JPH01196154A - Manufacture of capacitor - Google Patents

Abstract

PURPOSE:To realize a high electrostatic capacity value with a small size and to enhance accuracy, stability and yield by a method wherein an ion of a specific metal is implanted into an oxide film on the main surface of a semiconductor film and a metal oxide film is generated by heat-treating it. CONSTITUTION:A first insulating film 2 and a semiconductor layer 12 are formed on a silicon semiconductor substrate 1; after that, a second insulating film 15 composed of a silicon oxide film using a dielectric of a capacitor as a base material is formed on this semiconductor layer 12; after that, Ti ions 13 whose number is sufficient to transform at least the second insulating film 15, i.e. the silicon oxide film, into a titanium oxide layer are implanted into the insulating film 15 by an ion implantation method. Then, the second insulating film 15 composed of the silicon oxide film is transformed into the titanium oxide layer by a heat treatment; the second insulating film composed of this titanium oxide layer is constituted. In addition to Ti, an element such as Pb, Ta or the like may be used; two kinds of elements of Ti and Ba or Ti and Si may be used.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a capacitor used in a semiconductor integrated circuit, and particularly relates to a technology for manufacturing a small capacitor with high precision and high capacitance value. It is.

[Conventional technology]

An example of a method for manufacturing a conventional capacitor used in semiconductor devices such as ICs and LSIs will be explained with reference to FIG. In FIG. 7, 1 is a silicon (Si) single crystal semiconductor substrate of the first conductivity type, 2 is a first insulating film, 3 is a lower metal electrode, and 4 is a second silicon (Si) semiconductor substrate for preventing mutual interference between capacitors. An insulating film, 5 is a third insulating film used as a dielectric of the capacitor, and 6 is an upper metal electrode.

First, as shown in FIG. 7(a), the first conductivity type Sf
After forming a first insulating film 2 made of a silicon oxide film on the main surface of a single crystal semiconductor substrate 1, a metal film 3, which is conveniently used as a lower electrode for a capacitor, is deposited on the insulating film 2. Next, as shown in FIG. 7(b), after processing the metal film 3 to a predetermined size, a second insulating film 4 made of a silicon nitride film is formed on the main surface side of the semiconductor substrate 1, The insulating film 4 is etched to expose at least a portion of the surface on the lower electrode 3. Thereafter, as shown in FIG. 7(C), a third insulating film 5 to be used as a dielectric of the capacitor is formed on at least the exposed surface of the lower electrode 30, and then at least a portion on this insulating film 5 is formed. A capacitor having the structure shown in FIG. 7(C) is manufactured by depositing a metal film 6 for an upper electrode on the portion and processing it to a predetermined size.

In this case, in a capacitor having such a structure, the third insulating film 5 is usually a tantalum pentoxide film (ε: about 5
000), titanium oxide film (ε; 14-110), silicon nitride film (ε: 5-7), or silicon oxide film (ε;
Approximately 4) have been used. The main reason for this was that it was relatively easy to manufacture using conventional techniques.

On the other hand, there is another conventional manufacturing method shown in FIG. 8, and its outline will be explained below. In this manufacturing method, first, as shown in FIG. 8(a), an insulating film 10 for electrically isolating a capacitor in the lateral direction is placed on a first conductivity type St single crystal semiconductor substrate 1, and an insulating film 10 is formed on the semiconductor substrate. Thin oxide film 8 on part of main surface
form a. Next, as shown in FIG. 8(1), a predetermined impurity is ion-implanted to form a high impurity concentration region 7 of the first or second conductivity type in the substrate 1 through the insulating film 8a. After the impurities are introduced by the method, the impurities in the high impurity concentration region 7 are activated by heat treatment.

Thereafter, the thin insulating film 8a is removed and at least a portion of the main surface of the substrate 1 is oxidized again to form an insulating film 8 made from a silicon oxide film to be used as a dielectric of the capacitor. Next, as shown in FIG. 8(c), after forming an upper electrode 9 on this insulating film 8, the insulating film 11
By forming υ on the main surface of the semiconductor substrate 1, a capacitor having the structure shown in FIG. 8(c) is manufactured. At this time, a semiconductor or metal is used for the upper electrode 9, and the insulating film 11 is for ensuring electrical insulation between the base electrode 9 and other electrodes or wiring materials.

The reason why capacitors with this structure were used is because the film quality and uniformity of the dielectric of the capacitor is good.

Since a silicon oxide film with excellent reproducibility can be used, the yield of capacitors can be improved.

[Problem to be solved by the invention]

By the way, in the conventional method shown in FIG. 7 described above, the third
As the insulating film 5, a tantalum pentoxide film, a titanium oxide film, a silicon nitride film, etc. having a high dielectric constant are used.The methods for forming these insulating films are usually sputtering and carbon dioxide.
The VD method has been adopted. However, the sputtering method lacks a high-quality target with a low impurity concentration to form these insulating films, and the film quality is not reproducible. Also CVD
With this method, the deposition must be carried out at a low temperature of around 300 degrees Celsius to protect the lower electrode, which poses the problem of not being able to produce a high-quality thin film without pinholes. Therefore, due to the limitations of the manufacturing method, the thickness of the insulating film 5 has to be increased, which poses the problem of hindering the high integration of analog integrated circuits in which the area of the capacitor is extremely large. was there.

Further, in the conventional method shown in FIG. 8, since the dielectric is a silicon oxide film, the dielectric constant is small, and the only way to increase the capacitance is to reduce the thickness of the silicon oxide film or expand the electrode area. Therefore, an increase in the electrode area causes a decrease in the degree of integration of the integrated circuit, and a reduction in the thickness of the silicon oxide film causes a decrease in yield.

However, due to these problems, it has not been possible to miniaturize semiconductor devices using this type of capacitor.

In view of the above points, the present invention has been made to solve such problems, and its purpose is to achieve a high capacitance value with a small size in a capacitor used in a semiconductor integrated circuit, and to An object of the present invention is to provide a method for manufacturing a capacitor that can improve its accuracy, stability, and yield.

[Failure to solve the problem]

In order to achieve the above object, the method for manufacturing a capacitor according to the present invention uses a silicon semiconductor substrate or a semiconductor thin film as a base material, forms an oxide film on the main surface of the semiconductor film, and injects into the oxide film. A metal oxide film is generated by heat treatment by introducing at least one metal, titanium (TI), tantalum (Ta), or lead (Pb), which can form a stable alloy layer with the semiconductor, by ion implantation. It is characterized by:

[Effect]

Therefore, in the present invention, by using a newly generated metal oxide film with a high dielectric constant as a dielectric film, not only the capacitance per unit area of the capacitor is dramatically increased, but also the base material is made of silicon oxide. Since it is a film, it is possible to stabilize the operating characteristics of the capacitor and improve yield.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a process sectional view showing an embodiment of a method for manufacturing a capacitor according to the present invention. In FIG. 1, 1 is a silicon single crystal semiconductor substrate of the first conductivity type, 2 is a first insulating film made of a silicon oxide film, and 12 is a single crystal, polycrystal, or amorphous base material for the lower electrode. 12a is a semiconductor layer formed from a high-quality silicon film, and 12a is a semiconductor layer that functions as a part of the lower electrode;
12b is an alloy layer that functions as a part of the lower electrode; 13 is Ti ion implantation; 14 is a second insulating film that functions as a dielectric film made of titanium oxide; 16 is the upper electrode of the capacitor; 17 is a third insulating film for preventing mutual interference between the capacitors, and is made of a silicon nitride film or the like.

In the method of this embodiment, first, as shown in FIG. A second insulating film 15 made of a silicon oxide film to be used as a base material of the dielectric is formed, and then a few Ti ions are added at least enough to convert the second insulating film 15, that is, the silicon oxide film, into a titanium oxide layer. 13 is implanted into the insulating film 15 by ion implantation. At this time, there is no problem even if the implanted Ti ions 13 enter the semiconductor layer 12. Next, as shown in FIG. 1(b), the second insulating film 15 made of a silicon oxide film is changed into a titanium oxide layer by heat treatment, and the second insulating film 14 made of this titanium oxide layer is Configure. Here, the symbol 12b is the semiconductor layer 12
Of these, L12a is an alloy layer formed by Ti ion implantation, and L12a is a remaining semiconductor layer that did not become an alloy layer. After that, the semiconductor layer 12a and the alloy layer 12b
In order to constitute the lower electrode of a capacitor, these semiconductor layers 12a, 12b and the second insulating film 14 are processed and formed into predetermined dimensions. Finally, as shown in FIG. 1(C), after depositing a third insulating film 17 for protecting the capacitor, a part of the upper surface of the lower electrode of this insulating film 17 is removed by etching. By forming the upper electrode 16 on the insulating film 14 made of a titanium oxide layer, υ, as shown in FIG.
A capacitor having the structure shown in C) can be manufactured.

By using a silicon oxide film with excellent film quality as the dielectric base material of the capacitor manufactured in this way, the operating characteristics of the capacitor can be stabilized, and
Yield 9 can be improved.

Furthermore, by using titanium oxide, which has a large relative dielectric constant, as a dielectric material, there are advantages such as the ability to increase the capacitance per unit area of the capacitor.

FIG. 2 is a first embodiment showing another embodiment of the manufacturing method according to the present invention.
It is a process sectional view corresponding to the figure. This embodiment differs from the one shown in FIG. 1 in that the semiconductor layer 12 on the first insulating film 2 is processed and formed to a predetermined size, and then the surface of this semiconductor layer 12 is coated with the base material of the dielectric of the capacitor. After forming an insulating film 15 made of a silicon oxide film to be used as a silicon oxide film, Ti ions 13 are ion-implanted into this insulating film 15 and a silicon oxide film is generated by heat treatment. This is because it is configured as the second insulating film 14.

In other words, in this method, as shown in Figure 2(a),
A first insulating film 2 and a semiconductor layer 12 are formed on a semiconductor substrate 1. Next, as shown in FIG. 2(b), the semiconductor layer 12
is processed and formed into a predetermined size with the lower electrode and 1~, and then,
On the surface of this semiconductor layer 12, an insulating film 15 made of a silicon oxide film to be used as a base material for the dielectric of the capacitor is formed 7, and at least an amount of Ti ions 13 necessary to convert this insulating film 15 into a titanium oxide film is applied. Ions are implanted into the insulating film 15. At this time, Ti ions may be implanted into the semiconductor layer 12. Next, Figure 2 (
As shown in c), the semiconductor substrate 1 is heat-treated to modify a portion of the insulating film 15 into an insulating film 14 made of a titanium oxide film. At this time, the semiconductor layer 12 used as the lower electrode
It does not matter if a part of it changes into an alloy film with Ti. 7
After that, an insulating film 17 for protecting the capacitor is formed on the main surface side of the semiconductor substrate 1, and a part of the insulating film 17 is removed by etching to expose the insulating film 14 on the lower electrode. By forming the upper electrode 16 on the surface of the insulating film 14, a capacitor having the structure shown in FIG. 2(c) can be manufactured. Therefore, the same effect as that in FIG. 1 can be obtained in the capacitor of this embodiment. Hiko, in the figures, the same reference numerals indicate the same or corresponding parts.

FIG. 3 is a cross-sectional view of the process shown in FIG. 1 showing another embodiment of the present invention. The difference between this embodiment and the one in Fig. 1 is that
The semiconductor layer 12 on the first insulating film 2 is processed and formed to a predetermined size, and then an insulating film 17 for protecting the capacitor is deposited 2 and etched on the exposed area of the semiconductor layer 12. After forming an insulating film 15 made of a silicon oxide film to be used as the base material of the dielectric of the capacitor, Tj ions 13 are implanted into this insulating film 15 in the same manner as in the above embodiment. In this way, a silicon oxide film is generated.

That is, in this method, as shown in FIG. 3(a),
A first insulating film 2 and a semiconductor layer 12 are formed on a semiconductor substrate 1. Next, as shown in FIG. 3(b), the semiconductor layer 12
is processed and formed into a predetermined size as a lower electrode. after that,
As shown in FIG. 3(C), an insulating film 17 for protecting the capacitor is deposited on the main surface side of the semiconductor substrate 1, and the semiconductor layer 1
A part of the insulating film 17 is removed by etching to expose a part of the surface of the insulating film 17. After that, this semiconductor layer 12
on the exposed area of the capacitor dielectric matrix,
An insulating film 15 made of a silicon oxide film to be used as a titanium oxide film is formed, and at least an amount of Ti ions necessary to change the insulating film 15 to a titanium oxide film is implanted into the inside of the insulating film 15.

At this time, Ti ions may be implanted into the semiconductor layer 12. Next, as shown in FIG. 3(d), the semiconductor substrate 1 is heat-treated to modify a portion of the insulating film 15 into an insulating film 14 made of titanium oxide. At this time, a part of the semiconductor layer 12 used as the lower electrode may be changed into an alloy film with Ti. After this, the exposed insulating film 1
It is preferable to form an upper electrode 16 on the upper surface of the third electrode 4.
A capacitor having the structure shown in Figure (d) can be manufactured. In this embodiment as well, effects similar to those in FIG. 1 can be obtained.

FIG. 4 is a process sectional view showing still another embodiment of the present invention. In FIG. 4, 1 is a silicon single crystal semiconductor substrate of the first conductivity type, 7 is a highly impurity-concentrated semiconductor region of the first or second conductivity type which is conveniently used as a lower electrode of a capacitor, and 7a is this semiconductor. T ion implanted into a part of region 7
7b is a semiconductor region layer with a high impurity concentration that remains without becoming an alloy layer; 8
9 is an insulating film made of silicon oxide film used as the base material of the dielectric of the capacitor; 9 is the upper electrode of the capacitor; 1
0 is an insulating film for electrical isolation from other adjacent capacitors or semiconductor devices, and 11 is an insulating film for ensuring electrical insulation between the upper electrode 9 and other electrodes or wiring materials. Further, 13 is Ti ion to be ion-implanted, and 1
8 is a titanium oxide film as a dielectric film.

In the manufacturing method of this embodiment, first, as shown in FIG. A film 10 and a thin insulating film 8a are formed. Next, as shown in FIG. 4(b), ions of a predetermined amount of a predetermined impurity are implanted into a region of the main surface side of the semiconductor substrate 1 where the thin insulating film 8a is atomized, and the semiconductor substrate is heat-treated. The impurities are activated to form a semiconductor region 7 with a high impurity concentration.

Thereafter, the thin insulating film 8a is etched and removed, and an insulating film m8 made of a silicon oxide film used as a base material for the dielectric of the capacitor is formed on the semiconductor region 7 with a high impurity concentration, and at least this insulating film 8 is made of titanium. Ti ions 13 in an amount necessary to convert it into an oxide film are implanted into the inside of the insulating film 8. At this time, Ti ions may be implanted inside the semiconductor region 7. Next, as shown in FIG. 4(C), the semiconductor substrate is heat-treated to modify a portion of the insulating film 8 into an insulating film 18 made of a titanium oxide film. At this time, there is no problem even if a part of the semiconductor region T used as the lower electrode changes into an alloy film with Ti. After that, the insulating film 18
After forming the upper electrode 9 thereon, an insulating film 11 for protecting the capacitor is formed on the main surface side of the semiconductor substrate, thereby manufacturing a capacitor having the structure shown in FIG. 4(C).

In the capacitor manufactured in this way, the same effects as in the above-mentioned embodiments can be obtained.

FIG. 5 shows, as an example, the relationship between the sheet resistance value of a silicon oxide film and the heat treatment temperature when a sample in which Ti 2 was actually introduced into the St 2 oxide film by ion implantation was heat treated. Ti is 1×10 at an accelerating voltage of 50 kV
Piece/cIn typed. The sheet resistance value increases rapidly when the heat treatment temperature is 600° C., and the silicon oxide film whose resistance has been reduced by introducing Ti becomes an insulating film again. Note that in FIG. 5, Xl indicates the state immediately after ion implantation.

Furthermore, FIG. 6 shows the results of examining the dependence of the depth distribution of Ti in the same sample on the heat treatment temperature using Auger electron spectroscopy. Here, when heat treatment is performed at 600°C, silicon Sl in the silicon oxide film decreases, but oxygen (
0) increases, 5i02 + Ti − + Ti
It can be seen that the silicon oxide film changes to a titanium oxide film due to the O2+Si reaction. However, in Fig. 6, the horizontal axis is the sputtering time (minutes), and the vertical axis is the atomic weight (%), where the solid line is the characteristic curve of Ti, the -dotted line is the characteristic curve of 0, and the dotted line is the characteristic curve of St. It is. Figure (a) is a graph immediately after ion implantation, and Figure (a) to (d) are graphs at a heat treatment temperature of 50%, respectively.
It is a graph of 0°C, 600°C, and 700°C.

In the above-mentioned embodiment, the case where Ti is used as the metal source for implanting hay ions into the silicon oxide film is shown, but the present invention is not limited to this.
In addition, elements such as pb or Ta may be used, or Ti and Ba may be used.
(barium) or two types of elements, Ti and Sr (strontium), can also be used. In addition, polycrystalline or amorphous silicon semiconductor substrates are used in addition to single crystal, and the underlying material for single-crystal, polycrystalline, or amorphous silicon semiconductor thin films is not limited to insulating films. , a silicon semiconductor substrate, etc., and many modifications are possible.

[Effects of the Invention] As explained above, according to the present invention, by using a silicon oxide film with excellent film quality as the dielectric base material of the capacitor, the electrical characteristics of the capacitor can be stabilized and the yield can be improved. Improvements can be made. Furthermore, in addition to using a metal oxide film such as titanium oxide, which has a high dielectric constant, as a dielectric, it is also possible to make the base material extremely thin beforehand, so that the electrostatic charge per unit area of the capacitor can be reduced. Capacity can be increased. Therefore, the area occupied by the capacitor within the integrated circuit can be significantly reduced, which has the effect of increasing the degree of integration of the analog integrated circuit.

[Brief explanation of the drawing]

FIG. 1 is a process cross-sectional view showing one embodiment of the capacitor manufacturing method according to the present invention, FIGS. 2 to 4 are process cross-sectional views showing other embodiments of the present invention, and FIG. Fig. 6 is a diagram showing the relationship between the sheet resistance value of the silicon oxide film and the heat treatment temperature when a sample in which Ti was actually introduced into the 81 oxide film by ion implantation was heat-treated to be used in the example.
The figure shows the results of examining the depth distribution of Ti in the same sample using Auger electron spectroscopy. Figures 7 and 8 are process cross-sectional views showing an example of the conventional capacitor manufacturing force □ method, respectively. 0 1...Silicon single crystal semiconductor substrate, 2...First
insulating film, 7...first or second conductivity type semiconductor region with high impurity concentration, 7a...alloy layer, 7b...
- Semiconductor region layer, 8... second insulating film (silicon oxide film), 9... upper electrode, 10.11... insulating film, 12... base material of lower fist electrode a semiconductor layer, 12
a: Semiconductor layer, 12b: Alloy layer, 1
3... Ti ions, 14... Insulating film (dielectric film) made of titanium oxide, 15... Second insulating film (
silicon oxide film], 16...upper electrode, 1T...
・Insulating film, 18...Titanium oxide film. Patent applicant Nippon Telegraph and Telephone Corporation

Claims (2)

[Claims] (1) A step of forming a monocrystalline, polycrystalline, or amorphous silicon semiconductor thin film on the surface of a base, a step of forming an oxide film on the main surface of the semiconductor thin film, and a step of forming at least titanium, 1. A method of manufacturing a capacitor, the method comprising at least the step of ion-implanting either tantalum or lead, and then generating a metal oxide film by heat treatment. (2) Forming an oxide film on the main surface of a single-crystal, polycrystalline, or amorphous silicon semiconductor substrate, and ion-implanting at least one metal of titanium, tantalum, or lead into the oxide film. A method for manufacturing a capacitor, comprising at least the step of: generating a metal oxide film by heat treatment.