Method for detecting PN junction effective depth of tellurium cadmium mercury chip

Abstract

The application provides a method for detecting the effective junction depth of a tellurium-cadmium-mercury chip PN junction, and belongs to the technical field of semiconductors. The method comprises the following steps: selecting a tellurium-cadmium-mercury chip which has been formed through an ion implantation and annealing junction process and has been passivated; dividing the ion implantation area of the tellurium-cadmium-mercury chip into multiple regions, removing the passivation layer in each region and part of the ion implantation area below the passivation layer, and forming multiple contact holes arranged in a preset depth gradient; growing a metal electrode on each contact hole; measuring the voltage-current curve of each metal electrode at different etching depths; and determining the corresponding PN junction depth as the effective junction depth of the tellurium-cadmium-mercury chip when the voltage-current curve changes from a Schottky curve to a linear curve. The application is the same as the original chip manufacturing process of tellurium-cadmium-mercury, can be applied to the process production process of a tellurium-cadmium-mercury infrared detector, and can monitor the effective junction depth of the tellurium-cadmium-mercury after ion implantation in real time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, in particular to a method for detecting PN junction effective junction depth of tellurium cadmium mercury chip. BACKGROUND

[0002] Infrared focal plane detector has been developed for a long time, and tellurium cadmium mercury has been in a dominant position in the field of infrared detector technology. Tellurium cadmium mercury infrared detector covers the entire infrared waveband from short wave to very long wave, and each waveband shows good performance.

[0003] In the manufacturing process of tellurium cadmium mercury infrared detector, ion implantation technology is widely used for PN junction formation. PN junction formation is a key step in the preparation process of infrared detector chip. The PN junction depth after ion implantation plays an important guiding role in the subsequent etching of contact hole depth and back thinning process. The junction depth of PN junction directly affects the core performance of the detector, such as quantum efficiency, detection rate and response rate.

[0004] However, due to the particularity of tellurium cadmium mercury material, tellurium cadmium mercury ion implantation process mainly relies on damage to form junction, and the damage layer of tellurium cadmium mercury is often deeper than the implantation layer. Therefore, unlike silicon and other materials, only the implantation layer depth can be obtained by traditional secondary ion mass spectrometry analysis, and the effective junction depth of tellurium cadmium mercury PN junction cannot be obtained.

[0005] Patent CN110676188A forms a corrosion slope by immersing antimony indium material with PN junction structure into a corrosion agent, measures the first width of the corrosion slope and the second width of the color partition at the top of the corrosion slope according to the color boundary of the surface of the corrosion slope, and then measures the height of the corrosion slope by using a step meter to obtain the PN junction depth; but this invention can only obtain the implantation layer depth, and cannot be used for characterization of the damage layer depth after tellurium cadmium mercury ion implantation.

[0006] Patent CN110011617A adopts a stripping method, removes the oxide layer with a hydrofluoric acid solution, measures the resistivity by using a four-probe method, repeats the steps of generating an oxide layer, measuring the film thickness, etching the oxide layer and measuring the resistivity until the resistivity is equal to the substrate resistivity. However, this method is difficult to be used for tellurium cadmium mercury material, because the resistivity of n-type and p-type of tellurium cadmium mercury material does not differ much, and the voltage-current curve obtained by this measurement method is easily affected by the base region. Therefore, this method is not completely suitable for measuring the junction depth of tellurium cadmium mercury ion implantation. SUMMARY

[0007] The technical problem to be solved by the present application is how to more conveniently detect the PN junction effective junction depth of tellurium cadmium mercury chip. The present application provides a method for detecting the PN junction effective junction depth of tellurium cadmium mercury chip, comprising:

[0008] Selecting a tellurium cadmium mercury chip which has been ion implanted and annealed to form a junction and has been passivated, at this time, the PN junction of the tellurium cadmium mercury chip has been formed;

[0009] Dividing the ion implantation area of the tellurium cadmium mercury chip into multiple areas, removing the passivation layer in each area and part of the ion implantation area under the passivation layer, and forming multiple contact holes arranged in a preset depth gradient;

[0010] Growth of a metal electrode on each of the contact holes;

[0011] Measurement of the voltage-current curve of each of the metal electrodes at different etching depths;

[0012] When the voltage-current curve is converted from a Schottky curve to a linear curve, the corresponding PN junction depth is determined as the effective junction depth of the tellurium cadmium mercury chip.

[0013] According to an embodiment of the present application, the depth range of the multiple contact holes arranged in the preset depth gradient is 1-4 μm.

[0014] According to an embodiment of the present application, the depth difference between adjacent contact holes is 0.1-0.3 μm.

[0015] According to an embodiment of the present application, the passivation layer at the position corresponding to the contact hole is removed by using a wet etching solution.

[0016] According to an embodiment of the present application, the wet etching solution is hydrochloric acid or phosphoric acid.

[0017] According to an embodiment of the present application, the metal electrode is generated by using one of the following methods: ion beam deposition, magnetron sputtering and thermal evaporation.

[0018] According to an embodiment of the present application, the metal electrode is made of one of the following materials: Cr, Au and Pt.

[0019] According to an embodiment of the present application, the ion implantation of the tellurium cadmium mercury chip is performed under the condition of 100-400 KV, and the ion implantation dose is 1×1010-1×1012 / cm2. 14 16 / cm3.

[0020] According to an embodiment of the present application, the ion implantation method of the tellurium cadmium mercury chip comprises: forming an ion implantation area on the tellurium cadmium mercury chip by using a photolithography method; and performing ion implantation and annealing on the ion implantation area.

[0021] According to an embodiment of the present application, before photolithography, the surface of the tellurium cadmium mercury chip is cleaned by using alcohol and acetone.

[0022] ​The present application provides a method for characterizing effective junction depth of mercury cadmium telluride ion implantation, which can be applied to the process production of mercury cadmium telluride infrared detector, and can monitor the effective junction depth of mercury cadmium telluride after ion implantation in real time, and plays an important guiding role for subsequent processes, and the beneficial effects include:

[0023] Firstly, the method is the same as the original chip manufacturing process of mercury cadmium telluride, can monitor the effective junction depth of mercury cadmium telluride after ion implantation in real time in the process production of mercury cadmium telluride infrared detector, and has important guiding significance for subsequent processes.

[0024] Secondly, compared with the traditional secondary ion mass spectrometer analysis and the extended resistance method, the grinding angle dyeing method and other technologies, the method of the present application can more accurately characterize the effective junction depth of mercury cadmium telluride. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The method flow chart for detecting the effective junction depth of the mercury cadmium telluride chip according to the embodiment of the present application is shown in the figure;

[0026] Figure 2 The schematic diagram of the mercury cadmium telluride chip after ion implantation annealing and junction forming process and after passivation is shown in the figure;

[0027] Figure 3 The schematic diagram of the mercury cadmium telluride chip after removing the passivation layer at the contact hole position is shown in the figure;

[0028] Figure 4 The schematic diagram of the mercury cadmium telluride chip after etching the passivation layer and ion implantation area at multiple contact hole positions is shown in the figure;

[0029] Figure 5 The schematic diagram of the mercury cadmium telluride chip after growing metal electrodes on each contact hole at different etching depths is shown in the figure;

[0030] Figure 6 The voltage-current curve when the etching depth is less than the effective junction depth is shown in the figure;

[0031] Figure 7 The voltage-current curve when the etching depth is greater than or equal to the effective junction depth is shown in the figure.

[0032] Reference signs:

[0033] Base region 100, ion implantation region 200,

[0034] Passivation layer 300, contact hole 400,

[0035] Metal electrode 500, etching depth H1. DETAILED DESCRIPTION

[0036] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose, the present invention is described in detail below with reference to the accompanying drawings and preferred embodiments.

[0037] like Figure 1 As shown, a method for detecting the effective junction depth of a PN junction of a mercury cadmium telluride chip according to an embodiment of the present invention includes:

[0038] S110 , a passivated HgCdTe chip formed through an ion implantation and annealing process is selected. At this point, the PN junction of the HgCdTe chip is already formed. The present invention can select a passivated N-type or P-type HgCdTe chip and use photolithography to create an ion implantation region 200 . After ion implantation, the chip is annealed to form a HgCdTe chip with a PN junction. Figure 2 As shown, N-type HgCdTe ions are implanted into a P-type HgCdTe chip to form a PN-type HgCdTe chip with the P-type HgCdTe chip as the base region 100 and the N-type HgCdTe ions as the ion implantation region 200. The passivated passivation layer 300 is located on the upper layer of the PN-type HgCdTe chip.

[0039] S120, dividing the ion implantation area 200 of the mercury cadmium telluride chip into multiple areas, removing the passivation layer 300 in each area and part of the ion implantation area 200 below the passivation layer 300, and forming multiple contact holes 400 arranged according to a preset depth gradient. The contact holes 400 are mainly used to lead out electrodes on the surface of the mercury cadmium telluride. Figure 4 It shows that after etching the passivation layer 300 and the HgCdTe in the ion implantation area 200 in each region, the depths of the plurality of contact holes 400 are within a set gradient range.

[0040] S130, growing metal electrodes 500 on each contact hole 400. Figure 5 As shown, the electrodes in the base region 100 and the electrodes in the injection region need to be separated. Generally, the electrodes in the contact holes 400 in the injection layer are separated from the electrodes in the base region 100 by photolithography and etching techniques.

[0041] S140, measuring the voltage-current curves of each metal electrode 500 at different etching depths H1. Generally, a semiconductor parameter meter is used to measure the voltage-current curves from the contact hole 400 to the base region 100 at different etching depths H1.

[0042] S150, when the voltage-current curve changes from a Schottky curve to a linear curve, the corresponding PN junction depth is determined to be the effective junction depth of the HgCdTe chip. Generally, when the corrosion depth H1 is continuously distributed, the effective junction depth can be obtained through measurement.

[0043] According to the method described herein for measuring the effective junction depth of a HgCdTe (HgCdTe) PN junction, by comparing the voltage-current curves from the contact hole 400 to the base region 100 at different etching depths H1, the device's effective junction depth is determined by observing that when the etching depth H1 just exceeds the effective junction depth, the voltage-current curve transitions from a Schottky junction characteristic to a linear one. This method, while maintaining consistency with the original chip manufacturing process, accurately measures the effective junction depth of each pixel, enabling real-time monitoring of the effective junction depth of HgCdTe after ion implantation. This method has significant application value in the production process of HgCdTe infrared detectors.

[0044] According to an embodiment of the present invention, the depth range of the plurality of contact holes 400 formed in the depth gradient arrangement is: 1μm-4μm. In this embodiment, a 25mm×25mm size and passivated P-type HgCdTe is used, and the N-type HgCdTe corrosion depth H1 in the ion implantation area 200 is distributed in the range of 1μm-4μm. After measurement, the corrosion depth H1 is within the range of 1μm to 3.4μm, and the voltage-current curves all show Schottky junction characteristics. Figure 6 This is the voltage-current curve when the corrosion depth H1 is 3.4μm. When the corrosion depth H1 is 3.6μm~4μm, the voltage-current curve is all linear. Figure 7 This is the voltage-current curve for an etching depth of 13.6 μm. Therefore, the effective junction depth obtained by using the relevant implantation parameters in this embodiment is 3.6 μm.

[0045] According to an embodiment of the present invention, the depth difference between adjacent contact holes 400 is 0.1 μm-0.3 μm.

[0046] According to an embodiment of the present invention, a wet etching solution is used to remove the passivation layer 300 at a position corresponding to the contact hole 400 .

[0047] According to an embodiment of the present invention, the wet etching solution is hydrochloric acid or phosphoric acid.

[0048] According to an embodiment of the present invention, the metal electrode 500 is formed by one of the following methods: ion beam deposition, magnetron sputtering, and thermal evaporation.

[0049] According to an embodiment of the present invention, the metal electrode 500 is made of one of the following materials: Cr, Au, and Pt.

[0050] According to an embodiment of the present invention, the ion implantation conditions of the mercury cadmium telluride chip are 100KeV-500KeV energy, and the implantation metering range is: 1×10 14 ~1×10 16 / cm3. The implanted elements are B, As, Be, etc.

[0051] According to the embodiment of the present application, the ion implantation method of the mercury cadmium telluride chip comprises: forming an ion implantation area 200 on the mercury cadmium telluride chip by using a photoetching method; performing ion implantation on the ion implantation area 200 and annealing.

[0052] According to the embodiment of the present application, before photoetching, the surface of the mercury cadmium telluride chip is cleaned by using alcohol and acetone. For example, the P-type or N-type mercury cadmium telluride after passivation can be selected, and the surface of the mercury cadmium telluride chip is cleaned by using alcohol and acetone before photoetching the ion implantation area 200.

[0053] In summary, according to the embodiment of the present application, the effective junction depth of the device is obtained by comparing the voltage-current curves of the implantation area with different etching depths H1 to the base area 100. The method is the same as the original chip manufacturing process of mercury cadmium telluride, and can be applied to the process production of the mercury cadmium telluride infrared detector, and the effective junction depth of the mercury cadmium telluride after ion implantation can be monitored in real time, which has important guiding significance for the subsequent process.

[0054] Through the description of the specific embodiments, the technical means and effects taken by the present application to achieve the predetermined purposes can be understood more deeply and specifically. However, the accompanying drawings are provided for reference and illustration only, and are not used to limit the present application.

Claims

1. A method for detecting the effective junction depth of a mercury cadmium telluride chip PN junction, characterized in that: include: A mercury cadmium telluride chip that has been formed through an ion implantation annealing process and has been passivated is selected. At this time, the PN junction of the mercury cadmium telluride chip has been formed; Dividing the ion implantation area of ​​the mercury cadmium telluride chip into multiple regions, removing the passivation layer in each region and a portion of the ion implantation area below the passivation layer to form multiple contact holes arranged according to a preset depth gradient and a contact hole in the base region; growing a metal electrode on each of the contact holes; measuring the voltage-current curves of the metal electrodes at different corrosion depths; By comparing the voltage-current curves from the contact hole to the base region at different etching depths, when the voltage-current curve changes from a Schottky curve to a linear curve, the corresponding PN junction depth is determined to be the effective junction depth of the mercury cadmium telluride chip; The ion implantation method of the mercury cadmium telluride chip comprises: forming an ion implantation region with uniform depth on the mercury cadmium telluride chip by using a photolithography method; Ion implantation and annealing are performed in the ion implantation region.

2. The method for detecting the effective junction depth of the PN junction of a mercury cadmium telluride chip according to claim 1, characterized in that: The depth range of the plurality of contact holes arranged with a depth gradient is: 1 -4 .

3. The method for detecting the effective junction depth of the PN junction of a mercury cadmium telluride chip according to claim 1, characterized in that: The depth difference between adjacent contact holes is 0.1 -0.3 .

4. The method for detecting the effective junction depth of the PN junction of a mercury cadmium telluride chip according to claim 1, characterized in that: A wet etching solution is used to remove the passivation layer at a position corresponding to the contact hole.

5. The method for detecting the effective junction depth of the PN junction of a mercury cadmium telluride chip according to claim 4, characterized in that: The wet etching solution is hydrochloric acid or phosphoric acid.

6. The method for detecting the effective junction depth of the PN junction of a mercury cadmium telluride chip according to claim 1, characterized in that: The metal electrode is formed by one of the following methods: ion beam deposition, magnetron sputtering and thermal evaporation.

7. The method for detecting the effective junction depth of the PN junction of a mercury cadmium telluride chip according to claim 1, characterized in that: The metal electrode is made of one of the following materials: Cr, Au and Pt.

8. The method for detecting the effective junction depth of the PN junction of a mercury cadmium telluride chip according to claim 1, characterized in that: The ion implantation of the HgCdTe chip is carried out under the conditions of 100KV-400KV, and the ion implantation metering range is: 1×10 14 ~1×10 16 / cm 3 .

9. The method for detecting the effective junction depth of the PN junction of a mercury cadmium telluride chip according to claim 1, characterized in that: Before photolithography, the surface of the mercury cadmium telluride chip is cleaned by using alcohol and acetone.

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