TWI575578B - Semiconductor process - Google Patents

Description

Semiconductor process

This invention relates to a semiconductor process, and more particularly to a semiconductor process for modifying the surface of a recess.

As semiconductor processes enter the deep submicron era, such as processes below 65 nanometers (nm), the drive current of MOS transistor components has become increasingly important. In order to improve the performance of components, the so-called "strained-silicon technology" has been developed in the industry. The principle is mainly to strain the germanium lattice of the gate channel portion, so that the charge passes through the strain gate channel. The movement force at the time increases, thereby achieving the purpose of making the MOS transistor operate faster. Among the currently known techniques, MOS transistors using strained silicon as a substrate have been used which utilize the lattice constant of bismuth (SiGe) or bismuth carbon (SiC) and single crystal Si (single crystal Si). Different characteristics cause the structure of the germanium epitaxial structure to strain and form strain enthalpy. Since the lattice constant of the germanium epitaxial structure or the germanium carbon epitaxial structure is larger than or larger than the germanium, this causes the band structure of the germanium to change, resulting in an increase in carrier mobility. The speed of the MOS transistor can be increased.

Furthermore, in addition to the type of epitaxial structure that affects the stress applied to the gate channel of the MOS transistor, the shape of the epitaxial structure also affects the stress performance applied to the gate channel of the MOS transistor, particularly epitaxial The shape of the structure controls the local stress applied to the gate channel, and the electric energy of the MOS transistor can be more accurately achieved or improved. Sexual performance. However, the shape of the epitaxial structure changes during the manufacturing process due to process conditions such as process temperature, resulting in the shape of the finally formed epitaxial structure being different from the originally set and etched shape, making it difficult to accurately control the shape. The quality of the formed transistor.

The present invention provides a semiconductor process for performing a surface modification process on the surface of a recess to control the shape of the recess formed and the material content of the surface.

The present invention provides a semiconductor process comprising the steps described below. First, a second gate is formed on a substrate. Next, a recess is formed in the substrate on the side of the gate. Then, a surface modification process is performed on a surface of the recess to reshape the groove and modify the surface.

Based on the above, the present invention proposes a semiconductor process in which the shape of the groove is trimmed and the surface of the groove is modified by performing a surface modification process. For example, the shape of the originally etched groove can be restored through the surface modification process, which may be changed in various processes after etching due to various process environments; further, the groove surface may be modified to have a follow-up The amount of epitaxial structure formed thereon to promote bonding between the two and reduce interface defects.

110‧‧‧Base

120‧‧‧ gate

122‧‧‧ dielectric layer

124‧‧‧electrode layer

126‧‧‧ cover

130‧‧‧ spacer

140‧‧‧ seed layer

150‧‧‧ epitaxial structure

C‧‧‧gate channel

D1‧‧‧ thickness

E1‧‧‧ Hydrogen baking process

E2‧‧‧dry etching process

E3‧‧‧Surface modification process

P1, P2, P3, P4, P5, P6, P7‧‧‧ steps

R, R1‧‧‧ groove

S, S1‧‧‧ surface

T‧‧‧ sharp corner

1 is a flow chart showing a semiconductor process according to an embodiment of the present invention.

2-7 are cross-sectional views showing a semiconductor process in accordance with an embodiment of the present invention.

1 is a flow chart showing a semiconductor process according to an embodiment of the present invention. 2-7 are cross-sectional views showing a semiconductor process in accordance with an embodiment of the present invention. Please also refer to Figure 1 and Figure 2-7.

First, according to step P1 of Fig. 1, a second gate is formed on a substrate. As shown in FIG. 2, a substrate 110 is provided, wherein the substrate 110 is, for example, a germanium substrate, a germanium-containing substrate, a tri-five-layered germanium substrate (eg, GaN-on-silicon), and a graphene-coated substrate (graphene). -on-silicon) or a semiconductor substrate such as a silicon-on-insulator (SOI) substrate. Next, two gates 120 are formed on the substrate 110. Each gate 120 can include a dielectric layer 122, an electrode layer 124, and a cap layer 126 stacked from bottom to top. In detail, a dielectric layer (not shown), an electrode layer (not shown), and a cap layer (not shown) on the substrate 110 may be completely and sequentially covered, and then the cap layer is patterned (not An electrode layer (not shown) and a dielectric layer (not shown) are formed to form a dielectric layer 122, an electrode layer 124, and a cap layer 126 stacked on the substrate 110. The second gate 120 is shown in FIGS. 2-7 in order to clearly disclose the present invention, but the number of the gates 120 is not limited thereto; in other embodiments, the number of the gates 120 may be one or more. Two, depending on actual needs.

The invention can be applied to a polysilicon gate process, a gate-first process, a gate-high-potential constant gate (Gate-Last for High-K-First) process, and a pre-buffer layer. Post-high dielectric constant post gate (Gate-Last for High-K-Last, Buffer Layer-First) process or a post-buffer layer after high dielectric constant post gate (Gate-Last for High-K- Last, Buffer Layer-Last) process. Therefore, the dielectric layer 122 may include an oxide layer, a buffer layer, or/and a high-k dielectric layer, but the invention is not limited thereto. For example, when the hair When applied to a polysilicon gate process, the dielectric layer 122 is a dielectric material suitable for a polysilicon gate, such as an oxide layer; when the invention is applied to a front gate process or a pre-high dielectric constant During the gate process, the dielectric layer 122 may include a buffer layer and a high-k dielectric layer; when the present invention is applied to a pre-buffer layer after a high dielectric constant and then a gate process, the dielectric layer 122 may include a buffer layer and a sacrificial dielectric layer, wherein the sacrificial dielectric layer is replaced with a high-k dielectric layer in a subsequent metal gate replacement (Metal Gate Replacement) process; The dielectric layer 122 can be a sacrificial dielectric layer after a high dielectric constant is followed by a gate dielectric process, wherein the sacrificial dielectric layer is in the subsequent metal gate replacement (Metal Gate Replacement) process. The replacement is a buffer layer and a high-k dielectric layer. The buffer layer may be, for example, an oxide layer, which is formed, for example, by a thermal oxidation process or a chemical oxidation process, but the invention is not limited thereto. The high-k dielectric layer is, for example, a metal-containing dielectric layer, which may contain a hafnium oxide or a zirconium oxide, but the invention is not limited thereto. Furthermore, the high dielectric constant gate dielectric layer may be selected from the group consisting of hafnium oxide (HfO2), hafnium silicon oxide (HfSiO4), and hafnium silicon oxynitride. , HfSiON), aluminum oxide (Al2O3), lanthanum oxide (La2O3), tantalum oxide (Ta2O5), yttrium oxide (Y2O3), zirconium oxide (ZrO2), titanium Strontium titanate oxide (SrTiO3), zirconium silicon oxide (ZrSiO4), hafnium zirconium oxide (HfZrO4), strontium bismuth tantalate (SrBi2Ta2O9, SBT), zirconium A group consisting of lead zirconate titanate (PbZrxTi1-xO3, PZT) and barium strontium titanate (BaxSr1-xTiO3, BST). The electrode layer 124 can be, for example, a polysilicon layer. The cap layer 126 is, for example, a single layer or a two-layer structure including a nitride layer, an oxide layer, or the like.

Next, a spacer 130 is formed on the substrate 110 on the side of the gate 120 to define the position of the subsequently formed epitaxial structure. The spacer 130 may be a single layer structure composed of tantalum nitride, hafnium oxynitride or the like, or a two-layer structure composed of hafnium oxide/tantalum nitride or the like, but the invention is not limited thereto. In detail, the method of forming the spacers 130 may be, for example, depositing a spacer material on each of the gates 120 and the substrate 110, and performing an etching process to form the spacers 130. The spacer 130 referred to in this embodiment is a spacer for defining and forming an epitaxial structure. Therefore, before or after the spacer 130 is formed, other thin spacers may be additionally formed to form a lightly doped source. / drain region (not shown) or otherwise form other thicker spacers to form a source/drain region (not shown) or the like. In order to simplify and clearly disclose the present invention, FIGS. 2-7 only show the spacers 130 for forming an epitaxial structure.

Next, according to step P2 of Fig. 1, a groove is formed in the substrate on the side of the gate. As shown in FIG. 3, an etching process is performed to etch the exposed substrate 110, and a recess R is formed in the substrate 110. Still further, the etching may include at least one dry etching step or/and at least one wet etching step, such as etching the substrate 110 to a predetermined depth by a dry etching step, and then laterally etching in a wet etching step to form a desired recess. The outline of the groove R, but the invention is not limited thereto. Therefore, the thickness d1 of the bottom of the spacer 130 contacting the substrate 110 affects the distance of the recess R relative to the gate 120, which is an important factor affecting the stress applied to a gate channel C. In the present embodiment, the groove R has a diamond-shaped cross-sectional structure, but the invention is not limited thereto, and the groove R may have different cross-sectional structures as needed. The sharp corner T of the groove R can increase the local stress applied to the gate channel C by the epitaxial structure formed therein, and the local stress can improve the performance of the epitaxial structure and can more accurately control the applied to the gate channel C. The stress to each part, and thus the function of improving the electrical properties of the component. Therefore, by adjusting the concave The distance of the groove R with respect to the gate 120, and the shape of the groove R (the number of sharp angles T and the position of the sharp angle T which can be formed), and the epitaxial structure formed in the groove R is applied to the gate The stress of the pole channel C and the distribution of the local stress.

Thereafter, a wet cleaning process (not shown) may be selectively performed to clean the surface S of the etched groove R. The wet cleaning process can be, for example, a process including dilute hydrofluoric acid (DHF), but the invention is not limited thereto.

Continued, according to step P3 of Figure 1, a hydrogen baking process is performed in the groove. A hydrogen baking process E1 is selectively performed in the recess R to form a recess R1 as shown in FIG. The purpose of performing the hydrogen baking process E1 is to further clean the surface S1 of the groove R1, volatilize the material which is not required on the surface S1 of the groove R1 or which may deteriorate the subsequent process, for example, forming the groove R in the step of FIG. Residues left by process gases during the etching process. In one embodiment, the hydrogen baking process E1 has a process temperature of 725 ° C, and the crucible can effectively remove unnecessary substances. However, the hydrogen baking process E1 has a process temperature of, for example, 725 ° C, which causes a substance (for example, ruthenium) of the surface S of the groove R to migrate, and changes the shape of the original groove R, particularly the arcuate groove R. Each of the sharp corners T forms a groove R1 having a gentle cross-sectional profile. This profile degrades the local superimposed stress applied to the gate channel C due to the lack of the sharp corner T.

According to step P4 of Figure 1, a dry etching process is performed in the recess. Optionally, a dry etching process E2 is performed in the recess R1 as shown in FIG. The selective dry etching process E2 further cleans the residue of the surface S1 of the groove R1 and repairs the performance defect. In a preferred embodiment, the dry etching process E2 can be, for example, a hydrogen chloride gas or a chlorine gas as an etching gas, and a hydrogen gas is used as a carrier gas, but the invention is not limited thereto. In other embodiments, the dry etching process E2 can be, for example, hydrogen fluoride (HF), fluorine (F2), hydrogen bromide (HBr), bromine (Br ₂ ), or the like. A gas such as a tantalum material is etched as an etching gas. In a preferred embodiment, the dry etching process E2 has a process temperature of 600 ° C to 750 ° C; in a more preferred embodiment, the dry etching process E 2 has a process temperature of less than 720 ° C and can be effectively cleaned at a high temperature. The residue of the surface S1 of the groove R1, and repairing the performance defect, but can minimize the problem of the arc of the surface S1 of the groove R1. Even by adjusting the process temperature (for example, 671 ° C) and the introduced gas (for example, hydrogen chloride gas as an etching gas and hydrogen as a carrier gas), the dry etching process E2 can be supplemented by a etch back mechanism. The function of slightly restoring the shape of the groove R. In addition, in this embodiment, the hydrogen baking process E1 is performed first and then the dry etching process E2 is performed. However, in other embodiments, the hydrogen baking process E1 and the dry etching process E2 can be simultaneously performed, that is, the hydrogen baking process E1 is performed. At the time, the etching gas of the dry etching process E2 is passed.

Further, according to the step P5 of FIG. 1, a seed layer is formed on the surface of the groove. As shown in Fig. 5, a seed layer 140 is formed on the surface S1 of the recess R1. The seed layer 140 can be, for example, a tantalum layer formed on the substrate 110 of the enamel, but the invention is not limited thereto. In an embodiment, the tantalum layer may be formed, for example, by a deposition process of dichlorosilane (DCS) gas, but the invention is not limited thereto. Forming the seed layer 140 on the surface S1 of the recess R1 can reduce defects on microstructures such as staggered epitaxial structures formed in the recesses. However, the process of forming the seed layer 140 will typically have a process temperature of, for example, 735 ° C, which is sufficient to more round the shape of the recess R1.

After the seed layer is formed on the surface of the groove, according to step P6 of FIG. 1 , a surface modification process is performed on a surface of the groove to reshape the shape of the groove and to surface Upgraded. As shown in FIG. 6, a surface modification process E3 is performed on the surface S1 of the groove R1 to reform the groove R1 into the shape of the groove R shown in the original figure 3, which has a diamond shape. The cross-sectional structure has a plurality of complete sharp corners T to superimpose local stress on the gate channel C. In this embodiment, the surface modification process E3 is performed to restore the shape of the groove R1 to the shape of the groove R after the original etching; in other words, the shape of the groove R after etching is not caused by subsequent processes. The effect is deformed, but the invention is not limited thereto. In other embodiments, the surface modification process E3 can be used to change the shape of the recess R1 to another desired groove shape so that the formed transistor or the like can achieve the desired electrical requirements.

Specifically, the surface modification process of the embodiment is a synchronous etching and deposition process; that is, the process performs a deposition process while etching the surface S1 of the groove R1. The main purpose of the etching is to restore the shape of the groove R (or change the groove R1 to other desired shape), and the main purpose of the deposition is to form the desired component on the surface S of the groove R, thereby Surface S is modified. Of course, these two effects also have an auxiliary function to each other. In a preferred embodiment, the etching rate of the surface S1 is greater than the deposition rate of the synchronous etching and deposition process. Thus, in the surface modification process E3, no additional material layers are formed by the deposition, but the etching is performed. The portion that is arcuate (especially at the sharp corners) with a moderate repair effect to transform the shape of the groove R1 back to the shape of the original groove R. Therefore, the surface modification process E3 preferably does not create an additional material thickness on the recess R.

In detail, the general synchronous etching and deposition process can pass at least one deposition gas and at least one etching gas, and the ratio of the deposition gas and the etching gas is adjusted during the process to control the groove R1. The shape of the transformation, as well as the concentration of the modified components. In a preferred embodiment, the etching gas may, for example, comprise hydrogen chloride gas, and the deposition gas may, for example, comprise helium gas (or more methylene chloride gas) for use in conjunction with subsequent formation of a germanium epitaxial structure in the recess R. in. For example, the ratio of helium gas: methylene chloride gas: hydrogen chloride gas may be between 1:1:1 or 0:1:1. In this way, on the one hand, the excess portion of the arc of the surface S1 can be etched with hydrogen chloride gas, and on the other hand, the strontium-containing component is deposited on the surface S1 in a trace amount, so that the content of the surface S1 can be changed, thereby making the surface S contain锗, but can be used as a buffer for the subsequent formation of 矽锗 epitaxial structure. In other embodiments, the etching gas may be etched by, for example, hydrogen fluoride (HF), fluorine (F2), hydrogen bromide (HBr), bromine (Br ₂ ), or the like. Gas such as material. In addition, the surface modification process E3 may further comprise hydrogen as a carrier gas, and control the total process gas pressure, adjust the process rate and the uniformity of etching and deposition. In a preferred embodiment, the process temperature of the surface modification process E3 is 600 ° C ~ 750 ° C, and the process can maintain the process rate to effectively modify without affecting the shape of the groove R to be formed, but The invention is not limited to this.

Furthermore, as described above, when the process for forming the seed layer 140 is a deposition process for introducing methylene chloride gas, the hydrogen chloride gas and the helium gas may continue to be introduced into the same process chamber, thereby being in situ (in -situ) Perform a surface modification process E3. In other words, the process of forming the seed layer 140 and the surface modification process E3 are preferably performed to improve the process efficiency in the same process cavity, and more preferably included in the formation of the seed layer 140 and the surface modification process E3. This can only be achieved by introducing different gases.

Then, according to step P7 of FIG. 1, an epitaxial structure is formed in the recess. As shown in FIG. 7, an epitaxial structure 150 may be formed in the recess R. In the present embodiment, the epitaxial structure 150 is a tantalum epitaxial structure. As described above, it is preferably matched with the surface modification process E3 containing helium, so that the surface S of the groove R contains a germanium component. It is easier to bond the epitaxial structure 150 to the surface layer of the recess R and reduce interface defects, but the present invention does not This is limited to this. In other embodiments, if other epitaxial structures such as a germanium carbon epitaxial structure or a germanium phosphorite epitaxial structure are formed, it is preferred that at least one of the deposition gas and the epitaxial structure be the same, which may contribute to Subsequent formation of epitaxial structures. In addition, the epitaxial structure 150 may have a plurality of cladding structures having different layers from the inside to the outside or/and from the bottom to the top by different concentrations of the components such as the enthalpy. Thereafter, subsequent semiconductor processes, such as metal gate replacement processes, can be performed.

In the above, the present invention proposes a semiconductor process in which the shape of the groove is trimmed and the surface of the groove is modified by performing a surface modification process. For example, the shape of the originally etched groove can be restored through a surface modification process, which may be changed in various processes after etching due to various process environments; further, the groove surface may be modified to have at least The content of part of the epitaxial structure facilitates the bonding of the two and reduces interface defects. However, the purpose of the modification may also be other considerations, and the present invention is not limited thereto, and may be determined according to actual needs.

In a preferred embodiment, the surface modification process is a synchronous etching and deposition process, in which at least one deposition gas and at least one etching gas are introduced, and in the process, the ratio of the deposition gas and the etching gas can be adjusted by The shape of the groove formed and the substance content of the surface of the groove are controlled. For example, the methylene chloride gas can be selectively introduced to form a seed layer covering the surface of the groove; then, in the same process, helium gas is introduced as a deposition gas, and hydrogen chloride is used as an etching gas to perform surface modification. The quality process is followed by the formation of a germanium epitaxial structure in the recess. In this way, since the seed layer is formed and the surface modification process is performed in the same process chamber, the process rate can be improved. Furthermore, since the surface of the groove already contains a bismuth component during the surface modification process, the growth of the epitaxial structure can be promoted, the interface defects can be reduced, and the interface bonding can be improved, thereby improving the reliability of the formed component. .

110‧‧‧Base

120‧‧‧ gate

122‧‧‧ dielectric layer

124‧‧‧electrode layer

126‧‧‧ cover

130‧‧‧ spacer

C‧‧‧gate channel

E3‧‧‧Surface modification process

R‧‧‧ groove

S‧‧‧ surface

T‧‧‧ sharp corner

Claims (19)

A semiconductor process includes: forming a gate on a substrate; forming a recess in the substrate on a side of the gate; performing a surface modification process on a surface of the recess to refurbish the recess Shape and modifying the surface; and forming a seed layer on the surface of the recess prior to performing the surface modification process. The semiconductor process of claim 1, after performing the surface modification process, further comprising: forming an epitaxial structure in the recess. The semiconductor process of claim 2, wherein the epitaxial structure comprises a germanium epitaxial structure. The semiconductor process of claim 1, wherein the surface modification process comprises a synchronous etching and deposition process. The semiconductor process of claim 4, wherein the simultaneous etching and deposition process has an etch rate for the surface greater than a deposition rate. The semiconductor process of claim 4, wherein the synchronous etching and deposition process is coupled to at least one deposition gas and at least one etching gas. The semiconductor process as described in claim 6 of the patent application, after performing the surface modification process, further comprises: An epitaxial structure is formed in the recess, and the deposition gas is the same as one of the constituents of the epitaxial structure. The semiconductor process of claim 6, wherein the synchronous etching and deposition process is performed by introducing helium gas and hydrogen chloride gas. The semiconductor process of claim 8, wherein during the synchronous etching and deposition process, the shape of the groove is controlled by adjusting a ratio of the helium gas and the hydrogen chloride gas. The semiconductor process of claim 4, wherein the synchronous etching and deposition process further comprises introducing methylene chloride gas. The semiconductor process of claim 4, wherein the process temperature of the synchronous etching and deposition process is 600 ° C to 750 ° C. The semiconductor process of claim 1, wherein the seed layer is formed and the surface modification process is performed in the same process chamber. The semiconductor process of claim 12, wherein the seed layer is formed and a different gas is introduced into the surface modification process. The semiconductor process of claim 1, wherein the seed layer comprises a tantalum layer. The semiconductor process as described in claim 1 of the patent application, before performing the surface modification process, further comprises: A hydrogen baking process is performed in the groove. The semiconductor process of claim 15, wherein after performing the hydrogen baking process, further comprising: performing an etching process on the recess. The semiconductor process of claim 16, wherein the etching process comprises introducing hydrogen chloride gas or chlorine gas. The semiconductor process of claim 16, wherein the process temperature of the etching process is lower than 720 °C. The semiconductor process of claim 1, wherein the groove has a diamond-shaped cross-sectional structure.