Method for epitaxial-process concentration monitoring

Abstract

The present invention provides a method for epitaxial-process concentration monitoring. The method comprises: providing a substrate, and forming an N-type epitaxial layer on the substrate; forming a deep trench on the epitaxial layer, and forming a P-pillar in the deep trench by means of epitaxy, wherein one P-pillar and a corresponding adjacent N-pillar form a super junction unit; selecting at least one test region on the P-pillar for heavy P-type ion doping implantation, so as to form a P-type heavily doped region; and forming, on the P-type heavily doped region, a metal silicide layer having a resistance value not greater than a preset value, and using the metal silicide layer to perform an electrical test to obtain a resistance test value of the P-pillar, wherein the resistance test value is used for representing the charge amount of deep trench epitaxial filling, so as to monitor a charge matching state of a PN super junction. The present invention employs a simple short-cycle metal silicide process, thereby achieving the purpose of rapid monitoring of epitaxial-process concentration.

Description

Methods for monitoring concentration in epitaxial processes 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: Form deep trenches on the epitaxial layer, and use the epitaxial layer to form P-pillars in the deep trenches. One P-pillar and a corresponding adjacent N-pillar form a superjunction unit.

[0009] Step 3: Select at least one test region on the P-pillar for P-type ion heavy doping implantation to form a P-type heavy 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 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-pillar, the number of P-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 shows a schematic diagram of the method for monitoring epitaxial process concentration according to the present invention;

[0022] Figure 2 shows a schematic diagram of the metal silicide layer on the P-pillar of the present invention;

[0023] Figure 3 shows a schematic diagram of the test data of the present invention on metal silicides. 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 refer to 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-pillars in the deep trenches. A P-pillar and a corresponding adjacent N-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-pillar 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 according to the size of the P-pillar, the number of P-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 pillar. The resistance test value is used to characterize the amount of charge filling the deep trench epitaxial layer in order to monitor the PN charge matching state of the superjunction.

[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 refer to Figure 3. The test pull-off trend on the metal silicide is normal, and the repeated test is stable. The existing method requires approximately 60 process steps and takes seven days. The existing method only requires 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: Form deep trenches on the epitaxial layer, and use the epitaxial layer to form P-pillars in the deep trenches. One P-pillar and a corresponding adjacent N-pillar form a superjunction unit. Step 3: Select at least one test region on the P-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 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: In step three, the test area is selected based on the size of the P-pillar, the number of P-pillars, and the size of the metal silicide layer.

4. 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.

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

6. The method for monitoring epitaxial process concentration according to claim 1 or 4, characterized in that: The metal layer mentioned in step four is Ti.

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

8. 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.

9. 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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