JPS59150419A - Manufacture of compound semiconductor device - Google Patents

Abstract

PURPOSE:To avoid corrosion and resist remnants of a selective ion-implantation process securely and improve characteristics of the element by a method wherein an impurity ion is implanted into a substrate using the 2nd film as a mask and the 1st film is processed by wet-etching, while ultrasonic wave is applied to the film upto the halfway of the etching process. CONSTITUTION:An SiO2 film (the 1st film) 12 is deposited by sputtering on an N type InSb substrate 11 pre-processed by lactic acid system etchant and a Ti film 13 and an Al film 14 are deposited by an electron beam deposition method on the film 12 as the 2nd film. Then a negative type photoresist of a required pattern is formed on the Al film 14 and the Al film 14 and the Ti film 13 are selectively etched using the photoresist as a mask. Then Mg ion is implanted into the InSb substrate 11 using the Al film 14 and the Ti film 13 as a mask. After that the Al film 14 and the Ti film 13 are removed. Then, the SiO2 film 12 is processed by wet-etching with fluoric acid system etchant, while ultrasonic wave is applied to it, until approximately half the thickness of the film 12 is etched. After that, the SiO2 film 12 is completely etched by fluoric acid without application of ultrasonic wave.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a compound semiconductor device, and particularly to an improvement in an ion implantation process into a compound semiconductor substrate.

[Technical background of the invention and its problems]

Recently, compound semiconductor devices using compound semiconductors have been researched and developed, but these devices require various ion implantation processes. Conventionally, when performing selective ion implantation into a semiconductor substrate, impurity ions are implanted into the semiconductor substrate 3 using a resist 1 shown in FIG. 1 or an oxide film 2 shown in FIG. 2 as a mask. The structure shown in FIG. 2 is formed by patterning the oxide film 2 using a resist (not shown) on the oxide film 2 as a mask, and then peeling off the cysts as described above. .

However, when a compound semiconductor such as InSb is used as the semiconductor substrate 3, the above method has the following problems. That is, in the method shown in FIG.
The substrate 3 is severely eroded by the resist stripping solution. moreover,
If the dose of ion implantation is increased, the resist 1 will solidify, and there is a possibility that the resist 1 will not be able to be peeled off from the surface of the substrate 30. Furthermore, in the method shown in FIG. 2, the resist remains on the pattern edge of the oxide film 2 even after the resist is removed, and when the oxide film 2 is removed with a hydrofluoric acid-based etchant,
There is a problem that a thin resist film remains attached to the surface of the substrate 30. Such resist residue, substrate corrosion, etc. are major causes of deterioration of the element characteristics of the compound semiconductor device fabricated in subsequent steps.

[Purpose of the invention]

An object of the present invention is to provide a method for manufacturing a compound semiconductor device that can prevent resist residue and substrate erosion caused by ion implantation into a compound semiconductor substrate, and can contribute to improving device characteristics.

[Summary of the invention]

The gist of the present invention is to perform the ion implantation process without bringing the resist and resist stripping solution into direct contact with the surface of the compound semiconductor substrate.

As mentioned above (for compound semiconductors such as InSb, the substrate surface becomes brittle due to damage from ion implantation, and is severely eroded by the resist stripping solution. Also, if the dose is large, the resist may not be completely stripped). Therefore, an ion implantation process in which a resist and a resist stripping solution come into contact with the substrate surface is not preferred.On the other hand, as shown in FIG.
Even when a turned oxide film is used instead, the resist attached to the pattern edge may be affected. As a result of extensive research, the present inventors formed an insulating film over the entire surface of a compound semiconductor substrate 1, and formed a mask for selective ion implantation by photolithography using a resist on this insulating film. It has been found that, in particular, the adverse effects of the resist and resist stripping solution on the substrate surface can be prevented. In addition, to prevent dust such as resist on the insulation film from coming into contact with the substrate surface when peeling off the insulation film after ion implantation, the insulation film is wet-etched to about half its thickness while being removed using ultrasound, and then It has been found that by completely wet-etching the insulating film with hydrofluoric acid without etching, corrosion of the substrate surface and residual resist can be reliably prevented.

The present invention has focused on such points, and in a method for manufacturing a compound semiconductor device, after forming a @1 coating made of an insulating film on a compound semiconductor substrate, an etching layer having an etching selectivity with that of the coating is formed on the coating. A second film is formed, and then the second film is pattern-edged using a photoresist as a mask, the resist is removed, and impurity ions are implanted into the substrate by pressing the second film with a mask.
, and then wet-etching the first film,
In this method, ultrasonic waves are projected onto the first film until part way through the etching of the first film.

〔Effect of the invention〕

According to the present invention, it is possible to reliably prevent corrosion of the substrate surface and residual resist during selective ion implantation into a compound semiconductor substrate.

Therefore, it is possible to improve the device characteristics of a semiconductor device formed on a compound semiconductor substrate. Furthermore, since ion implantation into the substrate is performed through the insulating film, damage to the substrate surface due to ion implantation can be extremely minimized.

[Embodiments of the invention]

FIGS. 3(-) to 3(-) are process cross-sectional views showing one embodiment of the present invention. First, as shown in FIG. 3(,), a 100 mm thick film was deposited on an N-type InSb substrate (compound semiconductor substrate) 11 pretreated with a lactic acid-based etchant (volume ratio: lactic acid: nitric acid = 6:1) using the snob vine method. A 5IO2 film (first film) 12 of (^) is deposited, and a second film 12 is deposited on this 8102 film 12.
The TI film 13 and the At film 14 as coatings were deposited by electron beam evaporation to a thickness of 100 mm, respectively, and a so'ooC film.
X) K was deposited.

Next, a negative photoresist (not shown) is formed in four desired turns on the At film 14, and using the resist as a mask, the At film 14 and the TI film 13 are selectively etched as shown in FIG. 3(b). did. This Toki, 100[x]T
The i film 13 serves as a stopper to prevent the At etchant from penetrating the InSb substrate 11 through the pinholes in the 5IO2 film 12.

Next, using the At film 14 and the TI film 13 as masks, Mg ions were implanted into the InSb substrate 11 at an acceleration voltage of 20 Q (k@V ball dose of 5×10 14 [crn-2]). Since ions are implanted into the InSb substrate 11 through the 5IO2 film 12, damage caused by the ion implantation is extremely small.

Next, as shown in FIG. 3(C), the At film 14 and the T1 film 13 were removed using an appropriate etchant.

After that, using a hydrofluoric acid-based etchant, ultrasonic waves (output 8
0W), the 5I02 film 12 was wet-etched to about half its thickness. Subsequently, by applying ultrasonic waves, the 5io2 film 12 was completely wet-etched with hydrofluoric acid as shown in FIG. 3(d).

The surface of the InSb substrate 11 thus obtained was in good condition with almost no damage caused by ion implantation and no residual resist at all. Therefore, the effects of the method of this embodiment are obvious, and the device characteristics of various semiconductor devices fabricated in subsequent steps can be significantly improved.

Note that the present invention is not limited to the embodiments described above, and can be implemented with various modifications without departing from the gist thereof. For example, there is no need to provide it if it does not exist.

Further, the first film is not limited to the 5102 film formed by sputtering, but may be an SiO2 film formed by CVD, thermal oxidation, or anodic oxidation, or other insulating films.

The second film is not limited to a metal film such as AA, but may be a nitride film, as long as it has an etching selection ratio with respect to the first film. Furthermore, the semiconductor substrate is not limited to InSb, but is InP.
It is possible to apply to r GaAs and various other compound semiconductors.

[Brief explanation of drawings]

1 and 2 are cross-sectional views for explaining a conventional ion implantation process, respectively, and FIGS. 3(a) to 3(d) are process cross-sectional views showing one embodiment of the present invention. 11... In8b substrate (compound semiconductor substrate), 12.
...Sin, membrane, 13...T+ membrane, 14...AI!
Membrane 11: i ['i person's proxy dialect j''ij 1 Takehiko Suzue Figure 1 Figure 2

Claims (2)

[Claims] (1) A step of forming a first film made of an insulating film on a compound semiconductor substrate, a step of forming a second film having an etching selectivity with that of the first film, and a step of forming a photoresist. a step of turning the second film as a mask and then removing the resist; a step of ion-implanting impurities into the substrate using the second film as a mask; a step of removing;
j~ After a while, wet etching the first film,
A method for manufacturing a compound semiconductor device, further comprising the step of projecting ultrasonic waves onto the first film halfway through etching the first film. (2) The method for manufacturing a compound semiconductor device according to claim 1, wherein an oxide film is used as the first film, and a nitride film or an aluminum film is used as the second film.