JP2894099B2 - Method for manufacturing compound semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates relates to a method for manufacturing a compound semiconductor device, in particular a compound semiconductor substrate (wafer) surface of the recess (recesses) a gate electrode in the method of manufacturing a compound semiconductor device is formed披着Things.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional compound semiconductor device and a method of manufacturing the same. First, as shown in FIG. 2A, an ohmic source electrode 22 and a similarly ohmic drain electrode 23 are formed on the surface of a compound semiconductor substrate (wafer) 21, and an insulating film 24 is formed between the two electrodes. For example, a silicon dioxide film is formed. Next, as shown in FIG. 2B, a photoresist 25 having an opening 26 is formed, and an opening 27 is formed in the insulating film 24 by isotropic wet etching using the photoresist 25 as a mask. The opening 27 is larger than the end of the opening 26 of the photoresist 25 by the same amount W on the source electrode 22 side and the drain electrode 23 side by side etching. Next, as shown in FIG. 2C, a recess 28 is formed from the surface of the compound semiconductor wafer 21 further by isotropic wet etching. This recess 28
The opening 2 of the insulating film 24 is also etched by side etching.
7 is larger by the same amount X on both the source electrode 22 side and the drain electrode 23 side than the end. Therefore, the center of the opening 26 of the photoresist 25 coincides with the center of the recess 28. Next, as shown in FIG. 2D, a gate electrode 29 is formed on the bottom surface in the recess 28 by self-alignment using the opening 26 of the photoresist 25 by a lift-off method. Thus, the gate electrode 29 of the prior art is formed such that its center coincides with the center of the recess 28.

[0003]

As described above, in the conventional manufacturing method, the gate electrode is formed at the center of the recess. Accordingly, when the distance between the end of the recess on the source electrode side and the gate electrode is reduced to reduce the resistance between the source electrode and the gate electrode, the distance between the end of the recess on the drain electrode side and the gate electrode is also reduced. It becomes short and the drain withstand voltage deteriorates, giving rise to a problem that the DC characteristics are adversely affected.

[0004]

[0005]

Means for Solving the Problems The feature of the present invention, a compound semiconductor substrate surface to the source electrode of the drain electrode is formed, a continuous silicon dioxide film on the surface of the substrate from the source electrode to the drain electrode Forming, and forming a first photoresist film provided with a first opening exposing a first portion of the silicon dioxide film between a gate forming region and the drain electrode; It said first portion by an impurity is ion-implanted into the first portion of the silicon dioxide film using the first photoresist film as a mask
Converting the component into a glass film, a first portion that has become the glass film, and a second portion of the silicon dioxide film that has been masked by the first photoresist film during the ion implantation. Is exposed , and the lower part is narrow and the upper part is
Forming a second photoresist film provided with a second opening having a wide shape, and performing wet etching using the second photoresist film as a mask, thereby forming the glass film under the second opening. And removing the silicon dioxide film, and removing the first portion that has become the glass film by side etching from below the second opening to a greater extent than the second portion that is still the silicon dioxide film ; Forming a recess from the surface of the compound semiconductor substrate below the portion where the glass film and the silicon dioxide film are removed, and thereafter, a lift-off method using the second photoresist film , In the recess
Is narrow, and the portion protruding from the recess is wide.
The gate electrode is formed of, and the Li from the source electrode
The surface of the substrate up to
And a substrate from the drain electrode to the recess.
Obtain a configuration in which the surface of the plate is continuously coated with the glass film.
In the production method of a compound semiconductor device having a that step.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing a compound semiconductor device according to one embodiment of the present invention and a method for manufacturing the same.

First, as shown in FIG. 1 (a), an ohmic source electrode 2 and an ohmic drain electrode 3 are formed on the surface of a compound semiconductor substrate (wafer) 1 and an insulation is provided between the two electrodes. A film 4, for example, a silicon dioxide film is formed. Next, a first opening 6 exposing a first portion 7 of the insulating film 4 between the gate forming region 9 and the drain electrode 3 is formed by applying and patterning a photoresist.
A first photoresist film 5 provided with
Using the photoresist film 5 as a mask, an impurity 17 is ion-implanted into the first portion 7 of the insulating film 4 to make the portion a doped oxide. For example, if the insulating film is a silicon dioxide film and phosphorus is ion-implanted as an impurity ion, the first portion 7 is made of phosphosilicate glass (PSG).
It becomes the film 11. The first photoresist film 5 is masked by the first photoresist film 5 during the ion implantation and the first portion 7 which has become the doped oxide 11 such as a phosphosilicate glass (PSG) film substantially under the end of the first photoresist film 5. A boundary 10 between the second portion 8 of the insulating film 4 and the silicon dioxide film remains.

Next, as shown in FIG. 1B, after the first photoresist film 5 is removed, a second photoresist film 12 having a second opening 13 through which the boundary 10 is exposed is provided.
To form After that, using the second photoresist film 12 as a mask, the insulating film is formed on the insulating film by, for example, P etching (hydrofluoric / nitric acid based).
Is performed, thereby removing the insulating film under the second opening 13, and removing the insulating film more laterally than under the second opening by side etching. At this time, the amount Y of side etching of the first portion 7 of the insulating film serving as the phosphosilicate glass (PSG) film 11 is different from that of the insulating film remaining as the silicon dioxide film due to the difference in etching rate. Is removed by more than the amount W of side etching of the portion 8 of the second photoresist film 12.
Is formed on the drain electrode 3 side with respect to the center of the opening 13 of FIG.

Next, as shown in FIG. 1C, the surface of the compound semiconductor substrate 1 is etched from the opening 14 of the insulating film 4 (using the insulating film 4 as a mask) by isotropic wet etching. Then, a recess (recess) 15 is formed.
The upper portion of the recess 15 is larger than the end of the opening 14 of the insulating film 4 by the same amount X on the source electrode 2 side and the drain electrode 3 side by side etching. Therefore, since the center of the recess 15 coincides with the center of the opening 14 of the insulating film 4, the center of the recess 15 is shifted toward the drain electrode 3 with respect to the center of the second opening 13 of the second photoresist film 12. Will be formed.

Next, as shown in FIG. 1D, a metal is deposited by self-alignment with the second opening 13 of the second photoresist film 12, and a gate electrode 16 is formed by a lift-off method.
Is formed on the bottom surface in the recess 15 so that the gate electrode 16 is formed in the recess 15 so as to be shifted toward the source electrode 2.

As the ion implantation in the step of FIG. 1A, boron may be ion-implanted instead of phosphorus. In this case, the first portion 7 of the insulating film 4 becomes a borosilicate glass (BSG) film.

[0012]

As described above, according to the present invention, the gate electrode is formed so as to be shifted toward the source electrode in the recess. Therefore, since the distance between the gate electrode and the end of the recess is short on the source side and long on the drain side, the resistance between the gate electrode and the source electrode is reduced, and the drain withstand voltage is also improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view showing a conventional technique.

[Explanation of symbols]

Reference Signs List 1 compound semiconductor substrate (wafer) 2 source electrode 3 drain electrode 4 insulating film (silicon dioxide film) 5 first photoresist film 6 first opening formed in first photoresist film 7 first insulating film 4 1 part 8 second part of insulating film 4 9 gate forming region 10 boundary between first part and second part of insulating film 4 11 doped oxide (phosphosilicate glass) 12 second photoresist film 13 The second photoresist film 12 formed on the second photoresist film 12
Opening 14 of insulating film 4 15 recess 16 gate electrode 17 impurity (phosphorus) 21 compound semiconductor substrate (wafer) 22 source electrode 23 drain electrode 24 insulating film (silicon dioxide film) 25 photoresist 26 photoresist opening 27 Opening of insulating film 24 28 Recess 29 Gate electrode

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/337-21/338 H01L 27/095 H01L 27/098 H01L 29/775-29/778 H01L 29 / 80-29/812

Claims (1)

(57) [Claims] A source electrode on a surface of the compound semiconductor substrate;
Forming a drain electrode and continuously forming a silicon dioxide film on the surface of the substrate from the source electrode to the drain electrode; and forming a first portion of the silicon dioxide film between the gate formation region and the drain electrode. Forming a first photoresist film provided with an exposed first opening;
Wherein said first photoresist film as a mask dioxide
Ion-implanting an impurity into the first portion of the silicon film
A step of converting the glass film said first portion by, before
Serial had been masked by the first photoresist film as the first part during the ion implantation became glass film two
The boundary with the second portion of the silicon oxide film is exposed and
Forming a second photoresist film provided with a second opening having a narrow portion and a wide upper portion; and performing wet etching using the second photoresist film as a mask, thereby forming the second photoresist film. The glass film and the silicon dioxide film under the opening are removed, and the glass film is formed by side etching from under the second opening.
The first portion the increase removed than the second portion remains of the silicon dioxide film was further formed a recessed into the glass film and the surface of said compound semiconductor substrate under the removed portion of the silicon dioxide film And then, by a lift-off method using the second photoresist film , the portion in the recess is narrow,
The protruding portion forms a wide gate electrode , and
The surface of the substrate from the source electrode to the recess is continuously
Covered with the silicon dioxide film, the drain electrode
The surface of the substrate from the recess to the recess is continuously covered with the glass film.
Obtaining a configuration covered with a compound semiconductor device.