Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1998-04-13
2002-12-24
Picardat, Kevin M. (Department: 2822)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S650000, C438S658000, C438S660000
Reexamination Certificate
active
06498097
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority from commonly-assigned Republic of Korea Application Serial No. P97-17209 (filed May 6, 1997) and Serial No. P97-17211 (filed May 6, 1997).
BACKGROUND OF THE INVENTION
The present invention relates to a technique for depositing a platinum film, which is used as a bottom electrode for memory cells or film sensors, and to a method of manufacturing such a film, particularly to a platinum film, which is deposited under an atmosphere containing an oxygen component (O
2
, O
3
, O
2
+N
2
, N
2
O, or mixtures thereof) together with an inert gas (Ar, Ne, Kr or Xe) so that its orientation and microstructure can be controlled, and to an electronic device comprising such a platinum film as an electrode and a method of manufacturing the electronic device. In the below description, oxygen component means O
2
, O
3
, O
2
+N
2
, N
2
O, or mixtures thereof. More particularly, the present invention relates to a technique improving characteristics of a platinum film in the course of manufacturing the platinum film used as a bottom electrode, wherein a preferred orientation of the platinum film is controlled toward a predetermined direction(s) and the platinum film is controlled to have a microstructure without any defects such as hillocks, pinholes and pores to be sufficiently useful as an electrode for memory cells, or ferroelectric sensor devices.
Semiconducting, dielectric, ferroelectric, superconductive and magnetic ceramic materials, used in electronic devices tend to become thinner in line with the trends of miniaturization, high-density integration and functional elevation of electronic ceramic parts or devices. Therefore, thin film type ceramic parts have been widely used in electronic industries. The substrates used for thin film type ceramic parts can be classified into three types. The first type comprises single crystal silicon generally referred to as silicon wafers. The second type comprises the other single crystals such as MgO, SrTiO
3
or Al
2
O
3
. The third type comprises polycrystal materials such as alumina or diamond. Among them, silicon wafers have been widely used in the conventional manufacturing processes of various types of electronic devices such as memory devices, or sensor devices.
Polysilicon has been widely used as a bottom electrode material in the conventional memory cells without any critical problems. However, it is generally accepted that polysilicon cannot be used any more as a bottom electrode to manufacture DRAMs (Dynamic Random Access Memories) with over 1 Gigabit and FRAMs (Ferroelectric Random Access Memories) which is a new type of non-volatile memory, because high dielectric or ferroelectric oxide thin films such as perovskite structure oxides, bismuth-layered perovskite structure oxides, tungsten-bronze type structure oxide, ReMnO
3
(Re: rare-earth element), and BaMF
4
(M: Mn, Co, Ni, Mg, Zn), are used on FRAMs, on DRAM devices requiring high degree of integration over 1 Gigabit, or around the core part of all types of oxide thin film sensors or actuators. That is, forming such high-dielectric oxide films requires an oxidation atmosphere and high temperature (higher than 500° C.), which may cause problems relating to the polysilicon. For example, if polysilicon is employed as the bottom electrode in a DRAM cell using high-dielectric material for a capacitor, serious problems may occur due to oxidation of the polysilicon under the high temperature (over 500° C.) and oxidation atmosphere during formation of the high-dielectric oxide thin films. For this reason, platinum is being investigated for use in place of polysilicon as an electrode of a memory cell employing a high-dielectric or ferroelectric oxide, because platinum is stable under high temperature and an oxidation atmosphere.
However, depositing platinum thin films by means of conventional methods has been known to pose a number of problems. First, the interface between an insulating oxide layer and the platinum layer does not allow chemical bonding, thereby weakening the adhesion strength between the platinum film and the substrate. One of the attempts that has been made to solve this problem is using an adhesion layer between a platinum layer and an insulating oxide layer. A thin film composed of any one or two of Ta, Ti, TiN or W has been formed on an insulating oxide layer before depositing a platinum thin film so that the thin film composed of any one or two of Ta, Ti, TiN or W serves as an adhesion layer between the insulating oxide layer and the platinum film.
However, employment of this method is known to not only complicate the process of forming a bottom electrode but also generate additional problems. In particular, oxygen gas introduced during the post-annealing or high-dielectric/ferroelectric oxide film depositing process can diffuse through voids formed between grain boundaries in the platinum film. Because the grains of the platinum films deposited by conventional processes have vertical columnar structures with inter-columnar voids, oxygen introduced from the above-mentioned process can easily diffuse through the platinum film to the adhesion layer. The oxygen gas diffused through the platinum film then oxidizes the adhesion layer and forms an oxidized insulation layer such as TiO
2
and Ta
2
O
5
between the substrate and the platinum film. Consequently, the function of the platinum film as an electrode can become deteriorated or even lost. In particular, if the adhesion layer is formed from TiN, N
2
gas is produced while an oxidized layer of TiO
2
is formed on the surface of TiN layer, and the N
2
gas can cause the platinum film to expand and become released from adhesion layer. This phenomenon is known as “buckling.”
In a conventional depositing method of a platinum thin film, hillocks, pinholes or pores are formed on the platinum film after annealing treatment or deposition of an oxide film. These hillocks, pinholes or buckling cause either shorting of the circuits or heterogeneity of a high dielectric or ferroelectric oxide layer.
Because of these problems, the use of oxide conductors such as IrO
2
, RuO
2
, LSCO, YBCO, etc., and platinum-oxide hybrid structures such as IrO
2
/Pt, RuO
2
/Pt, LSCO/Pt, YBCO/Pt, etc., as a bottom electrode have been investigated. However, when the former is used as the bottom electrode, the surface is not smooth enough and/or leakage currents increase. Furthermore, in the latter case, the manufacturing processes become complicated.
A solution for these disadvantages of conventional arts was addressed in two Korean patent applications (Serial Nos. 94-31618 filed Nov. 26, 1994 and 95-40450 filed Nov. 8, 1995) in the name of the present applicants. It is well known that oxygen may be contained in the depositing atmosphere when employing an insulating thin film on a substrate. The working effect of the two inventions addressed in said Korean applications filed in the name of the present applicants suggests a new technique. According to these inventions, a platinum thin film is deposited on an insulating oxide layer on a silicon wafer in two steps. The first step is to form a platinum thin film containing oxygen, as opposed to platinum, under an oxygen-containing atmosphere. The second step is to form a platinum layer on the Pt films formed at the first step under an inert gas atmosphere. The gases incorporated in the film during the first step are removed by annealing the film to a temperature higher than the decomposition temperatures of platinum oxides (PtO
2
: higher than 450° C., PtO: higher than 550° C.). Through this annealing process, the oxygen contained in the platinum film during the deposition thereof is removed and the remaining platinum film becomes stable. As a result, an adhesion layer is not required and thus problems related to the adhesion layer are solved.
According to the description in said Korean applications, “an oxygen containing gaseous atmosphere” means a mixture of inert gas (Ar, Kr, Xe, or Ne) with either oxygen or ozone gas mixtur
Chun Dong Il
Lee Dong Su
Park Dong Yeon
Woo Hyun Jung
Yoon Eui Joon
Picardat Kevin M.
Tong Yang Cement Corporation
Townsend and Townsend / and Crew LLP
LandOfFree
Apparatus and method of forming preferred... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method of forming preferred..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method of forming preferred... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2993569