JPH01241132A - Electrode of semiconductor element and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent a diffusion to a semiconductor substrate of Au due to heat at the time of subsequent film growth even when an uppermost layer is composed of Au by forming a lower layer section except the uppermost layer onto the semiconductor substrate to a trapezoid shape and forming the uppermost layer onto the lower layer section positioned inside the lower layer section. CONSTITUTION:Ti27/Pt28/Au29 multilayer-structure electrodes are manufactured onto a compound semiconductor substrate 22 through a lift-off method. An uppermost layer is shaped onto trapezoid lower layer sections while being positioned inside the lower layer sections on the semiconductor substrate 22 according to the difference of incident angles at the time of the evaporation of electrode metals 27-29, thus manufacturing the electrodes. According to the electrodes, the uppermost layer is not brought into contact with the semiconductor substrate 22 because the uppermost layer is located inside the lower layer sections. Consequently, even when the uppermost layer consists of Au29, a diffusion to the semiconductor substrate 22 by heat at the time of subsequent film growth of the Au29 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a multilayer electrode in a semiconductor device and a method for manufacturing the same.

[Prior Art] For example, when forming an electrode on a metal semiconductor substrate, a lift-off method is used as disclosed in Japanese Patent Application Laid-Open No. 100432/1983. That is, Fig. 5 (a
), a resist 2 is coated on a compound semiconductor substrate 1, and a tapered opening 3 with a wide bottom side is formed in this resist 2 by a normal photolithography process. Next, an electrode metal 4 is applied over the entire surface. The resist 2 is deposited by evaporation (electron beam evaporation or resistance heating evaporation) or sputtering, and then the resist 2 is dissolved and removed. Then, as shown in FIG. 5(b), the electrode metal 4 on the resist 2 is removed together with the resist 2, but the electrode metal 4 deposited on the compound semiconductor substrate l through the opening 3 of the resist 2 remains as an electrode. is formed. In such a lift-off method, a single-layer resist or a two-layer resist is used as the resist 2 as a mask. Furthermore, instead of only resist, a two-layer structure of s+o,/resist is also used.

By the way, when an n-type active layer is formed on a compound semiconductor substrate and a sirot key electrode is formed on it, Au is used as the top layer in order to reduce the resistance, Ti/PL/A
The electrodes are formed in a u-multi-WJ structure or a Mo/Pt/Au multilayer structure.

In addition, in the above lift-off method, there is a rotary evaporation method as a evaporation method that is one of the methods for depositing electrode metal. FIG. 6 shows an electron beam rotary evaporation method. That is, electrons collide with the electrode metal (source) 12 in the crucible 11 to melt and evaporate the metal 12, thereby depositing the electrode metal onto the substrate 14 on the rotating holder 13.

In this rotary evaporation method, as shown in FIG. 7, the substrate 14 is attached to the holder 13 with the longitudinal direction of the strip-shaped opening 15 (corresponding to the opening 3 in FIG. 5) of the resist directed toward the center of the holder 13. It is held at 13. Moreover, the crucible 11 containing the vapor-deposited metal is one diameter line of the holder 13! 1 above,
It is arranged offset from the center O of the holder 13. Then, the diameter line l! of the holder 13 perpendicular to 2. The evaporated metal is obliquely incident on the substrate 14 so that the angle θ is maximum when the substrate 14 is positioned above. Moreover, the diameter a ml is set to the base FLL at opposite positions above.
4 is reversed by 180°, the deposited metal is incident on the substrate 14 from opposite directions at an angle θ.

FIG. 8 shows how Ti21°Pt22 is deposited by the rotary evaporation method on a compound semiconductor substrate l on which a resist 2 is applied in order to form the Ti/Pt/Au multilayer structure electrode by the lift-off method.
and Au23 are sequentially deposited.

As shown in this figure, the substrate 1 inside the opening 3 of the resist 2
Since the vapor-deposited metal is incident on the opening 3 of the resist 2 at an angle θ facing in opposite directions, the Ti21
．． Pt22. Au23 is deposited in a trapezoidal shape. As a result of such a deposition state, the uppermost layer of Au 23 also comes into contact with the substrate 1 at the outer peripheral edge portion A.

(Problem to be Solved by the Invention) However, when the top layer of Au 23 comes into contact with the substrate 1, the heat of 300 to 400°C when growing the interlayer film and the protective layer 11 on the electric scraper after forming the electrode. As a result, Au diffuses into the substrate 1, and if that portion is n-type, carriers will be trapped, deteriorating the characteristics of the device.

An object of the present invention is to provide an electrode for a semiconductor device and a method for manufacturing the same that can solve these conventional problems.

(Means for Solving the Problems) In the present invention, in an electrode having a multilayer structure in a semiconductor device, the lower layer portion except the uppermost layer is formed in a trapezoidal shape on the semiconductor substrate, and the inner side of the lower layer portion is formed on the lower layer portion. The uppermost layer is formed by positioning the uppermost layer.

Further, the present invention provides the following manufacturing method for manufacturing the electrode having the above structure. First, a resist is formed on a semiconductor substrate, and a tapered opening is formed in the resist with the bottom side widened. After that, the electrode metal of the lower layer part of the multilayered electrode except the top layer is evaporated on the entire surface by making it incident at a predetermined incident angle, and then the electrode metal of the top layer is evaporated on the entire surface with the incident angle smaller than that incident angle. Finally, the resist is dissolved and unnecessary electrode metal on it is also removed at the same time.

(Function) When an electrode is manufactured in the above manner, due to the difference in the incident angle during vapor deposition of the electrode metal, on the semiconductor substrate, the metal is located on the trapezoidal lower layer and on the inside of the lower layer. A top layer is formed to fabricate the electrode.

According to this electrode, since the uppermost layer is located inside the lower layer part, the uppermost layer does not come into contact with the semiconductor substrate. Therefore, even if the top layer is ^U, the Au is
The heat generated during subsequent film growth prevents the film from diffusing into the semiconductor planting board.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

In an embodiment of the manufacturing method of the present invention, a Ti/PL/Au #71114 electrode is manufactured on a compound semiconductor substrate by a lift-off method. That is, a resist is applied onto a compound semiconductor substrate, and this resist is coated with a normal photolithography process.
A tapered opening with a wide bottom side is formed. Next, Ti, PL, and Au are sequentially deposited in MW over the entire surface of the substrate using a rotary evaporation method. After that, the resist is dissolved and at the same time the Ti, PL, and Au on it are removed.

Then, only the portions of the metals Ti, Pt, and Au deposited on the compound semiconductor substrate through the openings in the resist remain, and electrodes are formed using these metals.

In such a manufacturing method, when metals such as Ti, Pt, and Au are deposited on the entire surface of the substrate by a rotary evaporation method, in the embodiment of the present invention, the angle of incidence of Ti, Pt, and Au in the M deposition area is change.

FIGS. 3(a) and 3(b) are diagrams showing the rotary evaporation method and explaining the method of changing the incident angle of the evaporated metal, and 2
1 is a holder; 22 is a substrate held by the holder 21; Further, 23 is a crucible arranged below the holder 21, and 24 is a vapor-deposited metal (24) housed in the crucible 23.
electrode metal).

The metal 24 housed in the crucible 23 is bombarded with electrons to melt and evaporate the metal, and the rotating holder 2
Metal is deposited on the entire surface of the substrate 22 on the substrate 1, but at this time,
When depositing Ti and PT, the holder 21 and crucible 23
The distance between them is set to X as shown in FIG. 3(a). Then, the vapor-deposited metal (Ti or pt in this case) is incident on the incident angle α determined by the distance Mx and is vapor-deposited on the entire surface of the substrate 22.

On the other hand, when Au is M'4, the distance between the crucible 23 and the holder 21 is set to X+a (a>
0). Then, the deposited metal (Au in this case)
The incident angle of β is smaller than the α (approximately vertical)
Therefore, Au is deposited by being incident at that angle.

When Ti, Pt, and Au are deposited as shown in step 2, as shown in FIG.
t28 is formed in a wide trapezoidal shape, but Au29 is formed in β
Therefore, even if the trapezoid is the same, the above T
It is formed on the lower layer of i27 and Pt28, located inside the lower layer.

Therefore, next, if the resist 25 is dissolved and unnecessary Ti27, pi28 and Au29 thereon are removed, the above-mentioned Ti27. Pt2B, Au29, Ti27
Then, an electrode having a structure in which Au 29 is formed on the lower layer of Pt 28 and positioned inside the lower layer is manufactured.

According to this electrode, since Au29 is located inside Ti27 and Pt28, Au29 does not come into contact with the substrate 22, and therefore Au is prevented from diffusing into the substrate 22 due to heat during subsequent film growth. Prevented.

FIG. 4 is a diagram showing a second method of vapor depositing Ti, pt, and Au by changing the incident angle, and (a) is a plan view;
Φ) is a side view. In this method, a first crucible 30 containing Tt or P[ and a second crucible 31 containing Au are shifted on the diameter line 21 of the holder 21,
That is, the second crucible 31 is placed on the inside, and the first crucible 30 is placed on the outside. Then, from this arrangement, Ti or pi is transmitted from the first crucible 30 to the substrate 22 at an incident angle α.
From the second crucible 31, Au
is incident on the substrate 22 at an incident angle β (β × α). Therefore, an electrode as shown in FIG. 1 can be manufactured in the same manner as in the first method shown in FIG.

Note that when depositing Au, β-0 is 8 from the vertical direction.
As shown in Figure 2, the resist 2
On the substrate 22 in the opening 26 of No. 5, Au 29 with a rectangular cross section is obtained, and the top layer of Au 29 is an electrode with a rectangular cross section (of course, the Au 29 is located only on the inner side of the lower layer).
is manufactured.

(Effects of the Invention) As detailed above, according to the present invention, when depositing an electrode metal when forming a multilayered electrode by a lift-off method,
Since the incident angle of the electrode metal is controlled, the electrode can be manufactured with a structure in which the uppermost layer is located inside the trapezoidal lower layer. According to the electrode with this structure, since the uppermost layer is located inside the lower layer, it is possible to prevent the uppermost layer from coming into contact with the underlying semiconductor substrate, so even if the uppermost layer is made of Au, the subsequent It is possible to prevent Au from diffusing into the semiconductor 'J+E due to the heat generated during film growth, and it is possible to prevent deterioration of device characteristics.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a first example of the vapor deposition state of the electrode metal according to the present invention, FIG. 2 is a cross-sectional view showing a second example of the vapor deposition state of the electrode metal according to the present invention, and FIG. A diagram for explaining the first example of the method for controlling the incident angle of vapor deposited metal, FIG. 4 is a diagram for explaining the second example of the method for controlling the incident angle of vapor deposited metal, and FIG. 5 is a diagram for explaining the lift-off method. 6 is a diagram showing the electron beam rotary evaporation method, FIG. 7 is a plan view showing the arrangement of the holder, substrate, and crucible in the rotary evaporation method, and FIG. 8 is the conventional method. FIG. 3 is a cross-sectional view showing the state of electrode metal vapor deposition according to the method. 21... Holder, 22... Substrate, 23... Crucible, 24... Vapor deposited metal, 25... Resist, 26...
...Opening, 27-Ti, 2B-Pt, 29-A
u, 30-first crucible, 31... second crucible. ″)−

Claims (2)

[Claims] (1) In the electrode of a semiconductor element formed in a multilayer structure on a semiconductor substrate by a lift-off method, (a) the lower layer portion except the top layer is formed in a trapezoid shape on the semiconductor substrate, and (b) the lower layer portion is formed on the semiconductor substrate in a trapezoidal shape. , an electrode of a semiconductor device in which an uppermost layer is formed inside the lower layer portion. (2) (a) forming a resist on a semiconductor substrate and forming an opening in the resist with a wider bottom side; (b) forming a multilayer structure electrode on the entire surface of the semiconductor substrate having the resist; (c) Next, a step of depositing the electrode metal of the lower layer portion excluding the uppermost layer by making it incident at a predetermined incident angle, and forming the lower layer portion of the electrode in a trapezoid shape on the substrate within the opening of the resist; By depositing the uppermost electrode metal at an incident angle smaller than the incident angle, the uppermost layer of the electrode is positioned on the lower layer and inside the lower layer on the substrate within the opening of the resist. (d) Thereafter, the resist is removed and, at the same time, unnecessary electrode metal thereon is removed.