JP3670533B2 - Substrate processing apparatus and cleaning method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a substrate processing apparatus and a method for cleaning a substrate holder of a substrate processing apparatus.
[0002]
[Prior art]
When a SiN film forming process is performed on a silicon wafer by CVD, for example, SiN is deposited not only on the wafer but also on the wafer holder. If a large amount of SiN is deposited on the wafer holder, a problem occurs in the processing. Therefore, it is necessary to periodically clean the wafer holder. Cleaning is performed, for example, by etching the deposited film on the wafer holder with an etching gas containing ClF ₃ .
[0003]
However, if the etching is further continued after the deposited film on the wafer holder is removed, the wafer holder is damaged by overetching. Even if the wafer holder is made of a material that can have a selectivity of etching rate with respect to SiN, damage to the wafer holder cannot be ignored if over-etching is repeated. If this damage is repeated, the wafer holder becomes unusable and the wafer holder needs to be replaced. However, an increase in the frequency of wafer holder replacement is a factor that reduces the operating efficiency of the substrate processing apparatus, and is a major problem from the viewpoint of improving throughput. Become. Therefore, it is necessary to avoid overetching of the wafer holder as much as possible.
[0004]
For this reason, it is desirable to end the cleaning at the moment when the deposited film is just removed, but it is extremely difficult to accurately determine the end point of the cleaning. In particular, when the deposited film on the wafer holder is a transparent film such as an SiN film, it is practically possible to visually determine whether the deposited film has been removed even if there is a viewing window in the substrate processing apparatus. Impossible.
[0005]
Therefore, the deposition rate of SiN on the wafer holder during the film formation process is experimentally obtained in advance to estimate the thickness of the deposited film after the film formation process for a predetermined time, and the etching rate during the cleaning is previously tested. Conventionally, the required cleaning time is obtained based on these data. However, even when this method is used, in order to eliminate the SiN leftover, for the sake of safety, the etching is performed for an excessive time, that is, overetching.
[0006]
Normally, the heater for heating the wafer is installed at the lower part of the wafer holder. However, as the heater member, a material having a selectivity ratio between SiN and etching rate cannot be used as much as quartz. Damage may occur, and when this damage accumulates, the heater must be replaced in the same manner as the wafer holder.
[0007]
[Problems to be solved by the invention]
As described above, if the wafer holder and the heater are damaged by the etching gas at the time of cleaning, it is necessary to frequently perform maintenance work accompanied by time-consuming component replacement, and the productivity of the entire substrate processing apparatus is lowered. End up.
[0008]
The present invention has been made in view of the above circumstances, and is capable of cleaning deposits on a substrate holder in the shortest optimal time, and a cleaning method capable of reducing damage to the substrate holder, and cleaning An object of the present invention is to provide a substrate processing apparatus capable of reducing damage to a heater sometimes.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a first feature of the present invention is a method for cleaning deposits on a substrate holder made of SiC-coated carbon, SiC, SiO ₂ or Al ₂ O ₃ on which a substrate to be processed is installed. When a cleaning process is performed using a ClF ₃ gas, NF ₃ gas, HCl gas, F ₂ gas, or HF gas at a predetermined position on the substrate holder prior to processing the substrate to be processed, The object is to perform coating with a film made of poly- Si or amorphous Si that is etched at a faster rate than a film made of SiN, SiC, or SiO ₂ formed by processing the substrate to be processed.
[0010]
The film to be coated on the wafer holder may be made of a material that is etched at a rate faster than the etching rate of the deposit on the wafer.
[0011]
The film to be coated on the wafer holder may not be optically transparent (not transmissive).
[0012]
Further, when performing the cleaning method, the optical characteristics of the substrate holder may be monitored during cleaning, and the end point of cleaning may be set based on the detection result.
[0014]
Furthermore, the second feature of the present invention is a substrate processing apparatus for performing a film forming process on a substrate to be processed, provided in a processing chamber, a substrate holder provided in the processing chamber, and a lower portion of the substrate holder, A heater for heating the substrate holder; an enclosure provided below the substrate holder and defining a space surrounding the heater; and a means for supplying a gas into the space. A portion located below the substrate holder and outside the enclosure, and having a portion that overlaps the enclosure when viewed from the side, the substrate holder and the enclosure A passage is formed between the space defined by the enclosure and a space outside the enclosure, and the passage includes a first portion and a space outside the enclosure from the first portion. On the side close to the first part In that it has a second portion located below, the.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. Note that the present invention can be applied to a general substrate processing apparatus that performs a film formation process (may be an apparatus that performs both film formation and etching) on a substrate. An example will be described in which a wafer holder (substrate holder) of a substrate processing apparatus that performs SiN film formation on a wafer is cleaned with a gas containing ClF ₃ .
[0016]
FIG. 1 is a diagram schematically showing a configuration of a low pressure CVD apparatus as an example of a substrate processing apparatus to which the present invention is applied. In FIG. 1, reference numeral 1 denotes a processing chamber, and reference numeral 2 denotes a gas supply pipe for supplying a processing gas G (film forming gas or etching gas) into the processing chamber 1. The inside of the processing chamber 1 can be depressurized by a vacuum pump VP.
[0017]
A wafer holder 3 for placing the wafer W is provided in the processing chamber 1. The wafer holder 3 is made of an optically transparent material, quartz in this example. Below the wafer holder 3, a heater 4 for heating the wafer W via the wafer holder 3 is provided.
[0018]
A cylindrical enclosure 5 is provided below the wafer holder 3 along the outer peripheral edge of the wafer holder 3. The heater 4 is located in the space 6 surrounded by the enclosure 5. The space 6 surrounded by the enclosure 5 communicates with the space 8 inside the processing chamber 1, that is, the space outside the space 6 only through the gap between the wafer holder 3 and the enclosure 5, that is, the passage 7. A gas supply device 9 is connected to the space 6, and the space 6 can be filled with an inert gas by the gas supply device 9.
[0019]
FIG. 2 is a diagram showing in detail the positional relationship between the wafer holder 3 and the enclosure 5 in the region II of FIG. As shown in FIG. 2, the wafer holder 3 has a portion 3 a that is located outside the envelope 5 and overlaps the envelope 5 with an overlap width L when viewed from the lateral direction. According to the configuration of FIG. 2, the passage 7 is located on the portion 7 a between the lower surface of the wafer holder 3 and the upper end portion 5 a of the enclosure 5 and on the side closer to the space 8 than the portion 7 a, and the portion 7 a of the passage 7. And a portion 7b located on the outer side and the lower side. Therefore, if the space 6 is filled with a gas having a specific pressure and a light specific gravity, the gas can be retained in the portion 7a so as not to flow out to the space 8 side, and the gas from the space 8 side to the space 6 side can be prevented. A barrier that prevents inflow can be formed.
[0020]
In addition, as shown in FIG. 3, you may comprise so that the clearance gap 7, ie, the channel | path 7, may repeat raising / lowering in multiple times, and by comprising in this way, the part 7a, ie, the site | part in which a barrier is formed in several places Can be provided.
[0021]
Further, a radiation thermometer 10 for detecting the radiant light intensity of the wafer holder 3 is provided above the wafer holder 3 (above the peripheral edge of the wafer holder 3 in this example). The radiation thermometer 10 is preferably movable in the direction of the arrow in FIG. 1 so that it can be retracted from above the wafer holder 3 when it is not necessary.
[0022]
Next, a method for cleaning the wafer holder 3 will be described with reference to FIG.
[0023]
First, the wafer holder 3 is coated with a material other than the film forming material, for example, polysilicon (step 101).
[0024]
Next, SiN film formation is performed for a predetermined time or a predetermined number of times (step 102). At the end of step 102, a polysilicon film is sequentially laminated on the wafer holder 3, and an SiN film is further laminated thereon.
[0025]
After completion of step 102, an inert gas is supplied to the space 6 (step 103), and then the heater is turned on to supply an etching gas to the wafer holder 3 to start cleaning (step 104). Note that monitoring of the indicated value of the radiation thermometer 10 is started simultaneously with the start of cleaning (step 105).
[0026]
As the cleaning progresses, the surface emissivity of the wafer holder 3 (of the film on the wafer holder 3) changes, or the amount of light transmitted through the wafer holder 3 and the layer formed thereon changes from the heater 4 side. The intensity of the radiation received by the total 10 changes. That is, as shown in FIG. 5, when the upper SiN film disappears (see time t1 in FIG. 5), the indicated value of the radiation thermometer 10 starts to increase rapidly thereafter. If the cleaning is further continued, the underlying polysilicon film also disappears. Then, the indicated value of the radiation thermometer 10 becomes equal to or higher than a predetermined value (in this example, about 500 ° C.), and thereafter becomes substantially constant (see time t2 in FIG. 5). Therefore, cleaning may be finished at this time (step 106). ).
[0027]
As described above, the cleaning end point can be reliably detected by monitoring the radiation intensity of the wafer holder 3 during cleaning.
[0028]
In addition, in this example, there exists the following advantage by having coated polysilicon. First, since polysilicon is not transparent, the end of cleaning can be determined visually by providing a viewing window on the wall of the processing chamber 1. Second, since the etching rate of polysilicon is significantly faster than that of SiN, even a part of the SiN layer is etched, and when the underlying polysilicon layer is exposed, the underlying polysilicon layer is rapidly etched laterally. proceed. For this reason, the substantial etching rate can be improved and the cleaning time can be shortened.
[0029]
Further, when an inert gas is supplied to the space 6 at the time of cleaning and the heater 4 is heated, the inert gas heated by the heater 4 has a property of rising due to buoyancy. The gas stays in the gap, that is, the portion 7 a of the passage 7. Since this staying gas functions as a barrier that prevents the cleaning gas from entering the space 6 from the passage 7, damage to the heater 4 can be avoided.
[0030]
In the above embodiment, a coating made of a polysilicon layer is provided, but the polysilicon layer is not necessarily provided. That is, even if there is no polysilicon layer, it is possible to detect the end point of cleaning based on the difference in optical characteristics between the wafer holder 3 itself and the SiN layer.
[0031]
In the above embodiment, the cleaning progress is detected by monitoring the radiation intensity on the wafer holder surface as an optical characteristic. However, the present invention is not limited to this. The progress of cleaning can also be confirmed by monitoring the target characteristics. Hereinafter, another method for monitoring optical characteristics will be described with reference to FIGS. 6 to 9, the layer 12 on the wafer holder 3 may be composed of a multilayer of the lower polysilicon layer and the upper SiN layer, or may be a single layer consisting of only the SiN layer. Although it is possible to confirm the progress of cleaning by means of typical monitoring (in the former case, the curve of the monitored detection value is only complicated), the explanation relating to the following FIGS. 6 to 9 The case where the layer 12 is composed of a single layer consisting only of the SiN layer will be described.
[0032]
In the graphs of FIGS. 6B, 7B, and 8B, the horizontal axis represents the cleaning time t, and the vertical axis represents transmitted light and reflected light detected by the radiation thermometer 10 or the detector 10A. Or the intensity I of radiant light is shown.
[0033]
First, the first method will be described with reference to FIG. In this method, as shown in FIG. 6A, a light source 11 is provided below the wafer holder 3, and a detector 10 </ b> A such as a photodetector is provided at a position facing the light source 11 above the wafer holder 3. At the time of cleaning, the light source 11 is turned on, and the change with time in the intensity I of the light transmitted through the wafer holder 3 is measured by the detector 10A. In this case, as shown in FIG. 6B, when damage starts to occur on the layer 12 on the wafer holder, the intensity of light incident on the detector 10A starts to increase. When the layer 12 is completely removed, the intensity of light incident on the detector 10A thereafter becomes substantially constant. This event can be used to detect the end point of cleaning. This method is based on the premise that the wafer holder 3 is made of an optically transparent material such as quartz.
[0034]
Next, the second method will be described with reference to FIG. In this method, as shown in FIG. 7A, the light source 11 is provided above the wafer holder 3, and the half mirror 13 is provided between the light source 11 and the wafer holder 3. At the time of cleaning, the light source 11 is turned on to irradiate the wafer holder 3 with light, the reflected light from the wafer holder 3 is guided to the detector 10A through the half mirror 13, and the change with time of the reflected light intensity I is measured. Also in this case, since the reflected light intensity I changes as shown in FIG. 7B depending on the state of damage to the layer 12, the end point of cleaning can be detected using this phenomenon. This method can be performed regardless of whether the wafer holder 3 is transparent or opaque.
[0035]
Next, the third method will be described with reference to FIG. In this method, as shown in FIG. 8A, the light source 11 is provided below the wafer holder 3, and the radiation thermometer 10 is provided at a position facing the light source 11 above the wafer holder 3. At the time of cleaning, the light source 11 is turned on, and a change with time in the intensity I of light transmitted through the wafer holder 3 is measured by the radiation thermometer 10. In this case, as shown in FIG. 8B, while the layer 12 is present on the wafer holder 3, the light directly directed from the light source 11 to the radiation thermometer 10 and the radiation thermometer diffracted in the layer 12. As shown in FIG. 8B, the detected value of the light intensity I oscillates as a result of interference with the light traveling toward 10. The amplitude of the detected value increases as the thickness of the layer 12 decreases, and becomes zero when the layer 12 disappears. This event can be used to detect the end point of cleaning.
[0036]
Next, the fourth method will be described with reference to FIG. In this method, as shown in FIG. 9, the light source 11 and the detector 10 </ b> B are provided above the wafer holder 3. At the time of cleaning, the light source 11 is turned on, and the film thickness is measured (film thickness measurement by spectroscopic ellipso) using the change in the detection value of the detector 10B due to the polarization phenomenon caused by the layer 12.
[0037]
In the above embodiment, the case where the substrate processing apparatus is a low pressure CVD apparatus has been described. However, the present invention can also be applied when the processing apparatus is an atmospheric pressure CVD apparatus, a plasma CVD apparatus, or the like. Further, the substrate processing apparatus may be an apparatus for performing a film forming process on an LCD substrate or the like in addition to an apparatus for performing a film forming process on a semiconductor wafer.
[0038]
In the above embodiment, ClF ₃ is used as an etching gas used for cleaning, SiN is used as a deposit to be removed in _the cleaning process, that is, a growth film, and poly-Si is used as a film to be coated prior to the cleaning process. As described above, the embodiment of the present invention is not limited to this combination, and can be implemented by an appropriate combination of the etching gas, the deposit to be removed, and the coating film exemplified below.
[0039]
That is, (1) ClF _3, NF ₃ , HCl, F ₂ , HF, CF ₄ , C ₂ F _6, etc. can be used as the etching gas used for cleaning. The following deposits or growth films include SiN, (Si ₃ N ₄ ), SiO ₂ , WSi, AlN, GaN, InGaP, GaAs, InGaAlP, InGaN, InAlN, InAlP, BPSG, PSG, diamond, SiC, Al ₂ O. ₃ , ZrO ₂ , WO ₃ , BN, TiC, TiN, poly-Si, amorphous Si, single crystal Si, and the like. (3) As a film to be coated prior to the cleaning step, poly-Si, Amorphous Si, metal Al, SiO ₂ , graphite, diamond, W, Mo, Cu and the like can be used.
[0040]
Further, (4) as a substrate holder to be cleaned, quartz, carbon, SiC coated carbon, SiC, Al ₂ O ₃ , Si ₃ N _{4 and the} like can be targeted.
[0041]
Examples of suitable combinations of (1) etching gas, (2) deposit (growth film), (3) coating film, and (4) substrate holder will be described below.
[0042]
First, as a first preferred combination, the etching gas is ClF ₃ , NF ₃ , HCl, F ₂ or HF, the deposit is SiN, SiC or SiO ₂ , the coating film is poly-Si or amorphous Si, and the substrate holder is SiO. ₂ or Al ₂ O ₃ . In the case of this combination, the method described in FIGS. 6 and 8 (method using transmission) is suitable as a method for monitoring the progress of cleaning.
[0043]
As a second preferred combination, the etching gas is ClF ₃ , NF ₃ , HCl, F ₂ or HF, the deposit is SiN, SiC or SiO ₂ , the coating film is poly-Si or amorphous Si, and the substrate holder is Si-coated carbon. Or the combination of SiC is mentioned. In the case of this combination, the method described in FIGS. 7 and 9 (a method using radiation or reflection) is suitable as a method for monitoring the progress of cleaning.
[0044]
A third preferred combination includes a combination of ClF ₃ , NF ₃ , HCl, F ₂ or HF, a deposit of SiC, a coating film of SiN, and a substrate holder of SiO ₂ or Al ₂ O ₃ . . This combination is suitable for the method described in FIGS. 6 and 8 (method using transmission).
[0045]
As a fourth preferred combination, a combination of an etching gas of ClF ₃ , NF ₃ , HCl, F ₂ or HF, a deposit of SiC or SiN, a coating film of diamond, and a substrate holder of SiO ₂ or Al ₂ O ₃ is used. Can be mentioned. This combination is suitable for the method described in FIGS. 6 and 8 (method using transmission).
[0046]
As a fifth preferred combination, the etching gas is CF ₄ or C ₂ F ₆ , the deposit is SiN, SiC or SiO ₂ , the coating film is W, Mo or Cu, and the substrate holder is SiO ₂ or Al ₂ O ₃ . Combinations are listed. This combination is suitable for the method described in FIGS. 6 and 8 (method using transmission).
[0047]
【The invention's effect】
As described above, according to the present invention, deposits on the substrate holder can be cleaned in the shortest optimum time, and damage to the substrate holder can be reduced. In addition, damage to the heater can be reduced during cleaning. Thereby, the maintenance frequency of a substrate processing apparatus can be lowered | hung and productivity can be improved significantly.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing a configuration of a substrate processing apparatus according to the present invention.
FIG. 2 is a diagram showing in detail a positional relationship between a substrate holder and an enclosure.
FIG. 3 is a diagram showing in detail another positional relationship between the substrate holder and the enclosure.
FIG. 4 is a flowchart showing an operation procedure of the substrate processing apparatus when the cleaning method according to the present invention is applied.
FIG. 5 is a graph showing how the indication value of the radiation thermometer changes as the film on the substrate holder disappears as cleaning progresses.
FIG. 6 is a diagram for explaining another technique for optically detecting the disappearance of the film on the substrate holder.
FIG. 7 is a view for explaining still another technique for optically detecting disappearance of a film.
FIG. 8 is a diagram for explaining still another technique for optically detecting disappearance of a film.
FIG. 9 is a diagram for explaining still another technique for optically detecting disappearance of a film.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Processing chamber 3 Substrate holder 4 Heater 5 Enclosure 9 Means for supplying inert gas

Claims (3)

A method of cleaning deposits on a substrate holder made of SiC coated carbon, SiC, SiO ₂ or Al ₂ O ₃ on which a substrate to be processed is installed,
Prior to processing on the substrate to be processed, when the cleaning process is performed using a ClF ₃ gas, NF ₃ gas, HCl gas, F ₂ gas or HF gas at a predetermined position on the substrate holder, the processing target A cleaning method comprising coating with a film made of poly- Si or amorphous Si etched at a faster rate than a film made of SiN, SiC or SiO ₂ formed by processing on a substrate. 2. The cleaning method according to claim 1, wherein an optical characteristic of the substrate holder is monitored at the time of cleaning, and an end point of cleaning is set based on a detection result. In a substrate processing apparatus for performing a film forming process on a substrate to be processed,
A processing chamber;
A substrate holder provided in the processing chamber;
A heater provided below the substrate holder for heating the substrate holder;
An enclosure provided below the substrate holder and defining a space surrounding the heater;
Means for supplying gas into the space,
The substrate holder is a portion located below the substrate holder and outside the enclosure, and has a portion that overlaps with the enclosure when viewed from the side, and the substrate A passage is formed between the holder and the enclosure to communicate the space defined by the enclosure and the space outside the enclosure ,
The passage has a first portion and a second portion located closer to the space outside the enclosure than the first portion and below the first portion. A substrate processing apparatus.

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