JP2001093897A - Device and method for manufacturing semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and method for manufacturing a semiconductor for properly controlling oxidation reaction by secularly tracing the progress level of the oxidation reaction with respect to aging changes. SOLUTION: A semiconductor precursor 12 in an oxidizing furnace 10 is irradiated with a light from a white light source 14, reflected light from the semiconductor precursor 12 during oxidation reaction is detected by a reflected light detecting means 16, and reflectivity, mean reflectivity, rate of change of the reflectivity, or rate of change of the mean reflectivity is calculated by a computer 18 based on the detected reflected lights, and the calculation result is displayed at a monitor 20. Also, the oxidation reaction is controlled based on the calculation result, and one part of the region capable of oxidizing the semiconductor precursor 12 is selectively oxidized and a semiconductor can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor manufacturing apparatus and a semiconductor manufacturing method, and more particularly, to a semiconductor manufacturing apparatus and a semiconductor for manufacturing a semiconductor by selectively oxidizing a part of an oxidizable region of a semiconductor precursor. It relates to a manufacturing method.

[0002]

2. Description of the Related Art A vertical cavity surface emitting laser (VCSE)
L: Vertical Cavity Surface EmittingLaser has many advantages, such as lower production cost, higher production yield, and easier two-dimensional integration, as compared with the edge-emitting type. , Optical communication, optical information processing,
It is expected to be used in many fields such as optical recording.

[0003] VCSELs are classified into several types based on their basic structure. The most promising in terms of laser characteristics, such as threshold current value, response speed, and power consumption, are selective oxidation type VCSELs. Is what is called.
For example, KD Choquette etal. "Low threshold volta
ge vertical-cavity lasers fabricated by selective
oxidation "Electron. Lett., Vol. 30, pp. 2033-2044,
As described in the literature such as 1994, the AlAs selective oxidation type VCSEL is manufactured as follows.

First, a metal organic chemical vapor deposition (MOCVD) method
GaAs and Al on the n-type GaAs substrate_0.9Ga
_0.1As each film thickness becomes 1/4 of the wavelength in the medium
N-type DBR (Distri
buted Bragg Reflector) layer, InGaAs quantum well active
The film thickness of the three conductive layers and the GaAs spacer layer is
The undoped active region is the wavelength in the medium and the film thickness is the wavelength in the medium
1/4 of Al_0.98Ga _0.02As current confinement layer, GaAs
And Al_0.9Ga_0.1As is the film thickness of each medium
Lower n-type D laminated alternately 25 periods so as to become 1/4
A BR layer.

Next, when the crystal layer is formed into a mesa shape having a depth of 5 μm and a side of 105 μm by reactive ion etching, the side surface of the Al _0.98 Ga _0.02 As current confinement layer is exposed. From this exposed surface, the Al _0.98 Ga _0.02 As current confinement layer is selectively oxidized except for a few μm at the center. Finally,
Ti / Au and AuGe / Ni / Au are deposited as electrodes on the upper and lower surfaces, respectively, to complete the selective oxidation type VCSEL.

As described above, the selective oxidation type VCSEL has a feature of forming a current confinement structure by using a selective oxidation process of AlAs or AlGaAs after crystal growth. As a result, all the crystal growth is performed on the flat surface, and a crystal layer with good characteristics can be used. Further, there is no need to worry about damage to the active layer caused by the implantation.

Further, for example, the VC manufactured by the above method is used.
When a current is injected into the SEL through the electrodes on both sides, the injected current is confined to only a few μm of the center of the mesa shape that has not been oxidized, and exhibits a low threshold current value of 900 μA. Has laser characteristics.

In the selective oxidation type VCSEL, the AlAs or AlGaAs layer remaining without being oxidized is called an aperture. The selective oxidation type VCSEL has excellent laser characteristics such as a low threshold current value, but various laser characteristics largely depend on the aperture diameter.

For example, DLHuffaker et al. "Multiwave
length, Densely-Packed 2x2 Vertical-Cavity Surface
-Emitting Laser Array Fabricated Using Selective O
xidation ", IEEE Photon. Technol. Lett., Vol. 8, p.
p.858-860, 1996, as shown in FIG. 11, the selective oxidation type VC having an aperture diameter of 2, 2.5, 3, 3.5 μm.
The current-light output characteristics of SEL have been reported. As can be seen from FIG. 11, the threshold current value and the efficiency are greatly different data depending on the aperture diameter. Although not shown, the maximum light output also depends on the aperture diameter. There is also a report that the single mode maximum optical output or the transverse mode of the selective oxidation type VCSEL greatly depends on the aperture diameter.

In the oxidation process for forming an aperture, a wet oxidation method as described in US Pat. No. 5,262,360 is generally used. This method uses nitrogen as a carrier gas,
Bubbling pure water heated in a furnace, and transporting the steam to a furnace to selectively oxidize only a part of the AlAs or AlGaAs layer. The temperature of the oxidation furnace is usually 400 to 500 ° C. Conventionally, oxidation experiments by this oxidation process are repeatedly performed under various conditions using an actual oxidation furnace, and oxidation is performed under optimized conditions based on the obtained results to produce a selective oxidation type VCSEL. Was.

[0011]

SUMMARY OF THE INVENTION However, KMGe
ib et. al. "Fabfication issues of oxide-confinedVC
SELs ", SPIE Vol.3003, pp.69-74, 1997 and many other reports show that AlAs or AlG
The oxidation rate of aAs is as follows: sample temperature, pure water bubbler temperature, nitrogen gas transport rate, AlAs concentration in AlGaAs,
Further, it is affected by various factors such as the thickness of a natural oxide film attached to the side surface of the AlAs or AlGaAs layer.

[0012] For this reason, it is difficult to control the oxidation distance from the side of the mesa with good reproducibility for each process and form the aperture diameter according to the design value only by performing the oxidation under the condition set once. As a result, there has been a problem that the laser characteristics of the VCSEL differ from one production to another, which causes a reduction in the production yield.

The present invention has been made in view of the above problems, and an object of the present invention is to enable the progress of the oxidation reaction to be tracked over time, thereby appropriately controlling the oxidation reaction. An object of the present invention is to provide a semiconductor manufacturing apparatus and a semiconductor manufacturing method which can be performed.

[0014]

According to a first aspect of the present invention, there is provided a semiconductor manufacturing apparatus, comprising: a light source for irradiating an object to be measured in an oxidation furnace with a light source; Reflected light detecting means for detecting reflected light from the object, and calculating means for calculating a reflectance, an average reflectance, a change rate of the reflectance, or a change rate of the average reflectance based on a detection signal of the reflected light detecting means And characterized in that:

According to the first aspect of the present invention, by providing a light source for irradiating the object to be measured in the oxidation furnace with light and a reflected light detecting means, the reflected light from the object to be measured during the oxidation reaction is detected. By calculating the reflectance and the like based on the detection signal of the reflected light detecting means by the calculating means, it is possible to know the degree of progress of the oxidation reaction from the reflectance of the oxide to be oxidized during the oxidation reaction. That is, the progress of the oxidation reaction can be tracked over time. In addition, the oxidation reaction can be appropriately controlled.

[0016] with AlAs (or AlGaAs) is insulated is formed AlO _x in portions oxide, the refractive index and thickness affect the optical characteristics change. For example, as shown in FIG. 12, as the oxidation reaction progresses, the reflection spectrum of the resonator of the VCSEL also changes. The reflection spectrum of a resonator having a non-oxidized AlAs layer is shown by a solid line, and the reflection spectrum of a resonator having an AlO _x layer formed by oxidizing the entire AlAs layer is shown by a broken line.

The structure of the resonator is aluminum gallium arsenide.
Element (Al_0.9Ga_0.1As / Al_0.3Ga_0.7As)
Lower DBR and Al_0.6Ga_0.4Lower space made of As
Sensor layer, Al_0.11Ga_0.89As quantum well layer and Al
_0.3Ga_0.7Quantum well active layer composed of As barrier layer, Al
_0.6Ga_0.4Active region including upper spacer layer made of As
Area, Al_0.9Ga_0.1As / Al_0.3Ga_0.7Consists of As
An upper DBR and a GaAs contact layer are sequentially laminated.
It is. Where Al_0.9Ga_0.1Top to enter As
An AlAs layer is inserted in the lowermost layer in the DBR. A
lAs layer, AlO _xBoth layers have a film thickness of the wavelength in the medium.
1/4, AlO_xHas a refractive index of 1.7.

Both reflection spectra have a center wavelength of 78.
It has a dip around 0 nm and 82 from around 750 nm.
It shows high reflectance up to around 0 nm. At the scale of this graph, there is no significant difference between the spectra in this wavelength band. On the other hand, in other wavelength bands, periodically oscillating side lobes appear. At the wavelength where this side lobe appears, it can be seen that the reflectance greatly differs between the case with the AlAs layer and the case with the AlO _x layer. For example, the average reflectance in the wavelength band of 800 to 1000 nm is about 0.45 when the AlAs layer is provided, and about 0.58 when the AlO _x layer is provided. Therefore, if the average reflectance of the oxide to be oxidized during the oxidation reaction can be measured, the progress of the oxidation reaction can be tracked over time.

FIG. 13 shows the change in the thickness of the oxidized portion.
It can be seen that even if the film thickness changes by ± 20%, the reflection spectrum is not significantly affected.

According to a second aspect of the present invention, in the semiconductor manufacturing apparatus according to the first aspect, the object to be measured is a semiconductor precursor or a monitor sample arranged near the semiconductor precursor.

According to a third aspect of the present invention, there is provided a semiconductor manufacturing apparatus according to the first or second aspect, further comprising display means for displaying a result of the calculation by the calculation means. By providing the display means, the operator can visually know the degree of progress of the oxidation reaction.

According to a fourth aspect of the present invention, there is provided the semiconductor manufacturing apparatus according to any one of the first to third aspects, further comprising a reaction control unit for controlling a reaction based on a calculation result by the calculation unit. It is characterized by. By providing the reaction control means, tracking of the degree of progress of the oxidation reaction and control of the oxidation reaction can be performed by one apparatus.

According to a fifth aspect of the present invention, in the semiconductor manufacturing apparatus according to any one of the second to fourth aspects, the monitor sample is formed such that the reflectance increases or decreases in proportion to the oxidation time. It is characterized by having been done. If the reflectance of the monitor sample increases or decreases in proportion to the oxidation time, tracking the change over time of the reflectance,
Since the time when the oxidizable region disappears appears as a singular point, the operator can easily visually recognize the end point of the reaction.

According to a sixth aspect of the present invention, there is provided a semiconductor manufacturing method for manufacturing a semiconductor by selectively oxidizing a part of an oxidizable region of a semiconductor precursor, wherein the semiconductor precursor or the semiconductor precursor in an oxidation furnace is manufactured. The monitor sample placed near the semiconductor precursor is irradiated with light to detect reflected light from the semiconductor precursor that is undergoing the oxidation reaction or the monitor sample placed near the semiconductor precursor, and the detected reflection is detected. Based on the light, the reflectance, the average reflectance, the rate of change of the reflectance, or the rate of change of the average reflectance is calculated, and based on the calculation result, the oxidation reaction is controlled to manufacture a semiconductor. .

According to a seventh aspect of the present invention, in the semiconductor manufacturing method according to the sixth aspect, the oxidation reaction is performed based on the fact that the rate of change in reflectance of the monitor sample when the oxidizable region disappears becomes zero. Is controlled. When the area of the unoxidized region of the semiconductor precursor reaches a desired value, using a monitor sample designed so that the oxidizable region disappears, when the rate of change in the reflectance of the monitor sample becomes zero If the control is performed so that the oxidation reaction is terminated in the above, a semiconductor precursor having an unoxidized region having a desired area can be easily obtained.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a semiconductor manufacturing apparatus and a semiconductor manufacturing method according to the present invention will be described in detail based on embodiments.

(First Embodiment) A semiconductor manufacturing apparatus according to a first embodiment is an apparatus for performing steam oxidation. As shown in FIG. 1, an oxidizing furnace 10 shown in FIG. Square (rectangular) oxidizable region 12A to be measured
(Precursor), semiconductor precursor 12 and oxidation furnace 10
A white light source 14 for irradiating light to the semiconductor precursor 12 disposed therein, a reflected light detecting means 16 for detecting reflected light from the semiconductor precursor 12, a computer 18, and a monitor as a display means connected to the computer 18 20.

The oxidation furnace 10 is provided with a heater 22 and an inlet pipe having a valve 24 for introducing steam. A driving circuit for the heater 22 and a driving device (not shown) for the valve 24 are Each is connected to a computer 18. The light source 14 has heat resistance via a chopper 26.
One end of the moisture-resistant optical fiber 28 is optically coupled to one end of the optical fiber 28 and the other end of the semiconductor precursor 12 in the oxidation furnace 10.
The semiconductor precursor 12 is fixedly disposed above and irradiates the semiconductor precursor 12 with light.

The reflected light detecting means 16 includes a plurality (n) of filters (not shown) that transmit light in different wavelength bands,
A photodetector 29 disposed on the light transmitting side of the filter. Each photodetector 29 is optically coupled to one end of a heat-resistant and moisture-resistant optical fiber 30, and the other end of the optical fiber 30 is fixedly disposed above the semiconductor precursor 12 in the oxidation furnace 10. And outputs a detection signal. The photo detector 29 is connected to the computer 18 via an A / D converter (not shown), and the detection signal output from the photo detector 29 is converted into a digital signal by the A / D converter. Is input to the computer 18. When the S / N ratio of the detection signal is low, an amplifier such as a lock-in amplifier may be inserted between the photo detector 29 and the A / D converter.

The computer 18 has a CPU 32, a ROM
And a RAM 36.
32 performs processing based on a control routine program described below stored in the ROM 34.

A control routine executed by the computer 18 will be described with reference to FIG. In step 100, takes in a signal from the photodetector 29 provided corresponding to the n-number of filters, the incident light intensity I ₀ from a light intensity I _k of light received by each photodetector 29, stored in the ROM source , The reflectance I _k / I ₀ in each wavelength band is obtained, and the sum of the reflectances I _k / I ₀ for the n photodetectors is divided by the number n to obtain a value in step 102. Calculates the average reflectance r (= Σ (I _k / I ₀ ) / n) in the predetermined wavelength band.

Next, the average reflectance r calculated in step 104 is displayed on the monitor 20, and it is determined in step 106 whether or not the reaction stop condition is satisfied. In a semiconductor precursor having a square (rectangular) shape oxidizable region as shown in FIG. 2, the oxidizable region is oxidized from each side toward the center. It increases in proportion to the square of time. Since the reflectance of the oxidized region and the reflectance of the non-oxidized region are each constant, the average reflectance r changes as the oxidized region increases (specifically, it increases in proportion to the square of time t (r ∝t ² )),
It becomes constant when all of the oxidizable region 12A of the semiconductor precursor is oxidized. Therefore, using the map shown in FIG. 4 showing the correlation between the average reflectance r and the area s of the unoxidized region previously stored in the ROM, the area s of the desired unoxidized region is obtained.
Determine the average reflectance r _x corresponding to the reaction stopped condition is determined to be satisfied when the average reflectance r matches the average reflectance r _x.

Alternatively, it may be determined that the reaction stop condition is satisfied when a stop signal is input to the computer 18 by the operator. That is, the operator may determine whether to stop the reaction by looking at the value of the average reflectance r displayed on the monitor 20 and stop the reaction manually. Here, if the reaction stop condition is satisfied, the semiconductor precursor 12 is carried out of the oxidation furnace 10 by a transfer device (not shown) in step 108 to stop the oxidation reaction.

(Second Embodiment) A semiconductor manufacturing apparatus according to a second embodiment has a monitor as an object to be measured, which is arranged near the semiconductor precursor 12 only for tracking the progress of oxidation. Since the configuration is the same as that of the first embodiment except that the use sample 13 is used, the description of the same parts will be omitted.

The monitor sample 13 has a stripe-shaped oxidizable region 13A (open area) shown in FIG. 5, and when the area of the unoxidized region of the semiconductor precursor reaches a desired value, the oxidizable region 13A is designed to disappear. In the monitoring sample 13 having the stripe-shaped oxidizable region shown in FIG. 5, the oxidizable region is oxidized from two opposing sides toward the center. At this time, since the oxidation rate is constant, the oxidized region takes time. Increase in proportion. Since the reflectance of the oxidized region and the reflectance of the non-oxidized region are constant, the average reflectance r changes as the oxidized region increases (specifically, increases in proportion to time t (r∝ t)), becomes constant when all of the oxidizable region 13A is oxidized.

A control routine executed by the computer 18 in the second embodiment will be described with reference to FIG. In step 200, a signal from each photodetector 29 provided corresponding to the n filters is fetched, and the amount of light I received by each photodetector 29 is obtained.
_k is divided by the amount of incident light I ₀ from the light source stored in the ROM in advance to obtain the reflectivity I _k / I ₀ at the current time in each wavelength band, and the reflectivity I _k for the n photodetectors is _obtained. / I
By dividing the added value obtained by adding ₀ by the number n, the average reflectance r _new (= Σ) in the predetermined wavelength band at the current time is obtained.
(I _k / I ₀ ) / n). RAM calculated similarly
The average reflectance r _old in the previous predetermined wavelength band stored in
To the average reflectance r _new in the given wavelength band at the current time
Is subtracted, and the change rate Δr of the average reflectance is calculated in step 202.
(= R _old -r _new ).

Next, the change rate Δr of the average reflectance calculated in step 204 is displayed on the monitor 20, and
At 6, it is determined whether or not the reaction stop condition is satisfied. In the monitoring sample 13 having the stripe-shaped oxidizable region 13A, the average reflectance change rate Δr is constant until the oxidizable region 13A disappears, and becomes 0 when the oxidizable region 13A disappears. Therefore, it can be determined that the reaction stop condition has been satisfied when the average reflectance change rate Δr = 0.

Alternatively, the operator observes the value of Δr displayed on the display device and inputs a stop signal by operating a switch when Δr = 0, and the stop signal is input to the computer 18 by the operator. May be determined when the reaction stop condition is satisfied. Here, if the reaction stop condition is satisfied, the semiconductor precursor 12 is carried out of the oxidation furnace 10 by a transfer device (not shown) in step 208 to stop the oxidation reaction.

In the first embodiment, the average reflectance of the semiconductor precursor is calculated, and the oxidation reaction is controlled based on the calculated average reflectance. However, as in the second embodiment, the average reflectance is controlled. May be calculated, and the oxidation reaction may be controlled based on the calculated change rate of the average reflectance. Further, in the second embodiment, the change rate of the average reflectance is used. However, as in the first embodiment, the average reflectance is calculated based on the detection signal of the reflected light detecting means, and the calculation is performed. The oxidation reaction may be controlled based on the average reflectance.

In the second embodiment, the object to be measured is
A monitor sample 13 having a stripe-shaped oxidizable region shown in FIG. 5 and designed so that the oxidizable region disappears when the area of the unoxidized region of the semiconductor precursor reaches a desired value was used. However, the present invention is not limited to the stripe shape, and a monitor sample having an oxidizable region similar to a semiconductor precursor such as a rectangle, a circle, and an ellipse may be used.

For example, when a monitor sample having a square (rectangular) oxidizable region similar to the semiconductor precursor is used as the object to be measured, the average reflectance increases in proportion to the square of time. Therefore, the rate of change of the average reflectance Δr
Decreases as the degree of oxidation of the object to be measured advances, and becomes 0 when the oxidizable region disappears. Therefore, RO
Using the map shown in FIG. 7 showing the correlation between the change rate Δr of the average reflectance stored in M and the area of the unoxidized area, the average reflectance corresponding to the area s ₀ of the desired unoxidized area the rate of change [Delta] r ₀ determined, it can be determined that the change rate [Delta] r of the average reflectance is the average reflectance change rate [Delta] r ₀ and the reaction stopped condition when a match is established.

In the first and second embodiments, a white light source is used as a light source and the light is spectrally separated by a filter to measure the average reflectance in a specific spectral range. However, the light source may be an LED. The reflectance at a specific wavelength used can also be measured.

In the first and second embodiments, the apparatus for performing steam oxidation has been described. However, it is needless to say that the present invention can be applied to other oxidation methods.

In the first and second embodiments, the semiconductor precursor is carried out of the oxidation furnace by the transfer device to stop the oxidation reaction. However, the drive circuit of the heater provided in the oxidation furnace is turned off. Alternatively, the oxidation reaction may be stopped by an operation such as closing a valve for introducing steam.

Next, the semiconductor manufacturing apparatus of this embodiment is
9 shows an example applied to the manufacture of the selective oxidation type surface emitting semiconductor laser shown in FIG.

An n-type GaAs buffer layer 2 and an n-type aluminum gallium arsenide (A
lower n-type DBR 3 made of l _0.9 Ga _0.1 As / Al _0.3 Ga _0.7 As), lower spacer layer 4 made of undoped Al _0.6 Ga _0.4 As, undoped Al _0.11 Ga _0.89
As quantum well layer and undoped Al _0.3 Ga _0.7 As
Quantum well active layer 5 composed of a barrier layer, undoped Al
_An active region 7 including an upper spacer layer 6 made of _0.6 Ga _0.4 As, and a p-type Al _0.9 Ga _0.1 As / Al _0.3 Ga _0.7
An upper DBR 8 made of As and a p-type GaAs contact layer 9 were sequentially laminated to obtain a laminate. However, a p-type AlAs layer 10 was inserted at a place where the lowermost layer Al _0.9 Ga _0.1 As in the upper DBR 8 should enter. Up to the active layer 5 of this laminate, boron trichloride and chlorine (BCl
₃ + Cl ₂ ) gas was removed by reactive ion etching using a gas to form a mesa shape. Thereby, the AlAs layer 10
The sides were exposed.

An inlet pipe for transporting steam obtained by bubbling pure water heated to 95 ° C. to the oxidation furnace using nitrogen as a carrier gas, and opening and closing the inlet pipe. Of the AlAs layer 10 was placed in an oxidizing furnace of a semiconductor manufacturing apparatus of the present invention equipped with a valve and a heater for heating to 400 ° C., and a portion of the AlAs layer 10 was selectively oxidized from the exposed surface by heated steam.

Here, it is easy to quantitatively determine in advance the relationship between the aperture diameter of the VCSEL to be actually manufactured and the reflectance of the monitor sample, and by doing so, it is possible to control the aperture diameter more accurately. It becomes possible.
For example, as shown below,
The relationship between the aperture diameter at L and the reflectance of the monitor sample can be determined by experiment.

A monitor sample having the above-mentioned VCSEL laminated structure and etched in a stripe shape was prepared. The stripe width is about 15 μm, and the stripe period is about 1
00 μm, the area for measuring the reflection spectrum (〜5 m
(m square) stripes are periodically formed over the entirety. Oxidation reaction was carried out by changing the treatment time to prepare samples in which the ratio of the oxidized portion to the stripe width was different. Each sample was observed with an infrared microscope and the width of the unoxidized region (VC
(Corresponding to the aperture diameter of the SEL), and the reflectance of each sample with respect to light having a wavelength of 920 nm was measured. The width of the unoxidized area narrowed in direct proportion to the processing time, and the reflectivity increased in direct proportion to the processing time.

The relationship between the aperture diameter of the VCSEL to be actually manufactured and the reflectance of the monitor sample can be predicted by calculation. As an object to be measured, a monitor sample A having a square (rectangular) oxidizable region as shown in FIG. 9A and a monitor sample B having a stripe-shaped oxidizable region shown in FIG. Changes with time in the reflectance and the aperture diameter for light having a wavelength of 920 nm until all the layers were oxidized were calculated. The reflectivity was measured at three locations: 1) mesa bottom, 2) oxidized portion (in the mesa), and 3) unoxidized portion (in the mesa), and calculated based on the following formula in consideration of the area ratio of each portion. The reflectance.

R (total reflectance) = R₁S₁+ R_TwoS_Two+ R_ThreeS_Three R₁: Reflectivity R at the bottom of the mesa_Two: Reflectance of oxidized part R_Three: Reflectance of unoxidized part S₁: Area ratio of mesa bottom In sample A for monitor, S₁= 1− (B / L)^Two  In monitor sample B, S₁= 1-B / LS_Two: Area ratio of oxidized part In monitor sample A, S_Two= (B^Two-A^Two) / L^Two  In monitor sample B, S_Two= (BA) / LS_Three: Area ratio of unoxidized part In monitor sample A, S_Three= A^Two/ L^Two  In monitor sample B, S_Three= A / L In the sample A for monitoring, the relation of A = B-2vt
The engagement is established.

As can be seen from FIG. 10, the aperture diameter (represented by the line C) decreases in proportion to the time, and the reflectance (represented by the line A) of the monitor sample increases by drawing a parabola. The reflectivity of the sample (represented by line B) increases linearly. In addition, this result was in good agreement with data obtained by experiments.

Based on the above relationship, when the reflectance of the monitor sample reached a value corresponding to the desired aperture diameter, the laminate was taken out of the oxidation furnace and the oxidation reaction was terminated.

After completion of the oxidation reaction, a silicon oxynitride film 11 is further deposited to a thickness of about 1 μm by plasma-assisted chemical vapor deposition at 250 ° C. so as to cover the mesa. Then, a p-type electrode 12 made of a laminated film of Ti / Au was formed except for the emission port, and connected to the p-type GaAs contact layer 9. On the back surface of the substrate, n
A mold electrode 13 was formed.

Here, the lower DBR 3 is made of n-type Al._0.9G
a_0.1Al with As layer_0.3Ga_0.7Each of the As layers and the thickness λ
/ (4n_r) (Λ: oscillation wavelength, n_r: Refractive index of medium)
It is formed by alternately laminating 40.5 cycles.
Silicon concentration of 2 × 10 ¹⁸cm^-3It is. p-type
The AlAs layer 10 has a thickness of λ / (4n_r), Of the dopant
Carbon concentration is 3 × 10¹⁸cm^-3It is. Upper DBR8
Is p-type Al_0.9Ga_0.1Al with As layer_0.3Ga_0.7As
And each of the layers has a thickness λ / (4n_r) 30 cycles alternately
The carbon concentration of the dopant is 3
× 10¹⁸cm^-3It is. Finally, p-type GaAs contact
The layer 9 has a thickness of 20 nm and a carbon concentration of 1 × 10²⁰c
m^-3It is. The number of cycles (the number of layers) of the upper DBR 8 is changed to the lower DB
What makes R3 less than that of R3
This is because the emitted light is extracted from the upper surface of the substrate. Dopa
The types of components are not limited to those listed here.
Use selenium for p-type, zinc or magnesium for p-type
It is also possible. Although not described in detail,
To reduce the series resistance, Al_0.9G
a_0.1As layer and Al_0.3Ga_0.7Between the As layers
So-called transition region with an aluminum composition ratio of
You. The insulating film covering the mesa is made of silicon oxide or silicon nitride.
An oxide film or the like can also be used.

The obtained selective oxidation type VCSEL is configured as described above, and can perform laser oscillation by flowing a current between the n-type electrode 13 and the p-type electrode 12. The laser having an oscillation wavelength λ: 780 nm Light can be extracted from the substrate surface.

In the above description, a VCSEL having a near infrared wavelength using AlGaAs for the active layer has been described as an example. However, the present invention is also applicable to a surface emitting laser for infrared using GaAs or InGaAs, and for red using InGaP or AlGaInP. it can. Further, a blue or ultraviolet surface emitting laser such as a GaN-based or ZnSe-based laser, or a 1.3-based laser such as an InGaAsP-based laser.
Of course, it can also be used for a surface emitting laser having a band of 1.5 μm. The DBR layer is not limited to a semiconductor material, but may be an insulating film. Also, Al
The example in which the As layer is oxidized has been described.
In the case of oxidizing the same, all other materials that cause an oxidation phenomenon in the semiconductor layer can be similarly used.

Although an example in which only one AlAs layer is inserted directly above the active layer has been described, the present invention is not limited to the position where the AlAs layer is inserted just above the active layer, and the present invention is applicable even if the number of AlAs layers is plural. Available.

In addition, a structure has been proposed in which an oxide aperture is formed by providing an oxidation hole in a substrate without using a mesa shape in an oxidized VCSEL. However, the semiconductor manufacturing apparatus and the semiconductor manufacturing method of the present invention have been proposed. , All oxidized VCS
It can be used effectively for EL.

Further, the semiconductor manufacturing apparatus and the semiconductor manufacturing method of the present invention can be used not only as a measure for improving controllability when forming the aperture diameter of the oxidized VCSEL, but also by using the DBR mirror of the VCSEL using an oxidizing process. It can also be used when manufacturing.

As described above, when the semiconductor manufacturing apparatus and the semiconductor manufacturing method of the present invention are applied to the manufacture of a selective oxidation type VCSEL, the oxidation distance, that is, the aperture diameter can be determined by observing the reflectance of the VCSEL resonator over time. The selective oxidation type VC can be measured during the process, the aperture diameter can be formed as designed, and VCSELs without variation in laser characteristics can be manufactured with high yield.
The reproducibility of the SEL manufacturing process can be improved.

[0062]

According to the semiconductor manufacturing apparatus and the semiconductor manufacturing method of the present invention, the degree of progress of the oxidation reaction can be tracked over time, whereby the oxidation reaction can be appropriately controlled.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a semiconductor manufacturing apparatus according to a first embodiment.

FIG. 2 is a schematic diagram of an object to be measured in the semiconductor manufacturing apparatus according to the first embodiment.

FIG. 3 is a flowchart illustrating a control routine performed in the semiconductor manufacturing apparatus according to the first embodiment.

FIG. 4 is a graph showing a correlation between an area of an unoxidized region and an average reflectance.

FIG. 5 is a schematic view of an object to be measured in a semiconductor manufacturing apparatus according to a second embodiment.

FIG. 6 is a flowchart illustrating a control routine performed in the semiconductor manufacturing apparatus according to the second embodiment.

FIG. 7 is a graph showing a correlation between the area of an unoxidized region and the rate of change in average reflectance.

FIG. 8 shows a selective oxidation type VC to which the present invention can be applied.
FIG. 3 is a schematic cross-sectional view illustrating a configuration of an SEL.

FIG. 9 is a schematic diagram showing a model of an object to be measured used for calculating a temporal change of an aperture diameter and a reflectance of a VCSEL.

FIG. 10 is a graph showing the change over time in the aperture diameter and the reflectance of the VCSEL obtained by calculation.

FIG. 11 is a graph showing aperture diameter dependence of current-light output characteristics of a selective oxidation type VCSEL.

FIG. 12 is a spectrum diagram for comparing the difference between the reflection spectra of AlAs and AlO _x .

FIG. 13 is a spectrum diagram showing an influence of a change in film thickness due to oxidation of AlAs on a reflection spectrum.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Oxidation furnace 12 Semiconductor precursor 13 Monitor sample 14 White light source 16 Reflection light detection means 18 Computer 20 Monitor 22 Heater 24 Valve 26 Chopper 28, 30 Optical fiber 29 Photodetector

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4M106 AA01 AA13 BA04 CA70 DH04 DH12 DH31 5F045 AA20 AB31 AF05 CA12 GB04 5F073 AA65 AA72 AB17 AB28 BA02 BA06 CA04 CA05 CA07 CA12 CA14 CA22 DA27

Claims (7)

[Claims] 1. A light source for irradiating an object to be measured in an oxidation furnace with light, reflected light detecting means for detecting reflected light from the object being oxidized, and a detection signal based on the detection signal of the reflected light detecting means. Calculating means for calculating the reflectance, the average reflectance, the change rate of the reflectance, or the change rate of the average reflectance. 2. The semiconductor manufacturing apparatus according to claim 1, wherein the object to be measured is a semiconductor precursor or a monitor sample arranged near the semiconductor precursor. 3. The semiconductor manufacturing apparatus according to claim 1, further comprising display means for displaying a calculation result by said calculation means. 4. On the basis of a calculation result of the calculation means,
The semiconductor manufacturing apparatus according to any one of claims 1 to 3, further comprising reaction control means for controlling a reaction. 5. The semiconductor manufacturing apparatus according to claim 2, wherein the monitor sample is formed so that the reflectance increases or decreases in proportion to the oxidation time. 6. A semiconductor manufacturing method for manufacturing a semiconductor by selectively oxidizing a part of an oxidizable region of a semiconductor precursor, wherein the semiconductor manufacturing method is disposed in the oxidation furnace or in the vicinity of the semiconductor precursor. The monitor sample is irradiated with light to detect reflected light from the semiconductor precursor undergoing the oxidation reaction or the monitor sample arranged near the semiconductor precursor, and the reflectance and the average are determined based on the detected reflected light. A semiconductor manufacturing method for calculating a reflectance, a change rate of a reflectance, or a change rate of an average reflectance, and controlling an oxidation reaction based on a calculation result to manufacture a semiconductor. 7. Based on the fact that the rate of change of the reflectance of the monitor sample when the oxidizable region disappears becomes zero,
7. The method according to claim 6, wherein the oxidation reaction is controlled.