From nbelov at nanochip.com Mon Sep 12 16:01:21 2005 From: nbelov at nanochip.com (Nickolai Belov) Date: Mon, 12 Sep 2005 16:01:21 -0700 Subject: Etching fused silica wafers in PQuest ECR etcher Message-ID: Dear PQuest user, I would like to etch fused silica wafer at PQuest ECR etcher. The wafer is 4" with SEMI standard flat. Wafer thickness is 500 um. I consider two options of doing that: Option 1 Mount fused silica substrate on a silicon carrier wafer using small pieces of Kapton tape and etch the fused silica wafer this way. Kapton tape will not go under the clamps in the system and will not go to the back side of the carrier wafer. Option 2 Etch fused silica wafer without carrier wafer. Concern with the first option is overall thickness of the stack (about 1 mm). Most likely this thickness is ok. Concern with the second option is breakage of the fused silica wafer due to clamping in the chamber. I incline to the first option as it is safer. Please, let me know if you have any relevant experience / recommendations. If I don't have definite response then I'll try to find answer either in the PQuest documentation or contacting the manufacturer. With respect Nickolai Belov -------------- next part -------------- An HTML attachment was scrubbed... URL: From mwiemer at stanford.edu Mon Sep 12 17:13:09 2005 From: mwiemer at stanford.edu (Michael Wiemer) Date: Mon, 12 Sep 2005 17:13:09 -0700 Subject: Etching fused silica wafers in PQuest ECR etcher In-Reply-To: Message-ID: <001101c5b7f7$eed07090$766140ab@longmorn> Are we etching Fused Silica in the chamber these days? As I remember the gases needed for that were CF4 + other stuff (maybe O2, Ar). I am worried that the CF4 can polymerize in the chamber under the right circumstances (particularly while developing a process). Anybody have any thoughts on this? Jim McVittie perhaps? Thanks, -Mike -----Original Message----- From: Nickolai Belov [mailto:nbelov at nanochip.com] Sent: Monday, September 12, 2005 4:01 PM To: pquest at snf.stanford.edu Cc: Nickolai Belov Subject: Etching fused silica wafers in PQuest ECR etcher Dear PQuest user, I would like to etch fused silica wafer at PQuest ECR etcher. The wafer is 4" with SEMI standard flat. Wafer thickness is 500 um. I consider two options of doing that: Option 1 Mount fused silica substrate on a silicon carrier wafer using small pieces of Kapton tape and etch the fused silica wafer this way. Kapton tape will not go under the clamps in the system and will not go to the back side of the carrier wafer. Option 2 Etch fused silica wafer without carrier wafer. Concern with the first option is overall thickness of the stack (about 1 mm). Most likely this thickness is ok. Concern with the second option is breakage of the fused silica wafer due to clamping in the chamber. I incline to the first option as it is safer. Please, let me know if you have any relevant experience / recommendations. If I don't have definite response then I'll try to find answer either in the PQuest documentation or contacting the manufacturer. With respect Nickolai Belov -------------- next part -------------- An HTML attachment was scrubbed... URL: From mcvittie at snf.stanford.edu Mon Sep 12 17:23:10 2005 From: mcvittie at snf.stanford.edu (Jim McVittie) Date: Mon, 12 Sep 2005 17:23:10 -0700 Subject: Etching fused silica wafers in PQuest ECR etcher References: Message-ID: <43261BEE.C3B503D8@snf.stanford.edu> Nickolai, The PQuest is not an oxide etching tool. Its primary purpose is to etch III-V materials. Since there is time available on the tool, processes compatible with III-V etching are allowed. The III-V etch processes in the tool are all Cl based. All the SiO2 etching processes that I am familiar with are F based. There are problems in mixing Cl and F bases chemistries in the same tool. In particular, F compounds and F based polymers on the chamber walls tend to depress the etch rates of Cl based etch processes. This means that chamber needs cleaning and reconditioning after the use of F. While it is not that hard to get the chamber back after a short F based process, a long oxide etch will be a problem. Especially, since we do not have an easy way of determining when the chamber conditioning is back to where it should be. If you want to proposed an oxide etch for the PQuest, I am willing to discuss it with the PQ III-V users. I am doubltful, they will allow it. Jim Nickolai Belov wrote: > Part 1.1 Type: Plain Text (text/plain) > Encoding: quoted-printable -------------- next part -------------- A non-text attachment was scrubbed... Name: mcvittie.vcf Type: text/x-vcard Size: 422 bytes Desc: Card for Jim McVittie URL: From nbelov at nanochip.com Thu Sep 15 09:42:53 2005 From: nbelov at nanochip.com (Nickolai Belov) Date: Thu, 15 Sep 2005 09:42:53 -0700 Subject: Proposing a test on compatibility of fluorine and chlorine chemistry Message-ID: Dear PQuest users, This week there were several discussions on influence of fluorine etching processes on subsequent chlorine etching processes of III-V materials. It does not look like some solid data characterizing the influence is available. I would like to propose the following test(s) in order to experimentally characterize this influence. 1. Prepare two identical (or very similar) samples of III-V materials for etching in Cl plasma. 2. Prepare a set of samples for etching in F plasma. 3. Do oxygen plasma cleaning and pre-conditioning of the chamber for Cl-based etching. 4. Etch the first III-V sample in Cl-plasma. 5. Do oxygen plasma cleaning and pre-conditioning of the chamber for F-based plasma. 6. Etch the samples prepared for F plasma processing in fluorine plasma. 7. Do oxygen plasma cleaning and pre-conditioning of the chamber for Cl-based plasma. 8. Etch the second III-V sample in Cl-plasma using the same process as the first III-V sample. 9. Do comparative analysis of the two III-V samples etched in Cl-plasma. There many details that have to be worked out. There are some suggestions related to some of the details: - Processing history prior to the test may affect results of the etching of the first III-V sample. Therefore, it makes sense to do the test after III-V Cl-etching processes which deliver good (expected) results. - Similarity of III-V samples should include size of the sample, thickness of the film / material to be etched, pattern, and size of the open for etching area as percentage of the sample area. Samples should be prepared at the same time using the same masking material. If samples are going to be etched on a carrier then the same type of carrier (e.g., covered with photoresist or oxidized Si wafer) and same method of mounting should be used for both of them. - Cl-based etching process should be long enough to allow accurate etch depth measurements. It should not be a self-stop process (e.g. etch through a film and stop on a stop layer). - Oxygen plasma cleaning and pre-conditioning processes are not defined. Suggested oxygen cleaning process: OXYGEN3 for 10 minutes. Pre-conditioning might use the same process as will be used for etching. - Results may vary depending on parameters of the F-based etching process, its duration and a mask used on the sample etched in F-based chemistry. Several tests may be suggested (short etching process with low power, long etching process with high power, etc.). However, it seems to be beneficial to do characterization for some processes that are currently being used by active users who employ F-based etching. - It is suggested that the comparative analysis of the III-V samples includes etching depth and surface roughness measurements as well as profile parameters (side wall angle, undercut) evaluation. Measurements can be done using non-contact optical profilometer first (Zygo) and contact profilometer after that. Hopefully, as a result of couple of the above-described tests, some recommendations for "standard" cleaning and chamber-conditioning processes for PQuest users will be worked out. I will be happy to participate in the tests as I have been using both F-based and Cl-based processes. If the suggested test is accepted by PQuest community and details are worked out then I'll be happy to offer some machine time for etching two III-V samples with Cl-based processes before and after etching some of my substrates which will be done with F-based chemistry. Your suggestions and responses are very welcome. With respect Nickolai Belov -------------- next part -------------- An HTML attachment was scrubbed... URL: From mcvittie at snf.stanford.edu Thu Sep 15 13:59:14 2005 From: mcvittie at snf.stanford.edu (Jim McVittie) Date: Thu, 15 Sep 2005 13:59:14 -0700 Subject: Proposing a test on compatibility of fluorine and chlorine chemistry References: Message-ID: <4329E0A2.3B864E16@snf.stanford.edu> Nickolai, I guess I disagree with your statement that there is no solid data characterizing the influence F on Cl based etching process. I have been going to plasma etch talks for over 25 yrs and I have heard many talks over the years where data has been presented on the decrease in Cl based etch rates in the presence of leftover F on the reactor walls. In fact, last week at the monthly bay area plasma etch user meeting in Santa Clara, there were 2 talks, which discussed this issue regarding Si etching. In addition, there will a number of talks on the influence of chamber conditioning on etching at the upcoming AVS mtg in Boston in late Oct. However, I agree that we have not put any effort into quantifying the issue in any of etchers in SNF. I did purchase an optical spectrometer sometime back specifically for looking chamber conditioning issues. Your proposed experiment is similar to what Jim Kurger and I have discussed in the past. You propose to do the comparison on final etch results. I think it would better to initially focus on quick real-time measurements, such as optical emission lines and etch rate. And then to confirm the results with SEM images of the etch results. For the data I have seen from other groups, if the emission and etch rates look good, I would be very surprised if the etch profile and roughness are off. With optical emission, one can evaluate the plasma during the different conditioning steps and hopefully determine how long to run a conditioning step. As for the F exposure, I would run it a factor of 5 to 10x longer than the expected etch process to give us a safety margin and to make the response larger and easier to see. I would look at both low and high power processes. As for pressure, I would run at the highest pressure likely to be used since free radical F concentrations tend to increase with pressure and the Pquest does have any ion bombardment.on the chamber wall. I am willing to works anyone who wants to do this study. Jim Nickolai Belov wrote: > Part 1.1 Type: Plain Text (text/plain) > Encoding: quoted-printable -------------- next part -------------- A non-text attachment was scrubbed... Name: mcvittie.vcf Type: text/x-vcard Size: 422 bytes Desc: Card for Jim McVittie URL: From mwiemer at stanford.edu Thu Sep 29 13:53:58 2005 From: mwiemer at stanford.edu (Michael Wiemer) Date: Thu, 29 Sep 2005 13:53:58 -0700 Subject: Pquest and CF4 Message-ID: <000d01c5c537$ea114280$766140ab@longmorn> Pquest users, Over the last couple of weeks GaAs users - mostly Harris group people who are by far the group with the most people using the tool - have discussed the question of opening the tool for CF4 etching. The question was basically, "Should CF4 etching of SiO2 and other materials widely used in the lab be allowed in the Pquest and if so, under what circumstances". Nickolai Belov proposed a test to investigate the effects of CF4 on GaAs etching to help answer this question. In the end, little support was voiced for the tests proposed by Nickolai Belov (test CF4 effect on GaAs etching), or for Flourine etching in the Pquest in general. I will try to summarize the main points which came out in the discussion in this email. Currently, O2 with small amounts of CF4 is used to clean the chamber as well as etch some polymers (BCB for example). No one really had a problem with this as it is a necessary cleaning procedure, nor with the BCB etch, being so similar to the clean. The issues, as well as I can summarize them here, follow below. While reading, keep in mind that this is not a "etch anything" tool. It is the only III-V etch tool in the lab and its integrity as a III-V etch tool must be maintained. This can only be done with good policy (I fully recognize that policy on this tool has not always been stellar). And any good policy is simple, so here we go.... 1.) CF4 polymerization Instead of using an oxygen rich plasma like the CF4/O2 clean, the proposed etching would involve little to *no* O2 and 100% CF4. With this kind of etch, there is the concern that this etch will deposit/build up a teflon-like polymer film in the chamber. 2.) F affects the GaAs (and, more dramatically, the AlGaAs) etch rate. This this is well documented. There is no desire among the users to re-prove this. Conditioning the chamber after a F etch can return the chamber to good Cl2/BCl3 GaAs etching condition. The question is what kind of conditioning and how long should the conditioning be. However, there was little desire to put the effort into researching this. Just like tests which may address problem 1 above, the test to address this problem is time consuming and may ultimately be inconclusive. And any test only tests 1 particular condition - other CF4 users in the future would surely want to alter the process a little and then we can be faced with the same problems all over again - this leads to the next problem.... 3.) What about other people and the future? One of the biggest problems which came out during the discussion is that etching of SiO2 opens the door to more SiO2 etching. 90% of the lab users are Silicon people and if the word gets out that the Pquest can be used for SiO2 etching, there would probably be significantly more interest in the future. Considering there are at least 6 SiO2 etch tools in the fab, why do we have to make the Pquest another one? People do not want to open this tool to SiO2 (Fluorine) etching and then deal with these issues above continually as the next and then the next person decides that Pquest is their best-bet tool for their Fluorine etch. If we make an exception here, or there, we will CONSTANTLY have to deal with issues of process compatibility. The tool must be maintained as a III-V etch tool. Why do these questions never come up with the P5000? Answer: because there is a strong policy on that tool about what gases/materials can be run in each chamber. Proposal: We propose that CF4 etching is eliminated from the "list" of possible Pquest etches. High O2-low CF4 flow etches will still be OK. And the week will stay split: GaAs etching Wed-Sat, non-GaAs etching Sun-Tues. If you want to use CF4 in the Pquest and are unhappy by this, perhaps the best way to communicate is to get together (email is so difficult and time consuming). Contact people: Rafael Aldaz (aldaz at stanford.edu) and Mike Wiemer (mwiemer at stanford.edu). We are in contact with other GaAs users. From nbelov at nanochip.com Thu Sep 29 14:50:24 2005 From: nbelov at nanochip.com (Nickolai Belov) Date: Thu, 29 Sep 2005 14:50:24 -0700 Subject: PQuest Message-ID: Hello Michael, Thank you for your response. I'll be happy to meet and discuss the proposed "no CF4 without O2" rule. Process/tools related restrictions usually require either executive decision or have to be proven experimentally. You are trying to solve the CF4 etching issue using executive decision. If the decision will be made then I'll follow it. I believe that experimental comparison of results of Cl2 etching versus (CF4 etching - oxygen cleaning - Cl2 etching) should be the main argument in the discussion. It is likely that we'll be able to find a "common ground". Please, suggest meeting time and I'll try to be there. I hope that some other PQuest users will join us as well. I'll be out of area this Friday (09/30). I have several regular meetings in my schedule (Monday 1 p.m. - 3 p.m.; Wednesday, Friday 9-10 a.m.). With respect Nickolai Belov Tel: (510)-770-2516 -----Original Message----- From: Michael Wiemer [mailto:mwiemer at stanford.edu] Sent: Thursday, September 29, 2005 1:54 PM To: Nickolai Belov Cc: 'Rafael Aldaz' Subject: PQuest Hi Nickolai, First, I am sorry this has taken so long. And second, I brought up the issue of testing the CF4 etching in the Pquest with other GaAs users. As you can see below, it did was not met with much enthusiasm. I am sure you do not like this proposal (see below). So perhaps the best thing at this point is to get you together with some of the strongest opponents to this etch, along with Jim McVittie, and we can discuss. If you are interested, when are you going to be on Campus? Please read below. This was sent out to the Pquest list. Im not sure if you are on the pquest list and I wanted to make sure this got to you. Pquest Users, Over the last couple of weeks GaAs users - mostly Harris group people who are by far the group with the most people using the tool - have discussed the question of opening the tool for CF4 etching. The question was basically, "Should CF4 etching of SiO2 and other materials widely used in the lab be allowed in the Pquest and if so, under what circumstances". Nickolai Belov proposed a test to investigate the effects of CF4 on GaAs etching to help answer this question. In the end, little support was voiced for the tests proposed by Nickolai Belov (test CF4 effect on GaAs etching), or for Flourine etching in the Pquest in general. I will try to summarize the main points which came out in the discussion in this email. Currently, O2 with small amounts of CF4 is used to clean the chamber as well as etch some polymers (BCB for example). No one really had a problem with this as it is a necessary cleaning procedure, nor with the BCB etch, being so similar to the clean. The issues, as well as I can summarize them here, follow below. While reading, keep in mind that this is not a "etch anything" tool. It is the only III-V etch tool in the lab and its integrity as a III-V etch tool must be maintained. This can only be done with good policy (I fully recognize that policy on this tool has not always been stellar). And any good policy is simple, so here we go.... 1.) CF4 polymerization Instead of using an oxygen rich plasma like the CF4/O2 clean, the proposed etching would involve little to *no* O2 and 100% CF4. With this kind of etch, there is the concern that this etch will deposit/build up a teflon-like polymer film in the chamber. 2.) F affects the GaAs (and, more dramatically, the AlGaAs) etch rate. This this is well documented. There is no desire among the users to re-prove this. Conditioning the chamber after a F etch can return the chamber to good Cl2/BCl3 GaAs etching condition. The question is what kind of conditioning and how long should the conditioning be. However, there was little desire to put the effort into researching this. Just like tests which may address problem 1 above, the test to address this problem is time consuming and may ultimately be inconclusive. And any test only tests 1 particular condition - other CF4 users in the future would surely want to alter the process a little and then we can be faced with the same problems all over again - this leads to the next problem.... 3.) What about other people and the future? One of the biggest problems which came out during the discussion is that etching of SiO2 opens the door to more SiO2 etching. 90% of the lab users are Silicon people and if the word gets out that the Pquest can be used for SiO2 etching, there would probably be significantly more interest in the future. Considering there are at least 6 SiO2 etch tools in the fab, why do we have to make the Pquest another one? People do not want to open this tool to SiO2 (Fluorine) etching and then deal with these issues above continually as the next and then the next person decides that Pquest is their best-bet tool for their Fluorine etch. If we make an exception here, or there, we will CONSTANTLY have to deal with issues of process compatibility. The tool must be maintained as a III-V etch tool. Why do these questions never come up with the P5000? Answer: because there is a strong policy on that tool about what gases/materials can be run in each chamber. Proposal: We propose that CF4 etching is eliminated from the "list" of possible Pquest etches. High O2-low CF4 flow etches will still be OK. And the week will stay split: GaAs etching Wed-Sat, non-GaAs etching Sun-Tues. If you want to use CF4 in the Pquest and are unhappy by this, perhaps the best way to communicate is to get together (email is so difficult and time consuming). Contact people: Rafael Aldaz (aldaz at stanford.edu) and Mike Wiemer (mwiemer at stanford.edu). We are in contact with other GaAs users.