A method of manufacturing an injecting contact to monosulfide samaria

 

(57) Abstract:

Usage: during the formation of metallization of semiconductor devices on the basis of monosulfide Samaria. The inventive method is applied to the substrate monosulfide Samaria when the temperature of the substrate 100-200oC two-layer metallic coating speed , and the first layer of chromium, is applied directly to the substrate within 50-100, and the second layer, the cobalt - on top of the chrome layer within 300-400 C. 2 Il., 7 table.

The invention relates to semiconductor electronics and can be used when forming the metallization of semiconductor devices on the basis of monosulfide samarium using methods of thermal evaporation, magnetron and ion-plasma sputtering, etc.

The known method of forming ohmic contact to monosulfide Samaria, including the metal coating of cobalt (Co) on the substrate monosulfide Samaria, and is soldered to the plated wire output (and. C. Czechoslovakia N 238434, H 01 L 23/00, 1983)

The advantages of such contact are low resistance transition layer, good mechanical strength and stability. The combination of these properties is achieved by using the proposed method is a method of making ohmic contact to monosulfide samarium, representing a two-layer coating. C. the USSR N 1829769, H 01 L 21/283, 1991) as a first layer directly on the film monosulfide Samaria is covered with a layer of titanium over 50-100, then a layer of Nickel over the 300-OO with, and the layers are applied with the speed when the temperature of the substrate 100-200oC. This method is chosen for the prototype.

However, this solution has several disadvantages: 1) low reproducibility of the characteristics of the contacts; 2) short life of contacts; 3) high contact resistance.

The aim of the invention is to reduce the contact resistance with increasing stability and reproducibility characteristics of the contacts, to increase the service life of the contacts.

This goal is achieved by the fact that in the proposed method of manufacturing an injecting contact by applying onto the substrate monosulfide Samaria when the temperature of the substrate 100-200oC with the speed of a two-layer metallic coating consisting of a first layer within 50-100, and the second layer within 300-400, new is the fact that the coating consists of a layer of chromium deposited directly on the substrate, and a layer of cobalt, nasenkorrektur on a substrate, and a layer of cobalt, of a thickness of from to .

The proposed two-layer coating on a substrate at a temperature of 100-200oProvides an injecting contact, characterized superlinear current-voltage characteristic (I-V) and resistance management structure through the main injection of charge carriers from the received contact layer monosulfide Samaria, as well as high stability and reproducibility of the parameters and long life.

The essence of the method consists in the following.

Monosulfide samarium is one of the materials is very sensitive to mechanical deformations. Therefore, when forming the contact should be minimized to reduce mechanical tense, resulting in the deposition of the metal film of the contact material. To do this: 1) use of plastic materials; 2) to carry out the deposition at lower temperatures; 3) to exclude cyclic heat treatment.

In addition, monosulfide Samaria in the presence of oxygen is oxidized, resulting in either drastically limit the contact with air, or use the sublayer strong getter. As a getter us ispolzovatblizhny characteristics, and lower the work function of the metal into the semiconductor for carriers (see also Fomenko C. C. Emission properties of materials. Kiev, Naukova Dumka, 1970 148 C. ) Getter action of chromium is to reduce the partial pressure of oxygen during the deposition due to desorption chemisorbing layer of oxide on the surface of monosulfide Samaria as a result of chemical reaction with chromium her.

Chrome also has a high plastic properties. However, he has a fairly high resistance to 13.2 mcomm at 20o(Smits K. J. The metals. M. metallurgy, 1980, 448 C.) Therefore, the thickness of the chromium layer to be selected in such a way that the manifestation of getter properties, this layer had little resistance.

As the second layer contact us selected cobalt. It is a plastic metal, provides a low resistance when the thickness from to not corrode under cyclic mechanical loads two-layer plated chrome-cobalt does not change their electrophysical and mechanical characteristics. Deposition of both layers is performed at the temperature of the substrate 100-200oC. At lower temperatures, rapidly deteriorating the adhesion of the contact, and at a higher uwee. The use of double-layer deposition of chromium-cobalt allowed to obtain an injecting contact with low resistance decreases with increasing voltage applied to the structure of the contact monosulfide Samaria, with high reproducibility, stability and enhanced life.

An injecting contact in comparison with the ohmic possesses a number of advantages, both physical and technical nature. It is known (see Lampert, M., mark P. Injection currents in solids. M. Mir, 1973, 416 S.) that the injection of carriers from the contact in the solid body can lead to an improvement of a number of parameters, the most important of which is performance. In our case, the use of an injecting contact to monosulfide samarium can improve this important parameter. In addition, when the voltage is rising due to sverginate WAH decreases the resistance patterns contact monosulfide Samaria, and this resistance change is controlled by the applied voltage, which can be important in specific applications monosulfide Samaria as the strain gauge.

The proposed solution allows comparison with the prototype to increase the stability of contact to manage it with themperature (from 100 to 200oWith the substrate) the application of metals due to the high getter activity of chromium and a low work function of electrons. This increases the reproducibility of the contact and decreases its resistance.

The variation of the thickness of the getter layer and the contact layer made it possible to find the optimum conditions to achieve the goal, and the temperature range allowed us to obtain an injecting contact without residual stress, which is especially important when using monosulfide Samaria as the strain gauge.

In Fig. 1 shows the volt-ampere characteristic (double logarithmic scale) patterns contact monosulfide Samaria, obtained by the proposed method.

In Fig. 2 presents the dependence of the degree WAH dlnI/dlnV from tension, in double logarithmic scale.

Getting the contacts of the proposed method was carried out in a vacuum unit UVR-SM when the vacuum 510-6Torr. The volt-ampere characteristic of the structure shown in Fig. 1. In Fig. 2 shows the dependence of the degree WAH (differential tilt WAH) adlnI/dlnV tension in double logarithmic scale. This dependence pne in semiconductors. Kiev, Naukova Dumka, 1981, 256 C.), to fix ohmic ( a 1) and injection ( a > 1) plots. Of the dependence in Fig. 2 should the range of obecnosci contact from 1.0 V to 30 C.

In table. 1 shows the study of the influence of the modes of deposition of chromium at fixed modes of deposition of cobalt (time spraying tco=350oC, the speed of deposition temperature deposition T=150oC) resistance range resistance layout of strain gages.

Measurement of resistance of the layout of the strain gauges with contacts were made with an applied voltage of V=0.1 V, where the injection of carriers from the contact was still weak, and ran Ohm's law ( 1). For each mode was determined by the average value of the resistance in the party by the formula

< / BR>
where n is the number of samples in the party, Rarrthe resistance of the sample.

In our experiments the value of n ranged from 20 to 30. The deviation of the resistance R from the average value was determined by the formula

< / BR>
The average value of the deviation resistance was determined by the following formula

< / BR>
From the data table. 1 shows that the rate of deposition of chromium and time of deposition 50-100 with the average resistance of mock-UPS and medium rejected is Balta at fixed modes of deposition of chromium (time spraying tcr=70 C, the deposition rate , the temperature of deposition T=150oC) resistance range resistance layout of strain gages.

From the data table. 2 it follows that the rate of deposition of cobalt and time of deposition 300-400 with the average resistance of the layouts and the average value of the deviation of the resistance minimum.

In table. 3 research data on the effect of temperature regimes of deposition of the contact.

From table. 3 shows that the optimum temperature of the substrate is in the range from 100 to 200oC.

Below is the reproducibility of the resistance layout of strain gages, obtained by metallization contacts on one of the best available technologies (PL. 4) and sub-optimal technology (PL. 5).

From the data table. 4 and 5 it follows that the nonoptimality of the regime applying only sublayer of chromium leads to a decrease of reproducibility and increased resistance layouts.

The study of the stability and lifetime of the layout of the strain gauge with contacts, obtained by optimal technology ( tcr= 70 c, tco= 350 c, Tdastardly=150oC) presented in table. 6 and 7. Here Rarris determined by the formula

< / BR>
where Rarr. 0the beginning of the table shows within 4 h care resistance did not exceed 0.25 (table. 6). The resistance change within 60 days did not exceed 0,35 (PL. 7).

As follows from Fig. 1, the resistance of the layout of the strain gauge at V=1.0 is 190 Ohms, V=10.0 V 60 Ω and V=20,0 In 42,0 Ohms. In other words, by using the applied voltage can control the resistance of the layout of the strain gauge, in this case within 40-2000 Ohms.

A method of manufacturing an injecting contact to monosulfide Samaria, including the application of a two layer metallic coating on the substrate monosulfide Samaria, and the first layer is applied directly to the substrate during the 50 100, and the second layer within 300 400 rate of deposition of the layers 10 and 20 and the temperature of the substrate 100 200o, Characterized in that the first layer using chrome, as well as a second layer of cobalt.

 

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