JPS62247571A - Manufacture of mos type semiconductor device - Google Patents

Abstract

PURPOSE:To prevent a disadvantage such that an inverted layer is formed on a surface of a semiconductor substrate by providing a step of forming a crystalline BeO coat as a gate insulating coat. CONSTITUTION:Ionized Be atoms, neutral Be atoms, or a cluster of Be or cluster ions further advance toward a substrate 11 as an oxygen mixture including oxygen existing in their course. If a shutter 33 is released, they bump against a surface of the substrate 11 through an opening of a mask 40 and deposit there to form a BeO coat 41. Next, during an etching step, the BeO coats 41a-41c are formed on the substrate 11 and the BeO coat 41a becomes a gate insulating coat. Meanwhile, the BeO coats 41b and 41c function as insulating films for electrically insulating a source electrode 43 and a drain electrode 44 respectively from the substrate 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a MOS semiconductor device using beryllium oxide (hereinafter referred to as BeO) as a gate insulating film.

[Prior Art] For example, as a semiconductor element structure for an integrated circuit, a MOS type semiconductor element is often used because it has low power consumption, can be miniaturized, is easy to integrate, and is easy to manufacture. There is.

The basic structure of this MOS type semiconductor device is as shown in FIG. Further, an insulating film 6 is formed on the surface of the substrate l between the p shadow regions 2.3. Further, a gate electrode 7 made of a metal such as Au, Al or MO is deposited on this insulating film 6, and a source electrode 4 and a drain electrode made of metal are formed using the p shadow regions 2.3 as a source and a drain, respectively. 5 is applied.

Incidentally, the insulating film 6 is an important part that greatly influences the characteristics of the manufactured device.

Sono material Toshiteha, S i O2, S i 3 N 4
An alloy such as A n 203 can be used, but in general, 5i, which has excellent electrical characteristics and is easy to manufacture, is used.
02 is the most commonly used.

In other words, a mirror-polished semiconductor substrate of one conductivity type is
The substrate is placed in a furnace heated to about 00°C to 1100°C, and dried oxygen (02) or water vapor is introduced into the furnace to form a SiO2 film on the surface of the substrate by a thermal oxidation method. .

Thereafter, a photoresist is coated on this SiO2 film, a mask is applied to expose the required portions, and a predetermined portion of the SiO2 film is removed by etching. After performing the opening operation and forming a p shadow region by diffusing 1-Punt, a SiO2 film for the gate insulating film was formed by the above-mentioned thermal oxidation method, and each layer was deposited on the source, drain and gate insulating films. It is formed by forming electrodes.

In addition, as a method of forming an S*02 film on the substrate surface,
In addition to the thermal oxidation method described above, for example, SiH402-based gas is introduced onto the substrate and thermally decomposed here to form SiO2.
Insulating films have also been formed by vapor phase growth methods in which films are deposited.

[Problems to be Solved by the Invention] Generally speaking, the SiO2 film obtained by the former thermal oxidation method has better electrical properties than the SiO2 film obtained by the vapor phase growth method. It is said that even in the thermal oxidation method, the substrate is exposed to high temperatures of about 1000°C during the process, so the p-n junction built into the substrate deteriorates and the resulting device deteriorates. There are problems in that leakage current increases and lattice defects occur on the surface of the substrate l in contact with the insulating film 6, which causes deterioration of the characteristics of the element.

Furthermore, the insulating film obtained by either the thermal oxidation method or the vapor phase growth method does not have a perfect crystal structure;
Generally, it is a polycrystalline or amorphous film.

Therefore, in this insulating film, there are vacancies, cracks, increased charge density due to structural defects, and various other impurity levels, and contamination during the process, especially contamination due to high temperature oxidation, causes Na+ ions, etc. that can easily move through the insulating film are mixed into the surface of the substrate 1.
This causes the formation of a shape inversion layer.

On the other hand, as semiconductor devices tend to become smaller and operate at higher speeds,
Even in MOS type semiconductor devices, the density of each element has been increased.

This higher density requires shorter or narrower channels, but as the channel dimensions become smaller, the above-mentioned imperfections in the crystallinity of the insulating film are formed in semiconductor devices. This has become a major cause of hindering the improvement of the characteristics of

Furthermore, in recent years, semiconductor devices with this MO3 type structure have been applied not only to integrated circuits but also to various semiconductor devices such as high voltage transistors and power transistors, and the breakdown voltage and thermal characteristics of these devices have increased. In order to prevent destruction, an insulating film that is free from structural defects and pinholes and has good thermal conductivity is required. However, S i O2tl! obtained by conventional thermal oxidation method or vapor phase growth method! and Si3N
Insulating films such as 4-film cannot fully satisfy these characteristics, and are insufficient to improve the electrical and thermal characteristics of MOS type semiconductor devices.

[Object of the Invention] The present invention has been made in view of the above-mentioned circumstances, and is intended to realize a MOS type semiconductor device having excellent characteristics as an integrated circuit or various transistors. It is an object of the present invention to provide a method for manufacturing a MOS type semiconductor device having a crystalline BeO film having excellent thermal conductivity.

An embodiment of the method for manufacturing a MOS type semiconductor device according to the present invention will be described below with reference to the drawings. First, a crystalline BeO film, which is the gist of the present invention, will be described.

BeO has a hexagonal Wurtz crystal structure and has an extremely large forbidden band width of about 11.2 eV, so its electrical resistance is also 10
BeO has a large dielectric constant of I0Ω・cm or more and is a good insulator. Furthermore, the relative permittivity of BeO is about 6 to 8, which is A l 2
It is considerably smaller than 03, has excellent electrical properties, has extremely good heat conduction properties, and is chemically stable.1 For example, it can be used as parts of microwave power equipment, lining materials for high-temperature combustion chambers, etc. It is used in things such as moderators and reflectors in nuclear reactors, and window materials in X-ray tubes.

By the way, this BeO has an extremely high melting point of 2,570°C, making it difficult to form a film, so conventionally, BeO fine powder was pressure-molded using a hot press method to form a plate shape.
This is what is currently being used.

In addition, some attempts have been made to grow single crystals by a flux method using molybdenum oxide (MOO3) as a flux, but the ones obtained by this method are just single crystal pieces and are not suitable for industrial use. It has not yet been used for

On the other hand, as mentioned above, BeO has high thermal conductivity and high insulation properties, and is an excellent insulating material both thermally and electrically. Furthermore, it is an extremely hard material with a Mohs hardness of 9. be.

Therefore, this BeO can be applied directly to various electrical and electronic parts.
If a film can be formed, it is expected that electrical and electronic parts with excellent heat dissipation properties and high breakdown voltage can be obtained.Moreover, if crystallinity can be controlled and a BeO film with good crystallinity can be obtained, it will be possible to obtain a BeO film with good crystallinity. It is believed that an insulating film with excellent properties can be obtained.

As a result of various studies focusing on the excellent properties of BeO mentioned above, the present inventor has found that by bombarding a substrate with vapor of metal Be, at least a part of which is ionized, and oxygen (O2), crystallization can be achieved. We have already demonstrated that a BeO film with good quality can be obtained, and have already proposed this BeO film and its specific manufacturing method.

The method for manufacturing a MOS type semiconductor device according to the present invention uses the BeO film already proposed by the present inventors as the oxide film of the MOS type semiconductor device, and specific examples will be described below.

First, a semiconductor substrate to be used as a substrate for a MOS type semiconductor device is prepared. For example, when manufacturing a P-channel MOS type semiconductor device, an n-type Sl substrate or an Sl substrate having an n-shaded region is used as the first conductivity type substrate.

First, crystalline Bo was deposited on this substrate.

Deposit and form a film.

The BeO film is deposited in the following manner using, for example, an apparatus as shown in FIG.

In this FIG. 2, 21 is 0.5 layer to 2. OI
It is a closed crucible having one or more nozzles 22 with a pore diameter of about 100 mL. Here, the thickness of the nozzle 22 in the axial direction is desirably made as thin as possible, and the so-called 7 spectral ratio, which is at least thinner than the nozzle diameter, is set to 1 or less.
It is filled with metal Be23 in the form of flakes or pellets formed by appropriately processing the flakes.

Reference numeral 24 denotes a heating device provided around the crucible 21. In this embodiment, a coiled filament for electron emission is arranged around the crucible 21 and heated, and a power source (not shown) is connected to the heating device. applying a positive potential to the crucible 21 to accelerate electrons from the filament,
An electron impact type heating device is used which raises the temperature of the crucible 21 by projecting it onto the surface of the crucible 21.

In addition, as a method of heating the crucible 21,
1 is made of a conductive material, this crucible 21
The crucible 21 can be heated by a resistance heating method in which specific terminals are provided at the top and bottom of the crucible 21 and the entire crucible 21 is heated by applying a low voltage and large current to the inner body of the crucible 21, or by placing a heater around the crucible 21. The radiation heating method and the heating method using a combination of these methods can be appropriately selected and used as necessary.

Further, 25 is a heat shield plate, 26 is an ionization chamber, and a net-like ionization anode 2 formed in the shape of a cylinder, square cylinder, or parallel plate so as to surround the passage of vapor of metal Be, which will be described later.
7, an electron-emitting filament 28 and a shielding plate 29 arranged around the anode.

31 is a substrate holder that holds a semiconductor substrate 11 having a BeO film deposited on its surface, and 33 is a shutter that prevents Be or oxygen (O2) from hitting the substrate 11 when unnecessary.

Furthermore, 35 is an oxygen supply pipe provided with one or more nozzles 36. In this case, the nozzle 3
6 is arranged near the nozzle 22 of the crucible 21, but the nozzle 36 may be arranged near the substrate 11.

Further, 37 indicates the ionization chamber 26 and the substrate 1 as necessary.
A negative potential is applied to the crucible 21 by a power source (not shown) provided between the crucible 21 and the ionized Be described later.
40 is an accelerating electrode for accelerating vapor, and 40 is a mask for evaporation, which is provided in close contact with the substrate 11 or with a small interval therebetween, as required, and is used to form a BeO film on a predetermined region of the substrate 11. be.

Furthermore, although not shown in the drawings, the substrate 11 may be
A heating device for heating the substrate may be provided near the substrate.

Each of the above-mentioned parts is disposed within a vacuum container (not shown) and supported by appropriate support members.

The inside of this vacuum container is evacuated to a high vacuum atmosphere of at least 10 Torr or less.

In this state, the nozzle 36 is
Oxygen 36a is supplied into the vacuum container from the inside of the vacuum container, and the pressure inside the vacuum container is maintained at about 10 Torr to 10 ↑orr.

In this case, if the pressure of the oxygen 36a introduced into the vacuum container is low, formation of a high-quality BeO film can be expected, but it is necessary to evacuate the inside of the vacuum container to a high vacuum or ultra-high vacuum state before introducing oxygen. In practice, it is appropriate to adjust the amount of oxygen introduced so that the pressure inside the vacuum container is about 10 Torr to 10 Torr. .

Then, the heating device 24 is activated to heat the crucible 21 and heat and melt the metal Be filled in the crucible 21 to generate metal Be vapor 23a.

In this case, the heating temperature of the metal Be is set according to the surrounding space of the crucible 21, that is, the pressure inside the vacuum container. When set as PO, P/P o≧10
2. Preferably, P/P o≧104 is set.

For example, since the melting point of metal Be is 1280°C, the vapor pressure P is approximately 5 x 10''2 Torr at a heating temperature of 1300°C.
r, lXl0 jorr at 1380°C. Therefore, the pressure inside the vacuum container is between 10 Torr and 10 Torr.
If it is about Torr, the heating temperature is 1300℃~1
The temperature may be set to about 400°C.

Furthermore, in order to increase the vapor pressure P and increase the film formation rate, the heating temperature may be increased within a range that does not impair the quality of the BeO film to be formed.

Due to the pressure difference between the inside and outside of the crucible 21, the vaporized metal Be 23a is ejected from the nozzle 22 to the outside of the crucible 21, obtains kinetic energy corresponding to the ejection speed, and forms a vapor flow 23b heading toward the substrate 11. Become.

In this case, the shape of the nozzle 22 and the pressures P and Po may be adjusted appropriately according to the conditions described above, or the crucible 22 may be
By devising the shape of the nozzle 22, a supercooling phenomenon based on adiabatic expansion is utilized during ejection to form a cluster, which is a powerful aggregate of vaporized Be atoms and molecules loosely bonded by van der Waals forces. By doing so, it is possible to improve the ionization efficiency in the ionization chamber 26, which will be described next, or to form a film of better quality on the substrate 11.

By the way, the metal Be vapor flow 23b which has gained kinetic energy by being ejected outside the crucible 21 enters the ionization chamber 26 and is at least partially ionized there.

That is, electrons emitted from the heated filament 28 are accelerated by a voltage of about 100 to 100 OV applied between the filament 28 and the mesh anode 27, and pass through the mesh anode 27 to form the vapor flow 23a. and ionize at least a portion of it.

In addition, a vapor flow 23b of metal Be ejected from the nozzle 22
form a cluster, the ionization chamber 26
One atom of the atomic group constituting the cluster is ionized by the electronics company, forming a so-called cluster ion. Furthermore, a portion of the oxygen ejected from the nozzle 36 also enters the ionization chamber 26 and is ionized.

In this way, ionized Be atoms, neutral Be
Atoms or Be clusters or cluster ions travel further toward the substrate 11 as an oxygen mixture containing oxygen in the path, and when the shutter 33 is open, they are projected onto the surface of the substrate 11 through the opening of the mask 40. Then, a BeO film 41 is formed by adhering thereto.

In this case, the metal Be vapor flow 23b impinging on the substrate 11
As described above, since at least a portion of the ions are ionized by passing through the ionization chamber 26, the electric field of these ions acts effectively in the initial stage of film formation.

That is, the electric field of these ions promotes the formation of nuclei for crystal growth, and also effectively acts on so-called coalescence, in which atoms gather around the formed nuclei to form island-like regions.

Moreover, the effect of this ionization also promotes the reaction between Be and oxygen, making it possible to form a film with good crystallinity that matches the stoichiometric composition.

Furthermore, since the vapor flow 23b of metal Be impinges on the substrate 11 with the kinetic energy obtained at the time of ejection, the BeO film 41 with strong adhesion can be formed on the substrate 11 by this incident energy. , Be
This greatly contributes to increasing the backing density and improving the crystallinity of the O coating 11i41, allowing the formation of a high quality coating.

In this case, the accelerating voltage applied to the anode 27 is adjusted,
By changing the ionization current drawn from the filament 28, the ionization rate of the metal Be vapor flow 23a can be controlled, and thereby the crystallinity and various properties of the BeO film deposited on the substrate 11 can be controlled.

By the way, in the embodiment described above, the steam 23a is ejected outside the crucible ff21 by utilizing the pressure difference between the inside and outside of the crucible 21 to obtain kinetic energy, but the ionization chamber 26
The vapor flow 23b, at least a part of which has been ionized, may be accelerated by an electric field to further increase the kinetic energy to control or improve crystallinity.

That is, if a negative voltage with respect to the crucible 21 is applied to the accelerating electrode 37, for example, an appropriate accelerating voltage of about 0 to 10 V, the particles in the vapor flow 23b that have passed through the ionization chamber 26 and been ionized are removed. is accelerated and gains kinetic energy,
This energy effectively acts to improve and control crystallinity during film formation, making it possible to form a high quality BeO film fi41.

Further, if it is desired to particularly improve the crystallinity of the BeO film 41 to be formed, it is necessary to heat the substrate 11 to some extent, but the substrate heating temperature in this case is about 300°C,
A heating temperature of at most 500° C. or less is sufficient.

Therefore, in order to remove a required portion of the BeO film 41 deposited on the substrate 11 through the above-described steps, the BeO film 41 is removed.
A photoresist is applied to the surface of the O film 41, a mask is applied, and required portions are exposed, developed, and removed.

Next, the required portions of the BeO film are removed by etching, and a gate insulating film is formed and a window is opened to introduce a p-type dopant.
As the first etching method, for example, a known method such as plasma etching or ion etching can be used.

Through this etching process, BeO films 41a, 41b and 41c are formed on the substrate 11 as shown in FIG. 3, the BeO film 41a becomes a gate insulating film, and the
The eO layers M41b and 41c act as an insulating film for electrically insulating the source electrode and drain electrode from the substrate 11, respectively.

Thereafter, through the window-opened portion of the etching process, a group Ⅰ element such as B or Al, which will become a p-type dopant, is introduced at a high concentration into the substrate 11 by thermal diffusion or ion implantation. As shown in FIG. 4, a source 12 and a drain 13 as a second conductivity type semiconductor
form.

Further, a gate electrode 42 made of a metal such as Al or Au is deposited on the BeO film 41a, and the source 12 and drain 13 are covered with the BeO film 41a.
A source electrode 43 and a drain electrode 44 are applied while being insulated from the substrate 11 by the aO skins 11141b and 41C.

45 is deposited on the back side of the substrate 11, and generally the source 4
It is a substrate electrode connected to the same potential as 3, and leads to each of these electrodes! By connecting 146, a MOS type semiconductor device is completed.

That is, the MOS type semiconductor device manufactured by the method of this embodiment has a structure using the BeO film 41a as the gate oxide film.

Moreover, this BeO coating 11!241a can be obtained as a coating with extremely good crystallinity through the manufacturing process described above.

Here, in the above-mentioned embodiment, a case is described in which a crystalline BeO film is formed directly on the surface of an St substrate and this BeO film is used as a diffusion mask having a gate insulating film, an electrode insulating film, and a dopant introduction window. Although,
As shown in FIG. 5(a), the dopant diffusion mask and the electrode insulating film are Si
By using the O2 film 61, removing the SiO2 film 61 in the gate region after dopant diffusion, and forming the BeO film 62 which becomes the gate insulating film by the method described above as shown in FIG. 5(b), It is also possible to create a MOS type semiconductor device. That is, in this case, unlike the previous embodiment, the process of forming the BeO film is performed after the process of forming the second conductivity type semiconductor.

In addition, in the case of a large-sized semiconductor device, etc., when forming the BeO film described above, the openings of the mask 40 for vapor deposition shown in FIG. It is advantageous to form a BeO film using a Si substrate of one conductivity type on which source and drain regions are formed in predetermined regions by a known method in advance, since the process for manufacturing a semiconductor device is simplified. .

By the way, the good crystallinity of this BeO film is clear from the measurement results shown in FIGS. 6 and 7.

Figure 6 shows the second
A BeO film was deposited on a glass substrate using the apparatus shown in the figure, and a scanning electron micrograph image of the obtained BeO film is shown. Figure 3 shows the X-ray diffraction pattern of the deposited BeO film.

As is clear from FIGS. 6 and 7, the BeO film obtained through the above-mentioned process has a columnar structure characteristic of hexagonal crystals, and it is clear that it is preferentially oriented in the C-axis direction. It is.

Therefore, in a MOS type semiconductor device, when the gate oxide film is formed of an insulating film with good crystallinity, the following advantages arise.

First, if the crystallinity of the BeO film 41a is close to perfect, the density of charges due to vacancies, classical defects, structural defects, etc. will be extremely low, and there will be no movement of charges, and the surface level of the surface of the substrate 11 will be becomes small and an inversion layer is not formed on the surface of the substrate 11.

Therefore, an element having excellent characteristics can be formed.

Furthermore, the formation of this BeO film can be performed at a temperature of at most 500°C, compared to the case where a 5iOz film is formed by, for example, a thermal oxidation method.
Since the process can be carried out at a low temperature of about 100 mL, it is possible to miniaturize the structure of the device without causing structural defects near the surface of the substrate 11.
- It does not destroy the n-junction.

Furthermore, since the BeO film is formed in a low temperature process as described above, there are advantages such as less penetration of Na + ions and the like and less diffusion of impurities.

The above-mentioned good crystallinity of the BeO film 41a greatly contributes to improving the electrical characteristics of the resulting MOS type semiconductor device.

For example, as shown in FIG. 8(a), a crystalline BeO film 52 is deposited on the surface of a p-type semiconductor substrate 51, and this B
FIG. 8(b) shows the C-V characteristics when a pair of metal electrodes 53 made of Au are deposited on the back surface of the eO film 52 and the substrate 51, and an AC voltage of IKHz is applied between the electrodes 53. .

As is clear from this FIG. 8(b), the BeO film 52
It is clear that no hysteresis occurs in the C-■ characteristic at a frequency of IKHz, and that there are few high-density traps in the portion near the interface of the substrate 51.

Therefore, a semiconductor device with good electrical efficiency and high frequency characteristics can be obtained.

In addition, as mentioned above, the electrical resistance of the BeO skin @ 41a itself is extremely high at over 10I0Ω・Cff1, and its thermal conductivity is also extremely excellent, making it an excellent material for use as a high-voltage semiconductor device or a power semiconductor device. Characteristics can be obtained.

By the way, in the above-mentioned embodiment, MO3 of the Brener structure
Although the present invention has been explained using a semiconductor device, it can also be applied when manufacturing a MOS type semiconductor device with a V-groove structure or an offset gate structure used as a power semiconductor device.
Of course, the present invention can be applied.

Further, as the substrate 11, in the above-mentioned embodiments, an example is explained in which an n-type silicon substrate is used as the first conductivity type substrate, but as the substrate 11, p-type silicon or Ga
Compound semiconductors such as As can be arbitrarily selected, and in particular, since the BeO film 41a can be formed in a low-temperature process, a MOS type semiconductor device can be constructed with a compound semiconductor that tends to cause lattice defects in high-temperature processes. advantageous in some cases.

In addition, the present invention is not limited to the embodiments described above and shown in the drawings, but can be practiced by making various changes to the processes and manufacturing equipment without changing the gist thereof.

[Effects of the Invention] As described above, the method of manufacturing a MOS type semiconductor device according to the present invention includes the step of forming a crystalline BeO film as a gate insulating film.

According to the method for manufacturing a MOS type semiconductor device according to the present invention, since there are very few lattice defects in the gate insulating film, the charge density in the insulating film is low, and it is possible to form an inversion layer on the surface of the semiconductor substrate. This has the effect of providing a high quality semiconductor device with excellent characteristics that does not cause any defects.

In addition, structural defects on the semiconductor substrate side due to BeO film deposition can be significantly suppressed, making it possible to create finer structures in devices, making it possible to manufacture devices with high integration and large capacity, for example, in MOS semiconductor devices. The effects that can be obtained from the perspective of expanding the field of application are extremely large.

Furthermore, since the BeO film itself is a highly insulating film and has high thermal conductivity, it can be used, for example, in MOS
If the present invention is applied to the manufacture of high-voltage transistors and power transistors, great effects can be expected, such as the production of semiconductor devices with excellent electrical and thermal characteristics.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the general structure of a MOS type semiconductor device, and FIG. 2 is a diagram showing a schematic configuration of an apparatus used to form a beryllium oxide film in an embodiment of the present invention. , FIG. 3 is a diagram showing an intermediate manufacturing process of the MOS type semiconductor device in the same example, FIG. 4 is a cross-sectional view of the main part of the MOS type semiconductor device manufactured in the same example, and FIG. 5 (fL), 6(b) is a diagram showing an intermediate manufacturing process of another embodiment of a MOS type semiconductor device according to the present invention; FIG. FIG. 7 is a diagram showing the X-ray diffraction pattern of the beryllium oxide film formed in the same example, and FIG. 8(a). (b) is a diagram showing the CV characteristics of the beryllium oxide film formed in the same example. 11... N-type substrate as a first conductivity type substrate, 12.
... p-type source as a second conductivity type semiconductor, 13.
... p-type drain as a second conductivity type semiconductor, 41
a~4Lc, 62...Beryllium oxide film, 42...
- Gate electrode, 43...source electrode, 44...drain electrode. Patent Applicant Futaba Electronics Co., Ltd. Agent/Patent Attorney Norihiro Nishimura Mitsuki L Figure 2 Figure 3 Figure 4 Figure 5 (a) (b) Figure 6 Figure 8 (b) Vg (V ) procedural amendment

Claims (2)

[Claims] (1) In a vacuum atmosphere, the metallic beryllium vapor to be combined with oxygen to form beryllium oxide and at least a portion of the beryllium oxide formed by combining with oxygen are ionized and bombarded onto the first conductivity type substrate. By forming a beryllium oxide film on the substrate, forming a second conductivity type semiconductor on the substrate, and forming an electrode on each of the beryllium oxide film and the second conductivity type semiconductor. A method of manufacturing a MOS type semiconductor device consisting of: (2) The MOS according to claim 1, wherein at least a portion of the metal beryllium vapor forms a cluster.
A method for manufacturing a shaped semiconductor device.