CN102841281B - Detection method and device for LED epitaxial wafer - Google Patents

Abstract

The invention discloses a detection method and device of an LED epitaxial wafer. The method includes: applying an AC square wave voltage between the upper and lower end faces of the LED epitaxial wafer, and the magnitude of the AC square wave voltage is sufficient to drive the LED epitaxial wafer to emit light. The device includes: a conductive base for carrying the LED epitaxial wafer, and the conductive base is in contact with the lower end surface of the LED epitaxial wafer; a conductive probe, which is in contact with the upper end surface of the LED epitaxial wafer, and is used to connect the conductive base to the upper end surface of the LED epitaxial wafer. An AC square wave voltage source applying an AC square wave voltage between the conductive probe and the AC square wave voltage is sufficient to drive the LED epitaxial wafer to emit light. Compared with the existing probe-type electroluminescence (EL) testing method, the present invention only needs a single probe and does not need to perform operations such as pointing In. It is not only simple to operate, but also efficient and fast, low in cost, and will not pollute or damage the LED epitaxial wafer. , and the test results are stable and accurate, and can realize online EL testing of various types of LED epitaxial wafers, with strong versatility.

Description

Method and device for detecting LED epitaxial wafers

technical field

The invention particularly relates to a detection method and device for an LED epitaxial wafer.

Background technique

With the continuous advancement of semiconductor technology, semiconductor devices such as LEDs, photovoltaic cells, semiconductor lasers, etc. have been widely used in people's daily life and work. In order to ensure quality and cost control in the production process of semiconductor devices, it is generally necessary to perform various online performance tests on semiconductor devices during the production process. Taking LED as an example, in the LED manufacturing process, it is usually necessary to perform EL testing (electroluminescent performance testing) on LED epitaxial wafers. For example, referring to Fig. 1, for an LED epitaxial wafer 10 having an insulating substrate 12 such as sapphire, the existing EL test method is generally to point an In point 20 on one side of the semiconductor material layer 110 of the LED epitaxial wafer 10, and use a conductive The probe is in contact with the upper surface of the LED epitaxial wafer, and then a DC voltage is applied between the conductive probe and the In point 20, so as to realize the EL test. However, there are many defects in this EL testing method, such as:

First, the test method is inconvenient to operate. For example, because In is used as a contact, it is necessary to heat the In application point during operation, and the cost of high-purity In is high;

Second, after the test method is completed, In will remain on the LED epitaxial wafer, thereby polluting the LED epitaxial wafer and affecting its quality;

Third, at least two conductive probes are required in this test method, and DC voltage is used. The EL test wavelength will vary with the current, which will not only affect the accuracy of the test results, but may also cause damage to the LED epitaxial wafer.

Contents of the invention

One of the objectives of the present invention is to provide a method for testing LED epitaxial wafers, which has the characteristics of easy operation, low cost, and accurate test results, thereby overcoming the shortcomings of the prior art.

In order to achieve the purpose of the above invention, the LED epitaxial wafer detection method adopted in the present invention may include:

An AC square wave voltage is applied between the upper and lower end faces of the LED epitaxial sheet, and the magnitude of the AC square wave voltage is sufficient to drive the LED epitaxial sheet to emit light.

Further, the LED epitaxial wafer detection method may also include:

placing the LED epitaxial wafer on a conductive substrate, and making the upper and lower end surfaces of the LED epitaxial wafer contact with a conductive probe and the conductive substrate respectively,

And, an alternating current (AC) alternating current square wave voltage is applied between the conductive substrate and the conductive probe, and the magnitude of the alternating current square wave voltage is sufficient to drive the LED epitaxial wafer to emit light.

Another object of the present invention is to provide a LED epitaxial wafer detection device, comprising:

A conductive base for carrying the LED epitaxial wafer, and the conductive base is in contact with the lower end surface of the LED epitaxial wafer;

a conductive probe, which is in contact with the upper surface of the LED epitaxial wafer,

And, an AC square wave voltage source for applying an AC square wave voltage between the conductive substrate and the conductive probe, the magnitude of the AC square wave voltage is sufficient to drive the LED epitaxial wafer to emit light.

As one of the preferred solutions, the magnitude of the aforementioned AC square wave voltage is 2-250V, especially preferably 3-60V.

As one of the preferred schemes, the frequency of the AC square wave voltage is 50-1 MHz.

Further, a substrate is provided on the lower part of the LED epitaxial wafer, and the lower end surface of the substrate is in contact with the conductive base.

Further, the conductive probe can be electrically connected to one pole of the AC square wave voltage source, and the conductive substrate can be grounded or electrically connected to the other pole of the AC square wave voltage source.

Further, the foregoing substrate can be selected from various conductive or insulating substrates known in the art, especially insulating substrates made of sapphire and the like, but not limited thereto.

Further, the conductive base may include a metal disc, but is not limited thereto.

Compared with the prior art, the present invention has at least the following positive effects:

(1) The LED epitaxial wafer detection method does not need to spot In on the LED epitaxial wafer, but only needs to use a conductive substrate and a conductive probe to implement. The operation is simple, the cost is low, the efficiency is high, and online detection can be realized without Cause any pollution to the LED epitaxial wafer, so as to effectively guarantee its quality;

(2) The LED epitaxial wafer detection method uses AC voltage, especially AC square wave voltage to test the LED epitaxial wafer. The wavelength is not easy to change with the current, the result is stable, and it will not cause damage to the structure of the LED epitaxial wafer.

(3) The LED epitaxial wafer detection method and device are suitable for performing EL testing on any type of LED epitaxial wafers, are universal, and can effectively reduce user costs.

Description of drawings

Fig. 1 is the schematic diagram of existing LED epitaxial wafer EL test method;

Fig. 2 is the schematic diagram of LED epitaxial wafer EL testing method of the present invention;

Fig. 3 is one of equivalent circuit diagrams of LED epitaxial wafer EL testing method of the present invention;

Fig. 4 is the second equivalent circuit diagram of LED epitaxial wafer EL testing method of the present invention;

Fig. 5 is the structural representation of LED epitaxial wafer EL testing device in a preferred embodiment of the present invention;

Explanation of reference numerals: LED epitaxial wafer 10 , semiconductor material layer 110 , semiconductor material P-type layer 11 , semiconductor material multiple quantum well (MQW) layer 11 ′, semiconductor material N-type layer 11 ″, insulating substrate 12 , In point 20 , conductive substrate 30, conductive probe 40, equivalent series resistance R _s , equivalent parallel resistance R _p , equivalent capacitance C, equivalent diode D, sapphire substrate 111, U-type GaN layer 112, N-type GaN layer 113 , MQWs (Multiple Quantum Well Structure) 114 , P-type GaN layer 115 , metal disc 3 , metal probe 4 .

Detailed ways

In view of the many defects of the existing EL testing methods, the present invention provides a method and device for testing LED epitaxial wafers, and the technical solution thereof is further explained as follows.

The LED epitaxial wafer detection method of the present invention is mainly realized through the following technical scheme, that is, an AC square wave voltage is applied between the upper and lower end faces of the LED epitaxial wafer, and the magnitude of the AC square wave voltage is sufficient to drive the LED epitaxial wafer glow.

Further, referring to FIG. 2, the LED epitaxial wafer detection method can be implemented by means of an LED epitaxial wafer detection device, which can include a conductive substrate 30, a conductive probe 40 and an AC square wave voltage source ( not shown in the figure).

The LED epitaxial wafer detection method may include:

The LED epitaxial wafer 10 is placed on a conductive substrate 30, and the upper end surface of the LED epitaxial wafer 10 and the lower substrate 12 are respectively in contact with a conductive probe 40 and the conductive substrate 30,

And, an AC square wave voltage is applied between the conductive substrate 30 and the conductive probe 40 , and the magnitude of the AC square wave voltage is sufficient to drive the LED epitaxial wafer 10 to emit light.

3 is the equivalent circuit diagram formed by the conductive substrate, the conductive probe and the tested LED epitaxial wafer in the LED epitaxial wafer EL testing method. If the aforementioned substrate 12 is an insulating substrate, the equivalent circuit system includes An equivalent PN junction diode D and an equivalent parallel resistance Rp formed by semiconductor material P-type layer 11, multi-quantum well (MQW) layer 11' and N-type layer 11" _in LED epitaxial wafer 10 are mainly composed of semiconductor material P-type An equivalent series resistance R _s is formed by the resistance of the layer 11 and the N-type layer 11 ″ itself, and an equivalent capacitance C is formed between the conductive substrate 30 and the N-type layer 11 ″ of semiconductor material.

When applying an AC square wave voltage sufficient to drive the LED epitaxial wafer 10 to emit light between the conductive substrate 30 and the conductive probe 40, if the LED epitaxial wafer 10 is normal, then:

When the conductive probe is at a high potential, the equivalent diode D is turned on, the equivalent capacitor C is charged, and the current flows in one direction in the equivalent circuit, so that the LED epitaxial wafer 10 emits light;

When the conductive probe is at a low potential, the equivalent diode D is turned off, the equivalent capacitor C is discharged through the equivalent parallel resistor R _p , and the LED epitaxial wafer 10 does not emit light.

The magnitude and frequency of the aforementioned AC square wave voltage can be appropriately selected by those skilled in the art according to the needs of practical applications.

As one of the preferred solutions, the magnitude of the aforementioned AC square wave voltage may be 2-250V, especially preferably 3-60V.

As one of the preferred solutions, the frequency of the aforementioned AC square wave voltage may be 50-1 MHz.

Furthermore, the aforesaid AC square wave voltage source can be realized by means of various common AC square wave voltage generating devices.

Furthermore, as an optional embodiment of the present invention, in the LED epitaxial wafer testing method, the conductive probe 40 can be electrically connected to one pole of the AC square wave voltage source, and the conductive base 30 can be grounded or connected to the AC The other pole of the square wave voltage source is electrically connected.

The aforementioned substrate 12 may include a sapphire substrate, but is not limited thereto.

And if the aforementioned substrate 12 is a conductive substrate, then in the EL test method, the structure of the equivalent circuit diagram formed by the conductive substrate, the conductive probe and the tested LED epitaxial wafer is as shown in Figure 4, which includes LED An equivalent PN junction diode D and an equivalent parallel resistance _Rp formed by the semiconductor material P-type layer 11, the multi-quantum well (MQW) layer 11' and the N-type layer 11" in the epitaxial wafer 10 are mainly composed of the semiconductor material P-type layer 11 and the resistance of the N-type layer 11" itself forms an equivalent series resistance R _s .

When applying an AC square wave voltage sufficient to drive the LED epitaxial wafer 10 to emit light between the conductive substrate 30 and the conductive probe 40, if the LED epitaxial wafer 10 is normal, then:

When the conductive probe is at a high potential, the equivalent diode D is turned on, and the current flows in one direction in the equivalent diode, so that the LED epitaxial wafer 10 emits light;

When the conductive probe is at a low potential, the equivalent diode D is turned off, and the LED epitaxial wafer 10 does not emit light.

The technical solution of the present invention will be further described below in conjunction with a preferred embodiment.

Referring to Fig. 5, the present embodiment relates to a method for carrying out EL testing on a conventional LED epitaxial wafer, the method is by means of an LED epitaxial wafer EL testing device, which includes a metal disc 3, a metal probe 4 and an AC Square wave voltage source (not shown in the figure).

The common LED epitaxial wafer includes a sapphire substrate 111 with a thickness of about 5-1000 μm, on which a U-type GaN layer 112, an N-type GaN layer 113, MQWs (multiple quantum well structure) 114, a P-type GaN layer 115 .

During the EL test, the conventional LED epitaxial wafer is placed on the metal disc 3, the bottom surface of the substrate is in contact with the metal disc 3, and the metal probe 4 is in contact with the upper end surface of the conventional LED epitaxial wafer,

The metal probe 4 is also electrically connected to one pole of an AC square wave voltage source, and the metal plate 3 can be grounded or electrically connected to the other pole of the AC square wave voltage source. When the AC square wave voltage source is turned on, and When an AC square wave voltage is applied between the metal probe 4 and the metal plate 3, the LED epitaxial wafer will normally emit light when the conductive probe is at a high potential, and the LED epitaxial wafer will not emit light when the conductive probe is at a low potential.

The magnitude of the aforementioned AC square wave voltage may be 2-250V, preferably 3-60V, and the frequency may be 50-1MHz.

In this way, with the simple test method and device mentioned above, the EL test of the common LED epitaxial wafer can be completed. Compared with the existing EL test method, only a single probe is needed, and no operations such as pointing In are required. Not only is the operation simple, Efficient, fast, low cost, will not pollute or damage LED epitaxial wafers, and the test results are stable and accurate.

The invention can realize online EL testing of various types of LED epitaxial wafers.

The above-mentioned embodiments are only to illustrate the technical concept and characteristics of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and not to limit the scope of protection of the present invention. All equivalent changes or modifications made according to the spirit of the present invention shall fall within the protection scope of the present invention.

Claims (8)

1. a LED detection method, is characterized in that, it comprises:

LED is placed in a conductive substrates, and the upper surface of the semiconductor material layer being positioned at described LED top is contacted with a conducting probe, make the lower surface of the substrate being positioned at described LED bottom contact with a conductive substrates simultaneously,

And, between described conductive substrates and conducting probe, apply an ac square-wave voltage, and the size of described ac square-wave voltage is enough to the luminescence of driving LED epitaxial wafer.

2. LED detection method according to claim 1, is characterized in that, the size of described ac square-wave voltage is 2-250V.

3. a LED pick-up unit, is characterized in that, it comprises:

For carrying the conductive substrates of LED, and described conductive substrates contacts with the lower surface of the substrate being positioned at LED bottom;

Conducting probe, it contacts with the upper surface of the semiconductor material layer being positioned at LED top,

And for applying the ac square-wave voltage source of an ac square-wave voltage between described conductive substrates and conducting probe, the size of described ac square-wave voltage is enough to the luminescence of driving LED epitaxial wafer.

4. LED pick-up unit according to claim 3, is characterized in that, the size of described ac square-wave voltage is 2-250V.

5. LED pick-up unit according to claim 4, is characterized in that, the size of described ac square-wave voltage is 3-60V.

6. the LED pick-up unit according to any one of claim 3-5, is characterized in that, described conducting probe is electrically connected with a pole in ac square-wave voltage source, described conductive substrates ground connection or be electrically connected with another pole in ac square-wave voltage source.

7. LED pick-up unit according to claim 3, is characterized in that, described substrate comprises dielectric substrate or conductive substrates, and described dielectric substrate comprises Sapphire Substrate.

8. LED pick-up unit according to claim 3, is characterized in that, described conductive substrates comprises metal dish.