JPH06232344A - Capacitor of semiconductor device - Google Patents

Abstract

(57) [Summary] (Modified) [Objective] To provide a capacitor for a semiconductor device. A dielectric film 13 made of one of a high dielectric material and a ferroelectric material is formed on the first electrode 11, and a heat-resistant metal film or a heat-resistant metal film is formed on the dielectric film 13. Second electrode 1 having any one selected from a nitride film of a functional metal and a buffer film formed thereon
4 and 15 are capacitors of a semiconductor device. As a result, the characteristics are prevented from deteriorating due to the intermediate heat load in the manufacturing process, and excellent characteristics are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device capacitor, and more particularly to tantalum pentoxide (Ta ₂ O ₅ ; tantalum pento).
xide) capacitors.

[0002]

2. Description of the Related Art As a memory device formed on a semiconductor substrate, in a DRAM in which a memory cell is composed of one MOS (metal oxide semiconductor) transistor and one MOS capacitor, whether or not charges are accumulated in the MOS capacitor. Information is stored by the
Information can be read by a method of discharging charges of a MOS capacitor to a bit line through an OS transistor and detecting a potential change thereof.

In the DRAM, the increase of the cell capacitance improves the read capacity of the memory cell and causes a soft error.
Since it plays a role of reducing the rate, it greatly contributes to improving the characteristics of the cell memory. However, while the DRAM integration has increased four times every three years, the area of the chip is only 1.4 times, and the area of the memory cell is 1 / relatively.
Although the cell capacitance required by the unit cell is constant, the cell capacitance is reduced, resulting in a decrease in electrical characteristics of the memory device due to the decrease in cell capacitance.

Since the existing capacitor structure cannot secure a sufficiently large cell capacity within a limited area, it has been proposed to increase the area of the capacitor in order to increase the cell capacity. That is, many methods for forming a capacitor structure in three dimensions have been proposed. A trench type capacitor, a stack type capacitor, and a stack-trench merged type capacitor are typical structures of a three-dimensional capacitor. However, the trench capacitor is advantageous for securing a large capacitance, but the device characteristics are reduced due to the leakage current between the trenches and complicated parasitic transistors such as MOS parasitic transistors existing on the surface of the trenches. In addition, the manufacturing process is very strict. On the other hand,
The stack type capacitor has an advantage that the number of parasitic transistors is smaller than that of the trench type and the manufacturing process is easy, but it is disadvantageous for high integration because a sufficient capacitance cannot be obtained. Therefore, a new capacitor that can secure a large cell capacitance while requiring a simple device manufacturing process has been required.

As another method for increasing the cell capacity, there is a method of reducing the thickness of the dielectric film or using an insulating film having a large dielectric constant. Among them, thinning the dielectric film is considered to be undesirable because it reduces the reliability of the semiconductor device. ONO (oxide / nitride / oxid), which is a material used for existing capacitor dielectric films
e), NO (nitride / oxide), etc. have a low dielectric constant of the substance itself (about 3.8 for oxide and about 7. for nitride).
8) When applied to the next generation DRAM of 64M class or higher, there is a problem that the structure becomes very complicated and the thickness is thin and the reliability is low. In order to improve this, a high dielectric material or a ferroelectric material is used for manufacturing a dielectric film of a capacitor. Examples include Ta ₂ O ₅ , PLZT, PZT, etc., but especially Ta ₂ O ₅
Research into introducing dielectrics into the production of dielectric films is actively underway.

At Sony Corporation, C. Isobe and M. saitoh are
ppl. Phys. Lett., vol.56, No.10, pp907 ~ 909, 1990 “Effect of ozone annealing on the dielectric p
roperties of tantalum oxide thin films grown by ch
"Shamp Vapor Deposition" was announced at Sharp Corporation.
Koji Yamagishi and others are IEEE Transaction on electron
device, p2439, 1988 “Stacked capacitor DRAM pr
ocess using photo-CVD Ta ₂ O ₅ film ”and Hitachi. H. Shinriki et al. Tech. Dig. Symp. VLSITech., p.
p25-26, 1989 “Leakage current reduction and r
eliability improvement of effective 3nm-thick CVD
Ta ₂ O ₅ film by two-step annealing ”was announced.

However, the above-mentioned Ta ₂ O _{5 is used} as the dielectric film.
If a substance having a large dielectric constant such as the above is used, the dielectric constant is high, but there are problems such as high leakage current and low breakdown voltage in a thin film state, and it is a fact that it has not yet reached the stage of practical use.
On the other hand, the details are as follows. The electrical characteristics of Ta ₂ O ₅ as a capacitor dielectric film depend on the electrode material of the capacitor, and the electrode material with the best electrical characteristics is known as TiN. As a dielectric film for capacitors
When Ta ₂ O ₅ is used and TiN is used as the electrode material, polycrystalline silicon is used as the usual lower electrode and TiN is used as the upper electrode because of process compatibility. However, T
The iN electrode forms a Ta ₂ O ₅ dielectric film with improved electrical characteristics compared to the polycrystalline silicon electrode, but after the Ta ₂ O ₅ formation, D
BPSG (borophosph), which is an essential process in the RAM manufacturing process
An o-silicate glass) reflow process (typically performed at a temperature of about 850 ° C. for about 30 minutes) deteriorates the capacitor. Therefore, in manufacturing a capacitor in which a Ta ₂ O ₅ dielectric film is formed under the TiN electrode, it is essential to develop a stable process for the subsequent heat treatment process.

FIG. 1 shows a conventional capacitor in which polycrystalline silicon is used for the lower electrode 1, TiN is used for the upper electrode 3, and Ta ₂ O ₅ is used for the dielectric film 2. The deterioration phenomenon of the dielectric film due to the BPSG reflow process after forming the capacitor will be described with reference to the related art. Figure 2
Is a conventional technology, in which a high dielectric material Ta ₂ O ₅ is used as a dielectric film of a capacitor, a lower electrode is made of polycrystalline silicon, and an upper electrode is made of TiN, that is, TiN / Ta ₂ O ₅ / Poly.
The relationship between the applied effective electric field and the leakage current in the -Si system is shown. In the drawing, the characteristics before BPSG reflow are shown. Graph a is 350 ° C, b is 390 ° C, and c is 410 ° C.
And d are the characteristics corresponding to the vapor deposition temperature of 430 ° C. or higher, and g is the characteristic at all the vapor deposition temperatures after the BPSG reflow and in all + & − biases. in this case,
An example of Ta ₂ O ₅ film deposited at 350 ° C. which is the optimum condition is as follows: Leakage current of 10 ⁻⁸ A / cm at effective electric field of ± 5 MV / cm without BPSG reflow. The leakage current increases to 10 A / cm or more when the BPSG heat treatment process is performed at a temperature of 650 ° C. or more.

The deterioration of the capacitor due to the heat treatment such as the BPSG reflow as described above occurs regardless of the deposition temperature of Ta ₂ O ₅ . The reason why Ta ₂ O ₅ is not practically applied in the DRAM manufacturing process at present is that the subsequent heat treatment deteriorates the capacitor as described above. However, Ta
_When polycrystalline silicon is used for the upper and lower electrodes of a capacitor that uses ₂ O ₅ as the dielectric film, the electrical characteristics of Ta ₂ O ₅ in the as-deposited state without heat treatment are Although not worse than the capacitor used as the electrode, the characteristic deterioration after BPSG reflow is less.

On the other hand, if TiN is used for the electrode of the capacitor, the subsequent cleaning and etching processes should be carried out on the basis of metal, so that the compatibility of the process is deteriorated.

[0011]

SUMMARY OF THE INVENTION The object of the present invention is BPS
It is an object of the present invention to provide a semiconductor device capacitor with excellent performance in which characteristic deterioration due to heat load according to G reflow is prevented.

[0012]

To achieve the above object, the present invention provides a first electrode, a dielectric film formed on the first electrode, and a second film formed on the dielectric film.
In a capacitor of a semiconductor device having an electrode, the dielectric film is made of one of a high dielectric material and a ferroelectric material, and the second electrode is a heat resistant metal film or Provided is a semiconductor capacitor comprising one of heat-resistant metal nitride films and a buffer film formed on the selected one.

The first electrode is made of polycrystalline silicon, and TiN, Ti, W, and TiW are formed on the polycrystalline silicon.
Preferably, a layer of at least one refractory metal selected from the group consisting of Pt, Pt and Pd, or a compound thereof is formed. The polycrystalline silicon is preferably polycrystalline silicon doped with impurities or polycrystalline silicon treated with POCl ₃ .

The refractory metal of the second electrode is Ti, W,
TiW, Pt, Pd and at least one selected from the group consisting of Au, the nitride film of the refractory metal is TiN,
It is preferably at least one selected from the group consisting of WN, TiWN and PtN. The buffer film is preferably polycrystalline silicon or silicide.
Examples include Si, TiSi, TaSi, MoSi, polycide, and the like.

The dielectric film is Ta₂O_Five, TiO₂, HfO₂Etc high
Dielectric material or PbTiO₃, Pb (Zr, Ti) O ₃ PZT compound such as
Thing, (Pb, La) (Zr, Ti) O₃PLZT compounds such as BaTiO₃, Sr
TiO₃Manufactured from ferroelectric materials such as BST compounds
It

[0016]

In general, if one of the high dielectric material and the ferroelectric material is used as the dielectric film, the capacitor deteriorates after the BPSG reflow process as described above. In the present invention, by configuring the second electrode composed of a film made of any one selected from the heat-resistant metal film or the nitride film of the heat-resistant metal and the buffer film formed on the film, The above problem is solved.

[0017]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. By forming a film made of a heat resistant metal or a metal nitride thereof on a dielectric film made of a high dielectric material or a ferroelectric material, the interface characteristics with the dielectric film are improved, and the heat resistant metal or metal nitride is formed. By forming the buffer film on the top of the substrate, deterioration due to the subsequent heat treatment can be prevented. It is considered that the buffer film has a function of compensating for deterioration of electrical characteristics due to thermal stress of the dielectric film, the second electrode, the BPSG film and the like in the conventional capacitor and eventually preventing the deterioration.

Implementation of the method of manufacturing a capacitor according to the present invention
The following is a brief description of an example. First, the 1st Den
Form a pole. Forming a dielectric film on the first electrode
It For example, as a chemical vapor deposition CVD method, 60 to 200 Å
Thickness in Ta₂O_FiveEvaporate this Ta₂O_FiveTo improve the film quality of
UV-O at 300 ℃₃Treatment and dry-O at 800 ℃ ₂
Carry out each processing. At this time, the ozone under the ultraviolet light
Treatment is concentration 100-200g / Nm³For a few minutes to an hour
The heat treatment in the oxygen atmosphere is performed for several minutes to 1 hour.
It

A heat-resistant metal or a nitride thereof, for example, titanium nitride TiN is added to the upper portion of the formed dielectric film in an amount of 100 to 1,
After depositing a thickness of 000Å, doped polysilicon is deposited to a thickness of 1,000 to 2,000Å to form a second electrode capped with a buffer film. Then, patterning of the upper electrode and general processes are performed to complete the capacitor of the present invention.

Hereinafter, the method of manufacturing a capacitor according to the present invention will be described in detail through specific embodiments, but it should be understood that the present invention is not limited to the embodiments described below. (Example 1) First, as the first electrode, the sheet resistance Rs was 30.
A storage node was formed from polycrystalline silicon having Ω / □. A chemical vapor deposition method C is formed on the storage node.
Ta ₂ O ₅ was vapor-deposited by VD to a thickness of 100 Å. Vapor deposited
In order to improve the film quality of Ta ₂ O ₅ , UV-O ₃ treatment was performed at 300 ° C. and dry-O ₂ treatment was performed at 800 ° C., respectively.
At this time, the ozone treatment under the above-mentioned ultraviolet rays has a concentration of 100 to 200 g / Nm.
^And the heat treatment under the oxygen atmosphere is ³ for 30 minutes.
I ran for 0 minutes. After depositing titanium nitride TiN to a thickness of 600 Å on the formed Ta ₂ O ₅ dielectric film, polysilicon doped with impurities is deposited to a thickness of 1600 Å, and the second electrode is capped with a buffer film. To form. Then, patterning of the upper electrode and general steps were performed to complete the capacitor of the present invention.

FIG. 3 shows a schematic cross-sectional view of a capacitor completed according to this embodiment. There is a dielectric film 13 made of a high dielectric material above the first electrode 11 which is a lower electrode,
On top of this, a TiN film 14 made of a refractory metal nitride and a buffer film 15 made of an impurity-doped polycrystalline silicon film.
Is a structure equipped with. (Comparative Example 1) The same method as in Example 1 is performed, but the buffer film forming step is omitted, that is, a conventional capacitor having no buffer film formed on the TiN film, that is, TiN / Ta ₂ O ₅ / s. -pol
y System capacitors manufactured.

Example 2 A storage node, which is a first electrode, made of polycrystalline silicon and a TiN metal film formed on the polycrystalline silicon was formed. Then, the same method as in Example 1 was performed to complete the capacitor of the present invention. First
By forming the heat-resistant metal nitride film on the upper part of the electrode layer, the deterioration of the capacitor due to the subsequent heat treatment process could be better prevented. This is because the heat-resistant metal film formed on the upper and lower parts of the dielectric film is It is considered that this is to more efficiently prevent an increase in stress due to heat of the dielectric film.

A schematic cross-sectional view of the capacitor completed according to this embodiment is shown in FIG. This is a first electrode 11 made of polycrystalline silicon, a TiN film 12 formed by vapor deposition on top of it, a dielectric film 13 of a high dielectric material and a second electrode 14, 1.
Composed of 5. In order to check the electrical characteristics of the capacitor of the present invention and the conventional capacitor, FIG. 5 shows IV curves of the capacitor formed according to Example 1 and the capacitor manufactured according to Comparative Example 1.

FIG. 5 shows that a cell having an area of about 3 μm ³ is 1,0
It is a graph showing a leakage current-voltage relationship measured with 1K cell blocks formed by collecting 00 pieces, and is a result measured after passing through a BPSG reflow. The curve h is the first embodiment
The capacitor of the present invention manufactured by the method of d.
For the ly / TiN / Ta ₂ O ₅ / s-poly system, i is the conventional capacitor manufactured according to Comparative Example 1, namely TiN / Ta ₂ O ₅ / s-po.
for ly system.

According to the drawings, the conventional capacitor shows a leakage current value of about 1 EO-2A at 1.7V, but according to the present invention.
In the case of a capacitor capped with impurity-doped polycrystalline silicon on the TiN electrode, a leakage value of about 5.85E-12A is shown. As shown in FIG. 5, even if Ta ₂ O ₅ is used for the dielectric film, the capacitor of the present invention can be prevented from being deteriorated by the subsequent heat treatment process.

[0026]

As described above, according to the capacitor manufactured by the present invention, since the high dielectric material or the ferroelectric material is used as the dielectric film component, the electric characteristics are improved, but It has excellent characteristics without being deteriorated by the heat treatment in the subsequent process. Also, in the case of the second electrode, which was formed of metal such as TiN on the top of the conventional Ta ₂ O ₅ dielectric film, the subsequent cleaning process and etching process should be performed on the basis of metal, so the compatibility of the process deteriorates. However, in the capacitor having the non-metal buffer film on the second electrode as in the present invention, not only the effect of preventing deterioration due to the subsequent heat treatment but also the post-process is performed on the non-metal basis because the post-process proceeds. The suitability of is also improved.

[Brief description of drawings]

FIG. 1 is a schematic view of a conventional capacitor.

FIG. 2 is a graph showing a comparison of electrical characteristics before and after performing BPSG reflow on a capacitor having a dielectric film manufactured using Ta ₂ O _{5 according} to a conventional method.

FIG. 3 is a schematic cross-sectional view of a capacitor according to an exemplary embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view of a capacitor according to another embodiment of the present invention.

FIG. 5 is an IV curve showing characteristics of a capacitor according to an embodiment of the present invention, which is shown in comparison with a conventional capacitor.

[Explanation of symbols]

 11 1st electrode 12 TiN film 13 Dielectric film 14 2nd electrode 15 2nd electrode

Front page continuation (72) Inventor Xuan Yue, Republic of Korea, Gyeonggi-do, Suwon-si, Chang'an-gu, Usubin-dong, 129-1, Hyundai Apartment 19 501

Claims (9)

[Claims] 1. A first electrode, a dielectric film formed on the first electrode, and a second film formed on the dielectric film.
In a capacitor of a semiconductor device having an electrode, the dielectric film is made of one of a high dielectric material and a ferroelectric material.
A capacitor of a semiconductor device, wherein the electrode comprises one of a heat-resistant metal film or a nitride film of a heat-resistant metal and a buffer film formed thereon. 2. The capacitor of the semiconductor device according to claim 1, wherein the first electrode is made of impurity-doped polycrystalline silicon. 3. TiN, Ti, W on top of the polycrystalline silicon
The capacitor of the semiconductor device according to claim 2, wherein a layer made of at least one heat-resistant metal or heat-resistant metal alloy selected from the group consisting of TiW, Pt, and Pd is formed. 4. The refractory metal is Ti, W 3, TiW 3, Pt or Pd.
2. The capacitor of the semiconductor device according to claim 1, wherein the capacitor is at least one selected from the group consisting of Au and Au. 5. The refractory metal nitride is TiN, Wn, or Ti.
The capacitor of the semiconductor device according to claim 1, wherein the capacitor is at least one selected from the group consisting of WN and PtN. 6. The capacitor of the semiconductor device according to claim 1, wherein the buffer film is polycrystalline silicon or silicide. 7. The capacitor of the semiconductor device according to claim 6, wherein the buffer film is at least one of WSi, TiSi, MoSi and TaSi. 8. The high dielectric material of the dielectric film is Ta ₂ O ₅ , Ti
The capacitor of the semiconductor device according to claim 1, wherein the capacitor is any one selected from the group consisting of O ₂ and HfO ₂ . 9. The capacitor of the semiconductor device according to claim 1, wherein the ferroelectric substance of the dielectric film is at least one selected from the group consisting of PZT compounds, PLZT compounds, and BST compounds. .