Method for monitoring concentration of epitaxial process

Abstract

The invention provides an epitaxial process concentration monitoring method, which comprises the following steps of: providing a substrate, and forming an N-type epitaxial layer on the substrate; a deep groove is formed in the epitaxial layer, P columns are formed in the deep groove through epitaxy, and one P-type column and one corresponding adjacent N-type column form a super junction unit; selecting at least one test area on the P column to carry out P-type ion heavy doping injection so as to form a P-type heavy doping area; and forming a metal silicide layer of which the resistance value is not higher than a preset value on the P-type heavily doped region, and performing an electrical test by using the metal silicide layer to obtain a resistance test value of the P column, the resistance test value being used for representing the quantity of charges filled in the deep trench epitaxy so as to monitor the PN charge matching state of the super junction. According to the method, the metal silicide process which is simple in process and short in period is adopted, and the purpose of monitoring the epitaxial process concentration can be achieved quickly.

Description

Technical Field

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

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

[0003] The existing technology requires a series of process steps such as Photo (photolithography), CVD (chemical vapor deposition), ETCH (etching), Implant (ion implantation) etc. on silicon, which has a long cycle.

[0004] In order to solve the above problems, a new method of epitaxial process concentration monitoring needs to be proposed. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a method for monitoring the concentration of an epitaxial process, so as to solve the problem that the monitoring of the doping concentration of an online epitaxial process in the prior art has many process steps and a long cycle.

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

[0007] Step 1: providing a substrate, and forming an N-type epitaxial layer on the substrate;

[0008] Step 2: forming a deep trench on the epitaxial layer, forming a P column in the deep trench by epitaxy, wherein one P column and a corresponding adjacent N column form a super junction unit;

[0009] Step 3, selecting at least one test area on the P column to perform P-type ion heavy doping injection to form a P-type heavily doped area;

[0010] Step 4: forming a metal silicide layer with a resistance value not higher than a preset value on the P-type heavily doped region, and performing an electrical test on the metal silicide layer to obtain a resistance test value of the P column, wherein the resistance test value is used to characterize the charge amount of the deep trench epitaxial filling to monitor the super junction PN charge matching state.

[0011] Preferably, in step 2, the deep trench is formed by photolithography and etching.

[0012] Preferably, in step three, the test area is selected according to the size of the P column, the number of the P columns 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 blocking layer on the epitaxial layer; opening the metal silicide blocking layer on the test area; sequentially forming a metal layer covering the test area; forming the metal silicide layer on the test area by thermal annealing; and removing the remaining metal layer.

[0014] Preferably, in step 4, the metal silicide barrier layer on the test area is opened by 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 4 is TiSi2.

[0017] Preferably, the material of the metal silicide barrier layer in step 4 is silicon dioxide.

[0018] Preferably, in step 4, the resistance test value is obtained by testing using a wafer electrical acceptance test method.

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

[0020] The present invention adopts a metal silicide process with a simple process and a short cycle, and can quickly achieve the purpose of epitaxial process concentration monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Shown is a schematic diagram of a method for monitoring epitaxial process concentration according to the present invention;

[0022] Figure 2 Shown is a schematic diagram of a metal silicide layer on a P column of the present invention;

[0023] Figure 3 It is a schematic diagram showing the test data on metal silicide of the present invention. DETAILED DESCRIPTION

[0024] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0025] See also Figure 1 The present invention provides a method for monitoring concentration in an epitaxial process, comprising:

[0026] Step 1: providing a substrate, and forming an N-type epitaxial layer on the substrate;

[0027] Step 2: forming a deep trench on the epitaxial layer, and forming a P column in the deep trench by epitaxy, wherein a P column and a corresponding adjacent N column form a super junction unit;

[0028] In some embodiments, step 2 forms deep trenches by photolithography and etching.

[0029] Step 3: Select at least one test area on the P column to perform P-type ion heavy doping injection to form a P-type heavily doped area to facilitate subsequent formation of ohmic contacts;

[0030] In some embodiments, see Figure 2 In step three, the test area is selected according to the size of the P column, the number of P columns 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 area, and use the metal silicide layer to perform electrical testing to obtain a resistance test value of the P column. The resistance test value is used to characterize the amount of charge filled in the deep trench epitaxial growth to monitor the super junction 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 the 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 by thermal annealing; and removing the metal layer.

[0033] In some embodiments, in step 4, the metal silicide barrier layer on the test area is opened by photolithography and etching methods.

[0034] In some embodiments, the metal layer in step 4 is Ti.

[0035] In some embodiments, the material of the metal silicide layer in step 4 is TiSi2.

[0036] In some embodiments, the material of the capping layer in step 4 is titanium nitride.

[0037] In some embodiments, the material of the metal silicide barrier layer in step 4 is silicon dioxide, that is, a metal silicide layer is formed on the test area, and silicon dioxide is retained on other non-test areas.

[0038] In some embodiments, in step 4, a wafer electrical acceptance test (WAT) method is used to test and obtain a resistance test value, that is, a resistance test is performed directly by piercing the metal silicide barrier layer with a needle.

[0039] See also Figure 3, the test on the metal silicide shows a normal pulling trend, and the repeated test is stable. The method in the prior art requires about 60 process steps and takes seven days. The method in the prior art only requires about 20 process steps and takes two days.

[0040] It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner. Therefore, the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0041] In summary, the present invention adopts a metal silicide process with a simple process and a short cycle, and can quickly achieve the purpose of epitaxial process concentration monitoring. Therefore, the present invention effectively overcomes various shortcomings of the prior art and has a high industrial utilization value.

[0042] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may 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 a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall 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: Step 1: providing a substrate, and forming an N-type epitaxial layer on the substrate; Step 2: forming a deep trench on the epitaxial layer, forming a P column in the deep trench by epitaxy, wherein one P column and a corresponding adjacent N column form a super junction unit; Step 3, selecting at least one test area on the P column to perform P-type ion heavy doping injection to form a P-type heavily doped area; Step 4: forming a metal silicide layer with a resistance value not higher than a preset value on the P-type heavily doped region, and performing an electrical test on the metal silicide layer to obtain a resistance test value of the P column, wherein the resistance test value is used to characterize the charge amount of the deep trench epitaxial filling to monitor the super junction PN charge matching state.

2. The method for monitoring concentration in an epitaxial process according to claim 1, characterized in that: Step 2: forming the deep groove by photolithography and etching.

3. The method for monitoring concentration in an epitaxial process according to claim 1, characterized in that: In step three, the test area is selected according to the size of the P column, the number of the P columns and the size of the metal silicide layer.

4. The method for monitoring concentration in an epitaxial process 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 by thermal annealing; and removing the remaining metal layer.

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

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

7. The method for monitoring concentration in an epitaxial process according to claim 6, characterized in that: The material of the metal silicide layer in step 4 is TiSi2.

8. The method for monitoring concentration in an epitaxial process according to claim 1, characterized in that: The material of the metal silicide barrier layer in step 4 is silicon dioxide.

9. The method for monitoring concentration in an epitaxial process according to claim 1, characterized in that: In step 4, the resistance test value is obtained by testing using a wafer electrical acceptance test method.

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