JP3007789B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device in which a transistor and a resistor on a semiconductor substrate are integrated with a capacitor using a metal oxide dielectric known as a ceramic material having an extremely high dielectric constant as a capacitance insulating film, and a semiconductor device. It relates to a manufacturing method.

[0002]

2. Description of the Related Art With the advance in the field of information and communication, high integration of semiconductor integrated circuit devices such as semiconductor memories has been progressing in order to realize high-speed processing of large amounts of data. Further, for the purpose of downsizing and cost reduction of information and communication equipment, reduction in chip area and reduction in the number of components due to high integration are being promoted.

Under these circumstances, in recent years, a capacitor is formed on a semiconductor integrated circuit device using a metal oxide dielectric material having a perovskite structure and a large dielectric constant (eg, barium strontium titanate, lead titanate, etc.). The technology to do this is being actively researched. Generally, such a ferroelectric material has a high dielectric constant, and is several tens to several hundred times larger than a silicon oxide film or a silicon nitride film which is a capacitance insulating film of a capacitor conventionally used in a semiconductor integrated circuit device. Has a dielectric constant.

[0004] By forming a capacitor using a ferroelectric layer as a capacitance insulating film in this way, the area occupied by the capacitor in a semiconductor integrated circuit device can be reduced from several tenths to several hundredths in the past. Thus, high integration can be achieved. Since a capacitor using a ferroelectric layer has spontaneous polarization, spontaneous polarization remains even when the applied electric field is removed. Memory can be realized.

Hereinafter, a conventional semiconductor device and a method of manufacturing the same will be described with reference to the drawings.

FIGS. 7A to 7F are cross-sectional views in the order of steps showing a conventional method for manufacturing a semiconductor device.

First, as shown in FIG. 7A, a silicon oxide film 8 serving as a base of a capacitor is deposited on a semiconductor substrate 1 on which circuit elements are formed by a CVD method. Next, FIG.
As shown in FIG. 2B, after a titanium film 9 is formed by vapor deposition, a platinum film 3 serving as a lower electrode of the capacitor, a ferroelectric film 4, and a platinum film 5 serving as an upper electrode of the capacitor are sequentially formed. Next, as shown in FIG. 7C, using a photoresist mask, the platinum film 5 and the ferroelectric film 4 are etched by an ion milling method or an RIE method.
As shown in FIG. 7D, the platinum film 3 and the titanium film 9 are etched. Next, as shown in FIG. 7E, a silicon oxide film 10 serving as an interlayer insulating film is deposited by a CVD method using silane gas. Finally, as shown in FIG. 7 (f), an opening is provided in a necessary region of the silicon oxide film 10, and then an electrode wiring 7 is formed to make the platinum films 3, 5 upper and lower electrodes, thereby forming a ferroelectric film. A semiconductor device incorporating a ferroelectric capacitor using 4 as a capacitive insulating film is completed.

In the above-described manufacturing method, the ferroelectric film 4 is deposited by a sputtering method, a CVD method, an organometallic thermal decomposition method, etc. In any case, in order to promote crystallization and improve the film quality, 500 ° C.-80 in oxygen atmosphere after deposition
A high temperature treatment of 0 ° C. is performed. Therefore, platinum having a high melting point and less interfacial reaction with oxide is used as the lower electrode material. A capacitor using a ferroelectric material as a capacitive insulating film (hereinafter referred to as a ferroelectric capacitor) is generally formed on a silicon oxide film which is an insulating film. Has no chemical bond and the adhesion is only an intermolecular force, so that it is very weak, and it is necessary to interpose titanium as an adhesion strengthening layer between the two.

[0009]

However, in the above-mentioned conventional structure, since the titanium of the adhesion strengthening layer has a getter function of bonding with oxygen very easily, the titanium in the high-temperature processing step after the deposition of the ferroelectric film is formed. Oxygen in the ferroelectric film is deprived and combined through the platinum electrode, and as a result, oxygen defects are induced in the vicinity of the electrode of the ferroelectric film, thereby deteriorating capacitor characteristics such as a decrease in dielectric constant and an increase in leak current. Had the problem of causing it.

On the other hand, if titanium in the adhesion strengthening layer is omitted in order to avoid such a problem, the adhesion between the upper and lower platinum electrodes and the silicon oxide film as the interlayer insulating film is weak, so that a hole is formed in the silicon oxide film. At the time of the provision, the silicon oxide film near the opening is easily peeled off from the platinum electrode, causing a new problem that the production yield is deteriorated.

Further, in the conventional manufacturing method, when a silicon oxide film is deposited by a CVD method using silane gas as a raw material,
The ferroelectric film is exposed to the atmosphere of silane gas and its by-product hydrogen, but both silane and hydrogen have strong reducing properties. As a result, oxygen defects are generated in the ferroelectric film, and there is a problem that the capacitor characteristics are deteriorated.

The present invention solves the above-mentioned problems, and improves the adhesion between an underlying silicon oxide film and a lower platinum electrode without using titanium as an adhesion strengthening layer, thereby generating oxygen defects in a metal oxide dielectric film. To prevent deterioration of capacitor characteristics and improve the adhesion between the platinum electrode and the silicon oxide film as the protective insulating film to prevent the yield and reliability from dropping due to the peeling of the protective insulating film and further protect Provided is a semiconductor device having a built-in capacitor capable of suppressing deterioration of capacitor characteristics by making a silicon oxide film serving as an insulating film a manufacturing process in which a metal oxide dielectric film is not easily subjected to a reduction reaction, and a method of manufacturing the same. With the goal.

[0013]

[MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
Further, according to the first aspect of the present invention, a circuit element is formed.
Phosphorus-containing first silicon oxide film on a doped semiconductor substrate
Is formed directly on the first silicon oxide film.
A first platinum layer, a metal oxide dielectric layer and a second platinum layer
Capacitors are formed and at least
A second silicon oxide containing phosphorus directly over the capacitor
A film is formed, and an opening provided on the second silicon oxide film is formed.
The electrode wiring is formed including the hole. Ma
The invention described in claim 2 of the present invention is the same as the half described in claim 1.
In the conductor device, silicon of the first and second silicon oxide films
The molar concentration ratio of phosphorus to phosphorus is in the range of 0.2% to 4%
It is characterized by that. Claim 3 of the present invention
The invention described in the first aspect is the semiconductor device according to the first aspect,
A palladium layer was used instead of the first and second platinum layers.
It is characterized by the following. Claim 4 of the present invention
The above-mentioned invention discloses a method of forming a phosphor on a semiconductor substrate on which circuit elements are formed.
Depositing a first silicon oxide film containing
A first platinum layer and a metal oxide layer directly on the first silicon oxide film;
Sequentially depositing an electrical conductor layer and a second platinum layer;
Second platinum layer, metal oxide dielectric layer and first platinum layer
Forming a capacitor by sequentially etching
At least a second layer containing phosphorus directly over the capacitor;
Depositing a silicon oxide film. Also
According to a fifth aspect of the present invention, there is provided a semiconductor device according to the fourth aspect.
In the method for manufacturing a layer device, the first and the second
2 has a molar ratio of phosphorus to silicon of 0.2
% To 4%.
A method of manufacturing a semiconductor device according to claim 6 of the present invention.
Is a method for manufacturing a semiconductor layer device according to claim 4,
After forming the first platinum layer, the metal oxide dielectric layer
Before forming an inert gas atmosphere with a dew point of -200 ° C or less.
Heat treating the semiconductor substrate at 300 ° C. or more in an atmosphere
It is added. In addition, a half of the seventh aspect of the present invention.
A method of manufacturing a semiconductor device according to claim 4, wherein
Forming a second silicon oxide film containing phosphorus in the fabrication method
Is performed by the thermal decomposition method of tetraethoxysilane.
It is characterized by the following. Claims of the present invention
The method of manufacturing a semiconductor device according to claim 8, wherein
Production method odor body apparatus Te, the first and second platinum layer
Instead, a palladium layer is used.
You.

[0014]

With the above structure, the chemical bonding force between the lower platinum electrode of the metal oxide dielectric capacitor and phosphorus is large, so that it is not necessary to use titanium of the adhesion strengthening layer, and the base electrode can be formed only with the platinum electrode. Oxygen deficiency in the metal oxide dielectric film due to the oxygen getter effect of titanium can be prevented, and problems caused by oxygen deficiency can be solved.

The adhesion strength between the PSG film and the platinum film is 25.
It has been confirmed that the temperature increases at 0 ° C. or higher. In the structure of the present invention that does not use titanium, high-temperature treatment can be performed after the formation of the lower platinum electrode, and the adhesion can be further improved.

Furthermore, in the step of forming a PSG film on a metal oxide dielectric capacitor, a thermal decomposition method of tetraethoxysilane is used, and since it does not contain a strongly reducing hydrogen component such as silane, metal oxide is used. The material dielectric film is not reduced. At this time, the metal oxide dielectric film is exposed to an atmosphere of tetraethoxysilane and by-products of ethanol and diethyl ether. However, since these substances have almost no reducibility, the film undergoes a reduction reaction. Therefore, deterioration of the capacitor characteristics can be prevented.

[0017]

An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1A to 1F are views showing a manufacturing process of a semiconductor device according to an embodiment of the present invention, in which a metal oxide dielectric film is capacitively insulated on a GaAs substrate on which circuit elements are formed. Capacitors used as membranes (hereinafter simply referred to as capacitors)
The case of forming is described as an example.

First, as shown in FIG. 1A, semi-insulating GaAs on which circuit elements such as transistors and resistors are formed.
A PSG film 2 having a phosphorus concentration of 4% is formed on a substrate 1 by a CVD method. After forming circuit elements on the GaAs substrate 1,
The illustration of the insulating film formed thereon is omitted. Next, as shown in FIG. 1B, after a platinum film 3 is formed by a sputtering method, a solution obtained by diluting an organic metal of barium, strontium and titanium with an organic solvent is spin-coated, and a high-temperature treatment at 700 ° C. is performed. Barium strontium titanate film (hereinafter referred to as BST film) 4 to be a ferroelectric film
Is formed, and a platinum film 5 is further formed thereon. next,
As shown in FIG. 1C, the platinum film 5 and the BST film 4 are etched by an ion milling method to form an upper platinum electrode 5a and a capacitor insulating film 4a. Next, FIG.
As shown in (d), the platinum film 3 is etched by an ion milling method to form a lower platinum electrode 3a. afterwards,
A PSG film 6 is deposited. Next, as shown in FIG. 1E, an opening is provided in a necessary region of the PSG film 6, and an electrode wiring 7 is formed.
To form Thereafter, if necessary, a silicon nitride film is formed as a protective film, a bonding pad portion is opened, and a semiconductor integrated circuit device incorporating a ferroelectric capacitor is completed. It is preferable to use a thermal decomposition method of tetraethoxysilane for depositing the PSG film 6.

In the semiconductor device of this embodiment, the PSG
No peeling of the ferroelectric capacitor on the film 2 was observed,
It was confirmed that the adhesion between the SG film and the lower platinum electrode 3a was sufficiently large for practical use. FIG. 2 is a diagram showing a relationship between the electrode material of the capacitor and the adhesion between the silicon oxide film and the adhesion between the silicon oxide film and the platinum film. That is, when a platinum film is formed on a non-doped silicon oxide film (hereinafter, referred to as an NSG film) via a titanium film, the adhesion of the platinum film is about 480 kg / cm ² (a), whereas the adhesion of the platinum film is NSG. When a platinum film is formed directly on the film, the adhesion of the platinum film is about 100 kg / cm ² (b), which is about 1/5. On the other hand, in the case of the platinum film formed on the PSG film having a phosphorus concentration of 4% as in this embodiment, the adhesion is about 420 kg / cm.
² (c) is comparable to a platinum film (a) formed on a NSG film via titanium.

The distribution of oxygen and titanium in the cross sections of the capacitor formed by the manufacturing method of the present invention and the capacitor formed by the conventional manufacturing method was measured by Auger electron spectroscopy. (B). In these figures, the horizontal axis indicates the depth from the upper platinum electrode, and the vertical axis indicates the Auger electron intensity. First, FIG. 3 (a) is a measurement of a capacitor formed by a conventional manufacturing method. A titanium layer, a lower platinum electrode layer, a BST film, and an upper platinum electrode layer are sequentially formed on an underlying NSG film. Is formed. The solid line indicates oxygen and the dotted line indicates titanium. Focusing on the Auger electron intensity from oxygen atoms shown by the solid line, the intensity decreases on the right side of the BST film, that is, on the titanium layer side. On the other hand, in the capacitor formed by the manufacturing method of the present invention shown in FIG.
The intensity of Auger electrons from oxygen atoms is constant in the BST film. This means that when a titanium layer is present below the lower platinum electrode, as in the conventional capacitor configuration, BS
Although oxygen of the T film is deprived by the titanium layer through the lower platinum electrode, in the structure of the present invention, oxygen is not deprived in the BST film, which means that the distribution is uniform.

In a capacitor formed by a conventional manufacturing method, the dielectric constant of the BST film constituting the capacitive insulating film is 250 when the film thickness is 200 nm, and the leakage current density of the capacitor is about 3 V at an applied voltage of 3 V. 10 ^-6 A
/ Cm ² . On the other hand, in the capacitor formed by the manufacturing method of this embodiment, the dielectric constant is 2 for the same film thickness.
At 500 times, the leakage current density was about 10 ⁻⁸ A / cm ^{2 at an} applied voltage of 3 V, which was reduced by a factor of 100.

As described above, it has been confirmed that the characteristics of the ferroelectric capacitor can be significantly improved by forming the lower platinum electrode on the PSG film and removing titanium which has been used as the conventional adhesion reinforcing layer.

In this embodiment, the sputtering method is used to form the lower platinum electrode. However, when the electron beam evaporation is used, the adhesion force after the evaporation is low because the energy for forming the deposited platinum film is small. Tends to be short. In such a case,
It is effective to add a high temperature treatment of 300 ° C. or more after the vapor deposition.

FIG. 4 shows the processing temperature dependence of the adhesion between the lower electrode of the capacitor and the silicon oxide film. The high-temperature treatment at about 300 ° C. or higher sufficiently improves the adhesion. In addition, regarding this high-temperature treatment, if moisture is contained in the atmosphere, the adhesion strength is reduced. If such a gas is a gas having a source of liquid nitrogen, liquid argon, or the like, the dew point of moisture contained in the gas is equal to or lower than its liquefaction temperature. Therefore, it is easy to set the dew point to −200 ° C. or lower. It is. By using the gas obtained in this way, the problem of deterioration of the adhesion strength due to moisture is solved.

The PSG film is formed by a plasma CVD method using tetraethoxysilane (TEOS) at a substrate temperature of 300 ° C., a flow rate of 30 sccm, and a power of 100 W.
/ Cm ² , 13.56 MHz high-frequency discharge with a film thickness of 30
As shown in FIG. 5, the magnitude of the leak current of the PSG film deposited at 00 [deg.] Is approximately one time smaller than that obtained with a deposited film having the same power and the same film thickness using SiH ₄ (silane) and oxygen. A reduction effect of an order of magnitude or more was obtained. As a result, it was confirmed that the overall capacitor characteristics were improved.

Although a semi-insulating GaAs substrate is used as a semiconductor substrate in this embodiment, the same effect can be obtained when a semiconductor memory device is formed using a silicon substrate.

In the present embodiment, the BST film has been described as an example of the metal oxide ferroelectric film as the capacitor insulating film of the capacitor. However, the semiconductor device of the present invention and the method of manufacturing the same may be any metal oxide dielectric material. A similar effect can be obtained if the spontaneous polarization is a feature of the ferroelectric material. That is, even in strontium titanate and other general metal oxide dielectric materials having a perovskite structure, which have a high dielectric constant but no spontaneous polarization, the leakage current is caused by oxygen defects, and the same in a reducing atmosphere. Needless to say, the structure and the manufacturing method of the present invention can be applied in view of the problem.

Although the adhesion of the platinum film can be improved by using the PSG film, when the phosphorus concentration in the PSG film is increased, the hygroscopicity due to phosphorus oxide increases, and
By making the G film water-containing, the adhesive strength is reduced. FIG. 6 shows the relationship between the concentration of phosphorus in the silicon oxide film and the adhesion between the platinum film and the silicon oxide film.
When the content is 4% or less, the adhesion between the PSG film and the platinum film can be improved without increasing the hygroscopicity.

Further, by using the PSG film as the interlayer insulating film used on the upper portion covering the capacitor, the adhesion between the PSG film and the upper platinum electrode of the capacitor is sufficiently increased for the same reason, and an opening is provided in the interlayer insulating film. In this case, peeling of the interlayer insulating film can be suppressed, and the manufacturing yield can be greatly improved.

[0031]

According to the present invention, there is provided a capacitor using a metal oxide dielectric as a capacitor insulating film, a structure using a silicon oxide film containing phosphorus as an interlayer insulating film on a base of a lower platinum electrode and on an upper platinum electrode. By doing so, the adhesion between the lower platinum electrode and the silicon oxide film containing phosphorus can be secured to a practically sufficient value without using a titanium film that causes deterioration of the characteristics of the capacitor insulating film, Further, by forming the capacitor in a non-reducing reaction gas atmosphere, deterioration of the capacitor can be suppressed, and an excellent semiconductor device incorporating a capacitor having a metal oxide dielectric as a capacitance insulating film and a method of manufacturing the same can be realized. .

[Brief description of the drawings]

FIGS. 1A to 1F are cross-sectional views showing a method of manufacturing a semiconductor device according to an embodiment of the present invention in the order of steps.

FIG. 2 is a diagram showing the relationship between the electrode material of a capacitor and the adhesion between a silicon oxide film.

FIG. 3 (a) is a diagram showing an analysis result by Auger electron spectroscopy of a capacitor formed by a conventional manufacturing method; FIG. 3 (b) is an analysis result by Auger electron spectroscopy of a capacitor formed by a manufacturing method of the present invention; Figure showing

FIG. 4 is a graph showing the processing temperature dependence of the adhesion between a lower electrode of a capacitor and a silicon oxide film.

FIG. 5 is a diagram showing the amount of leakage current depending on the type of gas used in a manufacturing process of an insulating film.

FIG. 6 is a diagram showing the relationship between the concentration of phosphorus in a silicon oxide film and the adhesion between a capacitor electrode material and the silicon oxide film.

7A to 7F are cross-sectional views in a process order showing a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

 Reference Signs List 1 GaAs substrate (semiconductor substrate) 2 PSG film (first silicon oxide film) 3a Lower platinum electrode (first platinum layer) 4a Capacitive insulating film (metal oxide dielectric layer) 5a Upper platinum electrode (second platinum) Layer) 6 PSG film (second silicon oxide film)

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-6-21334 (JP, A) JP-A-4-287968 (JP, A) JP-A-4-269859 (JP, A) JP-A-7- 50394 (JP, A) JP-A-7-263637 (JP, A) JP-A-7-111318 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 27/04 H01L 21 / 822

Claims (8)

(57) [Claims] A first silicon oxide film containing phosphorus is formed on a semiconductor substrate on which a circuit element is formed;
A capacitor comprising a first platinum layer, a metal oxide dielectric layer and a second platinum layer is formed directly on the first silicon oxide film, and at least directly covers the capacitor. A semiconductor device in which a second silicon oxide film containing phosphorus is formed, and an electrode wiring is formed including an opening provided in the second silicon oxide film. 2. The semiconductor device according to claim 1, wherein the molar ratio of phosphorus to silicon in the first and second silicon oxide films is in the range of 0.2% to 4%. 3. The semiconductor device according to claim 1, wherein a palladium layer is used instead of said first and second platinum layers. 4. A step of depositing a first silicon oxide film containing phosphorus on a semiconductor substrate on which circuit elements are formed, and a first platinum layer and a metal directly on the first silicon oxide film. Sequentially depositing an oxide dielectric layer and a second platinum layer; sequentially etching the second platinum layer, the metal oxide dielectric layer and the first platinum layer to form a capacitor; A second containing phosphorus directly over the capacitor
A step of depositing a silicon oxide film. 5. The method for manufacturing a semiconductor layer device according to claim 4, wherein the molar ratio of phosphorus to silicon in the first and second silicon oxide films containing phosphorus is in the range of 0.2% to 4%. . 6. A heat treatment of the semiconductor substrate at 300 ° C. or higher in an inert gas atmosphere having a dew point of −200 ° C. or lower after forming the first platinum layer and before forming the metal oxide dielectric layer. 5. The method according to claim 4, further comprising the step of: 7. The method of manufacturing a semiconductor device according to claim 4, wherein the step of forming the second silicon oxide film containing phosphorus is performed by a thermal decomposition method of tetraethoxysilane. 8. The method according to claim 4, wherein a palladium layer is used instead of the first and second platinum layers.