JPH0917705A - Continuous heat treatment method - Google Patents

Abstract

PURPOSE: To nearly completely eliminate the occurrence of natural oxide and to improve throughput by continuously performing a plurality of different heat treatments to a body to be treated while the temperature of the body is maintained high in the same treatment oven. CONSTITUTION: When continuously forming polysilicon film and tungsten silicide, first a non-treated semiconductor wafer W housed in a load lock room 30 is taken out of a carrying arm 34 in a transfer chamber 32 and is carried into a treatment oven 28, the wafer W is heated to a specific temperature, and polysilicon is formed. When the film-forming treatment of the polysilicon layer is completed, the film-forming treatment of tungsten silicide initiated. First, N2 gas is allowed to flow to purge a harmful phosphine from a treatment room 28 and at the same time the temperature of the wafer W is slightly lowered to a process temperature of the tungsten silicide, and silane and WF6 are supplied into the treatment room as the treatment gas for tungsten silicide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous heat treatment method for continuously performing different treatments on an object to be treated such as a semiconductor wafer.

[0002]

2. Description of the Related Art Generally, in a process of manufacturing a semiconductor integrated circuit, a desired element is obtained by repeatedly performing film formation and pattern etching on a semiconductor wafer, a glass substrate, or the like, which is an object to be processed. For example, when a gate element of a MOSFET is formed on the surface using a semiconductor wafer, as shown in FIG. 6 (A), impurities are diffused on the surface of the wafer W at the positions where the source 2 and the drain 4 should be formed. A gate oxide film 6 made of, for example, SiO ₂ is formed on the surface between them, and a channel between the source and the drain is formed thereunder. Then, a gate electrode 8 of a conductive film is stacked on the gate oxide film 6 to form one transistor. The gate electrode 8 is not a single layer,
Recently, it has a two-layer structure in consideration of conductivity and the like. For example, the gate electrode 8 is formed by sequentially stacking a phosphorus-doped polysilicon layer 10 and a metal silicide such as a tungsten silicide layer 12 on the gate oxide film 6.

By the way, with the miniaturization and high integration of a semiconductor integrated circuit, a processing line width and a gate width are becoming narrower, and a film thickness tends to become thinner in accordance with a demand for multilayering. Regarding the electrical characteristics between the layers, even if the line width or the like becomes narrow, high performance is required as before or higher. In response to such demands, for example, as described above, the gate electrode 8 has also adopted a two-layer structure of polysilicon and tungsten silicide. By the way, when a film made of a silicon material, for example, the surface of the polysilicon layer 10 is exposed to the atmosphere or moisture, a natural oxide film tends to easily adhere to the surface. When the tungsten silicide layer 12 which is the layer is laminated, there arises a problem that the adhesion between the two is deteriorated, or the electrical conductivity between the two is not sufficiently secured, and the electrical characteristics are deteriorated. Also, this polysilicon layer 1
0 is usually formed by a batch process in which a large number of sheets, for example, 150 sheets are set as one unit, whereas the tungsten silicide layer 12 is formed by a single-wafer process in which film formation is performed for each sheet. Therefore, naturally, the time of exposure to the atmosphere and the like varies from wafer to wafer, and the thickness of the native oxide film also varies. Therefore, immediately before the tungsten silicide layer 12 is stacked, wet cleaning using, for example, HF vapor is performed to remove the polysilicon layer 1 as shown in FIG. 6B.
The natural oxide film 14 that has adhered to the surface of the oxide film is peeled off.

However, although the natural oxide film can be removed by this wet cleaning, when the film thickness and the like become thin, the effect of dry unevenness (watermark) in the wet cleaning cannot be ignored and impurities are hardened in that portion. ,
Alternatively, a new problem has occurred such that the film easily peels off from that point. Therefore, as a method of forming the tungsten silicide layer without exposing the polysilicon layer 10 to the air after forming the polysilicon layer 10, a processing apparatus as shown in FIG. 7 has been proposed. In FIG. 7, a relatively large transfer chamber 16 that has been evacuated
Two load lock lock chambers 18A, 18
B, two polysilicon processing furnaces 20A, 20B and 2
The two tungsten silicide processing furnaces 22A and 22B are connected to each other through a gate valve (not shown), and the wafer W is flown by using the transfer arm 24 as shown by a dashed arrow.
Polysilicon layer 10 and tungsten silicide layer 12
Are sequentially laminated. In the illustrated example, a pair of load lock lock chambers and processing furnaces are provided, but it goes without saying that only one of each may be provided.

[0005]

As described above, since the wafer W is transferred through the transfer chamber 16 which is maintained in the vacuum state, compared with the conventional case where the wafer W is exposed to the atmosphere. Therefore, the generation of a natural oxide film can be suppressed. However, even though the inside of the transfer chamber 16 is in a vacuum state, the present situation is that the expected effect of suppressing the native oxide film cannot be exerted.
The reason is that even if the inside of the transfer chamber 16 is evacuated, a large amount of nitrogen gas, which has a light mass and is easily pumped, is evacuated first, and conversely, a gas with a large mass, such as water vapor components and oxygen, is relatively large. Since the residual water vapor and oxygen react with each other to form a natural oxide film, a sufficient effect of suppressing the natural oxide film cannot be exerted.

[0006] Further, it is necessary to repeat heating and temperature rise each time processing is performed in each processing furnace, and to sufficiently perform gas purging in order to prevent harmful residual processing gas from flowing into the transfer chamber 16. Therefore, there is a problem that the time required for raising and lowering the temperature and the purging time become long, and the throughput is considerably lowered. Furthermore, if even one of the plurality of processing furnaces goes down, there is a problem that the system flowing using the processing furnace is completely stopped and the processing itself cannot be performed. Furthermore, as is clear from the figure, since only one treatment is carried out in one treatment furnace, the number of installed treatment furnaces increases, which not only increases equipment investment but also occupies a large space. There was also a problem. The present invention has been devised in view of the above problems and effectively solving them. An object of the present invention is to provide a continuous heat treatment method capable of almost completely eliminating the generation of a natural oxide film.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a continuous heat treatment method in which a plurality of different heat treatments are performed on an object to be processed, wherein the plurality of different heat treatments are performed in the same processing furnace. In the above, the process is continuously performed while the temperature of the object to be processed is kept high.

[0008]

As described above, according to the present invention, a plurality of heat treatments are continuously carried out in the same processing furnace. For example, a film formation process of tungsten silicide is continuously performed in the same processing furnace without taking out from the furnace. Therefore, the natural oxide film does not adhere to the polysilicon layer, and the electrical characteristics of the device can be improved. Further, since the continuous processing is performed in the same processing furnace, it is not necessary to lower the temperature inside the furnace and perform the temperature raising operation for the next processing in order to transfer the processing target, and the processing target is brought to a high temperature state. Continuous processing is carried out while maintaining the temperature, and therefore time loss due to temperature rise / fall can be eliminated and throughput can be improved. Further, even when the process is changed to another process, since the furnace is not opened, it is not necessary to perform a strict purge even if the high temperature process gas is harmful, and therefore the purge time can be shortened.
Also, if a certain number of objects to be processed are heat treated,
For example, if the cleaning process is performed using ClF ₃ gas or the like, it is possible to suppress the generation of particles and the like.

[0009]

An embodiment of the continuous heat treatment method according to the present invention will be described below in detail with reference to the accompanying drawings. 1 is a schematic plan view showing a cluster tool device used for carrying out the method of the present invention, FIG. 2 is a schematic sectional view taken along line II-II in FIG. 1, and FIG. 3 is one process used in the cluster tool device. It is sectional drawing which shows a furnace. First, before explaining the method of the present invention, a cluster tool device will be described. This cluster tool device 26 includes one transfer chamber 3
2 to 3 processing furnaces 28 and 1 load lock chamber 3
Gate valves G1 to G4 are provided between the chamber 32 and each furnace and the load lock chamber 30 to open and close them. The processing furnaces 28 are configured in exactly the same manner, and as will be described later, a plurality of different heat treatments, for example, a polysilicon film forming process and a tungsten silicide film forming process are continuously performed in each process furnace 28. The transfer of the semiconductor wafer W is performed by using the multi-joint transfer arm 34 in the transfer chamber 32 and between the load lock chamber 30 and each processing furnace 28 by the arrow 36.
The process is performed directly as shown in FIG. In the illustrated example, three processing furnaces 28 are connected based on an actual device example, but one or two processing furnaces 28 are connected.
Of course, it may be a base.

Next, a specific structure of the processing furnace 28 will be described with reference to FIG. In the present embodiment, a single-wafer heat treatment furnace that uses a heating lamp as the processing furnace 28 and is capable of high-speed temperature rise will be described as an example. The processing furnace 28 has a processing chamber 38 formed of aluminum or the like in a cylindrical shape or a box shape. Inside the processing chamber 38, for example, a cross section is formed on a column 40 standing upright from the bottom of the processing chamber. L-shaped holding member 4
A mounting table 44 for mounting the semiconductor wafer W as the object to be processed is provided via the substrate 2. The support column 40 and the holding member 42 are made of a heat ray transmissive material such as quartz, and the mounting table 44 is made of a carbon material, an aluminum compound or the like having a thickness of about 1 mm. A plurality of, for example, 3
A book lifter pin 46 is provided so as to stand upright with respect to a support member 48, and the lifter rod 50 provided penetrating the bottom of the processing chamber moves the support member 48 up and down to lift the lifter pin 46. The wafer W can be lifted by inserting it into a lifter pin hole 52 provided through the mounting table 44.

The lower end of the push-up bar 50 has a processing chamber 38.
Bellows 54 that can expand and contract to maintain the airtight condition inside
Is connected to the actuator 56 via. A ring-shaped ceramic clamp ring 58 for holding the peripheral edge of the wafer W and fixing it to the mounting table 44 side is provided at the peripheral edge of the mounting table 44. The clamp ring 58 is The holding member 42 is connected to the support member 48 through a support rod 60 penetrating the support member 42 in a loosely fitted state, and is configured to move up and down integrally with the lifter pin 46. Here, a coil spring 62 is provided on the support rod 60 between the holding member 42 and the support member 48, which assists in lowering the clamp ring 58 and the like and ensures the wafer clamping. These lifter pins 46 and support members 4
8 and the holding member 42 are also made of a heat ray transmitting member such as quartz.

A transparent window 64 made of a heat ray transparent material such as quartz is provided in an airtight manner at the bottom of the processing chamber immediately below the mounting table 44, and a box shape is provided below the transparent window 64 so as to surround the transparent window 64. The heating chamber 66 is provided. This heating chamber 66
Inside, a plurality of heating lamps 68 as heating means are attached to a turntable 70 that also serves as a reflecting mirror.
Zero is rotated by a rotary motor 72 provided at the bottom of the heating chamber 66 via a rotary shaft. Therefore, this heating lamp 6
The heat rays emitted from 8 are transmitted through the transmission window 64 to irradiate the lower surface of the mounting table 44 to heat it. On the side wall of the heating chamber 66, the heating chamber 66 and the transparent window 64 are provided.
Cooling air inlet 7 for introducing cooling air for cooling
4 and a cooling air discharge port 76 for discharging this air are provided.

A ring-shaped straightening plate 80 having a large number of straightening holes 78 is provided on the outer peripheral side of the mounting table 44 so as to be supported by a support column 82 which is vertically formed in an annular shape. A ring-shaped quartz attachment 84, which is in contact with the outer peripheral portion of the clamp ring 58 and prevents gas from flowing therethrough, is provided on the inner peripheral side of the current plate 80. An exhaust port 86 is provided at the bottom below the flow straightening plate 80, and an exhaust passage 88 connected to a vacuum pump (not shown) is connected to the exhaust port 86, so that the inside of the processing chamber 38 has a predetermined degree of vacuum (eg, It can be maintained at 100 Torr to 10 ⁻⁶ Torr).

On the other hand, a gas supply unit 90 for introducing a necessary gas such as a processing gas and a cleaning gas into the processing chamber 38 is provided on the ceiling of the processing chamber facing the mounting table 44. Specifically, the gas supply unit (shower head) 90 has a shower head structure, and has a head main body 92 formed of, for example, aluminum in the shape of a circular box. 94 is provided. The gas inlet 94 is supplied with N ₂ , PH ₃ , WF ₆ , and a gas passage 96 and a plurality of branch passages, respectively.
It is connected to a gas source 98, 100, 102, 104 such as SiH ₄ and a cleaning gas source 106 for ClF ₃ , and a flow control valve 108 and an on-off valve 110 are provided in each branch passage.

A large number of gas holes 112 for discharging the gas supplied into the head main body 92 are evenly arranged in the surface of the surface of the head main body 92 facing the mounting table, which is on the wafer surface. The gas is discharged evenly over the entire area. Further, in the head main body 92, two diffusion plates 116 having a large number of gas dispersion holes 114 are arranged in upper and lower two stages so that the gas is more evenly supplied to the wafer surface. .

Next, the method of the present invention, which is carried out based on the example of the apparatus configured as described above, will be explained. FIG.
(A) is a time chart showing the process of the method of the present invention. A feature of the present invention is that a plurality of different heat treatments are continuously performed in the same processing furnace. Here, a case where a polysilicon film and a tungsten silicide are continuously formed will be described. First, the load lock lock chamber 30
The unprocessed semiconductor wafer W accommodated therein is taken out by the transfer arm 34 in the transfer chamber 32, which has been evacuated in advance, and the wafer W is placed in a vacant processing furnace 28 with a gate valve. Wafer W by loading via lifter pin 46
Is delivered to the lifter pin 46 side. And lifter pin 4
6 by lowering the push-up bar 50,
The wafer W is mounted on the mounting table 44, and the push-up bar 50 is further lowered to press the peripheral edge of the wafer W with the clamp ring 58 to fix it. Incidentally, the unprocessed semiconductor wafer W means here that the gate oxide film 6 is formed in another processing furnace in FIG. First, a polysilicon film forming process is performed. While evacuating the inside of the processing chamber 38, the heating lamp 68 in the heating chamber 66 is driven and rotated to radiate heat energy.

The radiated heat rays pass through the transmission window 64 and then through the quartz support member 48 and the like to irradiate the back surface of the mounting table 44 and heat it. Since the mounting table 44 is as thin as about 1 mm as described above, it is heated quickly, and therefore, the wafer W mounted thereon can be heated rapidly to a predetermined temperature. If the wafer W reaches the process temperature, eg, about 630 ° C., the gas source 9
Pour on N ₂ , carrier gas from 8, 100, 104
H ₃ (phosphine) and SiH ₄ (silane) are carried and this gas is supplied into the processing chamber 38 via a shower head. The supply amount of phosphine and silane is about 10 each.
SCCM and about 200 SCCM. The supplied mixed gas causes a predetermined chemical reaction to form a polysilicon layer 10 (see FIG. 6) doped with P (phosphorus) as an impurity on the gate oxide film 6 of the wafer W. In addition to phosphorus, As, Sb, B or the like can be used as the dopant. This film forming process is performed with a predetermined film thickness, for example, 200
It takes about 4 minutes, for example, to obtain 0Å. The process pressure at this time is approximately several Torr, and the film forming rate is approximately 500Å / min.

After the film formation process for the polysilicon layer is completed in this way, the process proceeds to the film formation process for the tungsten silicide. First, the supply of PH ₃ and SiH ₄ is stopped, N ₂ gas is caused to flow to purge harmful phosphine from the processing chamber 28, and the power of the heating lamp 68 is adjusted so that the wafer W is processed at the tungsten silicide process temperature, for example, 520. Decrease the temperature by a small amount to ℃. This N ₂ purge period is approximately several minutes. When the process temperature is reached, silane and WF ₆ are then supplied into the processing chamber 38 with or without a carrier gas as a processing gas for tungsten silicide. The flow rates of silane and WF ₆ are approximately 300 SCCM and approximately 3 S, respectively.
It is about CCM. Dichlorosilane or the like can be used as the processing gas instead of silane, and argon or helium can be used as the carrier gas instead of N ₂ gas. The supplied mixed gas causes a predetermined chemical reaction to form a tungsten silicide film on the polysilicon layer. This film forming process is performed for about 2 minutes, for example, in order to obtain a predetermined film thickness, for example, 1500 Å. The process pressure at this time is also about the same number TORR as in the previous polysilicon film forming process, and the film forming rate is about 750 Å / min.

When the film formation of tungsten silicide is completed in this manner, the temperature of the wafer W is adjusted to a temperature suitable for transfer while purging the remaining processing gas with N ₂ gas.
For example, the temperature is lowered to about 300 ° C., the gate valve is opened, and the processed wafer is unloaded. When the unloaded wafer is finished, the unprocessed wafer is loaded in the same manner as described above. Thereafter, in the same manner, the continuous film formation heat treatment on the wafer W is repeatedly performed. And a predetermined number, for example 25
When the processing of one wafer is completed, some film is deposited on the inner wall surface of the processing chamber and the surface of the internal structure.
ClF ₃ was used as a cleaning gas to remove this.
A gas is supplied and a cleaning process is performed at a temperature of, for example, about 200 ° C. for about several minutes. Thus, unnecessary film attached to the treatment chamber can be removed, so that generation of particles or the like due to separation of the film can be suppressed. This cleaning operation may be performed according to the film formation amount, for example, every time one wafer is processed, and the number of times may be performed in consideration of the throughput and the amount of particles generated. Further, as the cleaning gas, it is preferable to use a ClF ₃ -based gas which can effectively remove both polysilicon and tungsten silicide, but is not limited thereto.

As described above, in the method of the present invention, after forming the phosphorus-doped polysilicon layer 10, the wafer W is not unloaded in the same processing furnace.
Since the temperature is slightly adjusted, the process proceeds to the film formation process for the next tungsten silicide layer 12 as it is.
There is almost no risk that a natural oxide film will be formed on the polysilicon layer 10. Therefore, the adhesion between both layers becomes good,
In addition, this electrical characteristic can be greatly improved. In addition, similar continuous processing is performed in the other two processing furnaces 28.
Of course, it is done independently and individually. Also,
FIG. 4B is a time chart showing a conventional film forming method performed by using the apparatus shown in FIG. 7. In this case, the wafer W is processed every time one film forming process is performed as described above. Since the wafer is transferred to another processing furnace, the wafer temperature must be lowered and raised each time, which causes a decrease in throughput. As shown in FIG. As described above, in the case of the method of the present invention, although there is a slight amount of temperature change due to the difference in both process temperatures, basically one temperature lowering and temperature raising operation can be omitted. Throughput can be improved by the time required for the temperature lowering and temperature raising operations. Further, when the wafer W is unloaded / loaded after the continuous process is finished, the wafer temperature is once lowered to the transferable temperature as described above, but the lamp heating method is adopted like this type of processing furnace. As a result, the rate of temperature rise is increased, and it is possible to save wasteful time and improve the throughput above this point.

Further, if dichlorosilane is used instead of silane in the film forming process of the polysilicon layer, this process temperature is approximately the same as that of the tungsten silane layer.
Since the temperature is about 0 ° C., the continuous process can be performed with almost no temperature change, and the throughput can be further improved. Further, in the conventional processing method, as described in FIG. 7, for example, when one processing furnace goes down for some reason, the film forming route in which the processing furnace is incorporated must be stopped. However, when a plurality of different film forming processes are performed in the same process furnace as in the method of the present invention, only that process furnace needs to be stopped and the other process furnaces are operated independently to perform the film forming process. Therefore, the operating rate can be improved accordingly.

Further, even if the dopant phosphorus is mixed in the tungsten silicon layer, it does not adversely affect the electrical characteristics. Therefore, N _{2 at} the time of transition from the polysilicon film formation to the tungsten silicide film formation. The purging of phosphorus by gas does not have to be performed so strictly, and the purging period can be shortened by that much, which can contribute to the improvement of throughput. In addition, in the above-described embodiment, a lamp heating type processing furnace capable of high-speed heating due to a small heat mass has been described as an example. However, the present invention is not limited to this and, for example, as shown in FIG. It is also applicable to a so-called resistance heating type processing furnace in which a susceptor 120 having a large heat mass is provided and a susceptor 120 is provided with a resistance heater 122. Further, the present invention is not limited to this type of processing furnace, but can be applied to other single-wafer CVD processing furnaces such as an ECR (electron cyclotron resonance) type CVD apparatus. Further, the type of film formation is not limited to tungsten silicide, and it is needless to say that the present invention can be applied to the case of forming a metal or metal compound such as tungsten, titanium, titanium nitride, or titanium silicide. Further, there are two different film forming processes.
The number of layers is not limited, and continuous treatment of three layers or more may be performed.

[0023]

As described above, according to the continuous heat treatment method of the present invention, the following excellent operational effects can be exhibited. Since different heat treatments are continuously performed in one processing furnace, unlike the conventional method in which the processing furnace is changed for each processing, it is possible to significantly suppress the adhesion of the natural oxide film on the film formation surface. It is possible to significantly improve the adhesive strength between layers and the electrical characteristics. Further, since the processing is performed while maintaining the high temperature of the object to be processed for the reason described above, it is almost unnecessary to perform the temperature lowering or the temperature increasing operation of the object to be processed between the film forming operations, and the throughput is increased accordingly. Can be improved. Further, even if one processing furnace goes down, each processing furnace individually and continuously performs continuous processing. Therefore, compared to the conventional method, it is not necessary to stop a sound apparatus, and the operation rate of the apparatus is increased. be able to. Further, the number of devices to be installed can be reduced to about half, and not only the equipment cost can be deleted, but also the occupied space can be saved.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing a cluster tool device used for carrying out the method of the present invention.

FIG. 2 is a schematic cross-sectional view taken along the line II-II in FIG.

FIG. 3 is a sectional view showing one processing furnace used in the cluster tool device.

FIG. 4 is a diagram showing a time chart of a continuous heat treatment method of the present invention and a conventional method.

FIG. 5 is a schematic sectional view showing a resistance heating type heat treatment furnace.

FIG. 6 is a cross-sectional view showing a gate structure of a MOS transistor.

FIG. 7 is a schematic plan view showing a cluster tool device for performing a conventional continuous heat treatment method.

[Explanation of symbols]

6 Gate Oxide Film 8 Gate Electrode 10 Polysilicon Layer 12 Tungsten Silicide Layer 14 Natural Oxide Film 26 Cluster Tool Device 28 Processing Furnace 30 Load Lock Chamber 32 Transfer Chamber 34 Transfer Arm 38 Processing Furnace 44 Mounting Platform 64 Transmission Window 68 Heating Lamp 90 Gas Supply unit 98 N ₂ gas source 100 PH ₃ gas source 102 WF ₆ gas source 104 SiH ₄ gas source 106 ClF ₃ gas source 122 resistance heater W semiconductor wafer (processing target)

Claims (6)

[Claims] 1. A continuous heat treatment method in which a plurality of different heat treatments are performed on an object to be processed, the plurality of different heat treatments are continuously performed in a state where the temperature of the object to be processed is kept high in the same processing furnace. A continuous heat treatment method characterized by being configured to perform. 2. The continuous heat treatment method according to claim 1, wherein the plurality of different heat treatments are film formation treatments having different film qualities. 3. The film forming process of different film quality includes a film forming process of polysilicon doped with impurities and a film forming process of tungsten silicide.
The continuous heat treatment method described. 4. The continuous heat treatment method according to claim 1, wherein when a predetermined number of the objects to be treated are subjected to the heat treatment, the treatment furnace is subjected to a cleaning treatment. 5. The continuous heat treatment method according to claim 1, wherein the cleaning treatment uses a fluorine-based cleaning gas. 6. The continuous heat treatment method according to claim 1, wherein the processing furnace is a single-wafer processing furnace capable of high-speed heating by lamp heating.