JP2020057670A - Active gas reaction amount evaluation method and evaluation device used therefor - Google Patents

Abstract

To provide a method capable of easily and inexpensively evaluating the amount of an active gas such as HF that is consumed by being adsorbed on a device material.SOLUTION: A method of the present invention uses a stainless steel chamber 5 into which a target gas can be introduced from a mass flow rate control device 4, arranges a test piece 7 made of a target material inside the chamber 5, and performs one of a gas sealing test and an actual flow rate test, and the gas sealing test is performed by filling the chamber 5 with a target gas into a sealed state and leaving the chamber for a predetermined time to measure the reduced amount of the pressure in the chamber 5, and the actual flow rate test is performed by obtaining the actual flow rate from the pressure rise per unit time in the chamber measured when a valve V5 on the downstream side of the chamber 5 is closed and the target gas is flown into the chamber 5 at a predetermined set flow rate by the gas mass flow rate control device 4.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for evaluating a reaction amount of an active gas with an apparatus constituent material in a process apparatus using an active gas such as hydrogen fluoride (hereinafter, referred to as HF) in a semiconductor manufacturing process, and an evaluation apparatus used for the method.
In this specification, “reaction” includes not only a chemical reaction but also adsorption and adhesion.

  An active gas such as HF gas is used in various processing steps, for example, an etching process of a silicon oxide film in a semiconductor manufacturing step. In such a processing step, it is necessary to make the processing speed uniform in order to make the product quality uniform. For this reason, the active gas flowing into the processing chamber is subjected to a precise mass flow rate using a mass flow controller or the like. Control is being performed.

However, active gases, particularly HF gases, are known to adsorb to and react with the surface of various metals. When the HF gas is consumed for adsorption or reaction on the metal constituting the inner wall of the processing chamber, even if the mass flow rate of the HF gas flowing into the processing chamber is precisely controlled, the mass of the HF gas used for the original processing is reduced. And the processing speed fluctuates (for example, Patent Document 1).
In particular, this problem is apparent because the weight of the equipment has been required to be able to be installed on the grating floor of a semiconductor manufacturing plant, and chambers made of aluminum, which is a lighter metal, have been used instead of stainless steel. It is becoming.

In order to prevent this problem, Patent Document 1 abolishes the surface oxidation treatment of Al on the inner surface of the Al chamber and prevents the HF from adhering to the inner surface of the Al chamber and the like. It is proposed that Ra be 6.4 μm or less.
In Patent Literature 1, as a method of evaluating the amount of HF adsorbed on a chamber material, a chamber is trial-produced with a candidate material and an HF sealing test, an actual flow rate test test, and the like are performed.
In the HF sealing test, the inside of the chamber (the processing chamber 41) is filled with HF gas to be in a sealed state (initial pressure: about 5 Torr), left as it is for several minutes, and the amount of decrease in pressure is measured to determine the amount of HF adsorption. (Experiment 1).
In the actual flow rate test, when the HF gas is supplied to the chamber at a predetermined set flow rate, the actual supply flow rate (actually measured flow rate) of the HF gas measured in the chamber is checked, and the difference between the set flow rate and the measured flow rate is determined. The amount of HF adsorption is determined (Experiment 3).

Patent No. 4805948

  It should be noted that Patent Document 1 points out a problem such as the adsorption of HF gas to the metal material forming the inner wall of the processing chamber as described above, and also presents a method for evaluating the amount of adsorption, etc. Literature. However, in the evaluation method of Patent Document 1, it is necessary to make a chamber with the material to be evaluated and incorporate it into an actual machine. In particular, when the number of target materials increases, it is necessary to prototype many chambers. There is a disadvantage that this is the case. Also, the specific method of the HF actual flow rate test is unknown.

  An object of the present invention is to solve the above problems, clarify the evaluation method, and evaluate the amount of an active gas such as HF gas that is consumed by being adsorbed on a metal material or the like constituting a device in a simple and easy manner. An object is to provide a method that can be performed at low cost.

The method of the present invention is a method for evaluating the reaction amount of a target gas with a target material, and using a stainless steel chamber capable of introducing a target gas from a mass flow controller, the inside of the chamber is A method of arranging a test piece made of a target material and performing at least one of a gas sealing test and an actual flow rate test,
The gas sealing test is to fill the inside of the chamber with a target gas to make it a hermetically sealed state, leave it for a predetermined time, and measure the decrease in pressure inside the chamber,
The actual flow rate test is performed by closing a valve on the downstream side of the chamber and measuring a pressure per unit time in the chamber measured when the gas of interest is introduced into the chamber at a predetermined set flow rate by the gas mass flow controller. The actual flow rate is obtained from the rise.

  Preferably, a configuration can be adopted in which the target gas is HF gas.

  More preferably, in addition to the sealing test or the actual flow rate test for the target gas, the sealing test or the actual flow rate test for an inert gas is further performed as a comparative test. . This is preferable because the validity of the test result can be verified.

Preferably, a configuration can be employed in which the inert gas is N ₂ gas.

  More preferably, a configuration may be adopted in which the sealing test or the actual flow rate test is further performed as a background test without placing a test piece in the chamber. This is preferable because the validity of the test result can be verified.

  Preferably, a configuration in which the chamber is purged with a gas used in each test immediately before each sealing test and each actual flow rate test can be adopted.

  The evaluation device of the present invention is an evaluation device used in the method, including a stainless steel chamber in which a test piece can be placed, and a mass flow controller for supplying gas to the chamber, and the active gas sealing device. A stop test and the actual flow rate test are possible.

  According to the method of the present invention, a gas sealing test or an actual flow rate test is performed using a stainless steel (hereinafter referred to as SUS) chamber and a test piece of the target material. It is not necessary to manufacture and incorporate it in an actual machine, and the amount of HF consumed by being absorbed into a target metal material or the like can be evaluated simply and at low cost.

It is a block diagram showing an evaluation device of an embodiment of the present invention. It is the table | surface and graph which show the result of the sealing test of embodiment of this invention, (a) is a background test, (b) is a test piece A, (c) is a graph which shows each result in the test piece B. And (d) is a table summarizing the results. It is a table | surface which shows the result of the actual flow rate test of embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram illustrating an evaluation device according to an embodiment of the present invention.
As shown in FIG. 1, the evaluation device includes an N ₂ supply source 1, an HF supply source (HF tank) 2, a gas supply system 3, a gas mass flow controller (FCS) 4, a chamber 5, And an exhaust system 6.

The N ₂ supply source 1 is a line for supplying high-purity nitrogen (N ₂ ) volatilized from commercially available bottled liquid nitrogen.
The HF supply source 2 is a tank filled with HF gas obtained by heating and evaporating commercially available liquid hydrogen fluoride (the boiling point at 1 atm is 19.4 ° C.) to 30 ° C.
The gas supply system 3 is connected to the N ₂ supply source 1 and the HF supply source 2 and has some open / close valves V1 to V3 on the way, and is a line for selectively supplying gas from these supply sources. is there.
The gas mass flow controller 4 is provided downstream thereof and controls the flow rates of these gases, and uses a model FCS-P made by Fujikin. This FCS is calibrated for N ₂ control, also used to control the HF, that case was calculated HF flow rate multiplied by a predetermined coefficient. As the FCS, a test sample in which HF gas flows at 295 sccm at a flow rate setting of 100% was used.
The chamber 5 is connected downstream thereof, is made of stainless steel (SUS316L-EP), and has a capacity of 5L. The inner surface is subjected to an electrolytic polishing treatment, so that the reaction with the HF gas and the adsorption of the HF gas are extremely unlikely to occur. In the chamber 5, a test piece 7 described later can be arranged, and a thermometer T and a pressure gauge P are provided so that the internal temperature and pressure can be monitored. The internal temperature is set to 25 ° C. An upstream valve V4 and a downstream valve V5 are also provided upstream and downstream of the chamber 5, respectively.
The exhaust system 6 is a line that is connected downstream of the exhaust system and includes an exhaust pump (not shown) and exhausts gas in the chamber 5.

  The temperature of the HF tank 2 is set at 30 ° C., the temperature of the gas supply system 3 is set at 40 ° C., and the temperature of the gas mass flow controller 4 is set at 45 ° C., so that the temperature increases as going downstream. This prevents the HF gas from cooling down and liquefied during the supply.

The test piece 7 used for this evaluation is two kinds of aluminum pieces (test pieces A and B), for example, an aluminum alloy such as A5052 material. Specimen A had its surface oxidized under a certain condition (for example, anodized alumite treatment using oxalic acid), and specimen B had another surface (for example, anodized alumite treatment using sulfuric acid). ). Each type of test piece is composed of two pieces so as to enter the chamber 5, and has a total surface area of 858 cm ² .
The evaluation was performed under the following three conditions.
・ When the test piece is not put in the chamber 5 (background)
When the test piece A is placed in the chamber 5 (condition A)
When the test piece B is placed in the chamber 5 (condition B)

Next, using the evaluation apparatus and the test piece prepared in this way, the above-mentioned “background”, each condition of condition A and condition B were evaluated in the following procedure.
(1) Inspection of Leakage in Chamber A test piece is put into the chamber 5 (not in the case of “background”), and the chamber 5 is evacuated to high vacuum with the upstream valve V4 closed, and then the downstream valve V5 Was also closed and allowed to stand, and the pressure inside the chamber was monitored with a pressure gauge P to confirm that there was no pressure increase due to leakage.
(2) by opening the valve V1 and V3 cycle purge gas supply system 3 of the N ₂ by closing the valve V2 is introduced only N ₂ gas, an exhaust system by opening the valve V4, V5 upstream and downstream of the chamber 5 6 exhausted the inside of the chamber 5. The N ₂ flow gas mass flow controller 4 is set to 257Sccm, after N ₂ purged in the chamber to a pressure 100Torr by adjusting the opening of the chamber downstream valve V5, the N ₂ in the high vacuum pressure 1Torr Exclusion and purging with N ₂ at a pressure of 100 Torr were repeated 10 times.
(3) Temperature Setting of Gas Mass Flow Controller The temperature of the gas mass flow controller 4 was set to 45 ° C. as described above.
(4) N ₂ purge The N ₂ flow rate was set to 257 sccm by the gas mass flow controller 4, the pressure in the chamber 5 was set to 100 Torr, and N ₂ purge was performed for 1 hour.
(5) N ₂ gas sealing test The pressure in the chamber 5 was set to 20 Torr (the temperature was set to 25 ° C.), and the chamber 5 was filled with N ₂ at a pressure of 20 Torr. The side valve V5 was closed and left for 2 hours, and the pressure inside the chamber was monitored with a pressure gauge P.
(6) N ₂ purge The N ₂ flow rate was set to 257 sccm by the gas mass flow controller 4 and the inside of the chamber 5 was purged with N ₂ for 5 minutes.
(7) _{N 2} gas actual flow rate test (a build-up method)
Closing the downstream valve V5 of the chamber 5, the setting of the gas mass flow controller 4 to 100% (N ₂ flow 257Sccm) allowed to flow into the N ₂ to the chamber 5, to monitor the increase in pressure at the pressure gauge P. N ₂ (the unit mol) of the amount of change Δn and pressure increase ΔP of the chamber (in ratio 1 atm) and the time taken for it Delta] t (in minutes) (the unit cc) volume V of the chamber 5 and 5 From the absolute temperature T (unit: K), the actual flow rate Q (unit: sccm) was obtained by the following equation.
Q = (Δn / Δt) · V ₀ = ΔP · V · 273 / (T · Δt)
The variation Δn of N _2, i.e., increase ΔP of pressure, volume V of the chamber 5, the value calculated from the absolute temperature T of the chamber 5, is divided by inflow time, the flow rate Q.
This measurement was repeated five times without releasing the inside of the chamber 5 to the atmospheric pressure.
(8) HF gas supply, HF purge The valves V2 and V3 of the gas supply system 3 are opened, the valve V1 is closed, only the HF gas is introduced, and the valves V4 and V5 on the upstream and downstream sides of the chamber 5 are opened, and the exhaust system is opened. 6 exhausted the inside of the chamber 5.
The HF flow rate was set to 300 sccm by the gas mass flow controller 4, and the inside of the chamber 5 was purged with HF for 5 minutes.
(9) HF gas sealing test The pressure in the chamber 5 is set to 20 Torr (temperature setting is 25 ° C.), the chamber 5 is filled with HF at a pressure of 20 Torr, and the chamber upstream valve V4 and the downstream valve are set. V5 was closed and left for 2 hours, and the pressure inside the chamber was monitored with a pressure gauge P.
(10) HF Purging The HF flow rate was set to 300 sccm by the gas mass flow controller 4 and the inside of the chamber 5 was purged with HF for 5 minutes.
(11) HF gas actual flow rate test (build-up method)
The downstream valve V5 of the chamber 5 was closed, the setting of the gas mass flow controller 4 was set to 100% (HF flow rate 300 sccm), HF was allowed to flow into the chamber 5, and the pressure increase was monitored by the pressure gauge P. HF change amount Δn (unit is mol), pressure rise ΔP (unit is relative to 1 atm), time required for it Δt (unit is minute), volume V in chamber 5 (unit is cc), and From the absolute temperature T (unit: K), the actual flow rate Q (unit: sccm) was obtained by the following equation.
Q = (Δn / Δt) · V ₀ = ΔP · V · 273 / (T · Δt)
The flow rate Q is a value obtained by dividing the amount of change Δn of HF, that is, the value calculated from the pressure rise ΔP, the volume V in the chamber 5 and the absolute temperature T of the chamber 5 by the inflow time.
This measurement was repeated five times without releasing the inside of the chamber 5 to the atmospheric pressure.

The results of the N ₂ gas sealing test and HF gas sealing test shown in FIG. 2 (a) ~ (d) .
First, when the test piece is not put in the chamber 5 (background), the pressure in the chamber 5 decreases even if the chamber 5 is left at 20 Torr for 2 hours in the N ₂ gas sealing test and the HF gas sealing test. Was hardly observed at 0.11 Torr at the maximum (Fig. 2 (a)). This is because the amount of N ₂ gas and HF gas consumed and reacted or adsorbed on the inner wall (electro-polished SUS316L-EP) of the chamber 5 is extremely small, and as a gas during the sealing test, presumably because the amount of existing N ₂ and HF were hardly changed.

On the other hand, when the test piece A was put in the chamber 5 (condition A) and when the test piece B was put in the chamber 5 (condition B), in the N ₂ gas sealing test, the chamber 5 was left at a pressure of 20 Torr for 2 hours. However, the pressure in the chamber 5 was hardly reduced to 0.02 Torr at the maximum, but in the HF sealing test, a remarkable pressure drop of 18.1 Torr was observed under the condition A and 1.89 Torr under the condition B. A pressure drop was observed (FIGS. 2B and 2C).
This is because, during the sealing test, the amount of the N ₂ gas consumed and reacted or adsorbed on the surfaces of the test pieces A and B was extremely small, while the amount of the HF gas was reduced on the surfaces of the test pieces A and B. It is considered that the amount consumed by reaction or adhesion was large, and as a result, the amount of HF present as a gas in the chamber 5 was reduced.

FIG. 3 shows the results of the N ₂ gas actual flow rate test and the HF gas actual flow rate test (build-up method).
First, when the test piece was not put into the chamber 5 (background), the deviation of the measured flow rate value from the set flow rate value in the N ₂ gas actual flow rate test and the HF gas actual flow rate test was small at all five times (N _{(The difference is} 0.02% maximum in the actual gas flow test and 0.03% maximum in the actual HF gas flow test).
This is because, of the N ₂ and HF gases supplied from the mass flow controller, the amount consumed by reacting or adsorbing on the inner wall of the chamber 5 (electropolished SUS316L-EP) is extremely small. Therefore, it is considered that almost all of N ₂ and HF were present as gases in the chamber 5.

On the other hand, when the test piece A is put in the chamber 5 (condition A) and when the test piece B is put in the chamber 5 (condition B), in the actual N ₂ gas flow rate test, the deviation of the measured flow rate from the set flow rate is different. Was as small as 0.07% at maximum, but in the actual HF gas flow test, a very large deviation of 12.56% was observed at the maximum on the negative side at 48.65% under condition A, and a maximum deviation of 0.77% at the negative side under condition B. Was done.
This is because, among the N ₂ and HF gases supplied from the mass flow controller, the amount of N ₂ gas consumed by reacting or adsorbing on the surfaces of the test pieces A and B was extremely small. It is thought that while the entire amount was present as a gas in the chamber 5, the HF gas was consumed by reacting or adhering to the surfaces of the test pieces A and B, and as a result, the amount of HF present as a gas in the chamber 5 was reduced. Can be
In addition, under the condition A of the actual HF gas actual flow rate test, an extremely large deviation of 48.65% was observed on the minus side in the first measurement among the five repeated measurements, but the deviation width decreased as the number of times was increased. did. This is probably due to reaction or adhesion during the first measurement and HF remaining on the surface of the test piece A, and hindering the reaction and adsorption of new HF during the second and subsequent measurements.

Based on the above results, the following can be said when the quality as the evaluation method of the present application is examined.
(1) Consistency between test results in HF The amount of pressure drop in the sealing test with HF gas is almost zero when the test piece is not put in the chamber 5 (background), and the test piece is placed in the chamber 5. When B was inserted (condition B), when the test piece A was inserted into the chamber (condition A), the order became larger.
The amount of decrease in the actual flow rate in the actual flow rate test using HF gas was almost zero in the background, and increased in the order of condition B and condition A.
Therefore, both test results are consistent and both test results are considered valid.
In accordance with the verification N ₂ gas comparison tests with (2) N ₂ gas, the test piece A, regardless of the type of B, the actual flow reduction in pressure drop and actual flow test in the sealing test it was observed. Therefore, it is considered that the result of (1) appropriately reflects the reaction or adsorption to the test pieces A and B, which is a phenomenon peculiar to the active gas HF.
(3) In the background test not put specimen verification chamber 5 by the background test, the actual flow reduction in pressure drop or actual flow tests in sealing tested with N ₂ and HF was observed. Therefore, it is considered that the surface of the chamber 5 does not disturb the test.
(4) Cost and easiness of evaluation Since a gas sealing test and an actual flow rate test were performed by using a SUS chamber and placing a test piece of the target material, a chamber was manufactured using the target material and incorporated into an actual machine. It was not necessary, and the amount of HF consumed by being adsorbed on the target metal material or the like could be simply and inexpensively evaluated.
As described above, the test method of the present invention is useful as a method for evaluating the reaction amount of an active gas such as HF.

  Although both the sealing test and the actual flow rate test are performed for each test piece and each gas in the above embodiment, only one of them may be performed in the evaluation method of the present invention. However, it is desirable to perform both because the validity of the measurement results can be verified.

  In the sealing test of the above embodiment, the initial pressure was 20 Torr and the measurement time was 2 hours. In the actual flow test, the flow rate of the mass flow controller was measured five times at 100%. Is not limited to these, and can be appropriately changed according to the use conditions of the material to be evaluated.

The comparison tests and in N ₂ is an inert gas was performed in the above embodiment, the background test not put specimen chamber 5, but not necessarily in the evaluation method of the present invention, the measurement results Relevance It is desirable to do so because it can be verified.

  Further, the purge immediately before each measurement performed in the above embodiment is not essential in the method of the present invention, but is preferably performed to remove impurities that affect the measurement accuracy. The purge time, gas flow rate, number of times, and the like can also be set as appropriate.

Further, in the comparative test performed in the above embodiment, N ₂ was used as the inert gas, but Ar, He, Ne, or the like may be used in the evaluation method of the present invention.

1: _{N 2} supply source 2: HF source (HF tanks)
3: Gas supply system 4: Gas mass flow controller 5: Chamber 6: Exhaust system 7: Test piece P: Pressure gauge T: Thermometer V1 to V5: Valve

Claims (7)

A method for evaluating a reaction amount of a target gas with a target material, comprising using a stainless steel chamber into which a target gas can be introduced from a mass flow controller, and forming a test piece made of the target material inside the chamber. And performing at least one of a gas sealing test and an actual flow rate test.
The gas sealing test is to fill the inside of the chamber with a target gas to make it a hermetically sealed state, leave it for a predetermined time, and measure the decrease in pressure inside the chamber,
The actual flow rate test is performed by closing a valve on the downstream side of the chamber and measuring a pressure per unit time in the chamber measured when the gas of interest is introduced into the chamber at a predetermined set flow rate by the gas mass flow controller. A method that determines the actual flow from the rise.   The method of claim 1, wherein the gas of interest is HF gas.   3. The method according to claim 1 or 2, wherein in addition to the sealing test or the actual flow test for the gas of interest, the sealing test or the actual flow test for an inert gas is further performed as a comparison test. . It said inert gas is N ₂ gas, The method of claim 3.   The method according to any one of claims 1 to 4, wherein the sealing test or the actual flow rate test is further performed as a background test without placing a test piece in the chamber.   The method according to any one of claims 1 to 5, wherein the chamber is purged with a gas used in each test immediately before each of the sealing tests and each of the actual flow rate tests. The evaluation device used in the method according to claim 1, comprising a stainless steel chamber in which a test piece can be placed, and a mass flow controller for supplying gas to the chamber, wherein the active gas sealing test; An evaluation device, wherein the actual flow rate test is possible.

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