Method for etching phase change material layer

Abstract

The present invention relates to the field of semiconductor integrated circuit manufacturing, and provides a method for etching a GST layer. The method of the present invention comprises: a stacked body formation step of forming a stacked body on a semiconductor substrate, the stacked body comprising a GST layer, a TiN layer, an SiN layer, a carbon HM layer, an SHB layer, and a PR layer, which are sequentially formed from bottom to top; a photolithography step of exposing and developing the PR layer to form a patterned PR layer; a first etching step of etching the SHB layer and the carbon HM layer by means of the patterned PR layer to form a patterned carbon HM layer; a second etching step of etching the SiN layer by means of the patterned carbon HM layer to form a patterned SiN layer; and a third etching step of etching the TiN layer and the GST layer by means of the patterned SiN layer to form a patterned TiN layer and a patterned GST layer. Using the method of the present invention can improve CD uniformity and reduce defects, thereby increasing the product yield. In addition, the manufacturing process is simplified, and the manufacturing costs are reduced.

Description

Etching method of phase change material layer Technical Field

[0001] The present invention relates to the field of semiconductor integrated circuit manufacturing, and in particular to an etching method for a phase change material layer. Background Art

[0002] In the manufacture of semiconductor integrated circuits, especially phase-change memory (PCM) devices, the requirements for etching GST (phase-change material) layers are becoming increasingly stringent. As shown in Figure 7, in conventional techniques, etching of a GST layer 91 typically involves sequentially forming a TiN (titanium nitride) layer 92, a SiN (silicon nitride) layer 93, a carbon HM (mask) layer 94, a SiO2 (silicon dioxide) layer 97, an ARC layer (anti-reflective layer) 95, and a PR (photoresist) layer 96 on the GST layer 91, thereby forming a laminate 900. The PR layer 96 is then photolithographically processed to form a patterned PR layer. The ARC layer 95, SiO2 layer 97, carbon HM layer 94, SiN layer 93, TiN layer 92, and GST layer 91 are then etched sequentially through the patterned PR layer to form a patterned GST layer.

[0003] The ARC layer 95 absorbs reflected light during the photolithography process, improving lithography accuracy. The SiO2 layer 97 serves as a mask during the etching of the carbon HM layer 94. Because both the PR layer 96 and the ARC layer 95 are relatively soft and cannot serve as masks during the etching of the carbon HM layer 94, a SiO2 layer 97 must be formed beneath the ARC layer 95. This SiO2 layer 97 is used as a mask to etch the carbon HM layer 94. This SiO2 layer 97 is typically formed using a CVD (chemical vapor deposition) process. However, the U% (thickness uniformity) of this SiO2 layer 97 is poor, which affects the CD (feature dimension) uniformity of the PR layer 96 and the ARC layer 95 during photolithography, and thus the CD uniformity of the resulting GST layer. Furthermore, etching the SiO2 layer 97 produces products that can eventually land on the GST layer, causing defects. Furthermore, the existing process is complex and the manufacturing cost is high.

[0004] Therefore, the industry urgently needs a GST layer etching method that can improve CD consistency, reduce defects, simplify the process, and reduce manufacturing costs. Technical issues

[0005] The present invention aims to provide a method for etching a GST layer, which can improve CD consistency, reduce defects, simplify the process and reduce manufacturing costs. Technical Solutions

[0006] The etching method of the GST layer of the present invention comprises:

[0007] a laminate forming step of forming a laminate on a semiconductor substrate, wherein the laminate comprises a phase change material layer, a titanium nitride layer, a silicon nitride layer, a carbon mask layer, a silicon-containing anti-reflection layer, and a photoresist layer formed in sequence from bottom to top;

[0008] a photolithography step of exposing and developing the photoresist layer to form a patterned photoresist layer;

[0009] a first etching step of etching the silicon-containing anti-reflection layer and the carbon mask layer through the patterned photoresist layer to form a patterned carbon mask layer;

[0010] a second etching step of etching the silicon nitride layer through the patterned carbon mask layer to form a patterned silicon nitride layer; and

[0011] A third etching step is performed to etch the titanium nitride layer and the phase-change material layer through the patterned silicon nitride layer to form a patterned titanium nitride layer and a patterned phase-change material layer. Beneficial effects

[0012] The GST layer etching method of the present invention can improve CD consistency and reduce defects, thereby improving product yield, simplifying the manufacturing process and reducing manufacturing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG1 is a flow chart of a method for etching a GST layer according to the present invention;

[0014] 2 to 6 are schematic diagrams of various steps of forming a patterned GST layer according to the present invention; and

[0015] FIG. 7 is a schematic diagram of a laminated structure of a GST layer etching method in the prior art.

[0016] Explanation of symbols

[0017] 100,900 laminated body

[0018] 1,91 GST layer

[0019] 2,92 TiN layer

[0020] 3,93 SiN layer

[0021] 4,94 carbon HM layer

[0022] 5 SHB layer

[0023] 6,96 PR layer

[0024] 11 Patterning GST layer

[0025] 12 Patterned TiN layer

[0026] 13 Patterning SiN layer

[0027] 14 Patterned carbon HM layer

[0028] 15 Patterned SHB layer

[0029] 16 Patterned PR layer

[0030] 95 ARC layer

[0031] 97 SiO2 layer Best Mode for Carrying Out the Invention

[0032] The following describes the GST layer etching method of the present invention with reference to Figures 1 to 6. As shown in Figure 1, the GST layer etching method of the present invention includes: a laminate formation step S001, a photolithography step S002, a first etching step S003, a second etching step S004, and a third etching step S005. Each step will be described in detail below with reference to the accompanying figures.

[0033] In a laminate formation step S001, as shown in FIG2 , a laminate 100 is formed on a semiconductor substrate (not shown). The laminate 100 includes a GST layer 1, a TiN layer 2, a SiN layer 3, a carbon HM layer 4, an SHB layer (Si rich hard mask bottom ARC, silicon-containing anti-reflection layer) 5, and a PR layer 6, which are sequentially formed from bottom to top.

[0034] In this embodiment, a GST layer 1 and a TiN layer 2 are first formed on a semiconductor substrate using a PVD (physical vapor deposition) process. The GST layer 1 and the TiN layer 2 can be formed directly on the semiconductor substrate, or with other layers between the semiconductor substrate and the GST layer 1 and the TiN layer 2. A SiN layer 3 is then formed on the TiN layer 2 using a CVD process. The SiN layer 3 can be formed directly on the TiN layer 2, or with other layers between the TiN layer 2 and the SiN layer 3. A carbon HM layer 4, an SHB layer 5, and a PR layer 6 are then sequentially formed on the SiN layer 3 using a coating process.

[0035] Due to the properties of the GST layer 1 and the TiN layer 2, SiN must be used as a mask for etching. Therefore, a SiN layer 3 must be formed on the GST layer 1 and the TiN layer 2. Before etching the GST layer 1 and the TiN layer 2, the SiN layer 3 must be etched to form a patterned SiN layer. The GST layer 1 and the TiN layer 2 are then etched through the patterned SiN layer. Because the SiN layer 3 is relatively hard and difficult to etch, the PR layer 6 and the SHB layer 5 cannot be used directly as a mask for the SiN layer 3 when etching the SiN layer 3. Instead, a carbon HM layer 4 must be formed on the SiN layer 3 and used as a mask for etching the SiN layer 3.

[0036] Among them, the SHB layer 5 can play an anti-reflective role, thereby absorbing reflected light in the photolithography process and improving the photolithography accuracy. In addition, because the SHB layer 5 contains silicon, its hardness is relatively high, so it can be used as a mask for etching the carbon HM layer 4. In this way, there is no need to form a SiO2 layer on the carbon HM layer 4. In addition, the U% of the SHB layer 5 is relatively good, which will improve the CD consistency of the final GST layer. In addition, because there is no SiO2 layer, the products generated when etching the SiO2 layer will not appear, and will not fall on the GST layer to cause defects. This also reduces the defects on the final GST layer. In addition, there is no need to use a CVD process to form a SiO2 layer, which can simplify the manufacturing process and reduce manufacturing costs.

[0037] In the photolithography step S002, as shown in FIG3 , the PR layer 6 is exposed and developed to form a patterned PR layer 16. The PR layer 6 can be exposed and developed by any suitable method in the prior art, which will not be described in detail here.

[0038] In the first etching step S003 , as shown in FIG. 4 , the SHB layer 5 and the carbon HM layer 4 are etched through the patterned PR layer 16 to form a patterned carbon HM layer 14 .

[0039] In the second etching step S004 , as shown in FIG. 5 , the SiN layer 3 is etched through the patterned carbon HM layer 14 to form a patterned SiN layer 13 .

[0040] In the third etching step S005, as shown in FIG6 , the TiN layer 2 and the GST layer 1 are etched through the patterned SiN layer 13 to form a patterned TiN layer 12 and a patterned GST layer 11. Furthermore, after the patterned TiN layer 12 and the patterned GST layer 11 are formed, a thin layer of SiN remains on top of the patterned TiN layer 12. This SiN layer can serve as a protective layer and an insulating layer for the patterned TiN layer 12 and the patterned GST layer 11 in subsequent processes.

[0041] The carbon HM layer 4 , the SiN layer 3 , the TiN layer 2 and the GST layer 1 may be etched using any suitable method in the prior art, which will not be described in detail herein.

[0042] The GST etching method of the present invention can improve CD consistency and reduce defects, thereby improving product yield. In addition, it simplifies the manufacturing process and reduces manufacturing costs.

[0043] Although the present invention has been disclosed in the form of embodiments as described above, they are not intended to limit the present invention. Any professional and technical personnel in this field may make various necessary changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the attached claims.

Claims

1. A method for etching a phase change material layer, comprising: A laminate forming step S001, forming a laminate (100) on a semiconductor substrate, wherein the laminate (100) comprises a phase change material layer (1), a titanium nitride layer (2), a silicon nitride layer (3), a carbon mask layer (4), a silicon-containing anti-reflection layer (5), and a photoresist layer (6) formed in sequence from bottom to top; Photolithography step S002, exposing and developing the photoresist layer (6) to form a patterned photoresist layer (16); A first etching step S003, etching the silicon-containing anti-reflection layer (5) and the carbon mask layer (4) through the patterned photoresist layer (16) to form a patterned carbon mask layer (14); A second etching step S004, etching the silicon nitride layer (3) through the patterned carbon mask layer (14) to form a patterned silicon nitride layer (13); as well as A third etching step S005 is to etch the titanium nitride layer (2) and the phase change material layer (1) through the patterned silicon nitride layer (13) to form a patterned titanium nitride layer (12) and a patterned phase change material layer (11).

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