JPS6235614A - Substrate for vapor growth - Google Patents

Abstract

PURPOSE:To contrive improvement in the yield of production by a method wherein, after AlxGa1-xAs (0.4<x<1) is deposited on a GaAs substrate, the GaAs containing one or more of Sn, Te, Se and S is deposited thereon. CONSTITUTION:The GaAs having the main surface inclined at an angle of 2 deg. or more in the direction from {100} to <110> is used as the main substrate, and after AlxGa1-xAs (0.4<x<1) is deposited in 2 micrometers or more thereon, GaAs containing at least 10<17>/cc or mroe of one of Sn, Te, Se and S is deposited in 5 micrometers or more. As a result, the title substrate having no mechanical damage can be manufactured easily and the yield of production can also be improved.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a substrate for vapor phase growth.

[Prior art]

In recent years, there has been a demand for higher performance in semiconductor devices used in the microwave and millimeter wave regions, and GaAs, in particular, has become widely used because its electron mobility is about six times higher than that of silicon, etc. It's here. However, GaAs has a thermal conductivity that is three times lower than that of silicon, so in order to fully demonstrate its performance, it is necessary to reduce the thickness of the device as much as possible, and the final thickness is 10 micrometers or less. There are times when you have to.

Conventionally, for example, when manufacturing millimeter wave devices.

After forming a device on a substrate, a metal electrode is formed on the entire surface, and a material with high thermal conductivity such as gold, silver, or copper with a thickness of 50 micrometers or more is deposited on it by electroless or electrolytic methods. After plating, the back surface of the device is mechanically or chemically polished or etched to make a thin layer using this as a support base, and the back surface electrode of the device is formed using well-known metal electrode forming technology and photo-etching technology. After forming and separating individual devices by chemical or electrochemical etching, the supporting base metal plate is cut to separate individual device chips. The supporting substrate metal not only serves as a support for thinning the device, but also acts as a heat sink, and is usually plated.
It is called ``ated heat 5 ink''.

However, this method has the following drawbacks. That is, a thick plating layer usually tends to have thick edges, and the plated surface itself often only has a flatness of about 10 micrometers. Since the final thickness of a microwave or millimeter wave device itself is about 10 micrometers, in order to use such a thickly plated metal as a support base, it is necessary to flatten the plated metal itself.

After flattening in this way, it is necessary to use this as a reference plane to thin the GaAs containing the device to a desired thickness by polishing, chemical etching, or the like. However, GaAs has lower hardness than silicon and is mainly used (I
The crystal plane of the QO) plane has strong interwall properties and anisotropy in mechanical properties, which has the drawback of being easily damaged during thin layer polishing.

Among millimeter-wave devices using GaAs, examples of devices that require particularly thin layers are devices that generate a lot of heat, such as Invat diodes, Mitat diodes, Tunnet diodes, and Gunn diodes. can. All of these are active elements and are widely applied to oscillation and amplification. These devices are used at frequencies ranging from 50 GHz to 400 GHz, and as the operating frequency increases, the conversion efficiency from direct current to millimeter waves decreases, so they must have a thinner structure. For example, in the case of a tannet exceeding 300 gigahertz, it is said that the thickness of the device is desirably 5 micrometers or less. In order to manufacture this without mechanical damage, it is necessary to rely on chemical or electrical corrosion, but since the (100) plane that is mainly used is not the closest crystallographic plane, the above chemical Depending on the method of target or electrochemical etching, the controllability of the thickness is not only poor, but also the thickness varies significantly within the wafer plane, resulting in a decrease in device manufacturing yield and, as a result, an increase in cost.

[Specific measures to solve the problem]

As a result of intensive research into specific means for solving the above-mentioned problems, the inventors of the present invention used GaAs, whose main surface is tilted by more than 2 degrees from the (100) to <110> direction, as the main substrate, and on this GaAs After depositing Ga+-xAs (z>0°4) to a thickness of 2 micrometers or more, Sn, Te,
At least one of Se and S at 10'/cc
The present invention has been completed based on the finding that by depositing GaAs containing the above to a thickness of 2 micrometers or more, the above-mentioned problems can be solved, and it can be manufactured extremely easily and the yield can be significantly increased while completely eliminating mechanical damage. It is.

[Effect]

The substrate for vapor phase growth of the present invention has a main surface of (100) Ga.
As, AQxGa+-x As (z>0.4)
Since the rate of chemical corrosion is greatly different between the two, it is possible to make the substrate thinner, and in this case, by tilting the main surface of the GaAs twice in the <110> direction, it is possible to prevent the occurrence of surface defects. Ga that becomes the element formation region layer
Hole mobility can be increased by including at least one of Sn, Te, Ss, and S in As.

[Embodiments of the invention]

It is well known that the GaAs (100) surface is easily chemically corroded by a mixture of ammonia and hydrogen peroxide. For example, 28% ammonia water (NH40H),
! l:30% hydrogen peroxide solution (7) In a 1:10 mixture, GaAs dissolves at a rate of approximately 15 micrometers per minute, and in a 1:20 mixture, GaAs dissolves at a rate of approximately 10 micrometers per minute. It is known that it is corroded and dissolved. On the other hand, in Ga x A Q +-xlhi, χ
In the case of 0.4, the thickness is less than 0.75 micrometers per minute as it is dissolved and removed by chemical corrosion for a 1:10 mixture, and the same <0.0 for a 1:20 mixture.
It is known to be less than 5 micrometers per minute. This means that GazAQ+-:I: As (z<
0.4) and GaAs, the rate of chemical corrosion is greatly different, and it can be seen that if a mixed solution of ammonia water and hydrogen peroxide water is used, only GaAs can be effectively and selectively dissolved and removed.

On the other hand, GaAs suffers almost no chemical corrosion from hydrofluoric acid, but GaLAQl-X As (z<0.4
) is known to be extremely easily subject to chemical corrosion.

Furthermore, since the lattice constants between GaAs and GayAQt -x As (χ 004) are extremely close, epitaxial growth can be easily performed in multiple layers.

Therefore, using qaAs as a substrate, Gax, AQ
, - air As (χ(0,4)) is deposited, and G
The substrate on which aAs is deposited is used as the starting substrate, and the top layer of GaA is
A new final desired device is formed on the s-plane, a gold plating layer is applied thick enough to support the thin device (e.g., 50 micrometers or more), and then the first GaAs substrate on the opposite side is treated with ammonia. When removed with hydrogen peroxide solution, chemical corrosion becomes GaEAQl-X, As(χ<0
．． It almost stops automatically at 4). This allows devices to be made thinner without causing mechanical damage, but GaxA
Since As (χ<0.4) has lower electron mobility than GaAs, Gax
. If a predetermined device is separated into a predetermined size by chemical etching, the device can be formed without being damaged by machining.

As explained in detail above, GaAs −GaχAQ+−
A substrate having a three-layer structure of As-GaAs is very effective in forming millimeter-wave devices, but in order to apply this to actual millimeter-wave devices, it is necessary to add the following conditions. GaAs has extremely low hole mobility compared to its electron mobility, so in practice, the conductivity type of GaAs used in millimeter wave devices is often that at least the starting substrate should be N-type conductivity type. . In addition, this N-type conductive region generally has an impurity density of at least 1017/cc because it is necessary to finally provide a resistive contact metal electrode.
It is necessary that it is above.

Furthermore, in millimeter-wave devices, the active layer has an extremely thin thickness of several micrometers or less, so the molecular beam epitaxial growth method is used to form the active layer.
al Organic Chemical Vapor
It is necessary to use epitaxial growth methods capable of forming thin active layers, such as MOCVD or vapor phase growth using halides.

In these growth methods, for example, when the (100) main surface of GaAs is used, unless a crystal surface is provided in which the main surface is cut at a certain angle with respect to a specific crystal orientation, epitaxial growth will not occur. It is known that surface defects such as unevenness, pyramids, voids, and pits are likely to occur on the surface during the process. Therefore, GaAs-Gar-A
12t-CAs (Z < 0, 4)-GaAs
The GaAs layer, which is the largest layer of the three-layer structure substrate, contains at least one of Sn, Te, Se, and S, an impurity that provides N-type conductivity of at least 1017/cc, and (100) 110 towards the surface>2 in the direction
The board must be tilted by at least 100 degrees.

〔effect〕

As is clear from the above explanation, the substrate for vapor phase growth according to the present invention can be manufactured extremely easily using chemical corrosion, that is, with no mechanical damage.
Moreover, the yield rate can be significantly increased.

Procedural amendment November 1985 Second H 1.Display of the incident 1985 Patent Application No. 176120 2. Name of the invention Substrate for vapor phase growth 3. Person who makes corrections Relationship to the case Patent applicant 4. Agent Self-originated 6. Number of inventions increased by amendment 7. Subject of correction Full statement 8. Contents of amendment (1) The entire specification is revised as shown in the attached sheet.

Description 1, Title of the Invention Substrate for Vapor Phase Growth 2, Claims GaAs whose main surface is inclined at least 2 degrees from the (100) to <110> direction is used as the main substrate, and A Q
G a l −X A S ("j〈After depositing
A substrate for vapor phase growth, characterized in that GaAs containing at least one of S at a concentration of 1017/cc or more is deposited to a thickness of 2 micrometers or more.

3. Detailed description of the invention [Industrial application field] The present invention relates to a substrate for vapor phase growth.

[Prior art]

In recent years, there has been a demand for higher performance in semiconductor devices used in the microwave and millimeter wave regions, and Ga AS- has come to be widely used because its electron mobility is about six times higher than that of silicon, etc. It has become. However, GaAs has a thermal conductivity that is three times lower than that of silicon, so in order to fully demonstrate its performance, it is necessary to make the device as thin as possible, and the final thickness is 10 micrometers. You may also need to:

Conventionally, for example, when manufacturing a millimeter wave device, after forming the device on a substrate, a metal electrode was formed on the entire surface, and a metal electrode with a thickness of 50 micrometers or more was made using a material with high thermal conductivity such as silver or copper. A high-quality material is plated by electroless or electrolytic methods, and then, using this as a supporting substrate, the back surface of the device is mechanically or chemically rubbed or etched to make it a thin layer, using well-known metal electrode forming techniques. After forming the back electrode of the device using photolithography and separating the individual devices by chemical or electrochemical etching, the supporting base metal plate is cut to separate the devices into individual device chips. The supporting substrate metal not only serves as a support for device thinning, but also acts as a heat sink, and is usually plated.
It is called ed heat 5 ink).

However, this method has the following drawbacks. That is, a thick plating layer usually tends to have thick edges, and the plated surface itself often has a flatness of only about 10 micrometers. Since the final thickness of a microwave or millimeter wave device itself is about 10 micrometers, in order to use such a thickly plated metal as a support base, it is necessary to flatten the plated metal itself.

After flattening in this way, it is necessary to use this as a reference plane to thin the GaAs containing the device to a desired thickness by polishing, chemical etching, or the like. However, GaAs has lower hardness than silicon and is mainly used (1
The crystal plane of the 00) plane has strong interfolding and anisotropy in mechanical properties, which has the drawback of being easily damaged during thin layer polishing.

Among millimeter-wave devices using GaAs, examples of devices that require particularly thin layers are devices that generate a lot of heat, such as Invat diodes, Mitat diodes, Tannet diodes, and Gunn diodes. be able to. All of these are active elements and are widely applied to oscillation and amplification. These devices are used at frequencies ranging from 50 GHz to 400 GHz, and as the operating frequency increases, the conversion efficiency from direct current to millimeter waves decreases, so they must have a thinner structure. For example, in the case of a tannet exceeding 300 gigahertz, it is said that the thickness of the device is desirably 5 micrometers or less. If we are to manufacture this without mechanical damage, we must rely on chemical or electrochemical corrosion, but since the (100) plane that is mainly used is not the closest crystallographic plane, the above chemical Depending on the method of corrosion or electrochemical corrosion, not only is the thickness controllable, but
Due to significant variations within the wafer plane, the manufacturing yield of devices is reduced, and as a result, costs are forced to increase.

[Specific Means for Solving the Problem] As a result of intensive research into specific means for solving the above-mentioned problem, the present inventor found that the main surface of the main substrate is from (100) to (1,10).
GaAs tilted by more than 2 degrees in the direction is used, and AQx
After depositing 2 micrometers or more of Gal-xAs (6~x(1)), Ga containing at least one of Sn, Te, Se, and S at least 1017/cc is deposited.
By depositing AS of 5 micrometers or more,
The above problems have been solved, and while there is no mechanical damage,
The present invention was completed based on the discovery that it can be manufactured extremely easily and the yield can be significantly increased.

[Effect]

The substrate for vapor phase growth of the present invention has a main surface of (100) Ga.
As and A Q K Ga t-x
A s (Ocl- The generation of surface defects can be prevented by adding Sn, T, etc.
e, Se.

By containing at least one of S, hole mobility can be increased.

[Embodiments of the invention]

It is well known that the (100) plane of GaAs is easily chemically corroded by a mixture of ammonia and hydrogen peroxide. For example, 28% ammonia water (NH40
In a 1:10 mixture of H) and 30% hydrogen peroxide, G
aAs dissolves at a rate of approximately 15 micrometers per minute.
:20 is known to be corroded and dissolved at a rate of about 10 micrometers per minute. On the other hand, in the case of AQξGa+-As, the thickness that is dissolved and removed by chemical corrosion in a 1:10 mixture is less than 0.75 micrometers per minute when 0''+χ<1. , 1:20 is also known to be less than 0.05 micrometers per minute. This means that A Q ++, G a 1-χAs (0+ η<
It can be seen that the rate of chemical corrosion differs greatly between 1) and GaAs, and that if a mixed solution of aqueous ammonia and hydrogen peroxide is used, only GaAs can be effectively and selectively dissolved and removed.

On the other hand, G a A s hardly undergoes chemical corrosion by hydrofluoric acid, but A Q, G a +−x A s
It is known that (o,'+<or <1) is extremely easily subjected to chemical corrosion.

Furthermore, GaAs and A Q
Since the lattice constants between (“+”<1) are extremely close, epitaxial growth can be easily performed in multiple layers.

Therefore, using GaAs as a substrate, depositing An-Ga, -2A S (o, 'l- < 1) on it, and using the substrate on which GaAs is deposited as a starting substrate, A new final desired device is formed on the topmost GaAs surface, a gold plated layer of sufficient thickness (e.g., 50 micrometers or more) to support the thin device is then applied to the first layer on the opposite side. When the GaAs substrate is removed with ammonia and hydrogen peroxide, chemical corrosion almost automatically stops at the Au:cGat-xAs (X<l). This allows the device to be made thinner without causing mechanical damage, but AQCG a I-
Since the electron mobility of x, A s (Q<x<l) is lower than that of Ga A s, A
Only the layer QK Ga If a predetermined device is separated into a predetermined size by chemical etching, the device can be formed without being damaged by machining.

As explained in detail above, a substrate with a three-layer structure of GaAs-AQ, GaI-x, and As-GaAs is very effective in forming millimeter-wave devices, but it is difficult to actually implement this. In order to apply it to millimeter wave devices, it is necessary to add the following conditions. GaAs has extremely low hole mobility compared to its electron mobility, so in practice, the conductivity type of GaAs used in millimeter wave devices is often that at least the starting substrate should be N-type conductivity type. . Further, since it is generally necessary to finally provide a resistive contact metal electrode in this N-type conductive region, the impurity density in this region must be at least 10 17 /cc or higher.

Furthermore, in millimeter-wave devices, the active layer is extremely thin, several micrometers or less, so molecular beam epitaxial growth or Me
tal Organic Chemical Vapo
It is necessary to use epitaxial growth methods capable of forming thin active layers, such as rDeposition (MOCVD) or vapor phase growth using halides.

In these growth methods, for example, Q aA s (10
0) as the main surface If the crystal surface is not cut off from the main surface at a certain angle with respect to a specific crystal orientation, unevenness, pyramids, voids, pits, etc. will occur on the surface during the epitaxial growth process. It is known that surface defects are more likely to occur. Therefore, G a A s
A Q <Gal-χAs(C)・Feng<x<l
) For GaAs three-layer substrates, the topmost GaAs layer is doped with at least 10''/cc of N-type conductivity, ie, Sn.

The substrate needs to contain at least one of Te, Se, and S, and be inclined by 26 or more in the 110> direction with respect to the (100) plane.

〔effect〕

As is clear from the above explanation, the substrate for vapor phase growth according to the present invention can be manufactured extremely easily using chemical corrosion, that is, with no mechanical damage.
Moreover, the yield can be significantly increased.

Claims (1)

[Claims] GaAs whose main surface is inclined by more than 2 degrees from {100} to <110> direction is used as the main substrate, and Al_xGa
After depositing 2 micrometers or more of _1_-_xAs (x>0.4), 2 micrometers of GaAs containing 10^1^7/cc or more of at least one of Su, Te, Se, and S is deposited. A substrate for vapor phase growth characterized by having the above deposited.