Methods for monitoring concentration in epitaxial processes

Abstract

This invention provides a method for monitoring epitaxial process concentration. A substrate is provided, and an N-type epitaxial layer is formed on the substrate. A deep trench is formed on the epitaxial layer, and P-type pillars are formed in the deep trench using epitaxy. Each P-type pillar and its corresponding adjacent N-type pillar form a superjunction unit. At least one test region is selected on the P-type pillar for heavy P-type ion implantation to form a heavily doped P-type region. A metal silicide layer with a resistance value not exceeding a preset value is formed on the heavily doped P-type region. Electrical testing is performed on the metal silicide layer to obtain the resistance value of the P-type pillar. The resistance value is used to characterize the amount of charge filling the deep trench, thereby monitoring the PN charge matching state of the superjunction. This invention employs a simple and short-cycle metal silicide process, which can quickly achieve the purpose of monitoring epitaxial process concentration.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a method for monitoring the concentration in an epitaxial process. Background Technology

[0002] The performance of superjunctions is closely related to their charge matching state, and P-EPI (P-type epitaxial layer) epitaxial process directly affects PN charge matching. How to quickly and accurately monitor the doping concentration of the online epitaxial process is a key focus of widespread attention.

[0003] Existing technologies require a series of process steps on silicon, such as photolithography, CVD (chemical vapor deposition), ETCH (etching), and implantation, which are time-consuming.

[0004] To address the above issues, a novel method for monitoring the concentration in epitaxial processes is needed. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for monitoring the doping concentration in epitaxial processes, which solves the problems of multiple process steps and long cycles in the monitoring of doping concentration in online epitaxial processes in the prior art.

[0006] To achieve the above and other related objectives, the present invention provides a method for monitoring concentration in an epitaxial process, comprising:

[0007] Step 1: Provide a substrate and form an N-type epitaxial layer on the substrate;

[0008] Step 2: A deep trench is formed on the epitaxial layer, and a P-type pillar is formed in the deep trench using the epitaxial layer. One P-type pillar and a corresponding adjacent N-type pillar form a superjunction unit.

[0009] Step 3: Select at least one test area on the P-type column and perform P-type ion heavy doping implantation to form a P-type heavily doped region;

[0010] Step 4: Form a metal silicide layer with a resistance value not higher than a preset value on the P-type heavily doped region. Use the metal silicide layer to perform electrical tests to obtain the resistance test value of the P-type pillar. The resistance test value is used to characterize the amount of charge filling the deep trench epitaxial layer in order to monitor the superjunction PN charge matching state.

[0011] Preferably, step two involves forming the deep trench using photolithography and etching methods.

[0012] Preferably, in step three, the test area is selected based on the size of the P-shaped pillar, the number of P-shaped pillars, and the size of the metal silicide layer.

[0013] Preferably, the method for forming the metal silicide layer in step four includes: forming a metal silicide barrier layer on the epitaxial layer; opening the metal silicide barrier layer on the test area; sequentially forming a metal layer covering the test area; forming the metal silicide layer on the test area using a thermal annealing method; and removing the remaining metal layer.

[0014] Preferably, in step four, the metal silicide barrier layer on the test area is opened using photolithography and etching methods.

[0015] Preferably, the metal layer in step four is Ti.

[0016] Preferably, the material of the metal silicide layer in step four is TiSi2.

[0017] Preferably, the material of the metal silicide barrier layer in step four is silicon dioxide.

[0018] Preferably, the resistance value is obtained in step four using a wafer electrical acceptance test method.

[0019] As described above, the method for monitoring epitaxial process concentration of the present invention has the following beneficial effects:

[0020] This invention employs a simple and short-cycle metal silicide process, which can quickly achieve the purpose of monitoring the concentration in the epitaxial process. Attached Figure Description

[0021] Figure 1 The diagram shows a method for monitoring epitaxial process concentration according to the present invention.

[0022] Figure 2 The diagram shows a metal silicide layer on the P-type pillar of the present invention.

[0023] Figure 3 The diagram shows test data on metal silicides according to the present invention. Detailed Implementation

[0024] The following specific examples illustrate the implementation 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 embodiments, and 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.

[0025] Please see Figure 1 This invention provides a method for monitoring concentration in an epitaxial process, comprising:

[0026] Step 1: Provide a substrate and form an N-type epitaxial layer on the substrate;

[0027] Step 2: Form deep trenches on the epitaxial layer, and use epitaxy to form P-type pillars in the deep trenches. A P-type pillar and a corresponding adjacent N-type pillar form a superjunction unit.

[0028] In some embodiments, step two uses photolithography and etching methods to form deep trenches.

[0029] Step 3: Select at least one test area on the P-type column for P-type ion heavy doping implantation to form a P-type heavy doped region, which facilitates the subsequent formation of ohmic contacts.

[0030] In some embodiments, please refer to Figure 2 In step three, the test area is selected based on the size of the P-type pillars, the number of P-type pillars, and the size of the metal silicide layer.

[0031] Step 4: Form a metal silicide layer with a resistance value not higher than a preset value on the P-type heavily doped region. Use the metal silicide layer to perform electrical tests to obtain the resistance test value of the P-type pillar. The resistance test value is used to characterize the amount of charge filling the deep trench epitaxial layer in order to monitor the superjunction PN charge matching state.

[0032] In some embodiments, the method for forming the metal silicide layer in step four includes: forming a metal silicide barrier layer on an epitaxial layer; opening the metal silicide barrier layer on the test area; sequentially forming a metal layer covering the test area; forming a metal silicide layer on the test area using a thermal annealing method; and removing the metal layer.

[0033] In some embodiments, in step four, the metal silicide barrier layer on the test area is opened using photolithography and etching methods.

[0034] In some embodiments, the metal layer in step four is Ti.

[0035] In some embodiments, the material of the metal silicide layer in step four is TiSi2.

[0036] In some embodiments, the material of the capping layer in step four is titanium nitride.

[0037] In some embodiments, the material of the metal silicide barrier layer in step four is silicon dioxide, that is, a metal silicide layer is formed on the test area, while silicon dioxide is retained on other non-test areas.

[0038] In some embodiments, the resistance test value is obtained in step four using the wafer electrical acceptance test (WAT) method, that is, the resistance test is performed by directly inserting a pin into the metal silicide barrier layer.

[0039] Please see Figure 3The test results on the metal silicide showed a normal bias trend, and repeated tests were stable. Existing methods require approximately 60 process steps and take seven days. The method in this application requires only approximately 20 process steps and takes two days.

[0040] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0041] In summary, this invention employs a simple and short-cycle metal silicide process, enabling rapid monitoring of epitaxial growth concentration. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and possesses high industrial applicability.

[0042] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for monitoring concentration in an epitaxial process, characterized in that, At least including: Step 1: Provide a substrate and form an N-type epitaxial layer on the substrate; Step 2: A deep trench is formed on the epitaxial layer, and a P-type pillar is formed in the deep trench using the epitaxial layer. One P-type pillar and a corresponding adjacent N-type pillar form a superjunction unit. Step 3: Select a test area based on the size of the P-type pillar, the number of P-type pillars, and the size of the metal silicide layer. Select at least one test area on the P-type pillar for P-type ion heavy doping implantation to form a P-type heavy doped region. Step 4: Form a metal silicide layer with a resistance value not higher than a preset value on the P-type heavily doped region. Use the metal silicide layer to perform electrical tests to obtain the resistance test value of the P-type pillar. The resistance test value is used to characterize the amount of charge filling the deep trench epitaxial layer in order to monitor the superjunction PN charge matching state.

2. The method for monitoring concentration in epitaxial processes according to claim 1, characterized in that: Step two involves forming the deep trench using photolithography and etching methods.

3. The method for monitoring concentration in epitaxial processes according to claim 1, characterized in that: The method for forming the metal silicide layer in step four includes: forming a metal silicide barrier layer on the epitaxial layer; opening the metal silicide barrier layer on the test area; sequentially forming a metal layer covering the test area; forming the metal silicide layer on the test area using a thermal annealing method; and removing the remaining metal layer.

4. The method for monitoring concentration in epitaxial processes according to claim 3, characterized in that: In step four, the metal silicide barrier layer on the test area is opened using photolithography and etching methods.

5. The method for monitoring concentration in epitaxial processes according to claim 3, characterized in that: The metal layer mentioned in step four is Ti.

6. The method for monitoring epitaxial process concentration according to claim 5, characterized in that: The material of the metal silicide layer in step four is TiSi2.

7. The method for monitoring concentration in epitaxial processes according to claim 1, characterized in that: The material of the metal silicide barrier layer mentioned in step four is silicon dioxide.

8. The method for monitoring concentration in epitaxial processes according to claim 1, characterized in that: In step four, the resistance value is obtained by using the wafer electrical acceptance test method.

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