JPS58161369A - Manufacture of schottky electrode of electronic device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a Schottky electrode for an electronic device.

2. Description of the Related Art In electronic devices such as integrated circuits, in recent years, due to demands for higher speed and higher density of elements, attempts have been made to three-dimensionally reduce element dimensions. Along with this, the thickness of the epitaxial layer and the depth of the P-N junction that make up the electronic device are also increasing.
Thin ones of about 000A or less have come to be used frequently.

Therefore, techniques for forming shallow Schottky electrodes and ohmic electrodes on these thin Si layers have become increasingly important. Currently, aluminum-based thin films are most widely used as electrode wiring materials for electronic devices, but when this aluminum-based thin film is used for Schottky electrodes,
Even in annealing at around 0°C, aluminum and substrate S
Interdiffusion occurs between t and t, causing problems such as variations in the height of the Schottky barrier.

In order to eliminate such drawbacks, recently, Pd, Pt, etc. have been developed. Attempts have been made to use silicides of high melting point metals such as I4, Ta, and Mo as shimmit key electrodes, but since the electrical resistance of these silicides is several times higher than that of pure metals of Atmium, A method of forming an electrode wiring made of At or an M-based metal containing trace amounts of St, Cu, etc. in At is being considered on a silicide electrode. Conventionally, to fabricate such an electrode, Pd is deposited on an exposed 7'cSi substrate on which a Schottky electrode is to be formed.
, Pt, Ta, or the like is formed by a vapor deposition method, and then a heat treatment is performed at about 400 to 600°C to cause the Si substrate and the metal thin film to react to form a metal silicide. Electrode wiring of At-based metal was formed. However, the Schottky electrode formed by this method has the disadvantage that it is not stable during heat treatment that is usually performed after electrode formation. In other words, silicides of noble metals such as Pd and Pt are At and 4
It reacts easily even by low-temperature annealing at about 00° C. or lower, and compounds such as ALsPd At1P are formed, and the pre-formed noble metal silicide layer disappears. On the other hand, silicides of high melting point metals such as Mo and Ta and A
The reaction with t is less likely to occur than in the case of the above-mentioned noble metals, and 550
Although the silicide layer remains after heat treatment at a temperature of about °C and is stable in terms of reaction with M, the following problems arise due to the metallurgical properties of the high melting point metal silicide formed by the heat treatment described above. There is a point. Namely, G, J, Van Gu.
rp) et al., Journal of Applied Physics (Journal of Applied Ph.
ysics) Magazine Vol. 50 No. 11 No. 6915-692
6 (November 1979), after forming MO silicide with a thickness of 2500X on the St substrate by the heat treatment described above, an At film with a thickness of 5000A was formed on the silicide, and then an electrode was heated at 534°C for 30 minutes. The interfacial reaction after heat treatment is reported in detail, and according to the report, the growth of large particles containing many components of 81 was observed on the surface of the MO silicide that etched the At film after heat treatment. , point out that a reaction occurs between MO silicide and the substrate Si. The growth mechanism of large particles containing a large amount of Sl is that the substrate S1 diffuses through the crystal grain boundaries of MO silicide.

Furthermore, it was also reported that the uniformity of the MO silicide formed by the heat treatment described above was not good, and several pinholes were observed, and interdiffusion of At and Si occurred through all of the pinholes. are doing. In this way, the substrate S
The high melting point metal silicide obtained by simply performing heat treatment after forming a high melting point metal layer such as MO on l is a polycrystalline thin film, so the underlying substrate St is likely to diffuse through the grain boundaries, and the uniformity is low. However, the stability of the Schottky electrode formed by the above method during heat treatment is poor.

Furthermore, in general, when a silicide reaction occurs between the metal and the substrate S1, the substrate St is consumed during the reaction, so a part of the metal silicide is formed buried in the Si substrate. For this reason, when metal silicide with a thickness of several thousand is formed, a buried region of at least 1000A or more is formed, and from the viewpoint of forming a shallow Schottky electrode, it is difficult to Thickness'i 50
It is necessary to reduce the current to about 0 A or less, but as described above, it is difficult to form a thin and uniform high melting point metal silicide only by heat treatment.

In view of such circumstances, the object of the present invention is to
An object of the present invention is to provide a method for manufacturing a shallow Schottky electrode in which the height of the Schottky barrier does not change even after heat treatment at 50° C. or lower.

As a result of a detailed study of the relationship between the formation method of high-melting point metal silicide and the metallurgical properties of the silicide, the present inventors found that
This led to the idea of the present invention. The high melting point metal silicide formed by performing heat treatment after ion implantation through a thin high melting point gold maple layer formed on the substrate S1 is
According to the results of evaluation by transmission electron microscopy, etc.
This is a single-crystalline thin film with no grain boundaries observed over an area of several square micrometers, which is significantly different from the polycrystalline thin film of high-melting-point metal silicide, which is formed only by heat treatment using the conventional method described above. It was issued. Furthermore, the high melting point gold silicide obtained by forming a thin layer of high melting point metal on the substrate St, performing ion implantation and subsequent heat treatment, remains flat and uniform even when formed into a thin film of several hundreds. Evaluations using SEM and the like have revealed that it has various advantages such as: The inventors of the present invention have discovered a method of manufacturing a stable shallow Schottky electrode with good overall reproducibility by using a single-crystal high-melting-point metal silicide having such advantages for the Schottky electrode.

In the present invention, after exposing the Si surface of the substrate on which the Schottky electrode is to be formed, a refractory metal layer with a thickness of 500A or less is formed on the upper surface of the structure, and S (ion or Ar) is formed from the upper part of the refractory metal layer. After injecting inert gas ions such as ions under conditions that mix the high melting point metal and the substrate St, approximately 60
Heat treatment is performed at 0°C or higher, and then, by etching the unreacted high melting point metal, a thin high melting point metal silicide is selectively formed only on the exposed Si surface, and electrode wiring is formed on the surface of the high melting point metal silicide. to form′
tl - A method for manufacturing a Schottky electrode featuring features.

Using an n-type St substrate with a carrier concentration of 1.4X10''(7)-3, the Schottky electrode created according to the present invention was heat-treated at 50 to 550°C for 30 minutes after forming the A/= system electrode electrode wiring. The measured height of the Schottky barrier was constant at 0.6V, confirming the effectiveness of the present invention.

Hereinafter, a typical embodiment of the present invention will be described in detail using the drawings.

Figures (a) to (d) are schematic cross-sectional views showing an example of the manufacturing process of the present invention. First, as shown in FIG. , the St surface 13 refractory metal film (Mo
The film 14 is formed by sputter deposition. Next, from above, Sl ions or inert gas ions tl-MO and S
Conditions necessary for complete mixing with t, for example, acceleration voltage of 50
kev at a dose of 5×10101l1''.

After that, H! Heat treatment is performed at 600° C. for 20 minutes in a gas atmosphere. At this time, as shown in Figure (bl), Mo silicide 1
5 is formed. Next, the unreacted MO film 16 on the oxide film
is etched using an H, O, and etching solution. However, Mo silicide is stable against the etchant, and as shown in Figure (C), a uniform thin Mo silicide is formed in a self-aligned manner on the Si surface where the Schottky electrode is to be formed. Next, an At-based metal 17 is deposited on the entire surface, and after death, patterning is performed using a normal method.
A shallow Schottky electrode with the structure shown in ) is obtained.

The thickness of the Mo silicide formed according to the present invention is about 400A, and the thickness of the Mo silicide formed in the present invention is about 400A.
o The depth of the silicide is at least 400A or less,
It was formed shallow enough. Furthermore, in this example,
Sl ions f: A case is described in which Mo silicide is formed by implanting from the top of a Mo film. Similar excellent results were obtained when high melting point metals such as Ta and Ti were used.

[Brief explanation of the drawing]

Figures (al to (d)) are schematic partial cross-sectional views showing the main steps of an embodiment of the manufacturing method of the present invention. 11: Silicon substrate, 12: Oxide film, 13 Silicon on which a rainbow key electrode is to be formed. Surface, 14: Film thickness 200A
Mo film, 15: Mo silicide, 16: unreacted Mo
Film, 17: At-based electrode wiring. Patent Applicant: NEC Co., Ltd. Procedural Amendment (KEN) 57.6.23 Showa Year, Month, Day 1, Case Indication: 1988 Patent Application No. 225
43 No. 3, Relationship with the case of the person making the amendment Applicant: 33-1 Shiba 5-chome, Minato-ku, Tokyo (423) NEC Corporation Representative: Tadahiro Sekimoto 4, Agent Address: 108 Shiba 5-chome, Minato-ku, Tokyo No. 37-8 Sumitomo Sanda Building (Contact information: NEC Corporation Licensing Department) 5. Claims column of the specification to be amended. Detailed description of the invention in the specification. 6. Contents of amendment (1) The scope of the specification and claims will be amended as shown in the attached sheet. (2) Delete the phrase "buried" from line 11 to line 12 of page 5 of the specification. (3) Correct the statement “approximately 600″0 or more” on page 7, line 10 of the specification to “r 40 total 400″C” @(
4) In the 13th line of page 7 of the specification, the phrase "selectively forming a melting point metal silicide and the high melting point" has been changed to "forming a melting point metal silicide in a self-aligned manner, and then in a non-reducing gas atmosphere". Heat treatment is performed to a temperature of 800"0 or more, and further correction is made to the high melting temperature". (5) Insert the following sentence after "Manufacturing method" on the 15th line of the same page. The method of Aji's invention is a two-stage heat treatment method in which ion implantation is followed by heat treatment at a relatively low temperature of 400-600" O, followed by heat treatment at 800°C or higher after removing unreacted high-melting point metals. However, this two-stage heat treatment is extremely important in forming a uniform and smooth high melting point metal silicide in a self-aligned manner with respect to the Si surface where the electrode is to be formed.In other words, ion implantation After the first anneal, e.g.
If it is carried out at a high temperature of about 800° C. or higher, silicide will be formed protruding from the 8i surface on which the electrode is to be formed. Therefore, after first annealing at a low temperature, the unreacted high melting point metal is removed to form the Si electrode.
A silicide is formed in self-alignment on the surface. The reason for limiting the temperature range is that at 400°C, the minimum temperature at which the mixed layer of high melting point metal and 8i formed by ion implantation turns into silicide is 60''C, which is the minimum temperature at which the mixture layer of 8i and high melting point metal formed by ion implantation becomes silicide, and the temperature range is 400°C. This is because this is the upper limit temperature at which silicide is not formed.After that, the temperature was increased to 800°C for the purpose of reducing the resistivity of the silicide layer and electrically activating the implanted ions.
A heat treatment of a certain degree or more is carried out. If this heat treatment is performed in a reducing gas atmosphere containing H gas, the uniformity and smoothness of the silicide formed by the low-temperature heat treatment will be lost, and defects such as pinholes will occur as a result. Since a large number of these electrodes are formed, it is not suitable for forming a Schottky electrode. Therefore, heat treatment of 800° or more in a non-reducing gas atmosphere, such as nitrogen, inert gas, oxygen, water vapor, or a combination of these gases, or in vacuum improves the uniform and smooth properties of the silicide. It is important to maintain (6) Insert the following sentence after "will be" in the fourth line of page 9 of the specification. "Next, heat treatment is performed at 800'O or more in a non-reducing gas atmosphere, such as nitrogen gas." Attachment 2, Claims (1) An insulating film is formed on the silicon substrate, and a Schottky electrode is formed. The insulating film is removed only in the portion to be formed to expose a part of the silicon substrate, and a film with a thickness of 500 mm is deposited on the exposed surface.
After forming a high melting point metal film of A or less and implanting silicon ions or inert gas ions into the upper part of the high melting point metal film under conditions necessary to mix the high melting point metal and the silicon of the substrate, The feature is that heat treatment is performed at a temperature of -600°C, and then unreacted high melting point metal is removed by etching treatment, and electrode wiring is formed only on the exposed surface of the silicon substrate on the high melting point side surface. IA manufacturing method for Schottky electrodes for electronic devices
No. 43 No. 2, Title of the invention Method for manufacturing Schottky electrodes for electronic devices 3, Relationship to the amended case Applicant 5-33-1 Shiba, Minato-ku, Tokyo (423) NEC Corporation Representative Sekimoto Tadahiro 4, Agent Address: 5 Sumitomo Sanda Building, 5-37-8 Shiba, Minato-ku, Tokyo 108, Detailed explanation of the invention in the specification subject to amendment 6, Contents of the amendment (1) Specification, page 6 From line 9 to line 18 [
The inventor conducted transmission electron microscopy, etc....
・・・・・・・・・・Delete the statement that the result is -1 when formed into a thin film of several hundred years. (2) "Single crystal" in the first line of page 7 of the specification is corrected with "smooth and uniform" K. Agent Patent Attorney Susumu Uchihara

Claims (1)

[Claims] (1) An insulating film is formed on a silicon substrate, and the insulating film is removed only in the portion where a Schottky electrode is to be formed to expose a part of the silicon substrate, and a film with a thickness of 500 mm is formed on the exposed surface.
After forming a high melting point metal film of A or less and injecting silicon ions or inert gas ions from above the high melting point metal film under conditions necessary to mix the high melting point metal and the silicon of the substrate, approximately 600 m A heat treatment is performed at a temperature of 100° C. or higher, and then all unreacted refractory metals are removed by etching, a silicide layer of the refractory metal is formed only on the exposed surface of the silicon substrate, and a silicide layer of the refractory metal is formed on the silicide surface. A method for manufacturing a Schottky electrode for an electronic device, characterized by performing electrode wiring.