JPH11100675A - Vapor growth method - Google Patents

Abstract

(57) [Summary] In film formation by a vapor phase growth method such as thermal CVD, dispersion between film formation surfaces is minimized. SOLUTION: At least a reaction furnace, a reaction gas supply means for supplying a reaction gas into the reaction furnace, and a susceptor arranged in the reaction furnace, wherein the susceptor is mounted on an upper surface thereof In a vapor phase growth method of forming a vapor phase growth film on the surface of a wafer using a single wafer type vapor phase growth apparatus having a heating means for heating a wafer, a film formation start temperature is set for each film formation process. Film formation is performed between substrates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a vapor phase growth method. More specifically, the present invention relates to a film forming method by thermal CVD.

[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. The CVD method includes three methods: a normal pressure method, a reduced pressure method, and a plasma method.

For example, a monosilane gas such as SiH ₄ has been used as a material for forming a silicon oxide film. However, a reduction in step coverage has become a problem with miniaturization of semiconductor devices. Instead of this monosilane gas,
Recently, liquid tetraethylorthosilicate (TEO)
S) [Si (OC ₂ H ₅ ) ₄ ] has been used. This is because TEOS can form a dense film with excellent step coverage. When a silicon oxide film is formed using TEOS, TEOS is heated and vaporized,
It is supplied to the reactor as TEOS gas. The Ta ₂ O ₅ film of the tantalum oxide film is formed by evaporating 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 an oxygen gas or an ozone gas and used for a film forming reaction.

FIG. 1 shows an example of a conventional vapor phase growth apparatus 1 using such a vaporized Si (OC ₂ H ₅ ) ₄ or Ta (OC ₂ H ₅ ) ₅ gas. This apparatus has a reaction furnace 10. 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. In the gas manifold 4, a vaporized gas (for example, Si (OC ₂ H ₅ ) ₄ or Ta (O
A gas conduit 5a for supplying C ₂ H ₅ ) ₅ ) and a gas conduit 5b for supplying oxygen gas are provided. This gas conduit 5a
And 5b are gas conduits 5 of the gas head base 3, respectively.
a ′ and 5b ′, respectively, and further to gas conduits 5a ″ and 5b ″ provided in the gas head 2. Gas conduits 5a ″ and 5 provided in gas head 2
A small gas outlet 6 opening toward the inside of the reaction furnace is provided at the lower end side of b ″. In addition, in the gas manifold 4 and the gas head base 3, a conduit 7 for circulating a heating medium for heating in order to prevent re-liquefaction of the vaporized gas.
Is provided. Instead of providing the heating medium circulation path 7, another heating means (for example, a coil heater or the like) can be used.

A quartz hood 12 is provided on a chamber base 11. The quartz hood 12 is provided detachably by fastening means 13. A heater unit 14 is housed inside the quartz hood 12. Heater unit 1
An insulating material 15 made of quartz is disposed below the insulating material 4, and a reflector 16 having a three-stage structure is disposed below the insulating material 15. Although it is not necessary to use the reflector 16, use of the reflector 16 increases the thermal efficiency. When used, at least one reflector 16 may be used. The material of the reflector is not particularly limited. For example, molybdenum or the like is suitably used as a material for the reflector 16. As the heater unit 14, for example, all known units such as SiC, nichrome wire, and carbon can be used. The heater unit 14 is divided into a plurality of pieces along the circumferential direction, and can drive only necessary portions (for example, only the outermost peripheral portion) as desired.

An appropriate 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 in the portion. A window 23 made of quartz is provided substantially at the center of the heater base 22. A radiation thermometer 24 is provided so as to face the window 23. Also, openings 25 and 2 are provided at respective positions of the heater unit 14 and the reflector 16 corresponding to the quartz window 23 of the heater base 22.
6 are provided. Since the quartz hood 12 and the insulating material 15 are each made of quartz and transparent, the susceptor 1
The temperature of 8 can be measured by a radiation thermometer 24 provided outside the reactor.

[0007] The thickness of the quartz hood 12 is not particularly limited. Any thickness may be used as long as it is strong enough to withstand the pressure fluctuation in the reactor 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 FIG. 1 is used as a low pressure CVD apparatus, the pressure in 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 feet is about 20 mm.
mm. Other thicknesses can of course be used. If the pressure in the furnace and the pressure in the quartz hood 12 are adjusted to be the same, the thickness of the quartz hood 12 can be reduced. However, when the pressure in the hood is lower than the pressure in the furnace, heat dissipation to the quartz hood 12 is prevented, and the thermal efficiency is improved. For this reason, 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 substantially the center 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. The material for forming the inner susceptor 18a and the outer susceptor 18b is not particularly limited. However, it is preferable that the inner susceptor 18a and the outer susceptor 18b be made of, for example, glassy carbon in order to avoid contamination of the wafer with heavy metals. A lifting claw 20 for raising and lowering the wafer on the inner susceptor 18a for transferring the wafer is provided beside the quartz hood 12.

A load lock chamber 30 that can be hermetically sealed is provided on one side wall 21 of the reaction furnace 10. A gate 31 that separates the load lock chamber 30 from the reaction furnace 10 is opened and closed so that a wafer can be taken in and out. Do.

In the reaction process, the load lock chamber 30
Open the gate 31 of the carriage (not shown)
A substrate (not shown) is loaded by the
8 is placed substantially at the center of the upper surface. After the gate 31 is closed and the inside of the reactor is evacuated from a duct (not shown) to a predetermined degree of vacuum, or without evacuating, the susceptor 18 is heated by the heater unit 14. A predetermined reaction gas (for example, TEOS and oxygen gas) is fed into the reaction furnace from the gas head 2. After the film forming process is performed for a predetermined time, the reaction gas remaining in the reaction furnace is exhausted, the gate 31 is opened, the substrate is carried out of the furnace from the carriage, and a new substrate is carried in the furnace. I do. Then, the above-described heating, film formation, and unloading processes are repeated.

However, when the film forming process is performed by an apparatus as shown in FIG. 1, the temperature of the sample stage slightly fluctuates depending on the substrate used, and the variation between the film forming surfaces is deteriorated.

[0012]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a vapor phase growth method in which the variation between the film forming surfaces is reduced.

[0013]

Means for Solving the Problems The above object is achieved by making the film formation start temperature constant between the substrates for each film formation process when the substrate mounted on the susceptor is formed by heating. Is done.

[0014]

FIG. 2 is a characteristic diagram showing the relationship between the film forming sequence and the temperature in the vapor phase growth method of the present invention. "Transfer" in the figure is a process in which the substrate is carried out of the furnace and the substrate is carried into the furnace. Therefore, the film formation sequence is basically:... Transport-heat-film-transfer-heat-film-.
・ ・ It consists of repetition. According to the method of the present invention, the film formation process is performed by controlling the heating time of the susceptor so that the film formation start temperature is always constant. Therefore, according to the method of the present invention, the heating time for heating and the heating time for heating may be the same or different in the film forming sequence shown in FIG. In a conventional film forming sequence, a film forming process is performed with a constant heating time. Therefore, the susceptor is not sufficiently heated due to a change in a factor such as a substrate and a reaction gas or some other factor,
In some cases, the reaction gas is introduced into the furnace before the substrate reaches a predetermined film forming temperature, and the film forming process is started. For this reason, the variation between the deposition surfaces has been large.

FIG. 3 is a block diagram showing an example of heating control in the vapor phase growth method of the present invention. In the vapor phase growth method of the present invention, a susceptor temperature measuring device 300 is used.
Since the temperature of the wafer itself cannot be measured directly,
The temperature of the susceptor is taken as the temperature of the wafer. However, there is always a difference between the temperature of the susceptor and the temperature of the wafer. The magnitude of this difference can be known empirically from the size of the wafer and the like. In a thermal CVD apparatus, when the susceptor temperature is in the range of 450 ° C. to 550 ° C., the wafer temperature is generally in the range of 400 ° C. to 500 ° C.
The type of the susceptor temperature measuring device 300 is not particularly limited. As shown in FIG. 1, besides an optical (for example, radiation thermometer, pyrometer, etc.) measuring device arranged outside the furnace,
Any mechanical (eg, thermocouple, etc.) or electrical (eg, thermistor, etc.) temperature measurement device can be used, such as to contact the susceptor at an appropriate location or to be in proximity to the susceptor.

The susceptor temperature measuring device 300 periodically measures the current temperature of the susceptor 18 at a predetermined cycle. The measurement result is sent to the interface 320,
Interface internal registers (not shown)
Is set to When the interface 320 receives the setting of the measured temperature in the register, the microprocessor 320 (MP)
U) Generate an interrupt signal at 340. Upon receiving the interrupt signal, the MPU 340 activates the temperature monitoring program stored in the memory 400, and compares the current temperature indicated by the temperature measurement data with a predetermined reference temperature T when in the temperature heating state. When the current temperature of the susceptor reaches the reference temperature T, a signal for stopping the heating of the heater unit 14 is sent to the heater unit control circuit 36 via the interface 320.
Send to 0. At the same time, a signal for starting the supply of the reaction gas is sent to the reaction gas supply control circuit 380 via the interface 320. The supply and stop of the reaction gas are performed by opening and closing a valve (not shown) provided at an appropriate position in the reaction gas supply path.
It is performed by driving with.

The memory 400 can store a program for the entire film forming sequence. Therefore, for example, when a predetermined film forming time has elapsed, a signal for stopping the supply of the reaction gas is sent to the reaction gas supply control circuit 380 via the interface 320, and the opening and closing provided at an appropriate position in the reaction gas supply path is performed. Activate a valve (not shown). Thereafter, a signal for starting wafer transfer is sent to the wafer transfer control circuit 420 via the interface 320, and a carriage (not shown) is driven.
Unloading and loading of wafers. When loading of a new wafer is completed (that is, when a predetermined transfer time has elapsed),
A signal to start heating the heater unit 14 is sent to the heater unit control circuit 360 via the interface 320. At the same time as the heating of the heater unit 14 is started, the susceptor temperature measurement device 300 starts measuring the temperature of the susceptor.

The vapor phase growth method according to the present invention is a well-known and ordinary atmospheric pressure thermal CVD comprising heating a wafer to form a film.
The present invention can be implemented in all vapor phase growth apparatuses such as an apparatus, a low pressure thermal CVD apparatus, and a plasma thermal CVD apparatus.

[0019]

In the thermal CVD apparatus as shown in EXAMPLES 1, as the reaction gas, using Ta (OC ₂ H _{5) 5} gas was deposited the Ta ₂ O ₅ film on the silicon wafer surface of a diameter of 8 inches . 25 according to the film forming sequence shown in FIG.
Films were continuously formed. The heating was performed at a susceptor temperature of 500 ° C. and a wafer temperature of 450 ° C. As a comparative example, 25 films were continuously formed by a conventional film forming sequence in which the heating time of the substrate was constant. The thickness of the obtained film was measured. FIG. 4 shows the results. As shown in FIG.
The variation between the deposition surfaces of the film deposited by the method of the present invention was within a range of ± 3%. Further, it can be understood that the variation from the fifth sheet to the 25th sheet is even smaller than ± 3%. The variation up to the fifth sheet is probably due to the unstable device. On the other hand, as shown in FIG. 4B, in the conventional deposition sequence in which the heating time is kept constant, the variation between the deposition surfaces of the deposited films doubled to ± 6%. In addition, since a stable state is not formed in the apparatus itself, the variation between the film forming surfaces is not settled in each stage up to the 25th sheet.

[0020]

As described above, according to the present invention,
By keeping the film formation start temperature constant between the substrates in each film formation process, the variation between the film formation surfaces can be minimized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of a conventional vapor phase growth apparatus.

FIG. 2 is a characteristic diagram showing a relationship between time and temperature in a film forming sequence by the vapor phase growth method of the present invention.

FIG. 3 is a block diagram showing an example of heating control in the vapor phase growth method of the present invention.

FIG. 4 is a characteristic diagram showing a change in film thickness of each film when 25 films are continuously formed. FIG. 4A shows a film thickness when a film formation start temperature is constant between substrates according to the method of the present invention. Show fluctuations,
(B) shows the variation in film thickness when the substrate heating time is kept constant according to the conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conventional vapor phase growth apparatus 2 Gas head 3 Gas head base 4 Gas manifold 10 Reactor 12 Quartz hood 14 Heater unit 16 Reflector 18 Susceptor

Claims (3)

[Claims] 1. At least a reaction furnace, a reaction gas supply means for supplying a reaction gas into the reaction furnace, and a susceptor disposed in the reaction furnace, wherein the susceptor is mounted on an upper surface thereof. In a vapor phase growth method for forming a vapor phase grown film on the surface of a wafer using a single wafer type vapor phase epitaxy apparatus having a heating means for heating a wafer to be heated, a film forming start temperature is set for each film forming process. A vapor phase growth method characterized by keeping the same between substrates. 2. An unprocessed wafer is loaded into a reactor, the wafer is placed on an upper surface of a susceptor, and the susceptor is heated by the heating means. When the susceptor reaches a set temperature, a reaction is performed. A reaction gas is introduced into the furnace, a film forming process is started on the wafer on the susceptor, and after the film forming process is completed, the wafer is carried out of the reaction furnace, and a new unprocessed wafer is carried into the reaction furnace again. Then, the wafer is placed on the upper surface of the susceptor, the susceptor is heated by the heating means, when the susceptor reaches the same temperature as the temperature set in the previous film forming process, into the reaction furnace A reaction gas is introduced, a film formation process is started on the wafer on the susceptor upper surface, and after the film formation process is completed, the wafer is carried out of the reaction furnace, and this operation is performed on a predetermined number of wafers to be subjected to the film formation process. Claim 1 comprising repeating
Vapor phase growth method. 3. The vapor phase growth method according to claim 1, wherein a Ta ₂ O ₅ film is formed by a low pressure thermal CVD apparatus.