JP3324573B2 - Semiconductor device manufacturing method and manufacturing apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device capable of removing impurities formed on the back surface of the semiconductor device.

[0002]

2. Description of the Related Art A conventional SiGe epitaxial film forming process will be described using a UHV-CVD apparatus as an example.

FIG. 8 is a sectional view of a UHV-CVD apparatus.

This apparatus is separated into a growth chamber 3 and a heater chamber 4 by a susceptor 2 provided for supporting a silicon substrate 1, and each chamber is controlled by a vacuum pump 5 to 1 × 10 ⁻⁹ Torr or less. Is reduced to a high vacuum.

[0005] A heater 6 is provided in the heater chamber 4, and the silicon substrate 1 is passed through the susceptor 2.
To the desired temperature. A process gas introduction pipe 7 is connected to the growth chamber 3 side, and a process gas such as disilane is introduced into the growth chamber 3 during growth. The pressure during the growth is 1 × 10 ⁻³ Torr or less.

FIGS. 9A and 9B are views showing the shape of a plate type susceptor, wherein FIG. 9A is a plan view and FIG. 9B is a sectional view.

FIGS. 10A and 10B are views showing the shape of the ring type susceptor, wherein FIG. 10A is a plan view and FIG. 10B is a sectional view.

[0008] The shape of the susceptor 2 shown in FIG. 8 is a disk-shaped one such as a plate type susceptor 20 shown in FIG.
In addition, there is a ring-shaped susceptor 21 shown in FIG.

In forming the SiGe epitaxial layer, the Ge concentration is controlled to a desired value by adjusting the flow rate of the germane gas using disilane gas and germane gas. Diborane gas is used for boron doping. The formation temperature is 550 to 750 ° C., and the pressure during growth is 1 × 10 ⁻⁴ to 1 × 10 ⁻³ Torr.

[0010]

However, conventionally, S
During the growth of the iGe epitaxial film, the germane gas may flow into the heater chamber 6, which causes a problem that granular Ge adheres to the back side of the silicon substrate.

Since the disilane gas has high reactivity, it is consumed in a region where the peripheral portion of the silicon substrate is in contact with the susceptor. However, the germane gas enters the unresolved region between the back surface of the silicon substrate and the susceptor. Then, Ge is deposited on the back surface of the silicon substrate.

At this time, since Ge and silicon on the silicon substrate have poor wettability, the precipitates become granular. The Ge formed on this back surface needs to be removed because there is a risk of causing a bad influence on the device.

It is an object of the present invention to remove Ge adhered to the back surface of a silicon substrate in a CVD apparatus for forming a Ge or SiGe film.

[0014]

Ge or S to be formed
After forming the Si layer on the outermost surface of the iGe film, an etching gas such as Cl ₂ is flowed at a temperature of 750 ° C. or less to remove Ge on the back surface of the silicon substrate. Further, in order to increase the efficiency of removing Ge, C
to constitute a manufacturing apparatus to supply Cl ₂ gas by installing a gas line of the l _2.

The manufacturing method was configured by performing the following steps after forming the SiGe epitaxial film. That is, Si epitaxial growth is performed on the SiGe film,
The outermost surface is capped with a Si layer. Move the silicon substrate to a position where the gas reaches the back of the Si substrate, and set the substrate temperature to 750 ° C.
In the following, an etching gas such as Cl ₂ is introduced to etch Ge on the back surface. In order to avoid a decrease in throughput, the introduction of the etching gas is performed at the time of temperature decrease after the film formation. In order to enhance the etching effect, an etching gas introduction pipe may be provided near the back surface.

At 750 ° C. or lower, etching of the Si film by Cl ₂ does not occur, but etching of the Ge film is possible. For example, the etching rate of Ge by Cl ₂ at 570 ° C. is 300 A / min or more.
Therefore, if the outermost surface is covered with Si, even if Cl ₂ flows, the SiGe film will not be etched if the temperature is lower than 750 ° C. On the other hand, the amount of Ge attached to the back surface is at most 500 A or less when a SiGe film of 1000 A is grown, and even when the temperature is 600 ° C. or less, the Ge attached to the back surface can be sufficiently etched by flowing Cl ₂ for 2 minutes. .

Thus, Ge, S adhered to the back surface of the substrate
iGe can be removed. In addition, since Ge on the back surface is present in the form of particles on the back surface of the silicon substrate, etching is easier than that of Ge in the form of a film.

[0018]

FIG. 1 shows a UHV-CVD used for forming a SiGe epitaxial film according to a first embodiment of the present invention.
(Ultra High Vacuum Chemical
FIG. 2 is a cross-sectional view of a growth chamber of an al Vapor Deposition apparatus.

The present CVD apparatus is separated into a growth chamber 3 and a heater chamber 4 by a susceptor 2 provided to support a silicon substrate 1, and each chamber is separated by a vacuum pump 5 to 1 × 10 ^−9. The pressure is reduced to a high vacuum of Torr or less.

The silicon substrate 1 is heated to a desired temperature by a heater 6 through a susceptor 2. Further, a process gas introduction pipe 7 is connected to the growth chamber 3 side, and a process gas such as disilane is introduced into the growth chamber 3 during growth. The pressure in the growth chamber 3 during growth is 1 × 10 ⁻³ Torr.
r or less.

FIGS. 2 (a), 2 (b) and 2 (c) are views for explaining the unloading step of the silicon substrate 1 in the first embodiment of the present invention.

First, as shown in FIG. 2A, the lift pins 8 in the heater chamber 4 rise, and as shown in FIG. 2B, the silicon substrate 1 is lifted. Then, FIG.
The transfer arm 9 enters into the gap formed between the silicon substrate 1 and the susceptor 2 as shown in FIG. 3 and then the lift pins 8 move downward, and the silicon substrate 1 is placed on the transfer arm 9 and the growth chamber 3 It is carried out from.

The loading process of the silicon substrate 1 is the reverse of the unloading process. That is, when the silicon substrate 1 is carried over the susceptor 2 in the growth chamber 3 by the transfer arm 9, the lift pins 8 rise to lift the silicon substrate 1, and the silicon substrate 1 is separated from the transfer arm 9. State. The transfer arm 9 includes the silicon substrate 1 and the susceptor 2
And moves out of the growth chamber 3. Thereafter, the lift pins 8 are lowered and settled in the heater chamber 4, and the silicon substrate 1 is placed on the susceptor 2.

Next, the operation of the first embodiment of the present invention for forming a SiGe epitaxial film on the silicon substrate 1 using a UHV-CVD apparatus will be described.

The first embodiment is an example in which the base layer of a bipolar transistor is formed of a SiGe epitaxial film.

FIGS. 3A and 3B are views for explaining a base layer formed in the first embodiment of the present invention. FIG. 3A is a sectional view of the base layer, and FIG. It is a figure of the graph which shows a density.

As shown in FIG. 3A, the base layer 10
Is composed of two layers, a Ge-graded SiGe layer 11 and a silicon cap layer 12.

As shown in FIG. 3B, the first layer formed directly on the silicon substrate 1 has a Ge gradient in which the Ge concentration changes from 10% to 0% from the substrate toward the surface. This is the SiGe layer 11. Ge graded SiGe layer 11
Above is a silicon cap layer 12 of a silicon epitaxial film as a second layer.

The Ge gradient type SiGe layer 11 has a thickness of 70 nm, and the silicon cap layer 12 has a thickness of 30 nm. Both of them are doped with boron at a maximum of 1 × 10 ¹⁹ .

For the formation of the base inclined SiGe layer 11, the Ge concentration was controlled by adjusting the flow rate of germane gas using disilane gas and germane gas. Diborane gas was used for boron doping.

For forming the silicon cap layer 12, disilane gas and diborane gas for boron doping were used. The formation temperature was 550 to 750 ° C., and the pressure during growth was 1 × 10 ⁻⁴ to 1 × 10 ⁻³ Torr.

As a result, the base layer 10 having a thickness of 100 nm was formed. At the same time, the gas flowed to the back surface of the silicon substrate 1 and Ge particles adhered. The size of the Ge particles was 30 nm at the maximum when the film thickness of the Ge gradient type SiGe layer 11 was 70 nm.

FIG. 4 shows a first embodiment of the present invention.
FIG. 4 is a diagram illustrating an operation of removing Ge particles on the back surface of the silicon substrate 1.

Next, as shown in FIG. 4, with the lift pins 8 raised to lift the silicon substrate 1, an etching gas is flowed to remove Ge particles on the back surface of the silicon substrate 1.

In the first embodiment, chlorine gas is used as an etching gas, and the temperature at the time of etching is 500 ° C.
It was set between 700 ° C. At this temperature, the base layer 10 is not etched because no silicon etching occurs, but Ge is etched, so that Ge
Only particles can be removed. For example, the Ge film is etched at 30 nm or more per minute by chlorine gas at 570 ° C. In this embodiment, Ge particles on the back surface of the silicon substrate 1 could be completely removed by flowing chlorine gas at 570 ° C. for 2 minutes.

In the first embodiment, the back surface is etched with respect to the SiGe film of 70 nm. However, when the growing SiGe epitaxial film is thick, if the etching time is increased or the temperature is increased, Ge particles on the back surface can be removed even if the diameter is large.

Next, a second embodiment of the present invention will be described.

In the second embodiment, a UHV-CVD apparatus of a type different from that of the first embodiment is used.

FIG. 5 is a sectional view of a CVD apparatus used in the second embodiment of the present invention.

This CVD apparatus has a ring shape in which the susceptor 13 has a center cut out. The ring-shaped susceptor 13 has a donut shape with a hole in the center when viewed from above, and the silicon substrate 1 rests on the ring-shaped susceptor 13 only in the peripheral portion.

When this ring type susceptor 13 is used,
Since the silicon substrate 1 can be directly heated by the heater from the back surface, there is an advantage that the temperature of the silicon substrate 1 can be quickly increased and decreased.

In this embodiment, the etching gas introduction pipe 14 is connected to the heater chamber 4, and chlorine gas is used as the etching gas in the same manner as in the first embodiment.

The SiG formed in the second embodiment
The e-epitaxial film and the forming conditions are the same as in the first embodiment. For the Ge particle etching of the back surface of the silicon substrate 1, the silicon substrate 1 is placed on the ring-type susceptor 13 and the etching gas introduction pipe 14 is applied at a substrate temperature of 500 ° C. to 700 ° C. in the same state as when the epitaxial film is formed. Chlorine gas was flowed.

In the second embodiment, etching is performed by flowing chlorine gas while the temperature is lowered from the process temperature to unload the silicon substrate 1 without specially providing a process time for etching the Ge particles. Was. FIG. 6 shows a time chart at that time.

FIG. 6 shows a second embodiment of the present invention.
5 is a time chart showing a substrate temperature in an operation from formation of an epitaxial film to unloading of a silicon substrate.

As shown in FIG. 6, the process temperature is set to 650.
When the silicon substrate 1 was carried out at 550 ° C. and at 550 ° C., the time during which chlorine gas was flown during the temperature reduction until the silicon substrate 1 was carried out was 2 minutes. Thereby, the Ge particles on the back surface of the silicon substrate 1 were completely removed.

Next, a third embodiment of the present invention will be described.

In the third embodiment, the present invention is applied to SiGe epitaxial growth using a low pressure CVD apparatus.

FIG. 7 is a sectional view of a low-pressure CVD apparatus used in the third embodiment of the present invention.

The silicon substrate 1 rests on the susceptor 15 as in the first embodiment, and is heated by the lamps 16 disposed therearound. The process gas is introduced from a gas inlet 17 on the side of the susceptor 15 and discharged from a gas outlet 18 on the opposite side of the silicon substrate 1.

The SiGe epitaxial film of the third embodiment has the same structure as that of the first embodiment. The epitaxial film was formed at a temperature of 750 to 850 ° C. and a growth pressure of 10 to 300 Torr. For growth,
Dichlorosilane gas and germane gas were used, and hydrogen was used as a carrier gas. Further, a hydrogen chloride gas was introduced at the same time to improve the film quality. At the time of boron doping, diborane gas was used. Thereby, the film thickness 10
A 0 nm epitaxial film was formed.

Next, the silicon substrate 1 is lifted by the lift pins 19 to form a gap between the susceptor 15 and the silicon substrate 1, and an etching gas is caused to flow on the rear surface of the silicon substrate 1 so as to adhere to the rear surface of the silicon substrate 1. Ge
The particles were removed.

In the third embodiment, hydrogen chloride was used as an etching gas and hydrogen was simultaneously supplied as a carrier gas. By setting the temperature to 650 ° C. and flowing the gas for 2 minutes, the Ge particles on the back surface of the silicon substrate 1 were completely removed.

[0054]

As described above, according to the present invention.
By providing a chlorine gas etching step after the epitaxial film was formed, Ge particles on the back surface of the silicon substrate 1 could be removed. The top surface of the epitaxial film is shown in FIG.
As shown in (a), since the silicon cap layer 12 covers the silicon substrate, Ge is not exposed on the silicon substrate.

As described above, when the silicon substrate 1 is advanced to the next step, there is no danger of Ge contamination on the next-step apparatus and other substrates, and there is no longer any limitation in device fabrication for the silicon substrate 1 on which a SiGe epitaxial film is formed. .

More specifically, it is possible to share an apparatus to be used after the formation of SiGe with another device.

In the case where the base film is formed by selective epitaxial growth in which the base film is grown only on the silicon substrate without growing on the insulating film, an insulating film is required also on the back surface. This eliminates the need for an extra step of forming the back surface insulating film.

[Brief description of the drawings]

FIG. 1 is a sectional view of a growth chamber of a UHV-CVD apparatus used for forming a SiGe epitaxial film according to a first embodiment of the present invention.

FIGS. 2 (a), (b) and (c) show the first embodiment of the present invention.
FIG. 8 is a view for explaining a process of unloading the silicon substrate 1 in the example of FIG.

3A and 3B are diagrams illustrating a base layer formed in the first embodiment of the present invention, wherein FIG. 3A is a cross-sectional view of the base layer, and FIG. 3B shows the Ge concentration in the base layer shown in FIG. It is a figure of a graph.

FIG. 4 is a diagram illustrating an operation of removing Ge particles on the back surface of the silicon substrate 1 in the first embodiment of the present invention.

FIG. 5 is a sectional view of a CVD apparatus used in a second embodiment of the present invention.

FIG. 6 is a time chart showing a substrate temperature in an operation from formation of an epitaxial film to unloading of a silicon substrate in a second embodiment of the present invention.

FIG. 7 shows a low pressure CVD used in a third embodiment of the present invention.
It is sectional drawing of an apparatus.

FIG. 8 is a sectional view of a UHV-CVD apparatus.

FIG. 9 is a view showing the shape of a plate-type susceptor;
(A) is a plan view and (b) is a cross-sectional view.

FIG. 10 is a view showing a shape of a ring type susceptor;
(A) is a plan view and (b) is a cross-sectional view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Susceptor 3 Growth chamber 4 Heater chamber 5 Vacuum pump 6 Heater 7 Process gas introduction pipe 8 Lift pin 9 Transfer arm 10 Base layer 11 Ge inclined SiGe layer 12 Silicon cap layer 13 Ring type susceptor 14 Etching gas introduction pipe 15 Susceptor 16 Lamp 17 Gas inlet 18 Gas exhaust port 19 Lift pin 20 Plate type susceptor 21 Ring type susceptor

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-10-41235 (JP, A) JP-A-5-190471 (JP, A) JP-A-4-345022 (JP, A) JP-A-7- 37815 (JP, A) JP-A-63-25924 (JP, A) JP-A-10-223537 (JP, A) JP-A-6-45257 (JP, A) JP-A-10-64865 (JP, A) JP-B-41-5361 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/205

Claims (3)

(57) [Claims] A step of forming a Ge or SiGe film on a silicon substrate by a CVD method; and flowing an etching gas to a back surface of the silicon substrate to form a Ge or SiGe film. A step of removing Ge formed on
And removing Ge formed on the back surface of the silicon substrate.
From the end of the film formation of the silicon substrate.
A method for manufacturing a semiconductor device, wherein the method is provided at the time of temperature decrease before carrying out . 2. A G layer formed on a back surface of the silicon substrate.
during enough before or該工step of removing e, claims and comprising a step of generating a gap between the susceptor for supporting the silicon substrate and the silicon substrate
Item 2. A method for manufacturing a semiconductor device according to item 1 . 3. A G layer formed on a back surface of the silicon substrate.
3. The method according to claim 1 , wherein the temperature of the silicon substrate in the step of removing e is 750 ° C. or less.