A method for measuring the true physical thickness of LED evaporation coating layer

Abstract

The present invention relates to a method for measuring the real physical thickness of an LED evaporated coating layer. The measuring method comprises: (1) preparing a companion film; (2) preparing a film layer; (3) measuring the thickness of the film layer; (4) calculating a relative value; and (5) calculating the thickness of the film layer. The present invention realizes timely measurement of the real physical thickness of the evaporated coating layer on the surface of a single batch of LED chips by introducing a companion film. As long as the position of the companion film is fixed, the relative value of the real physical thickness of the evaporated coating layer on the surface of the companion film at that position and the real physical thickness of the evaporated coating layer on the surface of the LED chip at the position to be measured is calculated during the first thickness test. After that, the real physical thickness of the evaporated coating layer on the surface of the LED chip in each batch can be measured by measuring the real physical thickness of the evaporated coating layer on the surface of the companion film. After each batch of evaporation production, it is only necessary to measure the real physical thickness of the evaporated coating layer on the surface of the companion film, and the real physical thickness of the evaporated coating layer on the surface of the LED chip can be immediately obtained.

Description

Technical Field

[0001] The invention relates to a method for measuring the real physical thickness of an LED evaporation coating layer, and belongs to the technical field of semiconductor processing. Background Art

[0002] Light Emitting Diode, or LED, is a semiconductor device, known as the third generation lighting source, which can directly convert electrical energy into light energy to emit light. Light Emitting Diode has the following advantages: small size, light weight, easy miniaturization and integration, long life of the lamp beads, short response time, ability to produce light of various wavelengths, high brightness, low power consumption, and a completely solid light emitting device.

[0003] At present, the evaporated coating layers of LED are mainly current spreading layer, metal electrode film layer and current blocking layer. There are generally two methods for making current spreading layer, metal electrode film layer and current blocking layer, one is sputtering coating, the other is electron beam evaporation, and the production of metal film layer, which is less used, also uses chemical plating. Sputtering and electron beam evaporation are the most commonly used. Whether it is sputtering or electron beam evaporation, the equipment itself will provide a set of measurement methods for the thickness of evaporated coating layer, which can be displayed in real time on the equipment to control the film forming requirements. However, in the actual production process, the monitoring or measurement of the film thickness of the film forming process often fluctuates, so that the real physical thickness has a large error, and subsequent methods are needed to further measure its real thickness to remedy and reduce the error. At present, the commonly used methods are usually the following: one is to mark the test points on the surface of the LED wafer of the film layer to be made through the preset pattern of the photolithography plate, and after the film layer is completed, the test points are made by etching or stripping, and then the actual thickness is measured using equipment such as a step meter. The disadvantage of this method is that it cannot test the surface of the LED wafer with full film coverage of the evaporated coating layer; the other is to monitor the thickness of the film layer with high light transmittance, and the film thickness can be measured and monitored using optical film thickness measuring instruments, ellipsometers and other measuring instruments after film formation. However, for materials such as metals that block light seriously, especially LED wafers with full film coverage of evaporated coating layers, accurate measurement is impossible. At present, the thickness can only be measured by making a mask pattern in advance for stripping test or making a protective pattern after film formation for corrosion. The process is relatively cumbersome and not timely, and the feedback equipment is relatively lagging.

[0004] Chinese patent document CN102005401A proposes a method for measuring the thickness of an epitaxial film, which includes the following steps: a reference film forming step for directly forming a reference film with a pattern on the substrate of a wafer; an epitaxial film forming step for directly forming an epitaxial film in other areas of the substrate of the wafer other than the area where the reference film is formed; and a measuring step for measuring the thickness of the epitaxial film based on the reference film. The method for measuring the thickness of an epitaxial film according to the present invention provides a reference film that is also formed on the wafer substrate as a reference, so that the thickness of the epitaxial film can be measured simply and quickly with high precision. This is a conventional method of measuring the film thickness by making additional graphics (test points). At present, this method is widely used, but it requires additional photolithography or special photolithography board production to achieve it. It is ineffective for full-filming and still has great limitations in timeliness and wide applicability.

[0005] Chinese patent document CN105448765A proposes a method for measuring the thickness of a metal film, which includes the following steps: providing multiple online produced product wafers; forming metal films of different thicknesses on different product wafers; measuring the radius of curvature of each product wafer after the metal film is formed; calculating the warpage height of each product wafer; performing data fitting on the metal film thicknesses on multiple product wafers and their corresponding warpage height values ​​to obtain a relationship between the metal film thickness and the warpage height value; providing a product wafer to be tested, forming a metal film to be tested on the surface of the product wafer to be tested; measuring the radius of curvature of the product wafer to obtain the radius of curvature value to be measured; calculating the warpage height value to be measured by the radius of curvature value to be measured; substituting the warpage height value to be measured into the relationship between the metal film thickness and the warpage height value to obtain the metal film thickness value to be measured. This method can avoid damage to the product wafer and realize online measurement of the thickness of the metal film. However, the error will be larger for wafers with smaller warpage heights, that is, for values ​​with smaller film thicknesses, the measurement accuracy fluctuates greatly.

[0006] Therefore, in summary, considering the drawbacks and complexity of the current measurement method, it is necessary to improve the drawbacks of the measurement method of the evaporated coating thickness in the LED manufacturing process and develop a process method suitable for measuring the thickness of all evaporated coating layers. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention provides a method for measuring the true physical thickness of an LED evaporated coating layer.

[0008] The technical solution of the present invention is as follows:

[0009] A method for measuring the real physical thickness of an LED evaporated coating layer comprises the following steps:

[0010] (1) Preparation of the accompanying film: After cleaning the surface of the accompanying film, use an adhesive film to cover part of the surface of the accompanying film and prepare it for use;

[0011] (2) Film layer production: placing the companion film in step (1) at a fixed position, and then performing evaporation coating together with the LED wafer to produce a film layer, and taking out the companion film after the evaporation is completed;

[0012] (3) Film thickness measurement: remove the sticky film on the surface of the companion wafer in step (2), measure the height difference between the area covered by the sticky film and the area not covered by the sticky film, which is the real physical thickness of the evaporated film layer on the surface of the companion wafer; after taking out the LED wafer in step (2), make a protective pattern on its surface, make a measurement pattern by etching, and measure its thickness after removing the glue, which is the real physical thickness of the evaporated film layer on the surface of the LED wafer;

[0013] (4) Relative value calculation: The actual physical thickness of the evaporated film layer on the companion wafer surface obtained in step (3) and the actual physical thickness of the evaporated film layer on the LED wafer surface are calculated to obtain a relative value caused by the evaporation position;

[0014] (5) Calculation of film thickness: Before each evaporation, the evaporated film layer is prepared according to steps (1) and (2). After the preparation is completed, the actual physical thickness of the evaporated film layer on the surface of the companion wafer is measured according to step (3). The actual physical thickness of the evaporated film layer on the surface of the companion wafer minus the relative value is the actual physical thickness of the evaporated film layer on the surface of the LED chip after this evaporation.

[0015] According to the preferred embodiment of the present invention, in step (1), the adhesive film is a high temperature resistant tape, one side is smooth and the other side is adhesive, and the material is polyimide silicone, and the temperature resistance is above 150° C. It has the advantages of demagnetization, anti-static, high temperature resistance, no glue falling off, and no residue left on the adhered surface after being torn off.

[0016] According to the preferred embodiment of the present invention, the partial area in step (1) is 10-90% of the surface area of ​​the companion film, and more preferably 10-30%. The area covered by the adhesive film will form a film on the surface of the adhesive film during evaporation, and the size of the area can be adjusted according to measurement needs to achieve subsequent measurement of the measuring equipment.

[0017] According to the preferred embodiment of the present invention, in step (1), the companion sheet is an optical glass or stainless steel sheet, and the smoothness of its surface will not affect the thickness of the film-forming surface.

[0018] Preferably, according to the present invention, in step (2), the fixed position is any position of the fixture and does not occupy the normal LED chip placement position. The companion wafers are then placed at this position during vapor deposition.

[0019] According to the preferred embodiment of the present invention, in step (2), the LED wafer includes but is not limited to GaN, GaAs, and Si wafers. All materials suitable for making surface film layers can have their thickness measured by the method of the present invention.

[0020] Preferably, according to the present invention, in step (3), the instrument used for the measurement is a step profiler with a measurement accuracy of up to 1 angstrom, and the model is XP-2.

[0021] In the present invention, the manufacturing of the protective pattern, the etching and the degumming are all carried out according to the prior art.

[0022] The present invention has the following beneficial effects:

[0023] 1. The present invention realizes the timely measurement of the real physical thickness of the evaporated film layer on the surface of a single batch of LED chips by introducing a companion chip. As long as the position of the companion chip is fixed, the relative value of the real physical thickness of the evaporated film layer on the surface of the companion chip at this position and the real physical thickness of the evaporated film layer on the surface of the LED chip at the position to be measured is calculated during the first thickness test. After that, the real physical thickness of the evaporated film layer on the surface of the LED chip in each batch only needs to be measured. There is no need to measure the real physical thickness of the evaporated film layer on the surface of the LED chip due to different evaporation furnaces. After each batch of evaporation, only the real physical thickness of the evaporated film layer on the surface of the companion chip needs to be measured, so that the real physical thickness of the evaporated film layer on the surface of the LED chip can be immediately obtained. If the thickness fluctuates, the coating can be supplemented in time, which greatly guarantees the product quality.

[0024] 2. The measurement method provided by the present invention is easy to operate. It is not necessary to make a photoresist mask pattern on the surface of the LED chip according to the traditional measurement method, and then perform the steps of baking the companion film - spinning the glue - intermediate baking - exposure - development - hard film - corrosion - microscopy - degumming - cleaning - drying - measurement, etc., thereby reducing additional stripping and corrosion processes. After the first relative value measurement, it only takes 3 to 6 minutes to complete the measurement of the true physical thickness of the evaporated film layer on the surface of a single furnace of LED chips. Compared with the 5 to 6 hours of the traditional measurement method, the measurement time is greatly shortened, the method has excellent flexibility, and the size and material of the companion film are extremely optional. It does not occupy an additional position for placing the LED chip in the evaporation table, and the cost can be reduced by 0.3% to 3%, which greatly reduces the production cost. The method is suitable for large-scale quantitative production and is commonly used for thickness monitoring and measurement in all thin film production processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the structure of a companion sheet with a sticky film on the surface.

[0026] Figure 2 This is a schematic diagram of the structure after the evaporation coating layer is completed on the surface of the companion wafer.

[0027] Figure 3 Schematic diagram of the structure of the companion film surface after removing the sticky film.

[0028] Among them: 001, companion film, 002, adhesive film, 003, film layer. DETAILED DESCRIPTION

[0029] The present invention will be further described below with reference to the embodiments and drawings, but is not limited thereto.

[0030] The step profiler described in the embodiment has a measurement accuracy of up to 1 angstrom, and its model is XP-2, which is available from Ambios.

[0031] Example 1

[0032] A method for measuring the real physical thickness of an LED evaporated coating layer comprises the following steps:

[0033] (1) Preparation of companion film: After cleaning the surface of the companion film, use a high temperature resistant tape to cover part of the surface of the companion film, the covering area is 10% of the surface area of ​​the companion film, and prepare it for use;

[0034] (2) Film layer production: placing the companion film in step (1) at a fixed position, and then performing evaporation coating together with the LED wafer to produce a film layer, and taking out the companion film after the evaporation is completed;

[0035] (3) Film thickness measurement: remove the high temperature resistant tape on the companion wafer surface in step (2), measure the height difference between the area covered by the high temperature resistant tape and the area not covered by the adhesive film, that is, the actual physical thickness of the evaporated film layer on the companion wafer surface is 3000 angstroms; after taking out the LED wafer in step (2), make a protective pattern on its surface, make a measurement pattern by etching, and measure its thickness after removing the adhesive, that is, the actual physical thickness of the evaporated film layer on the surface of the LED wafer surface is 3200 angstroms;

[0036] (4) Relative value calculation: The actual physical thickness of the evaporated film layer on the companion wafer surface obtained in step (3) and the physical thickness of the evaporated film layer on the LED wafer surface are calculated, and the difference obtained is the relative value caused by the evaporation position, which is -200 angstroms;

[0037] (5) Calculation of film thickness: Before evaporation, the evaporated film layer is prepared according to steps (1) and (2). After the preparation is completed, the actual physical thickness of the evaporated film layer on the companion wafer surface is measured according to step (3) to be 2900 angstroms. The actual physical thickness of the evaporated film layer on the companion wafer surface minus the relative value is the actual physical thickness of the evaporated film layer on the LED chip surface after this evaporation, which is 3100 angstroms.

[0038] In step (1), the high temperature resistant tape is smooth on one side and sticky on the other side, made of polyimide silicone, with a temperature resistance of above 150°C, and has the advantages of demagnetization, anti-static, high temperature resistance, no glue falling off, and no residue left on the adhered surface after being torn off. The accompanying sheet is optical glass.

[0039] In step (2), the LED chip is a GaN chip.

[0040] The structure of the accompanying sheet covered with an adhesive film on the surface of this embodiment is as follows Figure 1 As shown, the structure of the companion chip after the evaporation coating layer is completed is as follows Figure 2 As shown in the figure, the surface structure of the companion film after removing the sticky film is as follows Figure 3 shown.

[0041] In this embodiment, after the relative value is measured, the actual physical thickness measurement of the evaporated film layer on the surface of the LED wafer after each batch of LED wafer evaporation is completed only takes 5 minutes to complete.

[0042] Example 2

[0043] A method for measuring the real physical thickness of an LED evaporated coating layer comprises the following steps:

[0044] (1) Preparation of companion film: After cleaning the surface of the companion film, use a high temperature resistant tape to cover part of the surface of the companion film, the covering area is 20% of the surface area of ​​the companion film, and prepare it for use;

[0045] (2) Film layer production: placing the companion film in step (1) at a fixed position, and then performing evaporation coating together with the LED wafer to produce a film layer, and taking out the companion film after the evaporation is completed;

[0046] (3) Film thickness measurement: remove the high temperature resistant tape on the companion wafer surface in step (2), measure the height difference between the area covered by the high temperature resistant tape and the area not covered by the adhesive film, that is, the actual physical thickness of the evaporated film layer on the companion wafer surface is 5000 angstroms; after taking out the LED wafer in step (2), make a protective pattern on its surface, make a measurement pattern by etching, and measure its thickness after removing the adhesive, that is, the actual physical thickness of the evaporated film layer on the surface of the LED wafer surface is 4900 angstroms;

[0047] (4) Relative value calculation: The actual physical thickness of the evaporated film layer on the companion wafer surface obtained in step (3) and the physical thickness of the evaporated film layer on the LED wafer surface are calculated, and the difference is the relative value caused by the evaporation position, which is 100 angstroms;

[0048] (5) Calculation of film thickness: Before evaporation, the evaporated film layer is prepared according to steps (1) and (2). After the preparation is completed, the actual physical thickness of the evaporated film layer on the companion wafer surface is measured according to step (3) to be 4500 angstroms. The actual physical thickness of the evaporated film layer on the companion wafer surface minus the relative value is the actual physical thickness of the evaporated film layer on the LED chip surface after this evaporation, which is 4400 angstroms.

[0049] In step (1), the high temperature resistant tape is smooth on one side and sticky on the other side, made of polyimide silicone, with a temperature resistance of above 150°C, and has the advantages of demagnetization, anti-static, high temperature resistance, no glue falling off, and no residue left on the adhered surface after being torn off. The accompanying sheet is optical glass.

[0050] In step (2), the LED chip is a GaAs chip.

[0051] In this embodiment, after the relative value is measured, the actual physical thickness measurement of the evaporated film layer on the surface of the LED wafer after each batch of LED wafer evaporation is completed only takes 4 minutes.

[0052] Comparative Example

[0053] According to the traditional measurement method, a photoresist mask pattern is made on the surface of the LED chip, and then the wafer is baked - the resin is spun - the intermediate bake is performed - the exposure is performed - the development is performed - the hard film is formed - the corrosion is performed - the microscopic inspection is performed - the resin is removed - the cleaning is performed - the drying is performed - the measurement is performed, and the actual physical thickness of the evaporated film layer on the surface of the LED chip is obtained.

[0054] The time for measuring the real physical thickness of the evaporated film layer on the surface of the tablet in this comparative example is 5 hours.

[0055] It can be seen from the embodiments and comparative examples that the present invention realizes the timely measurement of the real physical thickness of the evaporated film layer on the surface of a single batch of LED chips by introducing a companion chip. As long as the position of the companion chip is fixed, the relative value of the real physical thickness of the evaporated film layer on the surface of the companion chip at that position and the real physical thickness of the evaporated film layer on the surface of the LED chip at the position to be measured is calculated during the first thickness test. Thereafter, the real physical thickness of the evaporated film layer on the surface of the LED chip in each batch can be measured by measuring the real physical thickness of the evaporated film layer on the surface of the companion chip. There is no need to measure the real physical thickness of the evaporated film layer on the surface of the LED chip due to different evaporation furnaces. After each batch of evaporation, it is only necessary to measure the real physical thickness of the evaporated film layer on the surface of the companion chip, so that the real physical thickness of the evaporated film layer on the surface of the LED chip can be immediately obtained, which greatly saves time and reduces production costs. The method is suitable for large-scale quantitative production and is commonly used for thickness monitoring and measurement in all thin film production processes.

Claims

1. A method for measuring the real physical thickness of an LED evaporated coating layer, comprising the following steps: (1) Preparation of the accompanying film: After cleaning the surface of the accompanying film, use an adhesive film to cover part of the surface of the accompanying film and prepare it for use; (2) Film layer production: placing the companion film in step (1) at a fixed position, and then performing evaporation coating together with the LED wafer to produce a film layer, and taking out the companion film after the evaporation is completed; (3) Film thickness measurement: remove the sticky film on the surface of the companion wafer in step (2), measure the height difference between the area covered by the sticky film and the area not covered by the sticky film, which is the real physical thickness of the evaporated film layer on the surface of the companion wafer; after taking out the LED wafer in step (2), make a protective pattern on its surface, make a measurement pattern by etching, and measure its thickness after removing the glue, which is the real physical thickness of the evaporated film layer on the surface of the LED wafer; (4) Relative value calculation: The actual physical thickness of the evaporated film layer on the companion wafer surface obtained in step (3) and the actual physical thickness of the evaporated film layer on the LED wafer surface are calculated to obtain a relative value caused by the evaporation position; (5) Calculation of film thickness: Before each evaporation, the evaporated film layer is prepared according to steps (1) and (2). After the preparation is completed, the actual physical thickness of the evaporated film layer on the surface of the companion wafer is measured according to step (3). The actual physical thickness of the evaporated film layer on the surface of the companion wafer minus the relative value is the actual physical thickness of the evaporated film layer on the surface of the LED chip after this evaporation.

2. The method for measuring the real physical thickness of an LED evaporated coating layer according to claim 1, characterized in that: In step (1), the adhesive film is a high temperature resistant tape, one side of which is smooth and the other side is sticky, and the material is polyimide silicone with a temperature resistance of more than 150°C.

3. The method for measuring the real physical thickness of an LED evaporated coating layer according to claim 1, characterized in that: In step (1), the partial area is 10 to 90% of the surface area of ​​the companion sheet.

4. The method for measuring the real physical thickness of an LED evaporated coating layer according to claim 1, characterized in that: In step (1), the partial area is 10 to 30% of the surface area of ​​the companion sheet.

5. The method for measuring the real physical thickness of an LED evaporated coating layer according to claim 1, characterized in that: In step (1), the companion sheet is optical glass or stainless steel sheet.

6. The method for measuring the real physical thickness of an LED evaporated coating layer according to claim 1, characterized in that: In step (2), the LED chip is a GaN, GaAs or Si chip.

7. The method for measuring the real physical thickness of an LED evaporated coating layer according to claim 1, characterized in that: In step (3), the instrument used for the measurement is a step profiler with a measurement accuracy of 1 angstrom, model XP-2.

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