JPH04311036A - Insulating film formation method - Google Patents

Abstract

PURPOSE:To form the title insulating film at the truly required gas flow rate by a method wherein the stop valves on the flowing in and out sides of mass flow controllers are closed to calculate the corrected flow rate from the zero shift amount so that the set up signal corresponding to the flow rate added to the true flow rate may be transmitted to the mass flow controllers. CONSTITUTION:The stop valves before and after respective mass flow controllers 11, 12 are closed to boost the set up control voltage to the full scale. At this time, the differential pressure across the mass flow controllers 11, 12 is eliminated to indicate zero shifting amount, next, this zero shift amount is led in a programmable controller 100 to compute the arithmetical mean value of the sampling values. Finally, this arithmetical mean value is stored in a higher level controller 101 so that the total amount of required flow rate and this stored value may be set up in the mass controllers 11, 12 while displaying the indicated flow rate value with the stored value substracted therefrom to the operators in front of the high level controller 101.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to an insulating film forming process in the manufacturing process of DRAM by microfabrication of semiconductor integrated circuits, especially LSI, etc.
More specifically, a magnetic field that satisfies the electron cyclotron resonance conditions with the introduced microwave is formed, and the flow rate is controlled by a mass flow controller equipped with stop valves on the inflow and outflow sides, so that the introduced plasma generation gas is directed into the magnetic field. A plasma generation chamber is provided with a microwave introduction window and a plasma extraction port on both end faces, respectively, and generates plasma under the resonance conditions of the microwave electric field and the microwave electric field; A reaction chamber into which a reaction gas whose flow rate is controlled by a mass flow controller each equipped with a stop valve; and a high frequency power source that applies an RF bias to the substrate to be processed are provided. An ECR plasma processing apparatus is used in which a thin film is formed on the surface of a substrate to be processed while moving reaction gas into a reaction chamber through a plasma extraction port and decomposing the reaction gas. .

0002

2. Description of the Related Art First, the structure of this type of ECR plasma processing apparatus and a conventional method of forming an insulating film will be explained with reference to FIG.

The device includes a microwave power source 3 that generates microwaves, a waveguide 4 made of a hollow conductor that constitutes a microwave transmission path, and a microwave introduction window 2 formed in a cylindrical shape on each end face. A plasma generation chamber 1 is equipped with a plasma generation chamber 1 and a plasma extraction port 6, and an electron cyclotron resonance (Electron
Cyclotron Resonance, hereafter E
A solenoid 5 forms a magnetic field region that satisfies conditions, a reaction chamber 7 communicates with the plasma generation chamber 1 through a plasma extraction port 6, and a substrate to be processed (hereinafter also referred to as a wafer) 8 disposed in the reaction chamber 7. The main components are a substrate table 9 on which the substrate is placed, and a high frequency power source (hereinafter also referred to as an RF electrode) 10 that applies an RF bias to the substrate 8 via the substrate table 9.

[0004] With the ECR plasma processing apparatus configured as described above, an insulating film of, for example, Si is formed on the surface of the substrate 8.
When forming an O film, after evacuating the inside of the plasma generation chamber 1 and the reaction chamber 7 to a high vacuum, the current flowing through the solenoid 5 is adjusted and the ECR is placed near the microwave introduction window 2 in the plasma generation chamber 1. After forming a magnetic field region and introducing microwaves from the microwave power supply 3 into the plasma generation chamber 1 through the microwave introduction window 2, N2O or O2 gas whose flow rate is controlled to a predetermined value by the mass flow controller 11 is used to generate plasma. SiH4, Si2 H6 or (C
2 H5 O) 4 Si gas is sent into the reaction chamber 7 as a reaction gas. N sent into plasma generation chamber 1
2 O or O2 gas efficiently absorbs microwave power in the ECR magnetic field region, becomes plasma, moves into the reaction chamber 7 along the lines of magnetic force of the divergent magnetic field formed by the solenoid 5, and forms a circle inside the reaction chamber 7. The reaction gas blown out from the annular gas nozzle 14 is decomposed and activated, and Si is deposited on the surface of the substrate 8.
Form an O film. At this time, the high frequency power supply 10 is attached to the board 8.
RF bias is applied from O+ in the plasma.
is accelerated, the film is densified by ion bombardment, or the film quality at the stepped portion is improved by the sputtering action of O+.
Sputtering and film formation proceed simultaneously to flatten the film in the wiring area including the recesses between the wirings.

[0005]

[Problem to be solved by the invention] Currently, SiO film is
It is known that when a film is formed using gas and SiH4 gas, the film characteristics greatly depend on the flow rate ratio of O2 and SiH4 in the case of film formation by ECR plasma processing. FIG. 2 shows the relationship between the flow rate ratio (SiH4/O2) and the etch rate, which is an index of film properties. As seen in the figure, when the flow rate ratio is 0.9 or more, the etch rate shows a small, almost constant value, and the film maintains sufficient density, whereas when the flow rate ratio is 0.9 or less, the etch rate decreases. The temperature rises rapidly, the film becomes rough, and properties such as insulation deteriorate. On the other hand, even in the flow rate ratio range where the etch rate is small, if the flow rate ratio is too large, the formed SiO film becomes a Si-rich film, making it difficult to etch with hydrofluoric acid, which is normally used as an etching solvent. Because this is necessary, it is not preferable in the etching process after film formation (the figure shows the etch rate with fluoronitric acid in order to see the change in film quality over a wide range of flow rate ratios). For this reason, in film formation using an ECR plasma processing apparatus, there is a problem in that the area width that can be used as a flow rate ratio is extremely small. Moreover, in order to maintain the high film-forming efficiency, which is a feature of the ECR plasma CVD apparatus, in terms of the absolute value of the flow rate, the flow rates of O2 gas and SiH4 gas are each reduced to about 20 SCCM, and the gas pressure inside the apparatus is kept low. Therefore, the flow rate is 0.2SCCM
Even a deviation would lead to a flow rate error of 1%, which was the biggest source of instability in maintaining process stability.

For reference, FIG. 2 shows the characteristics of a SiO film produced by thermal CVD. Thermal CVD method uses O2
A mixed gas of SiH4 and SiH4 is introduced to the heated substrate surface, and the SiH4 is decomposed on the substrate surface and reacts with O2.
A SiO film is deposited on the surface of the substrate. The etch rate is constant regardless of the flow rate ratio, and in this method the EC
Although microfabrication such as the R process CVD method is difficult, a highly dense SiO film is always formed, so controlling the flow rate ratio does not require very high accuracy.

By the way, a flow rate control means called a mass flow controller is widely used to control the flow rate of O2 gas, SiH4 gas, etc. This flow rate control means includes a detection unit that detects the flow rate, a display unit that displays the detected flow rate, and a control valve that is a flow rate adjustment unit, and allows the flow rate of the pipe through which the gas passes to be set from the outside. Control signal value (
It has a function to control the flow rate value corresponding to the voltage (usually 0 to 5V). The accuracy of the set flow rate is ±1 of the full scale flow rate.
%, and since the absolute value of this error is constant regardless of the set flow rate, the general specification is that it cannot be set in the range of 0 to 5% of the full scale flow rate.

In addition to the above-mentioned setting accuracy, this mass flow controller has a practical problem that even when using the same mass flow controller, the setting time may be different from yesterday.
There was a problem with temporal reproducibility, where the actual flow rate differed by about 0.5% of the full-scale flow rate even if the set control voltage value was different if the time differed from today to the day.

An object of the present invention is to control plasma generation when forming an insulating film using an ECR plasma processing apparatus in which the flow rates of plasma generation gas and reaction gas are controlled using the mass flow controller that is currently widely used. An object of the present invention is to provide an insulating film forming method in which both the flow rates of gas and reaction gas are controlled with high precision.

0010

[Means for Solving the Problems] In order to solve the above problems, in the present invention, a magnetic field is formed that satisfies the electron cyclotron resonance conditions with the introduced microwave, and stop valves are provided on the inflow and outflow sides. A plasma having a microwave introduction window and a plasma extraction port on each end face, in which the flow rate is controlled by a mass flow controller and the introduced plasma generating gas is turned into plasma under resonance conditions of the magnetic field and the microwave electric field. A generation chamber; A reaction chamber in which a substrate to be processed is arranged and a reaction gas whose flow rate is controlled by a mass flow controller equipped with stop valves on the inflow and outflow sides; An RF bias is applied to the substrate to be processed; ECR equipped with a high frequency power supply to apply;
As an insulating film forming method when forming an insulating film on a substrate to be processed using a plasma processing apparatus, before forming an insulating film, close the stop valves on the inflow and outflow sides of each mass flow controller, and A method of forming an insulating film is used in which a corrected flow rate is calculated from the displayed zero shift amount, and the corrected flow rate is added to the true flow rate of each of the plasma generation gas and reaction gas used for forming the insulating film, and the flow rate is set in the mass flow controller. shall be taken as a thing.

[0011] In this case, the correction flow rate added to the true flow rate used for forming the insulating film is calculated by sampling the zero shift amount displayed on the mass flow controller at minute time intervals after a certain period of time after the inflow and outflow side stop valves of the mass flow controller are closed. It is best to obtain it as an arithmetic average value of sampled values.

[0012] Also, when the sampling value exceeds the allowable error for the full scale flow rate of the mass flow controller during sampling of the zero shift amount, an abnormality is displayed;
In addition, it is preferable to use an insulating film forming method that stops the progress of the step toward forming the insulating film.

[0013]

[Operation] First, the relationship between the set flow rate and the actual flow rate when the zero shift amount is not corrected will be explained using FIG. Assuming that there is no setting error in the mass flow controller,
When a setting control signal corresponding to the flow rate Q0 is given to the mass flow controller, the gas flow rate passing through the pipe is equal to the set flow rate and becomes Q0. However, if there is a setting error in the mass flow controller, the absolute value of this error is constant regardless of the magnitude of the set flow rate, and the smaller the set flow rate, the larger the relative error becomes. For this reason, a mass flow controller with a full scale flow rate (FS) close to the actual flow rate was used. However, the full-scale flow rate of a mass flow controller varies stepwise depending on the size of the mass flow controller, and if the actual flow rate slightly exceeds the full-scale flow rate, the next full-scale flow rate must be used, resulting in setting errors. becomes relatively large. However, as in the present invention, prior to forming the insulating film, the stop valves on the inlet and outlet sides of each of the mass flow controllers are closed, the corrected flow rates are determined from the zero shift amount displayed on each mass flow controller, and the corrected flow rates are By giving the mass flow controller a setting control signal corresponding to the true flow rate of each of the plasma generation gas and reaction gas used for forming the insulating film, the truly necessary The insulating film can be formed at a gas flow rate of

[0014] Then, when this corrected flow rate is determined as the arithmetic average value of a plurality of sampled values of the zero shift amount displayed on the mass flow controller display at minute time intervals after a certain period of time after the inflow and outflow side stop valves of the mass flow controller are closed, Since the zero shift amount displayed on the display section of the mass flow controller is sampled after the time when the differential pressure across the mass flow controller substantially disappears after the valve is closed, the corrected flow rate can be determined digitally and with high accuracy.

Furthermore, since the corrected flow rate is obtained by sampling the zero shift amount, if there is an abnormality in the stop valve or an abnormality in the mass flow controller, the sampling value may differ from the full scale flow rate of the mass flow controller during sampling of the zero shift amount. If the tolerance is exceeded, it can be easily displayed as an abnormality. Moreover, it becomes possible to easily stop the operation of the apparatus for forming an insulating film by using the display signal at the time of this abnormality display, and it is possible to prevent unnecessary operation.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the overall configuration of an ECR plasma processing apparatus in which the gas flow rate is controlled by the method of the present invention. In the figure, the same members as in FIG. 4 are given the same reference numerals.

[0017] In addition to the main body of the apparatus shown in FIG.
The carrier cassette 23 is taken out from the carrier cassette 23 in the atmosphere by the atmosphere transfer robot 22 constituting the atmosphere transfer section, using a transfer mechanism consisting of a rotary arm 22a that can rotate 360 degrees and a telescoping arm 22b that can extend and contract. A loading wafer tray 20a on which unprocessed wafers are placed and an unloading wafer tray 20b on which processed wafers are placed are housed.
a second load-lock chamber 16 incorporating a vacuum transfer robot 17 that transfers wafers between the first load-lock chamber 19 and the reaction chamber 7 in vacuum;
It is equipped with The inside of the second load lock chamber 16 is always maintained at a high vacuum, and the inside of the first load lock chamber 19 is opened to the atmosphere by opening the gate valve 21 every time a wafer is transferred to the atmosphere side, and the transfer is completed. The gate valve is opened and the vacuum is maintained again, and the wafers in the chamber are kept in a vacuum until they are moved to the next process. During film formation, the gate valve 18 is opened and the unprocessed wafer on the loading wafer tray 20a is taken into the second load lock chamber 16 by the vacuum transfer robot 17, and then the gate valve 18 is closed, and then the gate valve 15 is opened. The gate valve 15 is opened, the unprocessed wafer is carried into the reaction chamber 7 and placed on the substrate stage 9, and the gate valve 15 is closed.

The above-mentioned transport system automatically takes out wafers one by one from the supply side carrier cassette of the atmospheric transport section, sends them to the reaction chamber, and after processing, stores the processed wafers in the storage side cassette in the reverse order. It takes about 2 minutes for the wafer to enter the reaction chamber 7. The operation of the apparatus from the start of automatic operation of the apparatus for film formation to the gas flow rate setting will be described below.

Immediately after automatic operation starts, if the stop valves at the front and rear of each mass flow controller 11 and 12 are closed at the same time as conveyance starts, and the set control voltage is set to full scale, the differential pressure across the mass flow controller will increase in about 30 seconds. disappears, and the mass flow controllers 11 and 12 begin to display their respective zero shift amounts. This zero shift amount is input at approximately 0.2 second intervals with an accuracy of 1/4000 using a ±5V analog/digital input card (12 bits).
0 times, it is imported into the programmable controller 100, where the arithmetic mean value of the 30 sampled values is calculated, this is stored in the host controller 101, and the amount obtained by adding this stored value to the required flow rate is set in the mass flow controller. In both cases, the value obtained by subtracting the stored value from the flow rate display value of the mass flow controller is shown to the operator at the front of the host controller 101. As a result, the operator is shown the true required flow rate, which does not include the amount of zero shift, and the stability of the process is improved, making it possible to form an insulating film with a uniform quality level.

[0020] Furthermore, the maximum and minimum values of the sampling values during the 30 samplings are 1 of the full scale.
% or not, and if there is an abnormality, an alarm is displayed and this display signal is used to stop the device operation for film formation.

Furthermore, during equipment operation, the difference between the flow rate set value to the mass flow controller and the flow rate display value is monitored to see if the mass flow controller is in an abnormal state, and the operator is reminded of the accuracy of the mass flow controller. It is now possible to operate the device without having to pay.

[0022]

Effects of the Invention In the present invention, since the method of forming an insulating film by ECR plasma treatment is as described above, the following effects can be obtained.

In the method of claim 1, the flow rate ratio between the reaction gas and the plasma generating gas, to which the film quality reacts so sensitively that it can be said to be unique to an ECR plasma processing apparatus, is determined based on the inherent accuracy of each mass flow controller. In addition, regardless of the point in time when the flow rate is set, it can be automatically corrected to the truly required flow rate ratio, making it possible to stabilize the process and form an insulating film with a uniform quality level. This results in
SiO film or P formed during the conventional DRAM manufacturing process
The reliability of SG (phosphorus glass) films, especially those films formed as interlayer dielectric films, has been improved.

In the method of the second aspect, since the corrected flow rate is obtained digitally by sampling the zero shift amount, it can be determined with high accuracy and the uniformity of the film quality can be further improved.

In the method of claim 3, since the corrected flow rate is obtained digitally by sampling the zero shift amount, the maximum and minimum values of the sampled values are compared with the allowable error for the full scale flow rate of the mass flow controller during sampling. This makes it easier to detect abnormalities in the inlet and outlet stop valves of the mass flow controller, as well as abnormalities within the mass flow controller, making it possible to prevent unnecessary operation of the equipment.

The method of the present invention can be applied not only to ECR plasma processing apparatuses but also to all apparatuses in which the gas flow rate is controlled using a mass flow controller, and in which it is desirable that the obtained actual flow rate matches the required flow rate with high precision. can be effectively applied.

[Brief explanation of the drawing]

FIG. 1: EC in which the flow rates of plasma generation gas and reaction gas are controlled to the true required flow rates by the method of the present invention.
A diagram showing an example of the overall configuration of the R plasma processing apparatus

[Figure 2
] Etch rate/flow rate ratio characteristic diagram showing the dependence of the insulating film quality on the raw material gas composition ratio for a film produced by ECR plasma CVD method and a film produced by thermal CVD method.

[Figure 3] Diagram showing the relationship between the set flow rate and the actual flow rate of the mass flow controller

[Fig. 4] A diagram showing the configuration of the source gas introduction system in the ECR plasma processing apparatus together with the configuration of the apparatus main body.

[Explanation of symbols]

1 Plasma generation chamber 2 Microwave introduction window 5 Solenoid 6 Plasma outlet 7 Reaction chamber 8 Substrate 9 Substrate stand 10 High frequency power supply 11 Mass flow controller 12 Mass flow controller 13 Stop valve 14 Stop valve 100 Programmable controller 101
Upper controller

Claims (3)

[Claims] Claim 1: A magnetic field is formed that satisfies electron cyclotron resonance conditions with the introduced microwave, and the flow rate is controlled by a mass flow controller having stop valves on the inflow and outflow sides, respectively, so that the introduced plasma generating gas is A plasma generation chamber that generates plasma under resonance conditions between a magnetic field and a microwave electric field and has a microwave introduction window and a plasma outlet on both end faces; It is equipped with a reaction chamber into which a reaction gas whose flow rate is controlled by a mass flow controller equipped with a stop valve on each side; and a high frequency power source that applies an RF bias to the substrate to be processed are used to generate plasma in the plasma generation chamber. An insulating film used when forming an insulating film on a substrate to be processed using an ECR plasma processing apparatus that moves the reacted gas into the reaction chamber through a plasma outlet to decompose the reaction gas and forms a thin film on the surface of the substrate to be processed. The forming method includes, prior to forming an insulating film, closing the stop valves on the inflow and outflow sides of each of the mass flow controllers, determining each corrected flow rate from the zero shift amount displayed on each mass flow controller, and calculating the corrected flow rate by An insulating film forming method, characterized in that a flow rate added to the true flow rate of each of the plasma generating gas and the reaction gas used for forming the insulating film is set in each mass flow controller. 2. In the method for forming an insulating film according to claim 1, the correction flow rate added to the true gas flow rate used for forming the insulating film is performed for a minute period after a certain period of time when the inflow and outflow side stop valves of the mass flow controller are closed. An insulating film forming method characterized in that the zero shift amount of a mass flow controller display is obtained as an arithmetic average value of a plurality of sampling values sampled at intervals. 3. In the insulating film forming method according to claim 2, an abnormality is displayed when the sampling value exceeds an allowable error for the full scale flow rate of the mass flow controller during sampling of the zero shift amount; A method for forming an insulating film, characterized in that the progress of the process to formation is stopped.