Method for measuring width range of pn junction region of tellurium-cadmium-mercury pixel

Abstract

The invention relates to a method for measuring the width range of a pn junction region of a tellurium-cadmium-mercury pixel, which comprises the following steps of: preparing electrodes with different diameters in an etching small hole or an ion implantation surrounding region, judging whether a diode characteristic exists or not according to an integral I-V curve, then judging the width range of inversion after etching according to the radius of an electrode region, and meanwhile, measuring the width range of the pn junction region of the tellurium-cadmium-mercury pixel. Whether pn junctions in opposite directions exist or not can be judged through an I-V curve between two pixel electrodes so as to judge the width range of an inversion region. According to the method for measuring the width range of the pn junction region, more measurement data can be provided under the condition of limited electrode pins, and a finer width range can be obtained at a time.

Description

Technical Field

[0001] The invention relates to the field of infrared and optoelectronic technology, and relates to a method for measuring the width range of a mercury cadmium telluride pixel pn junction region. Background Art

[0002] Mercury cadmium telluride thin film materials have long been used in the preparation of infrared photodetectors due to their advantages such as adjustable band gap, high mobility, and long carrier lifetime.

[0003] The junction width of an infrared detector can be measured using the laser beam induced current method, or LBIC. LBIC focuses laser light into a micron-sized spot, creating localized photoexcitation on the material surface. The LBIC then relies on the electric field of the PN junction within the material to collect photogenerated carriers. The decay of the photocurrent is then used to approximate the junction width of the semiconductor.

[0004] As demand for smaller pixels in HgCdTe photodetectors increases, controlling the pixel junction width becomes crucial. For pixels with a center-to-center spacing of less than 10 microns, the junction width is less than 3 microns, making it difficult to measure using LBIC.

[0005] The Chinese invention application, publication number CN105047574A, discloses a variable-pitch measurement method for the lateral widening of the N region of a mercury cadmium telluride detector. The method uses a chip that has been prepared with a ZnS barrier layer and alignment marks. Then, through a photolithography process, a series of ion implantation masks with different PN junction spacings are designed. After the ion implantation, a passivation layer and metallized ohmic contacts are prepared through conventional processes, and then peeled off to obtain a series of test patterns for the widening of PN junctions with different spacings. Finally, a low-temperature cold probe system is used to perform current and voltage tests on each pair of PN junctions, and the lateral widening width is determined by combining the current and voltage test results and the spacing between each pair of PN junctions.

[0006] The above method uses the voltage-current curve between two adjacent junctions to determine whether the areas of the two junctions overlap, and then infers the junction width based on the actual designed pixel spacing. However, this method has low experimental efficiency and is not accurate enough. In addition, the process is very difficult when the spacing between two adjacent electrodes is very small.

[0007] Therefore, a more efficient method for finely measuring the pn junction width of HgCdTe pixels is currently needed. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for measuring the width range of the pn junction region of a mercury cadmium telluride pixel, which solves the problem that the existing technology is not precise enough and cannot measure when the distance between adjacent electrodes is very small.

[0009] To achieve the above object, the technical solution of the present invention is:

[0010] A method for measuring the width range of a pn junction region of a mercury cadmium telluride pixel is provided. A common electrode and two or more pixels are provided on a p-type mercury cadmium telluride thin film, and an n region is prepared at the center of the pixel. The method comprises the following steps:

[0011] S1, arranging pixel positions, including setting the spacing between adjacent pixels and setting the positions of the pixels and the common electrode;

[0012] S2, prepare the pixel electrode at the center of the pixel and lead it to the test pin;

[0013] S3, measure the current between the test pins of two adjacent pixels and obtain the corresponding IV curve;

[0014] S4, measuring the current between the test pin of a single pixel and the common electrode to obtain the corresponding IV curve;

[0015] S5 , determining the width range of the junction region based on the IV data obtained in S3 and the IV data obtained in S4 .

[0016] In step S1 , when there are more than two pixels, the spacing between adjacent pixels is designed to be arranged from small to large; the distance between the pixel and the common electrode is greater than the preset junction width of the pixel.

[0017] In step S2, looking down at the pixel structure, the pixel electrode 2 and the junction region are arranged as concentric circles, and the radius of each pixel electrode is designed and arranged from small to large according to the spacing between pixels.

[0018] Step S5 specifically includes the following steps:

[0019] S501, determining the junction width interval using the IV curve between two adjacent pixel test pins in step S3. If the IV curve shows the characteristics of two reverse junctions, the pixel spacing is greater than twice the junction width; if the IV curve does not show the characteristics of two reverse junctions, the pixel spacing is less than twice the junction width.

[0020] S502, determine the interval of the junction area width using the IV curve between the single pixel test pin and the common electrode in step S4. If the IV curve shows a pn junction characteristic, the pixel junction area width is larger than the pixel electrode area; if it does not show a pn junction characteristic, the pixel junction area width is smaller than the pixel electrode area.

[0021] The advantages of the present invention are: 1. Electrodes of different diameters are prepared in the area around the etched hole, and the presence of diode characteristics is determined based on the overall IV curve. Then, the width range of the inversion after etching is determined based on the radius of the electrode area. At the same time, the width range of the inversion area can be determined by judging whether there is a pn junction in opposite directions through the IV curve between the two pixel electrodes. 2. While adopting the method of measuring the IV curves of adjacent pixels, the measurement of the IV curve between the pixel electrode and the common electrode is added. By judging whether there is a pn junction IV characteristic curve between the pixel and the common electrode to infer the junction area range, the data of the fine junction area width that can be measured in one experiment is increased, thereby improving the test efficiency and test accuracy. 3. The measurement method of the present invention can provide more measurement data within the limited electrode test tube foot, and obtain a finer width range at one time. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the overall flow chart of the present invention;

[0023] Figure 2 It is a distribution diagram of electrodes and pixels of a single test unit of the present invention;

[0024] Figure 3 This is a schematic diagram of the principle of determining the range of a junction area by using IV curves of adjacent pixels of the present invention;

[0025] Figure 4 This is a schematic diagram of the principle of determining the junction area range through the electrode size and the IV curve between the pixel and the common electrode of the present invention.

[0026] In the figure: 1-etching area; 2-pixel electrode; 3-common electrode; 4-n area. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to the accompanying drawings, which are for illustrative purposes only and are not to be construed as limiting the present invention.

[0028] To more concisely illustrate this embodiment, some components well known to those skilled in the art but not relevant to the main content of this invention may be omitted from the drawings or descriptions. In addition, for ease of description, some components may be omitted, enlarged, or reduced in size in the drawings, but they do not represent the dimensions or entire structure of the actual product.

[0029] The present invention discloses a method for measuring the width range of the pn junction region of a mercury cadmium telluride pixel, such as Figure 1-4 As shown, a common electrode 3 and two or more picture elements are provided on a p-type HgCdTe film, and an n-region 4 is prepared at the center of the picture element; Figure 1 As shown, the following steps are included:

[0030] S1, arrange pixel positions; Figure 2 As shown, it includes setting the spacing between adjacent pixels and setting the position of the pixel and the common electrode 3; when there are more than two pixels, the spacing between adjacent pixels is arranged from small to large; the distance between the pixel and the common electrode 3 is greater than the preset junction width of the pixel.

[0031] S2, prepare the pixel electrode 2 at the center of the pixel and lead it to the test pin; looking down at the pixel structure, the pixel electrode 2 and the junction area are set in concentric circles. When there are more than two pixels, the radius of each pixel electrode 2 is designed and arranged from small to large according to the spacing between the pixels.

[0032] S3, measure the current between the test pins of two adjacent pixels and obtain the corresponding IV curve;

[0033] S4, measuring the current between the single pixel test pin and the common electrode 3 to obtain the corresponding IV curve;

[0034] S5, judging the width range of the junction region based on the IV data obtained in S3 and the IV data obtained in S4. Specifically comprising the following steps:

[0035] S501, determine the junction width interval using the IV curve between two adjacent pixel test pins in step S3. If the IV curve is as shown below Figure 3 If the two reverse junctions are shown, the pixel spacing is greater than twice the junction width; if the two reverse junctions are not shown, the pixel spacing is less than twice the junction width;

[0036] S502, determine the junction width interval using the IV curve between the single pixel test pin and the common electrode 3 in step S4. If the IV curve is as shown below Figure 4 If the pn junction characteristics are shown, the pixel junction area width is larger than the pixel electrode 2 area; if the pn junction characteristics are not shown, the pixel junction area width is smaller than the pixel electrode 2 area.

[0037] According to the present method, a module for testing was prepared. Relevant parameters include: 25 electrodes, one of which is directly connected to the common electrode 3, and the remaining 24 are pixel electrodes 2; pixel pitch increases from 5 microns to 300 microns; the area used for ion implantation or etching area 1 is a circle with a diameter of 2 microns; and the size of the pixel electrodes 2 increases from 2.2 microns to 10 microns. This module can measure junction areas ranging from 0.1 to 150 microns in a single measurement.

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. That is, any equivalent changes and modifications made according to the content of the patent application of the present invention should fall within the technical scope of the present invention.

Claims

1. A method for measuring the width range of a pn junction region of a mercury cadmium telluride pixel, wherein a common electrode (3) and two or more pixels are provided on a p-type mercury cadmium telluride thin film, and an n region (4) is prepared at the center of the pixel; the method is characterized in that: The following steps are involved: S1, arranging pixel positions, including setting the spacing between adjacent pixels and setting the positions of the pixels and the common electrode (3); S2, prepare a pixel electrode (2) at the center of the pixel and lead it to the test pin; S3, measure the current between the test pins of two adjacent pixels and obtain the corresponding IV curve; S4, measuring the current between the single pixel test pin and the common electrode (3) to obtain the corresponding IV curve; S5 , determining the width range of the junction region based on the IV data obtained in S3 and the IV data obtained in S4 .

2. The measuring method according to claim 1, wherein: In step S1, when there are more than two pixels, the spacing between adjacent pixels is designed to be arranged from small to large; the distance between the pixel and the common electrode (3) is greater than the preset junction width of the pixel.

3. The measuring method according to claim 2, wherein: In step S2, looking down at the pixel structure, the pixel electrode (2) and the junction area are arranged in concentric circles, and the radius of each pixel electrode (2) is designed and arranged from small to large according to the spacing between pixels.

4. The measuring method according to claim 1, wherein: Step S5 specifically The following steps are included: S501, determining the junction width interval using the IV curve between two adjacent pixel test pins in step S3. If the IV curve shows the characteristics of two reverse junctions, the pixel spacing is greater than twice the junction width; if the IV curve does not show the characteristics of two reverse junctions, the pixel spacing is less than twice the junction width. S502, determining the interval of the junction area width using the IV curve between the single pixel test pin and the common electrode (3) in step S4, if the IV curve presents a pn junction characteristic, the pixel junction area width is greater than the pixel electrode (2) area; if it does not present a pn junction characteristic, the pixel junction area width is less than the pixel electrode (2) area.

Images