JPH07106688A - Semiconductor device and fabrication thereof - Google Patents

Abstract

PURPOSE:To prevent exfoliation of an electrode deposited thickly on a substrate due to stress. CONSTITUTION:In one embodiment, a vertical resonator type surface emission laser comprises a p-type mirror 103, an active layer 104, and an n-type mirror 105 formed on a substrate 101. Furthermore, an electrode 107, an Au layer 108, and an Ni layer 109 are formed on the n-type mirror 105. Since the layer 108 of Au having Young's modulus of 7.8X10<10> is formed below the layer 109 of Ni having Young's modulus of 20X10<10>, exfoliation of Ni layer 109 is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a mask for dry etching and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, resists, insulators such as SiO ₂ and metals such as Ti and Ni have been used for dry etching masks. In particular, when dry etching is performed with a mixed gas containing a strongly corrosive gas such as chlorine gas or bromine gas, a metal mask such as Ni is effective.
When performing dry etching with a mixed gas containing a corrosive gas, if the ultimate vacuum is a high vacuum, resist or SiO
Sometimes ₂ is used.

[0003]

However, the above-mentioned conventional structure has the following problems.

When the crystal to be etched is etched by a mixed gas containing a strongly corrosive gas such as chlorine, resist or SiO ₂ may not be used depending on the etching conditions. In such a case, metal is used as a mask, but if the selection ratio of crystal and mask is not large,
The metal mask must be deposited thick. However,
A metal having a large Young's modulus has a large stress due to a slight strain due to a temperature change during vapor deposition, and overcomes the bonding force with the base to be peeled off. For this reason, the mask may or may not be formed well, and there is a problem in reproducibility.

The present invention solves the above-mentioned conventional problems, and provides a semiconductor device having a dry etching mask / electrode which has good reproducibility and does not come off even when a metal having a large Young's modulus is vapor-deposited, and a manufacturing method thereof. With the goal.

[0006]

In order to solve this problem, the present invention relates to an electrode deposited on a semiconductor thin film, and a metal 1 deposited on the electrode and having a Young's modulus of less than 11 × ^{10 10} Pa. , Young's modulus of 11 × ^{10 10} deposited on the metal 1.
The metal 2 having Pa or more prevents the metal 2 having a large Young's modulus from peeling off.

Alternatively, the metal 1 deposited on the semiconductor thin film
And the Young's modulus of 11 × ^{10 10} Pa deposited on the metal 1.
And a metal 3 deposited on the metal 2 and having a Young's modulus of 11 × ^{10 10} Pa or more. However, as the metal 1 in this case, one having good adhesion is used.

[0008]

With this structure, the metal A having a small Young's modulus relaxes the strain of the metal B having a large Young's modulus. If Young's modulus is E, strain is ε, and stress is σ,
.epsilon. =. sigma./E (Equation 1).
According to (Equation 1), even if the strain ε is the same, the stress σ increases as the Young's modulus E increases. The stress σ causes the metal to peel off. When the metal A having a small Young's modulus E is formed below, the metal A itself is distorted, so that the strain of the metal B is relaxed. As a result, the stress σ generated in the metal B is also relaxed. Further, the adhesion force between metals may be larger than the adhesion force between metals and crystals. Therefore, without directly forming a metal with a large Young's modulus on a crystal, by sandwiching a metal with a small Young's modulus between them, It is possible to prevent the peeling of metal having a large Young's modulus.

[0009]

EXAMPLES Example 1 Hereinafter, examples of the present invention will be described in detail. In FIG. 1, a surface emitting laser will be described as an example. FIG. 1 shows that the present invention has a Young's modulus of 7.8 × 10.
¹⁰ is a cross-sectional view of a vertical cavity surface emitting laser in which a metal (Au) of ¹⁰ is formed under a metal (Ni) having a Young's modulus of 20 × ^{10 10} , and Ni functions as a mask for dry etching.

When a current is passed through Ni109, InGa
Carriers are confined in the As / GaAs quantum well (QW) layer 104 to emit light. The light is reflected by the upper and lower Bragg reflectors 103 and 105, and laser oscillation occurs. Although the upper reflector has a smaller number of laminated layers than the lower reflector, AuGe
Since the reflectance is improved by the Ni electrode 107, light emission is emitted from the back surface of the substrate 101. Ni115 is a mask used in the dry etching for forming the mesa of the surface emitting laser, and is 2200Å in this embodiment. Ni
When only 115 is vapor-deposited around 2000 Å, it peels off due to the stress of Ni itself, so the AuGeNi electrode 113 and Ni1
The Au 113 is sandwiched between 15. In this embodiment, 2000
It has a thickness of Å.

By laying Au whose Young's modulus is smaller than that of Ni, a part of the strain of Ni115 becomes the strain of Au114 and is relaxed, and the stress of Ni115 is also reduced by (Equation 1). Since the bonding force between Ni and Au is larger than this stress, Ni cannot be peeled off.

On the other hand, the Young's modulus of Au114 is Ni11.
5, the strain amount is considered to be about the same as that of Ni115. Therefore, the stress generated between the Au114 and the AuGeNi electrode 113 is smaller than the stress between the Au114 and the Ni115. In this way, the stress generated in Ni115 is reduced by forming a metal having a small Young's modulus thereunder, and peeling is prevented.

In the present embodiment, Au114 is set to 200
Although 0Å and Ni115 are set to a thickness of 2200Å, if it is desired to change the thickness of Ni115 depending on the dry etching conditions and time, the thickness of _Au is t _Au and the thickness of Ni is t.
_{When Ni} , Ni so that the relationship of (Equation 2) below is satisfied
If the thickness of 115 is increased or decreased, it can be formed without causing peeling of Ni115. Further, the results of examining the presence or absence of peeling while changing the thicknesses of Ni and Au are listed in (Table 1).

The meanings of the symbols are as follows. ⊚ indicates that there was no peeling at all, ◯ indicates that there was partial peeling, and X indicates that the peeling was complete. Although Au is used as the metal that relaxes the stress of Ni in the present embodiment, Sn, Zn, Al, Ag, or the like may be used. When the dry etching mask is formed directly on the crystal without forming the AuGeNi electrode 113, 100 Å of Ti is formed to improve the adhesiveness, and Sn or Zn is formed on it to match the conductivity type of the crystal. Finally, Ni may be formed.

T _Ni / t _Au ≤0.38 ... Equation 2

[0016]

[Table 1]

(Embodiment 2) FIGS. 2A to 2D are sectional views of steps in one embodiment of the present invention. Here, a method of manufacturing the surface emitting laser shown in FIG. 1 will be described as an example.

MBE is used on the n-GaAs 201 substrate to p-GaAs buffer layer 202 and p-GaAs / p.
-AlAs 203, InGaAs / GaAs QW (quantum well) 204, n-GaAs / n-AlAs 20
5, n ⁺ -GaAs 206, Au 208, and Ni 209 are grown in this order (FIG. 2 a).

Next, AuGeNi electrode 207 and Au20
8 and Ni209 are formed by the photolithography method and the lift-off method (FIG. 2b). AuGeNi electrode 207, Au2
The thicknesses of 08 and Ni 209 are as described in Example 1. The Young's modulus of Au is 7.8 × ^{10 10} Pa and the Young's modulus of Ni is about 20 × ^{10 10} Pa. For the reason explained in Example 1, the thickness relationship between Au 214 and Ni 215 should satisfy (Equation 2). For example, Ni215 is 200
It does not peel off even if vapor deposition is performed over 0Å.

Dry etching using a mixed gas containing chlorine and argon (reactive ion etching; RI
In step E), the surface emitting laser mesa is formed (FIG. 2C). At this time, Ni 215 and Au 214 act as a mask for dry etching. Dry etching can be performed under the conditions described below.

[0021] The back pressure (ultimate vacuum) is 9X10 ^over 6 Torr
Hereinafter, the etching power is 100 W or more, the reaction pressure is 0.5 mTorr or more and 50 mTorr or less, the chlorine flow rate is 1 sccm or more, and the argon flow rate is 1 sccm or more. Of these, the optimum conditions, the back pressure 1X10 ^over 6 Torr
Hereinafter, the etching power is 300 W or more and 600 W or less,
Reaction pressure is 10 mTorr or more and 30 mTorr or less, both chlorine flow rate and argon flow rate are 2 sccm or more and 10 sccc
When it is m or less.

In this embodiment, a mixed gas of chlorine gas and argon gas was used for dry etching.
1, a mixed gas containing a strongly corrosive gas such as HBr or Br ₂ ,
Alternatively, dry etching may be performed with a mixed gas of a gas containing a halogen element such as SiCl ₄ .

Although Ni209 is left as it is after the dry etching in this embodiment, if it is necessary to remove it after the dry etching is finished, the resist is used as a mask and
It can be removed by dipping in dilute hydrochloric acid.

[0024]

As described above, the present invention has a Young's modulus of 1 or less.
Young's modulus is 11X1 on metal 1 of less than 1X10 ¹⁰ Pa
By forming the metal 2 of 0 ¹⁰ Pa or more, the strain of the metal 2 is relaxed by the strain of the metal 1. As a result, the stress generated between the metal 1 and the metal 2 is relaxed, and the peeling of the metal 2 is prevented.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a surface emitting laser according to an embodiment of the present invention.

FIG. 2 is a sectional view of a manufacturing process of a surface emitting laser according to an embodiment of the present invention.

[Explanation of symbols]

101 n-GaAs substrate 102 p-GaAs buffer layer 103 p-GaAs / AlAs 104 InGaAs / GaAs QW 105 n-GaAs / AlAs 106 n ⁺ -GaAs 107 AuGeNi electrode 108 Au 109 Ni 201 n-GaAs substrate 202 p-GaAs Buffer layer 203 p-GaAs / AlAs 204 InGaAs / GaAs QW 205 n-GaAs / AlAs 206 n ⁺ -GaAs 207 AuGeNi electrode 208 Au 209 Ni

Claims (7)

[Claims] 1. A substrate, a semiconductor thin film deposited on the substrate, an electrode deposited on the semiconductor thin film, a first metal deposited on the electrode, and the first metal. A semiconductor device comprising a second metal deposited on a metal, wherein a difference in Young's modulus between the first metal and the second metal is 8 × ^{10 10} Pa or more. 2. A substrate, a semiconductor thin film deposited on the substrate, a first metal deposited on the semiconductor thin film, and the first metal.
A second metal deposited on the second metal and a third metal deposited on the second metal, the first metal and the second metal
A semiconductor device having a Young's modulus difference of 8 × ^{10 10} Pa or more. 3. A substrate, a semiconductor thin film deposited on the substrate, a first metal, a second metal deposited on the first metal, the first metal and a semiconductor. A third metal is provided between the surface atom of the semiconductor thin film and the third metal, and the binding energy between the surface atom of the semiconductor thin film and the third metal is the binding energy between the surface atom of the semiconductor thin film and the second metal; 3. The semiconductor device according to claim 2, wherein the bond energy between the surface atoms of the semiconductor thin film and the first metal is larger. 4. A step of forming an electrode on a semiconductor thin film deposited on a semiconductor substrate, a step of forming a first metal on the electrode, and a step of forming the first metal on the first metal. A method of manufacturing a semiconductor device, comprising: a step of forming a second metal having a Young's modulus difference of 8 × ^{10 10} Pa or more; and a step of dry-etching the semiconductor thin film on the semiconductor substrate. 5. The method of manufacturing a semiconductor device according to claim 4, wherein the dry etching uses a mixed gas containing a strongly corrosive gas. 6. The dry etching uses a mixed gas containing a gas containing a halogen element.
A method for manufacturing a semiconductor device as described above. 7. The method of manufacturing a semiconductor device according to claim 4, further comprising a step of removing the metal 2 by wet etching subsequent to the dry etching.