JP3117059B2 - Cleaning method for silicon oxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a process for forming a film such as CVD, vacuum deposition, sputtering, thermal spraying, epitaxy, spin coating, dipping, whisker, and particle forming process. It relates to a method of easily removing and cleaning.

[0002]

2. Description of the Related Art Silicon oxide is used very widely, such as an impurity diffusion preventing film in a glass substrate, an insulating film of a thin film applied device such as an LSI, and a passivation film. As a method for forming the silicon oxide film, a sol-gel method using TEOS, fluoroteos, or the like, and a CVD method using a silicon-containing gas such as TEOS, fluoroteos, or SiH ₄ are known. However, when these films are formed, unnecessary films are formed not only on substrates such as glass and silicon wafers but also on the inner walls of the apparatus. The silicon oxide deposited on such a portion is generally cleaned with a buffered hydrofluoric acid aqueous solution, but this method has the following problems. It significantly erodes metals and quartz, including stainless steel, which is a reactor material. Reactor disassembly, cleaning, drying, assembling and much more work are required. Therefore, a gas cleaning method (gas cleaning) that does not have these problems is desired. Regarding the gas cleaning method, plasma cleaning using NF ₃ or C ₂ F ₆ is partially performed. However, since NF ₃ and C ₂ F ₆ are inert to silicon oxide by themselves, silicon oxide deposited outside the plasma region in the reactor cannot be removed, and a mechanism for generating plasma is provided. Of course, no device can do this.

[0003]

[Means for Solving the Problems] As a result of intensive studies, the present inventors have found that a bromine fluoride-based gas is effective as a cleaning material for silicon oxide, and furthermore, BrF ₃ ,
When each of BrF ₅ is a main component, the present inventors have found that use conditions and methods effective for cleaning are different from each other, leading to the present invention.

[0004] As for BrF ₃ and BrF ₅ , an agent for removing impurities from the inner surface of a resinous container (Japanese Patent Laid-Open No. 3-112632).
), A reactor having a gas inlet dedicated to bromine fluoride gas (JP-A-2-185977), and contaminants remaining in a reactor cleaned with bromine fluoride are removed by SiH _4.
(JP-A-2-190472). However, etching of silicon oxide with BrF ₃ and BrF ₅ is described in Japanese Patent Publication No. 60-12779 in a method of manufacturing a semiconductor device characterized by performing plasma etching and sputter etching.
There is no known method of cleaning the inside of a reactor without plasma or a method of generating plasma, and there is no known method of removing silicon oxide deposited outside a plasma atmosphere, and specific conditions and methods that can be used are also known. Absent. Plasmaless dry etching (J. App.
l. Phys. , 56 (10) (1984) 2939).
However, there is only a description that silicon oxide cannot be etched without plasma.

[0005] Each of bromine trifluoride its physical and chemical properties significantly differ _{BrF, BrF 3, BrF 5,} BrF 7
The supply conditions and the silicon oxide cleaning conditions differ depending on which one is contained as the main component.

Particularly, the supply conditions of BrF ₃ and BrF ₅ are as follows:
Since rF ₃ is a liquefied gas having a boiling point of 127 ° C. and BrF ₅ is a liquefied gas having a temperature of 41 ° C., it is theoretically possible to supply them without any problem if the cylinders and pipes filled with the gas are heated above this temperature. Is the cylinder temperature, the pipe connecting the cylinder and the gas flow controller, the gas flow controller, and the pipe connecting the gas flow controller and the reactor have a temperature difference. Specifically, about -5 ° C from the side closer to the cylinder It is preferable to have a temperature gradient of In addition, stainless steel and Hastelloy are used as materials for gas contact parts of cylinders, pipes, flow controllers, and valves, but the corrosion resistance of BrF ₃ and BrF ₅ with these metals was examined. , 260 ° C
It was found that it was necessary to keep the gas at the following temperature and distribute the gas. That is, when the pipe is heated to a temperature higher than these temperatures and the gas is allowed to flow, stainless steel and Hastelloy are corroded, causing serious damage to the system.

Next, cleaning conditions will be described. T
The etching rates of BrF ₃ and BrF ₅ on a silicon oxide film manufactured using EOS and oxygen were measured. Br
Stated case of F _3, was found to have the inflection point of the two positions in relation to the etching rate and temperature as shown in FIG. That is, the etching rate is 150 ° C.
From 250 ° C. to 250 ° C., and the etching rate rapidly increased at a temperature of 150 ° C. or less or at a temperature of 250 ° C. or more. Therefore, cleaning is 1
It must be carried out at a temperature of 50 ° C. or lower, or 250 ° C. or higher, in a temperature range of 0 to 150 ° C., or 250 to 90 ° C.
It is preferably carried out in a temperature range of 0 ° C.

As shown in FIG. 2, in the case of BrF ₅ , similarly to the case of BrF ₃ , the etching rate shows a remarkable increase from 180 ° C., and the etching rate shows a tendency to increase even at 40 ° C. or less. Therefore, cleaning is 40
It is necessary to carry out at a temperature of not higher than 180 ° C. or lower, preferably at a temperature of 0 to 40 ° C. or 180 to 900 ° C. Further, in consideration of damage to the device material, the faster the silicon oxide is etched, the better it is for cleaning. However, at the same time as the etching rate for silicon oxide is high, damage to the device material is also large. Further, silicon oxide has a different content of -OH groups and the like depending on the manufacturing method. Therefore, it is necessary to appropriately select the cleaning conditions depending on the manufacturing method and the reaction apparatus used.

[0009] Silicon oxide produced by thermal CVD is more difficult to clean than that produced by other methods.
It is common to use quartz as the reactor material. In such a case, the cleaning temperature is 600 ° C.
At this point, it is necessary to optimize the conditions for removing silicon oxide and maximize the selectivity of the reaction with quartz as much as possible.
The present inventors have conducted intensive studies and found that B used for cleaning
It has been found that quartz can be cleaned without damaging the quartz by controlling the gas partial pressure of rF ₃ and BrF ₅ .

That is, in the temperature range of 900 to 600 (° C.), cleaning is preferably performed in the range of the formulas (II) and (IV) when the temperature is lower than 600 ° C. Further, when the gas partial pressure is less than 0.1 Torr, a long time for cleaning is required, which is not preferable. If the temperature is higher than 900 (° C.), even if the partial pressures of BrF ₃ and BrF ₅ are smaller than 0.1 Torr, damage (devitrification) of quartz becomes severe, which is not appropriate.

When alumina or aluminum nitride is used as the material for the apparatus, it is not necessary to specify the pressure conditions. When stainless steel or Hastelloy is used, the place where they are used is changed to BrF ₃ is 215
° C or lower, and BrF ₅ must be 260 ° C or lower. Films and particles produced by plasma CVD or films and particles produced by the sol-gel method are easier to gasify and remove than those produced by thermal CVD, so they can be cleaned even at low temperatures,
A method of keeping the inside of the reactor at 150 ° C. or less for F ₃ and 40 ° C. or less for BrF ₅ , and introducing a liquid into the inside of the reactor for cleaning can be employed.

[0012] In some cases, it is difficult to introduce BrF ₃ into a reactor having a high boiling point and a relatively low temperature in a large amount for cleaning. In such a case, BrF ₅ can be used as BrF ₃ by heating it to 150 ° C. or higher before introducing it into the reactor, and dissociating and introducing a part of it into BrF ₃ + F ₂ .

Strictly speaking, the silicon oxide which is the object to be cleaned in the present invention may not have a composition of Si and O of 1: 2, and can also be applied to those containing F, Cl, B and P. . By using a gas containing bromine fluoride as described above, it is possible to easily clean an SiO ₂ film-forming apparatus, which has conventionally been difficult to perform gas cleaning.

[0014]

The present invention will be described below in detail with reference to examples. Examples 1 to 7, Comparative Examples 1 to 5 A stainless steel cylinder filled with bromine fluoride was a (° C), and a pipe connecting the cylinder and the mass flow controller was b.
(° C), the mass flow controller was heated to c (° C), the piping connecting the mass flow controller and the reactor was heated to d (° C), the pressure in the reactor was controlled to 100 Torr, and the flow state of the bromine fluoride gas was observed. did. Table 1 shows the results of observation by cutting the state of the inside of the pipe after distribution.

[0015]

[Table 1]

Examples 8 to 51 Comparative Examples 6 to 23 A quartz wafer (4 inches) on which a quartz plate (1 mm × 1 mm) is placed is placed in a thermal CVD apparatus made of quartz, and TEOS and the atmosphere are heated to 700 to 900 ° C. Introduced into the reactor
An iO ₂ film was grown to about 1 μm. Thereafter, bromine fluoride was introduced to clean the inside of the reactor and the oxide film on the wafer. Whether or not cleaning was possible was measured by using a stylus type surface shape measuring device to measure the level difference between the portion under the quartz plate placed on the wafer and the periphery of the oxide film thickness on the wafer. The results are shown in Table 2, Table 3,
The results are shown in Tables 4 and 5. A similar experiment was performed with silicon oxide containing phosphorus and boron manufactured using TEOS and oxygen, trimethyl phosphate, and trimethyl borate, but the same result was obtained.

[0017]

[Table 2]

[0018]

[Table 3]

[0019]

[Table 4]

[0020]

[Table 5]

COMPARATIVE EXAMPLE 24 A soda lime was filled into an exhaust gas treatment chemical filling tube having a diameter of 10 cm and a length of 1.3 m, the reaction tube was set at 25 ° C. with an external heater, N ₂ : 0.9 SLM, BrF ₅ : 0. .1 SLM
(10%) was fed to the reactor where the SiO ₂ had been deposited for 20 minutes. When the gas discharged from the reactor before entering the processing agent filling tube was analyzed by FT-IR, gas chromatography, and UV, Br ₂ , F ₂ , BrF, BrF ₃ , SiF
₄ was detected. Also collected and a portion of the outlet gas, was similar _{analysis, BrF 3, BrF, F 2} , SiF 4 but concentration was less than quantitative lower limit (1 ppm) Br ₂ is detected not handle Was.

EXAMPLE 52 Soda lime is filled in a 10 cm diameter, 1.3 m long exhaust gas treatment chemical filling tube, and activated carbon is filled and connected to a 25 A diameter, 30 cm length exhaust gas treatment chemical filling tower. Next, the reaction tube was set to 25 ° C. with an external heater, and N ₂ : 0.9 S
LM, BrF _5: 0.1SLM (10%) 20 min S
The reactor was fed with iO ₂ deposited. When the gas discharged from the reactor before entering the treatment chemical filling tube was analyzed by FT-IR, gas chromatography, and UV,
r ₂ , F ₂ , BrF, BrF ₃ , BrF ₅ and SiF ₄ were detected. In addition, a part of the outlet gas was collected and analyzed in the same manner. As a result, BrF ₅ , BrF ₃ , BrF, F ₂ , Si
The F ₄ and Br ₂ concentrations were below the lower limit of quantification (1 ppm).

Example 53 In the same manner as in Example 45, N ₂ : 0.9 SLM and BrF ₅ : 0.1 SLM were introduced into the inside of the reactor having SiO ₂ adhered thereon, and cleaning was performed. Next, the outlet gas was supplied to a scrubber filled with a lashing ring having a diameter of 4 inches and a height of 1 m, and washed with a 20% NaOH solution. As a result, the fluorine content of the exhaust gas was below the lower limit of quantification (1 ppm).

Example 54 A gas decomposition tank made of stainless steel was set in front of a reactor for forming a silicon oxide film, the decomposition tank was heated to 150 ° C., and a reactor (400 ° C., 10 Torr) on which a silicon oxide film was deposited was formed.
to _{r) N 2: 0.9SLM, BrF} 5: 0.1SLM was introduced 60 minutes. Thereafter, after purging with N ₂ , the inside of the reactor and the gas decomposition tank was observed. As a result, the silicon oxide film deposited inside the reactor was completely removed.
There was no corrosion inside the gas decomposition tank.

Example 55 A gas decomposition tank made of quartz was installed in a stage preceding a reactor for forming a silicon oxide film, and the decomposition tank was heated at 250 ° C., 300 ° C. and 500 ° C.
° C. was heated to the reactor (400 ° C. to SiO ₂ film is deposited,
10 Torr), N ₂ : 0.9 SLM, BrF ₅ : 0.
1 SLM was introduced for 60 minutes. Then, after purging with N ₂ , the inside of the reactor and the gas decomposition tank was observed. As a result, the SiO ₂ film deposited inside the reactor was completely removed. The gas decomposition tank did not devitrify.

Embodiments 56 and 57 A quartz wafer (4 inches) on which a quartz plate (1 mm × 1 mm) was placed was placed in a quartz thermal CVD apparatus, and silicon oxide was formed at 600 ° C. using SiH ₄ and N ₂ O. Filmed. Then _{BrF 5: 0.1SLM, N 2:} 0.9SLM, 10T
When the inside of the reactor was cleaned at 600 ° C. for 60 minutes at orr, unnecessary SiO ₂ deposited inside the reactor was removed.
Was completely removed. Also, instead of BrF ₅ , BrF
Similar results were obtained using ₃ .

Examples 58 and 59 Using TEOS and O ₂ , a SiO ₂ film was deposited to a thickness of about 1 μm on an electrode substrate (400 ° C.) using a parallel plate type plasma CVD apparatus. At that time, SiO around the electrode (≦ 400 ° C.)
₂ had been deposited. Next, the electrode substrate temperature was maintained at 400 ° C., and 13.56 MHz high-frequency power was applied to the electrodes to generate plasma. BrF ₅ was 0.1 SLM, the reactor pressure was 0.1 Torr, and the electrode substrate temperature was 400 ° C. For 20 minutes. As a result, both SiO ₂ on the electrode substrate and surrounding SiO ₂ could be completely removed. In addition, BrF ₅
The same result was obtained when BrF ₃ was used instead of

Examples 60 and 61 Using TEOS and O ₂ , a SiO ₂ film was deposited to a thickness of about 1 μm on an electrode substrate (400 ° C.) using a parallel plate type plasma CVD apparatus. At that time, SiO around the electrode (≦ 400 ° C.)
₂ had been deposited. Next, the electrode substrate temperature was maintained at 200 ° C., and a high frequency power of 13.56 MHz was applied to the electrodes to generate plasma. BrF ₅ was 0.1 SLM, the reactor pressure was 0.1 Torr, and the electrode substrate temperature was 400 ° C. For 20 minutes. As a result, both SiO ₂ on the electrode substrate and surrounding SiO ₂ could be completely removed. In addition, BrF ₅
The same result was obtained when BrF ₃ was used instead of

Embodiments 62 and 63 A quartz plate (1 mm × 1 mm) was placed in a quartz thermal CVD apparatus.
Place the placed quartz wafer (4 inch)
Introduce rotriethoxysilane and oxygen into the reactor at 120 ° C
Approximately 1000 A of silicon oxide film containing fluorine
Lengthened. After that, keep the temperature inside the reactor at 120 ° C
And BrF_FiveTo remove the oxide film inside the reactor and on the wafer.
Cleaned. Whether or not cleaning is required
The area under the quartz plate with the oxide film thickness on the wafer and its surroundings
Was measured with a stylus type surface profiler. The result
Oxidized in the reactor, supply pipe and exhaust pipe
Decomposition products of fluorotheos such as silicon can be completely removed.
I was Further, the gas is BrF _ThreeWas changed to
Gave the same result.

[0030] Example 64-68 the TEOS in a stainless steel vessel in the apparatus interior of granulating the silicon oxide by hydrolyzing silicon oxide to SiO ₂ particles and the reactor wall which remains not retrieved is deposited as a product. Liquid bromine fluoride was introduced into this container to clean the inside, and then bromine fluoride was drawn out from the drain attached to the bottom of the reactor, and the inside was observed. Table 6 shows the results.

[0031]

[Table 6]

[0032]

According to the method of the present invention, cleaning can be easily performed by reacting silicon oxide and bromine fluoride deposited on a CVD apparatus or the like under specific conditions.

[Brief description of the drawings]

FIG. 1 shows the relationship between the temperature by BrF ₃ and the etching rate.

FIG. 2 shows a relationship between a temperature by BrF ₅ and an etching rate.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI H01L 21/304 648 H01L 21/304 648L 34 (58) Field surveyed (Int.Cl. ⁷ , DB name) B01D 53/34 C23C 14/00-14/58 C23C 16/00-16/56 C23F 1/00-4/04 H01L 21/205 H01L 21/302

Claims (4)

(57) [Claims] 1. An apparatus for producing silicon oxide,
The silicon oxide deposited on the reactor and the jig is treated with BrF _{3 in} a temperature range of 600 to 900 ° C. in the general formula (I) 0.1 ≦ P ≦ −0.6T + 560 (I) [P: BrF ₃ partial pressure (Torr) , T: temperature (° C.)] and a reaction pressure of BrF ₃ . 2. An apparatus for producing silicon oxide,
The silicon oxide deposited on the reactor and the jig is treated with BrF _{3 in} a temperature range of 250 to 600 ° C. in a general formula (II) 0.1 ≦ P (II) [P: BrF ₃ partial pressure (Torr), T: temperature ( ° C)]. A method for cleaning silicon oxide, characterized in that the reaction is removed at a partial pressure of BrF ₃ indicated by: 3. An apparatus for producing silicon oxide,
The silicon oxide deposited on the reactor and the jig is converted to a general formula (III) 0.1 ≦ P ≦ −9.3T + 857 (III) by BrF _{5 in} a temperature range of 600 to 900 ° C. [P: BrF ₅ partial pressure (Torr) , T: temperature (° C.)] and a reaction pressure of BrF ₅ partial pressure. 4. An apparatus for producing silicon oxide,
The silicon oxide deposited on the reactor and jig is treated with BrF _{5 in} a temperature range of 180 to 600 ° C. in the general formula (IV) 0.1 ≦ P (IV) [P: BrF ₅ partial pressure (Torr), T: temperature ( the cleaning method of silicon oxide, which comprises reacting removed BrF ₅ partial pressure represented by ° C.)].