KR20090035307A - Pulse gas flow deposition method, device for the same andmanufacturing method for epitaxial wafer using the same - Google Patents

Abstract

A method and a device for the pulse gas flow depositing and an epitaxial wafer manufacturing method using the same are provided to have the nitrogen having the uniform concentration on the whole of the wafer distributed. An epitaxial wafer manufacturing method using the pulse gas flow depositing device comprises: a step of providing the wafer in a chamber of nitrogen doped doping source gas atmosphere in order form a nitrogen doped epitaxial layer(S1); a step of providing the purge gas and performing the atomic layer deposition while performing the nitrogen and oxygen doping(S3); and a step of exposing the doped wafer to a silane(PH4) mood in order to form a silicon layer(S4). The step for performing atomic layer deposition is performed in the pressure condition of the temperature of 500 ~700°C and 0.2 - 1.5 Torr. The step exposing the doped wafer to the silane mood is performed in the condition of the pressure of the temperature of 500~ 700°C drawing and 0.2 - 1.5 Torr. The pulse gas flow method for depositing is severally repeated and performed and then epitaxial wafer growth is performed.

Description

Pulse gas flow deposition method, apparatus and method for manufacturing epitaxial wafer using same {PULSE GAS FLOW DEPOSITION METHOD, DEVICE FOR THE SAME AND MANUFACTURING METHOD FOR EPITAXIAL WAFER USING THE SAME}

The present invention relates to a pulsed gas flow deposition method, an apparatus and a method for fabricating an epitaxial wafer using the same. More specifically, the doping of nitrogen is carried out when the epitaxial layer is grown, not during crystal growth by the Czochralski method. Pulse gas flow evaporation method, apparatus for uniform nitrogen concentration and accurate concentration distribution over the entire wafer surface, and high temperature heat treatment process is not required for formation of defect element layer And a method for manufacturing an epitaxial wafer using the same.

In epitaxial silicon wafers used in semiconductor devices, the quality of the epitaxial silicon wafer varies greatly depending on impurities. That is, the presence of heavy metal impurities on the surface of the wafer deteriorates various davias characteristics, such as a change in electrical property values, a decrease in yield, and poor reliability.

Therefore, efforts to remove such heavy metal impurities have been actively developed. One of them is a gathering technique, and the importance thereof is increasing day by day. In particular, in the element of the image sensor system, the dark current due to white defects is known as a major defect that leads to a decrease in yield, and the cause is known as contamination by heavy metal impurities. .

In addition, due to the high temperature growth of the epitaxial layer of the epitaxial wafer fabrication process, BMD (Bulk Micro Defect) nuclei below the critical size disappear, so it is very important to secure the gathering effect in epitaxial wafer fabrication.

The conventional technique used to obtain a sufficient gathering effect on an epitaxial wafer is to grow a silicon single crystal rod doped with nitrogen by Czochralski method, and then cut and process the silicon single crystal rod, It is produced by forming a silicon epitaxial layer on the surface of a single crystal wafer.

Oxygen precipitated nuclei that do not reach critical sizes are extinguished in the epitaxial growth phase at high temperatures, and thus have no sufficient oxygen precipitation concentration, resulting in poor gathering effect. Nitrogen atoms are very effective in preventing these nuclei from extinction. Nitrogen doping to silicon substrates is widely used in wafer fabrication.

In addition, after a long time heat treatment at high temperature for the purpose of removing defects on the surface of the wafer and forming a dedened zone through out-gassing of nitrogen and oxygen before the epitaxial layer is grown. The epitaxial layer is grown. As such, conventional nitrogen doping is performed at the time of colon growth by the Czochralski method.

However, this conventional technology has the following problems.

First, when nitrogen doping is performed on a single crystal growth rod, it is doped not only in the active region where the device is manufactured, for example, but also in the entire wafer region, and thus has a BMD concentration for gathering. In the case of a high resistance power device, there is a problem that a heat treatment for forming the defect free area layer must be performed at a high temperature for a long time before the epitaxial layer is grown.

In addition, it becomes difficult to obtain a uniform concentration distribution according to the position of the single crystal growth rod and a uniform concentration distribution in the substrate. Therefore, there are cases where the target BMD concentration does not come out consistently, and a fatal defect may occur in the device such as a nitrogen induced stacking fault due to excessive nitrogen concentration.

Therefore, there is a need for a method in which the nearest gathering is possible and the nitrogen doping concentration can be adjusted while maintaining a constant nitrogen concentration. Conventional close gathering method is known to ion implantation and annealing (annealing) method of impurities, but has the disadvantage that it does not completely damage recovery by annealing the damage (damage) during ion implantation.

One object of the present invention for solving the above problems is to perform a pulsed gas flow for maximizing the gathering effect by performing nitrogen doping during the epitaxial layer growth, not during crystal growth by the Czochralski method. The present invention provides a deposition method, an apparatus, and an epitaxial wafer manufacturing method using the same.

Another object of the present invention is to provide a pulse gas flow deposition method capable of uniform nitrogen concentration and accurate concentration distribution over the entire surface of the wafer, an apparatus thereof, and a method of manufacturing an epitaxial wafer using the same.

Another object of the present invention is to eliminate the need for a high temperature heat treatment process for the formation of a defect-free element layer, which is an essential element of epitaxial wafer manufacturing for high-resistance power devices, simplifying the manufacturing process, shortening the manufacturing time, and manufacturing cost. The present invention provides a pulsed gas flow deposition method, an apparatus, and an epitaxial wafer manufacturing method using the same.

According to a preferred embodiment of the present invention for achieving the above object of the present invention, the pulse gas flow deposition method of the present invention is a chamber of nitrogen-doped source gas atmosphere to form an epitaxial layer doped with nitrogen Providing a wafer to the wafer, performing nitrogen and oxygen doping to the wafer, and providing a purge gas to perform atomic layer deposition (ALD), and the doped wafer Exposing to a silane (PH4) atmosphere to form a silicon layer.

Performing the atomic layer deposition and exposing the doped wafer to a silane (PH4) atmosphere are preferably performed at a temperature of 500 to 700 degrees and a pressure of 0.2 to 1.5 Torr.

In this environment, the pulsed gas flow deposition method is repeatedly performed several times, and then epitaxial growth is performed on the wafer.

The exposing the doped wafer to the silane (PH4) atmosphere may include a doping source gas flow controller that controls the flow rate of the doped source gas and a silane gas flow controller that controls the flow rate of the silane gas, wherein each flow controller Is always switched on, but uses a diverter valve connected to the doping source gas flow controller to direct the doping source gas to an exhaust line rather than the chamber, and to the silane gas flow controller. It is possible to configure the silane gas to be connected to the chamber rather than to the discharge line using a connected switching valve.

Further comprising a heat treatment step of heat-treating the wafer, the size of the oxygen precipitates on the wafer to have a gathering effect.

In the method for manufacturing an epitaxial wafer according to the present invention, the method includes: providing a wafer, removing a native oxide film of the wafer, and performing nitrogen and oxygen doping on the wafer, but alternately purging gas. Performing atomic layer deposition (ALD), exposing the wafer to a silane gas atmosphere to form a silicon atomic layer, and forming an epitaxial growth layer on the wafer. It includes.

The pulsed gas flow deposition step is repeatedly performed to realize a target atomic layer thickness, and further comprising a heat treatment step of heat treating the wafer, wherein the size of oxygen precipitates is grown on the wafer to have a gathering effect. do.

Pulse gas flow deposition apparatus according to the present invention is a chamber for receiving a wafer, a doping source gas flow controller for providing a doping source gas containing nitrogen in the chamber, a silane gas flow controller for providing a silane gas to the chamber, and the And a purge flow controller providing a purge gas to the chamber, performing atomic layer deposition (ALD) of nitrogen and oxygen doping on the wafer, and turning on the silane gas flow controller in the chamber. The silicon layer of the silane gas is deposited on the wafer.

The chamber has a temperature of 500 to 700 degrees and a pressure condition of 0.2 to 1.5 Torr, and includes a growth chamber provided separately from the chamber, wherein the growth chamber moves the wafer in the chamber to form an epitaxial growth layer. It is preferable to form on a wafer. At this time, the growth chamber is preferably at least 900 degrees.

In this way, the nitrogen doping is carried out when the epitaxial layer is grown when the crystal is not grown by the Czochralski method to maximize the gathering effect, as well as uniform nitrogen concentration and accurate concentration distribution over the entire wafer surface. It is possible to eliminate the need for a high temperature heat treatment process for the formation of the defect-free layer.

As described above, according to the present invention, the doping effect is maximized by performing the nitrogen doping at the growth of the epitaxial layer instead of the crystal growth by the Czochralski method.

In addition, there is an effect capable of uniform nitrogen concentration and accurate concentration distribution over the entire wafer surface.

In addition, a high temperature heat treatment process is not required for the formation of a defect-free element layer, which is an essential element of epitaxial wafer manufacturing for high resistance power devices, which simplifies the manufacturing process, shortens manufacturing time, and reduces manufacturing cost. It has an effect.

As described above, although described with reference to the preferred embodiment of the present invention, those skilled in the art various modifications and variations of the present invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited or limited by the embodiments. In the present invention, an epitaxial wafer has been described as an example, but it should be understood that the present invention is not limited thereto.

1 is a flowchart illustrating a method of manufacturing an epitaxial wafer according to the present invention.

As shown therein, first, a wafer is provided and loaded into the apparatus for epitaxial growth or the like (S1).

Next, the native oxide is removed (S2).

Next, deposition is performed using pulse gas flow (S3), which will be described in detail below.

In the present invention, the pulsed gas flow refers to ALD (Atomic Layer Deposition) when a doping source gas is flowed to enable doping of nitrogen and oxygen to grow a silicon single crystal layer. It means the flow of gas with added purge function used in atomic layer deposition process.

In more detail, the reason why nitrogen doping is difficult during the growth of the silicon epitaxial layer is the growth of the silicon nitride thin film by the reaction of the silicon doped source with the epitaxial growth. Although thermal decomposition occurs, the chemical reaction of the growth of silicon nitride occurs faster. In order to prevent this, the purge gas used in the ALD process is used. The ALD process is a method of depositing an atomic layer while repeating the adsorption step and purge step of a chemical precursor. While the surface adsorption layer for chemisorption remains, the layer thereon has a physical adsorption where the bonding force is weaker than chemical adsorption, so that only the atomic layer remains.

By the way, the silane gas (PH ₃ gas) used as a silicon source is a representative gas with high chemical reactivity, and nitric oxides (NO, N ₂ O) and the like are physically adsorbed. Removed. However, doping is done by some of the remaining precursors.

The pulsed gas flow deposition process is a process in which the gas flow is pulsed, and the gas flow operation of the unit cycle is repeated several tens to several hundred times in sequence. That is, the on / off operation of the switch of the mass flow controller (MFC) is repeated or the flow controller is always on, but the on / off operation of the diverter valve is repeated several tens to hundreds of times to flow into the chamber. It is a method of growing a deposition layer while giving a pulse waveform to the flow of gas.

In order to form a layer for nearest gathering, that is, a nitrogen doped epitaxial layer, the following unit cycle is repeated several times. A more detailed description of the unit cycle process sequence follows.

end. In the doping source gas (mixing of N ₂ , NO, N ₂ O, O _2, etc.), the nitrogen and oxygen doping is generated using the purge of the ALD process. At this time, the process conditions include a temperature of 500 to 700 degrees, a pressure of 0.2 to 1.5 Torr, and argon (Ar) or helium (He) as an inert gas.

I. The flow rate controller of the doped source gas is switched off, and the silane gas flow rate controller is switched on to expose the doped silicon surface to the silane (PH ₄ ) gas atmosphere.

Alternatively, instead of switching off the flow rate controller of the doped source gas, the flow rate controller of the doped source gas is always switched on, but by switching on a diverter valve attached to the gas line to the chamber. It is also possible to direct gas to an exhaust line rather than to a chamber. Alternatively, instead of the silane gas flow controller being switched on, the silane gas flow controller is always switched on and switches off a switching valve attached to the gas line to the chamber to allow the silane gas to pass into the chamber rather than to the discharge line. You may.

In this step, the silicon layer is formed as the dopants on the surface diffuse infiltrate. At this time, an incubation time is required for the silicon layer to grow. At this time, the process conditions include a temperature of 500 to 700 degrees, a pressure of 0.2 to 1.5 Torr, and argon (Ar) or helium (He) as an inert gas.

All. After the incubation time, the growth of the silicon atomic layer proceeds rapidly.

The unit cycle in the above manner is repeated until a nitrogen, oxygen doped layer of a predetermined thickness is formed. For a more detailed description, FIG. 2 is presented.

As shown in FIG. 2, at the time between t1 and t2, the surface of the silicon wafer is desorbed by the physical adsorption and purging of the doping source gas (mixing of N ₂ , NO, N ₂ O, O _2, etc.). Doping proceeds. It is the time that dopants (nitrogen, oxygen) existing on the surface are diffused between the time t2 and t3, and the time between t3 and t4 is the diffusion of dopant existing on the surface, and epitaxially on the silicon surface in the silane gas atmosphere. Growth begins to progress, and incubation time is required for this.

Finally, at the time between t4 and t5, the silicon primary layer grows rapidly, ending one process cycle. At this time, the incubation time is increased in proportion to the concentration of the doping (nitrogen, oxygen). Such doping cycles in the pulsed gas flow deposition method are repeated several tens to several hundred times, so that the deposition takes place to a desired thickness.

As such, as shown in FIG. 1, after the deposition S3 is performed using pulse gas flow, the wafer is moved to undergo a silicon epitaxial layer growth process S4.

In order to form an epitaxial layer, the surface of the silicon is exposed, which includes at least one of SiCl ₄ , SiHCl ₃ , SiH ₂ Cl ₂ , SiH ₃ Cl, or SiH ₄ . This atmosphere is typically provided with hydrogen (H ₂ ) as a carrier gas (Carrier gas). While epitaxial deposition is carried out, if SiH ₂ Cl ₂ is used as the source gas, the pressure in the reaction chamber is 500 to 760 Torr. In the case of SiH ₄ , the pressure in the reaction chamber is preferably 80 to 100 Torr, approximately 100 Torr. The degree is good. The most preferred source gas is SiHCl _3, which is much cheaper than other source gases and can run under atmospheric pressure, so that no vacuum pump or the like is required. During epitaxial deposition, the surface of the wafer is preferably maintained at a temperature (approximately 900 degrees or more) sufficient to prevent the atmosphere with silicon from depositing polycrystalline silicon (or oxide film) on its surface. Thereafter, the wafer is unloaded (S5).

The reactor as a whole has a cluster form, and a reactor for forming a nitrogen doped silicon epitaxial layer through a pulsed gas flow deposition process is separated from a reactor for forming an epitaxial layer without nitrogen doping.

In order to obtain the size growth of the oxygen precipitates of the epitaxial wafer manufactured by the above method and to obtain a sufficient BMD concentration, the heat treatment process is performed, and the nearest gathering is performed by the growth of the oxygen precipitate size of sufficient concentration in the nitrogen and oxygen doped layer. The effect can be obtained.

Fig. 3 (a) is a view after epitaxial layer growth, and Fig. 3 (b) is a sectional view showing a wafer cross section after heat treatment. As shown therein, the epitaxial layer 20 epitaxially grown by nitrogen doping on the wafer substrate 10 is grown, and a region 30 on which the device is manufactured is formed.

Doping of impurities to obtain the desired electrical properties can be doped in the process of forming the region 30 in which the device is fabricated. After the heat treatment proceeds, the size of the oxygen precipitate is grown, and the gathering heat treatment process is performed in one step of the conventional two-stage heat treatment (heat treatment for nucleation: 600 to 800 degrees, heat treatment for nucleation: 800 to 1100 degrees). This alone is enough to help you increase your productivity. It is transformed into an epitaxial growth layer 40 grown above a critical size that can produce an effect.

In the heat treatment process, a single step of heat treatment is achieved at the existing two-step heat treatment, that is, heat treatment for nucleation: 600 to 800 degrees, and heat treatment for nucleation growth: 800 to 1100 degrees, thereby greatly improving productivity.

1 is a flowchart illustrating a method of manufacturing an epitaxial wafer according to the present invention.

2 is a graph for explaining pulsed gas flow deposition.

Fig. 3 (a) is a view after epitaxial layer growth, and Fig. 3 (b) is a sectional view showing a wafer cross section after heat treatment.

<Description of the symbols for the main parts of the drawings>

10 wafer substrate 20 epitaxial layer

30: Area where the device is manufactured

40: epitaxial growth layer grown beyond the critical size

Claims (19)

Providing a wafer in a chamber in a doped source gas atmosphere containing nitrogen to form an epitaxial layer doped with nitrogen; Performing nitrogen and oxygen doping to the wafer and providing a purge gas to perform atomic layer deposition (ALD); And Exposing the doped wafer to a silane (PH4) atmosphere to form a silicon layer; Pulse gas flow deposition method comprising a. The method of claim 1, Performing the atomic layer deposition is a pulsed gas flow deposition method characterized in that the carried out at a temperature of 500 ~ 700 degrees, pressure conditions of 0.2 ~ 1.5 Torr. The method of claim 1, The exposing the doped wafer to the silane (PH4) atmosphere may include a doping source gas flow controller that controls the flow rate of the doped source gas and a silane gas flow controller that controls the flow rate of the silane gas, wherein each flow controller Is always switched on, the divert valve connected to the doping source gas flow controller allows the doping source gas to pass through the exhaust line rather than the chamber, and the silane gas flow controller And the silane gas is connected to the chamber rather than the discharge line by using a switching valve connected to the pulse gas flow deposition method. The method of claim 1, Exposing the doped wafer to a silane (PH4) atmosphere at a temperature of 500 to 700 degrees and a pressure of 0.2 to 1.5 Torr. The method of claim 1, The pulsed gas flow deposition method is repeated several times, after which epitaxial growth is performed on the wafer. The method of claim 5, Wherein said epitaxial growth is performed by exposing to at least one of SiCl ₄ , SiHCl ₃ , SiH ₂ Cl ₂ , SiH ₃ Cl, or SiH ₄ . The method of claim 1, The heat treatment step of heat-treating the wafer, the pulse gas flow deposition method for growing the size of the oxygen precipitates on the wafer to have a gathering effect. Providing a wafer; Removing the native oxide film of the wafer; Nitrogen and oxygen doping are performed on the wafer, alternately providing a purge gas to perform atomic layer deposition (ALD), and the wafer is exposed to a silane gas atmosphere to form silicon. Pulsed gas flow deposition forming an atomic layer; And Forming an epitaxial growth layer on the wafer; Method for producing an epitaxial wafer comprising a. The method of claim 8, And repeating the pulsed gas flow deposition step to realize a target atomic layer thickness. The method of claim 8, The pulse gas flow deposition step is a method of manufacturing an epitaxial wafer, characterized in that carried out under the conditions of the temperature of 500 ~ 700 degrees, the pressure of 0.2 ~ 1.5 Torr. The method of claim 8, Forming an epitaxial growth layer on the wafer is a method of manufacturing an epitaxial wafer, characterized in that the growth is performed by exposure to SiH ₃ Cl gas. The method of claim 8, Forming an epitaxial growth layer on the wafer is SiH ₂ Cl ₂ Method of manufacturing an epitaxial wafer, characterized in that the growth is performed by exposure to 500 ~ 760 Torr under pressure conditions. The method of claim 8, Forming the epitaxial growth layer on the wafer is exposed to SiH ₄ to perform the growth, the manufacturing method of the epitaxial wafer, characterized in that carried out under a pressure condition of 70 ~ 150 Torr. The method of claim 8, A method of manufacturing an epitaxial wafer further comprising a heat treatment step of heat treating the wafer, wherein the size of oxygen precipitates is grown on the wafer to have a gathering effect. A chamber containing a wafer; A doping source gas flow controller providing a doping source gas containing nitrogen to the chamber; A silane gas flow controller providing silane gas to the chamber; And A purge flow controller providing a purge gas to the chamber; And an atomic layer deposition (ALD) of nitrogen and oxygen doping on the wafer and turning on the silane gas flow controller in the chamber to form a silicon layer of the silane gas on the wafer. Pulse gas flow deposition apparatus for depositing. The method of claim 15, Each of the flow controllers is always switched on, using a diverter valve connected to the doping source gas flow controller to direct the doping source gas to an exhaust line rather than to the chamber, the silane And a silane gas is connected to the chamber instead of a discharge line by using a switching valve connected to a gas flow controller. The method of claim 15, The chamber has a temperature of 500 to 700 degrees, pressure conditions of 0.2 to 1.5 Torr, characterized in that the pulsed gas flow deposition equipment. The method of claim 15, And a growth chamber provided separately from the chamber, wherein the growth chamber moves the wafer in the chamber to form an epitaxial growth layer on the wafer. The method of claim 18, The growth chamber is pulse gas flow deposition equipment, characterized in that more than 900 degrees.

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