CN106505007B

CN106505007B - An endpoint monitoring method for back hole etching of high electron mobility transistors

Info

Publication number: CN106505007B
Application number: CN201611219617.8A
Authority: CN
Inventors: 孔欣
Original assignee: Chengdu Hiwafer Technology Co Ltd
Current assignee: Chengdu Hiwafer Technology Co Ltd
Priority date: 2016-12-26
Filing date: 2016-12-26
Publication date: 2019-03-26
Anticipated expiration: 2036-12-26
Also published as: CN106505007A

Abstract

The present invention provides a kind of endpoint monitoring suitable of high electron mobility transistor dorsal pore etching, and in device front, two kinds of metals of the wiring layer alternating growth of technique form periodical metal layer, and periodical metal layer is located above the position of backside through vias to be etched；The endpoint monitoring suitable is the following steps are included: S1, the real-time etch spectra signal of acquisition；S2, judge whether periodical spectral signal occur；S3, it is etched if so, crossing stopping after quarter 30s；S4, if not, repeating step S2.The present invention improves the identification and sensitivity of endpoint detection system endpoint signal by the periodic stack design of front wiring periodicity metal layer, improve the accuracy and validity of terminal decision, silicon carbide-based GaN high electron mobility transistor dorsal pore particularly suitable for exposed area ratio not high (< 2%) etches, it can obviously improve process degree when dorsal pore etching, have higher practical value.

Description

A kind of endpoint monitoring suitable of high electron mobility transistor dorsal pore etching

Technical field

The present invention relates to technical field of semiconductors, and in particular to a kind of terminal of high electron mobility transistor dorsal pore etching Monitoring method.

Background technique

GaN base high electron mobility transistor (HEMT) is close with its distinctive high electron mobility, high two-dimensional electron gas face Degree, high breakdown electric field become the one preferred technique of next-generation RF/Microwave power amplifier.

GaN HMET technique is divided into positive technique and back process, wherein back process mainly complete wafer be thinned and back The work of hole interconnection.Wherein, dorsal pore technique is particularly important, is the interconnection approach of front device Yu back metal ground plane, dorsal pore The quality of technique directly decides the height of product quality.

At present GaN HEMT dorsal pore processing technology mainly by SiC etching, GaN/AlGaN etching and etc. constituted, core Difficult point is the control and the selection of etching technics terminal of the pattern of etched hole.For the selection of etching technics terminal, commonly Method includes endpoint detection system and process time control.Wherein, process time control requires stability pole between process batch Height will be unable to make reply in time once there is the variation of technological parameter, therefore there is more obvious drawback；And terminal is supervised Examining system then can real-time monitoring technical process, once etching reach home can be reflected on monitor signals in real time, facilitate The control of technical process.

Endpoint detection system mainly has following two classification: laser interferance method and characteristic spectrum analytic approach.Laser interferance method Detection precisely, is not influenced by minimum exposure area in hot spot, and hot spot must be in detected region laser-irradiated domain temperature It can increase quickly, cause the variation of etch rate, if being etched rough surface injustice, can also make to detect signal weaker and precision It is lower.Characteristic spectrum analytic approach is passive detection type detection device, does not influence etching process, can detect slight change, can To carry out very sensitive detection, but precision is influenced by minimum exposure area, and the signal of endpoint detection system can change, The intensity for detecting light wave is directly proportional to etch rate, when etch rate is slow, detection difficult.Since dorsal pore diameter is only dozens of Micron, and general laser spot diameter is all larger than 100 microns, so GaN HEMT dorsal pore etching technics, selects characteristic light spectrometry It is more feasible.However to have the disadvantage in that dorsal pore exposed area accounts for smaller for characteristic light spectrometry, causes endpoint detection system signal It is weaker, it is difficult to screen.

Summary of the invention

The purpose of the present invention is to provide a kind of endpoint monitoring suitable of high electron mobility transistor dorsal pore etching, the party Method can well solve problem above.

To reach above-mentioned requirements, the technical solution adopted by the present invention is that: a kind of high electron mobility transistor dorsal pore is provided The endpoint monitoring suitable of etching, in device front, two kinds of metals of the wiring layer alternating growth of technique form periodical metal layer, week Phase property metal layer is located above the position of backside through vias to be etched；The endpoint monitoring suitable the following steps are included:

S1, real-time etch spectra signal is obtained, and spectral signal is analyzed；

S2, judge whether periodical spectral signal occur；

S3, it is etched if so, crossing stopping after quarter 30s；

S4, if not, repeating step S1.

Compared with prior art, present invention has the advantage that

(1) it is improved by the periodic stack design of front wiring periodicity metal layer (being also dorsal pore etching barrier layer) The identification and sensitivity of endpoint detection system endpoint signal improve the accuracy and validity of terminal decision, are particularly suitable for using In the not high silicon carbide-based GaN high electron mobility transistor dorsal pore etching of exposed area ratio, back can obviously improve Process degree when hole etches, has higher practical value；

(2) this method only adjusts wiring metal structure, have it is good implantable, without increasing additional technique step Suddenly.

Detailed description of the invention

The drawings described herein are used to provide a further understanding of the present application, constitutes part of this application, at this The same or similar part, the illustrative embodiments and their description of the application are indicated using identical reference label in a little attached drawings For explaining the application, do not constitute an undue limitation on the present application.In the accompanying drawings:

Fig. 1 is flow diagram of the invention.

Fig. 2-Fig. 8 is the flow diagram of dorsal pore of the present invention etching.

Specific embodiment

To keep the purposes, technical schemes and advantages of the application clearer, below in conjunction with drawings and the specific embodiments, to this Application is described in further detail.For the sake of simplicity, it is omitted that well known to a person skilled in the art certain skills in being described below Art feature.

The present embodiment is by taking a kind of silicon carbide-based GaN high electron mobility transistor as an example, dorsal pore etching and terminal prison The entire flow of control is as follows:

A, periodical metal layer 3, periodical metal are formed in two kinds of metals of wiring layer alternating growth of device front technique Layer 3 is located above the position of backside through vias to be etched, as shown in Figure 2；The metal of alternating growth is platinum and gold, or for nickel and Gold constitutes the periodic structure of Pt/Au/Pt/Au/Pt/Au or Ni/Au/Ni/Au/Ni/Au, typical thickness 500/2000/ 500/2000/500/4500, overall thickness is about 1 μm.The intensity that signal is grabbed according to endpoint monitoring system, can be to periodicity The periodicity of metal layer 3 is adjusted, but at least has 2 periods；For SiC base GaN HEMT, usually can all there is one Walk special technique for complete device metal line, interconnection, while this layer of metal be also in back process dorsal pore etch Barrier layer should stop when dorsal pore is etched to the layer i.e.；

B, the transistor left-hand thread is bonded to sapphire by bonding material to carry in support, front description is protected at this time, such as Shown in Fig. 3；

C, 1 back side of SiC layer is thinned, is thinned to 70 ~ 120 μm；1 back spatter furling plating of SiC layer, material are Ti and Au, Middle Ti with a thickness of 200 ~ 500, Au with a thickness of 1000 ~ 2000；Ni is then made by way of plating, with a thickness of 5 ~ 10 μm, as shown in Figure 4；

D, the photoetching of dorsal pore figure, development, as shown in Figure 5；

E, W metal, 0.5 ~ 1 μm/min of corrosion rate are corroded using the concentrated sulfuric acid, hydrogen peroxide mixed solution；It is dedicated using Au Corrode corrosion Au；Using 10% HF solution corrosion Ti, as shown in Figure 6；

F, photoresist is removed, with Ni for hard exposure mask, using ICP-RIE equipment etching SiC layer 1, etching gas is F base gas Body, exemplary options SF₆+O₂, 0.5 ~ 1.0 μm/min of rate, as shown in Figure 7；

G, use the concentrated sulfuric acid, hydrogen peroxide mixed solution corrosion W metal to completely remove W metal, 0.5 ~ 1 μ of corrosion rate m/min；Use the dedicated corrosion corrosion Au of Au to completely remove metal Au；Use 1% ~ 10% HF solution corrosion Ti to go completely Except metal Ti；

H, using SiC as exposure mask, using ICP-RIE equipment, using Cl₂And BCl₃Etch GaN/AlGaN layer 2, etch rate 0.1~0.2μm/min.After complete etching layer thoroughly, gas can start etching cycle metal layer 3；Once being etched to periodicity Metal layer 3 is acquired and is analyzed by the spectrum to special metal element in periodical metal layer 3, and spectral signal can be in Reveal the alternating variation for gradually increasing and weakening, shows apparent periodicity；Determine whether to reach the specific step of etching terminal It is rapid as follows:

Endpoint detection system acquires real-time etch spectra signal, and analyzes collected spectral signal；

When there is periodical spectral signal, illustrate to reach etching terminal, stops etching after crossing quarter 30s；

When there is not periodical spectral signal, endpoint detection system continues to acquire real-time etch spectra signal and divide Analysis.

Eventually form device architecture as shown in Figure 8.

Above-mentioned ICP-RIE equipment should be equipped with the endpoint detection system using characteristic spectrum analytic approach, detectable exposed area Than < 5%, and should have broad spectral analysis ability, the elements such as Ni, Pt, Au can be parsed.

Embodiment described above only indicates several embodiments of the invention, and the description thereof is more specific and detailed, but not It can be interpreted as limitation of the scope of the invention.It should be pointed out that for those of ordinary skill in the art, not departing from Under the premise of present inventive concept, various modifications and improvements can be made, these belong to the scope of the present invention.Therefore this hair Bright protection scope should be subject to the claim.

Claims

1. a kind of endpoint monitoring suitable of high electron mobility transistor dorsal pore etching, which is characterized in that in device front technique Two kinds of metals of wiring layer alternating growth form periodical metal layer, the periodicity metal layer is located at backside through vias to be etched Above position；The endpoint monitoring suitable the following steps are included:

S2, judge whether periodical spectral signal occur；

S3, it is etched if so, crossing stopping after quarter 30s；

S4, if not, repeating step S1；

The metal of the alternating growth is platinum and gold, or is nickel and gold.

2. the endpoint monitoring suitable of high electron mobility transistor dorsal pore etching according to claim 1, which is characterized in that The periodicity metal layer at least has 2 periods.

3. the endpoint monitoring suitable of high electron mobility transistor dorsal pore etching according to claim 1, which is characterized in that It is described periodicity metal layer with a thickness of 0.8 μm -1.2 μm.