JPH08222399A - High-frequency plasma generator - Google Patents

Abstract

PURPOSE: To enable a base of a large area to be processed with a plasma by providing a plurality of downwardly open plasma generation chambers on the upper-end wall of a plasma reaction chamber, and supplying a reaction gas into each of the plasma generation chambers. CONSTITUTION: A base support stand 3 for supporting a large base 2 is installed in the lower inside portion of a plasma reaction chamber 1 covered with a wall body, and a plurality of plasma generation chambers 5 open downward at an upper-end wall 4 are placed in the upper inside portion. A plurality of electrode blocks 8a to 8e are aligned on the upper end wall to correspond to the plural lines of plasma generation chambers 5. Gas introduced into each plasma generation chamber 5 sandwiched between alternating electrodes consisting of the array of electrode blocks 8 produces a plasma state. Therefore, large-area base processing can be carried out effectively and uniformly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma generator, and more particularly to a high frequency plasma generator for etching or ashing a substrate surface and performing chemical vapor deposition (CVD).

[0002]

2. Description of the Related Art A high-frequency plasma generation method in a plasma process apparatus has various differences in electrode structure, reaction chamber shape, high-frequency power application method, frequency and the like. A reaction chamber having a single plasma generating part with a single electrode structure was used for one object. Therefore, as the size of the object increases, the single reaction chamber and related structures also increase, making it difficult to increase the uniformity of the plasma density and the plasma density within the surface of the object.

[0003]

The conventional plasma generator as described above has various problems due to the structure of the single plasma generator. Generally, the electrode structure of the plasma generator is roughly classified into an externally installed electrode structure and an internally installed electrode structure. Among them, in the externally installed electrode structure, an electrode for applying a high frequency voltage is formed so as to surround the outer wall of the plasma generation chamber, and the plasma gas generated in the plasma generation chamber is generally downflowed. Is. In the case of such an externally installed electrode structure, as the size (surface area) of the plasma reaction target increases, the outer diameter of the plasma generation chamber also increases, making it difficult to maintain a uniform plasma density in the plasma generation chamber. There is a problem that a large density difference occurs in each part of the room.

The fact that the uniformity of the plasma density becomes worse as the surface of the object becomes larger as described above means that the uniformity of the ion density and the electron density at the surface of the object becomes worse. The non-uniformity of the ion density and the electron density causes, for example, destruction of the gate insulating film and partial under-etching or over-etching in etching. Further, in CVD, the uniformity of the deposited film thickness is naturally affected.

Further, considering the size of the plasma generator from another point of view, the basic operation of the device is to apply high-frequency energy to the gas to turn it into plasma, but a single electrode for a single reaction chamber. In the method that uses the structure and plasma generation chamber, as the electrode structure and plasma generation chamber are enlarged, the electrode area that directly acts on the gas becomes relatively smaller than the gas volume, and the amount of energy replacement per unit gas volume. As a result, it was difficult to increase the plasma density.

On the other hand, in the case of the internal installation type electrode structure, the electrode can be made large in area corresponding to a large area object, and the uniformity with respect to the surface of the object can be maintained relatively easily. There was a problem that the electrode itself in 1 was sputtered by plasma.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention has a top surface of a plasma reaction chamber that surrounds a wafer support table and opens downward so that substantially the entire surface of the wafer support table is covered. A plurality of plasma generation chambers arranged so as to correspond to the range were provided, and a high-frequency plasma generation device having a plurality of gas inlets with control valves for supplying reaction gases to the plurality of plasma generation chambers was configured. It is a thing.

According to a preferred aspect of the present invention, the plurality of plasma generating chambers are arranged in a plurality of rows, and high frequency energy is supplied to these chambers by electric field type discharge (E discharge) to generate plasma. In the case of using the means, the plasma generating means, a pair of electrode blocks arranged along the outside of the plasma generation chambers of the outer row,
The same high-frequency voltage is formed between each pair of electrode blocks sandwiching the plasma generation chamber of each row by connecting at least one electrode block alternately arranged between the columns of the plasma generation chamber and alternately connecting these electrode blocks together. 2 for applying
The terminal electrode circuit is configured.

According to another preferred aspect of the present invention, the plurality of plasma generating chambers are arranged in a plurality of rows, and high frequency energy is supplied to these chambers by magnetic field type discharge (H discharge) to generate plasma. In the case of using the means for providing, the plasma generating means is provided with a pair of network electrode plates having a plurality of node openings corresponding to the plurality of plasma generating chambers above and below the array, and the pair of electrode plates face each other. Each of the nodes is connected to an antenna element composed of a helical coil to surround the corresponding plasma generation chamber, and one high frequency voltage is applied between the pair of electrode plates.

Further, in another preferred embodiment of the present invention,
Means for applying a bias voltage may be added between the block electrode or network electrode plate and the wafer support.

According to one embodiment of the present invention, the electrode block or electrode plate is located outside a wall of a closed space surrounded by the plurality of plasma generation chambers and the plasma reaction chamber, It is physicochemically isolated from the plasma reaction gas.

According to still another embodiment of the present invention, means for applying a DC or high frequency bias voltage or applying a magnetic bias is added to the wafer to be processed in the plasma reaction chamber.

[0013]

According to the above basic structure, the high-frequency plasma generator of the present invention is provided with a plurality of plasma generation chambers as compared with the system having the single electrode structure and the plasma generation chamber.
The effective area of the electrode acting on the gas increases per the same gas volume, and the energy conversion efficiency for replacing the high frequency energy with the plasma energy increases. That is, the equivalent impedance of the plasma generation chamber is lowered, and the high frequency power supplied to the plasma generation chamber can be increased at the same high frequency applied voltage, which makes it possible to improve the plasma density.

Further, it is possible to individually provide a gas controller for each of the plurality of plasma generating chambers, and even if the area of the object is increased, the gas flow is uniformly controlled and the in-plane direction of the object is increased. Uniformity can be easily controlled.

As described above, in the system in which the gas controller is provided for each plasma generation chamber, a plurality of gas streams can be supplied to a plurality of plasma generation chambers in each plasma at the same time or in a switched manner. It has become possible to have general versatility.

Further, the area required for a large-diameter silicon substrate or a large-area glass substrate can be easily dealt with as an entire array pattern by increasing the number of plasma generation chambers arranged vertically and horizontally. Even in the plasma processing for these large areas, plasma with high density and good uniformity can be generated, and thus the uniformity of ion and electron densities with respect to the object can be improved. Therefore, in the etching, it is possible to prevent destruction of the gate insulating film and generation of under-etching or over-etching, and in CVD, it is possible to improve the uniformity of the generated film thickness.

The improvement of the plasma uniformity with respect to the target surface by the plurality of plasma generation chambers as described above makes it possible to make the distance between the plasma generation chamber and the substrate closer to each other, and the lifetime of the plasma ions according to the distance. In this, the plasma ion density is relatively improved.

Further, since the electrode structure of the present invention is of an external type, the electrode itself is not directly exposed to the gas plasma, and there is no problem that the electrode or the coupling coil is sputtered.

Further, in the system using the means for applying the DC bias voltage or the high frequency bias voltage in the plasma reaction chamber, it becomes easy to provide the ion trap and the grid, and the ions down-flowing from the plasma generation chamber can be controlled and indirectly. It is possible to find optimal processing conditions that also control radicals.

A counter electrode is provided at a position facing the wafer support, and a bias voltage is formed between the counter electrode and the wafer support so that a potential gradient in which the wafer surface side is substantially negative is formed in the reaction chamber. , The degree to which the plasma ions generated in the plasma generation chamber (most of which are positively charged) are scattered and stray to the side, and the vertical directivity of the plasma ions with respect to the wafer surface is increased.
As a result, anisotropy in etching can be increased. Further, by using this bias voltage as a high frequency voltage and arranging a blocking capacitor on the wafer support side, a negative bias is given to the wafer side in terms of direct current component, and the above-mentioned action can be effectively achieved. Plasma generation is promoted in the reaction chamber by the components, and as a result, the anisotropy of etching can be increased as described above.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a side sectional view showing an embodiment of a high frequency plasma generator having a plurality of plasma generating chambers provided with external electrodes in the E discharge system. In FIG. 1, a plasma reaction chamber 1 covered with aluminum or another wall.
A substrate support base 3 for supporting a relatively large substrate 2 is installed in the lower part of the inside, and a plurality of quartz glass plasma generation chambers 5 opening downward in an upper end wall 4 are arranged in the upper part. In this case, the plasma generation chamber 5 corresponds to the entire surface of the substrate 2 on the support base 3 in a square array of 4 rows and 4 columns, and the upper end thereof is open to each branch pipe of the plasma gas introduction pipe 6. A valve 7 for individually controlling the gas flow rate is arranged in each branch pipe.

On the upper end wall 4, a plurality of electrode blocks 8a to 8e are arranged corresponding to a plurality of rows of plasma generating chambers 5. 9 is a matching circuit for applying a high frequency voltage between each pair of adjacent electrode blocks 8a to 8e,
Reference numeral 10 is a power supply circuit that supplies high frequency power to the matching circuit.

The positional relationship between the plurality of plasma generating chambers 5 and the electrode blocks 8a to 8e associated therewith is as shown in the partial sectional view of FIG. The electrode blocks 8a to 8e are formed of copper or aluminum and have corrugated side surfaces corresponding to the side surfaces of the rows of the plasma generation chambers 5, whereby the electrode blocks 8a and 8b sandwich the plasma generation chambers 5 in the leftmost row, The blocks 8b and 8c sandwich the plasma generation chamber 5 in the next row, the electrode blocks 8c and 8d further sandwich the plasma generation chamber 5 in the next row, and the electrode blocks 8d and 8e are the plasma generation chambers in the final row (rightmost row). 5, the wavy concave surfaces of the pair of electrode blocks facing each other form a coaxial cylindrical surface that closely corresponds to the peripheral wall of the plasma generation chamber 5. In this case, since the same high-frequency voltage is applied between each pair of electrode blocks, one terminal of the matching circuit 9 has electrode blocks 8a, 8c,
8e is connected, and the electrode blocks 8b and 8d are connected to the other terminals to form a parallel two-terminal electrode circuit.

The matching circuit 9 has a combined load impedance of a plurality of plasma generation chambers 5 to which high-frequency power is supplied via such a parallel two-terminal electrode circuit and an output impedance of the high-frequency power source 10 (generally Z = 50Ω). To match.

Therefore, the gas introduced into each plasma generation chamber 5 sandwiched between the alternating electrodes composed of the electrode block group 8 is an ion by a high frequency electric field (E discharge) generated by a voltage applied between the electrodes, It separates into radicals and electrons, and creates a completely integrated plasma state. Since the opposing electrode surface is a partial cylindrical surface that is coaxial with each plasma generation chamber and faces each other, the lines of electric force are evenly generated through the electrode surface, the uniformity of the electric field is improved, and the electric field strength distribution becomes almost constant. .

Further, in order to provide a condition in which plasma is more easily generated, a magnetic bias acting on the plasma generation chamber 5 can be added. This is, for example, arranged on both side walls of the plasma reaction chamber 1 so as to have a magnetic field extending from the lower end opening of each plasma generation chamber 5 or a pole for permanent magnets or a coil for generating magnetism. If a static positive magnetic field is applied, the electrons in the plasma will get Lorentz force from the electromagnetic field and will undergo E × B drift while performing a cycloidal motion, and more efficiently generate high-density plasma under low pressure. You can
Further, in order to control the anisotropy or the like of the CVD deposited film, a DC or high frequency bias voltage is applied to the object. This is done by applying those voltages to the support 3.

In FIG. 3, the arrangement of the plasma generating chambers 5 and the electrode blocks 8'is changed from the orthogonal arrangement of FIG. 2 to a honeycomb arrangement. According to this honeycomb arrangement, the inter-row electrode blocks 8b, 8c, 8d required in the orthogonal arrangement are provided.
Plasma generation chamber 5 required to correspond to the minimum thickness such as
Since the interval between them can be omitted, the ratio of the cross-sectional area of the plasma reaction chamber to the effective electrode area can be increased, and more effective and high-density plasma can be generated.

Reference will now be made to FIG. 4 to consider the relationship between the number of plasma generation chambers and the plasma generation efficiency. FIG.
(A) is a schematic view of a main part of one plasma generation chamber 5a (range in which electrodes work in the E discharge method),
If the counter electrode covers the entire circumference of the generation chamber main part 5a of radius R within the range of height h in the study model, the electrode effective area is 2πR × h, and the plasma acting area for the object to be processed is For the time being, πR ² corresponds to the disk within the opening diameter D, but it is considered that the larger the electrode effective area with respect to the plasma working area, the better the plasma generation efficiency. Here, as shown in FIG. 4B, when four plasma generation chambers are arranged in a section obtained by dividing a square having the diameter D as one side into four, if the thicknesses of the peripheral walls are ignored. , While the total of each opening area (operating area) is πR ² as in the case of (A), the electrode effective area is each plasma generating chamber (height h)
4 times the value πRh at, that is, 4πRh,
This is twice the case of the unit structure of (A). This means that the plasma generation efficiency is improved, and by dividing the area into four, the plasma action on the action surface below the plasma generation chamber is averaged. Further, when the square of the one side D is formed in 3 rows and 3 columns (not shown), the electrode effective area is 9/30 · 2πRh = 6πRh, which is three times as large as (A). However, since the peripheral wall of the generation chamber 5a and the electrode 8 are actually thick, it is necessary to allow for them to be about ⅕ of the radius. For example, in the case of four divisions, FIG.
As shown by the four solid circles in (B), the inner diameter of each chamber is 0.
8 × 1/2 · R = 0.4R, but even in this case, the total effective electrode area is 4 × 2 (0.4) πRh = 3.2πR
It becomes 1.6 times as large as (A) at h. However, since the downdraft from the opening of each plasma generation chamber diffuses, the plasma action area is simply 4 times (0.8πR) of each opening area 0.2πR ^2.
R ² ), not the area corresponding to the circle having the diameter D. It should be noted that with the honeycomb-shaped arrangement, it is apparent that the plasma generation chambers having the same diameter can be arranged at a higher density, so that the plasma generation efficiency can be further improved.

FIG. 5 shows a structure similar to that of the plasma generator shown in FIG. 1. Instead of using the electrode blocks 8a to 8e, a pair of network electrode plates 11 and 12 are used, and the nodal openings 11a and 12a of the plasma electrode plates are formed. The helical coil 1 is located between the nodes of the electrode plates 11 and 12 located at the upper and lower ends of the outer periphery of the generation chamber and facing each other.
This is an embodiment of a plasma generator in which an H-discharge abandonment is made by inserting an antenna element consisting of 3 and fitting the outer periphery of each plasma generation chamber. In the embodiment of FIG. 5, the parts designated by the same reference numerals as those of the device of FIG. 1 are the same components, and the description thereof will be omitted.

The relationship between each generation chamber 5 and the electrode plates 11 and 12 is as shown in FIG. 6, and both ends of the helical coil 13 are securely connected near the openings of the electrode plates 11 and 12. As shown in FIG. 7, the nodal opening of the electrode plate is a circular opening corresponding to the outer diameter of the plasma generation chamber, and the plate area is made as large as possible, so that the electrostatic capacitance formed between the electrode plates 11 and 12 is formed between the electrode and the helical coil. Although it can be positively used as a parallel capacitor, the opening may be a square or a hexagon corresponding to a honeycomb arrangement in the connectable range of the helical coil 13.

Also in this H discharge type embodiment, a similar magnetic bias and voltage bias type for applying a DC voltage or a high frequency voltage to the substrate support 3 can be selectively adopted.

Device Configuration Example 1. E-Discharge System 8-inch Semiconductor Wafer Etching Device This device has 16 plasma generating chambers arranged in a square array on a square plasma reaction chamber having a bottom area of, for example, 30 × 30 cm ² . The wafer to be processed is a silicon single crystal (diameter 8 in) with a crystal axis 100 having a thermal oxide film.
Is. The conditions of the plasma reaction chamber are as follows. Ion density: 3 × 10 ¹¹ ions / cm ² SiO ₂ Etching: 1200Å / min Reaction gas conditions: CHF ₃ 200SCCM Ar 750SCCM He 25SCCM Reaction chamber pressure: 2m Torr High frequency power: 13.56MHz 750W Effective under these conditions, and Oxide film etching of a uniform semiconductor wafer can be performed.

2. H discharge type liquid crystal etching device This device forms a plasma reaction chamber having a bottom area of, for example, 70 × 70 cm ² , and provides 64 plasma generation chambers arranged in a square shape on the upper part of the plasma reaction chamber. It was configured to apply an RF bias voltage. The substrate to be processed is a large liquid crystal glass substrate of 65 × 55 cm ² .
The conditions of the plasma reaction chamber are as follows. Ion density: 4 × 10 ¹¹ ions / cm ² P-SiO ₂ Etching: 1200Å / min Reaction gas condition: CHF ₃ 620SCCM Ar 1460SCCM He 60SCCM Reaction chamber pressure: 2m Torr High frequency power: 400KHz 3KW

In the device configuration examples 1 and 2, the RF
When the bias voltage is applied, the power supply supplies less than 1/2 of the main power supply described above.

Next, FIG. 8 shows an embodiment of the plasma generator of the E discharge system (FIGS. 1 and 2), which is connected to the electrode blocks 8b and 8d at positions facing the wafer 2 and is connected to the counter electrode 1.
4 is provided, and an output 4
This is an example in which a high frequency power source 15 of 00 KHz is connected.
The counter electrode 14 is made of a conductor such as copper or aluminum and has a size capable of facing substantially the entire surface of the wafer 2. The counter electrode 14 is connected to and held by the lower surfaces of the electrode blocks 8b, 8c and the lower surfaces of the electrode blocks 8a, 8c, 8d. Is insulated from. The blocking capacitor 15 is connected to the wafer side of the high-frequency power source 15, and the filter 17 is connected to the counter electrode side. With respect to the direct current, a negative bias voltage on the wafer side is applied between the counter electrode 14 and the wafer by the capacitor 16, whereby plasma ions generated in each plasma generation chamber 5 (most of them are positive ions). The vertical directivity of the downflow toward the wafer surface is promoted, the side-scattering stray of plasma ions can be largely prevented, and the anisotropy in etching is improved. Further, the high frequency generated by the high frequency power supply 15 prevents the plasma state in the reaction chamber 1 from disappearing (recombination with free electrons), which further promotes plasma generation. The filters 17 and 18 are both power sources 10 (13.56 MHz) 15 based on the fact that the counter electrodes are electrically connected to a part of the electrode block for plasma generation.
This is to prevent mutual interference of (400 KHz). The other reference numerals in the figure indicate the same parts as those of FIG.

FIG. 9 shows an embodiment of the H discharge type plasma generator in which a bias voltage is applied between the counter voltage and the wafer support in the embodiment (FIGS. 5, 6, and 7).
In this case, the counter electrode 14 is characterized in that it is integrally formed with the network electrode plate 12, which is a component of the antenna element. That is, one of the network electrode plates
By providing the bias power supply 15 between the wafer 2 and the wafer support 3, the same operation and effect as described with reference to FIG. 8 can be obtained. The other reference numerals in the figure indicate the same parts as those of FIG. It should be noted that in the embodiment of FIGS.
Although an example using a high frequency power source of about 0 KHz has been shown, this bias voltage may be a DC voltage, and in this case, it is desirable that the wafer support base side be on the negative potential side.

According to the embodiments shown in FIGS. 8 and 9, a plurality of plasma generations are performed by providing the counter electrode in a state in which it is connected to the plasma generating electrode block, or by also serving as a network electrode. The present invention has a further advantage that the anisotropy of etching is improved with a simple structure while utilizing the feature of the present invention in which a chamber is provided.

[0038]

As described above, according to the present invention, by providing a plurality of plasma generating chambers, a large area substrate can be plasma-processed. In particular, in the case of manufacturing a large-sized liquid crystal display device, it is possible to process a large-area liquid crystal substrate by the device of the present invention as a single unit, which brings various advantages such as enhancing the plasma processing capacity itself.

[Brief description of drawings]

FIG. 1 is a cross-sectional view and a diagram schematically showing a typical embodiment according to an E-discharge method.

FIG. 2 is a partial perspective view showing a typical example of the plasma generation chamber and electrode arrangement in the embodiment of FIG.

3A and 3B are a plan view and a block diagram showing a modified example of the arrangement of FIG.

FIG. 4 is a diagram for explaining the relationship between the effective electrode area and the working area, where (A) shows the dimensions of the main part of the plasma generation chamber, and (B) shows the cross section in section. Is.

FIG. 5 is a cross-sectional diagram schematically showing a main part of an embodiment of the device of the present invention by the H discharge method.

FIG. 6 is a partial cross-sectional view showing a relationship between a plasma generation chamber, an electrode plate, and a helical coil.

FIG. 7 is a partial perspective view showing a node opening of an electrode plate.

8A and 8B are a sectional view and a diagram schematically showing another embodiment of the E discharge method.

9A and 9B are a sectional view and a diagram schematically showing another embodiment of the H discharge method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma reaction chamber 2 Substrate 3 Substrate support 4 Upper end wall 5 Plasma generation chamber 6 Plasma gas introduction pipe 7 Valve 8 Electrode block group 9 Matching circuit 10 High frequency power supply 11 and 12 Network electrode plate 13 Helical coil 14 Counter electrode 15 High frequency power supply 16 blocking capacitors 17 and 18 filters

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 21/205 H01L 21/205 21/3065 21/302 B

Claims (7)

[Claims] 1. A plurality of plasma generation chambers are provided which are open downward at an upper end wall of a plasma reaction chamber surrounding a wafer support and are arranged so as to correspond to substantially the entire range of the surface of the wafer support. A high-frequency plasma generator comprising a plurality of gas inlets with a control valve for supplying reaction gases to a plurality of plasma generating chambers. 2. When the plurality of plasma generation chambers are arranged in a plurality of rows and a means for supplying high frequency energy by electric field type discharge to generate plasma in these chambers, the plasma generation means is used. It is composed of a pair of electrode blocks arranged along the outside of the plasma generation chambers in the outer row and at least one electrode block arranged between the rows of the plasma generation chambers, and these electrode blocks are alternately and collectively connected together. 2. The apparatus according to claim 1, wherein a parallel two-terminal electrode circuit for applying the same high-frequency voltage is configured between each pair of electrode blocks sandwiching the plasma generation chamber of each row. 3. A counter electrode, a part of which is connected to one side of the electrode block, is provided at a position facing the wafer support, and a means for applying a bias voltage is added between the counter electrode and the wafer support. The device according to claim 2, wherein 4. When the plurality of plasma generation chambers are arranged in a plurality of rows and a means for supplying high frequency energy by magnetic field type discharge to generate plasma in these chambers, the plasma generation means is used. A pair of network electrode plates having a plurality of node openings respectively corresponding to the plurality of plasma generation chambers are provided above and below the array, and an antenna element formed of a helical coil is provided between the nodes facing each other in the pair of electrode plates. 2. The apparatus according to claim 1, wherein the apparatus is configured to be connected to surround a corresponding plasma generation chamber and to apply one high-frequency voltage between the pair of electrode plates. 5. The apparatus according to claim 4, further comprising means for applying a bias voltage between the electrode plate on one side of the network electrode plate and the wafer support. 6. An electrode block or an electrode plate is located outside a wall of a closed space surrounded by the plurality of plasma generating chambers and the plasma reaction chamber, and is physically and chemically isolated from the plasma reaction gas. Claim 2 characterized by the above-mentioned.
5. The device according to any one of 5 above. 7. The apparatus according to claim 3, wherein the bias voltage applying means is a high frequency power source, and a blocking capacitor is connected to a conductive line to the side of the wafer support.