JPH0691024B2 - Dry thin film processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to CVD (Chemical Vapor Deposition) for growing a thin film particularly on a semiconductor substrate by using ECR plasma to react solid substances on the substrate. The present invention relates to a film forming apparatus. More specifically, a plurality of electrodes are arranged in a pair in a substantially one plane, and the electrodes of each pair are applied with different polarities from a DC power source and Sometimes it is equipped with an electrostatic chuck that electrostatically attracts and holds a flat plate sample that is nearly parallel to the plane, and uses an ECR plasma to etch or form a film on the side opposite to the flat plate sample. A thin film processing apparatus.

[Conventional technology]

In recent years, process technology using ECR plasma has attracted attention,
Research and development is in progress. When this CVD technique is used to form a fine wiring film of an LSI, the growth rate and the density of the film are different between the top of the wiring and the side wall, and the film quality on the side wall is particularly bad. As a countermeasure to this, there is a method of forming a film on a semiconductor wafer while applying a high frequency voltage,
It has been found that this method eliminates the drawbacks mentioned above. This method is called the RF bias ECR plasma method. RF bias on the substrate (RF is radio frequency 13.56MHz)
The method illustrated in FIG. 3 has been attempted as a method of applying a voltage. That is, for example, a water-cooled wafer stage 9 on which a semiconductor wafer 10 is mounted is connected to a ground potential via an RF generator 12 and a matching box 11 in a reaction tank 8 constituting a dry thin film processing apparatus, and the potential of the semiconductor wafer is Is changed to positive or negative polarity at a high frequency with respect to the reaction tank. On the other hand, with the miniaturization of LSIs, the decrease in yield due to dust generated during the CVD process has become an important issue. In particular, the RF bias ECR plasma method is considered to be an effective technique for the submicron rule, so dust removal is an important issue.

[Problems to be solved by the invention]

For removing dust, conventionally, by growing the film on the surface of the wafer downward, it is possible to prevent the dust from falling onto the wafer surface due to the influence of gravity, and the adhesion of dust can be drastically reduced. Known experimentally. However, holding the wafer surface downward is particularly important because the wafer transfer system for transferring wafers from the load cassette chamber that stores unprocessed wafers to the reaction chamber where etching or film formation processing is performed, and the reaction chamber. The device for holding the wafer surface downward is not yet completed as an actual machine, probably because it is difficult to deliver it to the wafer holding part. The reason is as follows. That is, as a means for holding a wafer in a vacuum, an electrostatic chuck utilizing an attractive force of static electricity is known, and the attractive force is as shown in FIG. Drastically decreases with the air gap between the wafer and the surface to be attracted of the wafer. In the electrostatic chuck in this figure, the electrodes forming the electrostatic chuck are formed in a flat plate shape and embedded in the dielectric body, and the embedded depth, that is, the thickness of the adsorption side insulating layer on the electrode surface is 100 μm. It is a thing.

In this way, since the change in the suction force due to the air gap is large, when the wafer is transferred from the wafer transfer system to the electrostatic chuck, the wafer is not uniformly pressed against the electrostatic chuck with sufficient contact pressure. And there is a risk that the adsorption will fail. Therefore, if the transfer system is not evacuated after adequately confirming the adsorption by appropriate means, the wafer will drop and be damaged, and the fragments will be scattered in the container. Is required. Of course, this is often unacceptable.

As a means for confirming the adsorption, first, a commercially available proximity sensor may be attached to the electrostatic chuck. But,
Commercially available proximity sensors use organic substances as their constituent members, while in dry thin-film processing equipment that uses ECR plasma, the inside of the equipment container is filled with active gas, and all organic matter is attacked. There is a problem.

An object of the present invention is to provide a structure of a dry thin film processing apparatus which enables confirmation of a state of adsorption of a wafer in an active gas without causing a problem in a material.

[Means for solving problems]

In order to achieve the above object, according to the present invention, a plurality of electrodes are arranged in a pair in substantially one plane, and the electrodes of each pair are applied with different polarities from a DC power supply and Sometimes it is equipped with an electrostatic chuck that electrostatically attracts and holds a flat plate sample that is nearly parallel to the plane, and uses an ECR plasma to etch or form a film on the side opposite to the flat plate sample. The thin film processing apparatus includes a high-frequency power source capable of simultaneously supplying a high-frequency voltage to the electrodes of each pair, and current measuring means for measuring a high-frequency current output from the high-frequency power source. The power supply from the DC power source is performed through the high resistance arranged on the power source side and the inductance arranged on the electrode side in series, and the high frequency from the high frequency power source between the pair of electrodes. The pressure is supplied by connecting a high-frequency power source to a connection point between the high resistance and the inductance via a capacitor, and at the same time, the capacitance of the capacitor, the static chuck formed by the electrostatic chuck, and the flat sample are formed. It is assumed that the combined capacitance with the capacitance is set to be in series resonance with the inductance at the frequency of the high frequency power supply.

[Action]

Such an apparatus is configured such that the electrostatic chuck and the wafer are sufficiently attracted to each other and the electrostatic chuck and the wafer are incompletely contacted with each other or the contact pressure is small. It was made based on the experimental results that the capacitance of the capacitors formed in the is significantly different, supply a high-frequency current from a high-frequency power source having a capacity capable of simultaneously supplying a voltage between all pairs of electrodes, By measuring the supplied current, it becomes possible to confirm whether or not the wafer is sufficiently attracted to the electrostatic chuck. An example of the experimental result will be described below.

FIG. 5 shows the relationship between the electrostatic chuck and the wafer when the electrostatic chuck and the wafer are not in contact with each other, that is, when the air gap between the attracting surface of the electrostatic chuck and the attracted surface of the wafer is 5 mm. 3 is an oscillogram showing the relationship between the voltage of the high frequency power source applied to the capacitor formed in and the high frequency current supplied from this power source to this capacitor. In this oscillogram, the one with the larger amplitude is the voltage,
The smaller one is the current, and the scale has a voltage of 5 per scale.
V, current is set to 0.5mA and time axis is set to 2μs. Also, of course, the current leads the voltage by 90 ° in phase. The capacitance of the capacitor formed between the electrostatic chuck and the wafer is calculated from this oscillogram to be 8 pF.

FIG. 6 shows an oscillogram when the electrostatic chuck and the wafer are in contact with each other with no load.
The smaller one is the current, and the setting of the scale is the same as in FIG. If the capacitance is calculated from this oscillogram, it is 15
It becomes pF.

FIG. 7 shows a case where the electrostatic chuck and the wafer are in contact with each other with a sufficient pressure. Here, the smaller amplitude is the voltage and the larger amplitude is the current. The capacitance obtained from this oscillogram is 146 pF, which is significantly larger than the capacitances of 8 pF and 15 pF in the cases of FIGS. 5 and 6 above. The electrostatic chuck used in this experiment had a disk-shaped electrode embedded in a dielectric body having a diameter of 10 cm and an electrode-side embedded depth of 100 μm on the adsorption side.

In this way, even if they seem to be adsorbed in the same way at first glance, the capacitance of the capacitor remarkably changes depending on whether they are barely contacting with no load or contacting with sufficient pressure. . Therefore, by applying a high-frequency voltage to this capacitor and measuring the magnitude of the high-frequency current flowing through the capacitor at that time, it is possible to easily determine whether the adsorption state is good or bad.

〔Example〕

FIG. 1 shows the structure of a dry thin film processing apparatus according to an embodiment of the present invention. ECR plasma generation method is the same as before,
Inside the plasma chamber 4, a magnetic solenoid 3 placed outside
A static magnetic field is generated in advance, and the microwave guided by the waveguide 1 is sent through the microwave window 2. When a gas such as N ₂ or O ₂ is flown through the plasma gas introducing pipe 6, plasma corresponding to each gas is generated in the plasma chamber 4, and the plasma flows out into the reaction tank 8 due to the magnetic diffusion effect. To do. By flowing a film forming material gas such as silane into the reaction tank, ions and active species generated by the interaction between the plasma and the material gas react on the wafer surface to form a nitride film, an oxide film, or the like.

The apparatus of FIG. 1 is different from the conventional one in that the arrangement of the apparatus is upside down and the electrostatic chuck 13 is fixed to the water-cooled stage 9 so that its suction surface faces downward in the gravity direction. This electrostatic chuck 13 is, as shown in FIG. 2, a semicircular plate electrode arranged in a plane and forming a pair.
A disk-shaped electrode 33, 34 is embedded together with electrode terminals 36, 37 in a dielectric made of aluminum oxide, so-called alumina.
Electrode leads 38 and 39 are drawn out from the respective electrode terminals 36 and 37. As shown in FIG. 1, the electrode leads 38 and 39 are connected to a DC power source 18 via an inductance L of the order of 0.1 mH and a high resistance R of the order of MΩ, and the electrodes 33 of the electrostatic chuck are connected from this DC power source. A voltage on the order of kV is supplied between the and 34. Further, the electrode leads 38 and 39 are respectively connected to one terminal of the RF generator 12 via the matching circuit 11 after passing through the capacitor C ₂ and RF
The other terminal of the generator is connected to ground potential and to the reaction vessel 8. By connecting the DC power source 18 and the RF generator 12 in this way, the voltage of the DC power source is blocked by the capacitor C ₂ and the outlet side of C ₂ , that is, the right side of the figure is short-circuited, so that the RF generator is It does not enter at all, and since the radio frequency voltage of the RF generator is applied to both terminals of the DC power supply through the high resistance R and with the same polarity, it does not affect the DC power supply at all. A high frequency power supply 14 according to the present invention is connected to a connection point between the high resistance R and the inductance L connected to the DC power supply side via a capacitor C ₁ and a current measuring means 15.

The frequency of the high frequency power supply 14 is set to the order of ₁₀₀ KHz in this embodiment, and the combined capacitance of the capacitance of the capacitor C _{1 and} the capacitance formed by the electrostatic chuck and the wafer is at this frequency. It is set to a value close to the inductance L and a DC resonance state. This has the advantage of significantly improving the measurement sensitivity.

Since the high frequency power supply 14 and the direct current power supply 18 are connected via the high resistance R and the capacitor C ₁ , the voltage of the direct current power supply is not blocked by the capacitor C ₁ and does not enter the high frequency power supply. The high resistance R suppresses the current flowing to the DC power supply, and does not substantially affect the DC power supply. Further, the voltage from the high frequency power supply 14 to the RF generator 12 is short-circuited on the right side of the capacitor C ₂ , and the RF generator 12 outputs a high frequency power supply 14
Since the voltage going to the same polarity is applied to both terminals of the high frequency power supply, the high frequency power supply 14 and the RF generator 12 do not influence each other. Therefore, with the DC power supply 18 and the RF generator 12 connected, that is, with the device kept in an operating state, the current flowing out of the high frequency power supply 14 without being affected by these power supplies, that is, the electrostatic chuck 13 and the wafer. It is possible to measure the current passing through the capacitor formed between 10 and.

Therefore, the operation of the apparatus configured as described above is performed as follows. First, when the preparation for plasma generation is completed, a gate valve (not shown) provided in the reaction chamber 8 is opened, and a carrier system waiting in the load lock chamber is introduced into the reaction chamber, and is carried into the reaction tank by the carrier system. The wafer is pressed against the attraction surface of the electrostatic chuck 13 by the mechanism of the transfer system. In this state, the voltage of the DC power supply 18 is applied between the electrodes of the electrostatic chuck by turning on a switch (not shown). At this time, if the pressing is normal, the wafer is attracted to the electrostatic chuck, and if the pressing is insufficient, it is not attracted. Therefore, the voltage of the high-frequency power source 14 is applied to a capacitor formed between each electrode of the electrostatic chuck and the wafer by turning on a switch at the power source outlet (not shown), and the current passing through the capacitor is measured as a current. Measure using the means 15. The current measuring means 15 measures a sufficient current, and when the adsorption of the wafer is confirmed, the power outlet switch is turned off, the mechanism of the transfer system pressing the wafer is released, and the transfer system is moved from the reaction tank to the load lock chamber. Preparation for film formation is completed by retracting and closing the gate valve.

Especially when an RF bias is applied to the wafer in order to improve the film quality of a fine fine wire coating such as LSI, all electrodes of the electrostatic chuck are turned on by turning on a switch (not shown) provided in the RF generator 12. When a radio frequency voltage is applied to the electrodes with the same polarity, a capacitor with a relatively large capacitance formed between this electrode and the wafer and a relatively large capacitance formed between the wafer and the reaction tank The RF bias voltage is piezoelectrically divided by the capacitor having a small value, and the RF bias is applied to the wafer almost completely with respect to the reaction tank.

When the RF bias is applied in this manner, a well-known self-bias voltage is generated on the wafer surface due to the interaction between plasma and alternating current. Since this voltage is a negative DC voltage, the attracting force on the wafer becomes strong at the electrode position of the electrostatic chuck connected to the positive terminal of the DC power supply 18, and the attractive force at the electrode position connected to the negative terminal. Will be weakened, but there is no practical harm.

〔The invention's effect〕

As described above, according to the present invention, a plurality of electrodes are arranged in a pair in a substantially one plane, and the electrodes of each pair are applied with different polarities from the DC power supply, Equipped with an electrostatic chuck that electrostatically adsorbs and holds a flat plate sample that is nearly parallel to the flat surface, and uses an ECR plasma to perform dry etching or film formation on the non-adsorbed surface side of the flat plate sample. In the device, when adsorption to the flat plate sample is sufficient and when adsorption is insufficient, for example, how the flat plate sample is barely in contact with the adsorption surface of the electrostatic chuck. Based on the experimental result that the electrostatic capacitance of the capacitor formed between the electrostatic chuck and the flat plate sample is significantly different from the case of, the result of adopting the above configuration in the dry thin film processing device is Prior to At the time of adsorption of the flat plate-shaped sample, the high-frequency power source is connected to the electrodes of each pair, and the current flowing through the capacitor formed between the electrostatic chuck and the flat-plate sample, that is, the high-frequency current output from the high-frequency power source is measured. By doing so, it is possible to easily determine the quality of the suction state,
An apparatus in which the adsorption surface of the electrostatic chuck is directed downward in the direction of gravity without the need to attach a discrimination unit having an organic substance as a constituent member such as a proximity sensor in the active gas in which the electrostatic chuck exists, unlike the conventional device. As a result, it becomes possible to form a film with less dust adhesion, and it is possible to obtain an effect of significantly improving the yield and reliability of a device incorporating a flat plate sample processed by using this apparatus.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the constitution of a dry type thin film processing apparatus according to an embodiment of the present invention, FIG. 2 is a detailed constitution view around an electrostatic chuck shown in FIG. 1, and FIG. ,
(B) is a plan view, FIG. 3 is an explanatory cross-sectional view showing a conventional configuration example of a dry thin film processing apparatus especially for LSI, and FIG. 4 is a view showing an attracting surface of an electrostatic chuck and an attracted surface of a wafer. FIG. 5 is a diagram showing the relationship between the air gap and the attraction force between the electrodes, and FIG. 5 is an electrode constituting the electrostatic chuck when an air gap exists between the attraction surface of the electrostatic chuck and the attraction surface of the wafer. Fig. 6 is an oscillogram showing the waveforms of the high-frequency voltage applied to the capacitor formed between the capacitor and the wafer, and the high-frequency current passing through the capacitor under this voltage. The oscillograms showing the waveforms of the high-frequency voltage and the current at the time of no contact pressure, which barely make contact with the surface to be attracted, and Fig. 7 shows sufficient contact between the surface to be attracted of the electrostatic chuck and the surface to be attracted of the wafer. When in contact with pressure Frequency voltage, a oscillogram showing the respective waveforms of the current. 1: Waveguide, 3: Magnetic solenoid, 4: Plasma chamber, 6: Plasma gas introduction line, 7: Film forming material gas introduction line, 8: Reaction tank,
10: Wafer (flat sample), 13: Electrostatic chuck, 14: High frequency power supply, 15: Current measuring means, 18: DC power supply, 33, 34: Electrodes,
R: high resistance, L: inductance, C _1: the capacitor.

Claims (1)

[Claims] 1. A flat plate in which a plurality of electrodes are arranged in pairs in substantially one plane, and the electrodes of each pair are charged with different polarities from a DC power source and, at the time of this voltage application, are approached substantially parallel to the plane. Electrode of each pair in a dry thin film processing apparatus that is equipped with an electrostatic chuck that electrostatically attracts and holds a flat sample, and uses an ECR plasma to perform etching or film formation processing on the side opposite to the suction surface of the flat sample. A high-frequency power supply capable of supplying a high-frequency voltage and a current measuring means for measuring a high-frequency current output from the high-frequency power supply are provided, and the charging from the DC power supply to each pair of electrodes of the electrostatic chuck is performed by The high resistance arranged on the power supply side and the inductance arranged on the electrode side are connected in series, and the high frequency voltage is supplied from the high frequency power supply between the pair of electrodes to the high resistance and the inductor. The This is done by connecting a high frequency power source to the connection point with a capacitor via a capacitor, and the combined capacitance of the electrostatic capacitance of this capacitor and the electrostatic capacitance formed by the electrostatic chuck and the flat sample is The dry thin film processing apparatus is set so as to be in series resonance with the inductance at the frequency of the high frequency power supply.