JPH0311551B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and in particular to a method for manufacturing a semiconductor device, particularly for a dynamic memory element having a one-transistor/one-capacitor structure in which a capacitor is connected in series to an insulated gate transistor. Regarding the manufacturing method.

(b) Conventional technology and problems In dynamic MOS memory devices, MOS
By increasing the capacitance of the capacitor connected in series with the transistor, the signal margin increases.
Memory reliability has improved, but as memories have become larger in capacity and memory cell patterns have become more dense, the capacitor area has also been reduced, which tends to reduce the reliability of memory devices. .

Therefore, attempts have been made to use a silicon nitride film, which has a dielectric constant about twice that of the conventional dielectric film made of silicon oxide, as the dielectric film of the capacitor. The film tends to contain defects such as pinholes, making it leakier than silicon oxide dielectric films, which poses a serious problem of shortening the lifespan of information written to the capacitor.

(c) Purpose of the Invention The present invention provides a method for manufacturing a dynamic memory device using a silicon oxy nitride film as a dielectric film. The purpose is to improve the reliability of memory.

(d) Structure of the Invention In other words, the present invention provides a method for manufacturing a semiconductor device having a structure in which a capacitor is connected in series to an insulated gate transistor.
forming a silicon nitride film on a semiconductor substrate by chemical vapor deposition, ion-implanting oxygen into the silicon nitride film, and performing an annealing process to form a dielectric film made of silicon oxy nitride; Alternatively, it has a step of forming a silicon oxide film on a semiconductor substrate by a thermal oxidation method, implanting nitrogen ions into the silicon oxide film, and performing an annealing treatment to form a dielectric film made of silicon oxy nitride. It is characterized by

(e) Examples of the invention The present invention will be described in detail below with reference to the following figures.

FIGS. 1A to 1H are process sectional views in one embodiment of the method of the present invention, and FIGS. 2A to 2B are process sectional views in another embodiment of the method of the present invention.

When forming a dynamic MOS memory having, for example, one transistor and one capacitor structure using the method of the present invention, for example, as shown in FIG. is separated and exposed by a field oxide film 2, using a normal chemical vapor deposition (CVD) method, for example, to a thickness of 100~
A silicon nitride (Si ₃ N ₄ ) film 3 having a thickness of about 200 Å is formed. Note that the Si ₃ N ₄ film may contain defects such as pinholes as described above.

Next, as shown in FIG. 1B, the Si ₃ N ₄ film 3
For example, several [KeV]
After implanting the desired number of oxygen ions (O ⁺ ) with an acceleration energy of ~10 [KeV], the sample is heated to a temperature of about 900 [℃] in an oxygen (O ₂ ) atmosphere. An annealing treatment is performed for about 5 to 6 minutes to transform the Si ₃ N ₄ film 3 into a silicon oxy nitride (Si _x O _y N _z ) film 4' having a desired composition. Note that the oxidation treatment removes defects in the Si ₃ N ₄ film, making it an uncommon silicon film with no defects such as pinholes.
An oxy nitride film 4' is obtained.

Next, using a resist pattern corresponding to the capacitor formed using a normal photo process as a mask, a normal etching gas using carbon tetrafluoride (CF ₄ ) or methane trifluoride (CHF ₃ ) as the main etching gas is etched. The silicon oxy nitride film 4' is selectively etched by dry etching means such as reactive ion etching.
As shown in FIG. 1C, a silicon oxy nitride dielectric pattern 4 corresponding to a capacitor pattern is formed on an exposed Si substrate 1.

Next, as shown in FIG.
N ⁺ type polycrystal with a thickness of about 5000 to 6000 [Å] doped with, for example, phosphorus (P) at a high concentration by CVD method
A Si layer 5' is formed, and then a resist pattern corresponding to a capacitor formed using a normal photo process is used as a mask. The n ⁺ type polycrystalline Si layer 5' is selectively etched by dry etching means such as normal reactive ion etching using an etching gas such as CF ₄ +O ₂ to form a silicon oxy An n ⁺ type polycrystalline Si capacitor electrode 5 is formed on the nitride dielectric pattern 4 .

As described above, the present invention is characterized by the conventional
A capacitor having a dielectric constant of about 1.5 to 1.8 times that of a SiO ₂ dielectric film and having a larger capacity than the conventional capacitor is formed using an uncommon silicon oxy nitride as a dielectric film. In addition, silicon, oxy,
The dielectric constant of the nitride film can be varied within the above range by changing the amount of O ⁺ ions implanted.

Thereafter, according to the usual manufacturing ^method , first, as shown in _FIG . Then, a gate oxide film 7 of, for example, about 300 to 500 [Å] in thickness is formed by thermal oxidation on the exposed surface of the p-type Si substrate.

Next, a layer with a thickness of 5000~ is deposited on the substrate using the CVD method.
A non-doped polycrystalline Si layer of about 6000 [Å] is formed,
Patterning the non-doped polycrystalline Si layer and the gate oxide film 7 by a normal photo-etching technique using dry etching means,
As shown in FIG.
Adjacent through a SiO ₂ insulating film 6, with a gate oxide film 7 below, a portion is above the capacitor electrode 7.
A non-doped polycrystalline Si pattern 8' corresponding to the gate electrode stacked with the SiO ₂ insulating film 6 interposed therebetween is formed.

Next, as usual, using the non-doped polycrystalline Si pattern 8' and the capacitor electrode 7 as a mask, p-type Si is deposited.
Arsenic ions (As ⁺ ) are selectively implanted into one surface of the substrate, and a normal annealing process is performed to form an n ⁺ -type source/
A drain region 9 is formed. At this time, As ⁺
is implanted to form an n ⁺ type polycrystalline Si gate electrode 8. Through the above steps, a dynamic MOS memory element is formed in which a capacitor using silicon oxy nitride as a dielectric film is connected in series to an insulated gate transistor.

In another embodiment of the present invention, a silicon oxy nitride dielectric film for a capacitor in a dynamic MOS memory device is formed as follows.

That is, first, as shown in FIG. 2A, a substrate to be processed in which one surface of a p-type Si substrate is separated and exposed by a field oxide film 2 is oxidized by a normal thermal oxidation method, and one surface of the exposed Si substrate is oxidized. For example, with a thickness of about 100 to 200 [Å]
A SiO ₂ film 10 is formed. It is well known that the SiO ₂ film 10 formed by thermal oxidation is an uncommon film without defects.

Next, as shown in FIG. 2B, a desired number of nitrogen ions (N ^{+ ) are implanted into the substrate surface with an acceleration energy of, for example, several [KeV] to 10 [KeV], and then the nitrogen ions (N +} ) are implanted into a nitrogen (N ₂ ) atmosphere. 5 ~ at a temperature of about 900 [℃]
After annealing for about 6 minutes, the SiO ₂ film 1
0 is transformed into a silicon oxy nitride (Si _x O _y N _z ) film 4' having a desired composition. This silicon oxy nitride film 4' is an unclean film with no defects.

Thereafter, a capacitor having the silicon oxy nitride film as a dielectric film is connected in series to an insulated gate transistor in the same manner as in the first embodiment described with reference to FIGS. A dynamic MOS memory device is provided.

Also in this method, silicon oxy nitride dielectric films having various dielectric constants within a range of about 1.5 to 1.8 times that of the SiO ₂ film can be formed by changing the amount of n ⁺ implanted.

(f) Effects of the Invention As explained above, according to the method of the present invention, an unclean silicon oxy nitride film having a higher dielectric constant than silicon dioxide and having no defects can be easily formed. .

Therefore, it is possible to form a capacitor with a larger capacity than the conventional one using a silicon oxy nitride film with a high dielectric constant as the dielectric film, which improves the reliability of dynamic memories in which the capacitor is connected in series with an insulated gate transistor. Improvements can be made.

[Brief explanation of the drawing]

FIGS. 1A to 1G are process sectional views in one embodiment of the method of the present invention, and FIGS. 2A to 2B are process sectional views in another embodiment of the present invention. In the figure, 1 is a p-type silicon substrate, 2 is a field oxide film, 3 is a silicon nitride film, 4' is a silicon oxy nitride film, 4 is a silicon oxy nitride dielectric pattern, and 5' is a n ⁺ type polycrystalline silicon layer, 5 is n ⁺ type polycrystalline silicon layer;
Capacitor electrode, 6 is silicon dioxide insulating film, 7
is a gate oxide film, 8' is a non-doped polycrystalline silicon pattern, 8 is an n ⁺ type polycrystalline silicon gate electrode, 9 is an n ⁺ type source/drain region, 1
0 represents a silicon dioxide film, O ⁺ represents an oxygen ion, N ⁺ represents a nitrogen ion, and As ⁺ represents an arsenic ion.

Claims (1)

[Claims] 1. In a semiconductor device having a structure in which a capacitor is connected in series to an insulated gate transistor, when forming the capacitor, a silicon nitride film is formed on a semiconductor substrate by chemical vapor deposition. A method for manufacturing a semiconductor device, comprising the steps of: forming a dielectric film made of silicon oxy nitride by ion-implanting oxygen into the silicon nitride film and performing an annealing process. 2. In a semiconductor device having a structure in which a capacitor is connected in series to an insulated gate transistor, when forming the capacitor, a silicon oxide film is formed on the semiconductor substrate by a thermal oxidation method, and nitrogen is added to the silicon oxide film. 1. A method for manufacturing a semiconductor device, comprising the steps of forming a dielectric film made of silicon oxy nitride by implanting ions and performing an annealing process.