CN113314951B - VCSEL chip oxidation real-time monitoring method and device - Google Patents

VCSEL chip oxidation real-time monitoring method and device Download PDF

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CN113314951B
CN113314951B CN202110654563.2A CN202110654563A CN113314951B CN 113314951 B CN113314951 B CN 113314951B CN 202110654563 A CN202110654563 A CN 202110654563A CN 113314951 B CN113314951 B CN 113314951B
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oxidation
capacitance
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CN113314951A (en
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鄢静舟
王坤
杨奕
糜东林
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Fujian Huixin Laser Technology Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/18—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities
    • H01S5/183—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/18—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities
    • H01S5/183—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]
    • H01S5/18308—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL] having a special structure for lateral current or light confinement
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/18—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities
    • H01S5/183—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]
    • H01S5/18344—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL] characterized by the mesa, e.g. dimensions or shape of the mesa

Abstract

The invention discloses a VCSEL chip oxidation real-time monitoring method and a device thereof, wherein the method comprises the following steps: depositing a p-type contact metal electrode on the top of an epitaxial wafer to be oxidized, dividing the epitaxial wafer into a monitoring area and a target chip area, and etching a monitoring oxidation table top and a target oxidation table top respectively; placing the epitaxial wafer into an oxidation chamber, and connecting a p-type contact metal electrode of a monitoring area and the back of a substrate to a capacitance meter; starting an oxidation process, acquiring and monitoring capacitance-voltage curves of the oxidation table board in different oxidation time in real time through a capacitance meter, and acquiring a capacitance C before oxidationsAnd oxidizing the capacitor C at any timedepAnd an oxidized part of the capacitor Csox(ii) a Calculating the oxidized area A of the monitoring oxidation table-board in real time, and further obtaining the oxidation depth D of the monitoring oxidation table-board; and drawing a curve relation graph of the oxidation depth and the oxidation time by taking the oxidation depth and the oxidation time as oxidation monitoring reference indexes, and controlling the oxidation depth of the target chip area in real time.

Description

VCSEL chip oxidation real-time monitoring method and device
Technical Field
The invention relates to the technical field of semiconductor photoelectron, in particular to a VCSEL chip oxidation real-time monitoring method and VCSEL chip oxidation real-time monitoring equipment.
Background
With the continuous development of science and technology, various VCSEL chips are widely applied to daily life, work and industry of people, and bring great convenience to the life of people. Oxide confinement processes are one of the core technologies of VCSEL chips. The oxide limiting method which is popular at present is to first obtain high AlxGa1-xAs is designed into one layer or two-layer structure, is arranged on one side or two sides close to the active layer by means of epitaxial growth, and then is used for AlxGa1-xThe As layer is selectively oxidized. Al (Al)xGa1-x The oxidation of As layer proceeds laterally from the outer edge toward the center, and electrically insulating Al is generated2O3. Therefore, by controlling the oxidation process,the Al may be addedxGa1-xThe As layer becomes the outer ring of oxidized Al2O3An electrically insulating region, and an inner ring is an unoxidized current injection region.
The physical parameters to be controlled in the oxidation process are many, including: temperature uniformity, water vapor flow pattern, epitaxial thickness and composition uniformity, oxidation initiation delay, etch skirt size, wafer surface pretreatment, and the like. At present, when an oxidation process is carried out, a VCSEL epitaxial wafer sample is generally taken to carry out the oxidation process, and an engineer continuously corrects parameters through multiple trial and error to finally obtain the oxidation rate under a specific oxidation condition; and then, the oxidation rate of the sample is utilized to calculate the oxidation time required by the same batch of VCSEL epitaxial wafers to realize the specific oxidation area/oxidation aperture under the same oxidation condition. This method is difficult to ensure that all physical parameters related to the oxidation process of each batch are stable and constant for different oxidation batches. Therefore, the oxidation method often causes the situation that the VCSEL epitaxial wafers in different batches are over-oxidized or under-oxidized, the consistency of the product is poor, and the yield is low.
Therefore, a VCSEL chip oxidation real-time monitoring method and a VCSEL chip oxidation real-time monitoring device are provided.
Disclosure of Invention
The invention provides a VCSEL chip oxidation real-time monitoring method and VCSEL chip oxidation real-time monitoring equipment, and mainly aims to solve the problems that the existing VCSEL chip is poor in product consistency, low in yield and the like due to the fact that an oxidation control method is unreasonable.
The invention adopts the following technical scheme:
a VCSEL chip oxidation real-time monitoring method and equipment comprise the following steps:
(1) pretreating an epitaxial wafer to be oxidized, depositing a p-type contact metal electrode on the top of the epitaxial wafer, then performing oxidation mesa etching, dividing the epitaxial wafer into a monitoring area and a target chip area, etching a monitoring oxidation mesa in the monitoring area, and etching a target oxidation mesa in the target chip area;
(2) placing the pretreated epitaxial wafer into an oxidation chamber of oxidation real-time monitoring equipment, wherein a capacitance meter outside the oxidation chamber is connected to a p-type contact metal electrode of the monitoring area through a positive connecting wire and is connected to the bottom surface of a substrate of the epitaxial wafer through a negative connecting wire and a negative probe;
(3) starting an oxidation process, acquiring capacitance-voltage curves of the monitoring oxidation table surface of the epitaxial wafer in different oxidation time in real time through a capacitance meter, and acquiring the capacitance C before oxidation according to the characteristics of the capacitance-voltage curvessAnd the capacitance C at any time of oxidationdepThen, the capacitance C of the oxidized part is calculated in real time according to the formula (a)sox；
Figure 321971DEST_PATH_IMAGE002
（a）；
(4) The oxidized part of the capacitance C is deduced by using the concept of parallel capacitor platessoxCalculating the oxidized area A of the monitored oxidation table top in real time according to a formula (b) of monitoring the oxidized area A of the oxidation table top, and further calculating the oxidation depth D of the monitored oxidation table top based on the structural characteristics of the monitored oxidation table top;
Figure 894772DEST_PATH_IMAGE004
（b）
in the formula: doxIs the thickness of the oxide layer; epsilonoxIs an oxide layer (Al)2O3) The dielectric constant of (a); epsilonsIs the dielectric constant of a GaAs semiconductor; wmThe thickness between the p-type contact metal electrode and the bottom surface of the substrate;
(5) and drawing a curve relation graph of the oxidation depth and the oxidation time by taking the oxidation depth and the oxidation time as oxidation monitoring reference indexes, and controlling the oxidation depth of the target chip area.
Further, the monitoring oxidation table-board and the target oxidation table-board are both circular, and the diameter of the monitoring oxidation table-board is larger than that of the target oxidation table-board.
Furthermore, the calculation formula of the monitoring oxidation depth D and the oxidized area A of the oxidation mesa is as follows:
Figure 347006DEST_PATH_IMAGE006
（c）
in the formula: dmesaTo monitor the diameter of the oxidation mesa.
Further, in the step (3), the capacitance C before oxidationsAnd the capacitance C at any time of oxidationdepThe capacitance value corresponding to the midpoint voltage within the reverse bias voltage range is taken.
Further, the scanning interval of the capacitance-voltage curve can be obtained through a pre-test, in the pre-test, the capacitance-voltage curve of different monitored oxidation table sizes before oxidation is scanned, and therefore a proper reverse bias voltage range and a proper forward bias voltage range are intercepted to serve as the scanning interval.
Further, in step (3), the scan interval of the capacitance-voltage curve is [ -5V,2V ].
Furthermore, in the pre-test, a plurality of monitoring oxidation mesas with different sizes can be etched in the same monitoring area.
A VCSEL chip oxidation real-time monitoring device comprises an oxidation chamber, a heating furnace, a first carrier gas channel, a capacitance meter and a control box; the heating furnace is arranged at the bottom of the oxidation chamber, and the oxidation chamber is sequentially connected with a first regulating valve, a bubbler, a first gas flowmeter and a first nitrogen source through the first carrier gas channel; the epitaxial wafer is placed in the oxidation chamber and is electrically connected to the capacitance meter; the control box is electrically connected with the capacitance meter and the first regulating valve, and is used for receiving data collected by the capacitance meter, completing the calculation steps and controlling the oxidation process of the epitaxial wafer through the first regulating valve.
And one end of the second carrier gas channel is communicated with the inside of the oxidation chamber, and the other end of the second carrier gas channel is sequentially provided with a second regulating valve, a second gas flowmeter and a second nitrogen source.
Further, the oxidation chamber is made of a quartz tube, and a carrying platform is arranged in the oxidation chamber, is used for placing the epitaxial wafer and is provided with a negative probe electrically connected to the capacitance meter.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a VCSEL chip oxidation real-time monitoring method which is simple to operate, high in flexibility and good in applicability, can ensure that the oxidation process of epitaxial wafers is accurate and controllable, cannot cause the problem of over oxidation or little oxidation even if the oxidation physical control parameters of the epitaxial wafers in different batches fluctuate, can accurately control the consistency of the oxidation aperture of products in each batch, and effectively improves the yield, the performance and the reliability of the products.
Drawings
Fig. 1 is a schematic structural diagram of an epitaxial wafer according to the present invention.
Fig. 2 is a schematic view of a monitoring area and a target chip area of an epitaxial wafer according to the present invention.
Fig. 3 is a schematic diagram of monitoring an oxidation mesa in accordance with the present invention.
Fig. 4 is a graph of capacitance versus voltage for different specifications of monitored oxidation mesas before oxidation.
Fig. 5 is a graph of capacitance versus voltage for monitoring oxidation mesas at various oxidation times.
FIG. 6 is a graph of oxidation depth versus oxidation time.
FIG. 7 is a schematic structural diagram of an oxidation real-time monitoring apparatus according to the present invention.
Detailed Description
The following describes embodiments of the present invention with reference to the drawings. Numerous details are set forth below in order to provide a thorough understanding of the present invention, but it will be apparent to those skilled in the art that the present invention may be practiced without these details.
As shown in fig. 1 to 7, a VCSEL chip oxidation real-time monitoring method is characterized in that: the method comprises the following steps:
(1) pretreating an epitaxial wafer to be oxidized, depositing a p-type contact metal electrode on the top of the epitaxial wafer, then performing oxidation mesa etching, dividing the epitaxial wafer into a monitoring area B and a target chip area C, etching a monitoring oxidation mesa in the monitoring area B, and etching a target oxidation mesa in the target chip area C; preferably, a Ti/Au metal film is deposited on top of the epitaxial wafer as a p-type contact metal electrode.
Referring to fig. 2, in particular, the monitor area B is disposed at an edge portion of the epitaxial wafer, and the target chip area C is disposed at a middle portion of the epitaxial wafer. In practical application, the monitoring oxidation mesa and the target oxidation mesa may be selected from regular patterns that are symmetrical to each other, such as a circle or a square, and it should be noted that the area of the monitoring oxidation mesa must be larger than that of the target oxidation mesa. Preferably, in the present embodiment, the monitor oxidation mesa and the target oxidation mesa are both circular, and the diameter D of the monitor oxidation mesa is the diameter DmesaLarger than the diameter of the target oxidation mesa.
(2) Placing the pretreated epitaxial wafer into an oxidation chamber 1 of oxidation real-time monitoring equipment, wherein a capacitance meter 3 outside the oxidation chamber 1 is connected to a p-type contact metal electrode of a monitoring area through a positive connecting wire and is connected to the bottom surface of a substrate of the epitaxial wafer through a negative connecting wire and a negative probe;
(3) starting an oxidation process, acquiring capacitance-voltage curves of a monitoring oxidation table surface of the epitaxial wafer in different oxidation time in real time through a capacitance meter 3, and acquiring a capacitance C before oxidation according to the characteristics of the capacitance-voltage curvessAnd the capacitance C at any time of oxidationdepThen, the capacitance C of the oxidized part is calculated in real time according to the formula (a)sox. Wherein the capacitance C before oxidationsThe capacitance between the p-type contact metal electrode and the substrate before oxidation is referred to; oxidizing the capacitance C at any momentdepThe capacitance between the p-type contact metal electrode and the substrate at any time in the oxidation process is referred to; capacitor C of oxidized partsoxRefers to the capacitance of the oxidized part of the oxide layer at that moment;
Figure DEST_PATH_IMAGE008
（a）；
specifically, in this step, the scan interval of the capacitance-voltage curve may be obtained by a pre-test in which the capacitance-voltage curve before oxidation is monitored by scanning different monitored oxidation mesa sizes, thereby intercepting appropriate reverse bias voltage ranges and forward bias voltage ranges as the scan interval. Preferably, four specifications of the monitoring oxidation mesa with the diameter of 27 μm,35 μm, 43 μm and 52 μm are selected for the pre-test in the present example, and the capacitance-voltage curves of the monitoring oxidation mesa with the four specifications before oxidation are shown in fig. 4. Referring to fig. 4, the capacitance is constant over the reverse bias voltage range of 0 to-5V for each oxidation mesa size; and the smaller the oxidation mesa diameter, the smaller the capacitance under reverse bias voltage. In the range of 0 to 2V forward bias voltage, the capacitance gradually increases with increasing voltage. For forward bias voltages greater than 2V, the capacitance decreases with increasing voltage due to the forward bias condition of the p-n junction. Therefore, in the formal oxidation process of this embodiment, the scan range of [ -5V,2V ] can be selected as the scan range of the capacitance-voltage curve. As shown in fig. 3, in the pilot test, four monitoring oxide mesas of different sizes were etched in the same monitoring area, thereby facilitating the control test.
Next, the monitored oxidation mesa of this example, preferably 52 μm in diameter, was subjected to an oxidation monitoring test at an oxidation temperature of 400 c, and the capacitance-voltage curves for oxidation for 10 minutes, 35 minutes and 80 minutes were scanned, respectively, and it can be seen from fig. 5 that the capacitance-voltage curve after oxidation was shifted to a higher forward voltage direction compared to the capacitance-voltage curve before oxidation, indicating the presence of negative charges in the oxide layer. As the oxidation time increases, the capacitance of the depletion layer decreases with negative bias (voltage below 0V) due to the capacitance change caused by the oxide layer formed in the mesa structure. Therefore, the oxidation depth D of the oxidation layer under different oxidation times can be represented by the change of the capacitance between the p-type contact metal electrode and the substrate at any time in the oxidation process.
In formula (a), the capacitance C before oxidationsAnd the capacitance C at any time of oxidationdepThe capacitance values corresponding to the midpoint voltage in the reverse bias voltage range are all taken, so that the values are more representative. As shown in FIG. 5, the capacitor C before oxidation in this embodimentsAnd the capacitance C at any time of oxidationdepThe capacitance corresponding to-2.5V voltage is selected.
(4) The capacitance C of the oxidized part in the oxidation is deduced by utilizing the concept of parallel capacitor plate devicesoxCalculating the oxidized area A of the monitored oxidation table top in real time according to a formula (b) of monitoring the oxidized area A of the oxidation table top, and further calculating the oxidation depth D of the monitored oxidation table top based on the structural characteristics of the monitored oxidation table top;
Figure DEST_PATH_IMAGE010
（b）
in the formula: doxIs the thickness of the oxide layer; epsilonoxIs an oxide layer (Al)2O3) The dielectric constant of (a); epsilonsIs the dielectric constant of a GaAs semiconductor; wmIs the thickness between the p-type contact metal electrode and the bottom surface of the substrate.
Since the monitor oxidation mesa and the target oxidation mesa of the present embodiment are both circular, the calculation formula of the oxidation depth D and the oxidized area a of the monitor oxidation mesa is as follows:
Figure DEST_PATH_IMAGE012
（c）
in the formula: dmesaTo monitor the diameter of the oxidation mesa.
(5) And drawing a curve relation graph of the oxidation depth and the oxidation time by taking the oxidation depth and the oxidation time as oxidation monitoring reference indexes, and controlling the oxidation depth of the target chip area. Referring to fig. 6, as the oxidation time T increases, the oxidation depth D also gradually increases, and the two are in a one-to-one curve relationship. Because the oxidation of the monitoring area B and the target chip area C is carried out simultaneously, the oxidation process of the target chip area C can be strictly controlled by referring to the curve, the oxidation time T is controlled according to the required oxidation depth D, once the ideal oxidation depth D is reached, the oxidation process in the oxidation chamber 1 is immediately stopped through oxidation real-time monitoring equipment, and the purpose of accurate and intelligent control is achieved.
Next, a VCSEL chip oxidation real-time monitoring device is introduced based on the VCSEL chip oxidation real-time monitoring method:
referring to fig. 7, the oxidation real-time monitoring apparatus includes an oxidation chamber 1, a heating furnace 2, a first carrier gas channel, a capacitance meter 3 and a control box 4; the bottom of the oxidation chamber 1 is provided with a heating furnace 2, and the oxidation chamber 1 is sequentially connected with a first regulating valve 51, a bubbler 52, a first gas flowmeter 53 and a first nitrogen source through a first carrier gas channel; the epitaxial wafer is placed in the oxidation chamber 1 and is electrically connected to the capacitance meter 3; the control box 4 is electrically connected to the capacitance meter 3 and the first regulating valve 51, and is configured to receive data collected by the capacitance meter 3, complete the calculation steps as described above, and control the oxidation process of the epitaxial wafer through the first regulating valve 51.
Referring to fig. 7, the oxidation chamber further comprises a second carrier gas channel, one end of the second carrier gas channel is communicated with the oxidation chamber 1, and the other end of the second carrier gas channel is sequentially provided with a second regulating valve 61, a second gas flowmeter 62 and a second nitrogen source. Besides, an exhaust gas treatment device is arranged outside the oxidation chamber 1.
As a preferable scheme: the oxidation chamber 1 is made of a quartz tube, which has good sealing properties and high temperature resistance. A carrying platform 11 is arranged in the oxidation chamber 1, the carrying platform 11 is used for placing an epitaxial wafer, and a negative electrode probe electrically connected to the capacitance meter 3 is arranged for the epitaxial wafer. Specifically, the negative probe selects pogo pin, which is embedded on the carrier 11 and connected with the negative connecting wire of the capacitance meter 3, when the epitaxial wafer is placed on the carrier 11, the needle of the pogo pin is in mutual contact with the bottom surface of the substrate corresponding to the monitoring area B of the epitaxial wafer, so that the connection between the epitaxial wafer and the negative electrode of the capacitance meter is realized, and the positive electrode of the capacitance meter 3 is connected with the p-type contact metal electrode of the monitoring area through the positive connecting wire, so that the circuit conduction is realized.
The working mode of the oxidation real-time monitoring equipment is briefly described as follows:
1. an epitaxial wafer to be oxidized is placed on a carrying table 11 in an oxidation chamber 1 (namely, a quartz tube), and the electric connection between the epitaxial wafer and the capacitance meter 3 is completed.
2. The oxidation starts by first supplying nitrogen gas from the second nitrogen gas source, and performing pressure reduction and flow rate control by the second gas flow meter 62 to remove oxygen gas from the quartz tube.
3. And then starting the heating furnace 2 to heat the epitaxial wafer, wherein the temperature range of the heating furnace 2 is controlled to be 400-480 ℃, meanwhile, nitrogen is sent into a bubbler 52 for water bath heating (such as 95 ℃) from a first nitrogen source through a first carrier gas channel, sufficient mixed gas of water vapor and nitrogen is generated through the bubbler 52, and then the mixed gas is sent into a quartz tube through the first carrier gas channel to participate in reaction. The gas flow rate during oxidation can be controlled by the first regulating valve 51.
4. During the oxidation reaction, the capacitance table 3 sweeps the gate voltage from-5V to 2V at fixed time intervals (for example, once every 1 min) in steps of 0.1V to plot capacitance-voltage curves for different oxidation times, and then transmits the data of the capacitance-voltage curves for different oxidation times to the control box 4. And (3) calculating the oxidized area A of the monitored oxidation table top in the oxidation process in real time by a processing module in the control box 4 according to the mathematical relation of the combination formulas (a), (b) and (c), and further obtaining the oxidation width D of the monitored oxidation table top in the oxidation process in real time. Once the desired oxidation width is reached, the control box triggers a preset cut-off condition, sending a command to close the first regulating valve 51 below, thus stopping the oxidation process.
The above description is only an embodiment of the present invention, but the design concept of the present invention is not limited thereto, and any insubstantial modifications made by using the design concept should fall within the scope of infringing the present invention.

Claims (8)

1. A VCSEL chip oxidation real-time monitoring method is characterized in that: the method comprises the following steps:
(1) pretreating an epitaxial wafer to be oxidized, depositing a p-type contact metal electrode on the top of the epitaxial wafer, then performing oxidation mesa etching, dividing the epitaxial wafer into a monitoring area and a target chip area, etching a monitoring oxidation mesa in the monitoring area, and etching a target oxidation mesa in the target chip area;
(2) placing the pretreated epitaxial wafer into an oxidation chamber of oxidation real-time monitoring equipment, wherein a capacitance meter outside the oxidation chamber is connected to a p-type contact metal electrode of the monitoring area through a positive connecting wire and is connected to the bottom surface of a substrate of the epitaxial wafer through a negative connecting wire and a negative probe;
(3) starting an oxidation process, acquiring capacitance-voltage curves of the monitoring oxidation table surface of the epitaxial wafer in different oxidation time in real time through a capacitance meter, and acquiring the capacitance C before oxidation according to the characteristics of the capacitance-voltage curvessAnd the capacitance C at any time of oxidationdepThen, the capacitance C of the oxidized part is calculated in real time according to the formula (a)sox；
Figure DEST_PATH_IMAGE002
（a）；
(4) The oxidized part of the capacitance C is deduced by using the concept of parallel capacitor platessoxCalculating the oxidized area A of the monitored oxidation table top in real time according to a formula (b) of monitoring the oxidized area A of the oxidation table top, and further calculating the oxidation depth D of the monitored oxidation table top based on the structural characteristics of the monitored oxidation table top;
Figure DEST_PATH_IMAGE004
（b）
in the formula: doxIs the thickness of the oxide layer; epsilonoxIs the dielectric constant of the oxide layer; epsilonsIs the dielectric constant of a GaAs semiconductor; wmThe thickness between the p-type contact metal electrode and the bottom surface of the substrate;
the monitoring oxidation mesa and the target oxidation mesa are both circular, and the diameter of the monitoring oxidation mesa is larger than that of the target oxidation mesa, so that the calculation formula of the oxidation depth D and the oxidized area A of the monitoring oxidation mesa is as follows:
Figure DEST_PATH_IMAGE006
（c）
in the formula: dmesaTo monitor the diameter of the oxidation mesa;
(5) and drawing a curve relation graph of the oxidation depth and the oxidation time by taking the oxidation depth and the oxidation time as oxidation monitoring reference indexes, and controlling the oxidation depth of the target chip area in real time.
2. The method of claim 1, wherein the VCSEL chip oxidation real-time monitoring comprises: in step (3), the capacitor C before oxidationsAnd the capacitance C at any time of oxidationdepThe capacitance value corresponding to the midpoint voltage within the reverse bias voltage range is taken.
3. The method of claim 1, wherein the VCSEL chip oxidation real-time monitoring comprises: in the step (3), the scanning interval of the capacitance-voltage curve can be obtained through a pre-test, in the pre-test, the capacitance-voltage curve before oxidation is scanned by different monitored oxidation mesa sizes, and therefore a proper reverse bias voltage range and a proper forward bias voltage range are intercepted to serve as the scanning interval.
4. The VCSEL chip oxidation real-time monitoring method of claim 3, wherein: in step (3), the scanning interval of the capacitance-voltage curve is [ -5V,2V ].
5. The VCSEL chip oxidation real-time monitoring method of claim 3, wherein: in the pre-test, a plurality of monitoring oxidation table tops with different sizes can be etched in the same monitoring area.
6. A VCSEL chip oxidation real-time monitoring equipment is characterized in that: comprises an oxidation chamber, a heating furnace, a first carrier gas channel, a capacitance meter and a control box; the heating furnace is arranged at the bottom of the oxidation chamber, and the oxidation chamber is sequentially connected with a first regulating valve, a bubbler, a first gas flowmeter and a first nitrogen source through the first carrier gas channel; the epitaxial wafer is placed in the oxidation chamber and is electrically connected to the capacitance meter; the control box is electrically connected with the capacitance meter and the first regulating valve, and is used for receiving data collected by the capacitance meter, completing the calculation steps as claimed in claim 1, and controlling the oxidation process of the epitaxial wafer through the first regulating valve.
7. The VCSEL chip oxidation real-time monitoring device of claim 6, wherein: the oxidation chamber is characterized by further comprising a second carrier gas channel, wherein one end of the second carrier gas channel is communicated with the inside of the oxidation chamber, and the other end of the second carrier gas channel is sequentially provided with a second regulating valve, a second gas flowmeter and a second nitrogen source.
8. The VCSEL chip oxidation real-time monitoring device of claim 6, wherein: the oxidation chamber is made of a quartz tube, and a carrying platform is arranged in the oxidation chamber, is used for placing the epitaxial wafer and is provided with a negative probe electrically connected with the capacitance meter.
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US6658040B1 (en) * 2000-07-28 2003-12-02 Agilent Technologies, Inc. High speed VCSEL
CN102163803A (en) * 2006-06-20 2011-08-24 索尼株式会社 Semiconductor device and method of manufacturing it

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