TWI300268B - Suppression of n-type autodoping in low-temperature Si and SiGe epitaxy - Google Patents

Description

1300268 A7 _____B7 V. DESCRIPTION OF THE INVENTION (1) The present invention relates to a method of manufacturing a semiconductor device as defined in the foregoing paragraph 1 of the patent application. The method is related to a method of growing a doped system Si or Sii-xGex (SiGe) layer by chemical vapor deposition (c VD ) on a single crystal germanium layer, and it is known to control the dopant concentration and doping in the epitaxial layer. The quality profile is a challenge. It is well known in the art that when epitaxially doped s- or siGe is combined at low temperatures, the mixing of the dopants is continued after the supply of the dopant is turned off. This process is a well-known autodoping effect. In this epitaxial growth process, due to this effect, a dopant profile different from the desired profile is obtained. Since the dopant generally diffuses from the lower layer (high temperature) to the growing epitaxial layer, the absorption of the dopant species from the walls of the epitaxial reaction cell and the substrate holder, and the evaporation of the dopant species from the front and back ends of the substrate, This automatic doping effect occurs. Therefore, the automatic doping effect will clearly change the dopant concentration in the epitaxial layer in an unexpected state. Traditionally, wafers are exposed to high temperatures (~1〇〇〇〇c or more) in a hydrogen-containing environment to remove the native oxide layer from the surface before starting the shading growth process, especially at low pressures. The high temperature treatment of the crucible can also reduce the adsorption of the dopant species on the surface of the reaction chamber and the surface of the wafer, which is usually a method of reducing the automatic doping; however, due to the high temperature, the feature size and blending of the device The mass diffusion length is still small compared, so the high temperature is still detrimental to the manufacture of electronic devices. A method for growing an epitaxial layer on a single crystal Si with a minimum doping effect is known from US Pat. No. 3,669,769. This method provides a very low initial growth rate of the epitaxial layer, after obtaining a certain minimum thickness. Increase growth -4-

1300268

Rate, the temperature in this process is between 8 〇〇 and i30 (TC. US 6,007, 624 discloses a method of controlling the auto-doping of the grown epitaxial Si layer' in a low temperature super-South vacuum chemical vapor deposition process (at 5〇) 〇-85〇^), grows a thin epitaxial layer of cap. After forming this cap layer, it increases the temperature and grows the epitaxial layer. Worse, due to the low process temperature when growing the cap layer, the cap layer is not It will be completely epitaxial, and the method of us 6 〇〇 7,624 is only related to the automatic doping of the buried layer. JP-8-20383 1 A discloses a chemical vapor deposition epitaxial process, including growth A method of one or more single crystal layers having different electrical (secondary) layers, the method of JP-8-20383 1 A and the epitaxial growth at high temperature (1〇8〇-112〇.〇) Furthermore, the method is related to a relatively thick Si epitaxial layer (at least 8 microns). Inferiorly, the conventional methods are all related to an epitaxial layer having a thickness of at least 丨 micron; in addition, each of the conventional methods The same point is that the semiconductor material is exposed to high temperature steps, due to This relatively high temperature diffusion at high temperatures degrades the contour of the support in the semiconductor material. Furthermore, if a conventional method is used, it is impossible to form a shallow layer with a well-defined and steep n-type dopant profile (ie, lower than丨micron) ^ The object of the present invention is to provide a method for fabricating a semiconductor device as defined in the preamble of the scope of the patent application, in which the occurrence of n-type autodoping in the epitaxial layer can be strongly suppressed. The method of fabricating a semiconductor device as defined in the preamble of the first item achieves this object, wherein the stack is grown in a continuous growth cycle. -5- 1300268 A7 - a B7 V, invention) ' '~- / = Preferably, the purge cycle is omitted in a single continuous growth cycle, and the effect of n-type autodoping is suppressed, and the growth method according to the present invention results in a well defined definition and shape of the dopant profile in the epitaxial layer; In addition, the method can grow thin doped epitaxial layers (spikes). The invention will be explained with reference to a number of drawings, wherein the drawings are for illustrative purposes only and are not intended to limit the scope of the invention as defined in the appended claims. Figure 1 shows the growth method using conventional SiH4 gas flow, resulting in

Sl-coated P-doped epitaxial Si layer (P-peak) with a secondary ion mass spectrometer (SIMS) curve. Fig. 2 shows a secondary ion mass spectrometer curve for generating a p-spike having a Si coating layer by a conventional growth method using a SiH2Cl2 gas stream. Figure 3 shows a secondary ion mass spectrometer curve that produces a p-spike with a Si cap layer using conventional growth methods that interrupt the SiH4 gas stream. Fig. 4 shows a secondary ion mass spectrometer curve of the 'doped matter distribution' in the epitaxial Si-SiGe-Si multilayer in accordance with the growth method of the present invention. Figure 5 is a schematic illustration of the switching of individual gas flows during a growing process in accordance with the present invention. The following can be used to explain the growth method according to the present invention, in which the growth of the n-type dopant epitaxial 3丨 or SiGe layer is demonstrated, and the dopant profile obtained by these experiments is measured by a secondary ion mass spectrometer. The results of the analysis clearly show that the growth of this doped Si or SiGe layer can be improved by the method of the present invention. Figure 1 shows a secondary ion mass spectrometer curve of a p-doped epitaxial Si layer (P-spike) with a Si cap layer, which is conventionally used as a carrier gas-6 - 本 2 as a carrier gas-6 - this paper scale applies to China Standard (CNS) Α4 size (210 X 297 public attack) 1300268 A7 B7

V. Inventions (4) Body growth methods. The secondary ion mass spectrometer curve shows that the profile of phosphorus (P) in the sample is a function of the iridium plating depth. The Si surface is exposed to the PH3 vapor without the Si precursor SiH4 to grow the P spike, and the P3 source is turned off or the ray is continued. Crystal growth. The autodoping effect is clearly observed and the P-peak is at a depth of ~100 nm. In the P signal, a long auto-doped tail is displayed between ~100 nm and ~25 nm: on the surface side of the p-peak, the p-concentration does not fall to the detection limit of the secondary ion mass spectrometer; However, when it is about ten times that of the autodoped tail, a P spike can be used. Figure 2 shows a secondary ion mass spectrometer curve using a conventional growth method using a siH2Cl2 gas stream to produce a p-spike with a Si blanket. The secondary ion mass spectrometer curve shows the profile of phosphorus (P) in the sample as a function of sputtering depth. . In order to show this P-peak, a process similar to the above was carried out by replacing SiH4 with SiCh4 as a precursor of Si, and Figure 2 shows an example of a P-peak of a conventionally grown cap layer grown from SiH2Cl2. . Compared with the dopant profile of Figure 1 using SiH4 as the precursor of S i , there is no spike in this example, only the doping is automatically doped, and the difference between the two profiles is mainly caused by the presence of C1 in SiH2Cl2. . When attempting to use a dopant profile similar to that shown in Figure 1, for example, in the collector of a heterojunction bipolar transistor (HBT), the P spike is at each interface (Si/SiGe, SiGe/SiGe[B], The SiGe/Si) pops up, thus destroying the target profile β. The airflow is used to interrupt the growth to stabilize the layer composition, and ρ is still transmitted to the wafer surface and accumulated. This paper scale applies to the Chinese National Standard (CNS) A4 specification (210X 297 mm)

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Line 1300268 A7 B7 V. INSTRUCTION DESCRIPTION (5) - Figure 3 shows a secondary ion mass spectrometer curve that produces a p-tip with a Si-clad layer using conventional growth methods that use interrupted gas flow. This secondary ion mass spectrometer curve shows the profile of phosphorus (p) in the sample as a function of sputtering depth. From this figure, an epitaxial layer grown in the same manner as in Fig. i can be obtained except that the intermediate interrupt cover layer is grown for one minute and then continues to grow. As is well known to those skilled in the art, the growth of complex epitaxial multilayers, such as Η BT... requires several growth interruptions, when 8 turns to and from turn, or self-doping to doping There will be this interruption. The accumulation of n-type doping is particularly detrimental to the transition at Si/SiGe and not at low temperature and low pressure using in-situ n-type dopants. Although there is a long auto-doped tail, the ρ-profile, as shown in Figure 1, can be used as part of the collector of the 掺杂 Τ structure, which can be achieved by avoiding the growth process of the second Ρ spike. . The method of growing a semiconductor epitaxial layer according to the present invention shows the importance of the growth process discontinuity. It has been found that if the growth is not interrupted, the dopant element ρ does not accumulate at the layer transition and the second peak can be suppressed. In practice, this means skipping the flow-stable phase of the growth process, which causes a transient of the gas > watt when changing the composition of the layer, which results in an increased transient width that is generally not harmful to the performance of the transistor. Needed/Intended By using the method of the present invention, the combination of ASH3 and SiH4 can form a long As peak and cause an A s profile similar to the ρ spike shown in Figures 1, 2 and 3. In low temperature and low pressure epitaxial growth of n-type doped Si and SiGe layers in each interface -8 · This paper scale applies Chinese National Standard (CNS) A4 specifications (210 X 297 public y ----, one --- ---- — 1300268 A7 ----- - B7 V. Inventive Note (6) ' " -- The problem of n-type doping spikes can be avoided by changing the layer composition without interrupting the growth process. The deterioration of the interlayer transition width is generally not harmful. Among all other growth methods, it has been found to be advantageous for growing the collector having an instant n-type doping step. Figure 4 shows the growth using the invention according to the present invention. The method produces a secondary ion mass spectrometer curve of a dopant distribution in a multilayer of conventional epitaxial Si[P]/SiGe/SiGe[p]/SiGe/Si[B]. The secondary ion mass spectrometer curve shows phosphorus in the sample ( The outlines of P), germanium (Ge) and boron (B) are functions of the sputter depth and their outlines are indicated by their respective chemical codes. The multilayer consists of the following, which grows on the surface of the semiconductor as the first layer of scale The Si[P] layer grows an intrinsic meso-SiGe layer on the Si[P] layer. Here, the intrinsic shy crystal S i G e On the deposition of boron-doped SiGe [BJ layer; then, the growth of the second intrinsic SiGe SiGe layer; finally, the deposition of insect crystals replaced Si[B] surface layer. In the low temperature and low pressure process (that is, 700 ° C, 2.66 X 103 Pa) uses a gas flow and flow switching scheme to grow multiple layers, and can be explained with reference to Figure 5. In Figure 4, it is important to note that the distribution of phosphorus between about 50 and 100 nm is important. The known method of growing the contour has no major P spikes and interferes with the function of the device. After the PH3 stream has been turned off, the P hierarchy will fall, and the arrow A1 will not be used to close the PH3 stream. Some segregation will still occur: by the arrow The release of B2H6 marked by A 2 will increase the P signal in the growing environment (at a thickness of ~68 nm); however, the paper size applies to the Chinese National Standard (CNS) A4 specification (210 X 297 dong) A7 B7

1300268 V. Inventive Note (7) However, maintaining a sufficiently low P-level does not have a bad response to the ΗB T structure. It has also been found that the new growth method is slightly detrimental to the porch <in the SiGe/SiGe[B]/SiGe layer), the slope of the head and tail of the SiGe/SiGe[B]/SiGe layer is not used as it grows. The method of interrupting the airflow is as steep as the mountain. It is important to note that the reduction in slope steepness is not only related to the underlying problem, but also to certain defects in the hardware of the i-crystal reactor. Fig. 5 schematically shows the growth process for the switching reactant (process gas), the x-axis is indicated as the size of the gas stream, and the X-axis is indicated as time, and both axes are used in arbitrary units. It should be noted that the exact ratio of process time to layer thickness is not given, and the relative height of each flow is not indicative of the ratio of individual flows. Each gas flow is indicated by a slashed area and is marked by the chemical formula of each gas. At the beginning of the growth process, the gas flow of the S i precursor (ie SiH4) is turned on while the PH3 gas flow is turned on. After a certain period of time, the PH3 gas flow is slightly reduced, and after the growth of the Si[P] layer is completed, the ph3 gas flow is stopped. At the same time, the GeH4 gas stream is turned on to start growing the SiGe layer. After the first intrinsic SiGe layer is grown, the B2H6 gas stream is turned on to dope boron into the SiGe layer and form a doped SiGe[B] layer. After completion of the doped SiGe[B] layer, the B2H6 gas stream is stopped and the Si precursor gas stream and the GeH4 gas stream are still turned on to grow the second intrinsic SiGe layer. Finally, the GeH4 gas stream is stopped and the B2H6 gas stream is turned on to grow the boron-doped Si[B] layer. After completing the epitaxial Si[P]/SiGe/SiGe[B]/SiGe/Si[B] multilayer, stop -10- The paper scale applies to the Chinese National Standard (CNS) A4 specification (210 X 297 mm)

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Line 1300268 A7 B7 V. INSTRUCTIONS (8) Stop the S i precursor gas stream and the B2H6 gas stream, as is well known in the art, to end the process cycle with a final cycle to purge the process chamber and cool the deposited multilayer semiconductor Wafer. It should be noted that in the Si[P]/SiGe/SiGe[B]/SiGe/Si[B] multilayer, no cleaning cycle is applied between the grown layers. According to the conventional method, the washing cycle is omitted instead of using the medium-breaking growth cycle, and the entire epitaxial layer is grown in a continuous growth cycle, and the dopant depicted by the secondary ion mass spectrometer curve of FIG. 4 is improved. profile. Furthermore, it should be noted that the method of the present invention can also be used to fabricate a doped ytterbium-tellurium-carbon alloy (SiGe:C) layer to inhibit the automatic doping of the n-type in this SiGe:C layer. -11 - This paper size is applicable to China National Standard (CNS) Α4 specification (210 X 297 mm)

Claims (1)

6. Patent application scope i. A method for manufacturing a semiconductor device. The method includes at least another layer of a semiconductor material (the step of 'flying crystal growth—a step of laminating a η impurity layer containing a semiconductor material> In a continuous growth and growth in the soil, it should be eager to cut. The alloy is sintered and carbonized as the semiconductor material of the n-type doping layer, in which the application of Shi Xiqi·褚^ or shredded-锗U gold is used as the at least Further, a semiconductor material layer, and a semiconductor material of the at least n-type impurity layer and the at least another layer are used as the semiconductor material of the at least-n-type impurity layer. 曰2. Method \ wherein a p-type impurity layer or an unintentionally doped layer is used as the at least one other layer. 3. If the application is for (4), or the method of the second item, or the growth process is performed under sub-atmospheric pressure 4. The method of claim 3, wherein the growth process is performed at a sub-atmospheric pressure between about 6 6 5 and 13300 Pa. 5. A method of applying for a patent range liu, wherein an n-type is used. a susceptor gas grows the n-type doped layer, and Use a phosphorus-containing compound or an arsenic-containing compound as the n-type dopant gas. " 6. If applying for the method of (4), the application of the cut compound and its application of phosphine (ΡΗΟ) A phosphorus compound. 7. The method of claim 5, wherein the dicing compound and the arsine (AsH3) thereof are used as the quinone compound. 8. The method wherein the growth process is carried out at a temperature of about 8 ° C or less. 9. The method of claim 8 wherein the growth process is about 7 〇〇 1300 268 - C8 D8 6. Patent application range °c The temperature is carried out. The semiconductor device package 10. The method of claim 1 or 2 comprising a heterojunction bipolar transistor. _-2- This paper scale applies to Chinese National Standard (CNS) A4 specification (210 X 297 mm)