Accordingly, the supply of the hydrogen inside the first silicon nitride film to the film can be blocked by the second silicon nitride film.
According to the second, fourth, and sixth aspects of the invention, the first silicon nitride film formed by applying bias is disposed on the side which is in contact with the film desired to be supplied with hydrogen, and the second silicon nitride film formed without applying any bias is disposed on the opposite side. Accordingly, the hydrogen inside the first silicon nitride film can be efficiently supplied to the film.
Hereinbelow, a silicon nitride film of a semiconductor element and a method and an apparatus for manufacturing a silicon nitride film according to the present invention will be described through embodiments with reference to
First, the configuration of an apparatus used in this example to manufacture a silicon nitride film (SiN film) will be described with reference to
As shown in
An RF antenna 15 configured to generate plasma is placed on top of the top panel 13. An RF power source 17 being a high-frequency power source is connected to the RF antenna 15 through a matching box 16. Specifically, the RF power supplied from the RF power source 17 is supplied to plasma through the RF antenna 15.
In an upper portion of a sidewall of the tubular container 12, there is placed a gas supply pipe 18 through which raw material gases serving as raw materials for a film to be formed and an inert gas are supplied into the vacuum chamber 11. A gas supply amount controller configured to control the amounts of the raw material gases and the inert gas to be supplied is placed on the gas supply pipe 18. In this example, SiH4 and N2, or the like are supplied as the raw material gases, while Ar which is a noble gas or the like is supplied as the inert gas. By supplying these gases, plasma of SiH4, N2 and Ar, or the like is generated in an upper portion of the inside of the vacuum chamber 11.
A substrate support table 20 configured to hold a substrate 19, or the film formation target, is placed in a lower portion of the inside of the tubular container 12. This substrate support table 20 is formed of a substrate holding part 21 configured to hold the substrate 19, and a support shaft 22 configured to support this substrate holding part 21. A heater 23 for heating is placed inside the substrate holding part 21. The temperature of this heater 23 is adjusted by a heater control device 24. Accordingly, the temperature of the substrate 19 during plasma processing can be controlled.
A bias power source 26 (bias supplying means) is connected to the substrate holding part 21 through a matching box 25 so that bias power can be applied to the substrate 19. Accordingly, ions can be drawn from the inside of the plasma onto the surface of the substrate 19. Further, an electrostatic power source 27 is connected to the substrate holding part 21 so that the substrate 19 can be held by electrostatic force. This electrostatic power source 27 is connected to the substrate holding part 21 through a low-pass filter 28 so that the power from the RF power source 17 and the bias power source 26 does not flow into the electrostatic power source 27.
In addition, in the plasma CVD apparatus 10 described above, there is placed a master control device 29 capable of controlling each of the bias power, the RF power, the pressure, the substrate temperature, and the gas supply amounts respectively through the bias power source 26, the RF power source 17, the vacuum device 14, the heater control device 24, and the gas supply amount controller. Here, the dashed lines in
A SiN film can be formed on the substrate 19 through plasma processing in the plasma CVD apparatus 10 described above by controlling the bias power, the RF power, the pressure, the film formation temperature, and the gas supply amounts through the master control device 29. Not only is the plasma CVD apparatus 10 capable of forming a SiN film by applying bias power, but it is also capable of forming a SiN film without applying any bias power as a matter of course.
Here, hydrogen escape due to annealing performed in a semiconductor manufacturing process was checked for a SiN film formed by applying bias power (hereinafter, referred to as the biased SiN film) and for a SiN film formed without applying any bias power (hereinafter, referred to as the unbiased SiN film) by measuring stress changes in the SiN films.
In the stress measurement on each SiN film, as for the stress measurement device, FLX-2320 manufactured by KLA-Tencor was used. Moreover, as for the stress measurement method, in a heater inside the stress measurement device, a substrate with the SiN film formed thereon was heated from normal temperature to 450° C. by spending 1 hour, maintained at 450° C. for 30 minutes, and then cooled down, and the stress changes during these periods were measured. This stress measurement method used 450° C. which produced a larger temperature load than with 400° C. being the temperature of the annealing performed in the semiconductor manufacturing process.
Meanwhile, the film formation condition for each SiN film was as follows.
RF power: 2.0 kW, Bias power: 2.4 kW, SiH4: 40 sccm, N2: 80 sccm, Ar: 20 sccm, Pressure 25 mTorr, Film thickness 4513 Å
RF power: 3.0 kW, Bias power: 0 kW, SiH4: 30 sccm, N2: 800 sccm, Ar: 0 sccm, Pressure 25 mTorr, Film thickness 4226 Å]
Note that this film formation condition is only an example. In the case of the unbiased SiN film, falling within the following film formation condition can offer later-described properties:
Film formation temperature: 50° C. to 400° C. RF power with respect to the total flow rate of SiH4 and N2: 7 W/sccm or lower
Gas flow ratio: SiH4/(SiH4+N2)=0.036 to 0.33
As shown in Part (a) of
Moreover, as shown in Part (a) of
Meanwhile, the hydrogen content of each SiN film was checked through an IR analysis (infrared analysis, e.g. FTIR or the like). As shown in Table 1, the hydrogen content of the biased SiN film is 5.1×1021 [atoms/cm3] while the hydrogen content of the unbiased SiN film is 0.1×1021 [atoms/cm3]. Thus, the hydrogen content of the unbiased SiN film is 2% or below of the hydrogen content of the biased SiN film, showing that the unbiased SiN film is a dense film with a small hydrogen content. Note that in this instance, as the hydrogen content of each SiN film, the number of Si—H bonds found based on the peak area of Si—H bonds present around 2140 cm−1 was measured.
Next, the unbiased SiN film 32 was formed on the Si substrate 19 and the biased SiN film 31 was stacked thereon as shown in Part (a) of
As a result of measuring the stacked unbiased SiN film 32 and biased SiN film 31 together with the Si substrate 19 by the stress measurement method described above, the stress immediately after the film formation was found to be a compressive stress of −218 MPa. Moreover, as shown in Part (b) of
Next, an unbiased SiN film 32a was formed on the Si substrate 19, the biased SiN film 31 was stacked thereon, and an unbiased SiN film 32b was stacked thereon as shown in Part (a) of
As a result of measuring the stacked unbiased SiN film 32a, biased SiN film 31, and unbiased SiN film 32b together with the Si substrate 19 by the stress measurement method described above, the stress immediately after the film formation was found to be a compressive stress of −354 MPa. Moreover, as shown in Part (b) of
As can be appreciated from the graphs shown in Part (b) of
Thus, in this example, in order to block the diffusion (supply) of the hydrogen inside the biased SiN film 31 (first silicon nitride film), the unbiased SiN film 32 (second silicon nitride film) is disposed on the side (s) where the diffusion is desired to be blocked. Specifically, as shown in Part (a) of
As mentioned above, since the unbiased SiN film 32 has a small hydrogen content and is dense, inserting it between the biased SiN film 31 and the film 41 allows the blocking of the diffusion of the hydrogen inside the biased SiN film 31 even when annealing is performed. Accordingly, it is possible to perform annealing in a semiconductor manufacturing process while maintaining the embedding performance offered by the biased SiN film 31. Note that the film 41 desired to avoid the diffusion of hydrogen thereto include a ferroelectric film of a ferroelectric memory, for example, and using the above configuration can prevent deterioration of the ferroelectric film due to hydrogen reduction.
Parts (a) and (b) of
In this example, in order to supply the hydrogen inside a biased SiN film 31 to an upper or lower side thereof, an unbiased SiN film 32 is disposed on the opposite side to the side where the hydrogen is desired to be supplied. Specifically, as shown in Part (a) of
As mentioned above, since the unbiased SiN film 32 has a small hydrogen content and is dense, disposing it on the opposite side of the biased SiN film 31 from the film 51 (the upper side in Part (a) of
The present invention is applicable to silicon nitride films used in semiconductor elements, and is preferable particularly for the lenses of CCD/CMOS image sensors and the final protection films (passivation) of wirings.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-122252 | May 2010 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2011/061363 | 5/18/2011 | WO | 00 | 12/6/2012 |
