JPH06163469A - Semiconductor etching using method and manufacture of photodetector by using the same - Google Patents

Abstract

PURPOSE:To provide a method of etching a semiconductor substrate, wherein the substrate can be accurately etched as deep as prescribed with gas plasma even if gas plasma fluctuates in state. CONSTITUTION:A semiconductor layer 12 different from a semiconductor substrate 11 in composition is formed on the semiconductor substrate 11, the semiconductor layer 12 is dry-etched from above toward the semiconductor substrate 11, the concentration of elements contained in plasmatic gas inside an etching chamber 21 where the semiconductor substrate 11 is placed is detected, a point at which elements contained in plasmatic gas inside an etching chamber 21 are changed in concentration is detected at the time when the semiconductor layer 12 is etched up to a boundary surface 13 between the semiconductor layer 12 and the semiconductor substrate 11, and then an etching operation is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound semiconductor layer formed on a substrate or a method for etching a compound semiconductor substrate, and more particularly to a one-dimensional or two-dimensional photodetector on the compound semiconductor layer or compound semiconductor substrate. The present invention relates to an etching method for forming an inter-element isolation groove when it is selectively formed.

Infrared detectors are one-dimensionally mounted on a compound semiconductor substrate such as mercury, cadmium, tellurium (HgCdTe),
Alternatively, in the case of arranging two-dimensionally, an element isolation groove for element isolation between the elements is required.

[0003]

2. Description of the Related Art Such element isolation trenches are formed by using a dry etching method or the like. As such a dry etching method, Japanese Patent Laid-Open No. 55-85674 discloses a dummy etching method in a dry etching apparatus. There is a method of previously detecting an etching amount with respect to an etching time using a substrate and etching a predetermined semiconductor substrate to be etched to a predetermined depth based on the detected information.

Alternatively, as another method, JP-A-61-1
As disclosed in Japanese Patent No. 15326 and shown in FIG. 3, impurity atoms are introduced in a predetermined pattern from the surface of the semiconductor substrate 1 to a predetermined depth d to be etched by using the insulating film 2 as a mask. 1 is gas-etched from the surface, and the element contained in the etched gas is detected.

When the semiconductor substrate 1 is etched to a predetermined depth to be etched from the surface, the impurity atoms introduced from the surface of the semiconductor substrate 1 cannot be detected. Therefore, a method of setting that point as the end point of etching is adopted. ing.

[0006]

However, in the first method described above, the gas plasma, which is the etching atmosphere, is kept in the same state when the dummy substrate is etched and when a predetermined non-defective substrate is etched. This gas plasma is liable to be affected by the concentration of the plasma etching gas, the high frequency power used for the plasma etching, etc., and it is difficult to maintain the gas plasma at a constant level.

In the second method, it is necessary to introduce impurity atoms for detecting the end point of etching into the semiconductor substrate to be etched. During the etching process, the introduced impurity atoms evaporate and the etching container is etched. There is a risk that the semiconductor substrate to be filled and etched will be contaminated.

The present invention solves the above-mentioned problems and provides a condition for forming a gas plasma which is an etching atmosphere, that is, an etching gas concentration for forming a gas plasma or a high frequency power, while introducing an impurity atom. It is an object of the present invention to provide a method for etching a semiconductor which does not require and prevents the semiconductor substrate to be etched from being contaminated by the introduced impurity atoms.

[0009]

According to a first aspect of the present invention, there is provided a method for etching a semiconductor substrate, wherein a semiconductor layer having a composition different from that of the substrate is formed on the semiconductor substrate, and the semiconductor substrate is formed on the semiconductor layer. While performing dry etching along the direction of, detecting the concentration of the elements contained in the plasma-like gas in the etching chamber in which the semiconductor substrate is installed, when the boundary surface between the semiconductor layer and the semiconductor substrate is etched, It is characterized in that the point where the concentration of the element contained in the plasma-like gas in the etching chamber changes is set as the end point of the etching.

Further, as described in claim 2, dry etching is performed along the bottom surface side from the surface of the semiconductor substrate formed of the semiconductor layer in which the composition of the contained element is continuously changed, and the semiconductor substrate is installed. Detects the concentration of the element contained in the gas in the etching chamber, and detects the layer in which the concentration ratio of the element contained in the detected gas in the etching chamber matches the predetermined layer of the semiconductor layer whose composition continuously changes. Then, the etching depth from the surface of the semiconductor substrate is detected.

According to a third aspect of the present invention, the semiconductor substrate according to the first or second aspect is made of lead / tin / tellurium.
It is characterized by being a ternary compound semiconductor of mercury, cadmium, tellurium, or mercury, zinc, tellurium.

The method for manufacturing a photo-detecting element of the present invention is characterized by including a step of forming an element isolation groove in a semiconductor substrate by using the etching method according to the above-mentioned claim 1 or 2. .

[0013]

According to the etching method of the present invention, the composition ratio of the semiconductor substrate or the semiconductor layer formed on the substrate
Alternatively, the detection is performed by the emission intensity ratio of each element forming the semiconductor layer.

As shown in FIG. 1 (b), Hg _1-x Cd _x Te (x = 0.
3) A Hg _1-x Cd _x Te (x = 0.2) layer 12 is grown on the substrate 11 to a thickness similar to the depth to be etched, and the Hg _1-x Cd _x Te (x = 0.
2) Dry etching is performed from the surface of the layer 12 along the depth direction using chlorine gas plasma. And this Hg _1-x Cd _x Te
(x = 0.3) Etching chamber 21 shown in FIG.
The element concentration of each element contained in the gas inside the emission spectroscopic analyzer installed in the etching chamber 21 through the light transmission window 23
Detect at 22.

The depth of this dry etching is Hg
_1-x Cd _x Te (x = 0.3) substrate 11 and Hg _{1- x} Cd _x Te (x = 0.2) layer
When reaching the boundary surface 13 of 12, the emission intensity ratio of each element of mercury and cadmium changes, and the end point of etching can be detected by detecting it.

Further, in FIG. 1 (c), along the depth direction of the substrate
Hg _1-x Cd in which the x value fluctuates sequentially such as 0.2, 0.25, 0.3
_In the process of forming a Hg _1-x Cd _x Te substrate 15 composed of _x Te layers 12, 12A and 12B and dry etching the Hg _1-x Cd _x Te substrate 15, the emission intensity ratio of each element of mercury and cadmium is Change,
By detecting it, the concentration ratio of each element of mercury and cadmium can be known, so that the composition ratio (x value) is known, and this value makes it possible to detect the dimension of the depth etched from the substrate surface.

By such a method, it is possible to perform etching to a depth of a predetermined dimension even in the state of gas plasma having different etching rates, and this method does not adopt a method of introducing impurity atoms into the substrate. Therefore, the contamination of the semiconductor substrate by the impurity atoms is eliminated.

[0018]

Embodiments of the present invention will be described in detail below with reference to the drawings. 1 (a) is an explanatory view of an apparatus used in the method of the present invention, FIG. 1 (b) is a sectional view of a semiconductor substrate used in the first embodiment of the present invention, and FIG. 1 (c) is a second embodiment of the present invention. It is sectional drawing of the semiconductor substrate used for an example.

[First Embodiment] FIG. 1A is a plan view showing a substrate mounting table 24 in an etching chamber 21 of the dry etching apparatus shown in FIG.
The Hg _1-x Cd _x Te substrate 11 shown in (b) is placed. This substrate has a thickness equal to the depth to be etched on a Hg _1-x Cd _x Te substrate 11 with an x value of 0.3, as shown.
The Hg _1-x Cd _x Te layer 12 having a value of 0.2 is formed by the vapor phase growth method or the like.

After the inside of the etching chamber 21 accommodating the Hg _1-x Cd _x Te substrate 11 described above is evacuated, chlorine gas is introduced into the plasma generation chamber 25 connected to the etching chamber 21 from the gas introduction port 26. The chlorine gas introduced into the plasma generating chamber 25 becomes plasma by the microwave of 2.45 GHz introduced from the microwave oscillator 27 connected to the plasma generating chamber 25, and resonates by the exciting coil 28. Ion extraction power supply 29
As a result, chlorine gas ions from this plasma-like gas
_{The 1-x} Cd _x Te substrate 11 is pulled out to reach the substrate 11 and the substrate is etched.

Further, a transparent light transmitting window 23 made of quartz glass or the like is provided in the etching chamber 21, and an emission spectroscopic analyzer 22 is installed so as to face the light transmitting window 23, and a plasma-like inside the etching chamber 21 is provided. By detecting the wavelength of light generated from the gas with the emission spectroscopic analyzer 22, the concentration of the element contained in the plasma-like gas is continuously detected.

In this case, since it is a substrate etching process, unlike the vapor deposition or the like, the light transmitting window 23 is less likely to be fogged. Then, when the Hg _1-x Cd _x Te layer 12 with an x value of 0.2 is etched and reaches the Hg _1-x Cd _x Te substrate 11 with an x value of 0.3, the amount of each element of mercury and cadmium changes. So
That point is the end point of etching.

[Second Embodiment] In the second embodiment of the present invention, FIG.
A Hg _1-x Cd _x Te substrate 15 as shown in 1 (c) is placed. This Hg _1-x Cd _x Te substrate 15 is a Hg _1-x Cd _x Te layer in which the x value continuously changes as 0.2, 0.25 and 0.3 along the dimension of a predetermined depth from the surface of the substrate. It is a semiconductor substrate having 12,12A, 12B.

Thus, the x values are 0.2, 0.25, 0.3
Hg that changes continuously like_1-xCd _xTe layers 12, 12A, 12B
Consists of Hg_1-xCd_xEtching the Te substrate 15 from the surface,
Mercury and cad of plasma-like gas contained in the etching chamber
Continuous measurement of the concentration of elemental elements of
The elemental amount of Mium is Hg_1-xCd_xTe layer 12, 12A, 12B prescribed
If a point that matches the layer is detected, Hg_1-xCd_xTe substrate 15 table
Hg etched from the surface_1-xCd_xTe layer 12, 12A, 12B depth
Can be detected.

FIG. 2 shows a manufacturing process diagram of a two-dimensional infrared sensing element having an element isolation groove (depth of 5 μm) formed by the method of the present invention. As shown in FIG. 2 (a), a ternary compound semiconductor substrate of HgCdTe is used as a semiconductor substrate used for forming the photodetector, and a ternary compound semiconductor substrate of HgCdTe is formed on the p-type Hg _1-x Cd _x Te (x = 0.3) substrate 11. Grows a p-type Hg _1-x Cd _x Te layer (x = 0.2) 12 with a size of 5 μm,
Element isolation trenches are formed to a depth of 5 μm from the surface of the 5 μm p-type Hg _1-x Cd _x Te layer (x = 0.2) 12.

Next, as shown in FIG. 2 (b), Hg _1-x Cd _x Te
Boron atoms are ion-implanted into a predetermined region of the layer (x = 0.2) 12 to form an n ⁺ layer 31. Then, as shown in FIG. 2 (c), the Hg _1-x Cd _x Te layer (x = 0.2) was formed using the method of the first embodiment of the present invention.
Hg _1-x Cd _x Te (x = 0.3) from the surface of 12 Boundary 13 of substrate 11
Until, etching with chlorine gas plasma, element separation groove 32
To form.

Then, as shown in FIG.
A surface protective film 33 made of a zinc sulfide (ZnS) film is formed on the surface of the substrate 11 on which the film 32 is formed by vapor deposition. Then, as shown in FIG. 2 (e), a contact hole is formed at a predetermined position of the surface protection film 33, an n ⁺ layer electrode 34 made of In and a gold electrode 35 are formed on the p type layer, and then a photo-voltaic material is formed. A power type infrared detector is formed.

[0028]

As described above, according to the present invention,
Even if the state of plasma gas changes, the semiconductor substrate can be etched to a predetermined depth, and impurity atoms do not evaporate during the etching process. Therefore, there is an effect that a highly reliable infrared detecting device can be formed.

[Brief description of drawings]

FIG. 1 is an explanatory view of an etching apparatus and a semiconductor substrate used in a method of the present invention.

FIG. 2 is a cross-sectional view showing a manufacturing process of a photo detector using the method of the present invention.

FIG. 3 is an explanatory diagram of a conventional method.

[Explanation of symbols]

11,15 Hg _1-x Cd _x Te substrate 12,12A, 12B Hg _1-x Cd _x Te layer 13 Interface 21 Etching chamber 22 Emission spectroscopy analyzer 23 Light transmission window 24 Substrate installation table 25 Plasma generation chamber 26 Gas introduction Mouth 27 Microwave oscillator 28 Excitation coil 29 Ion extraction power supply 31 n ⁺ layer 32 Isolation groove between elements 33 Surface protective film 34,35 Electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yuko Nakamura 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited Fujitsu Limited (72) Nobuyuki Kajiwara, 1015, Kamikodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Fujitsu Limited

Claims (4)

[Claims] 1. A semiconductor layer (12) having a composition different from that of the substrate is formed on a semiconductor substrate (11), and dry etching is performed on the semiconductor layer (12) along the direction of the semiconductor substrate (11).
The concentration of an element contained in the plasma-like gas in the etching chamber (21) in which the semiconductor substrate (11) is installed is detected, and the boundary surface (13) between the semiconductor layer (12) and the semiconductor substrate (11) is detected. A method for etching a semiconductor, characterized in that a point at which the concentration of an element contained in a plasma-like gas in an etching chamber (21) fluctuates at the time of etching, and is set as an end point of etching. 2. A semiconductor substrate (15) consisting of semiconductor layers (12, 12A, 12B) in which the composition of the contained elements continuously changes, and dry etching is performed along the bottom surface side from the surface of the semiconductor substrate (15). ) Is installed to detect the concentration of the element contained in the gas in the etching chamber (21), the concentration ratio of the element contained in the gas in the detected etching chamber (21), the composition continuously changes Semiconductor layer (12,12
(A, 12B) Detects the layer that matches the specified layer and the semiconductor substrate (1
A method for etching a semiconductor, which comprises detecting the etching depth from the surface of 5). 3. The semiconductor substrate according to claim 1 or 2.
(15) is lead, tin, tellurium, mercury, cadmium, tellurium,
Alternatively, it is a semiconductor etching method characterized by being a ternary compound semiconductor of mercury, zinc and tellurium. 4. A method for manufacturing a photo-sensing element, comprising the step of forming an element isolation groove (32) in a semiconductor substrate (11) by using the etching method according to claim 1. .