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CN-121985574-A - Forming method of embedded epitaxial layer for reducing LK film loss

CN121985574ACN 121985574 ACN121985574 ACN 121985574ACN-121985574-A

Abstract

The invention discloses a forming method of an embedded epitaxial layer for reducing LK film loss, comprising the steps of firstly, providing a semiconductor substrate with a grid structure with LK film formed on the side surface. And secondly, performing an atomic layer deposition process to form a hard mask layer formed by the first silicon nitride layer. The atomic layer deposition process does not adopt plasma and hydrogen and adjusts the deposition rate by increasing the film forming temperature so as to eliminate the damage to the surface of the LK film layer when the plasma and the hydrogen are introduced in the atomic layer deposition process. The process gas adopts DCS and ammonia gas and is introduced in a circulation mode, and in each circulation, the DCS adopts pulse type and direct current type. And thirdly, opening the forming area of the embedded epitaxial layer and etching to form a groove. And step four, performing epitaxial growth. And fifthly, removing the hard mask layer. The invention can eliminate the loss generated to the LK film layer in the growth and removal process of the hard mask layer defining the embedded epitaxial layer, thereby increasing the process window of the device.

Inventors

  • YAO JIANYU

Assignees

  • 上海华力集成电路制造有限公司

Dates

Publication Date
20260505
Application Date
20260130

Claims (9)

  1. 1. The forming method of the embedded epitaxial layer for reducing the LK film loss is characterized by comprising the following steps: Providing a semiconductor substrate, wherein a grid structure is formed on the semiconductor substrate, and an LK film layer is formed on the side surface of the grid structure; step two, performing an atomic layer deposition process to form a first silicon nitride layer and forming a hard mask layer by the first silicon nitride layer; The atomic layer deposition process does not adopt plasma and hydrogen and adjusts the deposition rate by increasing the film forming temperature so as to eliminate the damage to the surface of the LK film layer when the plasma and the hydrogen are introduced into the atomic layer deposition process; The atomic layer deposition process gas adopts DCS and ammonia gas and is introduced in a circulating mode; in each cycle of the cycle mode, the DCS adopts pulse type DC charging; step three, opening a forming area of the embedded epitaxial layer and etching the semiconductor substrate to form a groove; step four, performing epitaxial growth to form the embedded epitaxial layer in the groove; and fifthly, removing the hard mask layer, and reducing the loss of the LK film layer generated in the process of removing the hard mask layer by utilizing the characteristic that the surface of the LK film layer is not damaged.
  2. 2. The method of forming an embedded epitaxial layer with reduced LK film loss as claimed in claim 1, wherein said semiconductor substrate comprises a silicon substrate.
  3. 3. The method for forming an embedded epitaxial layer with reduced LK film loss as claimed in claim 1, wherein said gate structure comprises a gate dielectric layer and a polysilicon gate sequentially stacked.
  4. 4. The method of forming an embedded epitaxial layer with reduced LK film loss as claimed in claim 1, wherein the LK film is a LK SiN layer.
  5. 5. The method of claim 1, wherein in the second step, the atomic layer deposition process has a deposition temperature of 575 ℃.
  6. 6. The method of claim 5, wherein in the second step, after the DCS is introduced in each cycle of the cycle mode, the ammonia gas is introduced in a DC manner.
  7. 7. The method of forming an embedded epitaxial layer with reduced LK film loss as claimed in claim 6, wherein in step two, in each cycle of said cycle mode, said ammonia gas on time is increased according to an increase in DC on time of said DCS.
  8. 8. The method of claim 1, wherein the embedded epitaxial layer comprises an embedded SiP epitaxial layer, and the formation region of the embedded SiP epitaxial layer is located on two sides of the gate structure of the NMOS formation region.
  9. 9. The method of claim 1, wherein in step five, the process of removing the hard mask layer comprises dry etching.

Description

Forming method of embedded epitaxial layer for reducing LK film loss Technical Field The present invention relates to a method for manufacturing a semiconductor integrated circuit, and more particularly, to a method for forming an embedded epitaxial layer for reducing the loss of an LK film layer. Background In some semiconductor device processes, it is desirable to form an embedded silicon-phosphorus (SiP) epitaxial layer on both sides of a gate structure, such as on both sides of an NMOS gate structure, such that atomic layer deposition of silicon nitride is required as a hard mask layer defining the SiP formation region, which uses a plasma source during film deposition. Since the side surface of the gate structure is generally formed with a low dielectric constant (LK) film (film), the plasma may damage the surface film of the LK film of the substrate, so that the etching resistance of the LK film may be lowered, and more LK film is lost in the subsequent process of removing the hard mask layer, which may be a smaller process window of the whole product. As shown in fig. 1, the method for forming the embedded epitaxial layer comprises the following steps: In step S101, LK SiN, that is, a gate structure with LK SiN formed on the side surface is provided, and the gate structure is formed on the semiconductor substrate. In step S102, siP HM SiN, i.e. a hard mask layer for defining a SiP formation region, i.e. SiP HM, composed of silicon nitride is formed by an Atomic Layer Deposition (ALD) process, in which a plasma is used. As shown in fig. 2, a graph of process gas introduction in one cycle when forming a hard mask layer in a conventional method for forming an embedded epitaxial layer is shown, wherein in fig. 2, the abscissa indicates time, and the ordinate indicates pressure, i.e., P. It can be seen that between t0 and t1, DCS is pulsed, H2 is pulsed between time t1 and t2, and ammonia (NH 3) is pulsed after time t 2. Step S103, dip ET, namely Etching (ET) the semiconductor substrate of the dip forming region to form a recess. And step S104, performing Epitaxial (EPI) growth to form a SiP epitaxial layer. Step S105, HMRM, remove (RM) the hard mask layer. As shown in fig. 3, the conventional method for forming an embedded epitaxial layer is a photograph of a device after the hard mask layer is removed, and the step S105 is completed, in fig. 3, a dotted line frame 101 is a top region of the gate structure, a bottom region of the gate structure and the semiconductor substrate are not shown, a film layer shown by a mark 102 is the LK film layer, and in fig. 3, the thickness of the LK film layer on a side surface of each gate structure is 4-point multiple nanometers, for example, 4.5nm, so that the thickness of the LK film layer is lossy. Disclosure of Invention The invention aims to provide a forming method of an embedded epitaxial layer for reducing LK film loss, which can eliminate the loss generated to the LK film in the growth and removal process of a hard mask layer for defining the embedded epitaxial layer, thereby increasing the process window of a device. In order to solve the technical problems, the method for forming the embedded epitaxial layer for reducing the LK film loss provided by the invention comprises the following steps: providing a semiconductor substrate, forming a grid structure on the semiconductor substrate, and forming an LK film layer on the side surface of the grid structure. And secondly, performing an atomic layer deposition process to form a first silicon nitride layer and forming a hard mask layer by the first silicon nitride layer. The atomic layer deposition process does not adopt plasma and hydrogen, and the deposition rate is regulated by increasing the film forming temperature, so that the damage to the surface of the LK film layer caused by introducing the plasma and the hydrogen in the atomic layer deposition process is eliminated. The atomic layer deposition process gas adopts DCS and ammonia gas and is introduced in a circulating mode. In each cycle of the cycle mode, the DCS uses pulsed plus dc charging. And step three, opening a forming area of the embedded epitaxial layer and etching the semiconductor substrate to form a groove. And fourthly, performing epitaxial growth to form the embedded epitaxial layer in the groove. And fifthly, removing the hard mask layer, and reducing the loss of the LK film layer generated in the process of removing the hard mask layer by utilizing the characteristic that the surface of the LK film layer is not damaged. A further improvement is that the semiconductor substrate comprises a silicon substrate. The grid structure comprises a grid dielectric layer and a polysilicon gate which are sequentially overlapped. A further improvement is that the LK film layer is a LK SiN layer. In the second step, the film forming temperature of the atomic layer deposition process is above 575 ℃. In the second step, after the DCS is introduced into