JPH09153485A - Vapor phase growth equipment - Google Patents

Abstract

(57) Abstract: [PROBLEMS] To provide a vapor phase growth apparatus capable of forming a film having a heater with a long service life and a uniform film thickness distribution. In a vapor phase growth apparatus having a reaction furnace, a gas head for blowing out a reaction gas, and a susceptor on a top surface of which faces the gas head, the susceptor being disposed, The susceptor is disposed on the upper surface of the quartz hood, the heater is housed in the quartz hood, the susceptor is composed of an inner susceptor and an outer susceptor, and the outer susceptor is vertically divided into a plurality of parts. Vapor phase growth apparatus in which a gap exists between the inner susceptor and the inner susceptor. The gap is in the range of 0.5 mm to 1.5 mm, and the gap between the gas head and the susceptor is 100 mm.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a vapor phase growth apparatus. More specifically, the present invention relates to a vapor phase growth apparatus capable of forming a film having a long heater life, being free from foreign matter contamination, and having a uniform film thickness distribution.

[0002]

2. Description of the Related Art In the manufacture of semiconductor ICs, there is a step of forming a thin film such as silicon oxide on the surface of a wafer.
Chemical vapor deposition (CVD) is used as a method of forming a thin film. There are three CVD methods, namely, an atmospheric pressure method, a reduced pressure method and a plasma method.

For example, SiH ₄ which is a monosilane gas has been used as a material for forming a silicon oxide film, but with the miniaturization of semiconductor devices, a decrease in step coverage has become a problem. Instead of this monosilane gas,
Recently, liquid tetraethyl orthosilicate (TEO
S) [Si (OC ₂ H ₅ ) ₄ ] has come into use. This is because TEOS can form a dense film having excellent step coverage. When a silicon oxide film is formed using TEOS, TEOS is heated and vaporized,
It is supplied to the reaction furnace as TEOS gas. The Ta ₂ O ₅ film of the tantalum oxide film is formed by vaporizing liquid Ta (OC ₂ H ₅ ) ₅ and introducing it into the reaction furnace. The vaporized Si (OC ₂ H ₅ ) ₄ or Ta (OC ₂ H ₅ ) ₅ gas is mixed with oxygen gas or ozone gas and used for the film formation reaction.

An example of a conventional vapor phase growth apparatus 100 using such vaporized Si (OC ₂ H ₅ ) ₄ or Ta (OC ₂ H ₅ ) ₅ gas is shown in FIG. In the figure, a reaction furnace (chamber) 110 is made airtight, a metal nozzle portion 130 is fixed to a gas head base 102 of the reaction furnace 110, and a micro hole 141 penetrating from the upper surface to the lower surface is made of aluminum under the nozzle portion 130. The disk-shaped gas head 140 having a large number is supported by the ring 103.

The susceptor 12 faces the gas head 140.
0 is provided. The susceptor 120 is supported by columns 125. A heater unit 121 is provided below the susceptor 120, and a heater cover 123 is provided around the susceptor 120 and the heater unit 121. The heater unit 121 has a heater made of nichrome wire or the like.

In the reaction process, the gate 15 of the load lock chamber 150 provided on the side surface 105 of the reaction furnace 110.
1 is opened, and the substrate 106 is carried in by the carriage 152 and placed on the upper surface of the susceptor 120 substantially at the center. Gate 1
After closing 51 and evacuating from the duct 104 to bring the inside of the reaction furnace to a predetermined degree of vacuum, the heater 121 heats the susceptor 120, and when the substrate placed on the susceptor 120 reaches a predetermined temperature, the inlet 134 is discharged from the inlet 134. A predetermined reaction gas (for example, TEOS and oxygen gas) is fed into the reaction furnace. The gas passes through the nozzle unit 130 and then the gas head 140.
It is ejected toward the substrate from the micro holes 141.

A conventional vapor phase growth apparatus 100 shown in FIG.
However, since the heater (for example, a nichrome wire) of the heater unit 121 is easily oxidized by the oxygen gas used for the film formation reaction and is quickly consumed, it has been necessary to replace the heater relatively frequently. Further, the silicon wafer may be contaminated by heavy metal derived from the heater. Furthermore, since the heating effect of the heater unit 121 is large, the temperature distribution of the wafer is likely to be uneven, and as a result, the film thickness distribution of the film formed on the wafer surface is likely to be non-uniform. Further, since the radiant heat from the susceptor 120 is low, unless the space between the susceptor 120 and the gas head 140 is narrowed, the temperature of the reaction gas flowing down from the gas head 140 is lowered, and a normal film is formed on the wafer surface. Becomes difficult. Therefore, the reaction gas must be sufficiently mixed in the nozzle 130.
Even within 30, the film forming reaction sometimes occurred, causing an undesired phenomenon such as an increase in foreign matter.

[0008]

Therefore, an object of the present invention is to provide a vapor phase growth apparatus capable of forming a film having a uniform film thickness distribution.

[0009]

Means for Solving the Problems The above-mentioned problems include a reaction furnace in which a gas head for blowing out a reaction gas and a susceptor on which an upper surface of a susceptor is placed facing the gas head. In the vapor phase growth apparatus having the above, the susceptor is arranged on an upper surface of a quartz hood, a heater is housed in the quartz hood, the susceptor is composed of an inner susceptor and an outer susceptor, and the outer susceptor is vertically arranged in plural. This is solved by a vapor phase growth apparatus which is divided into individual pieces and has a gap between the outer susceptor and the inner susceptor.

[0010]

1 is a schematic sectional view of an example of a vapor phase growth apparatus 1 of the present invention. This apparatus also has a reaction furnace 10 like the conventional apparatus. A gas head 2 is provided above the reaction furnace 10. The gas head 2 is mounted on the lower surface side of the gas head base 3, while the gas manifold 4 is mounted on the upper surface of the gas head base 3. A vaporized gas (for example, Si (OC ₂ H _2
5 ) ₄ or gas conduit 5a for feeding Ta (OC ₂ H ₅ ) ₅ )
And a gas conduit 5b for introducing oxygen gas.
The gas conduits 5a and 5b communicate with the gas conduits 5a ′ and 5b ′ of the gas head base 3, respectively, and further, the gas conduits 5a ″ and 5a provided in the gas head 2 are connected.
It communicates with b ''. At the lower ends of the gas guide paths 5a ″ and 5b ″ provided in the gas head 2, there are provided minute gas outlets 6 opening toward the inside of the reaction furnace. Further, in the gas manifold 4 and the gas head base 3, a guide path 7 for circulating a heating heat medium is provided in order to prevent reliquefaction of the vaporized gas. Instead of providing the heating medium circulating conduit 7, another heating means (for example,
A coil heater, etc.) can also be used. Further, instead of the gas head 2, the gas head base 3 and the gas manifold 4 as shown in the figure, a gas feeding means as shown in FIG. 5 can be used.

A quartz hood 12 is provided on the chamber base 11. The quartz hood 12 is detachably provided by a fastening means 13. A heater 14 is housed inside the quartz hood 12. An insulating material 15 made of quartz is arranged below the heater 14, and a reflector 16 having three layers is arranged below the insulating material 15. Although the reflector 16 does not necessarily have to be used, its use improves the thermal efficiency. If used, the reflector 16 may have at least one stage. The material of the reflector is not particularly limited. For example, molybdenum or the like is preferably used as the material for the reflector 16. The heater 14 is, for example,
All known materials such as SiC, nichrome wire and carbon can be used. The heater 14 is divided into a plurality of pieces in the circumferential direction, and can be driven only in a necessary portion (for example, only the outermost peripheral portion) if desired.

The thickness of the quartz hood 12 is not particularly limited. The thickness may be a necessary and sufficient thickness that can withstand the pressure fluctuation in the reaction furnace and the weight of the susceptor 18 placed on the upper surface of the quartz hood 12. For example, when the vapor phase growth apparatus of the present invention is used as a low pressure CVD apparatus,
Since the pressure inside the reaction furnace 10 is reduced to about 1 Torr, the upper thickness of the quartz hood 12 is about 25 mm, the thickness of the legs is about 10 mm, and the thickness of the legs is about 20 mm. It is a degree. Other thicknesses can of course be used. It is also possible to reduce the thickness of the quartz hood 12 by adjusting the pressure inside the furnace and the pressure inside the quartz hood 12 to match. However, lowering the in-hood pressure than the in-furnace pressure prevents heat dissipation to the quartz hood 12 and improves thermal efficiency. Therefore, an exhaust port 17 for exhausting the inside of the quartz hood 12 is provided.

A susceptor 18 is placed on the upper surface of the substantially central portion of the quartz hood 12. The susceptor 18 includes an inner susceptor 18a on which a wafer is actually placed and an outer susceptor 18b surrounding the inner susceptor. The outer susceptor 18b is also called a guide ring or a wafer guide. The materials for forming the inner susceptor 18a and the outer susceptor 18b are not particularly limited, but in order to prevent the wafer from being contaminated with heavy metals, it is preferable to be composed of, for example, glassy carbon. An elevating claw 20 for raising and lowering the wafer on the inner susceptor 18a is arranged beside the quartz hood 12 for delivering the wafer.

2A and 2B show the inner susceptor 18
It is a partial expanded sectional view near the boundary part of a and the outer side susceptor 18b. FIG. 2A shows an inner susceptor 1 according to the related art.
8A ′ is a partially enlarged cross-sectional view near the boundary between the outer susceptor 18b ′ and FIG. 2B, and FIG. 2B is a partially enlarged cross-sectional view near the boundary between the inner susceptor 18a and the outer susceptor 18b according to the present invention. As shown in FIG. 2A, the conventional outer susceptor 18b 'is made of a single molded body. On the other hand, as shown in FIG. 2B, the outer susceptor 18b of the present invention is configured by stacking the two disassembled parts in the horizontal direction, that is, the upper and lower parts. Further, in the present invention, the inner susceptor 18a and the outer susceptor 1 are
8b is not in contact, and a gap d exists at the boundary between both members. The division of the outer susceptor 18b of the present invention is not limited to two divisions. It may be divided into three or four. What is important here is that no measure is taken to bring the divided pieces into close contact. Therefore, the divided pieces may be simply stacked, the surfaces of the divided pieces may be used as they are without being mirror-finished, and non-uniform gaps may exist on the contact surfaces of the divided pieces. Further, the thickness of each divided piece may be the same or different from each other. Although not shown, each divided piece is positioned by a positioning pin. As shown in FIG. 2B, by dividing the outer susceptor into upper and lower parts and further providing a gap d between the outer susceptor and the inner susceptor, the heat conduction of the outer susceptor is effectively impeded, and the surface of the outer susceptor is effectively prevented. The temperature will be lower than the temperature of the inner susceptor. The gap d between the outer susceptor and the inner susceptor is not particularly limited, but is 0.5 m.
It is within the range of m to 1.5 mm. It is preferably about 1 mm.

FIG. 3A is a characteristic diagram showing a film thickness distribution of an oxide film formed by a conventional apparatus having an inner susceptor and an outer susceptor as shown in FIG. 2A. As shown in the drawing, when the film is formed by the conventional apparatus, the film thickness distribution in the wafer surface is thick at the center and extremely thin at the peripheral portion. In the process of pursuing this cause, the present inventors speculated that the temperature difference between the inner susceptor and the outer susceptor may be the cause of the nonuniformity of the film thickness distribution. In the case of the conventional inner susceptor 18a ′ and outer susceptor 18b ′ as shown in FIG. 2A, the inner susceptor temperature (ie,
Wafer temperature) <outside susceptor temperature, and the reaction gas (eg Si (O 2
C ₂ H ₅ ) ₄ or Ta (OC ₂ H ₅ ) ₅ ) reacts on the high temperature outer susceptor, so that the reaction gas is consumed and the amount of gas contributing to film formation at the wafer edge is reduced.

FIG. 3B is a characteristic diagram showing the film thickness distribution of the oxide film formed by the apparatus having the inner susceptor and the outer susceptor of the present invention as shown in FIG. 2B. As shown in the figure, the film thickness distribution in the wafer surface is substantially uniform at all the central and peripheral portions. When the outer susceptor of the present invention is used, the inner susceptor temperature (that is, the wafer temperature)> the outer susceptor temperature is satisfied, the reaction gas is not consumed by the influence of the outer susceptor temperature, and film formation occurs according to the wafer surface temperature. In particular, when the film forming temperature becomes high, the rate of the gas phase reaction increases due to the reaction changing from the reaction rate control to the supply rate control. In that case, it is considered that the oxide gas reacted in the gas phase (for example, SiO ₂ or Ta ₂ O ₅ ) is more likely to form a film on a high-temperature surface having a high sticking probability. When the split outer susceptor of the present invention as shown in FIG. 2B is used, the effect of improving the film thickness uniformity is higher when the film forming temperature is 500 ° C. than when the film forming temperature is 450 ° C. This is 5
This is probably because the temperature difference between the outer susceptor and the inner susceptor becomes clear in the case of 00 ° C.

Reactive gas (eg Si (OC ₂ H ₅ ) ₄
Alternatively, Ta (OC ₂ H ₅ ) _{5 and the} like) and O ₂ are separately supplied into the reaction chamber from separate gas conduits (nozzles). Conventionally, the distance D between the gas head and the susceptor is 5
It was 0 mm. As described above, the reason why the distance D between the gas head and the susceptor is set to 50 mm in the conventional technique is that the reaction gas can be expected to be uniformly mixed on the wafer when the distance between the gas head and the susceptor is narrow. Is. However, contrary to expectations, the reaction gas was not uniformly mixed on the wafer. FIG. 4A is a characteristic diagram showing the concentration distribution of the reaction gas (Ta (OC ₂ H ₅ ) ₅ ) and the oxygen and nitrogen gases on the wafer when the distance between the gas head and the susceptor is 50 mm. As a result of continued trial manufacture and research by the present inventors, the distance D between the gas head and the susceptor was 100 m.
We have found that when set to m, the reaction gases are uniformly mixed on the wafer. FIG. 4B is a characteristic diagram showing the concentration distribution of the reaction gas (Ta (OC ₂ H ₅ ) ₅ ) and the oxygen and nitrogen gases on the wafer when the distance D between the gas head and the susceptor is 100 mm. As shown in the figure, when the distance between the gas head and the susceptor is 100 mm, the concentration distribution of the reaction gas (Ta (OC ₂ H ₅ ) ₅ ) and the oxygen and nitrogen gases is almost uniform. Uniformity of film thickness is ± 1 when a film is formed at a film forming temperature of 500 ° C. using an apparatus having a conventional non-divided outer susceptor and a gas head / susceptor distance of 50 mm.
Although it was 1%, the film thickness uniformity was ± 4% when a film was formed at a film forming temperature of 500 ° C. using an apparatus having the split outer susceptor of the present invention and a gas head / susceptor interval of 100 mm. Dramatically improved.

The quartz hood 12 has a high transmittance of heat rays from the heater 14, but the quartz hood 12 itself is gradually heated, and the quartz hood 12 also functions as the heater 14 to further improve the heating effect. Therefore, the effect of preventing the temperature variation of the wafer on the inner susceptor 18 is enhanced.

Another feature of the vapor phase growth apparatus of the present invention is that the heater 14 is housed in the quartz hood 12, and
That is, the inner wall surface of the reaction furnace 10 is mirror-finished. This specularly reflects the heat rays emitted from the quartz hood 12, uniformly heats the inside of the furnace, and makes the temperature distribution of the wafer uniform. As a result, the film thickness distribution of the film formed on the wafer surface is also made uniform. At least the side wall portion 21, the gas head 2, and the gas head base 3 of the reactor are mirror-finished.
Is the entire wall surface inside the reactor. If desired, the inner wall surface side of the chamber base 11 can also be mirror-finished.

In order to avoid heavy metal contamination of the wafer, it is preferable that the gas head base 3, side wall portion 21, chamber base 11 and gas head 2 of the reaction furnace 10 are all made of aluminum.

A suitable portion of the chamber base 11 covered with the quartz hood 12 is cut out, and a heater base 22 made of, for example, aluminum or stainless steel is provided at that portion. A window 23 made of quartz is provided substantially in the center of the heater base 22. A radiation thermometer 24 is arranged facing the window 23. Further, openings 25 and 26 are also provided at respective portions of the heater 14 and the reflector 16 corresponding to the quartz window 23 of the heater base 22. Since the quartz hood 12 and the insulating material 15 are made of quartz and are transparent, the temperature of the susceptor 18 can be measured by a radiation thermometer 24 provided outside the reaction furnace.

A load lock chamber 30 that can be sealed is also provided on one side wall portion 21 of the reaction furnace 10 of the vapor phase growth apparatus of the present invention, and a gate 31 that separates the load lock chamber 30 from the reaction furnace 10 is provided. Wafers are taken in and out by opening and closing.

Although not shown, a vacuum exhaust system for adjusting the pressure inside the reaction furnace 10 is connected to the reaction furnace 10. Therefore, the vapor phase growth apparatus 1 of the present invention can be used, for example, as a normal pressure or low pressure CVD apparatus.

[0024]

As described above, in the vapor phase growth apparatus of the present invention, the outer susceptor is vertically divided into a plurality of parts, and there is a gap between the outer susceptor and the inner susceptor. Since the surface temperature of the wafer is lower than the temperature of the inner susceptor (that is, the wafer temperature), the reaction gas is not consumed on the surface of the outer susceptor. for that reason,
Film formation occurs according to the wafer surface temperature, and the film thickness distribution becomes uniform. In addition, the space between the gas head and the susceptor is 1
By setting the length to 00 mm, the reaction gas is uniformly mixed on the wafer, and the film thickness uniformity is further improved.

Since the heater is hermetically enclosed in the quartz hood, the heater itself does not come into contact with oxygen gas or the like used in the film forming reaction. Therefore, not only various kinds of heaters can be used as the heater but also the service life of the heater can be extended. Further, the contamination of the wafer due to the heater made of metal such as nichrome wire is prevented. Further, the doughnut-shaped heater can make the temperature distribution on the wafer surface uniform as compared with the conventional full-heat heater.

The quartz hood has a low thermal conductivity and a high transmittance of heat rays from the heater. As a result, the quartz hood itself also functions as a heater, and the heating effect is further improved. Therefore, the effect of preventing the temperature variation of the wafer on the susceptor is enhanced. Further, since the inner wall surface of the reaction furnace is mirror-finished, the heat rays radiated from the quartz hood are mirror-reflected to uniformly heat the inside of the furnace and uniform the temperature distribution of the wafer. As a result, the film thickness distribution of the film formed on the wafer surface is also made uniform.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of a vapor phase growth apparatus of the present invention.

FIG. 2 is a schematic sectional view showing a structure of an inner susceptor and an outer susceptor, and FIG. 2 (A) is a schematic sectional view showing a structure of an inner susceptor and an outer susceptor according to a conventional technique,
(B) is a schematic sectional view showing the structure of the inner susceptor and the outer susceptor according to the present invention.

FIG. 3 is a characteristic diagram showing a film thickness distribution of a formed oxide film, (A) being formed by an apparatus having a conventional inner susceptor and an outer susceptor as shown in FIG. 2 (A). FIG. 3B is a characteristic diagram showing a thickness distribution of an oxide film, and FIG. 2B shows a thickness distribution of an oxide film formed by an apparatus having an inner susceptor and an outer susceptor of the present invention as shown in FIG. 2B. It is a characteristic view to show.

FIG. 4 is a characteristic diagram showing a gas concentration distribution on a wafer, where (A) shows a gap between a gas head and a susceptor of 50.
Reactant gas (Ta (OC
FIG. 2B is a characteristic diagram showing the concentration distributions of ₂ H ₅ ) ₅ ) and oxygen and nitrogen gas, and (B) shows that the distance between the gas head and the susceptor is 10
In the case of 0 mm, the reaction gas (Ta (O
C ₂ H _{5) 5)} and is a characteristic diagram showing the concentration distribution of oxygen and nitrogen gas.

FIG. 5 is a schematic configuration diagram of an example of a conventional vapor phase growth apparatus.

[Explanation of symbols]

 1 vapor phase growth apparatus of the present invention 2 gas head 3 gas head base 4 gas manifold 10 reaction furnace 12 quartz hood 14 heater 16 reflector 18 susceptor 18a inner susceptor 18b outer susceptor

Front page continued (72) Inventor Tomomi Kondo 3-16-3 Higashi, Shibuya-ku, Tokyo Inside Hitachi Electronics Engineering Co., Ltd. (72) Masato Kunito 2326 Imai, Ome-shi, Tokyo Hitachi Device Development Center Within

Claims (7)

[Claims] 1. A vapor phase growth apparatus comprising a reaction furnace, and a gas head for blowing a reaction gas in the reaction furnace, and a susceptor having an upper surface facing the gas head and having a substrate mounted thereon, The susceptor is disposed on an upper surface of a quartz hood, a heater is housed in the quartz hood, the susceptor includes an inner susceptor and an outer susceptor, and the outer susceptor is vertically divided into a plurality of parts. A vapor phase growth apparatus characterized in that a gap exists between the susceptor and the inner susceptor. 2. The distance between the gas head and the susceptor is 100.
The vapor phase growth apparatus according to claim 1, further characterized by being mm. 3. The outer susceptor is vertically divided into two parts, and the distance between the outer susceptor and the inner susceptor is 0.5 mm.
The vapor phase growth apparatus according to claim 1, wherein there is a gap within a range of ˜1.5 mm. 4. The vapor phase growth apparatus according to claim 1, wherein the inner wall surface of the reaction furnace and the outer peripheral surface of the gas head inside the reaction furnace are mirror-finished. 5. The vapor phase growth apparatus according to claim 1, wherein at least the side wall of the reactor, the gas head, and the gas head base supporting the gas head are made of aluminum. 6. The vapor phase growth apparatus according to claim 1, which is a low pressure CVD apparatus. 7. The vapor phase growth apparatus according to claim 1, which is an atmospheric pressure CVD apparatus.