JPH0719751B2 - Deposition method - Google Patents

Description

The present invention relates to a method for forming a semiconductor film using glow discharge.

[Prior Art] Conventionally, a method using a device as shown in FIG. 10 has been devised as a method of forming discharge on both sides of one RF electrode and forming a semiconductor film on both sides thereof. this is,
The substrates (4a) and (4b) are placed on the ground electrodes (3a) and (3b) on both sides of the RF electrode (1), and discharge is generated on both sides of the RF electrode (1), and the substrates (4a) and (4b) ) Film is formed on the substrate (4a) by heaters (5a) and (5b) if necessary.
The semiconductor film may be formed while heating a) and (4b). In this case, one RF electrode is used for the two film-forming surfaces,
It has the advantage that only one RF power supply and one matching circuit are required. However, if the left and right semiconductor layer formation rates are different, there is a drawback in that the rate cannot be adjusted.

In order to adjust the left and right semiconductor film formation rates, that is, the discharge strength, the substrates (4a) and (4b) are placed in the center and the RF electrode (1a) is placed outside, as shown in FIG. There is a method of placing a total of two (1b) so as to face each substrate.
In this case, an independent RF power source and a matching circuit are connected to each of the two RF electrodes, and the output of each of them is adjusted, whereby the intensity of the discharge can be adjusted. Therefore, although there is an advantage that the film formation speed can be controlled, it is necessary to take measures to prevent mutual interference by two RF power supplies, and in addition, two RF power supplies and two matching circuits are required, resulting in cost reduction. However, there are drawbacks such as high cost and restrictions on usable devices.

[Problems to be Solved by the Invention] The present invention is as described above, that is, a set of one RF electrode, an RF electrode and a matching circuit as shown in FIG.
Glow discharge decomposition on both sides of the electrode, which solves the problem of different deposition rates of the left and right semiconductor films, which occurs when semiconductor films are deposited on two substrates, as shown in FIG. , Two RF power supplies and two matching circuits are required, the cost of the device becomes high, there are restrictions on the devices that can be used, and it is necessary to prevent mutual interference by the two RF power supplies. Is.

[Means for Solving the Problems] The present invention, when forming a semiconductor film by glow discharge decomposition between an RF electrode and a ground electrode arranged so as to face each surface of the RF electrode, Using two metal plates that are electrically insulated as RF electrodes and are arranged parallel to each other,
One of the two metal plates has a variable circuit having an electric element composed of at least one of a capacitor and a coil, and one of the metal plates has a circuit having an electric element composed of at least one of a capacitor and a coil. In this case, the RF power is introduced from one matching circuit connected from one RF power source to each metal plate directly through the circuit and when not having the circuit, and The present invention relates to a film forming method characterized by forming a film while controlling plasma on both surfaces.

[Example] The method of the present invention will be described based on FIG. 1 showing one embodiment thereof.

The RF electrode is formed by sandwiching two metal plates (1a) and (1b) arranged in parallel with each other with an insulating material (2) interposed between them. An electric element such as a fixed capacitor (6b) is connected in series to each metal plate. And the variable capacitor (6a) is connected outside the reactor. On the other hand, the high frequency (RF) supplied from the RF electrode is divided into two through the matching circuit and supplied to the capacitor.

On both sides of the RF electrode, ground electrodes (3a) and (3b) serving as counter electrodes are arranged in parallel with the RF electrode surface, and the substrates (4a) and (4b) are placed thereon. As shown in FIG.
If necessary, heaters (5a) and (5b) may be arranged to heat the substrates (4a) and (4b).

The method for separating the metal plates (1a) and (1b) forming the RF electrode is
When the gas is introduced from the inside of the electrode, it is preferable to have a structure in which an insulating material (2) is sandwiched as shown in FIG. 1, but it is not limited to such a method and electrically insulated. Any method may be used as long as it is done.

By thus electrically dividing the metal plate forming the RF electrode into two parts and connecting a capacitor to each in series, film formation can be performed on both sides of the RF electrode, and if the left and right film formation rates are different. In the meantime, the film forming rate can be arbitrarily adjusted by changing the capacity of the condenser.

The film formation speed can be adjusted by measuring the thickness of the film once formed and adjusting it so that the left and right sides are the same, or by observing the discharge strength with the eyes so that the strength is roughly the same. , OES
(Plasma spectroscopic analysis) is used to detect the intensity of the discharge by means of detecting the plasma intensity, and the value can be adjusted manually by a human, or a combination of a controller and a servomotor suitable for the manual operation can be used. Examples of the method include automatic adjustment, and of these, the method of automatic adjustment using a combination of a controller and a servomotor is particularly desirable.

Instead of the condenser, a coil may be used as shown in FIG. Further, the capacitors and the coils may be connected in parallel as shown in FIGS. 3 and 4, or the coils and the capacitors may be connected in an appropriate combination as shown in FIG. Of course, the electric element may be connected to only one of the metal plates forming the RF electrode. In short, if the RF power supplied from one RF power source and the matching circuit is branched into two and the strength of the RF power can be appropriately adjusted, the film can be used in the film forming method of the present invention. At this time, it goes without saying that the coil and the condenser are preferably variable.

The coil referred to in this specification includes, in addition to a so-called coil in which an electric wire is wound in a spiral shape, a conductor having an appropriate inductance, for example, a copper plate used for introducing RF into a predetermined shape. It is a concept that also includes.

As shown in FIG. 6, even if the electric element is not inserted between two metal plates forming the RF electrode after branching the matching circuit into two, the RF electrode is formed from the two metal plates. If used, the discharge can be changed to some extent only by changing the length and shape of the RF-introduced copper plate as described above.

When the inductance or capacitance of these coils or capacitors is changed to change the left and right discharge intensities, the equivalent circuit of the entire system also changes the constants, so the matching circuit operation part (often a variable capacitor) )
It is necessary to adjust the matching to the frequency of the RF electrode by operating. In the specification, the matching circuit conventionally used as shown in FIG. 7 is referred to as such, but it may be referred to as a matching circuit including the electric elements used in the present invention.

The distance between the two metal plates separated by the insulating material (2) is arbitrary, but is usually 1 to 200 mm. The distance between the RF electrode and the substrate is preferably about 5 to 50 mm from the viewpoint of discharge stability and uniformity, and more preferably about 10 to 30 mm.

The area of the RF electrode is preferably less than 1 m ² , but if more area is required, divide it into less than 1 m ² and arrange multiple RF electrodes to use the structure shown in Fig. 8. do it. If necessary, the electrodes may be DC-connected in the longitudinal direction. When a large number of electrode pairs are arranged in a straight line, the film formation area can be increased, and theoretically can be increased to infinity. In the parallel plate method, one electrode area is 1m
^The limit is about ² .

Substrate moving means (not shown) may be provided on both sides of the RF electrode so as to move the substrate in parallel with the RF electrode. The substrate moving means may move the substrate to the RF electrode part and move it after film formation. However, while keeping the distance between the substrate and the RF electrode almost constant during film formation,
The substrate may be moved in one direction, or may be repeatedly moved in amplitude. By moving the substrate during film formation in this way, the thickness distribution of the formed film can be made extremely small.
A specific example of such substrate moving means is a multi-chamber in-line type device.

The RF electrode and the substrates transported to both sides thereof may be horizontal as long as they are substantially parallel to each other, may be vertical, or may be present by being bent at other angles. When these are arranged in a nearly vertical state, dust does not drop on the film formation surface, so that a good film is formed.

When a long continuous substrate is used as a substrate and a continuous film formation is performed, a method of moving the substrate to one side is suitable, but a short substrate is usually used.

The substrate may be heated by a heater provided as necessary so that the substrate can be heated. Substrate temperature varies depending on the type of film to be formed, purpose of use, etc.
About 50 to 400 ° C is preferable.

As shown in FIG. 9, when the RF electrode pairs arranged linearly are arranged in parallel, for example, 1 to 100 pairs, preferably 1 to 10 pairs, semiconductor layers are simultaneously formed on a large number of substrates. It is possible to increase the film formation area.

A film forming apparatus such as an amorphous semiconductor film to which the method of the present invention is applied has an RF electrode formed of two metal plates, and there is no particular limitation other than having an electric element on at least one of the metal plates. Any commonly used type of film forming apparatus can be used. For example, it may be a device having a multi-chamber structure, in which case at least one of the chambers constituting the multi-chamber structure (for example, one of the chambers forming p-layer, i-layer, and n-layer) The method of the present invention may be used.
When using a device with a multi-chamber structure as described above, since the substrate passes through each chamber, slits and gate valves are provided in the partition walls, but there are slits instead of gate valves. In order to improve productivity, it is preferable that a differential evacuation chamber having an ordinary differential evacuation means is provided and the substrate can be continuously moved.

As described above, the apparatus used in the present invention as shown in FIG. 1 is provided as a glow discharge decomposition film forming apparatus for forming an amorphous semiconductor film, and the frequency is about 1 to 100 MHz.
RF power per unit area of film formation is 0.003 to 0.2 W / cm ² , and when microcrystallizing is about 0.1 to 5 W / cm ² , a reactive gas such as a silicon compound, a carbon compound, a nitrogen compound, a doping gas. , Of raw material gas consisting of inert gas.
Glow discharge is performed in the presence of about 01 to 5 Torr to form a semiconductor layer on the substrate to a thickness of about 0.005 to 100 μm.

When a film is formed using the method of the present invention, it is easy to form a large-area film with a small device, and a uniform film thickness can be obtained. In addition, a film of uniform quality can be obtained, and since parasitic discharge is small, powder does not easily come out, a film with few pinholes is obtained, glow discharge is extremely stable, and RF utilization efficiency is high. ing. In addition, silicon-containing pins, pn, hetero or homojunction solar cells, sensors, TFTs (thin film)
In the case of devices such as transistor) and CCD (charge coupled device), especially in the case of solar cells containing amorphous silicon, plasma stability greatly affects the reproducibility of the efficiency. High conversion efficiency of over 100% can be obtained with good reproducibility in a large area. It is also suitable for use as a photosensitive material for electrophotography, a passivation film for LIS, and an insulating film for printed boards.

Next, the present invention will be described based on examples.

Example 1 An example of a film forming method using a glow discharge type film forming apparatus similar to that shown in FIG. 1 will be described.

We connected a capacitor and introduced RF divided into two parts through a capacitor with a 13.56MHz RF oscillator and matching circuit into two metal plates (560 x 560mm) sandwiching a 4mm insulating material. The used capacitors are fixed 250pF and Max 500
It was a variable capacitor of pF. 40 cm square IT as a substrate
SiH ₄ / CH ₄ at a substrate temperature of 200 ℃ using an O / SnO ₂ glass substrate
= 50/50, B ₂ H ₆ / (SiH ₄ + CH ₄ ) = 0.05% (mol%, the same applies below) for a p-layer of 100Å and SiH ₄ for an i-layer of 6000
Å, an n-layer consisting of PH ₃ / SiH ₄ = 0.2% was formed into a 500 Å film. The condenser was used at 250 pF and 350 pF. Then AI about 1000
Å It was vapor-deposited and the distribution of conversion efficiency of solar cells was obtained using AM-1, 100mW / cm ² solar simulator.
It was found that the minimum was 10.4%, the maximum was 11.7%, and the average was 11%, which was extremely uniform and high efficiency was obtained. In addition, the efficiency did not change even when the film was formed at a film forming rate of 10Å / sec. The thickness of the semiconductor layer was almost the same on the left and right.

Example 2 The film formation rate of the i layer was obtained in the same manner as in Example 1 except that the right capacitor of Example 1 was fixed at 250 pF and the left capacitor was changed to 10 to 500 pF. The results are shown in Table 1.

[Effects of the Invention] As described above, an electric element such as a capacitor or a coil is connected to two separated metal plates forming an RF electrode,
By manipulating them, the deposition rate of the left and right semiconductor films can be drastically changed.If the deposition rates of the left and right semiconductor films are different, adjust the electric elements such as capacitors or coils. Thus, the film forming rates can be easily made the same.

[Brief description of drawings]

FIG. 1 is an explanatory view of one embodiment of an apparatus used in the film forming method of the present invention, and FIGS. 2 to 5 are explanatory views of connection of electrodes, electric elements and matching circuits of different embodiments used in the present invention, FIG. 6 is an explanatory diagram when a matching circuit is directly connected to the electrodes used in the present invention, FIG. 7 is an explanatory diagram relating to one embodiment of the matching circuit used in the present invention, and FIGS. 8 to 9 are each used in the present invention. FIG. 10 to FIG. 11 are explanatory views relating to the arrangement of electrode pairs of different embodiments, and FIGS. (Main symbols in the drawings) (1), (1a), (1b): Metal plate forming RF electrode (2): Insulating material (3), (3a), (3b): Ground electrode (6a): Variable Capacitor (6b): Fixed capacitor (7a): Variable coil (7b): Fixed coil

Front page continuation (72) Inventor's fabric No. 25, Saiin Oiwake-cho, Ukyo-ku, Kyoto-shi, Shimadzu Corporation Gojo factory (56) References JP-A-58-48416 (JP, A) JP-A-59- 14633 (JP, A) JP-A-58-163436 (JP, A)

Claims (6)

[Claims] 1. When a semiconductor film is formed by glow discharge decomposition between a PF electrode and a ground electrode installed so as to face each of both surfaces of the PF electrode, it is electrically insulated as an RF electrode, Two metal plates arranged in parallel to each other are used, one of the two metal plates is provided with a variable circuit having an electric element composed of at least one of a capacitor and a coil, and one of the metal plates is provided with a capacitor. And a coil having an electric element consisting of at least one kind of coil, the circuit is connected through the circuit, and when the circuit is not provided, directly connected to each metal plate from one RF power source. Introducing RF power from one matching circuit,
A film forming method characterized by forming a film while controlling plasma on both sides of an RF electrode. 2. The film forming method according to claim 1, wherein the connection via the variable circuit having the electric element is connection of capacitors in series or in parallel. 3. When a condenser is connected to both of the two metal plates, the condenser is a fixed and variable condenser, and when the condenser is connected to only one of the two metal plates. In the meantime, the film forming method according to claim 2, which is a variable capacitor. 4. The film forming method according to claim 1, wherein the connection through the variable circuit having the electric element is a connection in which coil inductances are connected in series or in parallel. 5. When the coil is connected to both of the two metal plates, the coil is a fixed and variable coil, and when the coil is connected to only one of the two metal plates. In the meantime, the film forming method according to claim 4, wherein the coil is a variable coil. 6. The film forming method according to claim 1, wherein the control is a control for uniformly adjusting the film thickness distribution of the semiconductor film on both sides of the RF electrode.