JPH09162169A - Method and system for plasma processing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent abnormal machining while taking account of high speed plasma processing using negative ions by introducing positive and negative ions into a processing chamber provided with a sample stage and performing plasma processing by applying a high frequency AC voltage to a sample mounted on the sample state in the processing chamber thereby neutralizing the accumulated charges of positive ions. SOLUTION: Positive ions are generated in a low pressure positive ion generation chamber 16 provided, in the circumference thereof, with a plurality of longitudinal slits 12 and an annular negative ion generation chamber 17 is cooled down to -40 deg.C through the slits 12. The negative ion generation chamber 17 is fed with chlorine gas and generates negative ions. A sample stage 30 is disposed at the lower part of the positive ion generation chamber 16 while being insulated from the body through an insulator 14. A sample 5 is mounted on the sample stage 30 and applied with a high frequency AC voltage from a high frequency power supply 8 and processed by means of a plasma 4. According to the method, abnormal machining is prevented by neutralizing the accumulated charges of positive ions while taking account of negative ion plasma processing.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to semiconductor manufacturing and LC.
The present invention relates to a plasma processing method and apparatus used in a flat display panel manufacturing process such as D.

[0002]

2. Description of the Related Art In recent years, in the etching process for manufacturing integrated circuits, in order to improve the integration degree, the number of elements per unit area is increased and the chip area of the entire integrated circuit is increased to improve the integration degree and The economy is being improved. For this reason, the minimum processing width of the elements of the integrated circuit is becoming smaller year by year, and the diameter of the semiconductor object to be processed simultaneously increases. Conventionally, a plasma processing technique has been used for the semiconductor manufacturing as described above. Here, in the conventional plasma, the material gas is ionized by the high frequency power, and the positive ions generated by the ionization generate a potential difference (floating potential or self-bias potential) between the plasma and the workpiece in the direction perpendicular to the surface of the workpiece. ) Is performed, and the energy of the accelerated positive ions is used to perform etching, for example. Such plasma etching is often used for fine processing because the shape of the object to be processed is rectangular and the processing dimensions are accurate. Therefore, the plasma processing apparatus is required to perform a large-diameter, high-speed and uniform etching,
Moreover, since the processing width in the vertical direction also becomes smaller, it is required to further reduce the damage to the underlying film during processing. Generally, in anisotropic etching using plasma, etching is performed by the energy of ions accelerated by the above potential difference (floating potential or self-bias potential) generated between the object to be processed and plasma. Plasma is electrically neutral as a whole, and the charged particles that make up it are composed of electrons and ions. Since the ion has a mass 1000 times or more that of the electron, the moving speed of the ion is slower than that of the electron, and it is difficult to escape from the plasma.
On the contrary, electrons with negative charges move faster and can move faster than ions. Since plasma easily loses electrons due to the difference in its moving speed, it tries to maintain electrical neutrality as a whole and is positively charged to the periphery of plasma. That is,
The plasma is positively charged with respect to the outer wall and the object to be processed, and the electrons are attracted by the electrostatic force, and the plasma itself maintains the electrical neutrality and is stable. When an object to be processed is placed in such plasma, the object to be processed is negatively charged with respect to the plasma. The processing such as etching is performed mainly by the positive ions themselves or the energy of the positive ions drawn by the above-mentioned potential difference generated between the object to be processed and the plasma.
In addition, industrially, in order to adjust the attraction potential of the ions, a high frequency is applied to the electrode that is galvanically insulated from the object by a capacitor to adjust the potential of the object to the plasma. We are optimizing processing such as etching.

[0003]

However, in recent microfabrication, even if plasma having a uniform density distribution is used, the processing can be performed due to the processing dimension and the height of the desired aspect ratio of the processing. It has been reported that uniform treatment cannot be performed due to the fine shape effect of the shape to be performed. For example, in the polysilicon etching used in the step of forming the gate of an electric field effect transistor, when plasma etching is performed, the shape effect of a fine pattern causes abnormalities along the interface with the underlying silicon oxide film during etching. A so-called notch occurs, which is the progress of etching. Also,
In trench etching for capacitor formation and element isolation, vertical etching side walls cannot be obtained, and abnormal processing such as bowing in which the trench side walls are depressed occurs. The abnormal processing due to the shape effect due to these fine patterns is caused by the charge accumulation (charge-up) caused by the difference in the ratio of the inflow amount of electrons and ions into the processed object depending on the pattern. In addition, the present inventors reported in the previous application (Japanese Patent Application No. 7-8973) that the etching rate of negative ions was very high. However, it is difficult to simultaneously generate positive ions and negative ions with the same plasma generator. That is, as shown in FIG. 2, which shows the relationship between gas pressure and generated ion density, the pressure regions where positive ions and negative ions are generated deviate from each other, and the positive ions can efficiently etch the sample into a vertical shape. It was found that at low pressure, negative ions cannot be generated efficiently. Therefore, the object of the present invention is to prevent abnormal machining by neutralizing charge accumulation (charge-up) due to positive ions on the sample, which is the cause of abnormal machining in conventional plasma etching. At the same time, it is to provide a plasma processing method and apparatus capable of adding high-speed plasma processing with negative ions.

[0004]

In order to achieve the above object, the present invention in a method aspect is to generate a plasma containing a relatively large number of negative ions in a first plasma generating chamber set in a relatively high pressure environment. In addition, a plasma containing a relatively large number of positive ions is generated in the second plasma generation chamber set in a relatively low pressure environment, and the positive ions and negative ions are introduced into the processing chamber provided with the sample stage, The plasma processing method is characterized by applying a high frequency alternating voltage to the sample placed on the sample table in the processing chamber to perform plasma processing. Further, the present invention in terms of the apparatus includes a first plasma generating chamber set in a relatively high pressure environment for generating plasma containing a relatively large number of negative ions, and a relatively large number of positive ions set in a relatively low pressure environment. A second plasma generation chamber for generating a plasma containing helium, a processing chamber in which the positive ions and the negative ions are introduced, and a sample stage is provided therein, and the sample chamber is placed in the processing chamber. It is configured as a plasma processing apparatus characterized by comprising an alternating voltage applying means for applying a high frequency alternating voltage to a sample. The processing chamber can also serve as the second plasma generation chamber. By configuring the alternating voltage applying means by a high frequency transformer, simplification of the device can be measured. By providing a plurality of the first plasma generation chambers and / or the second plasma generation chambers, it is possible to achieve uniform plasma. By further providing a magnetic field adding means for applying a magnetic field to the second plasma generation chamber, electrons are confined in the positive ion generation chamber, the inflow of electrons is reduced, and ideal processing conditions with only positive and negative bipolar ions are provided. Can be approached to. By partitioning the first plasma generation chamber and the second plasma generation chamber with a slit plate or a perforated plate, it is possible to allow the particles to flow while maintaining the pressure in both chambers. By installing a cooling device for cooling the slit plate or the porous plate, it is possible to suppress the generation of radicals and promote the generation of negative ions. By forming the slit plate or the porous plate with a conductor, generation of negative ions can be promoted. By including the cooling device for cooling the first plasma generation chamber, it is possible to suppress the generation of radicals and promote the generation of negative ions. The first
By configuring the plasma generation chamber of
The generation of negative ions can be promoted. The high frequency waveform applied by the alternating voltage applying means may be any one of a sine wave, a rectangular wave, a triangular wave, or any other waveform. The etching rate can be improved by making the shape of the rectangular wave as close as possible. By configuring the alternating voltage applying means including the function of controlling the ON / OFF ratio of the high frequency, the ratio of the incident amount of positive and negative ions can be controlled and the charge-up can be mitigated. By mixing an element with a small contribution to etching or an element with no contribution to etching in the plasma atmosphere, it is possible to provide a plasma processing apparatus that reduces charge-up and is effective in preventing notches.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing specific embodiments, it will be easier to understand the present invention by explaining the principle of generating negative ions used in the present invention. In the normal plasma generation process, first, electrons accelerated by an electric field supplied from outside the plasma processing chamber collide with neutral particles in the material gas to give energy to the outer shell electrons of the neutral particles, The process involves the generation of new electrons and positive ions by desorbing from the neutral particles. The plasma is maintained by performing this process in a chain. Therefore, a large number of positive ions are inevitably present in the plasma generation region. However, it is known that positive ions and neutral particles recombine with electrons having relatively low energy to generate negative ions and radicals at a place apart from the plasma generation region. In particular, halogen, which has a high electronegativity, tends to attract electrons and generate negative ions.
In the present invention, this principle is used to generate negative ions. In addition, the amount of negative ions generated is closely related to the plasma pressure. That is, it is generally known that the average energy of particles in plasma changes with pressure. The lower the pressure, the longer the mean free path of the particles, and the effect of the plasma generation region easily extends to the periphery.
Also, since the acceleration time due to the electric field until the collision becomes long, the electrons are accelerated by the externally applied electric field for plasma generation, while the time until the collision becomes long, the average value of the energy of each electron is It becomes high, and it is easy to generate positive ions with high electron energy. On the other hand, under higher pressure, the mean free path is short, and if it is a little away from the plasma generation region, it is not affected by the plasma generation region, and a large number of particles collide, so the average energy of each electron decreases. And the proportion of slow electrons increases,
The probability of electron attachment near the plasma generation region increases, and as a result, the production of negative ions and radicals increases. As described above, generally, positive ions are more likely to be generated as the pressure is lower and closer to the plasma generation region, and negative ions are more likely to be generated as the pressure is higher and the region is farther from the plasma generation region. In particular, particles of halogen or the like containing atoms having high electronegativity recombine with electrons due to collision with a wall or the like, and radicals or negative ions are efficiently generated. In this case, the wall material is preferably composed of a conductive substance capable of continuously supplying electrons. In the present invention, two plasma generation chambers having different pressures are provided from the relationship between the pressure and the generation amount of positive and negative ions as described above, and a relatively large number of positive ions and a relatively large number of plasma ions are generated in each plasma generation chamber. Generate negative ions respectively,
It is intended to prevent the accumulation of electric charges (charge-up) on the surface of the sample by performing plasma processing with the plasma in which these are mixed, and to eliminate the above-mentioned inconvenience of the plasma processing due to the shape effect of the formation pattern. Further, by applying a high frequency alternating bias voltage to the sample by an alternating voltage applying means such as a transformer, plasma processing with positive and negative ions is enabled. Referring to the attached drawings,
Examples for embodying the present invention will be described to provide an understanding of the present invention. The following embodiment is an example embodying the present invention and is not intended to limit the technical scope of the present invention. 1 is a schematic side view showing a plasma etching apparatus according to one embodiment of the present invention, FIG. 2 is a graph showing the relationship between the pressure of the plasma chamber and the densities of positive ions and negative ions generated therein, and FIG. The contents of the negative ion generator used in the device shown in FIG.
Is a perspective view thereof, (b) is a plane sectional view thereof, (c) is a detailed sectional view of a microwave introducing portion, FIG. 4 is a conceptual diagram of a device for applying a high frequency voltage to a sample, and (a) is a capacitor. The case where a high frequency voltage is applied via the transformer and the case where a high frequency voltage is applied by a transformer are shown in FIG. 5 is a graph showing the relationship between the pressure in the plasma chamber and the etching rate of the silicon substrate as a function of the high frequency voltage value, and FIG. 6 is a graph showing the relationship between various high frequency waveforms and the etching rate.
(A) shows a sine wave, (b) shows a rectangular wave, and (c) shows an actual waveform added by a transformer. 7 is a cross-sectional view showing an SEM shape of an etching cross section by the apparatus according to the present embodiment, FIG. 8 is a side view showing an outline of another plasma processing apparatus, and FIG. 9 is a side view showing an outline of still another plasma processing apparatus. 10 (a) and 10 (b) are diagrams showing an outline of an apparatus for applying a magnetic field to the plasma processing apparatus, respectively. In the plasma processing apparatus shown in FIG. 1, a cylindrical positive ion generation chamber 16 is formed in a dome-shaped quartz glass 3 via an O-ring 11.
(One example of the second plasma generation chamber) is connected, and the material gas is introduced into the positive ion generation chamber 16 from the gas introduction port 9. A one-turn type antenna 2 is attached to the quartz glass 3, and a high frequency power source 8 is provided through a matching circuit 7.
From the above, high frequency power is supplied to the antenna 2, and the material gas is turned into plasma under a high frequency electric field to generate plasma 4. An insulator 14 is provided below the positive ion generation chamber 16.
The sample mounting table 30 insulated from the device is placed by the above, and the sample 5 is mounted thereon. A high frequency bias voltage is applied to the sample 5 by a high frequency power source 8 via a transformer 6. A plurality of vertical slits 12 are formed around the positive ion generation chamber 16 and an annular negative ion generation chamber 17 (first plasma generation) that can be cooled to -40 degrees by a chiller through the slits 12 is formed. An example of a room) is provided. Details of the negative ion generation chamber 17 are shown in FIG. The outer circumference of the annular negative ion generation chamber 17 is covered with Teflon resin, which is an example of a dielectric material, and the portion in contact with the gas inside is protected with quartz glass. A material gas such as high halogen is introduced. The reason why Teflon is wrapped around the outer circumference is to make microwave propagation uniform and plasma uniform. The microwave 10 is introduced into the annular negative ion generation chamber 17 through the waveguide, and the material gas is turned into plasma. As shown in FIG. 3C, the microwave introduction part is partitioned from the annular negative ion chamber 17 by a plate-shaped quartz glass plate 3a. Instead of the slit 12, a porous plate made of a carbon material can be cooled and used. In this case, the generation rate of negative ions is high, and the high frequency voltage Vs normal can be reduced from about 50V to about 30V. No heavy metals were detected in the processed sample. The value of Vs is as described below.
It is shown that the higher the potential is, the different mobility of positive ions and negatively charged particles, that is, it can be used as a parameter indicating the ratio of negative ions in plasma.
That is, a phenomenon is observed in which Vs decreases as the ratio of negative ions increases. Moreover, the negative ion chamber does not always have to be at the ground potential, and a negative potential may be extracted by applying a DC potential through the insulator. An example of the data of the implemented device is as follows. 1. Inner diameter of positive ion generation chamber 300 mm 2.1 High frequency applied by turn antenna 2 13.56 MHz 3. Pressure of positive ion generation chamber 10 mTorr to 20 mTorr 4. Size of slit 12 (number) 1mm width x 50mm length (20) 5. Pressure of negative ion generation chamber 40-60 mTorr 6. Material Gas Introduced into Negative Ion Chamber Halogen Gas (Chlorine Gas) In this embodiment, as shown in FIG. 1, positive ions are generated in the low-pressure positive ion generation chamber 16 and the slit 12 (or porous plate) is provided. By introducing chlorine gas into the relatively high pressure negative ion generating chambers 17 adjacent to each other via the slits 12 (or perforated plate), the negative ions are efficiently incident on the positive ion generating chambers 17. Therefore, we were able to provide a plasma processing device that can effectively use negative ions without charge-up. With respect to the pressure control of the positive ion generation chamber and the negative ion generation chamber, the result of an experiment conducted by the present inventor will be described with reference to FIG. Fig. 2 shows the ionic species in plasma generated by F ₆ gas when the pressure is changed.
The result measured with the quadrupole mass spectrometer is shown. FIG.
As can be clearly seen from the above, the pressure conditions at which the generation of positive ions and negative ions are maximum differ. This is because, as described above, the generation of negative ions occurs due to the attachment of electrons having weak energy, so that the pressure is relatively high and many low-energy electrons are actively used at high pressure. Next, regarding the control of the bias potential of the sample stage, the details of the transformer coupling used in the present invention will be described. By using a transformer to apply a high frequency to the sample substrate,
While keeping the substrate potential at the ground potential, it is possible to alternately change the ion attraction voltage by high frequency. Even in the case of a sample with an insulator, the insulator becomes a capacitor in the case of high frequencies and allows high frequencies to pass, so the pull-in voltage can be effectively applied. Also, by controlling the number of turns of the transformer coil,
Since impedance matching can be performed and an optimum high-frequency current can flow, negative ions can be more effectively drawn in and the reaction of negative ions can be used compared to the conventional method. In addition, an anisotropic magnetic material can be used in the core of the transformer to change the positive and negative peak voltages and effectively draw the negative ions. This will be described in more detail with reference to FIG. When there is a conventional capacitor between the sample electrode and the high-frequency power source (Fig. 4 (a)), the sheath of plasma and electrode forms a circuit equivalent to a diode due to the difference in mass of electrons and positive ions of plasma. I will end up. Since there is a capacitor in series with this, a rectifying circuit is formed as an equivalent circuit, and the sample electrode side is biased to a negative potential. Conventionally, the bias potential was effective in the treatment using positive ions, but in order to pull in negative ions, electrostatic repulsion force is generated and becomes an obstacle. On the other hand, as shown in FIG. 4B, when the dielectric coupling is performed by the transformer, an appropriate high frequency current is obtained and one end of the transformer is always grounded, which causes a problem when attracting negative ions. No negative bias potential is generated. Therefore, negative ions can be more efficiently attracted than in the conventional method. However, the sample is positive Vs (Vs will be described later)
Therefore, when the sample potential becomes positive by Vs, the potential that becomes a barrier to the incidence of negative ions disappears, but the actual etching occurs when the ion attraction energy rises above a certain level. Therefore, the etching is started from the place where the potential rises a little above Vs. here,
The effect of negative ion etching discovered by the present inventor will be described with reference to FIGS. FIG. 5 shows the etching rate of the silicon substrate when the pressure in the plasma chamber is changed. The experiment was conducted using SF6 as the gas. The high frequency is applied to the sample using a transformer. The etching rates are shown when the potential Vpp of the sample electrode is 100V and 200V. From this figure, it is apparent that the etching rate is higher when Vpp is 200V. This phenomenon will be described with reference to FIG. Even if the sample electrode is not negatively biased, the plasma is usually charged positively with respect to the outer wall due to the difference in mobility of electrons and positive ions. This potential is called space potential Vs. Therefore, the sample substrate is always lower in potential than plasma by Vs. Therefore, when viewed from the plasma side,
Electrostatic repulsion against negative ions disappears only when the electrode potential rises by Vs. This is because the sample essentially compensated for the fact that the sample was at a potential Vs lower than the plasma. In this way, the attraction of negative ions occurs only at the electrode potential higher than Vs. In FIG. 6A, Vpp
Shows that there is a portion where the electrode potential is higher than Vs and higher than the etching start voltage in the cases of 100 V and 200 V. Clearly, when Vpp is 200 V, the amount of negative ions drawn is large. This explains well the experimental results of FIG. In particular, it is noted that negative ions have a higher reactivity and a higher etching rate than positive ions, which is industrially advantageous and is noted. The effective waveform of the bias high frequency will be described. FIG. 6B shows that the rectangular wave is effective for attracting negative ions. As is clear from the figure, in the case of a rectangular wave, since the value of Vs is exceeded in a pulsed manner, negative ion attraction is performed quickly and the attraction time is long, which is advantageous for negative ion attraction. . For example, when the high frequency applied to the sample is a rectangular wave, the etching rate is
Increased from 10 microns to 12 microns per minute.
MNOS sample is used as the sample during processing and 3 for Ar plasma
The charge-up amount after exposure for 0 seconds was measured. When the ON / OFF control was not performed using the rectangular wave, charge-up was observed around the 6 inch diameter sample.
When F control was performed, the charge-up decreased below the measurement sensitivity. At this time, the duty ratio was 50%. In an actual circuit, the rising waveform tends to be rounded due to the inductance of the transformer, and the waveform is virtually the same as a combination of triangular waves. In addition, since electrons are present in the actual plasma to a large extent, it is possible that the electrons may follow the high frequency and flow in. Therefore, the high frequency is applied intermittently to mitigate the charge-up and to generate positive and negative ions. It is desirable to control the ratio. When the number of negative ions and positive ions is almost equal and there is no electron, ideal etching with positive and negative bipolar ions is achieved.
In order to adjust the quantitative ratio of positive and negative ions,
It is desirable to perform control to switch the ON / OFF cycle of the rectangular wave, sine wave, triangular wave, or the like. Positive ion generation chamber 1
By applying a magnetic field to 6, the electrons can be confined in the positive ion generation chamber, the inflow of electrons can be reduced, and the conditions for treatment with ideal bipolar ions can be approximated. FIG.
(A) shows a configuration in which a magnetic field is generated in the magnetic body 18 by the coil 31 and this magnetic field is applied to the dome-shaped quartz glass 3 (positive ion generation chamber 16) shown in FIG.
Further, FIG. 2B shows the permanent magnet 2 reinforced by the yoke 21.
The state where the magnetic field generated by 0 and 20 is applied to the quartz glass 3 is shown. The yoke 21 plays an important role in guiding the magnetic force lines so that the magnetic force lines do not cross the sample. As shown in these figures, when a magnetic field is applied so as not to cross the sample into the positive ion generation chamber 3 which is the electron generation source, the electron with a light mass easily moves to the magnetic field line and moves. Trapped in. On the other hand, positive ions have the same charge as electrons but have a mass of 10
Since it is more than 00 times larger, diffusion is performed with almost no effect on the magnetic field. Therefore, by confining the electrons in the positive ion generation chamber 16, the inflow of electrons can be reduced, and the conditions for treatment with ideal bipolar ions can be approximated. A plurality of positive ion generation chambers 16 and / or negative ion generation chambers 17 can be provided. Along with high-speed etching, a large-diameter sample is processed, and a large-diameter flat display device
As already mentioned, it is necessary to uniformly etch a large-diameter sample. In a large-diameter plasma as described above, when a strong magnetic field inhomogeneity occurs in the sample, as described above, the inhomogeneity of the electric field is generated in the plasma due to the difference in the behavior of ions and electrons. There is a problem of destroying.
Therefore, it is necessary to perform the processing in a uniform magnetic field or a state close to no magnetic field. Since it is industrially difficult to generate a uniform plasma by a uniform magnetic field, it is effective to place the sample in a place close to a non-magnetic field. In such cases, plasma uniformity is determined by plasma diffusion, so
It is important to control the plasma source that has a source in a specific region with respect to the sample. In general, for a circular sample, by separating the circular tubular plasma source appropriately,
Although a uniform plasma is generated, in the future, when handling a large-diameter plasma, it is desired to use a plurality of such plasma generation sources to diffuse the ions to create a uniform plasma. This is specifically solved by alternately forming the positive ion generation chambers 16 and the negative ion generation chambers 17 on concentric circles. In order to improve controllability, it is desirable that the electric fields for plasma generation supplied to the positive ion generation chambers 16 and the negative ion generation chambers 17 be controlled independently of each other. The negative ion generating chamber 17 and the slit 12 for partitioning the positive ion generating chamber 16 and the negative ion generating chamber 17
It is desirable to cool (or the perforated plate). As described above, since it is known that the generation of negative ions is due to weak electron coupling, it is easy for positive ions to recombine with electrons at the wall to generate negative ions. Guessed. However, the inner wall of the chamber that is normally exposed to plasma is at a high temperature, and thermal energy is given during the process of recombination, so that stable radicals are more likely to be generated than negative ions. Also, the probability that particles adhere to the wall surface due to thermal energy is reduced. Therefore, it is desirable that the negative ion generation chamber 17 and the slit 12 (or the perforated plate) be made of a conductor so that the negative ions are easily generated and electrons are easily given from the wall. When a metal is used for the conductor, it causes metal contamination, so a high-purity conductor material such as a carbon material is desirable. If the negative ion generation chamber 17 and the perforated plate were not cooled, the negative ion generation rate would decrease and the previously obtained Vs of 30V would be 35v.
Rose to the extent. When the positive ion generation chamber 16 was replaced with a cylindrical quartz glass and a magnetic field of 50 gauss (value at the center between the magnets) was applied, the value of Vs dropped to 20V. Further, it has been found that mixing a gas that does not contribute much to etching or a gas that does not contribute at all to plasma is effective in preventing the notch. An example of processing conditions at this time will be described below. Processing condition: Gas component of positive ion generation chamber: Gas 1: 70% chlorine, 20% HBr, 10% Xe (with noble gas) Gas 2: 70% chlorine, 30% HBr (no rare gas) Gas component of negative ion generation chamber: Chlorine 100% Pressure: Positive ion generation chamber 15mTorr Negative ion generation chamber 60mTorr Plasma generation method: Positive ion generation chamber ICP (inductively coupled plasma) Frequency 13.56MHz (1500W) Negative ion generation chamber Microwave plasma (surface wave) Frequency 2 .45 GHz (300 W) Bias high frequency: 400 KHz, Vpp = 200 V (transcouple) Etching rate: 700 nm / min Selectivity (silicon oxide film): 300 Etching shape: ○ No rare gas (0.5 micron line & 0.5 microspace) ) Causes notch (polysilicon film thickness 1.5 μm) To notch length 0.3 microns, overetching 100%) ○ rare gas added (in unnotched) the conditions under the above conditions, Xe becomes positive ions, chlorine,
Since etching can be performed only with negative ions of bromine, the underlying film is less damaged and high-speed etching can be performed. The sample electrode was cooled to −50 ° C. by using the above apparatus, and SF6 was used to set the positive ion generation chamber pressure 20 mTorr, the negative ion generation chamber 40 mTorr, RF power 1500 W, bias Vp.
It was possible to perform poly-silicon oxide film etching at a high speed of 10 microns per minute at p200V. Section S at that time
The EM shape is shown in FIG. When the negative ion generating chamber was set to 20 mTorr under the same conditions as this, etching mainly with positive ions was performed, and an inverse taper shape and a notch shape were observed (FIG. 7B). In the above-mentioned example, positive etching by negative ions is explained. However, it is also possible to use negative ions exclusively for preventing charge-up of the sample without participating in etching. This is particularly effective for processing that requires a positive suppression of negative ion reactions, such as when a high selection ratio is required.

[0006]

8 and 9 show a modification of the embodiment of the present invention. Regarding the reference numerals, the same reference numerals are used for the same elements as in FIG. In FIG. 8, two microwave-introducing negative ion generation chambers 17 are provided above the inductively coupled positive ion generation chamber 16, and the negative ion generation is performed facing the plasma 4 formed in the positive ion generation chamber 16. This is the case where the slit 12 of the chamber 17 is provided. In the case of FIG. 9, the negative ion generation chamber 17 penetrates the plasma 4 formed in the positive ion generation chamber 16. In any case, since a plurality of plasma generation chambers are provided, plasma is uniformly generated, and the device is suitable for large-diameter processing. In the above embodiment, the plasma processing chamber is also used as the second plasma generation chamber (positive ion generation chamber).
It is also possible to separately configure the plasma generation chamber of.

[0007]

Since the plasma processing method and apparatus according to the present invention are configured as described above, the accumulation of charges by positive ions on the sample which causes abnormal processing in the conventional plasma etching (charge). It is possible to provide an efficient plasma processing method and apparatus capable of eliminating abnormal processing by neutralizing (up) and preventing abnormal processing, and adding efficient plasma processing using negative ions.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing a plasma etching apparatus according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the pressure in the plasma chamber and the densities of positive ions and negative ions generated therein.

3 shows the contents of a negative ion generator used in the device shown in FIG. 1, (a) is a perspective view thereof, and (b) is a diagram thereof.
Is a plan sectional view thereof, and (c) is a detailed sectional view of the microwave introduction part.

FIG. 4 is a conceptual diagram of an apparatus for applying a high frequency voltage to a sample, (a) shows a case where a high frequency voltage is applied via a capacitor, and (b) shows a case where a high frequency voltage is applied by a transformer.

FIG. 5 is a graph showing the relationship between the pressure in the plasma chamber and the etching rate of the silicon substrate in relation to the high frequency voltage value.

FIG. 6 is a graph showing the relationship between various high-frequency waveforms and the etching rate. (A) shows a sine wave, (b) shows a rectangular wave,
(C) shows an actual waveform added by the transformer.

FIG. 7 is a cross-sectional view showing an SEM shape of an etching cross section by the device according to the present embodiment.

FIG. 8 is a side view showing the outline of another plasma processing apparatus.

FIG. 9 is a side view showing the outline of still another plasma processing apparatus.

10A and 10B are diagrams showing an outline of an apparatus for applying a magnetic field to a plasma processing apparatus, respectively.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Exhaust port 2 ... Antenna 3 ... Quartz glass 4 ... Plasma 5 ... Sample 6 ... Transformer 7 ... Matching circuit 8 ... High frequency power supply 9 ... Gas inlet 10 ... Microwave 11 ... O-ring 12 ... Slit (perforated plate) 14 ... Insulator 30 ... Sample stage 16 ... Positive ion generation chamber 17 ... Negative ion generation chamber 18 ... Magnetic material 20 ... Permanent magnet 21 ... Yoke 22 ... Shield plate 23 ... Teflon 31 ... Coil

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Haruo Shindo 910-1-6-301 Aiko, Atsugi City, Kanagawa Prefecture (72) Inventor Satoshi Narai 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Kobe Steel Ltd. Tokoro Kobe Research Institute

Claims (15)

[Claims] 1. A plasma containing a large number of negative ions is generated in a first plasma generation chamber set in a relatively high-pressure environment, and a plasma is generated in a second plasma generation chamber set in a relatively low-pressure environment. A plasma containing a relatively large number of positive ions is generated, the positive ions and negative ions are introduced into a processing chamber having a sample stage, and a high-frequency alternating voltage is applied to the sample placed on the sample stage in the processing chamber. A plasma processing method, characterized in that the plasma processing is performed. 2. The plasma processing method according to claim 1, wherein the processing chamber is also used as the second plasma generation chamber. 3. A first plasma generation chamber set in a relatively high pressure environment for generating a plasma containing a relatively large number of negative ions, and a plasma set in a relatively low pressure environment and containing a relatively large number of positive ions. A second plasma generating chamber for generating a high frequency, a processing chamber in which the positive ions and negative ions are introduced and a sample stage is provided inside, and a high frequency is applied to a sample placed on the sample stage in the processing chamber. And an alternating voltage applying means for applying the alternating voltage. 4. The plasma processing apparatus according to claim 3, wherein the processing chamber also serves as the second plasma generation chamber. 5. The plasma processing apparatus according to claim 3, wherein the alternating voltage applying means is a high frequency transformer. 6. The plasma processing apparatus according to claim 4, wherein a plurality of the first plasma generation chambers and / or the second plasma generation chambers are provided. 7. The plasma processing apparatus according to claim 3, further comprising magnetic field adding means for applying a magnetic field to the second plasma generation chamber. 8. The plasma processing apparatus according to claim 4, wherein the first plasma generating chamber and the second plasma generating chamber are partitioned by a slit plate or a perforated plate. 9. The plasma processing apparatus according to claim 8, further comprising a cooling device for cooling the slit plate or the perforated plate. 10. The plasma processing apparatus according to claim 8, wherein the slit plate or the perforated plate is made of a conductor. 11. The plasma processing apparatus according to claim 3, further comprising a cooling device that cools the first plasma generation chamber. 12. The plasma processing apparatus according to claim 3, wherein the first plasma generation chamber is made of a conductor. 13. The plasma processing apparatus according to claim 3, wherein the high-frequency waveform applied by the alternating voltage applying means is any one of a sine wave, a rectangular wave, and a triangular wave, or any other waveform. . 14. The plasma processing apparatus according to claim 3, wherein the alternating voltage applying means includes a function of controlling an on / off ratio of the high frequency. 15. The plasma processing apparatus according to claim 3, wherein an element that contributes little to etching or an element that does not contribute to etching is mixed in the plasma atmosphere.