JP3954833B2 - Batch type vacuum processing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vacuum processing apparatus used for removing a thin film formed on, for example, a semiconductor wafer.
[0002]
[Prior art]
In manufacturing a semiconductor element, various film forming processes such as ion implantation and wiring are performed on a substrate such as a semiconductor wafer. At this time, a natural oxide film made of silicon is easily formed with a very thin film thickness of about 10 to 20 mm on the wafer before the film formation process due to the ambient atmosphere, which causes various problems. That is, if a natural oxide film is interposed between a metal wiring material to be directly wired on a wafer and a wafer processed as a p-type or n-type semiconductor, it causes contact resistance, and a wafer made of single crystal silicon. When a thin film is formed on the wafer by epitaxial growth, if a natural oxide film is interposed between the thin film and the wafer, the thin film to be formed as a single crystal is polycrystallized, which is an obstacle to epitaxial growth. If a natural oxide film is formed on a wafer when a gate oxide film to be formed with a thin film thickness (about 50 mm) is formed, the film thickness of a thin film functioning as a gate oxide film is significantly difficult to control.
[0003]
Therefore, in order to remove the natural oxide film from the wafer before the film formation process, conventionally, a so-called wet process in which a cleaning process and a drying process using a chemical solution such as dilute hydrofluoric acid are repeated has been performed. However, when such a wet process is used, it is difficult to reach and circulate the chemical solution to the natural oxide film formed at the bottom of the contact hole for wiring that requires a design rule of 0.1 μm or less. Particularly, in recent years, it has not been useful as a method for removing a natural oxide film.
[0004]
For this reason, it is conceivable to use a dry process such as hydrogen reduction or hydrogen plasma as a method for reliably removing the natural oxide film on the wafer. However, the former hydrogen reduction method requires a high temperature of 800 ° C. or higher and is not practical. The temperature condition when performing the natural oxide film processing of the wafer by plasma etching of the wafer using the latter hydrogen plasma is about 450 ° C., but the damage caused by the plasma in the wafer has progressed and the thinning has progressed. The device is required to be further lowered in temperature, and it is desirable to remove the natural oxide film at 400 ° C. or lower, and this still has a problem.
[0005]
Therefore, a natural oxide film removal method by a dry treatment method using hydrogen radicals under a relatively low temperature treatment condition has been proposed. This can be one using N ₂ gas, NH ₃ gas, and NF ₃ gas. In this, a microwave is applied to a mixed gas of N ₂ gas and NH ₃ gas to generate hydrogen radicals (H ^* ), and this is reacted with NF ₃ gas to produce ammonia fluoride gas, Thereafter, this ammonia fluoride gas etches SiO ₂ constituting the natural oxide film. Moreover, although the ammonia complex which is a by-product is produced | generated, this ammonia complex is thermally decomposed at 100-200 degreeC. That is,
H ^* + NF ₃ → NHxFy (NHxFy etches the natural oxide film)
NHxFy + SiO ₂ → (NH ₄ ) ₂ SiF ₆ + H ₂ O ↑ (by-product)
The ammonia complex ((NH ₄ ) ₂ SiF ₆ ), which is thought to be generated by the reaction between ammonia fluoride (NHxFy) and the natural oxide film (SiO ₂ ), is decomposed into a gas with a high vapor pressure as follows: Evaporate.
(NH ₄ ) ₂ SiF ₆ → NH ₃ ↑ + HF ↑ + SiF ₄ ↑
At this time, the temperature required to remove the natural oxide film is about 100 to 200 ° C., which is within the temperature constraint condition of the wafer.
[0006]
The wafer that has completed the removal process of the natural oxide film in this manner is suitable as a hydrogen-terminated silicon wafer for the subsequent film formation process.
[0007]
[Problems to be solved by the invention]
By the way, as an apparatus for removing a natural oxide film from a wafer using this type of remote plasma processing method, a device disclosed in Japanese Patent Application Laid-Open No. 10-335316 has been known. FIG. 1 is a cross-sectional view of the main part of this. N ₂ gas and H ₂ gas are introduced into the plasma generator 1 to generate hydrogen radicals (H ^* ) and introduced into the processing apparatus 2, and then formed by the reaction between hydrogen radicals and NF ₃ gas. NHxFy gas considered to be sprayed onto the wafer 5 placed on the heating table 3 via the substrate holder 4 to etch the natural oxide film of the wafer 5 with NHxFy gas. Thereafter, the temperature of the wafer 5 is raised by the heating table 3 to remove the by-product ammonia complex. However, since this is a single wafer type, it takes about 3 minutes per substrate for a series of steps (preparation → etching → heating → removal) required for the removal process of the natural oxide film. It is not practical as a processing step.
[0008]
Therefore, it is conceivable to use a batch processing apparatus instead of the single wafer processing apparatus. A cross-sectional view of the main part of such a batch processing apparatus is shown in FIG. In this apparatus 6, about 50 wafers are made into one batch, the wafer batch 7 is attached to the wafer support 8, N ₂ gas and NH ₃ gas are introduced from the outside of the apparatus 6 into the plasma generator 9, and hydrogen radicals ( H ^* ) is generated, and then NF ₃ is introduced into the hydrogen radical stream, and NHxFy gas, which is considered to be generated by the reaction between the hydrogen radical and NF ₃ gas, is sprayed on the wafer batch 7 to naturally oxidize the wafer. Etch the film. Thereafter, the temperature of the wafer is raised by the heating source 10 provided outside the apparatus 6 to remove the ammonia complex. In this case, the heating source 10 is provided outside the device 6, but may be provided inside the device 6.
[0009]
In such a batch type processing apparatus, the number of wafers to be processed at one time increases, but after the etching reaction of the natural oxide film of the wafer is performed at about 25 ° C., the ammonia complex as a by-product is evaporated. It takes time to heat the entire apparatus 6 to about 150 ° C. by the heating source 10. That is, the etching reaction of the natural oxide film on the wafer is a so-called dry etching process. In general, the etching process improves the etching efficiency as the temperature is lower. Therefore, it is necessary to perform the reaction while maintaining a temperature of about 25 ° C. Then, the process proceeds to the heating process. In order to take out the wafer batch 7, it is necessary to cool to room temperature. If the waiting time is included, the time required for a series of steps for removing the natural oxide film is about 200 minutes, which is still not efficient. For this reason, it is conceivable to provide a quick cooling mechanism. However, the device 6 is often made of a corrosion-resistant metal such as aluminum, and by repeating rapid cooling on such a metal device, the device 6 is made of metal. There is a concern that particles may be generated due to repeated compression / expansion stress to adversely affect the yield of the processed substrate and the service life of the apparatus.
[0010]
In view of the above-mentioned problems, the present invention uses a plasma treatment such as a remote plasma treatment process, and can efficiently perform surface treatment such as removal of a natural oxide film on a wafer, and can reduce the burden on the apparatus. It is an object to provide a processing apparatus.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is an apparatus including a pair of chambers configured in a vertical shape so as to be able to communicate in the vertical direction in order to perform batch processing on one or more substrates. As a specific example using the apparatus having such a configuration, for the purpose of performing the surface treatment process with a heating step as described above, one chamber located on the upper side of the pair of chambers is set as a heating chamber, and the lower side is set on the lower side. The other chamber located can be used as a process chamber. Such a vertically configured device can be configured with a compact structure that occupies a small area compared to other types such as a horizontal type, and furthermore, a high temperature control is required by arranging a heating chamber in the upper part. Temperature control between a simple heating chamber and a process chamber that does not require this is facilitated.
[0012]
In this case, if a cooling mechanism is interposed between the heating chamber and the process chamber to insulate the heating chamber and the process chamber, temperature control between both chambers can be performed more reliably.
[0013]
Furthermore, in this case, plasma surface treatment is performed on the substrate disposed in the process chamber using the process chamber, that is, hydrogen radicals and NF ₃ gas are introduced into the process chamber as described above, so that The oxide film is subjected to an etching reaction, and thereafter, the substrate having the ammonia complex as a by-product is transferred to the heating chamber and subjected to surface treatment such as heat treatment to remove the ammonia complex on the substrate.
[0014]
Further, in the plasma surface treatment for such a substrate, if hydrogen radicals are used as the active species generated from the plasma generation source provided outside the pair of chambers, a natural oxide film on the substrate can be obtained by remote plasma surface treatment. Surface treatment such as removing the surface can be performed. Remote plasma treatment is useful for protecting the substrate because it is not necessary to expose the substrate directly to the plasma.
[0015]
In order to perform such remote plasma surface treatment, the process chamber is provided with a gas inlet and a gas outlet, and the central axis of the gas inlet and the central axis of the gas outlet are arranged on the same straight line. If the process chamber is configured, the reactive gas as described above can be evenly contacted as an air flow with each of the substrates in batch processing in which a plurality of substrates are provided simultaneously, so that each substrate can be reliably processed even in a batch system. is there.
[0016]
Furthermore, when performing plasma surface treatment or the like on the substrate, if the substrate is swung in the vertical direction and operated to rotate on a horizontal plane, the uniformity of the surface treatment is further improved in each of the above substrates. The efficiency of batch processing is improved.
[0017]
For example, when performing a process for removing a natural oxide film formed on a wafer, a plasma surface treatment process for the wafer is performed by a subsequent heating process while maintaining a vacuum by using a process chamber. Can be done reliably.
[0018]
If the heating chamber is configured to include an external heater provided outside the chamber and a lamp heater provided inside the chamber as an auxiliary heat source, when the heating chamber is maintained at a desired temperature by the external heater in advance, Thereafter, it is possible to quickly recover the temperature drop of the heating chamber when the substrate is transferred from the process chamber by operating the lamp heater, and thus the surface treatment such as removal of the ammonia complex from the wafer is efficiently performed. Can be done automatically.
[0019]
In addition, at least two or more fixed chambers located on the upper side and one chamber that can be moved in the horizontal direction located on the lower side are provided, and the lower chamber is moved in the horizontal direction to move the upper chamber. When the apparatus is configured so that each chamber communicates in the vertical direction when the upper and lower chambers are opposed to each other in the vertical direction, for example, as described above, Surface treatment, such as etching the natural oxide film of the wafer in the side chamber, then transporting the wafer to the upper chamber and performing a heating process to thermally decompose the ammonia complex to remove the natural oxide film from the wafer In addition, immediately after the surface treatment is performed in this manner, these wafers and the like are placed in a separate channel located on the upper side while maintaining the vacuum state during the surface treatment. It can be transferred to.
[0020]
If such another upper chamber is used as a film formation chamber, desired film formation can be efficiently performed on a wafer or the like while maintaining the vacuum state during the surface treatment. Examples that can be used for such a film formation chamber include an epitaxial film formation apparatus, an annealing treatment apparatus, a plasma reforming apparatus, a CVD apparatus, and an oxidation treatment apparatus. Needless to say, the substrate can be used not only for a silicon wafer but also for a glass substrate.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 3 is a cross-sectional view of the first embodiment of the batch type vacuum processing apparatus of the present invention. The processing apparatus 11 performs a process of removing a natural oxide film of about 50 batch-unit wafers 5, and is connected to the process chamber 12, the heating chamber 13, and the process chamber 12 through a reaction gas introduction pipe 14. And a plasma generation unit 15 that performs the above operation.
[0022]
The process chamber 12 and the reaction gas introduction pipe 14 are connected via a gas introduction port 16, and the gas exhaust port is positioned so that the central axis of the gas exhaust port 17 is positioned on an extension line of the central axis of the gas introduction port 16. 17 is provided, and the process chamber 12 is connected through this gas discharge port 17 to a gas discharge pipe 18 that is selectively connected to a mechanical booster pump and a dry pump (not shown). In the process chamber 12, a lifting platform 20 that can be lifted and lowered via a vertically extendable rod 19 is provided. The lifting platform 20 batches wafers 5 (one batch includes 50 to 100 wafers). A wafer support 8 that can be stored in units is placed via a rotation mechanism 21 for the wafer support 8. Then, the batch-unit wafers 5 are stored as wafer batches 7 on the wafer support table 8 or taken out from the wafer support table 8 via a purchase outlet, not shown. Further, below the process chamber 12, a cooling air pipe 22 that communicates with the outside of the process chamber 12 is provided. Further, a pipe (not shown) is wound around the lower portion of the process chamber 12 so that cooling water and heating oil can be selectively circulated in the pipe.
[0023]
A heating chamber 13 is attached to the upper portion of the process chamber 12 via a gate valve 23. An external heating source 24 such as a resistance heating furnace or a mantle heater and a turbo molecular pump 25 are attached to the outside of the heating chamber 13. Further, an auxiliary heat source 26 such as a lamp heater and a thermocouple 27 for temperature monitoring are attached inside the heating chamber 13. Further, a purge gas introduction pipe 28 communicating with the outside of the heating chamber 13 is attached above the heating chamber 13.
[0024]
A gate valve 23 interposed between the process chamber 12 and the heating chamber 13 is provided so as to be openable and closable in the horizontal direction. The rod 19 extends in the process chamber 12 and the wafer support base 8 on the lifting platform 20. When the wafer batch 7 supported by is inserted into the heating chamber 13, the gate valve 23 is opened. When the wafer batch 7 is raised so as to be placed in the heating chamber 13, the upper ends of the lifting platform 20 and the upper side wall of the process chamber 12 come into contact with each other, and the process chamber 12 and the heating chamber 13 are isolated. The Moreover, in order to perform this isolation reliably, the O-ring 20a is attached to the upper both ends of the lifting platform 20. Further, in order to ensure the heat insulation effect between the process chamber 12 and the heating chamber 13, a pipe (not shown) is wound around the connecting portion of both chambers, and the cooling water can be circulated in the pipe. .
[0025]
The plasma generation unit 15 connected from the outside in the side surface direction of the process chamber 12 through the reaction gas introduction tube 14 introduces a first introduction tube 29 for introducing N ₂ gas and NH ₃ gas, and introduces NF ₃ gas. The second introduction tube 30 and the microwave plasma generator 31 are configured. In this configuration, it is desirable that the second introduction tube 30 and the microwave plasma generator 31 are separated from each other at an optimal position. When the NF ₃ gas introduced from the second introduction pipe 30 flows backward and reaches the microwave plasma generator 31, and fluorine radicals are formed and flow into the process chamber 12, an undesirable side reaction is caused to occur in the process chamber 12. This is because the wafer 5 may be damaged. A shower nozzle (not shown) is provided near the inlet 16 of the reaction gas inlet pipe 14 in the process chamber 12, and the gas introduced from the plasma generator 15 is evenly diffused to face the inlet 16. Thus, the wafer batch 7 is positioned so as to be sprayed equally to each wafer 5.
[0026]
Note that the process chamber 12 and the heating chamber 13 constituting the batch type vacuum processing apparatus 11 of FIG. 3 are made of aluminum in order to suppress corrosion by halogen gas.
[0027]
When the natural oxide film is removed from each wafer 5 constituting the wafer batch 7 using the batch type vacuum processing apparatus shown in FIG. 50 to 100 wafers 5 are stored in a wafer support 8 such as a boat. After closing the gate valve 23 and the supply outlet, the mechanical booster pump and the dry pump (not shown) connected to the gas discharge pipe 18 are operated to reach the process chamber 12 to about 130 Pa. Then, for the purpose of optimizing the etching rate in the process chamber 12, cooling water is allowed to flow through a cooling pipe (not shown) connected to the process chamber 12, and the inside of the process chamber 12 is maintained at a temperature of about 25 ° C.
[0028]
On the other hand, in parallel with the above operation, in the plasma generator 15, a mixed gas of N ₂ gas and NH ₃ gas is introduced from the first introduction pipe 29, and this mixed gas is plasma-excited by the microwave plasma generator 31. Generate hydrogen radicals. Then, the NF ₃ gas introduced from the second introduction pipe 30 is reacted with this hydrogen radical to generate ammonia fluoride gas. These reactions are considered to be carried out in the following process.
H ^* + NF ₃ → NHxFy
Next, this ammonia fluoride gas is introduced into the process chamber 12. The ammonia fluoride gas is sprayed evenly on each wafer 5 constituting the wafer batch 7 by appropriate means such as the above-described shower nozzle. At this time, the natural oxide film of each wafer 5 is etched by an etching reaction.
[0029]
In order to ensure the uniform blowing of the ammonia fluoride gas to each wafer 5, the wafer support 8 in the process chamber 12 is rotated on the horizontal plane around the rotation axis at 10 rpm by the rotation mechanism 21, The rod 19 is swung in the vertical direction by the expansion and contraction operation.
[0030]
In this state, after the ammonia fluoride gas is sprayed for about 2 minutes, the introduction of the ammonia fluoride gas is terminated. Then, after the pressure state of the process chamber 12 is restored to about 130 Pa initially, the gate valve 23 is opened and the rod 19 is extended, and the wafer batch 7 is transferred to the heating chamber 13 integrally with the wafer support 8. When the wafer batch 7 is transported, the heating chamber 13 is previously maintained at 120 to 150 ° C., and when the wafer batch 7 is transported, a purge gas introduction pipe is provided so that residual gas in the process chamber 12 does not flow. The N ₂ gas is introduced at an appropriate flow rate from 28 to maintain the down flow from the heating chamber 13 to the process chamber 12. Further, when the wafer batch 7 is transported, the temperature in the heating chamber 13 temporarily decreases, so that the auxiliary heat source 26 is operated to reduce this. The state of the batch type vacuum processing apparatus 11 at this time is as shown in FIG.
[0031]
In this state, each wafer 5 of the wafer batch 7 is heated for about 3 minutes to decompose and evaporate the ammonia complex on the wafer 5. Further, in order to reliably perform the decomposition and evaporation, the turbo molecular pump 25 is operated for about 5 minutes after the heating. At this time, it is considered that the following processes are performed on each wafer 5.
(NH ₄ ) ₂ SiF ₆ → NH ₃ ↑ + HF ↑ + SiF ₄ ↑
In this manner, the ammonia complex on the wafer 5 generates highly volatile NH ₃ gas, HF gas, and SiF ₄ gas. As these gases evaporate, the wafer 5 is terminated with hydrogen.
[0032]
Then, after the processing in the heating chamber 13 is completed, the rod batch 19 is compressed and the wafer batch 7 is lowered to the process chamber 13, the gate valve 23 is closed, and then cooling N ₂ gas is blown from the cooling gas introduction pipe 22 for 5 minutes. After cooling to a certain degree, it is transferred to a purchase take-out chamber (not shown), further taken out of the apparatus 11, and transferred to a subsequent film forming process. In this way, the time required for removing the natural oxide film from the wafer is generally over 30 minutes.
[0033]
Furthermore, the 2nd embodiment of the batch type vacuum processing apparatus of this invention is shown in FIG. 3 and 4 is that the process chamber 12 also serves as a load lock chamber, and that the heating chamber 13 and the film forming chamber 32 are juxtaposed on the upper portion of the apparatus. By configuring the batch type vacuum processing apparatus in this manner, the surface treatment such as the removal process of the natural oxide film is completed using the process chamber 12 and the heating chamber 13 in the same manner as in the first embodiment. The wafer 5 is transferred as a wafer batch 7 in the load lock chamber 12 by the boat transfer mechanism 33 integrally with the lifting platform 20 and reaches directly below the film forming chamber 32. Further, the wafer 5 immediately after the completion of the surface treatment is transferred to the film forming chamber 32 as a wafer batch 7 by the lifting mechanism by the expansion and contraction of the rod 19. Although details in the film forming chamber 32 are omitted, as in the case of the heating chamber 13, the gate valve 34 can constitute a closed system, and the film forming process in the film forming chamber 32 is performed reliably. To be able to. With such a configuration, the surface-treated wafer 5 can be transferred to a subsequent film formation process in batch units while maintaining the vacuum state during the surface treatment.
[0034]
As an apparatus that can be used in the film forming chamber 32 in such a form, an epitaxial film forming apparatus, an annealing processing apparatus, a plasma reforming apparatus, a CVD apparatus, an oxidation processing apparatus, and the like can be given.
[0035]
【Example】
Using the batch type vacuum processing apparatus 11 shown in FIGS. 3 and 4, the natural oxide film was removed from the wafer by the method shown in the first embodiment. The processing conditions at this time are 1000 sccm for N ₂ gas, 100 sccm for NH ₃ gas, and 100 sccm for NF ₃ gas as the flow rate of the introduced gas. Further, the energy of the microwave applied to the N ₂ gas and the NH ₃ gas for generating hydrogen radicals was set to 1000 W, and the pressure in the process chamber was set to about 530 Pa. FIG. 6 shows the relationship between the processing time at this time and the etching amount (Å) with respect to the natural oxide film (SiO ₂ ). As can be seen from FIG. 6, the natural oxide film on the wafer, which is usually formed to about 10 mm, is etched by plasma surface treatment for about 1 to 2 minutes.
[0036]
Therefore, the ammonia complex as a by-product on the wafer can be reliably and efficiently removed by performing vacuum processing including the subsequent heat treatment for about 2 minutes by the batch type vacuum processing apparatus of FIGS. I understand.
[0037]
【The invention's effect】
As is apparent from the above description, when the apparatus of the present invention is used, a surface treatment such as a natural oxide film removal treatment is performed on wafers in batch units by a heating chamber and a process chamber configured to communicate vertically. Can be performed efficiently. In addition, since the apparatus of the present invention can suppress temperature fluctuations in each chamber, it is possible to reduce the burden on the apparatus. Furthermore, when the heating chamber and the film formation chamber are juxtaposed as the upper chamber of the apparatus of the present invention, the surface treatment such as the removal process of the natural oxide film on the wafer and the subsequent film formation process can be performed integrally. Furthermore, film formation can be performed efficiently.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a main part of a conventional single wafer surface treatment apparatus. FIG. 2 is a cross-sectional view of a main part of a conventional batch type surface treatment apparatus. FIG. 4 is a fragmentary cross-sectional view showing the first embodiment of the present invention. FIG. 4 is a fragmentary cross-sectional view showing the first embodiment of the present invention when the wafer is located in the heating chamber. FIG. 6 is a cross-sectional view of the main part showing the embodiment of the present invention. FIG. 6 is a graph showing the etching effect when the apparatus of the first embodiment of the present invention is used.
5 Wafer 12 Process chamber (lower chamber)
13 Heating chamber (upper chamber)
16 Gas inlet 17 Gas outlet 24 External heating source 26 Auxiliary heat source 32 Deposition chamber

Claims (8)

A pair of chambers that are vertically configured to be able to communicate in the vertical direction are provided , and one chamber located above the chamber is used as a heating chamber, and the other chamber located below is used as a process chamber. A batch type vacuum processing apparatus characterized in that a cooling mechanism is interposed between the heating chamber and the process chamber to insulate the heating chamber from the process chamber . The batch type vacuum processing apparatus according to claim 1 , wherein the process chamber is used for plasma surface treatment of a substrate in the chamber. 3. The plasma surface treatment performed on the substrate using the process chamber is a remote plasma surface treatment using active species generated from a plasma generation source provided outside the pair of chambers. The batch type vacuum processing apparatus as described. A gas introduction port and a gas exhaust port are provided in a process chamber used for plasma surface treatment of the substrate, and a central axis of the gas introduction port and a central axis of the gas exhaust port are arranged on the same straight line. The batch type vacuum processing apparatus according to claim 2 or 3 . The batch type vacuum processing according to any one of claims 2 to 4 , wherein when performing plasma surface treatment on the substrate, the substrate is swung vertically and rotated on a horizontal plane. apparatus. The batch type vacuum according to any one of claims 1 to 5 , wherein the heating chamber includes an external heater provided outside the chamber and a lamp heater provided inside the chamber as an auxiliary heat source. Processing equipment.   At least two or more fixed chambers located on the upper side, and one chamber horizontally movable on the lower side, wherein the lower chamber is moved horizontally and any of the upper chambers A batch type vacuum processing apparatus, wherein the chambers can be selectively opposed to each other, and when the upper and lower chambers face each other in the vertical direction, the chambers communicate with each other in the vertical direction. The vacuum processing apparatus according to claim 7 , wherein any one of the upper chambers is used as a film formation processing chamber.

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