JPH03120889A - Semiconductor device - Google Patents

Abstract

PURPOSE:To improve yield and reliability and to acquire a semiconductor device of a long life by forming a groove and an edge face structure by dryetching process and by forming a surface layer part thereof to a high resistance layer by irradiating it with proton. CONSTITUTION:An epitaxial film consisting of a first clad layer 2, an active layer 3, a second clad layer 4, and a cap layer 5 is formed successively on a substrate 1. A ridge part is formed thereon to form a stripe structure to carry out transverse confinement not to form an electrode 7 in a position to be etched. Edge face processing is carried out as far as a lower part of the active layer 3 by FIB 11. Then, a surface layer part is formed to a high resistance layer 9 by irradiation with proton 12.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to semiconductor devices, and particularly to semiconductor devices such as light emitting devices, light receiving devices, optical waveguides, etc., in which grooves or end face structures are formed in a semiconductor substrate. - [Prior Art] Conventionally, cleavage planes of crystals have often been used as the end face structure in this type of semiconductor device. For example, in a semiconductor laser, a resonator is constructed using a cleavage plane of a crystal as a mirror. After processing, devices in the wafer state are mounted through the steps of cleavage and scribing. As described above, the formation of the end face, which determines the length of the resonator, is performed by the complicated process of cleaving, which is one factor that reduces the yield of devices.

A method using etching has also been proposed as an end face forming method to improve yield. When manufacturing a semiconductor laser, a focused ion beam method (F r B) is used to form a mirror end face that is close to perpendicular to each other.

It can be processed by a dry etching process such as reactive ion etching (RIE) or reactive ion beam etching (RIBE).

(Problems to be Solved by the Invention) Among the above-mentioned conventional semiconductor devices, those whose end faces are formed using cleavage have a drawback of poor yield.

Further, in the case where the end face is formed by a tri-etching process, although the yield is improved, there is a drawback that the end face of the crystal is damaged to some extent. In some cases, such damage on the crystal surface can be removed by subsequent treatment (for example, anil treatment, chemical treatment, etc.), but in most cases it becomes a defect in the crystal and leads to device deterioration. In other words, damage to the end face increases leakage current due to surface recombination at the pn junction including the active layer, and optical damage (COD) on one end face of the mirror causes a decrease in output and device deterioration, which significantly reduces device reliability. It has the disadvantage of deteriorating health and lifespan.

The present invention has been made in view of the drawbacks of the above-mentioned prior art, and an object of the present invention is to realize a semiconductor device with improved yield and reliability and a long life.

(Means for Solving the Problems) A semiconductor device of the present invention is a semiconductor device in which a groove or an end structure is formed, in which the trench and end structure are formed by a dry etching process, and the surface layer portions of these are formed by proton irradiation. It is considered a high resistance layer.

[Effect]

Since the surface layer portions of the groove and end face structure have high resistance, leakage current and light absorption at these portions are reduced compared to conventional structures.

〔Example〕

1 and 2 are a longitudinal sectional view and a transverse sectional view, respectively, of the first embodiment of the present invention, and FIG.
) are the vertical end face 8 and the high resistance layer 9 in this example, respectively.
It is a figure which shows step by step the procedure when producing.

In Fig. 1, 1 is an n-GaAs substrate, 2 is an n-Al
6.7 The first cladding layer is GaAs, the active layer is 1-GaAs, the second cladding layer is p-AlGaAs, and the cap layer is p''-GaAs. 6.7
are u/AuGe and A u/Cr to h, respectively.
It is an electrode consisting of.

The vertical end face 8 was processed by the F1a method using Ga'' ions with an acceleration voltage of 50 keV.The effective range of Ga'' ions is 0.02 μm, and it is assumed that crystal defects occur in this range. Conceivable. Therefore, in this example, proton irradiation was performed on the processed end face 8 following the F1a method described above to amorphize it and form the high-resistance layer 9. The proton acceleration voltage was set to 100 keV so as to sufficiently cover the effective range of Ga+ ions (+1" ion effective range = 0.85 μm).

It has been shown that the characteristics of this example, in which the other end face (not shown) is a cleaved end face, can be stabilized by forming the high resistance layer 9.

The process procedure of the first embodiment will be described above.

An epitaxial film consisting of a first cladding layer 2, an active layer 3, a second cladding layer 4, and a cap layer 5 is grown in order on a substrate 1 by molecular beam epitaxy (MBE). A buffer layer made of GaAs may be formed at the interface with the substrate 1 if necessary. 1st. The thickness of the second cladding layer 2.4 is 1 μm
The Ifu thickness of the active layer 3 was approximately 0.1 μm. Next, a ridge portion having a width of 3 μm was formed on the upper portion by photolithography to form a stripe structure for lateral confinement.

After forming the ridge portion, a silicon nitride film 10 was deposited by plasma CVD, and a window was opened above the ridge by RIE. Subsequently, electrode 7.6 was deposited and alloyed to form an ohmic electrode.

FIG. 3(a) is a cross-sectional view of the device before forming a mirror-processed end face (etched mirror).

It is assumed that the electrode 7 is not formed at the location to be etched. Next, as shown in FIG. 3(b), the end face is processed down to the bottom of the active layer 3 using FIBII, and then, as shown in FIG. 3(C), the surface layer is raised by proton-12 irradiation. A resistive layer 9 is formed. In this way, electrode 7 will act as a mask. The fabricated device is
After cleavage, it is mounted on the stem and wire bonded to the electrodes to complete the process.

In the above process procedure, F is used as the end face forming process.
Although an example has been shown in which processing is performed by the IB method and proton irradiation is performed after forming the electrode 7, it is also possible to perform both steps one after the other. Furthermore, the laser is not limited to an etched mirror on one end surface, and may naturally be a laser having etched mirrors formed on both ends.

FIG. 4 is a diagram showing the main part configuration of a second embodiment of the present invention.

This embodiment is an example in which the processed end surface of the first example of 8 cages is used as an integrated coupler.

In the figure, 20 is a wedge-shaped slit groove formed by the FIB method, and 21 is a high resistance layer formed by proton irradiation. The other parts except for the coupler part formed in this manner have a ridge-type laser structure constructed in the same manner as in the first embodiment, and therefore are given the same reference numerals and a description thereof will be omitted.

This integrated coupler forms a wavefront splitting type branching coupler, and by controlling the position of the wedge-shaped tip, the efficiency of transmission and reflection can be set to a desired value. For example, by setting the tip position near the center of the light intensity distribution of the guided light in the layer direction, the ratio of transmission and reflection can be made approximately equal.

FIG. 5 is a top view showing the main structure of a third embodiment of the present invention.

This embodiment is an optical node using the integrated coupler shown in the second embodiment, which receives the signal content of the light wave 33 incident from above in the figure and emits it downward as output light 37. It is.

In the figure, 20' is a wedge-shaped slit groove formed by FIB processing and proton irradiation, and 30a.

Reference numeral 30b indicates an amplification region including an optical amplifier (not shown) which has a gain by current injection, and 31a and 31b indicate photodetection regions including photodetectors operated by application of a reverse bias. AR coats 38a and 38b are formed on the end faces, and Al2O3+ZrO2 is deposited by electron beam (EB) evaporation. 39 is a waveguide.

The waveguide 39 is formed in a cross shape on the upper surface, and the waveguide portions in the vertical direction from the center are amplification regions 30a, 30.
b, and the left and right directions are detection areas 38a and 38b. The slit groove 20' is provided approximately at the center of the waveguide 39 so that its longitudinal direction is inclined at 45 degrees with respect to each longitudinal direction of the cross-shaped waveguide 39 described above. As a result, the central portion of the waveguide 39 becomes an integrated coupler section 32 indicated by a broken line.

Next, the operation will be explained.

The incident light wave 33 enters the integrated coupler section 32 as an incident wave 34 amplified in the amplification region 30a, and the transmitted wave 3
6 and a reflected wave 35. The reflected wave 35 is the incident wave 33
The light wave 33 undergoes photoelectric conversion in the photodetection region 31a, and the signal component in the light wave 33 is monitored.

On the other hand, the transmitted wave 36 is further amplified in the amplification region 30b,
It is output as emitted light 37. If the light is incident from the opposite direction, monitoring is performed in the photodetection region 31b, and other amplification operations are the same.

If the optical amplification factor (gain) is set in such a way as to compensate for coupler loss and end-coupling loss, it will function as an apparently lossless light-receiving optical node, allowing multi-stage connection.

Although the above description has been made on the assumption that the optical node performs only reception, it is possible to realize an optical node capable of transmitting and receiving by providing a transmitting section and a receiving section.

FIG. 6 is a top view showing the main structure of a fourth embodiment of the present invention.

This example shows a composite cavity laser whose wavelength is stabilized by providing a cross-shaped active layer.

In the figure, 43 is an active layer formed in a cross shape similar to the waveguide 39 (see FIG. 5) explained in the third embodiment, and 44 is the slit groove 20 (see FIG. 5) explained in the third embodiment. (see Figure 5), 2 slit grooves for controlling reflection, 4
1a and 41b are the vertical ends (] described in the first embodiment).
A mirror formed in the same manner as 'i'i8 (see FIG. 3(C)), 42 is an electrode formed on the upper surface.

The active layer 43 formed in a cross shape has an input/output direction in the vertical direction, and mirrors 41a and 41b forming a composite resonator are provided at the left and right ends. The slit groove 44 has the above-mentioned cross-shaped active layer 43 in its longitudinal direction.
The active layer 43 is provided approximately at the center thereof so as to be inclined by 45'' with respect to each longitudinal direction.Thereby, the center portion of the active layer 43 becomes an integrated coupler section 40 shown by a broken line. ing.

Each of the mirrors 41a, 41b and the slit groove 44 are fabricated by proton irradiation after being processed by the FIB method. Since the cross-shaped laser resonator structure constitutes a type of Michelson interferometer, a composite resonator mode is formed and the oscillation wavelength can be stabilized. In this example, since the mirrors 41a and 41b have high resistance, leakage current and light absorption can be reduced, and luminous efficiency can be improved. In addition,
Regarding the above-mentioned interferometric laser with a cross-shaped resonator, see Reference J, Salzman at al: “Cross
coupled cavity semiconductor
t'or 1aser” Appl, Phys, [
, ett, 52°10, pp, 767-769 (
There is a report in March, 1988).

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

In the thing according to claim 1, the FIB method, RIBE
By further irradiating protons to the parts formed by dry etching processes such as etching and RIE methods to increase the resistance, semiconductor devices with reduced leakage current and light absorption due to damage caused by the dry etching process are formed. can do.

By suppressing leakage current, efficiency can be increased for lasers used in forward bias.
For photodetectors used in reverse bias, this has the effect of reducing dark current and improving the S/N ratio.

According to the second aspect of the present invention, an optical amplifier having the above-mentioned effects can be realized.

According to the third aspect of the present invention, there is an effect that a branch coupler having the above-mentioned effects can be realized.

According to the fourth aspect of the present invention, there is an effect that a semiconductor laser having the above-mentioned effects can be realized.

[Brief explanation of drawings]

1 and 2 are a longitudinal sectional view and a transverse sectional view, respectively, of a first embodiment of the present invention, and FIGS. 3(a) to 3(C)
) are diagrams showing step-by-step the steps for producing the vertical end face 8 and high-resistance layer 9 in the first embodiment, and FIGS. FIG. 2 is a diagram showing a main part configuration of an embodiment. 1... Substrate, 2... First crat layer,
3.43...Active layer, 4...Second cladding layer, 5...Cap layer, 6,7.42...Pole, 8...Vertical end surface, 9.21...Height Resistance layer, lO... silicon nitride film, 11... FIB, 12
...Proton, 20.20°, 44...Slit groove, 30a, 30b"-amplification region, 31a,
31b=-photodetection area, 32, 40... integrated coupler section,

Claims (1)

[Claims] 1. In a semiconductor device in which a groove or an edge structure is formed, the groove and the edge structure are formed by a dry etching process, and the surface layer thereof is made into a high resistance layer by irradiation with protons. A semiconductor device characterized by: 2. The semiconductor device according to claim 1, wherein an optical waveguide structure is formed on a semiconductor substrate. 3. The semiconductor device according to claim 2, wherein the groove or end face structure is formed to reach a part of the optical waveguide structure. 4. The semiconductor device according to claim 2, wherein the optical waveguide structure has an active layer and is capable of laser amplification;
A semiconductor device characterized in that the groove is used as a branch coupler and a resonant mirror for laser amplification, and the end face structure is used as a resonant mirror for amplification and an input/output section.