阅读说明：本技术 一种碳化硅外延层载流子浓度测试的方法及装置 (Method and device for testing carrier concentration of silicon carbide epitaxial layer ) 是由 陈志霞 林嘉伟 冉岩松 冯淦 赵建辉 于 2021-08-11 设计创作，主要内容包括：本发明涉及一种碳化硅外延层载流子浓度测试的方法及装置,所述方法为采用MCV设备测试碳化硅外延层载流子浓度,所述MCV设备包括载物台,所述载物台上方设置离子风帘盘,所述离子风帘盘通过一导管连接离子风枪；在测试碳化硅外延层载流子浓度之前,开启离子风枪,产生的离子风通过所述离子风帘盘对所述载物台上的碳化硅外延层进行吹扫,之后再进行碳化硅外延层载流子浓度的测试。所述装置包括MCV设备、离子风帘盘和离子风枪。本发明所述方法可以保证碳化硅外延片外延层载流子浓度测试结果的准确性,同时提高现有测试设备测试结果的重现性。(The invention relates to a method and a device for testing the carrier concentration of a silicon carbide epitaxial layer, wherein the method is to test the carrier concentration of the silicon carbide epitaxial layer by adopting MCV equipment, the MCV equipment comprises an object stage, an ion air curtain plate is arranged above the object stage, and the ion air curtain plate is connected with an ion air gun through a conduit; before the carrier concentration of the silicon carbide epitaxial layer is tested, the ion air gun is started, the generated ion air sweeps the silicon carbide epitaxial layer on the objective table through the ion air curtain plate, and then the carrier concentration of the silicon carbide epitaxial layer is tested. The device comprises an MCV device, an ion air curtain plate and an ion air gun. The method can ensure the accuracy of the test result of the concentration of the carrier of the epitaxial layer of the silicon carbide epitaxial wafer and simultaneously improve the reproducibility of the test result of the existing test equipment.)

1. A method for testing the carrier concentration of a silicon carbide epitaxial layer is characterized by comprising the following steps: testing the carrier concentration of the silicon carbide epitaxial layer by adopting MCV equipment, wherein the MCV equipment comprises an object stage, an ion air curtain plate is arranged above the object stage, and the ion air curtain plate is connected with an ion air gun through a guide pipe; before the carrier concentration of the silicon carbide epitaxial layer is tested, the ion air gun is started, the generated ion air sweeps the silicon carbide epitaxial layer on the objective table through the ion air curtain plate, and then the carrier concentration of the silicon carbide epitaxial layer is tested.

2. The method for testing the carrier concentration of the silicon carbide epitaxial layer according to claim 1, wherein: the ion air curtain plate is arranged right above the objective table, and the distance between the ion air curtain plate and the objective table is 5-15 cm.

3. The method for testing the carrier concentration of the silicon carbide epitaxial layer according to claim 1 or 2, wherein: the ion air gun is an induction type ion air gun, when an operator places a silicon carbide epitaxial sample wafer to be measured on the objective table, the induction type ion air gun induces the sample wafer, then blows ion air with positive and negative charges into the ion air curtain disc through a guide pipe, then sweeps the objective table through the ion air curtain disc, and after the ion air curtain disc sweeps for a period of time, the operator starts to measure the carrier concentration of the silicon carbide epitaxial sample wafer; and keeping purging in the measuring process until the test is finished, taking away the silicon carbide epitaxial sample wafer from the objective table by an operator, and finishing purging when the sample wafer is not sensed by the inductive ion air gun.

4. The method for testing the carrier concentration of the silicon carbide epitaxial layer according to claim 3, wherein: before the carrier concentration of the silicon carbide epitaxial sample wafer is measured, the purging time is more than or equal to 5 minutes, and the purging area is more than or equal to the surface area of the silicon carbide epitaxial sample wafer.

5. A silicon carbide epitaxial layer carrier concentration testing device, which applies the method for testing the carrier concentration of the silicon carbide epitaxial layer of any one of claims 1 to 4, and is characterized in that: the device comprises MCV equipment, wherein the MCV equipment comprises an object stage, an ion air curtain plate is arranged above the object stage, and the ion air curtain plate is connected with an ion air gun through a conduit;

the ion air curtain dish is circular, the ion air curtain dish is close to one side surface of objective table sets up a plurality of exhaust vents, the exhaust vent is the annular and distributes, the ring number more than or equal to 3 of exhaust vent to the diameter is the biggest the area more than or equal to the surface area of the silicon carbide epitaxial layer of awaiting measuring of circle that the exhaust vent encloses.

6. The apparatus for testing a carrier concentration of a silicon carbide epitaxial layer according to claim 5, wherein: the number of the air outlet holes is 3 rings, 4 rings or 5 rings.

7. The apparatus for testing a carrier concentration of a silicon carbide epitaxial layer according to claim 5, wherein: the diameter of the air outlet is 5-10 mm.

8. A silicon carbide epitaxial layer carrier concentration test apparatus according to any one of claims 5 to 7, wherein: the distance between two adjacent rings of the air outlet hole is 20-40 mm.

9. A silicon carbide epitaxial layer carrier concentration test apparatus according to any one of claims 5 to 7, wherein: the diameter of the ion air curtain plate is 20-30 cm.

10. A silicon carbide epitaxial layer carrier concentration test apparatus according to any one of claims 5 to 7, wherein: the ion air curtain plate is arranged right above the objective table, and the distance between the ion air curtain plate and the objective table is 5-15 cm.

Technical Field

The invention relates to a silicon carbide testing technology, in particular to a method and a device for testing the carrier concentration of a silicon carbide epitaxial layer.

Background

At present, in the industry, a mercury probe capacitance-voltage method is adopted for a silicon carbide epitaxial layer, namely, MCV equipment is used for measuring the carrier concentration of the epitaxial layer, the carrier concentration of the epitaxial layer can be used for evaluating the quality of the epitaxial layer, basis and support are provided for optimizing a silicon carbide epitaxial growth process, and the thickness of the epitaxial layer can be calculated by further combining other technologies, specifically refer to CN 113140478A. The method forms a Schottky barrier by contacting the front surface of a silicon carbide epitaxial wafer with a mercury probe to form a Schottky contact. A reverse bias voltage is applied between the mercury probe and the silicon carbide epitaxial wafer, and the barrier width of the junction is expanded into the epitaxial layer. And the carrier concentration of the silicon carbide epitaxial layer corresponding to the corresponding expansion width is obtained through the potential barrier capacitance of the junction, the change relation between the potential barrier capacitance and the bias voltage applied to the junction, and the relation between the potential barrier expansion width and the carrier concentration corresponding to the corresponding expansion width. It is thus important to obtain an accurate carrier concentration in the silicon carbide epitaxial layer.

However, because the silicon carbide wafer is a polar material, charges are easily accumulated on the surface of the silicon carbide epitaxial wafer, and when the charges are accumulated on the surface of the silicon carbide epitaxial wafer, the actual value of the reverse bias voltage applied to the surface of the silicon carbide epitaxial wafer is not consistent with the actual set value, that is, the accuracy and the repeatability of the carrier concentration test result are finally influenced.

Disclosure of Invention

The invention aims to solve the problem that the concentration test result of the epitaxial layer carrier of the silicon carbide epitaxial wafer by the existing test equipment (generally MCV equipment) is inaccurate, and provides an improved method for testing the concentration of the carrier of the silicon carbide epitaxial wafer.

The invention also provides a device for testing the carrier concentration of the silicon carbide epitaxial layer, so as to better realize the method, and more accurate carrier concentration test results can be obtained through the optimized design of the ion air curtain disk.

The specific scheme is as follows:

a method for testing the carrier concentration of a silicon carbide epitaxial layer comprises the steps of testing the carrier concentration of the silicon carbide epitaxial layer by adopting MCV equipment, wherein the MCV equipment comprises an object stage, an ion air curtain plate is arranged above the object stage, and the ion air curtain plate is connected with an ion air gun through a guide pipe; before the carrier concentration of the silicon carbide epitaxial layer is tested, the ion air gun is started, the generated ion air sweeps the silicon carbide epitaxial layer on the objective table through the ion air curtain plate, and then the carrier concentration of the silicon carbide epitaxial layer is tested.

Furthermore, the ion air curtain plate is arranged right above the objective table, and the distance between the ion air curtain plate and the objective table is 5-15 cm.

Furthermore, the ion air gun is an induction type ion air gun, when an operator places the silicon carbide epitaxial sample wafer to be measured on the objective table, the induction type ion air gun induces the sample wafer, then blows ion air with positive and negative charges into the ion air curtain disc through a guide pipe, then the objective table is blown by the ion air curtain disc, and after the ion air curtain disc blows the objective table for a period of time, the operator starts to measure the carrier concentration of the silicon carbide epitaxial sample wafer; and keeping purging in the measuring process until the test is finished, taking away the silicon carbide epitaxial sample wafer from the objective table by an operator, and finishing purging when the sample wafer is not sensed by the inductive ion air gun.

Furthermore, before the measurement of the carrier concentration of the silicon carbide epitaxial sample wafer is started, the purging time is greater than or equal to 5 minutes, and the purging area is greater than or equal to the surface area of the silicon carbide epitaxial sample wafer.

The invention also discloses a silicon carbide epitaxial layer carrier concentration testing device, which applies the method for testing the silicon carbide epitaxial layer carrier concentration, and comprises MCV equipment, wherein the MCV equipment comprises an object stage, an ion air curtain plate is arranged above the object stage, and the ion air curtain plate is connected with an ion air gun through a conduit;

the ion air curtain dish is circular, the ion air curtain dish is close to one side surface of objective table sets up a plurality of exhaust vents, the exhaust vent is the annular and distributes, the ring number more than or equal to 3 of exhaust vent to the diameter is the biggest the area more than or equal to the surface area of the silicon carbide epitaxial layer of awaiting measuring of circle that the exhaust vent encloses.

Furthermore, the number of the rings of the air outlet hole is 3, 4 or 5.

Furthermore, the diameter of the air outlet is 5-10 mm.

Furthermore, the distance between two adjacent rings of the air outlet is 20-40 mm.

Further, the diameter of the ion air curtain plate is 20-30 cm.

Furthermore, the ion air curtain plate is arranged right above the objective table, and the distance between the ion air curtain plate and the objective table is 5-15 cm.

Has the advantages that:

in the invention, MCV equipment and an ion air gun are connected in series to carry out high-speed ion air blowing on the surface of the silicon carbide epitaxial sample wafer, thereby eliminating the accumulated charges on the surface of the silicon carbide epitaxial sample wafer to be measured, solving the problem that the value of reverse bias voltage actually applied to the surface of the silicon carbide epitaxial wafer is inconsistent with an actually set value, and ensuring the accuracy of further calculating the carrier concentration of the silicon carbide epitaxial layer according to the reverse bias voltage.

Furthermore, the invention optimizes the structure of the ion air curtain disc and the relative position relation of the ion air curtain disc and the MCV equipment by optimizing the testing process, so that the accuracy of the carrier concentration determination of the silicon carbide epitaxial layer is improved, and the experiment has good reproducibility.

In a word, the method ensures the accuracy of the current test equipment (MCV equipment) on the concentration test result of the epitaxial layer carrier of the silicon carbide epitaxial wafer, and improves the reproducibility of the test result of the current test equipment.

Drawings

In order to illustrate the technical solution of the present invention more clearly, the drawings will be briefly described below, and it is apparent that the drawings in the following description relate only to some embodiments of the present invention and are not intended to limit the present invention.

Fig. 1 is a schematic structural diagram of an apparatus provided in embodiment 1 of the present invention;

FIG. 2 is a schematic view of a point location of a silicon carbide wafer provided in accordance with an embodiment 1 of the present invention;

FIG. 3 is a graph of the results of a test provided in accordance with one embodiment of the present invention without an ionic wind purge;

FIG. 4 is a graph of the test results after an ion wind purge provided in accordance with one embodiment of the present invention 1;

FIG. 5 is a graph of test results after sample 1 was purged for various periods of time as provided in one embodiment of the present invention 3;

FIG. 6 is a graph of test results after purging coupon 2 for various periods of time according to one embodiment of the present invention 3;

FIG. 7 is a top view of an ion curtain disk provided in accordance with one embodiment 4 of the present invention;

FIG. 8 is a front view of an ion curtain disk provided in accordance with one embodiment 4 of the present invention;

FIG. 9 is a left side view of an ion curtain disk provided in accordance with one embodiment 4 of the present invention;

FIG. 10 is a graph showing the test results of a sample 1 according to an embodiment 4 of the present invention;

fig. 11 is a graph showing the test results of the sample 2 according to embodiment 4 of the present invention.

Detailed Description

The definitions of some of the terms used in the present invention are given below, and other non-mentioned terms have definitions and meanings known in the art:

MCV: all are known as mercury probe capacitance voltage tester.

An ion air gun: the ion air gun can generate a large amount of air flow with positive and negative charges to neutralize the charges on objects. When the surface of the object is charged with negative charges, the air flow can absorb the positive charges in the air flow, and when the surface of the object is charged with positive charges, the air flow can absorb the negative charges in the air flow, so that the static electricity on the surface of the object is neutralized, and the purpose of eliminating the static electricity is achieved.

The ion air gun can adopt the existing equipment, the structure of the ion air gun is the prior art, and the invention is not described again. Preferably, an induction type ion air gun is adopted, so that the convenience of operation can be improved.

Ion air curtain dish: the disk-shaped ion wind curtain does not generate ion wind by itself, only serves as an air outlet channel, and is matched with the ion wind gun to provide annular ion wind flow. Because the silicon carbide epitaxial wafer is generally circular, the effect of adopting the ion air curtain plate to sweep the sample wafer is better. Conventional ion windscreens on the market are long and provide ion windings in rectangular areas, in which case the reproducibility of the test is poor depending on the charge distribution of the epitaxial layer. A unique disk-like appearance is used herein to make the purge more uniform.

Preferentially, the ion air curtain plate is close to a plurality of air outlets are formed in the surface of one side of the objective table, the air outlets are distributed in an annular mode, the number of the air outlets is larger than or equal to 3, and the diameter of the air outlets is the largest, the area of a circle formed by enclosing the air outlets is larger than or equal to the surface area of the silicon carbide epitaxial layer to be tested, so that the accuracy and the reproducibility of the test are guaranteed.

The source of the MCV device is not particularly limited in the present invention and can be obtained commercially.

The main improvement of the method provided by the present invention is the combined application of the MCV device and the ion wind, and other conventional steps for testing the carrier concentration of the silicon carbide epitaxial layer, the operation method of the MCV device, etc. may be the same as those in the prior art, and those skilled in the art will know that the description is omitted here.

Preferred embodiments of the present invention will be described in more detail below. While the following describes preferred embodiments of the present invention, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein. The examples do not specify particular techniques or conditions, and are performed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available. In the following examples, "%" means weight percent, unless otherwise specified.

Example 1

Referring to fig. 1, in a method for testing a carrier concentration of a silicon carbide epitaxial layer, an MCV apparatus is used for testing the carrier concentration of the silicon carbide epitaxial layer, the MCV apparatus includes an object stage 1, an ion air curtain plate 2 is arranged above the object stage 1, and the ion air curtain plate 2 is connected to an ion air gun 4 through a conduit 3.

Preferably, the ion air curtain plate is arranged right above the objective table, and the distance between the ion air curtain plate and the objective table is 5-15cm, so that the effect of ion air on a sweeping target is ensured.

Before the carrier concentration of the silicon carbide epitaxial layer is tested, the ion air gun 4 is started, the generated ion air sweeps the silicon carbide epitaxial layer on the objective table through the ion air curtain disc 2, and then the carrier concentration of the silicon carbide epitaxial layer is tested.

The points indicated by the dots in fig. 2 were sequentially tested using a silicon carbide sample as shown in fig. 2, and the test sequence is shown in table 1 below. According to the epitaxial growth principle, the concentration distribution should exhibit a centrosymmetric distribution.

Table 1 test sequence chart of point locations on sample sheet

The method is adopted for 5 sample wafers, the carrier concentration on the silicon carbide epitaxial wafer is detected by the conventional method (namely, the ion air gun 4 and the ion air curtain disk 2 are not adopted, and the original MCV equipment is only utilized), the result is shown in fig. 3 and 4, the test result after the ion air blowing is closer to the real concentration, and the test result before the ion removal is affected by the residual charges on the surfaces of the sample wafers, so that the accuracy of the test result is poor.

Therefore, the ion wind can effectively eliminate the accumulated charges on the surface of the silicon carbide epitaxial sample wafer to be tested, so that the accurate value of the reverse bias voltage on the surface of the silicon carbide epitaxial wafer can be obtained after the probe contacts the silicon carbide epitaxial layer, the accuracy of the concentration test result of the carrier of the silicon carbide epitaxial layer is further ensured, and the repeatability of the test result is improved.

Example 2

This embodiment improves on embodiment 1's basis, adopts ion air gun 4 to adopt induction type ion air gun, and is concrete, installs ion air curtain dish on the test chamber lid of 10cm directly over apart from the objective table, and the pipe of reuse links to each other induction type ion air gun air outlet with dress ion air curtain dish. When an operator places a silicon carbide epitaxial sample wafer to be tested on a test platform deck, the induction type ion air gun can sense the silicon carbide epitaxial sample wafer, then air mass with positive and negative charges is blown into the air curtain plate at a high speed through the guide pipe, the sample wafer on the vacuum platform deck is swept by the air curtain plate in a large area, after the air curtain plate is continuously swept for 5 minutes, the operator finishes measuring the carrier concentration of the sample wafer to be tested according to the test step of the MCV equipment and takes away the sample wafer to be tested from the test platform deck.

Through induction type ion air gun, can increase the convenience of operation.

Example 3

In this embodiment, an improvement is made on the basis of embodiment 2, and the influence of the ion purging duration before the probe test is started on the test result is studied, that is, after purging is not performed for 2min, purging is performed for 5min, and the probe contact with the silicon carbide epitaxial layer is performed for 8min, and 2 samples are tested, and the results are shown in fig. 5 and 6, respectively.

As can be seen from fig. 5 and 6, the concentration test result is substantially improved after ion purging is performed on the surface of the sample wafer for 5 minutes before the sample wafer is tested, and therefore, accurate test results can be obtained after purging for 5 minutes or more.

Example 4

The present embodiment is improved on the basis of embodiment 1, and the ion wind curtain disk is optimized, and the structure of the ion wind curtain disk is shown in fig. 7, fig. 8 and fig. 9.

The ion wind curtain plate comprises a plate base body 21, an ion wind channel 22 is arranged in the plate base body 21, and the ion wind channel 22 is communicated with a plurality of wind outlet holes 23 arranged on one side of the plate base body 21. The air outlet holes 23 are distributed annularly, and the number of the rings is 3. The area of a circle surrounded by the air outlet holes 23 with the largest diameter is larger than or equal to the surface area of the silicon carbide epitaxial layer to be tested. An ion wind inlet 24 of the ion wind passage 22 is provided in the center of the side of the disk base 21, and a duct for connection to an ion wind gun is connected through the ion wind inlet 24.

Preferably, the diameter of the air outlet is 5-10mm, for example 8 mm. The distance between two adjacent rings of the air outlet is 20-40mm, such as 30 mm. The adjacent air outlet holes of the same ring have the distance of 10-25mm, such as 19 mm. The ion curtain disk has a diameter of 20-30cm, for example 240 mm. The distance between the ion wind curtain plate and the object stage is 5-15cm, for example 10 cm.

The test is carried out by adopting a 240mm ion air curtain disk, the diameter of the air outlet is 8mm, and the distance between two adjacent rings is 30 mm. On the basis, the detection effect of the ion air curtain plates with different ring numbers is carried out, the ion air curtain plates with the ring numbers of 2, 3 and 4 are respectively tested, the test method is the same as that of the embodiment 1, and the results are shown in fig. 10 and fig. 11. As can be seen from fig. 10 and 11, the accuracy of the test can not be guaranteed by using the 2-ring ion air curtain disk, and when 3-ring and 4-ring ion air curtain disks are used, symmetry occurs, which indicates that the test is accurate and the reproducibility of the experiment is good.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. The invention is not described in detail in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.