JPS5882520A - Manufacture of ohmic electrode in electron device - Google Patents

Abstract

PURPOSE:To form an Al-group electrode endurable heat treatment at 500 deg.C or above by a method wherein ion implantation is applied from a thin metal layer with high melting point formed on an Si substrate and after that, a silicide layer is formed by executing heat treatment at relatively low temperature. CONSTITUTION:After forming an oxide film 12 on an Si substrate 11, the surface 13 of the Si substrate is exposed. Next, an Mo film 14 with a film thickness of 500Angstrom or less is formed and ion implantation is applied from the upper portion. After that when heat treatment at 400-600 deg.C is done under H2 gas atmosphere, Mo silicide 16 is selectively formed on only the surface of a layer 15 to be formed a contact layer. Next, the activation of implantation ion is done by performong heat treatment at 800 deg.C or more in N2. Then, after depositing Al17, an ohmic electrode is formed by performing patterning. This can prevent a remarkable increase in contact resistance and the occurrence of the short-circuit of a p-n junction as well even if heat treatment exceeding 500 deg.C is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing ohmic electrodes for electronic devices such as integrated circuits.

In recent years, in electronic devices such as integrated circuits, element dimensions have been reduced by 32 dimensions due to demands for higher speed and higher density. Nineteenth time, the depth of the pm junction formed under the open electrode has come to be less than several thousand λ. Currently, vapor-deposited thin films of aluminum (hereinafter abbreviated as AI) are most widely used as contact metals for integrated circuits. In case of use, p
It is known that defects occur due to short circuits in n-junctions. This is due to the substrate silicon (hereinafter referred to as 8
This is due to the interdiffusion between AI (abbreviated as M) and AI, but because this diffusion does not occur uniformly, the particles locally penetrate deeply into the substrate si.

Conventionally, the following two methods have been adopted in an attempt to prevent the above-mentioned defects. One method, instead of using pure AI as a contact metal, is to use a composition made of AI that already contains 8i in an amount of several percent by weight, which is slightly above the solid solubility limit. It is true that when a contact metal made of this composition is used, heat treatment at about 450° C. does not cause the above-mentioned defective bonding, unlike when pure AI is used. but,
In experiments conducted by the present inventor, the absolute value of the contact resistance value
In order to keep the value and variation as small as desired, it is necessary to select the heat treatment temperature in the range of about 400°C to 475°C. If heat treatment is performed at 500°C or higher, contact resistance increases and the The specific contact resistance value increases by more than an order of magnitude. Such restrictions on the heat treatment temperature cause major disadvantages in the following points.

In the conventional manufacturing method of MO8 integrated circuits, the patterning after forming the AI thin film and the combination of the optical exposure method and the wet etching method were used.
This method can no longer be applied to fine wiring patterns having dimensions of about 500 m or less, and a combination of electron beam exposure and dry etching is effective for patterning such fine patterns. With these changes in manufacturing methods, nine new problems have arisen as described below. In other words, due to damage induced at the MO8 interface during electron beam irradiation, fixed charges were generated in the interface unit, fluctuations in threshold voltage, etc. occurred, and neutral traps were generated in the gate oxide film. It has become known that reliability problems may arise due to the formation of Conventional heat treatment at about 450° C. is insufficient to recover from these damages, and heat treatment at 500° C. or higher is required. However, as described above, when an ohmic electrode using an A1 thin film containing several weight percent of Si as a contact metal is subjected to a heat treatment of 5001] or more, a disadvantage arises in that the contact resistance increases significantly.

Another method is to use Pd between the Si substrate and the A1 thin film.
silicides of noble metals such as Pt, or Ta.

This is an attempt to prevent mutual diffusion between the substrate 81 and the person 1 by interposing silicide of a high melting point metal such as Mo. However, when the former noble metal silicide is interposed and a 400°C heat treatment is applied to the nine oscilloscope electrode, a reaction occurs between AI and the silicide, and the silicide layer disappears.
Compounds such as l5Pd and A15Pt are formed, and A
Mutual diffusion between A1 and 81 occurs through 15Pd and AlgPt. Therefore, heat treatment at 500° C. or higher causes short circuits and leaks in the Pn junction, making it unusable as an ohmic electrode.

On the other hand, in the case of an ohmic electrode in which a silicide of a high-melting point metal such as Ta or Mo is interposed, the temperature at which the compound formation between A1 and the metal constituting the silicide begins is higher than in the case of intervening the above-mentioned noble metal silicide. However, as described below, there is still a problem with the heat resistance in heat treatment at 500° C. or higher.

G, J, van
Qurp et al., Journal of Applied Physics (Journal of Applied Physics)
hysics) Golden Brother Volume 50 No. 11 No. 6915-692
6 (November 1979), Mo
After depositing the film by sputtering, Hl gas and N
By performing heat treatment at 600° C. in a mixed gas atmosphere with snow gas, Mo8i* with a film thickness of 9,2500λ is formed, and a film thickness of soo is formed on the top by electron gun evaporation.

λ person! After forming a thin film on the sample and subjecting it to heat treatment at 534°C for 30 minutes, the upper AI was etched, and the results of a detailed study of the interfacial reaction are reported. In the report, it was determined that an interfacial reaction was occurring based on the growth of large particles containing many 81 components and the presence of several pits. , 81 is similar to the transport mechanism of 8i in solid phase epitaxy, and it is thought that the amount of s constituting the substrate is diffused through the grain boundaries of silicide. Previously, the cause of the bit generation was cited as the diffusion of SM into Al due to pinholes in the Mo1ls film. Furthermore, in the same report, a structure similar to the above structure was heat-treated at 545° C. for 1 hour, and then Mo was analyzed using a backscattering method.

As a result of investigating the movement of atoms such as AI, it has been reported that only a small amount of Mo moves into the Al on the surface. Therefore, electrode deterioration due to heat treatment is caused by MO and AI.
Rather than reacting to form a compound with Monj! This is considered to be due to the polycrystalline nature and non-uniformity of the material.

In addition, x, x, B Muraruka (8-P -Muri
rka) is the author of the Journal of Vacancy Science and Technology (Journal of V.
acum 5science and technology
gy) Soga Volume 17, No. 4, pp. 775-792 (19
(August 1980) reported on the results of interfacial reactions after heat treatment at 300' to 500°C on the 9 structure with Taxis interposed between At and the substrate 81; No reaction occurred. Therefore, heat resistance is improved when the noble metal silicide mentioned above is interposed, but there are no reports of experimental results at temperatures above 500°C, and it is unclear whether it can withstand heat treatment at temperatures above 500°C. It is. As mentioned above, currently, after forming the A1 thin film,
There is no At-based electrode that can withstand heat treatment at temperatures above 00°C.

In view of the above circumstances, the present invention provides a method for manufacturing an At-based ohmic electrode that can withstand heat treatment at 500° C. or higher.

The present inventor conducted a detailed study on the relationship between the metallurgical properties and the method of forming a high melting point metal silicide interposed between the thin film of mulch and the substrate 81, and as a result, the present invention was developed. Conventional methods for forming silicides of high-melting point metals include the above-mentioned G.J.
As reported by Mr. Qarp), a method is known in which a high melting point metal layer is formed on the substrate 1 and then subjected to heat treatment at a temperature of around 600°C.
After forming a thin high-melting point metal layer on N, ion implantation is performed, followed by heat treatment at around 600°C to form a silicide layer, and the metallurgical properties of these silicides are compared to those formed by conventional methods. As a result of a comparative study of the metallurgical properties of silicides, we found that the metallic properties of the silicides obtained by the two methods of formation differ greatly. The ion implantation is carried out by introducing Mul ions through an MO film with a thickness of 350 mm formed on the substrate 81 at an acceleration voltage of 160 mm.
key was used at a dose of 2X1G"-".

In the conventional method, many microstructures are observed on the surface, whereas in the latter method, no microstructures are observed. In order to examine this difference in more detail, we observed the surface using a scanning electron microscope and a transmission electron microscope.The scanning electron microscope revealed that the surface of Mo silicide formed by the conventional method had a surface that corresponded to the microstructure. Although unevenness was well observed, the surface of the Mo silicide formed using the latter ion implantation was extremely flat, and no surface unevenness could be observed.

These facts are further supported by transmission electron micrographs. Mo silicide formed by the conventional method is
It can be seen that the Mo silicide formed using the latter ion implantation is a single-crystalline film without grain boundaries, whereas the film is a polycrystalline film made up of a collection of minute grains with a grain size of several G^.

Furthermore, a Mo silicide film formed using ion implantation with a high surface flatness and uniformity is much better.

The present invention has a film thickness of 500λ on the surface of a Si substrate on which electrodes are to be formed.
After the following process of forming a high melting point metal layer and performing ion implantation from above the high melting point metal, heat treatment is performed at around 600°C to etch the unreacted high melting point metal and form a silicide layer of the high melting point metal. The method is characterized by comprising the steps of selectively forming the silicide on the exposed old surface, performing heat treatment at a temperature of 800° C. or higher, and bringing an AI electrode wiring into contact with a portion of the silicide surface. .

A high melting point silicide layer such as Mo silicide, which is formed using ion implantation and has the above-mentioned various features, is interposed between the thin film and the substrate to form an open electrode.
As a result of conducting heat treatment at 450'' to 550°C and examining the heat resistance, it was found that a highly conductive, self-contained electrode with sufficiently low contact resistance could be obtained even at temperatures above 500°C.

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

FIGS. 1(a) to 1(d) are schematic cross-sectional views showing one example of the manufacturing process of the present invention.

If, 7 years ago #ll) &6.5X10"car-"
A nor-type 8i substrate 11 is prepared, and this substrate is oxidized in an oxygen atmosphere to grow an oxide film 12 with a thickness of approximately 4oooA.The oxide film 12 is then etched using a photoresist as a mask, and the surface 13 of the 8i substrate is etched. Expose (Figure 1 (a)
)).

Next, a Mo film 14 with a thickness of 100λ is formed by sputter deposition, and A8 ions are applied from above at an acceleration voltage of 100 keV.
Inject at a dose of 5 x 10"cm-". After this, H
When heat treatment is performed at 600°C for 20 minutes in an S gas atmosphere, M is formed only on the surface of the n+ layer 15 where a contact is to be formed.
o-silicide 16 is formed (FIG. 1(b)).

Next, Mo on the oxide film is removed using HsOz-based etching solution.
Perform etching. At this time, since the Mo silicide 16 is not etched, the Si where the contact is formed
Mo silicide 16 is selectively formed only on the surface (FIG. 1(C)).

After this, N! The implanted 9λ$ ions are activated by heat treatment at 1000° C. for 20 minutes. Next, Al17 with a thickness of 1 .mu.m is deposited and then patterned by a conventional method to complete an oak-shaped electrode having the structure shown in FIG. 1(d).

In this example, As is implanted through a thin Mo film to
9, which is described for the case where o-silicide is formed, is similarly effective in the case of P ions.

The specific contact resistance at the contact interface obtained after heat-treating the oak-structured electrode formed according to the present invention at a temperature of 450°C to 550°C for 30 minutes in an H3 gas atmosphere is approximately constant at ~1O-69d. and s0
No significant increase in contact resistance was observed even during heat treatment above 0°C.

Further, no short circuit of the Pn junction was observed.

According to the present invention, heat treatment up to 550° C. may be performed after forming the A1 electrode wiring, and it is clear that the heat resistance of the heat treatment performed after forming the AI electrode wiring is improved compared to the conventional method. be. For this reason, in the conventional method, it is not possible to perform heat treatment to sufficiently recover damage caused by electron beam irradiation, etc., whereas in the present invention, damage can be sufficiently recovered by heat treatment at 500°C or higher. Significant improvements have been shown in this respect.

In addition, in the above embodiment, Mo was used as the intervening high melting point metal.
Although the case using silicide has been described, for example, W
, Ti, and Ta silicides were found to have similar effectiveness.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(d) are schematic sectional views showing the manufacturing process of an embodiment of the present invention. 11...81 substrate, 12...river/oxide film, 13
・The old surface of Kameyama where the group/contact should be formed, 14...
・・・・Mo Ks 1s・・・・・・n”L 16・
...Mo silicide, '17... River/A1 electrode wiring. v-1 Merit Procedures Amendment (Import) 57.6.23 Showa Year, Month, Day, Director General of the Patent Office, 1, Indication of Case 1937 Patent Application No. 180
No. 518 No. 2, Title of the invention: Method for manufacturing an electronic device's automatic electrode 3, Relationship with the amended case: Applicant: 5-33-1-4 Shiba, Minato-ku, Tokyo, Agent: 108 Minato, Tokyo 5-37-8 Shiba, Sumitomo Mita Building, NEC Corporation (6591) Patent Attorney Susumu Uchihara Telephone Tokyo (0
3) 456-3111 (main representative) (contact information: NEC Corporation Patent Department) 5. Claims column of the specification to be amended. A column for detailed explanation of the invention of Meishu-sho. 6.11i Correct contents (1) Amend the Claims column as shown in the attached sheet. (2) In the fifth line of page t1M5 of the specification, "r Pn junction" is corrected to "rpn junction". (3) In the 5th line of page 8 of the specification, ``Ittatta'' is amended to ``Attata.'' Correct to. (5) In the first line of page 10 of the specification, the statement ``Heat treatment was performed at around 600°C'' was corrected to ``Heat treatment was performed at r400-60Q°C''. (6) In the fourth line of page 10 of the specification, the phrase "a step of heat treatment at a temperature of ℃ or higher" has been changed to "a step of heat treatment at a temperature of ℃ or higher in a non-reducing gas atmosphere." to correct. (7) Insert the following sentence in IIK of ``It is the one'' on page 10 of the letter, line 6. In the method of the present invention, after performing ion implantation, 400-6
A two-stage thermal process is carried out in which heat treatment is performed at a relatively low temperature of 00°C, followed by heat treatment at a temperature of 800°C or higher after removing unreacted high-melting metals, but this two-stage heat treatment is uniform. Moreover, it is extremely important in forming a smooth high melting point metal silicide in a self-aligned manner with respect to the silicon surface on which an electrode is to be formed. For example, the first annealing after ion implantation is
If the process is carried out at a high temperature of about 800° C. or higher, silicide will be formed protruding from the silicon surface on which the electrode is to be formed. Therefore, by first performing annealing at a low temperature and then removing any unsuitable high melting point metal, a silicide is formed in self-alignment with the silicon surface on which the electrode is to be formed. The reason for limiting the temperature range is that 40G'OK is the minimum temperature at which the mixed layer of high melting point metal and Si, which is formed by ion implantation, turns into silicide, and 600°C requires a heat treatment time of about several tens of minutes. In order to prevent the formation of silicide by protrusion,
I! This is because the temperature is - After this, heat treatment is performed at a temperature of 800"O or more for the purpose of reducing the resistance of the silicide layer and electrically activating the implanted ions. This heat treatment is performed at H2 If the process is carried out in a reducing gas atmosphere containing gas, the uniformity and smoothness of the silicide formed by the low-temperature heat treatment will be lost.
1. As a result, many defects such as pinholes are formed, making it unsuitable for forming ohmic electrodes. Therefore, heat treatment at 800°C or higher in a non-reducing gas atmosphere, such as nitrogen, inert gas, oxygen, water vapor, or a combination thereof, or in vacuum maintains the uniform and smooth properties of the silicide. It is important to (8) The phrase "r Pn junction" on page 12, line 1 O of the specification is corrected to "vn junction." Claims: A step of forming a refractory metal layer with a thickness of 500A or less on the surface of the Siqcon substrate on which electrodes are to be formed, and after performing ion implantation from above the core refractory metal, heat treatment at 40Q-600°C. After that, the unreacted high melting point metal is etched away, and a silicide layer of the high melting point metal is selectively formed on the exposed silicon surface, and Oi1 is heated at 800° C. or higher.
1. A method for manufacturing an ohmitter electrode for an electronic device, the method comprising the steps of: performing heat treatment in a non-reducing gas atmosphere at a temperature of 30° C.; and attaching an aluminum electrode wiring to a portion of the silicide surface.

Claims (1)

[Claims] After forming a high melting point metal layer with a thickness of 500 mm on the surface of the silicon substrate on which electrodes are to be formed, and implanting ions from above the high melting point metal, heat treatment at around 600°C is performed to remove any unreacted metal. A step of etching away the high melting point metal and selectively forming a silicide layer of the high melting point metal on the exposed silicon surface, a step of performing heat treatment at a temperature of 800° C. or higher, and a step of etching aluminum on a portion of the silicide surface. A method for manufacturing an ohmic electrode for an electronic device, comprising the step of bringing electrode wiring into contact.