JP2011009762A - Method of manufacturing semiconductor and substrate processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust the transfer environment of a substrate in order to prevent contamination of a substrate surface by impurities.SOLUTION: A substrate processing method includes steps of: transferring the substrate from a spare chamber 1 to a processing chamber 2 through a transfer chamber 3; processing the substrate in the processing chamber; and transferring the processed substrate from the processing chamber 2 to the spare chamber 1 through the transfer chamber 3. At each step transferring the substrate, all exhaust systems connected to respective chambers are evacuated by using a vacuum pump, while an inert gas is supplied to all the chambers communicating to respective chambers in which the substrate resides.

Description

  The present invention relates to a semiconductor manufacturing method, a substrate processing method, and a semiconductor manufacturing apparatus, and in particular, by adjusting environmental conditions when transferring a substrate from a preliminary chamber to a processing chamber or from a processing chamber to a preliminary chamber via a transfer chamber. The present invention relates to a semiconductor manufacturing method and a substrate processing apparatus capable of eliminating the influence of substrate contamination due to impurities as much as possible.

  In recent years, with the miniaturization and high integration of semiconductor devices, the problem of chemical contamination (gaseous chemical contamination) due to gaseous particles has become obvious in addition to the suspended particles (mainly mechanical contamination) that were subject to regulation in the past. . Here, mechanical contamination is dust generated from mechanically moving parts such as a transfer robot, and chemical contamination (chemical trace component) is back-diffusion of oil from a vacuum pump or chamber structure (shaft seal material of the transfer robot). And contamination due to a minute amount of volatile impurities (degassing) from an O-ring as a chamber sealing material.

  As the manifestation of contamination, for example, in the HSG (Hemi-spherical Grained Silicon) formation technique described in JP-A-5-304273 (Patent No. 2508948), the unbonded hand density of Si molecules due to contamination by gaseous particles Has become non-uniform and has a problem that adversely affects the quality of products. In addition, in the epitaxial growth technology, there is a mismatch in the crystallinity of Si due to the presence of chemical contaminants (impurity molecules) (where the contaminants exist, Si grows regardless of the crystallinity of the Si substrate), Crystal defects and polycrystallization are caused, and there are also problems that adversely affect the quality of products. In addition, in the process of thinning the gate oxide film, etc., the proportion of one contaminant molecule in the total film thickness increases, so the influence on film thickness uniformity and device electrical characteristics cannot be ignored. It is coming.

  From the above background, in recent semiconductor device manufacturing, a cleaner environment that eliminates not only mechanical contamination but also chemical contamination is required, and it is desired to deal with clean rooms and manufacturing apparatuses.

  By the way, conventionally, a substrate is transferred between the load lock chamber for exchanging substrates with the outside, a processing chamber for performing predetermined processing such as thin film formation on the substrate, and the load lock chamber and the processing chamber. In a semiconductor manufacturing apparatus including a transfer chamber, when a wafer (substrate) is transferred from a load lock chamber to a processing chamber by a transfer robot in the transfer chamber, the pressure in the chamber (hereinafter also referred to as “chamber”) is a vacuum pump. The pressure was maintained under 0.1 Pa or less under the ultimate vacuum due to the exhaust gas.

  However, the chamber that maintains the vacuum state under the ultimate vacuum has a small amount of volatile impurity components from the back diffusion of oil from the vacuum pump and the chamber structure (O-ring as the shaft seal material or chamber sealing material of the transfer robot). There is a possibility that the wafer being transferred may be adversely affected.

Therefore, as a method of preventing such chamber contamination,
(1) Ultra high vacuum (10 ⁻⁶ Pa) compatible pumps such as turbo molecular pumps are installed in all chambers to reduce the partial pressure of impurities in all chambers.
(2) Make the transfer robot in the transfer chamber compatible with ultra-high vacuum.
(3) Adopt metal O-ring as chamber sealing material,
However, such a method has disadvantages such as high cost and difficulty in maintenance.

  By the way, in JP-A-6-104178 (hereinafter referred to as a known example), a plurality of vacuum processing chambers, a transfer chamber in which a transfer robot for transferring a substrate is installed, an introduction chamber for introducing or unloading a substrate, and an unloading chamber are disclosed. In the method of vacuum processing the substrate using the method, after evacuating the transfer chamber, the method of continuing to introduce an inert gas or nitrogen gas into the transfer chamber while the device is operating, or the gas used in the vacuum processing is operating, Methods have been proposed that continue to be introduced into the vacuum processing chamber. This is mainly to eliminate dust generation from the transfer robot, that is, mechanical contamination, by exhausting while supplying inert gas to the vacuum processing chamber and transfer chamber excluding the introduction chamber and unload chamber during substrate transfer. It prevents contamination. In addition, in the transfer chamber and vacuum processing chamber excluding the introduction chamber and the unloading chamber, the exhaust gas is exhausted while supplying an inert gas. Therefore, the chemical contamination described above should be excluded only in the transfer chamber and the vacuum processing chamber. Is considered possible.

  However, in the known example, the introduction chamber and the carry-out chamber (hereinafter simply referred to as the introduction chamber, etc.) are only exhausted without supplying an inert gas, despite having a vacuum pump. It is impossible to prevent back diffusion of oil from the vacuum pump and contamination by a small amount of volatile impurity components from the chamber structure (O-ring as a chamber sealing material, etc.). Therefore, the introduction chamber or the like and the entire semiconductor manufacturing apparatus cannot be kept clean, and contamination of the substrate surface cannot be effectively prevented.

  In addition, in the known example, instead of a cassette that supports a plurality of substrates, instead of a cassette that supports a plurality of substrates, a single wafer unit is directly introduced. However, when a cassette that supports a plurality of substrates is introduced, Later, even when the substrate is transferred to the processing chamber or the transfer chamber, the substrate is always present in the introduction chamber or the like. There is a problem that the substrate existing in the introduction chamber or the like is contaminated by chemical contamination such as reverse diffusion.

  In consideration of the above circumstances, the present invention can maintain not only the transfer chamber and the processing chamber but also the spare chamber in a clean state, thereby preparing a substrate transfer environment for preventing contamination by impurities on the substrate surface. An object of the present invention is to provide a low-cost and easy-to-maintain semiconductor manufacturing method and substrate processing apparatus.

  According to a first aspect of the present invention, there is provided a semiconductor manufacturing method comprising: a step of exchanging a substrate between a preliminary chamber and the outside; a step of performing a predetermined process on the substrate in the processing chamber; and a step between the preliminary chamber and the processing chamber. The method includes a step of transporting a substrate through a transport chamber provided, and a step of exhausting the substrate while supplying an inert gas to at least the chamber in which the substrate is present when transporting the substrate. The predetermined process may be any process as long as it handles a gas when manufacturing a semiconductor element, such as vapor phase growth. When transporting the substrate, a predetermined gas flow can be formed in the chamber in which at least the substrate is present by exhausting while supplying an inert gas to the chamber in which the substrate is present. By maintaining the state and carrying the substrate under the pressure, chemical contamination can be effectively prevented at least in the chamber where the substrate exists, and contamination of the substrate surface during conveyance can be minimized.

According to a second aspect of the present invention, there is provided a semiconductor manufacturing method comprising: exchanging a substrate between a spare chamber and the outside; performing a predetermined process on the substrate in the processing chamber; and between the spare chamber and the processing chamber. The method includes a step of transporting a substrate through a transport chamber provided, and a step of exhausting while supplying an inert gas to all the chambers when transporting the substrate. If exhaust is performed while supplying an inert gas to all the chambers, a predetermined gas flow can be formed in all the chambers, chemical contamination can be more effectively prevented, and transport efficiency is good.

  According to a third aspect of the present invention, there is provided a semiconductor manufacturing method comprising: a step of exchanging a substrate between a preliminary chamber and the outside; a step of performing a predetermined process on the substrate in the processing chamber; and a step between the preliminary chamber and the processing chamber. A step of transporting the substrate through the transport chamber provided, and a step of exhausting while supplying an inert gas to all the chambers having a vacuum pump when transporting the substrate. To do. Since all the chambers equipped with the vacuum pump are exhausted while supplying an inert gas to form a gas flow, it is possible to effectively prevent back diffusion of oil from the vacuum pump.

  In the first invention described above, the substrate exchange performed between the preliminary chamber and the outside is preferably performed by a cassette that supports a plurality of substrates. When a cassette that supports a plurality of substrates instead of a single substrate is carried into the spare chamber, the substrate is present in the spare chamber when the substrate is transported after the cassette is loaded. In consideration of prevention, it is necessary to exhaust the spare chamber while always supplying an inert gas. In this regard, in the present invention, since the inert gas is exhausted while being supplied to the spare chamber, which is one of the chambers where the substrate exists, contamination of the substrate surface always present in the spare chamber can be minimized. .

  In the first invention, it is preferable that the predetermined treatment applied to the substrate in the treatment chamber is HSG formation or epitaxial growth. In the case of the HSG forming step, the pressure in the chamber to be held is preferably higher than the conventional pressure, and is preferably set to, for example, 50 Pa or more. Moreover, in the case of an epitaxial growth process, it is desirable to set the pressure in the room | chamber to hold | maintain, for example to about 400-1333 Pa. In the HSG formation process, the dangling density of silicon molecules becomes non-uniform due to contamination by gaseous particles, and in the epitaxial growth process, there is a mismatch in Si crystallinity due to the presence of chemical contaminants, resulting in crystal defects and polycrystallization. However, in the present invention, since the exhaust gas is exhausted while supplying the inert gas to the chamber in which the substrate exists, such an influence can be reduced. In the process of thinning the gate oxide film, etc., the proportion of one contaminant molecule in the total film thickness increases, so the influence on film thickness uniformity and device characteristics cannot be ignored. However, such an influence can be reduced by the present invention.

  According to a fourth aspect of the present invention, there is provided a substrate processing method comprising: a step of exchanging a substrate between a preliminary chamber and the outside; a step of performing a predetermined process on a substrate in the processing chamber; and a space between the preliminary chamber and the processing chamber. The method includes a step of transporting a substrate through a transport chamber provided, and a step of exhausting the substrate while supplying an inert gas to at least the chamber in which the substrate is present when transporting the substrate. The substrate may be a glass substrate in addition to the semiconductor substrate. The predetermined process may be any process that handles gas when processing a substrate, such as vapor phase growth. When transporting the substrate, exhaust is performed while supplying an inert gas to at least the chamber in which the substrate is present. Therefore, chemical contamination can be effectively prevented in at least the chamber in which the substrate is present, and contamination of the substrate surface during transportation is prevented. It can be eliminated as much as possible.

According to a fifth aspect of the present invention, there is provided a semiconductor manufacturing apparatus comprising: a spare chamber for exchanging substrates with the outside; a processing chamber for performing a predetermined process on a substrate; and an internal transfer robot between the spare chamber and the processing chamber. A transfer chamber for transferring a substrate; an inert gas supply means provided in each chamber for supplying an inert gas; a gas exhaust means provided in each chamber for exhausting a gas in each chamber; And a control means for controlling the inert gas supply means and the gas exhaust means to supply the inert gas to the chamber where at least the substrate is present and to exhaust it. . The predetermined process may be any process as long as it handles a gas when manufacturing a semiconductor element, such as vapor phase growth. When transporting the substrate, it is possible to effectively prevent chemical contamination at least in the chamber where the substrate exists, by simply providing a control means for exhausting while supplying an inert gas to the chamber where the substrate is present. In addition, contamination of the substrate surface during transportation can be minimized.

  In the fifth invention, it is preferable that the preliminary chamber is a cassette chamber into which a cassette supporting a plurality of substrates is carried. If the spare chamber is a cassette chamber for loading a cassette that supports a plurality of substrates instead of a single substrate, the substrate is always present in the spare chamber after the cassette is loaded even when the substrates are transported. Therefore, considering prevention of chemical contamination, it is necessary to exhaust the spare chamber while always supplying an inert gas. In this respect, in the present invention, since the inert gas is supplied to the spare chamber which is one of the chambers in which the substrate is present by the control means, the substrate surface is exhausted. it can.

  According to the present invention, when transporting a substrate, by exhausting while supplying an inert gas to a preliminary chamber, a transport chamber, and a processing chamber, it is possible to adjust environmental conditions and suppress chemical contamination, As a result, the contamination of the substrate surface existing in the room can be eliminated as much as possible, and the quality and yield of the semiconductor element and the substrate can be improved. In addition, since it is only necessary to add a configuration of exhausting while supplying an inert gas to the chamber, it can be easily realized at a low cost without increasing maintenance.

It is a schematic explanatory drawing of the semiconductor manufacturing apparatus for enforcing the semiconductor manufacturing method and substrate processing method which concern on embodiment of this invention. It is a contamination analysis sample preparation flowchart. It is a figure which shows the contamination analysis result compared by the conventional conditions and this invention conditions. 1 is a cross-sectional structure diagram of a DRAM chip including a capacitor cell. It is a principal part enlarged view of FIG. It is a schematic plan view of the semiconductor manufacturing apparatus for HSG formation process implementation which concerns on embodiment of this invention. It is a longitudinal cross-sectional view of the reaction chamber in the semiconductor manufacturing apparatus of FIG. It is the figure transcribe | transferred so that it might be easy to understand the SEM photograph of the wafer after the HSG formation process in the case of not implementing this invention. It is the figure which transferred so that the SEM photograph of the wafer after the HSG formation process at the time of implementing this invention may be understood easily.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a semiconductor manufacturing apparatus for carrying out the semiconductor manufacturing method of the embodiment. This semiconductor manufacturing apparatus includes a load lock chamber 1 as a spare chamber for exchanging wafers (substrates) with the outside, a wafer processing chamber 2 for performing predetermined processing on the wafer, a load lock chamber 1 and a wafer processing chamber. 2 is provided with a transfer chamber 3 for transferring wafers to and from 2. The transfer chamber 3 is provided with a transfer robot 8 for transferring wafers. The predetermined processing includes HSG formation, epitaxial growth, vapor phase growth (formation of a thin film by a CVD method), formation of an oxide film, diffusion treatment, etching treatment, and the like. The spare chamber may be an N ₂ purge box in addition to the load lock chamber.

  The load lock chamber 1, the wafer processing chamber 2, and the transfer chamber 3 can be individually evacuated by a vacuum pump (gas exhaust means) 4, and the load lock chamber 1, the transfer chamber 3, and the transfer chamber 3 and the wafer processing chamber 2 are partitioned by gate valves 7 and 9 so as to be opened and closed.

An N ₂ supply line 5 is connected to the load lock chamber 1 and the transfer chamber 3 so that N ₂ gas (inert gas) can be supplied. Further, an N ₂ supply line 6 is connected to the wafer processing chamber 2 so that N ₂ gas can be similarly supplied. Further, when the wafer is transferred between the load lock chamber 1 and the wafer processing chamber 2, each N ₂ supply line and the vacuum pump 4 are controlled, and the load lock chamber 1, the transfer chamber 3, and the wafer processing chamber 2 are controlled. Control means 12 is provided for evacuating the N ₂ gas while supplying it to a predetermined chamber and maintaining the predetermined chamber at a predetermined pressure. The predetermined chamber (chamber) is a chamber (chamber) in which at least a wafer exists during wafer transfer. For example, when a wafer is transferred from the load lock chamber 1 to the transfer chamber 3, the load lock is set. These are the chamber 1 and the transfer chamber 3, and when the wafer is transferred from the transfer chamber 3 to the processing chamber 2, they are the transfer chamber 3 and the processing chamber 2. Of course, the predetermined chamber may be all the chambers. Rather, this can more effectively prevent chemical contamination, and the conveyance efficiency is also preferable. Further, the predetermined chamber may be all chambers equipped with a vacuum pump. Further, it is more preferable that the chamber is kept clean when it is evacuated while supplying N ₂ gas into the chamber when there is no wafer in the chamber other than during wafer transfer. Also, when the chamber is evacuated by a vacuum pump at the time of wafer conveyance or other than during wafer conveyance, the gas is always evacuated while supplying gas, and the gas flow from the upstream side of the pump to the downstream side is evacuated to the vacuum pump. More preferably, it is formed.

In this semiconductor manufacturing apparatus, when carrying out a predetermined wafer processing step, for example, all of the load lock chamber 1, the transfer chamber 3, and the wafer processing chamber 2 are preliminarily transferred before the wafer is transferred from the load lock chamber 1 to the processing chamber 2. While the N ₂ gas is supplied to the chamber, the vacuum pump 4 exhausts the chamber, and the load lock chamber 1, the transfer chamber 3, and the wafer processing chamber 2 are maintained at a predetermined pressure. Then, the wafer is transferred while maintaining the load lock chamber 1, the transfer chamber 3, and the wafer processing chamber 2 at a predetermined pressure.

Specifically, among the closed gate valves 14, 7, 9, first, the gate valve 14 that is a communication port with the outside is opened, and the cassette 13 containing a plurality of wafers is loaded into the load lock chamber 1. Then, the gate valve 14 is closed. Then, after evacuating the load lock chamber 1 to the ultimate vacuum pressure, the load lock chamber 1 is evacuated while introducing an inert gas (for example, N ₂ ), and the inside of the load lock chamber 1 is set as a transfer pressure. Thereafter, while the cassette 13, that is, the wafer exists in the load lock chamber 1 at least, the load lock chamber 1 is continuously evacuated while introducing an inert gas, and the load lock chamber 1 has a constant pressure. Maintained. The inside of the wafer processing chamber 2 and the transfer chamber 3 is previously evacuated while introducing an inert gas, and the pressure in the transfer chamber 3 is maintained at the transfer pressure. The wafer processing chamber 2 is maintained in this state except during wafer processing, and the transfer chamber 3 is maintained in this state during operation of the apparatus. When the pressure in the load lock chamber 1 becomes equal to the pressure in the transfer chamber 3, that is, the transfer pressure, the gate valve 7 is opened, the wafer is transferred to the transfer chamber 3, and the gate valve 7 is closed. Thereafter, when the internal pressure of the transfer chamber 3 and the internal pressure of the wafer processing chamber 2 become equal, the gate valve 9 is opened, the wafer is transferred to the processing chamber 2, the gate valve 9 is closed, and the wafer is processed. After the wafer processing, the wafer is transported in the reverse procedure.

  By doing so, it is possible to prevent back diffusion of oil from the vacuum pump 4 to the load lock chamber 1, the processing chamber 2, and the transfer chamber 3, and to prevent the chamber structure (as a shaft seal material and a chamber sealing material of the transfer robot). The volatilization of impurities from the O-rings, etc.) can be suppressed, and as a result, the influence of contamination by impurities can be eliminated as much as possible, and the wafer processing quality is improved.

In order to verify the effect of this embodiment, a polycrystalline Si film was deposited on a Si substrate using the semiconductor manufacturing apparatus, and the contamination analysis of the interface was performed. FIG. 2 shows a contamination analysis sample preparation flow at that time, and FIG. 3 shows the result of contamination analysis. Contamination analysis was performed on C (carbon), assuming organic substances that are highly likely to be degassed components from vacuum pump oil and structures. Referring to FIG.
S1: A Si substrate that has been subjected to a surface cleaning process such as natural oxide film removal in advance is put into a load lock chamber.
S2: Replace the atmosphere in the load lock chamber.
S3: The Si substrate is transferred to the processing chamber via the transfer chamber.
S4: A polycrystalline Si film is deposited to a thickness of 50 nm on the Si substrate in the processing chamber. The polycrystalline film forming conditions are as follows.
Processing temperature: 650 ° C
SiH ₄ flow rate: 0.3 slm
Pressure: 133Pa
S5: After film formation in the processing chamber, the Si substrate is returned to the load lock chamber.
In steps S2 to S5, a sample is prepared by setting the Si substrate transfer pressure to the following two conditions.
(A) 0.1 Pa or less: Conventional conditions (under ultimate vacuum due to vacuum pump exhaust)
(B) 133 Pa ... conditions of the present embodiment (exhaust while introducing N ₂ gas)
S6: Return the load lock chamber to atmospheric pressure.
S7: The Si substrate is taken out of the load lock chamber, and the contamination analysis of the Si substrate surface is performed. In the contamination analysis method, the carbon concentration at the interface (analysis surface) between the Si substrate and the polycrystalline Si film (50 nm) deposited on the Si substrate by the above steps was analyzed by SIMS (secondary ion mass spectrometry).

From the results shown in FIG. 3, the carbon concentrations in (a) the conventional conditions and (b) the present embodiment conditions are (a) 1.90 × 10 ¹⁴ atoms / cm ^{2, respectively.}
(B) 3.70 × 10 ¹³ atoms / cm ²
Therefore, the direction using the present embodiment showed a tendency to decrease by about one digit than the case using the conventional condition. In this regard, according to ITRS (International Technology Roadmap of Semiconductors) announced in 1999, the standard of organic substances on the processing substrate is predicted to be 4.10 × 10 ¹³ or less with a 100 nm device in 2005. The advantage of this embodiment reduced from 1.9 × 10 ¹⁴ to 3.7 × 10 ¹³ is clear.

In addition, it is said that the amount of organic substances must be regulated to 1.0 × 10 ¹³ atoms / cm ² or less depending on the literature.
On the other hand, as the data of the best carbon concentration obtained in the case of processing under the present embodiment conditions (exhaust while introducing N ₂ gas), 5.0 × 10 ¹² atoms / cm ²
The result is also obtained. From this, it can be said that this embodiment can also satisfy the standard of this organic substance. Note that the above two data processed using the conditions of the present embodiment are somewhat different values, but the measurement values are caused by variations in the measurement environment and the measurement method even in the same wafer measurement. Conceivable.

As described above, the present embodiment can satisfy the predetermined standard because all the chambers (processing chamber, transfer chamber, load lock chamber) having a vacuum pump are exhausted while introducing an inert gas, and the semiconductor This is because not only mechanical contamination but also back contamination of oil from the vacuum pump and chemical contamination due to a small amount of volatile impurities (degassing) from the chamber structure can be effectively eliminated in the entire manufacturing equipment. . In this regard, in the known method mainly for the purpose of preventing dust generation (mechanical contamination) from mechanically movable parts, the introduction chamber and the carry-out chamber are excluded as target chambers to be exhausted while introducing an inert gas. Therefore, effective elimination of chemical contamination cannot be realized. On the other hand, in the present embodiment, since the inert gas is introduced and exhausted in the load lock chamber, a plurality of wafers supported by a cassette existing in the load lock chamber during wafer transfer or processing. For all of the above, the above-mentioned standard can be satisfied.

In this embodiment, all the chambers are exhausted while supplying an inert gas to prevent back diffusion of the oil in the vacuum pump. Therefore, a turbo molecular pump with less oil back diffusion is provided in each chamber. There is no need to take measures such as devising members in the transfer chamber such as using metal O-rings or reducing the partial pressure of impurities in the transfer space under an ultrahigh vacuum of about 10 ⁻⁸ Pa. . Therefore, it is not necessary to increase the pressure in the processing chamber to the film formation pressure after the transfer, and the throughput does not decrease due to this. As a result, in the present embodiment, maintenance is easy at low cost.

  Next, as a specific example, a semiconductor manufacturing apparatus and a semiconductor manufacturing method for forming an HSG film on a substrate on which an amorphous silicon film serving as a capacitor electrode is formed will be described. HSG is a heavily undulating hemispherical crystal grain formed on the film surface. Since the HSG-formed film has a large surface area, a large capacity can be ensured. As a technique for forming HSG, for example, the one described in Japanese Patent Laid-Open No. 5-304273 (Patent No. 2508948) is known.

  Here, a manufacturing method of the semiconductor device (device) including the HSG film described above will be described. With reference to FIG. 4 and FIG. 5, a method of manufacturing a DRAM 500 including a capacitor cell to which the present invention is preferably applied will be described. Referring to FIG. 4, a field oxide film 52 is formed on the surface of a silicon substrate 51, and a large number of transistor formation regions are formed separately. A gate oxide film 55 is formed in each transistor formation region, and a gate electrode 56 is formed thereon. Impurities are introduced into the surface of the silicon substrate 51 by ion implantation using the gate electrode 56 and the field oxide film 52 as a mask to form a source 53 and a drain 54 in a self-aligning manner. Thereafter, an interlayer insulating film 57 is formed, and then a contact hole 58 exposing the source 53 is formed in the interlayer insulating film 57.

Next, an amorphous silicon film is deposited on the interlayer insulating film 57, patterned, the natural oxide film of the amorphous silicon film is removed, and polycrystallized to form the capacitor lower electrode 59. In this polycrystallization process, as shown in FIG. 5, hemispherical hemispherical crystal grains (HSG) 600 are formed on the surface of the amorphous silicon film 59, and the surface area is enlarged. Next, a capacitor insulating film 61 made of Ta ₂ O ₅ is formed, and a capacitor upper electrode 62 is formed thereon using a polycrystalline silicon film or the like. In this way, a DRAM in which the capacitor cell is connected to the source 53 of the MOS transistor can be realized.

  FIG. 6 is a plan view of a semiconductor manufacturing apparatus for forming an HSG film, and FIG. 7 is a longitudinal sectional view of a reaction chamber in the semiconductor manufacturing apparatus.

  In FIG. 6 showing the semiconductor manufacturing apparatus, reference numeral 20 denotes a transfer chamber, and a first load lock chamber 10, a first cooling chamber 80, and a first reaction chamber 30 that form a plurality of vacuum chambers radially around the transfer chamber 20. A second reaction chamber 35, a second cooling chamber 85, and a second load lock chamber 15, and a transfer chamber 20, a first load lock chamber 10, a first reaction chamber 30, a second reaction chamber 35, and a second load lock. Gate valves 40, 50, 60, and 70 are provided between the chambers 15, respectively. A wafer transfer robot 25 is built in the transfer chamber 20. In the case of this semiconductor manufacturing apparatus, the first reaction chamber 30 and the second reaction chamber 35 correspond to the “processing chamber” in the present invention.

In FIG. 7 showing the reaction chamber, the reaction chamber 30 connected to the transfer chamber 20 via the gate valve 50 has a nozzle 130 for supplying monosilane gas (SiH ₄ ) in a gas system necessary for film formation, Is flown from a single direction and is sucked by the turbo molecular pump 140 through the exhaust pipe 135 in the direction opposite to the nozzle 130 with respect to the wafer W. A flow rate control valve 315 is provided in a pipe leading to the nozzle 130 for supplying SiH ₄ , and this flow rate control valve 315 is provided by the flow rate control means 310 so that the flow rate of the SiH ₄ gas supplied into the reaction chamber 30 becomes a predetermined flow rate. Be controlled.

  By flowing monosilane from a single direction to the wafer surface, uniformity within the wafer surface can be secured with good selectivity. This is because monosilane is used which has a growth rate slower than that of disilane and can easily control the formation of HSG.

  When the reaction chamber pressure is lowered to 0.5 Pa or less, the gas flow rate is increased, and the in-plane uniformity of the wafer is excellent due to sufficient surface reaction rate control at 600 to 620 ° C. In addition, the reaction chamber 30 has a structure in which the upper and lower surfaces of the wafer W are heated by a face-to-face divided resistance heater 210 with respect to the surface of the wafer W, so that it is easy to ensure temperature uniformity in the wafer surface in a short time. It has become. The divided resistance heater 210 is controlled by the temperature control means 320 so that the temperature in the reaction chamber 30 becomes a predetermined temperature, for example, an arbitrary temperature within 600 to 620 ° C.

Next, a method for processing a wafer using the semiconductor manufacturing apparatus will be described. First, before a wafer having an amorphous silicon film formed on a predetermined capacitor electrode portion of a semiconductor chip to be a semiconductor element is transferred to the semiconductor manufacturing apparatus described above, a natural oxide film or NH ₄ OH + H ₂ O ₂ + H ₂ O is used. A chemical oxide film formed by such a mixed solution is removed by washing in advance with, for example, dilute hydrofluoric acid aqueous solution, followed by drying with a spin dry dryer or the like. The predetermined capacitance electrode portion is generally a lower electrode portion connected to the source / drain region of the MOS transistor. After performing the drying process, the gate valve 45 is opened in the load lock chamber 10 in the semiconductor manufacturing apparatus shown in FIG. The clean transfer is performed in order to prevent contamination by the atmosphere in the clean room and the re-formation of the natural oxide film, and it is necessary to quickly carry out the transfer to the load lock chamber 10. At this point, if there is a lot of contamination or natural oxide film adhering to or formed on the amorphous silicon surface, the bond density of silicon will depend on the state of the amorphous silicon surface and the state of the natural oxide film deposited on the amorphous silicon, for example. Therefore, there is a problem that the HSG is not formed or the formation state of the HSG, that is, the grain size or density of the HSG is different, which causes a decrease in the yield of the semiconductor device.

After the cassette containing a plurality of wafers is transferred to the load lock chamber 10 as described above, the load lock chamber 10 is evacuated to the ultimate vacuum pressure, and then high purity nitrogen (N ₂ ) is placed in the load lock chamber 10. Is exhausted (hereinafter referred to as “purging”), and the load lock chamber 10 is set as the transfer pressure. Thereafter, at least as long as a cassette, that is, a wafer exists in the load lock chamber 10, the load lock chamber 10 is continuously evacuated while introducing N ₂ gas, and the load lock chamber 10 is maintained at a constant pressure. Is done.

Here, exhausting while supplying high-purity nitrogen (N ₂ ) is to prevent air pollution by purging and back-diffusion of oil from the vacuum pump and contamination by a trace amount of volatile impurity components from the chamber structure. It is. Further, this is because the moisture is sufficiently saturated in the atmosphere by purging with dry nitrogen (N ₂ ). In addition, the water (liquid) adhering to the wafer surface and cassette due to sudden pressure reduction does not turn into water vapor (gas). This is also for preventing the above. Since the ice melts by heat after being transferred into the reaction chamber 30 and becomes water, a part of the surface is oxidized and becomes a factor that inhibits the formation of HSG. It is also effective to replace the residual material as much as possible by raising and lowering the pressure in the load lock chamber 10 several times.

The reaction chambers 30 and 35 and the transfer chamber 20 are previously evacuated while introducing N ₂ gas, and the pressure in the transfer chamber 20 is maintained at the transfer pressure. The reaction chambers 30 and 35 are maintained in this state except during wafer processing, and the transfer chamber 20 is maintained in this state during operation of the apparatus.

As described above, the N ₂ gas is introduced into the load lock chamber 10 and exhausted. When the pressure in the load lock chamber 10 becomes equal to the pressure in the transfer chamber 20, that is, the transfer pressure, the gate valve 40 is opened. Then, the wafer W is transferred to the transfer chamber 20 by the wafer transfer robot 25 and the gate valve 40 is closed. Thereafter, when the pressure in the transfer chamber 20 and the pressure in the processing chamber 30 become equal, the gate valve 50 is opened, the wafer W is transferred to the processing chamber 30, the gate valve 50 is closed, and the wafer W is processed. After the wafer processing, the wafer W is transferred in the reverse procedure to the above. The load lock chamber 10, the transfer chamber 20, and the reaction chamber 30 are constantly supplied with nitrogen (N ₂ ) and are exhausted, and impurity substances that are present and generated in the load lock chamber 10, the transfer chamber 20, and the reaction chamber 30 are exhausted. It prevents it from adhering to the wafer surface. That is, each chamber is prevented from being contaminated by a minute amount of volatile impurity components from the back diffusion of oil from the vacuum pump and the chamber structure (such as a shaft seal material of the transfer robot or an O-ring as a chamber sealing material). ing.

The apparatus in this case is not equipped with a pump for ultra high vacuum (10 ⁻⁶ Pa) except for the reaction chamber. As described above, the load lock chamber and the transfer chamber are evacuated while supplying N ₂ into the chamber at the time of transfer so that the wafer surface can be transferred to the reaction chamber while being clean. This is because the pump other than the chamber 30 does not require an ultra-high vacuum compatible pump. This not only lowers the cost of the apparatus, but also shortens the processing time.

  Next, the process performed in the reaction chamber will be described.

  As described above, the wafer W transferred to the reaction chamber 30 is stabilized at a preset reaction chamber temperature of 600 to 620 ° C. At this time, the atmosphere is a high vacuum or a non-reactive gas atmosphere that does not react with the amorphous silicon surface such as nitrogen or an inert gas. However, considering both temperature stability and crystallization, the temperature stabilization time is preferably about 5 minutes so that the in-plane temperature stability of the wafer and the underlying amorphous silicon are not polycrystallized. Thereafter, the reaction chamber temperature is maintained.

  Next, when the above atmosphere is a non-reactive gas atmosphere, after sufficiently removing them, fine nuclei are formed on the amorphous silicon surface by flowing monosilane at 150 to 200 cc / min for 2 to 2.5 minutes ( generate. The density of crystal nuclei tends to increase as the wafer temperature and nucleation time increase, and when the monosilane flow rate is reduced, the nucleation time needs to be increased.

  Finally, the supply of monosilane is stopped and crystal nuclei formed on the amorphous silicon surface are grown by migration of silicon atoms to form crystal grains. The size of the crystal grains tends to increase as the grain growth time increases, and the growth is almost maximized in 5 minutes. If the time is too long, the grains are combined to form large grains, and the target surface area increase rate in this step is reduced, so the time needs to be controlled. Note that “substantially” is because the growth conditions differ and the time during which the growth is maximum differs.

As a specific example, selectivity is achieved by performing the above-mentioned predetermined conditions, for example, reaction chamber temperature 610 ° C., temperature stabilization time 5 minutes, monosilane (SiH ₄ ) 200 sccm, nucleation time 2 minutes, and grain growth time 3 minutes. Stable HSG formation and HSG with good uniformity in the wafer surface could be formed. Similar results were obtained even at a reaction chamber temperature of 610 ° C., temperature stabilization time of 5 minutes, monosilane 150 sccm, nucleation time 2.5 minutes, and grain growth time 5 minutes. Further, by performing the processing under the above conditions, the number of wafers processed per unit time can be set to 20 / hr, which is higher than the number of wafers processed per unit time (16 / hr) in the vertical apparatus process. The number of sheets can be increased and the throughput can be improved.

  In the HSG formation process, FIG. 8 compares the results when the wafer is transferred under an ultimate vacuum (conventional example) and FIG. 9 shows the results when the wafer is transferred while purging with nitrogen (specific example of the present invention). It is the figure which transferred the SEM (scanning electron microscope) photograph to show.

As shown in FIG. 8, at the time of ultimate vacuum transfer, HSG formation is insufficient due to contamination of the wafer surface (surface irregularities are small), whereas load lock chamber 10, transfer chamber 20, reaction, as shown in FIG. When the nitrogen gas (N ₂ ) was supplied to the chamber 30 while being transported while being exhausted (supplied under the conditions of flow rate = 0.5 slm, transport pressure at that time = 50 Pa), good HSG could be formed. In addition, the same result was obtained if it conveyed by the pressure of 50 Pa or more.

Although the example which applied this invention when implementing the HSG formation process was demonstrated above, this invention is applicable also to the semiconductor manufacturing apparatus and manufacturing method which implement an epitaxial growth process. In that case, when the supply of N ₂ to the transfer chamber was set to a flow rate of 10 slm and a transfer pressure of 400 to 1333 Pa, crystal defects that occurred when the transfer was performed under the conventional ultimate vacuum were not generated. Similarly, the present invention can also be applied to a doping process such as P-doping or a film-forming process such as a Ta ₂ O ₅ film, a Si ₃ N ₄ film, or a polycrystalline Si film.

1 Load lock room (spare room)
2 Wafer processing chamber 3 Transfer chamber 4 Vacuum pump (gas exhaust means)
5 N ₂ supply line (inert gas supply means)
6 N ₂ supply line (inert gas supply means)
10 Load lock room (spare room)
12 Control means 13 Cassette 20 Transfer chamber 30 Reaction chamber (processing chamber)
W wafer (substrate)

Claims (2)

A step of transferring the substrate from the preliminary chamber to the processing chamber via the transfer chamber;
Processing the substrate in the processing chamber;
And transporting the processed substrate from the processing chamber to the preliminary chamber via the transfer chamber,
In each step of transporting the substrate, all the chambers communicating with the chamber in which the substrate exists are exhausted by using a vacuum pump from all of the exhaust systems connected to the chambers while supplying an inert gas. A method of manufacturing a semiconductor. A spare room for exchanging substrates;
A processing chamber for processing the substrate;
A transfer chamber for transferring the substrate between the preliminary chamber and the processing chamber by an internal transfer robot;
An inert gas supply means provided in each chamber for supplying an inert gas into each chamber;
A gas exhaust means provided in each of the chambers for exhausting each of the chambers by a vacuum pump;
The substrate is transferred from the preliminary chamber to the processing chamber via the transfer chamber, and after the substrate is processed in the processing chamber, the processed substrate is transferred from the processing chamber to the preliminary chamber via the transfer chamber. The gas exhaust means provided in each chamber while supplying an inert gas to all of the chambers communicating with the chamber in which the substrate is present when carrying each substrate. Control means for controlling exhaust from all of the above,
A substrate processing apparatus comprising:

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