JPH06151396A - Cleaning method - Google Patents

Abstract

PURPOSE:To efficiently perform a cleaning in a short time using various cleaning gases without damaging a treatment container and the like, by supplying a cleaning gas into the treatment container, and removing the coating film formed within the treatment container by means of the cleaning gas. CONSTITUTION:In a method for cleaning the inside of a reaction container 2 containing an object to be treated W and forming a BPSG film on the object to be treated W, a cleaning gas is supplied 52 into the reaction container 2 while keeping the cleaning temperature of the reaction container 2 in the vicinity of the temperature of the reaction container 2 kept at the time of treating the object to be treated W. By this cleaning gas, the BPSG film formed in the reaction container 2 is removed. This allows the cleaning to be efficiently performed in a short time using various cleaning gases, without damaging the treatment container and the like.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a cleaning method.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor device manufacturing process, a silicon film such as a polysilicon film or an amorphous silicon film, a silicon oxide film such as a PSG film or a BPSG film, or a film such as a silicon nitride film is subjected to a low pressure CVD or a normal process. It is widely practiced to form a film on an object to be processed such as a semiconductor wafer by a process such as pressure CVD.

In the process of forming such a silicon coating film, a heat treatment apparatus is generally used in which a heating furnace including a resistance heating element surrounding a reaction container made of ceramics such as quartz is arranged. . When performing heat treatment, a large number of objects to be processed such as semiconductor wafers are stored in a reaction vessel kept at a predetermined heat treatment temperature via a heat treatment boat made of ceramics such as quartz. A silicon film or the like is formed by introducing a reactive gas such as SiH ₄ , SiH ₂ Cl ₂ , NH ₃ , or O ₂ . After the film formation, the object to be processed is taken out from the reaction container via the heat treatment boat to accommodate the next object to be processed, but during this time, the reaction container is heated to the heat treatment temperature.

When the above-mentioned treatment is repeated, a coating such as a silicon coating is repeatedly formed on the quartz jigs such as the reaction vessel and the heat treatment boat, so that the thickness of the coating increases. If this coating is left unattended, the coating eventually peels off during the processing of the object to be treated to generate particles, and the particles float in the reaction vessel and adhere to the object to be treated, which causes a decrease in yield. Therefore, conventionally, the temperature of the reaction vessel is lowered to around room temperature at a certain frequency, then the reaction vessel and jigs are removed from a predetermined position, and wet cleaning is performed to remove those coatings.

However, in the above-described method of cleaning a reaction container or the like by wet cleaning, the temperature inside the reaction container is lowered every time the cleaning is performed, the reaction container or the like is temporarily removed and cleaned, and then the reaction container or the like is assembled. Gas leak test, etc.
Therefore, the operation of the heat treatment apparatus must be stopped for a long time of, for example, 20 to 30 hours, and there is a problem that the operation efficiency of the apparatus is reduced. Further, in the heat treatment apparatus as well, it is considered that the inside of the reaction vessel and the loading section are always kept in vacuum like a load lock system. In such a case, the object to be cleaned cannot be easily removed from the main body. There is also a problem, and such a problem also exists in the case of an apparatus that has been enlarged in size with the recent increase in the diameter of the object to be processed. Therefore, recently, a cleaning method has been used in which an etching gas is supplied as a cleaning gas into the reaction vessel and the coating film is removed by the cleaning gas.

[0006]

However, in the conventional cleaning method using the cleaning gas, the temperature of the reaction container kept at the processing temperature of the object to be processed and the temperature of the reaction container at the time of cleaning remarkably differ from each other. If there is, due to the difference between the linear expansion coefficient of the film formed in the reaction vessel and the linear expansion coefficient of the material used in the reaction vessel,
Due to the temperature difference between the temperature during heat treatment and the temperature during cleaning, thermal stress is generated between the reaction container and the film, and this thermal stress induces peeling of the film adhered to the surface of the reaction container during cleaning, Further, there is a problem in that the peeled coating film causes particles to reduce the yield of subsequent processing of the object.

The present invention has been made in order to solve the above problems, and is short without peeling the coating film from the processing container or the like at the time of cleaning and without damaging the processing container or the like by using various cleaning gases. It is an object of the present invention to provide a cleaning method capable of efficiently cleaning in time.

[0008]

As a result of various examinations on the cleaning conditions using a cleaning gas for the processing container, the present inventors have found that the coating film is peeled off by cleaning with the cleaning gas under a specific temperature condition. It was found that the processing container can be efficiently cleaned in a short time without causing damage to the processing container and the like. Further, as a result of the same examination of the cleaning conditions for the substance adhering to the processing container,
It has been found that the processing container can be efficiently cleaned in a short time by supplying a specific cleaning gas to a specific coating under specific conditions.

The present invention has been made based on the above findings, and the cleaning method according to claim 1 of the present invention is directed to a processing container for accommodating an object to be processed and forming a predetermined film on the object. In the method of cleaning the inside, a cleaning gas is supplied into the processing container while the cleaning temperature of the processing container is maintained in the vicinity of the temperature of the processing container that is held during the processing of the object to be processed, The coating film formed in the processing container is removed by a cleaning gas.

According to a second aspect of the present invention, in the cleaning method according to the first aspect, the coating is BP.
If it is an SG film, the cleaning temperature is set to 600
˜700 ° C., a mixed gas of chlorine trifluoride gas and nitrogen gas is used as the cleaning gas, the pressure is 0.5 to 2.0 Torr, and the chlorine trifluoride gas is 500 to 500 ° C.
The gas is supplied at 2000 sccm and nitrogen gas at 1500 to 2800 sccm.

[0011]

According to the first aspect of the present invention, after the object to be processed is processed in the processing container at a predetermined temperature, the cleaning temperature of the processing container is maintained during the processing of the object to be processed. While maintaining the temperature near the temperature of the processing container, supplying a cleaning gas into the processing container,
With this cleaning gas, the coating film formed in the processing container can be removed in a short time without peeling from the processing container or the like, and particles can be prevented from being generated during the subsequent processing of the object to be processed.

According to the second aspect of the present invention, when the object to be processed is processed at a predetermined temperature in the processing container to form a BPSG film in the processing container, the cleaning is performed. A mixed gas of chlorine trifluoride gas and nitrogen gas is supplied as a gas, and at the time of this supply, the cleaning temperature is set to 600 to 700 ° C., and the pressure is 0.5 to 2.0 Torr, chlorine trifluoride gas. 500 to 200
By setting 0 sccm and 1500 to 2800 sccm of nitrogen gas, the BPSG film can be removed in a short time without peeling from the processing container or the like, and particles can be prevented from being generated during the subsequent processing of the object.

[0013]

EXAMPLES A preferred embodiment of the cleaning method of the present invention will be described below by taking the case of cleaning the batch type vertical heat treatment apparatus shown in FIG. 1 as an example.

Before describing an embodiment of the cleaning method of the present invention, first, a vertical heat treatment apparatus to which this embodiment is applied will be described. The vertical heat treatment apparatus shown in FIG. 1 includes a heating furnace 1 and a heating furnace 1 as shown in FIG.
A reaction container 2 as a processing container made of ceramics such as quartz is disposed inside the container, and a plurality of objects W to be processed such as semiconductor wafers are horizontally held in the reaction container 2 as shown by arrows in FIG. And a heat treatment boat 3 made of ceramics such as quartz to be loaded and unloaded. Further, the reaction vessel 2 is formed by an outer cylinder 21 having an upper end closed and an opening at the lower end, and upper and lower ends which are arranged in the outer cylinder 21 with their axes aligned. The container 22 is provided with an inner cylinder 22, and is configured as a double-structured container having an opening formed at a lower end as a whole. When the heat treatment boat 3 is loaded into the reaction vessel 2,
The reaction vessel 2 is formed by sealing the opening of the reaction vessel 2 with a cap 4A formed on the heat insulation tube 4 at the lower end of the heat treatment boat 3.
It is configured to form an airtight state inside.

A gas supply pipe 5 is connected to the lower end of the reaction vessel 2, and the object W to be processed is connected through the gas supply pipe 5.
The reactive gas and the cleaning gas necessary for the heat treatment of are supplied into the reaction vessel 2. That is, the gas supply pipe 5 is branched into a first gas supply pipe 51 for supplying a reactive gas and a second gas supply pipe 52 for supplying a cleaning gas on the upstream side thereof, and each gas supply pipe 51, The valves 51A and 52A arranged at 52 are opened and closed to supply the respective gases into the reaction vessel 2 individually. In addition, the reaction container 2
The gas exhaust pipe 6 is connected to the lower end of the
The inside of the reaction vessel 2 is adjusted to a predetermined vacuum state by the vacuum pump 7 disposed in the above, and the processed gas is exhausted. Further, a gas processing device 8 for detoxifying the processing gas exhausted by the vacuum pump 7 is connected to the downstream end of the gas exhaust pipe 6. The gas processing device 8 is configured so that the processing gas is rendered harmless by the chemicals stored therein.

Further, the cleaning gas used in one embodiment of the present invention is supplied through the valve 52A to the second gas.
The cleaning gas supply device 9 connected to the upstream end of the gas supply pipe 52 supplies the cleaning gas into the reaction vessel 2. That is, this cleaning gas supply device 9
Is, for example, a first cylinder 91 that stores chlorine trifluoride that removes the film by etching, and a second cylinder 92 that stores nitrogen gas that dilutes this chlorine trifluoride and adjusts it as a cleaning gas. The first branch pipes 93 and 94 for supplying the gas of each of the cylinders 91 and 92 to the second gas supply pipe 52, respectively.
A mass flow controller 95 for controlling the gas flow rate is provided in the first branch pipe 93 for supplying the chlorine trifluoride.
And valves 96A and 96B located in front of and behind the mass flow controller 95, respectively, and are configured to adjust the supply flow rate of chlorine trifluoride by these three members. Further, a similar mass flow controller 97 and valves 98A and 98B are also arranged in the second branch pipe 94, respectively. Further, the first branch pipe 93 and its mass flow controller 95, valves 96A, 96
A tape heater 99 is wound around B, and the tape heater 99 is configured to prevent reliquefaction of chlorine trifluoride.

When a BPSG film is formed on the object W using the vertical heat treatment apparatus, the heat treatment is performed in the reaction furnace 2 heated to the heat treatment temperature in the heating furnace 1, for example, 600 to 700 ° C. A plurality of objects W to be processed, which are loaded with the boat 3 and held horizontally, are housed in the reaction container 2, and the opening of the reaction container 2 is sealed by the cap 4A of the heat insulating cylinder 4.
Then, the vacuum pump 7 is driven to reduce the pressure in the reaction vessel 2 to, for example, about 0.001 Torr, and then the valve 51A of the first gas supply pipe 51 is opened while maintaining the vacuum degree of 1.0 Torr to supply gas. Reactive gas, that is, TEOS, PH3, TMB, O2 and B-O2, is supplied at a predetermined supply amount for a predetermined time through the pipe 5 to maintain the pressure in the reaction container 2 at 1.0 Torr. Then, the processed object W has a B of 5 μm.
A PSG film is formed.

Next, after the heat treatment boat 3 is unloaded from the reaction vessel 2 and the object W to be processed is transferred from the heat treatment boat 3, an empty heat treatment boat 3 is placed in the reaction vessel 2 which is maintained at the temperature during the heat treatment. The reaction vessel 2 is sealed by loading as described above. After that, under the temperature near the heat treatment temperature, the inside of the reaction container 2 is decompressed as described above, the valve 52A of the second gas supply pipe 52 is opened, and the inside of the reaction container 2 is cleaned through the gas supply pipe 5. 5 gases of chlorine trifluoride
00 ~ 2000sccm and nitrogen gas 1500 ~ 2800
Sccm is supplied, the pressure of the cleaning gas at this time is set to 0.5 to 2.0 Torr, and the cleaning gas is supplied in this state to clean the inside of the reaction vessel 2. Then, the BPSG formed in the reaction vessel 2 is formed. The film can be efficiently removed in a short time of less than 1 hour. The concentration of chlorine trifluoride in the cleaning gas at this time is 15 to 57 vol.
%, And if this concentration is less than 15 vol%, B
The PSG film may not be removed in a short time, and if the supply amount of chlorine trifluoride exceeds 57 vol%, the reaction container 2 and the like may be damaged, which is not preferable. If the pressure is less than 0.5 Torr, the etching rate may decrease, and if it exceeds 2.0 Torr, the etching may vary, which is not preferable.

Further, as the etching gas used as the cleaning gas, other than chlorine trifluoride, for example,
Examples thereof include halogen compounds such as nitrogen trifluoride, hydrogen fluoride, carbon tetrafluoride, fluorine and sulfur hexafluoride.

Next, in the case of cleaning the reaction vessel 2 using the cleaning method of this embodiment, the cleaning temperature, the cleaning gas flow rate and the cleaning pressure, the inner surface of the outer cylinder 21 on which the BPSG film is formed, and the inner cylinder 22. As a result of various examinations of the cleaning state at each position on the inner and outer surfaces (see FIG. 2), the results shown in FIGS. 3 to 5 were obtained. In each figure, the numbers on the horizontal axis are (1) to (7).
Shows the measurement position when the inner surface of the inner cylinder 22 is equally divided from the lower end to the upper end of the inner surface of the straight body part, and the lower end is (1) and the upper end (7)
The number gradually increases until (8) to (13) is the outer cylinder 2.
1 shows the measurement position when the inner surface of the straight body portion and the outer surface of the straight body portion of the inner cylinder 22 are equally divided from the lower end to the upper end, and the upper end is (8) and the number gradually increases to (13) at the lower end. growing. The vertical axis shows the etching amount of the BPSG film.

As is clear from the results shown in FIGS. 3 to 5, in the reaction vessel 2, cleaning is easily performed in the vicinity of the upper ends of the outer cylinder 21 and the inner cylinder 22 where the BPSG film is easily formed, In addition, in the reaction vessel 2, B
It can be seen that the lower end portion of the inner cylinder 22 where the PSG film is hard to be formed is hard to be cleaned. Therefore, if the cleaning method of this embodiment is used, the BPS in the reaction vessel 2
It can be seen that the portion where the G film is easily formed can be efficiently cleaned in a short time. Further, when the temperature of the cleaning gas is set to 550 ° C., which is lower than the formation temperature of the BPSG film, it is clear that it is difficult to remove the BPSG film as is clear from FIG. If it exceeds 700 ° C., the etching rate becomes too fast. Further, when the concentration of chlorine trifluoride in the cleaning gas is set to 10%, which is lower than the concentration range of the present invention, it is clear from FIG. 4 that it is difficult to remove the BPSG film.

As described above, according to this embodiment, the inside of the reaction vessel 2 is cleaned with the cleaning gas at the same temperature as the temperature held during film formation.
The coating of the reaction vessel 2 and the quartz jigs such as the heat treatment boat 3 can be efficiently removed in a short time without raising or lowering the temperature of the reaction vessel 2 as in the conventional case, and the batch type vertical heat treatment is performed. The operating efficiency of the device can be significantly improved. Further, since cleaning is performed in the vicinity of the temperature held during film formation, there is no temperature rise / fall of the reaction container 2, and stress is generated due to the difference between the linear expansion of the coating film and the linear expansion of the material of the reaction container 2 due to the repetition of this temperature increase / decrease. It is possible to prevent the generation of microcracks in the reaction vessel 2 and prevent them from occurring. Further, it is possible to suppress the peeling of the coating due to the difference in the coefficient of thermal expansion between the coating and the reaction vessel 2 and to reliably prevent the generation of particles due to the peeling of the coating to improve the yield.

Next, in order to verify the presence or absence of microcracks due to the difference in the coefficient of thermal expansion between the reaction vessel 2 and the BPSG film, the quartz wafer W is subjected to a film formation process of the BPSG film according to the flowchart shown in FIG. After that, the quartz wafer W was cleaned. Here, as described below, a quartz wafer W made of the same material as that of the reaction vessel 2 is heat-treated and cleaned.
The presence / absence of microcracks was measured.

First, one quartz wafer W is inserted into the center of the heat treatment boat 3, and then the heat treatment boat 3 is, for example, about 6 pieces.
Load into reaction vessel 2 heated to 00 ° C
The opening of the reaction container 2 is sealed with the cap 4A (step 1). Then, the vacuum pump 7 is driven to reduce the pressure in the reaction vessel 2 to, for example, about 0.001 Torr, and then 1.0 Tor
While maintaining the vacuum degree of rr, the valve 51A of the first gas supply pipe 51 is opened and the reactive gas, that is, TEOS, PH3, TMB, O2 and B-O2 is introduced into the reaction vessel 2 through the gas supply pipe 5. Are supplied to the quartz wafer W at predetermined flow rates.
A BPSG film having a thickness of μm was formed (step 2).

Next, after the heat treatment boat 3 is unloaded from the reaction vessel 2 at the above-mentioned film forming temperature to lower the temperature of the quartz wafer W on which the BPSG film has been formed to room temperature (step 3), again. After the heat treatment boat 3 is loaded into the reaction container 2 at a temperature near the heat treatment temperature, the quartz wafer W is stored in the reaction container 2 and the temperature of the quartz wafer W is raised to a temperature near the heat treatment temperature. (Step 4) At that temperature, the pressure inside the reaction vessel 2 was reduced to 0.001 Torr, and then the valve 52A of the second gas supply pipe 52 was opened to maintain the vacuum degree of 1.0 Torr. A cleaning gas, that is, a cleaning gas consisting of chlorine trifluoride of 700 sccm and nitrogen gas of 2800 sccm, is supplied to the reaction vessel 2 through the supply pipe 5 for about 40 minutes to clean the quartz wafer W and the reaction vessel 2. Training was to remove the BPSG film (Step 5). Subsequently, the heat treatment boat 3 is unloaded from the reaction vessel 2 (step 6), and the quartz wafer W after cleaning is cleaned from the heat treatment boat 3 that has been cooled to room temperature.
The quartz wafer W was taken out as a sample No.1. Then, the surface condition of Sample No. 1 was measured to determine its average roughness (Ra), and the mass of Sample No. 1 was measured to determine the change in mass. The respective results are shown in Table 1 below. . In addition, FIGS. 7A and 7B show the measurement results of the surface states of the sample No. 1 before film formation and the sample No. 1 after cleaning in this sample.

Further, the quartz wafer W on which the BPSG film is formed in the above step 2 is not unloaded, but the step 5 is directly performed.
Then, the cleaning of step 5 is performed under the same conditions as the above-mentioned cleaning as it is, and after the cleaning, the heat treatment boat 3 is unloaded, and the quartz wafer W is subjected to the above measurement as the sample No. 2 and the sample No. 2 The results of average roughness (Ra) and mass change are shown in Table 1 below.
8A and 8B show the measurement results of the surface states of the quartz wafer W before film formation and the quartz wafer W after cleaning in this sample.

[0027]

[Table 1] However, A shows angstrom. The original surface condition of each sample was 20 to 30A.

According to the results shown in Table 1 above, the sample No.
1 and Sample No. 2 all show a decrease in mass, but Sample No. 1 unloaded before cleaning has an average surface roughness (Ra) of 85 A, which is comparable to the original average roughness (Ra). The surface of the sample No. was cleaned without being unloaded before cleaning.
No. 2 was 30 A, and it was found that the average roughness (Ra) did not change so much. From this result, it was found that the roughness of the inner surface of the reaction container 2, that is, damage can be suppressed by cleaning the reaction container 2 while maintaining the temperature of the reaction container 2 near the temperature of the object W to be processed.

Further, according to the results shown in FIGS. 7A and 7B showing the respective surface states of the sample No. 1 before film formation and after cleaning, microcracks were observed on the surface after cleaning. A peak was reached that reached approximately 1600 A based. On the other hand, according to FIGS. 8A and 8B showing similar results for the sample No. 2 which was directly cleaned at the heat treatment temperature without unloading, no peak was observed. From this result, if the temperature of the reaction container 2 changes up and down during cleaning, the reaction container 2 may be changed due to the difference between the thermal expansion coefficient of the BPSG film and the thermal expansion coefficient of the reaction container 2.
It was found that the microcracks are easily generated in the reaction container 2, whereas the microcracks in the reaction container 2 can be suppressed by cleaning at a temperature near the heat treatment temperature.

In the above embodiment, only the cleaning gas using chlorine trifluoride as the etching gas and nitrogen gas as the carrier gas for diluting the etching gas has been described. However, the cleaning gas used in the present invention is the same as the above embodiment. The etching gas is not limited to any example, and the etching gas is nitrogen trifluoride, hydrogen fluoride,
A halogen compound such as carbon tetrafluoride, fluorine or sulfur hexafluoride can be used, and a gas having no reactivity with an etching gas such as an inert gas can be used as a carrier gas.

Further, in the above-mentioned embodiment, only the cleaning method for removing the BPSG film has been described, but the cleaning method of the present invention is not limited to the above-mentioned embodiment, and for example, a PSG of the same kind as BPSG, BS
Silicon glass films such as G and AsSG, polysilicon,
It can also be applied to a silicon-based film such as amorphous silicon or a film such as a silicon nitride film.

Further, in the above embodiment, only the batch type vertical heat treatment apparatus was explained, but the present invention can be widely applied to the processing apparatus used in other film forming steps such as the single wafer type heat treatment apparatus.

In summary, the present invention supplies the cleaning gas into the processing container while keeping the cleaning temperature of the processing container near the temperature of the processing container which is held at the time of processing the object. Any cleaning method may be used as long as it removes the coating film formed in the processing container with a cleaning gas, and is not limited to the above-described embodiment.

[0034]

As described above, according to the first aspect of the present invention, the cleaning temperature of the processing container is
By cleaning in the state of being held near the temperature of the processing container held during the processing of the object to be processed, without peeling the coating film from the processing container during cleaning,
Moreover, it is possible to provide a cleaning method that can be efficiently cleaned in a short time without damaging the processing container or the like by using various cleaning gases.

According to the second aspect of the present invention, in order to remove the BPSG film formed in the processing container, a cleaning gas composed of chlorine trifluoride gas and nitrogen gas in a predetermined ratio is used. By using, it is possible to provide a cleaning method capable of efficiently removing the BPSG film in a short time without peeling the BPSG film from the processing container or the like during cleaning and without damaging the processing container or the like.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a heat treatment apparatus to which a preferred embodiment of a cleaning method of the present invention is applied.

FIG. 2 is an explanatory diagram showing measurement positions of a BPSG film in a reaction container.

FIG. 3 is a graph showing a relationship between a cleaning temperature and a cleaning state at each position in the reaction container.

FIG. 4 is a graph showing a relationship between a cleaning gas flow rate and a cleaning state at each position in the reaction container.

FIG. 5 is a graph showing the relationship between the cleaning gas pressure and the cleaning state at each position in the reaction container.

FIG. 6 is a flowchart showing the flow of a test for verifying the presence or absence of damage to the reaction container shown in FIG. 1 according to a preferred embodiment of the cleaning method of the present invention.

7 is a graph showing the surface condition of the sample obtained in the test shown in FIG. 2, where FIG. 7 (a) shows the surface condition of the sample before film formation, and FIG. 7 (b) shows cleaning after unloading. It is a figure which shows the surface state of the sample at the time of doing.

8 is a graph showing the surface condition of the sample obtained in the test shown in FIG. 2, where FIG. 8A shows the surface condition of the sample before film formation, and FIG. FIG. 3 is a diagram showing a surface state of a sample when the sample is directly cleaned at the temperature during the heat treatment.

[Explanation of symbols]

 W Object to be treated 2 Reaction container (treatment container) 3 Heat treatment boat 5 Gas supply pipe 7 Vacuum pump 9 Cleaning gas supply device 51 First gas supply pipe (for film forming gas) 52 Second gas supply pipe (for cleaning gas)

Claims (2)

[Claims] 1. A method of cleaning the inside of a processing container for accommodating an object to be processed and forming a predetermined film on the object, wherein the cleaning temperature of the processing container is maintained during the processing of the object. A cleaning method comprising supplying a cleaning gas into the processing container while maintaining the temperature near the temperature of the processing container, and removing the coating film formed in the processing container by the cleaning gas. 2. The coating is a BPSG film, the cleaning temperature is set to 600 to 700 ° C., and a mixed gas of chlorine trifluoride gas and nitrogen gas is used as the cleaning gas at a pressure of 0.5 to 2. Chlorine trifluoride gas is 500 to 2800 sccm and nitrogen gas is 1500 to 2 at 0 Torr
The cleaning method according to claim 1, wherein the cleaning is performed so as to be 800 sccm.