Preparation method and quality judgment method of mesa type SiGe HBT (Heterojunction Bipolar Transistor)

Abstract

The invention provides a preparation method of a mesa type SiGe HBT (Heterojunction Bipolar Transistor). The preparation method comprises the following steps: growing a Si collector region, a SiGe base region and a Si emitter region at one time by adopting molecular beam epitaxy; etching a base region mesa by adopting a selective corrosive liquid; depositing silicon dioxide on the surface of the device through a normal-pressure chemical vapor deposition method; and forming holes in the silicon dioxide on the surfaces of the Si collector region, the SiGe base region and the Si emitter region, and then performing metal reverse etching to complete preparation of a collector, a base and an emitter to obtain the mesa type SiGe HBT. Meanwhile, the invention also provides a method for carrying out quality judgment on the mesa type SiGe HBT prepared by the preparation method.

Description

Technical Field

[0001] The present disclosure relates to the technical field of semiconductor integrated circuits, and in particular to a method for preparing a mesa-type SiGe HBT and a method for determining its quality. Background Art

[0002] SiGe HBT (Heterojunction Bipolar Transistor) is a core device for future wireless communications. It uses strained silicon germanium (SiGe) compound material as the base, and SiGe and Si form a heterojunction. How to prepare and how to determine the growth quality of the SiGe base, and how to determine the quality of the SiGe / Si heterojunction are urgent issues to be solved in this device.

[0003] The material properties can be roughly estimated by testing the output characteristics of the device. Another method is to extract parameters after testing the device. The following references [1] and [2] use the parameter extraction method, but their method can only extract parasitic resistance, capacitance and inductance, and cannot determine the quality of the base region and heterojunction, and there is no accurate quantitative expression to describe it.

[0004] [1]HYChen, KMChen et al.Small-signal modeling of SiGe HBTs using direct parameter-extraction method.IEEE Trans.on Electron Devices, 53(9):2287-2295, 2006.

[0005] [2] Han Bo, Li Shoulin, et al. MEXTRAM model based SiGe HBT large-signal modeling. Journal of Semiconductors, 31(10): 32-37, 2010. Summary of the invention

[0006] Based on the above problems, the present disclosure provides a method for preparing a mesa-type SiGe HBT and a method for determining its quality, so as to alleviate the above technical problems in the prior art.

[0007] (I) Technical solution

[0008] One aspect of the present disclosure provides a method for preparing a mesa-type SiGe HBT, comprising: growing a Si collector region, a SiGe base region and a Si emitter region at one time by molecular beam epitaxy; etching a base mesa by a selective etching solution; depositing silicon dioxide on the device surface by atmospheric pressure chemical vapor deposition; and performing metal reverse etching after opening holes in the silicon dioxide on the surfaces of the Si collector region, the SiGe base region and the Si emitter region, thereby completing the preparation of a collector, a base and an emitter to obtain a mesa-type SiGe HBT.

[0009] According to the embodiment of the present disclosure, the selective etching solution only etches Si but not SiGe.

[0010] According to the embodiment of the present disclosure, the selective etching liquid is a solvent of isopropyl alcohol and H2O in a volume ratio of 1:4, and 20g KOH and 0.8g K2Cr2O3 are added to every 100ml of the solvent.

[0011] Another aspect of the present disclosure provides a quality determination method for a mesa-type SiGe HBT, which is used to determine the quality of a mesa-type SiGe HBT prepared by any of the preparation methods described above, and the quality determination method includes: testing the Gummel curve of the SiGe HBT device; obtaining the collector current and / or the base current according to the Gummel curve; obtaining the ideal factors of the collector current and the base current according to the current differential and the voltage differential of the collector current and / or the base current; transforming the Gummel curve into a relationship diagram between the ideal factor and the collector current or the base current; obtaining the series resistance of the collector or the base according to the relationship curve; extracting the collector reverse saturation current according to the Gummel curve; and obtaining the ideal diffusion current, recombination current, and ideal recombination current factor of the base region.

[0012] According to an embodiment of the present disclosure, the Gummel curve is transformed into a relationship diagram between the ideal factor and the collector current or the base current according to a formula transformation; the relationship diagram is a straight line with a certain slope, and the series resistance of the collector or the base is determined by the slope.

[0013] According to the embodiment of the present disclosure, when extracting the collector reverse saturation current, it is obtained by taking the intercept of the Gummel curve on the vertical axis.

[0014] According to the embodiment of the present disclosure, the base current I B It is expressed as:

[0015] I B =I B1 +I B2 =I B01 exp(V BE / V T )+I B02exp(V BE / mV T );

[0016] Among them I B1 and I B2 are the ideal diffusion current and recombination current of the base region, m is the ideal factor of recombination current, V BE is the emitter junction voltage, I B01 is the reverse saturation current in the diffusion current, I B02 is the reverse saturation current in the composite current, V T is the thermal voltage.

[0017] According to an embodiment of the present disclosure, in a quality determination method for a mesa-type SiGe HBT, let:

[0018] V′ BE =V BE -I B R S ;

[0019] but:

[0020] I B ≈I B01 exp(V′ BE / V T );

[0021] Among them, V BE is the emitter junction voltage, V′ BE is the voltage after translation, R S is the series resistance;

[0022] The V in the Gummel curve BE Change to V' BE , the intercept of the straight line on the vertical axis is I B01 , I B01 Extract descendants into I B expression:

[0023] I B2 =I B -I B1 ;

[0024] Thus I B2 With the emitter junction voltage V BE The changing curve, from which I B02 and the value of m.

[0025] (II) Beneficial effects

[0026] It can be seen from the above technical solutions that the preparation method and quality determination method of the mesa-type SiGe HBT disclosed in the present invention have at least one or part of the following beneficial effects:

[0027] (1) It can accurately determine the ideality factor and leakage current of the emitter and collector heterojunctions, and the proportion of the recombination current in the SiGe base region to the total current, thereby more accurately determining the quality of the fabricated transistor.

[0028] (2) By using a special selective etching solution, the base area table can be clearly obtained, which is superior to the table device preparation method in the prior art;

[0029] (3) When making quality judgments, both qualitative and quantitative analysis can be performed. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the structure of a mesa-type SiGe HBT according to an embodiment of the present disclosure.

[0031] Figure 2 FIG. 4 is a schematic diagram of the Gummel curve test results of the mesa-type SiGe HBT according to the embodiment of the present disclosure.

[0032] Figure 3 It is a curve diagram for extracting the series resistance of a mesa-type SiGe HBT according to an embodiment of the present disclosure.

[0033] Figure 4 V in the mesa-type SiGe HBT of the embodiment of the present disclosure BE 'Suit I B Schematic diagram of the changing curve.

[0034] Figure 5 The mesa-type SiGe HBT of the embodiment of the present disclosure is B2 With V BE Schematic diagram of the change curve.

[0035] Figure 6 FIG. 4 is a flow chart of a method for preparing a mesa-type SiGe HBT according to an embodiment of the present disclosure.

[0036] Figure 7 FIG. 4 is a flow chart of a method for determining the quality of a mesa-type SiGe HBT according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0037] The present invention provides a preparation method and quality determination method of a mesa-type SiGe HBT, which are used to find an accurate criterion for determining the quality of a base region and a heterojunction of a mesa-type SiGe HBT, solve the quality determination problem of heterojunction and base materials in SiGe HBT, establish a monitoring method for the process preparation of SiGe HBT by creating an effective theoretical method to establish the criterion, and provide a basic idea for model creation of such devices.

[0038] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0039] In an embodiment of the present disclosure, a method for preparing a mesa-type SiGe HBT is provided, Figure 1 and Figure 6 As shown, the method for preparing the mesa-type SiGe HBT comprises:

[0040] Operation S1: using molecular beam epitaxy to grow Si collector region, SiGe base region and Si emitter region at one time;

[0041] Operation S2: etching the base area mesa using a selective etching solution;

[0042] Operation S3: depositing silicon dioxide on the surface of the device by atmospheric pressure chemical vapor deposition; and

[0043] Operation S4: After opening holes in the silicon dioxide on the surfaces of the Si collector region, the SiGe base region and the Si emitter region, metal reverse etching is performed to complete the preparation of the collector, base and emitter to obtain a mesa-type SiGe HBT.

[0044] According to the embodiment of the present disclosure, the selective etching solution only etches Si but not SiGe. The selective etching solution is a solvent of isopropanol and H2O in a volume ratio of 1:4, and 20g KOH and 0.8g K2Cr2O3 are added to every 100ml of solvent.

[0045] According to the disclosed embodiment, the preparation process of the mesa-type SiGe HBT is as follows: Molecular beam epitaxy (MBE) is used to grow the collector region Si, base region SiGe and emitter region Si at one time, and a selective etching solution is used to etch out the base region mesa, which only corrodes Si but not SiGe. The etching solution composition is: 15 grams of KOH, 0.6 grams of K2Cr2O3, 15 milliliters of isopropanol, and 60 milliliters of H2O. After the two mesas are successfully etched, silicon dioxide is deposited by atmospheric pressure CVD (APCVD), and metal is reversely etched after the hole is opened.

[0046] The present disclosure also provides a method for determining the quality of a mesa-type SiGe HBT, which is used to determine the quality of the mesa-type SiGe HBT prepared by the above preparation method. Figure 7 and Figure 2-Figure 5 As shown, the quality determination method includes:

[0047] Operation S10: testing a Gummel curve of a SiGe HBT device;

[0048] Operation S20: obtaining a collector current and / or a base current according to the Gummel curve;

[0049] Operation S30: obtaining an ideality factor of a collector current and a base current according to the collector current and / or the base current;

[0050] Operation S40: transforming the Gummel curve into a relationship diagram between the ideality factor and the collector current or the base current;

[0051] Operation S50: obtaining a series resistance of a collector or a base according to the relationship curve;

[0052] Operation S60: extracting a collector reverse saturation current according to the Gummel curve; and

[0053] Operation S70: obtaining an ideal diffusion current, a recombination current, and a recombination current ideality factor of the base region.

[0054] According to the embodiment of the present disclosure, when making a quality judgment, the bare chip is placed on a probe station to test the Gummel curve of the device, such as Figure 2-Figure 3 As shown, the collector current (IC) and the base current (IB) are shown as two dotted lines in the figure. The method for extracting the ideal factor n of the collector current and the base current is as follows: Both the collector current and the base current can be expressed as I:

[0055]

[0056] Where I0 is the reverse saturation current, V is the applied voltage, n is the ideal factor, V T is the thermal voltage. Transform the above formula into:

[0057]

[0058] The ideal factor n can be obtained by obtaining dI / dV from the Gummel curve, where dI is the current differential and dV is the voltage differential.

[0059] The extraction process of the collector or base series resistance is as follows: The relationship between the ideal factor and the current can be obtained by the formula transformation method as follows

[0060]

[0061] like Figure 3 As shown, the Gummel curve is transformed into a curve of the relationship between n and I, and the slope of the straight line is R S / V T , thus obtaining the series resistance R S .

[0062] To extract the collector reverse saturation current, just take the Gummel curve I C -V BEThe intercept on the vertical axis is OK.

[0063] The ideal diffusion current and recombination current of the base region and their ideal factors are extracted as follows: B It is expressed as:

[0064] I B =I B1 +I B2 =I B01 exp(V BE / V T )+I B02 exp(V BE / mV T );

[0065] I B1 and I B2 are the ideal diffusion current and recombination current of the base region, m is the ideal factor of recombination current, V BE is the emitter junction voltage, I B01 is the reverse saturation current in the diffusion current, I B02 is the reverse saturation current in the composite current, V T is the thermal voltage.

[0066] V′ BE =V BE -I B R S ;

[0067] but

[0068] I B ≈I B01 exp(V′ BE / V T );

[0069] Among them, V′ BE is the voltage after translation;

[0070] Combination Figure 4 and Figure 5 As shown, the V in the Gummel curve BE Change to V' BE , the intercept of the straight line on the vertical axis is l B01 , I B01 Extract descendants into I B expression:

[0071] I B2 =I B -I B1 ;

[0072] Thus I B2 With the emitter junction voltage V BEThe changing curve, from which I B02 and the value of m.

[0073] At this point the extraction process is complete.

[0074] According to an embodiment of the present disclosure, the Gummel curve is transformed into a relationship diagram between the ideal factor and the collector current or the base current according to a formula transformation; the relationship diagram is a straight line with a certain slope, and the series resistance of the collector or the base is determined by the slope. According to an embodiment of the present disclosure, when extracting the collector reverse saturation current, it is obtained by taking the intercept of the Gummel curve on the vertical axis.

[0075] According to the embodiments of the present disclosure, the extraction method can be written in Verilog A language and embedded in a SPICE program, so that the circuit composed of SiGe HBT can be analyzed more accurately and the SiGe HBT can be modeled.

[0076] The optimized SiGe HBT has obvious advantages over traditional Si devices in RF integrated circuits and will be widely used in RF front-end integrated circuits.

[0077] The quality determination method and the extraction method disclosed in the present invention can also be written into a program and embedded in the parameter extraction software ICCAP to optimize the parameter extraction process of SiGe HBT. The monitoring of the process requires understanding the quality of the heterojunction and the growth quality of the SiGe material.

[0078] So far, the embodiments of the present disclosure have been described in detail in conjunction with the accompanying drawings. It should be noted that the implementation methods not shown or described in the drawings or the body of the specification are all forms known to ordinary technicians in the relevant technical field and are not described in detail. In addition, the above definitions of each element and method are not limited to the various specific structures, shapes or methods mentioned in the embodiments, and ordinary technicians in the field can simply change or replace them.

[0079] Based on the above description, those skilled in the art should have a clear understanding of the preparation method and quality determination method of the mesa-type SiGe HBT disclosed in the present invention.

[0080] In summary, the present disclosure provides a method for preparing a mesa-type SiGe HBT and a method for determining its quality. When determining the quality of the SiGe HBT prepared by the above preparation method, the required parameters need to be extracted. The extraction process disclosed in the present disclosure can accurately obtain the size of physical quantities such as the ideal factor and leakage current at the two heterojunctions of the emitter junction and the collector junction, and can also accurately obtain the proportion of the composite current of the SiGe base region to the total current, and judge the quality of the prepared transistor accordingly. In the preparation method, we use a special selective etching solution, which can clearly obtain the base mesa, which is better than the mesa device preparation method in the literature. Not only qualitative analysis can be done, but also quantitative analysis can be done.

[0081] It should also be noted that the above are different embodiments provided by the present disclosure. These embodiments are used to illustrate the technical content of the present disclosure, rather than to limit the scope of protection of the present disclosure. A feature of an embodiment can be applied to other embodiments through appropriate modification, replacement, combination, and separation.

[0082] It should be noted that, in this document, unless otherwise specified, “a” element is not limited to a single element, but may include one or more elements.

[0083] In addition, in this document, unless otherwise specified, ordinal numbers such as "first" and "second" are only used to distinguish multiple components with the same name, and do not indicate that there is a hierarchy, level, execution order, or process order between them. A "first" component and a "second" component may appear together in the same component, or appear in different components. The presence of a component with a larger ordinal number does not necessarily indicate the presence of another component with a smaller ordinal number.

[0084] In this document, unless otherwise specified, the so-called feature A "or" or "and / or" (and / or) feature B means that A exists alone, B exists alone, or A and B exist at the same time; the so-called feature A "and" (and) or "and" (and) or "and" (and) feature B means that A and B exist at the same time; the so-called "includes", "comprising", "has" and "containing" mean including but not limited to these.

[0085] In addition, in this document, the terms "upper", "lower", "left", "right", "front", "back", or "between" are only used to describe the relative positions between multiple elements, and can be extended to include translation, rotation, or mirroring. In addition, in this document, unless otherwise specified, "an element is on another element" or similar descriptions do not necessarily mean that the element contacts the other element.

[0086] In addition, unless the steps are specifically described or must occur in sequence, the order of the above steps is not limited to the above list, and can be changed or rearranged according to the required design. And the above embodiments can be mixed and matched with each other or with other embodiments based on design and reliability considerations, that is, the technical features in different embodiments can be freely combined to form more embodiments.

[0087] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A method for preparing a mesa-type SiGe HBT, comprising: Molecular beam epitaxy is used to grow Si collector region, SiGe base region and Si emitter region at one time; A selective etching solution is used to etch out the base area table; Depositing silicon dioxide on the device surface by atmospheric pressure chemical vapor deposition; and After opening holes in the silicon dioxide on the surface of the Si collector region, SiGe base region and Si emitter region, metal reverse etching is performed to complete the preparation of the collector, base and emitter to obtain a mesa-type SiGe HBT.

2. The method for preparing a mesa-type SiGe HBT according to claim 1, wherein the selective etching solution only etches Si but not SiGe.

3. The method for preparing a mesa-type SiGe HBT according to claim 2, wherein the selective etching solution is isopropanol and H2O in a volume ratio of 1:4 as solvent, and 20g KOH and 0.8g K2Cr2O3 are added to every 100ml of solvent.

4. A quality determination method for a mesa-type SiGe HBT, used for determining the quality of a mesa-type SiGe HBT prepared by the preparation method according to any one of claims 1 to 3, the quality determination method comprising: Test the Gummel curve of SiGe HBT device; Obtaining a collector current and / or a base current according to the Gummel curve; The ideality factors of the collector current and the base current are obtained according to the current differential and the voltage differential of the collector current and / or the base current; Converting the Gummel curve into a relationship diagram between the ideal factor and the collector current or the base current; Obtaining the series resistance of the collector or base according to the relationship curve; Extracting the collector reverse saturation current according to the Gummel curve; and Obtain the ideal diffusion current, recombination current, and recombination current ideality factor of the base region.

5. The quality determination method of mesa-type SiGe HBT according to claim 4, wherein the Gummel curve is transformed into a relationship diagram between the ideal factor and the collector current or the base current according to a formula transformation; the relationship diagram is a straight line with a certain slope, and the series resistance of the collector or the base is determined by the slope. 6 . The quality determination method of mesa-type SiGe HBT according to claim 4 , wherein when extracting the collector reverse saturation current, the collector reverse saturation current is obtained by taking the intercept of the Gummel curve on the vertical axis.

7. The quality determination method of mesa-type SiGe HBT according to claim 4, wherein the base current I B It is expressed as: I B =I B1 +I B2 =I B01 exp(V BE / V T )+I B02 exp(V BE / mV T ); Among them I B1 and I B2 are the ideal diffusion current and recombination current of the base region, m is the ideal factor of recombination current, V BE is the emitter junction voltage, I B01 is the reverse saturation current in the diffusion current, I B02 is the reverse saturation current in the composite current, V T is the thermal voltage.

8. The quality determination method of mesa-type SiGe HBT according to claim 7, wherein: V′ BE =V BE -I B R S ; but: I B ≈I B01 exp(V′ BE / V T ); in, V′ BE is the voltage after translation, R S is the series resistance; The V in the Gummel curve BE Change to V' BE , the intercept of the straight line on the vertical axis is I B01 , I B01 Extract descendants into I B expression: I B2 =I B -I B1 ; Thus I B2 With the emitter junction voltage V BE The changing curve, from which I B02 and the value of m.

Images