JP3349475B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a dielectric film of a capacitor of a semiconductor integrated circuit by a sputtering method.

[0002]

2. Description of the Related Art An active element or a semiconductor integrated circuit using an insulator film formed by a chemical vapor method or the like,
Alternatively, a capacitor using a dielectric film has attracted widespread attention.

As another method for producing an insulator at such a low temperature, a plasma CVD method and a sputtering method using 100% to 80% of Ar atoms as a sputtering gas are known.

This is because the probability that an inert gas such as Ar or the like strikes the target material (sputtering yield) is high. The present inventors have conducted extensive studies on the characteristics of an insulating film formed by a sputtering method, and as a result, the lower formed surface showing the performance of the insulating film, that is, the lower electrode active layer and the formed insulating film interface It was found that the interface states varied greatly with the amount of argon. As an extreme example, when tantalum oxide is used as a capacitor or gate insulator, the metal component (Ta component) of this component generates clusters (groups of particles having a particle size of 5 to 50 mm) because tantalum is stable. . The deviation (deterioration) of the flat band voltage from the ideal value which reflects the number of fixed charges in the insulating film due to the damage of the cluster and the underlying surface largely depends on the ratio of Ar gas at the time of sputtering. I found that.

Further, it has been attempted to produce a dielectric film of a capacitor by a photo-CVD method. 2 × 10 ¹⁰ eV ^-1 cm ^-2 with no reaction damage with the underlying semiconductor or electrode material
Although the interface state density of the order was obtained, the time required for film formation was long (the film formation speed was very slow), and thus it was not suitable for industrial applications. Further, since hydrogen is used to induce a hot electron effect, there is a problem in long-term characteristics.

[0006]

SUMMARY OF THE INVENTION The present invention is a method for solving the conventional problems, in which a metal oxide insulating film such as tantalum oxide, titanium oxide, barium titanate or lead titanate having good characteristics is formed in a film. Another object of the present invention is to provide a method for manufacturing a semiconductor device without using metal clusters and pinholes and using a low-temperature process without using hydrogen.

[0007]

According to the structure of the present invention, a metal oxide film such as a dielectric such as tantalum oxide or titanium oxide or a ferroelectric such as barium titanate is used as a dielectric film of a capacitor in a semiconductor integrated circuit. The present invention relates to a manufacturing method used for part of a semiconductor integrated circuit.

[0008]

In the present invention, such an insulating film is formed by a sputtering method. The gas used for sputtering is an oxide, for example, 75% by volume or more of oxygen relative to an inert gas such as argon, more preferably an oxide gas containing no inert gas at all, especially a metal oxide under the condition of only oxygen. Get sputtering is performed, and an oxide insulating film is formed by a stacked type (lamination method) covering an MIS FET formed on a semiconductor substrate.

In sputtering, a gas containing a sputtering gas as a part of a component of a formed film, for example, in a tantalum oxide film, oxygen is set to 100% or 80 to 100% by volume, and a target of tantalum oxide is formed. Is performed using a radio frequency (RF) sputtering method. Then, while the target material is flying, the oxidation reaction with oxygen as the sputtering gas can be more completely performed.

In order to further promote this, in addition to this, a gas containing a halogen element is simultaneously mixed in an amount of 0.2 to 20% by volume with respect to the oxide gas, so that alkali ions introduced at the same time to the silicide are unintentionally introduced. It also enables neutralization and neutralization of unpaired bonds.

As the sputtering method used in the present invention, any method such as RF sputtering and DC sputtering can be used. However, when the sputtering target is an oxide having poor conductivity, for example, a metal oxide such as Ta ₂ O ₅ , It is preferable to use a 13.56 MHz high frequency RF magnetron sputtering method to maintain stable discharge.

Hereinafter, the present invention will be described in detail with reference to examples.

[0013]

[Embodiment 1] FIG. 1 shows an embodiment of the present invention.

The present invention is used for manufacturing one cell of a 1 Tr / Cell DRAM (dynamic memory) of this embodiment. In the drawing, one gate type field effect transistor (20) is provided on a semiconductor substrate as a source or a drain.
(8), a drain or source (9), a gate electrode (7), and a gate insulating film (6).

Further, a capacitor (21) comprising a lower electrode (10), a tantalum oxide dielectric film (11), and an upper electrode (12) is connected in series to one drain or source (9) of the transistor. Provided. Buried insulating film around these outside
(5) This structure shows the shape of the memory cell of the stacked DRAM.

In this drawing, the dielectric film (11) of the capacitor is formed by coating the target of tantalum oxide of the present invention by an oxygen sputtering method.

On this, an insulating film of tantalum oxide was formed by the method of the present invention. The conditions are shown below.

Next, Al was formed as an upper electrode に よ り by electron beam evaporation to complete a capacitor.

In the case where an insulating film is formed in an atmosphere in which Ar gas is mixed at a ratio of 25% or less, the distance between the target and the substrate is set to be longer than that in the case where Ar gas is formed at 0%.
It is possible to obtain an insulating film having substantially the same film quality as in the case of manufacturing with 0% gas. Further, the gate insulating film formed by mixing at a ratio of Ar gas of 25% or less is irradiated with excimer laser light and flash annealed to activate a halogen element such as fluorine introduced into the film, thereby reducing the silicon content. It was also possible to eliminate the cause of the generation of fixed charges in the membrane by neutralizing with the incomplete bonds of.

It is preferable that all materials used for sputtering have high purity. For example, a sputtering target
The get is most preferably 4N or more of tantalum oxide, titanium oxide, barium titanate, and lead titanate. Since the tantalum oxide has a relative dielectric constant of 27 and has excellent frequency characteristics up to high frequencies, a large storage capacity can be obtained as compared with a silicon oxide film (relative dielectric constant: 3.8).

The gate insulating film of the insulated gate field effect transistor (20) is made of silicon oxide formed by thermal oxidation or silicon oxide formed by sputtering using 100% oxygen.
However, even if this gate insulating film was made of tantalum oxide or a multilayer film of silicon oxide and tantalum oxide, the interface state with the silicon semiconductor was only 2 × 10 ¹⁰ cm ⁻² , which was good.

The lower electrode (10) of the capacitor (21)
Was formed using a silicon semiconductor to which phosphorus was added.
However, this electrode material may be metal tantalum, tungsten, titanium, molybdenum, or a silicide thereof.

Further, an upper electrode (12) was formed of aluminum or a multilayer film of metal tantalum and aluminum to form a capacitor (21). Tantalum oxide thickness is 30
0 to 3000 mm. Typically, 500-1500Å, for example
1000 mm. However, since the relative permittivity of silicon oxide or the like is small, the thickness of the memory cell must be reduced to about 30 °. However, since tantalum oxide formed by the method of the present invention has a large relative dielectric constant, its thickness is, for example, 1000.
Å. As a result, the insulating properties were excellent, and the presence of pinholes could be reduced.

Therefore, in FIG. 1, the channel length of the insulated gate field effect transistor is set to 0.1 to 1 μm, for example, 0.5
μm, and 20 μm for the size of 1Tr / Cell
One memory (1 bit) could be manufactured in the box.

In forming the tantalum oxide, a sputtering method containing no hydrogen is used, and the upper and lower electrodes are formed by a sputtering method containing no hydrogen. It is also possible to prevent drift (diffusion) to the gate insulating film by the subsequent heat treatment and to become a hot carrier trap center.

[Embodiment 2] FIG. 2 shows a configuration in which cells of a dynamic memory are provided in a pair (2 bits).

In the drawing, a semiconductor substrate (1), a buried field insulating film (5), a drain or source (9) formed in a convex shape on a semiconductor surface, and a conductor electrode / leaf formed thereon are provided. Do
(19). On this side, a silicon oxide film (6) was formed as a gate insulating film. A pair of gate electrodes (7) and (7 ') are provided by anisotropic etching, and sources or drains (8) and (8') are provided. Channel formation area (15), (15 ')
Before the formation of the gate electrodes (7) and (7 '), boron ions are implanted into the substrate by using the convex regions (9) and (19) and the field insulating film (5) as masks. It was formed to a concentration of ^{15 ~5} × 10 ¹⁶ cm ^-3. Then, the source or drain (8), (8 ') is 1 ×
It was manufactured by ion implantation at a concentration of 10 ¹⁹ to 1 × 10 ²¹ cm ⁻³ . As the capacitor (21), a lower electrode (10), a tantalum oxide dielectric (11), and an upper electrode (12) were formed in the same manner as in Example 1.

A 1Tr / Cell having two bits in a size of 10 to 20 μm □ was successfully formed.

Further, since hydrogen, which is a factor for forming a hot carrier trap center in the gate insulating film, is not used, stable transistor characteristics can be obtained even with a channel length of 0.1 to 1 μm.

Further, although tantalum oxide is used in the embodiment of the present invention, a 1Tr / Cell dielectric may be used instead of the titanium oxide, barium titanate, and lead titanate shown in the constitution of the present invention.

[0031]

All of these can be achieved by reducing the oxygen or oxide gas by sputtering to zero or less than 25% of argon, which is the reverse of the conventionally known main gas of argon.
It is based on the fact that it has been experimentally discovered that a high-quality insulating film can be formed.

According to the method of the present invention, a thin film transistor having very good characteristics could be easily formed because the film was formed only by a low-temperature process and without using hydrogen as an electrode and a dielectric constituting a capacitor.

Further, since the generation of hot carriers and fixed charges in the gate insulating film can be reduced, it is possible to provide a highly reliable transistor and capacitor with little characteristic change in long-term use. It became.

The shape of the capacitor or the insulating gate type transistor used in the present invention is not limited to the staggered type, but may be an inverted staggered type or a vertical channel type transistor. Further, an insulated gate field effect transistor used as a part of a monolithic IC using single crystal instead of non-single crystal for silicon of the transistor may be used.

Also, the capacitor may be a multilayered multilayer structure instead of a single-layer dielectric capacitor, or may be a side-by-side system in which electrodes are sandwiched between left and right rather than vertically.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a semiconductor device which is a dynamic memory cell using the method of the present invention.

FIG. 2 shows an embodiment of a semiconductor device which is a dynamic memory cell using the method of the present invention.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-135777 (JP, A) JP-A-1-19055 (JP, A) JP-A-2-76257 (JP, A) JP-A-2- 60157 (JP, A) JP-A-2-47256 (JP, A) JP-A-2-94209 (JP, A) JP-A-59-52526 (JP, A) JP-A-59-211854 (JP, A) JP-A-62-23117 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/8242 H01L 21/316 H01L 27/108

Claims (4)

(57) [Claims] 1. A semiconductor device comprising: an insulated gate field effect transistor having a gate electrode formed on a side surface of a convex region formed in a semiconductor substrate; and a capacitor connected to the insulated gate field effect transistor. In the manufacturing method, when a metal oxide insulating film is formed as a dielectric of the capacitor by a sputtering method, an inert gas, an oxide gas of 75% by volume or more, and 0. A method for manufacturing a semiconductor device, comprising a gas containing 2 to 20% by volume of a halogen element. . 2. The method for manufacturing a semiconductor device according to claim 1, wherein the metal oxide insulating film is made of tantalum oxide or titanium oxide. 3. The method for manufacturing a semiconductor device according to claim 1, wherein the metal oxide insulating film is made of barium titanate or lead titanate. 4. The method according to claim 1, wherein
The method for manufacturing a semiconductor device, wherein the oxide gas is oxygen.