JPH10189456A - Manufacture of compound semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method in which a mesa comprising a mask is buried on a surface so as to be flat by an MOCVD method. SOLUTION: A manufacturing method is composed of a first deposition process in which the deposition speed of a buried layer 7 is faster in a part near a mask 2 than in a region separated from the mask 2 and of a second deposition process in which the deposition speed of the buried layer 7 is slower in the part near the mask 2 than in the region separated from the mask 2. The flow rate ratio of a group V source gas to a group III source gas is designated as UN/UM, and a deposition temperature is designated as T. Then, a constant A and a constant C for an expression of log (UN/UM)=A(1/T)+C are found on the basis of UN/UM and T when the deposition speed in the part near the mask is equal to that in the region separated from the mask, a first deposition condition is expressed by log (UN/UM)>A(1/T<0> )+C, and a second deposition condition is expressed by log (UN/UM)<A(1/T<0> )+C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a compound semiconductor device, and more particularly to a method of depositing a compound semiconductor in which a mesa provided with a selective deposition mask on its upper surface is buried flat by an organometallic chemical deposition method.

In the manufacture of a compound semiconductor device, it is often necessary to embed both sides of a mesa formed on a substrate surface with a compound semiconductor. For example, there is a case where a mesa stripe of a semiconductor laser is embedded. For such embedding, a metal organic chemical deposition (MOCVD) method is often used.

However, the upper surface of the buried mesa has SiO
_{When a second} mask or the like is provided, it is difficult to bury the mesa flatly because the deposition rates are different between near and far from the mask. Therefore, there is a demand for a metal organic chemical vapor deposition method of a compound semiconductor in which a mesa having a mask on the upper surface is buried flat.

[0004]

2. Description of the Related Art A mesa formation and a mesa embedding process in a conventional compound semiconductor device will be described below with reference to an example of a mesa stripe semiconductor laser.

FIG. 5 is a cross-sectional view of a conventional mesa.
5A shows a mesa formed on the surface of the compound semiconductor substrate, and FIGS. 5B and 5C show shapes of the mesa and the buried layer. First, referring to FIG. 5A, an InGaAsP active layer 4, an InP cladding layer 5, and an InP
The GaAsP contact layer 6 is deposited in this order. Next, a stripe-shaped SiO ₂ mask 2 is formed on the surface of the contact layer 6, and the contact layer 6, the cladding layer 5 and the active layer 4 are etched using the mask 2 as an etching mask. To form The mesa 3 is formed such that the width of the upper surface is smaller than the width of the mask 2. Therefore, the mask 2 is
Remains in an overhanging shape.

Next, referring to FIG. 5B, the mask 2 used as an etching mask at the time of forming the mesa 3 is used as it is as a selective deposition mask in the metal organic chemical deposition method, and the metal organic chemical A buried layer 7 made of a compound semiconductor, for example, InP is selectively deposited by a deposition method, and the mesa 3 is buried.

[0007] However, the conventional buried layer deposited in the above-described step, as shown in FIG. 5B, is directly under or in the vicinity of a protruding portion of the mask 2 in an eave-like shape (hereinafter referred to as an “eave portion”). Are formed on the surface of the buried layer 7, and a gap may be formed under the eaves of the mask 2 in some cases. Further, depending on the deposition conditions, referring to FIG. 5C, the surface of the buried layer 7 near both sides of the eaves portion of the mask 2 may be deposited abnormally fast, and a bulge 9 may occur. For this reason, it was difficult to bury the mesa 3 flatly.

The depressions and bulges on the surface of the buried layer in the vicinity of the eaves of the mask are highly toxic and are less toxic and are handled with a liquid instead of phosphine requiring a high-pressure cylinder. Libutylphosphine (TBP) is particularly prominent when it is used as a feed gas for phosphorus, which hinders the use of organic phosphorus which is easy to handle.

[0009]

As described above, in the conventional method of manufacturing a compound semiconductor device, when a compound semiconductor is deposited by an organic metal chemical deposition method and a mesa having a mask on the upper surface is embedded, the embedding near both sides of the mask is performed. Since the surface of the layer was depressed or raised, it could not be embedded flat. Further, since such depressions and swells become remarkable when organic phosphorus is used as a raw material gas, it is difficult to use organic phosphorus which is easy to handle.

According to the present invention, the buried layer deposited under the condition that both sides of the mask are depressed because the deposition rate of the buried layer near the mask is low, and the vicinity of both sides of the mask are raised because the deposition rate of the buried layer near the mask is fast. An object of the present invention is to provide a method of manufacturing a compound semiconductor device in which a mesa having a mask on an upper surface can be buried flat by an organic metal chemical deposition method by laminating and depositing a buried layer deposited under conditions.

[0011]

FIG. 1 is a cross-sectional view of a mesa according to an embodiment of the present invention, showing the surface shape of a buried layer. The plurality of lines in the buried layer 7 are markers 7a, and a layer rich in Ga is formed as a marker 7a by introducing trimethylgallium at regular intervals during the deposition of the buried layer 7.

The first object of the present invention for solving the above problems is as follows.
The configuration is as shown in FIG.
Forming mesa 3 of compound semiconductor covered with mask 2
And metalorganic chemical deposition (MOCVD).
III-V compound semiconductor or II on the substrate 1 outside the mesa 3
For depositing the buried layer 7 made of a -VI compound semiconductor
Manufacturing of compound semiconductor device having burying process of semiconductor device 3
In the method, the embedding step comprises depositing the embedding layer 7.
The product velocity is outside the mask 2 from a region far from the mask 2.
First deposition step fast near the edge and deposition of the buried layer 7
The outer edge of the mask 2 from the region where the velocity is far from the mask 2
Characterized by comprising a second deposition process that is slow in the vicinity
And the second configuration is a compound semiconductor of the first configuration.
In the method of manufacturing a body device, the deposition rate of the buried layer 7 is
Are in the vicinity of the outer edge of the mask 2 and in a region away from the mask 2
II or III under sedimentation conditions when equal
The flow rate U of the first source gas for supplying the element_M ^OV for
Flow rate U of the second source gas for supplying the group V or VI element
_N ^ORatio U_N ^O/ U_M ^OAnd deposition temperature T^OAnd measure
The specified ratio U_N ^O/ U _M ^OAnd the deposition temperature T^OUsing
And log (U_N ^O/ U_M ^O) = A (1 / T^O) + C Determine one or both of constant A and constant C in the equation
The first deposition step comprises:
Set the gas flow rate to U_M, The flow rate of the second source gas is U _Nas well as
When the deposition temperature in the embedding step is T, log (U_N/ U_M)> A (1 / T) + C, and the second deposition step is performed by log (U_N/ U_M) <A (1 / T) + C.
The third configuration is a compound semiconductor device of the first or second configuration
The embedding step, the organic phosphorus compound
Is that the metal organic chemical deposition method using
Configure as a sign.

The depressions and swells on the surface of the buried layer are
Simply the flow rate ratio in Group II or III elements first of second material gas supplied group V or group VI element to the raw material gas flow rate ratio U _N / U _M (herein supplies, the The flow ratio of the second source gas to the first source gas, U _N /
It refers to U _M. ) And the deposition temperature T. The inventor of the present invention has conducted an experimental study in order to clarify the relationship between the deposition conditions of the buried layer and the depressions and protrusions on the surface of the buried layer. As a result, it was clarified that the mesa was buried flat by depositing under the deposition condition where the buried layer surface is depressed and the deposition under the deposition condition where the buried layer rises. The present invention has been made based on this fact. In the following, the results of experiments examining the relationship between the buried layer and the depressions and swells on the surface of the buried layer will be described.

FIG. 2 is a cross-sectional view showing the dependency of the shape of the buried layer on the flow rate of the source gas, and shows the buried layer when the mesa buried layer is deposited by changing the flow rate ratio between the group III source gas and the group V source gas. This represents a change in surface shape.

First, referring to FIGS. 2A to 2D, I
On a nP substrate 1, a mesa 3 having a mask 2 made of a SiO ₂ film projecting like an eave on the upper surface was formed. The structure and forming method of the mesa 3 are the same as those of the conventional example described above. Next, a buried layer 7 made of a compound semiconductor for burying the mesa 3 was deposited by metal organic chemical deposition while changing the source gas flow ratio and the deposition temperature, and the surface shape of the buried layer 7 was observed.

The InP buried layer 7 is formed on both of the buried layers 7 by an organometallic chemical deposition method using trimethyl indium (TMI) as a source gas for supplying a group III element and tertiary butyl phosphine (TBP) as a source gas for supplying a group V element. FIG. 2 shows the results of deposition under conditions where the flow ratios of the source gases were different. Note that the same deposition conditions are maintained during the deposition period in which the buried layer 7 is formed. The deposition temperature was 843
K, the pressure during deposition was 76 Torr.

[0017] FIG. 2 (a), a group III element flow 300 cc / min of hydrogen gas which contains trimethylindium a feed gas as a carrier gas by Paburingu, flow rate U _N = 8 cc as feed gas V group element 4 shows the result of depositing an InP buried layer 7 using tert-butylphosphine / min. At this time, the flow rate ratio U _N / U _M of the feed gas of Group V element to the feed gas of the group III element was 80. In addition, the flow ratio in this specification was shown by the molar ratio. FIG.
Referring to (a), when the buried layer 7 is deposited on the substrate 1 at a position far from the mesa 3, that is, a region far from the mask 2, to a thickness substantially equal to the height of the mesa 3, the buried layer 7 is located near the mask 2. Deposits abnormally fast, causing a swell 9 that covers the mask 2. This excitement 9
Occurs because the deposition rate in the vicinity of the mask 2 is higher than the deposition rate in a region away from the mask 2. However, mask 2
Despite the rise 9 at both ends, a gap 8 is formed below both ends of the mask 2. This gap 8
This is generated because the source gas is not sufficiently supplied directly below the mask 2 and the deposition is delayed.

FIG. 2 (b) shows the supply gas of the group III element and V
Flow ratio U _N / U _M of the feed gas of group element is the case of 30. On both outer sides of the mask 2, bulges 9 smaller than those shown in FIG. In addition, a gap 8 is left below both sides of the mask 2. Note that a plurality of curves drawn in the buried layer 7 represent the markers 7a introduced at regular intervals.

FIG. 2 (c) shows the supply gas of the group III element and V
Flow ratio U _N / U _M of the feed gas of group element is the case of 20. Under this condition, no swell 9 is seen and the buried layer 7 is deposited flat. However, the gap 8 on the lower surface on both sides of the mask is larger than when the flow ratio U _N / _UM is 80 and 30.

FIG. 2D shows the supply gas of the group III element and V
Flow ratio U _N / U _M of the feed gas of group element is the case of 10. Under these conditions, no swelling occurs, but mask 2
Since the deposition rate in the vicinity becomes extremely slow, the surface of the buried layer 7 near both sides of the mask 2 is greatly depressed, and a large gap 8 is generated between the buried layer 7 and the lower surface of the mask 2.

The above experimental results show that the occurrence and size of the bulges and depressions of the buried layer on both sides of the mask are caused by the flow ratio U _N / U of the supply gas of the group III element and the supply gas of the group V element.
Depending on the _M, and the flow rate ratio U _N / U _M is mesa in the case of 20 reveals to be embedded in the flat. However, even in the case of this flat surface, the void or dent on the lower surface of the mask cannot be eliminated or sufficiently reduced.

Furthermore, the inventors of the present invention, the flow rate ratio U _N / U _M of the feed gas of the feed gas and the group V element of the Group III element is constant, depositing a buried layer by changing only the deposition temperature T An experiment was performed. As a result, the occurrence and size of the bulge and depression of the buried layer on both sides of the mask are determined by the flow rate ratio U _N /
Dependence on the deposition temperature T in addition to U _M , and the deposition conditions for embedding the mesa flatly depend on the deposition temperature T and the flow rate ratio U _M / U
_Clarified that it can be expressed in a simple relationship with _N. The result will be described in detail with reference to FIG.

FIG. 4 is a graph showing the dependence of the shape of the buried layer on the deposition conditions, and shows the range of deposition conditions in which bulges and depressions on the surface of the buried layer are experimentally confirmed. Referring to FIG. 4, the four points on the broken line a are the deposition conditions in the above-described experiment when the deposition temperature was kept constant and the flow rate ratio was changed.
_, The results are shown in Figure 2. On this broken line a _{, the} point b is a condition where the mesa is buried flat, and a bulge occurs in a range where the flow ratio U _N / _UM is large, and in a range where the flow ratio U _N / _UM is small. Depression occurs. A broken line B indicates the deposition conditions when the deposition temperature is changed while the flow rate ratio is kept constant. The point c on the broken line B is a condition where the mesa is buried flat, and a swelling occurs in a range where the deposition temperature T is lower than this, and a dent occurs in a range where the deposition temperature T is higher.

The conditions under which such mesas are buried flat are:
It can be determined by experiments in which the buried layer is deposited by changing the deposition temperature and the flow ratio. Points a to d in FIG. 4 show the deposition conditions when the mesa is buried flat in such an experiment. The curve C shows that the flow ratio U _N / _UM and the deposition temperature T of the supply gas of the group V element to the supply gas of the group III element are as follows.

## EQU1 ## log (U_N/ U_M) = A (1 / T) + C (Equation 1) represents one condition. Where A and C are constants
And determined so as to most closely match points a to d. FIG.
Is that points ad are on curve c, that is,_,
The deposition conditions under which the mesas are buried flat, specifically,
Flow ratio U_N/ U _MAnd the relationship between deposition temperature T
It is clear that it will be. Therefore, the upper right corner of the curve C
Territory, ie

## EQU2 ## Under the condition of log ( _UN / _UM )> A (1 / T) + C (Equation 2), the first deposition condition in which the swelling occurs because the deposition rate near the mask is faster than that at a distant place. , The lower left area of curve c,

Under the condition of log ( _UN / _UM ) <A (1 / T) + C (Equation 3), the second deposition condition that causes a depression near the mask because the deposition rate near the mask is slower than that at a distant place. Will be represented.

FIG. 3 is a cross-sectional view of a buried layer in which the mesa is buried flat. FIG. 3 shows the deposition process and surface shape of the buried layer deposited under the condition of burying the mesa shown at points a to d in FIG. ing. 3A to 3D correspond to points a to d in FIG. 4, respectively. Referring to FIG. 3, buried layer 7 is deposited along the side wall of mesa 3 in the initial stage of deposition. Thereafter, a specific crystal plane 8a, for example, a (111) plane generated from a contact portion between the upper surface of the mesa 3 and the mask 2 is developed. Since the deposition rate on the crystal plane 8a is low, in the subsequent deposition, a thick buried layer is deposited in a region where the crystal plane 8a does not develop because it is far from the mesa, and the crystal plane 8a
Since only a thin layer is deposited on a, a depression is formed on the surface of the buried layer 7. When such a depression is formed, the mask 2 protrudes above the eaves, so that the source gas, particularly the source gas for supplying the group V or group VI element, is difficult to diffuse into the depression on the lower surface of the mask 2, and the depression is formed. The deposition rate in the area becomes increasingly slower. As a result, the depression remains as the void 8 even after the mesa is buried flat.

In each of the above experiments, deposition was performed under certain deposition conditions as in the prior art. On the other hand, the inventor of the present invention has found that when the deposition conditions are changed during the deposition, the mesas can be buried flat without generating depressions, voids and swelling. That is,
After deposition under the first deposition condition in which the deposition rate of the buried layer is higher near the mask than in the distant area of the mask, and subsequently, deposition is performed under the second deposition condition in which the deposition rate is lower near the mask than in the distant area of the mask, The mesa is buried flat without generating voids and bulges. The same is true even if the first deposition condition and the second deposition condition are reversed, but the turbulence of the deposition surface tends to be smaller when the first deposition condition is deposited under the first deposition condition. From the viewpoint of forming a high-quality buried layer, it is more preferable to deposit first under the first deposition condition. In general, the difference in the deposition rate of the buried layer of the compound semiconductor between the vicinity of the mask and the distant place is caused by the migration of the metal element on the (111) crystal plane and the raw material, particularly the non-metal It is thought to be based on the balance with the diffusion of the element in the surface layer. Therefore, the results for the III-V group compound semiconductors described above are similarly applied to the II-VI group compound semiconductors.

The present invention has been devised based on such experimental facts. In the first configuration of the present invention, when a mesa whose upper surface is covered with a mask for selective deposition is embedded by metalorganic chemical deposition,
The buried layer is formed as a multilayer film of two or more layers, which are respectively deposited by both the deposition process under the first deposition condition and the deposition process under the second deposition condition. Therefore, as described immediately above, referring to FIG. 1, the mesa 3 can be buried and deposited flat without any depression, void or bulge. The buried layer is III-V
In addition to group II compound semiconductors, II-VI group compounds may be used.

The transition between such first and second deposition conditions, by changing the flow rate ratio U _N / U _M, or by changing the deposition temperature T, more flow ratio U _N / U _M and deposition temperature T You can do both. However, in order to ensure a quick transition, it is preferable to change the flow rate ratio while keeping the deposition temperature constant.

The first and second deposition conditions are the deposition temperature T and
Source gas flow ratio U_N/ U_MIs achieved by selecting
Can be For example, the first deposition condition is changed as shown in FIG.
Group II or III element shown in the upper right area of curve c
Flow rate U of the first source gas for supplying_MAnd V or VI
Flow rate U of the second source gas for supplying the group III element_NAnd the flow ratio
U_M/ U_NIs the condition that satisfies Equation 2, and the second deposition condition
Is shown in the lower left area of curve C in FIG.
Flow ratio U between gas and second source gas_N/ U_MSatisfies Equation 3.
It can be determined by adding conditions. Equation 2 and Equation
The constants A and C included in 3 indicate that a flat buried layer is deposited.
Flow ratio U_N ^O/ U_M ^OAnd deposition temperature T^OTo
It is determined experimentally and U_N/ U_M= U_N ^O/ U_M ^O,
T = T^OCan be determined. flat
Flow rate U at which a buried layer is deposited _N ^O/ U_M ^OAnd bank
Product temperature T^OIf two sets are determined experimentally, the constant A and
And C are determined, and if more than three sets are required,
The constants A and C can also be determined so that
The flow ratio U found_N ^O/ U_M ^OAnd deposition temperature T^Oof
In the case of one set, the constants A and C cannot be determined.
No. However, even in this case, the deposition temperature T or the flow ratio U_N/
U_MEither of T^OOr U_N ^O/ U_M ^OTo
Hold and the other T^OOr U_N ^O/ U_M ^OChanges across
Between the first deposition condition and the second deposition condition
A transition can be realized.

The present invention is particularly effectively applied to an organic metal chemical deposition method using organic phosphorus as a source gas. This is because, for example, organic phosphorus has a shorter diffusion length in gas than phosphine, so that the supply of phosphorus directly below the portion where the mask extends in an eaves-like manner is insufficient, and large depressions are likely to occur.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to an embodiment in which the present invention is applied to manufacture of a mesa stripe semiconductor laser.

First, referring to FIG. 1A, an InGaAsP active layer 4, an InP clad layer 5,
The InGaAsP contact layer 6 is deposited in this order.
Next, a stripe-shaped mask 2 of 3.0 μm width made of SiO ₂ or SiON is formed on the surface of the contact layer 6. Next, the contact layer 6, the cladding layer 5 and the active layer 4 are etched using the mask 2 as an etching mask,
An inverted mesa 3 having a height of 2.5 μm and including a contact layer 6, a clad layer 5, and an active layer 4 is formed under the mask 2. In addition, the width of the upper surface of the inverted mesa 3 is formed smaller than the width of the mask 2, and therefore, both sides of the mask 2 protrude horizontally on both sides of the mesa 3 like eaves.

Next, the InP buried layer 7 was deposited under the conditions that the flow rate ratio of the source gas and the deposition temperature were different, and the conditions under which the mesa 3 was buried flat were experimentally determined. The deposition of the buried layer 7 in this experiment was performed by a metal organic chemical deposition method using the mask 2 as a selective deposition mask. This experiment uses a plurality of experimental substrates on which mesas are formed in the same manner as the substrate 1 on which the mesas 3 are formed. In this deposition, tertiary butyl phosphine (TBP) is supplied as a source gas for supplying a group V element, and III
As a group element supply gas, trimethylindium (TMI) was supplied to bubbling hydrogen gas at a flow rate of 300 cc / min. The pressure is 76 Torr.

Subsequently, the embedded mesa 3 is broken by cleavage.
Then, the cross-sectional shape of the buried layer 7 is measured with a scanning electron microscope.
Observation shows that the burial layer 7 has a flat
Shaributylphosphine flow rate U_N ^OAnd trimethylin
Dium flow rate U_M ^OAnd the flow ratio U_N ^O/ U_M ^OAnd deposition
Temperature T^OI asked. The flow rate ratio U determined in this step _N
^O/ U_M ^OAnd deposition temperature T^OAre indicated by points a to d in FIG.
did. At point a, the flow of tertiary butyl phosphine was
Quantity U_N ^O= 65cc / min, flow ratio U_N ^O/ U_M ^O= 10,
Deposition temperature T^O= 823K, and at point b, U_N ^O= 24
cc / min, U_N ^O/ U_M ^O= 20, deposition temperature T^O= 843
K, U at point c_N ^O= 16cc / min, U_N ^O/ U_M ^O= 3
0, deposition temperature T^O= 853K, U at point d_N ^O= 8cc /
Minutes, U_N ^O/ U_M ^O= 80, deposition temperature T^O= 873K
there were. From these results, it is assumed that the points a to d best fit Equation 1.
The constants A and C were determined by trial and error. as a result,
Constant A = -1.58 × 10^FourAnd constant C = 20.0
Was called. The curve C in FIG.
The flow ratio U obtained by substituting_N/ U_MAnd the deposition temperature T
It depicts the relationship.

Next, using the mask 2 as a mask for selective deposition, both sides of the mesa 3 were buried with a burying layer 7 of InP. This embedding process is performed by the same metalorganic chemical deposition method as in the above-described experiment of embedding the mesa flatly.
It consists of a two-stage deposition process in which deposition conditions are changed on the way.

In the first first deposition step, a flow rate of 24 cc /
Of tertiary butylphosphine per minute and hydrogen gas containing trimethylindium by bubbling at a flow rate of 300 cc / min were supplied as raw material gases. In this case, the flow ratio of tertiary butyl phosphine to trimethyl indium was 30. The pressure is 76 Torr and the deposition temperature is 843K. At this time, the deposition rate at a distance from the mask was 3 μm / hour, and the deposition was 1.0 μm in 20 minutes. Referring to FIG. 4, since this deposition condition is located at the upper right of curve C, the deposition speed is high near the mask and slow at a distant location of the mask. Even if the deposition conditions are changed, the deposition rate far from the mask is constant, and the deposition near the mask fluctuates.

Subsequently, the following second deposition step in which the flow ratio of the raw material gas was changed was performed. In this second deposition step, the flow rate of tertiary butyl phosphine was set to 8 cc / min so that the flow rate ratio of tertiary butyl phosphine to trimethyl indium was 10, and the flow rate of 300 cc / min containing trimethyl indium by bubbling was used. Of hydrogen gas. 76 Torr pressure and 843K
Was maintained as it was. At this time, the deposition rate at a distance from the mask is 3 μm / hour, and 1.5 μm in 30 minutes.
m. Referring to FIG. 4, since the deposition condition is located at the lower left of curve C, the deposition speed is low near the mask and high at a distance from the mask. As a result, referring to FIG. 1A, a buried layer 7 for burying the mesa 3 flatly was formed.

Throughout the first and second deposition steps, referring to FIG. 1, trimethylgallium is supplied in a pulsed manner at regular time intervals to form a Ga-rich thin layer in the buried layer 7, and this is formed. It was used as a marker 7a indicating the deposition status.

Referring to FIG. 1A, the buried layer 7 deposited according to the present embodiment buryes the mesa 3 flat. On the other hand, the lower surface of the eaves-like portion of the mask 2 is completely filled with the buried layer 7, and no dents or voids on the surface of the buried layer 7 generated when deposition is performed by a conventional method are seen. In addition, the swelling of the surface of the buried layer 7 near both sides of the mask 2 is extremely small as compared with the conventional example. FIG.
(B) is a case where the first deposition step time and the second deposition step time are the same 25 minutes, and the marker 7a is formed near the crystal plane 8a formed on the lower surface of the eave-shaped portion of the mask 2.
1A is smaller than that of FIG. 1A, which means that the disturbance of the deposition is small.

Another embodiment of the present invention relates to an example in which the second deposition step of the above embodiment is performed at a high deposition temperature. That is, in the other embodiment, after the lower layer of the buried layer is deposited under the same conditions as the first deposition step of the above-described embodiment, the second deposition step is performed under the following conditions. The deposition temperature T in the second deposition step is 863 K, which is higher than the first deposition temperature 853 K, and the flow ratio of tertiary butyl phosphine to trimethylindium is maintained at 30, which is the same as in the first deposition step. All other deposition conditions are the same as in the first deposition step. Referring to FIG. 4, the deposition condition in the second deposition step in this other embodiment is located at the lower left of curve C, and the deposition rate is low near the mask and high in the distance to the mask. As a result, similarly to the buried layer shown in FIG. 1, a buried layer 7 which is flat and free from voids, depressions, and protrusions is deposited.

Another embodiment of the present invention is an example in which the order of the first deposition step and the second deposition step of the above embodiment is reversed. That is, after the buried layer is first deposited under the deposition conditions of the second deposition step, the deposition of the buried layer is continued under the deposition conditions of the first deposition condition in which the flow ratio of the source gas is changed. As a result, although the marker was slightly disturbed, a buried layer substantially similar to that of the above-described embodiment could be deposited.

[0042]

According to the present invention, a mesa having an eaves-shaped mask on its upper surface is formed by metal-organic chemical deposition.
When buried with a group I compound semiconductor or a group III-V compound semiconductor, dents and bulges formed on the surface of the buried layer can be reduced, so that a compound semiconductor device having excellent characteristics can be manufactured. It greatly contributes to improving the performance of the device.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a mesa according to an embodiment of the present invention.

FIG. 2 is a diagram showing the dependence of a buried layer shape on a flow rate ratio of a source gas.

FIG. 3 is a sectional view of a buried layer in which a mesa is buried flat.

FIG. 4 is a diagram showing the deposition condition dependence of the buried layer shape.

FIG. 5 is a cross-sectional view of a conventional mesa.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Mask 3 Mesa 4 Active layer 5 Cladding layer 6 Contact layer 7 Buried layer 7a Marker 8 Void 8a Crystal plane 9 Rise

Claims (3)

[Claims] 1. A step of forming a mesa of a compound semiconductor whose upper surface is covered with a mask for selective deposition on a substrate, and a step of forming a mesa on the substrate outside the mesa by using a metal organic chemical deposition (MOCVD) method. A buried layer of a mesa for depositing a buried layer made of a -V compound semiconductor or a II-VI compound semiconductor, wherein the burying step comprises the step of increasing the deposition rate of the buried layer away from the mask. A first deposition step faster near the outer edge of the mask than in the region;
A second deposition step in which the deposition rate of the buried layer is lower near the outer edge of the mask than in a region remote from the mask. 2. The method of manufacturing a compound semiconductor device according to claim 1, wherein the deposition rate of the buried layer is equal to that of a region near an outer edge of the mask and a region remote from the mask. flow rate U _N ratio of ^O U _N ^O / U of the second material gas supplied group V or VI element to the flow rate U _M ^O of the first material gas supplying or III group element
_M ^O and the deposition temperature T ^O were measured, and the measured ratio U _N ^O
/ Using U _M ^O and the deposition temperature T ^O, determine one or both of the ^{_{log (U N O / U M}} O) = A (1 / T O) + C becomes constant equations A and the constant C and a step of, said first deposition step, when the flow rate of the first material gas U _M, the flow rate of the second source gas deposition temperature of U _N and the embedding step is T, The deposition is performed under a condition of log ( _UN / _UM )> A (1 / T) + C, and the second deposition step is performed under a condition of log ( _UN / _UM ) <A (1 / T) + C. A method for manufacturing a compound semiconductor device, comprising: 3. The method of manufacturing a compound semiconductor device according to claim 1, wherein said embedding step uses an organometallic chemical deposition method using an organic phosphorus compound as a source gas. Production method.