Radio frequency CMOS chip and method for measuring conductivity of silicon substrate thereof

Abstract

The application discloses a radio frequency CMOS chip and a silicon substrate conductivity measurement method thereof, and the measurement method comprises the following steps: measuring S parameters of a first passive circuit and a second passive circuit respectively, obtaining a measurement value of insertion loss S21 of the first passive circuit and the second passive circuit at any frequency A; calculating a measurement difference value AS21 of the measurement value of the insertion loss S21 of the first passive circuit and the second passive circuit at any frequency A; simulating the insertion loss S21 of the passive circuit, and obtaining a silicon substrate conductivity value based on the measurement difference value AS21, that is, the actual conductivity of the silicon substrate of the radio frequency CMOS chip. The application can accurately measure the conductivity of the silicon substrate of the radio frequency CMOS chip by using a relatively simple circuit without making an ohmic contact pad, and eliminates the influence of a traditional Hall method ohmic contact on the measurement result of the silicon substrate conductivity.

Description

Technical Field

[0001] This invention relates to the field of conductivity measurement technology, and in particular to a method for measuring the conductivity of an RF CMOS chip and its silicon substrate. Background Technology

[0002] With the deepening commercial application of 5G wireless communication, the cost reduction and multi-functionality of RF transceiver chips are inevitable trends. CMOS silicon-based chips, with their low cost and high integration, are very suitable for developing wireless communication RF front-end chips. However, in the fabrication of CMOS integrated circuits, to prevent latch-up effects, p-type doping is usually performed on the silicon substrate to increase its conductivity. This has a significant negative impact on the fabrication of RF CMOS integrated circuits: high conductivity substrates cause high dielectric losses, thereby increasing the signal transmission attenuation of transmission lines and passive circuits on the silicon substrate, and deteriorating the overall performance of the RF circuit. Because the conductivity of the silicon substrate has a significant impact on the performance of RF CMOS chips, the conductivity of the silicon substrate is a key design parameter in the design process of RF CMOS circuits.

[0003] Circuit manufacturers typically provide reference values ​​for the conductivity of silicon substrates. However, due to process variations and deviations, the actual conductivity of the silicon substrate often differs from the reference value. This necessitates measuring the conductivity of the silicon substrate. The traditional Hall effect method requires generating ohmic contact pads on the silicon wafer under test. This method has significant drawbacks: impurities and defects on the silicon surface affect the quality of the ohmic contact formation, and the ohmic contact pads themselves can also influence the measurement results, leading to inaccuracies. Using inaccurate conductivity values ​​as a design basis will inevitably result in poor circuit performance or even incorrect design outcomes. Therefore, a method for measuring the conductivity of silicon substrates in RF CMOS chips that avoids the influence of ohmic contacts is needed. Summary of the Invention

[0004] In view of this, the present invention provides a method for measuring the conductivity of an RF CMOS chip and its silicon substrate, which eliminates the influence of Hall effect ohmic contacts on the conductivity measurement results of the silicon substrate.

[0005] This invention discloses an RF CMOS chip, which includes a first passive circuit and a second passive circuit; the first passive circuit and the second passive circuit have the same circuit structure; the first passive circuit is fabricated on a p-type doped silicon substrate; and the second passive circuit is fabricated on an undoped intrinsic silicon substrate.

[0006] Furthermore, the circuit structures of both the first passive circuit and the second passive circuit include an input pad, a spiral inductor, and an output pad disposed on a silicon substrate.

[0007] The input pad is connected to the output pad via the spiral inductor.

[0008] Furthermore, the input pad serves as the input terminal of the first passive circuit or the second passive circuit, and the output pad serves as the output terminal of the first passive circuit or the second passive circuit.

[0009] This invention also discloses a method for measuring the conductivity of a silicon substrate, applied to the aforementioned radio frequency CMOS chip, the method comprising the following steps:

[0010] The S-parameters of the first passive circuit and the second passive circuit are measured respectively to obtain the measured values ​​of the insertion loss S21 of the first passive circuit and the second passive circuit at any frequency A.

[0011] Calculate the measurement difference ΔS21 of the insertion loss S21 of the first passive circuit and the second passive circuit at any frequency A;

[0012] The insertion loss S21 of the simulated passive circuit is used to obtain the conductivity value of the silicon substrate based on the measured difference ΔS21, which is the actual conductivity of the silicon substrate of the RF CMOS chip.

[0013] Further, the measurement of the S-parameters of the first passive circuit and the second passive circuit includes:

[0014] S-parameters were measured at the input and output pads of the first passive circuit; S-parameters were also measured at the input and output pads of the second passive circuit.

[0015] Furthermore, the insertion loss S21 of the simulated passive circuit includes:

[0016] Simulate the insertion loss S21 of a passive circuit in an electromagnetic field solver.

[0017] Further, the step of obtaining the silicon substrate conductivity value based on the measurement difference ΔS21, which is the actual conductivity of the silicon substrate of the RF CMOS chip, includes:

[0018] The conductivity of the silicon substrate in the electromagnetic field solver is set to zero. At the frequency point A where the measurement difference ΔS21 is obtained, the insertion loss S21 of the second passive circuit is simulated and recorded as S21a. Then, the conductivity value of the silicon substrate in the solver is gradually increased to obtain the value of the insertion loss S21 corresponding to the conductivity value. When the difference between the value of the insertion loss S21 and S21a is equal to ΔS21, the corresponding conductivity value of the silicon substrate is the actual conductivity of the silicon substrate of the RF CMOS chip.

[0019] Furthermore, when the conductivity of the silicon substrate in the electromagnetic field solver is set to zero, the insertion loss S21 of the second passive circuit is minimized.

[0020] Furthermore, the value of the insertion loss S21 is approximately proportional to the conductivity of the silicon substrate.

[0021] Due to the adoption of the above technical solution, the present invention has the following advantages: it can accurately measure the conductivity of the silicon substrate of RF CMOS chip with a relatively simple circuit without fabricating ohmic contact pads, thus eliminating the influence of traditional Hall effect ohmic contacts on the conductivity measurement results of silicon substrate. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in the embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0023] Figure 1 This is a schematic diagram of the radio frequency CMOS chip according to an embodiment of the present invention. Detailed Implementation

[0024] The present invention will be further described in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art should fall within the protection scope of the present invention.

[0025] Figure 1 A schematic diagram of the radio frequency CMOS chip of the present invention is shown. (See attached diagram.) Figure 1 The test system includes a first passive circuit 1 and a second passive circuit 2. The first passive circuit 1 further includes an input pad 3, a planar spiral inductor 4, and an output pad 5. The first passive circuit 1 is fabricated on a p-type doped silicon substrate. The circuit structure of the second passive circuit 2 is exactly the same as that of the first passive circuit 1, but the substrate of the second passive circuit 2 is an undoped intrinsic silicon substrate 6.

[0026] An embodiment of a method for measuring the conductivity of a silicon substrate provided by the present invention includes the following steps:

[0027] exist Figure 1The S-parameters of the first passive circuit 1 and the second passive circuit 2 are measured at input pad 3 and output pad 5 to obtain the measured values ​​of the insertion loss S21 of the first passive circuit 1 and the second passive circuit 2 at a frequency of 1 GHz. The measurement difference ΔS21 between the measured values ​​of the insertion loss S21 of the first passive circuit 1 and the second passive circuit 2 at 1 GHz is calculated. It should be noted that the measurement frequency is not limited to 1 GHz and measurements can also be performed at other frequencies.

[0028] Simulating the insertion loss S21 of a passive circuit in an electromagnetic field solver: First, set the conductivity of the silicon substrate in the solver to zero. At the frequency point where the measurement difference ΔS21 is measured, simulate the value of the insertion loss S21 of the second passive circuit 2, denoted as S21a. Then, gradually increase the conductivity value of the silicon substrate in the solver. When the difference between the obtained insertion loss S21 and S21a is equal to ΔS21, the set silicon substrate conductivity value is the actual conductivity of the silicon substrate of the measured RF CMOS chip.

[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for measuring the conductivity of a silicon substrate, applied to radio frequency CMOS chips, characterized in that, The measurement method includes the following steps: The S-parameters of the first passive circuit and the second passive circuit are measured respectively to obtain the measured values ​​of the insertion loss S21 of the first passive circuit and the second passive circuit at any frequency A. Calculate the measurement difference ΔS21 of the insertion loss S21 of the first passive circuit and the second passive circuit at any frequency A; The insertion loss S21 of the second passive circuit is simulated, and the conductivity value of the silicon substrate is obtained based on the measured difference ΔS21, which is the actual conductivity of the silicon substrate of the RF CMOS chip. The process of obtaining the silicon substrate conductivity value based on the measurement difference ΔS21, which is the actual conductivity of the silicon substrate of the RF CMOS chip, includes: The conductivity of the silicon substrate in the electromagnetic field solver is set to zero. At the frequency point A where the measurement difference ΔS21 is obtained, the insertion loss S21 of the second passive circuit is simulated and recorded as S21a. Then, the conductivity value of the silicon substrate in the solver is gradually increased to obtain the value of the insertion loss S21 corresponding to the conductivity value. When the difference between the value of the insertion loss S21 and S21a is equal to ΔS21, the corresponding conductivity value of the silicon substrate is the actual conductivity of the silicon substrate of the RF CMOS chip.

2. The measurement method according to claim 1, characterized in that, The measurement of the S-parameters of the first passive circuit and the second passive circuit includes: S-parameters were measured at the input and output pads of the first passive circuit; S-parameters were also measured at the input and output pads of the second passive circuit.

3. The measurement method according to claim 1, characterized in that, The insertion loss S21 of the simulated second passive circuit includes: The insertion loss S21 of the second passive circuit is simulated in the electromagnetic field solver.

4. The measurement method according to claim 1, characterized in that, When the conductivity of the silicon substrate in the electromagnetic field solver is set to zero, the insertion loss S21 of the second passive circuit is minimized.

5. The measurement method according to claim 1, characterized in that, The insertion loss S21 is approximately proportional to the conductivity of the silicon substrate.

6. The measurement method according to claim 1, characterized in that, The radio frequency CMOS chip includes a first passive circuit and a second passive circuit; the first passive circuit and the second passive circuit have the same circuit structure; the first passive circuit is fabricated on a p-type doped silicon substrate; and the second passive circuit is fabricated on an undoped intrinsic silicon substrate.

7. The measurement method according to claim 6, characterized in that, Both the first passive circuit and the second passive circuit include an input pad, a spiral inductor, and an output pad disposed on a silicon substrate. The input pad is connected to the output pad via the spiral inductor.

8. The measurement method according to claim 7, characterized in that, The input pad serves as the input terminal of the first passive circuit or the second passive circuit, and the output pad serves as the output terminal of the first passive circuit or the second passive circuit.

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