JPH06177379A - Uhf-band mo gate power mosfet - Google Patents

Abstract

PURPOSE:To contrive the reduction of variability in the characteristics due to a shortening of the gate length and the improvement of the frequency characteristics in an Mo gate power MOSFET of a UHF band. CONSTITUTION:When a gate length is shortened, a gate resistance is increased, in particular in the case of a gate for power and having a long gate finger, when the film thickness of a gate Mo film is thin, the deterioration of the frequency characteristics of an Mo gate power MOSFET is generated and the gate is limited in design. The MOSFET has a structure, wherein (when the film thickness of the Mo film is made thick, the processing accuracy of the gate is deteriorated.) in order to remove this limitation, the Mo film of an Mo gate electrode 3 is applied thin, the processing accuracy is held, one or a plurality of pieces of through holes 9 are opened in places of the gate finger, (after a source and a drain are metallized,) the gate is made to connect with an extraction electrode (an Al upper layer gate electrode) 8 and the gate resistance is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a UHF band Mo gate MO.
SFET, especially Mo gate power MOSF used in inverters and amplifiers in UHF band frequencies
Regarding the structure of ET.

[0002]

2. Description of the Related Art Conventional Mo gate power MOSFET
Has a comb structure in which the source, gate and drain are alternately repeated as shown in FIG. The source / drain regions are stacked on the gate oxide film by RF sputtering, and then C
A gate electrode is formed by a dry etching technique using Cl ₂ F ₂ + SF ₆ gas, and by using the Mo gate pattern as a mask, AS ⁺ ion implantation and subsequent R are performed to make an N-type conductive layer of a source and a drain self-contained with respect to the gate. It was manufactured by forming it in alignment.

[0003]

In the conventional comb-shaped arrangement of the source, drain and gate, when designing a power FET that handles a large current, if the Mo film thickness of the gate material is 450 nm or more, for example, 800 MHz. UH
The accuracy of dry etching for a gate length of 1 to 1.5 μm capable of operating in the F band is significantly reduced, which causes variation in characteristics. However, when the thickness is 450 nm or less, the machining accuracy of the gate is significantly increased, but the parasitic resistance of the gate (referred to as gate resistance) is increased, which is a high-frequency characteristic item, particularly power gain (P _Gain ) and noise figure (NF). 2) is deteriorated, particularly for a power having a gate width (gate comb length) of about 1 nm or more, a gate length of 1 μm is 10 ⁻¹ Ω / comb, which is fatal. Therefore, keep the gate processing accuracy high,
In addition, reducing the gate resistance has become an issue.

It is an object of the present invention to improve the processing accuracy of the gate electrode without deteriorating the high frequency characteristics even when the gate electrode is made thin, and to reduce the variation of the characteristics and improve the yield, so that the UHF band MO gate MOSFET can be realized. To provide.

[0005]

According to the structure of the Mo gate power MOSFET of the present invention, in order to reduce the gate resistance, a through hole portion having one or a plurality of interlayer insulating films is provided in the middle of the wiring of the gate finger. A gate extraction electrode is provided immediately above.

[0006]

The present invention will be described below with reference to the drawings. FIG. 1 is a top view (A) and cross-sectional views (B) and (C) of a part of a semiconductor chip according to an embodiment of the present invention. As shown in the cross-sectional views (B) and (C), a thermal oxide film 2 having a thickness of 50 nm is formed on a P-type substrate 1, Mo3 of 400 nm is deposited by RF magnetron sputtering, and lithography using a photoresist and CCl _{2 are performed.} The lower-layer gate electrode 3 is formed by the re-scribe ion etching using a mixed gas of F ₂ and SF ₆ . The width of this gate electrode 3 is 1.0
It is set to about 1.5 μm. Here, as for the pattern of the gate electrode 3, a pattern having a portion of 4 μm is inserted in the subsequent step as shown in FIG. 7A to connect with the gate metal of the upper layer, and it is preferable that the pattern interval be several hundred μm.
After forming the Mo gate electrode 3, 120 ⁺ AS ⁺ ions are formed.
KeV, injection at 3 × 10 ¹⁵ cm ^-2 , 900 ° C. N ₂ + H
_The source / drain N-type conductive layer 4 is formed on the Mo gate electrode 3 by self-alignment by annealing for 230 minutes. After that, the interlayer insulating film 5 (SiO ₂ + PSG) 500n
m, the contact portions of the source and drain are opened by ordinary lithography and subsequent etching with a buffered hydrofluoric acid solution, and Ti-Pt is deposited by RF sputtering at 50 nm and 30 nm, respectively, and ion milling or CCl _{2 is performed.} Source / drain electrodes 6 and 7 are formed by reactive ion etching of F ₂ . Next, in FIG. 1 (c), X
_{As shown in the 1-} Y ₁ cross section, a 2 μm diameter opening is opened in the interlayer insulating film 5 on the 4 μm gate electrode by reactive ion etching using CF ₄ + H ₂ gas, and Al is deposited by 2 μm by vapor deposition, and the electrode is deposited. The processed gate electrode 8 is formed.

Although the lower and upper gate electrodes 3 and 8 are parallel to each other here, the second embodiment is a case where the lower and upper gate electrodes are orthogonal to each other as shown in FIG. There is an advantage that even if the sheet is skewed, it is possible to increase the degree of freedom of the pattern without deteriorating the characteristics.

[0008]

As described above, according to the present invention, since the upper layer electrode that reduces the gate resistance that deteriorates the high frequency characteristics is provided even when the gate electrode is made thin, the Mo thickness can be made thin, and thus the gate electrode can be processed. Can improve accuracy,
This has the effects of reducing the variation in characteristics and improving the yield, and also improving the high-frequency characteristics that have been limited by the gate resistance so far.

[Brief description of drawings]

FIG. 1 is a Mo gate power MOSF according to an embodiment of the present invention.
ET chip top view, XY cross-sectional view and X ₁ -Y
₁ is a cross-sectional view.

FIG. 2 is a top view of a chip showing another embodiment of the present invention.

FIG. 3 is a top view of a conventional Mo gate power MOSFET chip.

[Explanation of symbols]

1 P-type Si substrate 2 Gate oxide film 3 Mo Gate electrode 4 AS ⁺ ion implantation layer 5 Interlayer insulating film 6 Source electrode 7 Drain electrode 8 Upper layer gate electrode 9 Through hole

Claims (1)

[Claims] 1. A UHF band Mo gate MOSFET having a comb structure of a source, a drain and a gate, wherein P
A gate oxide film formed on the mold substrate; a molybdenum gate formed on the gate oxide film and having one or a plurality of through-hole patterns inside both ends of each gate finger; An interlayer insulating film formed so as to be covered and connected to a pattern for a through hole of the gate electrode through an opening provided in the interlayer insulating film,
A UHF band Mo gate MOSFET including an upper layer gate electrode provided on the interlayer insulating film.