JPH05211123A - Growth method of silicon epitaxial film - Google Patents

Abstract

PURPOSE:To realize epitaxial growth of hot wall system, by providing a process for supplying HCl gas before or after a process wherein silane based reaction gas is supplied and an epitaxial film is grown. CONSTITUTION:A P type silicon wafer 5 doped with boron is mounted on a wafer holder 4, the temperature inside a reaction pipe is set at 1080 deg.C with a resistance heating furnace 6, the degree of vacuum is set to be 10Torr, and the wafer holder 4 is rotated at 5rpm. From a first nozzle pipe 7A, H220SLM, SiH2Cl200sccm and B2H650sccm are supplied for 25 minutes. From a second nozzle pipe 7B, H220SLM for reduction are supplied for 25 minutes. Thereby a 10OMEGA-cm P-type silicon epitaxial film of 10mum in thickness is grown. Next, from the first nozzle pipe 7A, H220SLM and HCl1000sccm are supplied for 5 minutes, and a polysilicon film deposited on a quartz jig in the reaction pipe is etched and eliminated. Hence the growth of a thick silicon epitaxial film of hot wall type can be realized without generating particles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a silicon epitaxial film by a vapor phase growth method.

[0002]

2. Description of the Related Art Thin film forming technology has become an important technology in many industrial fields such as semiconductor, metal or ceramics industries. Particularly in the manufacturing process of a semiconductor device using a silicon wafer, a technique for uniformly growing an epitaxial film doped with P-type or N-type impurities or a polycrystalline silicon film on the wafer surface is required. In order to meet this demand, a chemical vapor deposition (CVD) method has been industrially used for high throughput and a high quality film can be obtained, and many apparatuses have been developed.

As a CVD apparatus for growing a polycrystalline silicon film which is grown at a relatively low temperature, an LPCVD apparatus using a hot wall type reaction furnace is used.
Nowadays, vertical furnaces are becoming the mainstream because they allow less wafer entrainment during wafer loading and easy wafer rotation.

Further, CVD for growing an epitaxial film
Since the epitaxial growth is a high temperature process, a cold wall type reaction furnace called a barrel type or a pancake type in which silicon is less likely to be deposited on a reaction tube has been conventionally used as an apparatus. However, with these cold wool type CVD devices, it has become difficult to meet the current requirements in terms of throughput as the diameter of processed wafers increases, and recently various new system devices have been prototyped. ing. For example, Japanese Patent Application Laid-Open No. 63-0086424 proposes a CVD apparatus capable of processing a large-diameter 6-inch wafer in a large amount by a hot wall method using a vertical reaction tube. 7A and 7B are a vertical sectional view and a horizontal sectional view of this CVD apparatus.

The reaction vessel has a double structure, and the outer tube 1 provided on the pedestal 3 holds the vacuum, and the first and second nozzle tubes 7A, 7A
The reaction gas is supplied from the gas introduction hole 10 of 7B. The reaction gas passes through the growth surface of the wafer 5 and is discharged through a large number of gas discharge holes 8 provided in the cylindrical surface of the inner tube 2. Conventional epitaxial growth is 900-1 under reduced pressure.
The wafer is heated to 200 ° C and PH ₃ , AsH ₃ , BH
_The epitaxial film was grown by supplying a doping gas such as ₃ and a silane-based reaction gas related to the growth to the surface of the wafer 5 using the nozzle tubes 7A and 7B.

[0006]

Since the hot wall type reaction furnace can easily and uniformly heat a large number of wafers, it is a technique that has been attracting attention as a method for mass producing silicon epitaxial films. However, in this method, the in-tube jig such as the reaction tube is heated to almost the same temperature as the wafer, so when the growth is performed under the same conditions as the cold wall type growth furnace, the jig such as the reaction tube is There is a problem that a large amount of polysilicon film is deposited and particles are generated. The hot wall type reactor is a CVD that can grow a large amount of silicon epitaxial film.
It is for the reasons described above that the device has been considered as a promising device but has not been realized in the past.

In order to solve the above-mentioned problems, HCl gas is added to a silane-based gas which is a growth gas as a reaction gas to suppress the deposition of a polysilicon film on an in-tube jig such as a reaction tube wall. Realized an epitaxial growth system. In fact, this CVD apparatus is being put to practical use as an apparatus for growing a thin epitaxial film such as Bi-CMOS.

However, this method of growing an epitaxial film while adding HCl gas has a drawback that the growth rate is slow for the reason described below. Therefore, the epitaxial method for a MOS transistor, which is regarded as a promising substrate for a next-generation CMOS, is expected. It is difficult to apply it to a method for forming a thick epitaxial film, which is expected to grow greatly in the future epitaxial market, such as a substrate or an epitaxial substrate for a CCD device.

As described above, in the conventional growth method, C
To suppress the deposition of the polysilicon film on the reaction tube wall of the VD device, HCl gas is added to the reaction gas. This method is an application of the well-known selective epitaxial growth technique for silicon. The selective growth is performed by adding HCl as an etching gas to the growth gas,
This is a technique for growing an epitaxial film only on a silicon substrate without growing a silicon film on an oxide film (SiO ₂ ). In the above-mentioned hot wall furnace, all the jigs inside the tube such as the reaction tube are made of quartz (SiO ₂ ), so that the deposition of the polysilicon film on the quartz jig such as the reaction tube is suppressed as in the case of the selective growth. is doing.

FIG. 3 shows the growth rate and the selective growth region of the epitaxial film with respect to the SiH ₂ Cl ₂ and HCl gas flow rate ratio. When the HCl flow rate ratio is small, non-selective growth occurs, and as the HCl flow rate ratio increases, the non-selective growth proceeds to the etching region via the selective growth region. As is apparent from FIG. 3, the growth rate in the selective growth region is much lower than that in the non-selection region. On the contrary, the increase in the growth rate deselects the growth, so that the deposition amount of the polysilicon film on the quartz jig such as the reaction tube is increased and particles are generated.

As described above, according to the conventional method, it is difficult to increase the growth rate of the epitaxial film on the wafer while suppressing the deposition of the polysilicon film on the jig in the reaction tube.

[0012]

According to the method for growing a silicon epitaxial film of the present invention, a nozzle having a reaction gas discharge hole is held in a wafer holder so that a plurality of wafers are stacked substantially horizontally in a reaction tube at a predetermined interval. In a method of growing a silicon epitaxial film, in which a reaction gas is flown from a tube to each growth surface of the wafer to form an epitaxial film, a silane-based reaction gas is supplied as an epitaxial film by supplying argon, nitrogen or xenon gas as a carrier gas. It has a step of growing a film and a step of supplying HCl gas before or after this growth step.

It will be described below that this method can solve the above-mentioned problems.

FIG. 4 shows the epitaxial film thickness distribution in the substrate surface depending on the carrier gas species for transporting the growth gas. When hydrogen or helium gas is used as the carrier gas, almost no epitaxial film grows on the wafer that is the substrate to be grown.
On the other hand, when argon, nitrogen or xenon gas is used as the carrier gas, the epitaxial film grows on the wafer.

On the other hand, FIG. 5 shows that the etching gas is HC.
1 is a graph showing the difference in carrier gas species for gas transportation. From FIG. 5, it can be seen that the etching effect on the polysilicon deposited on the jig in the reaction tube is greater when hydrogen or helium gas is used as the carrier gas.

Further, FIG. 6 shows the rate at which the wafer is etched during this etching process, measured in the plane of the wafer. However, when hydrogen or helium gas is used as the carrier, the wafer is almost etched. Absent.

The difference in the growth or etching action due to the difference in the carrier gas species is not due to the difference in the chemical reactivity of the carrier gas but to the difference in the reaction gas transport effect of the carrier gas. This difference in transport effect depends on the difference in self-diffusion coefficient η / ρ determined by the viscosity η and the density ρ of the element used as the carrier gas. From the above results, when the same nozzle tube is used, by using argon, nitrogen, or xenon gas, which is a relatively heavy element, as a carrier gas, an epitaxial film grows on the wafer that is the substrate to be grown, and it is relatively light. By using hydrogen or helium gas as the carrier gas, the polysilicon film deposited on the jig inside the reaction tube can be etched without affecting the wafer.

That is, if hydrogen or helium gas is used as a carrier gas and etching is performed with HCl gas before or after the epitaxial growth process, the polysilicon deposited on the jig in the tube by the epitaxial growth without affecting the wafer. The film can be etched away. Therefore, the epitaxial growth can be performed in the non-selected region, and the growth rate can be greatly increased. Furthermore, since the etching process does not affect the wafer, a large amount of HCl gas can be supplied, and the polysilicon film can be removed by high-speed etching.

In the present growth method, the number of steps involved in the epitaxial growth is increased because the step for etching the jig in the tube is added as compared with the conventional method. However, the total epitaxial growth step time is increased due to the increase in the number of steps. The effect of shortening the growth time by increasing the growth rate is far greater. This is particularly remarkable when growing a thick epitaxial film.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. In the example of the present invention, the vertical LPCVD apparatus shown in FIGS. 7A and 7B was used as an epitaxial growth furnace. In the first embodiment, a P type silicon epitaxial film is grown on a P ⁺ type silicon wafer (single crystal substrate). The epitaxial substrate of this structure is highly promising as a future CMOS device substrate because it has high resistance to soft errors due to latch-up and α rays.

First, 50 boron-doped P ⁺ -type silicon wafers 5 having a diameter of 150 mm and a resistivity of 0.01 Ω-cm are mounted on the wafer holder 4 of the apparatus shown in FIG.
The temperature inside the reaction tube was set to 1080 ° C. by the resistance heating furnace 6, and the degree of vacuum was set to 10 Torr. The wafer holder 4 is rotated at a speed of 5 revolutions per minute, and first the N ₂ 2 is fed through the first nozzle pipe 7A.
0 SLM, SiH ₂ Cl ₂ 200 sccm, B ₂ H ₆ 5
0 sccm, and H for reducing from the second nozzle tube 7B
10 Ω-cm by supplying _{2 20} SLMs for 25 minutes each
A P-type silicon epitaxial film was grown to a thickness of 10 μm (growth rate 0.4 μm / min). Then the first
(Or 2nd) H ₂ 20SLM, HCl 1 from nozzle tube
000 sccm was supplied for 5 minutes to remove the polysilicon film deposited on the quartz jig in the reaction tube by etching.

FIG. 1 shows an outline of the above steps for epitaxial growth in comparison with the conventional method. While the epitaxial growth process time according to the first embodiment is 70 minutes from the wafer load A to the wafer unload F, the conventional method (growth rate 0.1 μm /
min) is 130 minutes, and the epitaxial growth process time is about 1 / th according to the first embodiment.
Shortened to 2. In addition, the number of particles having a diameter of 0.3 μm or more was measured for the grown 50 epitaxial wafers. The number of particles was 5 on average per 150 mm wafer, and it was confirmed that no particles were generated in the first embodiment.

The second embodiment is an application of the method of the present invention to the growth of an N type silicon epitaxial film. The epitaxial film having this structure is applied to a CCD device or the like. Epitaxial growth was performed using the same LPCVD apparatus as in the first embodiment. In the second example, a P-doped N-type silicon wafer was used as the growth substrate.

First, as in the case of the first embodiment, 50 P-doped N-type silicon wafers having a diameter of 150 mm and a resistivity of 10 Ω-cm are mounted on the wafer holder 4 and the temperature inside the reaction tube is 1080 ° C. and the degree of vacuum is set. Was set to 10 Torr.
The wafer holder 4 is rotated at a speed of 5 revolutions per minute, and first the H ₂ 20SLM, HCl _{20 is} fed through the first nozzle pipe 7A.
00 sccm was supplied for 10 minutes to remove the polysilicon film deposited on the quartz jig in the reaction tube by etching. next,
From the first nozzle tube 7A, N ₂ 20SLM, SiH ₂ Cl ₂
500 sccm, PH ₃ 50 sccm, and H ₂ 50 sccm were supplied from the second nozzle tube for 40 minutes, respectively.
An Ω-cm N-type silicon epitaxial film was grown to 40 μm (growth rate 1 μm / min).

The feature of the second embodiment is that the etching process of the polysilicon film is performed in the preceding step of the epitaxial growth. FIG. 2 shows the steps of this epitaxial growth. In the case of the second embodiment, as in the case of the first embodiment, the conventional method (growth rate 0.1 μm / m
In), the epitaxial growth process time is significantly shortened (about 1/5 of the conventional method). Further, as shown in the second embodiment, generation of particles was not observed even when the polysilicon film was etched before the growth of the epitaxial film.

[0026]

As described above, the present invention provides a method for growing an epitaxial film using a vapor phase growth apparatus,
A step of supplying a silane-based growth gas using argon, nitrogen or xenon gas as a carrier gas to grow an epitaxial film, and a step before or after this growth step, using hydrogen or helium gas as a carrier gas to generate H
It has a step of supplying Cl gas. Therefore, it is possible to increase the growth rate of the epitaxial film on the substrate to be grown while suppressing the deposition of the polysilicon film on the jig in the reaction tube, and to increase the thickness of the thick silicon epitaxial film in the hot wall type epitaxial growth furnace. There is an effect that growth is possible without generating particles.

[Brief description of drawings]

FIG. 1 is a process drawing for explaining a first embodiment of the present invention.

FIG. 2 is a process drawing for explaining the second embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a flow rate ratio of a reaction gas and HCl and a growth rate.

FIG. 4 is a diagram showing the in-plane growth rate distribution of a wafer for various carrier gases.

FIG. 5 is a diagram showing etching rates of a polysilicon film with respect to various carrier gases.

FIG. 6 is a diagram showing the in-plane etching rate for various carrier gases.

FIG. 7 is a sectional view of a vertical LPCVD apparatus.

[Explanation of symbols]

 1 Outer Tube 2 Inner Tube 3 Stand 4 Wafer Holder 5 Wafer 6 Resistance Heating Furnace 7A First Nozzle Tube 7B Second Nozzle Tube 8 Gas Discharge Hole 9 Exhaust Port 10 Gas Inlet Hole

Claims (2)

[Claims] 1. A plurality of wafers are held in a wafer holder in such a manner that a plurality of wafers are stacked substantially horizontally in a reaction tube at a predetermined interval, and a reaction tube is provided with a reaction tube through which a reaction gas is supplied to each growth surface of the wafer. In the method for growing a silicon epitaxial film, which comprises forming a epitaxial film by flowing a hydrogen gas, a step of growing a epitaxial film by supplying a silane-based reaction gas with argon, nitrogen or xenon gas as a carrier gas, and before or after this growth step.
And a step of supplying Cl gas, the method for growing a silicon epitaxial film. 2. The method for growing a silicon epitaxial film according to claim 1, wherein the carrier gas for supplying the HCl gas is hydrogen or helium.