Method for monitoring epitaxial filling rate and doping concentration of deep-trench super-junction product

Abstract

The invention provides a method for monitoring epitaxial filling rate and doping concentration of a deep trench super junction product, which comprises the following steps of: providing a substrate, forming an N-type epitaxial layer on the substrate, defining an etching region and a measuring region of a deep trench on the N-type epitaxial layer by utilizing photoetching, and reserving a photoresist layer on the measuring region; the photoresist layer on the etching area is exposed and opened according to design, a deep groove is formed in the etching area of the N-type epitaxial layer through etching, and then the remaining photoresist layer is removed. And after same-type doping source IMP (ion implantation) and annealing are carried out, a P-type epitaxial layer for filling the deep groove is formed on the N-type epitaxial layer by using an epitaxial filling process, and the resistance value and the thickness of the P-type epitaxial layer on the measurement region are acquired so as to monitor the filling rate and the doping concentration of the P-type epitaxial layer. According to the monitoring method provided by the invention, the epitaxial filling rate and the doping concentration of the current deep groove super junction product can be monitored more directly.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly to a method for monitoring the epitaxial filling rate and doping concentration of deep trench superjunction products. Background Art

[0002] Since the width of the deep trench P-columns in deep trench superjunction products is relatively narrow, about 1 - 5 μm, and the P-region and N-region alternate, existing measurement means cannot directly measure the film thickness and sheet resistance after the epitaxial process to directly monitor the epitaxial filling rate and doping concentration of product wafers.

[0003] The method of the prior art is to indirectly monitor the epitaxial filling rate and doping concentration of deep trench superjunction products by measuring the epitaxial film thickness and sheet resistance after epitaxial growth on a bare wafer (without patterns). However, the monitoring of the epitaxial filling rate and doping concentration on a bare wafer cannot fully reflect the actual situation on deep trench superjunction products.

[0004] The epitaxial process of deep trench superjunction products is to fill a P-type doped epitaxial layer in the deep trenches, where the CD of the P-columns varies from 1 to 5 μm.

[0005] The spot diameter of the infrared light source emitted by the interferometer of the FTIR (Fourier Transform Infrared Spectroscopy) film thickness measurement device when irradiating the sample is about 10 mm. At the same time, it is required that the concentration difference between the measured epitaxial layer and the bottom medium exceeds 100 times. Therefore, it is impossible to directly measure the epitaxial film thickness grown in the deep trenches.

[0006] Please refer to Figure 1 , there needs to be a certain distance between the four probes of the four-probe resistance measurement device. The spacing between the probes is generally 3 mm, 7 mm, and 15 mm. Therefore, it is also impossible to directly measure the sheet resistance in the P-columns by the conventional method of the four probes.

[0007] To solve the above problems, a new method for monitoring the epitaxial filling rate and doping concentration of deep trench superjunction products needs to be proposed. Summary of the Invention

[0008] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a method for monitoring the epitaxial filling rate and doping concentration of deep trench superjunction products, which is used to solve the problem that in the prior art, the epitaxial filling rate and doping concentration of deep trench superjunction products are indirectly monitored, but the monitoring of the epitaxial filling rate and doping concentration on a bare wafer cannot fully reflect the actual situation on deep trench superjunction products.

[0009] To achieve the above purpose and other related purposes, the present invention provides a method for monitoring the epitaxial filling rate and doping concentration of deep trench superjunction products, including:

[0010] Step 1: Provide a substrate, form an N-type epitaxial layer on the substrate, and define an etching region and a measurement region of a deep trench on the N-type epitaxial layer by lithography. Among them, the photoresist layer on the measurement region is retained, and the photoresist layer on the etching region is exposed and opened according to the design.

[0011] Step 2: Form a deep trench on the etching region of the N-type epitaxial layer by etching, and then remove the remaining photoresist layer.

[0012] Step 3: Perform ion implantation and annealing of a P-type doping source on the N-type epitaxial layer in the etching region and the measurement region to form a P-type implanted layer on the surface of the N-type epitaxial layer, and obtain the thickness H1 of the N-type epitaxial layer and the P-type implanted layer and the resistance value Rs1 of the P-type implanted layer in the measurement region.

[0013] Step 4: Use an epitaxial filling process to form a P-type epitaxial layer filling the deep trench, and obtain the thickness H2 of the N-type epitaxial layer, the P-type implanted layer and the P-type epitaxial layer in the measurement region; obtain the parallel resistance value Rs2 of the P-type implanted layer and the P-type epitaxial layer.

[0014] Step 5: Obtain the thickness H3 and the resistance value Rs3 of the P-type epitaxial layer in the measurement region. The thickness H3 of the P-type epitaxial layer in the measurement region = H2 - H1, and the resistance value Rs3 of the P-type epitaxial layer in the measurement region = Rs1 * Rs2 / (Rs1 - Rs2) to monitor the filling rate and doping concentration of the P-type epitaxial layer.

[0015] Preferably, the size of the measurement region in Step 1 is not less than the minimum measurement area of the measurement equipment.

[0016] Preferably, in Step 2, a dry etching method is used to form the deep trench on the N-type epitaxial layer.

[0017] Preferably, in Step 2, an ashing process and a wet cleaning method are used to remove the photoresist layer.

[0018] Preferably, the critical dimension of the deep trench in Step 2 is 1 - 5 μm.

[0019] Preferably, the doping concentration of the P-type implanted layer in Step 3 needs to be close to the concentration of the P-type epitaxial layer grown later.

[0020] Preferably, the ion implantation of the P-type doping source in Step 3 is used to offset the influence of the PN junction on the epitaxial resistance.

[0021] Preferably, in Steps 3 and 4, an infrared mass spectrometer is used to measure the thickness in the measurement region to obtain the thickness.

[0022] Preferably, in steps three and four, the four-point probe resistance measurement method is used to measure the resistance value on the measurement area.

[0023] Preferably, in step five, the resistivity is calculated based on the thickness H3 and the resistance value Rs3 of the P-type epitaxial layer to monitor the filling rate and doping concentration of the P-type epitaxial layer.

[0024] As described above, the method for monitoring the epitaxial filling rate and doping concentration of a deep trench superjunction product according to the present invention has the following

[0025] Beneficial effects:

[0026] The monitoring method of the present invention can more directly monitor the epitaxial filling rate and doping concentration of the current deep trench superjunction product. Description of the Drawings

[0027] Figure 1 Schematic diagram of four-probe resistance measurement shown as the prior art;

[0028] Figure 2 Schematic diagram of the method for monitoring the epitaxial filling rate and doping concentration of a deep trench superjunction product according to the present invention;

[0029] Figure 3 Schematic diagram of the non-exposed area of the present invention on the wafer surface;

[0030] Figure 4 Schematic diagram of the top view after deep trench etching according to the present invention;

[0031] Figure 5 Schematic diagram of the cross-sectional view after deep trench etching according to the present invention;

[0032] Figure 6 Schematic diagram of the top view after epitaxy according to the present invention;

[0033] Figure 7 Schematic diagram of the cross-sectional view after epitaxy according to the present invention;

[0034] Figure 8 Schematic diagram of obtaining the thickness of the P-type epitaxial layer on the measurement area according to the present invention;

[0035] Figure 9 Schematic diagram of the parallel resistance of the ion implantation layer and the epitaxial layer according to the present invention;

[0036] Figure 10 Schematic diagram of the relationship between the thickness and the filling time in the monitoring methods of the present invention and the prior art;

[0037] Figure 11Schematic diagram showing the relationship between resistivity and filling time in the monitoring methods of the present invention and the prior art;

[0038] Figure 12 Schematic diagram showing resistivity under different monitoring mode conditions in the monitoring methods of the present invention and the prior art;

[0039] Figure 13 Schematic diagram showing the resistivity matching degree of the monitoring methods of the present invention and the prior art. Detailed implementation manners

[0040] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0041] Please refer to Figure 2 , the present invention provides a method for monitoring the epitaxial filling rate and doping concentration of deep trench superjunction products, including:

[0042] Step 1: Provide a substrate 101. Usually, the substrate 101 is a silicon substrate, and the silicon substrate is usually N-type doped with a resistivity less than 10 -3 , form an N-type epitaxial layer 102 on the substrate 101. The resistivity of the N-type epitaxial layer 102 is usually 0.1 to 10. Use photolithography on the N-type epitaxial layer 102 to define the etching area and measurement area of the deep trench. Among them, the photoresist layer on the measurement area is retained, and the photoresist layer on the etching area is exposed and opened according to the design; for example, the measurement area is Figure 3 the non-exposed area in;

[0043] In some embodiments, the size of the measurement area in Step 1 is not less than the minimum measurement area of the measurement device. For example, the measurement spot of the infrared mass spectrometer is about 10 mm, so the area of the non-exposed area is selected to be 20 mm * 20 mm.

[0044] Step 2: Use etching to form deep trenches on the etching area of the N-type epitaxial layer 102, and then remove the remaining photoresist layer; for example, please refer to Figure 4 , which shows a top view after etching, please refer to Figure 5 , which shows a cross-sectional view after etching;

[0045] In some embodiments, in Step 2, a dry etching method is used to form deep trenches on the N-type epitaxial layer 102.

[0046] In some embodiments, in Step 2, an ashing process and a wet cleaning method are used to remove the photoresist layer.

[0047] In some embodiments, the critical dimension of the deep trench in step two is 1 - 5 μm.

[0048] Step three: Perform ion implantation (IMP) of a P-type doping source on the N-type epitaxial layer 102 in the etching region and the measurement region and anneal it to form a P-type implanted layer 104 on the surface of the N-type epitaxial layer 102; obtain the thickness H1 of the N-type epitaxial layer 102 and the P-type implanted layer 104 and the resistance value Rs1 of the P-type implanted layer 104 in the measurement region.

[0049] In some embodiments, the doping concentration of the P-type implanted layer 104 formed by the ion implantation of the P-type doping source in step three needs to be close to the concentration of the subsequently grown P-type epitaxial layer 103.

[0050] In some embodiments, the ion implantation of the P-type doping source in step three is used to offset the influence of the PN junction on the epitaxial resistance.

[0051] In some embodiments, an infrared mass spectrometer is used in step three to measure the thickness of the epitaxial layer in the measurement region.

[0052] In some embodiments, the four-point probe resistance measurement method is used in step three to measure the resistance value in the measurement region.

[0053] Step four: Use an epitaxial filling process to form a P-type epitaxial layer 103 that fills the deep trench on the N-type epitaxial layer 102. The resistivity of the P-type epitaxial layer 103 is usually 0.1 to 10. Obtain the thickness H2 of the N-type epitaxial layer 102, the P-type implanted layer 104, and the P-type epitaxial layer 103 in the measurement region; obtain the resistance values Rs2 of the P-type implanted layer 104 and the P-type epitaxial layer 103. For example, please refer to Figure 6 , which shows a top view after etching. Please refer to Figure 7 , which shows a cross-sectional view after etching;

[0054] In some embodiments, an infrared mass spectrometer is used in steps three and four to measure the thickness of the epitaxial layer in the measurement region.

[0055] In some embodiments, please refer to Figure 8 , the method for obtaining the thickness of the P-type epitaxial layer 103 in the measurement region in step four includes: measuring the first thickness H1 of the N-type epitaxial layer 102 and the P-type implanted layer 104 in the measurement region before the epitaxial filling process; measuring the second thickness H2 of the N-type epitaxial layer 102, the P-type implanted layer 104, and the P-type epitaxial layer 103 in the measurement region after the epitaxial filling process; the third thickness H3 of the P-type epitaxial layer 103 in the measurement region = H2 - H1.

[0056] In some embodiments, in Steps 3 and 4, the four-point probe resistance measurement method is used to measure the resistance value on the P-type epitaxial layer 103 in the measurement region.

[0057] In some embodiments, please refer to Figure 9 , the method for obtaining the resistance of the P-type epitaxial layer 103 in the measurement region in Step 4 includes: after the ion implantation and annealing processes and before the epitaxial filling process, measuring the resistance Rs1 of the P-type implanted layer 104 in the measurement region; after the epitaxial filling process, measuring the parallel resistance Rs3 of the P-type implanted layer 104 and the P-type epitaxial layer 103 in the measurement region; the resistance value Rs2 of the P-type epitaxial layer 103 in the measurement region is Rs2 = Rs1 * Rs3 / (Rs1 - Rs3).

[0058] In some embodiments, based on the thickness and resistance value of the P-type epitaxial layer 103 obtained above, the resistivity Resistivity(RES) = RS (resistance value) * THK (thickness) / 10000 can be calculated to monitor the filling rate and doping concentration of the P-type epitaxial layer 103.

[0059] Please refer to Figure 10 , which shows a comparison schematic diagram of the epitaxial layer film thickness with different filling times between the present invention and the prior art. The film thickness of the monitoring method of the present invention is proportional to the filling time; at the same filling time, the film thickness of the monitoring method of the present invention is lower than that of the prior art, because the consumption of the silicon source by the deep trench filling next to it reduces the epitaxial growth rate of the non-exposed area.

[0060] Please refer to Figure 11 , which shows a comparison schematic diagram of the epitaxial layer resistivity with different filling times between the monitoring method (without IMP) of the present invention and the prior art. The resistivity of the prior art and the monitoring method (without IMP) of the present invention has a tendency to become thicker over time; mainly because when the epitaxial layer is thin, it is affected by the substrate N-EPI, resulting in a higher measured RES (resistivity).

[0061] Please refer to Figure 12 , which shows a schematic diagram of resistivity and thickness under different monitoring mode conditions. If a P-layer is implanted in advance on the N-type epitaxial layer 102, such as Figure 12 It can be seen from the test data that the numerical trends of the measured resistance and the converted resistance after IMP P- are very close, and the actual measured value can be approximately used as a direct reference.

[0062] This is because the PN junction peak after IMP is narrower than that of the prior art (Bare monitor) without IMP, so the influence of the PN junction on the measurement can be reduced when the film thickness is thin.

[0063] Please refer to Figure 13, the collected data shows that the monitoring method of the present invention is relatively matched with the prior art (Bare monitor).

[0064] Compared with the indirect monitoring method of the prior art, the monitoring method of the present invention can more directly monitor the epitaxial filling rate and doping concentration of the current deep trench superjunction product.

[0065] It should be noted that the illustrations provided in this embodiment only schematically illustrate the basic concept of the present invention. Therefore, only the components related to the present invention are shown in the drawings, rather than being drawn according to the number, shape and size of the components in actual implementation. The type, quantity and proportion of each component in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0066] In summary, the monitoring method of the present invention can more directly monitor the epitaxial filling rate and doping concentration of the current deep trench superjunction product. Therefore, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0067] The above embodiments only exemplarily illustrate the principles and effects of the present invention, rather than limiting the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for monitoring epitaxial filling rate and doping concentration of deep trench super junction products, characterized in that: At least: Step 1, providing a substrate, forming an N-type epitaxial layer on the substrate, and defining a deep trench etching area and a measurement area on the N-type epitaxial layer by photolithography, wherein the photoresist layer on the measurement area is retained, and the photoresist layer on the etching area is exposed and opened according to the design; Step 2, forming a deep groove on the etched area of ​​the N-type epitaxial layer by etching, and then removing the remaining photoresist layer; Step 3, performing ion implantation of a P-type doping source on the N-type epitaxial layer on the etching area and the measuring area and annealing to form a P-type implantation layer located on the surface of the N-type epitaxial layer, and obtaining the thickness H1 of the N-type epitaxial layer and the P-type implantation layer on the measuring area and the resistance value Rs1 of the P-type implantation layer; Step 4: Use an epitaxial filling process to form a P-type epitaxial layer filling the deep trench, and obtain the thickness H2 of the N-type epitaxial layer, the P-type injection layer and the P-type epitaxial layer on the measurement area; obtain the parallel resistance value Rs2 of the P-type injection layer and the P-type epitaxial layer. Step 5: Obtain the thickness H3 and resistance value Rs3 of the P-type epitaxial layer on the measurement area, the thickness H3 of the P-type epitaxial layer on the measurement area = H2-H1, the resistance value Rs3 of the P-type epitaxial layer on the measurement area = Rs1*Rs2 / (Rs1-Rs2) to monitor the filling rate and doping concentration of the P-type epitaxial layer.

2. The method for monitoring epitaxial filling rate and doping concentration of deep trench super junction products according to claim 1, characterized in that: The size of the measuring area in step 1 is not less than the minimum measuring area of ​​the measuring equipment.

3. The method for monitoring epitaxial filling rate and doping concentration of deep trench super junction products according to claim 1, characterized in that: In step 2, the deep trench is formed on the epitaxial layer by dry etching.

4. The method for monitoring epitaxial filling rate and doping concentration of deep trench super junction products according to claim 1, characterized in that: In step 2, the photoresist layer is removed by using an ashing process and a wet cleaning method.

5. The method for monitoring epitaxial filling rate and doping concentration of deep trench super junction products according to claim 1, characterized in that: The critical dimension of the deep trench in step 2 is 1-5 um.

6. The method for monitoring epitaxial filling rate and doping concentration of deep trench super junction products according to claim 1, characterized in that: The doping concentration of the P-type injection layer in step three needs to be close to the concentration of the P-type epitaxial layer grown later.

7. The method for monitoring epitaxial filling rate and doping concentration of deep trench super junction products according to claim 1, characterized in that: The ion implantation of the P-type doping source in step three is used to offset the influence of the PN junction on the epitaxial resistance.

8. The method for monitoring epitaxial filling rate and doping concentration of deep trench super junction products according to claim 1, characterized in that: In steps 3 and 4, the thickness is measured by using an infrared mass spectrometer on the measurement area to obtain the thickness.

9. The method for monitoring epitaxial filling rate and doping concentration of deep trench super junction products according to claim 1, characterized in that: In steps three and four, a four-point probe resistance measurement method is used to measure the resistance value on the measurement area.

10. The method for monitoring epitaxial filling rate and doping concentration of deep trench super junction products according to claim 1, characterized in that: In step five, the resistivity is calculated according to the thickness H3 and the resistance value Rs3 of the P-type epitaxial layer to monitor the filling rate and doping concentration of the P-type epitaxial layer.

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