JPH1027777A - Detecting method of etching end point - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-sensitive etching end point which is enhanced in response speed, sensitivity, and separating rate, by a method wherein an etching rate is controlled by taking advantage of a plasma emission light whose wavelength is close to a specific value and which appears at the reaction of In to Cl. SOLUTION: A window is provided to an etching device reaction chamber 1 to observe enough light emitted from the specimen surface of a wafer 7 by taking advantage of plasma emission light of wavelength 470nm or so which appears at the reaction of In to Cl, and light rays of wavelength 470nm or so are selected out of light rays emitted at etching through a monochromator or a monochromatic filter 3 or the like and sent to a multiplying device such as an photomultiplier 4. An etching rate is controlled on the basis of the output of the photomultiplier 4. By this setup, a thin film can be processed high in response speed, sensitivity, and separation rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to InGaAs, In
The present invention relates to the manufacture of a compound semiconductor device having a compound semiconductor heterojunction containing In such as P, and more particularly to a method of detecting an etching end point.

[0002]

2. Description of the Related Art Conventional compound semiconductor devices, for example, GaAs
In the manufacture of s / AlGaAs and InGaAs hetero devices, Journal of Electronic Materials, Vol. 18, Vol. 5, 1989, pp. 619-622.
(Journal of Electronic Materials, vol. 18, No.
5, 1989, pp. 619 to 622) and the like, a method using selective etching by a chemical stop layer has been mainly used. By the selective dry etching described above, the element manufacturing process has been significantly shortened, and performance improvement such as threshold voltage stabilization and yield improvement have been simultaneously achieved.

However, in recent years, with the improvement of element performance, In
Devices that actively use InP-based compound semiconductors such as P and InGaAs have become mainstream, and the processing itself of these InP-based compound semiconductors is difficult, and a method using dry etching utilizing physical impact is generally used. It is.
In this case, it is difficult to apply a stop layer due to a chemical reaction.
It was necessary to search for another method for controlling the etching amount.

For example, Japanese Patent Application Laid-Open No. 2-109329 discloses a method of monitoring the peak intensity of a specific mass number involved in etching using a mass analyzer. In addition, end-point detection by plasma emission during compound semiconductor etching is also being studied.However, various types of light emission are actually mixed in the plasma, and the emission wavelength with a high degree of separation that can be applied to end-point detection is limited. , SiO ₂ processing, etc.

[0005]

SUMMARY OF THE INVENTION GaAs / AlGaAs
s, GaAs / InGaAs, GaAs / InAs, G
In a compound semiconductor heterostructure of a combination such as aAs / InAlAs, selective etching in which a reactant such as In or Al having extremely low volatility is applied to a chemical stop layer is possible. However, in the case of selectively processing one of the In-containing layer itself and the heterojunction containing In both of them, another method as described above is required. However, in the method using mass spectrometry described above, the response speed until obtaining the target peak is as low as 0.1 to several seconds, tuning using a specific mass number is always required before use, and the ionization rate at the hetero interface is low. It is difficult to accurately detect the end point due to the influence of the so-called interface effect due to the fluctuation.
In particular, it is extremely difficult to cope with a semiconductor element having a reduced thickness, and a simple etching control method which has a high response speed, good sensitivity, and is desired.

The problem to be solved by the present invention is to selectively process an InP-based compound semiconductor heterostructure by dry etching or to process other In-containing thin films.
An object of the present invention is to provide a simple and easy method for detecting an etching end point with good response speed, sensitivity, and degree of separation, thereby achieving processing accuracy, shortening a manufacturing process, improving yield, and the like.

[0007]

In order to solve the above-mentioned problems, the degree of separation from other plasma emission wavelengths generated during the processing of InP-based compound semiconductors is extremely high, and around 470 nm which appears when a highly sensitive reaction between In and Cl occurs. Was used. Dry etching equipment to be used A window is installed at a position where the light emission from the sample surface in the reaction chamber can be captured sufficiently, and the light generated at the time of etching can be passed through a monochromator or a monochromatic filter, etc., and only the wavelength around 470 nm can be used as a photomultiplier tube. Send to multiplier. The amount of etching is controlled based on the output thus obtained.

According to the present invention, selective dry etching of an InP-based compound semiconductor can be performed using a relatively simple apparatus.

FIG. 1 shows that GaAs and In _0.5 Ga _0.5 As
with l _2, etching pressure 0.23MTorr, microwave output 700w, E under the conditions of RF discharge density 13 kW / m ²
FIG. 4 shows a state of plasma emission when a CR etching process is performed. A strong peak is observed at a position near 470 nm, which was hardly observed at the time of GaAs processing. This light emission does not hide in the background even in AlGaAs, InAlAs, InP, etc.
It has been confirmed that the degree of separation is good. Since the emission around 470 nm is not observed at all when the etching is performed using an etching gas other than Cl ₂ ,
It has also been confirmed that the light emission is peculiar light emission that appears during the reaction between n and Cl.

FIG. 2 is a diagram illustrating the system configuration of the present invention. The emitted light captured from the etching reaction chamber is passed through an optical fiber cable or the like, and only the emission wavelength near 470 nm is sent to the photomultiplier using a monochromator or a filter, and detected as an output accompanying the reaction between In and Cl.
Return this output to the dry etching equipment sequence,
The amount of etching is controlled. At this time, by setting the emission wavelength output set value around 470 nm for judging the stop of the etching to be arbitrary, it is possible to cope with various combinations of compound semiconductor heterostructures.

FIG. 3 shows In _0.6 Ga _0.4 A on a GaAs substrate.
A sample on which an s (30 nm) layer and an In _0.3 Ga _0.7 As (20 nm) layer were grown was subjected to ECR etching using Cl ₂ gas. Etching conditions: an etching pressure of 0.23 mTorr,
Microwave output 700w, RF discharge density 13kw / m ²
5 shows the change in the emission wavelength intensity at 470 nm when processing is performed by the method shown in FIG. Even with a thin layer structure such as a change in the In composition or a thickness of 20 to 30 nm, it is possible to relatively satisfactorily separate by light emission intensity. Further, since the present invention is a method using plasma emission, it is possible to monitor etching in almost real time.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

<Embodiment 1> FIG. 4 shows an embodiment of the present invention in which an HBT (Heterojunction Bi
Polar Transistor) This is an example of application to element manufacturing. This HBT element has an emitter cap layer 12, an emitter layer 13, a base layer 14, and a collector layer 1 as shown in FIG.
5, a sub-collector layer 16 and a substrate 17. This compound semiconductor heterostructure is manufactured in a self-aligned manner using tungsten silicide as the emitter electrode 11 as a mask.

First, as shown in FIG.
1 is used as a mask to etch from the n-In _0.5 Ga _0.5 As / n-GaAs emitter cap layer 12 to the n-Al _x Ga _{1 -x} As emitter layer 13. In this step, Cl
ECR etching using ₂ / CH ₄ gas, etching conditions: Cl ₂ / CH ₄ gas flow rate = 7 sccm / 3 sccm, etching pressure 0.25 mTorr, RF discharge density 25 kw / m ² ,
A microwave discharge power of 100 w is used.

FIG. 5 shows the result of monitoring the emission wavelength of 470 nm. From InGaAs layer to Ga
It can be seen that the etching progresses to the As layer and the peak at 470 nm sharply decreases. In this step, an emitter layer of several tens nm must be left from a process margin at the time of forming the next base electrode. Therefore, the progress of the etching can be accurately grasped by monitoring the wavelength of 470 nm, and the emitter formation with good reproducibility has become possible.

The above etching conditions and anisotropic Al
GaAs / GaAs selective etching, for example, etching conditions: SiCl ₄ / SF ₆ gas flow rate = ₆ sccm / 3 sccm, etching pressure 13.5 mTorr, RF discharge density 1.2 kw /
By combining with the reactive ion etching of m ² , emitter processing with higher accuracy and good reproducibility is possible.

Thereafter, as shown in FIG. 1C, an SiO ₂ film 18 was applied, and a base electrode 20 and a collector electrode 21 were formed, thereby obtaining a target HBT element. According to the present invention, the etching and the control of the SiO ₂ side wall length can be easily performed on the process, and the emitter resistance can be reduced on the device.
Suppression of element deterioration and improvement in production yield were achieved.

<Embodiment 2> The present invention is applied to an EA (Electron-Abso
An example in which the present invention is applied to the fabrication of an optical device such as a modulation device will be described. FIG. 6 illustrates the manufacturing process.

First, as shown in FIG.
2, a compound semiconductor structure composed of an upper cladding layer 33, a strained multiple quantum well layer 34, and a lower cladding layer 35,
Processing is performed using the SiO ₂ film 31 as a mask as shown in FIG. 3B, and then flattening 37 and electrode formation 3 as shown in FIG.
8 was performed to obtain a target device.

Etching conditions: Cl ₂ / CH ₄ gas flow rate =
7 sccm / 3 sccm, etching pressure 0.25 mTorr, RF
Discharge density 35 kw / m ² , microwave discharge power 100 w
By using the ECR etching by the
To the lower cladding layer 35 can be anisotropically processed at a constant speed. Applying the method of the present invention, the lower cladding layer InA
By monitoring a large change in the In composition of the lAs and the InP substrate, more accurate processing can be performed together with the prediction based on the etching rate. In addition, it greatly contributed to shortening the manufacturing process and improving yield.

The processing of the element is performed at a depth of 2
Since μm or more processing is performed, the detection window contamination during etching, but the detection level was a problem to decrease, for each wafer processing ends, the cleaning treatment with oxygen (e.g., O ₂ gas flow rate 10 sccm, pressure 1.0mTorr , A microwave discharge power of 700 W and an RF discharge density of 14 kW / m ² ), which is 80%
As described above, the detection level has been improved.

[0021]

As described above, according to the present invention, selective dry etching of an InP-based compound semiconductor multilayer film such as InP, InGaAs, InAlAs or an electrode material containing In, which has been difficult to selectively process, can be performed. Was. Therefore, the present invention has facilitated the manufacture of a semiconductor device which has been difficult to realize until now. In addition, since the etching state can be monitored almost in real time, high-precision etching control can be performed, and the production yield of semiconductor devices has been dramatically improved, and the performance of these devices has been greatly improved.

[Brief description of the drawings]

FIG. 1 is a spectrum diagram of an emission wavelength at the time of etching InGaAs.

FIG. 2 is a block diagram of an etching control system using an emission wavelength of 470 nm.

FIG. 3 is an explanatory diagram of processing control by observing an emission wavelength of 470 nm.

FIG. 4 is a sectional view showing an HBT element manufacturing process according to one embodiment of the present invention.

FIG. 5 is a diagram illustrating an example of 470n during HBT crystal processing according to an embodiment of the present invention.
Explanatory drawing of monitoring of m emission.

FIG. 6 is a sectional view showing a step of manufacturing an EA modulation element according to one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Etching reaction chamber, 2 ... Light receiving part, 3 ... Monochromator or monochromatic filter, 4 ... Photomultiplier, 5 ... End point controller, 6 ... Etching controller, 7 ... Wafer, 11
... Tungsten silicide emitter electrode, 12 ... nI
n _0.5 Ga _0.5 As / n-GaAs emitter cap layer, 1
3... N-Al _x Ga _{1 -x} As emitter layer (x = 0 → 0.
3), 14... P-Al _x Ga _{1 -x} As base layer (0.1 ⇒
0), 15 ... un-GaAs collector layer, 16 ... n-G
aAs subcollector layer, 17: semi-insulating GaAs substrate,
18 ... side wall SiO ₂ film, 19 ... SiO ₂ film, 20 ... base electrode 21 ... collector electrode, 31 ... SiO ₂ mask,
32 ... p-InGaAs cap layer, 33 ... p-InA
lAs upper cladding layer, 34... strained multiple quantum well layer, 3
5 ... n-InAlAs lower cladding layer, 36 ... n-In
P substrate, 37: planarization film, 38: electrode.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication location H01L 21/331 H01L 29/72 29/73

Claims (4)

[Claims] In a step of dry-etching a material containing In using a gas containing chlorine (Cl) as an element or a compound (hereinafter referred to as a chlorine-based gas),
An etching end point detection method, characterized in that etching is controlled by using an emission wavelength around 470 nm that appears based on a reaction between Cl and Cl. 2. The dry etching method according to claim 1,
An etching end point detection method which is a dry etching method using a chlorine-based gas, a mixed gas of a chlorine-based gas and a methane-based hydrocarbon gas, or an alkyl halide gas as an etchant. 3. The material according to claim 1, wherein the material to be etched has a compound semiconductor heterostructure including a compound semiconductor layer containing In and a layer not containing In or a layer having a different composition containing In. An etching end point detection method. 4. The etching end point detecting method according to claim 1, further comprising the step of cleaning the surface of the emission wavelength detection window with oxygen plasma immediately before etching to facilitate the detection of the emission wavelength near 470 nm.