JPH021908B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a vapor deposition apparatus.

In recent years, amorphous silicon (hereinafter referred to as a-Si) has been viewed as extremely useful as a constituent material for solar cells, electrophotographic photoreceptors, and the like. Also,
Hydrogen-containing a-Si (hereinafter referred to as a-Si) has improved dark resistance and photoconductivity by introducing hydrogen atoms into a-Si and filling the dangling bonds.
It is called H. )It has been known.

Until now, such a-Si:H has been produced as follows [1]
It is deposited on the substrate by the vapor deposition method of ~[3].

[1] Rf ion plating method [2] DC ion plating method [3] Ion or activated hydrogen introduction method (e.g. JP-A-56-78413) (a) Using a hydrogen discharge tube (b) DC ion gun (c) Using an Rf ion gun All of the vapor deposition devices based on these [1] to [3] heat and evaporate silicon in the presence of active or ionized hydrogen in a vapor deposition tank or a vacuum tank (belger). This is based on the following idea. That is, activated or ionized hydrogen is introduced into the vergeer, or at least one of hydrogen and silicon vapor is activated by being discharged by an Rf electric field or a DC electric field. However, upon further study by the present inventor, it was found that all of the above devices have problems and drawbacks that should be improved.
First, in the device [1] above, glow discharge is generated substantially throughout the bell gear, so elements that have already been isolated from impurity gases (for example, PH ₃ ) and attached to the inner surface of the bell gear are removed. (For example, P) re-evaporates during glow discharge and mixes into a-Si:H deposited on the substrate, causing film contamination. . In the device [2] above, thermionic electrons are emitted from the W electrode to the silicon vapor on the silicon evaporation source to ionize the silicon, but arc discharge is likely to occur between the counter electrode for electron attraction and the discharge becomes unstable, and film contamination due to impurities occurs during discharge as described above.
In addition, according to the device [3] above, hydrogen ions generated in the discharge tube are emitted toward the substrate, and a large amount of hydrogen atoms can be introduced into the a-Si film. The amount varies on the board surface,
For example, in the center of the substrate, the hydrogen ion distribution is large;
A problem of non-uniformity arises in that it is less at the periphery. In order to solve this problem, it is conceivable to swing the hydrogen ions supplied into the bell jar using deflection means using an electric field to uniformly scan the substrate surface, but it is not possible to swing the hydrogen ions in this way. This is not very easy and requires high voltage, which tends to cause arc discharge.

As a result of various studies in consideration of the above-mentioned situation, the present inventor has discovered that it is possible to uniformly introduce the above-mentioned modifying gas components such as hydrogen ions into the deposited film, and to stably and easily do this introduction into the deposited film. The present invention was achieved by discovering a vapor deposition apparatus that can also reduce contamination.

That is, in the vapor deposition apparatus according to the present invention, an evaporation source containing a vapor deposition substance such as silicon, and a substrate to be evaporated facing the evaporation source are arranged in a vapor deposition tank, and a modification gas inlet provided in the vapor deposition tank is provided. The device heats the evaporation source and evaporates the evaporation substance onto the substrate in the presence of a modifying gas such as hydrogen supplied into the evaporation tank from the evaporation tank, and emits an electron beam toward the substrate. The method is characterized in that an electron beam supply device for activating or ionizing the modifying gas in the vicinity of the substrate is disposed in the vapor deposition tank.

Therefore, according to the apparatus of the present invention, a modifying gas such as hydrogen is widely supplied into the vapor deposition tank as it is (that is, without being activated or ionized), and it is exposed to the vicinity of the substrate by an electron beam emitted toward the substrate. can be effectively activated or ionized and uniformly introduced into the deposited film. That is, by uniformly distributing the modifying gas near the substrate and exciting it with an easily deflected electron beam, it is possible to uniformly dope the gas component into the deposited film. In addition, since the excitation occurs near the substrate, even if the excitation life of the modifying gas is short, the activated or ionized modifying gas can reach the substrate efficiently, and the deposited film will not be contaminated compared to the above-mentioned full-area discharge. can be significantly reduced. Furthermore, since the modifying gas can be supplied into the deposition tank as it is, it is not necessary to use a discharge tube for activation or ionization, so spatter (for example, discharge of discharge electrode material) that occurs when using a discharge tube can be prevented. ,
Moreover, even if a wide range of gases is supplied, contamination or damage to the discharge tube due to decomposition (for example, contamination or damage due to decomposition of halogen gas such as fluorine) can be prevented.

In order to achieve these remarkable effects, the device according to the present invention applies a negative voltage (especially -
It is desirable to apply a DC voltage of 10 KV or less to attract ions generated near the substrate to the substrate side in order to improve mixing efficiency. In addition, the electron beam emitted toward the substrate is
It is best generated from a thermionic generator such as an electrode,
Alternatively, depending on the case, the gas may be selectively discharged from gas discharge tubes placed at similar positions. Furthermore, it is desirable to provide an acceleration device for accelerating the electron beam emitted from the electron beam supply device, and a magnetic field deflection device or an electric field deflection device for directing it toward the substrate. In addition, in order to uniformly illuminate the electron beam on the substrate surface, a magnetic field deflector or an electric field deflector is used to uniformly scan the substrate surface by changing (or vibrating) the traveling path of the electron beam toward the substrate. It is better to provide equipment.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.

FIG. 1 schematically shows the configuration of a vacuum evaporation apparatus according to this embodiment.

This apparatus includes a substrate 1 to be evaporated and a vacuum chamber (or bell jar) 3 containing, for example, a silicon evaporation source 2. Board 1 is heated to 350-450℃ with heater 4
While being heated to 0 to - by the DC power supply 5
A negative DC bias voltage of 10KV is applied. In the figure, 6 is an introduction pipe for introducing a modified gas such as hydrogen, 7 is an electron beam heating device for the evaporation source 2 (the path of the electron beam is shown by a broken line), and 8 is an exhaust pipe, which is a vacuum pump. (not shown). What should be noted is that the electron beam 9 is directed toward the substrate 1.
A thermionic generator 1 (for example, one having a W filament electrode 13) that emits .

By using this device, for example
At the same time, silicon 11 emitted from the evaporation source 2 is deposited as a-Si on the substrate 1 under a vacuum on the order of 10 ^-4 Torr, and at the same time, for example,
Thermionic electrons 9 emitted with an energy of 500 eV are applied to the modifying gas uniformly introduced into the vergeer 3 in the vicinity of the substrate 1. As a result, the generated activated or ionized gas (e.g. hydrogen ions) is attracted onto the negative potential substrate 1 and deposits e.g.
It is possible to obtain a deposited film of a-Si:H or the like that is efficiently introduced into the film and in which the dangling bonds described above are buried. For example, the hydrogen-containing a-Si obtained in this manner has sufficient dark resistance and photosensitivity, and has a uniform film quality with little variation.

FIG. 2 basically shows a situation in which hydrogen gas 12 as a modifying gas is ionized (or activated) by thermionic electrons 9 in the vicinity of the substrate 1. That is, the thermionic electrons 9 from the thermionic generator 10 collide with the hydrogen molecules 12, and the hydrogen molecules are dissociated (ionized) into hydrogen ions 12' by the energy, and the generated hydrogen ions 12' are attached to the substrate at a negative potential. A-Si is attracted to the 1 side and deposited on the substrate 1 at the same time.
Efficiently mixed into the membrane. On the other hand, the thermionic electron 9 that does not collide with the hydrogen molecule (and the electron 9' after the collision) is
By appropriately setting the potential of the substrate 1, it is repelled as shown in the figure, so that it does not enter the a-Si film. Therefore, the a- deposited on the substrate 1
The Si:H film is not damaged by irradiation due to electron collisions, and the film quality can be improved.

In practice, the thermionic generator 10 is preferably constructed as illustrated in FIG. That is, an alternating current voltage 14 (or a direct current voltage may be used) is applied to the W filament 13, and hot electrons 9 having an energy of, for example, 5000 eV are generated. For example, a ring-shaped accelerating electrode 16 is disposed on the W filament 13. Since this accelerating electrode 16 is given a positive potential, it attracts the thermoelectrons 9 from the filament 13 and accelerates them to a sufficient speed. Further, these accelerated electrons are vibrated back and forth and left and right (X and Y directions) by a deflection device 17 using an electric field, for example, so that their traveling path is changed to be uniform with respect to the surface of the substrate 1. desirable. As a result, the electron beam 9 can be uniformly scanned over the substrate surface, and the modifying gas can be locally activated or ionized near the substrate surface, so that the resulting a-Si:H film can be The distribution of hydrogen atoms, etc. inside becomes uniform, and the film properties are greatly improved. Note that the deflection device 17 includes pairs of deflection electrodes 18a, 18b and 19a, 19b arranged in the X direction and the Y direction, respectively.
A predetermined AC power source (not shown) is connected between each pair of electrodes, and the electron beam 9 is swung in a predetermined direction by application of the AC voltage. In this case, the thermionic beam 9 is made up of light particles and can therefore be easily deflected. On the other hand, as described above, deflecting hydrogen ions requires a large voltage and arc discharge occurs, which is not very good from a practical point of view.

The thermionic generator 10 shown in FIG. 3 is of a type called a point type, but in addition to this, linear type thermionic generators shown in FIG. 4 and surface type thermionic generators shown in FIG. 5 are used. be able to. In the example in Figure 4, W
By making the filament 13 longer than that shown in FIG.
is condensed into a linear parallel beam of constant width. In this case, the linear parallel beam 9 after passing through the slit 20 can be operated so as to be emitted linearly onto the substrate surface in either the X direction or the Y direction in FIG.
Even if the deflection electrodes 18a and 18b or 19 and 19b are omitted, it is possible to uniformly scan the electron flow over the substrate surface. Also, instead of using the flat plate shown in FIGS. 1 to 3 as the substrate 1,
If a rotating drum or moving film is used, the above-mentioned linear parallel beam is emitted at a fixed position in the width direction of the drum or film to uniformly introduce hydrogen atoms, etc. into the deposited film over the entire drum circumference. can do. The thermionic generator 10 in FIG.
The filaments 13 are arranged in parallel, and an electron beam can be emitted toward the substrate through the accelerating electrode 16 in an area corresponding to the area of the arrangement. Accelerating electrode 1
6 may have various shapes other than those shown, such as a lattice shape or a mesh shape. Therefore, in this case, even if the substrate is flat, the electron beam can be emitted over the entire area of the substrate, and the deflection device as described above is not required. The filament 13 shown in FIG. 5 can be spirally wound into a planar shape similar to that shown in FIG. Further, the W plate 13 having the outer shape shown by the dashed line in FIG. 5 may be used as a surface heater for generating thermoelectrons.

As explained above, the vapor deposition apparatus according to this embodiment is configured to emit thermionic electrons onto the substrate with a uniform supply of the modifying gas, which can easily and stably deflect the hydrogen. Ions and the like can be efficiently and uniformly introduced into the deposited film, and since the electron beam emission has little effect on parts other than the substrate, film contamination due to re-evaporation of adhering impurities can be significantly reduced.

In particular, by adjusting the gas pressure in the bell jar, the acceleration voltage of the electron beam, etc., it is possible to generate enough ions of the modification gas near the substrate, and to efficiently transfer hydrogen, which has a short excitation life, to the deposited film. This is extremely advantageous for mixing. Furthermore, since a discharge tube as described above is not used, there is no need to provide a discharge portion with high ion density and current density, and there is no contamination of the apparatus due to sputtering or the like. In this connection, since the apparatus is not contaminated by decomposition of the modifying gas due to discharge, a wide range of modifying gases can be selected and the range of application can be expanded.

Modifying gases that can be supplied in this example include oxygen, nitrogen, halogens such as fluorine, hydrocarbons such as ammonia, monosilane, phosphine, diborane, arsine, methane, and freon, in addition to hydrogen or in combination with hydrogen. Various types can be used, such as.
In addition to a-Si:H, the deposited film also includes a-Ge:H,
a-SIGe:H, a-SiC:H, a-SiGeC:H,
a-Si:F, a-SiGe:F, a-SiC:F, a-
SiGeC _: F, _Si3N4 , _SiO2 , _SnO2 , _{In2O3 ,}
MgF, Al ₂ O ₃ , as well as carbon and other carbon compounds, TiN
and nitrides such as BN may be deposited, for which appropriate evaporation sources and modifying gases may be selected.

According to the inventor's study, the optical properties of the vapor deposited film obtained using the apparatus of this example, such as an a-Si:H film, exhibit the tendency shown in FIG. 6 in relation to the substrate voltage. I found out. According to this, as the substrate voltage becomes more negative, △δ decreases from around -1KV and the photoconductivity (photosensitivity) deteriorates, but if the negative voltage is increased further, the photoconductivity decreases. sex is improving. This means that if the substrate voltage is negative, there is a voltage range (particularly around -1KV and -4KV or higher) that can repel the electron flow and prevent electrons from colliding with the deposited film, but at -2 to -4KV, the electron flow can be prevented. The hydrogen ions generated by
It is presumed that the Si:H flows into the film and deteriorates the film properties (photoconductivity). FIG. 7 shows the results of measuring the trend in FIG. 6 as an electron flow (amount of current) flowing into the substrate, and it can be seen that the results almost correspond to those in FIG. 6.

It will be understood from the results shown in FIGS. 6 and 7 that a deposited film of good quality can be obtained if the operation is performed under appropriate conditions (especially substrate voltage) in which no electron current flows into the substrate. In general, if the substrate voltage is increased to a negative value, the results will be better, but if it exceeds -10KV, arc discharge is likely to occur, so the substrate voltage should be increased to -10KV.
It is desirable to keep it within.

Note that, as shown in FIG. 8, an insulating layer 23 may be formed in advance on the evaporation source side of the substrate 1, and an a-Si:H film 24 may be deposited thereon using the above-described vapor deposition apparatus.
For example, a glass substrate 21 on which a gate electrode 22 is formed is used as the substrate 1, and a SiO ₂ film 23 as a gate oxide film is formed on the substrate 1, and a channel is formed on the gate electrode 1 with source and drain regions on both sides. The a-Si semiconductor layer 24 is stacked to form a MISFET (Metal Insulator Semiconductor).
Field Effect Transistor). In this case, due to the presence of the insulating layer 23 when the a-Si:H film 24 is deposited, charges due to hydrogen ions are accumulated (charge up), which generates an in-plane discharge and the a-Si:H film 24 is deposited. may be destroyed. However, according to this embodiment, by setting the substrate voltage to an appropriate negative voltage so that an appropriate amount of electrons can reach the substrate, the hydrogen ions on the substrate are neutralized by the arriving electrons. be able to. Therefore, charge up on the substrate can be suppressed and in-plane discharge can be effectively prevented. Note that in the structure shown in FIG. 8, the insulating film 2
It can also be applied as a photoreceptor for electrophotography using No. 3 as a blocking layer.

In FIG. 9, a shielding plate 25 is provided to shield the W filament 13 of the thermionic generator 10 from the evaporation source 2,
Furthermore, an example is shown in which the emitted thermoelectrons 9 are magnetically deflected or directed toward the substrate by a magnet 26, a magnet 27 with an AC drive coil 34, etc., and a scanning function is further provided.

According to this, the shielding plate 25 can prevent, for example, silicon vapor from the evaporation source 2 from adhering onto the tungsten filament 13 during vapor deposition. On the other hand, when there is no shielding plate 25, silicon vapor adheres to the filament 13 and forms tungsten silicide, which re-evaporates and tungsten flies toward the substrate, mixes into the deposited film, and improves the quality of the film. It causes deterioration.

FIGS. 10 and 11 show a vapor deposition apparatus according to another embodiment.

In this example, the filament (heater) portion 13 of the thermionic generator 10 described above is arranged outside the bell gear 3, and the configuration is such that the electron beam 9 is emitted onto the substrate surface by a guide tube 28 extending in the direction of the substrate 1. ing. This thermionic generator 10 has a filament 13 arranged in a thermionic generation chamber 30 surrounded by a glass wall 29, and this filament is heated by a DC power source 31. The guide tube 28 extends through the bell gear wall, and an accelerating electrode 33 connected to a DC variable power source 32 is provided on the inner peripheral surface near the outer surface of the bell gear.

Therefore, since the filament 13 of the thermoelectron generator 10 is isolated from the interior of the bell gear 3, the above-mentioned contamination due to adhesion of vapor from the evaporation source can be effectively eliminated.

Note that instead of the above-mentioned thermionic generator 10, a DC or AC type discharge tube 40 is provided outside the bell gear 3 as shown by the dashed line in FIG.
Even if the electrons generated at 0 are supplied from the introduction tube 34 toward the substrate 1, the object of the present invention can basically be achieved. Although not shown, such a discharge tube connects a cylindrical electrode with a negative potential on the inlet side and a cylindrical electrode with a positive potential on the outlet side with a water-cooled pipe to discharge the supplied gas, and the generated electrons are A structure configured such that it can be introduced into the bell gear 3 from the outlet side via the introduction pipe 34 may be used.

In this vapor deposition apparatus, since the discharge tube 40 is placed outside the bellgear 3, contamination is much less than when it is placed inside the bellgear 3, and the discharge tube is exposed to heat and gas inside the bellgear during operation. The electrodes and constituent materials will not be damaged. Therefore, the degree of freedom in selecting the material of the discharge tube is increased, and the construction and arrangement thereof can be carried out as desired. Further, the structure of the cooling water pipe (not shown) inside the discharge tube is easy to design, its cooling efficiency is good, and the discharge tube itself can be easily replaced outside the bell jar. However, in terms of feeding the electron beam, it goes without saying that the discharge tube may be provided within the bell jar.

The embodiments described above can be modified in various ways based on the technical idea of the present invention.

For example, the electrode (heater) used in the thermionic generator may be made of lanthanum polaroid or the like instead of tungsten, and its arrangement may be varied. Further, the above-mentioned deflection device may be one using an electric field or one using a magnetic field, or may be a combination of both. Various negative voltages can be selected to be applied to the substrate, and the voltage may also be varied over time. The evaporation source may be heated by a resistance heating method instead of an electron beam method. In addition,
Of course, the present invention is not limited to the above-mentioned mixing of hydrogen ions, but can also be applied to cases where impurities are mixed into a vapor deposited film by using the various modifying gases mentioned above, or when forming various vapor deposited films. It is.

[Brief explanation of drawings]

The drawings show embodiments of the present invention, in which FIG. 1 is a schematic cross-sectional view of a vacuum evaporation apparatus, FIG. 2 is a schematic diagram showing the state of activation or ionization of the modifying gas near the substrate, and FIG. The figure is a perspective view schematically showing a thermionic generator, its accelerating electrode, and a deflection device, FIG. 4 is a perspective view schematically showing another thermionic generator and its accelerating electrode, and FIG. A perspective view schematically showing a thermionic generator, FIG. 6 is a graph showing changes in the optoelectric properties of the deposited film depending on the substrate voltage, and FIG. 7 is a graph showing changes in the inflow electron flow depending on the substrate voltage.
FIG. 8 is an enlarged cross-sectional view of the main part of an element obtained by vapor deposition, FIG. 9 is a cross-sectional view schematically showing the arrangement of a thermionic generator and its deflection device according to another embodiment, and FIG. FIG. 11 is a schematic cross-sectional view of a vacuum evaporation apparatus according to another embodiment, and FIG. 11 is an enlarged cross-sectional view of the thermionic generator in FIG. 10. In addition, in the symbols shown in the drawings, 1...
...Substrate to be evaporated, 2...Evaporation source, 5...DC power supply,
6... Modification gas introduction tube, 9... Thermionic electron (electron beam),
10... Thermionic generator, 12... Hydrogen molecule, 1
2'... Hydrogen ion, 13... Filament or heater, 16, 33... Accelerating electrode, 17... Deflection device, 18a, 18b, 19a, 19b... Deflection electrode, 20... Slit, 23... Insulating layer ,2
4... Vapor deposited film, 25... Shielding plate, 26, 27...
Magnet, 28... guide tube, 40... gas discharge tube.

Claims (1)

[Scope of Claims] 1. An evaporation source that accommodates a deposition substance and a substrate to be evaporated facing the evaporation source are arranged in a evaporation tank, and a modification gas inlet provided in the evaporation tank is provided in the evaporation tank. The device heats the evaporation source to evaporate the evaporation substance onto the substrate in the presence of a modifying gas supplied to the substrate, the device emitting an electron beam toward the substrate to remove the modifying gas near the substrate. A vapor deposition apparatus characterized in that an electron beam supply device for activating or ionizing is disposed in the vapor deposition tank. 2 configured so that a negative voltage is applied to the base;
Apparatus according to claim 1. 3. The device according to claim 2, wherein the negative voltage is a DC voltage within -10 KV. 4. The device according to any one of claims 1 to 3, wherein the electron beam supply device comprises a thermionic generator disposed inside or outside the vapor deposition tank. 5. The device according to any one of claims 1 to 3, wherein the electron beam supply device comprises a gas discharge tube arranged inside or outside the vapor deposition tank. 6. The device according to any one of claims 1 to 5, which includes an accelerator for accelerating the electron beam emitted from the electron beam supply device. 7. The device according to any one of claims 1 to 6, comprising a magnetic field or electric field deflection device for directing the electron beam emitted from the electron beam supply device toward the substrate. 8. Claims 1 to 8 have a magnetic field or electric field deflection device for uniformly scanning the electron beam over the substrate surface by changing the traveling path of the electron beam toward the substrate. A device as described in any one of paragraphs 7.