Method for fabricating semiconductor device including forming a dielectric layer on a structure having a height difference using ALD

A method for fabricating a semiconductor device includes forming a structure with a height difference on a substrate and forming a dielectric layer structure on the structure using an atomic layer deposition (ALD) method. Forming the dielectric layer structure includes forming a first dielectric layer including silicon nitride on the structure with the height difference. Forming the first dielectric layer includes feeding a first gas including pentachlorodisilane (PCDS) or diisopropylamine pentachlorodisilane (DPDC) as a silicon precursor, and a second gas including nitrogen components into a chamber including the substrate such that the first dielectric layer is formed in situ on the structure having the height difference.

BACKGROUND

Exemplary embodiments relate to a method for fabricating a semiconductor device. Exemplary embodiments relate to forming thin films on substrates having a step coverage.

SUMMARY

Embodiments are directed to a method for fabricating a semiconductor device, including forming a structure with a height difference on a substrate and forming a dielectric layer structure on the structure using an atomic layer deposition (ALD) method. Forming the dielectric layer structure includes forming a first dielectric layer including silicon nitride on the structure with the height difference. Forming the first dielectric layer includes feeding a first gas including pentachlorodisilane (PCDS) or diisopropylamine pentachlorodisilane (DPDC) as a silicon precursor, and a second gas including nitrogen components into a chamber including the substrate such that the first dielectric layer is formed in situ on the structure having the height difference.

Embodiments are also directed to a method for fabricating a semiconductor device, including forming a structure on a substrate, and forming a silicon nitride layer on the structure inside a chamber using an atomic layer deposition (ALD) method. Forming the silicon nitride layer may include feeding a first gas including one of pentachlorodisilane (PCDS) and diisopropylaminopentachlorodisilane (DPDC) as a silicon precursor into the chamber, purging an unreacted portion of the first gas by feeding a first purge gas into the chamber, feeding a second gas including a nitrogen gas into the chamber, and purging an unreacted portion of the second gas by feeding a second purge gas into the chamber.

Embodiments are also directed to a method of forming a dielectric layer on a target object by atomic layer deposition, the target object including at least one structural feature having a sidewall including feeding a first gas including pentachlorodisilane (PCDS) or diisopropylamine pentachlorodisilane (DPDC) into a chamber including the target object to form a silicon precursor layer having an atomic layer thickness on the target object, feeding a first purge gas into the chamber to purge an unreacted or unadsorbed portion of the first gas from the chamber, feeding a second gas into the chamber, the second gas being nitrogen or a nitrogen compound containing gas, such that the second gas reacts with the silicon precursor to form a silicon nitride layer having an atomic layer thickness on the target object, feeding a second purge gas into the chamber to purge an unreacted or unadsorbed portion of the second gas from the chamber, and repeating feeding the first gas, feeding the first purge gas, feeding the second gas and feeding the second purge gas to form the dielectric layer to include a silicon nitride layer having greater than an atomic layer thickness.

DETAILED DESCRIPTION

The formation of a silicon nitride layer according to some exemplary embodiments will hereinafter be described with reference toFIG. 1.

FIG. 1illustrates a timing diagram showing the formation of a silicon nitride layer according to some exemplary embodiments.

A silicon nitride layer may be formed in situ using an atomic layer deposition (ALD) method according to the present disclosure. The ALD method may include feeding a first gas including a silicon precursor, purging an unreacted portion of the first gas using a first purge gas, forming a silicon nitride layer having an atomic-layer thickness by feeding a second gas comprising a nitride gas, and purging an unreacted portion of the second gas using a second purge gas.

For example, referring toFIG. 1, a target object (for example, a structure formed on a substrate) on which to form a silicon nitride layer may be placed inside a chamber. The height-to-width ratio, i.e., the aspect ratio, of the target object may be, for example, 10 or greater.

Thereafter, the temperature and pressure may be adjusted, and a first gas including a silicon precursor may be fed into the chamber. Then, the silicon precursor is adsorbed onto the target object.

The silicon precursor, unlike a typical organic silicon precursor comprising carbon (C) and nitrogen (N) components, may be a compound not including any C and N components. In some implementations, the silicon precursor may include C components.

The silicon precursor may be or include, for example, pentachlorodisilane (PCDS) represented by Formula 1 or diisopropylamino pentachlorodisilane (DPDC) represented by Formula 2:

When PCDS or DPDC is used as the silicon precursor, the surface reactivity of the silicon precursor may be improved, and thus, a growth per cycle (GPC) rate may be enhanced, compared to a case in which hexachlorodisilane (HCDS) or dichlorosilane (DCS) is used as the silicon precursor.

Thereafter, a portion of the silicon precursor that remains unreacted in the chamber may be purged by feeding a first purge gas such as, for example, a nitrogen (N2) gas, a helium (He) gas, or an argon (Ar) gas, into the chamber. As a result, the silicon precursor adsorbed onto the target object may be transformed into a layer having an atomic-layer thickness.

Thereafter, a silicon nitride layer may be formed by feeding a nitride gas comprising N components into the chamber. The nitride gas may include at least one of a N2, ammonia (NH3), and nitrogen monoxide (NO), as examples.

Thereafter, a portion of the nitride gas that remains unreacted in the chamber may be purged by feeding a second purge gas such as, for example, a N2, He, or Ar gas, into the chamber. In this manner, one cycle of the formation of a silicon nitride layer may be completed, and a silicon nitride layer having an atomic-layer thickness may be formed on the target object.

By repeatedly performing the forming of the silicon nitride layer having an atomic-layer thickness, a silicon nitride layer having a desired thickness can be formed on the target object.

The silicon nitride layer may be subjected to a thermal treatment process to improve the quality of the silicon nitride layer. The thermal treatment process may be performed at deposition temperature that is as high as a temperature used for forming a silicon nitride layer by chemical vapor deposition (CVD). For example, the thermal treatment process may be performed at a deposition temperature of about 850° C. to about 1,050° C.

The quality of the silicon nitride layer obtained by the ALD method may be superior to the quality of a silicon nitride layer obtained by, for example, CVD. The silicon nitride layer obtained by the ALD method described herein may have an excellent step coverage and thus may be conformally formed on a structure with a large height difference or a high aspect ratio without leaving any voids.

An experimental example of the formation of a silicon nitride layer according to some exemplary embodiments will hereinafter be described with reference toFIG. 2.

FIG. 2illustrates a graph showing experimental examples of the formation of a silicon nitride layer according to some exemplary embodiments.

Experimental Example—Measurement of GPC Rate According to Processing Temperature for PCDS and HCDS

Experiments were conducted as experimental examples and comparative examples, respectively.

In the experimental examples, a silicon nitride layer was formed by an ALD method using PCDS. In the comparative examples, a silicon nitride layer was formed by an ALD method using HCDS.

Referring toFIG. 2, silicon nitride layers were formed at temperatures of 300° C., 350° C., and 400° C., respectively, by using PCDS according to the experimental examples, and silicon nitrides layer were formed at temperatures of 300° C., 350° C., and 400° C., respectively, by using HCDS according to the comparative examples.

Bars a1, a2, and a3 represent GPC rate measurements obtained when forming a silicon nitride layer at temperatures of 300° C., 350° C., and 400° C., respectively, by using PCDS according to the experimental example. Bars b1, b2, and b3 represent GPC rate measurements obtained when forming a silicon nitride layer at temperatures of 300° C., 350° C., and 400° C., respectively, by using HCDS according to the comparative example.

Referring to bars a2 and b1, in the case of forming a silicon nitride layer at a temperature of 350° C., the GPC rate was shown to be higher when using PCDS according to the experimental example than when using HCDS according to the comparative example.

Referring to bars a3 and b2, in the case of forming a silicon nitride layer at a temperature of 400° C., the GPC rate was also shown to be higher when using PCDS according to the experimental example than when using HCDS according to the comparative example.

Referring to bar a1, in the case of forming a silicon nitride layer at a temperature of 300° C., no silicon nitride layer is formed when using HCDS according to the comparative example, but when using PCDS according to the experimental example, a GPC rate of 0.9 Å/cyc or higher is obtained.

From the above, it can be seen that a GPC rate of 0.8 Å/cyc or higher may be achieved when forming a silicon nitride layer using PCDS according to the experimental example. Also, a GPC rate is shown to be generally improved when using PCDS, compared to when using HCDS, and a silicon nitride layer with an excellent step coverage can be formed even in a low-temperature process performed at a relatively low temperature of 300° C. or greater but less than 350° C.

The fabrication of a semiconductor device using a method of forming a silicon nitride layer according to some exemplary embodiments will hereinafter be described.

A method for fabricating a semiconductor device according to an exemplary embodiment will hereinafter be described with reference toFIG. 3toFIG. 5.

FIG. 3toFIG. 5illustrate schematic views depicting stages of a method for fabricating a semiconductor device according to an exemplary embodiment. For example,FIG. 3toFIG. 5illustrate steps of a method for fabricating a flash memory device.

Referring toFIG. 3, a tunnel dielectric layer130and a charge storage layer140may be sequentially formed on a substrate110. The tunnel dielectric layer130may provide an energy band gap for the tunneling of electric charges.

The tunnel dielectric layer130may be formed of suitable materials in consideration of dielectric constant and energy band gap properties. The tunnel dielectric layer130may include, for example, silicon oxide, silicon nitride, or a high-k material.

The high-k material may include a metal oxide such as, for example, hafnium oxide, aluminum oxide, hafnium aluminum oxide, or zirconium oxide.

The charge storage layer140may store electric charges. When a flash memory device to be fabricated is of a floating gate type, the charge storage layer140may be formed of a conductive material such as polysilicon. When the flash memory device to be fabricated is of a charge trap type, the charge storage layer140may be formed of silicon nitride, hafnium oxide, zirconium oxide, tantalum oxide, hafnium oxynitride, hafnium silicon oxide, tungsten-doped aluminum oxide, or nanodots.

The tunnel dielectric layer130and the charge storage layer140may be formed in a suitable manner. For example, the formation of the tunnel dielectric layer130and the charge storage layer140may include sequentially forming a pre-tunnel dielectric layer, a pre-charge storage layer, and a mask layer on the substrate110, forming an isolation layer120by patterning the pre-tunnel layer, the pre-charge storage layer, and the mask layer, and removing the mask layer.

Referring toFIG. 4andFIG. 5, a dielectric layer structure150that includes a first dielectric layer151that is formed of silicon oxide, a second dielectric layer152that is formed of a material other than silicon oxide, and a third dielectric layer153that is formed of silicon oxide may be formed on the charge storage layer140using the ALD method as described herein. When the flash memory device to be fabricated is a floating gate type, the dielectric layer structure150may be an inter-gate dielectric layer. When the flash memory device to be fabricated is a charge trap type, the dielectric layer structure150may be a blocking dielectric layer.

The in-situ formation of the dielectric layer structure150having a silicon nitride layer as the second dielectric layer152will hereinafter be described.

A substrate110with a height difference and having the charge storage layer140formed thereon may be placed in a chamber. Thereafter, a first dielectric layer151including silicon oxide may be formed.

For example, the temperature and pressure may be appropriately controlled, and a first gas including a silicon precursor may be fed into the chamber. Then, the silicon precursor may be absorbed onto the first dielectric layer151. For example, one of PCDS and DPDC may be used as the silicon precursor.

Thereafter, a second dielectric layer152having an atomic-layer thickness and including silicon nitride may be formed on the first dielectric layer151by sequentially feeding a first purge gas, a second gas, and a second purge gas.

By repeatedly performing forming the second dielectric layer152having an atomic-layer thickness, the second dielectric layer152having a desired thickness may be formed on the first dielectric layer151as a silicon nitride layer.

Thereafter, a third dielectric layer153including silicon oxide may be formed on the second dielectric layer152.

The dielectric layer structure150may have an excellent step coverage and thus may be conformally formed in spaces between parts of the charge storage layer140having an aspect ratio of, for example, 10 or greater, without leaving any voids. When the first, second, and third dielectric layers151,152, and153are formed in situ, the amount of time that it takes to form the dielectric layer structure150may be reduced, and the formation of the dielectric layer structure150may be simplified.

Thereafter, a control gate160may be formed on the dielectric layer structure150. For example, the control gate160may be formed of polysilicon or a metal electrode material such as TaN, TiN, WN, W, or a combination thereof.

A method for fabricating a semiconductor device according to another exemplary embodiment will hereinafter be described with reference toFIG. 6toFIG. 8.

FIG. 6toFIG. 8illustrate schematic views depicting stages of a method for fabricating a semiconductor device according to another exemplary embodiment. For example,FIG. 6toFIG. 8illustrate steps of a method for fabricating a dynamic random access memory (DRAM) cell semiconductor device.

Referring toFIG. 6, which is a layout view of a DRAM cell region, gates230extend across active regions210of a substrate along a horizontal direction, and global bit lines (GBLs)240extend across the active regions210along a vertical direction. A part of the substrate other than the active regions210is an isolation region220.

Referring toFIG. 7andFIG. 8, which illustrate a memory cell region, a GBL240is formed on an active region210of a substrate. Thereafter, a first dielectric layer251including silicon oxide is formed on the sidewall of the GLB240. The first dielectric layer251may perform the functions of a spacer.

Thereafter, a second dielectric layer252including silicon nitride is formed on the first dielectric layer251. The second dielectric layer252may be formed using the ALD method as described above.

For example, the temperature and pressure in a chamber may be adjusted, and a first gas including a silicon precursor may be fed into the chamber. The silicon precursor may be adsorbed onto the first dielectric layer251. PCDS or DPDC may be used as the silicon precursor.

Thereafter, a second dielectric layer252having an atomic-layer thickness and including silicon nitride may be formed on the first dielectric layer251by sequentially feeding a first purge gas, a second gas, and a second purge gas. The reaction between the second gas and the silicon precursor may be reacted under thermal conditions or plasma conditions.

By repeatedly performing the step of forming the second dielectric layer252having an atomic-layer thickness, a second dielectric layer252having a desired thickness may be formed on the first dielectric layer251as a silicon nitride layer.

Thereafter, a third dielectric layer253including silicon oxide may be formed on the second dielectric layer252.

Since there is no need to form an impurity layer in the cell region, a photoresist pattern may be formed to cover the cell region. The photoresist pattern and the third dielectric layer253may be removed, and a nitride layer spacer may be formed by performing an anisotropic etching process on the second dielectric layer252. Thereafter, a part of the second dielectric layer252in contact with the active region210of the substrate may be removed.

A method for fabricating a semiconductor device according to another exemplary embodiment will hereinafter be described with reference toFIG. 9toFIG. 12.

FIG. 9toFIG. 12illustrate schematic views depicting steps of a method for fabricating a semiconductor device according to another exemplary embodiment. For example,FIG. 9toFIG. 12illustrate stages of a method for fabricating a semiconductor device having a stacked nanosheet transistor structure.

Referring toFIG. 9, a stack structure320in which a plurality of sacrificial layers321and a plurality of semiconductor layers322are alternately stacked may be formed on a substrate310.

The lowermost sacrificial layer321, which is in contact with the substrate310, may be bonded onto the substrate310through, for example, wafer bonding.

The semiconductor layers322and the non-lowermost sacrificial layers321may be alternately formed on the lowermost sacrificial layer321through, for example, epitaxial growth. The uppermost layer of the stack structure320may be, for example, a sacrificial layer321.

The sacrificial layers321and the semiconductor layers322may include different materials from each other. The sacrificial layers321may include a material having a different etching selectivity from that of the semiconductor layers322. The sacrificial layers321may include, for example, SiGe or Ge. The semiconductor layers322may include, for example, Si and a III-V group compound semiconductor.

Thereafter, referring toFIG. 10, a first mask pattern341, which extends in a first direction X, may be formed on the stack structure320.

The first mask pattern341may be formed of a material including, for example, at least one of a silicon oxide layer, a silicon nitride layer, or a silicon oxynitride layer. When the first mask pattern341includes a silicon nitride layer, the first mask pattern341may be formed by the ALD method as describe above.

For example, the temperature and pressure in a chamber may be adjusted, and a first gas including a silicon precursor may be fed into the chamber. Then, the silicon precursor may be adsorbed onto the stack structure320. PCDS or DPDC, as examples, may be used as the silicon precursor.

Thereafter, a first mask pattern341having an atomic-layer thickness and including silicon nitride may be formed on the stack structure320by sequentially feeding a first purge gas, a second gas, and a second purge gas. By repeatedly performing forming the first mask pattern341having an atomic-layer thickness, the first mask pattern341having a desired thickness may be formed on the stack structure320as a silicon nitride layer.

As illustrated inFIG. 10, a semiconductor pattern structure330may be formed by etching the stack structure320using the first mask pattern341as a mask. For example, the semiconductor pattern structure330may be formed by etching the stack structure320until the top surface of the substrate310is exposed.

The semiconductor pattern structure330may extend long in the first direction X. The semiconductor pattern structure330may include a plurality of sacrificial layers and a plurality of semiconductor layers that are alternately stacked on the substrate310.

For example, the semiconductor pattern structure330may include a first sacrificial layer331, which is formed on the substrate310, a first semiconductor layer334, which is formed on the first sacrificial layer331, a second sacrificial layer332, which is formed on the first semiconductor layer334, a second semiconductor layer335, which is formed on the second sacrificial layer332, and a third sacrificial layer333, which is formed on the second semiconductor layer335.

During the etching of the stack structure330, part of the substrate310may also be etched, thereby forming an active region AR. Thereafter, an interlayer dielectric layer may be formed to cover the substrate310and the first mask pattern341. The interlayer dielectric layer may then be subjected to a planarization process until the top surface of the first mask pattern341is exposed. As a result, an interlayer dielectric layer351ofFIG. 10may be obtained.

Thereafter, the first mask pattern341may be removed from the semiconductor pattern structure330.

Referring toFIG. 11, by performing an etching process using second mask patterns342, gate insulating layers353and sacrificial gates360, which both extend in a third direction that is perpendicular to the first direction X and a second direction Z, may be formed to intersect the semiconductor pattern structure330.

The second mask patterns342may be formed of a material including, for example, at least one of a silicon oxide layer, a silicon nitride layer, or a silicon oxynitride layer. When the second mask patterns342include a silicon nitride layer, the second mask patterns342may be formed by the ALD method described above.

The sacrificial gates360may be formed on the semiconductor pattern structure330. Also, the gate insulating layers353may be formed on the sides and the top surface of an insulating layer352and on the top surface of a field insulating layer354.

The insulating layer352may be formed between the semiconductor pattern structure330and the gate insulating layers353to cover the semiconductor pattern structure330. The insulating layer352may be, for example, an oxide layer, for example, a layer comprising SiO2.

For example, the gate insulating layers353may be silicon oxide layers, and the sacrificial gates360may include polysilicon or amorphous silicon.

Referring toFIG. 12, gate spacers370and dummy gate spacers380may be formed on the sidewalls of the sacrificial gates360.

For example, a spacer layer may be formed on the substrate310to cover the sacrificial gates360and the semiconductor pattern structure330. When the spacer layer includes silicon nitride, the spacer layer may be formed by the ALD method described above.

The temperature and pressure in a chamber may be adjusted, and a first gas including a silicon precursor may be fed into a chamber. Then, the silicon precursor may be adsorbed onto the sacrificial gates360and the semiconductor pattern structure330. PCDS or DPDC, for example, may be used as the silicon precursor.

Thereafter, as described above, a spacer layer having an atomic-layer thickness and including silicon nitride may be formed on the sacrificial gates360and the semiconductor pattern structure330by sequentially feeding a first purge gas, a second gas, and a second purge gas.

By repeatedly performing forming the spacer layer having an atomic-layer thickness, a spacer layer having a desired thickness may be formed on the sacrificial gates360and the semiconductor pattern structure330as a silicon nitride layer.

Thereafter, by etching back the spacer layer, the gate spacers370and the dummy gate spacers380may be formed on the sidewalls of the sacrificial gates360.

A method for fabricating a semiconductor device according to another exemplary embodiment will hereinafter be described with reference toFIG. 13andFIG. 14.

FIG. 13andFIG. 14illustrate schematic views depicting stages of a method for fabricating a semiconductor device according to another exemplary embodiment. For example,FIG. 13andFIG. 14illustrate stages of a method for fabricating a semiconductor device having spacers formed in the contacts thereof.

Referring toFIG. 13, first and second gate patterns may be formed on a substrate410to be spaced apart from each other. The first and second gate patterns may have substantially the same elements.

Each of the first and second gate patterns may include gate spacers450, an insulating layer pattern420, a gate electrode pattern430, and a capping pattern440.

The insulating layer pattern420may include an interface layer421and a gate insulating layer422.

The interface layer421may help to prevent a poor interface from existing between the substrate410and the gate insulating layer422.

The interface layer421may include a low-k material layer having a dielectric constant (k) of 9 or less. The interface layer421may include, for example, a silicon oxide layer having a dielectric constant (k) of 4 or a silicon oxynitride layer having a dielectric constant (k) of about 4 to 8, depending on the contents of oxygen and nitrogen atoms in the silicon oxynitride layer.

The interface layer421may be formed by, for example, chemical oxidation, ultraviolet (UV) oxidation, or dual plasma oxidation.

The gate insulating layer422may be formed on the interface layer421. When the interface layer421is not provided, the gate insulating layer422may be formed on the substrate410.

The gate insulating layer422may be formed to an appropriate thickness depending on the type of a semiconductor device to be fabricated. For example, when the gate insulating layer422includes HfO2, the gate insulating layer422may be formed to a thickness of about 50 Å (for example, to a thickness of about 5 Å to 50 Å).

The gate electrode pattern430may include a work function adjustment layer431and a gate metal432.

The work function adjustment layer431may be formed on the gate insulating layer422. The work function adjustment layer431may be formed to be in contact with the gate insulating layer422. The work function adjustment layer431may be used to adjust a work function.

The work function adjustment layer431may include, for example, a metal nitride. The material of the work function adjustment layer431may vary depending on the type of the semiconductor device to be fabricated. When the work function adjustment layer431is a p-type work function adjustment layer, the work function adjustment layer431may include, for example, at least one of TiN, WN, TaN, Ru, or a combination thereof. When the work function adjustment layer431is an n-type work function adjustment layer, the work function adjustment layer431may include, for example, at least one of Ti, Ag, Al, TiAl, TiAlN, TiAlC, TaC, TaCN, TaSiN, Mn, Zr, or a combination thereof.

When the work function adjustment layer431is a p-type work function adjustment layer, the work function adjustment layer431may be formed as a single layer including TiN and a double layer include a TiN lower layer and a TaN upper layer.

The gate metal432may be formed on the work function adjustment layer431. The gate metal432may be formed to be in contact with the work function adjustment layer431. For example, the gate metal432may be formed to fill the space formed by the work function adjustment layer431. The gate metal432may include a conductive material such as, for example, W or Al.

The capping pattern440may be formed on the gate metal432. The capping pattern440may be formed to be in contact with the gate metal432. The capping pattern440may include, for example, at least one of silicon nitride (SiN), silicon oxynitride (SiON), silicon oxide (SiO2), silicon carbonitride (SiCN), silicon oxycarbonitride (SiOCN), or a combination thereof.

An interlayer dielectric layer460may be formed on the substrate410to cover the first and second gate patterns. The interlayer dielectric layer460may include, for example, at least one of a low-k material, an oxide layer, a nitride layer, or an oxynitride layer. The low-k material may include, for example, flowable oxide (FOX), tonen silazene (TOSZ), undoped silicate glass (USG), borosilicate glass (BSG), phosphosilicate glass (PSG), borophosphosilicate glass (BPSG), plasma enhanced tetra ethyl ortho silicate (PETEOS), fluoride silicate glass (FSG), carbon doped silicon oxide (CDO), Xerogel, Aerogel, amorphous fluorinated carbon, organo silicate glass (OSG), parylene, bis-benzocyclobutene (BCB), SiLK, polyimide, a porous polymeric material, or a combination thereof.

After the formation of the first and second gate patterns on the substrate410, the interlayer dielectric layer460may be formed to cover the first and second gate patterns.

Thereafter, a trench T may be formed in the interlayer dielectric layer460to expose a part of the substrate410between the first and second gate patterns. The trench T may be formed in the interlayer dielectric layer460by removing part of the interlayer dielectric layer460using, for example, a dry etching process, a wet etching process, or a combination thereof.

Referring toFIG. 14, a spacer material470may be conformally formed on the sidewalls of the trench T. When the spacer material470includes a silicon nitride layer, the spacer material470may be formed by the ALD method according to the present disclosure.

For example, the temperature and pressure in a chamber may be adjusted, and a first gas including a silicon precursor may be fed into a chamber. Then, the silicon precursor may be adsorbed onto the sidewalls and the bottom of the trench T. As described above, PCDS or DPDC, for example, may be used as the silicon precursor.

A spacer material470having an atomic-layer thickness and including silicon nitride may be formed on the sidewalls and the bottom of the trench T by sequentially feeding a first purge gas, a second gas, and a second purge gas as described above.

By repeatedly performing forming the spacer material470having an atomic-layer thickness, a contact spacer having a desired thickness may be formed on the sidewalls and the bottom of the trench T as a silicon nitride layer.

By way of summation and review, as the integration density of semiconductor devices increases, it becomes more and more difficult to fabricate semiconductor devices, and particularly, to form thin films for use in the fabrication of semiconductor devices, such as, for example, silicon nitride layers, on a substrate to have step coverage. In the case of forming a silicon nitride layer through atomic layer deposition (ALD) using an organic silicon precursor such as bis(tertiary-butylamine)silane (BTBAS), improved step coverage may be provided, but the quality of the silicon nitride layer may deteriorate due to the carbon (C) and nitrogen (N) components included in the organic silicon precursor.

Methods of fabricating a semiconductor device according to exemplary embodiments can form a dielectric layer using a silicon precursor including PCDS and DPDC or using an ALD method. Thus, excellent step coverage may be obtained, compared to a case in which existing silicon precursors are used. Accordingly, a silicon nitride layer can be conformally formed on a structure with a large height difference or a high aspect ratio without leaving any voids.

Exemplary embodiments also provide a method for fabricating a semiconductor device that is capable of improving a growth per cycle (GPC) rate through atomic layer deposition (ALD) and forming a silicon nitride layer having an excellent step coverage even in a low-temperature process. As discussed above with the experimental and comparative examples, the GPC rate may be improved, compared to a case in which existing silicon precursors are used, and a silicon nitride layer having an excellent step coverage may be formed even in a low-temperature process performed at a relatively low temperature of 300° C. or greater and less than 350° C.

The ALD method according to the present disclosure can be used in various other methods of fabricating a semiconductor device that conformally form a dielectric layer comprising silicon nitride through ALD.